Patent GB-658617-A (GB)
Title: Improvements in devices for selectively positioning control shafts
IPC: G05D3/12
Filed: 1948-03-19
Abstract: 658,617. Adjusting tuning elements. MERLES, A. J. March 19, 1948, Nos. 8249 and 8250. Convention dates, April 22, 1947, and Dec. 20, 1947. [Class 40 (v)] [Also in Group XXIV] In a device for positioning a tuning element into one of a plurality of predetermined angular positions by positive locking means comprising a plurality of toothed levers engaging corresponding notched discs carried by a shaft coupled to such element, whereby the shaft is automatically arrested in the required position until the device is operated to rotate the shaft into another position, cam means driven from the same power source as the discs through at least one free-wheel device remove all the teeth from the corresponding notches before the shaft is rotated for positioning, and during positioning retain all the teeth away from the periphery of the discs with the exception of those of one preselected lever, which are allowed to contact the periphery of the corresponding disc when the operating means co-operating with the lever assembly is located in the appropriate position. In Fig. 1 a variable condenser, inductance, or resistance in radio apparatus (not shown) is driven to one of ten pre-set positions by ; a shaft a coupled to a reversible electric motor M through a friction clutch 8, an anticlockwise driving free-wheel 5, and a worm c. The shaft a carries ten stopdiscs having notches 1, which discs are normally clamped to the shaft by screw compression against intermediate spacers keyed thereto, and may be individually adjusted about the shaft when the clamping screw is slackened, Fig. 10 (not shown). The motor also drives a shaft h through a worm d and a clockwise driving free-wheel 6, which shaft carries ten cam discs D, each having a notch 4, which are arranged so that successive notches are spirally disposed at 36 degree intervals. Ten locking levers B pivoted at i are biassed by springs j so that projections 2 and 3 bear (in general) on the peripheries of the appropriate stop-discs and cam discs. The shaft a is positionally locked when the projection 3 of the appropriate lever is opposite the notch 4 of its cam disc, allowing the lever to pivot and projection 2 to enter the notch 1 of the appropriate stop-disc when the latter assumes the pre-selgeted position. The movement of the lever then opens the appropriate one of ten electrical contacts E which are serially connected and respectively operable by their associated levers. The shaft h also drives a notched conducting disc forming part of a ten contact switch G in which the notch sequentially breaks the circuit of each of the contacts which may be selectively energized by ten remote make-and-break contacts K1-K10 (Fig. 3) associated with pilot lamps. Initially shaft a and its driven element are assumed to be in the first selective position, so that projections 2 and 3 rest respectively in the notches 1 and 4 of the first positional stop-disc and cam-disc. Thus the shaft a is locked and the first contact E is open. To reposition the shaft in, e.g., the 3rd position, contact K3 (Fig. 3) is closed, and the relay R1 is operated through the switch G to energize motor M, which drives the cam disc and the disc of the switch G clockwise until the notch opens the circuit through the switch contact 3 to release relay R1. The third cam disc is now positioned with its notch 4 opposite the projection 3 of the third locking lever, and since the first lever has been lifted by the cam disc rotation, the first contact E is now closed, so that relay R2 operates to energize the motor M for rotation in the opposite direction. The switch and cam discs remain stationary, and the stop-discs A are rotated clockwise until the notch 1 of the third stop disc comes opposite the projection 2 of the third lever, which falls into the notch, arresting shaft a and its driven member in the third position. The movement of the third lever having opened the third contact E, relay R2 releases and stops the motor. The shaft and driven member may be driven to other predetermined positions by a similar sequence of operations. The multiple contacts E may be replaced by a single set of contacts opened mechanically by the displacement of any lever B, or relay R2 may be eliminated by the addition of a further pair of contacts E to be operated by the displacement of each lever. Shafts a and h may be fitted with knobs for manual adjustment which is permitted by the free-wheels and friction clutch without disconnection of the motor drive. A plurality of driven members may be selectively positioned by the same motor. In a modification, Figs. 4, 5 (not shown), wherein the driven member may turn only through 180 degrees, the motor is coupled to the drive shaft through a lostmotion device instead of a free-wheel, and is actuated first in one direction and then in the other through the operation of two limit switches by two 180 degrees spaced abutments on a disc carried by the drive-shaft. All the locking levers are lifted at the beginning of a setting operation by a cam driven from the motor shaft through a slipping clutch. When the driveshaft is locked in the selected position, the motor is stopped by the opening of contacts E as before. The disc cam and switch shaft may be operated through the drive-shaft lost-motion device, Fig. 6 (not shown). In further modifications, Figs. 7, 8, 9 (not shown), in which a drive-shaft is to be positioned with high accuracy or within a possible range of several revolutions, the drive-shaft is geared down to a plurality of auxiliary shafts, all of which carry banks of adjustable locking discs co-operating with locking levers operated as before, each of which carries a plurality of locking projections. The notches on the auxiliary discs are wider than their corresponding projections and the notches in the drive-shaft discs, while additional cam-operated retaining levers carry projections co-operating with narrow notches in the auxiliary discs to hold the latter in position once they have been selected. This form of the invention is applicable to revolution counting.