Patent GB-468357-A (GB)
Title: Improvements in and relating to vacuum pumps
IPC: F04B27/00
Filed: 1935-11-26
Abstract: 468,357. Vacuum-pump valves. UNGEFEHR, E., and KLEIN, SCHANZLIN, & BECKER AKT.-GES. Nov. 26, 1935, No. 32732. [Class 8 (i)] Reciprocating piston vacuum pumps of doubleacting single-cylinder or twin-cylinder form or of single - acting twincylinder form in which the ingress and egress of the charge to and from each cylinder is controlled by one or more rotary flat distributers functioning at a uniform speed are characterized in that each rotary distributer is provided with one or more pressure equalization ducts and in that the distance of the inner edges of the distributer duct apertures from the axis of rotation of the distributer is equal to or greater than the distance of the working surface of the cylinder(s) from said axis. In a form comprising, Fig. 1, double-acting pistons m, m<1> in cylinders arranged side by side, each of the rotary distributers a, a<1> is provided with an inlet duct e, an outlet duct i, and an equalizing duct l, arranged as shown in Fig. 5. In the position of the distributers shown in Fig. 1 the chamber h<1> above the piston m<1> communicates through the port g<1> and duct e with the container to be evacuated ; the chamber h<2> above the piston m communicates through the port g<2> and ductiwiththe atmosphere, a non-return valve x of known construction being provided ; the spaces h3, h' below the pistons m<1>, m are connected by the distributer a<1> to atmosphere and to the container being evacuated respectively. When the pistons reach the ends of their strokes, the distributers are in the position shown in Fig. 3, in which the chambers h<1> and h<2> are placed in communication for the equalization of pressure therebetween through the ports g<1>, g<2> and the duct l ; the chambers h<3>, h<4> are similarly placed in equalizing communication. The pistons m, m<1> are provided with plugs n<1>, n<2>, n<3>, n' which at the ends of the strokes enter the ports g<1>, g<2>, g3, g<4> so closing them and decreasing the clearance ; the connecting ducts can therefore be amply dimensioned so that the frictional resistance to the gas flowing therethrough is small. The distributers a, a<1> are mounted on a spindle b driven from the crankshaft d by bevel or helical gearing through a second spindle c ; the distributer a<1> is rigidly secured to the spindle b and the distributer a while rotating therewith can be moved axially for adjustment purposes ; the spindle b is provided with a spring-supported foot-step bearing w. In a modification, Figs. 7 and 8, the inlet duct e is elongated and serves as equalizing duct, the separate equalizing duct l being therefore omitted. In the position of the top distributer 16 shown in Fig. 7, the space 2 above the piston 14 communicates through port g<1>, (in the cylinder cover) inlet duct e, chamber 7 and port 8 (all in the distributer) and port 9 (in the cylinder cover) with the suction chamber 10 ; the space 11 above the piston 15 communicates through port g<2> and outlet duct i with the outer air or an equalizing chamber. When the pistons reach the ends of their strokes, the distributer turns to the position shown for the lower distributer 17 in Fig. 7, in which the spaces 18, 19 below the pistons 14, 15 are placed in communication for the equalization of pressure therebetween through the ports g<3>, g' in the cylinder cover and the inlet duct e and chamber 24 in the distributer ; the ports in the distributer are now out of register with the ports in the cylinder cover communicating with the suction chamber 10. In a further modification, Figs. 10, 11, the top and bottom chambers of each cylinder are placed in communication with each other, instead of in communication with the corresponding chambers of the other cylinder as in the forms previously described. The pressure equalizing position of the distributers is shown in the right-hand half of Fig. 10, in which the two chambers of the right-hand cylinder are placed in communication through port g<2> (in the cylinder cover), port 31, duct 29 and port 33 (all in the upper distributer), passage 36, port 33, duct 29 and port 31 (all in the lower distributer) and port g<4> (in the cylinder cover). The top lefthand chamber is shown communicating through the port g<1> and inlet duct with the suction chamber ; the bottom left-hand chamber is shown communicating through the port g<3> and outlet duct with the atmosphere; in both of these positions the ports 33 in the distributers are out of register with the passages 36. In a further modification, all four chambers are put in equalizing communication; in one position, Fig. 16, of the distributer, the port 8 in the distributer registers with port 9 (in the cylinder cover) so that the inlet duct e communicates with the suction chamber ; the outlet duct i communicates with the atmosphere ; in the other position, Fig. 17, of the distributer, the two top chambers are placed in communication through the inlet duct e and the two bottom chambers are placed in communication through the inlet duct e of the other distributer, the ports 8, 9 being now of register ; all as described above with reference to Figs. 7, 8; in addition, however, the inlet ducts of the two distributers are also placed in communication through a passage 37, which now registers with the port 8 in the distributer. The arrangements described above with reference to Figs. 5, 7 and 8, are applicable to a pump comprising two singleacting pumps side by side; those described with reference to Figs. 10, 11, 16 and 17, are applicable to a double-acting single cylinder pump.