Patent GB-257381-A (GB)
Title: Improvements in grinding or abrading machines
IPC: B24B47/06
Filed: 1925-07-11
Abstract: 257,381. Marks, E. C. R., (Giddings & Lewis Machine Tool Co.). July 11, 1925. Round holes, enlarging and tracing; gauges; spindles.-A grinding-machine comprises a workcarrying headstock on a carriage movable transverse of the machine base and a grinding-wheel carriage traversable along the base, and automatic means operable when the work has been ground to within a predetermined amount of the finished size to change the speed of such traverse for the final grinding of the work to size; a change of rate of the feed also takes place with change of speed of traverse. The machine consists of a base 17 with transverse walls 18, 22, 23 dividing the base into a side portion for a work headstock carriage 19, a base for a reciprocating grinding carriage 20, a reservoir for cooling fluid, and a reservoir for pressure fluid, for example oil. The headstock carriage 19 is slidably mounted on transverse ways 25 on the base 17 and carries a rotatable top section 26 in which is mounted a hollow work spindle 27 provided with a work holder 28. The section 26 extends down into the base and carries a motor 21 and change-speed gearing 30, a friction clutch 29 being provided for driving the spindle 27. The clutch is operated by a pivoted yoke 32 moved by a cam 35 on a shaft 36 operated by a handle 37. The gauging- mechanism comprises a rod 41 slidable in the spindle 27 and carrying a roughing gauge 42 and a finishing gauge 43 at its forward end; the rod is connected at its rear end by a bracket 44 to a parallel push rod 45 carrying a roller 46 adapted to be engaged by an abutment 49 on the grinding- spindle carriage 20 to move the gauges from the work blank A as the grinding-wheel 21 moves into the work, a spring 47 on the rod 45 moves the gauges into contact with the inner end of the work, and when the first gauge enters the work one of a pair of plungers 64 carried by the bracket 44 opens a trip 63 and allows a switch 52 carried in a casing 54 to close; when the second gauge enters the work a second switch 53 is similarly closed. The switches are re-set in the open position by a pin on the rod 45 when the clutch 29 is thrown into the open position. The grinding-spindle carriage 20, which reciprocates on the base 17, carries an electromotor which drives the spindle of the grinding wheel 21. The carriage is reciprocated by a cylinder 70 secured thereto which moves on a stationary hollow rod 72, tne fluid being supplied to the ends of the rod. The fluid is drawn from the reservoir by a pump 73, the speed of which may be varied, and is fed through a pipe 75 to a control valve 77 moved by a lever 87 pivoted at 88 having at its upper end a pivotal spring-pressed dog 89 normally maintained in the path of two dogs 90, 91, adjustably mounted to vary the stroke, on the carriage 20. When the carriage first moves to the left, the dog 90 depresses the dog 89, which then rises between the dogs 90, 91 and is engaged thereby to reverse the motion of the carriage. When the switch 53 is closed, a magnet 97 is energized and attracts an armature 98, which by means of a pin 99 lowers the dog 89 and allows the carriage to move in an extended stroke to the right; the armature is locked by the fall of a catch 103 which is moved to release the armature by a cam surface 105 on dog 90. When the grinding-wheel is separated from the work, a cam 106 on carriage 20 also moves the lever 87 into neutral position when the carriage reaches the inoperative position. The headstock carriage is fed along the ways 25 to move the work A against the grinding-wheel 21 by a screw 108, Fig. 9, extending through a feed box 110 and carrying a hand-wheel 111. On the screw is rotatably mounted a ratchet wheel 112 connected through gearing with the screw and operated by a coarse feed pawl 115 and a fine feed pawl 116, the strokes of which are controlled by a lever 121 operated by a piston 124 in a cylinder 125 which receives fluid through pipes 126, 127 from the valve 77. The levers carrying the pawls are moved by the engagement of cams 120 therein with eccentrics 122, 123. When the switch 52 is closed, the circuit of a magnet 128 is made and its armature lifts the pawl 115 from engagement with the ratchet wheel and rate of feed is reduced. Similarly when the switch 53 is closed the pawl 116 is lifted and the feed ceases. The pawls are re-set by levers moved by a handle 141. To obtain a relatively slow traverse of the grinding-wheel during the finishing cut, a part of the fluid normally passing through the valve 77 is. upon entry of the gauge 42 into the work, bypassed to the reservoir. This is achieved by means of a valve 153, Fig. 10, in a casing 143 having an inlet port 145 from the pipe 75 and an outlet 146. The ends of the valve sleeve 149 communicate with an exhaust chamber 150. The valve member 153 is moved by a stem 154 connected to the armature of an electromagnet 157, which is energized when the switch 52 is closed to cause connection of ports 145, 146 to by-pass a part of the fluid from valve 77. A spring 158 returns the valve to its initial position when the magnet is de-energized. In order to vary the pressure of the fluid according to the resistance imposed on the movement of the carriage 20, a valve is provided in the passage 146. This valve comprises a casing 159 with openings 160 and a slidable member 161 having openings 163. A spring 169 acts on the member 161 and is adjusted so that with normal pressure the ports 160, 163 are in full register. Variations of pressure cause the member 161 to move to cause the ports to be less or more in register. Specifications 227,160, 254,417, and 257,332 are referred to.