Pump drive

Abstract

A membrane or piston pump drive comprises a stepping motor ( 2 ) and a rotary-to-linear conversion mechanism for converting the rotary movement into a translation movement ( 6 ). The rotary-to-linear conversion mechanism comprises a rotary member ( 4 ) and a piston member ( 7 ) intended to move a piston or a membrane of the pump. The stepping motor comprises a rotor coupled to the rotary member which engages the piston member ( 7 ) in order to drive it in an essentially linear reciprocating movement.

1 . A membrane or piston pump drive comprising a stepping motor ( 2 ) and a rotary-to-linear conversion mechanism ( 6 ) converting rotary movement into a translation movement, the rotary-to-linear conversion mechanism comprising a rotary member ( 4 ) and a piston member ( 7 ) intended to move a piston or membrane of the pump, the stepping motor comprising a rotor coupled to the rotary member, which engages the piston member ( 7 ) in order to drive it in an essentially linear reciprocating movement, wherein the stepping motor and the rotary-to-linear conversion mechanism are adapted to drive the rotary member of the translation mechanism in a reciprocating angular movement at an angle of less than 360°.  
   
   
       2 . The pump drive according to  claim 1 , wherein the rotary member of the rotary-to-linear conversion mechanism comprises a cam surface engaging a complementary cam element fixed to the piston member.  
   
   
       3 . The pump drive according to  claim 2 , wherein the cam surface is formed on the periphery of an opening formed in an element in the form of a disc fixed to the output shaft of the step-down device.  
   
   
       4 . The pump drive according to  claim 2 , wherein the cam surface ( 20 ) comprises opposite cam surfaces ( 20   c ,  20   d ) for pushing, respectively pulling the piston member without a recoil spring.  
   
   
       5 . The pump drive according to  claim 1 , wherein the rotor of the stepping motor is coupled to the rotary member through a step-down device ( 5 ).  
   
   
       6 . The pump drive according to  claim 5 , wherein the step-down device comprises a pinion on the output shaft of the rotor of the stepping motor, coupled through gearwheels to an output shaft of the step-down device which is fixed to the rotary member of the rotary-to-linear conversion mechanism.  
   
   
       7 . The pump drive according to  claim 1 , wherein the drive comprises an electronic control able to control the rotation amplitude of the rotor in each direction as well as the frequency of the steps, so as to generate an asymmetric speed profile, where the linear movement speed of the piston member in one direction of suction of the pump fluid is different from the speed of movement of the member in the other direction.  
   
   
       8 . A method of controlling a pump drive according to  claim 1 , wherein the pump fluid output is varied by modifying the amplitude of angular movement and/or the frequency of the steps of the rotor in each direction.  
   
   
       9 . The method according to  claim 8 , wherein the angular speed of the rotor in one direction is regulated so as to be different from the speed in the other direction in order to obtain an asymmetric speed profile for the suction and expulsion of fluid.