Patent GB-871270-A (GB)
Title: A workpiece transfer mechanism for a machine tool
IPC: B24B5/35
Filed: 1959-08-20
Abstract: 871,270. Grinding machines. CINCINNATTI MILLING MACHINE CO. Aug. 20, 1959 [Nov. 14, 1958], No. 28480/59. Class 60. Means for feeding a workpiece 34, Fig. 1, (e.g. a ballrace) from its position in a delivery shoot 35 to its operative position in a grinding machine and transferring a finished workpiece to a discharge shoot 36 on the same side of the operative position as the shoot 35 comprises two pivoted arms 64, 65 which have workpiece-engaging means at their outer ends and are arranged to be simultaneously swung in different planes and in opposite directions about their pivots for the simultaneous transfer of a workpiece from the shoot 35 to the operative position and finished workpiece to the shoot 36. As shown, the lowermost workpiece in the shoot 35 is picked up by an arm 64 and swung into grinding position where it is positioned on two shoes 30, 31 carried by a support 22 and driven by a magnetic driver 33 ; at the same time, the second arm 65 swings the finished workpiece into the discharge shoot 36. The work support 22, headstock for driving the magnetic driver, housing 24 for mounting the arms 64, 65 and drive mechanism therefor, and vertical plate 37 mounting on one side, and in superposed relation, the two shoots 35, 36 are all adjustably mounted on a swivel plate 20 carried by a slide 18. Each of the shoots 35, 36 consists of an inclined base-plate 45, Fig. 3, which is fixed against a wear plate 39 on one side of the vertical plate 37 and has an adjustable angle structure 50 with a guide 51 for the outer edges of the workpieces 34 ; an upper angle 55 with a depending leg 56 guides the upper edges of the workpieces. Mounted for action between the lowermost workpiece in the shoot 35 and the next workpiece is an escapement detent 115 carried by a disc 88 which is faced on its front face with a layer 90 of non- magnetic material and mounted for oscillation in an aperture in the vertical plate 37 so that the detent 115 can be moved between one position in which it holds the second workpiece while the first is retained by a stop 69 and another in which it releases the second workpiece to take the place of the first in the shoot. The disc 88 is driven through mechanism positioned on the opposite side of the vertical plate 37 and consisting of a sleeve 78 driven through a pinion 79 and rack 107 which is itself intermittently reciprocated by an hydraulic motor 222, Fig. 7. The discharge shoot 36 is provided at the point at which it receives a finished workpiece with a de-magnetizer 120, Fig. 1, extending through an opening in the plate 37. The arms 64, 65 which have projecting fingers 66 at their outer ends for loose engagement with the insides of the workpieces, are carried on horizontal shafts 130, 131, Fig. 5, mounted for oscillating and axial movements in the housing 24. Oscillations of the shafts, and therefore the opposed swinging movements of the arms, are effected from a vertically-arranged hydraulic motor 172 having a rack piston 175 which, through a pinion 178, and crank mechanism 157, drives a vertical rack 145 having gear connections 180, 181, 182 with the two shafts.; this mechanism is such as to accelerate the rack during the first half of its stroke and retard it during the second half. Axial movements of the shafts for advancing the fingers 66 into the workpieces and withdrawing them therefrom are effected by an hydraulic motor 143, the piston rod 144 of which is connected to a cross-bar 187 fixed to the two shafts. The hydraulic motors 143, 172, 222 are arranged in an hydraulic circuit as shown in Fig. 7, which includes solenoid and other valves 163, 191, 204, 211, 235 arranged under the control of limit and other switches to provide for continuous operation upon a succession of workpieces. Pressure fluid supply is through a reversible solenoid valve 191, by-pass valve 204 (manually settable to permit manual control of the arms 64, 65 and detent 115), valve 163 arranged to be actuated at each end of stroke of the motor 172 to effect the timed operation of the motors 143,222, and throttle valves 211, 235 setting the speed of the motor 172. Included in a second hydraulic circuit, Fig. 8, also equipped with solenoid valves for control by switches in the machine cycle are an hydraulic motor 249 for rapidly advancing the grinding wheel slide to its feed position as set by a limit switch 2LS and retracting it therefrom, and a second hydraulic motor 259, which is set into action by the limit switch 2LS to feed the slide through worm gearing 277 first at fast speed and then, when a cam 286 driven by the worm gearing actuates a switch 22LS, at slow speed ; fast speed of the motor 259 is set by arranging for discharge from the motor to be through two throttle valves 268, 276 and slow speed is set by discharging through only the throttle valve 276. The hydraulic and electric circuits are so arranged that starting, for example, with the grinding wheel retracted, the motor 172 swings the arms 64, 65 anticlockwise and clockwise respectively, to the pick up positions shown in Fig. 1, the motor 222 is actuated to engage the detent 115 between the first and second workpieces on the shoot 35, and the motor-143 then advances the arms so that the respective fingers 66 engage inside the lowest workpiece in the shoot 35 and one on the supports 30, 31. Assuming that an electric probe 124, Fig. 1, has sensed the passage downwardly in the shoot 36 of a previously-finished workpiece from its deposited position where it was held by the de-magnetizer 120, the valve 191, Fig. 7, is then actuated to cause the arms and workpieces to swing to their delivery positions on the supports 30, 31 and shoot 36 respectively, and, in the course of this movement, to close a circuit to energise the magnetic driver 33 and de-magnetize 120 and start the motor 249 for the rapid advance of the grinding wheel. When the arms reach their delivery positions they are retracted (the workpieces being retained on the energised driver 33 and de-magnetizer 120), the detent 115 is actuated to release the next workpiece in the shoot 35, and the valve 191 is operated to swing the arms back to pick-up positions, during which time the workpiece on the supports 30, 31 is being ground ; this return swing of the arms does, however, only take place if an electric probe 105, Fig. 3, senses that the next workpiece is in correct position in the shoot 35. The actuation of the limit switch 2LS at the end of the rapid advance of the grinding wheel by the motor 249 has meanwhile resulted in the motor 259 taking over for successive fast and slow speeds as set by the switches 2LS, 22LS ; the actuation of the switch 22LS also deenergises the magnetizer 120 to release the previously-finished workpiece in the shoot 36. When the workpiece on the supports 30, 31 has been ground to size, a cam 285, Fig. 8, driven by the gearing 277, actuates a switch 3LS to stop the motor 259, and after an interval for " sparking out " determined by an electronic timer, starts the motor 249 in reverse for rapid retraction of the grinding wheel. At the same time, the magnetic driver 33 is temporarily connected in reverse to remove residual magnetism and then de-energised, the motor 259 rapidly reversed to reset the gearing 277 and the cycle continued as before.