Piston vacuum pump

Abstract

A piston vacuum pump comprises a cylinder ( 14 ) and a piston ( 12 ) that forms a compression chamber ( 28 ) with the cylinder ( 14 ). The piston ( 12 ) oscillates in the cylinder ( 14 ) with a compression stroke and an intake stroke. In a side wall ( 16 ) of the cylinder ( 14 ), a gas inlet ( 30 ) is provided, the gas inlet ( 30 ) being closed by the piston ( 12 ) at the beginning of the intake stroke and open at the end of the intake stroke. Further, an equalizing conduit and a valve are provided through which gas from the gas inlet ( 30 ) flows into the compression chamber ( 28 ) at the beginning of the intake stroke. This provides a simple arrangement of an equalizing conduit with a valve. The piston substantially forms the equalizing conduit and the valve. Thereby, the valve can act in the region of the piston end wall so that the dead volume is minimized.

1 . A piston vacuum pump, comprising 
 a cylinder and a piston forming a compression chamber with the cylinder and oscillating in the cylinder with a compression stroke and an intake stroke,    a gas inlet in a side wall of the cylinder, the gas inlet being closed by the piston at the beginning of the intake stroke and open at the end of the intake stroke, and    an equalizing conduit with a valve, gas flowing from the gas inlet through the equalizing conduit and the valve into the compression chamber during the beginning of the intake stroke,    the piston forming the equalizing conduit and the valve.    
   
   
       2 . The piston vacuum pump according to  claim 1 , wherein the equalizing conduit is formed in the piston between a piston side wall opening and a piston end wall opening, the piston end wall opening and the gas inlet being connected with each other at the beginning of the intake stroke.  
   
   
       3 . The piston vacuum pump according to  claim 1 , wherein the valve is a non-return valve blocking in the direction of the gas inlet and opening in the direction of the compression chamber.  
   
   
       4 . The piston vacuum pump according to  claim 3 , wherein the non-return valve is arranged at a piston end wall which faces the compression chamber.  
   
   
       5 . The piston vacuum pump according to  claim 1 , wherein the gas inlet has an annular groove in at least one of the cylinder side wall and the piston side wall.  
   
   
       6 . The piston vacuum pump according to  claim 1 , further including: 
 a storage chamber defined in the piston in the equalizing conduit.    
   
   
       7 . The piston vacuum pump according to  claim 1 , wherein the equalizing conduit and the valve are formed by a gap between a piston side wall and a cylinder side wall, the gap width being between 10 and 100 μm.  
   
   
       8 . The piston vacuum pump according to  claim 1 , wherein the equalizing conduit and the valve are formed by a substantially axial groove in a piston side wall or in a cylinder side wall.  
   
   
       9 . The piston vacuum pump according to  claim 1 , wherein the valve is configured as a throttle.  
   
   
       10 . A piston vacuum pump comprising: 
 a cylinder defined by a peripheral cylinder wall;    a gas inlet aperture defined in the cylinder side wall;    a piston mounted for reciprocating movement within the cylinder, the piston including a peripheral side wall and walls that define a storage chamber in the piston, the piston side wall having an aperture that communicates with the gas inlet at least at a beginning of an intake stroke, one of the piston end walls having an aperture in communication between the storage chamber and a compression chamber defined by the piston and the cylinder; and    a one-way valve mounted at the piston end wall aperture to permit gas flow from the storage chamber to the compression chamber and block the gas flow between the compression chamber to the storage chamber.    
   
   
       11 . A piston vacuum pump comprising: 
 a cylinder defined by a cylinder side wall;    a gas inlet defined in the cylinder side wall;    a piston mounted for reciprocating movement in the cylinder, the piston having a side wall facing the cylinder side wall, the piston and cylinder defining a compression chamber;    a gap between 10 and 100 μm defined from the gas inlet to the compression chamber between the piston side wall and the cylinder side wall such that gas flows from the gas inlet to the compression chamber during at least a portion of an intake stroke and is throttled from flowing from the compression chamber to the gas inlet during a compression stroke.