Related Applications

This application claims the benefit of U.S. Provisional Application No.

61/569,309 filed December 12, 201 1 , which is hereby incorporated herein by reference.

Field of Invention

The present invention relates generally to pressure reducing valves, and more particularly to a pressure reducing valve having integrated pressure relief.

Background

Typical direct acting pressure reducing valves provide a reduced pressure from a high pressure supply to a reduced pressure port. As the flow demand from the reduced pressure port passes, the spool throttles to limit the pressure downstream of the valve.

Summary of Invention

In order to prevent over-pressurization downstream of the valve once the pressure reducing valve is closed, integrated pressure relief is provided. For example, leakage past the pressure reducing valve spool (a continuous leak path past the reduced pressure valve is often a problem in low flow power units or on accumulator supplied circuits), thermal expansion of the downstream fluid, or other mechanisms can cause pressure to build up at the reduced pressure port. However, spool leakage to, for example, a third (tank) port that vents the spring chamber, prevents the reduced pressure from going over a predetermined setting.

According to one aspect of the invention, a hydraulic circuit for supplying reduced pressure includes a reduced pressure valve having an inlet and an outlet. The reduced pressure valve has a first position defining an open fluid path and a second position defining a closed fluid path, and reduced pressure valve is biased towards the first position. The circuit also includes a pressure relief valve having an inlet fluidly connected to the outlet of the valve, and an outlet fluidly connected to a drain outlet. The fluid pressure at the outlet of the reduced pressure valve urges the reduced pressure valve towards the second position, the reduced pressure valve being in the second position when the fluid pressure at the outlet of the reduced pressure valve is greater than or equal to a predetermined pressure.

Optionally, the pressure relief valve is configured to open when pressure at the inlet of the pressure relief valve is greater than or equal to a second predetermined pressure.

Optionally, the outlet of the pressure relief valve urges the pressure reduced valve towards the first position.

According to another aspect of the invention, a valve for supplying reduced pressure with integrated pressure relief includes a valve body including a supply port, a reduced pressure port and a drain port; a piston axially moveable from a first position to a second position within the valve body against a resilient biasing force, the piston having a first actuating area fluidly connected to the reduced pressure port and being configured to open a fluid passageway between the supply port and the reduced pressure port when in the first position and to close the fluid passageway between the supply port and the reduced pressure port when in the second position; and a pressure relief assembly including a relief passageway fluidly connecting the reduced pressure port to the drain port. The piston is moveable to the second position when pressure against the first actuating area of the piston is equal to or greater than a first

predetermined amount, thereby overcoming force biasing the piston towards the first position.

Optionally, the valve further includes a fluid passageway between the supply port and the drain port.

Optionally, the passageway is through the piston.

Optionally, the pressure relief assembly includes a pressure relief member biased by a pressure relief spring to block the passageway through the piston unless pressure against the pressure relief member is greater than a predetermined relief amount. Optionally, the valve further includes a pin rigidly connected to the valve body. The piston includes a bore defining the passageway, the bore includes a relief chamber having a relief valve seat, and the piston further includes a pressure relief member configured to seal against the relief valve seat. The pin is configured to displace the pressure relief member when pressure against the first actuating area is equal to or greater than a second predetermined amount, the second predetermined amount being greater than the first predetermined amount

Optionally, pressure against the first actuating area which is equal to or greater than the second predetermined amount causes the piston to move such that the pin extends into the bore to displace the pressure relief member from the valve seat.

Optionally, the piston includes a bore defining the passageway, the bore includes a relief chamber having a relief valve seat, and the piston further includes a pressure relief spring to bias a pressure relief member against the relief valve seat to block the passageway through the piston unless pressure against the pressure relief member is greater than a predetermined relief amount.

Optionally, the predetermined relief amount is greater that the first predetermined amount.

Optionally, the spring is adjustably settable by a cylindrical member that is axially adjustable within the bore of the piston.

The foregoing and other features of the invention are hereinafter described in greater detail with reference to the accompanying drawings.

Brief Description of the Drawings

Embodiments of this invention will now be described in further detail with reference to the accompanying drawings, in which:

FIG. 1 is a schematic of a hydraulic circuit having a pressure reducing valve and pressure relief;

FIG. 2 shows a cross-sectional view of an exemplary embodiment of a pressure reducing valve shown in a first position above the axial centerline and shown in a second position below the axial centerline; FIG. 3 shows a detail view of a portion of the valve shown in FIG. 2;

FIG. 4 shows a cross-sectional view of another exemplary embodiment of a pressure reducing valve shown in a first position above the axial centerline and shown in a second position below the axial centerline.

Detailed Description

A pressure reducing valve may be used to provide a reduced pressure from a high pressure supply to a reduced pressure port. As the flow demand from the reduced pressure port passes, the valve may throttle to limit the pressure supplied to the reduced pressure port.

In order to prevent over-pressurization at the reduced pressure port once the pressure reducing valve has closed, a pressure relief may be provided.

Typical systems used to control the pressure available to cylinders are exposed to a wide range of temperatures. The expansion of the fluid due to temperature variations could be excessive and damage hydraulic components in the system. The pressure relief feature prevents the buildup of pressure due to thermal expansion. The relief feature also prevents the buildup of pressure due to leakage from the inlet 1 to the reduced pressure port 2. Spool leakage to, for example, a third (tank) port that vents the spring chamber, prevents the reduced pressure from going over a predetermined setting.

Referring initially to FIG. 1 , a schematic representation of a hydraulic circuit 5 for supplying reduced pressure from an inlet 1 to a reduced pressure outlet 2 is shown. The hydraulic circuit 5 includes a reduced pressure valve 6 having an inlet and an outlet. The reduced pressure valve 5 has, for example, two or more positions. A first position defines an open fluid path and a second position defines a closed fluid path. The reduced pressure valve 5 is biased towards the first position. Fluid pressure at the outlet of the reduced pressure valve 6 urges the reduced pressure valve 6 towards the second position, the reduced pressure valve 6 being in the second position when the fluid pressure at the outlet of the reduced pressure valve 6 is greater than or equal to a

predetermined pressure. The circuit 5 also includes a pressure relief valve 7 having an inlet fluidly connected to the outlet of the reduced pressure valve 6, and an outlet fluidly connected to a drain 3.

The pressure relief valve 6 may be configured to open when pressure at the inlet of the pressure relief valve 6 is higher than a predetermined pressure, in order to regulate pressure being supplied to the outlet 2.

The outlet of the pressure relief valve 6 may urge the pressure reduced valve towards the first position.

Turning now to FIG. 2, an exemplary embodiment of the present invention is shown in a configuration like a pilot operated check valve or counterbalance valve. The valve 10 includes a valve body 12 having a central passageway 14 therethrough. The valve body 12 has a first spring retaining member 16 threadably secured at a first internal end thereof. A second spring retainer 18 is threadably secured to an insert 20 threadably secured to a second internal end of the valve body 12. Insert 20 is generally cylindrical and includes an internal passageway extending therethrough in which a poppet 22 is axially moveable therein and biased by spring 24 against a seat 26 formed in the insert 20 to close the passageway through the insert 20, and to keep poppet 22 pressed against piston 28.

The valve 10 is shown in a two ported configuration including a supply pressure port 1 and a reduced pressure port 2 as well as a drain 3.

The valve 10 includes a piston 28 axially moveable within the valve body 12 and biased by a main spring 30. The piston 28 includes a portion 32 extending through the seat 26 of the retainer 20 and contacting the inlet poppet 22.

In operation, flow travels into the supply pressure port 1 to exit at the reduced pressure port 2. In particular, flow travels through inlet poppet 22 which is held off its seat 26 by the portion 32 of the piston 28 which is biased in position by the main spring 30. Reduced pressure acts on the area of the piston 28 facing the reduced pressure chamber 34 against the main spring 30 that is used to set the predetermined reduced pressure. Flow travels freely from the supply port 1 to the reduced pressure port 2 until the reduced pressure exceeds the biasing force on the piston 28 (for example, the spring setting of spring 30). The pressure moves the piston 28 back against the spring 30 and allows the inlet poppet 22 on the supply port 1 to close. As long as the reduced pressure is maintained, the supply remains blocked from passing to the reduced pressure port 2. The piston 28 on the reduced pressure port 2 utilizes a seal for an external atmospheric vent of the spring chamber. The seal helps to prevent the reduced pressure from leaking down which would require the supply to pass the inlet poppet 22 to resupply the reduced pressure port 2.

Turning to FIG. 3, a thermal relief assembly 1 10 is provided in the piston 28 providing for a leakage passage from the reduced pressure port 2 to the drain line 3 of the spring chamber. Any leakage from the supply port 1 to the reduced pressure port 2, or thermal expansion of hydraulic fluid, could allow the reduced pressure to build up over the reduced pressure setting. Therefore, the thermal relief assembly 1 10 may be provided to limit the pressure at the reduced port 2. Further, the dual seal on the piston 28 provides a redundant seal should one wear over time

The valve 10, therefore, includes a pressure relief feature with an independent pressure setting over the reduced pressure setting. The thermal relief assembly 1 10 may include a passageway 1 12 through the reduced pressure side of the piston 28 to a central cavity or bore 1 13 in the piston 28. A spring 1 14 is adjustably settable by a cylindrical member 1 16 that is axially adjustable within the bore 1 13 of the piston. A valve member, for example ball 1 18, is biased against a seat 1 19 of the opening of the passageway 1 12 into the bore 1 13 of the piston. Sufficient pressure forces the ball 1 18 to move against the spring 1 14 and allow flow to the drain 3.

Turning now to Fig. 4, an exemplary embodiment of the pressure reducing valve is shown at 10'. The pressure reducing valve 10' is substantially the same as the above-referenced pressure reducing valve 10, and consequently the same reference numerals but including prime notation are used to denote structures corresponding to similar structures in the pressure reducing valve. In addition, the foregoing description of the pressure reducing valve 10' is equally applicable to the pressure reducing valve 10 except as noted below. Moreover, it will be appreciated upon reading and understanding the specification that aspects of the pressure reducing valves may be substituted for one another or used in conjunction with one another where applicable.

FIG. 4 shows an alternative configuration as valve 10' that utilizes the main spring 30' of the reducing valve to effectuate the pressure relief function. The reduced pressure acts to close the ball 1 18' against the relief seat 1 19' (not open it as in fig 1 ). A pin 120' positioned down the center of the spring 30' is used to actuate the ball 1 18' as the piston 28' is overstroked due to increased pressure in the regulated pressure chamber 34'. This configuration also provides the option for independent external adjustment of the main regulation pressure as well as the thermal relief pressure by adjusting the depth of the pin 120'. This configuration also allows for a reduced diameter of the reduced pressure piston which increases the range of pressures the valve can be used in.

FIG. 4 also depicts an alternative arrangement of the pressure reducing valve by including a ball 22' rather than a poppet, as in FIG. 2.

Although the invention has been shown and described with respect to a certain embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described elements (components, assemblies, devices, compositions, etc.), the terms (including a reference to a "means") used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiment or embodiments of the invention. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application.