Patent GB-1058882-A (GB)
Title: Improvements in or relating to apparatus and methods for making plastic articles
IPC: B29C51/26
Filed: 1964-01-13
Abstract: 1,058,882. Seaming non-metallic sheet material; making bags. GLOUCESTER ENGINEERING CO. Inc. Jan. 13, 1964 [Jan. 14, 1963], No. 1483/64. Headings B5D and B5K. [Also in Division B6] In a machine comprising a die such as a reciprocating die 25, Fig. 1, operating periodically to fuse together two layers of a web of fusible plastic material, fed continuously thereto, means are provided for causing the part of the web adjacent to the die to be stationary relative to the die during the fusing operation, such means comprising at least one guiding member which may be a roller such as 4, Fig. 1, around which the continuously moving web is trained to form a loop, the guiding member being reciprocated to take up and pay out the web, and the speed of the guide member in the take-up direction being so related to the web speed that when the die is performing a fusing operation the web length adjacent thereto is relatively stationary. The die may be mounted on a vertically movable platen 24, Fig. 1, or on a cylinder 238, Fig. 19, the surface speed of which is less than that of the normal web speed, and may comprise an ultra-sonic vibrator sealer or as shown, a heated die 25 and perforator 27 for forming bags from a flattened tubular web produced by a high-speed plastic extruder 50, Fig. 1. As shown in Fig. 1, the web first passes around a floating roller 44 actuating a potentiometer 52 which controls the speed of the driving motor 40 of the machine in accordance with the speed with which the web is extruded. From the roller 44 with its associated rollers 46, 48, the web passes to rollers 8, 4, 6, 10, the axes of the rollers 8, 10 being fixed. The rollers 4, 6 are mounted on a carriage 2 reciprocated horizontally by an hydraulic piston-and-cylinder 17, 16. Pressure fluid is supplied by pipes 38<SP>1</SP>, 39<SP>1</SP> alternately to the ends of cylinder 16 from a pump 32 producing a constant volume discharge for each cycle and is controlled by a valve 28 operated by a cam 30 on a shaft 29. The pump 32 is connected to the motor 40 by a drive 41 adjusted so that the carriage 2 moves with the required speed, i.e. at half the web speed in the present instance so that during rightward movement of the carriage the web below the die is stationary. The shaft 29 is also connected to the motor 40 through an adjustable drive 42 by means of which the frequency of reciprocation of the carriage relates to the web speed may be varied to change the length of web operated upon by the devices 25, 27. Another cam 26 on the shafts29 moves the platen 24 to operate on the web during the time the adjacent part of the web is relatively stationary, the cam being so shaped (Figs. 6, 7, not shown) that by axial adjustment thereof the time of dwell of the devices 25, 27 on the web may be varied. The rollers 4, 6, 8, 10 may be positively driven at the speed of the web by sprockets engaged by a chain 21 itself driven from the motor 40. A nipping roller 18 presses the web against the roller 10 to exert a slight feeding tension on the web. A mechanical drive for the carriage 2 may be provided (Fig. 8, not shown) instead of an hydraulic drive. The web may be preheated by heating the guide rolls 6 or the back-up plate 22. In another embodiment, Fig. 15, the web after being fed around the roller 4 and under the operating device 24a passes over, but not around the roller 6, to feed rollers 87, 89 and a cutter 91. The chain 21 coupling the rollers 4 ... 10 drives a pinion 85 which is coupled by chains 21<SP>1</SP>, 21<SP>11</SP> to the lower feed roller 87, so that the rollers 87, 89 are stationary whilst the carriage 2 is moving rightwardly. A cam 26a corresponding to cam 26, Fig. 1, operates a valve 28a to supply hydraulic fluid from a pump 32a to an hydraulic cylinder 166 operating the cutter 91 and the platen 24a. In a further embodiment, Fig. 19, the dies 230, 232 are mounted on a cylinder 238 driven at a surface speed less than that of the web from a chain 251 trained along the web path over the reciprocating rolls 208, 210 and moving at, the speed of the web. The drive is through a slipping clutch including a trip cam 256 engaged by a trip lever 260 operated by a cam 26 so as to hold the cylinder stationary with the dies 230, 232 in the inoperative position shown when the rolls 208, 210 are moving leftwardly. Modifications are described wherein (1) two devices such as 24 operate on the web at spaced positions (Figs. 10, 11, 18, not shown), (2) the reciprocating rolls move vertically in opposite directions (Fig. 14, not shown), (3) by means of a carriage 2 with pairs of rolls 4, 6 arranged one below the other (Fig. 12, not shown) the carriage speed can be one quarter that of the web speed and (4) the web may be fed into and out of the machine at one side of the machine (Fig. 13, not shown). Instead of rotatable rolls such as 4, 6, stationary rolls or curved shoes covered with antifrictional material may be used, or the rolls may have perforations through which lubricating air issues.