Patent GB-429746-A (GB)
Title: Improvements in or relating to stop motion devices
IPC: F16D67/02
Filed: 1933-11-28
Abstract: 429,746. Sewing-machines. BRITISH UNITED SHOE MACHINERY CO., Ltd., GOULDBOURN, J., and KESTELL, T. A., Belgrave Road, Leicester. Nov. 28, 1933, No. 7769/35. Divided out of 430,984. [Class 112] In order that suit-case sewing-machines of the type described in Specification 198,430, [Class 112], may be operated at higher speeds, the stop-motion devices are modified to avoid throwing excessive strain on the parts when bringing the machine quickly to rest from a high speed of operation. In the machine to be described, there is a two-speed drive controlled by the operator so that the machine may be run at a high speed, e.g. when sewing along a continuous seam, and at a much lower speed when inserting individual stitches round corners. The braking effect of the stop-motion device is applied by a dash-pot device. The mechanism for actuating the needle and awl are as described in Specification 410,463. A single treadle 17 causes a clutch member to set the machine in operation and cause the two-speed driving device to drive the pulley 13 at a high or low speed. The two-speed driving device comprises a gear-wheel 19 meshing with two pinions 21, Fig. 5, meshing in turn with internal teeth 27 on a drum 29. This drum is held stationary by a pawl 31 when the machine is to be driven at a slow speed. The counter shaft 5 has a rigidly fixed disc 35 with a leather friction face 37. A pulley 25 is slid into firm engagement with this disc when the machine is to be driven at a high speed, the epicyclic gearing 21 being then inoperative. For this purpose the clutch-pedal 17 is coupled to a quick-pitch plunger 39 bearing against a ball housed in a sleeve on the drum 29. Stop motion device. The pulley 13 on the shaft 15 is freely rotatable and has an internal dished clutching face 55. This co-operates with a member 57 capable of sliding along the shaft 15 to engage the clutch face 55 in one direction and the stationary braking face 59 in the other direction. The member 57 has a hub 61 with a cam groove 63 engaged by trip levers 67, 69. The cam groove moves the lower ends of these levers to and fro in opposite directions. The positions of these ends can be adjusted by the eccentric end of the rod 65. Four springs 73 urge the hub of the clutch member 57 into clutching engagement with the pulley 13 and latches 75, 77 engage the lower ends of the levers 67, 69 at certain times and cause the member 57 to release the pulley 13 and engage the braking face to stop the machine. The latch 77 operates to bring the machine to rest when operating at low speeds by the engagement of the end of the lever 69 with a shoulder 89. The latch 75 brings the machine to rest when operating at high speeds by the engagement of the lever 67 with the shoulder 91. To restart the machine at low speed, the latch 77 is drawn downwards out of engagement with the lever 69 and at high speeds, both latch are drawn downwards. To avoid too sudden or too weak a braking action a dash-pot device is incorporated. This comprises an oil chamber 93 with a vertical valve 95 on a seating 97. An oil duct 99 runs to a cylinder 101 with a piston 103 contacting with a rod 107 connected to the arm 85 of the bell crank to which the latches are pivoted. When either of the latches 75, 77 is moved, the arm 85 is swung downwards causing the piston 103 to be urged down the cylinder 101. This is resisted by the oil which escapes slowly through a port 109.