Sack Making Equipment

The present invention relates to sack or container making equipment and more particularly, but not exclusively, to a machine for making sewn-end multi-walled sacks.

Conventionally multi-walled sewn-end paper sacks are produced by passing a number of plies of paper, for example, from 2 to 6 plies, through a tubing machine, which folds the paper to form a composite or multi-walled tube having a number of concentric tubes corresponding to the number of plies used. Each ply of paper is glued along the longitudinal seams prior to folding in the tubing machine and the plies of paper are folded in such a manner to substantially prevent adjacent tubes from adhering to each other. The composite tube is then cut into lengths.

Further, there are generally two basic types of multi-walled tube produced on a tubing machine, namely a flat type and a gussetted type. The gussetted type is provided with a gusset along each longitudinal side of the tube and this type of tube is more generally used in the manufacture of sewn-end sacks, the gusset forming a box type end when open for filling. Further a lesser amount of sewing is required, due to the narrower width of the tube.

The conventional tubing machine discharges a continuous supply of multi-walled tube lengths which are stacked in bundles by hand or machine stackers. The bundles are then placed by hand onto a pallet which is subsequently moved to a sewing machine into which the tubes are individually fed by hand. One end of each tube is then sealed by sewing, usually over a crepe paper tape.

There are a number of variations in means used to transfer tubes from the tubing machine to the sewing machines but, as the output from the tubing machine is substantially greater than the maximum capacity of the sewing machines, the tubes still have to be hand fed into the sewing machines.

Further, automatic feeding of gussetted sacks into the sewing machines by conventional means is an extremely difficult and costly operation. In one known sack or bag making machine, the cut tubes are discharged in an axial direction from the tubing machine and are then oriented through 90 degrees such that an open end of each tube is aligned in the direction of discharge from the tubing machine. The tubes, thus aligned, may then pass through a tube-end sealing-machine. With such a sack making machine, it is difficult and extremely costly to adjust the machine to suit size changes in sack widths and lengths. It should be noted that such conventional sack or bag making machines have not been adapted for use with a sewing machine to seal the bag ends.

It is an object of the present invention to provide a machine substantially free of the above disadvantages.

It is another object of the present invention to provide means of automatically transferring tubes discharged from a tubing machine to the sewing machines and thereby eliminating work in progress and considerably reducing labour costs.

Accordingly the present invention in one general form is a transfer machine comprising a receiving station for receiving a succession of tube lengths axially discharged from a tubing machine, a plurality of tube-end sealing-machine feeding stations, and means directing the tube lengths to said plurality of feeding stations.

The present invention in another general form is a transfer machine comprising a receiving station for receiving a succession of tube lengths, a plurality of sewing machine feeding stations, means directing the tube lengths in succession to said plurality of sewing machine feeding stations, each said feeding station including means permitting alignment of an end of each tube length with respect to the sewing machine and means permitting the continuous feeding fo the tube lengths into the sewing machine for sewing.

The present invention in yet another general form is a tube-end sealing-machine comprising a sealing head, a conveyor having a receiving end and a discharge end, the sealing head located adjacent said discharge end, a plurality of abutment means arranged at predetermined intervals along the length of the conveyor and movable from said receiving end to said discharge end, whereby, upon receipt at said receiving end of a succession of tube lengths, the tubular axis of which is in transverse alignment with respect to said conveyor, an adjacent one of said abutment means abuts a trailing side of each successive tube length and urges the tube length towards said discharge end of the conveyor, and bias means causing each tube length to move forward with respect to said adjacent one of said abutment means and abut at its leading side against a forward and adjacent one of said abutment means.

The present invention in a further general form is a bag making machine comprising a tubing machine which forms a tube of suitable material, cuts the formed tube into tube lengths and axially discharges the tube lengths therefrom, a plurality of tube-end sealing-machines each having in association therewith a tube feed conveyor, which, upon receipt of a succession of tube lengths each having their tubular axis in transverse alignment with respect to the feed direction, feeds an open end of each tube length to the tube-end sealing-machine, means receiving the axially aligned tube lengths discharged from said tubing machine and means directing and feeding successive tube lengths in a cyclic predetermined sequence to a receiving end of the tube feed conveyor, the feed direction of which is transverse to that of said means directing and feeding tube lengths to said receiving end, whereby axially discharged tube lengths having a leading and trailing open end are traversed sideways to provide a leading and trailing closed side edge.

In a preferred form, the abovementioned transfer machine allows multi-walled tube lengths to be transferred directly from the tubing machine to the sewing machines without manual handling irrespective of the tube length discharge rate from the tubing machine and without orientating the tube lengths following receipt thereof from the tubing machine. In the preferred form of the invention, the tube lengths initially flow in a direction substantially parallel to the longitudinal axis of the tube to their respective sewing machine feeding stations. The tube lengths are then each stopped for an instant at the feed station and redirected in a sideways direction. Preferably the sewing machines and transfer machine drives are directly coupled with the tubing machine in order to simplify timing and changes of speed of the various machines and operations.

A preferred embodiment of the present invention will now be described by way of example with reference to the accompanying drawings, wherein:

FIG. 1 is a side elevation of a transfer machine in schematic form for delivery of multi-walled paper sacks to four sewing stations;

FIG. 2 is a plan view of the transfer machine illustrated in FIG. 1;

FIG. 3 is an end elevation along line 3--3 in FIG. 2; and

FIG. 4 is a side elevation of a transfer machine in schematic form for delivery of multi-walled paper sacks to six sewing stations.

Referring to FIG. 1, multi-walled or composite tubes are formed in a tubing machine in the conventional manner and cut on a cutting head 10, which, in the illustrated preferred embodiment, rotates at a predetermined and constant number of revolutions per minute. The cutting head 10 illustrated may be provided with two cutting edges on its circumference for cutting two tube lengths during every one revolution of the cutting head, however, any convenient number of cutting edges may be used as required. In order to vary the length of the cut tube within a range, the speed of drive rollers 11 may be adjusted with respect to the cutting head. If longer sacks are required then one cutting edge is removed and thus increasing the length of the tube which passes through the cutting head between each cutting operation of the head.

In operation with the tubing machine set-up with two cutting edges, i.e. known as a "2 up cut" to those skilled in the art, two tubes are discharged from the tubing machine for every revolution of the head. The flow of tube lengths is directed by conventional belt conveyors or any other suitable means to a two-way gate 12 which alternates between two positions. In one position the gate directs tube lengths to an upper belt transfer system 13 and in the other position to a lower belt transfer system 14. The gate speed is set to alternately direct successive tube lengths to the upper and lower transfer systems 13 and 14. These alternate tube lengths are then received by a pair of two-way gates 15 and 16, which also alternate between two positions to either direct tube lengths to sewing machine feeding stations 17 and 18 respectively or to feeding station by-passes 17' and 18' respectively.

Those tube lengths which are directed to by-passes 17' and 18' are transferred by belt conveyors 21 to a further two two-way gates 22 and 23 respectively, which, during normal operation with a "2 up cut", direct the flow of tube lengths in by-passes 17' and 18' to sewing machine feeding stations 19 and 20 respectively. Accordingly, during normal operation with a "2 up cut", the tube lengths discharged from the tubing machine may be directed in sequence to feeding stations 17, 18, 19 and 20, the gates 15, 16, 22 and 23 being time controlled with respect to the tubing machine cutting head 10.

When longer tube lengths are discharged from the tubing machine, i.e. during "1 up" operation, gate 12 is set to direct the flow of tube lengths to the upper transfer system 13 only and gate 15 subsequently distributes the flow alternately between stations 17 and 19.

If a malfunction occurs in a sewing machine or in a sewing machine feeding station, or threads or tape require changing or replenishing which may necessitate stopping a sewing machine; then its respective two-way gate 15, 16, 22 or 23 is operated to prevent that station from receiving any further tube lengths. The station may then be shut down for remedial action. However, it should be noted that an interlock is required to override shutting down of the sewing machine feed station and its respective two-way gate upon initiating station shut-down at an instant when the gate is in the process of receiving a tube length; namely, the gate should remain open until the tube length has passed through it before it operates to the feed station closed position. Also on restarting of the sewing machine feeding station an interlock is required to prevent the gate from operating to the feed station open position whilst a tube length is passing under the gate to the respective by-pass conveyor. The tube lengths normally destined for the shut-down station are conveyed, in the case of stations 19 and 20, by by-pass conveyors 19' and 20' to ends 24 and 25 respectively of the machine, where they may be stacked and stored for re-working at a later date. In a case where the malfunction occurs at either stations 17 or 18, the flow is directed along either by-pass 17' or 18' respectively. However, gates 22 or 23 respectively must now operate to direct the excess flow in by-passes 17' or 18' to the ends 24 or 25 of the machine.

Although downtime in production caused by maintaining sewing machines and tape cutters is generally relatively small, there are occasions when continuous production is of paramount importance. In these circumstances additional spare sewing machine feeding stations complete with sewing heads and cross-conveyors may be incorporated so that should one cross-conveyor or sewing station be stopped for any reason then tubes that would have been received at that station are directed to the spare station.

Accordingly the transfer machine of FIG. 1 may be adapted to include two spare sewing machine feeding stations 63 and 64 as shown in FIG. 4. For convenience stations 17, 19, 18, 20, 63 and 64 are also designated A, B, C, D, E and F respectively, and those tubes directed to station A will be called A tubes and those for stations B, C and D will be called B, C and D tubes respectively. In the arrangement shown in FIG. 4, operated under normal conditions when, say, a "2 up cut" is used, the tubes are directed in a sequence to stations A, B, C and D. Now should either cross-conveyor sewing station A or B be stopped, then A or B tubes destined for those stations may be directed to cross-conveyor sewing station E, likewise should either cross-conveyor sewing stations C or D be stopped then C or D tubes may be directed to cross-conveyor sewing station F.

For control and timing purposes it should be noted that all drives are coupled either mechanically or electrically to the tubing machine drive and hence to the tubing machine cutting head. Accordingly in the arrangement shown in FIG. 4, the cross-conveyor sewing stations E and F are each provided with a two position coupling mechanism which engages with the tubing machine drive. In the case of station E, in one position the station may receive A tubes and in the other position the station may receive B tubes.

The timing of the cross-conveyor sewing station E and gate 60 is coupled so that the timing of the complete unit can be adjusted to suit receipt of A tubes or B tubes, and similarly station F may be adjusted to receive C or D tubes as required.

Taking for example the case where it is necessary to stop cross-conveyor sewing station A, the drive of station A is disengaged and the A tube timing drive on cross-conveyor sewing station E is selected and engaged. When station A is stopped gate 15 closes and all A tubes are directed along conveyor 17' past gate 22 which is timed not to receive A tubes but only B tubes and then along conveyor 19' to gate 60 which will now operate to direct A tubes to station E.

Returning now to the arrangement shown in FIG. 1, the tube lengths are fed into the sewing machine feeding stations 17, 18, 19 and 20 by a series of belts and gates in the manner described above. The tube lengths are discharged out of belt conveyors 26, 27, 28 and 29 respectively onto tables 30, 31, 32 and 33 to abut against adjustable end stops 34, 35, 36 and 37 respectively. The four feeding stations illustrated in FIG. 1 are substantially identical with the exception that tables 30 and 32 of stations 17 and 19 are wider than that of stations 18 and 20 in order to accommodate longer tube lengths during "1 up" operation of the cutting head 10. For simplification of disclosure only station 17 will be described in detail.

For "2 up" operation as generally illustrated in FIG. 1, the end stop 34 is set to suit a predetermined tube length received by the feeding station. A series of fingers 38, as shown at station 17, act on the tube length to locate any malpositioned tube lengths, which are discharged from conveyor 26 onto the table 30 at the receiving end of a cross-conveyor 50. The cross-conveyor is provided with driving fingers or pins 40 attached to chains 39 or the like, which pins push the tube lengths sideways off the feeding table 30 onto belts 41 for delivery to the sewing machine 43. The tube lengths are identified in FIG. 2 by numeral 42. The belts 41 travel faster than the chains 39 and cause the tube lengths 42 fed off the table 30 to move forward and abut against an adjacent set of driving pins 40. As a result of the tube lengths being located with their forward edge against pins 40, timing of the position of the tube lengths with respect to the sewing machine, is greatly simplified. If the pins were to abut against the rearward edge of each tube length to push the tube length to the sewing machine, the pins would have to be so designed that they could be removed from the tube pushing position when the tube is entering the sewing machine, as the pins would normally be travelling faster than the feed speed of the tube lengths through the sewing head of the sewing machine, such a mechanism would require adjustment for every different tube width of bag manufactured. Such adjustment of pins 40 is particularly undesirable as it extends machine downtime between bag runs of different sizes.

It will be noted that the sewing machine 43 is positioned to sew the trailing edge 44 of the tube lengths, with respect to their direction of motion during discharge from conveyor 26 onto table 30. When a tubing machine having a substantially constant speed cutting head, is used, such as that described herein with reference to FIG. 1, the timing of gates 15, 22, 16 and 23 and cross-conveyor pins 40 are all timed in relationship to the trailing edge of the tube length as the relative position of the trailing edge during transfer to the cross-conveyor feeding station is substantially fixed for any length of tube cut on the tubing machine. Consequently timing of the cross-conveyor feeding station is not affected by varying tube lengths.

Further, if the sewing machine was arranged to sew the leading edge 45, end stop 34 would be located in fixed relationship to the sewing machine and at a position to suit the maximum capacity of the machine. Accordingly an additional conveyor would be required to transfer all tube lengths smaller than the maximum permissible in the machine to a position abutting against the end stop, which acts as a reference point for alignment of the tube lengths with the sewing head of the sewing machine. Therefore, it is preferable to provide an adjustable end stop which may be set to suit the tube length passing through the machine, as opposed to providing additional conveyors. Also it will be noted that such end stops minimises the adjustment required to handle varying widths and lengths of tubes.

In the arrangement shown in FIG. 2 an alignment belt 46 is provided and located along one side of cross-conveyor 50 to maintain the trailing edge 44 of the tube lengths in alignment with respect to the sewing head of the sewing machine. Further belts may be provided, similar to belts 41, but arranged to act on the other side of the tube lengths as they pass over belts 41 in order to hold the tube lengths in position. These additional belts may be inclined at an angle to the longitudinal direction of belts 41 in order to bias the tube lengths 42 towards the alignment belt 46.

The sewing machine 43 has associated therewith a further series of feed rollers 49 and belts 47, the speed of which is synchronised to suit the sewing speed of the sewing head. When the tube lengths 42 arrive at the discharge end of cross-conveyor 50, driving pins 40, which are immediately in front of the tube lengths, drop down to return and thus enabling the faster feed belts 41 to deliver the tube lengths to the sewing machine feed rollers 49 and belts 47. These feed rollers 49 run in cooperation with belts 47 to grip the tube lengths and control the feed of the tube lengths through the sewing machine. To assist transfer of the tube lengths from cross-conveyor 50 into the sewing machine feed control mechanism, rollers 49 are arranged to lift off belts 47, so that the leading side 48 of each successive tube length enters between the feed roller 49 and belt 47, and subsequently the rollers lower to grip the tube length.

The conveyors, which feed the tube lengths from the cutting head 10 of the tubing machine to the sewing machine cross feed stations 17, 18, 19 and 20, and the cross feed conveyors 50 and 51 (the cross conveyors associated with stations 18 and 20 are not illustrated in FIG. 2) are coupled to the drive of the tubing machine, all machine timing being controlled with respect to the cutting head 10 or drive of the tubing machine.

If on the other hand a variable speed cutting head tubing machine having a constant speed paper feed were required, then the transfer mechanism herein described should be coupled to the tubing machine feed drive as opposed to that of the cutting head.

In the embodiment illustrated the sewing machines and their associated feed control mechanisms are also coupled and controlled with respect to the tubing machine drive. In the normal operation of a sewing machine one revolution of the sewing machine drive mechanism produces one stitch and as the length of the stitches generally remain constant a narrow width tube requires less stitches and therefore less revolutions than a wider width tube. In order to allow adjustment of sewing machine speed to suit varying widths of tube a variable speed drive is provided between the tubing machine and sewing machine drives. Accordingly, to handle various tube lengths, it is only necessary to adjust end stops 34, 35, 36 and 37 and in order to handle different widths of sack it is only necessary to adjust the variable speed unit that drives the sewing machines. In the arrangement illustrated in FIGS. 1 to 3 or 4 the sewing machines are required to travel slower in relationship to the speed of the cross feed conveyors during a run of narrow width tubes as opposed to a run having wider tubes. It should be noted that the pitch between adjacent driving pins 40 is determined by the maximum width of tube produced by the tubing machine, and the relative speeds of feed control belts 47 and driving chains 39 are selected to provide substantially uninterrupted operation of the sewing machines. The relative speed of the drive chains 39 is such that the drive pins 40 travel one pitch for every two revolutions of cutting head 10. In two revolutions of the cutting head four tubes are produced and there are four cross-feed conveyor sewing units in the arrangement described in FIGS. 1 to 3, the additional sewing machine feed stations 63 and 64 as shown in FIG. 4 being only spare stations. Should a greater or lesser number of sewing heads be required for continuous use then the time cycle would be adjusted accordingly. Further, the sewing machines may be controlled by a triggering device which engages a clutch when the tube lengths are present at or adjacent the sewing head for sewing. Here it should be noted that reinforcement tape is normally sewn across and along the tube length end to be sealed when the sewing method of sealing is used. The tape is fed to the sewing machine from a convenient supply located adjacent the sewing head. Further during sewing, adjacent and successive bags are spaced apart to provide a nominal gap therebetween, the tape being continuous and extending from the sealed end of one bag to the adjacent bag. As the sewing head is normally operated continuously, the stitching continues into the tape in the gap between bags. Accordingly when the portion of the tape and stitching in the gap is cut to separate the bags, the additional stitching in that portion of the tape tends to prevent the stitching at the sealed end from becoming undone.

In the event of an interruption in the flow of tube lengths to the sewing machine it is desirable that the abovementioned triggering device, which operates a clutch to engage and disengage the sewing machine drive, stops the sewing machine with a tube length being sewn in a suitable position so that when the tube lengths are again received at the sewing machine it will restart to maintain the desired gap between bags.

It will be appreciated by those skilled in the art that the transfer machine disclosed above is equally applicable for coupling to sewing machines, tubing machines of other known types having any suitable number of cutting edges, the above type of tubing machine being described as an exemplary embodiment only. Alternatively the transfer machine of the present invention may be adapted to couple tubing machines of other known types to other forms of bottoming or sealing machines, for example, machines for sealing a stepped end type multi-walled sack. Further, it will be appreciated that any number of sewing machines and their associated feeding stations may be coupled to receive tube lengths from a tubing machine. Also by suitable operation of gates 12, 15, 16, 22 and 23 it is possible to feed the tube lengths to the sewing machine feeding stations in any required sequence and accordingly the transfer machine may be arranged in any suitable configuration as required.