摘要:
The present invention relates to a control valve for controlling flow of hydraulic fluid. The control valve comprises: a valve housing (10); a sleeve (11) slidable in a valve chamber in the valve housing (10); a first fluid conduit (12) for connecting the valve chamber to a source of pressurised hydraulic fluid; a second fluid conduit (14) for connecting the valve chamber to a fluid return for returning hydraulic fluid to a reservoir; and a third fluid conduit (16) for connecting the valve chamber to deliver hydraulic fluid to and receive hydraulic fluid from apparatus which uses the hydraulic fluid flow controlled by the control valve. The sleeve (11) is a tubular sleeve having, a tubular passage therethrough. The valve housing has a pair of spaced apart valve seat surfaces (22, 23), a first valve seat surface (22) which is engageable by a first end of the tubular sleeve (11) and a second valve seat surface (23) which is engageable by a second end of the tubular sleeve (11). The third fluid conduit (16) opens on to the valve chamber by way of a port which is surrounded by the first valve seat surface (22).
摘要:
The present invention (with reference to FIG. 1) is an arrangement of an internal combustion engine poppet valve and a hydraulic actuator therefor comprising: an actuator housing (16); spring means (104,105) for biassing the poppet valve (101) into engagement with a valve seat therefor; a first piston (1) of a first cross-sectional area slidable in a first chamber formed in the actuator housing (16), the first piston (1) having a passage therethrough for the flow of hydraulic fluid; and a second piston (15) of a second cross-sectional area smaller than the first cross-sectional area slidable in a second chamber formed in the actuator housing (16), the second chamber opening on to the first chamber; wherein: the first chamber is connectable to a pressurised hydraulic fluid supply line and to a hydraulic fluid return line; and the second piston has an upper surface (110) engageable by a lower surface of the first piston; and the first piston is configured without a passage which is both aligned with the second piston and which has a portion of constant cross-sectional area greater than the said second cross-sectional area.