Patent Application
20140353915
1. Field of the Invention
The invention relates to a seal arrangement having two machine components which are arranged so as to be able to be moved relative to each other along and/or about a movement axis, and having at least one resiliently deformable seal which is retained in a press-fitting manner on a seal retention structure on one of the two machine components, the seal forming a sliding guide for the two machine components. The seal has at least one sealing lip which is in sealing abutment with the other machine component in each case and which extends in an axial direction away from the seal retention structure.
Such a seal arrangement, as known, for example, from DE 195 13 727 A1, often has only an unsatisfactory sealing action during use. When such seal arrangements are used in environments with a very high degree of contamination, for example, when used in a shock-absorber, a hammer drill or the like, additional sealing components or wiping elements are therefore often required in order to seal the sliding guide in an adequate manner and to counteract excessive wear of the seal arrangement. This is costly and has little advantage in terms of technical production-related aspects.
An object of the present invention is to develop a seal arrangement of the type mentioned in the introduction in such a manner that it has an improved sealing action and less tendency to become worn. An object of the invention is further to set out a method for producing such a seal arrangement.
This object is achieved according to the invention by a seal arrangement having the features set out in the patent claims. The object relating to the production method is solved by a production method having the features set out in patent method claims.
The advantage connected with the seal arrangement according to the invention substantially involves an improved sealing function of the sealing lip. The free end portion of the sealing lip is supported in a resilient manner by means of the pretensioning element on one machine component and is pressed by the pretensioning element with a defined, that is to say, freely predeterminable, contact pressure against the other machine element, that is to say, the sealing face thereof. Consequently, even during use in highly contaminated environments, there is a clearly reduced introduction of contamination, such as, for example, particles of dirt, and/or an operating fluid in the region of the sliding guide. Furthermore, a discharge of lubricant which is arranged in the region of the sliding guide, that is to say, in the sealing gap which is intended to be sealed between the two machine components, for example, lubricating oil, is counter-acted in a more reliable manner. This applies to translatory and/or rotary movements of the two machine components with respect to each other. On the whole, the required maintenance intervals of the seal arrangement can thereby be extended and the service-lives of the seal arrangement can be increased as a whole. Furthermore, with the seal arrangement according to the invention, additional sealing and/or wiping elements to protect the sliding guide formed by the seal, in particular from abrasive particles of dirt or the like, are required only in exceptional cases or are completely superfluous. This enables a structurally more simple and more compact structure of the seal arrangement. This on the whole affords economic advantages.
The seal is retained on one machine component with radial and/or axial press-fitting and may be constructed as an inner or an outer seal. In the case of an inner seal, the seal is surrounded in an at least partially peripheral manner by one machine component which is constructed, for example, as a cylinder. If the seal is constructed as an outer seal, it surrounds one machine component, for example, a piston, at the peripheral side. This embodiment is preferred in the case of high demands in terms of the transverse stability of the seal and the sliding guide which is formed thereby. On the whole, a particularly good range of uses of the seal arrangement is thereby enabled.
According to a preferred development of the invention, the seal covers the seal retention structure in a radial direction and is preferably in direct abutment therewith. The sliding guide for both machine components can thereby be constructed in this region in a simple manner so as to be rigid, that is to say, non-flexible in a radial direction. This enables precise guiding or support of the two machine components relative to each other.
In the case of an axial press-fit of the seal on one machine component, it is preferably retained so as to be arranged in a clamped manner in a retention groove of the seal retention structure of the machine component. Alternatively or in addition, the seal can be retained by means of a groove flank which is directed away from the side to be sealed by the groove flank being introduced to a greater or lesser extent into the adjacent material of the seal. If the groove flank is not introduced into the adjacent material of the seal, the seal can be held in position in a positionally stable manner by means of auxiliary elements, such as pins, screws and/or wall projections.
On the whole, undesirable axial displacement or rotation of the seal relative to the seal retention structure of one machine component can thereby be prevented. Furthermore, the seal can be assembled in a particularly simple manner.
In the structurally most simple case, the seal according to the invention is arranged with one of the ends thereof in the retention groove. According to the invention, the other end of the seal then forms the sealing lip. The degree of transverse or radial rigidity of the sliding guide as required for the sliding guide of the two machine components can be adjusted by means of a (transverse or) radial support of the seal in the retention groove and an appropriately selectable elasticity modulus of the material of the seal. The retention groove of one machine component may further have at least one groove flank which extends directly as far as the sealing gap in order to axially support the seal in an optimum manner and thus to counteract excessive resilience of the seal in the event of radial loading.
The end portion of the sealing lip is preferably movably in abutment with the pretensioning element. The sealing lip can thereby carry out compensation movements with respect to the two machine components, as may be necessary, for example, in the case of a relative movement of the two machine components with respect to each other. It is thereby possible, for example, for shaft impacts or eccentricity of the machine components which can be moved with respect to each other to be compensated for, without loss of the sealing function and at the same time with reduced wear of the sealing lip, in particular in the region of the sealing edge thereof. Furthermore, particularly simple assembly and maintenance of the seal arrangement is thereby achieved. The pretensioning element can thus be individually replaced where applicable with a new pretensioning element.
Of course, the seal and the pretensioning element may also be constructed in an integral manner. The pretensioning element may in particular be formed on the seal.
According to a quite particularly preferred development of the invention, the seal device has two sealing lips. According to one embodiment of the invention, the sealing lips extend away from each other in an axial direction.
The sliding guide formed by the seal can thereby be protected axially at both sides in a structurally extremely simple manner against the introduction of in particular particulate contaminants and/or discharge of lubricant from the sealing gap. This construction type is distinguished by an increased range of use and increased service-life.
According to an alternative embodiment of the invention, the sealing lips may also be arranged parallel in an axial direction (tandem seal).
According to the invention, the sealing lips may correspond to each other, in particular in terms of shape, size, material and/or material properties.
An embodiment of the invention which is particularly advantageous with high mechanical loads of the seal arrangement is distinguished in that the seal has two seal elements which each have a sealing lip. In this instance, the seal is consequently constructed as two components, that is to say, in two parts. The two seals are preferably arranged so as to be spaced apart from each other according to the invention. The two seal elements can be arranged with the ends thereof facing each other in different retention grooves of one machine element. The machine component which has the seal retention structure may in this instance have a (rigid) bearing structure for the other machine component, which structure is arranged in an axial direction between the two seal elements. In this instance, the bearing structure with respect to the sliding guide formed by the seal is preferably even more rigid, that is to say, even less flexible in the case of loading in a radial direction. Particularly precise and at the same time robust support or guiding of the two machine components relative to each other is thereby achieved. At the same time, mechanical loads of the seal or the sliding guide can thus be limited during operation in a simple manner, which is advantageous for the service-life of the seal arrangement. The bearing structure is further effectively protected from contamination by means of the seal elements of the seal which are arranged at both sides (encapsulated construction), whereby operational failures of the bearing structure during operation can on the whole be minimized.
According to the invention, the bearing structure may have at the bearing face thereof facing the other machine component at least one, preferably a plurality of, recess(es) in order to receive possible contamination which has been introduced into the sealing gap axially delimited by the two seal elements between the two machine components. The recess or recesses is/are advantageously arranged transversely relative to the movement direction of the two machine components along/about the movement axis. On the whole, operational impairment of the seal arrangement, in particular the sliding guide, can again thereby be further reduced. Owing to the recesses, particularly low-friction resistance of the bearing structure can further be achieved.
According to a preferred embodiment of the invention, the seal device comprises a viscoplastic material. The viscoplastic material is preferably a polymer material, in particular polytetrafluoroethylene (PTFE). It is thereby possible, on the one hand, to achieve sealing of the two machine components with respect to each other which withstands thermal, mechanical or even chemical influences and plain bearing of the two machine components.
According to the invention, the pretensioning element is preferably arranged in a recess, for example, a groove of one machine component. The pretensioning element can thereby be secured in the most structurally simple manner possible with respect to undesirable position change relative to one machine component. On the other hand, this affords advantages in terms of technical production since the pretensioning element simply has to be placed in the groove of one machine component when the seal arrangement is assembled.
When the cross-section and material of the pretensioning element are selected in an appropriate manner, the pretensioning of the sealing lip with respect to the other machine component, that is to say, the contact pressure of the sealing lip against the other machine component, can be adjusted in a simple manner. Of course, the pretensioning element may have a circular, oval or even polygonal cross-section shape.
The pretensioning element may in particular be constructed in an annular manner (for example, as an O-ring) and preferably comprises an elastomer, in particular a thermoplastic elastomer.
The method according to the invention for producing the seal arrangement according to the invention has the following steps: arranging the at least one pretensioning element on one machine component, preferably in a groove of one machine component, and subsequently compressing at least one seal blank with the seal retention structure of one machine component, with the seal being formed. The seal blank may in particular have a sleeve-like or annular-disc-like structure.
The invention relates to a seal arrangement having two machine components which are arranged so as to be able to be moved relative to each other along/about a movement axis and having at least one resiliently deformable seal which is retained in a press-fitting manner on a seal retention structure on one of the two machine components. The seal forms a sliding guide for the two machine components and has at least one sealing lip which is in sealing abutment with the other machine component in each case and which extends away from the seal retention structure in an axial direction. A free end portion of the sealing lip is supported by means of at least one resiliently deformable pretensioning element on one machine component in such a manner that the free end portion is in abutment with the other machine component with a defined contact pressure.
Other advantages and advantageous embodiments of the subject-matter of the invention will be appreciated from the description, the claims and the drawings. The features which have been mentioned above and those which are set out in greater detail below can also be used individually or together in any combination.
The invention is explained below in greater detail with reference to embodiments set out in the drawings.
The embodiments which are shown and described are not intended to be understood to be a definitive listing, but instead are of an exemplary character in order to describe the invention.
The accompanying drawings illustrate the invention. In such drawings:
As shown in
The cross-section of the pretensioning element 38 is selected in relation to the groove depth of the groove 36 in such a manner that the pretensioning element 38 protrudes out of the groove 36 in the loaded state thereof shown here and presses the free end portion 32 of the sealing lip 30 with the seal edge 34 with a defined pretensioning onto the other machine component 14. The pretensioning element 38 comprises a commercially available elastomer which may have additives where applicable.
The seal 22 comprises a viscoplastic polymer material, in this instance polytetrafluoroethylene (PTFE). Of course, the polymer material of the seal may where applicable contain additives or reinforcement inserts which are not illustrated in greater detail in the drawings. [Para 40] The seal 22 forms with a sealing lip portion which axially adjoins the seal retention structure 20 a plain bearing 40 which is rigid (substantially non-flexible) in the radial direction for the two machine components 12, 14 which can be moved relative to each other. A groove flank 42a of the retention groove facing away from the sealing lip 30 protrudes, in order to axially support the sealing lip 30 with respect to the other groove flank 42b of the retention groove, radially further in the direction towards the machine component 14. As shown in
The two free end portions 32 are each in movable abutment with the pretensioning elements 38 and have in each case a thickness which decreases in the direction towards the free end thereof. A contact face 56 of the sealing lips 30 which is in abutment with the pretensioning element 38 is in this instance formed in accordance with an outer contour of the pretensioning element and is in this instance constructed in a (slightly) concave manner in an axial direction. The free end portions 32 of the sealing lips 30 are thus supported in an axial direction on the pretensioning elements 38.
The seal retention structure 20 formed by the outer covering face 54 of the piston, in a manner not shown in greater detail, may have one or more recesses in which the seal 20 engages and by means of which axial displacement or rotation of the seal with respect to the piston is prevented in a reliable manner.
The piston has at one end (wiping side) an annular collar 58 having a flattened outer side 60. The annular collar has an annular collar diameter DR which is reduced in comparison with the maximum outer diameter DD of the seal 22 in order to counteract the risk of particles (for example, contamination) becoming jammed between the annular collar 58 and the second machine component 14. The piston has at the other end (for instance, facing an oil side of the seal arrangement 10) a centering collar 62 having an outer side 60 which is constructed so as to be rounded in an axial direction.
In the seal arrangements explained above by way of example, the seals 22 and the associated pretensioning elements 38 may be constructed in one piece in a manner not set out in greater detail. Furthermore, the cartridge-like seal insert 18 and the machine component which has the seal insert may be constructed in one piece. Of course, the two machine components 12, 14 of the seal arrangements 10 explained above may additionally or alternatively be able to be movable (rotatable) relative to each other about the movement axis 16 shown.
The seal arrangement 10 according to the invention is particularly suitable for use in impact drilling machines, hammer drills, shock absorbers and the like.
Arranging 110 the at least one pretensioning element 38 on one of the machine components 12, 14 and subsequently compressing 120 at least one seal blank 70 with the seal retention structure 20 of one machine component 12, 14 with the seal 22 being formed. The compression of the seal blank can in the case of an inner seal to be formed particularly be carried out by means of a tool mandrel which is not shown in greater detail.
Although several embodiments have been described in detail for purposes of illustration, various modifications may be made to each without departing from the scope and spirit of the invention. Accordingly, the invention is not to be limited, except as by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2012 202 571.5 | Feb 2012 | DE | national |
This continuation application claims priority to PCT/EP2013/052850 filed on Feb. 13, 2013 which has published as WO 2013/124192 A1 and also the German application number 10 2012 202 571.5 filed on Feb. 20, 2012, the contents of which are fully incorporated herein with these references.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2013/052850 | Feb 2013 | US |
| Child | 14463327 | US |
