Patent GB-1240078-A (GB)
Title: Controlled rotation devices
IPC: G04B19/21
Filed: 1969-11-07
Abstract: 1,240,078. Intermittent-rotation devices; positive detents. ITT INDUSTRIES Inc. 7 Nov., 1969 [8 Nov., 1968], No. 54694/69. Heading F2E. [Also in Divisions G3, G4 and H1] A controlled rotation device applicable to time indicating, time alarms, and time switches, and to automatic control of equipment such as an oven is shown in principle in Fig. 1. A star wheel 3 is fitted on a rotatable shaft 1, the fit of the wheel on the shaft being such that if no restraint is applied to the wheel it will rotate with the shaft. A cam wheel 7 is securely fixed to the shaft. In operation, the shaft is rotated continuously, and for a large part of each revolution the star wheel 3 is restrained by a pivoted pin 5, but when the pin is raised by a cam 8 on the cam wheel 7, the star wheel 3 is permitted to rotate with the shaft. In Fig. 3, a shaft 20 is driven by a synchronous motor (not illustrated) at a speed of one revolution per hour. Indicia wheel 16 is driven from the shaft by clutch plate 22 continuously and has no provision for periodic restraint; its indicating ring 31 carries numbers representing minutes. Indicia wheel 15 is driven by clutchplate 21 and has in its left-hand face twelve indentations; for most of each hour it is held stationary by a ball 27 engaging one of the indentations. A drive control plate 26 is rotated continuously by the shaft, and has a single cut-out portion 26A so that once per revolution this cut-out portion coincides in position with ball 27, whereupon a spring 28 retracts the ball 27 from the indentation in wheel 15, the wheel is driven by the clutch for one twelfth of a revolution, and thereafter ball 27 engages the next succeeding indentation. Numbers on the indicating ring 31 of wheel 15 represent hours, so wheels 15 and 16 together indicate the time of day. The third indicia wheel 17 has associated with it an alarm wheel 38 and is unrestrained, so that once per hour, when the zero mark on its indicating ring passes a specific point, a groove 37 operates a micro-switch by means of a spring-loaded control member 36. This wheel and wheel 15 are knurled to permit ready setting. Indicia wheel 18 is a delayed start wheel, and is intended to close contacts to switch an oven on when its zero passes a certain point. By providing the wheel with one indentation engageable by a spring-loaded ball and a drive control plate 34 having a single recess 34A, the delay will be an integral number of hours. The duration of the delay may be selected by appropriate choice of number of indentations and number of recesses. Indicia wheel 19 is "set" for the cooking time, and when this cooking time has elapsed it triggers a microswitch to switch the main oven thermostat out of the oven control circuit and to switch a supplementary low-temperature thermostat in its place. (Indicia wheel 19 is initially prevented from rotating, by a solenoid brake or the like, until the oven is switched on by wheel 18.) All drive control plates are slidable on shaft 20 to facilitate manual re-setting of indicia wheels. Instead of the ball-and-indentation manner of restraining the indicia wheels, a brake pad may bear against a concentric circular flange provided on the wheel, or against the circumference of the wheel itself, and be released by a cam driven by the shaft; or a caliper brake may be used. The setting of the wheel may be changed without releasing the brake. Devices embodying the invention may be made as modules and combined end-to-end by providing the shaft with a tongue 2A at one end and a groove 2B at the other. Instead of a shaft a disc may be used as the driving member.