The present invention provides for a boot comprising a fold region and an attachment re- gion, the first attachment region comprising an inside with at least two circumferential ribs, as well as for a system comprising a boot in accordance with the present invention and a joint casing with an annular groove.

Due to the necessity of mounting boots on a joint casing by way of a binder element, a problem exists with respect to the fitting of the boot on the joint casing due to the stress exerted from the binder element and a flowing into spaces underneath the binder element, thereby loosening the connection with each other. In order to solve that problem, US 5,094,894 proposes a boot with at least one collar region, comprising on its outside an annular groove with a rectangular or trapezoidal cross-section for a tensioning element, said annular groove is provided for with a substantially flat bottom part resting against the tensioning element and is wider than an internal annular bead. The collar region, within the flat annular groove in the region of the internal annular bead comprises at least one recess-like annular gap with a rectangular or trapezoidal cross-section whose cross- sectional depth is greater than its width. Further, on the inner surface of the collar region resting against the joint casing two annular beads are assigned to the two recess-like annular gaps shown in the Fig. of US 5,094,894. However, the problem of the embodiment disclosed in US 5,094,894 is that it may not be fixed in a defined axial position in an annular groove of a joint casing. The boot in accordance with US 5,094,894 will show a high flexibility in the axial direction with respect to the fixing of the same by a binder element in an annular groove of a joint casing, whereby the flexibility will cause deformations during tensioning. Further, the pressure forces exerted by the binder element will flow in an uncontrolled way into the material of a boot in the binder seat region giving rise for sealing problems.

It is, thus, an object to the present invention to provide for a boot and a system comprising such a boot as mentioned above showing increased sealing and fixing properties compared to the boots known from the state of the art.

In accordance with the present invention, the object is solved by a boot as defined in the beginning comprising an inside with at least two circumferential ribs with a first rib and a second rib, whereby an inner diameter D2 of the second rib is smaller than an inner diameter D1 of the first rib. Thus, the first circumferential rib has a lower height than the second circumferential rib. Preferably, the boot comprises only one second circumferential rib. In a further preferred embodiment of the present invention, the boot comprises at least two first circumferential ribs. More preferred between two first circumferential ribs the one second rib is arranged. The boot in accordance with the present invention provides for an axial fixation in an annular groove in which the second rib is to be engaged is arranged for on the outer surface of a joint casing. Further, during assembly of the boot on a joint casing a good positioning is achieved.

In a further preferred embodiment of the present invention, the inner diameter D2 of the second circumferential rib is at least approximately 0,7 mm, more preferred at least approximately 0,9 mm, 1,0 mm or 1 ,4 mm and most preferred at least approximately 1 ,8 mm, smaller, and not smaller than more than approximately 6 mm, preferably more than approximately 5 mm, than the inner diameter D1 of the first circumferential rib or ribs. In a more preferred embodiment of the present invention, the second rib essentially, preferably completely over the whole widths, fills an annular groove of a joint casing. Preferably, the outer contour of the second rib suits to the contour of the annular groove of the joint casing at least in part, and especially in a peak region of the second circumferential rib.

Preferably, the depth of the groove between neighbouring second ribs is about 0.25 mm at the most. Preferably the depth D is in a region between about 0.04 mm to about 0.2 mm, most preferred in a region between about 0.06 mm to about 0.15 mm. Due to the provision of neighbouring second circumferential ribs being separated by a groove, it is achieved that the annular groove on the joint casing is in contact mainly only with the surface of the ribs, and, thus, the radial stiffness is reduced without any impact on the axial stiffness in the binder seat region, that is the region between a first side region and a second side region of the first attachment region, especially left and right, preferably vertical, side walls of each kind, and provides for a binder seat surface, the latter being the surface under a binder element.

In a most preferred embodiment of the present invention, the boot comprises one second circumferential rib arranged between three first circumferential ribs, whereby on one side of the second circumferential rib two first circumferential ribs are arranged for, whereas on the other side of the second circumferential rib one first circumferential rib is arranged for. Most preferred is an embodiment wherein in the first side region of the attachment region being opposite to the second side region of the attachment region being located near the fold region of the boot two first circumferential ribs are arranged for on the inside of the attachment region, followed by one second circumferential rib and one first circumferential rib being arranged for near the second side region of the attachment region, thus being near the fold region of the boot. However, in the context of the present invention also any other arrangement of the first and second circumferential ribs is possible, especially more than three first circumferential ribs may be arranged for on the inside of the first attach- ment region, for example four, five, six or more first circumferential ribs. Also two or more second circumferential ribs may be arranged for on the inside of the attachment region, preferably being arranged next to each other.

In a further preferred embodiment of the present invention, at least one of the first and/or second circumferential ribs has a cross-sectional curved shape, viewed in a direction of a main axis of the boot. Preferably, all of the first and second circumferential ribs have a cross-sectional curved shape. One may address the first and second circumferential rib having a cross-sectional curved shape as annular beads.

In accordance with the present invention, in a preferred embodiment the attachment region comprises an outside with at least two first and second circumferential slits extending from the surface of the binder seat region towards the inside. In a preferred embodiment, the first and/or second circumferential rib is assigned to at least one first and/or second circumferential slit. Most preferred, assigned to each first circumferential slit is a first circumferential rib. In a more preferred embodiment of the present invention, assigned to a second circumferential slit is a second circumferential rib, most preferred to each second circumferential slit a second circumferential rib is assigned to. These circumferential slits and/or circumferential ribs in accordance with the present invention of the first attachment region are preferably assigned to the region on the outside of the first attach- ment region providing for a binder seat for a binder element. In a most preferred embodiment of the present invention, all first and second circumferential slits are arranged for underneath the surface of the binder element and, thus, to the binder seat surface, conferring to a situation before fastening the binder element.

In a further preferred embodiment of the present invention, the first circumferential slit and/or the second circumferential slit has a rectangular or trapezoidal cross-section, viewed in a direction of the main axis of the boot. In a preferred embodiment, all first and second circumferential slits have the same contour if viewed in a direction of the main axis of the boot, and most preferred all first and second circumferential slits have a rectangular cross-section. However, the cross-sectional shape of the first and/or circumferential slit may also be designed in any other possible way. Further, the cross-sectional width and the cross-sectional depth of the first circumferential slit and the second circumferential slit are preferably essentially the same, however, the cross-sectional width and the cross- sectional depth can also deviate from each other, for example the cross-sectional depth may be greater than the cross-sectional width.

In a further preferred embodiment of the present invention, the cross-sectional width and the cross-sectional depth of the first and second circumferential slits are essentially the same. In another further preferred embodiment of the present invention, the cross- sectional depth of the first circumferential slit and/or the second circumferential slit is greater than the cross-sectional width. Further preferred, the cross-sections of the first circumferential slit and the second circumferential slit deviate from each other. In a more preferred embodiment of the present invention, a depth T2 of the second circumferential slit is greater than a depth T1 of the first circumferential slit. Further, the width of the first and second circumferential slits is preferably the same, most preferred the width of the first circumferential slit is slightly increased compared to the width of the second circum- ferential slit. In a further preferred embodiment of the present invention, the dimensions of the slits and the shape of the cross-sections of the first circumferential slit are all the same. Preferably, the depth T2 of the second circumferential slit is at least approximately 20 percent higher than the depth T1 of the first circumferential slit. Most preferred, the depth T2 of the second circumferential slit is at least approximately 33 percent higher than the depth T1 of the first circumferential slit.

Preferably, on the outside of the first attachment region and in the first side region of the same a ring element is arranged, providing for an orientating side surface for the binder element, preferably developed as a side wall, defining one boundary of the binder seat region. The orientating side surface for the binder element may be provided for by a vertical side wall. In a cross-sectional view, the ring element may have a rectangular or trapezoidal shape, however, also other possible cross-sectional shapes may be used. The other boundary of the binder seat region is defined by another orientating side surface, preferably a vertical side wall being arranged on the second side region opposite the first side region and forming the transition to the fold region of the boot.

First arrangement means may be arranged in the first side region of the first attachment region, preferably in pairs being opposite to each other. For example, eight arrangement means, thus, leading to four pairs of the arrangement means, may be arranged on the first side region on the outside of the first attachment region, and viewed in a direction to the main axis of the boot, preferably arranged for on an outside of the ring element. Similarly, on the outside of the first attachment region in the second side region next to the fold re- gion of the boot, second arrangement means are arranged, preferably next to the side wall of the second side region, most preferably lengthened the said second side wall. Preferably, said second arrangement means are arranged opposite first arrangement means, so that a pair of a first arrangement means and the second arrangement means is created. The second attachment means may have another shape than the first attachment means. Preferably, both first arrangement means and second arrangement means provide for positioning surfaces for the binder element. The binder element may with its side walls be in contact with the first and/or second arrangement means, however, this must not necessarily happen, because the binder seat region shows a greater width than the binder seat surface.

The present invention also refers to a system comprising a boot in accordance with the present invention as described before and in the following and a joint casing with an annular groove, in which the second circumferential slit engaged. Further preferred, the system in accordance with the present invention further comprises at least one binder element.

Other advantages and features of the invention will become apparent to one of skill in the art reading the following detailed description with reference to the drawings illustrating features of the invention by way of example.

Brief description of the drawings

For more complete understanding of this invention, reference should now be made to the embodiments illustrated in greater detail in the companion drawings and described below by way of examples of the invention.

In the drawings:

Fig. 1 is a side view of the first embodiment of a system in accordance with the present invention.

Fig. 2 is a partial cross-sectional view through an attachment region of a boot in accordance with the present invention. Detailed description and description of the drawings

While the present invention is described with respect to a boot, the present invention may be adapted and utilized for other fixable sealing applications mating with a circumferential surface of a stretchable part, including such applications outside of the constant velocity joint art. Especially, the boot in accordance with the present invention may be a roll boot or a convoluted boot. However, also any other machinery form parts may be protected by the boot in accordance with the present invention. The boot in accordance with the pre- sent invention usually shows two attachment regions. If the boot is designed to be fixed on a shaft and a joint casing, the first attachment region is assigned to the joint casing whereas the second attachment region is assigned to the shaft.

In the following detailed description, especially orienting terms are used such as "left", "right", "outside", "inside", "next to", "underneath", and the like. It has to be understood that these terms are used for convenience of description of the components or embodiments by reference to the drawings. These terms do not necessarily describe the absolute location in space, such as upward, downward, left, right etc., that any part must assume. Further, in the following description, various operating and numerical parameters and components are described for several constructed embodiments. These specific parameters and components are included as examples and are not meant to be limiting.

In the context of the present invention, the phrase "assigned to" means that circumferential slits and/or ribs, respectively, are arranged on the outside or the inside, respectively, of the attachment region in similar regions in a cross-sectional view in the direction of the main axis of the boot. Especially, the slits must not be arranged within the width of the ribs, but may also only partially be arranged in a region corresponding to the width as defined by a rib. However, it is preferred that the circumferential slits are arranged essentially centered within the width of a circumferential rib.

In the context of the present invention, the term "cross-sectional width" is to be understood as follows: the cross-sectional width refers to a cross-sectional view of the embodiment in question in accordance with the present invention. Said cross-sectional view is obtained when viewing in a direction of the main axis 16 of the embodiment being de- scribed, as may be taken from Fig. 2. In the context of the present invention, the term "cross-sectional depth" is to be understood as follows: the term "cross-sectional depth" T1 and T2 used throughout the present invention refers to the first and second slits assigned to the circumferential ribs and the additional rib in a cross-sectional view in the direction of the main axis. The cross- sectional depth is measured from a bottom of each slit defined by lines 52 and 54 in Fig. 2 up to the surface of the binder seat region 18, defined by the virtual line 19 in Fig. 1 and 2 of the present invention.

In the context of the present invention, the term "orientating" used in connection with side surfaces especially of the ring element or in the second side region is to be understood as follows: The binder element in no way must be in direct contact, neither in total, nor in part, with the orientating surface, however may be in contact with the same. The orientating surface only provides for a helping means for the mounting of the binder element. The same also holds for first and second arrangement means.

In the context of the present invention, the term "depth" D as used in connection with the grooves between neighbouring first circumferential ribs is to be understood as follows: The depth is measured between the maximum outer shape of first circumferential rib(s) as defined, for example, by line 38 and line 56 in Fig. 2. At least two neighbouring first circumferential ribs may be connected by said line 38, whereas if only one first circumferential rib is present, line 38 is the tangent through the maximum of the peak region of the first circumferential rib, and, thus, is parallel to the main axis of the boot. If, and that is preferred, a line 38 connecting the peaks of the first circumferential ribs is essentially parallel to the binder seat region plain (as is line 19 in Fig. 2), the depth is measured between said virtual line 38 as well as the bottom line 56 (see Fig. 2) connecting at least two neighbouring grooves being arranged between first circumferential ribs. Further, it is preferred that the bottom line 56 connecting the ground of all grooves between first circumferential ribs is essentially parallel to the main axis of the boot, and, thus, the binder seat region plain. In such a preferred embodiment said bottom line 56 as well as line 38 are essentially parallel to the main axis of the boot.

In the context of the present invention, the phrase "rectangular" means that in a cross- sectional view the first and second circumferential slits or the ring element has a rectangular contour, whereby the open side of the slits may be defined by the virtual line 19 in Fig. 2 defining the binder seat region 18. The cross-section of the first and second circumferential slits may also have a quadratic contour, being within the definition of the term "rectangular" in the sense of the present invention. The boots are usually made of a thermoplastic elastomere material or mixtures of ther- moelastic plastomere materials, for example based on polyurethane (TPU), polyamide (TPA) ₁ polyolefines (TPO), polyester (TPEE) or a thermoplastic elastomere vulcanizate (TPV), or a thermoplastic poly-ether-ester-elastomere (TEEE). The material or mixtures of materials of the boots in accordance with the present invention may be made of or may further comprise other materials, especially additives like diffusion-promoting add mixtures or any other additives a person skilled in the art will be aware of in view of the use of the boots in question, especially in view of the demands of automotive industry if the boots are used for automotives. However, the boots in accordance with the present invention may also be made of usual rubber-elastic materials, including mixtures thereof.

Advantages are provided by thermoplastic elastomer materials. These includes materials known from the prior art that has two different polymer segments, namely a relatively rigid resin segment and an elastic soft segment. The individual polymer segments are comprised of longer chains of similar monomers. The resin segments hold the soft segments together by physical, network-like bonds. A thermoplastic elastomer material for manufacturing boots in accordance with the present invention is the thermoplastic material marked under the brand name "Hytrel" by the DuPont company.

In another aspect of the invention, the first and/or a second attachment region of the boot is at least partially manufactured of an elastomer material. In contrast to thermoplastic elastomer materials, an elastomer material has the advantage of having a reduced so- called "cold flow" then situated underneath the fastening element. This cold flow is under- stood to be the phenomenon in which, when subjected to clamping or compression stress, the plastic material in the first, but also in the second attachment region "escapes" literally from the fastener, as a result of which the boot can come loose during operation, particularly when under thermal stress. Other regions of the first and/or second attachment region can nevertheless be manufactured of a thermoplastic elastomer material. The same advantage can also be achieved if a layer of the thermoplastic elastomer material is placed underneath the elastomer material. Possible elastomer materials include for example polyurethane rubber, polyester-based polyurethane/rubber mixtures or polycloro- prenes.

The first attachment region of the boot is advantageously at least partially comprised of a layer of a thermoplastic elastomer material or a layer of an elastomer material. To a great extent, this avoids the known disadvantages of using thermoplastic elastomer materials in the clamping region of the collar. It is also possible for the layer, which is comprised of an elastomer material, to be integrally joined in a permanent fashion to the fastening mechanism.

As the method according to the invention can be carried out in the form of a pressblower injection blow moulding process, however, may also be produced with an injection/intrusion process, an injection moulding process, an injection/pressing process and /or an extrusion/blow moulding process. The pressblower injection blow moulding process and the injection/extrusion process are advantageously used, because precisely- dimensioned boots may be produced by said processes.

The binder element may be selected from each kind of fasteners known from the prior art, such as clamping elements, especially clamping straps, but also clamp or compression rings. Useful fasteners exhibit clamping and/or compression forces on the binder seat region of the boot.

In the context of the present invention, the term "inner diameter" Dt and D2 as used in connection with the first and second circumferential rib is to be understood as follows: The inner diameter D1 and the inner diameter D2 are measured with respect to the whole boot in the attachment region in a cross-sectional view in direction of the main axis, and were defined as shown in Fig. 2. When viewed in a cross-sectional view, inner diameter D1 referring to the first circumferential ribs is defined and measured between the maximum of the peak region of the first circumferential rib on two points lying opposite to each other on the inside of the boot, whereas the inner diameter D2 referring to the second circumferen- tial ribs is measured and defined by the maximum of the peak region of the second circumferential rib on two points lying opposite to each other on the inside of the boot.

Referring now to the drawings where alike reference numerals are used to identify identical components in the various views, Fig. 1 illustrates a side view of the first embodiment of the system 50 in accordance with the present invention in form of a first attachment region 14 of a convoluted boot 10 mounted on a joint casing 44 of a constant velocity joint by way of a binder element 48. Boot 10 shows on an inside 40 (see Fig. 2) three first circumferential ribs 26.1 , 26.2 and 26.3 to which first circumferential slits 30.1 , 30.2 and 30.3 are assigned to in the first attachment region 14 in a centered way. The attachment region 14 comprises a binder seat region 18 defined by a vertical side wall 22 being part of a ring element 20 in a first side region 58 and a further vertical side wall 24 being located opposite to the vertical side wall 22 in a second side region 60. Underneath the binder element 48 that may be a compression ring, all first circumferential ribs 26.1 , 26.2 and 26.3 and first circumferential slits 30.1 , 30.2 and 30.3 are located.

Further, between first circumferential ribs 26.2 and 26.3 a second circumferential rib 28 is arranged for. Said second circumferential rib 28 engages in an annular groove 46 being arranged for on the outer surface of the joint casing 44. The first circumferential ribs 26.1 , 26.2, and 26.3, however, do not engage in the annular groove 48. The second circumferential rib 28 shows a difference in height being defined by the difference d between lines 38 and 39 being essentially parallel to a main axis 16 of the boot 10 (see Fig. 2), and be- ing defined as a tangent through the maximum of the peak region of the second circumferential rib 28 and anyone of the first circumferential ribs 26.1 , 26.2 or 26.3. All first circumferential ribs 26.1 , 26.2, and 26.3 show the same cross-sectional shape that is curved. Also the second circumferential rib 28 shows a curved cross-section.

Turning now to Fig. 2 being a cross-sectional view of a convoluted boot 10, one may easily derive that the inner diameter D2 of the second circumferential rib 28 is smaller than the diameter D1 of anyone of first circumferential ribs 26.1 , 26.2, and 26.3.

Further, the first circumferential slits 30.1 , 30.2, and 30.3 show a depth T1 defined be- tween lines 19 and 54, that is smaller than a depth T2 of the second circumferential slit 32 defined by line 19 and line 52. The cross-sectional shape of the first and second circumferential slits 30.1 , 30.2, 30.3, and 32 are essentially the same in that all of them show a rectangular cross-sectional shape. The width of all of said first and second circumferential slits 30.1, 30.2, 30.3, and 32 is also essentially the same. Each of the first and second circumferential slits 30.1 , 30.2, 30.3, and 32 are assigned to first and second circumferential ribs 26.1 , 26.2, 26.3, and 28 in a centered way.

Between the two first circumferential ribs 26.1 and 26.2 being located near the first side region 58, a groove 34 is located. The depth D of said groove 34 may be measured be- tween the bottom line 56 and the line 38 connecting all of the maximums of the peak regions of the first circumferential ribs 26.1 , 26.2, and 26.3. The depth of said groove 34 is around 0.1 mm.

Further, on both sides of the second circumferential rib 28, a groove 36.1 and 36.2 is lo- cated. The groove 36.1 is defined by the second circumferential rib 28 and the first circumferential rib 26.3 being near the second side region 60 of the first attachment region 14, whereas the groove 36.1 is located between the second circumferential rib 28 and the first circumferential rib 26.2 being located near the first side region 58 of the first attachment region 14. The depth of said groove 36.1 and 36.2 is defined by the bottom line 56 and the line 39 being a tangent through the maximum of the peak region of the second circumferential slit 28 and being essentially parallel to the main axis 16 of the boot 10. The depth D of said grooves 36.1 and 36.2 may be around 0.2 to 0.25 mm, however, may also be higher. The depth of the annular groove 46 of the joint casing 44 as shown in Fig. 1 may vary from about 0.1 to 0.15 mm, however, may also be higher.

The present invention consequently creates a boot that through the provision of different inner diameters of first and second circumferential ribs permits a good positioning of the boot on a form part, especially a joint casing, and, further, allows good axial fixation on said part.

While the inventive boot has been described in connection with one or more embodi- ments, that disclosure is not meant to be limiting. Rather, the invention covers all alternatives, modifications and equivalents within the spiritual scope of the appended claims taking into account the description.