Piston assembly

Abstract

A hydraulic pump includes a housing, at least two pistons mounted to the housing to rotate relative to the housing, and a transition arm coupled to each of the pistons to rotate therewith. The transition arm is set at a predetermined angle relative to a longitudinal axis of the pump. An adjustment mechanism sets the transition arm at the predetermined angle. A cylinder is mounted within the housing to rotate relative to the housing and defines pump cavities for receiving the pistons. A face valve defines inlet and outlet channels in fluid communication with the pump cavities. An apparatus for varying the output volume of a piston assembly includes at least two pistons, a transition arm coupled to each of the at least two pistons, and a rotatable member. The transition arm includes a nose pin, and the rotatable member is coupled to the transition arm nose pin. A radial position of the nose pin relative to an axis of rotation of the rotatable member is adjustable while the rotatable member remains axially stationary.

1 . A hydraulic pump, comprising: 
 a housing,    at least two pistons mounted to the housing to rotate relative to the housing, and    a transition arm coupled to each of the at least two pistons to rotate therewith.    
   
   
       2 . The hydraulic pump of  claim 1  wherein the at least two pistons are double ended pistons.  
   
   
       3 . The hydraulic pump of  claim 2  wherein each double ended piston has a first end and a second end and the transition arm is coupled to each of the double ended pistons between the first and second ends.  
   
   
       4 . The hydraulic pump of  claim 1  wherein the transition arm is set at a predetermined angle relative to a longitudinal axis of the pump.  
   
   
       5 . The hydraulic pump of  claim 1  further comprising an adjustment mechanism for setting the transition arm at a predetermined angle.  
   
   
       6 . The hydraulic pump of  claim 5  wherein the adjustment mechanism comprises first and second meshing gears.  
   
   
       7 . The hydraulic pump of  claim 6  wherein the first and second meshing gears are configured such that linear movement of the first gear causes rotary movement of the second gear, the second gear being coupled to the transition arm such that rotary movement of the second gear adjusts the predetermined angle of the transition arm.  
   
   
       8 . The hydraulic pump of  claim 1  further comprising a cylinder mounted within the housing to rotate relative to the housing and defining pump cavities for receiving the at least two pistons.  
   
   
       9 . The hydraulic pump of  claim 8  further comprising a face valve defining inlet and outlet channels in fluid communication with the pump cavities.  
   
   
       10 . The hydraulic pump of  claim 9  wherein each of the inlet and outlet channels includes a first section and a second section, the first section being located radially outward of the second section.  
   
   
       11 . The hydraulic pump of  claim 9  further comprising a face plate positioned between the face valve and the at least two pistons, a first end of each of the at least two pistons bearing against the face place, the face plate defining flow channels.  
   
   
       12 . The hydraulic pump of  claim 9  wherein the at least two pistons are double ended pistons each having a first end opposing the face valve and a second end spaced from the face valve, the pump including a cylinder mounted within the housing to rotate relative to the housing and defining pump cavities for receiving the at least two pistons, the cylinder defining a fluid channels providing fluid communication between the face valve and the second end of the pistons.  
   
   
       13 . The hydraulic pump of  claim 1  further comprising a face plate against which a first end of each of the at least two pistons bear.  
   
   
       14 . The hydraulic pump of  claim 1  wherein the transition arm has a first arm coupled to a first of the at least two pistons, and a second arm coupled to a second of the at least two pistons.  
   
   
       15 . The hydraulic pump of  claim 14  further comprising a first joint coupling the first arm to the first piston, and a second joint coupling the second arm to the second piston.  
   
   
       16 . The hydraulic pump of  claim 15  wherein the first and second joints are each configured to provide at least three degrees of freedom.  
   
   
       17 . The hydraulic pump of  claim 1  further comprising a universal joint supporting the transition arm.  
   
   
       18 . The hydraulic pump of  claim 17  wherein the universal joint is configured to rotate with the transition arm.