GB1353044A - Servomechanism - Google Patents

Abstract

1353044 Fluid-pressure servomotor systems W W TAYLOR 3 Sept 1971 [10 Sept 1970 1 June 1971] 41261/71 Heading G3P In a fluid-pressure servomotor, relay spools 24, 25, Fig.10, follow the movements imparted to a flapper arm 23, 124, Figs.2 and 3, by an input motor 22, the spool 24 controlling movement of a load 34 to the right while the spool 24 controls movement to the left. The spool 24 is reciprocably mounted in a sleeve 26 located in a bore 28 to provide a space 41 connected to a source of fluid under pressure, a space 49 connected to a return line, and spaces 45, 47 connected to opposite ends of the load through ports 32, 33. The spool 25 is similar to the spool 24 but is reversed in position. When the spools are moved to the right, the spool 25 does not provide any connection between the load and the supply and return lines, this connection being provided solely by the spool 24 which allows fluid to flow into the load from the space 41 and out of the load through spaces 45 and 49. Similarly, during leftward movement, the spool 25 provides the connection while the movement of the spool 24 has no effect. Each spool contains passages 68, 73, Figs. 13 and 14, which are angularly spaced from each other, supplied with fluid under pressure through orifices 70, 76 and discharge through nozzles 70, 71 against the flapper arm. A pressure difference is thus created between the ends of the spool when the flapper arm is moved from its null position so that the spool follows the movements of the arm. Screws 118, 119 enable the motor to be angularly adjusted on trunnions 108, 109 supported in V-shaped grooves 104 in a cylindrical block 101 which may be angularly adjusted about a vertical axis by a further pair of screws (not shown). This latter adjustment permits continuous centre flow through the spools to be adjusted to damp oscillation. The spools carry pins 910, 911, 912 and 913, Fig. 3 for engagement by the flapper arm 124 to prevent rotation. The details of the relay spools and sleeves are modified in a second embodiment to include an alternative arrangement of passages (406, 407) Fig. 31(not shown), within the spool and a dashpot (398) communicating with the passage (406) through a restriction (413) to prevent oscillation.