Patent GB-565498-A (GB)
Title: Improvements in or relating to fluid-controlled mechanisms adapted for use in sewingmachines or shoe making machines
IPC: D05B15/00
Filed: 1943-02-24
Abstract: 565,498. Sewing-machines. BRITISH UNITED SHOE MACHINERY CO., Ltd. (United Shoe Machinery Corporation). Feb. 24, 1943, No. 3016. [Class 112] The invention deals with liquid-controlled mechanisms arranged to lock a presser foot of a sewing or shoe-making machine and prevent it from moving away from a workpiece clamped between the presser foot and a work.support on the machine. The invention may be applied to a machine such as described in Specification 23478/10, [Class 112]. In one arrangement, the liquid system includes a double-acting piston 36, rotary valves 78, 71, with ports and passages for distributing the liquid, a supply pump 54, pressure reservoir 69 and a metering piston 94 with a screw 96 for adjusting the stroke of the piston and thus the lift of the presser foot. The valve 71 controls the liquid pressure so that the presser foot is automatically raised from the work as the machine is stopped, and clamps the workpiece when the machine starts. In a second arrangement, the presser foot is lightly positioned, mechanically, and clamped by a piston under liquid pressure in a cylinder having a rotary valve acting as a head for the hydraulic lock. Fig. 1 shows a machine for sewing together a welt and an outsole of a shoe, and has a curved needle 2 and an awl 4. The work is held between a work support 8 and a presserfoot lever 10 fulcrumed on a fixed shaft 12. The lever 10 is coupled by links 18, 20, 22 with a piston-rod -26 whose travel is limited by a stop 44. Mechanism for controlling measurement of thread in accordance with the thickness of the work, include an arm 28 connected to the lever 10, a link 30 and an arm 32 on a thread pull-off controlling rock-shaft 34. The upper end of the piston 36 is supplied with liquid from the pump 54 through the rotary valve 71 and pipe 46. The lower end of the piston cylinder is connected through a tube 50 to the valve casing 48. Pressure on the underside of the piston, Fig. 1, causes the presser foot to engage and clamp the work. Liquid passing from the cylinder 38 is exhausted through passages in the valve 71. The pump 54 maintains a uniform pressure and has a relief valve 55, and is driven through gearing 56, 58 and a belt drive 62 from the main driving mechanism. The pump is supplied from a reservoir 64 and discharges into a pipe 68, having a compressed air storage chamber 69 and a pipe 70 in the base 48 of the valve 71. Liquid stored in 69 supplies the system when the pump supply is momentarily insufficient. The valve 71 oscillates and has a circumferential groove 72 leading liquid under pressure to a passage 74, passage 75 in the housing 49 of the main valve 78 and into a pressure groove 76 for distribution to pressure ports 80, 82, both arranged to align with an opening 52 in the housing 49 leading through passages 84, 51, 50 to the lower end of the cylinder 38. To raise the presser foot, the groove 76 supplies pressure liquid to a port 86, which registers with an opening 88, and supplies passages 90 (leading to the metering cylinder 92). The opening 88 in housing 49 is afterwards connected to an exhaust port 1108 to allow liquid to pass from 92 through a passage 100, leading to the upper end of the cylinder 38. Exhaust passages 102, 104 are connected to a cavity 108 leading to the reservoir 64. The valve 78 is rotated by a shaft 112 driven from a shaft 16, and at the same speed. When the machine is brought to rest, the valve 71 is rocked, through links 120, 122, 124, in the direction of a "stop." arrow, and when it is started, in the direction of a "start" arrow. Exhaust port 126 in the valve 71 leads to a pipe 134 and reservoir 64. The second arrangement, Fig. 8, is also based on the machine described in Specification 23478/10, [Class 112], and has a mechanical control of the presser foot 210 through links 214, 230, floating lever 218 and links 236, 238 from a cam plate 216, but the foot is locked in position through liquid under pressure acting on a piston 242 in a cylinder 244. Needlethread-measuring levers 223 are coupled to the lever 218 and controlled by a spring 220 whose other end is connected to the machine frame. The fluid lock is connected to the pin 232 in the floating lever 218 and exerts a heavy clamping pressure after the presser foot is positioned by movement of the cam lever 214 and under light spring pressure from 220. The fulcrum of the lever 218 constantly shifts between the pins 228 and 232. Flow of liquid in the cylinder 244 is stopped intermittently to lock the presser foot, by the rotation of a valve 254 having a gear-wheel 258 controlled by a rocking arm 260 having rack teeth at its lower end. The arm 260 bears against a stop 265 when the valve is closed and is actuated through a lever 268.