Patent GB-617330-A (GB)
Title: Fluid pressure control mechanism
IPC: F15B11/20
Filed: 1945-06-27
Abstract: 617,330. Controlling reverse-gearing; locking levers. BENDIX-WESTINGHOUSE AUTOMOTIVE AIR BRAKE CO. June 27, 1945, No. 16412. Convention date, March 22, 1944. [Classes 80 (ii) and 80 (iii)] Relates to a selector-valve control-mechanism more particularly for use in a marine reversegear for supplying compressed air to inflate distensible annular members 8, 13, one, 8, of which, contracts friction clutch-segments to grip a driven member 10 and provide a direct forward drive between driving and driven shafts 5, 6; whilst the other, 13, contracts friction brake-shoes to station a carrier 15 of planets 17, arranged between a driving ring- gear 19 and a driven sun 18, thus providing reverse drive. The forward - neutral - reverse selector-valves 57, 58, 56, Fig. 1, and the engine-throttle are operated by a single controllever 98, Figs. 5 and 9, which is movable between positions 1 and 9, Fig. 2, and is moved from an engine-idling neutral position 1, Fig. 2, into a forward-gear position 2 and thence. laterally into a throttle-opening range 3-4, in a guided path 1, 2, 3, which, once started, cannot be retraced reversely, the return to neutral being only possible by first moving from position 3 to a further position 6 and thence laterally back to position 1, no step between positions 1, 2, 3, 6 and 1 being reversible. This, together with timed pressure-released locking- plungers 125, 126, 127, ensure that it is not possible to move the lever into the throttle-opening range 3, 4 (or 7, 8) or return to neutral, until after the forward-clutch (or reverse brake) has been fully engaged or to engage the reverse-brake until the pressure in the forward-clutch is below the minimum for complete disengagement. Partial engagement and thus slip and wear on the friction surfaces are thereby avoided. The invention is concerned with the provision of resiliently-biassed locking-rings 175, 176 (see below) which assist in enforcing the sequential operation of the lever in its closed path. Means is also provided for relieving the stationary pressure - seals 24, bearing on the driving-shaft 5, of all pressure during normal operation, to prevent wear on the seal. The selector - valve group comprises three dumb - belt - valves 56, 57, 58, Fig. 1, communicating with a common pressure-chest 43, supplied from a reservoir 44, and with a common open exhaust-duct 74. The outlet-chamber 50 of the valve 56 communicates through a conduit 78 directly with the reverse brake-annulus 13; that 51 of the valve 57, leads, through a conduit 79, to a non-rotating chamber 26, which supplies the forward clutch-annulus 8 through a spring- seated non-return valve 29; whilst the outlet of the third valve 58 leads, through a conduit 36 to a chamber containing an annular piston 35, which, through pins 36a and a sliding collar 32, opens the non-return valve 29 to vent the clutch-annulus 8 when forward drive is to be disengaged. The valves 56, 57 are fed through restrictor-orifices 48, 49 to ensure gradual engagement of the clutch and brake. The non-rotating chamber 26 has at each end pressure-seals 24, bearing on the driving shaft 5, and to prevent wear on the seals they are relieved of pressure when the forward-drive clutch 8 is engaged, by venting the chamber 26, working pressure being retained in the clutchannulus 8 by the non-return valve 29 and being made up manually as required, as described below. No seal is required for the reverse brake-annulus 13 which is kept under direct supply-pressure for all reverse operation. The selector-valves 56, 57, 58 are controlled by sliding and turning a cam-shaft 80, shown developed in Fig. 11, and having cam-slots 86, 85, 84, acting through balls 81, 82, 83 on hollow ported plungers 71, 72, 73, which operate the valves and also form exhaust-valve seats for their lower ends, the valve-axes lying on centrelines 90, 89, 88. The opposite side of the camshaft 80 has shaped apertures 128, 129, 130 for engagement with locking-plungers 125, 126, 127, which are actuated by air-pressure in the selector-valve outlet-conduits 78, 79, 36 to lock the cam-shaft positively for a predetermined time-interval to ensure the required sequential inflation and deflation of the clutch and brake annuli 8, 13, as described below. An allmechanical lock 41 also assists in this function and in controlling the sequence of the movements of the shift-lever 98. The selector-cam-shaft 80 is operated through a yoke 99, Fig. 9, pivoted to it at 102 and carried by the actuating-lever 98, fulcrumed at 106 on an extension-bracket of a collar 108, secured to an inner shaft 104, Fig. 1, which can rotate but not slide axially, whereby turning movement of the lever about the axis of the inner shaft 104 always turns that shaft, whilst lateral movement of the lever always moves the camshaft 80 axially and in the opposite direction to the lever. The shaft 104 is connected to the engine-throttle through a lost-motion connection (not shown), which permits sufficient idling travel for fully operating the selector-valves before the throttle-opening range is reached. The lever 98 is locked in a central neutral position by a pivoted latch 112, Fig. 5, engaging a notch 114 in a fixed endplate 115,. and released by fully'depressing a spring-loaded button 121 in the end of the lever. The latch 112 also carries a worm 117, which, by freely tracking a gap between two segments of wheel-teeth 118 on the fixed endplate 115, determines the limits of the idling arc, beyond which the worm must be lifted clear of the teeth by partly depressing the button 121 to pass to the throttle-opening range. Release of the button in this range engages the worm 117 with the fixed teeth 118, thereby locking the lever 98 in any set throttleopen position, which may be finely adjusted by turning the worm 117 by a hand-knob 124. The sides of the abutments forming the notch 114 also serve as an inner limit for the throttleoperating range of the lever, which can only be returned to neutral by fully depressing the button 121 to raise the latch 112 over the abutments. The sequence for selecting forward speed from neutral is as follows: Initially, the axial centre-line 87 of the selector-valves 56 &c. is disposed as shown in Fig. 11 in relation to the cam-slots 86 &c., all valves being down in the cam-slots and open to exhaust. The centreline 131 of the locking-plungers 125, 127 is also disposed as shown, the centre plunger 126 being up and in engagement with its aperture 129, but not obstructing a limited clockwise movement of the cam 80. Movement of the control-lever 98 from this position, shown as 1 in Fig. 2, to position 2, turns the selector-cam 80 clockwise, from the right-hand side, causing a shoulder 91 of the cam-slot 85 to raise the central valve 57 and supply air-pressure to the forward clutch-annulus 8 through the conduit 79, chamber 26 and non-return valve 29. At the same time pressure in the conduit 79 acts directly on the underside of a differential piston 150 on the locking plunger 127, to move the latter upwardly into engagement with its aperture 130, which it is able to occupy after a slight initial clockwise movement of the cam 80, thus preventing the operator from moving the cam 80 back again to neutral when the annulus 8 has been only partly inflated, which might result in excessive slip. Further clockwise movement of the lever 98 beyond position 2 to open the throttle is positively prevented by the locking plunger 126, now occupying a part 159 of its aperture 129, and also acting in combination with the mechanical lock 41, described below, to prevent axial movement of the cam as the operator loads the lever for movement to position 3 in order to reach the throttle-opening circumferential range 3 to 4. The locking-plunger 126 is retracted by airpressure acting on the upper face of its differential piston 138 through a conduit 157 fed from the clutch-inflating conduit 79 through a restrictor-orifice 160, acting, with a capacitychamber 161 to delay the retraction of the plunger until the clutch-annulus 8 is fully inflated, whereafter the lever is free to be moved to position 3 and thence in the throttleoperating range 3 to 4. In the leftward movement of the lever 98 from position 2 to 3, causing rightward axial movement of the cam 80, the plunger of the centre-valve 57 falls into the part 97 of its cam-slot, thereby venting the chamber 26 and relieving the seals 24 of pressure. Over the normal forward-drive range 3 to 4, make-up pressure can be applied to the clutch-annulus 8 at any time to compensate for leakage, by momentarily moving the lever to the right (cam 80 to the left), position-range 5, in opposition to a return-spring described below, so that the centre-valve 57 is raised by the edge 97 of its cam slot 85. To disengage the forward clutch-annulus 8 and return to neutral or engage reverse, the lever 98 is moved anticlockwise through position 3, idling the engine, to position 6, further movement being positively prevented by the locking-plunger 127, which is still operative, and also prevents rightward axial movement of the lever 98 towards the neutral position 1 (leftward axial movement of the cam 80) by engaging the curved end 164 of its aperture 130. In the movement to position 6, a shoulder 95 of the cam-slot 84 raises the valve 58 to supply pressure to depress the annular piston 35 which opens the non-return valve 29 and permits the clutch-annulus 8 to deflate through the exhaust of its valve 57. At the same time pressure in the piston-supply conduit 36 reaches the upper face of the differential piston 150 of the locking-plunger 127 through a restrictor-orifice 165, which, in conjunction with a capacity-chamber 167, delays the buildup of pressure so that the plunger 127 is retracted only after the clutch-annulus is deflated, whereupon the lever 98 is free to be moved to the neutral position 1. Pressure in the piston-supply c