Electricity: conductors and insulators – With fluids or vacuum – Boxes and housings
Reexamination Certificate
1999-03-30
2001-07-24
Richard, Dean A. (Department: 2831)
Electricity: conductors and insulators
With fluids or vacuum
Boxes and housings
C174S0170CT
Reexamination Certificate
active
06265654
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a thermal compensation device for at least one hydraulic support cell, the use of such a thermal compensation device in a lateral support as well as a support cell suitable for carrying out the invention.
BACKGROUND OF THE INVENTION
Under thermal compensation of storage cells, up to now only an arrangement was understood which limits an increase of the oil pressure in the total system as a consequence of a temperature increase. A thermally-caused displacement (for example, of a main mirror in a mirror telescope) was accepted and, if necessary, compensated by focusing the secondary mirror or by readjusting the main mirror.
Known lateral supports with support cells, which lie directly in the line of action of the mirror gravitational plane, function without reversals via levers but can mostly be used only at the outer periphery of the mirror.
By using a lever, the effective plane of the lateral force can, however, be shifted to the rear side of the mirror in the event a lever is used having a fixed pivot point for changing the force direction.
All three points of such a reversing lever should be free of friction forces and have angular-dependent return forces as low as possible. Furthermore, the lateral stiffness should be very high especially of the center joint. For this reason, the stated requirements partially contradict and apparently permit only compromise solutions.
Hydraulic compensation cells (support cells) are known, for example, from European patent publication 0,270,967 or from U.S. Pat. Nos. 4,775,230 and 5,151,809. In these known hydraulic support cells, a center membrane is provided above which the work chamber is configured and below which a compensation chamber lies for the hydrostatic pressure component. Each of the two chambers has a smaller central opening with a seal on the side lying opposite the center membrane. The two chambers are symmetrically built on the two mutually opposite sides of the center membrane in order to obtain the same hydraulic surfaces in both chambers.
Even though such a cell has three sealing systems in the form of membranes (planar membranes or roll membranes), its lateral loadability is so low that a lateral guidance system can only rarely be omitted. Furthermore, roll membranes have unwanted large friction values and spring forces and often become too hard at very low temperatures.
SUMMARY OF THE INVENTION
It is an object of the invention to provide thermal compensation for a hydraulic support cell wherein the compensating system for the hydrostatic pressure, which is anyway present, can simultaneously be used to compensate for the thermally-caused volume change.
The lateral support of the invention permits a reversing lever to be journalled utilizing hydraulic cells so that a movement parallel to itself can take place.
The hydraulic support cell according to the invention has spring stiffness as low as possible and permits a membrane to b omitted, in contrast to the state of the art.
The support cell according to the invention also has an improved lateral guidance behavior compared to the known hydraulic support cells.
The support cell according to the invention has a work chamber and a compensation chamber having the same hydraulic cross section without a seal being arranged between the two chambers.
For this purpose, the two chambers are mirror-image mounted to a non-elastic base plate of the cells which separates the chambers, but the chambers are not connected in the central axis as up to now conventional; rather, they are connected by at least one external wrap-around bridge outside about the two chambers.
The principle is also advantageously applicable for metal bellows as seals or conventional membranes.
The seal membrane can be configured as a metallic torus in the form of an omega. This affords the advantage with respect to a roll membrane that the fixed diameter and the movable diameter of the seal membrane are almost of the same size.
Compared to a flat membrane, the millable surface is larger by factors without the occurrence of a significant reduction of the hydraulic cell stiffness. The mechanical stiffness of the cell (without hydraulic liquid) should, in contrast, be as small as possible.
An omega torus has an especially flat spring characteristic line which runs linearly through the origin.
If three omega leaf springs are arranged each above and below the cell (which are pressed together during their assembly), then the maximum spring energy is stored in the center position. The omega leaf springs output energy with their deflection upwardly as well as downwardly.
The system would snap like a switch from one end position into the other end position without the omega torus. The omega leaf springs have a negative spring characteristic line at the origin which is so selected by the shape of the spring that, for the total system, an essentially still flatter characteristic line results than without the springs. The omega leaf springs simultaneously take on the lateral guidance of the movable parts of the cell whereby an additional lateral guide element is saved.
Further advantageous embodiments of the invention are described in the dependent claims.
REFERENCES:
patent: 3992946 (1976-11-01), Bradley
patent: 4757982 (1988-07-01), Rainer et al.
patent: 5074654 (1991-12-01), Alden et al.
patent: 5121904 (1992-06-01), Freudenberg
patent: 5151809 (1992-09-01), Meier
patent: 5741001 (1998-04-01), Bellamy et al.
patent: 3121961 (1982-12-01), None
patent: 4319453 (1994-09-01), None
Carl-Zeiss-Stiftung
Nguyen Charlie
Ottesen Walter
Richard Dean A.
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