Oscillating-piston drive for a vacuum pump and an operating method for said drive

Abstract

An oscillating-piston drive for a vacuum pump ( 1 ) with a piston ( 2 ), which presents has two piston sections ( 3,4 ) and an intermediate zone provided with a drive magnet ( 11 ). Cylinder sections ( 8, 9 ) slidingly receive the piston sections ( 3, 4 ). An annular recess ( 12 ) is defined between the cylinder sections ( 8, 9 ) at a central yoke ( 19 ). The recess provides space for movement of the drive magnet ( 11 ). An electromagnetic drive which surrounds the piston ( 2 ) includes yoke components ( 17, 18, 19 ) and coils ( 15, 16 ) situated to the sides of said central yoke. Negative influences on the delivery rate of the pump are reduced by a can ( 34 ) which delimits the recess ( 12 ) peripherally or by controlling the current supply to the coils, such that only one coil conducts current at a time.

1 . An oscillating piston drive for a vacuum pump comprising: 
 a piston having two piston sections and a central zone;    a drive magnet mounted in the central zone;    cylinder sections in which the piston sections are slidably received;    an annular recess located between the cylinder sections at the level of a central yoke said recess receiving and forming space for movement for the drive magnet;    an electromagnetic drive with yoke components encompassing the piston with coils located to the side of the central yoke; and    a can peripherally delimiting the recess.    
   
   
       2 . The drive according to  claim 1 , wherein the can is constructed of a material with good sliding properties.  
   
   
       3 . The drive according to  claim 1 , wherein the can is constructed of a ferromagnetic material.  
   
   
       4 . The drive according to  claim 3 , further including: 
 stator permanent magnets which delimit the recess in an axial direction and outside the central yoke zone, the can ( 34 ) extending into the area of the stator permanent magnets.    
   
   
       5 . The drive according to  claim 4 , wherein the stator permanent magnets ( 13 ,  14 ) are magnetized such that they exert a repelling force on the drive magnet.  
   
   
       6 . The drive according to  claim 3 , wherein the wall thickness of the can at least outside the central yoke zone is so selected, that the drive magnet magnetizes the respective can section to the saturation point when said magnet is located in the zones outside the central yoke.  
   
   
       7 . The drive according to  claim 6 , wherein the can has in the zone of the central yoke a greater wall thickness.  
   
   
       8 . The drive according to  claim 1 , wherein the drive magnet is a rare earth magnet.  
   
   
       9 . An operating method for an oscillating piston drive with the characteristics of  claim 1 , wherein current flow through the coils is controlled such that current passes through only one coil at a time.  
   
   
       10 . An operating method for an oscillating piston drive for a vacuum pump including a piston with two piston sections and a central zone equipped with a drive magnet, cylinder sections associated to the piston sections, an annular recess defined between the cylinder sections adjacent the central yoke, said recess forming space for movement for the drive magnet, and an electromagnetic drive with yoke components encompassing the piston with coils located to the side of the central yoke, the method comprising: 
 supplying an alternating current to the coils with only one current polarity being supplied to each of the coils.    
   
   
       11 . The operating method according to  claim 10 , wherein the current flows through the coils such that they alternately exert repelling forces on the drive magnet.  
   
   
       12 . The operating method according to  claim 10  further including: 
 adjusting amplitudes of the current flows to each of the coils with a thyristor regulator.    
   
   
       13 . The operating method according to  claim 12 , further including: 
 adjusting current amplitude to the coils by means of a phase angle regulator.    
   
   
       14 . The operating method according to  claim 13 , wherein an input signal for the phase angle regulator is one of: 
 defined at a fixed value for a given pump application,    dependent on the mains voltage,    defined by a sensor for detecting a position of the piston, or    defined by a sensor for observing valve movement.    
   
   
       15 . The operating method according to  claim 13 , wherein the current amplitude is adjusted with thyristor regulators.  
   
   
       16 . The oscillating piston drive according to  claim 1 , further including: 
 thyristor regulators for controlling current flow to the coils.    
   
   
       17 . The oscillating piston drive according to  claim 1 , further including: 
 a means for supplying an alternating current to the coils with only one current polarity being supplied to each of the coils.    
   
   
       18 . The oscillating piston drive according to  claim 17 , wherein the means for supplying alternating current to the coil includes: 
 a phase angle regulator and a means for supplying an input signal to the phase angle regulator which input signal is one of: 
 a fixed value for a given pump application,  
 dependent on a voltage of supply means,  
 defined by a sensor for detecting a position of the piston, or  
 defined by a sensor for observing valve movement.