The present invention relates to a method for the production of piston-type accumulators having an accumulator housing and a separating piston displaceable in the longitudinal direction in the accumulator housing and separating two working chambers from each other. The accumulator housing is sealed on each of the end sides by a cover component.
Piston-type accumulators are, in the broadest sense of the term, hydraulic accumulators, which among other things serve the purpose of receiving specific volumes of a pressurized liquid (hydraulic medium) of a hydraulic system and returning these volumes to the system when required. Since the hydraulic medium is pressurized, hydraulic accumulators are treated as pressure reservoirs and must be designed for the maximum excess operating pressure, the acceptance standards of various installing countries being taken into consideration. Hydropneumatic (gas-charged) accumulators with a separating element are currently used in most hydraulic systems. A piston separates a fluid space as working chamber from a gas space as additional working chamber, serving as separating element inside the accumulator housing of the piston-type accumulator. Nitrogen is generally used as the operating gas. The gas-tight piston to a great extent permits disconnection of the gas space from the fluid space.
The fluid component is connected to the hydraulic circuit so that, as the pressure rises, the piston-type accumulator admits or receives fluid and the gas is compressed in the process. As the pressure drops, the compressed gas expands and displaces the pressurized fluid back into the hydraulic circuit. One advantage of piston-type accumulators is they can “work” when in any position, but preference is given to vertical positioning with the gas side on top, so that settling of fouling particles from the fluid on the piston seals is prevented.
Consequently, the essential components of a piston-type accumulator are an outer cylindrical tube forming the accumulator housing, the piston forming the separating element with its sealing system, and the sealing covers on the housing ends. The cover elements also contain a fluid connection and a gas connection. Two functions are regularly assigned to the accumulator housing, specifically storage of internal pressure and ensuring control of the piston inside the accumulator housing. The cover components on the front surface sealing the interior of the accumulator housing off from the exterior are provided on the outer circumference with external threading which may be screwed into a corresponding inner threading along the free longitudinal edge over an assigned path. Production of the respective threaded connection is time-consuming; and correspondingly increases the production costs of the piston-type accumulator. In addition, safety measures must be taken to secure the cover component in its position.
An object of the present invention is to provide an improved manufacturing process for piston-type accumulators where a reliable operation of a cover component secured in position in the accumulator housing is guaranteed, and where the otherwise customary threaded connections are avoided.
This object is basically attained by a method or process in which the cover component on one of its sides is fastened by the free longitudinal edge of the accumulator housing, which housing edge is for this purpose moved onto the cover component. The otherwise customary screw connection is avoided for the cover component. A clamping onto the free end of the accumulator housing is achieved in which the cover component is clamped at least over the free longitudinal edge of the accumulator housing after this housing has been moved onto the cover component. It is sufficient if a part of the free longitudinal edge effects this clamping.
In one preferred embodiment of the method of the present invention, at least one of the two cover components is inserted until one cover side engages a stop in the interior of the accumulator housing such that the respective cover component is retained in its end position by the clamping force of the longitudinal edge introduced. If a stop is provided on the inside of the accumulator housing, the cover component may be immobilized against this stop during the positioning movement of the free longitudinal edge of the accumulator housing. In addition or as an alternative, however, the possibility exists of inserting the cover component into the free end of the accumulator housing and then initiating the positioning movement of the free end of the accumulator housing. The positioning movement may be effected toward the upper or outer side of the cover if the cover component is retained in a suitable position. An unrestrained positioning movement may also be effected for the longitudinal edge and then, in the state of readiness for operation, the cover component may be moved by the piston against the free longitudinal edge, which then effects the clamping there.
Preferably, a shaping tool is provided for the positioning movement of the longitudinal edge of the accumulator housing. The tool is provided with positioning bevels and positions the longitudinal edge of the accumulator housing on the cover component in such a way that this cover component is secured in the accumulator housing as the clamping seat.
In one especially preferred embodiment of the method of the present invention, two shaping tools positioned on opposite sides carry out the fastening process for the respective end cover component in a common positioning movement to the accumulator housing. These shaping tools act on the free longitudinal edge of the accumulator housing. It has been found to be highly advantageous for the purpose of generation of high fastening forces to position the two free ends of the cylindrical accumulator housing uniformly. The shaping tool which acts on one end of the accumulator housing is capable in addition of reliably withstanding the forces introduced onto the accumulator housing by the other shaping tool.
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.
Referring to the drawings which form a part of this disclosure:
The conventional piston-type accumulator shown in
Each of the two cover components 20, 22 is provided with external threading 28 which may be engaged with internal threading 30 extending along the free longitudinal edge 32 and outward to the exterior. On the external circumference side, each cover component 20, 22 is provided with a seal 34 for sealing the interior of the accumulator housing 10 from the exterior. Application of the lengths of threading 28, 30 entails a certain production effort making the prior piston-type accumulators complex and expensive to produce. It is also necessary to secure each cover component 20, 22 from rotation to ensure its fixing in position inside the accumulator housing 10. One possible method of securing the respective cover component 20, 22 from rotation involves providing a conventional adhesive seal along the threading 28, 30, or by keeping the cover component in its position by a conventional retention bore (with and without threading).
Based on this prior art, the method of the present invention will now be described in greater detail with reference to
The method of the present invention is among other things characterized in that the respective cover component, in this instance cover component 20, is inserted by its lower or inner side 36 to come into contact with a stop or shoulder 38 in the form of an annular surface in the interior of the accumulator housing 10. The cover component is secured on its opposite side 40 by the free longitudinal edge 32 of the accumulator housing 10. The longitudinal edge 32 undergoes a positioning movement relative to the cover component 20, as is to be explained in greater detail in what follows.
An axially movable shaping tool 42 serves to position the longitudinal edge 32 of the accumulator housing 10. This shaping tool 42 is provided with at least one positioning bevel 44 which positions the longitudinal edge 32 onto the cover component 10 so that this cover component is secured as a clamping seat in the accumulator housing 10 between the stop 38 and the longitudinal edge 32. For the purpose of establishing the respective clamping seat, the upper or outer side 40 of the cover component 20 is provided with a circumferential contact surface 46 tapering toward the longitudinal axis 48 of the accumulator housing 10 in the outward direction of the cover component. The inclination of the contact surface 46 corresponds to the inclination of the positioning bevel 44 of the shaping tool 42. However, other obvious inclinations or bevels are also conceivable. As is shown in
For the sake of greater clarity of illustration, the separating element in the form of the piston 12 is omitted from
As is shown in
To avoid endangering the secure position of the cover component 20 in the accumulator housing 10 and also to protect the cover component 20 from introduction of harmful forces, the free longitudinal edge 32 is, as shown in
Specifically, the method for producing a piston accumulator involves mounting a piston in an accumulator housing 10 for movement along a longitudinal axis 48 of the housing 10 with the piston separating an interior of the housing into two working chambers between first and second longitudinal ends of the housing. A first shoulder 38 in the interior of the housing 10 is provided adjacent to but spaced from the first longitudinal end 32 of the housing 10 to form a first end portion of the housing with a reduced wall thickness relative to an adjacent portion of the housing, with a transition part between different wall thicknesses forming the first shoulder 38. A first cover component 20 is inserted at least partially within the housing 10 through the first longitudinal end when open until an inner surface portion of the first cover component engages the first shoulder 38 preventing further insertion of the first cover component. The first end portion of the housing is deformed to form a bend 54 between the first shoulder and the first longitudinal end through an acute angle relative to the longitudinal axis against an axially facing outer circumferential contact surface 46 extending at a corresponding acute angle relative to the longitudinal axis and about an axially facing outer surface portion 40 of the first cover component radially within the outer circumferential contact surface to secure the first cover component in the housing with the first cover component sealing the first longitudinal end of the housing closed by moving a first shaping tool 42 only axially along the longitudinal axis, the first shaping tool being unitary without any relatively movable parts. The second longitudinal end of the housing is sealed closed in the same manner.
As shown in
As is illustrated in
In one especially preferred embodiment (not shown) of the method of the present invention, the fastening process for the end cover components 20, 22 is carried out in a common axial positioning movement of two shaping tools 42 on opposite ends of the accumulator housing 10 simultaneously with more or less equal shaping forces acting on the free longitudinal edges 32 of the accumulator housing 10. In such shaping method, each shaping tool can, during shaping, receive the forces of the other shaping tool such as occur during the forming process. Costly support devices may be dispensed with in this configuration on the respective opposite sides where the shaping tool 42 exerts no effect. Harmonious introduction of forces into the accumulator housing 10 without the occurrence of damaging power peaks also occur in this situation.
As is shown in
In the embodiments shown in
The same reference numbers are used for the same structural parts illustrated in
The cover components 20, 22 may accordingly be fastened with high fitting accuracy, reliably, and pressure-tightly in the accumulator housings 10 by the shaping process discussed, in the widest possible variety of embodiments. Screw connections that are cost-intensive in mounting, in addition remain to be secured in this position, and may be dispensed with in their entirety.
While various embodiments have been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the appended claims.
Number | Date | Country | Kind |
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103 03 988 | Feb 2003 | DE | national |
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Entry |
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Machine Translation of EP 1128073 A1, Audureau, Aug. 2001. |
Number | Date | Country | |
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20060016074 A1 | Jan 2006 | US |