Patent GB-764770-A (GB)
Title: Improvements in or relating to adjusting mechanisms for rotating a member to a number of desired positions
IPC: H03J5/20
Filed: 1954-11-24
Abstract: 764,770. Electric control systems. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Nov. 24, 1954 [Nov. 27, 1953], No. 34068/54. Class 40 (1). [Also in Group XXIV] In an adjusting mechanism for rotating a member to any one of a number of set positions by means of a shaft which is rotatable through more than 360 degrees, the direction of rotation of the member from one position to another is such that its angular displacement is a minimum, the member, however, always assuming the new position in the same direction of rotation. The member to be adjusted, which may be a tapping of an inductance coil, or a slide capacitor or the like, is driven by a shaft 16, Fig. 1. A switch 63, Fig. 8, which may be remote from the mechanism, when turned to a position corresponding to that desired for the member, energizes a relay 64 and closes some of the contacts of a group 65 to produce rotation of a motor 61. The motor 61 rotates a selector wheel 17 through a worm 3, worm-wheel 4, one-way clutch 6 and gearing 8, 11, 13, 15 until the selected position is reached when a distributer 10 on the shaft 9 of the gear 8 interrupts the circuit through the relay 64 and returns the group contacts 65 to the initial position shown. As a switch 62 operated by an overload clutch 20 is now closed, the motor 61 is reversed and the worm-wheel 4 now drives the shaft 16 through a one-way clutch 5, gears 18, 19, overload clutch 20, gear 22, differential gear 22a, shaft 14 and gears 23, 24. Shaft 16 has a set of primary locking rings 25 fixed thereto and a secondary set 32 free thereon. The rings 32 are rotated slower than the rings 25 through reduction gearing 26, 27, 30, 31 and a shaft 28 embodying a spring 29. A number of rockshafts 34 corresponding to the number of adjusted positions required are mounted around the locking rings and each has pawls 36, 37, coacting with the locking rings 25, 32, respectively, and projections 35, 38, co-operating with the selector ring 17 and a notched ring 33. When the shaft 16 has rotated the desired amount it is arrested by the pawls 36, 37, on one of the shafts 34 engaging recesses 42, 39 in a locking ring 25, 32. This produces disengagement of the overload clutch 20 which also switches off the motor 61 by opening the switch 62. Exact location of the selector 17 may be ensured by a ratchet disc 8a, Fig. 7, fixed to the gear 8 and provided with teeth 66 corresponding to the number of set positions desired. A spring-actuated pawl 68 engages between a pair of teeth 66. To permit rotation of the shaft 16 in a direction such that its movement to the desired position is a minimum the locking rings 32, Fig. 2, have the slot 39 for a pawl 37 separated by two arcs 40, 41, the radius of 40 being greater than the radius of 41. The perimeter 43, Fig. 3, of each locking ring 25 is less than the radius of 41 and has a single slot 42 for a pawl 36. If the pawl 37 is on the arc 40, the projection 38, Fig. 4a, closes a switch 45 so that a pawl 47 releases a ratchet-wheel 48, forming one of the output members of the differential 22a, so that the shaft 14 rotates in a direction to move the locking rings 25, 32, anticlockwise, Fig. 2, or to the left, Fig. 4a. When the pawl 37 partly enters the slot 39, the recess 42 has travelled beyond the pawl 36. The movement given to the pawl 37, however, breaks the switch 45, pawl 47 is released and holds the ratchetwheel 48 stationary causing reverse rotation of the shaft 14. Movement of the rings 32 is prevented by the contact of surface 50 and pawl 37, but the spring 29 permits further movement of the rings 25 until pawl 36 engages surface 49 of recess 42. The shaft 16 is now correctly positioned and the overload clutch 20 disengages and switch 62 is opened to stop the motor 61. If pawl 37 is on the arc 41, the switch 45 is open and the rings 32 rotate clockwise, Fig. 2, and the shaft 16 is finally held by the pawls engaging the surfaces 49, 50 without any reversal of the drive. An arrangement for the switch 45 comprises a ring 33, Fig. 5, capable of slight angular movement and having  slots 51 each receiving with play a projection 38 of a pawl 37. A lever 52, pivoted at 53, is connected to the ring 33 and to a spring 53a. The free end of the lever 52 operates the switch 45. When the free end of a pawl 37 is on the part 40 of a locking ring, the switch is closed and when the pawl engages a part 41 the ring 33 is given a slight turning movement which opens the switch. To permit of manual adjustment of the shaft 16, the gear 23, Fig. 6, is connected to the differential output shaft 14 by a clutch key 54. Depression of a knob 58 will disengage the gear 23 from the shaft 14 and will break a switch 60 in the circuit of the motor 61. Specifications 634,781 and 653,762, [both in Group XXIV], are referred to.