US 3007201 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
Nov. 7, 1961 F. BRUMMER 3, 1
METHOD AND APPARATUS FOR A CONTINUOUS PRODUCTION OF PLASTIC-FOIL ARTICLES IN DEEP DRAWING Filed Oct. 5; 1959 8 Sheets-Sheet 1 A Fig. 2. 15 .1. 7 7
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METHOD AND APPARATUS FOR A CONTINUOUS PRODUCTION OF PLASTIC-FOIL. ARTICLES IN DEEP DRAWING Filed Oct. 5, 1959 8 Sheets-Sheet 2 Th rottLe,
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METHOD AND APPARATUS FOR A CONTINUOUS PRODUCTION OF PLASTIC-FOIL. ARTICLES IN DEEP DRAWING Filed Oct. 5, 1959 8 Sheets-Sheet 4 Rectifer Indicator Lg luts FfiedrichBflimmcr Bfmm0%/M %/A%RNEYS Radiating System Nov. 7, 1961 F. BRUMMER 3 0 METHOD AND APPARATUS FOR A CONTINUOUS PRODUCTION OF PLASTIC-FOIL ARTICLES IN DEEP DRAWING Filed Oct. 5. 1959 s Sheets-Sheet 5 M watbcVaLve O p erat'ung C5 LL 1 Step by Ste Cross Bar suuichilg D istr Lbutor INVENTOR FrfwdrichBn'immcr W %NEYS Nov. 7, 1961 F. BRUMMER 3,007,201
METHOD AND APPARATUS FOR A CONTINUOUS PRODUCTION OF PLASTIC-FOIL ARTICLES IN DEEP DRAWING Filed Oct. 5, 1959 a Sheets-Sheet a ME 3 E 207 O 202 h a -.15. W L 2| Zl3 2n ZOI 204 INVENTOR. Ejedfuhfirzimmar BY z Z1 ATTORNEYS NOV. 7, 61 F. BRUMMER 3,007,201
. METHOD AND APPARATUS FOR A CONTINUOUS PRODUCTION OF PLASTIC-FOIL ARTICLES IN DEEP DRAWING Filed Oct. 5, 1959 8 Sheets-Sheet 7 k 4 A \Y\\\\\\\\\\\\\\\\\\\\ \\\\\\\\A INVENTOR I Friedrylahfimmmzr 442$ & igT oRNaYs Nov. 7,, 1961 F. BRUMMER METHOD AND APPARATUS FOR A CONTINUOUS PRODUCTION OF PLASTIC-FOIL ARTICLES IN DEEP DRAWING 8 Sheets-Sheet 8 Filed Oct. 5, 1959 INVENTOR From cur /H Compressor F116 (Lrjch Briimmer ATTORNEYS 3,007,201 Patented Nov. 7, 1961 tic METHOD AND APPARATUS FOR A CONTINUOUS PRODUCTIGN F PLASTIC-FOIL ARTICLES IN DEEP DRAWING Friedrich Briimmer, Dinkelsbnhl, Bavaria, Germany, assignor to Farbwerke Hoechst Aktiengesellschaft vormals Meister Lucius & Briining, Frankfurt am Main, Germany, a corporation of Germany Filed Oct. 5, 1959, Ser. No. 844,510 Claims priority, application Germany Dec. 13, 1958 19 Claims. (CI. 1819) It is known to produce plastic containers, boxes, cups, dishes etc. and the associate lids for the most varied purposes from a plastic foil by deep drawing. To this end cold or heated foil sections by varying sizes are placed on the cavity of a drawing die and are drawn into the cavity of the die either hydraulically, by employing compressed or evacuated air, or mechanically by means of a plunger matching the die cavity. 011 termination of the drawing process the die is opened and the foil section which now shows on its surface the hollow positive shapes of the die cavities, is removed from it. The finished article is obtained in that the cavity-moulded blanks are punched out of the foil section along their outer demarcation line by means of a punching tool. This method always requires a drawing die and a punching machine and its output is therefore limited because cutting of the foil sections to be treated, heating and shaping of the blank and its transfer from the drawing die to the punching machine require a comparatively large amount of time and could hardly be autornatized without the employment of relatively extensive apparatus.
The object of the present invention is a method of continuously producing moulded articles from thermoplastic foils of synthetic material by deep drawing which combines the operations of foil punching and deep drawing. A further object of the invention is a deep drawing process which allows perfectly neat production of drawn articles and yet furnishes an appreciably increased output. A further object of the invention is a device for carrying the above method into practical efi'ect.
According to the method of the invention, an endless foil web of a thermoplastic resin, for example polyvinyl chloride hard foil, is pre-heated to softening point prior to entering the shaping tool, is subsequently marked by mechanical means along the periphery of the drawn article to be produced, and finally, at the same temperature, deep-drawn in a draw die either hydraulically or mechanically, or by employing both operational means either simultaneously or successively. Cooling and setting of the marginal zones is effected by contact with the marking edges, while cooling and setting of the blank takes place in the tool cavity. The finished article is eventually severed from the foil web within the marking zone, embrittled during cooling, and ejected from the die. Preferably advance and heating of the foil web is here controlled in dependence upon the degree of softening attained immediately prior to entering the zone of treatment. If at this time the plasticity required for processing has already been attained, the advance mechanism is started which moves the particular zone of the foil web thus softened into the area of treatment. If plasticity is still too low, then the radiation intensity of the heating device is increased until plasticity has reached the correct degree. In this way it is ensured that during each cycle of advancement a transverse area of the foil Web moved into the processing zone has the same degree of plasticity previously determined in accordance with the processed foil type and the type and size of the draw die, and that the finished products will therefore be turned out in completely uniform quality.
If, as will be shown by the embodiment described below, heating of the foil takes place at full force, it is possible to place by way of protection, particularly in case of irregularities of interruption of the machine cycle, a curtain of cold air in the shape of a luminar current between heating elements and foil web, using a feeler exploring the foil web. This current can be generated by compressed air and serves to maintain, by. means of the issuing volume of air which is regulatable in dependence on pressure, the foil temperature at the level required for processing and to prevent burning or melting through of the foil web by overheating. In automatic operation the exploring feeler is preferably coupled to the stepping mechanism which triggers the next-following switching sequence and operational cycle.
Preferably the task of notching the foil web along the periphery of the blank to be processed is allotted to the drawing die which to this purpose is suitably shaped at its upper edge and carries out the marking process during a separate first motion in co-operation with a suitable counter edge. Any suitable device for carrying out the method according to the invention is to be characterized by the following essential elements:
(A) A guide track for the foil web comprising a feed roller, guide rollers and preferably also a take-off roller;
(B) A mechanism for the discontinuous advance of the foil web over a distance corresponding to the overall height of the components (C), (D), (E);
(C) A heating device for the foil web, arranged along the guide track (A), preferably composed of separate heater elements displaceable in accordance with the outline of the die in use;
(D) [A device for marking the foil web, arranged behind the heating device (C) in foil running direction and comprising a notching ring and a counter edge;
(E) Drawing die plate and die closure plate with drawing and punching tool interchangeably supported therein, arranged either behind the marking device (D) in foil running direction or preferably incorporating the latter, as described above;
(F) A pneumatic or mechanical, or a pneumatic-mechanical device for the relative displacement of drawing plate, die closure plate, marking ring and counter edge;
(G) A drive system com-prising a motor, oil pumps pressure reservoirs and pressure cylinders for all driven or displaceable parts; it necessary, dual-stage pump for high and low pressure;
(H) An electric relay circuit with magnetic air-oil valves for the automatic actuation of the movable parts in the operational cycle governed by the foil type and the draw die.
Useful additional developments are constituted by the auxiliary elements listed below:
(I) A feeler exploring the plasticity of the foil web in the heating region, including a temperature control device or a protective shield against burning;
(J) A braking device for the foil web;
'(K) A device eiiecting fine feed control for the foil web as well as shock attenuation;
(L) A stepping mechanism using eight or more time delay relays adjustable individually in their delay times, and also an associate plug switchboard for varying the progress-ion of the operational cycle, pre-determined by the time delay relays, in accordance with the requirements of the draw die in use and the type of material being processed.
In the attached drawings an exemplary embodiment of a device according to the invention is illustrated.
The method of the invention and the device intended for the realization of this method, in contradistinction from previous non-cutting shaping methods, aim at a sequence of the operational stages which form the drawn product comprising accurately stepped individual stages.
In deep drawing within the range of elastic elongation of the foil material, the operational stages following upon one another are listed below:
(1) Heating to within the temperature range of elastic elongation,
(2) Foil advance,
(4) Drawing or stretching,
(5) Pressing the drawn material to cold wall portions to achieve setting,
(6) Opening of the die,
(7) 'Detaching the blank,
( 8) Eject-ing the blank.
In drawing within the temperature range of plastic flow (a definition of this range is given in the Belgian Patents 597,545 and 550,620), which from certain points of view offers special advantages, the following operational stages take place:
(1) Heating to within the temperature range of elastic elongation,
(2) Advance and redirection of the foil web into a horizontal plane,
(3) Heating to within the temperature range of plastic flow,
(5) Drawing or stretching,
(6) Opening the die,
(7) Detachment and simultaneous ejection of the blank.
FIG. 1 shows a device in vertical section, without the draw die, die closure plate and notching device being fitted. FIG. 2 shows a section in the plane CD of H6. 1, FIG. 3, a. section in plane GH, FIG. 4, a section in the plane EF wherein the draw die, die closure plate and notching device are fitted. FIG. 5 shows, in a horizontal section, the interconnected movable and rigid parts of FIG. 4. FIG. 6 shows diagrammatically the action of the brake for the foil web (a) and the web path without such a brake (b). FIG. 7 shows details of the fine feed regulation, FIG. 8 details of the throttle device 61 of FIG. 1. FIGS. 9 and 9A represent the entire switching layout of the electric section of the machine. FIG. 10 shows details thereof. FIG. 11 is a diagram for carrying out the shaping of the foil web in the plastic flow range.
FIG. 12 is a diagrammatic view of a film clamping and advancing device in various phases of movement.
FIG. 13 shows a die with a plastic foil forming part of a punching device not further illustrated.
FIG. 14 shows a die according to FIG. 13, but with a support element inserted therein, said element being downwardly open, and with a pressure ring imposed.
FIGS. 15-17 show a device according to the invention constructed in a different way in various operational stages.
FIGS. 18 and 19 are cross-sectional views in elevation of other embodiments of this invention in two phases of operation, and
FIGS. 20 and 21 are views in elevation, partially in cross section and partially diagrammatic of pressure cylinders and associated devices for moving the die-carrying plates of embodiments of this invention.
Identical parts have identical reference symbols in all drawings.
The whole device is arranged in a structure constituted by an angle iron frame lower part 1, an angle iron frame upper part 2, a transverse beam 3 with longitudinal bars 4 and their extensions 5 and guide rods 6. The extension arms 5 serve for the deflection of the foil when shaping by drawing is not effected within the temperature range of elastic elongation, but in the higher temperature range of plastic flow. Shaping in this range when using suitable foil material offers advantages in regard to drawing and static stability. But during this kind of treatment the foil should extend horizontally and should be treated in this position, i.e. in a vertically directed drawing operation.
The guide train (A) for the foil web 34 consists of the feed spindle 35 and the roller 33 fitted thereto for receiving the foil web to be processed, deflecting rollers or deflecting surfaces 38, 72 and 72, 39 as well as the take-off spindle and take-off roll 40 fitted thereto which is driven by a motor 44 by means of a spindle-actuating drive with slipping clutch 43. In order to feed the leading end of the foil web on to the take-off reel 40, a trough 41 leading to the spindle is provided. The removal of the full take-off reel 40 and the insertion of a new empty reel are effected with the aid of a resilient spindle release 42 constructed in known manner (FIG. 3). Preferably the feed spindle 35 is also provided with a band brake 36 attached to the lever 37 one end of which is pivotaoly supported whereas the other end carries the deflection or conveying roller 38. The same applies to the previously mentioned take-off spindle 40. This arrangement ensures that the foil web running off the feed roll is correctly guided in a loop and that the advance movement does not jerk the entire mass of the roll into rotation but takes place gradually, taking into account the inertia of the roll.
The advance mechanism (B) for the foil web comprises the vertical guide rods 20--preferably constructed as tubes to provide a system for hydraulic communication between the cylinders 27 and 28 without additional ducts-which by the nuts 21 are fastened to the cross beams 18, I9, guide frames 29, 30, pressure frames 31, 32 and hydraulically actuated pressure cylinders 27, 28 and, finally, counter pressure supports 27a and 28a. The reciprocating vertical displacement of the foil advancing frame consisting of the above mentioned components is effected by the hydraulically actuated feed cylinder 26. In FIG. 1 the feed frame is shown in its lowest position and the hydraulic pressure cylinders 27, 28 hold the pressure frame 31, 32 against the counter pressure supports 27a and 28a and thus hold the foil web, situated between the counter pressure supports 27a and 28a and the pressure frames 31, 32, firmly secured between the latter. In this position the frame and the foil web arrested by it remain stationary for the duration of a notching and drawing operation to be described later. When the drawing operation is terminated and the blank ejected from the opened draw die, the pressure cylinders 27 and 23 pull back the pressure frames 31, 32 within the guide frame 29, 30 and release the hitherto arrested foil web. Subsequently, by actuation of the feed cylinder 26, the whole feed frame assembly is vertically displaced in an upward direction by one complete processing distance. When it has reached its upper position, the pressure cylinders 27, 28 become active again and move the pressure frames 31, 32 towards the counter pressure supports 27a and 28a until the foil web situated therebetween is again arrested. Now, owing to the opposite movement of the feed cylinder 26, the downward movement of the frame is initiated which in this way pulls downwardly to the extent of one processing distance the foil web gripped and arrested thereby, which means that the next-following foil region has been brought into the processing position. The entire assembly of pressure frames and feed frames may also be replaced by rollers. Instead of pressure frames and counter supports, 2 rollers pressing on one another are provided which are rotationally advanced in accordance with the desired feed stroke.
Under certain conditions it may be preferable to arrange the feed mechanism for the foil to be processed as a combination of a stationary and a movable clamping device for the foil web.
FIG. 12:: shows diagrammatically a simple movable clamping device in engagement with a vertically extending section of the foil web 34, whereas at 62 and 68 parts of the drawing and punching tool are indicated. In this arrangement the tool has to be opened before the movable clamping device can move downwardly together with the foil web clamped therein. Following this downward movement, the tool is closed while the movable clamping device has to remain stationary in its lower position. Only when the tool is again opened after the drawing operation, the clamping device can again be opened and moved upwardly. This clamping device, therefore, must necessarily have a long stationary period in its lower end position and should therefore be arranged outside the irradiation area of the heating device (not shown) for the foil web, in order to avoid that the clamping device when stationary in its lowest position for a prolonged period should screen off part of the heat rays directed on the foil and thus prevent them from reaching the foil, with the eifect that the heated area of the foil web is not heated and softened uniformly. However, the arrangement of the only available clamping device outside the heating area of the foil web necessitates an undesirably large overall height of the machine.
It is preferable, therefore, that the feed mechanism for the foil web consist of a combination of a stationary and a movable clamping device which in their movements are so related to one another that at any time either one or the other engages the foil web and clamps it, as shown in FIG. 12b. At first it is the movable clamping device, indicated by shaded areas, which engages the foil web and moves downwardly together with the latter to the extent of one feeding stroke, whereas the other clamping device, rigidly attached to the machine is opened (left drawing of FIG. 1211). As soon as the movable clamping device has reached the extreme point of its downward movement, the stationary clamping device closes and henceforth also clamps the foil web. It is thus not necessary to wait until the tool 6263 which during the downward movement of the movable clamping device was of course still open, closes again and thus clamps the foil. The clamping had already been effected by the stationary clamping device. Consequently, the movable clamping device may be returned upwardly to its uppermost position immediately after it has reached the lowest position of its feeding path and even before the tool has closed and gripped the foil. In order to attain independent and effective operation of the clamping device, this can be actuated independently of the switching cycle of the machine since the operation of foil advance remains always the same. Since in this way the movable clamping device effecting the foil advance always stops in its lowest position only for short periods and immediately, even before the tool has closed and gripped the foil, returns to its upper position, there is no objection to the movable clamping device moving across the area within which the heat rays of the heating device fall upon the foil. As the movable clamping device confronts any point of this area only for a short period, the intensity and uniformity of action of the heat rays on the foil web is substantially unimpaired.
This improved feed mechanism renders the machine suitable also for processing stretched foil webs and foils consisting of such synthetic materials which, as for instance polyolefine foils, tend to buckle and twist during heating for the deep drawing process unless they are firmly clamped.
The heating device (C) for the foil web consists of the mounting panel 51 with mounting screws 50 and 50a and the heat radiators 49, not shown in detail, for example constituting a bank of infrared radiators whose area must substantially correspond to at least the maximum width of the foil to be processed and to the maximum feed stroke, but should preferably amount to a multiple of the maximum feed stroke.
If a single radiator is used the dimension of which corresponds exactly with the width of the draw die and thus to a single feed stroke of the foil web, and if the operational cycle covers for example 2 seconds, then a foilsection corresponding to one feed stroke must be brought precisely to the processing temperature within 2 seconds by a single radiator. This necessitates a very high radiation intensity with a very steep heating slope, and the smallest transgression of the cycle period will immediately lead to the burning of the foil, whereas even a small shortening of the cycle period would result in the foil entering the operational area of the draw die with a temperature rise falling short of the predetermined processing temperature. On the other hand, if the heating area for the foil web is increased by the juxtaposition of five individual heater elements to five times the extent of one feed stroke While the operating cycle is again fixed at 2 seconds, heating of the foil to the desired identical processing temperature need not take place within one single operational cycle, but during a time corresponding to five subsequent operational cycles, i.e. within 10 seconds, and the heating slope may be kept much flatter. In order to heat the foil by means of five successively arranged heating elements, for example from 20 to 120 C., any single heater element only needs to impart to the foil section confronting it at any time a temperature rise of 20 C. The first radiator can here be so dimensioned that the foil in the compensated condition, i.e. when the irradiation is compensated by the heat losses, reaches a temperature of a little above 40 C. The second radiator is similarly adjusted to a compensated condition of 60 C., the third to one of C., the fourth to C. and the fifth to one of C. Consequently any shortening or prolongation of the pre-determined cycle period of 2 seconds can only lead to a fifth of a foil-endangering temperature rise or drop in the foil web, as compared with heating by a single radiator. The radiator bank radiates its heat to the foil area in opposite relationship with it and raises this area to the pre-determined processing temperature. Within the mounting slots the radiators 49 can be individually elevated up to an angle of 30 C. This arrangement is particularly advantageous for the working of round blanks in staggered arrangement, but can also be used in the production of any other drawn articles.
In the embodiment shown the notching device (D) and the draw die (E) are combined with one another.
On the longitudinal bars 4 with their extensions 5 are arranged the feed guide plate 52 and the front plate 53. The front closure plate and the end plate 10 are rigidly connected to the guide rods 6. A reciprocating movement is imparted to them by the elbow lever 11 under the action of the hydraulic cylinder 12. Between the support plate 16 and the draw plate 14 are provided spacing rods 15. The displacement of the movable parts on the guide rods 6 is effected by the hydraulically actuated main cylinder 17. The hydraulic cylinder 12 is pivotably supported in point 120. When the position is suitably vertical the piston rod is ejected from the cylinder 1'2 during a simultaneous tilting movement of the whole cylindereifected towards the right in this sectional view until the elbow joint is straightened. The tilting movement of cylinder 12 taking place when the piston rod is extended and the elbow lever straightened is indicated by the arrow in FIG. 1. In FIG.2, in the lower part of the section C-D, there appears the connecting shaft of the elbow lever assembly 73, indicated by a shaded area, which is provided with a U-shaped recess. This recess has been provided lest the cylinder when extending, contact the main cylinder 17 prematurely. The parallel longitudinal elements appearing in FIG. 2 laterally of this U-shaped shaft are the lever elements 11, composed by larninations and arranged to theleft and right thereof.
The elbow lever assembly is constructed in this way because, in it the pressure exerted in the straightened condition becomes infinite. But in many cases it will be sufficient if the elbow lever assembly and the hydraulic cylinder provided for its actuation is replaced by a directaction hydraulic cylinder.
The cylinder 26 is damped by a throttle 61 which is coupled to the lever movement of the throttle lever 23. The spring-loaded throttle lever moves upwardly when the feed mechanism is lifted. When the latter is lowered, it will first abut on the throttle lever 23 which is thereby sufficiently lowered to throttle the oil feed to the hydraulic cylinder 26. In this way the impact of the abutting feed mechanism is hydraulically damped and the machine made noiseless.
FIG. 11 shows diagrammatically the redirection of the foil web for drawing in the plastic flow temperature range. The foil web 34 arrives vertically and is deflected by means of a roller or the like U into the horizontal direction. An auxiliary movable radiator assembly S is moved out into a position below the horizontal portion of the web, in order to heat up this foil portion to the temperature of plastic flow. The tool W now works in vertical draw direction. When the blank is to be ejected, the movable radiator assembly S is preferably withdrawn. When this operational mode is chosen, the guide and pressure frames in the lower section of the machine must be extended in accordance with the length of the extension arms.
The 90-angle E in the foil web is only being formed when the tool W is closed. Prior to this, the foil web sags at this point, forming an are. This deflection of the foil web into a horizontal plane of treatment is necessary to achieve universally identical wall thicknesses in the drawn articles. If it were attempted to process foil heated to within the temperature range of plastic flow in a vertically extending plane, i.e. in a horizontally directed drawing operation, then the blanks would receive thicker walls in low situated regions during drawing, because the synthetic material in a state of plastic flow would already start to flow downwardly under its own weight even before the die could be closed. On the other hand, for drawing within the temperature range of elastic elongation processing of the foil in a vertical plane is more advantageous because then the heated foil web does not need any support which would always lead either to the occurrence of cooled areas in the foil or the foil material sticking to the heated support members. In the device according to the invention, however, supports are avoided in every case, irrespective of whether the processing plane extends vertically or horizontally.
The marking and drawing device (D), (E) consists of the drawing and notching die 62 with vacuum duct 66, annular notching ring 63. and movable clamping ring 65. This assembly is interchangeably mounted on the draw plate 14. The punching plate 75 with its notching counter edge 64 is mounted interchangeably to. the front plate 53. The die closure and notch limiting member 68 with its compressed air duct 69 and, if necessary, plunger 70 and the ball valve 71 for atmospheric compensation behind the plunger is interchangeably mounted on the die closure plate 7. Spacer bushes 8 and end caps 9 are provided on guide rods 6.
As is well known, it is impossible by punching to cut a synthetic article from a thermoplastic or similar foil since even the smallest gap in the tool components leads to inhaling of the plastic material. Here, the plunger draws a thin film through the gap between its cutting edge and the die recess without severing the blank from the foil or like substance. In order to avoid this disadvantage, it is possible to let the thermoplastic component to be punched out be pressed against a support situated in a die recess, in order thereafter to let the pressure-loaded sandwich consisting of the thermoplastic component and the support be driven through the die recess until the con- 8 nection between the foil or like substance and the blank to be punched is ruptured.
The advantage of this method rests in the fact that, when the thermoplastic blank is pressed against the support, the material of the blank is clamped in this region so that when a film is formed this is not supplied with further material and will therefore be ruptured.
It is particularly advantageous if the outer marginal region of the plastic foil which surrounds the thermoplastic blank to be punched out, is covered by a pressure ring so that during punching continued film formation between the plunger surface and the inner surface of the die recess is prevented also in regard to this area. After a very short period of film formation, the thermoplastic blank to be punched out is severed from the plastic foil.
In order further to reduce film formation between the thermoplastic blank to be punched out and the plastic foil, it is advisable that the thermoplastic blank should be pressed against a support fitting into the die recess. If this is done, especially in conjunction with the step described in the previous paragraph, only a very small amount of plastic material will be available for the formation of a film.
In order that the plunger and the thermoplastic component should be guided during the initial stage of punching it is preferable that the plunger in its co-operation with the die should at first travel a certain distance without pressing the thermoplastic component on a support; only then is the thermoplastic component pressed against the support and the pressure-loaded sandwich is driven through the die recess. Owing to the fact that there is no appreciable counter pressure during the first stage of plunger movement, the plunger is introduced in the (lie recess without the possibility of tilting. If counter pressure is encountered afterwards, the plunger will be incapable of evasive movement, owing to being guided in the die recess.
Taking into account these considerations, it is of particular advantage in the method according to the invention it punching and shaping of the thermoplastic blank is effected in one and the same operation in such a way that after pressing the thermoplastic component against a support, a pull (suction) or pressure is exerted which sucks or presses, in a shaping action, the thermoplastic blank which is heated to at least plastic flow temperature, into a cavity provided, for example, in said support.
To carry out this modification of the inventive method serves a device comprising a support preferably fitting into the die recess which support, together with the thermoplastic blank to be severed by the plunger, can be driven through the die recess by means of the plunger.
'Further details become apparent from the examples illustrated in the drawings.
There are shown:
In FIG. 13 a die with a plastic foil forming part of a punching device not further illustrated,
In FIG. 14 the die according to FIG. 13 but with a support element inserted therein, said element being downwardly open, and with a pressure ring imposed, and in FIGS. 15 to 17 a device according to the invention constructed in a different way, in various operational stages.
As shown in FIG. 13, a die 201 has a recess 202. A thermoplastic foil 203 is placed on the die 201.
Further during the course of the operation, a support element 205 is inserted from below, in the direction of arrow 204, its upper surface 206 being situated somewhat below the surface of the die 201, see FIG. 14. The support member 205 has a flange 207 bearing on the die 201 from below and determining the position of the surface 206 of the support element 205. The support 205 has a cavity 208 through which during the operation air can be discharged if necessary so that when a thermoplastic component is punched out of a heated foil 203, a container is formed in the space 208. The margin of the foil 203 adjacent a plunger 210 is pressed on the die 2M from above by means of a ring 209. A plunger 210 is provided above the foil 203 and the ring 209.
The device operates in the same way as will be described below.
From FIGS. 15 to 17 the various operational stages of a differently constructed device can be gathered.
The reference numeral 202 denotes the recess of the die 201, and 203 denotes the foil.
A plunger 211 movable in the direction of arrow 212 has an air passage 213 through which compressed air is led underneath the plunger 211. The support 214 fitting exactly into the recess 282 of the die 201 has a space 215 into which a suitably heated thermoplastic component 216 which is to be separated can be pressed by means of compressed air re-circulated through the duct 213. In the lower wall portion enclosing the recess 215 of the support 214 there may be provided small-diameter bores (not shown) to avoid the creation of an air cushion in the recess 215. The support 214 is pressed upward in the direction of arrow 2% by means of spring or like action not illustrated.
The device operates as follows: A suitably heated foil is placed upon the die 201, as apparent from FIG. 13, then the support 214 is pushed from below into the recess 262 up to a stop 214 and the plunger 211 is made to act. When the plunger 211 has partially introduced in the die the foil portion 216 which is to be punched out, the thermoplastic 216 is pressed against the support 214 with suitable force, and a pressure-loaded sandwich is thus formed. At the instant this sandwich is formed the plunger 211, therefore, is already guided in the die 20 1, see FIG. 15. The effect of the compressed air acting through the duct 213 of the plunger 21.1 on the thermoplastic blank is shown in FIG. 16. The blank 216 has now been drawn into the shape of a container 217 and is applied to the Wall of space 215 in the support memher 214.
A later stage is shown in FIG. 17. The sandwich constituted by the plunger 211, the support 214 and the container 217 is now pressed downwardly by the plunger 211 and pushed through the opening 202 of the die 2%1. Upon retraction of the Plunger 211 and removal of the support 214 carrying the container 217, an empty support 214 is introduced from below in the opening 282 of the die 261 in the manner shown in FIG. 14. The foil 203 has meanwhile been advanced suiliciently far for a new thermoplastic blank to be punched out.
Instead of air, an additional plunger can be used to press the thermoplastic blank into the recess 215.
The recess 215 can also be provided in the plunger in which case the upper surface of the support must be flat.
The device for producing a container may also be constructed as indicated in FIGS. 18 and 19.
A device of this type has a stationary flat plate 22%? and a vertically reciprocating plate 221 spaced a suitable distance from the plate 221). The plate 221 is connected by means of a linkage 222 with a device for lifting and lowering, not shown here. Below the movable plate 221 is provided a rigidly arranged annular knife 223 whose annular cutting edge points towards the movable plate 221 and is capable of co-operating with the latter. Above the movable plate 221 is provided a vertically reciprocating shaping plunger 225 (whose downward movement is limited by the stationary plate 2241) which is capable of passing through an aperture 221' of the plate 221.
This device operates as follows:
On the knife 224 is placed a suitably heated flat portion of synthetic material 226 and the movable plate 221 is then lowered towards the annular cutting edge 224 in the direction of arrow 227, and pressed thereon, until an annular notch 229 is formed in the flat portion 226 of the synthetic material and a thermoplastic blank 228 is marked by this annular notch 229 and held thereby by the pressure between the parts 221 and 224. If the shaping plunger 225 is now lowered in the direction of arrow 23%, from the position shown in the drawing to almost the position shown in FIG. 19, a container 231 is drawn into shape from the thermoplastic blank 228 held there in by the notch 229. Shortly before the shaping plunger 223 meets the stationary plate 220, the lowering of the plunger 223 having to be effected with suitably timed velocity, the material adjacent the notch 229 has set sufficiently, owing to heat conduction in the plate 221 and in the annular knife 223, that on the shaping plunger 225 being moved further, the container 231 is severed or torn from the marginal area 232 of the flat portion 226 of synthetic material. Thereupon the shaping plunger 225 presses the bottom of the container 231 on the stationary plate 226) whereby the bottom is pressed flat.
When the container 231 has been severed, the stressed portion of material forming the outer wall of the container 231 is urged in the direction of arrows 233 in a radial direction towards the shaping plunger 225 and may thus apply itself to the latter, whereupon it will be chilled. When the shaping plunger 225 is withdrawn into the initial position of FIG. 18, the container 231 slips off and is removed.
In FIG. 19 a stage is shown shortly after the container 231 has been severed from the fiat portion 226, the shaping plunger 225 having pressed flat the bottom of the container in co-operation with the plate 220.
In the case of containers which need not have a fiat bottom the plate 220 may be ommitted. Also, the plate 220 may have any desired shape, for example an annular ridge or the like while the lower plunger surface may be provided with a matching counter shape. The plate 220 can be made height-adjustable, according to the desired height of the container. In the drawings the draw die has been shown, for claritys sake, as a single die for a conical cup. It is also possible of course to insert in the machine multiple dies for blanks of the most varied shape. Above all, the machine also allows processing with dies of considerable depth which may amount to a multiple of the die diameter. It would also be possible, thanks to the ideal control adjustment possibilities, to draw with this machine elongated and very narrow cylinders (drinking straws).
The mechanical-hydraulic system for the mutual displacement of the various plates on the guide rods 6 comprising the main cylinder 17, the elbow lever closing mechanism 11 and the hydraulic cylinder 12 has already been described. To this must still be added the common drive unit comprising a motor 55, oil pump 56, oil reservoir 54, pressure reservoir 57, suction pipe 59 and pressure pipe 60 as well as the oil-air valves 58. This unit serves all the hydraulic and pneumatic elements (devices for ejecting the shaped articles from the mould and for cooling the heated foils).
Within the foil web track one or more cold air jets 48 may be provided, capable of issuing from a narrow slot orifice a curtain of cold air along the foil web it the latter is threatened with overheating by an interruption of the operational cycle or by excessive heat from the radiators.
The pressure cylinders for moving the die-carrying plates may be so devised that, as shown diagrammatically in FIG. 20, the full oil pressure is effective on the pressure face A, whereas on the differential face B only a smaller volume of oil, reduced owing to the large diameter of the rods of the differential pistons, is needed for the moving apart of the die components. In this way the output per unit of displacement of the oil pump needed for the intended number of operational cycles per minute for which the machine must be adjusted, is kept within tolerable limits. But this kind of arrangement of pressure cylinders necessitates a rather extended machine construction and the movement of the frontal die carrying plate, indicated by arrow, requires the additional 11 movement of the lateral bars which results in the necessity of having to move larger masses.
But the mechanism for actuating the die carrying plates can be made smaller, more easily accessible and movable in that pressure cylinders are replaced by draw cylinders.
FIG. 21 shows the die carrying plates movable towards one another in the directions of arrows in an arrangement such that they are moved by the draw cylinders C, C and D, D. The draw cylinders may be arranged diagonally on the stationary machine frame. The cylinders C, C and D, D act directly upon the die carrying plates to which they are allocated and draw them in the direction of the movement-indicating arrows. This results in a more compact construction than in the case of an arrangement as shown in FIG. 20 and comprising pressure cylinders. Access to the die carrying plates is not hindered by constructional components and the fitting and exchange of draw and punch tools is considerably facilitated. The draw cylinders may be equipped with thinner and lighter piston rods. On the whole, the weight of the moved parts is considerably reduced.
The fact that in this construction the draw face of the cylinders is utilized to generate high pressure may at first glance appear as a disadvantage, but this can be fully compensated by an additional step. The draw cylinder which is equipped with a light small-diameter piston rod needs a certain amount of oil for its movement, in accordance with its dimensioning and hydraulic relationships. The pressure face of the cylinder is constituted by the full piston surface which for the purpose of opening and moving apart the die components does not however require the application of the full volume. In order to avoid having to feed the oil by means of the pump, it is possible to stress the fully available piston surface with a constant air pressure. Then the oil situated in the rear part of the cylinder need not be conducted through the generator or the pump, but it can continuously pulsate in both directions, driven by the draw end of the cylinder.
FIG. 21 shows on the pressure side of the cylinders C, C a closed conduit system H leading to an oil reservoir F to which a constant air pressure G is applied by means of an air tank, not shown. All pressure conduits may be interconnected and are not controlled. The air pressure now capable of reduction and the oil pressure as constituted by the reservoir F acts with constant force upon the pressure side of the cylinders, stressed by the pistons. The draw side of the cylinders can in this case be controlled by three-way valves, as distinct from four-way valves. When the oil pressure on the draw side is increased by 10 atmospheres of excess pressure, for example, then, with counter pressure being constant, the oil volume present on the pressure side of the cylinder is simply urged back into the reservoir F as soon as the draw side is stressed by means of the associate electric valve. Here the controlled oil volume supplied by the pump only amounts to a little more than half the oil volume which must be controlled in the case of a pressure cylinder according to FIG. 20 (with a pressure of increase 10 atmspheres of excess pressure).
Obviously, the machine according to the invention is not confined to the relative distribution in space of the individual elements which has been shown in the embodiment described. It is not absolutely necessary that the draw plane and the heating plane extend perpendicularly.
In particular, it is also possible to arrange the draw plane and with it the assembly constituted by die closing plate, front plate, die covering plate etc. so as to extend horizontally in which case the longitudinal bars 4, and the guide rods 6 must be positioned vertically. The feed unit with its vertical guidance 20, pressure frames 31, 32 could here still remain in a vertical position or also be arranged horizontally.
The heating plane for pre-heating the foil web could also be arranged obliquely or horizontally. But the vertical arrangement shown in the described embodiment has proved itself particularly suitable in practical operation, for various reasons. The essential content of the invention is not a certain relative arrangement in space of the individual constructional components, but the combination and interaction of the functions of certain components indicated as being essential. The embodiments described here put into practical effect this combination of functions and have also been tested in practice as regards their distribution in space, without however this combination of functions being dependent upon the distributions in space presented here.
The electric part (H) of the machine consists of magnetic air/ oil valves 58 which actuate the various moving and movable elements of the machine. These electric valves are controlled electrically by relays. This is preferably done by means of a step-by-step switching mechanism (L) and with the aid of eight or more time deiay relays which are individually adjustable in their delay time. Each current pulse proceeds to two cross bar distributors one of which passes on the pulses for the connection of the relays and the other the pulses for the interruptors effecting disconnection of the relays. To start the machine, an extraneous pulse to the step-by-step switching mechanism is needed.
The relays act upon the magnetic air/oil valves or electric valves 58 which start up the various actuating and movable elements of the machine (excpt motor 55 which is supplied from the mains network).
The step-bystep switching mechanism is a time-dependent unit which serves for sub-dividing a certain period of time, i.e. the progress of one operational stage, into arbitrarily selectable partial periods. These partial periods are marked by a pulse which applies a voltage and at the same time serves as a disconnection pulse. These pulses are continued indefinitely since the last relay again triggers the first one. These finely graduated and freely selectable time steps are followed by an element which arranges the sequence of events, namly the cross bar distributor. At this point the magnetic valves are coordinated by means of associate relays so that the running off of the single events is put in order. When effecting this coordination, the switching sequences prompted by the step-by-step switching mechanism may be so chosen in their partial periods that individual events may overlap in any desired manner. It is possible, for instance, to let the first connection pulse of the step-by-step switching mechanism switch on the feed mechanism. The second connection pulse closes the die, the third marks the foil. The simultaneously created disconnection pulses which are transmitted by way of the other cross bar distributor, remain ineffective and are not employed for any of the functions. The fourth switching pulse is derived from the disconnection end and serves, for example, to return the feed mechanism again to its original position, by way of the magnetic valve; it is also feasible, by means of the simultaneously generated subsequent connection and disconnection pulses, to connect and disconnect in each case a plurality of elements and control means. In this way an untold amount of variants results in a system having 64 connection and 64 disconnection sockets on a plug panel, for example approximately 2815 10 variants. This enables the operational cycle of the machine to be set for the special requirements of each newly inserted die and of each new foil type. The optimum setting for each new die is at first ascertained empirically and entered according to plug positions on a chart showing the lay-out of the plug panel. Each draw die thus has its appropriate chart and when such a die is again fixed in the machine all that is needed is to insert the plugs in the panel in accordance with the appropriate chart so as to ensure optimum functioning of the machine with this die.
In FIG. 9 the electric section of the illustrated embodiment of the machine is shown with a panel of 8X8 switch sockets.
The device (I) for exploring the plasticity attained by the foil web in the heating area consists of a feeler 27 which indicates plasticity by the depth of its penetration into the foil web and acts through the parallelogram linkage 46 upon the magnetic valve for releasing the compressed air curtain which protects the foil from overheating. If desired the surface temperature of the foil can also be determined in another way, for example by pressing into con-tact a semiconductor device (electric resistance measurement), with the result that only the temperature of the foil surface is read directly or, upon a certain temperature being reached, the compressed air curtain is released or, upon a predetermined optimum processing temperature being reached, the step-by-step switching mechanism is triggered. The combination of feeler and foil brake provided in the illustrated embodiment was chosen for its convenience. But these two elements may very well remain completely separate from one another.
If the danger of scratching the foil surface is to be completely eliminated, braking of the foil may for example be effected by means of two rollers pressed against one another whose ability to rotate can be braked.
The foilbrake 45 has the object to prevent the foil web which is curved around various radii, from curving outwardly when the pressure frame 31 is opened and the feed mechanism travels upwardly. Its operation is illustrated diagrammatically in FIG. 6a. The foil brake 45 preferably consists of a pressure beam lined with foam rubber, the beam being capable of being pivoted upwardly about its pivoting point (on the left) which is necessary for the foil web to be introduced. The foil brake 45 acts continuously and guarantees that the foil web travels past its deflection rollers in a tensioned condition. If the foil brake is omitted, the foil web assumes arcuate positions and the feed distances become inaccurate (FIG. 6b). This is of particular disadvantage if foil webs are processed with printed images at regular successive intervals already printed thereon which require accurate register.
The fine feed regulation (K) with shock absorption is shown in FIG. 7. It comprises a transverse beam 24 whose end position is controlled by the two parts 23. The dotted space 25a is variable by means of a setting screw 25c in accordance with the depth of penetration of the setting spindle 25, by using a regulator wheel. The two regulator pins 25b thus emerge to a greater or lesser extent from the beam 24 or are further pushed in by the parts 23 upon contact with the feed mechanism. Coupled to the lever movement of the throttle lever 23 is the throttle 61. The throttle lever which is loaded by the spring 230 (FIG. 8) travels upwardly when the feed mechanism is lifted. On being lowered the latter first contacts the throttle lever, presses it downwardly and thus throttles the oil feed of the hydraulic cylinder, in order to elfect shock absorption. The feed regulation comprises a spacer 22 Whose length is matched with-the die in use and is interchanged along with the latter. If in the regulation of foil webs bearing printed images the spacer 22 does not accurately coincide with the printing register the described fine regulation is employed. It also allows, when the die is installed, to find and set the smallest possible distance between adjacent useful areas experimentally by reductions of this distance.
In the case of very thin-walled drawn articles the ejector provided here is not satisfactory by itself because, owing to the plastic material being charged with static electricity, the blanks may adhere to the dies too firmly. For this reason there are preferably provided, in addition to the ejector which removes the drawn article from the die without deformation, additional small pointed detaching members equipped with a small spring. They ensure that the drawn article is mechanically urged away from the ejector which is usually shaped with a flat surface, and thus also from its electric field. In this way it can be achieved that each drawn article drops out of the die fully automatically. In the case of a draw piston the provision of a rubber ring seal is recommended lest the piston during its return blow the air having entered into it in a directional air jet on to the drawn article which might cause the article to jump back into the draw die from which it is meant to be ejected.
The circuit arrangement is shown in FIGS. 9 and 10. The voltage derived from the mains is applied at 8 1 to a switch which transmits the current pulse through the relay 82 to the first time delay relay 83. The potentiometer 87 by which a time has been set allows, after this time has expired, the contact spring 85 to be released, which on the one hand, breaks the con-tact 86 and, on the other hand, makes the contact 34. The latter is made only for the fraction of a second, whereupon the relay, as shown, again drops back into its idle position. At the same time, however, the time delay relay 88 has started to function. Here the same process evolves as in the preceding time delay relay, in accordance with the time set on the associated potentiometer, and the pulse is now further transmitted to the time delay relay 89. Here, too, the described process is repeated and this is continued up to the last relay which then energizes again the first relay 83.
A voltage is applied to the cross bars 91, 9t) and 92. By connections made with the aid of special plugs this voltage may be selectively transmitted to the cross bars 93, in such a way that the voltage is applied to the holding contacts of the relays 96, $7, 98 coupled thereto. The connection pulse momentarily transmitted by way of contact 84 reaches the cross bar 99. If the latter is for example connected by the plug 1% to the cross bar 101, the pulse passes to the relay 96 and attracts the relay coil whereby the contact bridge 102I03 is closed. The contact 103 may for example be held in this position through the plug 104 as a holding contact in conjunction with the third time delay relay of the step-by-step switching mechanism. Only after the triggering and the expiry of the delay time of the third relay is this contact bridge interrupted at the relay 89 so that in this way the contact bridge 1021tl'3 is interrupted and the relay 96 d e-energized. At the same time, for example, the magnetic valve 105 is also connected, in conjunction with the connection pulse of the time delay relay and the closing of contact bridge 8483. The operating cylinder 106 moves in a pre-determined direction. The process is again reversed by the time delay relay 89 which, triggered by the time delay relay 88, momentarily interrupts the contact bridge leading to the cross bar 92. Thereby also the holding contact to 103 is interrupted and the relay 96 opened. At the same time the voltage supply at the magnetic valve 105 is interrupted and the operating cylinder 1% returns into its normal position. This perpetual cycle which is capable of accurate timing by means of the step-by-step switching mechanism and whose connection pulses are conducted through the above-described cross bar distributor in a suitably selected sequence, by means of associate relays, to magnetic valves and operating cylinders and other operating devices and in this arrangement can be cancelled also in a suitable manner by means of the cross bar distributor 9t 95 can also be changed over, in any phase, from its rhythm to hand switching. To do so the key 107 is depressed which in the illustrated position supplies a voltage to the holding contact for relay 82 and interrupts energization of this relay when actuated. Thus the voltage supplied to the stepby-step mechanism is interrupted and it ceases to function. At the same time the contact bridge 108109 is closed and a voltage supplied to 110' which then allows for example the magnetic valve 111 and thus the operating cylinder 112 to be triggered by hand. When the contact bridge 163-409 is interrupted, permanent connection to relay S2 is reestablished. A switching pulse through switch 81 triggers the step-by-step switching mechanism and the time delay relay 84 again starts, after the preset time has elapsed, with the above-described operation of the step-by-step switching mechanism. It is also possible of course to arrange hand switching in such a way that it closes the permanent contacts of the relays 96, 97, 98 and that a further switch effects interruption.
For claritys sake, in the diagram the only switching by permanent contact shown is through the contact bridge 1G8109, directly to the magnetic valve 111.
The operational cycle of the machine illustrated here evolves in the following manner:
At first the machine is set to Zero which comes about automatically by letting the motor start up for a short period while the step-by-step switching mechanism is disconnected and the hand switch not touched. Then the heater bank 49 and, if desired, the motor 55 are connected which are permanently supplied with current during operation of the machine. Both may also be connected and disconnected during operation of the machine, according to the repetitive cycle and the operating speed. Individual radiators may also be reguiated by means of electronic valves and a circuit breaker element (birnetal interrupter) and pulse transmissions. Then the beginning of foil web 34 is pulled off the roll 33 to such an extent that a sufiiciently heated foil section is situated in the plane of the draw operation and the leading end I of the web is fixed to the take-off spindle 40.
Now the machine is started by switching on the motor if this has not been done before, and an extraneous pulse is transmitted to the step-by-step switching mechanism. When the time set on the potentiometer has expired there is effected, on the one hand, an interruption of the supply voltage for an associate cross bar at the first time delay relay which interruption de-energizcs the electric valves. But there is also triggered a connection pulse for another cross bar which connects the valves. Besides the step-by-step switching mechanism ensures that together with this operation already the second time delay relay is actuated which, after expiry of the pre-set time, again transmits in one and the same operation an appropriate pulse to another two bars of the cross bars distributor for on and off and to the third relay. Between the cross bar distributor and the electric valve a relay is connected to allow time intervals between on and off switching to be bridged, since the step-by-step switching mechanism only transmits pulses. The first of these relays acts upon the associate electric valves 58. The latter moves the hydraulic cylinder 12 in an upward direction whereby the elbow lever 11 is stretched to the left. The latter pulls to the left the frame carrying the die closing plate 7 and the end plate 16, almost up to the foil web 34 situated in the plane of the draw operation. By now the first time delay relay has run off and transmits the second pulse which passes through the cross bar distributor to the second relay and to the second time delay relay; by means of the electric valve 58 allocated to the second relay the main cylinder 17 is actuated which displaces the draw die 62 with its annular marking edge 63 to the right in direction of the foil web until contact is made with the counter edge 64 of the draw die 67. In this way notching of the foil web along the outer periphery of the blank to be drawn is effected. By now the second time delay relay has run off and transmits a pulse passing to the third relay and the third time delay relay. The electric valve 58 allocated to the third relay now brings about in the now closed draw die reduced or excess pressure in the ducts 66 and 69 respectively, or actuates the draw plunger 70. It is also feasible, by the additional connection of a further relay and time delay relay, to generate reduced or excess pressure in a first operational phase and to actuate the plunger in a second phase, or vice versa.
Notching and drawing is thus terminated and the third time delay relay has run off. A fresh pulse is transmitted which is conducted to the fourth relay and the fourth time delay relay. The electric valve 58 allocated to the fourth relay releases the clamping pressure between the guide frame 29 and the pressure frame 31 so that the margin of the foil web is released. By then the fourth time delay relay has run off and transmits the next following pulse which is conducted to the fifth relay and the fifth time delay relay. By means of the electric valve 53 allocated to the fifth relay the feed cylinder 26 is actuated which displaces the feed frame 18, 19, 2t 21 upwardly during which movement the pressure frame 31, 32 remains in the open position, i.e. out of contact with the guide frame 29, 30.
The fifth time delay relay has now run off and transmits the next pulse to the sixth relay and the sixth time delay relay. The sixth relay actuates through its electric valve the pressure cylinders 27, 28 which urge the pressure frame 31, 32 against the guide frame 29, 30 and clamp the foil web therebetween. The operation of pressing and clamping the foil section, and of releasing it, and of its subsequent displacement by the feed mechanism can also be combined to form one distance-dependent function so that only one magnetic valve will be sufficient for its control since this operation is always repeated in the same way.
Pressure in the main cylinder 17 is still maintained at this stage. Running off of the sixth time delay relay however, by a pulse transmitted to the seventh relay and the relevant electric valve, actuates the hydraulic cylinder 12 in the opposite direction so that the elbow lever 11 is returned and lets the still loaded marking ring 62 penetrate the die 67 further, the die covering plate 68 acting as a limit so that the chilled marking area at the margin of the blank is ruptured and breaks away from the foil web. After the draw tool 62 has passed through the die 67 the draw plate 14 supporting the tool 62 is reversed while an ejector '76 arranged in the tool 62 still follows in the direct-ion of the die closure plate 63. In this way the drawn products are removed from the tool and, after being urged out of the static field of the ejector by the separator 77, fall by way of a chute or the like into a storage container (likewise not shown).
As soon as the tool 62 and die closure plate 68 are separated by the maximum possible distance, and ejector and plunger have been returned to their original positions, also the seventh time delay relay has run off and supplies a new pulse for the eighth relay and the eighth time delay relay. The eighth relay now actuates the feed cylinder 26 in opposite direction, by means of its associate electric valve, so that this cylinder returns the feed frame 18-32 together with the film web held between the pressure frame 31, 32 and the guide frame 29, 30 in a downward direction into the position shown in FIG. 1, while the pressure cylinders 27, 28 hold the pressure frame 31, 32 in the advanced clamping position.
Thus also the eighth time delay relay has run off and supplies a pulse which is conducted to the first relay and the first time delay relay, whereby the next-following operational cycle is set in motion.
The above-described embodiment relates to a timedependent control by means of time delay relays which has proved very satisfactory in practical operation. But it is also possible to make the control dependent on distance by providing end position switches instead of time delay relays which are actuated as soon as the member to which they are allocated has covered the distance prescribed for it. If necessary, it is possible also to combine within the machine time dependent and distance dependent control.
In a single-purpose machine, previously tested in regard to its tool performance by the above-described :multi-purpose machine, the cross bar distributor can be omrnitted and the step-by-step switching mechanism so devised that it. supplies the pulses directly to the valves.
. 17 But this is based on the assumption that the tool and its function have been irrevocably fixed and are not expected to be modified during the life of the machine.
As mentioned before, the punching and drawing operations may also be separated in time so that when the draw die is opened and the foil advanced, the blanks are still suspended in a marked condition in the foil web. Provided that the machine is further developed to this end, a subsequent station in the path of foil advancement can then be provided for carrying out the punching operation by which the blanks are separated from the foil web. Generally this will not offer any advantages. But this lay-out may be advisable if the draw tool must execute very complicated draw operations and it appears desirable, therefore, to devise it as a pure draw tool without any other functions. In this case pure punching tools, without additional functions, are then provided in a subsequent station along the feed track. An essential requirement in such a case will be a completely uniform and accurate functioning of the feed mechanism.
The present processis suitable for deep drawing plates and foils of all kinds of thermoplastic material which lend themselves to deep drawing. Apart from polyvinyl chloride and its co-polymers, with or without the addition of a plasticizer, it is equally possible, according to the method of the invention, to use for example polyvinylidene chloride, polyacrylic acid esters, polymethacrylic acid esters, polyacrylonitrile, polystyrene, polyethylene and polymeric higher olefines, polyisobutylene, poly-fiuorolefines and polychlorofiuorolefines as well as the co-polymers of the monomers corresponding to the above-mentioned polymeric products, and mixtures with one another of the quoted polymers.
1. A method of continuously producing deep drawn articles from a foil web of thermoplastic material comprising the steps of discontinuously feeding a foil web, making said foil web drawable by heating it, pre-grooving said foil to mechanically form a border along the peripheral outline of the drawn article to be produced, performing said drawing operation, allowing said foil to cool to embrittle its pre-grooved border, and subsequently ejecting said drawn article from the foil web by breaking said embrittled pre-grooved border.
2. A method of continuously producing deep drawn articles from a synthetic foil in a die comprising the steps of discontinuously feeding a foil web through said die, making the portion of said web in said die drawable by heating it, mechanically pro-grooving said foil along the outline within which the deep drawn article is to be drawn, effecting drawing at the same temperature as pre-grooving, chilling the marked peripheral zone of the blank to the point of brittleness, and finally ejecting the drawn article from the die and simultaneously breaking it away from the foil web at said pre-grooved outline.
3. A method as set forth in claim 2 wherein the foil web advance and the intensity of its heating is controlled in dependence upon its plasticity prior to entering the zone of treatment.
4. A method as set forth in claim 2 wherein said mechanical pre-grooving is accomplished by pressing the foil upon a support disposed within an aperture in a die, and subsequently driving the foil and support into the die to rupture the connection between the foil and the portion disposed upon said support.
5. A method of continuously producing deep drawn articles from a foil web of thermoplastic material comprising the steps of heating said foil web to an easily deformable condition, pressing said heated foil web a short distance through an aperture onto a support to score a grooved border around the portion of said web to be drawn into said article, forcing the portion of said foil web within said border into a cavity in said support to draw said article, allowing said foil web to cool to embrittle said grooved border, andthen driving said drawn portion of said foil web together with said support completely through said aperture to sever said drawn article from the remainderof said web. I
6. An apparatus for producing deep drawn articles from a plastic material comprising an apertured plate, a reciprocating plunger arranged to pass a predetermined distance through the aperture in said plate, a sharp-edged ring disposed upon the side of said aperture plate from which said plunger emerges, reciprocating means alternately driving said sharp-edged ring towards and away from said apertured plate for receiving and urging a heated plastic blank against said apertured plate and notching a border upon it, said predetermined movement of said plunger being sufiicient to first draw said article from said plastic blank held between said apertured plate and said ring and then sever it from said blank, and said plunger and ring being arranged to cumulatively absorb enough heat from said drawn article to embrittle said notched border before said plunger moves to its extremity of travel thereby facilitating the severance of said article from said plate.
7. An apparatus for continuously producing deep drawn articles from a foil web of thermoplastic material comprising an apertured plate, a plunger mounted to move through the aperture in said plate, a marking deviceincorporating a ring-shaped member having a sharp edge spaced slightly outside of the outline of said aperture disposed upon the opposite side of said plate from said plunger, a means for feeding said foil between said ringshaped member and said plate, heating means for softening said foil, and reciprocating drive means for first moving the sharp edge of said ring-shaped member into contact with said softened foil for marking it and for subsequently driving said plunger through said foil to deep draw it and then sever the deep drawn article from said foil at said marked edge when it has become brittle upon cooling.
8. An apparatus as set forth in claim 7 wherein an auxiliary plate is disposed beyond said ring-shaped member for cooperating with said plunger in forming the bottom of said deep drawn article and for conducting heat away from it to help embrittle said marked portion.
9. Anapparatus as set forth in claim 7 wherein said marking device is arranged within said apertured plate.
10. An apparatus as set forth in claim 7 wherein a cooling device which blows air upon said foil is provided, a feeler for determining the degree of softening of the foil web in the heating area is provided, and said feeler being connected to actuate said cooling device for protecting said foil Web from burning.
11. An apparatus as set forth in claim 10 wherein said feeler for the foil web is connected by means of a parallelogram linkage to a braking device which influences the foil web advance.
12. An apparatus as set forth in claim 7 wherein a fine-feed regulating mechanism and a shock absorber are connected to the means for feeding said foil to prevent it from breaking.
13. An apparatus as set forth in claim 7 wherein the heating system for the foil web is constituted by a bank of infra-red radiators, and the radiation area of such bank corresponds to the height of the foil web to be heated in any particular case.
14. An apparatus as set forth in claim 7 wherein a foil brake is arranged at the supply spindle and the take-off spindle for the foil web, said brake being connected to a lever pivotable about its own end point, and said lower carrying at its free end a conveying roller which fits into the first deflected loop of the foil web.
15. An apparatus as set forth in claim 7 wherein a permanent brake for the foil web is arranged at the point of deflection above the heating area, and said brake being constituted by a beam lined with resilient material which bears on the web.
16. An apparatus as set forth in claim ,7 wherein drawing cylinders are allocated to the die plates carrying a draw plate anda die closure plate, said drawing cylinders including a pressure ,side exposed to air pressure and a rear side exposed to oil pressure, the fully stressed piston surface representing the pressure side of the draw cylinder being stressed by a constant air pressure so that the oil present in the rear compartment of the cylinder is driven by the draw end of the cylinder which continuously pulsates in both directions with the piston movement, and said drawing cylinders being arranged diagonally on a stationary machine frame.
17. An apparatus as set forth in claim 7 wherein a discontinuous foil-feeding mechanism is provided, said mechanism including a double clamping device comprising a stationary and a movable clamping device, said clamping devices being mutually adjustable in their operational cycles so that at any time one of them engages the foil web and clamps it, the movable clamping device being arranged for again returning to its uppermost position immediately after having reached the extreme point of its downward movement eflFecting the foil advance, the path of the movable clamping device being situated within that portion of the guide track which is irradiated by the heating system, and the clamping device being automatically controlled independently of the switching cycle of the machine.
18. An apparatus for continuously producing deep drawn articles from a foil web of thermoplastic material comprising an apertured plate, a reciprocating plunger which passes through said aperture, a ring-shaped knife having an outline slightly larger than said aperture, said knife being disposed adjacent the aperture in said plate, and being disposed upon the side of said plate upon which said plunger passes out of said aperture with said knife encompassing said aperture, means for feeding a continuous foil web between said ring-shaped element and said apertured plate, the edge of said knife being sharpened for grooving said foil web by contact therewith when said foil web is made drawable by heating it, a heater for making said foil drawable when it is positioned between said apertured plate and said ring-shaped member, reciprocating means reacting between said apertured plate and said ring-shaped knife for forcing said sharpened edge of said knife into said foil web when it is backed up by said apertured plate to score a grooved outline upon it, coordinating means for driving said plunger through said heated foil web held between said apertured plate and said ring-shaped member for drawing said articles, said coordinating means subsequently holding said plunger and drawn article in contact with each other a sufficient time to absorb enough heat from it to embrittle the grooved portion of said web, and severing means for subsequently breaking said article from said web at said embrittled border by further movement of said plunger relative to said web.
19. An apparatus as set forth in claim 18 wherein an auxiliary plate is positioned a predetermined distance away from said aperture in front of the path of movement of said plunger, and the opposed surfaces of said plunger and said auxiliary plate being cooperatively formed to shape the bottom of said article between them.
References Cited in the file of this patent UNITED STATES PATENTS 2,282,423 Kopitke May 12, 1942 2,547,331 Lent Apr. 3, 1951 ,891,280 Politis -a June 23, 1959