Patent Application
20090078084
The present disclosure relates to a sealing assembly and, more particularly, to boot cover assembly typically used with a constant velocity joint.
Constant velocity joints and similar rotating couplings typically include a boot cover assembly and grease cover to enclose and protect the coupling during operation. Since the boot cover assembly is partially flexible, the boot cover assembly is able to seal around the joint while permitting articulation and relative axial movement of differing rotating members of the joint. The boot cover assembly seal lubricant in the joint so as to reduce friction and extend the life of the joint. The boot cover assembly also seal out dirt, water and other contaminants to protect the functionality of the joint. However, leaks may reduce the life of the joint, and contaminants in the grease may disturb the chemical composition of the grease, degrading its performance.
An important characteristic of the constant velocity joint is the ability of the joint to allow relative axial movement between two shafts while maintaining a seal to the outside environment. Examples of known joint assemblies are disclosed in commonly-owned U.S. Pat. Nos. 6,817,950, 6,776,720, 6,533,669 and 6,368,224, and U.S. Pat. No. 5,899,814, the disclosures of which are hereby incorporated by reference in their entireties.
Constant velocity joints require constant lubrication (grease) to remain in operation in the environment in which they are utilized. They typically use a sealed system to contain the grease, the main component of which is the boot and associated mounting can. Boots come in a variety of types. Some examples include: convoluted, internal rolling diaphragm (IRD) and external rolling diaphragm (ERD). Particularly relating to IRD and ERD boots, the current industry standard is to have the diaphragm boot crimped onto the mounting can, and then to have the mounting can fit onto the joint. The mounting can and boot are crimped together at the top only, which allows grease that is under pressure from centrifugal forces during the joint rotation to be pushed between the sides of the boot and the mounting can. The grease build-up causes bulging and distortion during high-speed operation, thereby weakening the boot. In some cases the distortion may be excessive and lead to a complete failure of the boot cover assemblies of the prior art by decoupling the boot from the mounting can.
What is needed, therefore, is a boot cover assembly that provides increased resistance to decoupling during normal operation from bulging grease, accommodates greater axial extension and relative angles within a joint assembly, and produces a more reliable boot cover assembly.
A boot cover assembly is disclosed. The boot cover assembly includes a generally cylindrical axially extending can, and a generally conical axially extending boot. The can has a first end, a central portion, and a second end. The boot includes inner and outer surfaces, a first large end, a central portion, a second small end. A portion of the second end of the can and a portion of the first large end of the boot are bonded together to form a coupling region. A portion of the inner surface of the second end of the can is bonded to a mounting face formed on an inner surface of the boot. A distal end of the can is also bonded to a mounting shoulder of the boot such that two surfaces of the can are secured to two surfaces of the boot.
Referring now to the drawings, preferred illustrative embodiments are shown in detail. Although the drawings represent some embodiments, the drawings are not necessarily to scale and certain features may be exaggerated, removed, or partially sectioned to better illustrate and explain the present disclosure. Further, the embodiments set forth herein are not intended to be exhaustive or otherwise limit or restrict the claims to the precise forms and configurations shown in the drawings and disclosed in the following detailed description:
With continual reference to
Can portion 154 is formed of a first substantially rigid material 162, and boot portion 156 is formed of a second substantially flexible material 164, as discussed below. A physical and/or chemical bond occurs at coupling region 158. In one representative embodiment, the bond in the coupling region 158 may be achieved by a two-step adhesive process (to be explained below in greater detail). Other processes for forming the coupling region 158 are also contemplated, such as simply molding boot portion 156 to can portion 154.
Can portion 154 includes a sealing portion 160 that forms a mounting face for a first rotational member (e.g., 42 in
Can portion 154 further includes an axially extending lip 174. Can portion 154 may also includes apertures 180 to allow fasteners (not shown) to directly fasten can portion 154 to a first rotational member.
Referring to
In one embodiment, the upwardly extending lip is oriented so as to be generally perpendicular to the mounting face 184, such that mounting shoulder 186 and mounting face 184 forms a generally right angle, as shown in
Distal end 188 of can portion 154 is shown in
It is also contemplated that distal end 188 and mounting shoulder 186 are not correspondingly oriented. In such instances, extra adhesive material may be employed to fill any gaps resulting from a non-corresponding orientation.
Coupling region 158 further includes an adhesive 190 that is positioned between bottom portion 182 and mounting surface 184, as well as distal end 188 and mounting shoulder 186. Adhesive 190 serves to physically and/or chemically bond can portion 154 to boot portion 156 along two surfaces, thereby providing improved resistance to decoupling stresses and forces than the prior art crimped connections.
Coupling region 158 may also be employed for all types of boots by limiting the length of coupling region 158 to a predetermined length that will permit full joint functionality. While an acceptable range of lengths for any given type boot may be determined by FEA analysis, taking into consideration other such factors such as joint type, maximum angle, operating angle and plunge capacity (if applicable), it is contemplated that a suitable range for the length of coupling region 158 is about 5-50 mm. Due to the configuration of coupling region 158, boot cover assembly 120 is less susceptible to deformation bulging (as illustrated in
Boot portion 156 may be formed by injection molding. In one embodiment a two-step adhesive process is utilized to form coupling region 158. In this example, during the molding process for boot portion 156, a mold (not shown) is prepared for injection with can portion 154 placed in the mold. The two-step adhesive process may be performed at this stage by pre-treating bottom surface 182 of can portion 154 and distal end 186 that forms part of coupling region 158 with a first adhesive or primer. After a predetermined time period to allow the primer to cure, approximately 2 minutes, a second adhesive or top coat material is added to the coupling region 158 to adhere can portion 154 to boot portion 156 during the molding process. The primer adheres to can portion 154. The top coat material adheres to the primer. The flexible boot material 164 is injected into the mold and is allowed to cure with a portion of the boot material being adhered to the top coat material. Using this process, boot portion 156, the primer, top coat material and can portion 154 cooperate to form coupling region 158, thereby adhering boot portion 156 to the pre-manufactured can portion 154 at two surfaces, as explained above.
Can portion 154 is constructed preferably of a relatively rigid material, and may be selected from the family of thermoplastic polyester resins, a resin and filler to increase rigidity and strength or a metal capable of being formed to the desired axial rotating shape.
Boot portion 156 is constructed preferably of a substantially flexible material 164, and may be plastic or any elastomer, such as rubber, silicone, or thermoplastic elastomer (TPE). Flexible material 164 has a hardness value in the range of about 55-75 Shore A or about 35-55 Shore D. In one embodiment, flexible material 164 has a hardness of about 40-44 Shore D. Materials that are specifically compatible with a typical boot cover assembly 120 environment are relatively rigid thermoplastic polyesters due to the desirable bonding formed in coupling region 158 during the molding process.
The adhesive as well as the pressures induced by the molding process ensures that the coupling region 158 provides a reliable bond between can portion 154 and boot portion 156. The pressures of the molding process, the flow of resins in the mold and the adhesives provide for a coupling region 158 that is both a chemical bond, as well as a physical bond. The coupling region 158 forms a bond between can portion 154 and boot portion 156 that is selectively in shear, compression and tension during operation of joint 20. These shear, compressive, and tensile forces are the result of at least deflection within boot cover assembly 120 due to torsional and rotational movement of joint 20.
The connection between can portion 154 and boot portion 156 provides improved resistance to decoupling stresses and forces than the prior art crimped connection. That is, values of stresses, forces, and deflection that can be tolerated in coupling region 158 of boot cover assembly 120 may not be tolerated in the crimped connection of boot cover assembly 30. Thus, the coupling region 158 may accept greater articulation and axial movement within joint 120.
The present invention has been particularly shown and described with reference to the foregoing embodiment, which are merely illustrative of the best modes for carrying out the invention. It should be understood by those skilled in the art that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention without departing from the spirit and scope of the invention as defined in the following claims. It is intended that the following claims define the scope of the invention and that the method and apparatus within the scope of these claims and their equivalents be covered thereby. This description of the invention should be understood to include all novel and non-obvious combinations of elements described herein, and claims may be presented in this or a later application to any novel and non-obvious combination of these elements. Moreover, the foregoing embodiments are illustrative, and no single feature or element is essential to all possible combinations that may be claimed in this or a later application.
