Patent GB-840596-A (GB)
Title: Improvements in or relating to machines for the production of bags
IPC: B29C65/00
Filed: 1957-12-13
Abstract: 840,596. Paper bag making machines. SCHWEIZERISCHE INDUSTRIE-GES. Dec. 13, 1957 [Dec. 21, 1956], No. 38814/57. Class 94(2). In a machine for making paper bags from a folded strip 1 of thermoplastic material, or a strip coated with such material on the inside, there are two pairs of heated clamping jaws 21, 22 and 21<SP>1</SP>, 22<SP>1</SP>, adapted to clamp the strip alternately to seal it along transverse longitudinally separated zones to form the bags. The strip 1 is drawn off a reel 2, folded longitudinally by guides 3 and a saddle 4, and passes between guide rollers 5 and feed rollers 6. There are two carriages 9, 10 adapted to be reciprocated along fixed bars, such as 7, by connecting rods attached to crank pins on gearwheels which are in mesh, one gear-wheel 13 being driven by a prime mover 151 through a shaft 15. On the carriage 9 are two slidable arms 19, 20 carrying, respectively, the electrically heated clamping jaws, 21, 22, these arms having inner rack teeth meshing with a gear-wheel 23 rotatably mounted on the carriage. The upper end of the gear-wheel shaft is connected to a lever arm 25 having a slider block 26 thereon which engages in a groove in a rail 27, so that when rail is reciprocated bodily, the gear-wheel 23 is rotated to open or close the jaws 21, 22. The carriage 10 is similar to the carriage 9 except that the arms 19<SP>1</SP> 201 and the gear-wheel 231 are arranged on the underside of the carriage, and the rail 27<SP>1</SP> is grooved at the top to receive the slider block 26<SP>1</SP>. The rails 27, 271 are reciprocated bodly and respectively by links 28, 28<SP>1</SP> pivoted levers 29, 29<SP>1</SP> and cams 33, 331. The shaft 32 on which the cam 33 is secured is driven from the shaft 15 by gears 17, 34, and the opposite end is formed with a crank 35 which drives a cutter device 36 for severing the bags from the strip 1. The cam 331 is secured on a shaft arranged below the shaft 32, and is driven in similar manner by the gear-wheel (in mesh with the gear-wheel 13) which serves to drive the carriage 10. The carriages 9, 10 carry, respectively, toothed racks 37, 38 which cooperate with free-wheel drives 39, 40 on the feed rollers 6. In operation, assuming the folded strip has been threaded through the machine as shown, the strip 1 is first gripped by the heated jaws 21, 22 to seal it along a transverse zone, the jaws 21<SP>1</SP>, 22<SP>1</SP> being opened to an extent H which is greater than the distance h which is the combined thickness of the closed jaws 21, 22. The carriage 9 is now moved to the right, and the carriage 10 is simultaneously moved to the left, the toothed rack 37 effects rotation of the feed rollers 6, and the jaws 21, 22 carry the strip 1 along a predetermined distance at a speed which is the same as that imparted to the strip by the rollers 6. When the jaws 21, 22 are opened, the jaws 21<SP>1</SP>, 221 close, and the carriage motions are reversed, and so on. The formed bags are severed in turn by the cutter 36. Accurate timing of the operations of the heated clamping jaws is determined by a photoelectric device in co-operation with printed marks on the strip 1. If the strip is not of register, a light ray 47 from a lamp 48, Fig. 4, acts on a cell 46 in a circuit 49 to energise a solenoid 50 and cause an abutment 51 to impede the full stroke of the connecting rod 11, and subsequent displacement of the carriage 9. The jaws 21, 22 are thus caused to engage the strip 1 at a different point. The rod 11 is mounted on a block 42 urged by a spring 43 in the gear-wheel 13, this arrangement allowing correcting displacement of the rod 11.