GB875697A - Improvements in or relating to mechanisms for initiating successive movements in a control gear for one or more gas plant valves - Google Patents

Abstract

875,697. Water-gas plant control gear. NORTH THAMES GAS BOARD. Jan. 20, 1959 [Oct. 21, 1957], No. 32859/57. Class 55 (1). [Also in Group XXIX] A control means for one or more valves of a gas-making apparatus has a cam mechanism adapted to initiate successive operations of control gear for the valve or valves and to move a part of a transmission capable of rendering the apparatus inoperative, means responsive to a condition of the apparatus indicative of whether the control gear has responded correctly to the initiation of the cam mechanism and adapted to impart a movement to the part of the transmission such that should the control gear correctly respond to the cam mechanism, a second movement imparted to the part of the transmission prevents it from rendering the apparatus inoperative and that if the control gear does not correctly respond to the cam mechanism, the second movement imparted to the part of the transmission renders the apparatus inoperative, the cam mechanism comprising two controlling parts rotating about the same axis and arranged to engage successively with controlled parts, both fixed to an element or linkage for imparting the first and second movements to the part of the transmission which is capable of rendering the apparatus inoperative. The control is particularly suitable to initiate the sequential operation of the valves of a watergas plant, the failure of a valve to respond to the control mechanism resulting in the plant being shut down. Fig. 1 of the Provisional Specification shows a valve 42 of a water-gas plant movable by the plunger 2 of a ram 43, the operation of which is controlled by means (not shown) associated with cam plates 1 and 20 of the control means. Plates 1 and 20 are axially spaced on a rotating shaft 21 and have pins 3 and 19 which as the plates rotate respectively engage the inclined faces of blocks 25a and 25b secured to the end of an element 26 movable in a guideway 5 and having at the other end pins 33 and 34, one on either side of a bar 6 of a transmission capable of shutting down the plant. The bar 6 is moved up and down with the plunger 2 through an hydraulic cylinder 11, the plunger 44 of which is moved by operation of a valve 10 admitting or draining pressure fluid to or from the cylinder 11 by an arm 7 on the plunger 2 contacting stops 8 and 9 on the control rod 36 of the valve. The upper end of the bar 6 has an off-set portion 37 which extends between abutments 13 and 18 on lever arms 14 and 16 respectively pivoted at 40 and 41 to a fixed part of the plant, lever arm 14 having a peg which strikes the lever arm 16 when lever arm 14 is rotated in an anti-clockwise direction. The lever arm 16 is arranged so that rotation in a clockwise direction operates to close the plant down, e.g. by the opening of electrical contacts (not shown). If the valve 42 has not opened or closed as predetermined, the position of the bar 6 is such that movement of the element 26 by contact of the pin 3 or 19 with its associated block causes the arm 6 to contact either the abutment 18 or the abutment 13 and effect clockwise rotation of the lever arm 16 to close down the plant. A single cam mechanism may be arranged to control a number of valves, each valve having an associated ram and plunger, bar 6 and element 26. In a modification the element 26 is not connected directly to the tracks traversed by the pins 3 and 19 but is linked at one end to the end of a pivoted lever, the other end of which carries a block in which the tracks are formed.