US 3397505 A
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Description (OCR text may contain errors)
1968 D. J CRITCHELL 3,397,505
PACKAGING MACHINE Filed March 15, 1965 DEA/V J. CR/TCHELL INVENTOR.
A TTORNEYS United States Patent 3,397,505 PACKAGING MACHINE Dean J. Critchell, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed Mar. 15, 1965, Ser. No. 439,731
Claims. (Cl. 53-74) ABSTRACT OF THE DISCLOSURE A packaging machine for sealing small parts in pouches formed in a folded web of thermoplastic film utilizing a reciprocating heatsealing member which cooperates with a rotating resilient surface to form a seal between adjacent articles.
The present invention relates to a packaging machine and more particularly to a high speed packaging machine adapted to use thermoplastic film materials.
In the art of film packaging machines, several approaches are known for enclosing, within pouches or bags, items to be protected by thin layers of plastic materials. Also, many film packaging materials are known. However, polyethylene, which provides certain advantages, has proved difficult to work with in certain applications because of its tendency to melt when worked with thermosealing devices. Because of this tendency, polyethylene handling equipment has often required extensive and expensive maintenance procedures.
Therefore, a general object of the present invention is to provide an improved packaging machine.
A more specific object of the present invention is to provide a new and improved method and apparatus for thermo-sealing of polyethylene type webbing.
In accordance with one embodiment of my invention, a folded web of polyethylene is intermittently driven past a filling station where a part is inserted therein, in a manner somewhat like that of my co-pending application Ser. No. 344,073 filed Feb. 11, 1964, now Patent No. 3,295,289. When the web is advanced, the inserted part is moved past a transverse sealing station wherein the web is bent over a back-up roller and engaged by a heated sealing unit to form a transverse seal. To overcome the tendency of polyethylene to stick to heated surfaces, the heater element carries spring means which bend the Web over the back-up roller prior to and during the sealing operation. This causes the heater to be effective to develop a seal during substantially its entire contact with the web as well as enhancing a precise control of contact duration.
The subject matter which is regarded as my invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. The invention, however, as to its organization and operation, together with further objects and advantages thereof, will best be understood by reference to the following description taken in connection with the accompanying drawing, in which:
FIG. 1 illustrates, in a simplified form, a front elevation view of a packaging machine using my invention;
FIG. 2 is a top plan view of the sealing unit taken along line 22 of FIG. 1;
FIG. 3 is an end view of the sealing unit of FIG. 2 partially in section to illustrate certain details of my invention; and
FIG. 4 is a similar end view in a substantially closed position.
Referring now to the drawing, in which like numbers indicate similar parts, in FIG. 1 I have illustrated a folded web passing from a supply reel (not shown) over a roller 11 so that a serrated roller knife 12 engaging it develops a series of slits 13 adjacent to the folded edge 3,397,505 Patented Aug. 20, 1968 14 of the web 10. I prefer that the roller 11 and the knife 12 be formed of a metal such as steel. The slits 13 assist the subsequent opening of the folded web without damage to the items stored therein, particularly if the item is a thin metal face plate or the like which is subject to bending under low stresses. The web 10 next passes between a pair of intermittently operable drive rollers 16 under the control of a clutch 17 and a brake 18 which are selectively energized by logic circuitry 20 to advance intermittently the web 10.
When the web 10 is held in a fixed or stopped position by the drive rollers 16, an item such as a lens 22 is inserted between the separated web layers under a web spreader 23 by means of a gravity feed chute 25 and an air jet assist means 26. As the particular lenses illustrated are generally cubical in overall form, they have several sharp corners which tend to prevent their removal except by opening the pouched web formed by the apparatus and method of my invention. Similarly the several corners of the lens 22 prevent loss through the open edge of the pouches formed by my invention.
As soon as the item is in place, it is sensed by a sensing device such as a photodetector 28 illuminated by a lamp 29. The photodetector 28 develops signal information for controlling the logic circuitry 20. The logic circuitry is relatively conventional and need not be discussed in detail herein. Such controls often consist of relays or gate circuits well known in the art which initiate power signals in response to various stimuli, such as the signal from the photodetector 28, to operate the clutch and brake 17-18 to advance the web. As soon as the advance is complete, e.g. the brake 18 is re-energized, a power signal is provided to operate a single revolution high-speed clutch mechanism indicated at 30 for advancing a sealing mechanism 31 to obtain the transverse sealing of each pouch of the web 10.
The completion of a sealing step, as indicated by termination of the single revolution clutch drive signal, results in signal information which causes a next item 22 to be inserted in the web- 10. Similarly, as soon as the insertion is complete, the control circuitry provides a power signal to commence the sealing operation. Controlled advance of the web in a downward direction is assured by a dancing roller 32 positioned therebelow. In the above described manner, about finished parts per minute may be placed within the protection of the pouched web by my invention. At this rate of bagging the items, the sealing engagement by operation of the clutch 31 takes only about 0.1 second. Such rapid sealing is much faster than is usual with 2 mil polyethylene.
Referring now to FIG. 2, I have shown a plan view of the sealing mechanism 31 in an open position with the folded web 10 positioned therein between a pressure member in the form of a back-up roller 34 and a heat sealing device 35. The roller 34 is preferably made of a high temperature rubber such as silicone rubber and is mounted on a rotatable shaft 37 supported on a back-up platform 38.
In prior art devices, it often developed that use of a solid back-up device in place of the roller 34 would result in projections or corners of a part damaging the back-up surface. However, with roller 34 in accordance 'with my invention, these projections merely assure rotation of the roller 34.
In order to provide a readily openable pouch, I prefer to use a series of separated seals 39 (FIG. 1) which may be termed a perforated seal rather than a continuous or line seal as is often used in prior art pouching devices of this type. To obtain such skip sealing, the heat sealing device 35 has thereon a plurality of tines 40 (FIG. 2) which are the only heated parts (as indicated in FIG. 4)
engaging the web 10 as it is folded over the roller 34. I have found using individual tines 40 for sealing the web, when using a conventional back-up surface, results in rapid wearing of mating detents. When such detents are present, the full surface 41 of the heater element 35 engages the back-up member. If a solid back-up member were used, it would be necessary to replace it frequently to prevent sufficient engagement between the web 10 and the heated surface 41 between the tines 40 to cause a continuous seal. Such a continuous seal, of course, causes the pouched web 10 to be unacceptably diflicult to open which would tend to damage fragile parts.
In order to be sure the web is entirely closed, e.g. the layers of the web are in contact over the roller 34 during all portions of the transverse sealing step, spring wires 44 of stainless steel or the like are provided to fold the web 10 over the roller 34. Thus, the wires 44 engage the web prior to the tines 40 (as indicated in FIGS. 3 and 4) when the single revolution clutch; 30 drives a cam 45 to move the tines 40 to the forward position as indicated in FIG. 4. When so folded, the Web 10 layers are in contact along the transverse seal line whereby the heated tines 40 commence a sealing connection as soon as they touch the nearer Web surface. Also the tines, being of a small surface area, tend to deform the plastic and thereby work the material during the sealing step to greatly facilitate a good seal.
In order to prevent the possibility of the wires 44 being heated to temperatures which might in any way melt the Web 10, I prefer to provide insulating washers 46 as shown in FIGS. 2 and 3. In certain applications and configurations of the present invention such washers are not necessary, because of the large radiant exposure of the wires 44 as compared to the heating contact areas.
Also, as indicated in FIG. 3, by the slant of the web 10, the dancing roller 32 (FIG. 1) is off-set to the right relative to FIG. 3 to draw the web 10 across the roller 34 and to substantially close the opening thereof caused by the spreader 23 (FIG. 1). Thus, web 10 is substantially closed prior to utilizing the force developed by the springs 44 to assure complete closing of the web prior to heat sealing.
I have found that this combination of springs 44 disposed in front of the heater device 35, as well as the use of a heater operating at a relatively low temperature, such as 200 F., assures consistent satisfactory perforated seals. Using the particular apparatus discussed herein, I have been able to obtain entirely satisfactory lateral seals at temperatures of about 200 F. to 300 F. while many prior art sealers use a sealing temperature of about 450 F. when working with polyethylene. A heater element 47 is provided within the sealing device 35 to maintain the desired elevated temperature.
Moreover, maintaining the web tightly against the roller 34 both immediately prior to the heat application and immediately thereafter substantially reduces the problem of polyethylene collecting on the heater. Thus, I am able to use a hard chromium heater surface wherein the tines 40 may be accurately formed and easily maintained.
While I have shown a particular embodiment of this invention, modifications thereof will occur to those skilled in this art. I intend, therefore, to have the appended claims cover such embodiments as properly fall within the scope of the present invention.
1. A packaging machine for securing items in a folded heat sealable thermoplastic web, comprising:
means for driving the folded web intermittently through a selected path;
means for spreading the folded web to allow insertion of an item;
means for inserting the item into the spread region of the folded web;
means for developing signal information of the pres- 4 ence of the item in the web for activating said driving means;
a heatable sealing member on one side of the web;
a pressure member on the other side of the web having a resilient surface for compressing the web against the heatable sealing member, said pressure member being rotably mountedto present diiferent surface areas to the sealing member'during successive sealing operations, said sealing and pressure members co-operating to form a transverse seal inthe web;
transverse drive means forcausing said sealing member to compress the layers of web against said pressure member to develop a transverse seal to thus form a pouch for securing the inserted item; anda pair of spring members associated with said sealing member and extending therefrom toward said pressure member to press the web thereagainst as said sealing member and said pressure member are brought together.-
2. A packaging machine according to claim 1 wherein said sealing member has a plurality of tine projections.
3. A packaging machine according to claim 1 wherein the selected path causes the web to continually engage said rotatable pressure member to cause rotation thereof during advance of the web.
4. A packaging machine according to claim 3 wherein said web driving means comprises a pair of intermittently operable drive rollers in advance of said pressure member and a dancing roller following said pressure member.
5. A packaging machine for securing items in pouches formed in a folded heat sealable thermoplastic web as it advances in a preselected path, comprising:
a pair of intermittently operable drive rollers for advancing' the web;
means including a dancing roller positioned to receive the web from said pair of drive rollers to establish the preselected path of the advance;
a slitter knife means for developing a series of slits in the web near the fold thereof;
a rotatable back-up roller having a resilient outer surface positioned to continuously engage a surface of the folded web in the preselected path and being between said pair of drive rollers and said dancing roller;
a transverse heat sealing member positioned on the other side of said back-up roller relative to the preselected path and intermittently movable to press the web against said back-up roller for forming a pouch therein, said sealing member having a plurality of tines positioned to engage the web to provide a perforated transverse seal;
means for heating said sealing member;
spring means for folding both layers of the web over said back-up roller prior to engagement thereof by said sealing member; 7
a web spreader positioned above said back-up roller to open the folded web;
an insert chute positioned between said back-up roller and said spreader to introduce items into the folded web; v
means for detecting the presence of an item in the web to provide signal information for causing said pair of drive rollers to advance the web one pouch length; and
means for intermittently moving said heat sealing member into a transverse seal-forming position relative to said back-up roller.
References Cited UNITED STATES PATENTS TRAVIS S. MCGEHEE, Primary Examiner.