Clutch cylinder circuit and charging valve therefor

Claim 1

Procedure involving a control spool having a double helix defined by two helical grooves on the surface of the spool so as to form long orifice means, for use with a source of fluid pressure and a drain to collect spent pressure fluid, for utilizing modulation in the operation of a work performing element so as to actuate same by pressure having an essentially linear rate of rise, comprising the steps of: directing pressure developed by fluid flow in a first fluid path to the work performing element; inserting in the first fluid path a control spool with long orifice means defined by two surface helical grooves of general V-shape in cross section, and forming a double helix with the grooves 180° out of phase with one another and with the same lead angle, by connecting a portion of the length of the orifice means defined by the double helix in the first path for restricting rate of rise of pressure to the work performing element to limit the rate of actuating same; directing flow in a second fluid path from the remaining portion of the length of the orifice means defined by the double helix to drain; said procedure further characterized by tapping pressure from a pressure tap point communicatively intersecting the orifice means, said tap point to the orifice means defined by the double helix defining the junction between the first and second paths and locatable with respect to the one end of the length of the orifice means defined by the double helix connected to drain, the characteristic of said location of the pressure tap point from said one end being such that the tap point at any given distance along the length of the orifice means defined by the double helix yields a tapped off pressure the magnitude of which is formed as a substantially linear function of the distance; connecting the tap point to the work performing element; causing relative movement at a constant rate of the pressure tap point with respect to the tapped orifice means defined by the double helix so that said one end of the latter and said point separate at a constant rate, insuring that the tapped off pressure to the work performing element has a rapid, essentially linear rate of rise, said work performing element comprising a fluid motor; and restricting the second fluid path into drain to yield an initially tapped off motor pressure of approximately 30 psi, the transition due to said rapid, essentially linear rate of raising motor pressure being from the 30 psi to approximately 250 psi final motor pressure and occurring within about one-half second.