Pumps

Abstract

An axial piston pump is adapted to pump concrete or other slurries. On the suction side a wedge device is arranged to direct the concrete into or away from the cylinders according to whether the solid lumps are correctly placed for easy entry into the cylinders or likely to cause an obstruction at the downstream end of the suction side. A water barrier separates the concrete space from the oil filled drive mechanism and there is water lubrication of the working face of the cylinder block.

We claim: 
     
       1. An axial piston pump adapted for pumping concrete or other abrasive media and slurries, including a cylinder block with an annular array of axially parallel cylinders, each with a reciprocable piston therein and a working end face to which the cylinders open; bearing means for locating said block in an axially fixed position; means co-operating with said face to divide it into an inlet and a delivery side; means for reciprocating the pistons to give them suction strokes on the inlet side and pressure strokes on the delivery side, the strokes commencing at an upstream end and finishing at a downstream end of the respective side to draw and discharge media progressively into and from the cylinders; guide means disposed in the circumferentially downstream portion of the inlet side, leaving the upstream portion of the inlet side free and the full diametral extent of said cylinders exposed in that upstream portion, said guide means having a first surface facing said cylinder block and forming a convergent tunnel therewith, open at the upstream end and narrowing in height .[.and width.]. towards the downstream end to urge media carried towards said guide means into the cylinders by a wedging action, and a second surface facing away from said cylinder block to reject and return to the upstream portion solids that are not correctly sized and/or positioned for entry into the cylinders in the downstream portion. 
     
     
       2. A pump as claimed in claim 1, wherein the piston heads are spring loaded on cores. 
     
     
       3. A pump as claimed in claim 1, wherein the trailing lip of each cylinder, where it meets the working end face of the cylinder block, is cut away. 
     
     
       4. A pump as claimed in claim 1, wherein said tunnel is inverted U or V shape. 
     
     
       5. A pump as claimed in claim 1, wherein said tunnel has an arcuate centre line overlying the path of the piston and cylinder axes. 
     
     
       6. A pump as claimed in claim 1, wherein the pump housing has trunnions for tiltable mounting about an axis transverse to the pump axis. 
     
     
       7. A pump as claimed in claim 1, wherein a kidney shaped port provides the outlet on the discharge side of the pump and a discharge pipe connection merging from the kidney shape to a circular shape is fitted thereon. 
     
     
       8. A pump as claimed in claim 1, wherein means are provided for water lubrication of the working end face of the cylinder block. 
     
     
       9. A pump as claimed in claim 8, wherein said lubrication means includes an annular water channel eccentric with respect to the pump axis, in part of the pump housing that co-operates with the periphery of said working end face. 
     
     
       10. A pump as claimed in claim 1, wherein the dividing means includes a valve blade diametrically across said working face and said second surface is in the form of a curved ramp leading up to said valve blade from the upstream end of said guide means. 
     
     
       11. A pump as claimed in claim 10, wherein said valve blade is offset a small angle circumferentially downstream from the plane through the upper and lower dead centre positions of the pistons. 
     
     
       12. A pump as claimed in claim 1, wherein a fluid barrier is continuously provided between the working faces of the pistons and said reciprocating means, the pistons being double headed with a space between the heads which is filled by fluid. 
     
     
       13. A pump as claimed in claim 12, wherein the cylinder block is hollow and provided with fluid supply and escape means, and the cylinders have ports for transverse flow of said fluid in the piston head spaces. 
     
     
       14. A pump as claimed in claim 13, wherein the fluid supply is central of the block, whose rotation provides centrifugal flow of said fluid to and through said cylinders. 
     
     
       15. A pump as claimed in claim 14, wherein an angled ramp supports the swash plate and spring means press the swash plate thereon, reacting against the cylinder block. .Iadd. 16. A pump as claimed in claim 1, wherein said convergent tunnel narrows in width towards the downstream end..Iaddend.