GB410811A - Improvements in pumps - Google Patents

Abstract

410,811. Reciprocating pumps. WEIR, Ltd., G. & J., and HILLIER, H., Holm Foundry, Cathcart, Glasgow. Oct. 25, 1932, Nos. 29820/32, 29822/32, and 29048/33. [Class 102 (i).] In a pump, e.g. a boiler feed-pump, of the type in which the discharge is varied by altering the phase relationship of two shafts 8, 8<a>, Fig. 1, driving pairs of plungers 7, 7<a> of equal displacement and working in a common chamber 1, the secondary motor 21, which effects the alteration of the phase relationship, is controlled both by the discharge pressure of the pump and by means acting simultaneously with the relative movement of the shafts 8, 8<a>. The shafts may be driven by separate motors, or by a single A.C. motor 9, the shaft 8 being driven through gearing 10, 11 of fixed ratio, while the shaft 8<a> is driven through epicyclic gearing 12-16 and gear wheels 17, 18. The casing 20 of the epicyclic gearing is rotatable by the auxiliary motor 21. The gearing may be such that the shafts 8, 8<a> rotate at the same speed when the casing 20 is stationary, or when the casing is rotating at a certain speed. When the pressure in the discharge pipe 6 rises, the pressure depresses a piston 24 carrying a contact 28 moving over a resistance 29 and thus either starts the motor 21, or alters its speed; so as to alter the position of the shaft 8a relative to the shaft 8. The shafts 8, 8<a> drive a differential shaft through gearing 30, 31, 30<a>, 31<a> and the differential casing 35 carries a cam 36 acting on a rod 37 connected to the resistance 29, so that the resistance is lowered and the contact 28 is returned to the equilibrium position. The pump then operates at reduced output and increased pressure. In a modification, Fig. 3, the contact 28 is carried by a lever, one end of which is connected to the rod 26 of the piston 24 exposed to the discharge pressure, while the other end is connected to the core of a solenoid 38 arranged in the circuit of the motor which operates the epicyclic gearing. When the piston 24 lowers one end of the lever the current energizes the solenoid 38 and raises the other end of the lever, thus returning the contact 28 to the equilibrium position. In a further modification, Fig. 4, a motor 41 in the circuit of the motor which operates the epicyclic gearing operates through gear wheels 43, 44 a cam 42 which varies the loading of the spring 27 acting on the piston 24. On decrease of discharge pressure the piston 24 rises and the cam then lowers the washer 40 on which the spring 27 abuts. The contact 28 is thus returned to the equilibrium position and the pump operates at increased output and reduced pressure. In the arrangement shown in Fig. 7, the loading of the spring 27 is varied by the auxiliary motor 21 through gearing 45, 46, 47. In this arrangement also, both the shafts 8, 8<a> are driven through epicyclic gearing. The two gear casings 20, 20<a> are geared together and are moved in opposite directions by the motor 21. Specifications 336,810 and 337,205, [both in Class 102 (i)], are referred to.