# Patent

## Title
Power transmission device with slip spline shaft assembly having boot integrated deflector

## Abstract

A power transmission device includes a housing, first and second shafts and a generally tubular boot. The housing has an aperture that at least the first shaft passes through. The first and second shafts are coupled together through a splined connection causing the shafts to rotate with one another while allowing axial translation between the shafts. The boot includes a first end engaged with the first shaft and a second end engaged with the second shaft. The first end of the boot includes a flange having an insert located therein. A portion of the first end biasedly engages the first shaft thereby eliminating the need for a clamp previously required.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This is a continuation application of U.S. patent application Ser. No. 11/249,245 filed Oct. 13, 2005, now U.S. Pat. No. 7,338,384. The entire disclosure of the above application is incorporated by reference herein.


FIELD OF THE INVENTION
The present invention relates to power transmission devices and, more specifically, to boots for sealing slip spline shaft assemblies in such power transmission devices.
BACKGROUND OF THE INVENTION
Convoluted elastomeric boots have been used to seal axially displaceable shafts, such as slip spline shaft assemblies, in power transmission devices for years. These shaft assemblies generally include two shafts having a splined connection such that the shafts rotate at the same speed. The splined connection allows relative axial translation between the shafts to account for suspension and/or component articulation. Flexible boots are commonly used to protect the slip spline connection between the shafts from contamination. One known boot includes a first end clamped to a first shaft and a second end clamped to a second shaft. The clamping force may be provided by a metal band encompassing each end of the boot. In addition, a bearing seal deflector shaped as a washer may be axially positioned between the rotating boot and a stationary housing of the power transmission device to reduce the likelihood of contamination reaching a seal positioned between one of the shafts and the housing.
Unfortunately, some prior boots are known to suffer from radial ballooning (or expansion) as the rotational speed of the shafts increases. This ballooning effect sometimes causes the seal between the boot and one of the shafts to fail, thereby allowing contaminants to possibly damage bearings rotatably supporting the shafts. Furthermore, the metal bands must be individually handled and installed with care to assure that the bands do not rupture the boot. Accordingly, a cost is associated with the use of metal bands. Additional costs are associated with the handling and assembly of the separate deflector washers.
Accordingly there is a need in the art for a robust protective boot for a power transmission device that exhibits a reduced ballooning effect for maintaining a proper seal. Furthermore, a boot having an integral bearing seal deflector that eliminates the need for a separate deflector washer would be beneficial.
SUMMARY OF THE INVENTION
The present invention provides a power transmission device including a housing, first and second shafts and a generally tubular boot. The housing has an aperture that at least the first shaft passes through. The first and second shafts are coupled together through a splined connection causing the shafts to rotate with one another while allowing axial translation between the shafts. The boot includes a first end engaged with the first shaft and a second end engaged with the second shaft. The first end of the boot includes a flange having an insert located therein. A portion of the first end biasedly engages the first shaft, thereby eliminating the need for a clamp as previously required.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.



BRIEF DESCRIPTION OF THE DRAWINGS 
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
FIG. 1 is a cross-sectional view of a power transmission device illustrating a first shaft in a first position with solid lines and in a second position with phantom lines in accordance with the teachings of the present invention;
FIG. 2 is an enlarged portion of the cross-sectional view of FIG. 1;
FIG. 3 is a perspective view of a boot;
FIG. 4 is a top view of an insert; and
FIG. 5 is a cross-sectional view of the insert.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
With reference to FIGS. 1 and 2, an exemplary power transmission device 10 is shown in accordance with the teachings of the present invention. Power transmission device 10 includes a housing 12, a first shaft 14, a second shaft 16 and a protective boot 18.
The housing 12 includes an aperture 20 having bearings 22 mounted therein for rotatably supporting the first shaft 14. An end portion 24 of the housing case 12 includes a seal 26 disposed within the aperture 20 between the first shaft 14 and the housing 12. The seal 26 functions to prevent ingress of contaminants into the aperture 20 for protecting bearings 22.
The shafts 14 and 16 are coupled to one another through a slip-type splined engagement, causing the shafts 14 and 16 to rotate with one another while allowing relative axial translation therebetween. The first shaft 14 is rotatably supported within the housing 12 and has an end portion 28 extending outwardly from end portion 24 of the housing 12. The end portion 28 of first shaft 14 is generally cylindrical and includes a recessed portion 30 circumferentially extending about the shaft 14 that is axially disposed between an end 32 of the first shaft 14 and the end portion 24 of housing 12. The first shaft 14 includes an elongated aperture 34 extending therethrough for receiving a portion of the second shaft 16. The second shaft 16 includes a first end portion 36 and a second end portion 38. The first end portion 36 is generally cylindrical. The second end portion 38 partially extends within aperture 34 of the first shaft 14 and has external splines 40 in driving connection with internal splines 41 of first shaft 14. The protective boot 18 is fixedly engaged with the first and second shafts 14, 16 while allowing axial translation therebetween.
Referring to FIGS. 1-3, the protective boot 18 is generally tubular and includes a first end 43, a second end 45 and a convoluted portion 47 disposed therebetween. The first end 43 of boot 18 is fixedly engaged with the first shaft 14. The second end 45 of boot 18 is fixedly engaged with the second shaft 16. The convoluted portion 47 allows the boot 18 to extend and contract axially as the first and second shafts 14, 16 translate axially relative to one another.
The second end 45 of boot 18 includes a generally tubular portion 42 having a recess 44 circumferentially disposed on an outer surface 46 for receiving a clamp 48. The clamp 48 functions to fix the second end 45 of the boot 18 to the first end portion 36 of the second shaft 16. The tubular portion 42 of boot 18 also includes a generally flat end surface 50 and an inner surface 52. The inner surface 52 includes a circumferentially disposed protrusion 54 radially inwardly extending therefrom. A series of lugs 56 are disposed circumferentially around the second end 45 of the boot 18 between the recess 44 and the convoluted portion 47 for providing radial reinforcement.
The convoluted portion 47 of boot 18 includes a plurality of convolutions 57. The convolutions 57 allow the boot 18 to extend and contract axially in response to axial translation between the first and second shafts 14 and 16. A boot 18 having three convolutions 57 is shown in the Figures. However, it should be noted that the number of convolutions 57 may vary depending on the application and the amount of axial translation required.
The first end 43 of boot 18 includes a flange 58. The flange 58 extends radially outwardly from the first end 43 of the boot 18. The flange 58 includes a ramped outer surface 60, an inner radial surface 62 and an end surface 64. The ramped outer surface 60 forms a generally conical section, extending increasingly radially outwardly as the ramped surface 60 approaches the end surface 64. The flange 58 extends radially outwardly beyond a radial extent of seal 26 to substantially cover the aperture 20 extending through housing 12. A substantially cylindrical outer surface 65 of flange 58 is aligned with an outer surface 67 of housing 12 to further limit possible ingress of contamination.
The inner radial surface 62 of flange 58 is generally cylindrical and includes a protrusion 66 which extends radially inwardly therefrom. The protrusion 66 is sized to engage the recessed portion 30 in the first shaft 14 in a snap-fit arrangement. The snap-fit provides greater ease of assembly by requiring the operator to merely urge the protrusion 66 on the boot 18 past a distal end portion 68 of the first shaft 14 until the protrusion 66 is seated in and biasedly engages the recessed portion 30. The end surface 64 of flange 58 is a generally flat surface which extends radially from the tubular body of the boot 18. The end surface 64 includes an annular recess 70. A plastic insert 72 is located in the first end 43 of the boot 18 within flange 58 proximate the end surface 64 and annular recess 70. Plastic insert 72 is shown completely encapsulated within boot 18. However, a portion of insert 72 may be exposed to the atmosphere without departing from the scope of the present invention. While the insert 72 is plastic in this example, it should be noted that the insert 72 could be constructed from a number of different materials commonly known in the art to provide rigid reinforcement.
As seen in FIGS. 2, 4 and 5, the plastic insert 72 is generally annular and has a generally U-shaped cross section. The U-shaped cross section has a base 74, a first leg 76 and a second leg 78. The base 74 is ring-shaped and includes a plurality of apertures 80 extending generally axially therethrough. A series of slots 82 also extend through the base 74 and are located radially inward of the apertures 80. The legs 76 and 78 of the U-shaped cross-section form inner and outer circumferential limits, respectively. The first leg 76 forms the inner circumferential limit and the second leg 78 forms the outer circumferential limit of the insert 72. A radial distance between first leg 76 and second leg 78 defines a radial extent of plastic insert 72. The overall distance that plastic insert 72 axially extends may be defined as an axial extent of plastic insert 72. The radial extent of plastic insert 72 is greater than the axial extent. The legs 76, 78 include recessed portions 84 circumferentially spaced apart from one another. The first leg 76 also includes a protrusion 86 at a top portion thereof extending radially outwardly therefrom.
The plastic insert 72 is generally positioned within the first end 43 of the boot 18 where a portion of the flange 58 is located radially inward of the insert 72 and a portion of the flange 58 is located radially outward of the insert 72. The insert 72 is generally axially aligned with the radially inward protrusion 66 on the inner surface 62 of the first end 43 of the boot 18. As a result of the relative positioning, the stiffness of the portion of the boot 18 located between the insert 72 and the first shaft 14 is substantially increased. An increased stiffness assures a robust engagement is maintained between protrusion 66 and first shaft 14. Furthermore, the insert 72 provides structural rigidity to boot 18 whereby the boot 18 is less likely to radially expand or balloon during rotation.
The boot 18 may be formed by an injection molding process. During the process, the insert 72 is placed within a cavity of the mold. Subsequently, molten elastomeric material is injected into the mold. The insert 72 is encapsulated within the elastomeric material. During the injection process, molten elastomeric material passes through the apertures 80 and slots 82 in the insert 72 and surrounds the leg portions 76, 78. This simple process eliminates the need for additional parts such as band clamps for attachment of the first end 43 of the boot 18 to first shaft 14. Having the insert 72 integrally formed and retained within the first end 43 of the boot 18 greatly simplifies assembly as well. The assembly time is reduced and the chances of an improper installation that would typically result in a failure of the part are decreased.
The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.

## Claims

1. A power transmission device comprising:
a first rotary member;
a second rotary member coupled for common rotation with and axial translation relative to said first rotary member; and
a tubular boot having a first end portion engaging said first rotary member, a second end portion engaging said second rotary member, and a convoluted portion interconnecting said first and second end portions, said first end portion including a radially extending flange having an annular insert at least partially encapsulated therein and an inwardly extending protrusion seated in an annular groove formed in said first rotary member, said insert being axially aligned with said protrusion so as to radially encircle said protrusion, and wherein said insert has a radial extent greater than its axial extent.

2. The power transmission device of claim 1 wherein said boot is molded from an elastomeric material and said insert includes apertures through which said elastomeric material extends.

3. The power transmission device of claim 1 wherein said insert includes inner and outer circumferentially extending legs interconnected to a ring-shaped base, and wherein said legs extend toward a terminal end surface of said flange.

4. The power transmission device of claim 1 further comprising:
a housing having an end portion through which an aperture extends;
a bearing rotatably supporting said first rotary member within said aperture; and
a seal disposed in said aperture between said housing and said first rotary member and axially positioned between said flange and said bearing.

5. The power transmission device of claim 4 wherein said end portion of said housing defines an end surface, wherein said terminal end surface of said flange is axially displaced from said end surface of said housing to permit rotation of said flange relative to said housing, and wherein said flange extends radially outwardly beyond said aperture in said housing.

6. The power transmission device of claim 4 wherein said first rotary member is rotatably supported by said housing such that said second rotary member axially translates relative to said first rotary member and said housing, and wherein said first rotary member has internal splines meshed with external splines formed on said second rotary member.

7. A power transmission device comprising:
a first shaft;
a second shaft drivingly coupled with said first shaft, said second shaft being axially movable relative to said first shaft; and
an elastomeric boot having a first end coupled to said first shaft and a second end coupled to said second shaft, said boot operable to axially expand and contract in concert with axial movement of said second shaft, said first end of said boot includes a radially extending flange having an annular insert positioned therein and a compressible portion engaging said first shaft to retain said first end of said boot on said first shaft, said insert having a ring portion defining an inner circumferential limit positioned adjacent said compressible portion and an outer circumferential limit proximate an outer portion of said flange.

8. The power transmission device of claim 7 wherein said boot is molded from an elastomeric material, and wherein said ring portion of said insert includes a plurality of apertures extending therethrough, said elastomeric material extending through said insert apertures.

9. The power transmission device of claim 8 wherein said insert is completely encapsulated within said flange.

10. The power transmission device of claim 7 further comprising a seal radially disposed between said first shaft and a housing, said seal contacting at least a portion of said first shaft and said housing, and wherein said first end of said boot extends radially beyond said seal.

11. The power transmission device of claim 7 wherein said compressible portion of said flange is positioned within an annular groove formed on said first shaft.

12. The power transmission device of claim 11 wherein said insert is located radially outward of said compressible portion and a ring portion of said insert surrounds said compressible portion.

13. The power transmission device of claim 7 wherein said inner circumferential limit and said outer circumferential limit define a radial extent greater than an axial extent of said insert.

14. A power transmission device comprising:
a housing having an aperture;
a first shaft rotatably supported by said housing and including an end portion axially extending beyond an end surface of said housing;
a second shaft coupled for rotation with and axial translation relative to said first shaft; and
an elastomeric boot having a first end fixed to said first shaft and a second end fixed to said second shaft, said first end of said boot including a radially extending flange having a rigid insert positioned therein and a compressible portion biasedly engaging said first shaft to retain said first end of said boot on said first shaft, said insert having at least a portion radially aligned with said end surface.

15. The power transmission device of claim 14 wherein said flange radially extends adjacent to said end surface to limit the ingress of contamination into said aperture.

16. The power transmission device of claim 15 further comprising a seal radially disposed between said first shaft and said housing, wherein said flange is positioned adjacent to said seal.

17. The power transmission device of claim 15 wherein said compressible portion of said flange is radially positioned between said first shaft and said insert.