| 摘要 |
1,200,436. Intermittent gearing. CONTRAVES A.G. 3 March, 1969 [5 March, 1968], No. 11234/69. Heading F2Q. A disengageable intermittent drive includes a continuously rotated input rotor 20 housing drive pins 21, 22 slidable in diametrically opposed bores parallel to the rotor axis AA, the pins being selectively movable magnetically from retracted positions to operative positions in which they can engage open slots 41 in a driven member 4 to advance the latter stepwise. The driven member 4 may be a rack bar with parallel slots 41, as shown, or a rotary member with radial slots. A polepiece 32 has a face 320 coaxial with the rotor 20 to provide a narrow air-gap therewith. A polepiece 31 has a part cylindrical face 310 centred on an axis B normal to the rotor axis AA. The polepieces 31, 32, rotor 20, and the pin opposite the face 310 form part of a ferro-magnetic circuit. The rotor is chamfered at 23 (Fig. 3, not shown) to concentrate the magnetic flux on the pins 21, 22. As a retracted pin 21 or 22 reaches top dead centre, it touches the face 310. If the magnetic circuit is operative the pin remains in contact with the face 310 as the rotor turns through 90 degrees, so that it drivingly engages a slot 41 during the next half turn. For the final 90 degrees, the face 310 pushes the pin back to its retracted position. With the circuit inoperative the pins remain retracted. Friction means 24 may hold the pins against random movement. In Fig. 1, the circuit is made operative by energizing a coil 3 having a core 30. In Fig. 4, the circuit includes a permanent magnet 35 and a shunt circuit including a gap 36 which is filled by a soft iron plug 5 to render the main ferromagnetic circuit inoperative. The plug 5 is movable by a pneumatic actuator 52, 53 controlled by a selector valve 54. A rack 4 is movable by two intermittent drives acting in opposite directions, a deflector ramp 42 at each end of the rack deflecting operative pins to limit travel. |
