Patent GB-143971-A (GB)
Title: Improvements in driving mechanism for valves and other devices
IPC: F16H1/28
Filed: 1919-03-05
Abstract: 143,971. Dean, P. P. March 5, 1919. Systems controlling travel for a fixed distance or number of revolutions.-Relates to motor-operated valve and like actuating-mechanism of the kind described in Specification 110,228 involving epicyclic, planetary, or similar gearing and consists in improved means for mechanically releasing the outer wheel 3, Figs. 1 and 2, and switching off the electric current at the end of each run of the motor. The wheel 3 has two peripheral grooves 21, 22, Fig. 2, each formed with a block 23, 24, Fig. 1, therein to abut against corresponding restraining-plugs 18, 19, Figs. 1 and 2. These plugs are operatively engaged with crank-levers 38, 40, which carry the bridging contacts 64, 65 of limit switches 60, 61 and 62, 63, Fig. 6, and are withdrawn at the proper time by rotary cams 35, 36, Figs. 1 and 5, operating through contact rollers 33, 34 on levers 30, 31. The bosses of the latter levers are engaged with the bosses of the crank levers 38, 40 by means of forks 30<a>, 31<a> and lugs 38<a> and 40<a> thereby providing lost motion. The cams 35, 36 are moved along a square shaft 45 by a bracket 37 on a traversing- screw 46. The shaft 45 is operated with a stepby-step movement and the screw 46 is constantly rotated by suitable toothed gearing from the driven shaft 1<a>. To aline the roller 33 correctly with its cam at the end of the motor run, the roller 33 is adjusted on a screw 42 carried, as shown, by two arms of the lever 30. At either end of the motor run when one of the cams 35, 36 operates its corresponding lever 30 or 31, the said lever first takes up the lost-motion and then operates the crank-lever 38 or 40, which withdraws a restraining-plug 18 or 19 from its block 23 or 24 to free the wheel 3 and disconnect the driven shaft 1<a> from the motor; at the same time it opens the corresponding limit switch to cut off the power current. The wheel 3, when freed, starts rotating idly, but is arrested before a revolution is completed by the second of the blocks 23, 24 engaging the second of the restraining- plugs 18, 19. This action restores the gearing connexion temporarily so that the unspent momentum of the motor is absorbed and exhausted in a slight hammer blow. In the initial movement of the released wheel 3, the inclined outer surface of the blocks 23, 24 operates on the end of the withdrawn plug 18 or 19 and rapidly moves the same outwards; this action, owing to the lost-motion at the lever bosses, operates the levers 38, 40 rapidly, and thereby effects a quick opening of the switches. The levers 38, 40 are held in their raised positions by spring latches 71 until the motor is reversed. When the motor is reversed it starts idle with the wheel 3 rotating freely in the reverse direction until the second of its blocks 23, 24 abuts against the second of the restraining-plugs 18, 19, whereupon the gearing connexion is restored for operation in the reverse direction. The motor is thus able to get up speed before operative connexion is made so as to start work with a slight hammer blow. When the operating-cam 35 or 36 releases the roller 33 or 34, a spring 39 or 41 re-closes the opened switch and returns the withdrawn plug 18 or 19 to its groove 21 or 22. The cam 36, Fig. 5, is adjustable relatively to the cam 35 by means of a toothed clutch 35a, 36<a>. The arrangement of the circuits is shown in Fig. 6, with the limits switches 61, 62 and reversing switch 75-88. In the position shown, circuit is established from line L through contacts 76, 78, line 79, motor armature A, line 80, contacts 81, 83, line 84, switch contacts 60, 64, 61, and motor field-magnet F, to the line L<1>. When the switch contacts 60, 64, 61 are opened at the end of a run, as shown, the motor stops and can only be re-started in the reverse direction by reversing the switch 75-88. The other limit switch 62, 65, 63 is then operative on the reverse run.