August 13, 2008 966 PA 08006 WO

Boot with an axially displaced first fastening region

The present invention relates to a boot with a first fastening region and to a system comprising such a boot and also a housing part.

Boots of the aforementioned type are used in particular for sealing joints, in particular in the automotive industry for sealing constant velocity sliding joints or else fixed joints. However, other applications outside the automotive industry are also possible. Boots within the context of the present invention can take the form in particular of rolling boots or folding boots.

Rolling boots of the aforementioned type are known from the prior art. For instance, figure 1 of the present application shows a section along a main axis 60 of a rolling boot according to the prior art having a first fastening region 12 intended for fastening to a joint housing and a second fastening region 14 intended for fastening to a shaft. Such a rolling boot, designated by the reference number 10 in figure 1 , is mounted on fixed joints, for example. The first fastening region 12 here has an outer part 34 and an inner part 36, wherein an accumulation of material 38 in the form, for example of a peripheral annular bear is arranged in the inner part 36 so as to provide a seat in a peripheral groove on the outer lateral surface of a housing part. The first fastening region 12 is adjoined by a fold region 16 having a first fold peak region 20 with a first fold flank 22 close to the fastening region 12 and, opposite this first fold flank, a second fold flank 24, the fold peak region 20 being adjoined by a fold trough 26. The fold peak region 20 has a fold peak 21 with a maximum M. Furthermore, the rolling boot 10 according to the prior art shown in figure 1 is provided in its interior with reinforcing ribs 40 which are arranged in the fold region 16.

Figure 4 of the present application shows a boot 10 according to figure 1 mounted on a housing part 54 of a fixed joint. The housing part 54 has an outer lateral circumferential surface 70 and also an end surface 68, between which surfaces a peripheral edge 55 is arranged. The boot 10 is mounted on the joint housing part 54 by a first fastening means 58, and on a shaft 56 in a second fastening region 14 using a second fastening means 62. The first fastening element 58 and also the first fastening region 12 of the boot 10 are in this case completely assigned to the outer lateral circumferential surface 70 of the joint housing part 54, or to the joint housing part 54 itself, and the first fastening region 12 is directly followed by a fold region 16 having exactly one fold in the example shown in figure 1 and figure 4.

A particular disadvantage with the known prior art as shown in figures 1 and 4 is that, because of the complete overlapping of the outer lateral surface of the joint housing by the first fastening means and the first fastening region, the fold region displays large deformations during operation of the boot, for example when used in a fixed joint. Given the forces which act, particularly at high rotational speeds, and the associated high mechanical loading, it may occur that boots will possibly even burst during operation.

It is therefore the object of the present invention to make available a boot and also a system comprising such a boot in which the deformations acting in particular on the fold region, in particular those in the first fold of the fold region that is near the first fastening region, are reduced.

This object is achieved according to the invention by a boot with a first fastening region, wherein the first fastening region is displaced axially, as viewed in the direction of a main axis of the boot, and with respect to a housing part, in particular a housing part of a constant velocity sliding joint or fixed joint, but also any other housing part, with further preference a joint on which the boot can be mounted, in such a way that the first fastening region at least partially projects beyond an edge of the housing part. In a particularly preferred embodiment of the present invention, the first fastening region is provided with a base surface which makes available a seat for a first fastening element and which at least partially projects beyond the edge of the housing part, with respect to the main axis of the boot.

By virtue of the projecting length made available according to the invention by the first fastening region, there finally occurs an only partial overlapping of the outer lateral circumferential surface by the first fastening region or the first fastening element arranged on the base surface thereof. The fastening element then has, in addition to the known sealing function, a supporting function by virtue of the possibility made available by the first fastening element to make available, in the region of the projecting length, a support for the fold region, and here in particular the first fold of the fold region that is near the first fastening region. As a result, the deformation of the boot during operation is reduced overall and an increased rotational speed stability is thereby achieved. This has a particularly advantageous effect when the boot according to the invention is designed as a rolling boot, it also being possible within the context of the present invention for the boot according to the invention to be designed as a folding boot having a plurality of folds in the fold region. However, a double-folding boot design is also possible, for example.

As already discussed above, the boot according to the invention finds a particularly preferred use in fixed joints or else constant velocity sliding joints. However, it can also be

arranged on any other type of joints, for example on ball joints, or else in pushrods, for sealing tube ends or other housing parts, in order to provide a sufficient degree of sealing and an additional supporting function. The present invention is thus not restricted in terms of the type of housing parts on which the boot can be mounted. Examples of applicable housing parts here are also tube ends of any type, push rods, shafts or the like, but also joints and their outer joint housing.

The projecting length of the base surface of the first fastening region of the boot according to the invention is advantageously situated in a range from approximately 20% to approximately 45%, preferably approximately 24% to approximately 35%, of a width of the first fastening element. With such a projecting length ratio, there is made available, on the one hand, a sufficient sealing function of the folding boot but also, on the other hand, a sufficient supporting function, provided by the first fastening element. If the projecting length were smaller, that is to say below approximately 20%, a sufficient supporting function would not be provided under certain circumstances; on the other hand, if the projecting length were too large, the sealing function of the boot could be diminished. The use of the word "approximately" in the present connection makes it clear to the person skilled in the art who is being addressed that embodiments somewhat outside the stated range are hereby readily also covered by the scope of protection of the present invention. In particular, deviations of approximately plus/minus 10%, preferably approximately plus/minus 5%, of the respective upper and lower limits do not, within the context of the present invention, go outside the scope of protection thereof since a sufficient sealing and protective function can still be provided within these ranges.

In a further preferred embodiment, the base surface of the first fastening region at least partially overlaps a transition region, as viewed in the direction of the main axis of the boot. The transition region adjoins the first fastening region in the direction of a second fastening region in the direction of the main axis of the boot, wherein the second fastening region often has a smaller inside and outside diameter than the first fastening region. Subsequently arranged after the transition region is a fold region which comprises at least one fold. If the fold region has exactly one fold, the boot according to the invention can be designed, for example, as a rolling boot; if it has two folds, it is designed in particular as a double-folding boot, or alternatively, if it has a plurality of folds, it is designed as a multi- folding boot. The transition region between the first fastening region and fold region can here be configured for example in such a way that it is thereby possible for the transition region to bear by way of its inner surface or an arrangement thereof closely against a peripheral end surface of a housing part. However, it is also possible to provide in the transition region for example a joint region which entails advantageous properties in the case of certain embodiments of folding boots in particular. Furthermore, additional

retaining or orienting means can also be arranged in the transition region, these means facilitating a fastening of a first fastening element in the first fastening region. The first transition region is preferably configured in such a way that its inner surface is arranged opposite a peripheral end surface of a housing part, and with further preference is in contact therewith, i.e. bears against this surface. Then, by virtue of the overlapping of this transition region by the base surface of the first fastening region which makes available the binder seat, and after mounting the first fastening element, there is advantageously achieved a situation whereby the forces exerted by the mounting of the fastening element are transmitted into the first transition region, making it possible to further reduce a more pronounced deformation of the boot according to the invention. A complete overlapping here means that the base surface overlaps the entire material thickness of the transition region, and in this region makes available a binder seat for the first fastening element. Preferably, as viewed in the direction of the main axis of the boot , the projecting length is arranged axially displaced in the direction of the fold region of the boot and at least partially outside the transition region.

In a further preferred embodiment, at least two outer ribs bridge the first fastening region and the transition region at least in parts, with respect to a direction perpendicular to the main axis of the boot. The outer set of ribs advantageously achieves a situation whereby the boot according to the invention can be designed to be even more compact, and in particular can have a smaller inside volume. The displacement of the first fastening region already advantageously achieves a reduction in the overall height of the boot according to the invention, this reduction being further supported by the provision of an outer set of ribs. An outer set of ribs here is particularly advantageous in the case of rolling boots since they provide a sufficient degree of stability during deformation, and, on the other hand, the inside diameter of these boots is reduced, with the result finally that a reduction in the grease pressure is also achieved and higher service lives and a lower susceptibility to wear can be achieved.

In a further preferred embodiment of the present invention, a plurality of ribs are arranged with a uniform distribution on an outer circumferential surface of the boot. Provision is preferably made for the respective ribs to be arranged oppositely in pairs on the outer circumferential surface of the boot. For example, four, six, seven, eight, nine, ten or more such pairs can preferably be arranged on the outer circumferential surface of the boot, depending on the requirements which are known to the person skilled in the art who is being addressed. Preference is given here to arranging the respective pairs with a uniform spacing from one another.

In a further preferred embodiment, at least one of the ribs protrudes beyond the base surface of the first fastening region to form a positioning and/or bearing surface. The first fastening region constitutes a binder seat surface for a fastening element, for example a clamping strap, a clamp or a compression ring. However, other fastening elements known to a person skilled in the art can also be used within the context of the present invention. The specific design of at least one of the outer ribs, preferably at least half the number of outer ribs, more preferably all the outer ribs, serves to facilitate the positioning of this fastening element in the first fastening region, it additionally being the case that the fastening element can also bear by way of its peripheral side edge at least partially against the bearing surface formed by the at least one outer rib, i.e. is in direct contact with this bearing surface. Here, contact does not have to be made by the entire side face of the fastening element with respect to the overall height or thickness of the fastening element. Rather, the positioning and/or bearing surface can also only be at most approximately 90 percent, more preferably at most approximately 60 percent, of the overall height of the fastening element. The fastening element will in this case protrude beyond the positioning and/or bearing surface. The positioning and/or bearing surface is designed to be substantially perpendicular in relation to the main axis of the boot, and is part of an offset which is arranged between that end of the first outer edge of the outer rib facing the first fastening region and the positioning and/or bearing surface. Here, this offset preferably has a second outer edge for the at least one outer rib, which edge is preferably oriented substantially parallel to the main axis of the rolling boot, and is part of the rib in question. However, provision can also be made here for this second outer edge for the at least one outer rib to have a slightly angled design, with respect to the main axis of the rolling boot, the angle between the second outer edge and the main axis of the rolling boot being smaller than that angle which is defined between the first outer edge of the at least one outer rib and the main axis of the rolling boot.

The outer rib preferably has a first outer edge which is directed away from the outer circumferential surface of the rolling boot. In a preferred embodiment, the first outer edge of the outer rib here starts approximately in the fold peak region of the first fold, more preferably exactly at the fold peak, i.e. the maximum of the first fold, and moreover preferably extends linearly and at an angle to the main axis of the rolling boot. However, provision can also be made for the first outer edge to have another design, for example to be curved.

Furthermore, the present invention relates to a system consisting of a housing part, which is preferably part of a joint, preferably part of a fixed joint, and with further preference a joint, and of a boot as defined above. More preferably, the system according to the invention comprises at least a first fastening element, more preferably in addition at least a

second fastening element for fastening the rolling boot in a second fastening region, in particular on a shaft. More preferably, the first fastening element bears at least by way of a portion of a side face against the positioning and/or bearing surface of at least one rib. More preferably, the side face of the fastening element protrudes beyond the positioning and/or bearing surface of the rib. More preferably, the base surface of the first fastening region, which base surface makes available a seat surface for the fastening element, is displaced axially with respect to the housing part and displaced with respect to the main axis of the boot in such a way that the base surface at least partially projects beyond an edge of the housing part, for example of a joint housing. The projecting length of the base surface here is preferably situated in a range from approximately 20 percent to approximately 45 percent, more preferably in a range from approximately 25 percent to approximately 35 percent, of a width of the first fastening element.

These and further advantages of the present invention will be explained in more detail below with reference to the following figures, in which:

figure 1 shows a cross section along a main axis of a rolling boot according to the prior art;

figure 2 shows a cross section on a line B-B in figure 3 along a main axis of a rolling boot according to the invention;

figure 3 shows an outer view of the rolling boot according to the invention as shown in figure 2;

figure 4 shows a sectional view through a system according to the prior art consisting of a housing part of a fixed joint, a rolling boot in accordance with figure 1 , a shaft and first and second fastening means; and

figure 5 shows a cross section on a line A-A in figure 3 through a system according to the invention consisting of a joint housing, a folding .boot according to figures

2 and 3 and a first fastening means for fastening the folding boot to the housing part.

It should be stated first of all that the features shown in the figures are not restricted to the individual embodiments. Rather, the features in each case shown and indicated in the description, including the description of the figures, can be combined with one another for development purposes, identical features, including those from the prior art, are designated here by the same references. In particular, the subject of the present invention is not restricted to the embodiment, shown in the figures, of the system according to the

invention for a fixed joint with a rolling boot. Rather, the present invention can be applied to boots of any type which are mounted on whatever parts for sealing purposes. In particular, it is also neither envisioned nor intended to restrict the invention to fixed joints in automobiles; rather, the boots according to the invention can be used in a large number of application areas, in particular in constant velocity sliding joints. Finally, it is also possible, in particular, to design the fold region in such a way that, if appropriate, second or other further folds can be provided.

Figure 1 shows the folding boot according to the prior art already described in the introduction, this boot having in its interior a plurality of inner ribs 40 arranged in the fold region 16 in order to achieve a sufficient degree of rigidity. It is clearly evident from figure 1 that the folding boot 10 according to the prior art shown therein is relatively bulky.

Figure 4 shows the folding boot 10 according to the prior art as shown in figure 1 mounted on a fixed joint housing having a housing part 54 with an outer lateral circumferential surface 70 and a shelf 56, the folding boot 10 being mounted in the first fastening region

12 on the housing part 54 using a first fastening means 58 and in the second fastening region 14 on the shelf 60 housing a second fastening means 62. This forms an overall system 74. The first fastening region 12 receives over its full surface the first fastening element 58, which comes to lie between a first retaining element 30 and a second retaining element 32. The first and second retaining elements 30 or 32 in this embodiment of a boot 10 according to the prior art can here be embodied as peripheral webs, but also as interrupted webs, for example also in the form of "ear webs", which have a rounded outer contour as viewed in a direction perpendicular to the main axis 60 of the boot 10. In the embodiment of the system 74 as shown in figure 4, in this case the base surface 28 of the first fastening region of the boot 10 is identical to the binder seat surface.

It is clearly evident from figure 4 that the first fastening region, and hence also the base surface 28 thereof, does not project beyond a housing edge 55 which is arranged in the transition from the outer lateral circumferential surface 70 to a peripheral end surface 68 of the housing part 54.

Figure 2 now shows a folding boot 10 according to the present invention with a first fastening region 12 and a second fastening region 14, wherein an interior 36 of the boot 10 is assigned, in the first fastening region 12, an accumulation of material 38, formed as a peripheral annular bead, which can engage in a corresponding peripheral annular groove on a housing part (see figure 5 in this respect). The first fastening region 12 makes available a base surface 28 which has a greater width than the width of a fastening element 58, as can be seen from figure 5. The first fastening region is adjoined by a

transition region 50 with an outer base surface 52 and an inner base surface 53. In the example shown here, this transition region is designed in such a way that it extends substantially perpendicularly to a main axis 60 of the boot 10, and moreover bears against the outer peripheral end surface 68 of the housing part 54 or is arranged close to it, as can also be seen from figure 5. Following the transition region 50 is provided a fold region 16 which has a first fold 18 with a first fold flank 22 near the first fastening region 12 and, opposite this first fold flank, a second fold flank 24. The first fold 18 here has a fold peak region 20 with a fold peak 21 and a maximum M. The first fold 18 is followed by a fold trough 26 which is directly adjoined by the second fastening region 14.

Furthermore, the boot according to the invention as shown in figure 2 has an outer rib 42 with a first outer edge 44, which starts at the maximum M of the fold peak region, i.e. at the fold peak 21 , and a second outer edge 43 which extends substantially parallel to the main axis 60 of the boot 10. The outer rib 44 here makes available a bearing and/or positioning surface 48 for the fastening element 58 (see figure 5). For this purpose, the outer rib 42 protrudes somewhat beyond the base surface 28 of the first fastening region 12, with the result that the second outer edge 43 also protrudes beyond the base surface 28 and in so doing is formed substantially parallel to this surface.

An angle α, which is approximately 110°, is formed between the outer base surface 52 and an outer side 23 of the first fold flank 22 of the fold I8. In principle, the angle α within the context of the present invention is measured between an outer base surface 52 of the transition region 50 and an outer side 23 of a first fold flank 22 of the first fold 18. The angle α is preferably situated in a range from approximately 90° to approximately 140°, with further preference in a range from approximately 100° to approximately 130°.

It is also evident from figure 2 how a height H of the first fold I8 within the context of the present invention is determined. This involves measuring the region between a tangent extending through the maximum M or the fold peak 21 of the first fold 18, this tangent being oriented perpendicularly to the main axis 60 of the boot 10, and an inner base surface 53 of the transition region 10. Since this base surface in the exemplary embodiment is likewise oriented perpendicularly to the main axis 60 of the boot 10, the tangent extending through the fold peak 21 of the maximum M of the first fold 18 extends parallel to this inner base surface 53 of the transition region 50. However, provision can also be made for the inner base surface 53 of the transition region 50 be arranged at an angle in relation to the main axis 60 of the rolling boot 10.

In the context of the present invention, the depth T of the fold trough 26 is determined by measuring the region between a tangent extending on an inner base surface 27, i.e. the

minimum of the fold trough 26 directed toward the interior of the boot 10, and perpendicularly to the main axis 60 of the boot 10, and that tangent which extends through the fold peak 21 or the maximum M of the first fold 18 and perpendicularly to the main axis 60 of the boot 10. Since both tangents thus extend parallel and perpendicularly to the main axis 60 of the boot 10, the depth T can be determined simply.

As can be seen from figure 2, the depth T is approximately 42 percent of the height H.

Figure 3 shows the line B-B along which was taken the section of the boot 10 which can be seen in figure 2. Furthermore, figure 3 shows particularly clearly that plurality of outer ribs 42, more precisely a total of 10 rib pairs 42, that is to say a total of twenty outer ribs

42, are arranged on an outer circumferential surface 11 of the boot 10. It can also be clearly seen that the outer ribs 42 fractionally protrude beyond the base surface 28 of the first fastening region 12 so as to form a bearing and positioning surface 48, the outer edge 43 for this purpose being indicated in figure 3 to make this clear.

Figure 5 now shows a system 74 according to the invention, comprising a boot 10 as shown in one of figures 2 and 3 and also a housing part 54, here a fixed joint, together with a first fastening means 58. Figure 5 also shows a shaft 56. The housing part 54 has an outer lateral circumferential surface 70 and an outer end surface 68, between which surfaces is arranged a housing edge 55. The fastening element 58 has a first side face 59.1 and a second side face 59.2, in one embodiment of the fastening element 58, for example as a compression ring, are to be regarded as peripheral side faces. Not shown in figure 5 is a second fastening element 62 which serves to fasten the boot 10 on the shaft 56 in the second fastening region 14. In the second fastening region can be clearly seen an offset 64 at which the fold trough 26 merges into the second fastening region 14. The offset 64 here is designed to be peripheral so as to produce a bearing and/or positioning surface for a second fastening element 16, not shown in figure 5. Moreover, the section through the system 74, with respect to the boot 10, was taken along a line A-A in figure 3.

In the system 74 according to the invention shown in figure 5, the fastening element 58 projects beyond the housing edge 55 by a projecting length 46. This projecting length 46 is determined by the outer end surface 68 of the housing part 54 on the one hand and, on the other hand, by the bearing and/or positioning surface 48, made available by the outer rib 42. This projecting length 46 is a portion of the base surface 28, but also of the binder seat surface, of the first fastening region 12. Figure 5 also shows the width B of the fastening element 58 determined by the two outer side faces 59.1 and 59.2 thereof. The projecting length 46 here is somewhat more than 25 percent of the width of the first fastening means 58.