A device for the separation of bags or finished items, pre-cut and formed by a thermal or high frequency welding process, from one or more continuous strips of heat-sealable plastic film

Abstract: The device falls within the art field of equipment for processing heat-sealable plastic film in strip format, typically in the manufacture of bags, and serves to bring about separation of the pre-cut and bonded bags (13) from one or more continuous strips (2) of material by tearing along their pre-cut outline; the separating action is automatic, with the bags detaching and passing onto a runout conveyor (12) and the offcut (15) directed away toward a disposal point by pinch rollers (14).

Description: The present invention relates to a device for separating bags or finished items generally, pre-cut and formed by a thermal or high frequency welding process, from one or more continuous strips of heat-sealable plastic film. In continuous processes for the manufacture of bags or comparable items utilizing heat-sealable plastic material, the question arises ultimately of how best to separate the single bags or items from the remainder of the continuous strip material as both advance along a conveyor. The finished bags or items are pre-cut, generally around their entire peripheral outline, and the conventional method of separation is simply for an operator to apply pressure to the pre-cut outline (a weakened area along which the plastic material can be torn easily and precisely) and detach the bag or item forcibly by hand. The prior art also embraces automatic systems for bringing about the separation in question, using intricate gripper mechanisms by means of which to lay hold on the edge of the bags advancing along the conveyor and detach them forcibly from the remainder of the continuous strips of film. Manual methods of separation betray a number of drawbacks connected with high costs and low hourly output rates. The automatic system mentioned is markedly complex in construction, and lengthy set-up and adjustment procedures are involved when adapting the grippers to the size and shape of different end-products. US-A-4,096,981 shows an apparatus according to the preamble of claim 1, for use in stripping a continuous web from at least along a portion of the marginal edge of a body comprising deflecting means pivotally connected to supporting means for assisting in directing the leading edge of the advanced continuous web vertically so as to facilitate a stripping thereof. The apparatus also comprises stripping means including a pair of cooperating rollers for grabbing therebetween the vertically deflected continuous web and stripping it from the body. Said apparatus does not completely solve the mentioned drawbacks, it is still rather complex and effective only for obtaining finished items of rigid type from a continuous web. The object of the present invention is to overcome the drawbacks mentioned above, and in particular to enable the separation of pre-cut bags or comparable items from continuous plastic film material using an automatic device that is simple in construction and easily adjusted, and thus affords a saving in capital outlay and a reduction in the set-up time required for a given end-product. A further object of the invention is to provide a device able substantially to match the output rate of a supply machine, in particular thermal or high frequency welding equipment, and capable therefore of being integrated into an existing line without causing any fall in productivity. The stated objects are fully realized in a device according to claim 1 by means of which to separate bags or other finished items, pre-cut and formed by a thermal or high frequency welding process, from one or more continuous strips of heat-sealable plastic film. The dependent claims relate to embodiments of the invention according to claim 1. The invention will now be described in detail, by way of example, with the aid of the accompanying sheet of drawings, in which: fig 1 illustrates the device in perspective; fig 2 is a further perspective illustrating means by which the bags are separated from the continuous film of material. With reference to the drawings, 1 denotes a table consisting in a plurality of wires 3 upon and along which to support and feed at least one continuous strip of heat-sealable material denoted 2. Such material is utilized in the production of bags or other comparable finished items fashioned by thermal or high frequency welding executed along pre-cut guide lines coinciding with the peripheral outline of the item. In the description of a preferred embodiment that follows by way of example, reference is made to the continuous production of bags. 4 denotes a pneumatic cylinder, associated rigidly with the fixed frame 6 of the device by way of a bracket 7 and disposed perpendicular to the table, of which the rod 5 impinges repeatedly on the strip of material 2 beneath at a point coinciding with a peripheral corner area of each successive bag 13, in such a way as to effect a partial separation of the bag from the strip along a pre-cut line that coincides with its own peripheral outline. The cylinder 4 and the relative rod 5 constitute partial separation means by which to restrain the continuous strip of material momentarily as it passes along the table 1 and thus bring about a partial separation of each finished bag 13. Thereafter, the strip is fed through a gap between two rollers 11 and 10 disposed substantially at 45° to the path followed by the strip along the table. More exactly, the rollers are positioned in such a manner that the pneumatic cylinder 4, or whatever partial separation means, will be encompassed within the 45° angle described by the axes of the rollers and the axis of the path followed by the strip. The first roller 11 encountered revolves freely, whereas the second roller 10 is live, power driven by means not shown in the drawings, and serves to transmit motion to a looped conveyor belt 12 along which the bags run out. 9 denotes a pressure wheel mounted to a relative bracket 21 and adjustable thereon for position, by means of which to press the material 2 directly against the rollers 11 and 10 at a point coinciding with the outermost edge of the strip on the side nearest the pneumatic cylinder 4, and thus favour a complete separation of the finished bags 13. The rollers 11 and 10 serve to divert the path of the strip or strips through 90° in a plane parallel to the table 1 and indeed substantially coinciding therewith, given that the intervening distance is equal to no more than the diameter of the rollers. Each bag 13 separated from the stip 2 passes under a second pressure wheel 20 and along the conveyor belt 12 to the runout. The film material from which the finished bags are separated, now reduced to one or more offcuts 15, passes from between the two rollers 11 and 10 and is drawn clear by a pair of pinch rollers 14, one of which power driven. The pinch rollers 14, thus constituting distancing means by which to distance the offcuts 15 from the device, are disposed with axes parallel to the direction followed by the strip 2 along the table 1. 18 denotes a bevel gear keyed to the shaft 19 of one of the pinch rollers 14 and in mesh with a further bevel gear 17 keyed to a drive shaft 16 disposed perpendicular to the roller shaft 19; the resulting bevel gear pair 17 and 18, arranged with axes at right angles, thus constitutes a mechanical coupling between the drive shaft 16 and the pinch rollers 14. 8 denotes a chain looped around a sprocket (not illustrated) keyed to one end of the drive shaft 16 and set in motion by means not illustrated in the drawings. The means in question will be one and the same as those by which rotation is transmitted via the live angled roller 10 to the conveyor belt 12. The angled rollers 11 and 10, pressure wheels 9 and 20 and pinch rollers 14 thus constitute separation means for completing the separation of the finished bags from the remainder, termed offcuts, of the continuous strips of film material 2 and directing them onto a conveyor belt for collection at the runout of the device, and for distancing waste or offcut film 15 from the device for disposal. In the event of a change in the size or shape of bag to be separated from the continuous strip, it suffices to adjust the position of the pneumatic cylinder 4 and the first pressure wheel 9 on their respective brackets 7 and 21, in such a way as will adapt the device to the new dimensions.

Claims: Device for separating bags or other finished items (13) from one or more continuous strips (2) of heat sealable plastic film, the finished items (13) being formed by thermal or high frequency welding of the one or more continuous strips (2), the continuous strips (2) being pre-cut along the periphery of the finished items, the device comprising separation means for completing the separation of the finished items (13) from the remainder, termed offcuts, of the continuous strips, the separation means comprising rollers with their axes in a plane parallel to the plane in which the one or more continuous strips (2) are advanced, the separation means being capable of diverting the path of the offcuts while collecting the strip of offcuts and transferring the finished items (13) to a conveyor belt for collection at a runout of the device, characterized in that: the device comprises means for advancing the one or more continuous strips (2) along a table (1) as well as partial separation means (4, 5) for pressing in the peripheral corner area of each finished item (13) comprised in the advancing one or more continuous strips (2) in such a way as to bring about a partial separation of the item from the film or films along a pre-cut outline; the separation means (9, 10, 11, 20) are arranged downstream of the partial separation means (4, 5), the roller axes describing an angle of 45 degrees with the feed direction of the one or more continuous strips (2), the angle encompassing the partial separation means (4, 5), the separation means (9, 10, 11, 20) being capable of diverting the path of the offcuts through 90 degrees substantially within the plane of the roller axes; the device further comprises distancing means to distance the offcuts (15) from the device following separation. A device as in claim 1, wherein the partial separation means consist of a pneumatic cylinder (4) of which the rod (5) extends perpendicular to the table (1) in such a way as to impinge on the strip material from above at a point coinciding with one peripheral corner area of each successive finished item (13) and thus bring about partial separation of the item from the continuous film material along the pre-cut outline. A device according to any of the preceding claims, wherein one of the angled rollers of the separation means is a power driven roller (10) driving the runout conveyor belt (12), the continuous strips being fed in between of the power driven roller and the other angled roller, and wherein separation means for completing the separation of the finished items (13) comprise: a first wheel (9) by which pressure is applied to the strip material along the outermost edge nearest the partial separation means (4) in such a way as to favour the passage of the material between the two angled rollers (11, 10) and bring about a complete and automatic separation alone the 45° axis, whereupon finished items (13) are directed onto the runout conveyor belt (12) and under a second pressure wheel (20), and offcuts (15) are directed toward the distancing means. A device according to claim 1 or 3, wherein the distancing means comprise a pair of rollers (14), one of which power driven, breasted in rotation with one another and disposed with axes parallel to the path followed by the strip material along the table (1), between which the offcut material is pinched and directed toward a disposal location. A device according to claim 4, comprising drive means by which power is transmitted both to the runout conveyor belt (12), by way of the corresponding power driven angled roller (10), and to the pinch rollers (14) by way of a mechanical driveline consisting in a chain (8), a drive shaft (16) set in rotation by a sprocket in mesh with the chain, and a bevel gear pair of which one member (17) is keyed to the drive shaft (16) and the remaining member (18) keyed to a shaft (19) disposed at right angles to the drive shaft (16) and supporting one of the pinch rollers (14).

Inventors: OLLARI ERMES, OLLARI FRANCESCO, OLLARI, ERMES, OLLARI, FRANCESCO
Applicants: GENERATORI ELETTRONICI ALTA FR, GENERATORI ELETTRONICI ALTA FREQUENZA G.E.A.F. S.R.L.
Application year: 1991
Main classification: B26D7
IPC codes: B26D7