Patent GB-815165-A (GB)
Title: Machine tool
Inventor: FARMER JAMES WOODRUFF
IPC: B24B47/04
Filed: 1957-01-03
Abstract: 815,165. Grinding. REID BROS CO. Inc. Jan. 3, 1957 No. 263/57. Class 60. [Also in Group XXXVII] In a machine tool such as a surface grinder, a cross-feed system for controlling the lateral advancing of a work table 12, Fig. 2, provided with means for driving it back and forth comprises driving means 85, Fig. 4, a clutch 83 for engaging the driving means with the table advancing means, and means synchronized with the back -and-forth movement of the table for periodically actuating the clutch at a predetermined position in the back-and-forth course of the table. The back-and-forth movement of the table, which is mounted on slideways 32 on a cross-slide 24 carried in slideways 30, is effected by a flexible rack 38 secured at its ends to the table and driven over rollers 44 by a pinion 40 which is slidable on a splined shaft 42 driven in opposite directions from a reversing mechanism 56 by a D.C. motor 52 and speedreduction gear 54. The reversing mechanism is operated at each end of the back-and-forth movement of the table by arms 68, 69 secured to the table and actuating the rocket 67 of a switch 66 so that two electro-magneticallyoperated clutches 59, 60 in the reversing mechanism 56 are alternately energized; the circuits of the electro-magnets controlling the clutches contain variable resistances which control the amount of slip of the clutches and, therefore, the abruptness of the reversal of the table. Variation of the voltage supplied to the armature of the D.C. motor 52 controls the speed of reciprocation of the table 12. Lateral advance of the cross-slide 24 on the slideways 30 is provided at either or both ends of the back-andforth movement by a three-phase motor 85 driving a speed-reduction gear 86 and the clutch 83 which, when engaged with a member 82 splined to a shaft 80, rotates a lead screw 48 to axially move a nut 46 secured to the crossslide; movement of the nut carries the pinion 40 along the shaft 42 to maintain the rack 38 in alignment; when the clutch 83 is disengaged, the member 82 is held against rotation by a brake clutch 84 secured to the frame 10 of the machine. The clutch 83 is engaged and clutch 84 disengaged at the same time as one or other of the clutches 59, 60 is operated under the control of relays actuated by the switch 66. Simultaneously, an adjustable time-delay relay-mechanism is operated to maintain the clutch 83 in engagement for a length of time depending upon the increment of lateral movement reauired; on the completion of the time delay, the clutch 83 is disengaged and clutch 84 engaged. Limit switches 88.7, which co-operate with lugs 88.8 on the cross slide 24 are provided on the frame at the limits of the full lateral movement in both directions to reverse the connections to the motor 85 and, therefore, the direction of lateral movement. The motor 85 may be connected by a clutch 105 to a shaft 106 which imparts vertical movement to a spindle head 26 and grinding wheel 14. The back and forth and lateral movements of the table are automatically controlled by relays which close circuits to energise the electro-magnets operating the clutches. Manual control of the clutches and motor 85 is provided by push-buttons arranged on a panel 110 mounted on the machine. Manual operation of the longitudinal movement of the table is provided by a handwheel 18 which, when a clutch 64 is engaged and the clutches 59, 60 are inoperative, is connected to the reversing mechanism 56 and shaft 42. The lateral movement may be similarly manually operated when the clutch 84 is disengaged by a handwheel 20 which is geared to the lead screw 48. Manual adjustment of the spindle head is provided by a handwheel 22 when the clutch 105 is disengaged.