Abstract:
The present invention relates to the field of rotary actuators. Specifically, the present invention relates to rotary actuators comprising a rotatable top piston assembly and a stationary bottom piston assembly wherein rotation of the top piston assembly can be caused by pressurizing one or more cavities between the top and bottom piston assemblies.

Description:
PRIORITY INFORMATION  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/658,254, filed on Mar. 3, 2005. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field Of The Invention  
         [0003]     The present invention relates to the field of rotary actuators. Specifically, the present invention relates to rotary actuators comprising a rotatable top piston assembly and a stationary bottom piston assembly wherein rotation of the top piston assembly can be caused by pressurizing one or more cavities between the top and bottom piston assemblies.  
         [0004]     2. Description Of The Prior Art  
         [0005]     A prior art rotary actuator is disclosed in U.S. Pat. No. 5,235,900 to Garceau. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  is an exploded isometric view of a first embodiment of the present invention.  
         [0007]      FIG. 2  is a top internal view of a first embodiment of the present invention excluding the upper housing in a first position.  
         [0008]      FIG. 3  is a top view of a first embodiment of the present invention in a second position.  
         [0009]      FIG. 4  is a partially exploded isometric view of a first embodiment of the present invention.  
         [0010]      FIG. 5  is an exploded isometric view of a second embodiment of the present invention.  
         [0011]      FIG. 6  is a top internal view of a second embodiment of the present invention excluding the upper housing in a first position.  
         [0012]      FIG. 7  is a top view of a second embodiment of the present invention in a second position.  
         [0013]      FIG. 8  is a partially exploded isometric view of a second embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]     Two embodiments described herein are a two piston embodiment comprising one upper piston and one lower piston, and a four piston embodiment comprising one pair of upper pistons and one pair of lower pistons. Those of ordinary skill in the art will understand that additional embodiments comprising equal numbers of upper pistons and lower pistons may be made using the principals disclosed herein. For each such embodiment, the number of pressurization cavities will equal the number of pistons.  
         [0015]     A first embodiment to the present invention is the four piston embodiment depicted in  FIGS. 1-4 . This embodiment comprises a lower housing  18  comprising a central channel, a mounting surface  17  and an outer wall  19 . In a preferred embodiment, the lower housing is cylindrical.  
         [0016]     This embodiment of the invention further comprises a first lower piston  13  attached to, and extending above, the mounting surface, and a second lower piston  15  attached to, and extending above, the mounting surface diametrically opposite the first lower piston. The term “diametrically opposite”, as used herein, is used in its broadest sense. It encompasses two pistons that are located on opposite sides of an axis which bisects the lower housing into two regions of equivalent area. Where the lower housing is cylindrical, such an axis would define the diameter of the housing. In a preferred embodiment, the first and second lower pistons are cylindrical. In another preferred embodiment, the first and second lower pistons are attached to the mounting surface by pins  11 . As shown in  FIGS. 1 and 4 , the lower housing comprises inner seal ring  21  located radially inside the first and second lower pistons, and outer seal ring  22  located radially outside the first and second lower pistons. In a preferred embodiment, the inner and outer seal rings have a dovetailed configuration to enable them to resist collapsing into the piston bore from operational pressure.  
         [0017]     This embodiment further comprises a rotatable central shaft  20  extending upward through the central channel and an upper housing  10  attached to the shaft above the lower housing. In a preferred embodiment, the upper housing has an outer diameter equal to the outer diameter of the lower housing.  
         [0018]     This embodiment further comprises a first upper piston  12  attached to, and extending below, the upper housing at a location between the first and second lower pistons so as to define a first pressure cavity  32  between the itself and the first lower piston, and to define a second pressure cavity  34  between the itself and the second lower piston. This embodiment further comprises a second upper piston  14  attached to, and extending below, the upper housing at a location between the first and second lower pistons, diametrically opposite the first upper piston, so as to define a third pressure cavity  36  between the itself and the first lower piston, and to define a fourth pressure cavity  38  between the itself and the second lower piston. In a preferred embodiment, the first and second upper pistons are cylindrical. In another preferred embodiment, the cross sectional area of the first upper piston, second upper piston, first lower piston, and second lower piston are substantially equal. In another preferred embodiment, the first and second upper pistons are attached to the upper housing by pins  11 .  
         [0019]     This embodiment further comprises a first pressurization line  26  extending through the outer wall to the side of the first lower piston adjacent the first pressure cavity, such that fluid can be injected into the first pressure cavity  32  through the first pressurization line to cause the first upper piston to move away from the first lower piston. This embodiment further comprises a second pressurization line  28  extending through the outer wall to the side of the first lower piston adjacent the third pressure cavity, such that fluid can be injected into the third pressure cavity  36  through the second pressurization line to cause the second upper piston to move away from the first lower piston. In a preferred embodiment, the first and second pressurization lines have substantially equivalent internal diameters.  
         [0020]     This embodiment further comprises a third pressurization line  27  extending through the outer wall to the side of the second lower piston adjacent the second pressure cavity, such that fluid can be injected into the second pressure cavity  34  through the third pressurization line to cause the first upper piston to move away from the second lower piston. This embodiment further comprises a fourth pressurization line  29  extending through the outer wall to the side of the second lower piston adjacent the fourth pressure cavity, such that fluid can be injected into the fourth pressure cavity  38  through the fourth pressurization line to cause the second upper piston to move away from the second lower piston. In a preferred embodiment, the third and fourth pressurization lines have substantially equivalent internal diameters. In another preferred embodiment, the first, second, third, and fourth pressurization lines have substantially equivalent internal diameters.  
         [0021]     In  FIG. 2 , the first upper piston  12  and the second upper piston  14  are shown in a first position with respect to the first lower piston  13  and the second lower piston  15 . In this first position, pressure cavities  32 ,  34 ,  36 , and  38  are of substantially equivalent size. If the first pressure cavity  32  or the fourth pressure cavity  38  is pressurized by injecting fluid through the first pressurization line  26  or the fourth pressurization line  29 , respectively, the resulting pressurization will result in a counterclockwise rotation of the first and second upper pistons relative to the first and second lower pistons, resulting in the pistons being located in a second position as shown in  FIG. 3 .  
         [0022]     In a preferred embodiment, the first pressure cavity  32  and the fourth pressure cavity  38  are simultaneously pressurized by injecting fluid through the first pressurization line  26  and the fourth pressurization line  29  to cause rotation of the first upper piston  12  and the second upper piston  14  from the first position shown in  FIG. 2  to the second position shown in  FIG. 3 . In the pressurization operations described above, when fluid is injected into first pressurization line  26 , it is vented through the second pressurization line  28 . When fluid is injected into the fourth pressurization line  29 , it is vented through the third pressurization line  27 .  
         [0023]     When the pistons are in the second position shown in  FIG. 3 , clockwise rotation of the first upper piston  12  and the second upper piston  14  can be caused by pressurizing the third pressure cavity  36  and/or the second pressure cavity  34  through the second pressurization line  28  and/or the third pressurization line  27 , respectively. Alternatively, these lines can be pressurized simultaneously to achieve this clockwise rotation. When the second and third pressurization lines are operated in this manner, fluid is vented through the first pressurization line  26  and the fourth pressurization line  29 , respectively.  
         [0024]     Persons of ordinary skill in the art will understand that a source of pressurization fluid, such as hydraulic fluid, may be coupled to each pressurization line via a control valve system so that the pressurization and venting operations described herein may be selectively achieved and reciprocated by operation of flow control valves installed in fluid communication between the reservoir of pressurization fluid and the first, second, third, and fourth pressurization lines. For a given embodiment having a set number of pistons, the longitudinal length of the pistons determines the pistons stroke and the degrees of rotation involved in traveling from a first position to a second position. As the number of pistons increases, the magnitude of piston stroke decreases for the same diameter rotary actuator of the present invention.  
         [0025]     This embodiment further comprises a bearing  24  mounted to the shaft and the upper housing. In a preferred embodiment, the bearing is a thrust bearing, as shown in  FIG. 1 .  
         [0026]     A second embodiment of the present invention is the two piston embodiment disclosed in  FIGS. 5-8 . This embodiment comprises a lower housing  48  comprising a central channel, a mounting surface  47  and an outer wall  49 .  
         [0027]     This embodiment further comprises a lower piston  43  attached to, and extending above, the mounting surface. This embodiment further comprises a rotatable central shaft  50  extending upward through the central channel, and an upper housing  40  attached to the shaft above the lower housing  48 . The lower housing  48  comprises an inner seal ring  41  located radially inside the first and second lower pistons, and an outer seal ring  42  located radially outside the first and second lower pistons. In a preferred embodiment, the inner and outer seal rings have a dovetailed configuration to enable them to resist collapsing into the piston bore from operational pressure.  
         [0028]     This embodiment further comprises an upper piston  32  attached to, and extending below, the upper housing at a location diametrically opposite the lower piston so as to define a first pressure cavity  62  and a second pressure cavity  64  between itself and the lower piston, as shown in  FIG. 6 .  
         [0029]     This embodiment further comprises a first pressurization line  66  extending through the outer wall to the side of the lower piston adjacent the first pressure cavity  62 , such that fluid can be injected into the first pressure cavity  62  through the first pressurization line  66  to cause the upper piston to move away from the lower piston, such that the volume of first pressure cavity  62  increases, as shown in  FIG. 7 .  
         [0030]     This embodiment further comprises a second pressurization line  68  extending through the outer wall to the side of the lower piston adjacent the second pressure cavity  64 , such that fluid can be injected into the second pressure cavity  64  through the second pressurization line  68  to cause the upper piston to move away from the lower piston, such that the volume of second pressure cavity  64  increases.  
         [0031]     Persons of ordinary skill in the art will understand that a source of pressurization fluid, such as hydraulic fluid, may be coupled to each pressurization line in this two piston embodiment via a control valve system so that the pressurization and venting operations described herein may be selectively achieved and reciprocated by operation of flow control valves installed in fluid communication between the reservoir of pressurization fluid and the first and second pressurization lines. In a preferred embodiment, the first and second pressurization lines have substantially equivalent internal diameters. This embodiment further comprises a bearing  54  mounted to the shaft and the upper housing. In a preferred embodiment, the bearing is a thrust bearing, as shown in  FIG. 5 .  
         [0032]     The foregoing disclosure and description of the inventions are illustrative and explanatory. Various changes in the size, shape, and materials, as well as in the details of the illustrative construction and/or a illustrative method may be made without departing from the spirit of the invention.