561,671. Fluid-pressure servomotor control systems. KALIN, A. July 11, 1941, No. 8806. Convention date, Aug. 3, 1940. [Class 135] A governor for prime-movers and other machinery having an hydraulic servomotor controlled by an axially movable control valve associated with the receiving piston of an hydraulic follow-up system is arranged so that the said piston is continuously rotated to eliminate static friction. In the form shown in Fig. 1, the piston control valve 20 is reciprocated against the action of an adjustable loading spring 48 by weighted bell-crank levers 40 engaging shallow depressions in a flange 45 on the valve member. A ball-bearing 47 is interposed between the spring abutment 49 and the control valve to permit the valve to rotate with the weighted levers. The bell-crank levers are pivoted at 42 to a carrier 11 formed with a tubular boss 13 rotatably mounted on a tubular extension of a ported seat liner 30 for the control valve. The boss 13 carries gear teeth 12 connected by gearing with a toothed wheel 7 on a short shaft 5 mounted in the base of the governor and formed with a splined socket 5a for attachment to a driving shaft. The wheel 7 engages a second wheel (not shown) to form a gear pump drawing oil from a sump S through a duct S<1> and delivering under pressure to an annular chamber P<1> surrounding the liner opposite ports 35. A passage 68 connected to the chamber P<1> is fitted with a spring-loaded relief valve 70 leading by way of recess S<2> back to the fluid reservoir S and is connected by passages 66, 67 with a spring - loaded accumulator (not shown). The main power piston 80 connected by a rod 87 with the throttle or other regulating element of the mechanism being controlled has a reduced part 81 working in a bore 76 to provide a loading chamber P<2> connected by a passage 69 with the annular chamber P<1>. The chamber S<4> above the part of smaller diameter is connected by a passage 92 with a space at negligible pressure while the chamber R<1> beneath the piston is connected by passages 94, 95 with a recess R connected by ports 34 with the axial bore in the seat liner. A port 35 leading to the recess P<1> and a port 36 leading to a recess S2 connected to the sump S are normally obturated by lands 25, 26 on the control valve, but when the valve is moved in one direction or the other consequent on a variation of speed, the power chamber R<1> is connected either to pressure or exhaust. When the valve is moved downwards, pressure is admitted to the chamber R<1> and the piston is moved upwards to actuate the regulator in the appropriate direction. At the same time a recess 82 in the piston slides over a fixed tubular member 83 to force liquid through passages 98, 99, 100, 101 to a chamber C<1> where it acts on a piston 50 integral with the control valve and tends to restore it to its neutral position. In order that the restoring action may fade away after an interval, the passage 98 is connected to a sump S<6> through a bleed passage 112 adjustably throttled by a needle 110. In order that the restoring pressure acting on the piston 50 may not hold the valve against' movement by the governor, the conduit 98-101 is fitted with elastically yielding means. In the form shown in the Figure, these means comprise a chamber C<3> formed by adjustably screwing a cap 116 into a recess 115 connected to the passage 98 and adapted to trap a volume of compressible gas. The cap may be replaced by a metallic bellows or by a spring-loaded piston. The metallic bellows may be secured to the lower end of the seat liner 30 and the piston may be slidable within the liner in which case it may be continuously rotated by a spring and stub shaft secured to the shaft 5. The passage 100 may be fitted with spring-loaded relief valve to allow fluid above or below predetermined pressures passing to and from the sump. In the form shown in Fig. 8, the follow-up arrangement comprises a cylinder 160 mounted on an extension of the control valve member so as to rotate with it and housing a piston 163 provided with an adjustable leak 168. The piston is connected by a spring 164 with a lever 165 turning on a fixed fulcrum 166 and coupled by a link 167 with the main power piston 80. The Specification as open to inspection under Sect. 91 states that the governor may be responsive to force factors other than speed, for instance fluid or current pressure or flow, gravity, &c. This subject-matter does not appear in the Specification as accepted.