Abstract:
There is provided an apparatus for measuring a position of a linear type valve which is open/shut by operation of a hydraulic cylinder. More particularly, the apparatus more accurately measures a valve position by outputting a rotation angle of a rotation sleeve which rotates by being operatively connected to a hydraulic cylinder which moves linearly, and by calculating a vertical movement distance of a valve gate which changes in proportion to the rotation angle. Further, since the structure of the apparatus is very simple, the cost of production is significantly reduced. In addition, for use, the apparatus is installed on the hydraulic cylinder by a simple method.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2009-0035223, filed on Apr. 22, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
     TECHNICAL FIELD 
     The present invention relates to a linear valve position measuring apparatus which is installed at a hydraulic cylinder to operate opening/shutting of various linear type valves, and more particularly, to a linear valve position measuring apparatus, whereby a valve position is measured by calculating a vertical movement distance of a valve gate which varies in proportion to a rotation angle of a rotation sleeve, to significantly improve the accuracy of valve position measurement and simplify the structure of the apparatus. 
     BACKGROUND 
     In general, various linear type valves are installed to be connected to valve switches. As a valve switch operates, a valve gate moves vertically to open/shut a path of flow of a fluid. 
     A linear type valve operates at the same time when a valve switch operates. Valve position measuring apparatuses are various. Preferably, a valve position measuring apparatus may be installed to be connected to a valve, to control a valve position based on a value of the valve position as measured. 
     An absolute majority of conventional valve position measuring apparatuses are structured to be connected to only a valve with a switch to move a valve gate vertically by operation of an electric motor. Therefore, most conventional valve position measuring apparatuses are limited in use. 
     That is, a conventional valve position measuring apparatus is installed to be connected to a rotary shaft of an electric motor. The valve position measuring apparatus measures the rotation number of the electric motor when a valve is open or shut, calculates a value of a valve position based on the rotation number of the electric motor, and indicates the value on a display. 
     Therefore, the conventional valve position measuring apparatus cannot be used in any other valves in which a valve gate moves vertically by operation of a hydraulic cylinder than the valve with a valve switch and an electric motor. 
     These days, a method for measuring a valve position by using a linear potentiometer has been suggested. The linear potentiometer is installed on a hydraulic cylinder. In this method, a valve position is measured based on a vertical movement distance of a piston rod which moves vertically in the hydraulic cylinder. The vertical movement distance of the piston rod is measured by the linear potentiometer. However, since the linear potentiometer is very expensive, the cost of production is high. Moreover, the work of installing the linear potentiometer is very complicated. In addition, since the linear potentiometer occupies considerable space, the volume of a valve position measuring apparatus is large. 
     Therefore, the present invention has been made to solve the aforementioned problems of a conventional valve position measuring apparatus, and to provide a linear valve position measuring apparatus, whereby a valve actual position is measured by measuring a rotation angle of a rotation sleeve which forwardly/reversibly rotates, depending on a vertical movement of a piston rod, and by calculating a movement distance of the piston rod (i.e., a movement distance of a valve gate) which changes in proportion to the rotation angle. 
     In accordance with an aspect of the present invention, there is provided a technique of measuring a valve position, by installing a rotation sleeve so as to be rotatable on a hydraulic cylinder, the rotation sleeve surrounding the outside of a piston rod; connecting a guide pin so as to protrude outwardly through a spiral groove formed on the rotation sleeve, the guide pin installed at an upper part of the piston rod; and installing a potentiometer at a top end of the rotation sleeve, the potentiometer outputting an electrical signal corresponding to a rotation angle of the rotation sleeve, wherein an electronic control unit (ECU) calculates a vertical movement distance of the piston rod by using the electrical signal of the potentiometer. 
     In accordance with another aspect of the present invention, there is provided a technique of preventing the guide pin from rotating when the piston rod moves vertically, by positioning the guide pin between a pair of supporting poles which are vertically installed. 
     In accordance with another aspect of the present invention, there is provided a technique of fitting a rod cap connected to a top end of the piston rod into a pin holder where the guide pin is installed, so that the rod cap freely rotates in the pin holder. 
     In accordance with the present invention, the potentiometer outputs the electrical signal corresponding to the rotation angle of the rotation sleeve which is operatively connected to the piston rod moving vertically and rotates, and the ECU calculates the vertical movement distance of the piston rod, thereby providing the effect of accurately measuring a valve actual position. 
     Consequently, the valve position is accurately measured by a simple method. Further, the structure of the valve position measuring apparatus is simplified. In addition, since an inexpensive component (potentiometer) is used, the cost is significantly reduced. Furthermore, since the linear valve position measuring apparatus is easily installed on the hydraulic cylinder, the work of installing the apparatus and the convenience are improved. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       These and other aspects and advantages of the present invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a front view illustrating a linear valve position measuring apparatus according to the present invention, which is installed at a bidirectional hydraulic cylinder; 
         FIG. 2  is a front view illustrating a rotation sleeve according to the present invention; 
         FIG. 3  is a longitudinal sectional view illustrating the operation of the valve position measuring apparatus; 
         FIG. 4  is a sectional view illustrating the valve position measuring apparatus, taken along Line A-A shown in  FIG. 3 ; 
         FIG. 5  is a longitudinal sectional view illustrating the connection of a piston rod, a rod cap and a pin holder according to the present invention; 
         FIG. 6  is a dissembled perspective view illustrating the rod cap and the pin holder; 
         FIG. 7  is an enlarged sectional view illustrating a sleeve cap, an upper supporting plate and a potentiometer according to the present invention, which are installed; 
         FIG. 8  is a longitudinal sectional view illustrating the sleeve cap and the potentiometer which are assembled according to an embodiment; 
         FIG. 9  is a longitudinal sectional view illustrating the sleeve cap and the potentiometer which are assembled according to another embodiment; and 
         FIG. 10  is a longitudinal sectional view illustrating the rotation sleeve which is rotatably supported by using rotation balls installed in a rotation supporting housing according to the present invention. 
     
    
    
     BRIEF DESCRIPTION OF REFERENCE NUMBERS OF MAJOR ELEMENTS 
     
       
         
               
               
               
               
             
           
               
                   
               
             
             
               
                 10: 
                 bidirectional hydraulic cylinder 
                 12: 
                 upper piston rod 
               
               
                 20: 
                 rotation supporting housing 
                 30: 
                 top supporting plate 
               
               
                 31, 32: 
                 supporting poles 
                 40: 
                 rotation sleeve 
               
               
                 42: 
                 spiral groove 
                 44: 
                 sleeve cap 
               
               
                 50: 
                 guide pin 
                 52: 
                 pin holder 
               
               
                 55: 
                 rod cap 
                 60: 
                 potentiometer 
               
               
                 63: 
                 variable shaft 
                 70: 
                 ECU 
               
               
                   
               
             
          
         
       
     
     DETAILED DESCRIPTION 
     In accordance with a preferred embodiment of the present invention, the above and other aspects can be accomplished by a linear valve position measuring apparatus comprising: a rotation supporting housing  20  installed on a bidirectional hydraulic cylinder  10 ; a top supporting plate  30  positioned above, spaced apart from and assembled with the rotation supporting housing  20  in a single body by a plurality of supporting poles  31  and  32 ; a rotation sleeve  40  positioned to surround the outside of an upper piston rod  12  of the bidirectional hydraulic cylinder  10 , top and bottom ends of the rotation sleeve  40  being rotatably connected to the rotation supporting housing  20  and the top supporting plate  30 , respectively, and the outer circumference of the rotation sleeve  40  including a spiral groove  42  formed to pass through the inside and outside of the rotation sleeve  40 ; a guide pin  50  with one end being connected to an upper part of the upper piston rod  12  and the other end protruding outwardly through the spiral groove  42 ; a potentiometer  60  installed through a potentiometer securing plate  61  connected to the top supporting plate  30 , and a variable shaft  63  positioned below the potentiometer  60  and connected to the rotation sleeve  40  in a single body, to output an electrical signal corresponding to a rotation angle of the rotation sleeve  40 ; and an electronic control unit (ECU)  70  to calculate a vertical movement distance of the upper piston rod  12  by using the electrical signal being output by the potentiometer  60 . 
     Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
     The present invention provides a linear valve position measuring apparatus which is easily and dedicatedly installed on a bidirectional hydraulic cylinder  10  to directly move a linear type valve vertically, whereby a valve position is measured. The bidirectional hydraulic cylinder  10  is open to enable vertical movement of a pair of an upper piston rod  12  and a lower piston rod  13  respectively installed at upper and lower positions of a piston  11  in a single body. 
     A gate of the valve is connected to the lower piston rod  13  to directly raise the gate or move it down. The upper piston rod  12  moves vertically, driving a rotation sleeve  40  to rotate forwardly/reversibly. Accordingly, it is possible to measure a vertical movement distance of the upper piston rod  12  which changes in proportion to a rotation angle of the rotation sleeve  40 . 
     A rotation supporting housing  20  is installed on the bidirectional hydraulic cylinder  10 , by passing through the upper piston rod  12  and it supports a lower part of the rotation sleeve  40  so as to be rotatable. 
     As illustrated in  FIG. 3 , the rotation supporting housing  20  includes a bearing  22  and a bearing receiving opening  21 . The bearing  22  is fitted into the bearing receiving opening  21 , and a rotation end  41  formed at a bottom of the rotation sleeve  40  is fitted into the bearing  22 , thereby enabling smooth rotation operation of the rotation sleeve  40 . 
     Further, as illustrated in  FIG. 10 , the rotation supporting housing  20  may include a rotation ball receiving opening  25  formed in a multiple step manner, to support the smooth rotation of the rotation sleeve  40 , without using any expensive bearings as the components. Rotation balls  26  are received in the rotation ball receiving opening  25 . The rotation balls  26  support a lower end of the rotation sleeve  40  and are secured to the outer circumference of a lower part of the rotation sleeve  40 , thereby frictionally supporting and enabling rotation of the rotation sleeve  40 . This structure reduces the cost. 
     A top supporting plate  30  is positioned to be spaced apart from the rotation supporting housing  20 . The top supporting plate  30  and the rotation supporting housing  20  are connected to each other in a single body by a plurality of supporting poles  31  and  32 , so that the top supporting plate  30  and the rotation supporting housing  20  are maintained in a firm assembly state. 
     The rotation sleeve  40  is positioned to surround the outside of the upper piston rod  12 . A spiral groove  42  in a spiral shape is formed on the outer circumference of the rotation sleeve  40 . The spiral groove  42  is formed to pass through the inside and outside of the rotation sleeve  40 . 
     A sleeve cap  44  with a rotation protrusion  43  is fitted into an upper part of the rotation sleeve  40  in a single body. A rotation bushing  45  is received around the outside of the rotation protrusion  43 . The rotation protrusion  43  with the rotation bushing  45  passes through the top supporting plate  30 , so as to be rotatably connected together. The lower part of the rotation sleeve  40  is rotatably connected to the rotation supporting housing  20 . 
     The spiral groove  42  provides a path through which a guide pin  50  connected to the upper piston rod  12  moves vertically. While the guide pin  50  moves, it pushes vertically the inside of the spiral groove  42 , so that the rotation sleeve  40  can rotate forwardly/reversibly. Upper and lower ends of the spiral groove  42  are positioned at different angles in a view from the position of a horizontal plane of the spiral groove  42 . The angle range corresponds to the maximum rotation angle range of the rotation sleeve  40 . 
     One end of the guide pin  50  is connected to an upper part of the upper piston rod  12  and the other end of the guide pin  50  passes through the spiral groove  42  and protrudes outwardly. Then, the guide pin  50  is positioned to pass through a guide space  51  formed between a pair of the supporting poles  32  which are positioned to be adjacent to each other as illustrated in  FIG. 4 , thereby preventing any rotation movement caused by resistance generating when the guide pin  50  pushes the inside of the spiral groove  42  during it moves vertically as the upper piston rod  12  moves. Therefore, in any cases, the guide pin  50  is prevented from rotating, so that it smoothly moves vertically. 
     The guide pin  50  may be directly installed at a rod cap  55  connected to the top end of the upper piston rod  12  in a single body. Otherwise, the guide pin  50  may be installed at one side of a pin holder  52  connected to the rod cap  55 , as illustrated in  FIGS. 5 and 6 . 
     However, when the guide pin  50  is installed at the pin holder  52 , a connection protrusion  55   a  is freely rotatably fitted into and connected to a rotation opening  53  formed at the pin holder  52 . 
     A piston ring fitted to be received around the outside of the general piston  11  is secured to be movable, along the inside of the cylinder. Thus, even though any rotation movement occurs during the piston  11  and the upper piston rod  12  move vertically, the rotation force is not transferred to the pin holder  52 , so that only the upper piston rod  12  can move to rotate. 
     Therefore, since the rotation force of the upper piston rod  12  is prevented from being transferred to the guide pin  50  in any case, the guide pin  50  provides the effect of driving the rotation sleeve  40  to smoothly rotate. 
     In accordance with the present invention, as illustrated in  FIG. 7 , a potentiometer securing plate  61  is spaced apart from and connected to a top side of the upper supporting plate  30  in a single body, by a plurality of space bars  62 . A potentiometer  60  is installed through the potentiometer securing plate  61 . A variable shaft  63  formed under the potentiometer  60  is connected to the rotation sleeve  40  in a single body, so that while the variable shaft  63  and the rotation sleeve  40  are operatively connected to each other and rotate, the potentiometer  60  outputs an electrical signal corresponding to a rotation angle of the rotation sleeve  40 . 
     As illustrated in  FIG. 8 , when the variable shaft  63  is inserted into a shaft receiving opening  64  formed in the sleeve cap  44 , the potentiometer  60  is secured by a securing member  65  connected to the variable shaft  63  by a screw, through the outside of the sleeve cap  44 . However, the present invention does not limit thereto. As illustrated in  FIG. 9 , the variable shaft  63  is inserted into the shaft receiving opening  64  but a rotation preventing groove  66  is formed at a bottom of the variable shaft  63 . Then, a rotation preventing protrusion  67  formed to protrude from a bottom of the shaft receiving opening  64  is fitted into the rotation preventing groove  66 , so as to be connected together. Therefore, the variable shaft  63  is operatively connected to the rotation sleeve  40 , to rotate together. 
     The potentiometer  60  is connected to an electronic control unit (ECU)  70  by a transmission line  71 . The ECU  70  calculates a vertical movement distance of the upper piston rod  12  corresponding to the rotation angle of the potentiometer  60 , by using the electrical signal being output by the potentiometer  60 , so that the valve position is accurately measured. A measurement value of the valve position is indicated on a display unit included in a control panel, to be easily confirmed by an operator. 
     Further, the present invention applies methods of limiting the vertical movement of the upper piston rod  12  and the guide pin  50 . As one method thereof, when the minimum and maximum rotation angle values of the rotation sleeve  40  are predetermined and the actual rotation angle values of the rotation sleeve  40  reach to the predetermined values, the movement of the upper piston rod  12  and the guide pin  50  are automatically limited by signals. As the other method thereof, when the guide pin  50  is in contact with limit switches  57  respectively installed adjacently to upper and lower sides of the spiral groove  42  as illustrated in  FIG. 3 , the movement of the guide pin  50  is mechanically limited. 
     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.