Control ring for a hydrostatical device

Abstract

A control ring is provided for controlling the flow of a pressure medium in a displacement pump. The control ring is centered about a rotational axis, and extends along the rotational axis. The control ring has inner and outer diameters and thereby inner and outer radial surfaces. The control ring further has first and second axial surfaces, wherein the first axial surface has an interface section provided with at least first and second openings. The first and second openings are separated by first and second intermediate sections, and the first and second openings mouth to a corresponding mouthing area provided at either of the inner and outer radial surfaces.

What is claimed is: 
     
         1 . A control ring for controlling flow of a medium in a displacement pump, the control ring comprising:
 an inner radial surface and an outer radial surface that respectively have an inner diameter and an outer diameter, the radial surfaces being centered about a rotational axis and extending along the rotational axis; and   a first axial surface and a second axial surface, the first axial surface having an interface section provided with at least first and second openings that are separated by first and second intermediate sections, wherein the first and second openings mouth to a corresponding mouthing area provided at either of the inner and outer radial surfaces.   
     
     
         2 . The control ring according to  claim 1  further comprising at least a first balance area at the second axial surface, wherein the first balance area is interconnected with one of the first and second openings via a pressure conduit. 
     
     
         3 . The control ring according to  claim 1  further comprising first and second balance areas at the second radial surface, wherein the first and second balance areas are interconnected with the first and second openings, respectively, and wherein a surface area of the first and second balance areas at least corresponds to an exposed radial area of the first and second openings, such that pressure upon the first and second balance areas essentially corresponds to pressure upon the exposed radial areas of the first and second opening. 
     
     
         4 . The control ring according to  claim 1  wherein the first opening mouths to the inner radial surface and the second opening mouths to the outer radial surface. 
     
     
         5 . The control ring according to  claim 1  wherein the first and second opening mouth to the inner radial surface. 
     
     
         6 . The control ring according to  claim 1  wherein the first and second openings mouth to the outer radial surface at different axial distances from the first axial surface. 
     
     
         7 . The control ring according to  claim 6  further comprising seal rings arranged upon the outer radial surface such that the seal rings define two separate axial areas in which the first and second openings mouth respectively. 
     
     
         8 . The control ring according to  claim 1  wherein the first opening comprises a plurality of channels and/or the second opening comprises a plurality of channels. 
     
     
         9 . The control ring according to  claim 1  wherein the first and second openings are arc shaped. 
     
     
         10 . The control ring according to  claim 1  further comprising balance valves arranged in the first and second intermediate sections, the balance valves connecting the first and second intermediate sections with a mouthing area of the first and/or second openings respectively, wherein the balance valves are adapted to open if a pressure at the first or second intermediate area rises above a predetermined threshold value. 
     
     
         11 . A displacement pump comprising:
 a pumping unit arranged within a housing and having pressure sections and therewith connected inlet and outlet ports; and   a control ring provided between the pressure sections and the inlet and outlet ports such that the control ring can be turned in order to control flow of a medium, the control ring including inner and outer radial surfaces centered about a rotational axis and extending along the rotational axis, and first and second axial surfaces, the first axial surface having an interface section arranged directed towards the pressure sections of the pumping unit and provided with at least first and second openings that are separated by first and second intermediate sections, wherein the first and second openings mouth to a corresponding mouthing area provided at either of the inner and outer radial surfaces.   
     
     
         12 . A control ring for controlling flow of a pressure medium in a displacement pump, the control ring comprising:
 an inner radial surface and an outer radial surface that are centered about a rotational axis; and   a first axial surface having an interface section provided with first and second spaced apart openings, wherein the first and second openings extend to a corresponding mouthing area provided at either of the inner and outer radial surfaces.