Abstract: A fluid control device comprising a pivotable member which has a planar major face and is mounted so as to enable pivotal motion about an axis parallel to the major face. The pivotable member including a fluid jet channel which directs a fluid jet towards a fluid receiving channel defined in a receiving member. The pivotable member is pivotally rotated about the axis by a device operable to pivot the pivotable member. This device may be an electromagnet disposed with its poles adjacent and parallel to the major face of the pivotable member. The motion of the pivotable member alters the relative positions of the fluid jet channel/channels and the fluid receiving channel/channels and thereby the quantity of fluid received by the fluid receiving channel/channels.

Abstract: A retarder, suitable when mounted in association with a rail of a railway track for reducing the speed of a wagon rolling along the track, includes an hydraulic unit which comprises a hollow member, a piston slidably housed in that member, and a piston rod. A portion of the hydraulic unit is, for retardation of the wagon, disposed in the path of a wagon wheel. When that portion is engaged, directly or indirectly, by a wheel it is deflected by, and out of the path of, the wheel to permit the wheel to pass the retarder. The ratio of the diameter of the piston to the diameter of the piston rod is in the range 2.80:1 to 6.00:1 and the ratio of the diameter of the piston to the length of stroke of the hydraulic unit is in the range 0.53:1 to 1.20:1.

Abstract: A retarder, suitable for mounting with respect to a rail of a railway track for reducing the speed of a wagon rolling along the track, includes an hydraulic unit a portion of which, for retardation of the wagon, is disposed in the path of a wheel of the wagon. That portion when engaged, directly or indirectly, by the wheel is deflected by, and out of the path of, the wheel. A thruster device, disposed alongside the unit and capable also of deflecting the portion out of the path, includes a displaceable element which is normally disengaged from the portion but which upon initial movement thereof is so tilted that a part thereof comes into driving engagement with the portion. On continued movement of the element the driving engagement is maintained and the portion moves from its position in the path of the wheel into another position out of the path.

Abstract: A rotary positive-displacement fluid-pressure machine of bi-directional type including a casing, intermeshing rotors, and a pressure-balancing arrangement, associated with the end face, remote from said rotors, of the or each end plate means of the machine. Each arrangement comprises sealing means which separate a plurality of areas on said end face, certain being subjectable to high, and others to low, fluid pressures. A further area defined by further sealing means and subjectable only to high fluid pressure is in a zone opposite, and is in positional correspondence with, that zone of the face of the end plate means engaging the rotors which is in registry with the region where the rotors mesh. The further area extends through and beyond the common plane of the rotor axes towards the low pressure side of the machine.

Abstract: An electro-hydraulic servo valve of two-stage type including a beam mounted for swinging movement with respect to the casing of the valve. One portion of the beam is engaged with the second-stage displaceable element of the valve and another portion of the beam carries an electrical sensor through which an electrical current is caused to pass. Magnet means are housed in the casing adjacent the other portion of the beam. As, on controlled movement of the displaceable element, the beam swings, the positional relationship of the sensor with respect to the magnetic fields of the magnet means changes, thus to so vary the electrical potential across the sensor that an electrical feedback signal is emitted by the sensor which is proportional to the displacement of said displaceable element.

Abstract: A retarder, suitable for reducing the speed of a wagon rolling along a railway track, includes a retainer, which is adapted to be secured upon or adjacent a rail of the track, and an hydraulic unit which is fitted in the retainer. A portion of the unit normally projects from the retainer thus to lie in the path of a wheel of the wagon so as to be engageable by that wheel. The portion is movable inwardly of the retainer to a position, out of the path, in which it permits the wheel to pass the retarder. The retarder includes holding mechanism for maintaining the portion in that position.

Abstract: An electrical force motor, suitable for use in electro-hydraulic servo valves, has a circular permanent magnet which is polarized across its diameter, which is disposed at least partly within one of the pole pieces of the motor and which is rotatable with respect to that pole piece to increase the effective strength of one pole of that pole piece and to decrease the effective strength of the other pole thereof.

Abstract: A pump or motor comprising a casing, housing at least one rotary member and having an inlet port and an outlet port, cam means rotatable by said member and a fluid displacement device which is driven by the cam means and which includes at least one reciprocable element. This element, upon rotation of said member through each revolution, so repeatedly projects into a chamber in the casing which is in communication with one of said ports as to effect a series of momentary decreases in the effective volume of that chamber and the element is also so repeatedly retracted from that chamber as to effect a series of momentary increases in the effective volume of the chamber. In this way momentary flow of fluid is caused repeatedly to occur out from, and back into, the chamber thereby substantially reducing pulsation of flow through the pump or motor, and also attendant noise, during operation.

Abstract: A rotary positive-displacement fluid-pressure motor which includes a casing, having an inlet port and an outlet port, at least two intermeshing rotors of toothed or lobed form housed for rotation in the casing, and means for conducting pressure fluid derived from the inlet port as far as a predetermined position in a face adjacent, and engaged by, a side of one of the rotors. A recess is so disposed in that face intermediate the predetermined position and the outlet port that, for facilitating starting of the motor when fluid under high pressure is directed into the inlet port, some of that fluid can gain access to the recess by way of said means and whichever intertooth or interlobe space of that rotor is so positioned as to place the means and the recess in communication.

Abstract: A rotary positive-displacement fluid-pressure machine which includes a casing, two intermeshing rotors, end plate means associated therewith, and a pressure-balancing arrangement associated with the end face of each end plate means remote from the rotors and with an adjacent casing face. The arrangement comprises sealing means which separate, one from another, a plurality of areas on said end face individually subjectable to fluid-pressures and which comprise resilient members disposed in respective grooves, as well as a non-extrudable element against portions of which those members bear. The members and element together establish fluid-sealing between the end face remote from the rotors and the adjacent casing face. At least one portion of said non-extrudable element is so disposed as to cross a respective land which is recessed to accommodate that portion.

Abstract: A buffer stop comprising an arm capable of being pivotally-mounted at or near one end portion on or adjacent a railway track, and a piston-and-cylinder device. One end portion of the piston-and-cylinder device is pivotally-connectible at or near the other end portion of the arm. The other end portion of the device is capable of being pivotally-mounted on or adjacent the railway track at a distance away from the one end portion of the arm.

Abstract: An axial piston machine comprising a casing which encloses and mounts the machine working parts therein and a cover of pliant material mounted externally of the casing to substantially entrap a quantity of air or other gas against at least a part of the outer surface of the casing to reduce noise radiation from the casing.