Pumps – With condition responsive pumped fluid control – Pressure responsive relief or bypass valve
Reexamination Certificate
1999-12-10
2001-10-02
Freay, Charles G. (Department: 3746)
Pumps
With condition responsive pumped fluid control
Pressure responsive relief or bypass valve
C417S299000, C417S308000, C417S441000
Reexamination Certificate
active
06296456
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to positive displacement pump systems and is more particularly concerned with such systems in which deliveries from two positive displacement pump sources are available to be fed to a common supply passage.
SUMMARY OF THE INVENTION
According to this invention there is provided a positive displacement pump system having first and second delivery passages for pumped fluid, a main discharge passage connected to receive a flow from the first delivery passage and to receive through a non-return valve a flow from the second delivery passage, a control orifice disposed in the main discharge passage at a location to receive the combined flows, and a control valve for apportioning the flow from the second delivery passage between the main discharge passage and overspill porting and controlling the by-passing of a proportion of the flow from the first delivery passage through the overspill porting. The control valve comprises a valve member slidably mounted in a bore in a valve body, and a first end of the bore is in communication with the main discharge passage at a location upstream of the control orifice. The control valve also comprises a spring which is disposed in a spring chamber in the valve body and which urges the valve member towards the first end of the bore. The spring chamber communicates with the main discharge passage at a location downstream of the control orifice. The valve member has a first metering land between the first end of the valve bore and the overspill porting, and a second metering land between the spring chamber and the overspill porting. The valve body has an annular by-pass port variably obstructed by the second land and connected to the second delivery passage at a location upstream of the non-return valve, and the by-pass port and the axial end portion of the second land nearer the overspill porting are so shaped in relation to each other that on movement of the valve member against the spring loading, the communication between the by-pass port and the space in the valve bore at the axial side of the second land nearer to the first end of the valve bore is initially at least, less than filly annular as the valve member moves against the spring loading. In addition, the control orifice has a variable size.
According to a preferred feature of the invention, the overspill porting comprises an annular overspill port extending about the valve bore. The edge ofthe overspill port nearer the first land and the end of the first land nearer the first end of the valve bore are so shaped in relation to each other that on movement of the valve member against the spring loading, the communication between the by-pass port and the first end of the valve bore is, initially at least, less than fully annular as the valve member moves against the spring loading.
The progressive increase in the area of communication towards fully annular communication in these constructions may be achieved by providing peripheral notches in the end face ofthe first and/or the second land or otherwise making the periphery of such end face non-circular. Alternatively, notches may be cut in an axial end edge of the port.
In some arrangements, the control orifice comprises a fixed orifice and an additional pressure sensitive orifice. The fixed orifice may be located in an axial through bore provided in the valve member. In other arrangements the control orifice comprises a pressure sensitive orifice having a number of orifice sizes dependent on pressure.
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Brighton Derek Keith
Thornelow Alec
Williamson Matthew
Dana Automotive Limited
Freay Charles G.
Solak Timothy P.
Wenderoth , Lind & Ponack, L.L.P.
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