Patent GB-1464141-A (GB)
Title: Valve mechanism for an elevator hydraulic system
IPC: F15B11/04
Filed: 1974-01-25
Abstract: 1464141 Fluid-pressure servomotor systems MAXTON MFG CO 25 Jan 1974 [15 Feb 1973] 03625/74 Heading G3P [Also in Division F2] A hydraulic elevator control system includes a valve assembly, Fig. 5, comprising a housing 21 containing a chamber 27 connected via checkvalve 28 to a supply line, a by-pass valve 36 between chamber 27 and tank line 26, a down valve 32 between chamber 27 and jack line 34, and fluid-pressure controlled stop means 40 for controlling the position of by-pass valve 36. The valve assembly is shown in the non-activated state with both valves 32, 36 fully closed. When an "up" elevator button is pressed a liquid supply pump 22 Fig. 11, is started and solenoids 72, 75 energized to close valves 70, 74. The pressure in supply line 30 thus builds up causing by-pass valve 36 to move downwards against the bias of spring 45. Simultaneously cylinder 42 begins to fill with fluid from line 54 via the parallel paths through restriction 62 and auxiliary valve 58 respectively. Thus stop means piston 40 is urged upwardly until its stop surface 124 meets the downwardly moving by-pass valve 36. Thereafter the two parts 36, 40 move  upwards together. The plunger 128 of auxiliary valve 58 is biased by spring 130 against piston 40 and thus follows the upward movement of the latter until shoulder 132 on the plunger engages seat 134 to prevent further flow of fluid to cylinder 42 via valve 58. However upward movement of parts 36, 40 continues, but at a slower rate, under the action of the fluid which still flows into chamber cylinder 42 via path 62, 60. The supply pressure build-up is also communicated via lines 54, 84 and check-valve 82 to down cylinder 50 to cause upward movement of stop piston 48 and thus an increase in the closing bias of spring 52 on down valve 32. Eventually by-pass valve 36 closes sufficiently for the supply pressure in line 30 to increase to the extent that valve 32, acting as a check-valve, unseats and moves downwards to the  fully open position. Fluid thus flows via line 34 to jack 20 which moves elevator 18 upwards at a steady maximum speed. When the elevator is slightly, e.g. 6 inches, below the level of the selected floor, a limit switch actuates solenoid 75 causing valve 74 to open. Fluid can thus escape from cylinder 42 to tank 26 via 60, 64, 66, 74, 76, 77 and 78. Piston 40 and by-pass valve 36 thus move downwards and the resulting supply pressure drop causes valve 32 to move upwards until rotary valve 78 connected thereto by linkage 146, 154 has closed to the point where fluid lost to tank 26 through valve 78 equals that injected into the system through restriction 62. By-pass valve 36 thus comes to a standstill at a mid position, the limited amount of fluid still flowing to jack 20 causing elevator 18 to rise at a reduced rate. When the latter is a fraction of an inch below the selected floor, another switch opens solenoid valve 70. Fluid thus exhausts again from cylinder 42 to tank 26 causing piston 40 and by-pass valve 36 to resume downwards movement. The resulting fall in supply pressure causes valve 32 to move to a fully closed position whereupon elevator 18 stops at the selected floor. Shortly after the opening of solenoid valve 70, pump 22 stops and the resulting fall in supply pressure in line 30 allows by-pass valve 36 to close so that both valves 32, 36 are once again in the Fig. 5 state. Operation of the system in the "down" mode of the elevator is somewhat similar to the "up" mode described except that pump 22 does not operate and solenoid valves 92, 104 control venting of down valve cylinder 50 to drain 26. In the down mode valve 36 acts as a check-valve. The maximum steady state down speed is determined by the setting of restriction 96 or, in a modification, by an additional valve 97 similar to auxiliary valve 58 and having a plunger (178), Fig. SA (not shown) spring-biased against by-pass valve 36 so as to move therewith. A manually operated emergency lowering valve 110 is provided.