Patent GB-810470-A (GB)
Title: Improvements in or relating to electrical control systems for group stitch sewing machine
IPC: D05B65/00
Filed: 1956-05-22
Abstract: 810,470. Sewing machines. PFAFF A. G., G. M. May 22, 1956 [June 1, 1955], No. 15716/56. Class 112 [Also in Group XXIV] Button attaching, starting and stopping. In a machine for attaching a four-hole button by means of two groups of stitches passing through respective pairs of holes, the machine being automatically stopped after each group, electrical control means are provided, whereby the machine is started manually to initiate sewing of the first group, and, upon stopping of the machine after completion of the latter, the thread is automatically broken and drawn out of the work, and the machine is automatically re-started after a lapse of time, by means responsive to movement of the machine. As shown, a starting lever 32, pivoted at 33, carries a fork 29 adapted to shift a belt 27 from a loose pulley 28 to a fast pulley 31. Lever 32 is coupled to a lever 34 which is pivoted at 35 and has an arm connected by a chain 36 to the armature of a solenoid 37, whereby energizing of the latter serves to move lever 32 to the driving position. A cam disc 19, which makes one revolution for each complete button-attaching operation, has a peripheral notch 21 which receives a roller 23 at the end of said operation. Roller 23 is carried by a lever 22 which is coupled to this button clamp 25, the arrangement being such that the latter is lifted when roller 23 enters notch 21. It is stated that a second control cam, not shown, also makes one revolution for each said operation, and serves to control the swinging of the needle bar and the backward and forward movement of the work clamp; and serves also to operate a lever for retaining lever 32 in the driving position, and to release lever 32 for stopping the machine after completion of the first and second group of stitches. The needle bar 39 is carried by a swinging gate 38 and the needle 41 co-operates with a main looper 42 and auxiliary looper 43. Thread cutting and controlling. The thread is broken under the throat plate, when the machine stops after the first group of stitches, by a swinging member 46 carried by an arm 47 fixed to the upper end of shaft 49. The lower end of the latter carries a crank 51 connected by a spring-biased rod 52 to one arm of a lever 53, the other end of which is connected by by a rod 54 to an arm 55 projecting from the starting lever 32. The swinging movement of the latter, when the machine is stopped, is thereby transmitted to the member 46. The loose end of the thread is drawn out of the work by a hook 74 carried by a lever 68 coupled to a lever 63 which is in turn coupled to the armature 62 of a solenoid 59, whereby energizing of the latter causes swinging of hook 74 to extract the thread. Operation. Lever 22 and rod 54 are respectively connected by flexible cables 87 and 88 to operating-members for double pole switches 79 and 81 respectively, the arrangement being such that, when the machine is stopped, contacts 147, 148 and 151, 152 of switch 79 are respectively open and closed, and contacts 155, 156 and 157, 158 of switch 81 are respectively closed and open. Closure of a switch 89 starts the driving motor 26, lights a pilot lamp 98, and energizes a rectifier 104 and a stepdonw transformer 107. Subsequent manual closure of a switch 77 serves to energize a relay 124, via contacts 151, 152 and a rectifier 111, for opening contacts 126, 127 and closing contacts 128, 129, whereby solenoid 37 is energized to start the machine. Cable 87 then operates switch 79 to open contacts 151, 152 and close contacts 147, 148, and cable 88 operates switch 81 to open contacts 155, 156 and close contacts 157, 158. When the machine stops after completion of the first group of stitches, contacts 157, 158 are opened, contacts 155, 156 are closed, and member 46 breaks the thread. Relay 114 is then momentarily energized via contacts 126, 127, a capacitor 163, contacts 156, 155 and contacts 148, 147, whereby contacts 118, 119 are also momentarily closed for energizing solenoid 59 to operate the thread extractor member 74. When contacts 116, 117 re-close, or de-energization of relay 114, relay 124 is energized via contacts 147, 148; 155, 156 and 116, 117, but operation of relay 124 is postponed by a time delay circuit associated therewith and comprising a capacitor 131 and variable resistor 172. Operation of relay 124 serves to energize solenoid 37, via contacts 128, 129 to start the machine, when cable 88 operates switch 81 to close contacts 157, 158, whereby capacitor 163 is discharged via a resistor 167. When the machine stops on completion of the second group of stitches, the lifting of the button clamp serves to break the thread, and switches 79 and 81 return to their original positions, whereby energizing of solenoid 59, to operate member 74, is prevented owing to the opening of contacts 147, 148.