Patent GB-458506-A (GB)
Title: Improvements in or relating to electrically actuated reversible step by step ratchet mechanism
IPC: G05D13/00
Filed: 1935-05-14
Abstract: 458,506. Ratchet gearing. GRANT, P., and RUSTON & HORNSBY, Ltd., Sheaf Iron Works, Waterside South, Lincolnshire. May 14, 1935, No. 14091. [Class 80 (iii)] [See also Group XXVI] Relates to controlling mechanism for loading the spring or springs of engine governors and embodying electromagnetically operated positive or frictional ratchet gearing for effecting a single or a series of control steps. In a governor for a compression-ignition engine suitable for driving an alternator, a horizontal spindle 1, Figs. 1, 2, extends lengthwise of the engine, is supported in brackets 3 extending from a supporting plate 4, and has fast thereon a ratchet wheel 2. The plate 4 also carries solenoids 5, 6 for actuating pawls 11, 12 pivoted in levers 7, 8, each of which is formed of a pair of spaced plates which straddle the ratchet wheel, the inner ends of lever 7 lying within the corresponding ends of lever 8. Each pawl is of angular form and comprises two arms at an obtuse angle, the pivot being at the bend. The tails 11<b>, 12b of the pawls are weighted to swing the pawls normally clear of the teeth, the swinging movement being limited by stops 13, 14 on the levers. The ratchet teeth are preferably parallel-sided with the crowns cut away. Each of the solenoids has a fixed core at its upper end and a lower axially slidable core which carries at its upper end a plunger, the ends 5<a>, 6<a> of the plungers engaging the tail portions of the pawls. Current from a suitable source may be passed through either solenoid by tappet or push-button switches, described with reference to Fig. 4 (not shown). Instead of two push-buttons, one for each solenoid, the two solenoids may be connected through a reversing switch and a single push-button. A long sleeve 15, Fig. 1, connected to the ratchet-wheel spindle 1 is screw-threaded over a spindle 16 connected to one arm of a lever 17, the other arm of which bears against a collar 18 forming an abutment for a spring 19 which bears at its other end against a collar 20 on a sleeve 21 connected to an arm of a lever 22, the other arm of which acts upon the governor weights 23 loaded by the main springs 24. A hand wheel 25 permits of independent adjustment of the governor loading. By pressing the push-button, the selected solenoid pushes up the pawl and advances the wheel. More than one impulse may be given by successive depressions of the button. If the adjustment is too great, the other push-button is actuated or the reversing switch employed. To hold the ratchet wheel after each adjustment, a detent is actuated by an auxiliary solenoid wound in series with the main solenoids, the clearances being so adjusted that the detent is removed from the wheel just as a pawl is about to move it. A succession of impulses may be imparted during one depression of a push button by employing an interrupter with a slow make-and-break. The actuation of the ratchet through the interrupter may be brought about automatically by providing two interrupters, two of the contacts of each of which are adapted to be connected with corresponding contacts on the usual tachometer, two contacts being provided for completing the circuit through the magnet of one interrupter when the speed rises and two further contacts for completing the circuit through the magnet of the second interrupter when the speed falls. The apparatus for imparting a single impulse may be combined with that for producing a number of successive impulses, two push-buttons and a reversing switch permitting of either being used. The positive ratchet drive may be replaced by a friction drive, Fig. 5, in which the wheel 40 is nearly encircled by strap gripping members 41, 42 with flanges 41a, 42<a> connected by bolts 43 against the action of springs 44. The upper member is maintained central by springs 45, 46. Below each flange is a rocking arm 48 mounted with clearance around the bolts 43 and provided with side guide-lugs 50. Each arm is of double wedge form lengthwise. The plungers 5a or 6<a> of the solenoids engage the inner end of a rocking arm which fulcrums on the head of the bolt and engages under a flange 42<a> which is swung upwardly, thus drawing together the members 41, 42 to grip the wheel. According to the Provisional Specification, the ratchet mechanism and its actuating parts may be employed for operating valves and ventilators and for opening and closing windows.