Patent GB-500726-A (GB)
Title: Improvements in and relating to grinding or abrading machines
IPC: B24B19/02
Filed: 1937-07-10
Abstract: 500,726. Grinding screw - threads. HORSTMANN, S. A., and HORSTMAN, Ltd. July 10, 1937, Nos. 19201/37 and 14163/38. [Class 60] In a machine for grinding screw-threads the work is driven by a liquid motor, and the liquid pressure also is applied to the workhead slide to bias it constantly in one direction, thus preventing backlash. The machine comprises a base 100 on which is mounted a bed 101, rubber or resilient pads being, if required, inserted between the parts. The base carries an electric motor 102 driving a fluid pump 103, from which oil is led through a speed control valve 105a to a fluid motor 105 serving to rotate the work and the lead screw. The head and tail stock carrying the work are mounted on a circular section bar 106 supported on the bed 101 and at the right hand end, Fig. 6, entering a cylinder 107. The left hand end of the bar is bored out and supports, in a conical or spherical seating 112, a nut 111, engaging the lead screw 110 and having secured thereto a lever provided with a ball end 155. The headstock 117 is clamped to the bar 106 and has a lug 119 engaging a bearing plate 121 resting on the bed 101, the lug having therein an adjusting screw 122a engaging the plate 121. The headstock has therein two housings 123, 124 respectively carrying a sleeve.holding a centre 126, and a sleeve 129 carrying a pinion 130 for driving the centre and splined to a shaft 131 connected by a ball joint 132 to a clutch sleeve 133 carrying a sprocket 134 driven by a chain 135 from the motor 105. The sleeve 133 also is connected by a ball joint to a shaft 137 extending into a gear box 138 in which is change speed gearing 139, 141, 142 for driving the lead screw 110; the screw may be adjusted axially by a screw 144. A compensator for adjustment of the pitch of the thread being cut is provided, consisting of a sine bar 151 angularly adjustable in a slot in the casing 109 of the lead screw, the sine bar being engaged by the ball 155 on the nut lever 111. The lead screw is biassed and backlash taken up by means of the cylinder 107 to which oil under pressure is supplied by a port 157; leakage of oil serves to lubricate the bar 106. The lead screw drive includes a differential reversing gear, Fig. 10, comprising a cage 160 carrying a sprocket 159 over which the driving chain 135 passes, the side gear 162 of the differential gear being driven through worm gearing by the liquid motor 105, and the side gear 164 being connected through a worm drive to an electric motor 158, so that when the gear 164 is stationary, the sprocket 159 rotates at one half the speed of the motor 105, whereas when the side gear 164 is rotated reversely by the motor the sprocket also may be driven reversely at any desired speed ; switch means is provided for starting and stopping the motor 158 and for preventing reverse driving until the grinding-wheel is separated from the work. The grinding-wheel 202, is mounted in a bracket secured to a slide bar 189 extending across the bed 101 and acted on at both ends by pressure fluid in cylinders 190, 192 at the rear and front ends respectively so that the slide bar mav be moved to cause the wheel to approach or recede from the work to an extent limited by screws 195, 194. Reversing mechanism for controlling movement of the wheel 202 comprises a hand lever 221 pivoted on the machine bed and engaging the plunger 224 of a reversing valve controlling admission of and exhaust from the cylinders 190, 192, or automatic reversal may be effected by dogs 237 mounted on a slide bar 235 and engaged by a member 236 on the plate 121. When a tap or other fluted work is under treatment, the speed of rotation may be increased between periods when the lands are opposite the. grinding-wheel by means of a cam rotated by the work rotating means and operating through links, levers, or solenoids to control a main valve in the fluid supply ; automatic feed of the grinder also may be effected by ratchet &c. means actuated by a piston having a variable stroke. Cooling fluid may be supplied by a pump. For dressing the wheel 202, this may be rotated by hand. Specification 492,591 is referred to.