Pump

Abstract

A pump assembly including a gerotor pump having an inlet and an outlet, and comprising an annulus and a lobed rotor, one, but not both, of the rotor or annulus being split axially into two parts, the pump further comprising indexing means for angularly shifting one part relative to the other part, the indexing means comprising a chamber having a first indexing port and a second indexing port, and a partition which divides the chamber into a first portion including the first indexing port and a second portion including the second indexing port, wherein the partition comprises a part which is pivotally mounted within the chamber for angular movement within the chamber.

1 . A pump assembly including a gerotor pump having an inlet and an outlet, and comprising an annulus and a lobed rotor, one, but not both, of the rotor or annulus being split axially into two parts, the pump further comprising indexing means for angularly shifting one part relative to the other part, the indexing means comprising a chamber having a first indexing port and a second indexing port, and a partition which divides the chamber into a first portion including the first indexing port and a second portion including the second indexing port, wherein the partition comprises a part which is pivotally mounted within the chamber for angular movement within the chamber. 
   
   
       2 . A pump assembly according to  claim 1  wherein the indexing means comprises first and second chambers each of which is provided with a first and second indexing port and a partition which divides the chamber into a first portion including the first indexing port and a second volume including the second indexing port, wherein each partition comprises a part which is pivotally mounted in the chamber for angular movement between a first orientation and a second orientation. 
   
   
       3 . A pump assembly according to  claim 2  wherein the first and second pivotal partition parts are mounted on a common pivot. 
   
   
       4 . A pump assembly according to  claim 1  wherein the pivotal part is rotatable between a first position in which the volume of the first portion of the chamber is minimised and the volume of the second portion of the chamber is maximised, and a second position in which the volume of the first portion of the chamber is maximised and the volume of the second portion of the chamber is minimised. 
   
   
       5 . A pump assembly according to  claim 1  wherein the indexing ports are arranged such that the first indexing port is in communication with the first portion of the chamber and the second indexing port is in communication with the second portion of the chamber when the pivotal part is in either the first position or the second position. 
   
   
       6 . A pump assembly according to  claim 5  wherein each of the indexing ports is located in a recess in a wall of the chamber. 
   
   
       7 . A pump assembly according to  claim 5  wherein the pivotal part is provided with a first and second cut out portion which each provide the pivotal part with an edge which extends around the periphery of the respective indexing port when the pivotal part is in its first or second position respectively. 
   
   
       8 . A pump assembly according to  claim 1  wherein the partition further includes an angularly fixed part which engages with a bearing portion of the pivotal part so as substantially to prevent leakage of fluid between the first portion and the second portion of the chamber. 
   
   
       9 . A pump assembly according to  claim 8  wherein the indexing means includes biasing means which engages with the angularly fixed part and biases the angularly fixed part into engagement with the bearing portion of the pivotal part. 
   
   
       10 . A pump assembly according to  claim 1  wherein the pump has a single annulus and the rotor being split axially into two parts such that the pump includes two rotors which are relatively angularly adjustable. 
   
   
       11 . A pump assembly according to  claim 10  wherein the first rotor is angularly fixed with respect to a drive shaft and the second rotor is movable relative the first rotor. 
   
   
       12 . A pump assembly according to  claim 11  wherein the second rotor is mounted on an eccentric mounting part carried by a second shaft which extends along the annulus axis. 
   
   
       13 . A pump assembly according to  claim 12  wherein the pivotal part of the indexing means is mounted on the second shaft, such that rotation of the pivotal part causes rotation of the shaft and the eccentric on which the second rotor is mounted. 
   
   
       14 . A pump assembly according to  claim 1  wherein the first and second indexing ports are connected to a valve, the valve having a first inlet port which is connected to a source of pressurised fluid and exhaust port which is connected to a low pressure fluid reservoir. 
   
   
       15 . A pump assembly according to  claim 1  wherein the valve includes a valve member which is movable between a first position in which the first indexing port is connected to the exhaust and the second indexing port is connected to a source of pressurised fluid, and a second position in which the first indexing port is connected to a source of pressurised fluid and the second indexing port is connected to the exhaust port. 
   
   
       16 . A pump assembly according to  claim 15  wherein the valve further includes biasing means which biases the valve member into the first position. 
   
   
       17 . A pump assembly according to  claim 16  wherein the valve member is be configured such that pressurised fluid from the first inlet port acts on the valve member so as to move the valve member from the first position to the second position when the fluid pressure at the first inlet port exceeds a predetermined amount. 
   
   
       19 . A pump assembly according to  claim 16  wherein the valve includes a second inlet port which is connected to a second source of pressurised fluid, pressurised fluid from the second inlet port acting on the valve member so as to move the valve member from the first position to the second position when the fluid pressure at the second inlet port exceeds a predetermined value.