Patent GB-792088-A (GB)
Title: Metal working machine
IPC: B24B7/07
Filed: 1955-11-25
Abstract: 792,088. Grinding. MID-WEST ABRASIVE CO. Nov. 25, 1955 [Jan. 10, 1955], No. 33871/55. Class 60. A grinding machine comprises a pivotallymounted boom 44, Fig. 3, a grinding wheel 78 mounted on the boom at one side of its pivot for operating upon a workpiece W, means for moving the grinding wheel in opposite directions along the longitudinal axis of the boom, means acting upon the boom for urging the portion thereof on the grinding wheel side of the pivot downwardly under a variable pressure, and control means operable in response to the movement of the tool along the longitudinal axis of the boom for progressively decreasing this downward pressure as the grinding wheel moves away from the pivot of the boom and progressively increasing it as the grinding wheel moves in the opposite direction. The boom is disposed on a carriage 12 provided with two sets of wheels 28, 30, Figs. 2 and 3, movable on rails 14, 16 arranged parallel to the length of the workpiece, the wheels 28 being driven through chain-andsprocket gearing from a fluid motor on the carriage. The boom is in the form of a long tube rotatable and slidable longitudinally in bearings in an elongated housing 138 which is mounted to swing vertically on horizontal trunnions journalled in bearings in members 178, 180 on the carriage 12. The boom tube is reciprocated longitudinally in its housing by a double-acting fluid motor 154, Figs. 3 and 6, the cylinder of which is secured to the underside of the housing 138 and the piston rod 158 pivotally connected to a clamp 160 encircling a reduced portion of the tube in a manner not interfering with its rotation ; the motor 154 is supplied with fluid pressure by a pump and controlled by a hand-settable valve 170, Fig. 3. The inner end of the tube carries a housing 48, Fig. 10, in which the grinding wheel 78 is rotatably mounted on a spindle 58 secured between the base of the housing and a normally-closed pivoted access door 52. The grinding wheel 78 is secured on a sleeve 74 journalled on the spindle and connected to a pulley 66 which is driven by belts 104 from an electric motor 86, Fig. 2, on a carriage 88 arranged to move on rails on the carriage 12 in synchronism with the axial movements of the boom tube ; the carriage 88 and boom tube are connected for this purpose by an adjustable tie rod assembly 106 comprising two interlocked rods associated with two sets of coil springs, Fig. 11 (not shown). At the end opposite to the grinding wheel, the boom tube is provided with a counterweight 192, Fig. 3, which slides longitudinally of the tube on rails 196 in an extension 194 of the housing 138 ; hangers 198 supporting the weight have rollers 200 engaging the rails. The counterweight is arranged always to move in a direction opposite to that of the boom tube by means of a sprocket-chain drive 210, Fig. 7, connected to the clamp 160 and driving a second sprocket-chain drive 216, 218, Figs. 3 and 7, connected with the counterweight. Swinging movement of the housing 138 (and therefore the boom tube) about its horizontal trunnions is effected by a double-acting fluid motor 222, Figs. 2 and 3, the cylinder of which is pivoted to the carriage 12 and the piston rod 228 secured to the housing 138, the motor being supplied with fluid by a pump through a handsettable valve 232, Figs. 2 and 3, and pressureregulating valve 286 ; the assembly is accurately guided during its swing by rollers 186 on a plate 150 secured to the housing 138 engaging vertical guides. During grinding, the motor 222 is used to provide a uniform downward grinding pressure since this cannot be obtained by the action of the counterweight alone, the valve 286 being automatically controlled so that the pressure supplied to the motor 222 is varied as the grinding wheel moves across the workpiece. For this purpose, the screw-threaded control needle of the valve 286 is rotated from the output shaft of a gear box 304, Fig. 2, which is driven by its connection through a cable 301 with the carriage 88 supporting the grinding wheel motor 86 so that the pressure of fluid supply is gradually reduced as the boom moves outwardly over the workpiece and correspondingly increased on the return movement ; the output shaft of the gear box 304 carries an adjustably-mounted disc having two diametrically-opposed pins which can be engaged with any two diametrically-opposed holes of a set circularly-arranged in a disc secured to the valve control pin. Tilting or oscillation of the boom tube about its axis is effected by an electric motor 266, Fig. 3, driving through a speed reducer 260, Fig. 14, a roller 256 engaging a slotted arm 250 projecting from a rod 236 having slidable but non-rotatable engagement in one end of the boom tube. Specifications 774,975 and 774,976 are referred to.