High-pressure small volume pump

Abstract

An improved high-pressure pump ( 1 ) for an accurate, largely pulsation-free flow of the working medium, more particularly an HPLC pump, includes one or a plurality of the following measures: reduced dead space due to adapted seals ( 48, 70 ); reduced dead space thanks to a device ( 15, 16; 32; 36, 38 ) for adjusting the length of the displacement piston; adjustable dead space and therefore adjusting capability of the pulsation freedom through a displacement chamber provided with an adjustable opposed piston ( 58 ); and seals compensating construction tolerances by a combination of a cambered sealing surface and a conical sealing surface.

1 . A pump for delivering precisely determined, small liquid flows comprising: at least one pump device including a displacement chamber, a piston that is movable in the displacement chamber, the piston having at least a first, foremost seal for sealing the piston against the displacement chamber, the first seal comprising a sealing element with a sealing lip surrounding the piston, the sealing lip having a first surface and a second surface; a spring-elastic element resting on the opposed second surface of the sealing lip for prestressing the first surface of the sealing lip against the piston, the second surface being in contact with the displacement chamber, the sealing element and the spring-elastic element are essentially C-shaped in cross-section; and a filling body that is essentially incompressible under operating conditions of the pump disposed in the chamber in order to reduce dead space of the pump device resulting from the seal. 
   
   
       2 . The pump according to  claim 1 , wherein the C-shaped profile of the spring element includes a slot having a width essentially equal to a height of the interior of the C, such that the filling body is axially insertable into the spring element and is shaped to substantially fill out the interior of the C at least preponderantly. 
   
   
       3 . A pump comprising at least a first and a second pump device each according to the pump of  claim 1  and each comprised of a displacement chamber and a piston, the second pump device being downstream of the first pump device and being operatable as a storage device of pulsation of the first pump device. 
   
   
       4 . A pump for delivering precisely determined, small liquid flows under high pressures comprising: at least one pump device including a displacement chamber, a piston that is movable in the displacement chamber; at least one working medium access bore of the pump device having a detachable connecting assembly including at least one pair of sealing surfaces forming a junction that is tight to a working medium, one sealing surface is essentially dome-shaped and convex and the other sealing surface is essentially concave and conical, and the sealing surfaces have a center with a respective opening of a channel for the working medium defining an annular contact line between the two sealing surfaces even if the channel openings are not precisely aligned to each other. 
   
   
       5 . The pump according to  claim 4 , wherein a seal is interposed between the sealing surfaces of at least one pair of the sealing surfaces. 
   
   
       6 . The pump according to  claim 4 , further comprising at least a first and a second pair of the sealing surfaces, a sealing body is disposed between the first and second pairs of the sealing surfaces, the first and second sealing surfaces including inner surfaces; the sealing body having the respective inner sealing surfaces of the two pairs of sealing surfaces formed thereon and the inner sealing body is comprised of a dimensionally stable, highly pressure-resistant synthetic material. 
   
   
       7 . The pump according to  claim 4 , further comprising at least a first and a third pair of sealing surfaces each including an inner and an external sealing surface, and the two inner sealing surfaces each face the other pair of sealing surfaces, a connecting body disposed between the external sealing surfaces of the two pairs of sealing surfaces, so that the two pairs of sealing surfaces each form a tight junction with the connecting body. 
   
   
       8 . The pump according to  claim 4 , further comprising a pair of a first and a second contact surface contacting each other, a second connecting body in the connecting assembly on which the first contact surface and the sealing surface are formed, the second connecting body being held between the second contact surface and the other one of the sealing surfaces; a duct for the working medium fixedly connected to the second connecting body wherein the duct communicates with the channel having the opening located in the sealing surface of the second connecting body. 
   
   
       9 . The pump according to  claim 8 , wherein the contact surfaces are cambered and complementary to each other to center the second connecting body in the second contact surface. 
   
   
       10 . A pump comprising at least a first and a second pump device each according to the pump of  claim 8  and each comprised of a displacement chamber and a piston, the second pump device being downstream of the first pump device and being operatable as a storage device of pulsation of the first pump device.