Abstract: Liquid flow through a passage (9) in a body member (7) is controlled by a relatively movable poppet valve member (8). A frusto-conical first guide surface (11) on the poppet valve (8) merges smoothly with a second guide surface (12 and 13) which, in cross-section, has part-circulr portion (12) and an outlet end (13). Liquid passing through an aperture (10) between the body member (7) and the poppet valve member (8) flows along the first guide surface (11) and the second guide surface (12 and 13) and adopts a toroidal vortex flow pattern and this controls the collapse of those bubbles which form as a result of cavitation so as to diminish audible and inaudible vibrations.

Abstract: Apparatus and method for determining the level of particulate contamination within the fluid of a hydraulic system. System fluid is introduced through a non-return valve into a space where it is contained by a piston. The structure of the piston includes relatively-movable parts defining a restricted orifice to which fluid, having passed through a drilling in the piston, may escape to drain. When the piston is moved so as to tend to reduce the trapped volume, fluid is expelled from the volume through the drilling and clearance until the clearance becomes blocked by contaminants. The degree of contamination may then be derived from the distance that the piston has moved. The separate parts of piston structure are then relatively-moved to clear the orifice and allow the rest of the trapped fluid to escape, after which the orifice is reset and another volume of fluid introduced to be tested. The piston may be driven by reaction with the system fluid, or alternatively by means independent of that fluid.

Abstract: Apparatus and method for determining the level of particulate contamination within the fluid of a hydraulic system. System fluid is introduced through a non-return valve into a space where it is contained by a piston. The structure of the piston includes relatively-movable parts defining a restricted orifice to which fluid, having passed through a drilling in the piston, may escape to drain. When the piston is moved so as to tend to reduce the trapped volume, fluid is expelled from the volume through the drilling and clearance until the clearance becomes blocked by contaminants. The degree of contamination may then be derived from the distance that the piston has moved. The separate parts of piston structure are then relatively-moved to clear the orifice and allow the rest of the trapped fluid to escape, after which the orifice is reset and another volume of fluid introduced to be tested. The piston may be driven by reaction with the system fluid, or alternatively by means independent of that fluid.

Abstract: A device for determining the level of particulate contamination in a hydraulic system. Between the inlet and outlet of the device the fluid passes through the narrow clearance between a piston and a surrounding bore. As the clearance becomes obstructed by contaminant, pressure rises in a chamber upstream of the piston. Rise of this pressure above a certain level is detected by a detector which both triggers a counter and operates a solenoid to withdraw the piston and release trapped contaminant, after which the piston returns and another cycle of contaminant build-up begins. The frequency of the release of the piston indicates the degree of contamination of the fluid. Instead of pressure build-up, parameters related to fluid flow may be used to trigger the counter and the release of contaminants from clearance, and means may be provided to meter individual, fixed-volume charges from the general body of fluid and discharge them through a clearance.