Pipes and tubular conduits – With pressure compensators – Variable capacity chambers
Reexamination Certificate
2002-03-13
2004-09-14
Hook, James (Department: 3752)
Pipes and tubular conduits
With pressure compensators
Variable capacity chambers
C138SDIG003
Reexamination Certificate
active
06789577
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a hydropneumatic pressure accumulator with an outer tube forming the accumulator housing. In the housing, a flexible separating element is formed by a section of a hose extending in the longitudinal direction of the tube. The hose is anchored on the tube, forming a seal, such that on the outside and inside of the hose, receiving spaces are formed within the tube which are each separate from one another. The hose surrounds a support body having fluid passages and having at least in sections a cross sectional shape which is not round.
BACKGROUND OF THE INVENTION
A pressure accumulator is disclosed in DE 1 165 362, particularly FIGS. 5 and 6. To prevent damage due to overloading of a hose forming the separating element between the receiving spaces, i.e., the gas chamber and the oil chamber of the pressure accumulator, during operation the pressure accumulator must be carefully watched such that allowable operating limits are not exceeded. In other words, the value of the allowable pressure ratios between the upper operating pressure p
2
and the gas pretensioning pressure p
0
resulting from the limits of the load capacity of the hose which is conventionally made of rubber would not be as high as would be desirable. In the conventional state-of-the art solution, stresses occur, especially in the form of cyclic bending stresses, at the clamping site. Over a longer time interval, such high dynamic stresses occur that material fatigue and ultimately material failure occur.
SUMMARY OF THE INVENTION
Objects of the present invention are to provide a pressure accumulator formed of a flexible hose in a tube having better operating behavior, especially a higher allowable pressure ratio, than conventional designs of such accumulators.
The foregoing objects are achieved for the present invention in that the hose is closed on one end and is anchored only on its other open end together with the adjacent end of the support body along the outer tube. The size of the outside surface of the hose is only slightly smaller than the size of the inner surface of the outer tube facing it.
The only “one-sided” clamping of the hose, forming the separating element and being open on only one side, together with the dimensioning of the areas of the surfaces of the hose and outer tube which correspond to one another, leads to the especially advantageous result that the hose in operation is hardly exposed to any tensile or bending forces which would be active at the anchoring site. Due to the dimensioning of the sizes of the corresponding surfaces according to the present invention, for example in operating states in which a gas-pretensioning pressure (p
0
) acting on the outside of the hose exceeds the prevailing operating pressure, or in which there is no operating pressure, the hose is guided adjoining the support body free of tensile stress and free of flattening. This guiding permits the pressure accumulator to be handled without difficulty in the prefilled state with the oil side unpressurized. Based on the arrangement of the present invention, distinctly increased alternating load numbers can be achieved without material failure. If, on the other hand, a loss of the pretensioning pressure (p
0
) should occur so that the gas side of the pressure accumulator becomes unpressurized, at the intended dimensioning, the hose is in contact with the inner surface of the outer tube without tensile stresses. In normal operation between these two extreme states, the hose in the free space between the support body and the outer tube in turn occupies the position which corresponds to pressure equalization without tensile stresses. As a result, the limit for the level of the allowable upper operating state (p
2
) is determined solely by the structural strength of the accumulator housing formed by the outer tube.
For dimensioning of the size of the outside surface of the support body relative to the facing inside surface of the hose, the size of the outside surface of the support body can be only slightly less than that of the inside surface of the hose facing it. In this case, the hose surrounds the support body comparatively loosely, i.e., that in the operating state in which the pretensioning pressure (p
0
) exceeds the operating pressure (p) or in the absence of operating pressure, the hose makes contact with the outside surface of the support body without tensile stress.
Alternatively, the arrangement can be made such that the outside surface of the support body is somewhat larger than the inside surface of the hose when the latter is in the unexpanded state. In this case, the hose is slightly pretensioned in all operating states.
The inner support body can be made in the form of a tube body having openings in the wall and indentations over most of its length between its two end areas. The indentations reduce the tube cross section, but not the area of the outside surface of the tube body. The compression or squeezing of the tube body which takes place in areas reduces the volume of the receiving space within the hose, normally the oil chamber. The maximum useful &Dgr;V of the tube accumulator is also hereby determined.
In preferred exemplary embodiments, the tube body is shaped and dimensioned in such a way that it extends in its end areas which are free of indentations along the inside surface of the outer tube, and, from this surface, at a distance which corresponds essentially to the thickness of the hose. In this way the hose in these surface areas is guided both on its inside, specifically on the tube body, and also on its outside, specifically by contact with the inside surface of the outer tube.
Preferably, the outside surface of the tube body in the longitudinal area having the indentations on the longitudinal extending peripheral areas of the outer tube is at a distance from its inside surface which corresponds essentially to the thickness of the hose. In this manner, it is also guided in areas over its entire longitudinal area between the tube body and the outer tube.
Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the present invention.
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patent: 3143144 (1964-08-01), Peet
patent: 3348578 (1967-10-01), Mercier
patent: 4166478 (1979-09-01), Sugimura et al.
patent: 4448217 (1984-05-01), Mercier
patent: 4610369 (1986-09-01), Mercier
patent: 4628964 (1986-12-01), Sugimura et al.
patent: 4732176 (1988-03-01), Sugimura
patent: 5505228 (1996-04-01), Summerfield
patent: 5860452 (1999-01-01), Ellis
patent: 6017099 (2000-01-01), Schneider et al.
patent: 6131613 (2000-10-01), Jenski, Jr. et al.
patent: 6314942 (2001-11-01), Kilgore et al.
Hook James
Hydac Technology GmbH
Roylance Abrams Berdo & Goodman L.L.P.
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