EP1606517B1 - Piston-type accumulator - Google Patents

Description

The invention relates to a piston accumulator with a storage housing in the form of a cylinder tube according to the feature configuration of the preamble of claim 1.

Piston accumulators belong in the broadest sense to the so-called hydraulic accumulators, which are used, inter alia, to take up certain volumes of pressurized fluid (hydraulic medium) of a hydraulic system and to return them to the system as required. Since the hydraulic medium is under pressure, the hydraulic accumulators are treated like pressure vessels and must be designed for the maximum operating pressure, taking into account the acceptance standards of various installation countries. Hydropneumatic (gas-loaded) accumulators with separating element are nowadays used in most hydrosystems, with a piston acting as a separating element in the piston accumulators, which separates a liquid space as a working space from a gas reservoir as an additional working space within the accumulator housing of the piston accumulator. Nitrogen is used regularly as working gas and the gas-tight piston largely allows a decoupling of gas storage space to liquid space.

The liquid part communicates with the hydraulic circuit, so that the piston accumulator absorbs fluid as the pressure increases and the gas is compressed. With decreasing pressure, the compressed gas expands, displacing the stored pressure fluid back into the hydraulic circuit. One advantage of piston accumulators is that they can "work" in any position, but a vertical arrangement with the gas side upwards is preferable in order to avoid settling of dirt particles from the liquid on the piston seals.

The essential components of a piston accumulator are therefore as an accumulator housing an outer cylinder tube, the piston as a separating element with its sealing system and the front-side closure parts, which at the same time as lid parts also include a liquid and gas connection. The memory housing regularly two functions, namely once to stockpile the internal pressure and to ensure the other hand, the leadership of the piston within the storage enclosure.

In an effort to make the production of hydraulic accumulators rational and inexpensive, one has already gone to provide at least at one end face of the cylinder tube not attached thereto, separate cover part as a closure member, but the closure member einstükkig form with the front end of the cylinder tube by the Wall is deformed in a forming area. The WO 98/55258 shows a corresponding example of the preparation of a hydraulic accumulator in the form of a membrane memory. In a manner known per se, the deformation forming the closure part takes place depending on the material type of the cylinder tube by cold or hot forming, for example, after the flame or induction heating by means of rolling or pressing, wherein the cylinder tube end is formed into a bottom with an outwardly everted collar on which a connection for the relevant working medium is formed. Although this simplifies the manufacturing effort required to produce a diaphragm accumulator, problems arise when such methods are to be used to produce piston accumulators.

By the WO 02/12731 A (KITAHARA TOSHIAKI; YUDA AKIO (JP); NOK CORP (JP) 14 February 2002 (2002-02-14) and EP 1308634 a diaphragm accumulator is known, which has a kind of piston-forming expansion diaphragm a longitudinally movable bottom plate, which is resiliently connected to the housing cover of a storage enclosure. The storage housing is formed in the manner of a cylinder tube and the diaphragm separating piston fluid-tightly separates two working spaces, wherein the cylinder tube is closed as a storage housing at both axial ends by a closure part, of which at least one by deforming a subsequent to the Kolbenhubbereich forming region of the wall the cylinder tube is formed as a one-piece part, wherein in the interior of the cylinder tube at the location of the transition from the piston stroke to the forming a movement of the separating piston before reaching the forming area limiting stop body is provided. In the known solution, the stopper body, which is provided with a projecting into the interior of the storage housing fluid passage, formed in the manner of a multi-dimensionally shaped sheet metal part as a sealing plate and accordingly has at least at the transition points to the inside of the storage housing (cylinder tube) an elastically resilient seal formed made of elastomeric material, on.

The pertinent sealing plate is used to avoid damage to the sensitive elastomeric material either in trained Nutverläufe inside the cylinder tube or, if the cylinder tube receives as a storage housing from the outside by rolling such an inwardly projecting Eingriffsnut to hold the seal assembly, additional dimensionally stable support rings inserted between the inner wall of the cylinder tube and the outer periphery of the sealing material. Furthermore, the piston in the form of the membrane separating arrangement can be provided at its free end on the outer peripheral side with a guide plate, which slides along the inner circumference of the cylinder tube, as soon as the piston performs an axial movement within the storage housing.

In another known solution according to the US 4 041 990 A is a multi-part storage enclosure formed from a screw-on housing head and a pot-shaped longitudinal housing part, in which a separating piston is guided longitudinally movable. In the open open end portion of the pot-like housing part this is provided with a stop body for the piston in the form of an annular body with a circular cross-section, wherein an incorporated in the inner wall of the cylinder tube, the first holding surface forming paragraph forms a curved surface part of a seat for this annular body. In the known solution of the annular body serves as a stop means only the limitation of the axial displacement movement for the piston and the extent open to the outside cylindrical storage housing part as a housing pot is closed by the lid-like housing head exclusively to the outside sealing.

Based on this prior art, the invention has the object to provide a piston accumulator whose construction opens up the possibility of simple and efficient production of the storage housing by end-side deformation of the cylinder tube, without resulting in problems in terms of the performance of a piston accumulator so manufactured. This object is achieved by a piston accumulator with the features of claim 1 in its entirety.

By the solution according to the invention it is achieved that a first, located at the end of Kolbenhubbereichs support surface is formed by a recess in the inner wall of the cylinder tube forming paragraph. In the manufacture of the piston accumulator, the stopper body is introduced into the cylinder tube from the adjacent open end before deformation of the wall of the cylinder tube and applied to the shoulder. For the forming part of the cylinder tube forming step, the stopper body is now in a defined position. A second, the stop body positively fixing, located within the forming area holding surface can now be formed by the closure member forming deformation of the wall of the cylinder tube by the wall of the cylinder tube is deformed during deformation around the lying in the forming wall portion of the stop body around.

Since the stopper body is a rigid component and has the shape of a flat plate having a convex convex curvature on the circumference, this "molding" of the stopper body is particularly advantageous because around the convex curvature around the wall of the cylinder tube in the formation of the closure member is deformed to form the second holding surface lying in the forming area.

When using a stopper body in the form of a plate, so a rigid component, which is located in the cylinder tube at the transition point to the forming, there is the additional advantage that the stopper body acts as a support body during the process of preforming, so that in the formation of the closure part of the is supported in front of the peripheral area Kolbenhubbereich and thus protected against a possibly caused by the deformation process change in its geometry.

Instead of using a plate-like stopper body, an annular body of round cross-section may be provided, for example a steel ring which is split into a seat forming the positive holding surface, which is incorporated in the inner wall of the cylinder tube.

By inventively provided limitation or blocking the piston movement to a piston end position in which the piston is still outside the forming area, the risk of malfunction is effectively avoided. If no defined piston end position was specified in the case of piston accumulators with a forming region provided on the cylinder tube at the end, so that the separating piston could enter the deformation region under certain operating conditions, for example gas loss in the gas reservoir or high fluid pressures, then there would be a risk of jamming or jamming of the piston due to the failure of the piston Deformation of the wall of the cylinder tube possibly altered geometry of the piston guide and due to the roughness caused by the forming inside the housing end. By arranged in the interior of the cylinder tube in such a position stop body that the end position of the piston is fixed to the end of Kolbenhubbereiches and thus before entering the forming area, it is ensured that through the inner wall the cylinder tube formed in Kolbenhubbereich, flawless and gas-tight leadership of the piston is maintained under all operating conditions.

The stop body is positively secured by the located on the inside of the wall of the cylinder tube retaining surfaces against axial movement, so that a safe stroke limitation of the piston is ensured even with hard starting against the stop body.

• Fig. 1 einen schematisch vereinfacht und abgebrochen gezeichneten Längsschnitt eines Ausführungsbeispieles des erfindungsgemäßen Kolbenspeichers, von dem nur der gasseitige Endbereich des Speichergehäuses gezeigt ist und wobei Kolbendichtungs- und Führungsmittel weggelassen sind, und
• Fig. 2 einen der Fig. 1 ähnlichen Längsschnitt eines zweiten Ausführungsbeispieles.

The invention with reference to exemplary embodiments illustrated in the drawing is explained in detail. Show it:

• Fig. 1 shows a schematically simplified and broken drawn longitudinal section of an embodiment of the piston accumulator according to the invention, of which only the gas-side end portion of the storage enclosure and wherein piston seal and guide means are omitted, and
• Fig. 2 is a similar to Fig. 1 longitudinal section of a second embodiment.

In the exemplary embodiments of the piston accumulator according to the invention shown in the drawing, the accumulator housing has a circular cylindrical tube 1 which defines a longitudinal axis 3. At its gas-side end region, the cylinder tube 1 has a gas supply chamber 5 delimiting closure part 7, which is formed as an integral part of the cylinder tube 1 by deforming the wall of the cylinder tube 1 in a forming region 9. As already mentioned, the forming the closure member 7 deformation is carried out according to a known in the art forming method, depending on the properties of the cylinder tube 1 forming metallic material cold or hot forming by means of rolling or pressing tools or the like is performed to the closure member 7 in the form of a closed bottom, on which a coaxially projecting to the axis 3 neck portion 11 is formed, on which a leading into the gas storage chamber 5 gas channel 13 and a terminal for a corresponding (not shown) connecting fitting are formed.

A separating piston 15, which forms the separating element between the gas reservoir 5 and a fluid chamber 6, has a concentric, inner trough-like depression 17 for increasing the volume of the gas reservoir 5 and is longitudinally movable within a piston stroke region 19 of the cylinder tube 1. The inside of the wall of the cylinder tube is feinstbearbeitet in Kolbenhubbereich 19, together with provided on the circumference of the piston 15 piston seal and piston guide means a gas-tight and low-friction piston guide within the To ensure Kolbenhubbereiches 19. The provided on the circumference of the piston 15 sealing and guiding means are not shown in the drawing. These seated in circumferential annular grooves 21 of the piston 15 means may be of conventional design.

At the end of Kolbenhubbereiches 19 is located on the inner wall of the cylinder tube 1 a recess of the inner wall forming paragraph 23. This provides a flat contact surface for a flat plate 25, for the positional fixing it forms a support surface, the plate 25 against axial movement in the direction of the piston stroke 19 secures positively. The plate 25 has a convex, spherically curved peripheral surface 27. In the deformation of the wall of the cylinder tube 1, in which the adjoining the Kolbenhubbereich 19 forming region 9 is formed, the wall of the cylinder tube 1 is formed around the spherical peripheral surface 27 of the plate 25 around , so that the deformed cylinder wall on the spherical peripheral surface 27 forms a second holding surface for fixing the position of the plate 25, so that it is fixed positively against axial movement in both directions.

The plate 25 is introduced during the manufacturing process of the piston accumulator from the initially open end of the cylinder tube and applied to the shoulder 23 and is thus positioned in the manner suitable for the deformation step. As an additional position assurance before performing the deformation forming the forming region 9, the recess 23 forming recess in the inner wall of the cylinder tube 1 may be formed so that the bottom of the recess together with the spherical peripheral surface 27 of the plate 25 forms a press fit, the plate 25th during the deformation of the circumferential portion 9 holds in position.

A centrally formed in the plate breakthrough 29 is provided as a gas passage. The designed as a relatively rigid component plate 25, for example, a steel material, not only forms a stop body for the piston 15, which blocks the piston movement before leaving the Kolbenhubbereiches 19, but also forms a rigid support body, the cylinder tube 1 at the transition from Kolbenhubbereich 19th is supported for deformation area 9 during the process of deformation so that the deformation forces acting on the deformation area 9 can not cause any changes in the geometry of the cylinder tube 1 in the piston stroke area 19. The piston 15 is thus performed perfectly in all operating conditions of the piston accumulator in the finest machined Kolbenhubbereich 19, which is ensured by acting as a stop body plate 25 that no shrinkage of the piston 15 can take place in the forming region 9, in which the inner wall of the cylinder tube 1, im Difference to the reaching to paragraph 23 Kolbenhubbereich 19, no Feinstbearbeitung the inside needs to have.

The embodiment shown in Fig. 2 differs from the example of Fig. 1 only insofar as the piston movement at the end of Kolbenhubbereiches 19 of the cylinder tube 1 limiting abutment body is not a plate, but a steel ring 31. In this embodiment, the shoulder 23 forms on the inside of the cylinder tube 1 at the end of Kolbenhubbereiches 19 a curved partial surface of a curved inner annular groove 33 which forms the seat for the steel ring 31. The curved surface of this annular groove 33, which extends around a sufficient peripheral region of the steel ring 31, forms the retaining surfaces which secure the ring 31 against axial movement in both directions in a form-fitting manner.

If the annular groove 33 is formed in the region axially remote from the shoulder 23 only by the deformation forming the deformation region 9, so that the steel ring 31 can be inserted from the open end of the cylinder tube 1 before deformation, a closed ring 31 can be used. Alternatively, i. if the annular groove 33 is not finished during the deformation process, d. H. as it were "closed", a slotted steel ring 31 can be blasted into an already fully formed annular groove 33.

In the example of Fig. 1, a plate 25 is shown with only one opening 29 as a gas passage. It is understood that a plate with several openings, for example, in the form of a mesh plate, could be provided.

Claims (2)

1. Piston store with a store housing in the form of a cylinder pipe (1), in which a separating piston (15) separating two working chambers (5 and 6) from each other can be displaced in an axial direction within a piston stroke area (19) of the cylinder pipe (1), the same being closed at both axial ends by a closure part (7), of which at least one is created by deforming a deformation (9) adjacent to the piston stroke area (19) of the wall of the cylinder pipe (1) in the way of a single piece, whereby an abutment body (25) limiting the movement of the separating piston (15) prior to the same reaching the deformation area (9) is envisaged inside the cylinder pipe (1) at the point of transition between the piston stroke area (19) and the deformation area (9), the same being supported by a shoulder (23) on the inside wall of the cylinder pipe (1) forming a first holding surface, characterised in that the abutment body is a rigid construction element and comprises the shape of a flat plate equipped with a spherical convex bead around its circumference (27), or in that an annular body (31) with a circular cross-section is envisaged as an abutment body, whereby the shoulder (23) forming the first holding surface provided on the inside wall of the cylinder pipe (1) forms a beaded part surface of a seat (33) for the annular body (31), and in that the wall of the cylinder pipe (1) around the beading of the plate or the annular body (31) is deformed by forming a closure part (7) in order to form the second holding surface positioned in the deformation area (9).
2. Piston store according to Claim 1, characterised in that the flat plate (25) is equipped with at least one through passage (29) as an outlet for a working medium located in the relevant working chamber (5).

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