GB2067462A - Welding filled plastics bags - Google Patents

Abstract

The apparatus for weld-sealing the open ends of filled bags comprises a plurality of boxes (2, 3, 4, 5), which are mounted on a rotatable column (1) with a predetermined angular spacing and adapted to hold respective bags in an upright position. A bag-stretching and welding unit (9) comprising bag-stretching fingers (10, 10a, 10b) and welding jaws (13) is disposed over each of the boxes and secured to the column, the latter being rotatable by drive means in steps corresponding to the angular spacing of the boxes. The bag in each box is welded as the box is moved from a loading station (A) to an unloading station (D). The welding jaws are stationary relative to the bag during the welding operation. A loader (16) may be provided, which has a delivery end at the loading station. An unloading conveyor (17) may be provided, which has a receiving end at the unloading station. A feed hopper (15) may be provided adjacent to the receiving end of the loader. <IMAGE>

Description

SPECIFICATION Apparatus for weld-sealing filled bags of plastic material This invention relates to apparatus for weldsealing filled bags of plastic material, particularly such bags filled with bulk material, comprising welding jaws arranged to be disposed on opposite sides of the top ends of the bags of plastic material.

In known apparatus for weld-sealing the openings of filled bags of plastic material, the bags are conveyed by a special conveyor and as the bags are thus conveyed the edges of the open ends of the bags are heat-sealed and cooled by means of heating jaws and cooling jaws, respectively, which are spaced apart along said conveyor and disposed on opposite sides thereof.

As the bags are continuously moved by the belt or chain conveyor, the welding operation must be performed in an instant in theory and in an extremely shorttime in practice and for this reason must be carried out at a very high temperature. Besides, apparatus of the kind described, which are shown, e.g., in German Specification 1,810,986; U.S. Patent Specification 3,150,478; German Patent Specification 2,323,247 and German Patent Publication 1,209,935, must be provided with means for moving the bags exactly in a horizontal direction in order that a satisfactory seam weld can be obtained. As the bags may be filled with certain materials which preclude the use of high welding temperatures, such high welding temperatures are generally undesirable.Another disadvantage of the known apparatus resides in their large space requirement, particularly when they succeed a plurality ofjuxtaposed bagfilling stations. The chains or belts required to move the bags and the special means for cooling the seam welds add to the cost of the apparatus and the latter are subjected to considerable wear. As a result, the costs involved in sealing the bags are unduly increased.

It is an object of the invention to provide apparatus of the kind described hereinbefore which is capable of weld-sealing filled bags at a high rate and with a relatively low heating power and within a predetermined welding time during which the bag is stationary.

Another object of the invention is to reduce the overall expenditure, to reduce the space required for the installation of the apparatus, and to improve the overall economy.

In apparatus of the type described hereinbefore that object is accomplished according to the invention in that a plurality of boxes are provided, which have a predetermined angular spacing and are nonrotatably connected to and spaced equal distances apart from a rotatably mounted column, which is adapted to be driven, said boxes are adapted to receive and hold respective filled bags in an upright position, the welding means comprise a number of welding units, which are connected to the column and disposed over respective boxes, each of said welding units comprises two welding jaws, which are pivotally movable relative to each other between a welding position and an inoperative position, and bag-stretching means comprising two or more pairs of bag-stretching fingers, which are movable in parallel to the welding jaws, and said column is adapted to be driven to rotate in steps corresponding to said angular spacing.

This invention comprises welding jaws arranged to be disposed on opposite sides of the top ends of the bags of plastics material, characterised in that a plurality od boxes are provided, which have a predetermined angular spacing and are non-rotatably connected to and spaced equal distances apart from a rotatably mounted column, which is adapted to be driven, said boxes being adapted to receive and hold respective filled bags in an upright position, the welding means comprising a number of welding units, which are connected to the column and disposed over respective boxes, each of said welding units comprising two welding jaws, which are pivotally movable relative to each other between a welding position and an inoperative position, and bagstretching means comprising two or more pairs of bag-stretching fingers, which are movable in parallel to the welding jaws, and said column being adapted to be driven to rotate in steps corresponding to said angular spacing.

In a preferred embodiment the rotatably mounted column is rigidly connected to four boxes, which are spaced 90 degrees apart and have a substantially horizontal bottom, a loader extends to a standstill station for the boxes, and an unloading conveyor extends from another standstill station for the boxes, which receives each box before the first-mentioned station and is spaced 90" from the latter. The welding and bag-stretching unit disposed over each box is preferably adjustable in vertical and horizontal planes for adaptation to the height and width of the bag held in the associated box. Each box may comprise of a frame having at its bottom a roller conveyor and having lateral guides disposed above and on opposite sides of said roller conveyor.Such boxes are light in weight and while having a simple structure ensure that each filled bag will be held upright and with the open end in the correct position and that the loading of the still open bag into the box and the unloading of the sealed bags from the box can be conveniently performed. In apparatus according to the invention, the opening movement of the welding jaws to their inoperative position may be initiated by electromechanical means in response to the stopping ofthe column afterthe completion of the welding operation. This can be accomplished without need for a substantial expenditure. Adjacent to the receiving end of the loader, a feed hopper may bs provided, which has a discharge opening disposed over the feed path defined by the loader.In this arrnngementthe distance between the bagfilling and bag-sealing apparatus is minimized and so is the space requirement.

The invention will now be explained more fully and by way of example with reference to the accompanying drawing, in which Figure 1 is a side elevation showing apparatus according to the invention and Figure 2 is a plan view from above showing the apparatus.

The apparatus shown on the drawings comprises a vertical column 1, which rises from the center of a square platform. The platform is suitably square because four boxes 2,3,4,5 are provided, which are fixed to the platform near respective corners of the latter. The longitudinal centre plane of each box is parallel to one edge of the platform. As a result, the boxes have a uniform angularspacing and are equally spaced apart from the column and from its axis of rotation. Each box comprises a frame Sand is adapted to hold an upright bag. The bottom ofeach box consists of or is covered by a roller conveyor 8.

Each box is provided on opposite sides of the ccn- veyor 8 with lateral guides 7. The rollers of the rollerconveyor 8 of each box are adapted to be driven in unison in the same direction of rotation so that a bag can be advanced in the box to an end position and away from said end position. The apparatus is provided with welding means and with bag-stretching means for stretching those edge portions of the bag which define the open end of the bag and are to be welded by the welding means. These welding and bag-stretching means consist of four units 9, which are non-rotatably connected to the column 1 and disposed above respective boxes.Each unit comprises a pair of welding jaws 13 and bag-stretching fingers 1D. The two welding jaws are parallel to the direction in which a filled bag is moved into and out of the box, i.e., in the present case they extend at right angles to the rollers of the bottom roller conveyor, and are secured to pivoted arms. The pivoted arms are parallel and secured to respective ends of the jaws and are pivoted to the box movable relative to each other between an operative position, in which they engage each other, and an inoperative position, in which they are spaced from each other.

The jaws are parallel to each other in all positions.

The number of bag-stretching fingers depends on the type of plastics bags to be sealed. Two pairs of bag-stretching fingers are provided where simple cushion-shaped bags are to be closed. Two pairs of bag-stretching fingers 10a and an additional pair of bag-stretching fingers lOb are provided where gusseted bags (box bags) are to be sealed. The bagstretching fingers are movable parallel to the welding jaws 13 an such a mannerthatthe pairs of outer fingers 10a are moved away from each other and the two inner fingers lOb are moved toward each other.

In each unit 9, the welding jaws and bag-stretching fingers are moved by common drive means, such as a pneumatic cylinder 11, which is centrally mounted on top of the frame of the unit. Bell crank levers 12 are provided which are pivoted attheirjunction.

Each bell crank lever 12 is connected at one end to one pair of bag-stretching fingers 1 ova orto one bag stretching finger lOb and is provided at its other end with a cam slot, through which a pin 1 lea extends that is fixed to the piston rod of the penumeatic cylinder 11. By means of the bag-stretching fingers, the edges of the open end of the bag are stretched to extend parallel to the welding jaws 13. The two arms which jointly carry a welding jaw have angled ends, in which opposite ends of a pressure roller 14 are pivotally mounted.As the jaws approach their operative position, the roller 14 engages the filed bag and is thus pivotally moved from a position remote from the welding jaw against the action of a spring to a position nearer to the jaw and thus squeezes air out of the bag and moves the previously stretched edges af the open end of the bag into contact with each other The edges of the open end of the bag are then held in contact with each other until they are engaged by the welding jaws. From the time in which the bag has reached the proper position in the box, which is defined by adjustable end stops mounted atthe front end of the box, the bag is stationary also relative to the welding and spreading unit. During the weld-sealing of the open end of the bag, the welding jaws are stationary relative to said open end.Forthis reason the welding time need not be extremely short so that welding can be effected at lower temperatures. The four boxes 2,3,4,5 are secured to the platform at respective corners thereof. When the boxes are provided with bottom roller conveyors, each bag is moved into and out of the box at right angles to the rollers of said conveyor and parallel to one edge of the platform. The center planes of the boxes are tangential to a cylindrical surface of revolution, which is coaxial with the column, along respective generatrices, which are spaced 90" apart.

A stepping mechanism drives the column in steps corresponding to the angular spacing of adjacent boxes, in the present case in steps of 9D9 and holds the column at a standstill for a selected time between successive steps. In this case there are four standstill stations, A, B, C and D, in which the boxes are stationary for a certain time. A loader 16 consisting, e.g., of a roller conveyor, has a delivery end at the standstill station A. An unloader 17, which may also consist of a roller conveyor, has a receiving end at the station D, which is spaced from the station A oppositely to the direction of rotation indicated by an arrow X.

The time each boxes is at each station must be sufficient for loading the box in station A with a filled, open plastics bag and for removing the sealed plastics bag from station D. The time required forthe movement of a box from station Ato station D must be sufficient for the performance of the welding operation.

As is apparent from Figure 1, a feed hopper 15 may be mounted near thus receiving end of the loader 16 beside the latter. The discharge opening of said feed hopper is disposed overthefeed path defined by the loader, e.g., ove; the center line of such path.

The feed hopper consUtutes part of a filling plant, which is installed near the apparatus according to the invention.

The sequence of tne operations performed by the several components of the apparatus and also the welding operation may be automatically controlled in a simple manner. Specifically, the opening of the welding jaws may be controlled to be initiated after the welding operation has been completed and the box has stopped at the unloading station D. This control may be effected by electromechanical means. When a filled plastics bag which is still open has been moved by the loader 16 so that one of the boxes 2, 3, 4, 5 is in station A, the bag-stretching fingers 10a, 10b of the welding and bag-stretching unit 9 associated with said box are operated to stretch the edges of the open end of the bag.As the revolution of the box is continued to move the box out of the station A, the welding jaws 13 approach each otherto grip the flat walls of the bag, and the welding operation is initiated. Because the jaws are stationary relative to the bag during the welding operation and sufficient time is available before the bag arrives in station D, the welding operation may be carried out at a relatively low temperature and there is no need for special cooling means, cooling jaws or the like. The welding operation is completed before the arrival in station D, in which the bag which has been sealed and is ready for transportation for removal by the unloading conveyor 17.

The boxes may be provided in a predetermined number, which depends on the rate at which the plastics bags are to be sealed.

As has been mentioned hereinbefore, the use of the apparatus according to the invention results in improved seam welds because welding is effected at a lower temperature and for a longer time. As a result, the bags are safely sealed in an operation which is reliable and does not involve any additional expenditure. Furthermore, less space is required than for conventional plants. This is particularly significant when the open bags come from a plurality of filling stations, e.g., from ten filling stations. The space saving may correspond to a shortening of the paths of travel by 20 meters, for example.

Claims (7)

1. Apparatus for weld-sealing filled bags of plastics material, particularly such bags filled with bulk material, comprising welding jaws arranged to be disposed on opposite sides of the top ends of the bags of plastics material, characterised in that a plurality of boxes are provided, which have a predetermined angular spacing and are non-rotatably connected to and spaced equal distances apart from a rotatably mounted column, which is adapted to be driven, said boxes being adapted to receive and hold respective filled bags in an upright position, the welding means comprising a number of welding units, which are connected to the column and disposed over respective boxes, each of said welding units comprising two welding jaws, which are pivotally movable relative to each other between a welding position and an inoperative position, and bagstretching means comprising hmo or more pairs of bag-stretching fingers, which are movable in parallel to the welding jaws, and said column being adapted to be driven to rotate in steps corresponding to said angular spacing.

2. Apparatus according to claim 1, characterised in that the rotatably mounted column is rigidly connected to four boxes, which are spaced 90 degrees apart and have a substantially horizontal bottom, a loader extends to a standstill station for the boxes, and an unloading conveyor extends from another standstill station forthe boxes, to receive each box from the first-mentioned station and is spaced 90" from the latter.

3. Apparatus according to claim 1 or 2, characterised in that the welding and bag-stretching unit disposed over each box is adjustable in vertical and horizontal planes for adaptation to the height and width of the bag held in the associated box.

4. Apparatus according to any of claims 1 to 3, characterised in that each box comprises a frame having at its bottom a roller conveyor and having lateral guides disposed above and on opposite sides of said roller conveyor.

5. Apparatus according to any of claims 1 to 4, characterised in that the opening of the welding jaws and their movement to their inoperative position is initiated by electromechanical means in response to the stopping of the column after the termination of the welding operation.

6. Apparatus according to any of claims 1 to 5, characterised in that a feed hopper is provided adjacent to the receiving end of the loader and has a discharge opening disposed over the feed path defined by the loader.

7. Apparatus for weld sealing filled bags of plastics materials substantially as described with reference to the accompanying drawings.