Fluidic feedback servo valve

Claim 2

A fluidic feedback servo valve comprising a metering stage including a metering spool, a pilot stage including a pair of parallel hydraulic paths between a fluid inlet and a fluid outlet each of which includes an upstream and a downstream metering orifice, an electrohydraulic transducer for providing a differential impedance between the downstream orifices in accordance with an electrical signal applied thereto and Means secured to the spool for providing a differential impedance between the upstream orifice which is a function of the position of the spool including conical targets on the ends of the spool which taper in opposite directions on the opposite ends of the spool, one of which conical targets is of smaller diameter than the metering spool and the other of which conical targets is of larger diameter than the metering spool whereby removal of the metering spool from the servo valve without movement of the upstream orifices is facilitated.

Claim 3

Structure as set forth in claim 1, and further including a flat side on the one conical target whereby on rotating the one conical target to position the flat side adjacent the associated upstream orifice the spool may be removed or replaced in the valve without disturbing the orifices in the valve.

Claim 4

Structure as set forth in claim 2, and further including a slot provided across one end of the spool and a locating pin carried by the valve extending within the slot off-center of the spool for preventing rotation of the spool in operation of the valve.

Claim 5

Structure as set forth in claim 1, wherein the downstream nozzles empty into a control chamber and the control chamber is connected by means of an orifice to the fluid outlet.

Claim 6

A fluidic feedback servo valve including a body having a metering spool passage extending therethrough, a hydraulic fluid input passage, a hydraulic fluid return passage and a pair of output passages in the body, a metering spool positioned in the spool passage in the body having metering lands thereon for metering fluid from the input passage into one of the output passages while simultaneously metering fluid from the other output passage to the return passage or preventing metering of fluid into or out of either of the output passages depending upon the position of the metering spool in the metering spool passage, and further comprising a pilot stage including a pair of parallel passages extending between the fluid input passage and fluid return passage, each including an upstream and a downstream nozzle therein which have metering orifices therein and boost chambers within the parallel passages between the nozzles receiving the opposite ends of the metering spool of the metering stage therein, an electromechanical transducer secured to the body of the valve and including a nozzle target positioned between the downstream nozzles and movable in opposite directions relative to the nozzles in accordance with an input electrical signal to the electromechanical transducer to provide a differential pressure across the orifices in the downstream nozzles and conical feedback targets secured to the opposite ends of the metering spool positioned with regard to the upstream nozzles so as to vary the pressure differential across the orifices provided by the upstream nozzles in accordance with the movement of the metering spool to provide an equilibrium pressure on the opposite ends of the spool on movement of the spool in response to the pressure differential across the downstream orifices resulting from movement of the control target whereby the movement of the metering spool is multiplied with respect to the movement of the control target, one of said feedback targets having a smaller diameter over the entire length thereof than the spool passage and includes a flat side thereon whereby on rotation of the metering spool to place the flat side over the upstream nozzle at the corresponding end of the metering spool the spool may be removed from the other end of the spool passage.

Claim 7

A fluidic feedback servo valve including a body having a metering spool passage extending therethrough, a hydraulic fluid input passage, a hydraulic fluid return passage and a pair of output passages in the body, a metering spool positioned in the spool passage in the body having metering lands thereon for metering fluid from the input passage into one of the output passages while simultaneously metering fluid from the other output passage to the return passage or preventing metering of fluid into or out of either of the output passages depending upon the position of the metering spool in the metering spool passage, and further comprising a pilot stage including a pair of parallel passages extending between the fluid input passage and fluid return passage, each including an upstream and a downstream nozzle therein which have metering orifices therein and boost chambers within the parallel passages between the nozzles receiving the opposite ends of the metering spool of the metering stage therein, an electromechanical transducer secured to the body of the valve and including a nozzle target positioned between the downstream nozzles and movable in opposite directions relative to the nozzles in accordance with an input electrical signal to the electromechanical transducer to provide a differential pressure across the orifices in the downstream nozzles and conical feedback targets secured to the opposite ends of the metering spool positioned with regard to the upstream nozzles so as to vary the pressure differential across the orifices provided by the upstream nozzles in accordance with the movement of the metering spool to provide an equilibrium pressure on the opposite ends of the spool on movement of the spool in response to the pressure differential across the downstream orifices resulting from movement of the control target whereby the movement of the metering spool is multiplied with respect to the movement of the control target, one of said feedback targets having a smaller diameter over the entire length thereof than the spool passage and includes a flat side thereon whereby on rotation of the metering spool to place the flat side over the upstream nozzle at the corresponding end of the metering spool the spool may be removed from the other end of the spool passage.

Claim 8

Structure as set forth in claim 5, and further including a slot across one end of the metering spool and a locating pin carried by the valve engageable with the slot off-center of the longitudinal axis of the metering spool to prevent rotation of the metering spool.

Claim 9

Structure as set forth in claim 6, wherein the downstream nozzles empty into a control chamber, and further including an orifice between the control chamber and the hydraulic fluid return passage.