Patent GB-799321-A (GB)
Title: Improvements relating to machine tools
IPC: B24B33/06
Filed: 1956-03-01
Abstract: 799,321. Honing machines. JONES & SHIPMAN, Ltd., A. A., and HOULDSWORTH, J. Feb. 26, 1957 [March 1, 1956], No. 6461/56. Class 60. The tool or work slide 5, Fig. 1, of a grinding machine is reciprocated between two limit positions by reversing means normally coupled by a clutch to the alternating rotary movements of a trip bar 12 resulting from the contact of a striker 11 alternately with two abutments 14, 15, one of which can, when required, be overrun to bring the striker into contact with a third abutment and the slide to a standstill in a third position, the arrangement being such that the clutch is manually or automatically adjustable so as to interrupt the coupling between the trip bar and the reversing means when, and only when, the latter are set to a position corresponding to upward travel of the slide or for the reversing means to be automatically brought into this setting by such adjustment of the clutch. As applied to a honing machine in which the slide 5 is reciprocated by hydraulic mechanism along guides 4 and carries a motordriven hone 6 operating on a workpiece 8, the striker 11 is carried on the slide and has inclined operating surfaces which contact rollers on the bottom and intermediate abutments 15, 14 to rotate the trip bar 12 and operate the reversing means controlling the direction of movement of the slide. A lower extension 23, Fig. 4, of the bar 12 is formed with a collar 24 having a recess which co-operates with a spring-urged pawl 34 carried on a pivoted clutch lever 29, provided at one end with a spring-urged plunger 31 which engages one or other of two detents 32, 33 in a rotatable sleeve 27; when the lever is in engagement with the upper detent, the pawl is disengaged from the collar 24 ,and, when in engagement with the lower detent, the pawl engages the collar and rotation of the bar 12 is communicated to the sleeve 27 which carries a pin 38 connected to a hydraulic device to reverse the direction of movement of the slide. The angular positions of the bar 12 are maintained by an arm 17, Fig. 9, carrying a stud 18 which engages one or other of a pair of notches 19, 20 in a spring-controlled arm 21. When it is desired to withdraw the hone from the workpiece, the clutch lever 29, Fig. 4, is depressed to disengage the pawl from the collar 24 and thus the sleeve 27 from the rotation of the bar 12. The lever 29 passes through a substantially triangular aperture 44, Fig. 6, in a front plate 40, Fig. 4, whereby, when depressed, the lever automatically positions the sleeve 27 and, hence the reversing valve, to move the slide upwardly ; when, during this upward movement the striker 11 contacts the abutment 13, the bar 12 is further rotated to cause a shoulder on the collar 24 to act upon a lever and so actuate a pilot vent valve whereby hydraulic pressure is applied to a slave vent valve to short-circuit the fluid from the main hydraulic driving mechanism to exhaust or vent and bring the tool slide to rest. The movement of the slave valve member is transmitted by means of a shaft 53, Fig. 4, to a hand lever 52 which is thereby moved to an " off " position from which it cannot be moved, because of the fluid pressure from the vent valve, until the lever 28 is again moved to a " down " position; with the lever 29 so moved, the fluid on the pressure side of the reversing valve is changed from pressure to exhaust which thus enables the lever 52 to be moved to an " on " position, the extent to which the lever is so moved controlling the speed of reciprocation. The rotation of the hone may be controlled manually or by single-pole limit switches 57, 58, Fig. 9, situated near the upper and lower ends of the extension 23 and controlled by the bar 12 and clutch lever 29. With the slide in the withdrawn position, both switches are open and the motor 7 driving the hone 6 will not operate until both have been closed. Switch 57 is closed by a lever 60 which is rocked by a stud 61, Fig. 4, carried on the pawl 34 when the lever 29 is raised, and the other switch 58 is only closed when the bar 12 is moved from the " down " position to the " up " position by a portion 63 of the arm 17 actuating a roller-carrying arm 62 of the switch. The arm 62 cannot be moved again to open the switch 58 until the lever 29 has been moved to the " withdraw " position and the collar 24 on the extension 23 moved sufficiently to operate the vent valve. Rotation of the tool, therefore, does not commence until the slide has reached the bottom position, and then continues until the lever 29 is moved to the " withdraw " position to open the switch 57. Withdrawal of the hone from the workpiece may be controlled automatically when the hone has reached a pre-determined size by means of a signal supplied from an electric or pneumatic device linked to the clutch lever 29 by a piston rod or like member ; the signal may also operate the switch 58 to stop the rotation of the tool before it is withdrawn. When it is desired to leave the machine for some time in the withdrawn position, the lever 52 is moved at rightangles to its on-off direction against spring action to move a bell-crank lever 77 and operate the pilot vent release valve which removes the fluid pressure holding the lever 52 in the " off " position, whereupon, since the clutch lever is set in the " up " position, the slide moves upwardly until a conical projection 65, Fig. 1, is gripped by arms 66 urged together by a spring 67. To lower the slide, a cam 68 is rotated to disengage the arms from the projection 65 by a cable 69 and lever 70, which, when rotated, also moves a cam against a spring-urged lever to move the clutch lever 29 to the " withdraw " position prior to its being manually positioned in the " down " position. More than one projection 65 may be provided to permit different secure positions. Instead of the tool working vertically as described above, the tool or work slide may be reciprocated horizontally.