Abstract:
A hydraulic actuator apparatus includes a hydraulic cylinder having a top and bottom face wherein a rotatable piston is movably disposed. Top and bottom pistons rods that are rotatably removable and couple to the top and bottom faces of the piston. The piston rods are interchangeable so that the top piston rod can be exchanged with the bottom piston rod. The hydraulic actuator apparatus further includes top and bottom end caps, which sealably couple to the top and bottom faces of the hydraulic cylinder, and the end caps support connection to external components and have thru holes, which allow their respective piston rods to emerge from the hydraulic cylinder. The end caps are also interchangeable so that the top end cap and the bottom end cap can be switched. The hydraulic actuator apparatus is symmetric and can be rotated with respect to its connection to external components.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not applicable. 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       REFERENCE TO A COMPACT DISK APPENDIX 
       [0003]    Not applicable. 
       BACKGROUND OF THE INVENTION 
       [0004]    1. Field of the Invention 
         [0005]    This invention generally relates to hydraulic actuators used for transforming pressurized hydraulic fluid to motion. In particular, this invention relates to hydraulic actuators that are symmetrical and having minimal directionality so internal parts are rotatable and interchangeable and so that both ends of the hydraulic actuator can be interchangeably used to couple to an external component to be moved by the hydraulic actuator. 
         [0006]    2. Description of Related Art 
         [0007]    Hydraulic actuators are commonly used to convert hydraulic fluid pressure supplied from an external source to controlled motion. An external source such as a pump pressurizes hydraulic fluid. This pressurized hydraulic fluid is subsequently used to supply the force to move parts within the hydraulic actuator. 
         [0008]    A hydraulic actuator typically consists of a cylinder, which is capable of withstanding the pressure of the hydraulic fluid. This cylinder has an inner chamber whose surface is smoothly finished. The cylinder is sealed with end caps so that hydraulic fluid used in the operation of the cylinder does not leak outside the cylinder and hydraulic pressure can build up within its inner chamber. A machined piston is disposed within the hydraulic cylinder&#39;s chamber and separates pressurized zones within the chamber. The piston is moveable within the inner chamber. A piston rod typically attached with threads bolts or nuts to the piston and passes through a seal portion of the end cap and transfers any motion of the piston within the chamber to any item coupled to the piston rod. 
         [0009]    Hydraulic fluid is brought to the hydraulic actuator by a feed line coupled to a port on the hydraulic actuator. The hydraulic fluid enters the inner chamber of at least one zone of the piston. In a single acting hydraulic actuator, the hydraulic fluid enters only one zone of the chamber divided by the piston. As the pressurized hydraulic fluid enters that zone of the chamber, the force within the zone increases, pushing the piston and correspondingly moving the piston rod and any external component connected to the piston rod. By decreasing or removing the pressurized hydraulic fluid, the force within the zone decreases and the piston returns to its restored position. A counter force such as an internal spring or gravity acts to move the piston and piston rod back to its original position. In a double acting hydraulic actuator, the hydraulic fluid enters a second zone and acts equivalent to a counter force to move the piston back to a restored position. 
         [0010]    Often, hydraulic actuators are installed in locations where it can be difficult to remove the complete actuator from the external component for servicing. Alternatively, removal and shipment of the actuator to a service location can result in prohibitively long downtimes. As a result, it is beneficial to service these actuator in the field. Often these hydraulic actuators can be serviced by those having little training in actuator repair and replacement. If the hydraulic actuator is reassembled improperly, the actuator can be damaged or may not function at all. 
         [0011]    Thus, there is a need for a hydraulic actuator having easy and straightforward assembly or reassembly. This is accomplished by having a actuator design where actuator components are as non-directional as possible and where similar parts are interchangeable. Symmetrical components are useful for such a design. With a symmetrical piston design, a person servicing the actuator does not have to consider whether the piston is facing the proper direction within the chamber—either way will work. Further, a symmetric actuator allows for non-directional installation to external components. Also, interchangeable parts reduce the risk of improper installation or reassembly. 
         [0012]    Further, actuator parts are subject to wear and inventory must be kept of replacement parts. As the number of distinct parts in an actuator decreases, the number of parts that must be kept as inventory also decreases. Thus interchangable parts also have the additional benefit that fewer inventory have to be kept in anticipation of a needed in field replacement. Increasing interchangeability is also beneficial for the manufacturers of hydraulic actuators who have to source less numbers of components and require less inventory. 
       SUMMARY OF THE INVENTION 
       [0013]    In accordance with the teachings provided herein for hydraulic actuators, one example provides a hydraulic actuator apparatus. The apparatus comprises an actuator body having an axial sleeve bore, wherein the actuator body has a first end and a second end. The apparatus further comprises a piston operationally disposed within the axial sleeve bore, wherein the piston has a first piston surface and a second piston surface that are substantially identical in shape and configuration such that the piston can be configured within the axial sleeve bore with the first piston surface facing either the first end or the second end of the actuator body. The apparatus further comprises a first end cap having a first end cap hole defined therein where the first end cap is removably coupled to either the first end or the second end of the actuator body. The apparatus further comprises a second end cap removably coupled to the actuator body on an end opposite of the first end cap. The apparatus further comprises a piston rod disposed in the first chamber and having a piston rod end removably coupled to either the first piston surface or second piston surface wherein the piston rod slidably traverses through the first end cap hole. 
         [0014]    In another example, a hydraulic actuator apparatus is provided comprising an actuator body having an axial sleeve bore, wherein the actuator body has a first end and a second end and a piston operationally disposed within the axial sleeve bore, wherein the piston has a first piston surface, a second piston surface, and a piston engaging face wherein the piston engaging face is in circumferential and contiguous engagement with the circumference of the axial sleeve bore to form a first chamber and a second chamber within the axial sleeve bore. The apparatus further comprises a first end cap having a first end cap hole defined therein, the first end cap being removably coupled to the first end of the actuator body and a second end cap removably coupled to the second end of the actuator body. The apparatus further comprises a piston rod disposed in the first chamber removably coupled to the first piston surface and slidably traversable through the first end cap hole, wherein the piston rod can be removed from the first chamber and decoupled from the first piston surface and placed within the second chamber and removably coupled to the second piston surface. 
         [0015]    In another example, a hydraulic actuator system is provided comprising a hydraulic actuator apparatus and an external component. The hydraulic actuator apparatus comprises an actuator body having an axial sleeve bore, wherein the actuator body has a first end and a second end, a first end cap having a first end cap hole defined therein and removably coupled to the first end of the actuator body, and a second end cap having a second end cap hole defined therein and removably coupled to the second end of the actuator body. The hydraulic actuator apparatus further comprises a piston operationally and removably disposed within the axial sleeve bore, wherein the piston has a first piston surface and a second piston surface, wherein the piston divides the axial sleeve bore into a first chamber and a second chamber, a first piston rod removably coupled to the first piston surface and slidably traversable through the first end cap hole, and a second piston rod removably coupled to the second piston surface and slidably traversable through the second end cap hole. The external component is removably coupled to the first end cap engaged with and removably coupled to the first piston rod, wherein the external component can be decoupled from the first end cap and first piston rod and removably coupled to the second end cap and removably coupled to the second piston rod. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0016]    The foregoing summary, as well as the following detailed description, will be better understood when read in conjunction with the appended drawings. For the purpose of illustration, certain embodiments of the present disclosure are shown in the drawings. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an implementation of system, apparatuses, and methods consistent with the present invention and, together with the description, serve to explain advantages and principles consistent with the invention. 
           [0017]      FIG. 1  illustrates a side view of one embodiment of a hydraulic actuator connected to an external adapter; 
           [0018]      FIG. 2  illustrates a cross-sectional view of one embodiment of the hydraulic actuator connected to an external adapter; 
           [0019]      FIG. 3   a  illustrates a detailed side view of a piston as it is attached to a piston rod used within the hydraulic actuator according to one embodiment of this invention; and 
           [0020]      FIG. 3   b  illustrates a detailed side view of the piston as it is attached to the piston rod used within the hydraulic actuator rotated ninety (90) degrees about a vertical axis in relation to  FIG. 3   a  and according to one embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The Figures and written description are provided to teach any person skilled in the art to make and use the inventions for which patent protection is sought. The invention is capable of other embodiments and of being practiced and carried out in various ways. Those skilled in the art will appreciate that not all features of a commercial embodiment are shown for the sake of clarity and understanding. Persons of skill in the art will also appreciate that the development of an actual commercial embodiment incorporating aspects of the present inventions will require numerous implementation—specific decisions to achieve the developer&#39;s ultimate goal for the commercial embodiment. While these efforts can be complex and time-consuming, these efforts nevertheless would be a routine undertaking for those of skill in the art having the benefit of this disclosure. 
         [0022]    In addition, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. For example, the use of a singular term, such as, “a” is not intended as limiting of the number of items. Also the use of relational terms, such as but not limited to, “top,” “bottom,” “left,” “right,” “upper,” “lower,” “down,” “up,” “side,” are used in the description for clarity in specific reference to the Figures and are not intended to limit the scope of the invention or the appended claims. Further, it should be understood that any one of the features of the invention can be used separately or in combination with other features. Other systems, methods, features, and advantages of the invention will be or become apparent to one with skill in the art upon examination of the Figures and the detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present invention, and be protected by the accompanying claims. 
         [0023]    Reference will now be made in detail to an implementation consistent with the present invention as illustrated in the accompanying drawings. For the purpose of clarification, embodiments described herein reference the term “fluid,” which refers to a gas, liquid, as well as liquid solution with solid aggregates, as well as any material that can reasonably be expected to flow. 
         [0024]    Referring to  FIG. 1 , by way of non-limiting example, and consistent with embodiments of the invention, a hydraulic actuator assembly  100  is shown. The hydraulic actuator assembly  100  includes a hydraulic chamber  110  having a bore (shown in  FIG. 2  as bore  320 ). The hydraulic actuator assembly  100  further consists of a top end cap  120  and a bottom end cap  130  which sealably engage with the hydraulic chamber  110 . The top end cap  120  couples to a top face  112  of the hydraulic chamber  110 . The top end cap  120  is substantially similar to the bottom end cap  130 . The bottom end cap  130  connects to a bottom face  113  of the hydraulic chamber  110 . Actuator bolts  140  traverse the top end cap  120  and the bottom end cap  130  and threadably engage with the hydraulic chamber  110  to retain the top end cap  120  and the bottom end cap  130  on the hydraulic chamber  110 . 
         [0025]    The hydraulic actuator assembly  100 , which converts pressure to controlled motion, typically connects to an external component (not shown) that requires the motion as part of its function. The bottom end cap  130  incorporates a bottom mating connection  160  that attaches to a coupling connection  170  through coupling bolts  190 . The top end cap  120  incorporates a top mating connection  150  that is substantially similar to the bottom mating connection  160 . In this way either the top end cap  120  of the hydraulic actuator assembly  100  or the bottom end cap  130  can connect to the external component (not shown) directly or through the coupling connection  170 . Because the top end cap  120  is substantially similar to the bottom end cap  130 , the coupling connection  170  can connect to the top end cap  120 . 
         [0026]    The hydraulic chamber  110  of the hydraulic actuator assembly incorporates a top hydraulic port  210  and a bottom hydraulic port  220 . The top hydraulic port  210  couples to a first portion of a bore  320  (not visible in  FIG. 1  but shown in  FIG. 2 ) of the hydraulic chamber  110  while the bottom hydraulic port  220  couples to the bottom portion of the bore  320  (not visible in  FIG. 1  but shown in  FIG. 2 ) of the hydraulic chamber  110 . 
         [0027]    The hydraulic chamber  110  is symmetric about a plane  200  shown as bisecting the hydraulic actuator assembly  100 . The plane  200  is depicted for reference purposes only and is not a physical element of the hydraulic actuator assembly  100 . Because the top end cap  120  and the bottom end cap  130  are substantially similar, the hydraulic chamber  110  coupled with the top end cap  120  and the bottom end cap  130  are symmetric about the plane  200 . The hydraulic actuator assembly  100  is symmetric and as a result, can be rotated such that the top end cap  120  is facing down while the bottom end cap  130  is facing upwards and capable to couple to an external assembly (not shown) without substantial modification. Further, the top hydraulic port  210  and the bottom hydraulic port  220  can be of substantially similar connection type and can be located at positions that are substantially mirrored across the plane  200 . This allows the hydraulic actuator assembly  100  to be rotated within its surroundings with minimal adjustment of any feed lines (not shown) that connect to the top hydraulic port  210  and bottom hydraulic port  220 . 
         [0028]    One of skill in the art will understand that other symmetrical arrangements would also permit the hydraulic actuator assembly  100  to be rotated in its external coupling from top to bottom. For example, the top hydraulic port  210  and the bottom hydraulic port  220  can be rotated 180 degrees with respect to each other so that the top hydraulic port  210  is on the left and the bottom port is on the right of  FIG. 1 . Such an arrangement would also allow the hydraulic actuator assembly  100  to be rotated top to bottom in it external coupling, and the top end cap  120  and the bottom end cap  130  remain symmetric across the plane  200 . 
         [0029]    As will be described, the hydraulic actuator assembly  100  incorporates a piston assembly  310  (not visible in  FIG. 1  but shown in  FIG. 2 ) that is movable within the hydraulic chamber  110 . The piston assembly  310  couples to an external component (not shown) which makes use of the force-to-motion transformation of the hydraulic actuator assembly  100 . The coupling connection  170  provides a means to attach the hydraulic actuator assembly  100  to the external component (not shown). One non-limiting example of an external component with which the hydraulic actuator assembly  100  can be used is a gate valve (not shown). The motion in the piston assembly  310  (shown in  FIG. 2 ) can be used to translate a gate (not shown) within the gate valve&#39;s body (not shown). As will be recognized by one of skill in the art, if the external component (not shown) and the top mating connection  150  or bottom mating connection  160  are designed such that they are compatible, i.e., they will mate together, a coupling connection  170  is not necessary and the hydraulic actuator assembly  100  can mate directly with the external component (not shown). Since the hydraulic actuator assembly  100  is designed so that the top mating connection  150  on the top end cap  120  or the bottom mating connection  160  on the bottom end cap  130  are substantially similar, the external component (not shown) can be easily attached to either the top mating connection  150  or bottom mating connection  160 . 
         [0030]    Referring now to  FIG. 2  showing a cross section of the hydraulic actuator assembly  100 , the components and operation of the hydraulic actuator assembly  100  will be described. The piston assembly  310 , previously mentioned, is operationally disposed within a bore  320  of the hydraulic chamber  110 . The bore  320  has a bore diameter  325  that is substantially constant throughout the hydraulic chamber  110 . The piston assembly  310  comprises a piston plate  315  that is formed and having a piston diameter  335  that is substantially equal to but slightly smaller than the bore diameter  325  so that the piston assembly  310  is able to move within the hydraulic chamber  110 . The piston plate  315  has an engaging face  350  that couples with the inner surface of the hydraulic chamber  110 . Three piston grooves  340  are formed on the engaging face  350  of the piston plate  315 . Piston seals  365  are disposed within a piston groove  340  that is disposed centrally within the engaging face  350  and the piston seals  365  compressively engages with the inner surface of the hydraulic chamber  110  to provide a seal and thereby separate the bore  320  of the hydraulic chamber  110  into an upper bore  370  and a lower bore  380 . The piston seals  365  maintain fluidic integrity so that the passage of hydraulic fluid between the upper bore  370  and the lower bore  380  is restricted. As a non-limiting example, the piston seals  365  can be an elastomeric O-ring. In addition, in order to prevent a metal-to-metal contact between the piston assembly  310  and the hydraulic chamber  110 , a bushing  360  is disposed in the piston grooves  340  not contain the piston seals  365 . As a non-limiting example, the bushing  360  can be made from material such as polytetrafluoroethylene (PTFE). One of skill in the art will also recognize that multiple piston grooves  340  with piston seals  365  and bushing  360  are not necessary to separate the hydraulic chamber  110  into an upper bore  370  and a lower bore  380  and that this can be accomplished with only one piston groove  340  and one piston seal  365  if a second piston seal  365  and bushing  360  are not required. 
         [0031]    The piston plate  315  of the piston assembly  310  includes a piston top surface  390  and a piston bottom surface  400  that are substantially identical. The piston assembly  310  further comprises a top lug portion  410  attached to the piston plate  315  at the piston top surface  390  and a bottom lug portion  412  at the piston bottom surface  400 . A top piston rod  450  couples to the piston top surface  390  at the top lug portion  410 . Similarly, a bottom piston rod  460  couples to the piston bottom surface  400  at the bottom lug portion  412  on the piston bottom surface  400 . The top lug portion  410  is substantially similar to the bottom lug portion  412 . The top piston rod  450  is substantially similar to the bottom piston rod  460  so that the top piston rod  450  can be interchanged with the bottom piston rod  460 . Further details on coupling the top piston rod  450  and bottom piston rod  460  to the piston assembly  310  are described below. One of skill in the art will understand that both the top piston rod  450  and the bottom piston rod  460  need not be necessary for a particular configuration. For example, if a use situation arises wherein the hydraulic actuator assembly  100  is only being engaged from one side, only one piston rod, either the top piston rod  450  or the bottom piston rod  460  is necessary. In this situation, the top piston rod  450  can be coupled to the piston bottom surface  400  either by rotating the piston assembly  310  within the hydraulic chamber  110  or by disposing the top piston rod  450  within the lower bore  380 . One of skill in the art will recognize that the length of hydraulic chamber  110  is determined by the length of travel required of the top piston rod  450  and bottom piston rod  460 . 
         [0032]    The top end cap  120  couples to the top face  112  of the hydraulic chamber  110 . The top end cap  120  comprises a lower end cap portion  490  having an end cap outer diameter  500  substantially equal to but slightly smaller than the bore diameter  325  of the hydraulic chamber  110 . The lower end cap portion  490  of the top end cap  120  incorporates top end cap grooves  510  on the outer surface of the lower end cap portion  490  wherein top end cap seals  515  are disposed within the top end cap grooves  510 . The top end cap seal  515  compressively engages with the inner surface of the hydraulic chamber  110  to provide a fluidic seal to thereby maintain fluidic integrity within the hydraulic chamber  110  such that hydraulic fluid within the upper bore  370  of the hydraulic chamber  110  cannot pass outside the chamber where the top end cap  120  meets the hydraulic chamber  110 , to enable hydraulic pressure to increase within the upper bore  370 . As a non-limiting example, the top end cap seal  515  can be an elastomeric O-ring. One of skill in the art will recognize that multiple top end cap grooves  510  with top end cap seals  515  can be used but are not necessary to isolate the upper bore  370  of the hydraulic chamber  110  and that this can be accomplished with only one top end cap groove  510  and one top end cap seal  515 . 
         [0033]    The top end cap  120  further comprises a top end cap lip  520  which overlays the top face  112  of the hydraulic chamber  110 . The top end cap lip  520  incorporates end cap thru holes  530 , which allow threaded actuator bolts  140  to pass thorough and threadingly couple within complementary threaded holes  540  in the top face  112  of the hydraulic chamber  110 . The thru holes  530 , threaded actuator bolts  140 , and complementary threaded holes  540  are used around the diameter of the hydraulic chamber and the top end cap  120  to removably fasten the top end cap  120  onto the hydraulic chamber  110 . 
         [0034]    The top end cap  120  also comprises a top end cap central hole  580  having a end cap hole diameter  585  that is substantially equal but slightly larger than the outer diameter of the top piston rod  450  so that the top piston rod  450  can pass through and travel within the top end cap central hole  580 . The top piston rod  450  passes outside of the remaining hydraulic actuator assembly  100  and through the top end cap  120  to engage with external components (not shown). The top end cap  120  also comprises top end cap hole grooves  590  long the central hole wall  579  at the outer diameter of the top end cap central hole  580 . Top central hole seal  597  are disposed within the top end cap hole grooves  590  and along the central hole wall  579  at the end cap hole diameter  585  of the top end cap central hole  580 . A top central hole bushing  595  is disposed in the top end cap hole grooves  590  where the top central hole seals  597  are not present to prevent metal-to-metal contact between the top end cap  120  and the top piston rod  450 . As the top piston rod  450  passes through the top end cap central hole  580 , it compressively engages with the top central hole seals  597  to provide a seal and thereby maintains fluidic integrity within the hydraulic chamber  110  such that hydraulic fluid within the hydraulic chamber  110  cannot pass outside the upper bore  370  where the top piston rod  450  meets the top end cap  120 , and hydraulic pressure can increase within the upper bore  370 . As a non-limiting example, the top central hole bushing  595  can be fabricated from PTFE and the top central hole seal  597  can be an elastomeric O-ring. 
         [0035]    The top end cap  120  also comprises a top mating connection  150  for coupling to external components (not shown). The top mating connection  150  comprises ring thru holes  630  through which bolts (not shown) can be used to affix the hydraulic actuator assembly  100  onto an external component (not shown). 
         [0036]    The bottom end cap  130  is substantially similar in structure and function to the top end cap  120 . In a substantially similar manner as regarding the top end cap  120 , the bottom end cap  130  can couple to the bottom surface of the hydraulic chamber  110 . The bottom end cap  130  is substantially similar to the top end cap  120  and also comprises a bottom end cap groove  511  accommodating bottom end cap seals  516  to seal the lower bore  380  where the bottom end cap  130  meets the hydraulic chamber  110 . Further, the bottom end cap  130  also comprises a bottom end cap lip  521  which overlays the bottom face  113  of the hydraulic chamber  110 . The bottom end cap lip  521  incorporates bottom end cap thru holes  531 , which allow the threaded actuator bolts  140  to pass through and threadingly couple with complementary bottom threaded holes  541  in the bottom face  113  of the hydraulic chamber  110 . Further, the bottom end cap  130  also comprises a bottom end cap central hole  581  that accommodates the bottom piston rod  460  so that the bottom piston rod  460  can pass through the bottom end cap  130 . Bottom central hole seals  598  are disposed in the bottom central hole groove  591  and compressively engages with the bottom piston rod  460  to seal the lower bore  380  where the bottom piston rod  460  meets the bottom end cap  130 . And substantially similar to the top end cap  120 , the bottom central hole bushing  596  is disposed in the bottom central hole grooves  591  where the bottom central hole seals  598  are not present to prevent metal-to-metal contact between the top end cap  120  and the top piston rod  450 . The material for the bottom central hole seals  598  and bottom central hole bushing  596  can be the same as that for the top central hole seals  597  and top central hole bushing  595 , respectively. 
         [0037]    The bottom end cap  130  couples to a coupling connection  170  or an external component (not shown but connecting in substantially the same way as the coupling connection  170 ) through the bottom mating connection  160  which is substantially similar to the top mating connection  150 . The bottom mating connection  160  couples to a complementary ring  680  on the external component having component engagement holes  690 . Coupling bolts  190  traverse the ring thru holes  630  and threadingly engage with the component engagement holes  690  to secure the hydraulic actuator assembly  100  via its bottom end cap  130  to the coupling connection  170 . Further, the bottom piston rod  460  engages with the coupling connection  170  or an external component (not shown) through an external piston attachment  660  which can be secured to the bottom piston rod  460  through a pin and lug assembly similar to that described in coupling the bottom piston rod  460  to the piston bottom surface  400  of the piston assembly  310 . By coupling the bottom piston rod  460  to the external component (not shown), any movement in the piston assembly  310  within the hydraulic chamber  110  relative to the bottom end cap  130  will result in a similar movement in portions of the external component (not shown) connected to the bottom piston rod  460 . 
         [0038]    In the described embodiment of the hydraulic actuator assembly  100 , the hydraulic chamber  110  has a top hydraulic port  210  and a bottom hydraulic port  220  that allows connection of hydraulic fluid hose connections (not shown) to the hydraulic actuator assembly  100 . The top hydraulic port  210  provides a connection to a bore through the wall of the hydraulic chamber  110  so that hydraulic fluid can pass through the wall of the hydraulic chamber  110  and fill the upper bore  370 . In a substantially similar manner, the bottom hydraulic port  220  allows hydraulic fluid to fill the lower bore  380 . When hydraulic fluid is forced into the upper bore  370 , the fluidic force will cause the piston assembly  310  to translate downward within the hydraulic chamber  110 . Similarly, when hydraulic fluid is forced into the lower bore  380 , fluidic force will cause the piston assembly  310  to translate upward within the hydraulic chamber  110 . The top piston rod  450  and bottom piston rod  460  attached to the piston assembly  310  move with the piston assembly  310  and translate through the top end cap  120  and the bottom end cap  130  respectively. One of skill in the art will recognize that in a single acting actuator, a single hydraulic port, either the top hydraulic port  210  or the bottom hydraulic port  220 , can be utilized whereby hydraulic force can move the piston assembly  310  in one direction while an inner spring (not shown) or gravity can supply the force to move the piston assembly  310  in the opposite direction. 
         [0039]    The bottom end cap  130  is substantially similar to the top end cap  120 ; the top face  112  of the hydraulic chamber  110  is substantially similar to the bottom face  113  of the hydraulic chamber  110 ; the piston top surface  390  is substantially similar to the piston bottom surface  400 ; and the top piston rod  450  is substantially similar to the bottom piston rod  460 . As a result, the bottom end cap  130  is functionally interchangeable with the top end cap  120 . When the bottom end cap  130  is exchanged with the top end cap  120 , the bottom end cap  130  will functionally couple with the top face  112  of the hydraulic chamber  110 . The top piston rod  450  will functionally engage with the bottom end cap  130 . Further any external components (not shown) engaging with the top end cap  120  can functionally engage with the bottom end cap  130  and any external components (not shown) engaging with the bottom end cap  130  can functionally engage with the top end cap  120 . Similarly, the top end cap  120  can couple with the bottom face  113  of the hydraulic chamber  110  and with the bottom piston rod  460  and engage with any external circuitry (not shown) that originally coupled to the bottom end cap  130 . 
         [0040]    In one embodiment of the hydraulic actuator  100 , a typical length of the hydraulic chamber  110  is nineteen (19) inches. For this embodiment, outer diameter (not shown) of the hydraulic chamber is twelve and one-half (12.5) inches. The bore diameter  325  is ten (10) inches. The piston diameter  335  is slightly smaller than the bore diameter  325 . The thickness of the piston plate  315  is two and three-quarters (2.75) inches. The length of the top piston rod  450  is substantially the same as the bottom piston rod  460  and is fifteen and one-quarter (15.25) inches. Dimensions of other portions and components of the actuator in this embodiment complement these dimensions and can be determined by one of skill in the art. One of skill in the art will also recognize that this embodiment is not limited to any particular size and the dimensions the hydraulic actuator  100  and its components of will depend upon the particular application for which it is employed. 
         [0041]      FIGS. 3   a  and  3   b  show a side view of the piston assembly  310  and detail its connection to the top piston rod  450  and bottom piston rod  460 . The bushing  360  and piston seals  365  are not shown.  FIG. 3   b , depicts the piston assembly  310  as coupled to the top piston rod  450  and bottom piston rod  460  in a view rotated 90 degrees with respect to  FIG. 3   a . The top piston rod  450  attaches to the piston assembly  310  through a tongue  780 , which is disposed in a lug groove  415 , formed in the top lug portion  410 . The tongue  780  has a thickness that is substantially the same as the lug groove  415  but allows the insertion of the tongue  780  within the lug groove  415 . The top piston rod  450  also has a top tongue  781  on the opposite end such that the top piston rod  450  is substantially symmetric and to enable the upper portion of the top piston rod  450  to be coupled to the piston assembly  310 . The lug groove  415 , in conjunction with the piston thru hole  795 , form the top lug portion  410 . A piston rod thru hole  800  within the tongue  780  aligns with the piston thru hole  795  to allow a pin  805  to engage with the top lug portion  410  and tongue  780  to matingly couple the top piston rod  450  to the piston assembly  310 .  FIG. 3   b  shows the alignment of the piston thru hole  795 , the piston rod thru hole  800 . One end of the pin  805  passes through the piston thru hole  795  on one side of the top lug portion  410 , through the piston rod thru hole  800  within the tongue  780 , and through the piston thru hole  795  on the opposite side of the top lug portion  410 . The pin  805  is long enough to traverse the entire thickness of the top lug portion  410  of the piston assembly  310  while at the same time allowing the piston assembly  310  to traverse freely within the hydraulic chamber  110 . The bottom lug portion  412  is substantially similar in structure and function as the top lug portion  410  and couples to the bottom piston rod  460  in substantially the same manner in which the top lug portion  410  couples to the top piston rod  450 . 
         [0042]    The piston assembly  310  is substantially symmetric about a plane  355  that perpendicular to its engaging face  350 . The plane  355  is depicted for reference purposes only as to the symmetrical design of the present embodiment and is not shown so as to represent a physical element of the piston assembly  310 . Because the top piston rod  450  and the bottom piston rod  460  are substantially symmetric, the top piston rod  450  and the bottom piston rod  460  is rotatable and both ends of the top piston rod  450  and the bottom piston rod  460  can be interchangeably affixed to the piston assembly  310 . Because the piston assembly  310  has substantially similar piston top surface  390  and piston bottom surface  400  wherein the top lug portion  410  and bottom lug portion  412  are substantially similar, the top piston rod  450  is interchangeable with the bottom piston rod  460 . Thus, the bottom piston rod  460  can connect to the piston assembly  310  on the piston top surface  390  while the top piston rod  450  can connect to the piston assembly  310  on the piston bottom surface  400 . Further, because the top end cap  120  is substantially similar to the bottom end cap  130 , the top piston rod  450  can usably pass through the bottom end cap  130  while the bottom piston rod  460  can functionally pass through the top end cap  120 . One of skill in the art will recognize that only a top piston rod  450  or a bottom piston rod  460  need be used with the hydraulic actuator assembly  100  in which case either the top piston rod  450  or bottom piston rod  460  can be used to connect to piston assembly  310  at the piston top surface  390  or the piston bottom surface  400 . Because of its substantial symmetricity, the piston assembly  310  can be rotated in the hydraulic actuator assembly  100  so that the piston bottom surface  400  faces upwards while the piston top surface  390  faces downwards within the hydraulic chamber  110 . Either one the top piston rod  450  or the bottom piston rod  460  can then couple to either the piston top surface  390  or the piston bottom surface  400  and pass through either the top end cap  120  or bottom end cap  130  which can be connected to either the top surface of the hydraulic chamber  110  or the bottom surface of the hydraulic chamber  110 . In sum, the piston assembly  310  is rotatable within the hydraulic chamber  110  so that the piston assembly  310  does not have a preferred orientation within the hydraulic chamber  110 . Thus, the top piston rod  450  and the bottom piston rod  460  are rotatable and interchangeable. The top end cap  120  and the bottom end cap  130  are interchangeable. Because the top mating connection  150  on the top end cap  120  is substantially similar to the bottom mating connection  160  on the bottom end cap  130 , the hydraulic actuator assembly  100  is also rotatable in its external connections (not shown) and both ends can interchangeably couple to an external component (see  FIG. 1  coupling connection  170 ). 
         [0043]    One of skill in the art will recognize that this embodiment is not limited to any particular size and the size of the hydraulic actuator will depend upon the particular application and intended external components such as a gate valve, a plug valve, a choke, etc. Further one of skill in the art will recognize that the hydraulic actuator assembly  100  is not limited to any type of material. As a non-limiting example, the hydraulic actuator assembly  100  is formed primarily from low alloy steel; the seals can be formed from elastomeric material; and bushings can be formed from PTFE. 
         [0044]    It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that the invention disclosed herein is not limited to the particular embodiments disclosed, and is intended to cover modifications within the spirit and scope of the present invention.