cylinder control valve

Abstract

Control valve (100) comprising: a valve body (102); a spool (120) in the valve body (102) configured to control the fluid allocation to a power cylinder (112), the spool (120) being controllable by a pilot valve (130) and having at least a first position, a second position, and an intermediate position between the first and second positions in the valve body (102); a pressure regulating part (128) in the control valve (100) in selective fluid communication with a rod-side chamber (116) of the power cylinder (112), the pressure regulating part (128) being configured to change the position of the spool (120), wherein a fluid pressure of the rod-side chamber (116) signals the pressure regulating part (128) to bias the spool (120) toward the first position with a biasing force against the spool (120) that is proportional to the fluid pressure of the rod-side chamber; and wherein a biasing element (122) in the control valve (100) is configured to bias the spool (120) toward the second position; wherein the control valve (100) is configured to reduce the fluid consumption of the power cylinder (112); and wherein the slider (120) is held in the intermediate position when a force exerted on a second end (120b) of the slider (120) and a force of the biasing element (122) are substantially equal to each other, and the control valve (100) is configured to prevent fluid from entering or exiting the cylinder when the spool (120) is in the intermediate position.

Description

FIELD OF THE INVENTION

[0001] The embodiments described below relate to valves and in particular to an improved cylinder control valve with pressure control and a related method. BACKGROUND

[0002] Power cylinders, often pneumatic or hydraulic, are used to convert pressurized fluid into linear motion of a piston rod to perform a mechanical task. The most basic design of a power cylinder includes a tube with a rod protruding from one end. A piston is attached to the rod, and the piston is located within the tube. Fluid pressure acts on the piston, causing it to move within the tube to cause the rod to reciprocate. The cylinder's operation must be controlled, and this can be achieved using a control or pilot valve.

[0003] A control valve dictates which chamber of the cylinder receives pressurized fluid, thus determining the cylinder's actuating state. Fluid flow from a control valve typically enters one of two ports on the cylinder. While there are numerous ways to configure a valve with a cylinder, frequently one port is pressurized while the other acts as a return port. Pressurized fluid acts on one side of the piston, in turn forcing the rod into or out of the end of the cylinder. The direction depends on which side of the piston is pressurized by the valve. When pressure is released, external forces acting on the rod cause the rod to move to the opposite position.By adjusting the valve configuration, the cylinder can be made to extend and retract under fluid control, without the need for external forces to trigger a return stroke.

[0004] The return stroke of a cylinder often requires little force to cause the rod to retract, as external forces from a workpiece connected to the rod contribute to the required retraction force. Therefore, there is a need for a control valve that utilizes the forces provided by external workpieces by reducing the pressure of fluid supplied to the cylinder for the return stroke to conserve energy and reduce operating costs. There is also a need to integrate a pressure regulator to assist in conserving fluid used in the return stroke. There is also a need for a cylinder control valve that performs these functions in a manner that can be implemented cost-effectively.

[0005] DE 10 2012 013 284 A1 relates to an energy-saving valve comprising a spool drive unit that changes the position of a spool to a position in which compressed air is discharged from a first output port without pressure control, and a pressure control unit that changes the position of the spool to a position in which compressed air is discharged from a second output port at a predetermined pressure level due to pressure control. The pressure control unit comprises a pressure control piston, a pressure-receiving surface that allows the air pressure in the second output port to act on the pressure control piston, a cylinder chamber, a pressure control channel, and an elastic element that exerts a biasing force on the pressure control piston in a direction opposite to the action of the air pressure on the pressure-receiving surface to determine the pressure.

[0006] DE 40 35 255 A1 relates to a pressure control valve which can be used in a power steering system for motor vehicles or other industrial equipment.

[0007] US 2 891 517 A relates to the control of hydraulic presses and similar devices with cylinder and piston drives operated with pressurised fluid from a primary high-pressure fluid source, and in particular it relates to a control system for such devices in which the high-pressure fluid supply is distributed and controlled by valves, some of which are operated with pressurised fluid from a secondary or pilot pressurised fluid source at a substantially lower pressure than the primary pressurised fluid.

[0008] DE 36 29 479 A1 relates to a hydraulic directional control valve. This directional control valve, in which two control pistons are aligned in a control bore of the valve housing and actuated by associated pilot valves to control consumer connections, allows multiple consumers to be controlled independently of one another.

[0009] Against the background of this prior art, it is an object of the present disclosure to provide a control valve and / or a method for producing this control valve which are suitable for enriching the prior art.

[0010] The embodiments described below overcome this prior art and other problems, and a technical advance is achieved. Thus, the object is achieved by the features of the independent claim. The independent claim and the dependent claims each contain optional developments of the disclosure. The embodiments described below provide a cylinder control valve for a cylinder with a pressure regulator configured to conserve and minimize the use of return stroke fluid. The result is a control valve that exceeds the performance of prior art units, is more cost-effective to operate, and also reduces implementation costs. SUMMARY OF THE INVENTION

[0011] A control valve having the features according to claim 1 is provided.

[0012] A method for producing a control valve having the features of claim 6 is provided. ASPECTS

[0013] According to one aspect, a control valve comprises a valve body and a spool within the valve body configured to regulate fluid allocation to a power cylinder, the spool being controllable by a pilot valve and having at least a first position, a second position, and an intermediate position between the first and second positions within the valve body. A pressure regulating portion within the control valve is in selective fluid communication with a rod-side chamber of the power cylinder, the pressure regulating portion configured to change the position of the spool, wherein fluid pressure of the rod-side chamber signals the pressure regulating portion to bias the spool toward the first position with a biasing force against the spool that is proportional to the fluid pressure of the rod-side chamber.A biasing element in the control valve is configured to bias the spool toward the second position, and the control valve is configured to reduce fluid consumption of a power cylinder.

[0014] The spool is preferably held in the intermediate position when a force exerted on a second end of the spool and a force of the biasing member are substantially equal to each other, and the control valve is configured to prevent fluid from entering or exiting the cylinder in the intermediate position of the spool.

[0015] The pilot valve is preferably configured to supply pressurized fluid from a fluid source to a control piston chamber of the pressure regulating member and apply fluid pressure to a second end of the spool and bias the spool toward the first position, wherein the control valve supplies fluid to the power cylinder to extend a piston rod therein, and wherein the cap-side cylinder chamber is brought into fluid communication with a fluid source.

[0016] The spool preferably comprises a spool port extending from an outer surface of the spool to a spool bore in the spool extending from a central portion of the spool to the second end of the spool, the spool port being in fluid communication with a spool-side chamber of the pressure regulating member, the spool port also being in fluid communication with a second discharge port in all spool positions, and the biasing member oppositely biasing the pressure regulating member, the spool being configured to remain in the intermediate position when a force on the spool from the biasing member is equal to the force exerted on the spool by a spool of the pressure regulating member, the spool being moved toward the first position when the spool-side chamber receives fluid pressure from the rod-side cylinder chamber.

[0017] The control valve preferably comprises: a fluid inlet port defined by the valve body, configured to be in fluid communication with a fluid source; a first discharge port configured to be in fluid communication with a cap-side chamber of the power cylinder; a second discharge port configured to be in fluid communication with a rod-side chamber of the power cylinder; a vent port configured to be in fluid communication with the first discharge port when the spool is in a first position; and a drain port configured to be in fluid communication with the second discharge port when the spool is in a second position, wherein no vent port is in fluid communication with a discharge port when the spool is in the intermediate position.

[0018] The control valve is preferably a 5 / 3 valve that can be operated as a 5 / 2 valve.

[0019] According to one aspect, a method of manufacturing a control valve includes the following steps: providing a valve body having first and second discharge ports, first and second drain ports, and a single fluid supply port; defining a spool cylinder projecting longitudinally within the valve body; placing a spool in the spool cylinder, the spool configured to regulate fluid allocation to a power cylinder by changing positions within the valve body; biasing the spool with a biasing element in a second direction; providing a pressure regulating part in the control valve that biases the spool in a first direction opposite to the biasing element; attaching a pilot valve to the control valve, the pilot valve triggering the pressure regulating part;and fluidly connecting a rod-side chamber containing the power cylinder to the pressure control part, wherein a fluid pressure of the rod-side chamber signals the pressure control part to bias the spool toward the first position, wherein a biasing force against the spool is proportional to the fluid pressure of the rod-side chamber;

[0020] The spool is preferably configured to move slidably within the spool cylinder to at least a first, a second, and an intermediate position between the first and second positions, wherein the first vent port is configured to be in fluid communication with the first discharge port when the spool is in a first position, and wherein the second vent port is configured to be in fluid communication with the second discharge port when the spool is in a second position, and wherein no vent port is in communication with a discharge port when the spool is in the intermediate position.

[0021] The method preferably includes the step of configuring the pressure regulating member to bias the spool toward the first position during a return stroke of the power cylinder, wherein the fluid pressure of the rod-side chamber moves the spool toward the first position, and wherein the spool is configured to remain in the intermediate position when the force on the spool from the pressure regulating member is equal to the force on the spool from the biasing member.

[0022] The method preferably includes the step of configuring the control valve to consume approximately half the fluid required for an inward stroke of the power cylinder as is required for an outward stroke of the power cylinder by supplying pressure from a rod-side chamber of the power cylinder to the pressure regulating member to position the spool in the intermediate position. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The same reference numbers identify the same elements in all drawings. The drawings are not necessarily to scale. Fig. 1 illustrates a cross-section of a control valve according to one embodiment; and Fig. 2 illustrates a schematic of the control valve of Fig. 1 in fluid communication with a pilot valve and a power cylinder; and Fig. Figure 3 illustrates a schematic of an alternative design of the control valve of Fig. 1 in fluid connection with a pilot valve and a power cylinder. DETAILED DESCRIPTION OF THE INVENTION

[0024] The Fig. 1-3 and the following description illustrate specific examples to instruct those skilled in the art in the implementation and use of the best mode of power cylinder control valve embodiments and related methods. For the purposes of teaching the inventive principles, some conventional aspects have been simplified or omitted. Variations to these examples will occur to those skilled in the art and are within the scope of the invention. Those skilled in the art will recognize that the features described below can be combined in various ways to form multiple variations of the invention. Accordingly, the invention is not limited to the specific examples described below, but only by the claims and their equivalents.

[0025] The Fig. 1 and Fig. 2 illustrate a control valve 100 according to one embodiment. For clarity, some parts of the illustration have been shown symbolically. Furthermore, some conventional components may be omitted from the illustrations for clarity. The control valve 100 has a body 102 with a spool cylinder 104 projecting longitudinally therein. A single fluid inlet port 106 is provided. The fluid inlet port 106 is connected to a fluid source 108. Also defined by the body 102 are a first discharge port 110a and a second discharge port 110b. The discharge ports 110a and 110b are in fluid communication with a power cylinder 112.While the illustrations show discharge port 110a connected to cap-side chamber 114 and discharge port 110b connected to rod-side chamber 116, it should be understood that in some embodiments, this could be reversed, such that discharge port 110a is connected to rod-side chamber 116 and discharge port 110b is connected to cap-side chamber 114. A first drain port 118a and a second drain port 118b are also defined by body 102.

[0026] A spool 120 slidably engages the spool cylinder 104 and can slide longitudinally therein. A plurality of seals 121 may be provided to seal the spool cylinder 104 from the body 102. In one embodiment, the valve body 102 may define a bore in which the spool 120 is located, and in this case, seals 121 may alternatively be provided on the spool 120 itself, and a separate spool cylinder 104 may not be present.

[0027] The first discharge port 110a is configured to be in fluid communication with the first drain port 118a, depending on the position of the spool 120 in the spool cylinder 104. This places the conduit 111 in fluid communication with the conduit 111a. Likewise, the second discharge port 110b is configured to be in fluid communication with the second drain port 118b, depending on the position of the spool 120 in the spool cylinder 104. This places the conduit 113 in fluid communication with the conduit 113a. In one embodiment, the conduits 111a and 113a may be connected to a common drain 117.

[0028] A biasing member 122 in control valve 100 biases spool 120 to a second position (toward the right of the control valve as illustrated). An end housing 123 may retain biasing member 122. End housing 123 may have a seal 125, such as, without limitation, an O-ring, to seal end housing 123 to body 102. A first biasing member end cap 124 contacts biasing member 122 and receives forces associated with the biasing member, which are transmitted to a first end 120a of spool 120, which also contacts first biasing member end cap 124. A second biasing element end cap 126 can be adjustably positioned on the biasing element 122 to increase or decrease the tension of the biasing element 122 so that the force applied by the biasing element 122 to the slider 120 is adjustable.Although a coil spring is illustrated, the biasing element 122 may also be another type of elastic element that applies a force to the spool 120. In one embodiment, the biasing element 122 may be replaced or supplemented by fluid pressure and a piston, a diaphragm, or a similar element.

[0029] A pressure regulating member 128 receives fluid pressure and applies a corresponding force to the spool 120. Fluid pressure from a pilot valve 130 is directed into a control member chamber 129, and this fluid pressure acts on a second end 120b of the spool 120. This force opposes the force of the biasing element 122. This force is proportional to the fluid pressure received by the pressure regulating member 128. The pressure regulating member 128 receives fluid from the pilot valve 130 and additionally from at least one line 111, 113 with the power cylinder 112.

[0030] In one embodiment, the pilot valve 130 is an electrically actuated solenoid valve. In another embodiment, the pilot valve 130 is a fluid-actuated valve. A supply line 132 in fluid communication with the fluid source 108 supplies fluid to the pilot valve 130. It should be noted that in one embodiment, the fluid supplied to the pilot valve 130 need not come from the fluid source 108 as illustrated, but may come from another fluid supply. A drain line 133 from the pilot valve 130 may be in fluid communication with the drain 117. When the pilot valve 130 is actuated, fluid from the supply line 132 is directed via an inlet port 135 of the pilot valve 130 to an exhaust port 134 of the pilot valve 130, which is in fluid communication with the pressure regulating chamber 129 of the pressure regulating part 128.Fluid pressure from supply line 132 via discharge port 134 and discharge line 136 exerts a force on the second end 120b of spool 120 opposite to the force generated by biasing member 122. This causes spool 120 to overcome the force of biasing member 122 and move to a first position (left as illustrated).

[0031] A control piston 138 can slidably engage a first bore 139 in the spool and can also slidably engage a second bore 141 defined by the control housing 143. The control housing 143 can retain the control piston 138. The control housing 143 can include a seal 125, such as, without limitation, an O-ring, to seal the control housing 143 to the body 102. Other seals 125 can also be present in the control valve 100, as will be well understood by those skilled in the art.

[0032] When the spool 120 is in a first position (to the left of the control valve 100 as illustrated), the second discharge port 110b is placed in fluid communication with the second drain port 118b. When the spool 120 is in a second direction (to the right of the control valve as illustrated), the first discharge port 110a is placed in fluid communication with the first drain port 118a. When the spool 120 is in an intermediate position at a location between the first and second directions, no discharge port 110a, 110b is in communication with a drain port 118a, 118b. As will be understood by those skilled in the art, the control valve 100 is a 5 / 3 valve that can be operated as a 5 / 2 valve.

[0033] When the pilot valve 130 is actuated, this causes an outward stroke of the power cylinder 112, while fluid supplied to the control chamber 129 causes the spool 120 to overcome the force of the biasing element 122 and move to the first position. Therefore, the fluid supply 108 is brought into fluid communication with the first discharge port 110a via the fluid inlet port 106, so that fluid enters the cap-side chamber 114 of the power cylinder 112 via the line 111, causing a piston 115 therein to move to the left (as illustrated, Fig. 2) so that a piston rod 140 attached thereto extends from the power cylinder 112. Simultaneously, fluid flows from the rod-side chamber 116 via line 113 to the second discharge port 110b, which is in fluid communication with the second vent port 118b, so that the pressure in the rod-side chamber 116 is relieved and the piston 115 can slide in a piston bore 142 of the power cylinder 112. It should be understood that a spool port 146 in the spool 120 is brought into fluid communication with the ports 110b and 118b, and the spool port 146 is further in fluid communication with the spool bore 148 positioned longitudinally in the spool 120. In one embodiment, depending on the position of the spool 120, a control piston bore 131 is brought into fluid communication with the rod-side chamber 116. The control piston bore 131 is also in fluid communication with the pressure control part 128 via a spool bore 148.At this point, the pressure in the control piston bore 131 is relatively low. It should also be noted that, in one embodiment, a bleed throttle 144 is located at bleed ports 118b, which assists in throttling the bleed rate and thus the sliding speed of the piston 115. The bleed throttle 144 may be adjustable.

[0034] When the pilot valve 130 is deactivated to initiate an inward stroke of the power cylinder 112, fluid previously directed to the control chamber 129 can escape through the conduit 36 ​​via a pilot bleed port 137 attached to the bleed line 133. This relieves pressure acting on the second end 120b of the spool 120 and allows the biasing member 122 to overcome the force of the fluid pressure in the control chamber 129, causing the spool 120 to move toward the second position (right as illustrated). Therefore, the fluid supply 108 is brought into fluid communication with the second discharge port 110b via the fluid inlet port 106, so that fluid enters the rod-side chamber 116 of the power cylinder 112 via the line 113, causing the piston 115 to move to the right (as illustrated) before retracting the piston rod 140 into the power cylinder 112.

[0035] However, during the inward stroke, fluid from the cap-side chamber 114 simultaneously flows via line 111 to the first discharge port 110a, which is now in fluid communication with the first bleed port 118a, thus relieving the pressure in the cap-side chamber 114 and allowing the piston 115 to slide within the piston bore 142 of the power cylinder 112. At this point, fluid pressure in line 110b is also in communication with the spool port 146 (located in the spool 120), so that the pressure therein initially rises to approximately the same level as the pressure of the fluid supply 108.Since the spool port 146 is further in fluid communication with the spool bore 131 via the spool bore 148, fluid from the fluid supply 108 enters a spool-side chamber 150 through the spool bore 131 and causes the spool 138 to move toward the spool 120 (left as illustrated) against the force exerted on the spool 120 by the biasing member 122. When the spool 120 reaches an intermediate position, the fluid inlet port 106 is no longer in fluid communication with the drain ports 118a, 118b or the discharge ports 110a, 110b, but instead, the rod-side chamber 116 is now in fluid communication only with the spool port 146 and ultimately with the spool-side chamber 150 via the second discharge port 110b.The biasing element 122 is configured to exert a force equal in magnitude to the force exerted by the control piston 138 due to the pressure of the rod-side chamber 116, so that the spool 120 is held in the intermediate position.

[0036] Therefore, it should be clear that the pressure regulating portion 128 is particularly relevant in assisting the return stroke of the power cylinder 112. While the pilot valve 130 is deactivated to initiate the return stroke, while the spool is in the intermediate position, pressure from the fluid source 108 no longer promotes the return stroke of the piston 115, but also does not promote extension of the piston 115. Furthermore, pressure from the rod-side chamber 116 to the pressure regulating portion 128 provides both pressure regulation (only for the return stroke of the power cylinder 112) and valve switching functionality via the actuation of the spool 120. It should also be clear that there is a net reduction in the fluid required to effect the inward stroke because the pressure of the rod-side chamber 116 is utilized by the pressure regulating portion 128 to regulate the pressure allocated for the inward stroke.In one embodiment, the fluid required to effect the inward stroke is approximately half that required to effect the outward stroke. This simultaneously eliminates the need for a separate pressure control valve, greatly reducing cost and complexity while increasing reliability. Note that this valve configuration also allows for separate bleed restrictors 144 on the bleed lines 118a and 118b, which assist in regulating the bleed rate and thus the sliding speed of the piston 115 during the inward and outward strokes.

[0037] Fig.Figure 3 shows one embodiment of the control valve 100. This embodiment provides a means for operating the power cylinder 112 at a relatively low speed. Specifically, while the spool 120 is in the intermediate position, rather than interrupting fluid communication through all of the drain ports 118a, 118b and discharge ports 110a, 110b, the drain port 118b and discharge port 110b are placed in fluid communication. Therefore, fluid from the rod-side chamber 116 is placed in communication with the conduit 113a, which can be throttled with a drain throttle 144 near the drain port 118b.

[0038] It will be apparent to one of ordinary skill in the art that the embodiments described above may be combined in whole or in part to produce additional embodiments within the scope and teachings of the invention.

[0039] The scope of the invention is to be determined by the following claims.

Claims

[1] Control valve (100) comprising: a valve body (102); a spool (120) in the valve body (102) configured to control the fluid allocation to a power cylinder (112), the spool (120) being controllable by a pilot valve (130) and having at least a first position, a second position, and an intermediate position between the first and second positions in the valve body (102); a pressure regulating part (128) in the control valve (100) in selective fluid communication with a rod-side chamber (116) of the power cylinder (112), the pressure regulating part (128) being configured to change the position of the spool (120), wherein a fluid pressure of the rod-side chamber (116) signals the pressure regulating part (128) to bias the spool (120) toward the first position with a biasing force against the spool (120) that is proportional to the fluid pressure of the rod-side chamber; and wherein a biasing element (122) in the control valve (100) is configured to bias the spool (120) toward the second position; wherein the control valve (100) is configured to reduce the fluid consumption of the power cylinder (112); and wherein the slider (120) is held in the intermediate position when a force exerted on a second end (120b) of the slider (120) and a force of the biasing element (122) are substantially equal to each other, and the control valve (100) is configured to prevent fluid from entering or exiting the cylinder when the spool (120) is in the intermediate position. [2] The control valve 100 of claim 1, wherein the pilot valve (130) is configured to supply pressurized fluid from a fluid source (108) to a control piston chamber (129) of the pressure regulating member (128) and to exert fluid pressure on a second end (120b) of the spool (120) and to bias the spool (120) toward the first position, wherein the control valve (100) supplies fluid to the power cylinder (112) to extend a piston rod (140) therein, and wherein the cap-side cylinder chamber (114) is brought into fluid communication with a fluid source (108). [3] Control valve (100) according to claim 1, wherein the slide (120) comprises: a spool port (146) extending from an outer surface of the spool (120) to a spool bore (148) in the spool (120), which extends from a central portion of the spool 120 to the second end (120b) of the spool (120), wherein the spool port (146) is in fluid communication with a control piston-side chamber (150) of the pressure regulating member (128), wherein the spool port (146) is also in fluid communication with a second discharge port (110b) in all spool positions, and wherein the biasing element (122) oppositely biases the pressure regulating member (128); and wherein the spool (120) is configured to remain in the intermediate position when a force on the spool (120) from the biasing member (122) is equal to the force exerted on the spool (120) by a control piston (138) of the pressure regulating part (128), wherein the control piston (138) is moved toward the first position when the control piston-side chamber (150) receives fluid pressure from the rod-side cylinder chamber (116). [4] Control valve 100 according to claim 1, comprising: a fluid inlet port (106) defined by the valve body (102) configured to be in fluid communication with a fluid source (108); a first discharge port (110a) configured to be in fluid communication with a cap-side chamber (114) of the power cylinder (112); a second discharge port (110b) configured to be in fluid communication with a rod-side chamber (116) of the power cylinder (112); a drain port (118a) configured to be in fluid communication with the first discharge port (110a) when the spool (120) is in a first position; and a drain port (118b) configured to be in fluid communication with the second discharge port (110b) when the spool (120) is in a second position; wherein no discharge port (118a, 118b) is connected to a discharge port (110a), (110b) when the slide (120) is in the intermediate position. [5] Control valve (100) according to claim 1, wherein the control valve is a 5 / 3 valve that can be operated as a 5 / 2 valve. [6] A method of manufacturing a control valve (100) comprising the following steps: Providing a valve body having first and second discharge ports, first and second drain ports, and a single fluid supply port; Defining a spool cylinder projecting longitudinally in the valve body; Placing a spool (120) in the spool cylinder, the spool (120) configured to control fluid allocation to a power cylinder (112) by changing positions in the valve body; Preloading the slider (120) with a preloading element (122) in a second direction; Providing a pressure regulating member in the control valve (100) that biases the spool (120) in a first direction opposite to the biasing member; Attaching a pilot valve to the control valve (120), the pilot valve actuating the pressure control part; and fluidly connecting a rod-side chamber containing the power cylinder (112) to the pressure control part, wherein a fluid pressure of the rod-side chamber signals the pressure control part to bias the slide (120) toward the first position, wherein a biasing force against the slide (120) is proportional to the fluid pressure of the rod-side chamber, and wherein the slider (120) is held in the intermediate position when a force exerted on a second end (120b) of the slider (120) and a force of the biasing element (122) are substantially equal to each other, and the control valve (100) is configured to prevent fluid from entering or exiting the cylinder when the spool (120) is in the intermediate position. [7] The method of claim 6, wherein the spool (120) is configured to slidably move within the spool cylinder to at least a first, a second, and an intermediate position between the first and second positions, wherein the first vent port is configured to be in fluid communication with the first discharge port when the spool (120) is in a first position, and wherein the second vent port is configured to be in fluid communication with the second discharge port when the spool (120) is in a second position, and wherein no vent port is in communication with a discharge port when the spool (120) is in the intermediate position. [8] A method according to claim 7, comprising the following step: Configuring the pressure regulating part to bias the spool (120) toward the first position during a return stroke of the power cylinder (112), wherein the fluid pressure of the rod-side chamber positions the spool toward the first position, and wherein the spool is configured to remain in the intermediate position when the force on the spool (120) from the pressure regulating part is equal to the force on the spool (120) from the biasing element. [9] A method according to claim 7, comprising the following step: Configuring the control valve (100) to consume approximately half the fluid required for an inward stroke of the power cylinder (112) as for an outward stroke of the power cylinder (112) by supplying pressure from a rod-side chamber of the power cylinder (112) to the pressure control member to position the spool in the intermediate position.

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