Feeding unit for plastic material or the like in a welding machine

Abstract

 A feeding unit for plastic material or the like in a welding machine, in particular adapted to promote a high-speed operation, of the type comprising a pair of upper (12) and lower (13) feeding rollers, superimposed to one another and provided with transversal slots or grooves (14, 15) that are staggered between the upper roller (12) and the lower roller (13), there being provided a blower unit above and below a plastic feeding material (11), wherein the blower unit comprises air feeding upper (16) and lower (17) nozzles, exiting from a respective header (18, 19), arranged downstream of said upper roller (12) and lower roller (13) and adapted to favour the flat laying of the fed material (11) passing into the rollers (12, 13). In particular, upstream of the rollers (12, 13) there are provided transversal supports (20, 21) for guiding lattens (22, 23) that insert into the slots (14, 15).

Description

[0001] The present invention relates to a feeding unit for plastic material or the like in a welding machine, in particular adapted to promote a high-speed operation.

[0002] In the machines for realising welded bags, both at a single end called "open-mouth bags" and at both ends, obtained by tubular plastic material or the like, the welding operation has increasingly quickened.

[0003] In particular, the stacked arrangement of bags directly in output from the transversal welding bars on a support provided and not with needles, has become widespread.

[0004] For the purpose of promoting the high operating speeds of the current welding machines, the bags in output from the bars are made to advance also with the cooperation of air blows exiting from small tubes suitably connected to headers, and fed with air at each stroke between the welding bars.

[0005] Such air feeding, for high speeds, that is, for a high number of strokes, implies a quick feeding and an equally quick interruption of the feeding air so as to not impair the following stacking operation.

[0006] Air headers are arranged upstream of the feeding cylinders of the feeding unit, and they extend between the recesses or the transversal grooves obtained on a rubber layer arranged on the surface of the feeding cylinders.

[0007] The amount of air present in the header and in the small tubes extending from upstream to downstream of the cylinders has a certain inertia to interrupt, due to the time needed for all the air present inside them to exit from the tubes and from the header.

[0008] Thus, due to the residual fed air, there is a troubling action on the welded bags passing between the cylinders and exiting to stack on the bar carrying the needles.

[0009] Moreover, the arrangement of small tubes into the feeding unit roller slots is not always easy, and it is necessary to individually adapt them in the respective slots, in case the same are not perfectly aligned with the same slots.

[0010] Moreover, the inertias due to the body of the single roller must be considered, which, even though it carries an inside tubular core element, exhibits a certain weight due to the quantity of the rubber thickness with which it is coated.

[0011] Both these problems cause several disadvantages for the user of the welding machine, and they do not allow increasing the production speed of the same.

[0012] Thus, a purpose of the present invention is that of determining a solution that, although solving the disadvantages mentioned above, should allow having as simple and fast a welding machine as possible.

[0013] Another purpose is that of realising a feeding unit for plastic material or the like which, although allowing an increase of the speed, should prevent a complex construction, if possible, minimising the masses and the moving elements.

[0014] Another purpose is that of minimising any necessary regulation, while having at the same time a simple assembly with a low production cost.

[0015] These and other purposes according to the present invention are achieved by realising a feeding unit for plastic material or the like, as illustrated in claim 1.

[0016] Further features are illustrated in the depending claims.

[0017] The functional and structural features and the advantages of a unit according to the invention shall appear more clearly from the description of an exemplificative and non-limiting embodiment made with reference to the attached schematic drawing.

[0018] In fact, the drawing schematically shows a side elevation section of a unit according to the invention, applied to a welding machine for producing welded bags in a welding position. It must be noted that in the drawing there is indicated with a solid line and spread a bag passing into the feeding unit of the present invention.

[0019] With reference to the drawing, there is shown a possible embodiment of a portion of a welding machine into which a tubular material 11, in a flattened shape, is fed, adapted for manufacturing small bags, bags and the like.

[0020] The structure of the welding machine is not important for the purposes of the present invention, since the new feeding unit is manufactured in such a way as to be applied to any machine; it can even be applied to an existing machine.

[0021] The welding machine in its feeding unit comprises a pair of upper 12 and lower 13 feeding rollers, superimposed to one another and provided - in a surface rubber layer - with transversal slots or grooves 14 and 15. Slots 14 and 15 are staggered between the upper roller 12 and the lower roller 13.

[0022] According to the present invention, the feeding rollers 12 and 13 are associated to a downstream blower unit that is above and below a plastic feeding material 11.

[0023] Such blower unit comprises air feeding upper 16 and lower 17 nozzles exiting from a respective header 18 and 19, adapted to promote the flat laying of the fed material 11, passing into rollers 12 and 13.

[0024] Upstream of rollers 12 and 13 there are provided upper 20 and lower 21 transversal supports for guiding lattens 22 and 23 that insert into slots 14 and 15, keeping the fed material 11 guided.

[0025] Since lattens 22 and 23 are flat, they also allow realising very small slots. It is thus possible to increase the diameter of a hollow tubular body 24 and 25 present inside the upper roller 12 and the lower roller 13. The maximum size of the hollow tubular bodies 24 and 25 of rollers 12 and 13 thus is a little less than that of the diameter of the same rollers 12, 13.

[0026] Thus, slots 14, 15 have a reduced depth size since the guiding lattens 22, 23 are almost flat.

[0027] By doing so, it is possible to obtain a decrease of the rubber coating thickness of the rollers and a decrease of their mass and weight.

[0028] A feeding unit of a welding machine is thus obtained, exhibiting an extremely simplified structure that solves the problems of the prior art units.

[0029] The air feeding upper 16 and lower 17 nozzles, exiting from a respective header 18 and 19, do not need any individual regulation since they do not depend on the size of slots 14 and 15 of rollers 12 and 13. In fact, it is possible to carry out a single regulation of their orientation with respect to the flattened tubular material 11 guided by them.

[0030] Moreover, the amount of necessary air is extremely reduced since nozzles 16 and 17 directly exit from headers 18 and 19. The control is thus quick, and the entrainment effect due to the quantity of residual air that continues to exit even after the blow has stopped is limited.

[0031] The increase of the diameter of the hollow tubular bodies 24 and 25 present inside the upper roller 12 and the lower roller 13 causes a considerable decrease of the masses, with a fall of the rotating inertias and a quickening of the operations. It is thus possible to use motors having less power, thus obtaining an energy saving.

[0032] The production costs of the rollers decrease since there is a significant reduction of the rubber layer, which is expensive, both for the same material and for the costs of its application to the inside tubular body.

[0033] Thanks to this simple provision, the problem caused by the prior art feeding units in welding lines of successive bags welded at a high speed is solved.

[0034] It is this evident that, according to the present invention, a new and original technical solution to the above problem in welding lines of successive bags has been found in a simple and convenient manner.

Claims

1. Feeding unit for plastic material or the like in a welding machine, in particular adapted to promote a high-speed operation, of the type comprising a pair of upper (12) and lower (13) feeding rollers, superimposed to one another and provided with transversal slots or grooves (14, 15), said slots (14, 15) are staggered between said upper roller (12) and said lower roller (13), there being provided a blower unit above and below a plastic feeding material (11), characterised in that said blower unit comprises air feeding upper (16) and lower (17) nozzles, exiting from a respective header (18, 19), arranged downstream of said upper roller (12) and lower roller (13) and adapted to promote the flat laying of said fed material (11) passing into said rollers (12, 13).

2. Feeding unit according to claim 1, characterised in that upstream of said rollers (12, 13) there are provided transversal supports (20, 21) for guiding lattens (22, 23) that insert into said slots (14, 15).

3. Feeding unit according to claim 1, characterised in that said slots (14, 15) exhibit a reduced depth size, said guiding lattens (22, 23) being flat.

4. Feeding unit according to claim 1, characterised in that said rollers (12, 13) comprise an inside hollow tubular body (24, 25) whose maximum size is a little less than that of the diameter of said rollers (12, 13) .

Drawing