Patent GB-649263-A (GB)
Abstract: 649,263. Operating clutches; ratchet gearing. TECALEMIT, Ltd., and MASON, V. B. H. Nov. 14, 1947, No. 30357. [Classes 80(ii) and 80(iii)] [Also in Group XXXVII] A timing device is adapted to operate one or more switches, valves or clutches at regular intervals, the duration of which may be adjusted. The Figs. show the device arranged to operate four switches in succession and then to interpose a time interval before repeating the operation of the switches. The switches are actuated by a cam wheel 1 having cams 2-5, the wheel being rigidly connected to a main ratchet wheel 6 which has certain of its teeth 12 removed to form deep notches 16 at 90 degrees intervals. A subsidiary ratchet wheel 8 of smaller diameter is coupled to the main ratchet wheel 6 by a spring 9, but may be directly driven by a resilient abutment 10 on the main ratchet wheel engaging a fixed abutment 11 on the subsidiary wheel. Similarly a movable abutment 18 on the subsidiary ratchet wheel may engage with the abutment 10 to drive the main ratchet wheel. The two wheels may be driven anti-clockwise by a pawl 22 on a driving lever 19, which is coupled by a rod 24 to an arm 27. The arm 27 is freely pivoted on a motor-driven worm wheel 30 but is driven by a pin 34 on the worm wheel, and by means of the rod 24 moves the lever 19 backwards against the tension of a spring 21. As the pin 34 passes over its dead-centre position 34a the spring 21 pulls the lever 19 rapidly forwards so that a " snap-action " switching impulse is obtained, which is followed by a dwell until the pin 34 again takes up the drive. Backward rotation of the two ratchet wheels is normally prevented by pawls 31, 32 and an interference pawl 29 which is pivoted on the arm 19 and guided by fixed pins 29b, 29c, Commencing at the position shown in Fig. 1, the subsidiary ratchet wheel 8 is stepped forward by one tooth 14 at each forward movement of the pawl 22 until the abutment 18 on the wheel 8 engages the abutment 10 on the main ratchet wheel, the main ratchet wheel meanwhile remaining stationary. The next forward movement of the pawl 22 moves the subsidiary wheel 8, which moves the main wheel the equivalent of one tooth. On its following backward movement, the pawl 22 rises over the first tooth 12 of the main ratchet wheel, so that on its forward movement it now moves the main ratchet wheel only forward one tooth and the cam 2 closes the first switch 37, Fig. 6, Backward rotation of the subsidiary wheel 8 under the tension of the spring 9 is prevented by the pawl 32 which is now in engagement with the subsidiary wheel. The next complete movement of the pawl 22 moves the main ratchet wheel one tooth so that the cam 2 opens switch 37 and closes switch 38. The subsidiary wheel 8 is now held against backward rotation by the interference pawl 29 only, so that on the succeeding backward movement of the lever 19 all restraint is removed from the subsidiary wheel which is turned backwards by the spring 9 until the abutment 11 again engages the abutment 10. Each forward movement of the pawl 22 now steps the whole mechanism forward one tooth and operates the remaining switches in turn, until the ratchet wheels again reach the position of Fig. 1. The time interval between each cycle of switch operations is adjusted by altering the position of the abutment 18 which screws into holes 17. In a modification the driving lever 19 may be moved by a solenoid actuated at regular intervals by an electric clock. Fig. 10 (not shown) illustrates the application of the device in actuating a single switch. The Specification sets out in some detail the manner in which the time interval between successive cycles of switch operations may be altered by using less cams or by using more notches on the main ratchet wheel, and also describes the application of the device in the lubricating system of Specification 648,759, [Group XXXIV].