GB112869A - Improvements in Multistage Compressors. - Google Patents

Abstract

112,869. Parker, N. J. April 10, 1917. Multi-stage piston pumps; pump-actuating mechanism; starting and stopping pumps automatically; valves, arrangement of.-In a multistage compressor of the kind comprising a number of cylinders of relatively different sizes and connexions therebetween, and a pressure-operated valve interposed between the cylinders and adapted to cause them to discharge either in parallel or in series into a reservoir according to the pressure of the fluid, the cylinders are formed in two blocks above and below a double crankshaft, and each crank is provided witH a block in a cross-head connected by rods to the pistons in the cylinders; a pneumatically operated beltshifter is provided to move the driving-belt on to the loose pulley when the reservoir pressure reaches a predetermined maximum under control of a multiple-valve device. As shown diagrammatically in Fig. 21, a unit of the compressor comprises cylinders 41-43, and a second unit comprises cylinders 44-48, the various pistons being connected to two slotted cross-heads 34, 35 engaged by bearing-blocks 33, Fig. 4, on diametrically opposed cranks of a crank-shaft 27. Tho cross-heads are guided by the sides of the crank casing 26 and by attached rods 36 working in sockets 37, three studs 38 adjustably screwed into each socket having balls at their inner ends in contact with the rod 36. The cylinders of the units are formed in upper and lower castings 39, 40 secured to the casing 26, which is mounted on a stand 25. Air is admitted from the atmosphere past a valve 55 to the cylinder 41, and is forced in succession to the cylinders 42, 43 of the first unit past valves 61, 65. These valves, and those of the second unit, are controlled by springs such as 66, Fig. 7, adjusted by screwed members 67. From the cylinder 43, the compressed air is forced past a valve 68 through a pipe 69 connected to a valve casing 70, which is connected by a pipe 71 and union 72 to the reservoir 73 and by a pipe 76 to the inlet valve 78 of the first cylinder 44 of the second unit. In the casing 70, Fig. 16, is a double valve 74, 75 with a stem engaging a guide block 79<1> in contact with a diaphragm 79 controlled by an adjustable spring 80. A second guide-block 84 is maintained against the valve by an adjustable spring 85 and is apertured so that air pressure thereon is balanced. Initially, the valve is in the position shown, allowing air to pass the valve 74 from the first unit to the reservoir, but when the reservoir pressure exceeds a predetermined amount, say fifty pounds, the pressure on the diaphragm 79 assisted by the spring 85 overcomes the spring 80 and the valve 74 is closed and the valve 75 opened to connect the first unit with the inlet to the second unit. The first cylinder 44 of the second unit may be supplied either from the atmosphere past a valve 88 or, as described, from the first unit, and the air is forced past valves 89-94, into and through the cylinders 45-48, and through a pipe 94<1> to the union 72. From this union, a pipe 95 leads to a multiple-valve casing 96, by means of which, when the reservoir pressure reaches a predetermined maximum, compressed air is allowed to pass through a pipe 109 and a flow-regulator 124, containing a spring-pressed valve normally held from its seat by an adjustable screw, to a cylinder 111 where it moves a piston against the action of an adjustable spring, the piston-rod 113 having attached to it a belt-shifter 114 whereby the driving-belt is moved from a fast to a loose pulley and the compressor is stopped. Decrease of pressure effects a restarting of the compressor. The casing 96, Fig. 17, contains a passage 103 normally separated from the pipe 95 by spring-pressed valves 97, 98, the valve 98 being first opened when the maximum pressure is reached, so that the air acts on a valve 104 rigid with the valve 97 to open this valve and cause a valve 106 on the valve 104 to contact with a seat above it. The air now enters a second passage 107, enters the pipe 109 leading to the cylinder 111, and acts on the upper of two diaphragms 101, 102, with a guide 101<1> and atmospheric pressure between them, so that the valve 98 is closed. At the same time, a spring-pressed valve 116, controlling passage to the atmosphere, is closed. When the pressure falls below the predetermined maximum, the valves 104, 97 close and the valve 106 opens, allowing air to pass from the passage 107 into a third passage 108 where it acts on a valve 117 rigid with a valve 118. which is thereby opened to allow air in the passage 103 to escape to atmosphere. An adjustable device 122 on the stem of the valves 117, 118 acts on a spring- pressed valve 119, free on the stem, to allow air in the passages 107, 108 to escape to atmosphere and thus cause a rapid exhaust of air from the belt-shifter cylinder. The valve 116 is now raised by its spring and all the valves return to their normal positions. Modifications of the arrangement of the valves and passages in the casing 96 are described.