Measuring and testing – Liquid analysis or analysis of the suspension of solids in a... – Content or effect of a constituent of a liquid mixture
Patent
1996-07-15
1999-11-30
Brock, Michael
Measuring and testing
Liquid analysis or analysis of the suspension of solids in a...
Content or effect of a constituent of a liquid mixture
73 6178, 374 46, 374 55, 92 33, 92 84, 92137, 74 58, G01N 2516, F04B 902
Patent
active
059922222
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to high pressure systems, more specifically to a high pressure system including a piston pump for producing a high and exactly controllable pressure level in a fluid, and to methods for operating such systems.
DESCRIPTION OF THE RELATED ART
In principle, it should be possible to produce a high pressure level in a fluid with any desired accuracy because a fluid to which a compressing force is applied exerts a counteracting force which is a smoothly varying direct function of the applied force.
However, by this date, close control of high pressure levels in fluids, e.g. in the range above 1 MPa (10 bar) up to e.g. 250 MPa (2,5 kbar) and more has been extremely difficult if not impossible for a number of reasons.
At present, controlled high fluid pressures can be obtained only by means of pumps of the cylinder-piston type. In such pumps, the seal between the movable piston and the cylinder (usually some type of O-ring) is a main cause of problems. For sealing a high fluid pressure, the seal must exert a correspondingly high pressure on the inner wall of the cylinder which creates high frictional forces between these relatively movable elements. This has not only the consequence that a high force is necessary for effecting the required relative motion but also makes the motion jerky because of repetitive transitions between static friction and sliding friction.
Another reason why a smooth, continuous relative motion between a piston and a cylinder of a high pressure pump is difficult to obtain is the presence of reaction forces which are caused by an unavoidable relative misalignment of piston and cylinder axes. Any deviation from an exactly coaxial relationship of piston and cylinder causes reaction forces which depend not only on the actual pressure but also on the relative physical position of the piston and the cylinder. This has prevented the use of a rigid coupling of the piston to a driving member, such as a spindle, which rigid coupling is, however, necessary to obtain close pressure control.
A well known device, the rotating piston balance, a gauging device, avoids the friction problem by using a liquid of high viscosity as seal between piston and cylinder, and by rotating the piston relative to the cylinder simultaneously with a relative axial motion of these elements. The piston is rigidly connected to a platform and the pressure generating force is provided by placing a known mass on the platform while the axis of piston and cylinder are vertical, see e.g. HIGH PRESSURE TECHNOLOGY, Vol. 1, Ian L. Spain et al., Ed., Marcel Dekker, Inc., New York, N.Y., 1977, pp. 285 to 294.
A main drawback of this device is that the axes of piston and cylinder must be exactly aligned with the direction of gravity and that an incremental and automatic pressure control is not feasible. A further, sometimes prohibitive limitation is the necessity to use a liquid of high viscosity for obtaining the required pressure seal.
Thus, generating an exactly controllable high pressure level by means of a piston pump actuated by an automatically controllable drive, as such as an electric motor, is still an unsolved problem.
SUMMARY OF THE INVENTION
It is an object of the invention, to provide a high pressure pump system suitable for producing high pressure levels which can be precisely and smoothly controlled.
Another object of the invention is to provide a high pressure pump system which avoids the above discussed friction and misalignment problems.
A still further object of the invention is to provide a high pressure piston pump system which does not rely on a highly viscose sealing fluid and which can be operated in any desired position.
The invention is embodied in a fluid pump system comprising a cylinder, a piston position within the cylinder and movable relative to it, and driving means for moving the piston and cylinder relatively longitudinally and relatively rotably with respect to each other, said driving means including an actuating member operatively associa
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Belonenko Vladimir
Bunau Eugenij
Funck Theodor
Nikolashev Vijcheslav
Brock Michael
UHP Corp.
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