Patent GB-736928-A (GB)
Title: Honing machine
IPC: B24B33/10
Filed: 1953-07-24
Abstract: 736,928. Control of several motors. BARNES DRILL CO. July 24, 1953 [March 4, 1953], No. 20631/53. Class 38 (3). [Also in Group XXIII] The expansion and contraction of a hone for internal grinding (see Group XXIII) are effected by a reciprocating shaft 55, Fig. 8, driven through differential gearing 34 from one or two motors which are controlled so as to cause rapid expansion of the hone until it engages the wall of the work and then slow-grinding feed. When two motors are employed, the ring gear 32 of the differential is driven through worm gearing 42, 45 from a motor 30, and the sun gear 33 is driven from a motor 31. The planet gears 38 are carried by a member 39 on a shaft 47 having a worm 51 meshing with a worm wheel 52 in screwthreaded engagement with the shaft 55 which thereby reciprocates and correspondingly reciprocates a rod 25 for expanding and permitting contraction of the hone; the worm 51 is slidable on the shaft 47 and normally urged against a stop 86, Fig. 2, by a spring 85 acting through a sleeve 96 having a cam 95 co-operating with the actuating pin 92 of a switch 90 in the circuit of .the motor 31. Rapid expansion of the hone is effected by high-speed drive from the motor 31, upon which is superimposed the negligible effect of the low-speed drive from the motor 30. When the hone engages the wall of the work, the build-up of torque in the drive results in the worm 51 being urged away from the stop 86 so that the cam 96 opens the switch 90 to stop the motor 31; the hone is then slowly expanded under the action of the. motor 30 alone and-the remaining slack in the drive is taken up by movement of the worm 51 against a stop on the shaft 47. Simultaneously with the de-energization of the motor 31 the sun gear 33 is abruptly stopped by a disc-type friction brake 63 mounted on the shaft of the motor 31 for operation by an electromagnetic clutch automatically actuated by switches in the control circuit of the machine; a rheostat in circuit with the clutch determines at what pressure the brake will slip when the hone is being expanded against the work by the slow drive of the motor 30. Switches 109, 134, which are actuated by a roller 106 on a rack rod 105 driven by a pinion 104 from a rack 103 at the upper end of the shaft 55 are provided for starting the motor 30 and stopping the reverse drive of the motor 31. The hone, together with the motors and gearing, is carried by a head 13 which is slidable vertically by an hydraulic motor 19 to move the hone to and from the work and also to reciprocate it for the grinding strokes; the motor 19 is controlled by valves arranged to be automatically reversed during the machine cycle by a cam disc 113 driven by a flexible transmission 114 from the reciprocating head 13. The control circuit of the machine is arranged to provide the following automatic cycle: (a) lowering of the head 13 ; (b) release of the brake 63 and energization of the motor 31 upon closure of a switch 130 by a cam 128 urged by a lug 126 on the cam disc 113; (c) energization of the motor 30 upon the closure of the switch 134 by the rack rod 105 consequent upon the lowering of the rod 55 by the motor 31; (d) stopping of the motor 31 and application of the brake 63 by the opening of the switch 90 upon the build-up of torque in the drive when the hone engages the wall of the work; (e) slow expansion of the hone by the motor 30 accompanied by reciprocation of the head and hone; (f) stopping of the slow expansion after a predetermined time by the provision in the control circuit of a timer 148 (Fig. 9, not shown) which, when closed, acts to cause upward movement of the head, release of the brake 63, energization of the motor 31 in a direction to collapse the hone, stopping of the motor 30, then stopping of the motor 31 by actuation of the switches 109, 134 by the rack rod 105, and finally stopping of the head in upper position. To reduce delay caused by the lengthening time required for the expansion and contraction of the hone as the latter wears away in use, the collapsing movement of the hone may be governed by a timer 170 (Fig. 9, not shown), which may be switched into the control circuit so as to start when the motor 31 starts to collapse the hone and de-energize this motor after a predetermined interval of shorter duration than required for complete collapse. In a modification, both the fast and slow motions of the hone are operated from a single motor 165, Fig. 7, fast speed being obtained by direct drive to the ring gear 32 of the differential and additional drive through an electromagnetic friction clutch 167 to the sun gear 33, and slow speed by the direct drive alone upon the actuation of the switch 90 as described above to de-energize the clutch.