Piston valves

Claim 2

A piston valve including a body formed of a plurality of metal sheets secured together in surface to surface relation by brazing or the like process to form a block, a cylindrical bore extending through the block transversely through the sheets of the block, a spool valve member mounted in the bore to cooperate with ports opening into the bore, which ports are formed by zones of some of the sheets cut away before the brazing or like process, the surface dimensions of the sheets being at least not substantially less than the axial length of the bore through the block whereby the block is of substantial strength and able to resist distortion by substantial force which might be applied to it during use, one or more electric force motors secured to the block, servo vent means controlled by the force motor or motors to adjust the axial position of the spool member within its bore, the or each force motor comprising a coil of wire movably supported in a magnetic field.

Claim 3

A piston valve including a body formed of a plurality of metal sheets secured together in surface to surface relation by brazing or the like to form a block, a cylindrical bore extending through the block transversely through the sheets of the block, a spool valve member mounted in the bore to cooperate with ports opening into the bore, which ports are formed by zones of some of the sheets cut away before the brazing or like process, the surface dimensions of the sheets being at least not substantially less than the axial length of the bore through the block, whereby the block is of substantial strength and able to resist distortion by substantial force which might be applied to it during use, one or more electric force motors secured to the block, servo vent means controlled by the force motor or motors to adjust the axial position of the spool member within its bore, said servo vent means including a vent nozzle for the or each force motor carried by the spool valve such that the spool valve will follow the movement of the force motor or motors.

Claim 4

A piston valve including a body formed of a plurality of metal sheets secured together in surface to surface relation by brazing or the like to form a block, a cylindrical bore extending through the block transversely through the sheets of the block, a spool valve member mounted in the bore to cooperate with ports opening into the bore, which ports are formed by zones of some of the sheets cut away before the brazing or like process, the surface dimensions of the sheets being at least not substantially less than the axial length of the bore through the block, whereby the block is of substantial strength and able to resist distortion by substantial force which might be applied to it during use, one or more electric force motors secured to the block, servo vent means controlled by the force motor or motors to adjust the axial position of the spool member within its bore, said servo vent means including a vent nozzle for the or each force motor carried by the spool valve such that the spool valve will follow the movement of the force motor or motors.

Claim 5

A piston valve as claimed in claim 2 wherein the plates are each formed with a second hole so arranged that the second holes produce a passage through the block when the plates are brazed together, one or more of the plates being formed by appropriate recesses before brazing so that its second hole is connected to a port opening into the bore, and fixed restrictor means mounted in the said second holes to control fluid flow to said vent nozzle or nozzles.

Claim 6

A piston valve as claimed in claim 3 including a third hole formed in each metal sheet which holes after brazing of the sheets form a passage appropriately connected to ports in the bore to carry return flow fluid from such ports.