Load Responsive Control Valve

This invention relates generally to pressure compensated load responsive control valves of direction control type, which in control of a load, while using a control load pressure sensing passage, automatically maintain pump discharge pressure at a level higher, by a constant pressure differential, than the pressure required by the controlled load, by either bypassing excess pump flow to system reservoir, or by varying displacement of the pump.

In more particular aspects this invention relates to load responsive direction control valves having load sensing ports and a control regeneration position, in which the motor ports are connected to each other and to system pump.

The direction control valves with regeneration position, in which motor ports are connected to each other and to system pump, while system reservoir is isolated, are well known in the art and have been used in conventional fluid power circuits for many years. These valves in the regeneration position permit the free fluid transfer between, for example, piston rod end and piston end of a hydraulic cylinder. The pump then supplies only the difference between flow in and flow out of a cylinder. In this way a very much faster extension of the cylinder is achieved than that equivalent to supplying all of the pump flow into the inlet port of the cylinder. Those valves suffer from one basic disadvantage in that all of the pump flow has to be used in regeneration cycle, thus limiting the choice of maximum cylinder speed.

It is therefore a principal object of this invention to control in a load responsive system the quantity of fluid delivered from the system pump into regeneration circuit, thus limiting the constant speed of a cylinder.

Another object of this invention is to provide a regeneration circuit, in which only a selected portion of the total pump flow is used in regeneration, the rest of the pump flow being available to perform other system functions.

Briefly the foregoing and other additional objects and advantages of this invention are accomplished by providing in a load sensing circuit a load responsive regeneration type valve with a feature of connecting, in regenerating position, both cylinder ports through a fixed metering orifice with the system pump, while connecting the load sensing port to both cylinder ports.

The single drawing shows diagramatically sections through two identical four position load responsive direction control valves with actuators, pump and other system components shown diagramatically.

Referring now to the drawing the hydraulic system shown therein comprises a fluid pump 10, equipped with a flow control 11, which regulates delivery of the pump 10 into a load responsive circuit, composed of identical direction control valve assemblies, generally designated as 12 and 13, controlling actuators 14 and 15 subjected to loads W.sub.1 and W.sub.2. The pump 10 may be of fixed or variable displacement type. With the pump 10 being of fixed displacement type the flow control 11, in a well known manner, regulates delivery from the pump to load responsive circuit by bypassing part of the pump flow to a system reservoir 16. With the pump 10 being of variable displacement type the flow control 11, in a well known manner, regulates delivery from the pump 10 to load responsive circuit by changing the pump displacement. Although in the drawing, for purposes of demonstration of the principle of the invention, direction control valve assemblies 12 and 13 are shown separated and the flow control 11 is shown mounted on the pump 10, in actual application valve assemblies 12 and 13 and the flow control 11 would be most likely contained in a single valve housing, or would be bolted together as sections of a sectional valve assembly. As shown in the drawing fixed or variable displacment pump 10 has inlet line 17, which supplies fluid to pump from the reservoir 16 and the pump 10 is driven through a shaft 18 by a prime mover not shown. The pump 10 has an outlet line 19 through which pressurized fluid is supplied to direction control valve assemblies 12 and 13.

The direction control valve 12 has a valve housing 20, which defines an inlet chamber 21 connected by outlet line 19 to the pump 10, transfer chambers 22 and 23 connected by a passage 24, load chambers 25 and 26 and exhaust chambers 27 and 28. Load chambers 25 and 26 are connected by lines 29 and 30 to the chambers of the actuator 14. Exhaust chambers 27 and 28 are connected with lines 31 and 32 with system reservoir 16. The valve housing 20 is provided with a bore 33 interconnecting exhaust chambers 27 and 28, load chambers 25 and 26, transfer chambers 22 and 23 and the inlet chamber 21 and axially guiding valve spool 34. The valve spool 34 has lands 35, 36, 37, 38 and 39, metering slots 40 and 41, unloading groove 42 with timing surfaces 43 and 44 and connecting slots 46. The housing 20 is also provided with load sensing ports 47 and 48, unloading port 49 and cutoff surface 50. Load sensing ports 47 and 48 and unloading port 49 are connected through line 51, check valve 52 and signal line 53 with the flow control 11 of the pump 10. The flow control valve 13 is identical to flow control valve 12 with its valve spool 34 displaced to regenerative control position. The load sensing and unloading circuit to flow control valve 13 is connected through check valve 54 with signal line 53. The same components and features of control valve 13 are denoted by the same numbers as those of control valve 12.

Control valve, generally designated as 12, is shown in its neutral position with lands of valve spool 34 blocking load chambers 25 and 26, the inlet chamber 21 and load sensing ports 47 and 48, while unloading groove 42 opens by timing surface 43 the unloading port 49 to the exhaust chamber 28, which is connected to the system reservoir 16. Therefore reservoir pressure is transmitted through line 51, check valve 52 and signal line 53 to the flow control 11. If a similar signal is transmitted from control valve 13, the flow control 11, in a well known manner, will maintain the pressure in outlet line 19 of the pump 10 at a minimum standby pressure level.

Assume that flow control valve 13 transmits from its load sensing circuit through check valve 54 to signal line 53 a zero pressure signal. Assume also that the valve spool 34 of flow control valve 12 was displaced in either direction from its neutral position. Initial displacement in either direction of the valve spool 34 will disconnect the unloading port 49 from the exhaust chamber 28. Upward movement of valve spool 34 will displace timing surface 43 past cutoff surface 50, isolating the unloading port 49, while by displacement of land 38 connecting the load chamber 26 with transfer chambers 22 and 23. Downward movement of valve spool 34, through displacement of timing surface 44, will isolate the unloading port 49, while by displacement of land 35 connecting the load chamber 25 with transfer chambers 22 and 23. Further displacement of the valve spool 34 in either direction will open load sensing port 47 or 48 to the transfer chamber 22 or 23, subjected to load pressure of load chamber 25 or 26, while land 37 still isolates the inlet chamber 21 from transfer chambers 22 and 23 and lands 35 and 38 still isolate load chamber 25 or 26 from exhaust chamber 27 or 28. Load pressure signal transmitted from load sensing port 47 or 48 to line 51 will open check valve 52, close check valve 54 and will react through signal line 53 on the flow control 11. The flow control 11, in a well known manner, will adjust the pressure in outlet line 19, to maintain a constant pressure differential between discharge pressure of the pump 10 and load signal pressure in signal line 53.

Still further displacement of the valve spool 34 will connect through metering slot 40 or 41 the inlet chamber 21 with transfer chambers 22 and 23, while simultaneously connecting one of the load chambers 25 or 26 to one of the exhaust chambers 27 or 28. Since a constant pressure differential is automatically maintained by the flow control 11 between the inlet chamber 21 and transfer chambers 22 and 23 connected to one of the load chambers 25 or 26, constant flow, proportional to the effective area of metering orifice 40 or 41 connected to the transfer chambers, will be delivered to load chamber 25 or 26. Since the flow from the inlet chamber 21 is proportional to the effective area of metering orifice it is also proportional to the displacement of the valve spool 34, thus controlling the velocity of the load W.sub.1.

With the valve spool 34 of flow control valve 12 in neutral position and the valve spool 34 of flow control valve 13 moved upward all the way, as shown in the drawing, the flow control valve 13 is in a regeneration position. In this control position load chambers 25 and 26 are interconnected with each other through transfer chambers 22 and 23 and passage 24 and are also connected with inlet chamber 21, through a fixed or variable metering orifice 55, determined by the cross-sectional area of land 36. Land 36, shown cylindrical in the drawing, in a well known manner, can be made conical and the size of metering orifice 55 can be varied by small adjustments in position of the valve spool 34. The connecting slot 46 conducts fluid pressure from interconnected load chambers to load pressure sensing port 47, from which it is transmitted through check valve 54 and signal line 53 to flow control 11. The pressure in load chambers 25 and 26 supports load W.sub.2 and is equal to the quotient of load W.sub.2 and the difference between the effective areas of actuator chambers 56 and 57. The pump 10, controlled by the flow control 11, will maintain in the inlet chamber 21 a pressure, higher by a constant pressure differential, than the pressure in load chambers 25 and 26. Therefore a constant pressure differential will be automatically maintained across orifice 55, resulting in a constant flow of fluid being delivered from the inlet chamber 20 to load chambers 25 and 26. The flow delivered from the pump 10 through orifice 55 to load chambers 25 and 26 will enter the actuator chamber 56 and will be supplemented by flow from the actuator chamber 57, proportionally increasing the velocity of load W.sub.2. Since, irrespective of the variation in the load W.sub.2, a constant flow, proportional to the effective area of the orifice 55, will be delivered from the pump 10 to load chambers 25 and 26, the load W.sub.2 will be moving at a constant velocity, utilizing only part of the total delivery of the pump 10. Therefore selection of area of orifice 55 will automatically determine the velocity of load W.sub.2 during regeneration.

If the controlled velocity of the load W.sub.2 would have to be adjusted land 36 would be made, for example, conical and the area of the orifice 55 changed with position of valve spool 34, while still maintaining the basic connections of regeneration cycle.

Although the preferred embodiment of this invention has been shown and described in detail it is recognized that the invention is not limited to the precise form and structure shown and various modifications and rearrangements as will readily occur to those skilled in the art upon full comprehension of this invention may be resorted to without departing from the scope of the invention as defined in the claims.