Background Of The Invention Drivelines are generally used in vehicles to transfer rotational motion from a transmission to an axle. When the connection points are misaligned, loads are created in the driveline which tend to vary the rate of rotation. The use of universal joints to compensate for misalignment is well known. When each yoke of a driveline is attached to a universal joint, substantially equal angles exist at both driveline connections and additional driveline loads are reduced or eliminated to allow a more consistent rotation rate.

In certain applications, the distance between driveline connections varies during operation. Slip joint drivelines are used to allow the yokes to move toward and away from one another without affecting the capability of the driveline to transmit power. Slip joint drivelines typically comprise male and female splined shafts connected to respective universal joint yokes. The splined connection permits the shafts to transfer rotational motion while allowing relative sliding movement to accommodate differences in driveline length.

Typical drivelines require periodic grease lubrication to accommodate the relative sliding motion between the shafts. It will be appreciated that periodic lubrication is relatively difficult, time consuming and expensive.

Another problem with slip joint drivelines is the need to prevent dirt, water, and other contaminants from infiltrating the splined connection. When a slip driveline extends, certain portions of the driveline are exposed to the elements. When the driveline subsequently contracts, any contaminants disposed on the exposed portions may be carried into the splined connection.

Over time, the contaminants may weaken the splines, thereby lowering the load capacity of the driveline or causing premature failure. Accordingly, seals have been proposed to prevent contaminants from infiltrating the driveline.

Unfortunately, conventional slip joint seals have not adequately remedied this problem. Some of these seals may only reliably engage costly machine-smooth surfaces, and are therefore uneconomical. Other typical seals utilize only a corner or edge interface for sealing the slip joint and therefore may not adequately scrape contaminants away from the splined area of the driveline. Still other proposed seals do not insure sealing engagement if the slip joint driveline is misaligned or dented.

Many conventional seals inadequately address internal pressures or pneumatic lock in the driveline which resist the extension or contraction of the yokes. As the driveline contracts, the air trapped inside the inner bore may resist the movement of the male spline. Similarly, extension of the driveline may create a vacuum in the inner bore which also resists movement of the male spline. In either situation, greater axial loads are placed on the driveline.

Conventional drivelines also require substantial investment in inventory to manufacture a complete family of drivelines sized for a particular load capacity. Each driveline family has a plurality of individual length drivelines, sometimes on the order of two dozen different length drivelines.

Unfortunately, heretofore, each individual driveline had to be separately manufactured from individual components. The individual components, including for exarnple the slip and stub shafts used in a particular driveline, were manufactured individually and were not interchangeable or easily

adapted for use in other length drivelines. Each driveline family, for example, may require 30-40 separate yoke shafts which must be individually forged and welded together. Thus, an extremely large inventory of individual parts were necessary to make a particular driveline family. The inventory problem is exacerbated by the fact that, since each driveline family is sized for a particular load capacity, manufacturers required a plurality of driveline families to meet their load capacity requirements. Therefore, inventory requirements resulted in an excessive number of parts for making the driveline family.

Summarv And Obiects Of The Invention In view of the foregoing, a general aim of the present invention is to provide a novel permanently lubricated slip joint driveline which does not require periodic lubrication.

Another object of the present invention is to provide a driveline having an improved seal for preventing infiltration of contaminants while permitting air communication with the interior of the driveline to prevent pneumatic lock.

In that regard, an object of the present invention is to provide a novel seal which reliably seals the slip joint driveline.

It is also an object of the present invention to provide a seal with increased sealing contact surface.

It is another object of the present invention to provide a family of drivelines which may be manufactured from common parts. A more specific object is to provide a modular driveline design which utilizes common components to manufacture a plurality of the different length drivelines.

It is a related object to provide a streamlined method for assembling a family of drivelines.

These and other objects and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

Brief Description Of The Drawings FIGURE 1 is a partial sectional side view of a driveline in accordance with the present invention.

FIG. 2 is an enlarged sectional detail of the driveline of FIG. 1 showing the seal of the present invention.

FIG. 3 is a front view of the seal in accordance with the present invention removed from the driveline assembly.

FIG. 4 is a sectional side view of the seal taken along line 4-4 of FIG. 3.

FIGS. 5 are cross-section view of a second embodiment of a driveline in accordance with the present invention positioned between retracted and extended positions, respectively.

While the invention is susceptible of various modifications and alternative constructions, certain illustrative embodiments thereof have been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions and equivalents falling within the spirit and scope of the invention as defined by the appended claims.

Detailed Description Of The Preferred Embodiment Referring now to the drawings, and specifically to FIG. 1, a slip joint driveline 10 is provided in accordance with the present invention. The driveline 10 comprises a weld yoke 12 and stub yoke 14 adapted for connection to universal joints. A proximal end 20a of a hollow cylindrical

tube 20 is rigidly attached to a collar 13 on the weld yoke 12 so that the tube 20 and yoke 12 rotate in unison together. In the illustrated embodiment, the tube 20 and yoke 12 are welded together at the collar 13. The weld yoke 12 has a central bore 15.

A proximal end 1 6a of a slip or female shaft 16, having inwardly disposed or female splines 17, is rigidly attached to a distal end 20b of the hollow cylindrical tube 20. Referring to Fig. 1, it will be seen that that the outer diameter of the proximal end 1 6a of the slip shaft 16 has a collar 21 for receiving the distal end 20b of the tube 20.

A stub or male shaft 18, having external or male splines 19, is rigidly attached to the stub yoke 14. The proximal end 18a of the stub shaft has a close tolerance diameter adapted by machining for engaging a central splined bore 23 of the stub yoke 14. It is preferable that such press fit be sufficiently secure to resist the forces exerted on the stub shaft 18 in response to the axial sliding movement of the stub and shift shafts 16, 18. In other embodiments, the proximal end 18a may be additionally or alternatively welded to insure that the stub shaft 18 is securely attached to the yoke 14.

The male splines 19 of the stub shaft 18 mechanically engage the female splines 17 of the slip shaft 16 so that the resulting splined connection 18, 19 transfers rotation and torque load between the stub yoke 14 and the weld yoke 12. The splined connection 18, 19 also allows the stub and weld yokes 14, 12 to move axially with respect to one another, between an extended position generally shown in broken lines in Fig. 1 and a retracted position generally shown in solid lines in Fig. 1, to accommodate varying distances between the yokes 12, 14 during operation. The precise length of the stub and slip shafts 18, 16 and the tube 16 may be adapted to suit the slip requirements and space constraints of a particular application. Such an arrangement compensates for applications in which there is misalignment

between the connection points of the driveline without introducing forces in the drive shaft which tend to vary the rate of rotational transmission.

In the embodiment illustrated in Fig. 1, it will be appreciated that the bore 15 is sized to receive the distal end 18b of the male shaft 18 during the retracted position, thereby increasing and maximizing the operational slip of the driveline. More specifically, the bore 15 permits the driveline to minimize its retracted length while maintaining the overall extended length of the driveline. In a preferred embodiment, the driveline has at least a 5 inch slip between retracted and extended positions, compared with many conventional drivelines which may have only two o three inches of slip. Therefore, a particular driveline may be utilized in a wider range of applications. One basic driveline may be used in a number of different applications on a given machine. Thus, the manufacture must manufacture fewer models and customers must stock fewer drivelines and parts for repair.

The male spline 19 or female spline 17 is preferably coated with a polymer coating which enhances relative sliding movement between the slip and stub shafts 16, 18. The polymer coating improves wear and fatigue resistance and reduces contact pressure between the slip and stub shafts 16, 18. Finally, the polymer coating also reduces the thrust loading from the slip spline to help increase the life of other powertrain components such as transmissions and axles. In the preferred embodiment, the polymer coating is Nylon 11 although other coatings will be known to those skilled in the art.

The female and male splines 17, 19 are also subjected to a unique hardening process which, in addition to the polymer coating, enhances the life of the drivelines. It is preferable that the splines have a hardness within the range of about 28-42 Rc. It is preferred that an induction hardening process be utilized, although other hardening processes will be known to those skilled in the art including, for example, quench hardening. Once a lubricant, such as molybdenum disulfide, is applied to the spline, the driveline may be

assembled and no further lubrication is required during the life of the driveline.

A cylindrical housing sleeve 22 is also rigidly attached to the rear of the stub yoke 14, by welding or other attachment means, for substantially covering and restricting access to the sealing mechanism and the male and female splines 19, 17. As illustrated in FIG. 1, the sleeve 22 extends along a substantial portion of the stub shaft 18 and substantially covers the slip shaft 16 when the driveline 10 is assembled. The housing sleeve 22 protects the male and female splines 19, 17 from direct exposure to the outside environment.

In accordance with certain aspects of the present invention, a seal 25 is provided for preventing contaminants from infiltrating the driveline 10 through the small gap 32 defined between the inner diameter 31 of the sleeve 22 and the outer diameter 33 of the slip shaft. In the embodiment best shown in FIG. 2, the seal 25 is carried in groove 26 located on the outer diameter of the distal end 16b of the slip shaft 16. As best shown in FIG. 4, the seal 25 has a generally annular base 27 and an inclined arm 28 projecting radially outward towards the inner diameter 31 of the housing sleeve 22. The proximal end of the arm 27 (adjacent the base) tapers towards a flat face 30.

The flat face 30 is disposed at the outer end of the arm 28 for engaging the inner diameter 31. As the driveline moves between the extended and contracted positions, it will be appreciated that the seal 25 slides along the inner diameter 31 of the housing sleeve 22 to scrape contaminants from the housing sleeve 22. Accordingly, the seal 25 prevents contaminants from entering the splined connection of the driveline 10.

In accordance with certain aspects of the present invention, the seal 25 presents a flat sliding face 30 for scraping contaminants from the inner diameter 31 of the housing sleeve 22. As shown in FIG. 2, the contact interface between the seal 25 and the housing sleeve 22 forms a cylindrical

band which is larger than conventional edge-type seals. The increased contact area improves the engagement between the seal 25 and the housing sleeve 22 and provides superior sealing and scraping characteristics.

In a preferred embodiment, the arm 28 is sufficiently long to span the distance between the outer diameter 33 of the slip shaft 16 and the inner diameter 31 of the housing sleeve 22, while simultaneously permitting the arm 28 to slightly flex or bow upon engagement with the housing sleeve 22. The tapered configuration of the arm insures that the flex occurs toward the distal end of the arm 27. The combination of the foregoing arcuate configuration and the resilient material of the arm creates a slight torque on the sealing face which enhances the seal at the interface.

To ensure that the seal 25 presents a flat face 30 for engagement with the housing sleeve 22, the sliding face 30 is slightly inclined before installation, as best shown in FIG. 4 to compensate for rotation resulting from the desired arcuate configuration. As a result, the seal 25 presents a properly oriented sliding surface 30 upon engagement with the sleeve 22 during installation. In the preferred embodiment, an angle of 6 degrees from a horizontal reference 34 has been found to be sufficient.

It will be appreciated that the improved seal 25 may restrict air movement through the gap 32 between the interior of the driveline 10 and the outside environment so that pneumatic lock may occur in response to axial movement of the driveline 10 between the extended and contracted positions.

Therefore, in accordance with certain objects of the present invention, the seal 25 comprises means for communicating air pressure between the interior of the driveline 10 and the outside environment. In the preferred embodiment, as best shown in FIG. 3, the air communicating means comprises at least one groove 40 spaced about an inner diameter 41 of the base 27. The grooves 40 extend entirely through the base 27 (FIGS. 3 and 4) so that air may pass through the grooves 40 to prevent pneumatic lock situations.

It will be appreciated that while the grooves 40 allow air to pass through, contaminants such as dust particles are restricted from access. As best shown in FIG. 2, the seal is disposed in the channel 26 so that the grooves 40 create a generally U-shaped path for air entering or exiting the driveline 10. The relatively convoluted path allows air passage, but restricts passage of relatively large contaminants such as dust particles.

In carrying out the present invention, the seal should be capable of operating in extreme heat and cold and should preferably be capable of withstanding temperature ranges of -60 to 230C Fahrenheit. It has been found that seals made of nitrile rubber are suitable, although other suitable materials known in the art may also be used.

The seal 25 of the present invention lends itself to permanently lubricated drivelines by providing an improved barrier to contaminants while preventing pneumatic lock. This feature is especially advantageous in permanently lubricated slip drivelines which may not have grease fittings through which air may enter or escape.

It will now be apparent that the present invention brings to the art a permanently lubricated slip joint driveline having new and improved sealing characteristics. The seal increases the contact area with the housing sleeve by providing a flat sliding surface better able to scrape contaminants from the sleeve as the driveline extends. Furthermore, the seal prevents pneumatic lock from occurring in the driveline by incorporating means for communicating air pressure between the interior of the driveline and the outside environment.

Figs. 5-6 illustrated an alternate embodiment of the driveline 110. The second embodiment of the driveline has weld and stub yokes 12, 14 similar in the pertinent aspects to the first embodiment. However, the second embodiment lacks a housing sleeve and is intended to depict a relatively shorter driveline 110. The proximal end 1 16a of the female spline 116 forms a shoulder on its outer diameter and a collar on its inner diameter for matingly

receiving the yoke collar 13. The housing sleeve 22 and the male shaft 18 are identical to the first embodiment except for their lengths. Similarly, the seal 25 is identical to the first embodiment.

Figs. 5-6 shows the driveline in the retracted and fully extended positions, respectively. It will be appreciated that the yoke bore 15 permits the driveline 110 to retract to a smaller length than conventional yokes lacking the bore. Thus, a particular driveline may be used for applications requiring its minimum length while maintaining the overall extended length.

In accordance with certain objects of the invention, a family of drivelines is provided which utilizes a modular concept to minimize the number of elements necessary to manufacture a complete line of drivelines.

The family preferably comprises the first and second sub-families corresponding to the first embodiment shown in Fig. 1 and the second embodiment shown in Fig. 2, but may include other such sub-families. The complete driveline family may be manufactured using the weld and stub yokes 12, 14, female shafts 16 and 116, tube 20, male shaft 18, housing sleeve 22, and a seal 25.

The cylindrical tube 20 and housing sleeve 22 may be manufactured in relatively long sections and preferably are 15-20 feet in length. The tube 20 may be subsequently cut to the desired length and are preferably cut in lengths from about 2 to about 70 inches. The sleeve 22 may be subsequently cut to the desired length and are preferably cut in lengths from about 3 to about 10 inches.

The male shafts 18 may be cold formed or hobbed as splined bars. The splined bars may be manufactured in lengths from about 8 to about 12 feet, and preferably may be cut in lengths of about 4 to about 15 inches. After the bars are cut to the desired length, the proximal end 18a may be cut to the desired diameter for press fit engagement with the stub yoke bore 23. It will be appreciated that the press fit attachment eliminates costly and time

consuming weld attachment methods typically used in conventional drivelines. Alternatively, the male shaft 18 may be welded to insure the fixed attachment.

The female shaft 16 used in the first sub-family and the female shaft 116 used in the second sub-family use the same stock material and may be manufactured in lengths from about 10 to about 20 feet and subsequently cut from about 4 to about 15 inches. After the shafts are cut to the desired lengths, to make the female shaft 16, the outer diameter may be cut to achieve the desired collar 21 at the proximal end 20a and the groove 26 at the distal end 20b. To make the female shaft 116, the cut bar 116 is counter-bored to form the cavity 1 16a dimensioned to receive the weld yoke collar 13. The cut bar is also turned to form the necked down diameter and cut to form the groove 26. The bars are broached to form the female splines. The shaft 16 may be attached to the tube 20 using conventional welding methods and the like.

The cut male or female shafts are coated with the polymer coating before they are subsequently assembled. The coated male shaft is then slidably inserted or pressure fit into the female shaft. The driveline may be used in its desired application.

It should now be appreciated that a modular driveline design has been provided which permits a complete driveline family comprised of different length drivelines to be manufactured from an inventory of less than eight common parts in contrast to conventional driveline families which may require an inventory of dozens or possibly hundreds of individual and separate components to assemble the individual drivelines.