RELATED APPLICATIONS 
     This application is a continuation application of U.S. Non-Provisional Application Ser. No. 09/641,586 filed Aug. 18, 2000 now abandoned. 
    
    
     FIELD OF INVENTION 
     The present invention relates generally to the field of hydraulic pumps, and in particular but not by way of limitation, to a hydraulic actuator used in a marine environment in conjunction with an outboard motor. 
     BACKGROUND OF INVENTION 
     The need for portable lifting power is widespread. Batteries provide a good source for power but the driven devices can be complicated, cumbersome and inadequate. To date, the most popular systems are driven by direct current (DC) electric motors. These motors generally drive screw type devices or hydraulic type devices. Screw type devices have proven adequate for some light duty applications but fall short when long-term rugged service is required. Hydraulic devices are inherently more suited to harsh service but tend to be more complicated and expensive. 
     Most hydraulic lifting systems consist of several separate components such as a motor, hydraulic pump, hydraulic fluid reservoir, hydraulic lines, assorted fittings, electric control solenoids and a hydraulic cylinder. These systems are functional but impractical for many portable applications, since each component must be mounted independently to operate as a unit. Space and weight restrictions are problems since each component must have a housing or enclosure. 
     Harsh environments also pose problems for these systems. Most hydraulic systems require use of breather tubes or vents that allow contaminants such as water, dirt and other foreign objects, to enter the system and such contamination often leads to component failure. The components are usually made from ferrous materials, making the components susceptible to corrosion. 
     Thus, prior art hydraulic systems have been found to be undesirable for marine applications. 
     SUMMARY OF INVENTION 
     The present invention provides a hydraulic actuator suitable for use in marine and other harsh environments. In the presently preferred embodiment, the hydraulic actuator includes a motor that is configured to operate in a first or second direction. A pump assembly is coupled to the motor and is configured to pressurize and displace hydraulic fluid. The hydraulic actuator also includes a cylinder bore that has an upper chamber and a lower chamber which are separated by a movable piston member. A first plurality of pressure actuated valves are used to regulate the flow of high pressure hydraulic fluid to the upper chamber and low pressure fluid from the lower chamber. The first plurality of pressure actuated valves are actuated in response to pressure generated by the pump assembly when the motor is operating in the first direction. A second plurality of pressure actuated valves are used to regulate the flow of high pressure hydraulic fluid to the lower chamber and low pressure fluid from the upper chamber. The second plurality of pressure actuated valves are actuated in response to pressure generated by the pump assembly when the motor is operating in the second direction. 
    
    
     Other objects, advantages and features of the present invention will become clear from the following detailed description and drawings when read in conjunction with the claims. 
     BRIEF DESCRIPTION OF DRAWING 
     FIG. 1 is a perspective view of a hydraulic actuator of the present invention showing the relative positions of the actuator, a mounting apparatus attached to a transom of a boat upon which the actuator is mounted, and a motor that is mounted on the mounting apparatus. 
     FIG. 2 is an elevational, front view of the hydraulic actuator of FIG. 1 FIG. 3 is a left side view of the hydraulic actuator of FIG.  1 . 
     FIG. 4 is a right side, cross-section view of the hydraulic actuator of FIG.  1 . 
     FIG. 5 is a plan view of the lower surface of the main body of the hydraulic actuator. 
     FIG. 6 is a view of the upper surface of the port body of the hydraulic actuator. 
     FIG. 7 is an exploded view of the hydraulic actuator of FIG.  1 . 
     FIG. 8 is a partial cutaway view of a portion of the left side of the hydraulic actuator of FIG. 1 showing the valves of the extend activation system. 
     FIG. 9 is a partial cutaway view of a portion of the left side of the hydraulic actuator of FIG. 1 showing the valves of the retract activation system. 
     FIG. 10 is a functional schematic showing the fluid paths during the extend operation. 
     FIG. 11 is a functional schematic showing the fluid paths during the retract operation. 
    
    
     DESCRIPTION 
     Referring to the drawings in general and particularly to FIG. 1, shown therein is a hydraulic actuator  10  constructed in accordance with the present invention. While the present invention will be described in relation to the embodiment shown in the appended drawings, it will be understood that the present invention can be adapted to other embodiments. 
     The hydraulic actuator  10  shown in FIG. 1 is connected to an outboard motor  12  that is pivotally mounted to a boat  14  via a transom bracket  16  such as that taught in my U.S. Pat. No. 4,482,330. The boat  14 , outboard motor  12 , and transom bracket  16  have been indicated in dashed lines in FIG. 1 to indicate the positioning of the hydraulic actuator  10  on the boat  14  and the positioning of the outboard motor  12  and transom bracket  16  in relation to the hydraulic actuator  10 . As shown in FIG. 1, the transom bracket  16  is mounted on the boat  14  such that the selected line of movement (indicated by arrow  18 ) is orientated relative to the boat  14  for vertical movement of the outboard motor  12  thereon. 
     The parts for the hydraulic actuator  10  are designed such that they can be manufactured from stock materials using standard machine tools. Because no special castings are necessary, small lot production is feasible. This construction is possible due to the novel valve system that controls fluid flow and direction without external electric solenoids. 
     As shown in FIG. 2, the hydraulic actuator  10  has an actuator body  19  made up of a main body  20  and a port body  22 . When connected, the main body  20  and the port body  22  contain a number of fluid conduits. These conduits direct hydraulic fluid to and from both ends of a rod  24  that is extended or retracted as needed. The rod  24  is disposed in a cylinder bore  26 , shown in dashed lines, that passes through the main body  20 . Also shown in dashed lines is a pump motor  28 , pump assembly  30  and reservoir  32  that are disposed in the main body  20 . Preferably, the reservoir  32  is used to store incompressible hydraulic fluid. The motor  28  is connected to a power cable  34  that can be attached to a 12 volt battery or other energy source. 
     FIGS. 3 and 4 show elevational views of the left and right side of the actuator  10 , respectively. As shown in FIG. 3, the body  20  includes a fill port  36  that is used to fill the reservoir  32 . Because the reservoir level is at the fill port  36  when full, the fill port  36  can also be used to the check the volume of the hydraulic fluid in the actuator  10 . FIG. 4 illustrates (in partial cross section) the relationship between the cylinder bore  26  and rod  24 . The rod  24  penetrates the port body  22  through the opening  38  and attaches to a reciprocating piston member  40  in the cylinder bore  26 . Cylinder bore  26  has two areas, an upper chamber  42  and a lower chamber  44 . A hole  46  on the rod  24  permits other devices to be connected to the rod member  24  for effective movement. 
     Turning now to FIG. 5, shown therein is a plan view of the bottom of the main body  20 . The first of three passageways in the main body  20  is a main longitudinal passageway  48  (shown in dashed lines) which runs through the main body  20  from the reservoir  32  toward the cylinder bore  26 . The main longitudinal passageway  48  does not intersect the cylinder bore  26 . A port  50  provides access to the main longitudinal passageway  48  and can act as a drain hole. 
     First and second lateral passageways  52 ,  58  also run through the main body  20  and are perpendicular to the main longitudinal passageway  48 . The first and second lateral passageways  52 ,  54  are in communication with the longitudinal passageway  48  through main-body bores  56 ,  58 , respectively, and first and second channels  60 ,  62 , respectively. First and second channels  60 ,  62  are defined by mating grooves at the interface of the bottom surface of the main body member  20  and top surface of the port body member  22 . 
     As shown in FIGS. 2 and 5, the first main body bore  56  and the second main body bore  58  of the main body  20  each have a ball check valve  64 . Two indentures in the port body  22  from two pump canals  66 ,  68  when the port body  22  is joined to the main body  20 . The pump assembly  30  includes two gears, and idler gear  70  and a drive gear  72 , that are disposed adjacent to, and in fluid communication with, pump canals  66 ,  68 . The idler gear  70  and drive gear  72 , are powered by the pump motor  28 , and work together to produce a pressure reduction in one of the two main-body bores  56 ,  58 . 
     Each ball check valve  64  will permit fluid to flow into the pump canals  66 ,  68  from the reservoir  32  but will close in response to increased fluid pressure in the pump canals  66 ,  68 . Each ball check valve  64  has a ball that is driven by pressure against a seat (not numerically designated in the drawings) in each of the main body bores  56 ,  58 . A spring (not shown in the drawings) can be used to displace the ball from the seat in the absence of such pressure. Thus each ball check valve  64  is open until hydraulic fluid pressure forces the ball to close the valve. These are valves similar to those taught in the Applicant&#39;s U.S. Pat. No. 5,181,835 but differ as designated by this invention. U.S. Pat. No. 5,181,835 is hereby incorporated by reference. 
     The two main body bores  56 ,  58  are both in fluid communication with the pump assembly  30 , the reservoir  32  and each other so that fluid can flow from the first main body bore  56  to the second main body bore  58  and vice versa. The fluid flow from the open check valve  64  in the first main body bore  56  can close the second main body bore  58  check valve  64  and cause the pressure to rise. As such, during the operation of the pump assembly  30 , only one check valve  64  is open. The closure of the check valves  64  is dictated by the direction in which the pump assembly  30  operates. 
     As shown in FIG. 5, an active bore  74  and a passive bore  76  intercept the first lateral passageway  52  and are included in an extend activation system  78 . The extend activation system  78  is responsible for extending the rod  24  from a retracted position. Similarly, a retract activation system  80  includes an active bore  82  and a passive bore  84 , which intercept the second lateral passageway  54 . The retract activation system  80  is responsible for retracting the rod  24  from an extended position. The independent operation of the extend and retract activation systems  78 ,  80  is automatically controlled by the direction in which the pump assembly  30  is operated. 
     Also shown in FIG. 5 is a return channel  86  that terminates on both ends at the reservoir  32 . The return channel  86  encapsulates the extend and retract activation systems  78 ,  80  and pump assembly  30 . As such, any hydraulic fluid that escapes its intended conduit at the interface of the main body  20  and port body  22  is captured in the return channel  86  and delivered to the reservoir  32 . A channel  87  connects the active bore  82  of the retract activation system  80  with the return channel  86 . 
     Turning to FIG. 6, shown therein is a plan view of the top surface of the port body  22 . The port body  22  has three port passageways that run through the port body  22 . A pump passageway  88  is used to connect a pump vent  90  with the reservoir  32 . During operation of the pump assembly  30 , excessive pressure can accumulate under the idler and drive gears  70 ,  72  and adversely affect the performance of the pump assembly  30 . Pump vent  90  is positioned below the idler gear  70  and relieves such pressure by returning the accumulated fluid to the reservoir  32  through pump passageway  88  and bore  92 . 
     An upper cylinder passageway  94  and a lower cylinder passageway  96  are in communication with the upper chamber  42  and lower chamber  44  of the cylinder bore  26 , respectively. The upper cylinder passageway  94  is connected to the cylinder bore  26  via bore  98  which extends from the upper cylinder passageway  94  through the port body  22  and main body  20 . The lower cylinder passageway  96  is connected to the lower chamber  44  through bore  100 . Indentation  102  receives the shaft of the idler gear  70 . The port body  22  also has an opening  104  to accept the rod member  24 . 
     FIG. 6 also shows a number of other indentations that combine with the main body  20  to form fluid passageways. Channel  106  connects active bore  74  with the reservoir  32  via drain bore  108 . A drain plug (not shown) can be inserted into drain bore  108  from the bottom of the port body  22  and removed when it is necessary to drain the hydraulic fluid. Channel  110  connects the active bore  82  with the reservoir  32  through return channel  86 . 
     FIG. 7 is an exploded view of the hydraulic actuator  10 , which demonstrates the connection between the main body  20 , the port body  22  and the rod  24 . As shown, the piston member  40  includes various washers and piston rings  110  and a nut  112 . In the preferred embodiment, the port body  22  is attached to the main body  20  through use of a plurality of fasteners (not shown) that extend through attachment bores  114  from below the port body  22  into the main body  20 . Suitable plugs can be used to cover any openings in the actuator  10 . 
     Turning now to FIG. 8, shown therein is a partial left side elevational view of the hydraulic actuator  10  with a cutaway cross-sectional view of the preferred structure of the valve assemblies used by the extend activation system  78 . The extend activation system  78  includes an active valve assembly  114  housed in active bore  74  and a passive valve assembly  116  housed in passive bore  76 . 
     The active valve assembly  114  includes a valve head  118  and a valve stop  120 . The valve head  118  fits tightly in a head seat  122  in the active bore  74  to prevent the passage of hydraulic fluid around the valve head  118 . While closed, the valve stop  120  fits tightly in a stop seat  124  (as shown), thereby prohibiting the movement of fluid across the stop seat  124 . A compression spring  126  is used to hold the active valve assembly  114  in the closed position. 
     The application of pressurized hydraulic fluid to the top surface of the valve head  118  forces the active valve assembly  114  downward, thereby unseating the valve stop  120 . When open, the active valve assembly  114  permits the flow of hydraulic fluid from lower cylinder passageway  96  across the stop seat  124  to the bottom of the valve head  118 . The hydraulic fluid is then conducted through a channel  106  formed at the interface of the main body  20  and port body  22 . 
     Continuing with FIG. 8, unlike the active bore  74 , the passive bore  76  includes an elliptical head seating  128  around a valve head  130 . The elliptical head seating  128  permits the passage of hydraulic fluid across the valve head  130  in the passive valve assembly  116 . While closed, a valve stop  132  fits tightly in a stop seat  134 , thereby prohibiting the movement of fluid across the stop seat  138 . A compression spring  140  is used to hold the passive valve assembly  116  in the closed position. 
     The initial application of pressurized hydraulic fluid between the valve stop  132  and valve head  130  of the passive valve assembly  116  forces hydraulic fluid up and around the valve head  130 . It will be noted that the elliptical head seat  128  permits an equalization of pressure around the valve head  130  of the passive valve assembly  116 . However, when sufficient pressure generates above the valve stop  132 , the passive valve assembly  116  is forced downward into an open position (as shown). In the open position, high pressure hydraulic fluid is allowed to pass through the stop seat  134  into the upper cylinder passageway  94  in the port body  22 . 
     Turning now to FIG. 9, shown therein is a partial left side elevational view of the hydraulic actuator  10  with a cutaway cross-sectional view of the preferred structure of the valve assemblies used by the retract activation system  80 . The retract activation system  80  includes an active valve assembly  142  housed in active bore  82  and a passive valve assembly  144  housed in passive bore  84   
     Like the active valve assembly  114 , the active valve assembly  142  includes a valve head  144  and a valve stop  146 . The valve head  144  fits tightly in a head seat  148  in the active bore  82  to prevent the passage of hydraulic fluid around the valve head  144 . While closed, the valve stop  146  fits tightly in a stop seat  150  (as shown), thereby prohibiting the movement of fluid across the stop seat  150 . A compression spring  152  is used to hold the active valve assembly  142  in the closed position. 
     The application of pressurized hydraulic fluid to the top surface of the valve head  144  forces the active valve assembly  142  downward, thereby unseating the valve stop  146 . When open, the active valve assembly  142  permits the flow of hydraulic fluid from upper cylinder passageway  94  across the stop seat  150  to the bottom of the valve head  144 . The hydraulic fluid is then conducted through the return channel  110  at the interface of the main body  20  and port body  22 . 
     Continuing with FIG. 9, the passive valve assembly  144  is housed in the passive bore  76  and includes an elliptical head seat  154  around a valve head  156 . The elliptical head seat  154  permits the passage of hydraulic fluid across the valve head  156  in the passive valve assembly  144 . While closed, a valve stop  158  fits tightly in a stop seat  160 , thereby prohibiting the movement of fluid across the stop seat  160 . A compression spring  162  is used to hold the passive valve assembly  144  in the closed position. 
     The initial application of pressurized hydraulic fluid between the valve stop  158  and valve head  156  of the passive valve assembly  144  forces hydraulic fluid up and around the valve head  156 . It will be noted that the elliptical head seat  154  permits an equalization of pressure around the valve head  156  of the passive valve assembly  144 . However, when sufficient pressure generates above the valve stop  158 , the passive valve assembly  144  is forced downward into an open position (as shown). In the open position, high pressure hydraulic fluid is allowed to pass through the stop seat  160  into the lower cylinder passageway  96  in the port body  22 . 
     EXTEND OPERATION 
     Referring to the drawings and to FIG. 2 in particular, shown is the hydraulic actuator  10 . Applying voltage from a source, through the power connection  34  drives the pump assembly  30  in one direction and if the polarity is reversed in the opposite direction. To extend the rod  24 , voltage is applied such that the pump assembly drive gear  72  rotates in a counterclockwise direction, when viewed from below. The cooperative rotation of the drive gear  72  and idler gear  70  positively displaces hydraulic fluid present in the pump canals  66 ,  68 . This creates a pressure reduction, which causes fluid to be withdrawn from reservoir  32  through passageway  48  by bypassing the ball check valve  64  in bore  58 . The transfer of fluid from bore  58  to bore  56  through the pump assembly  30  increases pressure against ball check valve  64  of bore  56  causing the ball check valve  64  to close. 
     Turning now to FIG. 10, shown therein is a functional schematic of the extend operation. Path  162  represents the fluid travel from the reservoir  32 , across the ball check valve  64  in main body bore  58  to the pump assembly  30 . High pressure fluid is then pumped along first channel  60  (path  164 ) from the pump assembly  30  to passive valve assembly  116  in passive bore  76 . The high pressure fluid travels around the head seat (not numerically designated) of the passive valve assembly  116  into first lateral passageway  52  (path  166 ) and against the valve head  118  (see FIG. 2) of the active valve assembly  114  in the active bore  74  (path  168 ). When the force exerted by the pressurized fluid on the valve head  118  exceeds the force exerted by the compression spring  126 , the active valve assembly  114  opens. 
     At this stage in the extend operation, the pressure of the hydraulic fluid above the valve head  118  of the active valve assembly  114 , in the first lateral passageway  52  and around the valve head of the passive valve assembly  116  is substantially equal. As the pump assembly  30  continues to displace hydraulic fluid, the pressure in these areas increases until the force exerted by the hydraulic fluid on the top of the valve stop of the passive valve assembly  116  exceeds the force exerted by the compression spring, thereby forcing the passive valve assembly  116  downward into an open position. When the passive valve assembly  114  opens, high pressure fluid travels down passive bore  76  into upper cylinder passageway  94  (path  168 ), up bore  98  and into the upper chamber  42  (path  170 ). 
     The introduction of high pressure fluid into the upper chamber  42  forces the piston  40  and rod  24  down the cylinder bore  26 . As such, any hydraulic fluid remaining in the lower chamber  44  is evacuated through bore  100  into the lower cylinder passageway  96  (path  172 ). The low pressure return is conducted through the lower cylinder passageway  96 , up the active bore  74  and across the open active valve assembly  114 . Generally, the presence of low pressure returning fluid will not close the active valve assembly  114 . The low pressure fluid is returned to the reservoir  32  from the active bore  74  across channel  106  at the interface of the main body  20  and port body  22  (path  174 ). 
     At the extent of the piston stroke, the pressure in the upper chamber  42  may equalize with the pressure exerted against the passive valve assembly  116 , allowing the spring to return the passive valve assembly  116  to a closed position. If excess pressure then accumulates around idler and drive gears  70 ,  72  of the pump assembly  30 , hydraulic fluid can be vented through vent hole  90  to the reservoir  32  through pump passageway  88 . 
     RETRACT OPERATION 
     The rod member  24  is retracted by reversing the polarity of voltage applied to the pump motor  28 , thus causing the drive gear  72  to rotate in a clockwise direction, when viewed from below. The idler gear  70 , which is meshed with the drive gear  72 , then rotates counterclockwise driving the positive displacement gear pump assembly  30 . This creates a pressure reduction, which causes fluid to be withdrawn from reservoir  32  through passageway  48  and bore  56  by passing the open ball check valve  64 . 
     The transfer of fluid from bore  56  to bore  58  through the pump assembly increases the pressure against ball check valve  64  of bore  58  causing the ball check valve  64  to close. 
     Turning now to FIG. 11, shown therein is a functional schematic of the retract operation. Path  176  represents the fluid travel from the reservoir  32 , across the ball check valve  64  in main body bore  56  to the pump assembly  30 . High pressure fluid is then pumped along second channel  62  (path  178 ) from the pump assembly  30  to passive valve assembly  128  in passive bore  84 . The high pressure fluid travels around the head seat  132  of the passive valve assembly  128  (see FIG. 9) into the second lateral passageway  54  (path  180 ) and against the valve head of the active valve assembly  130  in the active bore  82 . When the force exerted by the pressurized fluid on the valve head of the active valve assembly  130  exceeds the force exerted by the compression spring, the active valve assembly  130  opens. 
     At this stage in the retract operation, the pressure of the hydraulic fluid is in equilibrium above the valve head of the active valve assembly  130 , in the second lateral passageway  54  and around the valve head  134  of the passive valve assembly  128 . As the pump assembly  30  continues to displace hydraulic fluid, the pressure in these areas increases until the force exerted by the hydraulic fluid on the top of the valve stop  136  exceeds the force exerted by the spring  140 , thereby forcing the passive valve assembly  128  down into an open position. When the passive valve assembly  128  opens, high pressure fluid travels down passive bore  84  into the lower cylinder passageway  96 , up bore  100  and into the lower chamber  44  (path  182 ). 
     The introduction of high pressure fluid into the lower chamber  44  forces the piston  40  and rod  24  up the cylinder bore  26 . As such, any hydraulic fluid remaining in the upper chamber  42  is evacuated through bore  98  into the upper cylinder passageway  94  (path  184 ). The low pressure return is conducted through the upper cylinder passage way  94 , up the active bore  82  and across the open active valve assembly  130 . The low pressure fluid is returned to the reservoir  32  from the active bore  82  across channel  87  to the return channel  86  at the interface of the main body  20  and port body  22  (path  186 ). 
     When the rod side chamber has reached its maximum volume, the pressure in the rod side chamber  42  may equalize with the pressure exerted against the passive valve assembly  128 , allowing the spring  140  to return the passive valve assembly  128  to a closed position. If excess pressure then accumulates around idler and drive gears  70 ,  72  of the pump assembly  30 , hydraulic fluid can be vented through vent hole  90  to the reservoir through pump passageway  88 . 
     STATIC OPERATION 
     With the rod member  24  at any position and common voltage applied to both armature leads, the pump motor  28  is at rest. Lack of flow causes ball check valves  64  in bores  56  and  58  to lose sealing action. Hydraulic pressure then equalizes throughout the actuator  10 . As this occurs, valve assemblies  114 ,  116 ,  128  and  130  close, blocking fluid flow from either end of cylinder bore  26  causing rod  24  to be locked into place. 
     It will be clear that the present invention is well adapted to attain the ends and advantages mentioned as well as those inherent therein. While a presently preferred embodiment has been described for purposes of this disclosure, numerous changes may be made which will readily suggest themselves to one skilled in the art and which are encompassed in the spirit of the invention disclosed and as defined in the appended claims.
The present invention provides a hydraulic actuator suitable for use in marine and other harsh environments. In the presently preferred embodiment, the hydraulic actuator includes a motor that is coupled to a pump assembly that is configured to displace hydraulic fluid. The hydraulic actuator also includes a cylinder bore that has an upper chamber and a lower chamber which are separated by a movable piston member. Pressure actuated valves are used to regulate the flow of high pressure hydraulic fluid to the cylinder bore. The pressure actuated valves are actuated in response to pressure generated by the pump assembly.