Fluid pressure actuator apparatus

Claim 2

An improved fluid-pressure actuator apparatus comprising: a source of fluid at supply pressure, an assemblage including fluid-pressure actuator means and pivotal work member means actuable angularly, said assemblage having a transmission efficiency in driven and backload states, an on-off-type valve means for controlling supply and release of fluid under pressure to and from said actuator means, and overload-preventing means including a relief-valve means for bleeding off acTuator pressure above a certain release-pressure value; wherein the improvement resides, in said relief-valve means having a release-pressure value below said supply-pressure value, and in the inclusion of an interlock means operative to render said relief-valve means ineffective and effective responsively to flow and cessation of flow, respectively, to said actuator means.

Claim 3

The improved actuator apparatus of claim 1, wherein: the release-pressure value for said relief-valve means is substantially no greater than the product of the supply pressure and the square of the transmission efficiency.

Claim 4

The improved actuator apparatus of claim 1, wherein: said actuator means is double-acting, and said relief-valve means functions to bleed off fluid from one pressure side to the other in said actuator means.

Claim 5

The improved actuator apparatus of claim 1, wherein: said interlock means comprises, casing means having inlet-port means open to said on-off-type valve means, an outlet-port means open to said rotary actuator means, and a relief-port means open to said relief valve means, an isolation-valve means actuable to seated and unseated positions to open and close said relief-port means to said outlet-port means, a piston means having a central opening extending axially therethrough, a spring-biased check valve means normally closing an inlet-port-adjacent end of said central opening and having a fluted stem extending therethrough in interconnection with said isolation-valve means at its projecting end, a return-spring means urging said piston means toward a repose position in the direction of said inlet-port means, and bleed-port means establishing restricted communication between said inlet-port means and said outlet-port means while said check valve means is closed; the aforesaid being so constructed and arranged that: flow of fluid under pressure supplied to said inlet-port means en route to said outlet-port means first moves said piston means, check valve means and isolation-valve means in unison until the latter becomes seated, thereafter continuation of such flow effects continued movement of said piston means relative to said check valve means and isolation-valve means, thereby, permitting such flow to continue to said outlet-port means via the unseated check valve means and the interior of said piston means; upon cessation of such flow, said return-spring means will move said piston means toward its repose position, first reseating said check valve means and unseating said isolation-valve means, and in such repose position, release of fluid under pressure from said outlet-port means can transpire to said relief-port means and/or to said inlet port via said check valve means according to relative pressure and flow conditions established therein.