Patent GB-579765-A (GB)
Title: Improvements in or relating to governor
IPC: G05D13/06
Filed: 1943-08-09
Abstract: 579,765. Fluid-pressure servomotorcontrol systems. STEVENS, A. H. (United Aircraft Corporation). Aug. 9, 1943, No. 12866. [A Specification was laid open to inspection under Sect. 91 of the Acts, Oct. 1, 1943.] [Class 135] [Also in Group XXVI] In a governor for regulating the speed of a prime mover, the flyballs 9 actuate a piston valve 23 to supply pressure fluid to, or drain it from, a servomotor piston 64 which alters the throttle through the intermediary of a lever 32 ; and the piston 64 is formed as a cylinder housing a piston- 62 whose movements alter the spring loading of the governor to give a temporary speed droop characteristic. The normal loading of the flyballs comprises a spring 50 positioned between disc 17 of a thrust bearing with which the flyballs are in contact and a crosshead 54 whose ends slide into grooves in the casing. The loading is set by a screw 56 which presses on an abutment on a lever 61 pivoted at 60, the -lever pressing on the cross-head 54. A further spring 77 is positioned between the cross-head and a lever 81, the latter being pivoted on a pin 82 which is slidable along the casing and moves in a slot in the lever to vary the length of the arm. The lever 81 also carries the piston 62 and a further spring 89 of which the other end is fastened to the casing. The flyballs are carried by, and rotate with, a sleeve 11 housing the piston 23 which is connected to the thrust bearing. Fluid is supplied to the gear pump 37, 38 from whence it enters a passage in communication with a groove 43 in the sleeve 11, and the end of this passage joins a sleeve housing a spring-loaded piston relief valve which opens on abnormal pressures to allow fluid to return to the inlet of the passage of the pump. When the speed of the engine drops, the flyballs move inwards and the piston valve 23 descends to allow pressure fluid to flow through a port 24 to the underside of the servomotor piston 64 which will be pushed upwards. The upper end of this piston acts on a pivoted lever 32 connected through levers &c. with the engine throttle to open the latter. The piston 64 is a loose fit in its cylinder so that fluid in the chamber 26 seeps through ports 70 into a groove 67 in the piston 62, and from here the fluid can flow through a passage 75, past a needle valve 73, through a passage 76, and into the space in the servomotor piston underneath the piston 62. The cylindrical surface 67 of the upper part of piston 62 is fluted so that fluid can also flow from the groove 68 past the inturned upper end 69 of the servomotor piston, and escape into the governor casing. When the servomotor piston moves upwards, the fluid in space 71 will cause the piston 62 to move with the servomotor piston, and the consequent upward movement of lever 81 will put springs 77, 89 under tension. Spring 77 will now counteract the effect of spring 50 and the piston 23 will be re-centred at the lower engine speed giving speed droop. The tension in springs 77, 89 will also draw piston 62 down towards its normal position as soon as the fluid in space 71 can escape past the needle valve 73. This further movement of lever 81 increases the setting of the governor and the throttle will be opened still further until the original governor setting has been restored. As the throttle opening remains in its new position with the original governor setting, the speed droop will be only temporary. In response to overspeeding of the engine, piston valve 23 will be raised and the fluid under piston 64 will drain away through port 24 and ,passage 95 ; and the above operations will be reversed to give a lower throttle opening.