Abstract:
To protect a joint from exposure to contaminants and loss of lubricant disposed within a joint a traditional joint includes a sealing system. Typically the sealing system includes a boot and a boot cover. To produce a more effective joint, the sealing system of the present invention further includes a shield to protect the boot and the boot cover from exposure to contaminants by providing a barrier therebetween. The joint of the present invention includes a shield having several embodiments including an elastomer sleeve, a rigid cylindrical tube and a thermoplastic second boot.

Description:
FIELD OF THE INVENTION 
   The present invention generally relates to joint having a sealing system, and more particularly relates to a joint having a shielded sealing system for preventing exposure of the sealing system to contaminants. 
   BACKGROUND 
   Joints are common components in today&#39;s automotive vehicles. Typically, joints are used for transmission of a rotating motion. When transmission of a rotating motion is desired at a generally constant velocity a constant velocity joint (CVJ) is utilized. Various styles of constant velocity joints are common and include ball-type fixed joints, tripod fixed joints, plunging ball joints, and the like. The various styles of joints are currently used in front-wheel drive vehicles, rear-wheel drive vehicles and on propeller shafts (propshafts) found in rear-wheel drive, all-wheel drive and four-wheel drive vehicles. The constant velocity joints are generally grease lubricated for life and sealed by a sealing system when used on propshafts. Therefore, constant velocity joints are sealed in order to retain grease inside the joint while keeping contaminants and foreign matter, such as dirt, water, and the like out of the joint. To achieve this protection the constant velocity joint usually includes a sealing system. The CVJ is usually enclosed at an open end of an outer race by a sealing boot and boot cover made of a rubber, thermoplastic, silicone type material, and the like. The opposite end of the outer race is generally enclosed by a dome or cap, commonly known as a grease cap. A monoblock or integral stem and race style joint is sealed at the opposite end by the internal geometry of the outer race. This sealing and protection of the constant velocity joint is necessary because contamination of the inner chamber of the joint generally will cause internal damage and destruction of the joint. Furthermore, once the inner chamber of the joint is partially filled and thus lubricated, it is generally lubricated for life. 
   A main function of a CVJ is the transmission of rotational forces. During operation, the constant velocity joint transmits torque. The torque transfer generates heat by the internal friction of the joint along with other transmission inefficiencies. Generally, as the speed and torque increase, the heat generation of the constant velocity joint also increases. A further effect of increased speeds is that the velocity of the grease increases because the internal action of the joint acts like a pump to causes the grease to be pumped out of the joint and into the sealing system. This phenomenon increases pressure on the sealing system. The high internal temperatures in the constant velocity joint also affect the lubricant grease, which is in contact with the sealing system. With higher temperatures the boot and boot cover of the sealing system become more vulnerable to cracking and rupture and the durability of the constant velocity joint that is generally sealed for life is reduced. Furthermore, heat that is generated within the sealing system is transferred to the outer race of the CVJ. As a result, premature cracks, ruptures and blowouts of the sealing system further reduce the life of the boot. With the heat affecting the life and material of the sealing system, the boot and boot cover are also more vulnerable to external damage due to strikes or blows by contaminants from the environment of the automotive vehicle. These contaminants can be anything from rocks, mud, road debris, or any other object capable of being thrown by the tires or deflected into the boot or boot cover of the sealing system of the constant velocity joint. These contaminants striking the boot will further reduce the sealability of the boot and boot cover while increasing the possibility of ruptures, blowouts, and the like. Accordingly, life of the constant velocity joint is ultimately reduced. 
   Therefore, there is a need in the art for a joint having a sealing system that is protected from contact with foreign objects found in the outside environment of the joint. The ability to protect the sealing system from external objects will reduce early deterioration of the boot and boot cover that may result in eventual failure of the sealing system and ultimate failure of the joint. 
   SUMMARY OF THE INVENTION 
   The inventors of the present invention have recognized these and other problems associated with joints having sealing systems. To this end, the inventors have developed a joint having a shielded sealing system to prevent exposure of the sealing system to contaminants. 
   Specifically, a joint receiving a shaft comprises a sealing system and a shield secured to the sealing system. The shield protects portions of the sealing system from exposure to contaminants. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
       FIG. 1  is a plan view of a vehicle driveline system; 
       FIG. 2  is a partial cross-sectional view of a joint having a shielded sealing system according to a first embodiment of the present invention; 
       FIG. 3  is a partial cross-sectional view of the joint of the first embodiment having a shaft articulated at an operating angle; 
       FIG. 4  is a partial cross-sectional view of the joint of the first embodiment including a deflector about the shaft; 
       FIG. 5  is a partial cross-sectional view of a joint having a shielded sealing system according to a second embodiment of the present invention; 
       FIG. 6  is a partial cross-sectional view of the joint of the second embodiment having a shaft articulated at an operating angle; and 
       FIG. 7  is a partial cross-sectional view of a joint having a shielded sealing system according to a third embodiment of the present invention. 
   

   DETAILED DESCRIPTION 
   Referring to the drawings, a joint according to the present invention is generally shown at  10 . Joint  10  may be any type of joint commonly referred to in the art as a constant velocity joint such as a fixed ball joint, tripod joint, plunging joint, and the like. 
     FIG. 1  illustrates a typical driveline  12  of an automotive vehicle. The driveline  12  of  FIG. 1  is a typical all-wheel drive vehicle, however, it should be noted that the joints  10  of the current invention can also be used in rear-wheel drive vehicles, front-wheel drive vehicles, all-wheel drive vehicles and four-wheel drive vehicles. The driveline  12  includes an engine  14  that is connected to a transmission  16  and a transfer case  18 . A front differential  20 , adjacent engine  14 , has a right hand front half shaft  22  and a left hand front half shaft  24 , each of which are connected to a wheel  25  to deliver power to each of those wheels  25 . On both ends of the right hand front half shaft  22  and the left hand front half shaft  24  are constant velocity joints  10 . A front propeller shaft  27  connects the front differential  20  to the transfer case  18  and includes constant velocity joints  10  at each end. A rear propeller shaft  26  connects the transfer case  18  to a rear differential  28 , where the rear differential  28  includes a right hand rear half shaft  30  and a left hand rear half shaft  32 , each of which ends with a wheel  25  on one end thereof. Constant velocity joints  10  are located on both ends of the rear half shafts  30 ,  32  that connect to the wheels  25  and the rear differential  28 . The rear propeller shaft  26 , shown in  FIG. 1 , is a two-piece propeller shaft  26   a, b  that includes a cardan joint  34  and two high-speed constant velocity joints  10 . The constant velocity joints  10  of the rear propeller shaft  26  transmit power to the wheels  25  even if the wheels  25  or the shaft  26  have changing angles due to steering, raising or lowering of the suspension of the vehicle. The constant velocity joints  10  may be of any of the standard types known in the art, such as plunging tripods, cross groove joints, fixed joints, fixed tripod joints, double offset joints, and the like, all of which are commonly known terms in the art for different varieties of constant velocity joints  10 . The constant velocity joints  10  facilitate transmission of rotational motion at generally constant velocities for various angles which are found in everyday driving of automotive vehicles in both the half shafts and propeller shafts of these vehicles. 
     FIGS. 2–7  illustrate various embodiments of the constant velocity joint  10  of the present invention have a sealing system generally illustrated at  36 . Generally, like numbers between the Figures represent like elements. The constant velocity joint  10  illustrated in the Figures is a traditional fixed ball joint, however, any type of joint is contemplated by the present invention. The illustrated constant velocity joint  10  of  FIGS. 2–7  is generally used with the rear propeller shaft  26  of  FIG. 1  in an all-wheel drive vehicle. 
   Specifically, the constant velocity joint  10  includes an outer race  38  which has an integral shaft  40  attached to one end thereof. In one configuration, the shaft  40  connects to the rear differential  28  of  FIG. 1 . In a second configuration the shaft  40  connects to the transfer case  18 . An inner wall  42  of the outer race  38  generally defines a constant velocity joint chamber  44 . An inner race  46  is located or housed within the outer race  38 . The inner race  46  is connected to the propeller shaft  26  of the vehicle by a ring retainer  48  located on an inside surface  50  of the inner race  46 . However, any type of connection to join the propeller shaft  26  to the joint  10  is contemplated by the present invention. A plurality of balls or rolling elements  52  are located between an outer surface  54  of the inner race  46  and the inner wall  42  of the outer race  38 . The balls  52  are held in position between the outer race  38  and inner race  46  surfaces by a cage  56 . Each ball  52  is located within tracks (not shown) of the inner wall  42  of the outer race  38 . Further, each ball  52  is located within tracks (not shown) of the inner race  46 . Rotation of the shaft  40  and outer race  38  rotates the inner race  46  at a generally constant speed thus allowing for constant velocity to flow through the joint  10  and between the shaft  40  and propeller shaft  26  that is disposed at an angle in relation to the shaft  40 . 
   The sealing system  36  includes a boot cover  58  and a boot  60 . The boot cover  58  is connected to an end  62  of the outer race  38 . The boot  60 , which is generally made of a urethane, has one end secured within a channel  64  of the boot cover  58  while an opposite end of the boot  60  engages the propeller shaft  26 . Other materials for boot  60  such as hard or soft plastic, rubber, and the like are also contemplated by the present invention. The boot  60  is held in place about the propeller shaft  26  by a boot clamp  66 . The sealing system  36  seals the constant velocity joint  10  from any outside contaminants, such as water, dirt and road grime. Further, the sealing system  36  maintains grease within the joint  10  to provide lubrication and resist high temperatures and friction wear common to constant velocity joints  10  rotating at high speeds. The suppleness of the boot  60  allows for a seal to be maintained to any angle of inclination that the propshaft  26  or shaft  40  may encounter during normal and off-road driving operations. 
   Referring to  FIGS. 2–4 , a first embodiment of the constant velocity joint  10  also includes a shield  68 . The shield  68  is arranged around an end of the boot cover  58 . Optionally, the shield  68  can be connected directly to an outer surface of the outer race  38  if design requirements so provide. The shield  68  connects to the boot cover  58  by any connecting technique such as welding, press fitting, crimping, chemical bonding, and the like. 
   The shield  68  generally has a sleeve portion  70  including a reinforced end portion  72 . Reinforced end portion  72  is illustrated as being reinforced by an edge that is folded-over in an outward direction to provide for a double thickness of material at the end of the sleeve  70 . This folded-over region increases the stiffness of the shield  68  and increases the capability of the shield  68  to withstand the high speeds and temperatures of the constant velocity joint  10 . Additionally, other techniques common for reinforcing an end portion  72  of a sleeve  70  are also contemplated by the present invention. By way of example, the reinforced end portion  72  may include a generally rigid ring  74  made of metal, plastic, a composite material, and the like. The ring  74  is a separate item disposed at the reinforced end portion  72  and encapsulated by the folded-over edge. Accordingly, the shield  68  may be one material while the ring  74  is a separate material. Shield  68  is made of any type of elastomer capable of withstanding speeds of at least 6,000 rpm and high under body temperatures of a vehicle that often exceed 120° C. Soft pliable materials such as elastomers, composites, plastics, and the like are used for the shield  68 . Further, shield  68  may also be comprised of any type of metal composite or hard plastic material depending upon the overall length of the shield  68  and the operation angle of the joint  10 . 
   Additionally, constant velocity joint  10  includes a gap, G, disposed between the propeller shaft  26  and the outer surface of the constant velocity joint  10 . The gap, G, maintains separation between the shield  68  and the propeller shaft  26  when the propeller shaft  26  is articulated, even at a maximum operating angle of the joint  10 . As shown in  FIG. 3 , the propeller shaft  26  is disposed at a maximum operating angle for the joint  10  and the shield  68  is separated from contact with the propeller shaft  26 . The separation between the shield  68  and the propeller shaft  26  facilitates drainage of water, mud and debris, while still protecting sealing system  36  from exposure to contaminants. 
   Referring to  FIG. 4 , the constant velocity joint  10  of the first embodiment may optionally include a deflector  75 . The deflector  75 , as illustrated, has a disk  76  defining an opening therethrough and an orthogonally extending cylindrical flange  78  extends from the disk  76 . The flange  78  is disposed about the propeller shaft  26  axially in front of the sealing system  36  protected by the shield  68 . The flange  78  is connected to the propeller shaft  26  via any known fastening techniques common in the art. The deflector  75  extends a predetermined radial distance to help protect the sealing system  36  from contact with contaminants. The deflector  75  may be made of any rigid material such as metal, plastic, composites and the like. Rigid materials, along with the configuration of the deflector  75 , assist with the deflector  75  withstanding the high speed and high temperature environment of the constant velocity joint  10 . The more rigid the material, the less likely the deflector  75  will become unstable and eccentric. 
   The shield  68  reduces the area of the sealing system  36  exposed to contaminants and thus reduces or prevents the impact of foreign objects upon the sealing system  36 . Accordingly, the useful life of the sealing system  36  and the useful life of the constant velocity joint  10  are increased. Therefore, many designs or variations of the shield  68  are contemplated by the present invention as a result of changes in sizes and shapes of various features of the shield  68 . Meanwhile, the illustrated embodiment of  FIG. 4  shows a combined deflector  75  and shield  68  to reduce exposure of the sealing system  36  to contaminants. It is further contemplated to only incorporate the deflector  75  and not include the shield  68  to continue to reduce exposure of the sealing system while utilizing a minimal amount of material. Further, while deflector  75  is illustrated as a disk  76  having a flange  78 , any other shape of defector  75  that minimizes exposure of the sealing system  36  to contaminants is contemplated by the present invention. 
   Now referring to  FIGS. 5–6 , a second embodiment of the constant velocity joint  10  having a shield  268  is illustrated wherein like numbers throughout the figures refer to like elements. The shield  268  of the second embodiment is generally similar to the shield  68  of the first embodiment; however, a tube  270  replaces sleeve  70 . The tube  270  is generally cylindrical and includes a first end  280  secured to the boot cover  258 . Optionally, the shield  268  can be connected directly to an outer surface of the outer race  238  if design requirements so provide. The shield  268  connects to the boot cover  258  by any connecting technique such as welding, press fitting, crimping, chemical bonding, and the like. 
   The cylindrical tube  270  includes a reinforced end portion  272 . The reinforced end portion  272  is illustrated as being reinforced by an edge that is folded-over in an outward direction to provide for a double thickness of material at the end of the tube  270 . This folded-over region increases the stiffness of the shield  268  and increases the capability of the shield  268  to withstand the high speeds and temperatures of the constant velocity joint  10 . Additionally, other techniques common for reinforcing the end portion  272  of the tube  270  are also contemplated by the present invention. By way of example, the reinforced end portion  272  may include a generally rigid ring  274  made of metal, plastic, a composite material, and the like. The ring  274  is a separate item disposed at the reinforced end portion  272  and encapsulated by the folded-over edge. Accordingly, the shield  268  may be one material while the ring  274  is a separate material. Shield  268  is made of any type of elastomer capable of withstanding speeds of at least 6,000 rpm and high under body temperatures of a vehicle that often exceed 120° C. Soft pliable materials such as elastomers, composites, plastics, and the like are used for the shield  268 . Further, shield  268  may also be comprised of any type of metal composite or hard plastic material depending upon the overall length of the shield  268  and the operation angle of the joint  10 . 
   Additionally, constant velocity joint  210  includes a gap, G 2 , disposed between the propeller shaft  226  and the outer surface of the constant velocity joint  10 . The gap, G 2 , maintains separation between the shield  268  and the propeller shaft  226  when the propeller shaft  226  is articulated, even at a maximum operating angle of the joint  10 . As shown in  FIG. 6 , the propeller shaft  226  is disposed at a maximum operating angle for the joint  10  and the shield  268  is separated from contact with the propeller shaft  226 . The separation between the shield  268  and the propeller shaft  226  facilitates drainage of water, mud and debris, while still protecting sealing system  236  from exposure to contaminants. 
   A distinguishing feature of the second embodiment of  FIGS. 5 and 6  is the axial length of the cylindrical tube  270  of the shield  268 . The cylindrical tube  270  of the second embodiment is generally longer than the axial length of the sleeve  70  of the first embodiment. The length of cylindrical tube  270  is generally dependent upon the maximum operating angle of the constant velocity joint  10 . The shield  268  extends over the boot cover  258  and the boot  260  that is connected to the shaft  226 . Therefore, the shield  268  completely covers the boot  260  and provides protection thereto in the constant velocity joint  210  environment. Further, the cylindrical tube  270  has a gradually reducing diameter from a mid-portion  282  to the first end  280  and to the reinforced end portion  272 . As illustrated, the cylindrical tube  270  has its widest diameter near the mid-portion  282  thereof and adjacent a channel  264  of the boot cover  258 . The smaller diameters of the cylindrical tube  270  are disposed at the reinforced end portion  272  and the first end  280 . Further, it is also contemplated to have the cylindrical tube  270  of the shield  268  one predetermined diameter for the entire axial length. 
   The shield  268  reduces the area of the sealing system  236  exposed to contaminants and thus reduces or prevents the impact of foreign objects upon the sealing system  236 . Accordingly, the useful life of the sealing system  236  and the useful life of the constant velocity joint  10  are increased. Therefore, many designs or variations of the shield  268  are contemplated by present invention as a result of changes in sizes and shapes of various features of the shield  268 . 
   Now referring to  FIG. 7 , a third embodiment of constant velocity joint  10  is illustrated wherein like numbers throughout the figures refer to like elements. The constant velocity joint  10  includes a shield  368  that is disposed between the outer race  338  of the joint  10  and the propeller shaft  326 . Further, the shield  368  may be connected directly to the boot cover  358  if design requirements so provide. The shield  368  is a second boot  384  that creates a boot-in-boot arrangement to protect the interior boot  360  and constant velocity joint  10 . The second boot  384  is connected to the propeller shaft  326  by any fastening technique generally known in the art. As illustrated, the second boot  384  is fastened to the propeller shaft  326  by a clamp  386 . The opposite end of the second boot  384  is secured to the outer race  384  by any fastening technique generally known in the art. In the illustrated embodiment, the second boot is secured to the outer race  338  by a boot clamp  388 . 
   In the illustrated embodiment, the second boot  384  will cover and completely seal off the more fragile interior boot  360  from contact with any contaminants found in the environment of the vehicle. Optionally, thermoplastic, hard or soft plastic, metal, composite, fabric, and the like, may be used for the second boot  384  of the present invention. The second boot  384  is preferably made of a thermoplastic material, which is much more durable than the traditional material of interior boot  360 . Accordingly, second boot  384  provides a larger area to absorb the impact of contaminants to protect the sealing system  336  while not requiring an increase in the amount of lubricant. Instead, the lubricant, typically a grease, remains contained within the interior boot  360 . The use of this second boot  384  protects the interior boot  360  through even the most abusive of situations and environments a vehicle may encounter in normal and off-road conditions. 
   As illustrated, the second boot  384  has a plurality of bellows  390  along the surface of its entire axial length. The second boot  384  also has a shape that is generally convex as compared to concave. In contrast, the interior boot  360  has a generally concave shape and may accumulate or capture debris therein without the incorporation of the shield  368 . The convex shape for the second boot  384  eliminates the collection of contaminants about the constant velocity joint  10  including the boot cover  358 , boot  360  and other connections on the constant velocity joint  10  between the outer race  338  and the propeller shaft  326 . The elimination of contaminants about the joint  10  will thus further reduce any wear on the constant velocity joint  10  and increase the useful life of the constant velocity joint  10 . Hence, the propeller shaft  326  and constant velocity joint  10  of the automotive vehicle are improved in both normal road conditions and off-road conditions. 
   In some specific applications the second boot  384  is vented to allow pressures built up within the second boot  384  to equalize on both the inside and outside of the shield  368 . The vent as illustrated in  FIG. 7 , takes the form of a small orifice  392  or a small slit  394  through the second boot  384 . The incorporation of the orifice  392  and the slit  394  may be utilized alone or in combination. Further, the orifice  392  or slit  394  may be formed or machined into the thermoplastic material on the second boot  384 . Therefore, the second boot  384  will create a generally impenetrable shield  368  for the constant velocity joint  10  thus greatly increasing the service life and robustness of the constant velocity joint  10  in both the normal and off-road environments. 
   The boot shields  68 ,  268  and  368  of each embodiment protect the sealing systems  36 ,  236 , and  336  from exposure to contaminants and thus greatly increase the useful life, robustness and efficiency of the constant velocity joint  10  by preventing impact of foreign objects with the sealing systems  36 ,  236 ,  336 . The shields  68 ,  268 ,  368  prevent the sealing systems  36 ,  236 ,  336  from becoming compromised, thus the grease used to lubricate the interior of the constant velocity joint  10  will not leak or become contaminated. Accordingly, the useful life of the propeller shafts  26 ,  226 ,  326  increases because the constant velocity joints  10  will operate with increased longevity and more robustness. Therefore, many designs or variations of the shield  68 ,  268 ,  368  are contemplated by changing various dimensions and surface configurations. Various changes are contemplated by the present invention to further increase the effectiveness and protection offered by the shields  68 ,  268 ,  368  to the constant velocity joint  10 , and specifically the sealing systems  36 ,  236 ,  336 . 
   It is to be understood that the above description is intended to be illustrative and not limiting. Many embodiments will be apparent to those of skill in the art upon reading the above description. Therefore, the scope of the invention should be determined, not with reference to the above description, but instead with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.