Abstract:
An electro-hydraulic actuator includes a hydraulic pump, an electric motor operatively connected to the hydraulic pump and operable for driving the pump, an actuator moveable in response to fluid flow from the pump, and a housing for the pump, electric motor and actuator. The housing has a base member that is adapted to be modified into various configurations for forming an attachment interface for mounting of the electro-hydraulic actuator.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of the filing date of U.S. Provisional Patent Application Ser. No. 60/954,391 filed Aug. 7, 2007, the disclosure of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     This invention relates to an electro-hydraulic actuator. More particularly, this invention relates to an electro-hydraulic actuator in which the housing includes a base member that is adapted to be modified into various mounting configurations. 
     BACKGROUND OF THE INVENTION 
     Electro-hydraulic actuators are generally known. A typical electro-hydraulic actuator includes an electric motor that drives a hydraulic pump to move fluid from a reservoir to a hydraulic actuator for actuating the actuator. When the electric motor is driven in a first rotational direction, the hydraulic fluid moved by the hydraulic pump extends a rod of the actuator. When the electric motor is driven in a second rotational direction, opposite the first rotational direction, the hydraulic fluid moved by the hydraulic pump retracts the rod of the actuator. 
     The components of an electro-hydraulic actuator are supported in a housing. The housings of many known electro-hydraulic actuators include a first portion for the actuator and a second portion, connected to the first portion, for the electric motor, hydraulic pump, and reservoir. 
     Some electro-hydraulic actuators include an attachment interface for use in mounting the housing to another structure. The attachment interface is cast as part of the housing. For example, one known electro-hydraulic actuator includes a male clevis that is cast as a finished part with the housing. With known electro-hydraulic actuators, each unique attachment interface requires unique tooling for the manufacture of the housing. 
     SUMMARY OF THE INVENTION 
     The present invention relates to an electro-hydraulic actuator. The electro-hydraulic actuator comprises a hydraulic pump, an electric motor, an actuator, and a housing for the pump, electric motor and actuator. The electric motor is operatively connected to the hydraulic pump and is operable for driving the pump. The actuator is moveable in response to fluid flow from the pump. The housing has a base member that is adapted to be modified into various configurations for forming an attachment interface for mounting of the electro-hydraulic actuator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an electro-hydraulic actuator constructed in accordance with the present invention; 
         FIG. 2  is an elevation view of the electro-hydraulic actuator of  FIG. 1 ; 
         FIG. 3  is an enlarged view of a portion of  FIG. 2  and illustrates a base member of the housing; 
         FIGS. 4A-4D  illustrate various configurations of attachment interfaces that may be formed from the base member of the electro-hydraulic actuator of the present invention; 
         FIG. 5  illustrates the electro-hydraulic actuator with the base member completely removed; 
         FIGS. 6A-6B  illustrate an alternative attachment interface that may be formed from the base member of the electro-hydraulic actuator of the present invention with  FIG. 6A  being a partial sectional top view and  FIG. 6B  being an elevational view; and 
         FIG. 7  is a schematic illustration of an electro-hydraulic actuator. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 7  is a schematic illustration of an electro-hydraulic actuator  10 . The electro-hydraulic actuator  10  includes an electric motor  12  that is operatively coupled to a hydraulic pump  14 . The electric motor  12  is operable for driving the hydraulic pump  14  in opposite first and second rotational directions for driving the hydraulic pump. The hydraulic pump  14  draws fluid from a reservoir  16  and provides the fluid to an actuator  18 . The actuator  18  includes a piston  24  that is movably mounted within a cylinder bore  26 . The piston  24  divides the cylinder bore  26  into first and second chambers  28  and  30 , respectively. A rod  32  of the actuator  18  which is affixed to or integral to the piston  24  extends through the second chamber  30  and outwardly of a housing  40  ( FIG. 1 ) of the electro-hydraulic actuator  10 . 
     The electro-hydraulic actuator  10  is operable for extending or retracting the rod  32  relative to the housing  40  for causing relative movement of two structures, one attached to the housing and the other attached to the rod. To extend the rod  32  of the electro-hydraulic actuator  10 , the electric motor  12  is operated to drive the hydraulic pump  14  in a first rotational direction causing hydraulic fluid drawn from the reservoir  16  to be directed into the first chamber  28  of the actuator  18 . The fluid directed into the first chamber  28  creates a pressure differential between the first and second chambers  28  and  30  of the actuator  18  that moves the piston  24  to increase the volume of the first chamber  28  and decrease the volume of the second chamber  30 , thus extending the rod  32 . To retract the rod  32 , the electric motor  12  is operated to drive the hydraulic pump  14  in a second rotational direction, opposite the first rotational direction, causing hydraulic fluid drawn from the reservoir  16  to be directed into the second chamber  30  of the actuator  18 . The fluid directed into the second chamber  30  creates a pressure differential in which the pressure in the second chamber is higher than that in the first chamber  28 . As a result of the differential pressure, the piston  24  moves to increase the volume of the second chamber  30  and decrease the volume of the first chamber  28 , thus retracting the rod  32 . 
       FIG. 1  illustrates an assembled electro-hydraulic actuator  10  constructed in accordance with the present invention. As shown in  FIG. 1 , the electro-hydraulic actuator  10  includes a housing  40 . The housing  40  includes (i) an actuator portion  42  having opposite first and second ends  44  and  46  ( FIG. 2 ), respectively, and (ii) a drive device portion  50  having opposite first and second ends  52  and  54 , respectively. As best shown in  FIG. 2 , the actuator portion  42  and drive device portion  50  of the housing  40  are interconnected adjacent their respective second ends  46  and  54 . Fluid flow conduits located internal to the housing  40  extend between the actuator portion  42  and the drive device portion  50 . Flow control devices, such as valves, may be associated with these fluid flow conduits for controlling fluid flow through the housing.  FIGS. 1-3  illustrate one of the valves at reference numeral  56 . 
     The drive device portion  50  of the housing  40  supports the drive components of the electro-hydraulic actuator  10 . The drive components include at least the electric motor  12  and a hydraulic pump  14 . In an exemplary embodiment, the hydraulic pump  14  is a gerotor type pump that is located within the drive device portion  50  of the housing  40 . Those skilled in the art will recognize that any one of various types of hydraulic pumps may be used. In the embodiment of  FIG. 1 , the reservoir  16  is also located within the drive device portion  50  of the housing  40  adjacent the second end  54 . Also, as illustrated, the housing of the electric motor  12  extends outwardly of a first end  52  of the drive device portion  50  of the housing  40 . Those skilled in the art will recognize that a separate reservoir, such as a plastic reservoir, may be used with the electro-hydraulic actuator  10 . Further, the motor  12  may be located, if desired, within the drive device portion  50  of the housing  40 , in which case the drive device portion may be elongated relative to that illustrated. For simplifying the packaging, the drive device portion  50  of the electro-hydraulic actuator  10  illustrated includes an integral reservoir  16  that is cast in the drive device portion during casting of the housing  40 . 
     An interior surface of the actuator portion  42  of the housing  40  defines the cylinder bore  26  of the electro-hydraulic actuator  10 . The cylinder bore  26  extends into the actuator portion  42  of the housing  40  from the first end  44  and terminates at an end wall (not shown) located a spaced distance from the second end  46 . Various sealing components and closure methods may be used for closing the opening to the cylinder bore  26  located on first end  44  of the actuator portion  42  and sealing about the rod  32 , when installed. The cylinder bore  26  may be cast in the actuator portion  42  during casting of the housing  40  and later honed to its desired diameter. 
     As set forth above, a piston  24  is located in the cylinder bore  26  of the assembled electro-hydraulic actuator  10  for dividing the cylinder bore into the first and second chambers  28  and  30 . Various known sealing methods for sealing the circumference of the piston  24  may be used to prevent fluid flow between the first and second chambers  28  and  30 . Movement of the piston  24  upward, as viewed in  FIG. 1 , results in an extension of the rod outwardly of the first end  44  of the actuator portion  42 . Movement of the piston  24  downward, as viewed in  FIG. 1 , results in a retraction of the rod  32  relative to the first end  44  of the actuator portion  42  of the housing  40 . 
     A base member  60  extends outwardly of the second end  46  of the actuator portion  42  of the housing  40 . Alternatively, the base member  60  may extend outwardly of the second end  54  of the drive device portion  50  of the housing  40 . The base member  60  is a monolithic structure that is formed as one piece with the remainder of the housing  40 . Preferably, the base member  60  is formed as one piece with the housing  40  during a casting process in which the housing as a whole is formed. Typically, the housing  40  is cast from aluminum. 
       FIG. 3  illustrates an enlarged view of a portion of  FIG. 2  and illustrates the base member  60  of the housing  40 . As illustrated in  FIG. 2 , the base member  60  extends axially outwardly from the second end  46  of the actuator portion  42  of the housing  40  in a direction parallel to a centerline  66  of the actuator portion. Thus, the cylinder bore  26 , which is also centered along the centerline  66  of the actuator portion  42 , and the base member  60  are coaxial. The base member  60  includes a cylindrical portion  70  located immediately adjacent the second end  46  of the actuator portion  42  and a tapered end portion  72  located a spaced distance away from the second end  46 . The base member  60  is a solid structure. The axial distance from the second end  46  of the actuator portion  42  by which the base member  60  extends may be varied. The base member  60  enables late stage configuration of the electro-hydraulic actuator  10  by enabling adaptation of the housing  40  to include any one of various attachment interface configurations. 
     The housing  40  of the electro-hydraulic actuator  10  may be a short bore housing or a long bore housing. A short bore housing is a housing in which the axial distance between the first and second ends  44  and  46  of the actuator portion  42  is relatively short, such as having a distance of approximately four inches. A long bore housing is a housing in which the actuator portion  42  of the housing  40  is relatively long, such as eight inches. The base member  60  may be used with various configurations and various sizes of the actuator portion  42  of the housing  40 . For example, it may be used with any bore size and any stroke size. 
       FIGS. 4A-4D  illustrate various configurations of attachment interfaces that may be formed from the base member  60  of the electro-hydraulic actuator  10  of the present invention. Each of the various configurations of the attachment interface illustrated in  FIGS. 4A-4D  is formed by machining the base member  60  into the desired configuration.  FIG. 4A  illustrates a female clevis  80 . In forming the female clevis  80 , a groove  82  is machined in the base member  60  to bisect the base member. A through hole  84  is machined into the base member  60  in a direction perpendicular to the centerline  66  of the actuator portion  42 . The groove  82  is sized for receiving a male clevis and, the through hole  84  is sized for receiving a locking pin.  FIG. 4B  illustrates a male clevis  90 . To configure the base member  60  into a male clevis  90 , a through hole  92  is machined into the base member  60  in a direction perpendicular to the centerline  66 . Also, flats  94  are formed on opposite sides of the male clevis  90  for sizing the male clevis for insertion into a groove of female clevis.  FIG. 4C  illustrates a threaded stud  100 . To form the base member  60  into a threaded stud  100 , the base member  60  is machined into a cylindrical member having an outer diameter equal to that of the outer thread diameter of the stud  100  and threads thereafter are machined into the outer surface of the cylinder.  FIG. 4D  illustrates a threaded bore  110  formed in the base member  60 . To form the attachment interface of  FIG. 4D , the base member  60  is machined to the desired dimensions and a threaded bore is machined into an end surface. 
     In  FIG. 5 , the base member  60  is completely removed from the housing  40 . In certain applications an end user may prefer to have no attachment interface extending outwardly from a second end  46  of the actuator portion  42  of the housing  40 . In such case, the base member  60  may be machined completely off of the housing  40  and attachment features, such as threaded blind holes  112  may be machined into the second end  46  of the actuator portion  42 . 
       FIGS. 6A and 6B  illustrate another advantage of including the base member  60  with the housing  40  of the electro-hydraulic actuator  10 . The cylindrical portion  70  of the base member  60  enables the attachment interface to be formed at any one of various angles relative to the remainder of the housing  40 . The reference to angles in  FIGS. 6A and 6B  are references relative to a plane that extends through the centerlines of both the drive device portion  50  and the actuator portion  42  of the housing  40 . The plane is shown at reference numeral  120  in  FIG. 6A . In prior art electro-hydraulic actuators, each angle of the attachment interface, such as a female clevis, required casting a separate housing. Each housing requires dedicated tooling. The base member  60  of the present invention allows a single housing  40  to be cast and thereafter, machined into the desired configuration including the angle of orientation.  FIGS. 6A and 6B  illustrate a female clevis  124  with a groove  126  that is at an angle offset relative to the plane  120 .  FIG. 4A  illustrates a female clevis  80  with a groove  82  that is parallel to the plane  120 . Both the female clevis  80  of  FIG. 4A  and the female clevis  124  of  FIG. 6A  are formed by machining the base member  60 . 
     As stated earlier, the inclusion of the base member  60  enables late stage configurability of the electro-hydraulic actuator  10 . The electro-hydraulic actuator  10  may be completely assembled prior to configuration of the attachment interface from the base member  60 . For example, the electric motor  12 , pump  14 , reservoir  16  and all relevant valving, as well as the piston  24  and rod  32  may all be built into the electro-hydraulic actuator  10  prior to configuration of the attachment interface from the base member  60 . The inclusion of the base member  60  advantageously enables stocking of only a single unit for each bore size and stroke size electro-hydraulic actuator  10  offered. This reduces inventory relative to that required with prior art designs in which a different part number and different tooling is required for the formation of each variation of the attachment interface for the housing. 
     According to one method of manufacturing the electro-hydraulic actuator  10  of the present invention, the housing  40  is cast as a single monolithic piece including the actuator portion  42 , the drive device portion  50  and the base member  60 . The housing  40  is appropriately honed to complete the cylinder bore  26  and all desired machining for receptacles for valving and other devices is completed. The electro-hydraulic actuator  10  then is assembled by placing the piston  24  in the cylinder bore  26  and appropriately closing the opening to the cylinder bore and sealing about the rod  32 . The desired valving is inserted into the machined receptacles in the housing  40 . The electric motor  12  is drivingly attached to the hydraulic pump  14  and the pump and motor are attached to the drive device portion of the housing  40 . Such connection may be by threading or any other means. Appropriate amounts of fluid are inserted into the reservoir  16  of the housing  40  and the reservoir is appropriately plugged and sealed. The fully assembled electro-hydraulic actuator  10  then may be stocked in inventory until an order is received indicating the desired configuration of the attachment interface. After receipt of the order from the customer, the base member  60  of the housing  40  may be machined into the desired attachment interface configuration. 
     Although the principles, embodiments and operation of the present invention have been described in detail herein, this is not to be construed as being limited to the particular illustrative forms disclosed. They will thus become apparent to those skilled in the art that various modifications of the embodiments herein can be made without departing from the spirit or scope of the invention.