EP0310454B1

EP0310454B1 - Compensated individual segment flow regulator

Info

Publication number: EP0310454B1
Application number: EP19880309199
Authority: EP
Inventors: James Patrick Janecke
Original assignee: Applied Power Inc
Current assignee: Enerpac Tool Group Corp
Priority date: 1987-10-02
Filing date: 1988-10-03
Publication date: 1994-08-24
Anticipated expiration: 2008-10-03
Also published as: EP0310454A2; JPH01145401A; CA1302203C; DE3851193T2; DE3851193D1; EP0310454A3

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates generally to the art of hydraulic valves used to regulate fluid flow. More specifically, the present invention relates to a valve which controls the flow across the spool opening of a proportional, directional valve as load or system pressures fluctuate.

Description of Related Area of Art

Other valves and devices used to control the flow of a fluid have been developed in the past. United States Patent No: 4,361,169 issued to Williams on November 30, 1982 shows a multiple section control valve bank. Metering and logic elements comprise a control valve section which is connected to a signal chamber designed to change the flow of fluid through the inlet of the valve depending on the signals generated from the metering and logic elements. Williams employes a spool and a bore requiring a number of lands and U-shaped passages to generate the proper signals and control characteristics.
United States Patent No. 4,352,375 issued to Williams on October 5, 1982 also discloses a control valve bank. As with the earlier Williams patent, a number of lands are employed along with an intricate heart-shaped flow passage to control fluid flow around a dual supply passage.
United States Patent No. 4,519,419 issued to Petro on May 28, 1985 discloses a hydraulic valve which utilises a hollow piston having several separate lands with different diameters and various seal diameters.
United States Patent No. 4,574,839 issued on March 11, 1986 to Yeh, et al discloses a pressure compensated directional control valve. The valve allows the flow rate to a given hydraulic load to be constant regardless of the load imposed and uses a piston mounted within a sleeve valve insert and a number of springs, wherein the piston moves to create a variable orifice to control the hydraulic fluid flow to the load. An adjustable sleeve works in connection with a hollow piston to provide for proper operation of the valve.
FR-A-2180912 discloses a flow regulating valve designed to regulate flow of a fluid to a hydraulic device supporting a load, said valve having a valve body with means for supplying fluid to said body and comprising a first work port designed to be coupled to a hydraulic device supporting a load; means for controlling fluid flow in said valve to selectively seal off said first work port, permit fluid to flow to said first work port from said supply means or permit fluid to be exhausted from said first work port; means for sensing the load pressure induced by a load coupled to said first work port; means for generating feedback pressure representative of the flow of fluid from said supply means to said first work port; and means for comparing said load pressure and said feedback pressure, said comparing means comprising a generally cylindrical regulator spool axially movable within said valve and positioned so that feedback pressure is sensed on the lower face of said spool and the load pressure is sensed on the upper face of said spool, the position of said spool thereby being determined by the difference between the load pressure and the feedback pressure.

OBJECTS AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved individual segment flow regulator, the operation of which is simpler and less expensive than devices utilised in the past.
It is another object of the present invention to provide a compact individual segment flow regulator which does not require the use of special sleeves or differential areas to properly regulate the flow to a changing load.
It is a different object of the present invention to provide an individual segment flow regulator which utilises a single spring in connection with a single spool to regulate flow to a load.
According to the invention there is provided a flow regulating valve including a valve body having a supply port, a work port designed to be coupled to a hydraulic device which creates a load pressure at said work port, an exhaust port capable of exhausting fluid from said work port, a horizontal bore intersecting said work port and said exhaust port, a vertical compartment intersecting said horizontal bore and said supply port, said vertical compartment having an upper bore land and lower bore land, said supply port being located between said upper and lower lands in said vertical compartment, a main spool in said horizontal bore being moveable to allow a first orifice to be opened to a preselectable area between said work port and said vertical compartment, and movable to a position in which said work port communicates with said exhaust port, a regulator spool biased towards the horizontal bore by a biasing force in said vertical compartment, said regulator spool having an upper land and a lower land, said upper land of said vertical compartment and said upper land of said regulator spool forming a fluid seal and bearing support that defines an upper chamber in said vertical compartment and lower chamber in said vertical compartment, and a sensing passage connecting said upper chamber to said work port to allow the load pressure to be sensed in said upper chamber, characterised by the regulator spool being solid with a lower face that confronts the horizontal bore, the lower land of the regulator spool and the lower land of the vertical compartment forming a second orifice of variable size, the size of the second orifice being determined by the position of said regulator spool in said vertical compartment, wherein when said main spool is positioned to open the first orifice to a preselected area, the load pressure is sensed in said upper chamber and pushes downwardly on the upper face of said regulator spool, a feedback pressure in said lower chamber pushing upwardly on the lower face of said regulator spool, the position of said regulator spool thereby being determined by the difference in the feedback pressure exerted on the bottom of said regulator spool and the combined pressure of said biasing force and the load pressure exerted on the top of said regulator spool.
The regulator can also act as a maximum segment pressure limiter by inclusion of an orifice in the communicating line between the main spool load sensing flow passage and the load sensing spring chamber of the regulator valve. Once the pressure drop caused by a pilot relief valve exceeds the spring pre-load force on the regulator spool the regulator spool will close off flow to the main spool and will create a slight amount of leakage to maintain the pilot relief set pressure.
This invention will now be further described, by way of example only with reference to the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

FIGURE 1 is a front cross-sectional view of the regulator valve of the present invention in its neutral state;
FIGURE 2 is a front cross-sectional view of the regulator valve supplying regulated fluid flow to a work port;
FIGURE 3 is a side cross-sectional view of the valve taken along line 3--3 of FIGURE 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The regulator of the present invention is shown in FIGURE 1 embodied in a housing 20. Two bores are drilled through housing 20, the first being the main spool bore 22 and the two landed regulator compartment 24. Cylinder ports 26, 27 are in communication with the main spool bore 22. Main spool bore 22 intersects regulator compartment 24 perpendicularly, with regulator compartment 24 terminating at it lower end at the main spool bore 22.
A generally U-shaped chamber 28 connects sides of the main spool 30 on either side of the regulator compartment 24. The main spool 30 has a pair of lands 32 which permit or restrict fluid communication between chamber 28 and compartment 24. Additionally, main spool 30 has lands 34 which permit or restrict fluid communication between the chamber 28 and the cylinder ports 26, 27. Movement of the main spool 30 either to the left or the right will permit selective communication between one of the cylinder ports 26, 27 and the regulator compartment 24. When main spool 30 is shifted, the cylinder port which does not receive fluid from the supply communicates with the appropriate exhaust port 36 or 37.
Regulator compartment 24 is sealed at its upper end with a plug 38 utilizing an O-ring 40 to assure a tight seal. Compartment 24 has a first metering land 42 and an upper slidable spool land 44 which acts as a bearing support for the spool 46. Fluid from a supply port 48 enters the regulator compartment 24 between lands 42 and 44. As seen in FIGURE 3, regulator spool 46 also has two lands - a metering land 50 and an upper land 52 which slides within the upper bore land 44. In the preferred embodiment, regulator spool lands 50 and 52 and bore lands 42 and 44 all have the same nominal diameters. A bias spring 54 biases the regulator spool 46 downward toward the main spool bore 22. This downward displacement is limited by a limiting ring 53 on spool 46. A spring chamber 56 is defined by the upper portion of regulator spool 46, the plug 38 and the walls of regulator compartment 24. The U-shaped chamber 28 is in fluid communication with the spring chamber 56 by way of a sensing passage 58 therebetween.
The lower surface 60 of regulator spool 46 serves as a feedback surface. That is, fluid under pressure within the regulator compartment 24 beneath land 42 induces a feedback signal on the lower surface 60 of regulator spool 46 which counteracts the force caused by bias spring 54.

Operation

FIGURE 1 shows the valve of the present invention in its neutral state, that is, with regulated fluid flow to neither cylinder port 26 nor 27. As can be seen in FIGURE 1, handle 31, which controls the position of main spool 30, may be arcuately moved either up or down. Movement of handle 31 induces movement of the main spool 30.
FIGURE 2 shows the main spool shifted to the right as a result of handle 31 being raised. This right hand movement of the main spool 30 causes fluid communication to open between cylinder port 26 and vent 36, thereby permitting passage of fluid from cylinder port 26 to the exhaust port 36. In a similar fashion, fluid communication is permitted between cylinder port 27 and the supply bore 48.
Supply flow from port 48 is throttled across the unsupported land 50 of the regulator spool 46 as it opens away from the valve bore land 42. The only time the metering land 50 of the regulator spool 46 is supported is when it is shut off.
A load pressure from port 27 is transmitted to the spring chamber 56 above regulator spool 46 when the main directional control spool 30 is shifted to the right, as shown in FIGURE 2. As the main spool 30 opens its metering area along land 34, the load pressure will be sensed in the spring chamber 56. The load pressure acting on the top of the regulator spool 46, will cause the regulator spool metering land 50 to open away from bore land 42. As the regulator spool land 50 opens, the increasing flow to the main spool 30 will result in an increasing pressure drop across the main spool area opening at land 32. When the pressure drop across the main spool 30 is equal to the spring force from spring 54 acting on the end of the regulator spool at surface 60, then the spool 46 will modulate around its steady state position. This state of equilibrium is created, in part, by the load pressure acting in the spring chamber on the upper face of regulator spool 46 in addition to the bias spring 54 pre-load force. These combined forces cause the regulator spool metering land 50 to open. Both of these forces are equally opposed by regulated pressure acting on lower face 60 of spool 46.
This opposing force is a feedback force that is used to close down the regulator spool metering land 50 as flow and the pressure drop across the main spool 30 increase beyond the pre-load force of the bias spring 54. The regulated/feedback pressure is upstream of the main spool area opening at land 32, making it a higher pressure than the load pressure due to the pressure drop across the main spool 30. Therefore, the pressure drop across the main spool 30 will equal the spring pre-load force acting on the regulator spool 46 since the load pressure plus the spring pre-load force will collectively equal the regulated pressure. The regulator spool metering land 50 will position itself to allow for the forces to become balanced, and the metering land 50 will automatically adjust its position within chamber 24 as the main spool metering area along land 32 changes and/or as the load pressure or supply fluid pressure to the regulator spool 46 itself changes.
The feedback surface 60 at the end of the spool 46 is part of the metering land 50 that throttles the supply pressure from port 48 to the regulated pressure. As the supply fluid pressure is throttled down to a lower "regulated" pressure, the fluid flows around the metering land 50 of the spool 46 to act directly on the area 60 at the end of the spool 46. The regulated pressure creates a feedback force directly upon end 60 of the spool 46 as the fluid flows to the main spool area opening at land 32. An angle 51 is added to the regulator spool metering land 50 to compensate for the flow forces acting on the spool 46. With angle 51 on the spool 46, the spool displacement greatly increases as the flow forces tend to close down the spool opening between metering land 50 and valve bore land 42. The spool displacement causes the effect of the spring pre-load to increase, which offsets the opposing flow forces.
Another feature which may be added to the system is the ability of the regulator to act as a maximum segment pressure limiter. If an orifice 62, as seen in shadow in FIGURE 2, is installed in the communicating line 58 between the main spool load sensing flow passage 28 and the load sensing spring chamber 56 of the regulator valve, then a pressure drop will be taken across the orifice 62 when a pilot relief valve is connected into the spring chamber 56 and as the relief valve is cracked open to its preset valve. Once the pressure drop exceeds the spring pre-load force of spring 54 on the regulator spool 46, the regulator spool 46 will close off flow to the main spool 30 and will create just enough leakage between land 50 and land 42 to maintain a pressure at which the pilot relief was set. This is done to limit the maximum pressure to a function or to maintain a fixed clamping force on a cylinder or a fixed torque on a rotary motor.
Variations, modifications and other applications will become apparent to those skilled in the art. Therefore, the above description of the preferred embodiment is to be interpreted as illustrative rather than limiting. The scope of the present invention is limited only by the scope of the claims that follow.

Claims

A flow regulating valve including a valve body (20) having a supply port (48), a work port (26, 27) designed to be coupled to a hydraulic device which creates a load pressure at said work port, an exhaust port (36, 37) capable of exhausting fluid from said work port, a horizontal bore (22) intersecting said work port and said exhaust port, a vertical compartment (24) intersecting said horizontal bore and said supply port, said vertical compartment having an upper bore land (44) and a lower bore land (42), said supply port being located between said upper and lower lands in said vertical compartment, a main spool (30) in said horizontal bore being movable to allow a first orifice to be opened to a preselectable area between said work port and said vertical compartment, and movable to a position in which said work port communicates with said exhaust port, a regulator spool (46) biased towards the horizontal bore by a biasing force (54) in said vertical compartment, said regulator spool having an upper land (52) and a lower land (50), said upper land (44) of said vertical compartment and said upper land (52) of said regulator spool forming a fluid seal and bearing support that defines an upper chamber in said vertical compartment and a lower chamber in said vertical compartment, and a sensing passage (58) connecting said upper chamber to said work port to allow the load pressure to be sensed in said upper chamber, characterised by the regulator spool (46) being solid with a lower face (60) that confronts the horizontal bore, the lower land (50) of the regulator spool and the lower land (42) of the vertical compartment forming a second orifice of variable size, the size of the second orifice being determined by the position of said regulator spool in said vertical compartment, wherein when said main spool is positioned to open the first orifice to a preselected area, the load pressure is sensed in said upper chamber and pushes downwardly on the upper face of said regulator spool, a feedback pressure in said lower chamber pushing upwardly on the lower face (60) of said regulator spool, the position of said regulator spool thereby being determined by the difference in the feedback pressure exerted on the bottom of said regulator spool and the combined pressure of said biasing force and the load pressure exerted on the top of said regulator spool.
A valve as claimed in claim 1 characterised in that said vertical compartment is sealed at its upper end with a plug (38) and said biasing force is caused by a spring (54) located between said plug and the upper face of said regulator spool.
A valve as claimed in claim 1 or 2 characterised in that said lower land of said regulator spool is tapered (51) to compensate for flow forces acting on said regulator spool.
A valve as claimed in claim 1, 2 or 3 characterised in that an intermediate, U-shaped chamber (28) is positioned with its upper ends intersecting said horizontal bore on either side of the intersection of said horizontal bore said vertical compartment, said intermediate chamber connecting said work port, said sensing passage, and said first orifice.
A valve as claimed in any one of claims 1 to 4, characterised in that a fixed third orifice (62) is placed in said sensing passage and a pilot relief valve (63) is coupled to said upper chamber, thereby limiting the maximum pressure within said horizontal bore.
A valve as claimed in any one of claims 1 to 5 characterised in that said regulator spool further includes a limiting ring (53) to limit the downward movement of said regulator spool in said vertical compartment.