GB1112741A - Improvements relating to sewing machines - Google Patents

Abstract

1,112,741. Sewing machines. GENERAL AUTOMATED MACHINERY CORPORATION. 27 May, 1965 [15 Feb., 1965], No. 22 547/65. Heading DIG. A sewing machine has a presser foot, thread tensioning and releasing means, a thread cutoff device, a needle positioner, and a driving motor controllable by a pedal. The machine is driven by depressing the forward edge of a pivoted treadle and stopped by releasing the treadle. If the rear edge of the treadle is then depressed, two microswitches MS1 and MS2 are closed. Current then flows via closed contacts 49, 50 and one of a pair of knee press-actuable microswitches 117 to energise a relay R<SP>1</SP> and solenoid valves 10 and D<SP>1</SP>. Relay R<SP>1</SP> then opens contacts in the circuits of solenoid valves A<SP>1</SP> and C<SP>1</SP>, valve 10 releases air pressure from one end of cylinders 9 and 24, and valve D<SP>1</SP> admits air to the other ends of cylinders 9, 24 for respectively releasing the break on the driving shaft and moving the piston rod 23 outwardly. Piston rod 23 thereby rotates the driving shaft via a slip clutch until a rotary cam 39 opens contacts, 49, 50 to de-energise relay R<SP>1</SP> and valves 10 and D'. Thereby, the brake, is applied, piston rod 23 moves inwardly, and a solenoid valve C<SP>1</SP> is energised via relay R<SP>1</SP> and a microswitch 65 to raise the presser foot with the needle fully lowered. If the microswitches 117 are actuated by the knee press while the rear edge of the treadle is depressed relay R<SP>1</SP> and the solenoid valves 10 and D<SP>1</SP> are energised via a pair of closed contacts 44, 45 and the main shaft rotates until cam 39 opens the contacts 44, 45 when the needle is in the fully-raised position. Solenoid valve A<SP>1</SP> thereby energised via the right hand microswitch 117, the closed contacts of relay R<SP>1</SP> and the closed contacts of a relay R<SP>2</SP>, to supply air to a cylinder 95 for moving apart a pair of thread-tensioning discs 95c, 95d, and to a cylinder 82 for moving the piston rod 81 inwardly against the bias of a spring 85. A block 68 on piston rod 81 thereby releases a lever 87 to allow closure of a thread clamp 90, and also allows microswitch 65 to open and microswitch 65a to close. During the movement of block 68, a pair of hooks 79, 80 thereon serve to draw off the thread between the tensioner and clamp. At the end of its inward movement, block 68 closes a microswitch 64, whereby a solenoid valve B<SP>1</SP> is energised to supply air to a cylinder 108 for actuating a thread-severing device 99, 100, and a relay R2 is energised for closing a holding circuit via the microswitch MS2 and for opening the contacts in the circuit of solenoid valve A<SP>1</SP>. The thread tension is thereby re-applied and piston rod 81 moves outwardly, when block 68 allows microswitch 64 to open and finally closes microswitch 65, whereby solenoid valve C<SP>1</SP> is energised to raise the presser foot.