GAS PISTON ACCUMULATOR

Abstract

A gas piston accumulator with a piston-cylinder unit, the hydraulic space of which can be connected to a hydraulic line. A pressure piston biased with a biasing force acts on the hydraulic space in order to pressurize the hydraulic fluid in the hydraulic line with an accumulator pressure. The biasing force is achieved by a gas pressure in a gas space which is separated from the hydraulic space via the pressure piston, at least one cylinder base of the gas piston accumulator being assigned to the pressure piston as a mechanical stop, and the pressure piston having an axially set back piston main body, on the gas side of which and/or on the hydraulic side of which there protrudes a stop structure which is of reduced area compared to the respective pressure piston side and which can be brought into pressure contact with the cylinder base.

Claims

1-10. (Canceled)

11. A gas piston accumulator comprising: a piston-cylinder unit, a hydraulic space of which can be connected to a hydraulic line, wherein a pressure piston pre-loaded with a biasing force acts on the hydraulic space in order to pressurize the hydraulic fluid in the hydraulic line with an accumulator pressure, wherein the biasing force is achieved by a gas pressure in a gas space which is separated from the hydraulic space via the pressure piston, wherein at least one cylinder base of the gas piston accumulator is associated with the pressure piston as a mechanical stop, and wherein the pressure piston has an axially set back piston main body, on the gas side of which and/or on the hydraulic side of which there protrudes a stop structure which is of reduced area compared to the respective pressure piston side and which can be brought into pressure contact with the cylinder base, wherein the stop structure formed on the pressure piston has a sleeve-shaped extension which protrudes from the piston main body and whose outer diameter is smaller than the circumferential diameter of the pressure piston and whose free annular end face can be brought into pressure contact with the cylinder base.

12. The gas piston accumulator of claim 11, wherein the sleeve-shaped extension of the pressure piston stop structure is arranged concentrically to the pressure piston circumference and/or coaxially to a gas piston accumulator longitudinal axis.

13. The gas piston accumulator of claim 11, wherein radial webs project from the outer circumference of the sleeve-shaped extension of the pressure piston stop structure, the radially outer web sides of which are spaced apart from the pressure piston circumference by a radial offset.

14. The gas piston accumulator of claim 11, wherein the sleeve-shaped extension of the pressure piston stop structure defines a radially inner blind hole-like recess , and, when completely emptied or completely filled with hydraulic fluid, the free annular end face of the stop structure is in pressure contact with the cylinder base and the blind hole-like recess is decoupled radially outwards in a fluid-tight manner

15. The gas piston accumulator of claim 11, wherein the gas piston accumulator is of double-walled design, namely with an inner tube, in which the pressure piston is axially guided, and with an outer tube, which surrounds the inner tube, forming an annular gap.

16. The gas piston accumulator of claim 15, wherein the pressure piston divides the tube interior of the inner tube into the hydraulic space and the gas space, and/or the annular gap is separated from the hydraulic space in a fluid-tight and pressure-tight manner and is fluidically connected to the gas space, and/or the gas space formed in the inner tube is connected to the annular gap via at least one flow passage.

17. The gas piston accumulator of claim 15, wherein the hydraulic space of the inner tube is bounded in the axial direction by a hydraulic-side cylinder base of the gas piston accumulator, and/or the gas space of the inner tube is bounded in the axial direction by a gas-side cylinder base of the gas piston accumulator, and/or the hydraulic-side cylinder base and/or the gas-side cylinder base act as mechanical piston stops for the pressure piston, and/or the outer tube merges materially and/or integrally into the two axially opposite cylinder bases, forming a gas piston accumulator housing.

18. The gas piston accumulator of claim 11, wherein, when emptied, the pressure piston together with the hydraulic-side cylinder base delimits a hydraulic-side filling chamber, and, during a charging process of the gas pressure accumulator, hydraulic fluid flows from the hydraulic line into the hydraulic-side filling chamber in order to assist a detachment of the pressure piston from the hydraulic-side cylinder base.

19. The gas piston accumulator of claim 11 wherein, when completely filled with hydraulic fluid, the pressure piston together with the gas-side cylinder base delimits a gas-side filling chamber, and, during a discharging process of the gas piston accumulator, the gas expands from the annular gap via the flow passage into the inner tube and further into the gas-side filling chamber and flows in, in order to help detach the pressure piston from the gas-side cylinder base.

20. The gas piston accumulator of claim 18, wherein the filling chamber extends continuously in the circumferential direction annularly around the sleeve-shaped extension of the pressure piston stop structure.

21. The gas piston accumulator of claim 12, wherein radial webs project from the outer circumference of the sleeve-shaped extension of the pressure piston stop structure, the radially outer web sides of which are spaced apart from the pressure piston circumference by a radial offset.

22. The gas piston accumulator of claim 12, wherein the sleeve-shaped extension of the pressure piston stop structure defines a radially inner blind hole-like recess, and, when completely emptied or completely filled with hydraulic fluid, the free annular end face of the stop structure is in pressure contact with the cylinder base and the blind hole-like recess is decoupled radially outwards in a fluid-tight manner

23. The gas piston accumulator of claim 13, wherein the sleeve-shaped extension of the pressure piston stop structure defines a radially inner blind hole-like recess, and, when completely emptied or completely filled with hydraulic fluid, the free annular end face of the stop structure is in pressure contact with the cylinder base and the blind hole-like recess is decoupled radially outwards in a fluid-tight manner

24. The gas piston accumulator of claim 12, wherein the gas piston accumulator is of double-walled design, namely with an inner tube, in which the pressure piston is axially guided, and with an outer tube, which surrounds the inner tube, forming an annular gap.

25. The gas piston accumulator of claim 13, wherein the gas piston accumulator is of double-walled design, namely with an inner tube, in which the pressure piston is axially guided, and with an outer tube, which surrounds the inner tube, forming an annular gap.

26. The gas piston accumulator of claim 14, wherein the gas piston accumulator is of double-walled design, namely with an inner tube, in which the pressure piston is axially guided, and with an outer tube, which surrounds the inner tube, forming an annular gap.

27. The gas piston accumulator of claim 16, wherein the hydraulic space of the inner tube is bounded in the axial direction by a hydraulic-side cylinder base of the gas piston accumulator, and/or the gas space of the inner tube is bounded in the axial direction by a gas-side cylinder base of the gas piston accumulator, and/or the hydraulic-side cylinder base and/or the gas-side cylinder base act as mechanical piston stops for the pressure piston, and/or the outer tube merges materially and/or integrally into the two axially opposite cylinder bases, forming a gas piston accumulator housing.

28. The gas piston accumulator of claim 12, wherein, when emptied, the pressure piston together with the hydraulic-side cylinder base delimits a hydraulic-side filling chamber, and, during a charging process of the gas pressure accumulator, hydraulic fluid flows from the hydraulic line into the hydraulic-side filling chamber in order to assist a detachment of the pressure piston from the hydraulic-side cylinder base.

29. The gas piston accumulator of claim 13, wherein, when emptied, the pressure piston together with the hydraulic-side cylinder base delimits a hydraulic-side filling chamber, and, during a charging process of the gas pressure accumulator, hydraulic fluid flows from the hydraulic line into the hydraulic-side filling chamber in order to assist a detachment of the pressure piston from the hydraulic-side cylinder base.

30. The gas piston accumulator of claim 14, wherein, when emptied, the pressure piston together with the hydraulic-side cylinder base delimits a hydraulic-side filling chamber, and, during a charging process of the gas pressure accumulator, hydraulic fluid flows from the hydraulic line into the hydraulic-side filling chamber in order to assist a detachment of the pressure piston from the hydraulic-side cylinder base.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0019] In the following, an embodiment of the invention is described with reference to the accompanying figures.

[0020] In detail: [0021] FIG. 1 shows a sectional view of a gas piston accumulator; [0022] FIG. 2 shows a sectional view of the gas piston accumulator in an operating position; [0023] FIG. 3 shows a sectional view of the gas piston accumulator in an operating position; [0024] FIG. 4 shows a view of the pressure piston; [0025] FIG. 5 shows a view of the pressure piston; [0026] FIG. 6 shows a view of the pressure piston; [0027] FIG. 7 shows steps for filling the gas piston accumulator with gas; and [0028] FIG. 8 shows steps for filling the gas piston accumulator with gas.

DETAILED DESCRIPTION

[0029] FIG. 1 shows a gas piston accumulator which is formed as a piston-cylinder unit. In FIG. 1, the gas piston accumulator is double-walled with an inner tube 1 and an outer tube 3.

[0030] A pressure piston 5 is axially guided in the inner tube 1. The pressure piston 5 divides the tube interior of the inner tube 1 into a lower hydraulic space 7 and an upper gas space 9. The inner tube 1 is spaced from the outer tube 3 by a radial distance, forming an annular gap 13.

[0031] In FIG. 1, the gas space 9 located in the inner tube 1 is bounded upward in the axial direction by a gas-side cylinder base 15. Similarly, the hydraulic space 7 located in the inner tube 1 is bounded downward in the axial direction by a hydraulic-side cylinder base 17 in which a mouth (oil inlet) 19 of a hydraulic line 21 is formed. The two cylinder bases 15, 17 together with the outer tube 3 form an outer cylindrical gas piston accumulator housing 23.

[0032] As further shown in FIGS. 1, 2, and 3, a hydraulic-side tube end 25 of the inner tube 1 is conically expanded in the direction of the hydraulic-side cylinder base 17, whereby the annular gap 13 is bridged radially outward. The conically expanded, hydraulic-side tube end 25 is welded at the inner corner region between the outer tube 3 and the hydraulic-side cylinder base 17 by a pressure-resistant and fluid-tight welded joint.

[0033] Similarly, a gas-side, upper tube end 27 is conically expanded in the direction of the gas-side cylinder base 15, thereby bridging the annular gap 13 radially outward. In FIG. 1 or 3, the conically expanded gas-side tube end 27 is attached to the inner corner area between the outer tube 3 and the gas-side cylinder base 15. In this way, the overall result is a dimensionally stable double-wall structure in which less material is required compared to a single-wall structure.

[0034] The inner circumference of the inner tube 1 acting as a pressure piston running surface is completely smooth cylindrical between the two tube ends 25, 27.

[0035] FIG. 3 shows the gas piston accumulator in completely oil-empty state after an discharging process. Accordingly, the pressure piston 5 is pressed in pressure contact against the hydraulic-side cylinder base 17 by a biasing force F.sub.v generated by a gas pressure p.sub.gas as in the gas space 9. If there is an excessively large contact area between the pressure piston 5 and the hydraulic-side cylinder base 17, an adhesive connection (due to a suction cup effect) may occur between the pressure piston 5 and the hydraulic-side cylinder base 17 when a charging process is started. In order to help detach the pressure piston 5 from the hydraulic-side cylinder base 17 at the start of the charging process, the pressure piston 5 has a small-area stop structure 29, which protrudes from an axially set back piston main body 31 by an axial offset Aa (FIG. 1). When completely emptied according to FIG. 3, the pressure piston 5 is therefore supported on the hydraulic-side cylinder base 17 via its small-area stop structure 29. FIG. 3 further shows that, in oil-empty state, a hydraulic filling chamber 33 is defined between the piston main body 31, the stop structure 29, the inner tube inner circumference and the hydraulic-side cylinder base 17. Thus, when the charging process is started, hydraulic fluid from the hydraulic line 21 first flows into the filling chamber 33 to assist in detaching the pressure piston 5 from the hydraulic-side cylinder base 17.

[0036] In FIG. 2, the gas piston accumulator is completely filled with hydraulic fluid after a successful charging process. Accordingly, in FIG. 2, the pressure piston 5 is brought into pressure contact with the gas-side cylinder base 15 against the biasing force F.sub.v. On its gas side, the pressure piston 5 also has a stop structure 29 (FIG. 1) protruding by an axial offset Δa from the piston main body 31. In FIG. 2, the stop structure 29 defines a gas-side filling chamber 35 together with the inner tube inner circumference, the piston main body 31 as well as the gas-side cylinder base 15. When starting a discharging process, the gas expands and flows from the annular gap 13 via the flow passage 10 into the inner tube 1 and further into the gas-side filling chamber 35 in order to help detach the pressure piston 5 from the gas-side cylinder base 15. The pressure piston 5 therefore has a stop structure 29 which is of reduced area on both sides, i.e. both on its hydraulic side and on its gas side, which can be brought into contact with the associated cylinder base 15, 17.

[0037] According to FIG. 4, the pressure piston 5 has a circumferential piston ring seal 37 on its outer piston circumference to ensure smooth axial adjustment of the pressure piston 5 along the pressure piston running surface in the inner tube 1.

[0038] In FIG. 5, the stop structure 29 is shown on the gas side (i.e., bottom side) of the pressure piston 5. Accordingly, the stop structure 29 has a sleeve-shaped extension 39 protruding from the pressure piston main body 31 and positioned concentrically to the pressure piston circumference. The hydraulic-side filling chamber 33 extends continuously in an annular shape around the sleeve-shaped extension 39 of the pressure piston 5. Radial webs 41 project from the outer circumference of the sleeve-shaped extension 39 in a star shape and are uniformly distributed circumferentially, the radially outer web sides of which are arranged with a radial offset Δr (FIG. 5) within the pressure piston circumference.

[0039] In FIG. 6, the pressure piston 5 is shown on its gas side (i.e., top side). Accordingly, the gas side stop structure 29 is of substantially the same construction as the hydraulic side stop structure 29 (FIG. 5). The sleeve-shaped extension 39 formed both on the gas side and on the hydraulic side of the pressure piston 5 delimits a blind hole-like recess 40 radially on the inside in FIG. 2 or 3. When completely emptied of hydraulic fluid (FIG. 3) or when completely filled with hydraulic fluid (FIG. 2), the free annular end face of the respective sleeve-shaped extension 39 of the pressure piston stop structure 29 is in pressure contact with the respective cylinder base 15, 17. Therefore, when completely emptied of hydraulic fluid or when completely filled with hydraulic fluid, the blind hole-like recess 40 in FIG. 2 or 3 is completely fluid-tightly decoupled from the filling chamber 33, 35 located radially outside the sleeve-shaped extension 39.

[0040] Steps for filling the gas piston accumulator with gas are illustrated in FIGS. 7 and 8. Accordingly, in a piercing step I, a filling opening 43 is pierced into the outer tube 3. This is followed by an evacuation step II, in which the interior of the gas piston accumulator is evacuated of air. After completion of the evacuation step II, a filling step III (FIG. 8) is performed, in which the annular gap 13 and the gas space 9 in the inner tube 1, which is fluidically connected thereto, are filled with gas, in particular nitrogen, via the filling opening 43 formed laterally on the outer tube 3. After the filling process, the filling opening 43 is sealed, for example welded shut, in a sealing step IV.

REFERENCE NUMERALS

[0041] 1 inner tube

[0042] 3 outer tube

[0043] 5 pressure piston

[0044] 7 hydraulic space

[0045] 9 gas space

[0046] 13 annular gap

[0047] 15 gas-side cylinder base

[0048] 17 hydraulic-side cylinder base

[0049] 19 oil inlet

[0050] 21 hydraulic line

[0051] 23 gas piston accumulator housing

[0052] 25 hydraulic-side tube end

[0053] 27 gas-side tube end

[0054] 29 stop structure

[0055] 31 piston main body

[0056] 33 hydraulic-side filling chamber

[0057] 35 gas-side filling chamber

[0058] 37 piston ring seal

[0059] 39 sleeve-shaped extension

[0060] 40 blind hole-like recess

[0061] 41 radial webs

[0062] Δa axial offset

[0063] Δr radial offset

[0064] p.sub.gas pressure

[0065] p.sub.s accumulator pressure

[0066] F.sub.v biasing force

[0067] steps I to IV