Patent Publication Number: US-11384777-B2

Title: Double-acting hydraulic actuator with different pumps for each actuation direction

Description:
TECHNICAL FIELD 
     The present disclosure is directed, in general, to hydraulically-actuated valves, and more specifically to self-contained hydraulic valves and actuators. 
     BACKGROUND 
     Hydraulic actuators are commonly used in applications that require high levels of force, rapid movement, or both. Typical hydraulic actuators require a supply of high-pressure fluid that is provided by a remote, centralized source that provides high-pressure fluid to multiple actuators. Piping between the supply and the actuators can be expensive and can be a source for undesirable leakage. 
     SUMMARY 
     An actuator operable to move a valve stem between an opened position and a closed position includes a cylinder including an open side and a close side, the cylinder coupled to the valve stem, a first pump connected to the cylinder and operable to deliver a first high-pressure fluid to the open side of the cylinder to move the valve stem toward the opened position, and a second pump separate from the first pump, the second pump connected to the cylinder and operable to deliver a second high-pressure fluid to the close side of the cylinder to move the valve stem toward the closed position. 
     In another construction, an actuator operable to move a valve stem between an opened position and a closed position includes a cylinder including an open side and a close side, the cylinder coupled to the valve stem, a first pair of pumps connected to the cylinder and operable to deliver a first high-pressure fluid to the open side of the cylinder and to draw a first supply fluid from the close side of the cylinder to move the valve stem toward the opened position, and a second pair of pumps separate from the first pair of pumps, the second pair of pumps connected to the cylinder and operable to deliver a second high-pressure fluid to the close side of the cylinder and to draw a second supply fluid from the open side of the cylinder to move the valve stem toward the closed position. 
     In another construction, a method of operating an actuator includes connecting a cylinder having an open side and a closed side to a movable valve stem, operating a first pump to deliver a first high-pressure fluid to the open side of the cylinder to drive the movable valve stem toward an open position, and operating a second pump to deliver a second high-pressure fluid to the close side of the cylinder to drive the movable valve stem toward a closed position, the second pump separate from the first pump. The method also includes controlling the first pump and the second pump to operate in one of three modes comprising a first mode in which the first pump operates and the second pump is idle, a second mode in which the second pump operates and the first pump is idle, and a third mode in which the first pump and the second pump are idle. 
     The foregoing has outlined rather broadly the technical features of the present disclosure so that those skilled in the art may better understand the detailed description that follows. Additional features and advantages of the disclosure will be described hereinafter that form the subject of the claims. Those skilled in the art will appreciate that they may readily use the conception and the specific embodiments disclosed as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. Those skilled in the art will also realize that such equivalent constructions do not depart from the spirit and scope of the disclosure in its broadest form. 
     Also, before undertaking the Detailed Description below, it should be understood that various definitions for certain words and phrases are provided throughout this specification and those of ordinary skill in the art will understand that such definitions apply in many, if not most, instances to prior as well as future uses of such defined words and phrases. While some terms may include a wide variety of embodiments, the appended claims may expressly limit these terms to specific embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of a self-contained hydraulic actuator. 
         FIG. 2  is a schematic illustration of the self-contained hydraulic actuator of  FIG. 1  in a first mode of operation. 
         FIG. 3  is a schematic illustration of the self-contained hydraulic actuator of  FIG. 1  in a second mode of operation. 
         FIG. 4  is a perspective exploded view of a pump and motor. 
     
    
    
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
     DETAILED DESCRIPTION 
     Various technologies that pertain to systems and methods will now be described with reference to the drawings, where like reference numerals represent like elements throughout. The drawings discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged apparatus. It is to be understood that functionality that is described as being carried out by certain system elements may be performed by multiple elements. Similarly, for instance, an element may be configured to perform functionality that is described as being carried out by multiple elements. The numerous innovative teachings of the present application will be described with reference to exemplary non-limiting embodiments. 
     Also, it should be understood that the words or phrases used herein should be construed broadly, unless expressly limited in some examples. For example, the terms “including,” “having,” and “comprising,” as well as derivatives thereof, mean inclusion without limitation. The singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Further, the term “and/or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. The term “or” is inclusive, meaning and/or, unless the context clearly indicates otherwise. The phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like. 
     Also, although the terms “first”, “second”, “third” and so forth may be used herein to refer to various elements, information, functions, or acts, these elements, information, functions, or acts should not be limited by these terms. Rather these numeral adjectives are used to distinguish different elements, information, functions or acts from each other. For example, a first element, information, function, or act could be termed a second element, information, function, or act, and, similarly, a second element, information, function, or act could be termed a first element, information, function, or act, without departing from the scope of the present disclosure. 
     In addition, the term “adjacent to” may mean: that an element is relatively near to but not in contact with a further element; or that the element is in contact with the further portion, unless the context clearly indicates otherwise. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise. Terms “about” or “substantially” or like terms are intended to cover variations in a value that are within normal industry manufacturing tolerances for that dimension. If no industry standard as available a variation of 20 percent would fall within the meaning of these terms unless otherwise stated. 
       FIG. 1  schematically illustrates a self-contained hydraulic actuator  10  that can be used to control movement of any number of devices including control valve stems  15 , stop valves, vane positioners, etc. The actuator  10  includes a cylinder  20 , a first pair of pumps  25  for moving the actuator  10  in a first direction  30 , and a second pair of pumps  35  for moving the actuator  10  in a second direction  40  opposite the first direction  30 . 
     The cylinder  20  in the illustrated construction is a double acting cylinder with a biasing member in the form of a spring return  43  and a cushion on the closing side of the cylinder  20 . The cylinder  20  includes a movable piston  45  that divides the cylinder  20  into an open side  50  and a close side  55 . A shaft  60  extends out of the cylinder  20  and connects to an object to be moved such as the control valve stem  15 . The spring return  43  biases the piston  45  to one side of the cylinder  20 . In constructions in which a valve is operated, the bias is typically toward a closed position. However, different applications may bias the device or valve toward an open position. The cushion is provided to allow fast movement in one direction without causing damage to the cylinder  20 . While the illustrated cylinder  20  is a double acting cylinder with a biasing member and a cushion, other suitable cylinders could be single acting, and could omit or include any of the features discussed with regard to the cylinder  20 . In addition, the cushion or biasing member could be positioned on the opposite ends of the cylinder or omitted if desired. 
     The first pair of pumps  25  includes two substantially identical micro-piston pumps  65  as illustrated in  FIG. 4 . Each pump  65  is connected to a motor  70 , and preferably a DC motor that is operated at a desired speed to provide the desired quantity of fluid. The illustrated pumps  65  are fixed displacement pumps  65  which are preferable as the volume of fluid delivered can be easily controlled by varying the speed of the motors  70 . However, variable displacement pumps could also be employed if desired. The first pair of pumps  25  include an output  75  arranged to deliver a high-pressure fluid to the open side  50  of the cylinder  20  and an inlet  80  arranged to draw low-pressure fluid into the first pair of pumps  25 . 
     The second pair of pumps  35  is substantially the same as the first pair of pumps  25  and includes two pumps  65  each connected to and driven by its own motor  70 . The second pair of pumps  35  include an output  85  arranged to deliver a high-pressure fluid to the close side  55  of the cylinder  20  and an inlet  90  arranged to draw low-pressure fluid into the second pair of pumps  35 . While the illustrated construction illustrates two pairs of pumps  25 ,  35 , a single pump  65  for opening and a second single pump  65  for closing could be employed if desired. In addition, three or more pumps  65  could be employed in place of each pair of pumps  25 ,  35 . Two or more pumps  65  for each of the open side  50  and close side  55  are preferred as it provides some redundancy in case one of the pumps  65  fails or does not operate properly. 
     In some constructions, each of the pumps  65  includes a check valve that inhibits reverse flow through the pump  65  when the pump is idle. Some pumps  65  may omit this check valve as their design itself inhibits such flow. 
     A first accumulator  95  is provided to collect or hold excess fluid and to deliver low pressure fluid to the first pair of pumps  25  as will be described. A second accumulator  100 , similar to the first accumulator  95  is provided to collect or hold excess fluid and to deliver low pressure fluid to the second pair of pumps  35  as will be described. In some constructions, a single accumulator functions as the first accumulator  95  and the second accumulator  100 . 
     A controller  105  (e.g., a PLC) communicates with each of the motors  70  to control their operation and speed. External controllers such as a turbine control or other control device can be used as the controller. Each pump  65  of the pairs of pumps  25 ,  35  are operated together and in one of three modes including a first or open mode  200  in which the first pair of pumps  25  operate while the second pair of pumps  35  are idle, a second or close mode  205  in which the second pair of pumps  35  operate while the first pair of pumps  25  are idle, and a third or maintain mode in which both the first pair of pumps  25  and the second pair of pumps  35  are idle. In the third mode of operation, the flow paths into or out of the cylinder  20  are blocked such that the cylinder  20 , and the control valve stem  15  to which the cylinder  20  is attached remain fixed in their current position. Thus, the actuator  10  is able to selectively move the cylinder  20 , and the control valve stem  15  or other component connected thereto to any point between an open position and a closed position. 
     Four pilot-operated check valves  110 ,  115 ,  120 ,  125  and two check valves  130 ,  135  are provided to control the flow of fluid within the self-contained actuator  10 . The first check valve  130  is positioned in a first high-pressure line  140  between the output  75  of the first pair of pumps  25  and the open side  50  of the cylinder  20 . The first check valve  130  is arranged to open in response to pressure being produced by the first pair of pumps  25  during operation to allow for the delivery of high-pressure fluid to the open side  50  of the cylinder  20 . When the first pair of pumps  25  are not operating, the first check valve  130  moves to a closed position. The second check valve  135  is positioned in a second high-pressure line  145  between the output  85  of the second pair of pumps  35  and the close side  55  of the cylinder  20 . The second check valve  135  is arranged to open in response to pressure being produced by the second pair of pumps  35  during operation to allow for the delivery of high pressure fluid to the close side  55  of the cylinder  20 . When the second pair of pumps  35  are not operating, the second check valve  135  moves to a closed position. In some constructions, the pumps  65  each include a check valve that performs this function such that the check valve  135  is not needed. 
     The first pilot-operated check valve  110  is positioned between the first accumulator  95  and the inlet  80  of the first pair of pumps  25  to control access to the fluid within the first accumulator  95 . A first pilot line  150  extends from the second high-pressure line  145  to the first pilot-operated check valve  110  to open the first pilot-operated check valve  110  in response to operation of the second pair of pumps  35 . When the first pilot-operated check valve  110  opens, low-pressure fluid can fill a first suction line  155  that feeds fluid to the first pair of pumps  25 . The second pilot-operated check valve  115  is positioned between the second accumulator  100  and the inlet  90  of the second pair of pumps  35  to control access to the fluid within the second accumulator  100 . A second pilot line  160  extends from the first high-pressure line  140  to the second pilot-operated check valve  115  to open the second pilot-operated check valve  115  in response to operation of the first pair of pumps  25 . When the second pilot-operated check valve  115  opens, low-pressure fluid can fill a second suction line  165  that feeds fluid to the second pair of pumps  35 . 
     The third pilot-operated check valve  120  is positioned in a first connector line  170  that connects the second high-pressure line  145  to the first suction line  155 . A third pilot line  175  extends from the first high-pressure line  140  to the third pilot-operated check valve  120  to open the third pilot-operated check valve  120  in response to high-pressure fluid flowing from the first pair of pumps  25 . When the third pilot-operated check valve  120  opens, high-pressure is released from the first pilot line  150  which closes the first pilot-operated check valve  110  and cuts off any flow from the first accumulator  95  to the first pair of pumps  25 . The close side  55  of the cylinder  20  is then connected through the third pilot-operated check valve  120  to the first suction line  155  such that fluid for the first pair of pumps  25  is drawn from the close side  55  of the cylinder  20  and delivered to the open side  50  of the cylinder  20  at high pressure. 
     The fourth pilot-operated check valve  125  is positioned in a second connector line  180  that connects the first high-pressure line  140  to the second suction line  165 . A fourth pilot line  185  extends from the second high-pressure line  145  to the fourth pilot-operated check valve  125  to open the fourth pilot-operated check valve  125  in response to high-pressure fluid flowing from the second pair of pumps  35 . When the fourth pilot-operated check valve  125  opens, high-pressure fluid is released from the second pilot line  160  which closes the second pilot-operated check valve  115  and cuts off any flow form the second accumulator  100  to the second pair of pumps  35 . The open side  50  of the cylinder  20  is then connected through the fourth pilot-operated check valve  125  to the second suction line  165  such that fluid for the second pair of pumps  35  is drawn from the open side  50  of the cylinder  20  and delivered to the close side  55  of the cylinder  20  at high pressure. 
       FIG. 2  illustrates the first or open mode  200  of operation when the first pair of pumps  25  are operating to direct fluid to the open side  50  of the cylinder  20  and to move the control valve stem  15  toward the open position. High-pressure fluid flows from the output  75  of the first pair of pumps  25 , fills the first high-pressure line  140  and flows into the open side  50  of the cylinder  20 , in turn forcing the piston  45  to move toward the close side  55 . High-pressure fluid also flows along the second pilot line  160  to the second pilot-operated check valve  115 . The high-pressure fluid causes the second pilot-operated check valve  115  to open, thereby opening the second accumulator  100  to the second suction line  165  to allow the second pair of pumps  35  to draw fluid from the second accumulator  100  upon their start-up. 
     The first high-pressure line  140  is also connected to the third pilot-operated check valve  120  such that the high-pressure fluid within the first high-pressure line  140  opens the third pilot-operated check valve  120 . With the third pilot-operated check valve  120  opened, the first suction line  155  is directly connected to the close side  55  of the cylinder  20  such that fluid is drawn from the close side  55  by the first pair of pumps  25 , pressurized, and delivered to the open side  50  of the cylinder  20 . When the third pilot-operated check valve  120  is opened, pressure in the first pilot line  150  is reduced and the first pilot-operated check valve  110  closes to inhibit fluid from flowing from the first accumulator  95  to the first pair of pumps  25 . In preferred constructions, the third pilot-operated check valve  120  opens before the first check valve  130  opens to assure a supply of fluid is available to the first pair of pumps  25  during operation. 
     With continued reference to  FIG. 2 , the second pair of pumps  35  are in an idle state assuring that the second high-pressure line  145  is at a neutral or low pressure and the second check valve  135  is biased in its closed position. A small orifice  198  (0.01 GPM) or other passage may be provided between the third pilot line  175  and the first suction line  155 . When the first pair of pumps  25  are in an idle position, the orifice  198  relieves pressure in the third pilot line  175  by directing high pressure fluid to the first suction line  155  and to the first accumulator  95  via the first pilot operated check valve  110  to assure that the third pilot operated check valve  120  closes. The fourth pilot-operated check valve  125  is also closed to assure that high-pressure fluid from the first pair of pumps  25  is not fed to the second suction line  165 . The second pilot-operated check valve  115  is in the open position as noted such that the second accumulator  100  is in fluid communication with the second suction line  165 . 
     Immediately upon starting the first pair of pumps  25 , there is no pressure in the first high-pressure line  140 . Without high-pressure from the first pair of pumps  25 , the third pilot-operated check valve  120  is closed and the first pilot-operated check valve  110  is closed with an initial supply of fluid for the first pair of pumps  25  being disposed in the first suction line  155  after being supplied by the first accumulator  95 . Once pressure is established in the first high-pressure line  140 , the state of the third pilot-operated check valve  120  switches and fluid is drawn from the close side  55  of the cylinder  20  rather than the first accumulator  95 . 
     For clarity, the following table illustrates the state of the various valves  110 ,  115 ,  120 ,  125 ,  130 ,  135  during operation in the first, or open mode  200  in which the first pair of pumps  25  are active. 
     
       
         
           
               
               
               
             
               
                   
               
               
                   
                 Normal Operation of 
                 Initial Start of First 
               
               
                 Valve 
                 First Pair of Pumps 
                 Pair of Pumps 
               
               
                   
               
             
            
               
                 First Check Valve 130 
                 Opened 
                 Closed 
               
               
                 Second Check Valve 135 
                 Closed 
                 Closed 
               
               
                 First Pilot-operated  
                 Closed 
                 Closed 
               
               
                 Check Valve 110 
                   
                   
               
               
                 Second Pilot-operated  
                 Opened 
                 Closed 
               
               
                 Check Valve 115 
                   
                   
               
               
                 Third Pilot-operated  
                 Opened 
                 Closed 
               
               
                 Check Valve 120 
                   
                   
               
               
                 Fourth Pilot-operated  
                 Closed 
                 Closed 
               
               
                 Check Valve 125 
               
               
                   
               
            
           
         
       
     
     Turning now to  FIG. 3 , the actuator  10  is illustrated during operation in the second mode in which the second plurality of pumps  35  are active to direct high-pressure fluid to the close side  55  of the cylinder  20  to move the control valve stem  15  toward a closed position. 
     With the second pair of pumps  35  in operation, the second high-pressure line  145  fills with high-pressure fluid, the second check valve  135  opens, and high-pressure fluid is directed along the first pilot line  150  and the fourth pilot line  185  to open the first pilot-operated check valve  110  and the fourth pilot-operated check valve  125  respectively. With the first pilot-operated check valve  110  open, the first suction line  155  is open to the first accumulator  95  to allow starting of the first pair of pumps  25 . 
     The opening of the fourth pilot-operated check valve  125  exposes the second suction line  165  to the open side  50  of the cylinder  20 , thereby allowing the second pair of pumps  35  to draw fluid from the open side  50  of the cylinder  20 . Opening the fourth pilot-operated check valve  125  also removes pressure from the second pilot line  160  which allows the second pilot-operated check valve  115  to close to inhibit fluid flow from the second accumulator  100  to the second suction line  165 . In preferred constructions, the fourth pilot-operated check valve  125  opens before the second check valve  135  opens to assure a supply of fluid is available to the second pair of pumps  35  during operation. 
     When the second pair of pumps  35  operate, the first pair of pumps  25  remain idle, thereby reducing the pressure in the first high-pressure line  140  such that the third pilot-operated check valve  120  closes. A small orifice  199  (0.01 GPM) or other passage may be provided between the fourth pilot line  185  and the second suction line  165 . When the second pair of pumps  35  are in an idle position, the orifice  199  relieves pressure in the fourth pilot line  185  by directing high pressure fluid to the second suction line  165  and to the second accumulator  100  via the second pilot operated check valve  115  to assure that the fourth pilot operated check valve  125  closes. 
     Immediately upon starting the second pair of pumps  35 , there is no pressure in the second high-pressure line  145 . Without high-pressure from the second pair of pumps  35 , the fourth pilot-operated check valve  125  is closed and the second pilot-operated check valve  115  is closed such that the initial supply of fluid to the second pair of pumps  35  comes from fluid disposed in the second suction line  165  that was added to the second suction line  165  by the second accumulator  100  prior to the closure of the second pilot-operated check valve  115 . Once pressure is established in the second high-pressure line  145 , the state of the fourth pilot-operated check valve  125  switches and fluid is drawn from the open side  50  of the cylinder  20  rather than the second accumulator  100 . 
     For clarity, the following table illustrates the state of the various valves  110 ,  115 ,  120 ,  125 ,  130 ,  135  during operation in the second, or close mode  205  in which the second pair of pumps  35  are active. 
     
       
         
           
               
               
               
             
               
                   
               
               
                   
                 Normal Operation of 
                 Initial Start of Second 
               
               
                 Valve 
                 Second Pair of Pumps 
                 Pair of Pumps 
               
               
                   
               
             
            
               
                 First Check Valve 130 
                 Closed 
                 Closed 
               
               
                 Second Check Valve 135 
                 Opened 
                 Closed 
               
               
                 First Pilot-operated  
                 Opened 
                 Closed 
               
               
                 Check Valve 110 
                   
                   
               
               
                 Second Pilot-operated  
                 Closed 
                 Closed 
               
               
                 Check Valve 115 
                   
                   
               
               
                 Third Pilot-operated  
                 Closed 
                 Closed 
               
               
                 Check Valve 120 
                   
                   
               
               
                 Fourth Pilot-operated  
                 Opened 
                 Closed 
               
               
                 Check Valve 125 
               
               
                   
               
            
           
         
       
     
     In operation, the controller  105  or control system operates to control the control valve stem  15  or other device being controlled by the actuator  10 . In one example, the control valve stem  15  is a control valve stem  15  for a control valve in a steam turbine. The control system monitors speed or load and adjusts the position of the control valve stem  15  to achieve a desired speed or load. If the control system determines that the position of the control valve stem  15  needs to change, a signal is sent to the appropriate pair of pumps  25 ,  35  to activate the pair of pumps and to set a desired speed of operation. The speed of operation of the pair of pumps  25 ,  35  controls the rate of flow of fluid to the cylinder  20  and therefore controls the speed at which the control valve stem  15  moves. If the control valve is being opened, the first pair of pumps  25  operate and the valves  110 ,  115 ,  120 ,  125 ,  130 ,  135  are configured as illustrated and described with regard to  FIG. 2 . If the control valve is being closed, the second pair of pumps  35  operate and the valves  110 ,  115 ,  120 ,  125 ,  130 ,  135  are configured as illustrated and described with regard to  FIG. 3 . 
     In one construction, a programmable logic controller (PLC) is used to drive the motors  70  at the desired speed. In preferred constructions, pulse width modulation (PWM) is used to vary the speed of the motors  70 . 
     During operation, some fluid inevitably leaks from the actuator  10  or is otherwise lost. As illustrated in  FIGS. 1-3 , each of the first accumulator  95  and the second accumulator  100  includes a reservoir  188  and a level switch  190  that allows for the addition of fluid to the actuator  10  should such additions be necessary. In some actuators, a single reservoir  188  feeds both the first accumulator  95  and the second accumulator  100 . 
       FIGS. 1-3  also illustrate a relief valve  195  that is coupled to both the open side  50  and the close side  55  of the cylinder  20 . The relief valve  195  operates to drain high-pressure fluid should a predetermined pressure be reached or exceeded within the cylinder  20 . 
     While the actuator  10  is described as using DC motors  70 , other motors such as AC, brushless DC, or switched reluctance motors could also be employed if desired. 
     While the constructions described with regard to  FIGS. 1-3  include check valves and pilot operated check valves, other types of valves could be used in place of the check valves and the pilot operated check valves. As such, the invention should not be limited to constructions that include only check valves and the pilot operated check valves. For example, solenoid-operated valves could be employed in place of or in conjunction with the check valves and the pilot operated check valves. 
     Although an exemplary embodiment of the present disclosure has been described in detail, those skilled in the art will understand that various changes, substitutions, variations, and improvements disclosed herein may be made without departing from the spirit and scope of the disclosure in its broadest form. 
     None of the description in the present application should be read as implying that any particular element, step, act, or function is an essential element, which must be included in the claim scope: the scope of patented subject matter is defined only by the allowed claims. Moreover, none of these claims are intended to invoke a means plus function claim construction unless the exact words “means for” are followed by a participle.