Patent GB-808997-A (GB)
Title: Angular positioning system
Inventor: BARRE MAURICE
IPC: G05D3/12
Filed: 1957-01-30
Abstract: 808,997. Positioning shafts; securing discs on shafts. RADIO A.I.R. APPLICATIONS INDUSTRIELLES RADIOELECTRIQUES. Jan. 30, 1957, No. 3244/57. Class 80 (2). [Also in Group XXXVII] In a shaft positioning system wherein a sleeve 2, fast with a shaft 1 of a variable capacitor in radio-tune apparatus, is stopped in a selected one of a number of angular positions by engagement of stop pawls 26 with notched discs 18 adjustably mounted on the sleeve 2, positioning between adjacent selectable positions, is effected throughout one revolution in two stages, during the first of which a previously effective stop-pawl is released from its disc, whereafter during the second stage a common pawl-carrier is rotated, the next succeeding stop-pawl engages its disc and drives the complete disc-pack and the sleeve 2 to the next succeeding final locked position. The stoppawls 26 pivot in slots in an inner pawl-drum 31 rotatable relative to an outer drum 41 having worm teeth 42 engaging a motor-driven worm 43. During the first positioning stage the pawldrum 31 is held locked by a stationary latch 56 pressed about a fixed pivot 57 by a spring 65 to cause a nose 64 on the latch to engage a notch 58 in a disc 59 fast to the pawl-drum 31. At this time the motor-driven worm 43 turns the outer drum 41 alone to cause a single or multiple blade-spring 40 on the drum to release the previously effective stop-pawl 26 for disengagement from its stop-disc 18 by a pawlspring, and to bias the next succeeding stoppawl 26 towards engagement with its stop-disc 18, the relative angular movement between the outer drum 41 and pawl drum 31 being limited for this purpose by the following locking device. Carried by the pawl-drum 31 is a stepped pinion 46, 47, the smaller step 46 of which meshes teeth 45 on the outer drum 41, whilst the larger step 47 has long and short teeth 48, 49, meshing a limited arc of teeth 50 inside a free cam-ring 51 having an outer cam-recess 54 engaging a roller 55 on the stationary latch 56 which locks the pawl-drum 31. In operation the pawl-drum 31 is initially locked by the stationary latch 56 and when, during the first stage, the outer drum 41 is rotated by the worm 43, the gear teeth 45 on the drum turn the stepped pinion 46, 47 on its initially stationary axis, whereby its step 47 turns the cam ring 51 in the reverse direction through an angle limited by the length of the toothed arc 50. This first stage is terminated by a ramp 74 on the cam-ring 51 raising the stationary latch 56 to free the cam-drum 31, and by the long teeth 49 of the stepped pinion 46, 47, locking on a raised surface 53 following the toothed arc 50 on the cam-ring 51, thus preventing further rotation of the stepped wheel 46, 47 on its own axis and causing it to lock together the pawl-drum 31 and outer drum 41. During the ensuing second stage, the pawl-drum 31, cam-ring 51 and outer drum 41 rotate in unison in the forward direction and, when the next succeeding stop-pawl 26 registers with the notch in its stop disc 18, it is engaged therewith by the bias spring 40, whereafter the disc-pack 18 and inner sleeve 2 are taken along in rotation with the drums 31, 41. The second stage continues for one complete forward revolution of the pawl-drum 31, until the notch 58 in the end-plate 59 of the pawl-drum 31 again reaches the nose 64 of the latch 56, whereupon the latch springs in to lock the pawl-drum 31 and with it the inner sleeve 2 in the next succeeding position. Before this latch action, a notch 70 in the cam ring 51 reaches a hook 68 carried by the latch 56, which, whilst still lifted by engagement of its nose 64 with the surface of the endplate 59, presses the hook 68 into the notch 70, which holds the cam-ring 51 from further rotation, so that in the final arc of rotation of the pawl-drum 31, the stepped pinion 46, 47 is rolled over the teeth 50 to reach the other end of the toothed arc, resuming its initial position shown, and the engagement of the latch 56 in the pawl-drum notch 58 causes release of the hook 68 from the cam ring notch 70. The parts are now set in initial position ready for further operations through any desired number of positional steps. Stop disc setting adjustment. The stop discs 18 are frictionally mounted on the sleeve 2 by interposed friction discs 17 splined to the sleeve 2, the disc-pack being pressed axially against a back-plate 19 by a presser-wheel 4, screwed to the sleeve and acting through slidable pins 12, a cup 15 and plate spring 16<SP>1</SP>. To set any particular stop disc 18 circumferentially on the sleeve 2, that stop disc is held by its stop-pawl 26 with the pawl-drum 31 in locked condition, as above described. End-pressure on the discpack is then partly relieved by turning, with a suitable tool applied at 10, a pinion 6 meshing with the threaded presser-wheel 4 and carried by a knob 8 fast to the sleeve 2. The sleeve 2 can now be turned by the knob to a required set position, whilst the particular stop disc 18 remains locked by its pawl, and the other stop discs, unaffected, turn with the sleeve. End pressure is reapplied to the disc-pack by turning the pinion 6 and the device is set. The knob 8 has a permanent friction drag on the casing at 150. Control circuit. Fig. 6 shows an electrical control circuit for simultaneously operating three, one, or other number of positioning devices 83, 84, 85, as above described. A motor 89, through a reduction gear 87, drives the worms 43 of all the devices in unison and is energized through two circuits, one controlled by a manual rotary selector switch 107 (or pushbuttons) having ten positions corresponding to those of the positioning devices, and co-operating with a ten-position follower switch 102 driven through the reduction gear 87; the other controlled by a switch 98, operated by a pin 76 of one, 85, of the setting devices to effect a governor control of motor speed during the final setting phase. In any initial set position a relay 94 is energized, as shown, through contacts, e.g. 1, of the two rotary switches 102, 107. Shifting the manual switch 107 to select another setting requiring one or more positional steps breaks the circuit of the relay 94, contacts 93 of which close to energize the motor 89. When the motor-driven follower switch 102 reaches the setting corresponding to that selected by the manual switch 107, each positional step requiring a complete revolution of the positioning devices, the relay 94 is again energized to open the motor-energizing contacts 93, but the switch 98 has, in the meantime, been closed by the positioning device 85, to maintain energization of the motor 89 through an inertia-type speed governor 96, driven through the reduction gear 87, to ensure final positioning at a suitable governed speed, this circuit being broken at the switch 98 on final positioning. A signal lamp 113 energized by another contact of the relay 94 is also provided.