Patent GB-1140956-A (GB)
Title: Governor
IPC: G01P3/20
Filed: 1966-07-07
Abstract: 1,140,956. Change speed control. SUNDSTRAND CORP. 7 July, 1966 [9 Sept., 1965], No.30507/66. Heading F2D. [Also in Divisions G3 and H2] In, e.g. an aircraft, in which a number of alternators are driven at constant speed by the aircraft engines through fluid transmissions, and are connected to a common electrical bus, governors are provided, having a flyweight assembly sensitive to the output speed of the transmissions, each governor having four operative positions: (a) a first position range maintained during running of the transmission output in its normal speed range, in which the governor ports fluid to a servomotor and a pressure switch, operative, respectively, to vary the transmission ratio to maintain the output constant and to connect the respective alternator to the common bus; (b) a second or underspeed position maintained when the transmission output speed falls below a predetermined minimum due to the input speed from the prime mover falling below the rated normal minimum speed, or failure in the governor drive, in which the governor drains fluid from the pressure switch to disconnect the respective alternator from the bus; (c) a third or failsafe position maintained on further fall of the transmission output speed, and in which the governor continues to drain the pressure switch, and drains the servo to reduce the transmission ratio to a minimum; and (d) a fourth or shut-down position maintained when the transmission ceases to rotate, and in which the governor maintains the pressure switch and servo in full communication with drain, and control fluid is ported to the flyweight asesmbly to reduce time-delay of the governor on start up. Each governor comprises flyweight 92, 93, mounted in a cup-shaped member 77 connected to a valve sleeve 67 carrying a gear-wheel 51 rotated by the transmission output shaft, and adapted to axially slide a valve spool 56 in the sleeve 67, against springs 100, 101. The flyweights are permanent magnets, and additional control thereof is achieved by an electromagnet 125, the controlling direct current of which is variable in intensity and direction. In the normal speed range, a servo control port 58 is selectively connected by channel 155 to either a drain port 140 to reduce the transmission ratio, or to a pressure port 134 via port 136 to increase the ratio, the pressure switch control port 57 being connected by channel 161 to the pressure port 134 via port 135. On underspeed occurring, when the drive is no longer able to maintain the desired output speed, and the transmission ratio is at a maximum, spool valve 56 is urged when the influence of spring 100 to disconnect the pressure switch control port 57 from pressure port 135, and connect it to drain port 140. In the failsafe position, due to further reduction in speed, spring seat 106 abuts a stop and spring 101 urges the spool valve 56 down, the pressure switch control port 57 containing to drain fluid from the pressure switch through 161, and passage 155 connects pressure port 136 from the servo control port 58, and passage 161 connects the servo control port 58 to the drain port 140, shifting the transmission ratio from maximum to minimum. At shutdown, the pressure port 135 communicates with the interior 170 of the cup-shaped member 77 through a recess (171), Fig. 10 (not shown) in the spool valve 56, allowing a quick fill thereof on startup to reduce the time delay before governing begins at a predetermined higher speed. The sensitivity of the flyweight assembly is manually adjusted by a spur gear 115 connected to spring seat 102 to vary the compression of main compression spring 100.