US 2404630 A
Description (OCR text may contain errors)
J1 1946. T. @mFFnTi-as 2 YEX'IRUSION MACHINE Filed Sept. 1 1945 4 Sheets-Sheet 1 Attorneys July 23,1946.
F T. GRIFFITHS EXTRUSION MACHINE Filed Sept. 16, 1943 4 Sheets-Sheet 2 [nu enter fiancis 7. GriFfif/u- Attorney:
July23, 1 946. GRIFFITHS 2,404,630
. I 'EXTRUSION MACHINE I Filed Sept. 16, 1943 4 Sheets-Sheet a FIG. 3.
Inventor Francis T Criffi'fhs Attorney;-
July 23, 1946. I F. T. GRIFFITHS 2,404,530
EXTRU SION MACHINE Filed Sept. 16, 1945 I 4 Sheets-Sheet 4 Inventor Frdncis Tariff/H1;
mgm I device.
Patented July 23, 1946 EXTRUSION MACHINE Francis Tadman Grifliths, Gravesend, England;
assignor to W. T. Henleys Telegraph Works Company Limited, Dorking, England, a British company Application September 16, 1943, Serial No. 502,603 In Great Britain October 9, 1942 8 Claims.
1 This invention relates to machines for extruding plastic material, for instance, rubber mixes or synthetic plastic compositions such as polyvinyl chloride compositions and compositions con sisting principally of solidpolymers of ethylene. In machines of the kind with which the invention is concerned the plastic material is delivered to the feed end of a screw thread impelling device by means'of a pair of power driven feed rolls. The material passes throughthe hip in the rolls into a feed chamber with an outlet which leads to a feed opening at the rear end of the impelling A forced feed arrangement of this kind has many advantages and with certain materials-notably some synthetic plastics-is a practical necessity. However, periodically it is necessary to clean these feed rolls'and the feed chamher, for instance, when it is desired, to extrude a mix of a different composition or colour. In many machines it is impracticable to do this without dismantling the feed device, in others the operation of cleaning is facilitated to some extent by providing a' removable door in the feed chamber wall. By the present invention we provide an improved form of construction of extrusion machine which'permits of the feed device being more easily and thoroughly cleaned than has hitherto been possible without dismantling a large portion of the machine. In our improved form of construction the plastic material is delivered into a, feed chamber which is readily removable to expos the feed rolls and render them accessible on the delivery side without dismantling them and to give access to the interior of the feed chamber.
Preferably the feed chamber is arranged to slide in a direction perpendicular, or substantially perpendicular, to a plane containing the axes of the feed rolls into or out of an operative position in which its outlet registers with the feed opening of the impelling device, thewall of the chamber in which'the outlet is located making a sliding joint with a face around the feed opening. Preferably also the open front end of the chamber, that is the end adjacent the rolls, has edges which fit the rolls and serve as scrapers, provision'being made for limited adjustment of the operative position of the chamber to provide for clean scraping of the rolls or for leaving a film of plastic material thereon, whicheveris more suited to the working conditions. vThe feed chamber will generally extend the full effective width of the rolls, so that when it is withdrawn and removed, the rolls are exposed over their efl'ective 2 widths and the interior of the feed chamber is completely accessible. 7
The removable feed chamber is particularly advantageous when employed with machines com-' prising two impelling devices fed by a single pair of driven feed rolls. In this case the feed chamber is located between the two impellingdevices and furnished with an opening in each of two opposite walls which registers with the feed entrance of the adjacent impelling device. 'In such cases it is preferred to make provision for the insertion of a removable division plate in the chamber and for the insertion of'a co-operating, correspondingly located division plate on the approach side of the rolls, to allow the delivery of separate mixes to the two'imp'elling devices fed from the same removable chamber.
To enable the invention to be more fully understood an example of a multiple screw extrusion machine embodying the invention will now be described with the aid of the accompanying drawings wherein- Fig'."1,is a-view, partly in elevationand partly in section in a plane containing the axes of the impelling, devices, of a part of the extrusion machine. I
Fig. 2 is a sectional plan onthe line II'-IIf of V Figure 1,'
Fig. 3 is a cross-section on the line III-.III of Figure 1,
Fig. 4 is a view corresponding to Fig. 3 showing the machine fitted with division plates and spring-pressed hopper plates, and
Fig. 5 is a perspective View of the inner division plate.
The machine shown in the drawings is of th kind described in my co-pending Patent.2,367,394 and comprises two pairs of screw thread impelling devices, each of a type in which the "inner of two longitudinally extending concentric membersconstituting the impelling device" is rotatably driven, the two devices of each pair being in axial alignment and having their respective rotating parts integral with one another at the delivery 7 ends, the two pairs being disposed at diametrically opposite sides of the extrusion chamber .with their axes parallel with one another and at right angles with that of theextrusion chamber. Except for its drive, the machine is symmetrical about a vertical plane containing the axis of the extrusion chamber and consequently it is unnecessary to show or describe the complete machine.
The machine, of which rather more than one half is shown in Figures 1 and 2, is. built up of a pairof end blocks l, a pair of cylinders 2 and a I housed 'in the central block.
The central block 3 is for recesses I which receive correspondingly shaped projections 8 on the co-operating surfaces lcentral block from movingrelatively to the cylinders. The latter'have a smooth bore and form devices; The inner concentric member of each pair of axially aligned impelling devices is constituted by a shaft 9, of which the portions lying within the cylinder and to each side of a central portion Ill serving as a central bearing, e'achcarry a screw thread I'I the thread on one portion being of opposite hand to that on the other. The angle of the thread is advantageously about75- 30. At each end, the shaft 9 projects through a bushed opening I2 in the bottom wall of the recess 4 receiving the spigot end of its cylinder 2, and is rotatably supported by a ball bearing I3 housed in a bracket I4 extending from the-end block I. Delivery openings I5 are provided in the walls of the cylinders These are located one on each side of the bearing portion ID of the shaft and register with delivery ports I 6 in the opens into the upper wall of the passage 36; the
feed opening. of the lower device comprises a similar aperture 31 in the cylinder and a correspondingly inclined port 38 opening into the lower wall of the passage.
corresponding to that of the passage. The hori- Zontal edges of this block that lie at the front end thereoflby which is meant the end adjacent the the upper and lower roll surfaces.
chamfered edges. 49 the front face of the block 1s V the outer concentric members of the impelling lof the block and serve positively to restrain the feed rolls, are chamfered as shown at 46 to fit in'the form-of a rounded channel 4I, of which the depth increases from a minimum at each end to a maximum in the central part, as shown in Figures 2, and 3 of the drawings. In the central part of the wall of this channel fiI, is a recess 42 of cylindrical form which extends horizontally towards therear end of the block 39. Openings 13 are provided in the upper and lower walls of the recess 42, which respectively register with I of a removable feed chamber.
held'in position in the end block I by a lever acwall of the central block 3. and serve to place the four annular delivery chambers I1 in communicorrectly positioned in the bore of the block.
To one side of each end block area pair of feed rolls 25- mounted with their axes, one vertically above theother, parallel to those of the impelling devices and equidistant from a horizontal plane lying midway between the upper and lower pairs of impelling devices; The rolls are supported at :both ends by roll shafts turning in roller bearings 26 housediin brackets 21 on the end' blocks I, as
. will be seen from Figure 2. The roll shaft of the upper roll carries a' gear wheel 28 (Figure 1),
which meshes with a corresponding wheel 2'9 (Figure 2) on the projecting endof the lower shaft. Both rollsare driven by applying a drive from the part 32 of the upper impeller shaft to the upper roll by means of asecond gear wheel 30 on theupp'er roll shaft which meshes with a gear-wheel 31 on the part 32. This part 32 is supported by the bearing I 3 and by a 'second bear-- ing 33 mounted on a pedestal 34' and is driven by means of a wheel 35 on the end thereof which overhangs the bearing 33.
Inthe' block I is a passage 36, which extends from side to side of the block. As will be seen from the drawingsthis passage lies midway 'between the upper and lower impelling devices and respectively below and above the feed openings thereof and is of rectangular cross-section} In some cases, however, it may bean advantage to the upper and lower feed openings when thesliding block tdis in its operative position with its chamfered front edges 40 in, or almost in, engagement with the feedrolls-25. The channel 4| and recess 12 in the sliding block 39'form theinterior This chamber is tion bridge pi ce 44 which engages the rear end face of. the block 39. One end 'ofthe lever is of hook form and engages a fulcrum 45 carried by the end block I and the other end of the lever is engaged by a swing'bolt 46 by means of which, the position of the block 39 in the passage '35 can be adjusted, within limits, as required.
The rolls 2.5 are fitted with side plates, each of which is common to both rolls and is split in a vertical plane containing the axes of the rolls.
. The two parts 41 and 48 are coupled together by a hinge 49 at their lower ends and are held together and in engagement with grooves 50 in the rolls by a swing bolt 5I carried at the top of one part and engaging a lug. at the top of the other.
The part 131 of each side plate lying on the delivery side of the rolls 2'5 fits against the neighbouring wall of the end block I and forms a 1 smooth continuation of the adjacent side wall of the recess 36', which thus extends over the whole efiective width of the rolls, as will be most clearly seen inFigure 2. The outer parts 58 of the side ,1
plates, that is the parts that lie on the approach side of the rolls 25, are held;together by two tie bars 52 and form the side walls of a feed hopper, which may for cleaning purposes b swung down to give access to the rolls.
To render the machine capable of producing parti-coloured products by feeding different p coloured stocks to the upper and lower impelling'xdevices, the rolls ma be provided with removable central. division plates on their intake and deliv- As will be seen from Figure 4, the outer division plate 53 is shaped to fit against the outside halves of the circumferential surfaces ofthe .two rolls 25 and is held in position by. means of the two tie barsv 52. These have circumferential grooves 51 to provide parts of reduced diameter which enter one in each of two slots 5.6 in the outer edge of the plate, the sides of the groove forming shoulders which engage th sides "of the plate. To insert this outer dlVlSlOn" D13. te,,the
two'swing bolts 51 are released, the two outer parts 48 of the side plates lowere'd, the'centre' plate 53 dropped into position on the grooved tie bars 52 and the assembly of three platesj swung into the operative position and clamped there by" Slidably positioned in the passage 36 isia block 390i cross-sectional shape Between these the swing bolts; '-The inner division plate'58 is of twisted form with end portions lying at an angle of or more to one another. .The' widthof the plate is equalvto the diameter of the'cylindrical recess 42 in the feed cl'iamberblock 39. At its front end, the plate 58 lies verticallygits front edge being shaped, as shown in Figures 4 and 5,,to fit against the parts of the rollsurfaces lying between the chamfered edges 490i the feed chamber block 39. Within the part of the cylindrical recess 42 having the openings 43, the plate lies at an angleof 45 to'the vertical (or more, if the length of the'recess'permits) sothatit divides this part of the-recess intoupp'erand lower parts, one' 'of which'is in communication with the bite of the rolls lying to oneside'of the central division plates and th'e'oth'er with the bite lying to the other side of thatplate. This twisted form of division plate is preferably supported at its rear-end by a plunger 59 which'is a'working fit in the cylindrical recess 42. 'This permits .of the endwise adjustment of the plate without rendering 'it ineffective as'a separator. is effected'by means of a screw 60 working in the rear end wall of the feed chamber block 39, aocess to the head of which is obtained through anopening in the bridge piece '44 holding the block in place. Preferably, the two division plates 53 and 58 make a V join-t wth one anotherin the nip of the rolls, the tip of the division plate 58 forming a tongue Bl, which enters a groove of corresponding form in the tip 62 of the plate 53. The joint surface then extend inwardly from their outer edges in a direction counter to the directionof flow of stock past the entrances to the joint. V
As the flow paths to the two impelling devices are similar, whether'the central division plates are in position or not, the amountof stock fed to each device should normally be the same,
Provision may, however, be made to regulate the flow by. varying the cross-sectionalarea of the inclined portsSB leading from the feed chamber by means of adjustable plugs 65' which enter the Withdrawal of the feed chamber'for cleaning purposes is conveniently effectedby means of an extractor comprising a four-legged table 56 with feet 61, which hook over the two ti bolts 5 on the opposite side of the machine to that on which the feed rolls are disposed. In the table is a screw-threaded aperture inwhich works a screw 68 carrying a rotatable cup 69 which screws on an externally screw-threaded boss 10 on the rear face'of the block, as shown in broken lines in Figure 2 of the drawings. It will be apparent from this figure that by withdrawing th feed chamber block 39, unobstructed access is obtained to the delivery side of the rolls over their entire effective width. When withdrawn from its housing in the end block, the feed chamber is very accessible and can be cleaned much more readily than can feed chambers of existing forms of construction.
In some cases it is advisable forcibly to feed the plastic stock to the driven feed. rolls. An arrangement for doing this is shown in Figure 4.
, It comprises a pair of pressure plates H, one on each side of the division plate 53 and constituting the front walls of two feed hoppers of which the side walls are constituted by the plates 48 and 53. The plates H are pivotally supported near their lower ends, each on a spindle 12 and pressed inwardly towards the rolls 25 by means of spring actuated cranks 13 connected to the Adjustment 6 upper partof the plate by links 14. Each pressure plate may b heldopen to admit stock to the hopper by means of a handle 15 acting on the crank shaft, preferably'spring coupled to the crank shafts. Naturally theinvention is in no way limitedto this particular form of pressure device. Any other suitable device may be used or, as indicated above in many cases the machine maybe used without such 'a device.
What I claim as my invention is:
1. A machine for the extrusion of plastic material, comprising at least one pair of screwthread impelling devices each having its own feed opening, a readily removable feed chamber located between the two impelling devices and having a pair of outlets each registering with the; feed opening of the adjacent impelling device, apair of driven feed rolls for feeding plastic material into one endof said feed chamber, a
removable division plate in said feed chamber :the first said'division plate whereby to allow of the delivery by said rolls of different kinds of plastic material to the two impelling devices.
2. A machine for'the extrusion of plastic material, comprising at least one pair of screwthread impelling devices each having its own feed opening, a readily removable feed chamber 10- cated between the two impelling devices'and having a pair of outlets each registering with the feed opening of the adjacent impelling device,
r a pair of driven feed rolls for feeding plastic material into one end of said feed chamber, a pair of side plates for the feed rolls, each plate being received in circumferential grooves at the ends of said rolls and divided in a plane containing the axes of the rolls into inner and outer parts hinged together at their lower ends, means for detachably securing the inner and outer parts of each side plate together at their upper ends, means for tyingtogether the outer parts of the two side plates, a removable division plate in said feed chamber dividing said feedchamber into two parts each 'containingone-of said outlets; and an outer division plate on the approach side of said rolls correspondingly located by said tying means and shaped to fit the rolls and make joint in the nip thereof with saiddivision plate in said feed chamber, whereby to confine the delivery of plastic material fed to the part of said feed rolls lying to one side of said outer division plate to 7 one of said impelling devices and delivery of that fed to the part of said feed rolls lying to the other side of said outer division 'plate to the other of said impelling devices.
3. A machine for the extrusion of plastic material comprising a screw-thread impelling device having a feed opening for the introduction of the material, a readily removable feed chamber open at one end and closed at the other and having a lateral outlet and slidable across the face of said feed opening into and out of an operative position in which said lateral outlet in the said chamber registers with the feed opening, and a pair of driven rolls for forcing material into the open end of said slidable feed chamber when in its operative position, and releasable means for holding the said slidablefeed chamber in its operative position.
4. A machine for the extrusion of plastic material, comprising a screw-thread impelling device having a feed opening for the introduction aeogeso.
of the material, a, removable feed chamber closed at one end and open at the other end and havin I a lateral wall with anoutlet therein, and a pair of driven rolls for feeding material into the chamber through the open end thereof, said feed chamber being slidable across the face of said feed opening in a direction substantially perpen- 3 dicular to a plane containing the axes-ofsaid 1 feed rolls into and out of :an operative position in which the lateral outlet registers with the said feed opening and the lateral wall of the chamber in which'the outlet is located makes a 5. A machine for the extrusion of plastic material, comprising a screw-threaddmpelling device having a feed opening for the introduction of the material, a removable feed chamber open at one end and closed at the other and havin 1 a lateral wall with ,an outlet therein, a pair of rolls for feeding the material into the openend abutmentwhereby to adjust the operative position of said feed chamber to provide for clean scraping of the rolls or for leaving thereon a film of plastic material of appropriate thickness.
6. A machine for the extrusion of plastic'material, comprising a pair of laterally spaced screwthread impelling devices, a housing for the feed veends 'of both said devices having a through passage between, and extending transversely of, said devices and having ports in the wall of said passage each leading to the interior of one. of said impelling devices, a pair of driven feed rolls at one end of said through passage, and a feed chamber comprising a block ,removably positioned in said passage; said block being a sliding fit in said'through passage and having atione'enda pair of edges chamfered to fit the rollsurfaces, a channel between said edges of which the depth increases from a minimum at each end to a maximum in the central part, and a recess of cylindrical form opening into the central part of the channel and extending towards the end of the block remote-from the rolls. and having in its circumferential wall and on opposite'sides ofsaid recess, a pair of openings one of which registers with one of said ports andthe other of which sliding joint with a, face around the feed opening, and releasabl means for holding said r'emov- I able feed chamber in'said operative position.
register' 'with the other of said. ports, when the block is in an operative position and releasable I means engaging the end ofsaid block remote from said rolls, for holding said block inisaid operativepositiona 7. A machine for the extrusion of plastic material, comprising a pair of laterally spaced screwthread impelling devices, a housing for the feed ends of said both deviceshaving a through passage between; and extending transversely of said 7 devices and having ports in the wall of saidpassage each leading to the interior of one of said impelling devices, a pair of driven feed rolls at one end of said passage, and a feed chamber removably positioned in said passage, said feed chamber being a sliding fit in said passage and having an inlet end shaped to fit the delivery side of said feed rolls and lateral outlets which register with the ports in the Wall of the passage, whereby said feed chamber can be withdrawn from said passage to expose the delivery side of said rolls.
8. An extrusion machine as specified in claim 6, wherein the feed chamber is fitted with a division plate comprising a front portion, which fits against the portions of the rolls between the chamfered edges of the feed chamber and lies in a plane substantially radial to the axes of the rolls, a rear portion twisted at an angle to the front portion, and edges fitting the walls of the cylindrical recess, whereby to confine the flow of plastic material from one side of the said division plate toone of the impelling devices, and that from the other side to the other of the impelling devices. FRANCIS TADMAN GRIFFITHS.