Hydraulic control valve for fuel pumping system

In a low pressure drop valve connectible to a source of pressurized hydraulic fluid for modulating hydraulic fluid flow, the improvement combination comprising:

• (a) valve body means defining an axially extending tapered bore and having hydraulic flow inlet and outlet ports,
• (b) a plug valve movable axially in that bore and having an externally tapered surface facing the tapered bore and movable axially relative thereto to increase or decrease a gap formed between the tapered surface and the tapered bore, for controlling the flow of hydraulic fluid via the gap and at least one of said ports,
• (c) means responsive to a side stream of pressurized hydraulic fluid to control axial movement of the plug valve in the tapered bore, said means including first and second pistons connected with the plug valve to move axially therewith, the valve body means forming first and second cylinders respectively receiving the pistons for application of hydraulic fluid pressure to the pistons for displacing the pistons and plug valve axially, and protective O-rings in the cylinders acting to space the pistons from bores formed by the cylinders,
• (d) and stop means in the valve body means to limit axial movement of the plug valve so as to prevent closing of said gap, said stop means spaced from said gap and from said pistons and O-rings.