GB1241955A - Improvements in or relating to seals - Google Patents

Abstract

1,241,955. Shaft seals. SPEEDWELL RESEARCH Ltd. 19 Dec., 1968 [5 Oct., 1967], No. 45414/67. Heading F2B. An annular diaphragm which may be used in a centrifugal pump described in Specification 1,185,312 comprises a one-piece main body having radially-spaced outer and inner portions 11, 12 interconnected by a relatively thinner web 13, an insert 15 being provided in one of the outer or inner portions of material having a greater resilience than that of the main body. The main body may be made of metal (e.g. titanium or stainless steel), sintered or hard P.T.F.E., glass-loaded P.T.F.E., a fluorocarbon resin, a phenolic asbestos resin or a polyimide and the insert 15 may be made of compressed asbestos fibre or rubber. The web 13 may be corrugated and formed by a spiral or by concentric rings, the cross-section of the corrugations being V-shape, sinusoidal arcuate or square. As shown, the outer portion 11 is provided with the insert and clamped between two parts of the pump casing, while the inner portion 12 may be provided with either a wearresistant insert 12a, Fig. 1A, or a wear-resistant coating for making static sealing contact under the influence of liquid pressure against a shoulder 40 on the shaft when the pump is both stationary and filled with liquid. When the pump is stationary and empty, the diaphragm assumes the position shown clear of the shoulder 40. The seal chamber 50 is divided into two compartments 56, 57 by an annular partition 51 clamped at its periphery 52. A subsidiary impeller 46 having blades 69, 70 rotates within the compartment 56 of the seal chamber. When the pump is running and full of liquid, the subsidiary impeller 46 pumps liquid out of the compartment 57 of the seal chamber so that the diaphragm is again freed from the shoulder 40 and an annulus of liquid is formed between the blades 69 and the partition 51. If desired, the diaphragm may be urged by a spring into a static sealing position on the shoulder 40, the spring pressure being reduced when the pump is running as described above.