Piston Type Accumulator

Abstract

The piston-type accumulator comprises an accumulator housing (10) in which a separation piston (12) is guided so as to be movable in the longitudinal direction, the separation piston (12) separating two fluid chambers (14, 16), in particular a fluid chamber (14) containing a working gas from another fluid chamber (16) containing a liquid such as hydraulic oil, a damping piston (18) provided with a check valve (20) which is capable of entering a fluid port (24) while forming a throttle gap (22) which is a cylindrical annular chamber formed by adjacent walls (28, 32) of the accumulator housing (10) and the damping piston (18), and the check valve (20) comprises a valve ball (36) biased by an energy storage means which, in a closed position, blocks the flow path between the fluid port (24) and the piston fluid chamber (38) and which opens it in an open position.

Description

[Technical field]

[0001] The invention relates to a piston-type accumulator having an accumulator housing in which a separating piston is guided so as to be longitudinally movable, the separating piston separating two fluid chambers from one another, in particular separating a fluid chamber containing a working gas from another fluid chamber containing a liquid such as hydraulic oil, the separating piston having a damping piston with a check valve, the damping piston being able to enter a fluid port in the accumulator housing and forming a throttle gap. [Background technology]

[0002] Patent document 1 discloses a similar piston-cylinder unit with piston end position damping, which has a damping piston protruding from the end face of the piston, which can be stored in a damping chamber provided at the opposite cylinder end while forming a damping gap conically tapering towards the fluid port, and in order to introduce the return stroke movement of the piston, a flow passage is provided which leads from the fluid port of pressurized oil, bypassing the damping gap, to a pressure chamber in an accumulator housing adjacent to the main piston face of the piston and which includes a check valve. This flow passage, which can be controlled by a check valve, runs inside the piston between an inlet opening at the front end of the damping piston formed as a hollow sleeve and a through hole leading from the inside of this sleeve to the outside in the form of a transverse flow passage. The check valve used in this case has a solid valve plate controllable by an energy storage means in the form of a compression spring, which controls the large opening cross section of the damping piston, which leads to leakage in the closed position and is accompanied by disturbances in the flow pattern when the valve is opened. Furthermore, due to the inertial behavior of the valve plate, rapid opening and closing processes are not possible. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] European Patent Application Publication No. 0286777 Summary of the Invention [Problem to be solved by the invention]

[0004] The object of the present invention is therefore to proceed from this prior art and further improve the known solutions in order to provide a piston-type accumulator with improved end position damping for the separating piston and also with improved response behavior during the inflow and outflow of fluid into the hydraulic accumulator. [Means for solving the problem]

[0005] The above problem is solved by a piston-type accumulator having the overall features of patent claim 1.

[0006] According to the characterizing part of claim 1, the throttle gap is a cylindrical annular chamber formed by the adjacent walls of the accumulator housing and the damping piston, and the check valve has a valve ball biased by an energy storage means, which in the closed position blocks the flow path between the fluid port and the piston fluid chamber between the separating piston and the accumulator housing, and in the open position opens the flow path, thereby achieving a constant throttle gap width over the entire engagement length of the damping piston at the fluid port, which leads to a significantly improved end position damping. Since there is no need to consider a continuously changing gap shape with a conical section, as shown in the prior art, the engagement length of the damping piston at the fluid port can be selected to be very long within settable limits constrained by the shape to be maintained for the hydraulic accumulator, so that in conjunction with the constant gap size over the entire engagement length, a significantly improved piston end position damping is achieved. Furthermore, the valve ball of the check valve makes it possible to realize an improved valve seat shape with improved air tightness in the closed position and reduced disturbance of the flow pattern in the open position. Moreover, due to the small mass inertia of the valve or closing ball, designed with correspondingly small dimensions, the fluid flows occurring during the charging and discharging of the hydraulic accumulator, respectively, can be reliably controlled in a rapid time sequence, which is not comparable in the prior art.

[0007] In a preferred embodiment of the piston-type accumulator according to the invention, the damping piston is provided as a hollow cylinder having a hollow cylindrical passage in at least one damping position and forming a flow path between the fluid port and the non-return valve, the diameter of the hollow cylinder of the damping piston then substantially corresponds to the diameter of the valve closing ball, so that when the accumulator is filled with a fluid, such as hydraulic oil, the valve ball is subjected to a central flow and can float unhindered on its valve seat in the associated valve housing.

[0008] In another preferred embodiment of the piston-type accumulator according to the invention, the damping piston, viewed in the direction of the piston fluid chamber, transitions into an extension forming a shoulder with an annular surface, which is configured such that when the separate piston abuts against a part of the accumulator housing, such as the housing cover, it forms an annular gap whose gap dimension is greater than the gap dimension of the throttle gap. In this way, the movement of the separate piston continues to be damped via the annular gap until the separate piston abuts completely in its lower movement position on the adjacent upper side of the housing cover upon discharge of the accumulator, so that both the throttle gap and the annular gap provide damping for such movement of the separate piston.

[0009] In another preferred embodiment of the piston-type accumulator according to the invention, the annular surface is part of an insert that accommodates the check valve, which is fixed in the receiving part of the separation piston, preferably by means of a snap ring between the insert and the separation piston. Due to the check valve being an integral component of the insert, the damping device can be connected as a whole from a central position of the separation piston, in particular from the lower side of the separation piston, which is very easy to assemble and requires few work steps. In this respect, the piston-type accumulator solution according to the invention can also be produced cost-effectively.

[0010] In another preferred embodiment of the piston-type accumulator according to the invention, the check valve is designed as a valve cartridge, which together with the valve housing is screwed into the insert and the valve ball is permanently biased by an energy storage means, preferably in the form of a compression spring, and guided in the valve housing. Such valve cartridges are standard on the market and can be adapted to different hydraulic accumulator sizes, particularly in terms of the connection geometry, which contributes to a functionally reliable and cost-effective design of the entire end position damping.

[0011] The valve housing preferably has at least one transverse passage, which extends controllably by the valve ball of the check valve into the corresponding transverse passage in the insert. In this case, the valve housing advantageously has a groove, preferably in the form of an annular chamber, on the outer periphery, into which the respective transverse passage in the valve housing opens on one side and the corresponding transverse passage in the insert opens on the other opposite side. In this way, guidance of the entire fluid flow through the valve housing together with the insert is achieved. During the filling of the accumulator, the vertically entering fluid flow is deflected by approximately 90 degrees, so that this fluid flow is guided transversely towards the piston fluid chamber and deflected towards the piston fluid chamber. This is particularly advantageous in terms of energy and leads directly to a rapid actuation of the separating piston during filling.

[0012] In another preferred embodiment of the piston-type accumulator according to the invention, the separation piston, on the side facing the fluid port, defines a hollow-chamber-like recess opening into a ramp towards the snap ring, the bore axis of each transverse channel in the insert being flush with the wall of the separation piston that at least partially defines the recess of the separation piston and in which wall the ramp opens into the recess. The aforementioned preferably circumferentially extending ramp ensures a reliable positioning of the snap ring for fixing the insert in the separation piston, and can also be used as an inflow aid to directly convert the lateral forces introduced by the fluid flow into an upward movement of the separation piston within the framework of the accumulator filling process.

[0013] As already mentioned, it is particularly expedient if the axial length of the damping piston is configured to be greater than the comparable height of the piston fluid chamber in the separation piston, which is at least partially penetrated by the insert. Practical tests have shown that with such a length and height configuration, particularly good damping properties are obtained during the discharge process of the accumulator, and that in the reverse direction, when the accumulator is filled, the separation piston moves unhindered with the working gas towards the fluid chamber, whereby it is preloaded.

[0014] The present invention further comprises the following method steps: throttling a volumetric flow rate upon discharge of the piston-type accumulator by forming a hollow cylindrical throttle gap between a damping piston and a portion of the accumulator housing; bypassing the throttle gap by opening a check valve having a valve ball mounted on a separating piston and biased by an energy storage means, based on a pressure difference occurring in the throttle gap when the piston-type accumulator is filled; and applying fluid pressure across the free piston cross section to move the separated piston directly towards the other fluid chamber containing the working gas.

[0015] In the following, the piston-type accumulator according to the invention will be explained in more detail on the basis of an embodiment according to the drawings. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a vertical cross-sectional view of the lower part of a conventional piston-type accumulator, except for the features of the present invention, as illustrated in, for example, Patent Document 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The figure shows the lower part of a piston-type accumulator, generally designated 10, with a hollow cylindrical wall 8 of the accumulator housing. A separating piston 12 is guided for longitudinal movement in the accumulator housing, which separates two fluid chambers 14, 16 from one another, in particular the fluid chamber 14 containing a working gas, such as nitrogen, from another fluid chamber 16 containing a liquid, such as hydraulic oil. Furthermore, the separating piston 12 has a damping piston 18, which is provided with a check valve 20 at its free end face. The damping piston 18 can enter a fluid port 24 in the accumulator housing 10, forming a throttle gap 22. The figure shows the separating piston 12 in its lowest position in the accumulator housing 10, whereby the fluid flow from the side of the fluid chamber 16 towards the fluid port 24 is maximally throttled. The position of the separating piston 12 shown in this way corresponds to the maximum discharge situation of the entire hydraulic accumulator. The piston-type accumulator can be connected in the usual manner, via internal threads 26 in fluid port 24, to a hydraulic circuit of conventional design, not shown, by means of conduits, not shown.

[0018] As can be further seen, the throttle gap 22 is a cylindrical annular chamber or a hollow cylinder filled with fluid and is formed by an adjacent wall 28 of the accumulator housing 10 in the form of a housing cover 30 and a wall 32 of the damping piston 18 adjacent thereto. The housing cover 30 is screwed onto the bottom side of the hollow cylindrical wall 8 of the accumulator housing 10 as a part thereof and is sealed against the rest of the accumulator housing 10 via a ring seal, not shown in detail, in an annular groove 31. The separating piston 12 has two annular grooves 33 on its outer periphery for receiving sealing rings and guide bands, not shown in detail, of which only the upper annular groove is designated 33. The check valve 20 has a valve ball 36 which is constantly biased by an energy storage means in the form of a compression spring 34, which in the closed position shown blocks the flow path between the fluid port 24 and a piston fluid chamber 38 between the separation piston 12 and the accumulator housing 10 or the housing cover 30, and in the open position opens this flow path against the action of the compression spring 34. In this embodiment, the piston fluid chamber 38 is formed by a chamber-like recess provided in the underside of the separation piston 12, the outer periphery of which is surrounded by the wall of the separation piston 12 at the height of the sealing ring system in the annular groove 33.

[0019] As can be further seen from the figure, the damping piston 18 is formed from a hollow cylinder which in at least one damping position, in the fully damped position shown in the figure, defines a flow path between the fluid port 24 and the check valve 20 with the valve ball 36 by means of a hollow cylindrical passage 40. The damping piston 18 with its reduced diameter transitions, seen in the direction of the piston fluid chamber 38, into an expansion with an annular surface 44 of enlarged diameter forming a shoulder 42. This annular surface 44 forms an annular gap 46, the gap dimension of which is preferably selected to be greater than the free gap dimension of the throttle gap 22, when the separating piston 12 abuts against a part of the accumulator housing 10 in the form of the housing cover 30 according to the representation in the figure.

[0020] The annular surface 44 is part of an insert 48 which accommodates the entire check valve 20, which is held in a hollow cylindrical receptacle 50 of the separating piston 12 by a snap ring 52 between the insert 48 and the separating piston 12. In this case, the check valve 20 is designed as a valve cartridge, whose valve housing 54 is screwed into the insert 48 by means of a socket head bolt 55. According to the illustrated representation, the valve ball 36 is held in a leak-proof manner on a valve seat 56 in the valve housing 54 under the action of a compression spring 34 in the closed position. The valve housings 54 each have a transverse passage 58 diametrically opposite to the longitudinal axis 60 of the hydraulic accumulator, which is directly connected to the valve ball 36 and can be operated by the valve ball 36. Instead of a pair of transverse passages 58, a different number of transverse passages 58 can also be provided, in particular only a single transverse passage 58. Each transverse passage 58 opens in the valve housing 54 into another, possibly assigned transverse passage 62 in the insert 48. Between a pair of mutually assigned transverse passages 58, 62, the valve housing 54 has on its outer circumferential side a groove 64, preferably in the form of an annular valve chamber, into which the respective transverse passages 58 of the valve housing 54 open on one side and the respectively assigned transverse passages 62 in the insert 58 open on the other opposite side. On the side facing the fluid port 24, the separating piston 12 defines a hollow-chamber-like recess as part of the piston fluid chamber 38, which opens into an inclined section 66 in the separating piston 12, which runs conically upwards in the direction of the longitudinal axis 60 towards the snap ring 52. In this case, the bore axis of each transverse passage 62 in the insert 48 is flush with the upper wall border of the recess in the separating piston 12, into which the inclined section 66, guided circumferentially in the separating piston 12, opens. What is particularly important for the piston-type accumulator solution according to the invention is that, insofar as the damping piston 18 is engaged with a portion of the fluid port 24, the axial length of the damping piston 18 is in any case greater than the comparable height of the piston fluid chamber 38 formed by the recess in the separation piston 12 which is at least partially penetrated by the insert 46.

[0021] The illustrated piston-type accumulator can be operated with the device according to the invention as follows: By forming a hollow cylindrical throttle gap 22 between the damping piston 18 and a portion of the accumulator housing 10, the volumetric flow rate is throttled upon discharge of the piston-type accumulator, and the associated downward movement of the separating piston 12 forces fluid from the fluid chamber 16 through the throttle gap 22 towards the fluid port 24, which remains unpressurized, where it is further throttled through an annular gap 46 between the insert 48 and the adjacent upper wall of the housing cover 30. During filling of the piston-type accumulator, the pressure difference occurring in particular in the throttle gap 22 causes the check valve 20, which is integrated in the separating piston 12 and has a valve ball 36 biased by a compression spring 34, to open, thereby bypassing the throttle gaps 22, 46. The fluid pressure present in the fluid port 24 opens the aforementioned check valve 20, and the fluid flows through the hollow cylindrical passage 40 and the interior of the valve housing 54 towards the transverse channels 58 and 62, which are connected in fluid communication with the groove 64 in the valve housing 54. In this way, the fluid under pressure enters the piston fluid chamber 38 via the fluid port 24, and the separating piston 12 is lifted upwards in the direction shown. By further movement against the influence of the working gas in the fluid chamber 14, the fluid volume on the fluid side with the fluid chamber 16 increases. As a result, The fluid pressure acts over the entire free piston cross section, causing the separation piston 12 to move directly towards the other fluid chamber 14 containing the working gas. The movement of the separation piston 12 causes a large amount of fluid to flow from the hydraulic circuit towards the fluid chamber 16 as soon as the damping piston 18 completely opens the fluid passage 24 towards the fluid chamber 14. In this operating position, the hydraulic accumulator is again available for the above-mentioned discharge process.

[0022] In the region of the internal thread 26 of the fluid port 24 there is a damping valve, generally designated 68, which has a longitudinally movable valve plate 70 with a throttle bore 72 coaxially with the longitudinal axis 60 of the hydraulic accumulator. Such a valve plate 70 is accommodated in a valve housing 74, preferably designed as a tripod, which is screwed flush into the fluid port 24 along the internal thread 26. Between the legs of the valve housing 74 there is an inlet 76 in each case, so that in the illustrated position for filling the accumulator, when the non-return valve 20 is open, fluid can flow relatively unhindered from the hydraulic operating circuit via the fluid port 24 and via a bottom inlet 78 in the valve housing 74 at a settable pressure towards the fluid chamber 16 for the accumulator filling process. In the opposite direction, i.e. when the accumulator is discharged, the valve plate 70 moves from the upwardly moved position shown to the downwardly closed position in which it sits inside the valve housing 74, the fluid passage being then only provided via the throttle bore 72 in the valve plate 70, so that in addition to the already described throttle means 22, 46 a throttling of the fluid flow is achieved by the damping valve 68. Details of the functioning of such damping valves are described, for example, in DE 103 37 744 C1.

Claims

1. A piston-type accumulator having an accumulator housing (10) in which a separating piston (12) is guided so as to be longitudinally movable, The separating piston (12) separates two fluid chambers (14, 16) from each other, in particular separating the fluid chamber (14) containing the working gas from another fluid chamber (16) containing a liquid such as hydraulic oil, The separating piston (12) has a damping piston (18) equipped with a check valve (20), The damping piston (18) is capable of entering a fluid port (24) in the accumulator housing (10) to form a throttle gap (22); the throttle gap (22) is a cylindrical annular chamber formed by adjacent walls (28, 32) of the accumulator housing (10) and the damping piston (18); The check valve (20) has a valve ball (36) biased by an energy storage means, which, in a closed position, blocks a flow path between the fluid port (24) and a piston fluid chamber (38) between the separation piston (12) and the accumulator housing (10), and, in an open position, opens the flow path. A piston-type accumulator characterized by:

2. 2. The piston-type accumulator according to claim 1, wherein the damping piston (18) is formed from a hollow cylinder having a hollow cylindrical passage (40) in at least one damping position to form a flow path between the fluid port (24) and the check valve (20).

3. 3. A piston-type accumulator according to claim 1 or claim 2, characterized in that, when viewed in the direction of the piston fluid chamber (38), the damping piston (18) transitions into an expansion portion forming a shoulder (42) and having an annular surface (44), and when the separation piston (12) abuts against a part of the accumulator housing, such as a housing cover (30), the annular surface (44) forms an annular gap (46) having a gap dimension larger than the gap dimension of the throttle gap (22).

4. 4. The piston-type accumulator according to claim 3, wherein the annular surface (44) is part of an insert (48) that houses the check valve (20), and the insert (48) is fixed in a receiving portion (50) of the separation piston (12), preferably by means of a snap ring (52) between the insert (48) and the separation piston (12).

5. 5. A piston-type accumulator according to claim 4, characterized in that the check valve (20) is designed as a valve cartridge, which is screwed onto the insert (48) together with a valve housing (54), and the valve ball (36) is constantly biased by an energy storage means in the form of a compression spring (34) and is guided in the valve housing (54).

6. 6. The piston-type accumulator according to claim 5, wherein the valve housing (54) has at least one lateral passage (58) extending towards a corresponding lateral passage (62) in the insert (48) in a manner controllable by the valve ball (36) of the check valve (20).

7. 7. A piston-type accumulator according to claim 6, characterized in that the valve housing (54) has a groove (64) on its outer periphery, preferably in the form of a valve annular chamber, into which each of the transverse channels (58) of the valve housing (54) opens on one side and into which each of the corresponding transverse channels (62) of the insert (48) opens on the other opposite side.

8. the separation piston (12) defines, on the side facing the fluid port (24), a hollow chamber-like recess as part of the piston fluid chamber (38), which opens onto a sloped portion (66) in the separation piston (12) toward the snap ring (52); 7. The piston-type accumulator according to claim 6, wherein the bore axis of each of the transverse channels (62) in the insert (48) is flush with a wall of the separation piston (12) that at least partially defines the recess in the separation piston (12), and the ramp (46) opens into the recess.

9. 5. The piston-type accumulator according to claim 4, characterized in that the axial length of the damping piston (18) is greater than the comparable height of the piston fluid chamber (38) in the separation piston (12) that is at least partially penetrated by the insert (48).

10. A method for operating the piston-type accumulator of claim 1, comprising: throttling the volumetric flow rate at the discharge of the piston-type accumulator by forming a hollow cylindrical throttle gap (22) between the damping piston (18) and a portion of the accumulator housing (10); Bypassing the throttle gap (22) by opening the check valve (20) mounted on the separating piston (12) with the valve ball (36) biased by an energy storage means based on the pressure difference occurring in the throttle gap (22) when the piston-type accumulator is filled, and as a result wherein fluid pressure acts across the free piston cross section to move the separating piston (12) directly towards the other fluid chamber (14) containing the working gas.

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