Motors: expansible chamber type – Fluid supply through diverse paths to single expansible chamber – Second path activated in response to pressure or flow in...
Reexamination Certificate
1998-09-03
2001-12-11
Lopez, F. Daniel (Department: 3745)
Motors: expansible chamber type
Fluid supply through diverse paths to single expansible chamber
Second path activated in response to pressure or flow in...
C091S436000, C091S437000
Reexamination Certificate
active
06327956
ABSTRACT:
FIELD OF THE INVENTION
This invention related generally to hydraulic control systems, and more particularly to such a system having a unique regenerative valve apparatus and method.
BACKGROUND OF THE INVENTION
There are many hydraulic control applications where it is desirable to significantly reduce the time taken to move the primary force producing hydraulic piston of the system in one or both directions of its operative travel. The need can become very significant in physical systems having hydraulic cylinder prime movers that are very large, such as in automobile crushing systems. Depending on their particular designs, such systems may utilize very large prime mover cylinders connected to operate the crushing ram with, for example, bore diameters of 10 to 12 inches and piston strokes from 90 to 100 inches. In such systems, it is desirable not only to crush the automobile in a relatively short period of time, but to then rapidly return the crushing ram to its initial position for the start of the next crushing operation.
Regenerative hydraulic circuit principles have been used to reduce the cycle time of prime mover hydraulic cylinders. The general principal involved in a regenerative circuit is that special valving is used to connect the rod end of the prime mover cylinder with its blind or cap end in a manner so as to increase the rate of travel of the piston. For example, if it is desired to increase the piston travel speed in the primary working direction of the piston, from its blind end toward its rod end, the regenerative network would direct hydraulic system oil that would normally flow to the system tank or reservoir, from the piston's rod end, to supplement the pumped oil being supplied to the piston's blind end—causing the piston to advance at an increased rate of speed toward the rod end.
During a regenerative process, in essence, equal pressure is applied to both ends of the hydraulic cylinder, with the effect that the net thrust delivered by the cylinder rod will be the same as if the effective pressure were applied only to the rod cross-sectional area (i.e., thrust=system pressure×rod area). The oil redirected by the regenerative circuit from the rod end of the cylinder, fills an equivalent volume on the blind or cap side of the cylinder so that the hydraulic pump driving the cylinder needs to only fill a space equivalent to the volume of the rod. Such regenerative principles are well known to those skilled in the art.
While such known regenerative principles have been employed to advantage in reducing hydraulic cylinder cycle time, they have typically been employed to assist movement of the piston in only one direction and have typically only directly used a portion of the hydraulic fluid available for redirection. Further, the hardware that has been used to implement regenerative control functions has typically been very large, bulky, heavy, expensive and difficult to install. The ability to decrease cylinder movement cycle time is proportional to the volume of hydraulic oil that can be redirected by the regenerative circuit. However, due in part to the heretofore cumbersome implementation techniques of known regenerative control circuits, they have not been able to practically, effectively and efficiently handle regeneration applications for very large cylinders wherein it is desirable, for example, to redirect significant quantities of oil through oil passageways of greater than 1 inch in diameter.
The present invention addresses the above-described deficiencies of regenerative systems of the prior art. The present invention provides a relatively inexpensive, efficient and effective regenerative circuit that can be made with readily available technology and which gives significant cycle reduction time by enabling virtually 100% regenerative cylinder operation in both directions of travel of the cylinder's piston. These and other features of the invention will become apparent upon a more detailed description thereof.
SUMMARY OF THE INVENTION
This invention provides a hydraulic system particularly suitable for rapidly moving the piston of a primary hydraulic cylinder in both directions of travel by use of a regenerative valve member. The regenerative transfer of hydraulic fluid from one side of the piston to the other is accomplished by the regenerative valve without requiring the transferred fluid to be directed through the master control valve of the system which determines the direction of travel of the piston. The regenerative principles of this invention enable rapid movement of the piston in both directions of travel.
According to one aspect of the invention there is a provided a regenerative hydraulic control apparatus comprising: (a) a primary hydraulic power unit having a piston movable within a cylinder and dividing the cylinder between a blind side and a rod side; (b) a rod connected to the piston for motion therewith and longitudinally extending through the rod side; (c) a force imparting apparatus for applying force to the piston through the rod; (d) a regenerative valve having first and second chambers respectively operatively connected to the blind and the rod sides of the hydraulic power unit, and a movable member relative to the first and second chambers for selectively opening and closing fluid flow between the first and second chambers and through the valve; (e) a master valve suitable for operative connection with a pump and a reservoir and operatively connected to the primary power unit and to the regenerative valve for directing movement of the primary hydraulic power unit piston in its cylinder; and (f) wherein the regenerative valve provides regeneration fluid flow between the rod and the blind sides of the primary hydraulic power unit for both directions of travel of the piston. According to a further aspect of the invention the force imparting apparatus comprises a weight, and may include a ram member such as ram used in the crushing of objects. According to yet another aspect of the invention, the force imparting apparatus could comprise a bias member as, for example, a spring. According to a further aspect of the invention, the regenerative valve includes a pilot port operatively connected with the master control valve for controlling operation of the regenerative valve between its open and its closed states. According to yet a further aspect of the invention, a metering valve may be connected to the pilot port for regulating the length of time for transitioning the regenerative valve between its open and its closed modes of operation.
According to yet a further aspect of the invention, there is provided a method of providing regenerative drive fluid flow for a hydraulic control unit of the type having a primary hydraulic cylinder operatively connected to a master control valve that activates and controls the direction of travel of a piston within the primary hydraulic cylinder, comprising the steps of: (a) connecting a regenerative hydraulic control network to the primary hydraulic cylinder; (b) selectively causing the piston to cyclically move between retracted and power strokes; and (c) moving regenerative hydraulic fluid through said regenerative hydraulic control network from one side of the piston to the other during both the retracted and the power stroke movements of the piston. According to yet a further aspect of the invention, the transfer of regenerative fluid from one side of the piston to the other does not require flow of such fluid through the master control valve, but only through the regenerative hydraulic control network. The regenerative method principles of this invention can be applied to move a ram member, and particularly to such a ram member that is used in association with crushing items.
According to yet a further aspect of the invention, there is provided a hydraulic apparatus comprising: (a) a reservoir of hydraulic fluid; (b) a pump connected to the reservoir; (c) a primary hydraulic cylinder having a moveable piston; (d) a master control valve hydraulically connected to
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