Abstract:
An actuation system ( 200 ) is provided. The actuation system ( 200 ) includes a fluid operated actuator ( 211 ) and a control valve ( 230 ). The control valve ( 230 ) is movable between a first position and a second position and is adapted to open a fluid flow path from a pressurized fluid supply ( 240 ) to the actuator ( 211 ) when the control valve ( 230 ) is in the first position. A diverting fluid conduit ( 246 ) is provided that is adapted to divert a portion of the pressurized fluid supplied to the actuator ( 211 ) when the control valve ( 230 ) is in the first position. The pressurized fluid diverted through fluid conduit ( 246 ) biases the control valve ( 230 ) towards a second position.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a fluid operated actuator, and more particularly, to a valve control system for a fluid operated actuator. 
       BACKGROUND OF THE INVENTION 
       [0002]    Fluid controlled actuators are known in the art. According to one design, fluid provided to the actuator is controlled using a control valve actuated by two or more pilot valves. The pilot valves control a pressure supply to the control valve, which actuates the control valve to a first or a second position. Such a configuration has received some success, however, the system is complex, bulky, and requires excessive time to react and change the position of the actuator. 
         [0003]      FIG. 1  shows a valve control system  100  according to the prior art. The valve control system  100  as shown in  FIG. 1  includes an actuator  101 , a pressurized fluid conduit  102 , a first pilot valve  103 , a second pilot valve  104 , and a control valve  105 . In response to pressurized fluid acting on the actuator  101 , either through conduit  106  or through conduit  107 , the piston  108  of the actuator  101  moves between a first and a second position. The pressurized fluid may comprise any manner of substantially incompressible fluid, such as pneumatic or hydraulic fluid, for example. Typically, the pressurized fluid used will depend on the particular application. 
         [0004]    The pressurized fluid supplied to the actuator  101  is determined based on the position of the control valve  105 . The control valve  105  is actuated using the first and second pilot valves  103 ,  104 . In situations where the pilot valves  103 ,  104  comprise solenoid pilot valves, excitation of solenoid coils (not shown) will actuate the pilot valve, allowing the pressurized fluid to flow to the control valve  105 . For example, if the first pilot valve  103  is actuated, the port  112  of the pilot valve  103  is opened to the port  113 , thus allowing the pressurized fluid to act on the first side  127  of the control valve  105  through conduit  123 . Pressure acting on the first side  127  of the control valve  105  moves the control valve  105  to a first position. In the first position, port  115  of the control valve  105  is opened to the port  116 , thus providing an open path from the conduit  111  to the conduit  107 . In this position, pressure acts in chamber  125  moving the piston  108  to the left as shown in  FIG. 1 , while allowing fluid from chamber  126  to exhaust through port  119  of the control valve  105  via conduit  106 . 
         [0005]    When it is desired to move the piston  108  in the other direction, the first pilot valve  103  is de-actuated and the second pilot valve  104  is actuated, thereby closing the port  112  from the port  113  and opening the port  120  to the port  121  of the second pilot valve  104 . The pressurized fluid can then flow from the conduit  110  to the second side  128  of the control valve  105  to move the control valve  105  to a second position. In the second position, port  115  is opened to port  118  of the control valve  105 . The pressurized fluid can then flow from the conduit  111  to the conduit  106  to pressurize the chamber  126  of the actuator  101 , thereby moving the piston  108  to the right. 
         [0006]    Although the design described above can function in limited situations, the valve control system  100  requires an excessive amount of space, power, and components by requiring the use of two pilot valves. Furthermore, there is a delayed response time in switching the actuator  101  because one pilot valve needs to be de-actuated and another pilot valve needs to be actuated prior to any movement of the control valve  105 . In addition, each pilot valve has an inherent delay time, and therefore, providing multiple pilot valves compounds the problem. This delay can create problems in situations where the actuator is switched in a repetitive manner or in situations where a fast response time is required. 
         [0007]    Therefore there is a need for a fast responding fluid controlled actuator that also minimizes the materials and space required. The present invention solves this and other problems and an advance in the art is achieved. 
       ASPECTS 
       [0008]    According to an aspect of the invention, a method for operating a control valve adapted to selectively provide a pressurized fluid supply to an actuator, comprises the step of: 
         [0009]    actuating the control valve to a first position to open a fluid flow path from a pressurized fluid supply to the actuator, wherein the pressurized fluid supplied to the actuator also biases the control valve towards a second position. 
         [0010]    Preferably, the method further comprises the step actuating the control valve to the second position with the pressurized fluid supplied to the actuator. 
         [0011]    Preferably, the pressurized fluid biasing the control valve towards the second position is exhausted once the control valve is in the second position. 
         [0012]    Preferably, the step of actuating the control valve to the first position comprises applying a force to a first side of the control valve substantially equal to a pressure of the pressurized fluid biasing the control valve towards the second position. 
         [0013]    Preferably, the first position of the control valve opens a fluid flow path from the pressurized fluid supply to a first chamber of the actuator and wherein the second position of the control valve opens a fluid flow path from the pressurized fluid supply to a second chamber of the actuator. 
         [0014]    According to an aspect of the invention, an actuation system including a fluid operated actuator, comprises: 
         [0015]    a control valve movable between a first position and a second position; 
         [0016]    a first fluid conduit coupling the control valve to a first chamber of the fluid operated actuator, wherein the first position of the control valve opens a fluid flow path to pressurize the first fluid conduit and the first chamber with fluid from a pressurized fluid supply; and 
         [0017]    a second fluid conduit coupled to the first chamber and adapted to divert a portion of the pressurized fluid supplied to the first chamber to bias the control valve towards the second position. 
         [0018]    Preferably, the control valve exhausts the pressurized fluid biasing the control valve once the control valve is actuated to the second position. 
         [0019]    Preferably, pressurized fluid exhausted from the first chamber of the fluid operated actuator retains the control valve in the second position. 
         [0020]    Preferably, the actuation system further comprises a pressure regulator adapted to reduce the pressurized fluid biasing the control valve towards the second position. 
         [0021]    Preferably, the actuation system further comprises a biasing member adapted to substantially close the fluid flow path from the pressurized fluid supply to the fluid operated actuator. 
         [0022]    According to an aspect of the invention, an actuation system including a fluid operated actuator, comprises: 
         [0023]    a control valve movable between a first position and a second position, 
         [0024]    a first fluid conduit coupling the control valve to the fluid operated actuator, wherein the first position of the control valve opens a fluid flow path to pressurize the first fluid conduit and a first chamber of the fluid operated actuator with fluid from a pressurized fluid supply; and 
         [0025]    a second fluid conduit coupled to the first fluid conduit and adapted to divert pressurized fluid in the first fluid conduit to bias the control valve towards the second position. 
         [0026]    Preferably, the control valve exhausts the pressurized fluid biasing the control valve once the control valve is actuated to the second position. 
         [0027]    Preferably, pressurized fluid exhausted from the first chamber of the fluid operated actuator retains the control valve in the second position. 
         [0028]    Preferably, the actuation system further comprises a pressure regulator adapted to reduce the pressurized fluid biasing the control valve towards the second position. 
         [0029]    Preferably, the actuation system further comprises a biasing member adapted to substantially close the fluid flow path from the pressurized fluid supply to the fluid operated actuator. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0030]      FIG. 1  shows a prior art fluid controlled actuator. 
           [0031]      FIG. 2  shows a valve control system according to an embodiment of the invention. 
           [0032]      FIG. 3  shows the valve control system according to another embodiment of the invention. 
           [0033]      FIG. 4  shows the valve control system according to yet another embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0034]      FIGS. 2-4  and the following description depict specific examples to teach those skilled in the art how to make and use the best mode of the invention. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these examples that fall within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the invention. As a result, the invention is not limited to the specific examples described below, but only by the claims and their equivalents. 
         [0035]      FIG. 2  shows an actuation system  200  for a fluid operated actuator  211  according to an embodiment of the invention. The actuation system  200  shown in  FIG. 2  comprises the actuator  211 , a pilot valve  220 , a control valve  230 , and a fluid supply  240 . The fluid supply  240  may comprise a pneumatic or hydraulic fluid supply, for example. It should be understood however, that other fluids generally used to operate fluid actuated devices may be used as is known in the art. 
         [0036]    According to an embodiment of the invention, the actuator  211  comprises a linear actuator. However, it should be understood that other actuators may be used and the particular fluid operated actuator should not limit the scope of the invention. According to an embodiment of the invention, the actuator  211  includes a piston  212  along with fluid ports  213 ,  214 . Although two fluid ports are shown, the actuator  211  may comprise any number of fluid ports as required by the particular application. The piston  212  can move in response to fluid introduced through one of the ports  213 ,  214  while the other port is exhausted. For example, when fluid is supplied to the first port  213 , fluid can enter the chamber  215  to raise the pressure. In response to the raised pressure, the piston  212  can move to the left (as shown in  FIG. 2 ) and fluid in chamber  216  can be exhausted through the second port  214 . Similarly, when fluid is supplied to the second port  214  and chamber  216 , the piston  212  can move to the right and fluid in chamber  215  is exhausted through the first port  213 . 
         [0037]    According to an embodiment of the invention, the actuation system  200  includes a pilot valve  220 . According to an embodiment of the invention, the pilot valve  220  comprises a solenoid powered pilot valve  220 . However, it should be understood that other pilot valves may be used and are within the scope of the invention. The description that follows discusses the pilot valve  220  as a solenoid powered valve solely for the purpose of clarity and should not in any way limit the scope of the invention. When energized, the pilot valve  220  opens port  221  to port  222 . This pressurizes conduit  243  with fluid from conduit  242 . The pressurized fluid in conduit  243  acts on a first side  236  of the control valve  230  to bias the control valve  230  towards a first position. It should be understood that although the pressurized fluid in conduit  243  biases the control valve towards the first position, the valve will not be actuated unless the biasing force is sufficient to overcome the control valve&#39;s resistive forces, such as friction or existing fluid pressure. Once the biasing force is great enough, the control valve  230  will actuate to the first position. The first side  236  of the control valve  230  may comprise a fluid actuating switch, for example. 
         [0038]    According to an embodiment of the invention, the control valve  230  comprises a gate valve. However, it should be understood that the control valve  230  is not limited to gate valves and other suitable valves may be used and remain within the scope of the invention. In the embodiment shown in  FIG. 2 , the control valve  230  comprises a 5/2 valve, as it has five ports with two positions. In the first position, pressurized fluid is allowed to flow to the first chamber  215  of the actuator  211  while pressurized fluid is exhausted from the second chamber  216 . In the second position, pressurized fluid is allowed to flow to the second chamber  216  while being exhausted from the first chamber  215 . However, it should be understood that the control valve  230  according to other embodiments of the invention comprises other types of valves, for example, a 5/3 valve where three positions are available. A possible third position may close all ports of the control valve  230  thereby maintaining a current state of the actuator  211  (See  FIG. 4 ). 
         [0039]    Once the fluid in conduit  243  actuates the control valve  230  to the first position, port  231  opens to port  232 . Conduit  241 , which is coupled to the fluid supply  240  can then pressurize conduit  245 . The conduit  245  is coupled to the first port  213  of the actuator  211 . Thus, the pressurized fluid enters the first chamber  215  thereby acting on the right side of the piston  212  and moving it towards the left. In addition to port  231  being opened to port  232 , port  234  is opened to port  235 . According to one embodiment, the port  235  comprises an exhaust port, which exhausts to the atmosphere. However, in other embodiments where it is desired to recycle the fluid, the port  235  may be coupled to a reservoir (not shown) and stored for future use. Therefore, as the piston  212  moves to the left, fluid in chamber  216  can exhaust from port  214  through conduit  244  and ports  234 ,  235  of the control valve  230 . 
         [0040]    According to an embodiment of the invention, a diverting fluid conduit  246  is coupled to the actuator supply conduit  245 . The diverting fluid conduit  246  is also coupled to a second side  237  of the control valve  230 . Therefore, when the supply conduit  245  is pressurized, the diverting fluid conduit  246  is also pressurized. The pressure within the diverting conduit  246  acts on the second side  237  of the control valve  230  to bias the control valve  230  towards a second position. According to an embodiment of the invention, even though the pressurized fluid in the diverting fluid conduit  246  biases the control valve towards the second position, the control valve  230  does not change positions because the pressure acting on the first and second sides  236 ,  237  of the control valve  230  is substantially the same and therefore cancel each other out. This is because the fluid acting on both sides is from the same fluid supply  240 . In other words, the left and the right side of the control valve  230  are pressurized at substantially the fluid supply pressure acting on the actuator  211 . In other embodiments, the pressure in conduit  246  may be more or less than the pressure in conduit  243 . This may be accomplished using a pressure regulator (not shown), for example. It should be understood that in order for the control valve  230  to actuate to the second position, the biasing force provided by the pressure in the diverting fluid conduit  246  must be greater than any frictional force or actuating force applied opposite the pressure in the diverting fluid conduit  246 . 
         [0041]    According to an embodiment of the invention, the actuator  211  can be actuated in the opposite direction by de-actuating the pilot valve  220 . According to an embodiment of the invention, de-actuating the pilot valve  220  closes off port  221  from the port  222  and thus, the pressure acting on the first side  236  of the control valve  230  is exhausted through port  223 . However, the fluid pressure in conduit  246  still acts on the second side  237  of the control valve  230 . Thus, the biasing force provided by the pressure in the diverting conduit  246  actuates the control valve  230  to the second position. According to an embodiment of the invention, when the control valve  230  is in the second position, the port  231  is closed off from the port  232  and is opened to the port  234 , thereby supplying pressurized fluid to the conduit  244 , which enters chamber  216  to bias the piston  212  to the right. With chamber  216  being pressurized, fluid in chamber  215  is forced out of the actuator  211  through the port  213  to conduit  245 . In addition to the pressurized fluid being exhausted through conduit  245 , pressure is still applied to the second side  237  of the control valve  230  via conduit  246 . According to an embodiment of the invention, the pressure supplied to the second side  237  of the control valve  230  while chamber  215  is being exhausted is less than the pressure being supplied to the actuator  216 . According to another embodiment, as the pressure in the first chamber  215  decreases, the pressure in conduit  246  acting on the second side of the control valve  230  also decreases. Because at least some pressure remains on the second side  237  of the control valve  230 , the control valve  230  is retained in the second position. According to another embodiment of the invention, the conduit  245  may include a check valve, which would restrict flow to conduit  246  when chamber  215  is being exhausted. In this embodiment, the control valve  230  may not require a force to retain it in a given position. Therefore, in the brief time after pressure is restricted from acting on the first side  236  of the control valve  230 , the pressure still acting on the second side  237  of the control valve  230  could move the control valve  230  to its second position and once the valve  230  switches and the chamber  215  is exhausted, fluid pressure would be removed from the second side  237  of the control valve  230  as well. 
         [0042]      FIG. 3  shows the actuation system  200  according to another embodiment of the invention. In the embodiment shown in  FIG. 3 , the pilot valve  220  is omitted. Rather than using a pilot valve to actuate the control valve  230  to the first position, an electronic actuator  338  is provided. The electronic actuator  338  may comprise a solenoid or may comprise some other electronic actuator. In the embodiment shown in  FIG. 3 , the control valve  230  is actuated to the first position when the electronic actuator  338  is energized. As described above, when in the first position, the control valve  230  supplies the pressurized fluid to the first chamber  215  of the actuator  211 . In addition, the diverting fluid conduit  246  is now coupled directly to the first chamber  215  rather than being coupled to the fluid conduit  245 . Therefore, pressurized fluid in the first chamber  215  can be diverted to the second side of the control valve  230  using the diverting fluid conduit  246  to bias the control valve towards the second position. As mentioned above, the control valve  230  will not actuate to the second position unless the biasing force can overcome the friction force of the control valve  230  along with whatever actuating force is provided on the first side of the control valve. According to an embodiment of the invention, the electronic actuator  338  can provide substantially the same force as provided by the pressurized fluid supply. Therefore, when the control valve  230  is in the first position, the actuating force provided by the electronic actuator  338  is substantially the same as the biasing force provided by the fluid pressure via conduit  246 . Thus, while the electronic actuator  338  is actuated, the biasing force provided by the pressure in the diverting fluid conduit  246  does not result in any movement of the control valve  230 . 
         [0043]    According to an embodiment of the invention, once the electronic actuator  338  is de-energized, the fluid pressure in conduit  246  acting on the second side  237  of the control valve  230  actuates the control valve  230  to the second position in order to provide the pressurized fluid supply to the second chamber  216  of the actuator  211  and exhaust the first chamber  215  of the actuator  211 . It should be understood that although an electronic actuator  338  has been shown in place of the pilot valve  220 , other means of actuating the control valve  230  to the first position could be used. For example, a mechanical actuator, such as a spring, plunger, lever, cam roller, etc. may be used to actuate the control valve  230  to the first position. The control valve  230  can then utilize the pressurized fluid being supplied to the actuator  211  to actuate the control valve  230  to the second position. 
         [0044]      FIG. 4  shows the actuation system  200  according to another embodiment of the invention. In the embodiment shown in  FIG. 4 , the control valve  230  comprises a 5/3 way spring centered valve. As can be seen, the control valve  230  is actuated to the first position using a solenoid actuator  338  and actuated to the second position using the pressurized fluid supplied to the first chamber  215  of the actuator  211 . In addition, the control valve  230  is centered to a third position using biasing members  439 . In the third position, all of the ports of the control valve  230  are closed. Therefore, the current position of the actuator  211  is maintained as no fluid enters or leaves the actuator  211 . According to an embodiment of the invention, the control valve  230  shown in  FIG. 4  operates in substantially the same manner as the control valve  230  shown in  FIG. 3  with respect to the first and second positions. It should be understood that although the control valve  230  is shown with a pair of biasing members  439  used to center the valve  230  to the center position, other actuating members could be used and the present invention should not be limited to the use of biasing members. 
         [0045]    The invention described above comprises an actuation system  200  that uses the pressure acting on a fluid operated actuator to actuate the control valve  230  from a first position to a second position. Thus, invention eliminates the need for a second actuator, such as a second pilot valve. 
         [0046]    The detailed descriptions of the above embodiments are not exhaustive descriptions of all embodiments contemplated by the inventors to be within the scope of the invention. Indeed, persons skilled in the art will recognize that certain elements of the above-described embodiments may variously be combined or eliminated to create further embodiments, and such further embodiments fall within the scope and teachings of the invention. It will also be apparent to those of ordinary skill in the art that the above-described embodiments may be combined in whole or in part to create additional embodiments within the scope and teachings of the invention. 
         [0047]    Thus, although specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. The teachings provided herein can be applied to other actuator systems, and not just to the embodiments described above and shown in the accompanying figures. Accordingly, the scope of the invention should be determined from the following claims.