IE41775B1 - Improvements in and relating to cutting and sealing thermoplastic film web to produce bags - Google Patents

Abstract

1494542 Seaming non-metallic sheet material; making bags FMC EUROPE NV 10 Feb 1975 [20 Feb 1974] 5501/75 Headings B5K and B5D Apparatus 1 for cutting and sealing at least one thermoplastic film web to produce bags comprises a reciprocable cutting and sealing bar 15, a lower stationary assembly having two holding and coolings bars 17A, 17B adjustably mounted on a beam 18 extending transvesely to the web feed direction, an upper movable assembly having a support beam 13 carrying the bar 15 and resiliently carrying two holding and cooling bats 16A, 16B arranged symmetrically with respect to the bar 15, a coolant circuit for the bars 16A, 16B, 17A, 17B, and means for detaching the film from the bars 16A, 16B, 17A, 17B after operation of the bar 15. In the apparatus described, two longitudinally folded thermoplastic film webs (5), (6), Fig. 1 (not shown), are fed simultaneously by rollers (2A), (2B) to the apparatus 1 which transversely cuts and seals the webs to form individual bags which are removed by belts 3B, Fig. 3. The lower bars 17A, 17B, Figs. 2 and 3, separated by spacers 23 are mounted on a plate 19 secured to the beam 18 so as to be adjustable w.th respect to planes XX 1 and YY 1 . Cold water or refrigerant fluid is circulated through passages 24 in the bars 17A, 17B through inlet, outlet and connecting hoses 24A, 24B, 25, respectively. Nozzles 28 in the bar 17B are supplied w.th compressed air through tubes 27 connected by hoses 29 to two splitter boxes 30, 31 corresponding to the webs (5), (6), respectively. The boxes 30, 31 are supplied by a main hose 32 through a two-way control valve 33 and are provided with control valves so that, for example, the whole or only part of the nozzles 28 may be supplied continuously or intermittently. The bar 15 is heated by an electrical resistance 15B and is suspended from the vertically movable beam 13 by members 36. The beam 13 is provided with a locking bolt 14 to enable the upper assembly to be locked in its active position with the bolt 14 in an opening 39 in a member 41 or in an inactive position in which the bar 15 has no action of the film while the beam 13 continues to be raised and lowered, the bolt 14 being in an opening 40. Four lower bars 16A, 16B, 16C, two for each film web, are provided and are suspended from the beam 13 by adjustable supports 42 having guide rods 43 along which the bars 16A, 16B, 16C can be displaced upwardly against the action of springs 44. The bars 16A, 16B, 16C are provided with passages 45 and connecting hoses 46, 47 for the circulation of a refrigerant therethrough. The bars 16B, 16C have nozzles 28A supplied with compressed air by a system identical to that of the bar 17B. In operation, after a film feed step, the upper assembly is lowered and the bars 16A, 16B, 16C clamp the wdbs against the bars 17A, 17B. Continued lowering of the beam 13 causes the bar 15 to descend against the action of the springs 44 until it contacts the webs to effect sealing and cutting thereof. The dwell time of the bar 15 in this position is determined by the shape of a cam controlling the movement of the beam 13. When the beam 13 rises, the bar 15 and, subsequently, the bars 16A, 16B, 16C disengage the webs. Compressed air from the nozzles 28, 28A facilitates detachment of the film from the holding bars and assists forward feed thereof.

Description

This invention relates to apparatus fo.r cutting and sealing at least one thermoplastics film web to produce bags. According to the present invention there is provided apparatus for cutting and sealing at least one thermoplastic film web to produce bags, said apparatus comprising a reciprocal cutting and sealing bar, means for holding thermoplastic film web during the cutting and sealing operation, said holding means including a lower stationary assembly having two holding and cooling bars adjustably mounted on a beam extending transversely to the web feed direction, an upperj movable, assembly having a support beam carrying the cutting and sealing bar and resiliently carrying -two holding and cooling bars arranged symmetically with respect to the cutting and sealing bar, drive means for reciprocating the upper assembly, a coolant circuit for maintaining the holding and cooling bars of the upper and lower assembly at temperatures appropriate to the requirements of the film to be sealed and means for detaching the film from the holding and cooling bars after the sealing and cutting operation by the cuttina and sealing bar.

Further according to the present invention there ia provided apparatus for cutting and sealing at least one thermoplastic film Web to produce bags, said apparatus comprising a reci procable cutting and sealing bar, co-operating upper and lower bars for holding and cooling the film web during each cutting and sealing operation and means for supplying compressed gas to at least certain faces of the holding and cooling bars whereby to assist detaching and forward feed of the film after the completion of the cutting and sealing operation, Still further according to the present invention there - 2 41775 is provided apparatus for cutting and sealing at least one thermoplastic film web to form bags, said apparatus comprising a cutting and sealing bar, upper and lower bars for holding and cooling the web when the web is being cut and sealed by the cutting and sealing bar, means to Bupply to at least certain faces of the holding and cooling hars compressed gas to assist in detachment of the film after completion of cutting and sealing and a cooling circuit for circulating coolant through the holding and cooling bars.

Yet further according to the present invention there is provided a method of producing a succession of bags from a thermoplastic film web comprising the steps of bringing the web to an operational station, holding and cooling the web upstream and downstream of a cutting and sealing line, sealing and cutting the web at said line and releasing the web and the bag produced subsequently to .the cutting and sealing operation with the aid of a flow of compressed gas at the upstream zone which have been held.

An embodiment of cutting and sealing apparatus in accordance with the invention will now be described by way of example, with reference to the accompanying, diagrammatic drawings, in which: Figure 1 is a perspective view of cutting and sealing apparatus in accordance with the invention for films of thermoplastic material intended for the manufacture of bags; Figure 2 is a view, to an enlarged scale and partially cut-away showing a supply system for refrigerant liquid and compressed air for holding and cooling bars of the apparatus and for cooling in general; · Figure 3 is a section, to an enlarged scale, showing certain parts including the cutting and seating bar, the - 3 41775 holding and cooling bars of the apparatus of Figure 1; and Figures 4 to 9 ar® explanatory diagrams illustrating various phases of the operational cycle of the apparatus; Figure 7 showing, to a much enlarged scale, a central part of the apparatus shown in Figure 5.

The cutting and sealing apparatus in accordance with the invention which is shown in Figure d is designated generally by the reference d. This apparatus is disposed between a row of feed rollers 2A’ with controllable pressure, which rollers are mounted upstream of the apparatus d, and a series of take-off belts of which onl/ the lower belt 3b and an upstream roller 4β thereof have been shown for the sake of clarity in the drawing, these parts being mounted d5 downstream of the apparatus d.

The assembly illustrated, by way of example, in Figure d is so arranged that it can operate simultaneously on two webs 5 and 6 of thermoplastic film material, these webs passing through conventional feed rollers not shown, by which the webs are engaged.

In use, although not essentially so, each of the webs takes the form of a film folded longitudinally on itself so as to form a double thickness web which is open laterally.

It will be seen immediately that by intermittently advancing the webs 5 and 6, the apparatus d can cut and seal, transversely with respect to the direction of the advance, the double thickness web of film plastics material and transform both webs into bags 7 and 8 which are then entrained by the belts 3„ Each of the bags 7 and 8 is therefore consti30 tuted hy a sheet open laterally and closed at its two enas by - 4 41775 seals such as 7^, 7g θ^, the second seal of bag 8 not being visible in the drawings.

It will be noted that between the feed rollers and 2g and the cutting and sealing apparatus 1, a plurality of guide fingers such as 9, 10, 11 and 12 is provided which fingers facilitate the guidance of the webs 5 and 6 between the output of the feed rollers and the entry to the apparatus 1, and prevent any formation of creases or puckers in the film.

The cutting and sealing apparatus I comprises, in general terms, the following parts. An upper reciprocable assembly comprising a support beam 13 provided with a locking device 14 on which are secured the cutting and sealing bar 15 and two holding (or gripping) and cooling bars 16^ and 16^ arranged symmetrically with respect to the bar 15. A lower stationary assembly comprises two holding and cooling bars 17^ and 17g adjustably mounted on a beam 18 forming part of the structure (not shown) of the general assembly of the machine.

The two assemblies referred to will now be described in detail with reference, more particularly, to Figures 2 and 3.

The two holding and cooling bars 17A and 17B of the lower stationary assembly are mounted, separately, on a common mounting plate 19 which is itself secured to the channel section beam l3 for example by means of bolts. Each of these two bars 17A and 17B is secured at its two ends on the mounting plate 19 through the intermediary of a lower support bar 17θ or 17D, by a screw-threaded member 21^ or 21^ and nuts and lock nuts 22^ or 22g. In addition spacers 23 aro provided between the bars - 5 41775 17A and 17β· It will be apparent, that the space having a dimension i which separates the two bars 17A and 17-g, that the position of the bars 17A and 17g with respect to the plane of vertical symmetry XX^ and that the level of each of the bars with respect to the lower plane Υϊη of the path of the webs 5 and 6 can be controlled exactly* All of these control possibilities are important, and it should be noted that the best results during the course of tests were obtained with a spacing i of 5 millimetres Ί0 between the internal, opposed, surfaces of the holding and cooling bars 17ft and 17β.

Each of these two holding'and cooling bars 17^ ahd Ϊ7β comprises at its upper internal corner, a longitudinal passage 24 along.which cold water or other refrigerant fluid can circuit late. To this end the passages 24 are connected respectively to an inlet hose 24^ and an outlet hose 24^ and also to a connecting hose 25 at their ends. A refrigeration circuit for the bars 17A and 17-g is thus provided, which enables maintenance of the temperature of the latter below the most favourable threshold for the various manufacturing criteria so that the nature of the material forming the films of the webs 5 and 6, their thickness, lengths and breadths' of the bags to be manufactured etc. can be accommodated.

According to another important characteristic of the present embodiment, at least upstream of the holding and cooling bar Ι7β which is closer to the feed rollers 2^ anu 2g, a compressed air supply system is provided which can be controlled as will be apparent hereinafter in greater detail. The system serves to facilitate the supply of film to the interior of the cutting and sealing, apparatus by arranging this supply - 6 41775 on the air cushion principle, and to prevent adherence of the films on the support bars, after the sealing operation.

The holding and cooling bar 17β is provided, with this in view, with a series of inlet pipes 26 uniformly spaced along its face directed towards the feed rollers 2^, 2β. These pipes supply small internal tubes 27 whioh deliver the air to the upper face of the bar 17B at a series of uniformly-spaced orifices 28.

In order to adjust the characteristics of the air jet produced, that is to say its pressure, its breadth, its duration, and a continuous or intermittent ejection, all the supply pipes 26 are connected through the intermediary of individual hoses 29 to two splitter boxes JO and J1 corresponding respectively to the web 5 and the web 6. These two splitter boxes are supplied in parallel from a common souroe of compressed air connected to a main hose 32, by means of a two-way control valve 35 and two connecting pipes 34 and 35.

Each of the splitter boxes 30 and 31 comprises an inlet connected to the corresponding pipes 34 or 35 and as many outlets as one half of the number of pipes 26 to be supplied.

Each of the splitter boxes 30, 31 is provided with control valves enabling the precise control of the pressure, taking into account the distribution of pressure required at the outlets of the nozzles 28.

Similarly, it 'is possible to supply the whole or a part only of the nozzles 28 continuously or intermittently.

It will be clear that the holding and cooling bar 17^ can also be provided with a compressed air supply system although this is of less importance since the bag formed after the operation of cutting and sealing, is removed from the apparatus 1 by the belt 3g with which the hag remains in contact. - 7 The upper movable assembly which has already been referred to -will now be described in detail.

The cutting and sealing bar 15 comprises an edge portion 15A serving simultaneously to cut and seal and carries an internal electrical heating resistance 15B· The bar 15 is suspended from the beam 13 by means of thin metal connecting members 36, of V-section.

The beam 13 comprises at its two ends pivot pins 37 which are pivoted in bearings rigid with a conventional control system, (not shown for the sake of clarity in the drawings) which enables the beam 13 to be intermittently raised and lowered.

The beam 13 has at one of its ends a bolt 14 mounted on an overhanging support 36, this bolt being capable of insertion into one or other of two openings 39 and 40 formed substantially at 90° with respect to one another in a member 41 (chain lines) in the form of an arc of a circle which is secured by any appropriate means to the movable assembly.

The bolt, .its support and the member 41 together form a locking arrangement 14 which enables the cutting and sealing bar 15 to be locked either in an active position when the bolt 14 engages the opening 39, in which position the cutting and sealing bar can continue its normal action of sealing on each raising and lowering movement Of the beam 13 or in an inactive position When the bolt 14 engages in the opening 40. In the latter position the cutting and sealing bar has no action on the films 5 end 6, while the beam 13 continues its raising and lowering movements.

In order to provide an improved apportionment of the - 8 41773 holding or clamping action on both web3 5 and 6 to be cut and welded, the upper holding and cooling bar3 16^ and 16g are in fact divided, as will appear from Figures 1 and 2 in to two groups: 16^ and 16g on the one hand, and on the other hand there is a symmetrical pair of which the upstream bar 16c only is apparent in these Figures, The assembly of four upper holding and cooling bars is suspended from the beam 13 by means of angled supports 42» adjustably secured to and apportioned along the two lateral faces of the said beam for example two to each bar. Each of the supports 42 is provided with a vertical guide rod 43 along which each corresponding bar 16^, 16g, 16θ can be displaced vertically against the action of a return spring 44 the force in which is adjustable, as will be described in detail hereinafter. It should be understood that the initial length of the rods is adjustable so that the bars can be exactly located with respect to the vertical plane of symmetry XX^ and with respect to the horizontal plane Τϊη of the films.

Each of the upper holding and cooling bars has the general form of an L in the horizontal limb of which a longitudinal passage 45 is provided in which refrigerant liquid can be circulated. To this end, the passages 45 thus provided in the four support bars are connected in series by; connecting hose's ·. ... such as 46 between the bars 16g and 16θ; hose 47 between the bar 16θ and its corresponding downstream bar and in addition an inlet hose 48 and an outlet hose 49 are provided for the refrigerant liquid.

The upper, upstream, holding and cooling bars 16β and I6c are provided with a compressed air supply system identical to that of the lower holding and cooling bar 17θ. This system includes air admission· - 9 41775 passages 26^ with orifices 27^ distributed along the lower face of the bars 16g and 16θ, these passages being divided ' at splitter boxes 30^, 31^. The latter are connected by pipes 34^ and 35^ to a two-way control valve 33^ itself supplied by a main pipe 32^. As in the preceding case, it is thus possible to control exactly the pressure and also the distribution of pressures provided at the outlet of the nozzles 28^.

With a view of providing visual control during the positioning and the control operations for the cutting'and sealing bar 15 and the upper holding and cooling bars 16^, 16β and lower holding and cooling bars 17^, 1?B it is to advantage that the various members referred to above should not have the same length. Thus, for example, the lower 'bars 17ft, Ι7β have a length greater by 10 mm. than the length of the bar T5 while the upper bars I6ft and 16^ have a length which is shorter by 10 mm. than that of the bar 15· There will now be described, with reference to Figures 4, 5» 6> 7 and 8 various phases in an operational cycle of the apparatus for cutting and sealing.

TiJhen the doubled film 5 is supplied by the feed rollers 2^, 2jj and drawn by belts 3g in the direction of the arrow Fq, the upper movable assembly is in the raised position shown in Figure 4. During this phase, the flow of air indicated diagrammatically by arrows Fg which is generated between the upper and lower faces of the doubled film 5» on the one hand, and the upper-.holding and cooling bars 16β s. and lower holding and cooling_.b-ars Τ7β on the other hand, ·; facilitates the supply of the sa.id film, and prevents the latte»:'froni sticking on the said bars. .

At' an appropriate instant corresponding to the length - 10 41775 of the bag to be cut and sealed, tbe upper movable assembly of sealing bar 15 and holding and cooling bars 16A,'16g is lowered in the direction of the arrow Fj by the action of the beam 13» the lower holding and cooling bars 17^, 17g remaining stationary.

It will immediately be apparent that because of: d. The spacing between the respective lower levels of cutting and’the sealing bar 15 and the holding and cooling bars 16^ and 16g; and 2. the adjustability of the return springs 44, the holding and cooling bars 16ft and 16g grip or hold the film 5 against the lower holding and cooling bars 17A and 17g and maintain the film in place, the.cutting and sealing bar 15 notyet being in contact with the film and the flow of air being cut-off.

The part of the film which is to be cut and sealed is not supported from directly below but tensioned between the upper and lower holding and cooling bars. The various parts of the device then occupy the relative positions illustrated in Figure 5.

From this instant, the holding and cooling bars 16A and 15g are pressed against the film 5 and the beam d3 continues to descend in the direction of the arrow Fj< The cutting and sealing bar T5 also continues its descending movement against the action of the return springs 44, projects below the lower planes of bars 16^, 16^ and then cuts and seals the film 5· The penetration of the sealing bar should be controlled with exactness as a function of the thickness of the film. Thus, for example, for a film thickness of 15 microns, the penetration of the sealing bar is about 0.5 Dim. .Similarly, the temperature of the sealing bar depends on the thickness of the film. Thus, for example, for a thickness of film of 15 microns, the temperature of the bar is about 600°C. Finally,the temperature of the holding and cooling bars - Id 41775 must be maintained at about 15°C. At the termination of the cutting/sealing 'phase, the various parts are to be formed in the relative positions shown in Figure 6.

Referring to Figure 7 which is a very large scale enlargement of the central part of the arrangement of Figure 6, it will be seen that, in fact, the film 5 is out at the instant when it makes initial contact with the tip of the part 15a of the cutting and sealing bar as is indicated in chain fine while the sealing takes place by progressive fusion of the two parts of the film up to the cooled surfaces of the upper holding and cooling bars 16^, Ιδθ, and'the lower holding and cooling bars 17ft, I7g. The dwell time of the part 15^ of the cutting and sealing bar in this position is determined by the opening angle of the part of the cam controlling the raising and lowering movement of the cutting and sealing bar.

Immediately after the beam 13 rises in the direction of the arrow F^ (Figures 6 to 8), the sealing bar 15 disennages’ from the film 5 while the latter is again held in place between the lower holding and cooling bars 17^ and 17β ahd the upper holding and cool.ing bars 16^ ahd 16β, the latter being subjected to the action of the return springs 44, The various parts -re then to be found in the relative position shown in Figure 8.

Finally, the assembly of the sealing bar and upper holding and cooling bars 16^ and 16g continues its upwards movement in the direction of the arrow F^ while the released film 5 resumes its displacement in the direction of the arrow F^ under the action of the belt 3g for the new bag 7 which is just about to be completed, and the feed rollers 2^ 2β for the film 5· The latter is released even more readily when the compressed air indicated by arrows Fg resumes its flow and the film becomes detached from the holding and cooling bars 16^, 16β and 17^, 17β.

The various parts are then to be found in the relative positions illustrated in Figure 8 and a fresh cycle of operation can then commence.

Claims (12)

1. Apparatus for cutting and sealing at least one thermoplastic film web to produce bags, said apparatus comprising a reciproeable cutting and sealing bar, means for bolding thermoplastic film web during the cutting and sealing operation, said holding means including a lower stationary assembly having two holding and cooling bars adjustably mounted on a beam extending transversely to the web feed direction, an upper, movable, assembly having a support beam carrying the cutting and sealing bar and resiliently carrying two holding and cooling bars arranged symmetrically with respect to the cutting and sealing bar, drive means fop reciprocating the upper assembly, a coolant circuit for maintaining the holding and cooling bars of the upper and lower assembly at temperatures appropriate to the requirements of the film to be sealed and means for detaching the film from the holding and cooling bars after the sealing and cutting operation by the cutting and sealing bar.

2. Apparatus according to claim 1, wherein the detaching means include a compressed air supply arrangement for supplying an air flow at least to contact surfaces of the holding and cooling bars disposed upstream of the cutting and sealing bar, the air cushion thus formed serving both to assist movement of the web and to prevent the web from sticking to the said contact faces,

3. Apparatus according to claim 1 or claim 2, wherein the holding and cooling bars of the lower assembly are secured adjustably to said transverse beam whereby the space separating the two bars of the lower assembly and also the position of the ι latter with respect to the vertical Plane of symmetry of the fixed assembly and of the movable assembly and the level of each of these bars with respect to the lower plane of movement of the film with respect to the cutting and welding bar can be adjusted.

4. * Apparatus according to any one of dims 1 to 3, wherein the upper movable assembly comprises as many sets of said holding and cooling bars as there are webs of film to be simultaneously treated, each of the said hars being suspended from the support beam by means of at least two lateral fixed supports on the upstream or downstream faces of the beam and are provided with guide rods along which the corresponding holding and cooling bar can slide vertically under the action of return springs the stiffness of which is adjustable, the useful lengths of the rods and the stiffness of the springs being so determined that when the movable assembly descends towards its working position the holding and cooling bars come into contact with the film and hold it in place against the lower holding and cooling bars under the action of the return springs, this action occurring before the operation of the cutting and sealing bar, which cutting and sealing bar is rigidly connected to the support beam,

5. , Apparatus according to claim 2 wherein the supply of compressed air to the contact surfaces of the upper and lower holding and cooling bars disposed upstream of the cutting and sealing bar, is provided by means of a compressed air source connected to inlet ducting itself connected through the intermediary of at least two distribution boxes with control valves in the inlet ducting and serving uniformly to distribute the compressed air to the said upper and lower holding and cooling bars and to supply internal passages of these bars.

6. Apparatus according to any one of the preceding claims wherein the support beam of the movable assembly is provided with a locking device which enables the assembly to be locked either in its active position for which the cutting and sealing bar cuts and seals at each reciprocal stroke of the support beam, or in an inactive position in which the cutting and sealing bar has no action on the film while the support beam continues to undergo its raising and lowering movement.

7. Method of cutting and sealing thermoplastic material films to manufacture of bags or similar articles on the apparatus according to claim 1, the method comprising the steps of feeding the film web between the movable and stationary assemblies over a length corresponding to that of one bag, lowering the movable assembly towards the stationary assembly so that initially only the upper holding and cooling bars come into contact with the film web to hold it in place, continuing to lower the support beam and the cutting and sealing bar, which projects below the lower level of the upper holding bars against the action of return springs and carry out its cutting and sealing action, retracting the said cutting and sealing bar to its inactive position between the upper holding and cooling bars which continue to hold tbe film, under the action of the return springs,then to cause whole of the upper movable assembly to return to its initial upper position, the upper bolding and cooling bars freeing the film of all constraint and allowing the detaching means to carry out the action of detaching the film from the holding and cooling bars and enabling a drive system to displace the film towards a-new cutting and sealing position..

8. Apparatus for cutting and sealing at least one thermoplastic flilm web to produce bags, . said apparatus comprising a reciprocable cutting and sealing bar, co-operating upper and lower bars for holding and cooling the film web:during each cutting and sealing operation and means for supplying compressed gas.to at least certain faces of the holding and cooling bars whereby to assist detaching and forward feed of tbe film after the completion of the cutting and sealing operation,

9. Apparatus for cutting and sealing at least one thermoplastic film web to form bags, said apparatus comprising a cutting and sealing bar, upper and lower bars for holding and cooling the web when the web is being cut and sealed by the cutting and sealing bar,means to supply to at least certain faces of the holding and cooling bars compressed gas to assist in detachment of the film after completion of cutting and sealing and a cooling circuit for circulating coolant through the holding and cooling bars.

10. A method of producing a succession of bags from a thermoplastic film web comprising the steps of bringing the web to an operational station, holding and cooling the web upstream and downstream of a cutting and sealing line, sealing and cutting the web at said line and releasing the web and the bag produced subsequently to the cutting and sealing operation with the aid of a flow of compressed gas at the holding zone UDStream of the cutting and sealing line.

11. , Apparatus for cutting and sealing a thermoplastic film web to produce bags, substantially as hereinbefore described with reference to the accompanying drawings.

12. A method of cutting and sealing a thermoplastic film web to produce bags, substantially as hereinbefore described, with reference to the accompanying drawings.