The present invention concerns a folding bellows arrangement for a tripod joint unit, comprising a folding bellows and an adapter ring, and also concerns a suitable adapter ring.
Tripod joint units have joint outer parts whose outer circumference on the opening side has a trefoil shape in cross-section, in other words have three projections and three recesses with uniform angular spacing around the circumference corresponding to the tripod arrangement of trunnions and rollers of the joint inner part. The joint outer parts thus have lobular and flat regions and transition regions between the lobular and flat regions. Consequently, joint outer parts designed in this way do not provide the prerequisites for direct mounting of rotationally symmetric folding bellows, because the folding bellows, which are typically produced by blow-molding from tube sections, can only be made essentially rotationally symmetric, where even the forming of thickened areas for the collar region requires special measures.
For this reason, it is customary to use folding bellows arrangements which include an adapter ring and a folding bellows, wherein the adapter ring and the folding bellows can also be joined to one another as a single piece. Here, the appropriately shaped inner surface of the adapter ring can be mounted on the trefoil outer surface of a joint outer part.
DE 10 123,216 A1 discloses such a folding bellows arrangement in which the adapter ring is joined to the bellows section by thermal sealing or gluing. The adapter ring here is designed with radially thickened regions uniformly distributed over the circumference in order to provide appropriate seating on the lobular regions of the joint outer part. Due to this accumulation of material in the corresponding thickened regions, uniform inward radial compression distributed over the circumference is not possible in fastening the folding bellows arrangement onto the joint outer part by means of a binder, which is customarily designed as a collar band or other clamping means. T his can result in uneven sealing between the adapter ring and the joint outer part, so that contaminants can penetrate to the interior of the tripod joint unit.
EP 0,915,264 A2 discloses another folding bellows arrangement produced by a blow-molding method, wherein the folding bellows is joined to an adapter ring as a single piece. Viewed in cross-section, the adapter ring here has an inner wall section matched to a joint outer part and a cylindrical outer wall section. Provided between the inner wall sections and the cylindrical outer wall section are resilient radial ribs whose thickness corresponds approximately to the thickness of the wall sections. However, high radial compression for achieving adequate sealing between the adapter ring and the joint outer part in such a design of the adapter ring is limited by the elasticity of said ribs.
U.S. Pat. No. 6,672,596 B2 discloses a folding bellows arrangement incorporating a folding bellows and an adapter means, wherein these are designed as two parts and wherein reinforcing elements, preferably of metal, are placed in the wall sections of the adapter means. This measure is intended to achieve more uniform inward-directed compression when this folding bellows arrangement is fastened onto a joint outer part by means of a binder. Here too, however, the nonuniform arrangement of such reinforcing elements over the entire cross-sectional area of the adapter ring results in only an uneven sealing over the entire circumferential surface between the adapter ring and the joint outer part.
Lastly, WO 2005/010,387 A1 discloses a folding bellows arrangement incorporating a folding bellows and an adapter ring, wherein the folding bellows is made of a plastic material that is harder than the material of the adapter ring. Such materials are typically used in accordance with prior art as well. A special design of the geometry of the inner circumference of the adapter ring is intended to provide adequate sealing with the folding bellows arrangement disclosed there.
The object of the present invention is to provide a folding bellows arrangement that is simple to manufacture and that also provides uniform sealing over the entire region between the inner circumferential surface of the adapter ring and the outer circumferential surface of a joint outer part that has a trilobular design.
This object is attained through an inventive folding bellows arrangement for a tripod joint unit, comprised of a folding bellows with a first collar region for attachment to a shaft, a second rotationally symmetric collar region for attachment to a joint outer part and a bellows region arranged between the first and second collar regions, and an adapter ring with an inner surface that is matched in cross-section to the outer contour of the joint outer part, wherein the folding bellows is made of an elastic material, characterized in that the adapter ring consists of at least one first and one second plastic material, wherein the first plastic material has a Shore hardness pursuant to ISO 868 that is approximately equal to or higher than that of the material of the folding bellows.
The inventive folding bellows arrangement has the advantage that due to the at least approximately equal or greater hardness of the plastic material used for the adapter ring, and its preferably different material properties as compared to the material of the folding bellows, the radial clamping forces produced by a binder, for example a clamping ring, are transmitted directly to the inner surface of the adapter ring without resulting in flowing of the material in the adapter ring. The adapter ring here is advantageously made of at least the first and a second plastic material. With such an at least two-component design of the adapter ring, it is possible to optimize the design thereof as a function of application conditions. Such at least two-component, more preferably exactly two-component, adapter rings can be produced by multi-component injection molding, for example. However, other production methods are also possible, for example injection blow-molding. In this regard, the adapter ring can be advantageously joined with the bellows as a single piece, wherein this is achieved by their production together through injection blow-molding, for example, or else by later gluing of the adapter ring into the folding bellows, for example. However, every other way of joining the adapter ring to the folding bellows is also made possible, including in particular the options disclosed in DE 10 123,216 A1 of interlocking engagement or frictional engagement of the two parts.
In advantageous fashion, the side of the adapter ring facing away from the joint outer part is made at least partly, preferably completely, of the first plastic material, which has a higher Shore hardness than the second plastic material. In particular, the first plastic material here can be chemically similar, preferably also chemically identical to, the material of the folding bellows, in order to avoid incompatibilities of the immediately adjacent materials. The clamping forces are then first transmitted by the softer material of the collar region of the folding bellows to the harder, first plastic material of the adapter ring, and then to the second, softer plastic material of the adapter ring. The inventors of the present invention have recognized that, contrary to the preconception in the prior art, for a uniform transmission of the clamping forces with simultaneously good sealing in folding bellows arrangements for joints with trilobular design, it is not the material of the adapter ring adjacent to the outer circumferential surface of the trilobular joint outer part that needs to have a higher Shore hardness than the material of the collar region of the folding bellows, or the material of the entire folding bellows. This is because an extremely uniform transmission of the clamping forces to the outer circumferential surface of the joint outer part, without losses due to distance, takes place precisely because of the provision of a material with a higher Shore hardness, specifically in the flat regions, in the lobular regions, and in the transition regions located therebetween, which taken together constitute the outer contour of the joint outer part. In order to permit even greater optimization here, it is advantageously possible for the wall thickness of the adapter ring to be made in a two-component manner of two plastic materials, wherein at least approximately 10%, preferably at least approximately 30%, and even more preferably at least approximately 50% of the wall thickness of the adapter ring is made of the first plastic material, and hence of a plastic material having a higher Shore hardness. It is further preferred here for the second plastic material to be arranged over the entire surface on the inside of the adapter ring, preferably with a wall thickness of at least 1%, preferably with a wall thickness in a range from approximately 1% to approximately 40%, even more preferably with a wall thickness in a range from approximately 2% to approximately 30%, so that it is in direct contact with the outer circumferential surface of the joint outer part. The material thickness of the first and second plastic material can vary over the cross-sectional area as a whole, in particular in the lobular regions of the joint outer part as compared to the adjacent transition or flat regions, with the thinnest material thickness preferably being provided for the second plastic material in the transition regions. However, with a view to the simplest possible manufacture of the inventive folding bellows arrangement, it is also possible to arrange a uniformly thick layer of the second plastic material having a lower Shore hardness on the inside of the adapter ring. Within the context of the present invention, the Shore hardness is determined pursuant to ISO 868, with Shore A hardness or Shore D hardness being determined depending on the plastic material used. Shore A hardness and Shore D hardness can be placed in relationship to one another through comparison tables.
In advantageous fashion, the Shore hardness, especially Shore A hardness, of the second plastic material is at least 10%, more preferably at least 20%, even more preferably at least 25% lower than the Shore A hardness of the first plastic material. It is also preferred here for the Shore hardness of the second plastic material to be approximately equal to the Shore hardness of the plastic material used to produce the collar region of the folding bellows. It is also preferred for the Shore A hardness or Shore D hardness of the first plastic material to be at least approximately 10% higher than the Shore A (D) hardness of the folding bellows material, more preferred at least approximately 20%, and even more preferred at least approximately 25%. The Shore D hardness of the first plastic material here is preferably at least approximately 40, even more preferably at least approximately 50, and even more preferably at least approximately 55.
In a preferred embodiment of the inventive folding bellows arrangement, the adapter ring has, arranged on its inner surface facing the joint outer part, at least one, preferably exactly two, sealing lips, which preferably are made of the second plastic material. The sealing lips here can be arranged on the inner circumferential surface of the adapter ring to be continuous, but can also be discontinuous. The inventors have recognized that an even more extremely uniform transmission of the clamping forces occurs if only the at least one sealing lip is made of the softer, second plastic material, but the adapter ring otherwise is made of the first, harder plastic material. Naturally, however, provision can also be made for the inner side of the adapter ring facing the joint part to also be provided on its full area, which is to say in addition to the sealing lips, with the second plastic material, if applicable also in different material thicknesses.
Advantageously, the first plastic material is selected from a group comprised of polypropylenes, polyethylenes, polyacetal resins (POM), polyamides (PA), linear polyesters (especially polybutylene terephthalate (PBT)), and/or thermoplastic elastomer ether-esters (TEEE). In this connection, the first plastic material can also be composed of copolymers, block polymers, or random block copolymers of the aforementioned plastic materials. The material of the folding bellows is advantageously composed of a thermoplastic elastomer material (PTE), and in particular of a thermoplastic elastomer ether-ester (TEEE), and hence of a material which can be identical to the first plastic material. However, the first plastic material preferably has a higher Shore hardness than the plastic material of the folding bellows.
The second plastic material is advantageously composed of a group comprised of thermoplastic olefins, polychloroprenes, and/or thermoplastic elastomers (TPE), especially also thermoplastic vulcanized rubbers (TPV), but also TEEE of lower hardness.
The first thermoplastic material also has, in contrast to the second plastic material, higher values for tensile strength, elongation at break, and tensile modulus, each measured in accordance with the ISO 527 standard. Preferably, the tensile strength of the first plastic material is at least approximately 10%, preferably at least approximately 20%, above that of the folding bellows material and of the second plastic material. Preferably, the tensile strength of the first plastic material is at least approximately 16 MPa, more preferably at least approximately 18 MPa.
The elongation at break of the first plastic material is preferably at least approximately 150% (1 mm/minute), more preferably at least 170% (1 mm/minute). The tensile modulus of the first plastic material is preferably at least approximately 45 MPa, more preferably at least approximately 50 MPa, even more preferably at least 60 MPa, and is preferably in a range from approximately 45 to approximately 140 MPa, more preferably in a range from approximately 60 MPa to approximately 125 MPa. In contrast, the tensile modulus of the second plastic material is less than 45 MPa. Preferably, the first and/or second plastic material of the adapter ring has no anchoring agent. The melting point of the first plastic material is preferably at least 180° C., more preferably at least 200° C.
The present invention additionally concerns an adapter ring as defined above, for use in tripod joint units, in particular an adapter ring whose at least one sealing lip is made of the second plastic material, if applicable in further combination with an inner surface made at least partly of the second plastic material, which inner surface directly contacts the outer circumferential surface of the joint outer part, wherein different material thicknesses of the second plastic material may also be present in the adapter ring wall here as well, and otherwise consists of the first plastic material and is the same hardness or harder than the folding bellows material.
These and other advantages of the present invention are explained in detail on the basis of the attached figures. Shown are:
It is first necessary to mention that the features shown in the drawings are not restricted to the individual embodiment. Rather, the features disclosed in each case in the description, including the drawing description and the drawings, can be combined with one another further. Like features here are labeled with like reference numbers. In particular, the object of the present invention is not limited to the embodiments of the adapter ring shown in the figures. Rather, any additional possible embodiments of adapter rings may be used here, in particular also including such with specific designs of the regions with accumulations of material which engage the lobular regions of the joint outer part, such as are disclosed in EP 0,915,264 A2 or WO 2005/010,387 A1, for example.
The joint outer part 18 has three lobular regions 26, of which only one is shown, and correspondingly has three flat regions 30 with a transition region 28.1 being arranged between the lobular region 26 and the flat region 30. The trilobular joint outer part has a total of six transition regions 28.1 through 28.6 (not shown here). The inner surface 24 of the adapter ring 14, seen in cross-section, is matched to the outer contour of the joint outer part defined by said regions.
The collar region 20 has a binder seat 22 with a binder seat surface 23, in which engages a binder 32, designed, for example, as a tension band. The collar region 20 also includes an annular ridge 34, which engages in a recess 36 of the adapter ring 14 and rests its joint-side edge 21 against a suitably designed wall of the receptacle 36 of the adapter ring 14.
The folding bellows arrangement 10 from
Now,
Now,
In an alternative embodiment,
As illustrated by
The present invention advantageously makes it possible to provide a folding bellows arrangement with an adapter ring relatively economically, without the expensive use of, for example, metal reinforcement elements or the like, which bellows arrangement very uniformly transmits the clamping forces acting in fastening means, in particular clamping or tension elements including compression rings and tension bands, and thus provides a secure seat and seal on the joint outer part of the folding bellows arrangement.
Number | Date | Country | Kind |
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102006008558.2 | Feb 2006 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2006/012566 | 12/28/2006 | WO | 00 | 8/22/2008 |