| 摘要 |
484,364. Actuating machine slides. SOC. GENEVOISE D'INSTRUMENTS DE PHYSIQUE. May 24, 1937, Nos. 14362 and 14363. Convention dates, July 3, 1036 and Feb. 12, 1937. [Class 83 (iii)] [Also in Group XXIV] In a device for relieving wear on the operating screw of vertical machine tool slides, the screw drive actuates hydraulic gearing to supply fluid to a cylinder to exert a force on the slide during movement in opposition to the weight of the slide. In Fig. 1 a slide 1 is moved along guides 2, 3 by a screw 5 which rotates in a nut 8 fixed to the slide and which may be rotated by a motor 6 through gears 7. The motor 6 also drives a pump 9 delivering fluid at a pressure determined by a valve 12 to a hydraulic cylinder 11 the piston 18 of which is secured to the slide. The hydraulic pressure moving the slide upwards may be slightly greater than the weight of the slide so that the contact is transferred from the thread flanks, shown engaged in Fig. 2, which normally determine the slide position, to the opposite flanks. The hydraulic relieving force is not used during fine adjustment of the slide, which is manually effected by a wheel 13 and micrometer head 14. If it is essential to maintain the precise screw determined movement of the slide the hydraulic relieving force may be slightly less than the weight of the slide. In a modification, the screw may extend into a recess in the piston. In another modification the electric motor is connected to the screw through a clutch which is engaged only when a predetermined hydraulic pressure exists in the cylinder 11 so that the screw does not start to turn until the pressure on the threads has been relieved. In another modification, Fig. 5, the electric motor 30 driving the screw is connected through a switch 53 and a commutator 40 to a power supply which is also connected to a motor 43 driving the pump 44 which delivers to the relieving cylinder 32 and also to a switch cylinder 50 and a brake-relieving cylinder 39. The slide when stationary is braked by a shoe 36 on a lever 34 urged by a spring 37. When the motor 43 is started a coil 48 is excited to close the valve 49. The pump pressure then actuates the cylinder 39 to disengage the brake against the spring 37 and the cylinder 50 to engage the switch 53 of the motor 30 so that the screw 28 is driven. When the current is switched off by the commutator 40 the motors 30 and 43 both stop, and the valve 49 opened so that the switch 53 is disengaged and the brake 36 is reapplied. Liquid can escape from the cylinder 39 only through a narrow passage 55, the non-return inlet valve 54 being closed so that the return movement of the brake lever 34 is retarded. The motor 30 may be reversed by means of the commutator 40. |
