Patent Publication Number: US-6336391-B1

Title: Hydraulic rotating axial piston engine

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of copending International Application Ser. No. PCT/SE98/02218 filed Dec. 12, 1998 which designated the United States, and which claims priority to Swedish Patent Application 9704566-0, filed Dec. 8, 1997. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to hydraulic rotating axial piston engines. 
     BACKGROUND OF THE INVENTION 
     From U.S. Pat. No. 4,934,253, a pump is know that operates in either direction by means of a two part housing, including a housing part and a connection part. The connection part can be mounted in two alternative positions turned substantially through 180° about the center axis of the axial piston engine. The connecting part according to the known device is provided with four connecting holes adapted to be positioned coaxially with corresponding holes in the housing part which results in that the two alternative positions are exactly displaced relative to each other by 180°. This limits the possibilities to design the prior known pump with optimal performance with regard to capacity. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a hydraulic rotating axial piston engine of the above discussed type having increased capacity in either direction of rotation. 
     According to the present invention, a hydraulic rotating axial piston engine is provided having a housing enclosing a cylinder barrel rotatable in two directions. The cylinder barrel has a number of axial cylinders with a number of reciprocating pistons. The pistons reciprocate between two defined end positions, and cooperate with a plate angled relative to a rotational axis for the barrel in order to obtain the reciprocating movement. The cylinders have ports alternatively acting as inlet and outlet ports. The housing has at least one inlet and outlet channel, each channel having a kidney shaped port, facing towards the ports of the cylinders and communicating with a number of the cylinder ports. 
     The housing has at least two parts, one of said housing parts defining turning positions of the barrel in the end positions of the pistons. A second of the housing parts defining the turning positions of the kidney shaped ports, relative to the end positions. The first and second parts of the housing being alternatively positionable in two different turning positions for the chosen rotational direction of the cylinder barrel. The two turning positions of the first and second housing parts being at least two different positions deviating from a relative turning angle of 0° or 180°, and preferably deviating 6° to 30° for one rotational direction of the cylinder barrel, and 186° to 210° for the other rotational direction of the cylinder barrel, so that the kidney shaped ports are displaced a predetermined extent in the rotational direction. 
     The housing parts preferably have holes in appropriate locations, and fasteners are used to fasten housing parts together in the relative rotational position. 
     Further features of the present invention will become apparent to those skilled in the art upon reviewing the following specification and attached drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described in more detail with reference to a preferred embodiment shown in the drawings, in which: 
     FIG. 1 shows a side view of a pump according to the present invention; 
     FIG. 2 is an end view of the pump; 
     FIG. 3 is an axial section of the pump; 
     FIG. 4 is a plan view of a connecting part of the pump as seen separately from the inside; 
     FIG. 5 is an end view of a modified embodiment of a housing part of the pump according to FIG. 1; and 
     FIG. 6 is an end view of the connecting part of the pump, showing two alternative turning positions of the connecting part. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The hydraulic rotating axial piston engine according to the present invention is shown as an embodiment in FIGS. 1 and 2 as an axial piston pump, indicated generally at  1 , having a housing, indicated generally at  2 . The housing  2  is comprised by at least two parts, in the shown example three parts, namely a housing part  3  and a connecting part  4 . The connecting part  4  has connecting openings, namely an inlet opening  5  and an outlet opening  6  for connecting input and output conduits for hydraulic fluid to the pump. A third part  7  of the housing is a support part for the input shaft  8  which is provided to be connected with a drive motor, not shown. 
     In FIG. 3 the general parts of the pump are shown. The pump is of a so-called bent axis type, having a rotational axis  9 , forming a first rotational axis for the input shaft  8  and a second rotational axis  10  inclined relative to the first axis by an angle of 40°, for example. The second rotational axis  10  is an axis for a cylinder barrel  11  which is rotatably journalled in the housing. The cylinder barrel  11  has a number of axially extending pistons  12 , movable axially, i.e. substantially in parallel with the axis  10  in a reciprocating movement in a corresponding number of cylinders  13 . Cylinders  13  also extend axially with the axis  10 , and are circumferentially equally-spaced along a circle line  14  (see FIG.  5 ). Each cylinder  13  has a fluid passage  15  with a port  16  in the planar end surface  17  of the cylinder barrel  11 . Each port  16  has its largest length along the peripheral circle line  14 , and is kidney-shaped. 
     From FIG. 3 it is further apparent that each piston  12  has a piston rod  18  with a spherical head  19 , and is supported in a spherical bearing surface recess  20  in a swash plate  21 . Swash plate  21  forms an integral part of the input shaft  8 . The spherical recesses  20  are rotatable around a radial plane which is angled relative to the radial plane of the cylinder barrel  11 , which results in the reciprocating movement of the pistons  12  and the pumping action according to a prior known principle, in order to create vacuum, i.e., suction in the inlet opening  5  and pressure in the outlet opening  6  (see for example, U.S. Pat. No. 5,176,066). 
     Synchronizing means are arranged in order to synchronize the rotational movements of the cylinder barrel  11  with the rotation of the swash plate  21 . In the shown example the synchronizing means is made in the form of gear teeth formed by a tooth wheel rim  22  on the cylinder barrel  11  cooperating with a tooth wheel  23  of the input shaft  8 . A support pin  24  supports the cylinder barrel along the axis  10  cooperating with a shaft  25  which forms the rotational axis  10 . Shaft  10  projects through a bore  26  of the cylinder barrel and is supported in a bore  26 ′ of the connecting piece  4  of the housing. 
     FIG. 4 shows the connecting part  4  of the housing separately and from the inside. The connecting part  4  has on its inside a substantially planar, circular surface  27  which in the mounted position is facing the planar surface  17  of the cylinder barrel  11 . The two planar surfaces  17 ,  27  are arranged to contact each other with a sealing fit. On its inside the connecting part  4  is provided with one inlet port  28  and one outlet port  29 , which are kidney-shaped. The inlet port  28  communicates through a channel with the inlet opening  5 , and the outlet port  29  communicates through a separate channel with the outlet opening  6  on the outside of the connecting part  4 . The inlet and outlet ports  28 ,  29  extend along a peripheral circle line  30  which has a corresponding radius as the circle line  14  of the openings  16  of the cylinder barrel  11 . The inlet and outlet opening  28 ,  29  extend on each half of said circle line  30 , separated by a main plane  31  extending through the connecting part  4 . The inlet and outlet ports  28 ,  29  are further divided by a second main plane  32  extending 90° relative to the first main plane  31 . One of these main planes is normally a symmetrical plane for the connecting part  4 . The inlet and outlet ports  28 ,  29  further extend along the circle line  30  along a predetermined peripheral angle which in the shown example is somewhat larger for the inlet opening  5  than for the outlet opening  6 , and are arranged so that simultaneously more than one cylinder port  16  communicates with the inlet port  28  and the inner outlet port  29 , respectively. 
     According to the present invention, the connecting part  4  of the housing  2  is arranged to be mounted in at least two alternative positions in order to enable the pump to be operated by rotating the input shaft in two alternative directions of rotation. According to the present invention, it has been discovered that the flow capacity of the pump can be increased by extending the kidney-shaped inlet port  28  of the connecting part  4  in the chosen rotational direction of the cylinder barrel so that the cylinder ports  16  are open to the kidney-shaped inlet port  28  even when the corresponding piston  12  passes its lower dead center. According to the present invention, this is accomplished by the two alternative mounting positions of the connecting part  4  deviating from each other by a relative turning angle α of 6° to 30°, or alternatively, a turning angle β of 186° to 210° (that is, 180° from α), so that the kidney-shaped ports  28 ,  29  are displaced a predetermined extent in the respective rotational direction. This is preferably accomplished by enabling the fastening means  33 ,  34 ,  35 ,  36  between the connecting part  4  and the housing part  3  to fasten the connecting part in at least two alternative positions, so that the connecting part can be displaced according to the above intervals. 
     Main plane  37  is defined by the upper and lower dead centers of the pistons  12 , and main plane  31  is corresponding to this. Consequently, the main planes  31 ,  32  can be in two alternative positions displaced by substantially half of the above intervals relative to the two main planes  37 ,  38  defined for the housing part (see FIGS.  5  and  6 ). Main plane  38  extends 90° relative to main plane  37 . FIG. 6 shows the different mounting positions of the connecting part  4 . All main planes  31 ,  32 ,  37 ,  38  are crossing in the rotational axis of the cylinder barrel  11 . 
     The fastening means  33 - 36  are preferably screws extending through two alternative sets of holes  39 - 42  and  43 - 46 , respectively in the connecting part  4  and one set of holes  45 - 48  in the housing part  3 , as seen in FIGS. 4 and 5; or reversely, as seen in FIG.  6 . Consequently in the embodiment of FIG. 6, the connecting part  4  has one set of holes  39 ′- 42 ′ and the housing part  3  has two sets of holes (not shown). In the embodiment shown in FIG. 2, the fastening means  33 - 36  with their alternative sets of holes  39 - 42  and  43 - 46  lack symmetry with respect to their mutual positions in the connecting part as well as the housing part  3 . Merely two alternative positions are possible in this embodiment. In the modified embodiment shown in FIGS. 4-6, all holes are symmetrical with respect to their mutual positions. Four alternative positions are possible in this embodiment. Alternatively, the double holes can be replaced by oblong holes enabling that the connecting part can be positioned in a large number of positions within the defined angular intervals. 
     In the above embodiments the engine has been described as a pump, having an input shaft for a motor. The same principle can be used for an engine acting as a motor, driven by a hydraulic fluid, whereas the shaft  8  acts as an output shaft for driving a rotating engine, for example a drilling engine. 
     The principles, preferred embodiments and modes of operation of the present invention have been described in the foregoing specification. The invention which is intended to be protected herein should not, however, be construed as limited to the particular form described as it is to be regarded as illustrative rather than restrictive. Variations and changes may be made by those skilled in the art without departing from the scope and spirit of the invention as set forth in the appended claims.