GB2151181A

GB2151181A - Apparatus for uniting overlapping portions of synthetic plastic sheets

Info

Publication number: GB2151181A
Application number: GB08431809A
Authority: GB
Inventors: Bernd Ramcke
Original assignee: ECH Will GmbH and Co
Current assignee: ECH Will GmbH and Co
Priority date: 1983-12-17
Filing date: 1984-12-17
Publication date: 1985-07-17
Also published as: BE901231A; IT8423616A0; GB8431809D0; IT8423616A1; IT1177229B; GB2151181B; FR2556647A1

Abstract

Apparatus for welding portions of overlapping synthetic thermoplastic sheets 2, 2a which confine rows of stacked stationery products between them has two pairs of endless toothed belts 1, 1a, 101, 101a which engage the overlapping portions of the sheets from above and from below, a heated severing and welding tool 8, and a motor 9 which pivots the tool into and from the space between the two pairs of belts. The tool has an elongated severing edge 12 which is flanked by two heated bonding surfaces (13, 14 Figure 2) facing counter to the direction of transport of the sheets when the tool is held in the operative position between the two pairs of belts. At such time, the severing edge is inclined with reference to the plane of the overlapping portions of the sheets. A cooling device 118 is provided to direct compressed air against a guide for the belts at the severing and welding station so as to prevent adherence of severed surplus to the tool and/or to the seam or seams which are formed by the bonding surfaces, depending upon whether the tool is used between two rows of products or along an exposed lateral portion of a row. <IMAGE>

Description

SPECIFICATION Apparatus for uniting overlapping portions of synthetic plastic sheets The present invention relates to heat-sealing or welding apparatus in general, and more particularly to improvements in apparatus for bonding sheets or foils of synthetic plastic material to one another. Still more particularly, the invention relates to improvements in thermowelding apparatus which can be utilized with advantage in packing machines wherein groups or sets of properly arrayed (e.g., stacked) commodities are to be confined in transparent, translucent or opaque foils or sheets of synthetic plastic material.

It is already known to place one or more rows of arrayed commodities (e.g., stationery products including stacks of exercise books, steno pads, index cards, calenders and the like) between two sheets of synthetic plastic material and to bond the two sheets to each other so that all sides of each array are confined by welded seams. It is also customary to simultaneously separate the neighbouring rows of arrays from each other. The thus obtained individually wrapped arrays are then subjected to a treatment which involves a shrinkage of the wrappers so that the synthetic plastic material closely follows the outline of the respective array. This saves storage space while simultaneously ensuring that the confined commodities are shielded from moisture, dust and/or other undesirable influences.

In many heretofore known apparatus which are used to weld superimposed sheets or foils of ther moplastic material to each other, those portions of the sheets or foils which are to be bonded to each other and from which the surplus is to be removed are normally transported between pairs of endless belts. Such belts serve the additional purpose of securely gripping selected portions of the overlap ping sheets to thus reduce the likelihood of the development of wrinkles or other irregularities in the welded seam or in the region which is adjacent to the welded seam. The tool (such a heated knife which carries out a combined severing and weld ing operation) is normally disposed between the upper endless belts.Such tool can constitute a ro- tary disc, a vertically disposed blade or any one of a variety of otherwise configurated electrically heated severing and welding tools.

A drawback of heretofore known apparatus which employ the aforediscussed sheet transport ing, severing and welding means is that the sev ered and freshly welded sheets tend to adhere to the hot tool and/or that the separated surplus tends to cling and to be bonded to the material of the freshly formed welded seam. This can affect the appearance of the finished packages of wrapped commodities as well as the integrity of the wrappers of such commodities. Attempts to overcome the just discussed problems which arise in conventional apparatus include the provision of cooling devices, e.g. water-cooled sheet-contacting parts and/or additional or auxiliary belts which are designed to transfer heat from the separated surplus and/or from the still hot welded seam into the surrounding atmosphere.It was further proposed to impart to the tool a composite movement including a movement relative to the sheets of plastic material as well as an oscillatory movement which latter is intended to reduce the likelihood of adherence of plastic sheet material to the tool. The incorporation of such features into conventional apparatus not only involves substantial expenditures but it also contributes to the complexity and bulk of the apparatus. Moreover, the incorporation of the above outlined remedial features reduces the versatility of the apparatus which are then merely capable of forming a reliable lateral welded seam but not a welded seam between two rows of arrayed commodities.

The improved apparatus can be used for bonding portions of overlapping synthetic plastic sheets to each other, particularly for heat-sealing overlapping portions of two sheets which consist of a synthetic thermoplastic material and confine rows of commodities therebetween. The apparatus comprises means for transporting the overlapping portions of the sheets in a predetermined direction and along a predetermined path so that the overlapping portions are located in a predetermined plane, a tool having an elongated severing or cutting edge or two mutually inclined heated bonding surfaces which flank the severing edge, and means for moving the tool between an operative position in which the severing edge extends across a portion of the path and is inclined with reference to the aforementioned plane and the bonding surfaces face counter to the predetermined direction, and a second position in which the severing edge and the bonding surfaces are located outside of the path. The two bonding surfaces are or can be at least substantially mirror symmetrical to each other with reference to a plane including the severing edge of the tool.

The transporting means can comprise at least one pair of endless flexible conveyors (preferably toothed belts) having spaced-apart parallel sheetcontacting reaches, and the tool is disposed between the two reaches, at least while it is held in the operative position. In accordance with a presently preferred embodiment of the invention, the transporting means comprises a first pair of endless flexible conveyors having spaced-apart parallel reaches engaging one of the sheets along the path and a second pair of endless flexible conveyors having spaced-apart parallel reaches engaging the other sheet along the path opposite the parallel reaches of the first pair of conveyors. The tool is disposed between the parallel reaches of the first and second pairs of conveyors when it assumes its operative position.

The moving means preferably comprises means for pivoting the tool between its operative and second positions, and such pivoting means can include a fluid-operated motor, e.g., a suitable pneumatic motor.

The tool preferably further comprises a heating device for the bonding surfaces and a temperature monitoring device. For example, the tool can be provided with two blind bores, sockets or analogous receptacles one of which receives a remova ble heating cartridge and the other of which receives a removable temperature monitoring device which can regulate the heating action of the cartridge.

The apparatus preferably further comprises a source of gaseous coolant (e.g., a source of compressed air) and means for directing such coolant from the source against the portions of the sheets downstream of the aforementioned portion of the path, as considered in the direction of transport of the sheets. The arrangement is preferably such that the apparatus comprises suitable guide means for the transporting means in the region of the aforementioned path, and the coolant directing means can comprise one or more nozzles which direct coolant against the guide means downstream of the severing and bonding station.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved apparatus itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

Figure 1 is a schematic fragmentary elevational view of an apparatus which embodies one form of the invention, the tool being shown in the operative position; Figure 2 is an enlarged view of the tool as seen in the direction of arrow X in Fig. 1; Figure 3 is an enlarged view of the tool as seen in the direction of arrow Y in Fig. 1; and Figure 4 is a schematic plan view of two rows of stacked commodities between two overlapping sheets of synthetic plastic material which can be bonded to each other in the apparatus of Fig. 1.

Referring first to Fig. 4, there are shown two elongated parallel rows of commodities. The commodities of one of the rows form identical arrays (e.g., stacks) 50' each of which can contain twelve steno pads, a selected number of index cards, a selected number of memo pads or the like. The commodities of the other row form arrays 50 whose constituents may but need not necessarily be identical with those of the arrays 50". The two rows of arrays 50' and 50" are disposed between two thin light-transmitting sheets or foils 2 and 2a which consist of weldable synthetic plastic material and overlap each other all around each of the arrays 50' and 50". The purpose of the improved apparatus is to weld the two sheets 2 and 2a to each other along their marginal portions 2', along their marginal portions 2" or along the broken line 2"' which is disposed between the two rows of arrays.

After the welding operation along the marginal portions 2', 2" and along the line 2"' is completed, the sheets 2 and 2a are bonded to each other along lines 51 (indicated by dots), preferably by welding tools which simultaneously sever the two sheets so that the structure which is shown in Fig.

4 4 yields a number of discrete arrays 50' and 50" each of which is confined between portions of the two sheets 2 and 2a and such portions of the two sheets are bonded to each other all along the four sides of each confined array. In the next step, the wrappers of the individual arrays are caused to shrink so as to closely follow the outlines of the respective arrays. The thus obtained products are sent to storage or to stores, e.g., to stationery stores where they are provided with price tags and are put on display on shelves or the like.

As mentioned above, many heretofore known combined severing and welding apparatus are incapable of forming reliable seams along the marginal portions 2', 2" and much less along the line 2"' of Fig. 4, especially if such apparatus are equipped with cooling, vibrating and like devices.

The apparatus which is shown in Fig. 1 comprises a transporting unit with a first pair of endless toothed belts 1, la whose lower reaches are parallel to and spaced apart from each other, and a second pair of endless toothed belts 101, 101a whose upper reaches are spaced apart from and parallel to each other and respectively register with the lower reaches of the belts 1, la to define an elongated horizontal path for selected portions of the two synthetic plastic sheets 2 and 2a (denoted in Fig. 1 by a phantom line).The lower reaches of the belts 1, la are confined in a slotted guide 7, and a similar guide (which is preferably a mirror image of the guide 7 but is not specifically shown in Fig. 1) is provided for the upper reaches of the belts 101, 101 a. The belts 1 and la are trained over pulleys 3 and 4 and are tensioned by a roller 6 which is movable in directions indicated by a double-headed arrow C. The arrow B indicates the direction in which the pulley 3 and/or 4 is driven in order to advance the lower reaches of the belts 1 and la in the direction which is indicated by the arrow A. The means for mounting and driving the lower belts 101, 101a is analogous and is not specifically shown in Fig. 1.

The improved tool 8 is pivotable at 11 by a fluidoperated motor 9, preferably a pneumatic cylinder and piston unit, so that it can be moved between the illustrated operative position and a second or inoperative position in which the tool is remote from the path of the selected portions of the synthetic plastic sheets 2 and 2a. As can be seen in Figs. 2 and 3, the tool 8 comprises an elongated severing edge 12 which is flanked by two welding or bonding surfaces 13 and 14. The surfaces 13 and 14 are mirror symmetrical to each other with reference to a plane which includes the edge 12 and these surfaces face counter to the direction which is indicated by the arrow A when the tool 8 is held in the operative position of Fig. 1. The severing edge 12 is then inclined with reference to the plane of the sheets 2, 2a between the two pairs of conveyors and extends across the path of those portions of the sheets which are to be bonded to each other.

If the apparatus of Fig. 1 is used to bond the sheets 2, 2a to each other in the region of the line 2"' of Fig. 4, each of the bonding surfaces 13, 14 makes a welded seam and the edge 12 severs the sheets 2, 2a along the line 2"'. If the apparatus is used to bond the sheets 2, 2a to each other along the marginal portions 2' or 2" of Fig. 4, the edge 12 severs the surplus and one of the surfaces 13, 14 bonds the sheets 2 and 2a to each other. Thus, the improved apparatus can be used with equal advantage for simultaneous making of two welded seams or for the making of a single welded seam and for simultaneous severing of the surplus along the single seam.

The larger-diameter upper portion of the tool 8, as viewed in Fig. 1 or 2, has two spaced-apart parallel receptacles 16a, 17a in the form of blind bores or pockets. The receptacle 16a accommodates a removable heating cartridge 16 for the bonding surfaces 13, 14 and the receptacle 17a accommodates a temperature monitoring instrument 17 which ascertains the temperature of the tool 8 in the region of the surfaces 13, 14 and regulates the heating action of the cartridge 16 in a manner which forms no part of the present invention.

The apparatus further comprises a cooling unit including a source 118 of compressed gaseous coolant (e.g., air), one or more nozzles 18 which direct one or more jets of compressed coolant toward the guide 7 and toward the seam or seams downstream of the severing and bonding station (as considered in the direction of arrow A), and one or more conduits 218 connecting the source 118 with the nozzle or nozzles 18. The coolant reduces the likelihood of adherence of the initially soft welded seam or seams or severed surplus plastic material to the tool 8 and/or to the conveyors 1, la, 101, 101a of the transporting unit and/or to the guide 7.

The motor 9 is preferably actuated by the controls for the main prime mover of the machine or production line which embodies the improved apparatus so that the tool 8 is automatically pivoted to the second or inoperative position when the machine or production line is brought to a halt and that the tool 8 is automatically returned to the operative position of Fig. 1 when the conveyors 1, lea, 101, 101a begin to advance portions of two overlapping synthetic plastic sheets 2, 2a toward and past the combined severing and bonding or welding station.

A machine which can turn out arrays of stationery products suitable for packing between pairs of transparent, translucent or opaque synthetic plastic sheets or which can process packed arrays is disclosed, for example, in commonly owned U.S. Pat.

No. 4,223,777 granted September 23, 1980 to Kurt Aykut.

The improved apparatus is susceptible of many modifications without departing from the spirit of the invention. For example, the means for moving the tool 8 between its operative and inoperative positions can comprise a reversible electric motor, a a hydraulic motor, a hand-operated device, an electromagnet or any other suitable moving means. Furthermore, it is possible to utilize other types of transporting units. The illustrated toothed belts are preferred at this time because they reduce the likelihood of slippage of the sheets 2, 2a relative to each other and eventual wrinkling of the welded seam or seams.

An important advantage of the improved apparatus is its versatility, i.e., the apparatus can be used for the making of single seams or twin seams, for the making of two seams without segregation of surplus or for the making of single seams with simultaneous removal of surplus plastic material at one side of the severing edge 12.

Another important advantage of the improved apparatus is that the seam or seams and/or the strips of surplus plastic material are not likely to adhere to the tool 8 in spite of the fact that the tool need not be vibrated when in actual use. This is attributable to the ability of the tool 8 to leave the space between the neighbouring reaches of the belts 1, 1a and 101, 101a as well as to the cooling of the sheets 2, 2a, guide means 7 and the belts 1, 1a, 101, 101a by a suitable gaseous coolant. Were the cutting edge 12 and the surfaces 13, 14 retained in the operative positions of Fig. 1 when the transporting unit including the endless toothed belts 1, la, 101, 101a is arrested, the tool could cause pronounced localized melting of the sheets 2, 2a and/or burning or charring of the plastic material.

Claims

1. Apparatus for bonding portions of overlapping synthetic plastic sheets to each other, particularly for heat-sealing overlapping portions of two sheets which consist of synthetic plastic material and confine rows of commodities therebetween, comprising means for transporting the overlapping portions of the sheets in a predetermined direction and along a predetermined path so that the overlapping portions are located in a predetermined plane; a tool having an elongated severing edge and two mutually inclined heated bonding surfaces flanking said edge; and means for moving said tool between an operative position in which said edge extends across a portion of said path and is inclined with reference to said plane and said surfaces face counter to said direction, and a second position in which said edge is located outside of said path.

2. The apparatus of claim 1, wherein said bonding surfaces are at least substantially mirror symmetrical to each other with reference to a plane which includes said edge.

3. The apparatus of claim 1, wherein said transporting means comprises at least one pair of endless flexible conveyors having spaced-apart parallel sheet-contacting reaches, said tool being disposed between said reaches, at least in said operative position thereof.

4. The apparatus of claim 1, wherein said transporting means comprises a first pair of endless flexible conveyors having spaced-apart parallel reaches engaging one of the sheets along said path and a second pair of endless flexible conveyors having spaced-apart parallel reaches engaging the other of said sheets along said path opposite the parallel reaches of said first pair of conveyors, said tool being disposed between the parallel reaches of said first and second pairs of conveyors, at least in said operative position thereof.

5. The apparatus of claim 1, wherein said moving means includes means for pivoting said tool between said positions.

6. The apparatus of claim 1, wherein said moving means comprises fluid-operated motor means.

7. The apparatus of claim 6, wherein said motor means comprises a pneumatic motor.

8. The apparatus of claim 1, wherein said tool comprises a temperature monitoring device.

9. The apparatus of claim 1, wherein said tool comprises at least one heating device for said bonding surfaces.

10. The apparatus of claim 9, wherein said heating device comprises a heating cartridge.

11. The apparatus of claim 1, wherein said tool has a first and a second receptacle, a heating cartridge for said bonding surfaces in one of said receptacles, and a temperature monitoring device in the other of said receptacles.

12. The apparatus of claim 1, wherein said transporting means comprises toothed belts.

13. The apparatus of claim 1, further comprising a source of compressed gaseous coolant and means for directing coolant from said source against the portions of the sheets downstream of said portion of said path, as considered in said direction.

14. The apparatus of claim 1, further comprising guide means for the transporting means, said guide means extending along said path and further comprising means for cooling said guide means downstream of said portion of said path, as considered in said direction.

15. Apparatus for bonding portions of overlapping synthetic plastic sheets to each other, substantially as herein described with reference to the accompanying drawings.