Control of hydraulically powered equipment

DETAILED DESCRIPTION The present invention overcomes these problems of the prior art and provides a hydraulic switching system which is adjustable over a wide range without any loss in speed of valve action and without any loss in precision of timing.
According to the present invention, a pilot conduit system is provided at a fixed location in a hydraulic system to be controlled.
A fluid accumulation chamber is also provided to receive a flow of pressurized fluid from the pilot system.
This flow is initiated whenever the relatively moveable elements, i.
e.
the piston and cylinder, of the hydraulic system reach a set relative position.
The fluid accumulation chamber is provided with means responsive to the pilot actuation port of the main hydraulic valve for producing actuation thereof.
The time delay between the initiation of pilot fluid flow and main valve actuation can be controlled in various ways.
In one preferred embodiment, described hereinafter, the rate of flow of pilot fluid to the accumulation chamber is adjustably metered.
So long as the accumulation chamber volume is maintained large enough to permit the high pilot fluid flow rates, this pilot flow rate can be metered over a wide range to obtain a substantial variation in time delay without appreciably affecting the rapidity of valve actuation after the time delay has elapsed.
In another embodiment, also described herein, the time delay is adjusted by providing means for adjusting the chamber volume at which the switching of application of pilot flow forces to the hydraulic valve takes place.
According to this second embodiment, a moveable piston in the accumulation chamber is provided with stop means which prevent further piston movement in response to continued application of pilot pressure.
The distance between the normal position of the piston and the stop means is made adjustable.
Any flow of pilot fluid into the accumulation chamber after the piston has reached the stop means cannot continue to accumulate in the chamber and therefore it passes the chamber and flows to the actuation port of the main hydraulic valve