| 摘要 |
666,924. Chucks; screwing-up and unscrewing screws. WARNER & SWASEY CO. July 18, 1949 [July 30, 1948], No. 18881/49. Class 83 (iii). In a lathe or other machine tool provided with reversible power means including a friction clutch for operating the jaws of a chuck, means are provided for exerting a substantially constant predetermined clutch - engaging pressure when the power means are operated to close the chuck jaws so that the clutch transmits a substantially constant torque for closing the chuck jaws and means are also provided for automatically increasing the clutch - engaging pressure when the power means are operated to release the chuck jaws so that the clutch transmits a greater torque for releasing the chuck jaws. The chuck jaws 22 are operated by means of an axiallymovable wrench spindle 25 which is rotated by means of the engagement of a wormwheel 31, Fig. 5, thereon with a worm 52, Fig. 8, on a shaft 51 which is driven from a reversible electric motor 48 through a friction clutch 49. The members of the clutch are pressed towards each other by means of a rockable forked lever 58 provided with a roller 60 which'is engaged by the plunger 61 of a piston 62 associated with a piston 64. The wrench spindle is moved axially towards and away from an operating member in an opening 23 of the chuck by means of a handle 36 acting through the intermediary of a shaft 38, Fig. 5, racks 39, 42, and segmental pinions 40, 41. The handle 36 can be turned in either direction to control the position of the core member 70 of a rotary valve 68, Fig. 2, provided in a circuit containing a pump 86, a pressure regulator 69, and conduits 66, 67 leading to the spaces below the pistons 62, 64, respectively. The pressure of the fluid in the regulator 69 is adjustable by means of a knob 100 associated with a spring-pressed valve member 97 and is indicated by a gauge 101. The worm wheel 31 is associated with a lost-motion disc 28 which is provided with a segmental portion 34, Fig. 8, which is engageable by a lug 33 on the worm wheel. A spring-pressed plunger 44, Fig. 5, operated by the main control lever 43 of the headstock mechanism is adapted to engage a groove 45 on the shaft 38 to prevent engagement of the wrench spindle with the operating member in the chuck opening 23 .when the chuck is rotating. The direction of rotation of the motor 48 is controlled by means of switches operated by a member 103, Fig. 8, which rocks with the core member 70. A direction switch enables the chuck jaws to grip the work either internally or externally. In operation, the regulator 69 is adjusted and the direction switch actuated according as external or internal gripping by the chuck is desired. The control lever 43 is moved to its neutral position to disengage the plunger 44 from the groove 45. The handle 36 is then pulled outwardly so that the wrench spindle engages the operating member in the chuck opening 23 and is turned to the right, i.e. in the chuck-closing direction. The turning movement of the handle rocks the arm 103 to close the contacts of a switch for energizing the motor 48 to rotate in the forward direction. Turning of the handle also moves the core. member 70 of the valve 68 to supply pressure fluid to the space below the piston 62. This moves the piston upwardly and exerts a clutchengaging pressure upon the members of the clutch 49 through rocking of the lever 58. When the chuck has been properly tightened, the handle 36 is turned back to its neutral position to de-energize the motor 48 and move the core member 70 to its neutral position. The handle is also moved inwardly to disengage the wrench spindle from the chuck. The chuck is now rotated by operating the control lever 43 to disengage the plunger 44 from the groove 45. After the machining operation or operations have been completed, rotation of the chuck is stopped by operation of the lever 43, thus releasing the plunger 44 from the groove 45. The handle is now pulled outwardly to move the wrench spindle into engagement with the operating member in the chuck opening 23. The handle 36 is then turned to the left, i.e. in the chuck-opening direction, to cause the arm 103 to close the contacts of a switch for energizing the motor 48 to rotate in the reverse direction. Turning of the handle also positions the core member 70 so that pressure fluid passes through the regulator 69 to the space below the piston 62 and through the valve 68 to the space below the piston 64. Consequently, the clutchengaging pressure exerted upon the members of the clutch is increased over that which is exerted during closing movement of the chuck. The opening action is further assisted by the blow caused by the engagement of the portion 34 of the disc 28 with the lug 33 on the worm wheel 31.' After the chuck jaws have been opened sufficiently to release the work, the handle 36 is turned back to its neutral position to de-energize the motor 48 and move the core member 70 back to its neutral position. In a modification, Figs. 11 to 14 (not shown), the fluid-pressure operated mechanism is replaced by a lever pivoted at one end to the lever 58 and at its other end to one end of a link which is connected at its other end to an adjustable spring-pressed plunger which is associated with an electromagnet the armature of which is connected to the lever 58, the arrangement being such that when the chuck jaws are to be closed, the spring-pressed plunger rocks the lever 58 to exert a predetermined clutch-engaging pressure upon the members of the friction clutch, and when the chuck jaws are to be opened, the electromagnet is entergized so that both it and the spring-pressed plunger rock the lever 58 to exert an increased clutch-engaging pressure upon the members of the clutch. |
