GB673102A - Improvements in or relating to process timing and like devices - Google Patents

Abstract

673,102. Time switches. METROPOLITANVICKERS ELECTRICAL CO., Ltd. Aug. 15, 1950. [Aug. 31, 1949] No. 22620/49. Class 38 (v). A time switch for determining the duration of a manufacturing or other process has two rotatable striker members which are jointly effective to unlatch a switch at the end of the time interval, one of the members being driven at a fractional speed relative to the other. The switch has a drive motor 10, Fig. 1, which through a spring controlled friction clutch 17 and pinions 16, 18, 24, 36, 37 drives sun wheels 25, 35 of a differential gear, the sun wheels being freely rotatable on a shaft 26 to which is rigidly fixed the axle 33 of planet wheels 34. A plate element 40 of a friction clutch is secured to the shaft 26 and has depressions 43, Fig. 2, engaged by a bowed spring member 41 which may be set by a knob 3 and carries the striker member 61, Fig. 2. The other striker member 60 is carried by a pinion 48 driven by a pinion 44 on a shaft 21 driven by the motor through the pinions 16, 18. A knob 4 and pinion 45 permit the setting of the member 60 away from a zero position. In the arrangement shown, the gearing provides a 60 : 1 ratio between the "minutes" striker member 61 which is turned through one revolution in an hour, and the "seconds" striker member 60 which makes one revolution in a minute. In use, the knobs 3, 4 are turned to set the desired time interval in minutes and seconds which is indicated by pointers 5, 6 carried by the knob 3 and pinion 48 respectively. This moves the striker members 60, 61 away from the zero position indicated. in Fig. 2. A knob 12 on a shaft 11, is then depressed to close a microswitch 13 to initiate the process and to start the motor 10. The shaft 11 is latched down by a bar 50 which is biassed by a spring 52 into a slot 53 in the shaft 11. The bar 50 is provided with a pivoted lever 54 which co-operates with pins 56, 57 on the striker members 60, 61. At first, as the "seconds" striker member 60 passes through the zero position its pin 56 in engaging with the lever 54 merely pivots the lever 54 against the tension of a spring 55 as indicated in Fig. 4. This action is repeated as the member 60 rotates, on each subsequent revolution, 'until towards the end of the set period the pin 57 on the "minutes" striker member 61 engages the lower end of the lever 54, then as the striker member 60 moves into its zero position its pin. 56 in engaging the lever 54 causes the lever to pivot about the pin 57, so withdrawing the bar 50 and unlatching the shaft 11 to open the switch 13. In a modification, Fig. 6 (not shown) the differential gear arrangement is provided with friction clutches and brakes so that shaft 26 may be driven at any one of three different speeds. In Fig. 7 (not shown) each sun wheel has its own drive motor, the motors being selectively energized to provide the desired speed.