Abstract:
There is provided a multi-turn hydraulic actuator used to open/close a passageway in ground and sea industries including general industrial machines, oil refineries and chemical plants and power generating plants, among others, and more particularly, a multi-turn hydraulic actuator comprising: a hydraulic motor and a decelerator, among others, whereby high torque is efficiently obtained by using low electric power, compared to a conventional electric actuator, and whereby an operation part and a drive part are freely attached to/detached from at a user&#39;s necessity. 
     In the multi-turn hydraulic actuator, the hydraulic motor is driven by using hydraulic pressure generated by a hydraulic pressure generator, a rotational force of the hydraulic motor is transmitted to a worm shaft of the decelerator directly connected to the hydraulic motor so that a driving shaft is rotated in a reduced speed, and the rotation of the worm shaft is selectively manually operated by setting a manual mode switch and using a manual handle.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2008-0095532, filed on Sep. 29, 2008, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a multi-turn hydraulic actuator used to open/close a passageway in the ground and sea industries including general industrial machines, oil refineries and chemical plants, and power generating plants, among others, and more particularly, a technical field in which an actuator comprising a hydraulic motor and a decelerator is used to control the opening/closing of a valve which controls the flow of a fluid flowing through a path of a conduit, or a lock which is installed at a passageway. 
         [0004]    2. Description of the Related Art 
         [0005]    In general, major types of valve driving systems include a butterfly valve, a gate valve and a plug valve, among others, according to valve forms. Each valve is automatically driven by a 90 degree-turn or multi-turn actuator suitably selected according to use-environments. Examples of actuators include electric actuators, pneumatic actuators and hydraulic actuators by forms. Two functions, i.e., a stabilized actuation performance and a semi-permanent life span, are recognized as the most important factors in the actuators. 
         [0006]    To control a valve installed in an industrial conduit or a lock installed in a passageway, a shaft of the valve or lock needs to be rotated, to perform the opening/closing operation of the valve or lock. The valve performs its operation generally by using an actuator which is controlled remotely or in the spot. 
         [0007]    A conventional multi-turn electric actuator generally used comprises: a control unit including a 3-phase inverter converting single phase power into 3-phase power; a 3-phase electric motor operated by the control unit; a multi-unit with a rotation shaft installed perpendicularly to be rotated in either direction by the driving of the 3-phase electric motor; and a passageway switching unit for opening/closing a passageway. 
         [0008]    In the aforementioned multi-turn electric actuator, when electric power is applied to the control unit including the 3-phase inverter, the 3-phase electric motor is driven. The motive power generated in the 3-phase electric motor is transmitted to a worm gear through a gear inside the multi-unit, thereby ultimately driving a drive block of the passageway switching unit installed at an end of the rotation shaft. Consequently, the opening/closing of the valve is controlled by the torque. 
         [0009]    Further, the conventional multi-turn electric actuator is structured to monitor the operation of the gear inside the multi-unit, to perceive the extent of opening the valve and the drive of the actuator. For this purpose, an analog detection method and a digital detection method are used. In the former, an additional shaft is directly connected to the gear, to detect the number of times of rotation of the shaft by using variable resistance. In the latter, the number of times of rotation of the shaft is detected by using a sensor. 
         [0010]    In a manual method of manually operating the conventional multi-turn electric actuator, a manual switch lever is rotated by human power, to apply a change to a combination of the gear inside the multi-unit, thereby changing an automatic mode to a manual mode. 
         [0011]    When using the manual switch lever to change the mode of the actuator to the manual mode, sufficient rotational radius and space are required to operate the manual switch lever. Moreover, since all of the 3-phase electric motor, control unit, multi-unit, passageway switching unit and terminal unit forming the multi-turn electric actuator are structured in a single unit, it is impossible to install the manual switch lever in such a small space. 
         [0012]    Further, in the analog detection method to perceive the extent of opening the valve and the drive of the actuator, an assembling process is very complicated since many gears are combined. Moreover, since the gear combination needs to be mechanically changed in order to set or correct a display of the extent of opening, it is necessary to open a cover. Therefore, this is regarded as a very annoying factor. 
         [0013]    Further, in the digital detection method, one central processing unit of high-capacity is included in the control unit, to be used for the control and communication of the actuator. In addition, the central processing unit is used for a sensor of detecting the extent of opening. Therefore, high standby electric power is consumed at the moment when the actuator is not driven. 
       SUMMARY OF THE INVENTION 
       [0014]    The present invention provides a multi-turn hydraulic actuator which solves the above problems of a conventional multi-turn electric actuator needing to be improved and has the new concepts making it easy to be installed and operated even in a limited space and making it possible to minimize the use of electric power. 
         [0015]    It is therefore an object of the present invention to provide a multi-turn hydraulic actuator which uses a hydraulic motor, thereby using low electric power, significantly improving outputs and realizing fast response characteristics; which is formed in an assembly structure, thereby making it possible to detach/attach an operation part and a drive part so that only the drive part is installed in a limited space or in the spot where it is inconvenient to approach, and the operation part is separately installed at a desired place to be easily operated; which uses a manual mode switch to be input by a button, thereby minimizing a space for using the product; which uses a hydraulic pressure generator, thereby minimizing consumption of driving power; and which additionally includes a low-power processor needed for detecting the extent of opening, thereby minimizing standby electric power. 
         [0016]    According to an aspect of the present invention, there is provided a multi-turn hydraulic actuator comprising: an operation part and a drive part being separately formed to be assembled/dissembled, wherein the operation part comprises: a hydraulic pressure generator including a motor and a pump being formed together in a single unit, and the drive part transmits a rotational force of a hydraulic motor to a decelerator and rotates a driving shaft forwardly/backwardly by the decelerated force. 
         [0017]    The multi-turn hydraulic actuator further comprises: a manual mode switch and a manual handle, wherein the manual mode switch is installed between the hydraulic motor and the decelerator, to change the mode of the decelerator so as to be manually operated, and the manual handle is installed at the other end of the decelerator, to manually operate the decelerator. 
         [0018]    The multi-turn hydraulic actuator further comprises: a non-touch digital detector for detecting the extent of opening, wherein the non-touch digital detector comprises: a number of magnets for detecting the extent of opening, installed at a worm shaft forming the decelerator; and hole sensors installed to perceive signals of the magnets, thereby detecting a rotational direction of the worm shaft and the extent of opening. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: 
           [0020]      FIG. 1  is a partial plan view illustrating a multi-turn hydraulic actuator according to an embodiment of the present invention; 
           [0021]      FIG. 2  is an enlarged sectional plan view illustrating a motor disk, an automatic disk and a decelerator being assembled together in the multi-turn hydraulic actuator; 
           [0022]      FIG. 3  is a horizontal sectional view illustrating an automatic disk, a moving shaft and a manual disk being moved when the mode of the multi-turn hydraulic actuator is changed to a manual mode; 
           [0023]      FIG. 4  is a partial perspective view illustrating a manual mode switch in the multi-turn hydraulic actuator; 
           [0024]      FIG. 5  is a partial horizontal sectional view illustrating the manual mode switch in operation; 
           [0025]      FIG. 6  is an exploded perspective view illustrating a motor disk and a return protrusion in the multi-turn hydraulic actuator; 
           [0026]      FIG. 7  is a separated perspective view illustrating a non-touch digital detector for detecting the extent of opening and a worm shaft in the multi-turn hydraulic actuator; and 
           [0027]      FIG. 8  is a side sectional view illustrating magnets for detecting the extent of opening, which are installed at the worm shaft in the multi-turn hydraulic actuator. 
       
    
    
       [0028]      
         [0000]    
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 [Brief description of reference numbers of major elements] 
               
             
          
           
               
                   
                 A: operation part 
                 B: drive part 
               
               
                   
                   
               
               
                   
                 10: hydraulic pressure generator 
                 11: electric motor 
               
               
                   
                 20: housing of the drive part 
                 25: detector receiving part 
               
               
                   
                 30: hydraulic motor 
                 33, 63, 73, 93: rotation pins 
               
               
                   
                 34: motor disk 
                 40: decelerator 
               
               
                   
                 43: worm shaft 
                 44: driving shaft 
               
               
                   
                 45: worm wheel 
                 50: moving shaft 
               
               
                   
                 60: automatic disk 
                 70: manual disk 
               
               
                   
                 75: magnet 
                 80: manual mode switch 
               
               
                   
                 82: elastic member 
                 83: pusher 
               
               
                   
                 84: switch shaft 
                 84b: pivot piece 
               
               
                   
                 85: release bar 
                 87: fixing ball 
               
               
                   
                 89: ball receiving groove 
                 90: manual handle 
               
               
                   
                 100: non-touch digital detector for 
               
               
                   
                 detecting the extent of opening 
               
               
                   
                 100-1: magnet for detecting the 
               
               
                   
                 extent of opening 
               
               
                   
                 101: hole sensor 
                 102: low-power processor 
               
               
                   
                   
               
             
          
         
       
     
       DETAILED DESCRIPTION OF THE INVENTION 
       [0029]    The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. 
         [0030]    As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. 
         [0031]    As illustrated in  FIG. 1 , a multi-turn hydraulic actuator according to the present invention is characterized in that hydraulic pressure generated by a hydraulic pressure generator  10  is supplied to a hydraulic motor  30  through a hydraulic channel  21  formed in a housing  20  of a drive part B or a separate hydraulic hose so that the hydraulic motor  30  is driven, a rotational force of the hydraulic motor  30  is transmitted to a worm shaft of a decelerator  40  directly connected to the hydraulic motor  30  so that a driving shaft  44  is rotated at a reduced speed, and the rotation of the worm shaft  43  is selectively manually operated by using a manual handle  90  and setting a manual mode switch  80 . 
         [0032]    An outline of the whole technical constitution of a multi-turn hydraulic actuator according to a preferred embodiment of the present invention to achieve the aforementioned characteristics will be described with reference to  FIGS. 1 through 4 . The multi-turn hydraulic actuator has the correlative constitution comprising: a hydraulic motor  30  positioned at a front end of a housing  20  of a drive part B and operatively rotated by hydraulic pressure generated by a hydraulic pressure generator  10 ; a decelerator  40  including a worm  42 , a worm shaft  43 , a driving shaft  44  and a worm wheel  45 , wherein the worm shaft  43  with the worm  42  is rotatably installed in the middle of the housing  20  of the drive part B, and the worm wheel  45  connected to the driving shaft  44  in a single unit is engaged with the worm  42 , transmitting a rotational force of the worm  42  to the driving shaft  44  at a reduced speed; a moving shaft  50  operatively connected to the worm shaft  43  so as to be rotatable by penetrating the worm shaft  43  and to selectively slide in either direction; an automatic disk  60  connected to one end of the moving shaft  50  and being operatively rotated by a number of rotation pins  63  selectively meeting a number of rotation pins  33  of a motor disk  34 , respectively; a manual disk  70  connected to the other end of the moving shaft  50 ; a manual mode switch  80  wherein a release bar  85  positioned between the motor disk  34  and the automatic disk  60  pivots by operating a manual mode button  83   c , so that the automatic disk  60  is moved so as not to interfere with the motor disk  34  and the worm shaft  43  is switched so as to be manually operated; and a manual handle  90  installed at the other end of the housing  20  of the drive part B, wherein rotation pins  93  of a handle disk  94  positioned at a front end of a handle shaft  92  selectively meet rotation pins  73  of the manual disk  70 , respectively, thereby making the worm shaft  43  so as to be manually rotatable. 
         [0033]    Below, the multi-turn hydraulic actuator having the constitution outlined above will be described, in more detail, to be easily carried out. 
         [0034]    The hydraulic pressure generator  10  forming an operation part A in the multi-turn hydraulic actuator according to the present invention generates high hydraulic pressure. As illustrated in  FIG. 1 , a BLDC motor or electric motor  11  having high power efficiency is attached to one side of the hydraulic pressure generator  10 . The hydraulic pressure is generated by a gear pump  12  directly connected to the electric motor  11 . A controller  13  is provided at an upper position in the middle of the hydraulic pressure generator  10 . The controller  13  has the functions of changing a speed of the hydraulic motor  30  and a direction of a hydraulic fluid and stopping driving of the electric motor  11 , by controlling the operation of the hydraulic pressure generator  10 . 
         [0035]    The controller  13  does not need to be installed in the operation part A. When it is suitable to install the controller  13  in the drive part B by considering the conditions of the spot or the structural conditions of the operation part A and drive part B, the controller  13  may be installed in the drive part B. 
         [0036]    The hydraulic pressure generator  10  is attachable to or detachable from the housing  20  of the drive part B directly connected to a valve installed at a conduit or a lock of a hydraulic channel. The hydraulic pressure generator  10  may be installed at the housing  20  of the drive part B in a single unit or it may be installed at a third place, separately from the housing  20  of the drive part B, without any restriction with respect to an installation space. Therefore, the hydraulic pressure generator  10  is highly applicable in use. 
         [0037]    When the hydraulic pressure is generated by the gear pump  12 , it is supplied to the hydraulic motor  30  through a hydraulic channel  21  formed in the housing  20  of the drive part B or to the hydraulic motor  30  through a separate hydraulic hose, so that a motor shaft  31  of the hydraulic motor  30  generates the rotational force in forward/backward directions as illustrated in  FIG. 2 . 
         [0038]    The hydraulic motor  30  is fixedly installed at a motor fixing plate  32  attached to a front end of one end of the housing  20  of the drive part B. A motor disk  34  to which a number of rotation pins  33  are attached in a radial shape is connected to the motor shaft  31  in a single unit. The motor disk  34  operates to rotate in the forward/backward directions as the hydraulic motor  30  operates. A motor casing  35  is installed at the outside of the hydraulic motor  30  and covers the hydraulic motor  30 , thereby protecting the hydraulic motor  30  from any external forces. 
         [0039]    The hydraulic motor  30  generates high motive power by using low electric power. Further, as the hydraulic motor  30  uses an incompressible hydraulic fluid, it provides the effect of realizing much faster response characteristics, compared with a conventional electric actuation. 
         [0040]    The decelerator  40  is positioned in the middle of the housing  20  of the drive part B. The decelerator  40  reduces a speed of the rotational force of the hydraulic motor  30  and transmits the rotational force to the driving shaft  44  opening/closing the valve and lock. As illustrated in  FIG. 2 , the decelerator  40  includes the worm shaft  43  rotatably installed in the middle of the housing  20  of the drive part B by bearings  41 . The worm  42  is formed about the worm shaft  43 . The worm  42  is engaged with the worm wheel  45  connected, in a single unit, to the driving shaft  44  being vertically installed. Therefore, the driving shaft  44  is variously rotated, in the forward/backward directions, at a reduced speed. 
         [0041]    In the embodiment of the present invention, the decelerator  40  has the mutually connected constitution of the worm  42  and the worm wheel  45  but it may be realized in a different manner. Any element that is capable of reducing a rotational speed of the hydraulic motor  30  and transmitting the rotational force to the driving shaft  44  at the reduced speed is applicable within the scope of the present invention. 
         [0042]    As illustrated in  FIG. 3 , the moving shaft  50  penetrates the worm shaft  43  so as to be connected to each other. Key grooves  51  are each formed at both sides of the moving shaft  50  and the worm shaft  43 . Each key  52  is installed in each key groove  51 , so that the moving shaft  50  is operatively rotated with the worm shaft  43  and is smoothly moved to slide to either side. 
         [0043]    That is, the key  52  provides a connecting force between the worm shaft  43  and the moving shaft  50  and guides the moving shaft  50  to be smoothly moved by sliding horizontally. 
         [0044]    When the automatic disk  60  is fitted into one side of the moving shaft  50  so as to be in a single unit, the each key  52  is inserted into the key groove formed in an inner diameter of the automatic disk  60 . Then, a number of rotation pins  63  formed in a radial shape are attached to the side of the automatic disk  60  facing the motor disk  34  in a single unit. 
         [0045]    Thus, when the motor disk  34  is operated to rotate, the rotation pins  33  of the motor disk  34  and the rotation pins  63  of the automatic disk  60  meet each other in contact so as to be rotated. As a result, the rotational force transmitted to the worm  42  rotates the driving shaft  44  at a reduced speed. 
         [0046]    As illustrated in  FIG. 3 , the manual disk  70  is fitted to be connected to the other side of the moving shaft  50 . The manual disk  70  functions a medium to transmit the manual rotational force to the worm shaft  43  by selectively operating the manual handle  90 . The key  52  connected to the worm shaft  43  is simultaneously fitted into the key groove formed in an inner diameter of the manual disk  70 , so that the manual disk  70  is connected to the other side of the moving shaft  50  in a single unit. 
         [0047]    In the manual mode switch  80  provided in the multi-turn hydraulic actuator according to the present invention, the release bar  85  positioned between the motor disk  34  and the automatic disk  60  selectively pivots as illustrated in  FIGS. 4 and 5 , to move the automatic disk  60  so as not to interfere with the motor disk  34  and to manually operate the worm shaft  43 . 
         [0048]    That is, the manual mode switch  80  increases a distance between the rotation pins  33  of the motor disk  34  and the rotation pins  63  of the automatic disk  60  so that the rotation pins  33  do not interfere with the rotation pins  63 , thereby interrupting the motive power so that the rotational force of the hydraulic motor  30  is not transmitted to the worm shaft  43 . On the other hand, the manual mode switch  80  decreases a distance between the rotation pins  73  of the manual disk  70  and the rotation pins  93  of the handle disk  94  so that the rotation pins  73  and the rotation pins  93  meet each other, thereby changing the mode to the manual mode so that the actuator is operated by manipulating the manual handle  90 . 
         [0049]    In the manual mode switch  80 , a manual switch housing  81  is installed to be adjacent to the motor disk  34  and the automatic disk  60  through the housing  20  of the drive part B. As illustrated in  FIGS. 4 and 5 , a pusher  83  is installed in the manual switch housing  81 . The pusher  83  is elastically installed by a pair of elastic members  82  positioned vertically as shown, to move up/down. 
         [0050]    The pusher  83  includes an interference preventing groove  83   a  formed in the middle of the pusher  83 . The interference preventing groove  83   a  prevents the pusher  83  from contacting and interfering with a switch shaft  84  when the pusher  83  moves down. Pressing sides  83   b  are formed by being extended from both lower sides of the interference preventing groove  83   a . A manual mode button  83   c  exposed outward through the manual switch housing  81  is installed on an upper surface of the pusher  83 . 
         [0051]    The switch shaft  84  penetrating the inside/outside of the manual switch housing  81  is installed in the front of the pusher  83 , so as to be freely rotatable by a bearing  84   a . A pivot piece  84   b  protrudes in an inner front end of the switch shaft  84 . The pivot piece  84   b  pivots when it is pressed by the pusher  83 . The release bar  85  is attached to an outer front end of the switch shaft  84  in a single unit. A switch protrusion  85 - 1  and a roller  85 - 2  are respectively positioned at the opposite ends of the release bar  85 . The roller  85 - 2  pushes the automatic disk  60  to be forcibly moved. The release bar  85  is positioned between the motor disk  34  and the automatic disk  60 . 
         [0052]    When the manual mode button  83   c  is pressed, the pusher  83  is moved down so that the pressing sides  83   b  press the pivot piece  84   b . The pivot piece  84   b  pivots around the switch shaft  84 , irrespective of its original position, right or left, and simultaneously the release bar  85  is changed to be positioned a horizontal direction as illustrated in  FIG. 5 . Then, the roller  85 - 2  pushes the automatic disk  60  to be forcibly moved, so that the rotation pins  63  of the automatic disk  60  are spaced apart from the rotation pins  33  of the motor disk  34  so as not to interfere with each other, thereby temporarily interrupting the transmission of the motive power. 
         [0053]    An elastic element receiving groove  86  is formed in the manual switch housing  81 . The elastic element receiving groove  86  is connected to the switch shaft  84  at right angles. After a fixing ball  87  and an elastic member  82  are inserted into the elastic element receiving groove  86 , a set screw  88  is used to force the elastic member  82  against the fixing ball  87  so that the fixing ball  87  is tensioned by the elastic member  82 . Therefore, the fixing ball  87  is prevented from being loose and has elastic force. A ball receiving groove  89  is formed on an outer circumference of the switch shaft  84 . The fixing ball  87  is selectively fitted into the ball receiving groove  89 . Therefore, unless the rotational force is applied to the switch protrusion  85 - 1  of the release bar  85 , the release bar  85  is not changed in position due to the elastic force of the fixing ball  87  and is maintained in a fixed state. 
         [0054]    Further, to change the mode of the actuator to the automatic mode, without any additional manipulation, a return protrusion  34 - 1  is attached to an outer circumference of the motor disk  34  as illustrated in  FIG. 6 . The return protrusion  34 - 1  protrudes outwardly. When the motor disk  34  is rotated by the operation of the hydraulic motor  30 , the return protrusion  34 - 1  applies an impact to the switch protrusion  85 - 1  of the release bar  85  positioned in the horizontal state, so that the release bar  85  is rotated to the original state and simultaneously the automatic disk  60  is released from being pushed. 
         [0055]    As illustrated in  FIG. 3 , magnets  75  facing each other in the same pole direction are respectively buried in the sides of the manual disk  70  and the handle disk  94  facing each other, so that the manual disk  70  and the handle disk  94  have resistance. At the moment when the release bar  85  returns to the original state and the automatic disk  60  is released from being pushed, the moving shaft  50  is pushed towards the motor disk  34 . Therefore, the mode of the actuator is changed from the manual mode to the automatic mode by a simple method of operating the hydraulic motor  30 , without any special manipulation, thereby providing the conveniences in use. 
         [0056]    As illustrated in  FIG. 1 , a handle casing  91  is attached to the other side of the housing  20  of the drive part B. The manual handle  90  is positioned to be rotatable in the handle casing  91 . When the mode of the actuator is changed to the manual mode, the manual handle  90  is to manually operate the worm shaft  43  so as to be rotated. In the manual handle  90 , the handle disk  94  is installed at a front end of the handle shaft  92 . A number of the rotation pins  93  are radially attached to the handle disk  94 . The rotation pins  93  and the rotation pins  73  of the manual disk  70  selectively meet each other, so that the manual disk  70  is operatively rotated to make it possible to manually operate the worm shaft  43  to be rotated. 
         [0057]    To dedicatedly detect the rotational direction, the rotational speed and the extent of opening of the worm shaft  43 , the present invention provides a number of magnets  100 - 1  for detecting the extent of opening and a non-touch digital detector  100  for detecting the extent of opening, as illustrated in  FIGS. 7 and 8 . 
         [0058]    As illustrated in  FIG. 8 , three magnets  100 - 1  for detecting the extent of opening are installed at an outer circumference of the worm shaft  43 , at the equal intervals of 120 degrees in the circumference direction, along a spiral direction. The non-touch digital detector  100  for detecting the extent of opening includes hole sensors  101  for perceiving signals of the magnets  100 - 1  for detecting the extent of opening and is installed to be received in a detector receiving unit  25  formed in the housing  20  of the drive part B as illustrated in  FIG. 2 . 
         [0059]    The hole sensors  101  perceive signals of the magnets  100 - 1  for detecting the extent of opening three times during the worm shaft  43  rotates once, so that the measurement thereof is more minute and precise. A special low-power processor  102  is installed on the top of the non-touch digital detector  100  and calculates the rotational speed, the rotational direction and the extent of opening of the worm shaft  43 . After the low-power processor calculates these items, calculated results (signals) are transferred to the controller  13  installed in the operation part A or drive part B, through a signal line  103 . The controller  13  directly receives the signals detected by the non-touch digital detector  100  for detecting the extent of opening and controls the operation of the hydraulic pressure generator  10 . 
         [0060]    Further, the controller  13  may output outwardly the signals detected by the non-touch digital detector  100  for detecting the extent of opening and simultaneously controls the operation of the hydraulic pressure generator  10  by control instructions from the outside. 
         [0061]    Further, as illustrated in  FIG. 7 , a display  105  for displaying the extent of opening is assembled on the top of the non-touch digital detector  100  for detecting the extent of opening. The display  105  is capable of indicating the extent of opening by the power applied through the controller  13  of the operation part A at normal times and by the power applied through an additionally built-in battery  106  at the time when electricity fails. The display  105  is capable of easily setting/adjusting the accurate extent of opening by operating a button of the operation part A, without opening the housing. 
         [0062]    The multi-turn hydraulic actuator according to the present invention can be installed in a narrow and small space. A user can install the operator part (the hydraulic pressure generator) in a space where it is easy to operate the multi-turn hydraulic actuator, without any limitation with respect to an installation place. Therefore, the multi-turn hydraulic actuator provides the effect of stably obtaining high outputs by using low power. 
         [0063]    Furthermore, the multi-turn hydraulic actuator provides the effect of conveniently setting/adjusting the accurate extent of opening by operating only a button of the operation part A, without opening the housing when setting/adjusting the extent of opening, by using the non-touch digital detector for detecting the extent of opening. 
         [0064]    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.