GB526097A - Improvements in or relating to fluid-pressure servomotor systems - Google Patents

Abstract

526,097. Pneumatic single-stroke apparatus. HURST, W. F. F. MARTIN-, and BRITISH THERMOSTAT CO., Ltd. Dec. 6, 1938, No. 35538. [Class 8 (ii)] [Also in Group XXIX] A fluid-pressure servomotor comprises a cylindrical shell having within it a motor chamber in which a plunger or piston works and a valve chamber in which is disposed a valve mechanism operated electromagnetically from a thermostat or other device and arranged to control the supply and release of pressure fluid to the motor chamber. The piston comprises a pair of cup-washers 42, 43 held on either side of a plate 1 by a washer 44 having a serrated face engaging the cup-washer 43 and screwed onto a screwed tail 48 on a similar washer engaging the cup washer 42. The hollow piston rod is also screwed onto this tail and passes to the outside of the cylinder through a packing 4 arranged on the inside of a cover plate 46 where it is provided with a sealing collar 56 adapted to seat on a packing 57 mounted on the outside of the cover plate. The cover plate has an internal flange 51 adapted to secure an inner liner 2 in spaced relationship to the outer shell 2a. The control valve housing is secured in the end of the cylindrical shell 2a by a flanged and screwed sleeve 10 and supports a housing 49 for the actuating solenoid 52 a fluid-tight joint being secured by a packing 58. The control valve comprises a pair of shuttle-lift valve members 6, 7 mounted on a common spindle 24 having at one end an abutment 41 for loading spring 40 and at the other an abutment 37 adapted to receive the impact of the solenoid cone 36 slidably mounted on the spindle. Each valve member comprises two discs of rubber or the like material mounted on each side of a rigid element secured to the spindle and surrounded by a piece of light metal tubing spun down at each end. Alternatively metal valve members may co-operate with rubber seating washers. The valve members are housed in valve chambers 8, 9 formed by plugs 25, 27, 31 adjustably screwed into the main housing and rendered fluid-tight by packing 50. The chamber 8 is in permanent communication with one side of the piston through a passage 16, annular groove 17, port 18, and the annular space 19 between the inner and outer cylindrical members 2, 2a. The chamber 9 is in permanent communication with the other side of the piston through ports 21, 23 and passage 22. The inner faces of the valve members co-operate with opposed seats on the central plug to connect these chambers alternately with a compressed air or pressure fluid inlet by way of passages 13, 14, 15. The outer face of the valve 6 controls the communication between the chamber 8 and atmosphere by way of chamber 28 and passage 29, while the outer face of the other valve members controls the connection of the chamber 9 to atmosphere through chamber 33 and passages 34, 35.