Patent Publication Number: US-2019170196-A1

Title: Drive shaft engagement and methods

Description:
RELATED APPLICATIONS 
     The present application claims priority to U.S. Provisional Patent Application No. 62/338,328, filed May 18, 2016; to U.S. Provisional Patent Application No. 62/338,321, filed May 18, 2016; and to U.S. Provisional Patent Application No. 62/341,925, filed May 26, 2016, the entire contents of all of which are hereby incorporated by reference. 
    
    
     FIELD 
     The present invention generally relates to engagement of drive shafts and, more particularly, for such drive shafts including, for example, a splined engagement, an articulated arrangement and/or an indicator. 
     SUMMARY 
     Many tractors, trucks, or other off-highway vehicles are provided with power take-off shafts having terminal splined male coupling elements. Many implements with which such vehicles are used have flexibly-jointed and extensible driven shafts with female coupling elements (i.e., power input connection) adapted to receive the power take-off shaft of the vehicle. Inasmuch as neither the power take-off shaft nor the driven shaft can ordinarily be rotated by hand, it becomes a very difficult matter to register the splines of the respective coupling elements when they are not properly aligned. 
     Flexibly-jointed driven shafts for transmitting motion to an implement from the power take-off shaft of a vehicle weigh as much as 70 to 80 pounds. This can make connecting two devices together quite complicated if the splines are not properly aligned to allow for registration automatically. 
     In addition, some shaft engagement locations are in a confined space, hidden from view (such as due to guards or other obstructions), and/or ergonomically challenging, making alignment of the shafts difficult. As such, the operator may not be able to see the splines while trying to connect the assembly. 
     Attempts have been made at providing a taper to an end of the one of the splines, such as is shown in U.S. Pat. No. 3,249,377, the entire contents of which is hereby incorporated by reference. Although this arrangement may improve the rate of registration, several attempts to register the connection properly in certain circumstances may be required. For example, as shown in  FIG. 1  from U.S. Pat. No. 3,249,377, the splines  10  of the power take-off shaft  6  and the splines  14  of the female coupling element each terminate at a blunt end surface  22 . When these blunt end surfaces  22  happen to align (or partially align) during attempts to interconnect the coupling, the splines  10 ,  14  will not register. 
     Making the connection between the drive shaft and the driven shaft more complex is that many driven shafts have ends that are articulated. For example, many have a universal joint adjacent each end of the driven shaft. During connection, it is common to grasp the driven shaft primarily by the shaft, due to the weight, which will result in the articulated end pivoting into a non-aligned orientation. To further effectuate the connection, one must hold the driven shaft while also attempting to articulate the joint into alignment and while attempting to engage splines with tight tolerances. 
     Due to the weight of the shaft, tight tolerances of the splines, the articulated ends and/or other complicating factors, alignment and engagement of the splined connection between the drive shaft and the driven shaft can be quite difficult, with many attempts required before registry is made. 
     A need may exist for an easier way to register the splines of male and female members of a power take-off coupling without the need to make multiple attempts. 
     A need may exist to limit or prevent the articulation during engagement of the driven shaft with the drive shaft. 
     U.S. Pat. Nos. 4,900,181; 4,960,344; 5,632,568; and 6,666,614, the entire contents of each of which are hereby incorporated by reference, disclose couplers for removably locking a hub axially on a shaft. The hub can have an end which is the yoke of a universal joint for attachment to a power drive assembly rotating the shaft (e.g., the power input shaft of an agricultural implement to the power takeoff shaft of a tractor). As mentioned above, the hub is internally splined to match the external splines on the power takeoff shaft to establish rotary transmissive coupling between the hub and the power takeoff shaft. 
     The hub is typically locked onto the shaft by locking members that can slide in radially extending slots through the hub so as to engage a circumferential groove or raceway in the splined power takeoff shaft. A collar around the outside of the hub is biased into a locked position by a spring to prevent the locking members from disengaging or backing away from the shaft. 
     The coupler disclosed in U.S. Pat. No. 4,900,181 has a stop formed in the collar that extends radially inwardly to abut a stop in the hub when the collar is tilted or cocked with respect to the axis of the shaft. When the shaft is inserted into the hub, locking members in the hub are moved radially outwardly to center the collar and disengage the stops. The collar can then be moved to lock the hub onto the shaft under the bias of a spring. However, the collar can be locked in a disengaged position even though the shaft is fully inserted into the hub. Thus, the hub may appear properly locked onto the shaft despite the collar being disengaged. 
     U.S. Pat. No. 4,960,344 discloses a coupler in which an eccentrically biased control ring and a concentric locking ring inside the collar operate locking members so that the collar remains concentric with the hub throughout its range of movement. When the shaft is inserted into the hub the locking members drive the control ring outwardly, concentric with the axis to disengage from a stop surface and allow the collar to slide and lock the hub onto the shaft. In this position, the locking ring retains the locking members in engagement with the shaft. However, as with the coupler of U.S. Pat. No. 4,900,181, the locking collar can be moved and locked in the disengaged position even though the shaft is seated in the hub. 
     A need may exist for a coupler assembly that can provide clear indicia of whether the locking collar is locked in an engaged position with the shaft seated in the hub. 
     In one independent aspect, an engagement assembly between a drive shaft and a driven shaft for a vehicle may be provided. The engagement assembly may generally include a drive shaft including a plurality of first splines extending in an axial direction and having respective tapered ends tapering in an axial direction; and a driven shaft including a plurality of second splines extending in an axial direction and having respective tapered ends tapering in an axial direction. The first splines and the second splines may be adapted to inter-engage and form a driving connection, the tapered ends facilitating engagement and alignment of the first splines and the second splines. 
     In another independent aspect, a power take-off coupling for a vehicle and a driven implement may be provided. The coupling may generally include a power take-off shaft of the vehicle including a plurality of male splines extending in an axial direction and having respective tapered ends tapering in an axial direction; and a power input shaft of the implement including a plurality of female splines extending in an axial direction and having respective tapered ends tapering in an axial direction. The female splines may be adapted to receive the male splines and form a driving connection, the tapered ends facilitating engagement and alignment of the male splines and the female splines. 
     In yet another independent aspect, a method of engaging a drive shaft and a driven shaft may be provided. A connector may be coupled to the driven shaft by a universal joint, the connector being adapted to engage the drive shaft, the drive shaft having a first axis and the connector having a second axis. The method may generally include pivoting the connector relative to the driven shaft to orient the second axis in a predetermined orientation with respect to the first axis; holding the connector in position relative to the driven shaft with the second axis in the predetermined orientation relative to the first axis by locking the universal joint; and engaging the connector of the driven shaft with the drive shaft. 
     In a further independent aspect, an articulated drive shaft assembly adapted to connect to and be driven by a drive shaft may be provided. The drive shaft assembly may generally include a driven shaft having a first axis; a connector having a second axis and adapted to engage the drive shaft; and a universal joint connecting the connector to the driven shaft, the universal joint including a locking assembly to selectively hold the connector in a position relative to the driven shaft with the first axis in a predetermined orientation relative to the second axis during connection with the drive member. 
     In another independent aspect, a universal joint may generally include a first yoke having opposite arms each having a bore; a second yoke having opposite arms each having a bore; a cross-shaped trunnion body having four ends, each end being received in a bore of the first yoke and the second yoke; a cap received in each bore and at least partially defining a bearing surface of an associated end of the trunnion body; and a detent mechanism coupled to a cap and associated end of the trunnion body, the detent mechanism having an engaged state, in which pivoting movement between the cap and the associated end of the trunnion body prevented, and a disengaged state, in which pivoting movement between the cap and the end of the trunnion body is allowed. 
     In yet another independent aspect, a coupler assembly may generally include a hub having a bore defining a bore axis and operable to receive along the bore axis a shaft to be locked to the hub, the hub defining a slot communicating with the bore; a collar disposed about the hub and slidable along the hub between a released position to a locked position; a locking member movable in the slot to engage a recess in the shaft when the shaft is inserted into the bore; a first indicia on the hub indicative of a locked condition of the coupler assembly, in which the locking member engages the recess and the collar is in the locked position; and a second indicia on the hub indicative of an unlocked condition of the coupler assembly, in which the collar is in the unlocked position. In the unlocked condition, the collar may cover the first indicia and exposes the second indicia, and, in the locked condition, the collar may cover the second indicia and exposes the first indicia. 
     In a further independent aspect, a coupler assembly may generally include a hub having a bore defining a bore axis and operable to receive along the bore axis a shaft to be locked to the hub, the hub having an aperture formed therethrough extending in a direction generally perpendicular to the bore axis and extending at least partially through the bore; and a locking pin disposed in the aperture for movement along the direction between a locked position, in which the locking pin selectively extends into the bore and into a recess in the shaft to lock and prevent the removal of the shaft from the bore, and an unlocked position, the locking pin including a head portion extending outwardly from the hub through one end of the aperture, the head portion including indicia of when the locking pin is the locked position. 
     Independent features and/or independent advantages of the invention may become apparent to those skilled in the art upon review of the detailed description, claims and drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an illustration of a prior art drive shaft coupling. 
         FIG. 2  is an enlarged view of the partial cross-section of the female coupling of  FIG. 1 . 
         FIG. 3  is a partial cross-sectional view of the coupling taken generally along line  3 - 3  of  FIG. 2 . 
         FIG. 4  is a perspective view of a shaft, such as a power take-off shaft, embodying independent aspects of the present invention. 
         FIG. 5  is a side view of the shaft of  FIG. 4 . 
         FIG. 6  is an end view of the shaft of  FIG. 4 . 
         FIG. 7  is an enlarged side view of the shaft of  FIG. 4 . 
         FIG. 8  is a perspective view of a drive shaft having a coupling embodying independent aspects of the present invention. 
         FIG. 9  is a cross-sectional view of a portion of the drive shaft and coupling shown in 
         FIG. 8 . 
         FIG. 10  is a perspective view of a power take-off drive shaft prior to engagement with a yoke coupling. 
         FIG. 11  is a perspective partial cross-sectional view of the drive shaft and the yoke coupling of  FIG. 10 , illustrating a first alignment condition. 
         FIG. 12  is a side cross-sectional view of the alignment condition shown in  FIG. 11 . 
         FIG. 13  is a perspective partial cross-sectional view of the drive shaft and the yoke coupling of  FIG. 10 , illustrating a second alignment condition. 
         FIG. 14  is a side cross-sectional view of the alignment condition shown in  FIG. 13 . 
         FIG. 15  is an illustration of a drive shaft coupling between a power take-off shaft and a yoke having a power input connection. 
         FIG. 16  is an exploded view of a conventional universal joint. 
         FIG. 17  is perspective view of a drive shaft embodying aspects of the present invention. 
         FIG. 18  is a perspective view of a drive shaft illustrating a yoke coupled to the universal joint in a pivoted, non-aligned orientation. 
         FIG. 19  is a perspective view of a universal joint embodying aspects of the present invention. 
         FIG. 20  is a near end view (partially perspective) of the bearing cap embodying aspects of the present invention. 
         FIG. 21  is a cross-sectional perspective view of the trunnion body shown in  FIG. 19 . 
         FIG. 22  is a partial cross-sectional view of a trunnion end shown in  FIG. 21 . 
         FIG. 23  is a partial perspective view of another embodiment of a locking assembly of the present invention. 
         FIG. 24  is a side view of the bearing cap of  FIG. 23  engaged with a modified Belleville Spring. 
         FIG. 25  is a perspective view of the modified Belleville Spring of  FIG. 24 . 
         FIG. 26  is an exploded perspective view of a coupler assembly of the present invention. 
         FIG. 27  is a partial cross-sectional view of the coupler with the shaft partially inserted into the shaft and the collar in the released position with the elements  28  rotated into the same plane as the elements  38  for illustrative purposes. 
         FIG. 28  is a view similar to  FIG. 27  but with the shaft fully inserted into the hub and the collar in the locked position, 
         FIG. 29  is an end cross-sectional view showing a latch ring biased eccentrically within the collar about the hub when in the released position of  FIG. 27 . 
         FIG. 30  is a view similar to  FIG. 28 , but without a shaft illustrated. 
         FIG. 31  is a view similar to  FIG. 27 , but without the shaft illustrated. 
         FIG. 32  is a view partially in side elevation and partially in axial section on line  32 - 32  of  FIG. 33  showing a connection between the inner and outer shaft elements. 
         FIG. 33  is a view taken in cross section on the line  33 - 33  of  FIG. 32 . 
         FIG. 34  is an alternative embodiment of the device shown in  FIG. 33 . 
     
    
    
     DETAILED DESCRIPTION 
     Before any independent embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other independent embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
     Use of “including” and “comprising” and variations thereof as used herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Use of “consisting of” and variations thereof as used herein is meant to encompass only the items listed thereafter and equivalents thereof. 
       FIGS. 1-3  illustrate a conventional power take-off shaft  6  having a male coupling element  8  at its end provided with splines  10 . The female coupling element  12  of the universally jointed and extensible driven shaft is interiorly provided with splines  14  which, throughout the major portion of their length, are complementary to, and mate accurately with, the splines  10  of the driving coupling element  8  of the power take-off shaft  6 . As shown in greater detail in  FIG. 2 , each spline  14  of the female coupling element  12  has radial or involute side surfaces  18  taperingly convergent (at  16 ) toward the blunt end  22  of the respective spline  14 . 
     As shown in  FIGS. 1-3 , the ends of both splines  10 ,  14  have a square or blunt end  22 . As such, the splines  10 ,  14  may still meet “head-on” (i.e., the blunt ends  22  on each set of splines  10 ,  14  engaging to prevent registration of the splined engagement) in some circumstances. 
       FIGS. 4-7  illustrate a shaft, such as a power take-off drive shaft  106 , and  FIGS. 8-9  illustrate a connector  112 , alone or in combination embodying independent aspects of the present invention. The shaft  106  and/or the connector  112  may, for example, eliminate or reduce the likelihood of head-on engagement of the ends of splines  110 ,  114 , which would prevent engagement of the splined connection. The shaft  106  and/or the connector  112  may be used with tractors, trucks, other off-highway vehicles, etc., and the many implements for such vehicles 
     As shown in  FIGS. 4-7 , the shaft  106  has a male coupling element  108  at its end provided with splines  110 . Each spline  110  has a side surface extending from the shaft  106 . Depending upon the type of shaft, the side surfaces can be straight or involute. Furthermore, more or fewer splines  110  than the six illustrated can be utilized. 
     As best shown in  FIG. 7 , each spline  110  has a tapered end  116  terminating at a tip  128 ,  130  in the axial direction  124 . As discussed in greater detail below, a number of different tapers can be utilized. For example, as illustrated both sides  118  of each spline  110  taper in the axial direction  124 . However, in some embodiments (not shown), only one side is tapered to form a tip. 
     With continued reference to  FIG. 7 , each illustrated spline  110  has both an axial taper  126  and a radial taper  136 . With respect to the axial taper  126 , the taper  126  begins in the axial direction  124  at a first distance from the end of the spline  110  and terminates at the end of the spline  110 . In other words, the width (i.e., circumferentially) of the spline  110  changes with change in the axial direction. 
     With respect to the radial taper (or chamfer)  136 , the taper  136  starts at the outer radius R 2  and terminates at the end of the spline  110  at a second radius R 1 . In the illustrated embodiment, the inner radius is the radius of the shaft  106  at the base of the splines  110 . In other words, with a radial taper, the radial height of the spline changes along the length of a spline. 
     With the illustrated dual taper  126 ,  136 , the end of each spline  110  includes a first point  128  at a first radial distance R 1  and a second point  130  at a second radial distance R 2 . The points  128 ,  130  are separated along the length of the taper  126 ,  136  of the spline  110 . Surfaces  132  and  134  define the taper  126 ,  136  between the side surfaces  118  and the points  128 ,  130 . 
     Although, in the illustrated embodiment, the shaft  106  has a dual taper  126 ,  136 , in other embodiments, the shaft  106  may not have a dual taper. For example, in such embodiments (not shown), a taper may be provided only in the axial direction  124  (i.e., the spline is full height the entire length of the spline). 
     One way to further define a taper is to discuss angles in which surfaces are positioned relative to reference points, such as an axial direction, a transverse direction, a radial direction, another intersecting surface, etc. Some parameters of the taper of the splines  110  on the shaft  106 , which may be preferred in certain embodiments, will now be discussed. 
     The illustrated axial taper  126  of the splines  110  has a draft angle (e.g., a measure of the angle of surfaces  132  and  134  with respect to the axial direction of the spline  110 ) of about 34 degrees. As such, without considering the radial taper  136 , in the illustrated embodiment, the two surfaces  132 ,  134  intersect at an angle of about 68 degrees. 
     Although the illustrated embodiment utilizes a 34 degree draft angle, wider draft angles can be utilized with acceptable results. For example, draft angles of less than about 60 degrees, and, more preferably, less than about 40 degrees can produce acceptable results. Alternatively, the splines  110  may have a pointed edge defined by two surfaces  132  and  134  intersecting at an angle of less than about 80 degrees, or, in other embodiments, less than about 70 degrees. 
     Other narrower draft angles are also possible; however, when modifying the end on the splines  110  on the shaft  106 , applicable regulations and standards may permit only minor modifications. For example, in accordance with current regulations and standards, any modification must generally occur only within about the first one-quarter (¼) inch of the spline  110 . Based upon this exemplary limitation, it may difficult to implement narrower draft angles without extending the taper beyond the presently-allowable limits. It should be understood that, if the applicable regulations and standards change in the future (e.g., to allow for a longer modification region), narrower draft angles may be provided and may be preferable for a given application. 
     As discussed above, the illustrated splines  110  of the shaft  106  also have a radial taper  136 . This radial taper  136  is at least partially defined by a chamfer of the splines  110 . The illustrated splines  110  have a chamfer angle (e.g., measured as the angle the edge extending from  130  to  132  makes with respect to the axis  124  of the drive shaft  106 ) of about 29 degrees. 
     Although the illustrated embodiment utilizes a 29 degree chamfer angle, larger chamfer angles can be utilized with acceptable results. As discussed above, some embodiments do not include a radial taper  136 , and, in such an embodiment, the chamfer angle would be 90 degrees. However, when a chamfer is provided, chamfer angles of less than about 60 degrees, or, in some embodiments, less than about 30 degrees can produce acceptable results. 
     As mentioned above, due to applicable regulations and standards, shallower chamfer angles may not currently be permitted. However, to the extent that regulations allow modifications further along the length of the spline  110 , shallower chamfer angles may allow for easier registration of complementary splines  110 ,  114 . 
     As discussed above, the taper  126 ,  136  of the spline  110  terminates at a tip  128 ,  130 . This is not meant to mean only a pointed termination. Rather, the taper does not terminate at a surface that can abut head-on with a tapered spline  114  on the connector  112  and prevent engagement of the splines  110 ,  114 . In one example, this means that the spline  110  does not terminate in a large blunted surface (e.g., such as the blunt end  22  in  FIGS. 1-3 ). The term “tip” refers to ends that are pointed, rounded, curvilinear, have a cam-like or other profile that encourage two surfaces to slide past each other upon engagement of the shaft  106  and the connector  112 . 
       FIGS. 8-9  illustrate the connector  112 . The connector  112  is coupled to a driven shaft, such as a conventional telescoping driven shaft having a universal joint at each end. Such a connector  112  can be used as part of a power input connection on an implement. As illustrated in  FIGS. 10-14 , the connector  112  is adapted to work with the shaft  106 , discussed above, to prevent or reduce the likelihood of head-on engagement between the splines  110 ,  114  during attempts to register the drive shaft  106  and driven shaft. 
     As shown in  FIGS. 8-9 , the connector  112  includes a female coupling element with internal splines  114 . Like the splines  110  on the shaft  106 , each spline  114  has a tapered end  116 . In the illustrated embodiment, each spline  114  tapers only in the axial direction (e.g., an axial taper). In other words, the illustrated spline  114  changes in width along the axis (beginning at a first distance from the end of the spline  114  and terminating at the end of the spline  114 ) while retaining its full height along the length. As illustrated, both sides  118  of the spline  114  taper to form an edge defining a tip on the splines  114 . 
     A number of different tapers can be utilized for the splines  114 . For example, although both sides  118  of each spline  114  are shown to taper in the axial direction, in some embodiments (not shown), only one side tapers to form a point. Also, like the splines  110  of the shaft  106 , the splines  114  of the connector  112  may have a dual taper (i.e., both an axial taper and a radial taper). 
     Under current regulations and standards, a greater length region of the spline  114  is permitted for modification compared to the drive shaft  106 . As such, relatively shallower draft angles (compared to the splines  110  of the shaft  106 ) are permitted on the internal splines  114  of the coupler  112 . These shallower draft angles may provide smooth engagement between the splines  110 ,  114 . In the illustrated embodiment, the internal splines  114  have a draft angle of about 20 degrees. 
     Other draft angles are possible. Although the illustrated embodiment utilizes a 20 degree draft angle, wider draft angles can be utilized with acceptable results. For example, the draft angle can be less than about 60 degrees, less than about 40 degrees or less than about 20 degrees. 
     Alternatively, the taper of the female splines  114  can be defined by the angle formed by two surfaces intersecting. In the illustrated embodiment, the two surfaces of the spline  114  intersect at an angle of about 40 degrees. In some embodiments, the two surfaces intersecting at the tip intersect at an angle of less than about 60 degrees, less than about 50 degrees or less than about 40 degrees. 
     As noted above, the illustrated internal splines  114  do not have a radial taper or, in other words, do not have a chamfer provided. Again, the splines  114  generally retain their full height (or radius) along substantially the entire length of the spline  114 . Experiments have shown that a chamfer on the internal splines  114  may not be necessary if and when a chamfer is provided on the external splines  110 . 
     In some cases, with a chamfer is provided on both splines  110 ,  114 , engagement between the splines  110 ,  114  can be more difficult due to the two tips terminating at points, which may have a tendency to dig into the opposite spline  110  or  114 . If properly machined and held to tighter tolerances, chamfered ends on both sets of splines  110 ,  114  could be utilized without problem. However, for practical purposes (e.g., lower cost manufacturing, reduced risk of damage, tolerance issues, etc.), a chamfer is provided on only one of the sets of splines  110 ,  114 . 
     As mentioned above, the taper of the spline  114  terminates at a tip. This is not meant to mean only a pointed termination. Rather, the taper does not terminate at a surface that can abut head-on with a tapered spline  110  on the shaft  106  and prevent engagement of the splines  110 ,  114 . In one example, this means that the spline  114  does not terminate in a large blunted surface (e.g., such as the blunt end  22  in  FIGS. 1-3 ). The term “tip” again refers to ends that are pointed, rounded, curvilinear, have a cam-like or other profile that encourage two surfaces to slide 
       FIGS. 10-14  illustrate the interconnection of the illustrated shaft  106  and the connector  112 .  FIGS. 11-12  illustrate a first alignment condition of the splines  110 ,  114 , while  FIGS. 13-14  illustrate a second alignment condition of the splines  110 ,  114 . 
     In the first alignment condition (see  FIGS. 11-12 ), the splines  110 ,  114  are aligned for easy registration. In other words, the projections and grooves of the opposite engaging splines  110 ,  114  are illustrated in a generally well-aligned condition allowing for easy registration. 
       FIG. 13-14 , on the other hand, attempt to illustrate the tips or points of each spline  110 ,  114  in as close to a “head-on” configuration as is possible (the second alignment condition). However, even in such an alignment, during insertion of the shaft  106  into the connector  112 , the illustrated tips would slide or cam into the adjacent opening between splines  110 ,  114  to allow for proper registration. 
       FIGS. 8-10  illustrate an additional independent feature which can aid with alignment and registering engagement of the shaft  106  and the connector  112 . As shown, one or more alignment features  115  are provided on an exterior surface of the connector  112 . The illustrated alignment features  115  include indicators (e.g., notches, recesses, etc.) aligned with the structure of the internal splines  114  (e.g., in the illustrated embodiment, the recesses between the internal splines  114 ). However, in other embodiments (not shown), the alignment features  115  can, additionally or alternatively, take other forms (e.g., markings, projections, etc.) aligned with other structure (e.g., the projections of the splines  114 ). 
     In operation of the embodiment shown in  FIGS. 8-10 , an operator will lift and align the connector  112  on the driven shaft with the power take-off shaft  106 . Because the operator is not likely to see the location of the internal splines  114  of the connector  112 , the operator relies upon the alignment features  115  on the exterior of the connector  112  to indicate the location of, in the illustrated construction, the gaps between the internal splines  114 . The operator then aligns the alignment features  115  with the splines  110  of the shaft  106 . With these structures being substantially aligned, the splines  110  should properly engage and register with the internal splines  114  as the shaft  106  is inserted and connected to the connector  112 . 
       FIG. 15  again illustrates the conventional power take-off shaft  6 , having a male coupling element  8  at its end provided with splines  10 , and the female coupling element  12  of the universally-jointed and extensible driven shaft provided with internal splines  14 . 
       FIGS. 17-18  illustrate a universally jointed and extensible driven shaft  140 . The shaft assembly  140  includes a shaft  141 , which may telescope, with a connector  112  on each end. The shaft assembly  140  also includes a universal joint  142 ,  144  at each end between the shaft  141  and the connectors  112 . 
     As mentioned above, aligning splines between a power take-off shaft on a tractor and a power input connection on a driven shaft of an implement can be complicated by the size, weight, and complexity of the driven shaft of the implement. The connecting end of the driven shaft typically has a joint, such as a universal joint  142 , which can tend to rotate or pivot into a position not aligned with the shaft (see  FIG. 19 ). Thus, the weight combined with the typical misalignment can make connection between the power take-off shaft  106  and the power input connection  112  much more complicated. 
     As shown in  FIG. 16 , one particular configuration of a universal joint includes two yokes  146 ,  148  interconnected via a cross-shaped trunnion body  150  having four trunnion pins around which are positioned bearing elements. These bearing elements are received in bores formed in yoke arms. In particular, the bearing elements include bearings  152  and a bearing cap  154 , typically held in place via a snap ring  156 . 
     Within the trunnion  150  are bores which extend through the trunnion pins and intersect in a central cavity which is closed by a suitable lubricant fitting. Sealing rings are provided at the inner ends of each of the bearing caps  154  (see  FIGS. 21-22 ). These sealing rings will permit any excess lubricant supplied during lubrication to escape to the exterior of the universal joint but will prevent any dirt or water from entering into the bearing cavity within the bearing element. 
     As noted above, due to the construction of a universal joint, the axis of rotation of the two yokes  146 ,  148  will tend to gravitate toward a non-aligned condition ( FIG. 18 ) with respect to each other and/or the shaft  141  when not connected to a power take-off shaft  106 . 
     In independent aspects, a device for and method of orienting the yokes  146 ,  148  to assist with aligning the power take-off shaft  106  and the power input connection  112  is provided. In particular, a joint locking assembly  157  is operable to hold each joint  142 ,  144  in a predetermined orientation. The joint locking assembly  157  can be configured many different ways as long as it holds the joint in the predetermined orientation (e.g., with the connector  112  aligned with the shaft  141 ). 
       FIGS. 19-22  illustrate one construction of a joint locking assembly  157 . In this embodiment, the universal joint  142  is provided with a modified trunnion body  150 . In particular, at least two perpendicularly positioned trunnion ends are provided with a locking assembly  157  to lock the yokes  146 ,  148  in a specific predefined orientation. 
     In a conventional universal joint, the trunnion ends freely rotate within the bearing caps  154 . This allows the universal joint to gravitate toward the mis-aligned condition shown in  FIG. 18 . In the illustrated construction, a locking assembly  157  for each trunnion end includes a detent mechanism operable to selectively lock the trunnion  150  against rotation with respect to the bearing cap  154 . 
     The illustrated detent mechanism includes a projecting member  162  biased into engagement with a recess  164  of the bearing cap  154  to prevent rotation of the trunnion end with respect to the bearing cap  154 . As illustrated, a spring  160  within a bore  158  of the trunnion end biases a ball  162  into the recess  164  of the bearing cap  154 . With the ball  162  engaged with the recess  164 , the trunnion end is unable to rotate relative bearing cap  154 . 
     In the illustrated embodiment, four detent mechanisms are provided on a single trunnion end. However, in other embodiments, more or fewer detent mechanisms can be utilized. In some embodiments, as few as one or two detent mechanisms may operate well. In other embodiments, more than four may be used. 
     As shown in  FIGS. 19-21 , some embodiments, such as the illustrated embodiment, will incorporate one locking assembly  157  per axis of rotation. Thus, two locking assemblies  157  are illustrated on adjacent trunnion ends to control each axis of rotation of the universal joint  142 . However, in other embodiments, each trunnion end can be provided with a locking assembly  157 . 
     In some embodiments, the detent mechanism is specifically configured to hold the joint in a predetermined orientation when not connected to the drive mechanism and allow free movement of the joint when connected to the drive shaft and under a specific torque load. This configuration can be achieved by selecting a spring that will create a force to hold the ball  162  into engagement the recess  164  under the weight and resulting forces of the yokes  146 ,  148 . In other words, the spring  160  pushes the ball  162  into engagement with the recess  164  with greater force than is normally produced on the joint under the weight of the yoke  146  or  148  alone. 
     When the locking assemblies  157  are engaged (i.e., the detent mechanisms are aligned with the ball  162  engaging the recess  164 ) and the forces on the joint create a torque less than the threshold amount, the joint is locked against pivotal movement. As such, the connector  112  is oriented in a predetermined orientation for easy engagement between the shaft assembly  140  and the power take-off shaft  106 . In the illustrated embodiment, the locking assemblies  157  hold the yokes  146 ,  148  in an orientation that substantially aligns the axis of rotation of the connector  112  with the axis of rotation of the driven shaft  141 . With the connector  112  held in substantial alignment with the shaft  141 , connection between the power take-off shaft  106  and the power input coupling  12  can be completed substantially easier than is conventionally done. 
     As noted above, in some embodiments, the predetermined orientation aligns the axis of the connector  112  and the axis of the shaft  141 . However, for other embodiments (not shown), this particular orientation may not be very helpful, for example, if the opposite end  144  of the drive shaft assembly  140  is already connected to an implement and that connection is at a different height than the power take-off shaft  106 . Thus, in some embodiments, the predetermined orientation may be an orientation in which the axis of rotation of each coupler  112  is substantially parallel to each other but not parallel with the axis of rotation of the drive shaft  141 . 
     In some constructions the locking assembly  157  may be constructed to hold the joint in more than one predetermined orientation (e.g., with the connector  112  aligned with the shaft  141  or the axis of each coupler  112  parallel to each other but not parallel with the axis of rotation of the drive shaft  141 ). 
     During operation, after connection of the implement, the forces on the joint  142  increase quite substantially (i.e., exceeding the threshold), overcoming the force of the spring  160  and causing the ball  162  to retract into the bore  158  against the force of the spring  160 . Due to the configuration of the ball  162 , the relative torque created between the trunnion  150  and the bearing cap  154  causes the bearing cap  154  to cam the recess  164  to disengage the ball  162  and force the ball  162  against the spring  160  into the bore  158 . 
     When operation is complete and the driven shaft is disconnected, the detent mechanism can re-engage and hold the universal joint in the predetermined orientation for disconnection of and/or future connection of the shaft assembly  140  with a drive shaft  106  of a tractor. In other words, the balls  162  can be biased into engagement with recesses  164  upon disconnection to hold the joint in a desired orientation. During disconnection of the driven shaft  140  and the drive shaft  106 , the connector  112  may not be properly oriented to allow the detent mechanism to engage. As such, upon disconnection, the operator may have to manipulate the connector end and move it toward an aligned condition reengage the locking assembly  157  and hold the connector end and shaft  141  in a generally aligned orientation. 
     Although the illustrated embodiment utilizes a ball  162  as part of the detent mechanism, in other embodiments (not shown), other projecting structures can be utilized. For example, a pin with a generally rounded end can function much like the illustrated ball  162 , with the rounded end helping to create the camming effect that forces the detent mechanism into disengagement as discussed above. 
     In some embodiments, non-rounded pins and generally cylindrical recesses may also be used to prevent relative movement between the trunnion end and the bearing cap during engagement of the drive shaft. In such an embodiment, disengagement can be created by shearing the pin once sufficient torque is applied to the joint during use. Unfortunately, with such an embodiment, the locking assembly would not be reusable. 
       FIGS. 23-25  illustrate another embodiment of a locking assembly  157 . In this embodiment, a modified Belleville Spring  170  biases the trunnion  150  and bearing cap  154  into a locked orientation (see  FIG. 23 ). Belleville Springs, Belleville Washers or disk springs are conical shaped circular springs. The springs  170  are designed to be loaded in the direction perpendicular to the washer, i.e., by compressing the cone, and they may be loaded statically or dynamically. 
     As best illustrated in  FIG. 25 , the modified Belleville Spring  170  includes projecting members or detents  172 . As shown in  FIGS. 23-24 , these detents  172  can align with and engage corresponding recesses  174  on the trunnion body  150  and bearing cap  154 . When aligned as illustrated, the joint is prevented from rotating. When sufficient torque is applied to the joint, the detents  172  react against the recesses  174  and cause the Belleville Spring to flex into an orientation in which the detents  172  release from the recesses  174  on at least one of the bearing cap  154  or the trunnion body  150 . 
     In operation, the modified Belleville Spring  170  will lock the bearing cap  154  into a fixed orientation with respect to the trunnion body  150  via the engagement of the detents  172  on the top and bottom of the Belleville Spring  170  with the recesses  174  in the bearing cap  154  and the trunnion body  150 . When torque applied to the joint is below a predefined threshold, the Belleville Spring  170  will maintain its shape and hold the joint in a locked orientation. However, above the predefined threshold torque, the Belleville Spring  170  will flex, allowing the detents  172  to disengage from the recesses  174  of either the bearing cap  154  or the trunnion body  150 . In the configuration shown, the detents  172  will disengage from the recesses  174  of the bearing cap  154 . As shown in  FIG. 24 , the recesses  174  can be curved or rounded to provide a camming action between the recesses  174  and the detents  172  to drive the Belleville Spring  170  toward a flexed condition. 
     Once the torque on the joint drops below the threshold torque, the Belleville Spring  170  will return to its original condition. This will allow the detents  172  to reengage the recesses  174  and once again lock the joint against rotation. 
     In other constructions (not shown), a torsional spring having an end that disengages with either the trunnion body or the bearing cap can be used in place of the Belleville Spring. Alternatively, a detent can extend from the trunnion radially (opposed to axially as shown in  FIGS. 19-22 ) and engage recesses within a side wall of the bearing cap. 
     In other embodiments (not shown), separate external structures are added to the universal joint  142  to hold the yokes  146  and  148  in the predetermined orientation with respect to each other and to the shaft  141 . For example, structures (e.g., shims, wedges, blocks, etc.) can be placed in the gaps between the trunnion body  150  and the yokes  146 ,  148  to hold them in a predetermined orientation while the structures are engaged with the yoke. 
     In still other embodiments (not shown), a rigid structural member such as a bar, rod, or shaft can be connected between the shaft  141  and connector  112  to maintain a predetermined alignment. In particular, such a rigid structural member can be temporarily coupled to the connector  112  and the shaft  141  during alignment and engagement of the driven shaft with the drive shaft. 
     The rigid structural member can be coupled to the shaft  141  and connector  112  many different ways. For example, such a member can held in place (e.g., strapped to each item) with a band or a strap. In some embodiments (not shown), connecting members can be permanently added to the shaft  141  and connector  112  for receiving the rigid structural member. Such connecting members can include apertures for receiving a portion of the rigid structure member or more complex fastening devices such as latches, fasteners, catches, clasps, etc. 
       FIGS. 26-28  illustrated a coupling assembly  210  including locking indicia. It should be understood that, in other constructions, various other coupling assemblies can incorporate the locking indicia described. 
     As shown in  FIGS. 26-28 , the coupling assembly  210  includes, as main components, a hub  212 , a collar  214  and a latch assembly. Generally, the latch assembly locks or latches the collar  214  in a released position shown in  FIG. 27  until an axially-extending splined shaft  218  is inserted in the hub  212 , after which the collar  214  slides along the hub  12  to a locked position shown in  FIG. 3 . 
     As best seen in  FIGS. 26-28 , lock indicating indicia  260 ,  262  is provided on two locations on the hub  212 . The first indicia  260  is located adjacent the distal end of the hub  212  and the second indicia  262  is adjacent the yoke coupled to the hub  212 . The first indicia  260  is intended to indicate an unlocked condition, while the second indicia  262  is intended to indicate a locked condition. 
     The position of the collar  214  determines which indicia  260  or  262  is showing and the condition the coupling assembly  210  (i.e., locked or unlocked). In  FIG. 27 , the collar  214  is in the unlocked condition, and, in this condition, the first indicia  260  is showing while the second indicia  262  is covered by the collar  214 . In  FIG. 28 , the collar  214  is in the locked condition, and in this condition, the second indicia  262  is showing while the first indicia  260  is covered by the collar  214 . 
     In some embodiments, the indicia  260 ,  262  include colored sections, in which the first (unlocked) indicia  260  is red and the second (locked) indicia  262  is green. In other embodiments, the indicia  260 ,  262  include colors, words, symbols, or combinations thereof 
     Below, one particular embodiment of a coupling assembly  210  will be described. It should be understood that other known coupling assemblies can be used with the indicia  260 ,  262  of the present invention. 
     As shown in  FIGS. 26-28 , the collar  214  is biased toward the locked position by a compression spring  217  of the latch assembly disposed about the hub  212  and acting between a washer or stop ring  220  and an inner annular pocket  219  in the collar  214 . The stop ring  220  is affixed to the hub  212  by bias of the spring  17  although it could be formed integrally or connected (e.g., welded) thereto. A snap ring  222  fits in a circumferential groove at the front of the hub  212  to prevent the collar  214  from being pushed off the hub  212  by the spring  217 . 
     As discussed above, the bore  224  of the hub  212  is internally splined to mate with external splines of the shaft  218 . The rear end of the hub  212  forms a yoke  226  for attaching the hub  212  to a device to be driven by the shaft  218 . For example, the shaft  218  could be part of a power takeoff of a tractor and used to drive an agricultural implement. 
     The hub  212  and the shaft  218  are locked together by two locking members  228  disposed in corresponding radial slots  230  in the hub  212  angularly spaced apart by 180 degrees. The slots  230  open at the outer and inner diameters of the hub  212  and taper inwardly to have a reduced diameter at the inner diameter so that the locking members  228  may protrude into the bore  224  without passing completely through the slots  230 . There is sufficient clearance between the slots  230  and the locking members  228  to allow them to move radially in the slots  230 . 
     The locking members  228  preferably are balls that can roll and slide within the slots  230  so that, when the shaft  218  is inserted in the bore  224  of the hub  212 , the locking members  228  engage a circumferential groove or recess  232  about the periphery of the shaft  218  spaced in from the end. When the collar  214  is moved to the locked position, an annular cam surface  234  at the inner diameter of the collar  214  will contact and move the locking members  228  inwardly into the recess  232 . The collar  214  maintains the locking members  228  in this inward position so that the shaft  218  cannot be moved axially inward or outward and disengage from the hub  212 . 
     Referring now to  FIGS. 27 and 29 , the hub  212  also includes a set of four radial slots  236  spaced apart approximately 90 degrees around the circumference of the hub  212  and axially behind the locking member slots  230 . The slots  230  open at the outer and inner diameters of the hub  212  and taper inwardly to have a reduced diameter at the inner diameter so that ball-shaped release members  238  contained therein can protrude, but not pass into the bore  224  of the hub  212 . There is sufficient clearance between the slots  236  and the release members  238  when the collar  214  is in the released position such that the release members  238  can roll and slide radially therein. 
     A latch ring  240  is disposed about the release members  238  and contained in an annular channel  242  inside the collar  214  by a retaining ring  244  having a smaller inner diameter than the outer diameter of the latch ring  240 . A leaf spring  246  in the channel  242  biases the latch ring  240  eccentrically with respect to the hub  212 . 
     Referring to  FIGS. 26-27 and 29 , in the released position, opposite arcs of the latch ring  240  rest against the recessed outer diameter  248  of the hub  212  and the inner diameter of the collar  214  under the force of the leaf spring  246 . In this position, the latch ring  240  engages an annular ledge  250  extending radially outwardly around the outer diameter of the hub  212  on one side of the latch ring  240  and the inner radially-extending side face of the retaining ring  244  on the other side of the latch ring  240 . The collar  214  is thus prevented from being slid along the hub  212  by the spring  217  due to the contact of the latch ring  240  with the hub ledge  250  and the inner surfaces, particularly, the side face of the ring  244  and of the collar  214  defining the channel  242 . 
     The ledge  250  is sized so that the diameter of the release members  238  are at least equal to the distance from the inner diameter of the bore  224  to the radial outer edge of the ledge  250 . Thus, when the shaft  218  is inserted into the bore  224 , the raised spline surface of the shaft  218  cams the release members  238  radially outwardly. The release members  238  thereby push the latch ring  240  radially outwardly beyond the ledge  250  and concentric with the hub  212 . This movement releases the latch ring  240  from the ledge  250  of the hub  212  and allows the spring  217  to move the collar toward the locked position (right in  FIGS. 27-28 ). 
     As mentioned above, the annular cam surface  234  at the inner diameter of the collar  214  will contact and move the locking members  228  inwardly into the peripheral shaft recess  232 . The collar  214  maintains the locking members  228  in this inward position so that the shaft  218  cannot be moved axially to disengage from the hub  212 . 
     Thus, the collar  214  is initially latched in the released position (i.e., before the shaft  218  is inserted in the hub  212 ) with the unlocked indicia  260  showing. Upon insertion of the shaft  218  into the bore  224 , the locking members  228  are cammed radially outwardly in the slots  230 , as shown in  FIG. 27 . As the shaft  218  is inserted further, the release members  238  are cammed radially outwardly by the shaft  218  against the leaf spring  246  to disengage the latch ring  240  from the ledge  250  of the hub  212 , thereby allowing the spring  217  to move the collar  214  from the released position to the locked position shown in  FIG. 28 , which covers the unlocked indicia  260  and uncovers the locked indicia  262 . In doing so, the cam surface  234  of the collar  214  cams the locking members  228  radially inwardly into the groove or recess  232  of the shaft  218  to axially lock the hub  212  onto the shaft  218 . 
     As long as the shaft  218  is fully in the bore  224 , the release members  238  remain in the radially outward position to lockout the latch ring  240  so it cannot re-engage the ledge  250  in the event the collar  214  was moved back against the spring  217 . Thus, the collar  214  is prevented from latching in the released position when the shaft  218  is engaged with the hub  212 . 
     The shaft  218  can be disengaged from the hub  212  only by manually pulling the collar  214  backward (to the left in  FIG. 28 ) against the spring  217 . As mentioned above, the collar  214  will not latch in this position until the shaft  218  is pulled out of the bore  214 . Once the shaft  218  is removed, the latch ring  240  can re-engage with the ledge  250  and the collar  214  can be latched in the released position, concentric with the hub  212 , again with the unlocked indicia  260  showing. 
     As shown in  FIGS. 30-31 , in some embodiments, usage instructions are directly coupled to the coupler assembly  210 . As illustrated, the instructions are included on the collar  214 . The instructions can be a label or sticker coupled to the coupler assembly  210 . Alternatively, the instructions can be directly applied to the coupler assembly  210  via paint, engraving, etching, etc. 
     The instructions in  FIGS. 30-31  illustrate three steps. In the first step, the collar  214  is moved from the position shown in  FIG. 30  to the position shown in  FIG. 31  to place the collar  214  in the unlocked condition, which exposes the red (unlocked) indicia  260 . In the second step, the coupler assembly  210  is illustrated as being placed in engagement with a shaft while the collar remains in the unlocked condition of  FIG. 31 . Finally, in the third step, the instructions show the collar  214  in the locked condition (of  FIG. 30 ) when the coupler assembly  210  is properly engaged with the shaft. In this step, the green (locked) indicia  62  is visible, indicating that the coupler assembly  210  is in the locked condition, which will prevent release of the shaft until the collar  214  is manually moved to the unlocked position (shown in  FIG. 31 ). 
     As mentioned above, the visual indicia  260 ,  262  can be used with other shaft locking mechanisms, such as with a push pin style connector shown and described in U.S. Pat. Nos. 3,240,519 and 4,645,368, the entire contents of which are hereby incorporated by reference with respect to its teachings of the connector.  FIGS. 32-34  briefly illustrate how this concept would work. 
     In  FIG. 32 , the inner element is a shaft  305  having axial splines  306  defined by slots  307  opening to the end of the shaft  305 . The outer shaft element comprises the yoke hub  308  which, merely by way of exemplification, has integral arms  309 . Interiorly, the hub  308  has splines  310  complementary to the channels  307  of the inner shaft element  305  and it has spaces  311  complementary to the splines  306  of the inner shaft  306 . 
     The segments  332  of a peripheral channel have been cut in splines  306  of the inner shaft  306 . The outer shaft element  308  has a boss  315  provided with a transverse bore  366  tangential to at least one of the channel segments  332 . The locking pin  367 , reciprocable in the bore  366 , is biased by a compression spring  368  to a position in which the tapered portion  369  of the locking pin  367  wedge in engagement with that channel segment  332  which is intersected by the bore  366 . With the locking pin  367  positioned as shown in  FIG. 33 , the shaft elements  305  and  308  are securely coupled against axial separation (for rotational purposes, they are, of course, coupled by the splines  306 ,  310 ). 
     The spring  368  may bear directly against the end of bore  366 . At its other end, the bore  366  is swedged or staked to reduce its diameter at  370  to provide a stop abutted by the annular locking pin flange  371 , which fits the bore. The flange  371  has a shoulder  372  beyond which projects a reduced radius  373  of the locking pin  367 , this serving as a push button for displacing the locking pin  367  against the bias of spring  378 . When the locking pin  367  is thus displaced by pushing the projecting button  373  in the direction of arrow  374 , the reduced neck  375  of the locking pin  367  will register with the spline  306  with which the locking pin  367  was originally engaged. Because the neck  375  is sufficiently small so that the spline  306  will not be obstructed thereby, when the locking pin portion  67  is thus displaced against the pressure of its spring, the inner and outer shaft elements may readily be separated axially, or readily re-engaged. Nevertheless, with the locking pin  367  in the position shown in  FIG. 34 , the inner and outer shaft elements will be securely locked against axial separation. 
     As shown on  FIG. 33 , the visual indicia  260 ,  262  can be provided on the end of the locking pin  367 . Due to the construction of this device, only the unlocked indicia  260  will show in the unlocked condition (not shown) with the locking pin  367  pushed into the bore  366 . However, as shown in  FIG. 34 , the locked indicia  262  becomes visible when the locking pin  367  is moved to the locked position. 
       FIG. 34  illustrates an alternative embodiment of the locking pin  367  and bore of the embodiment shown in  FIG. 33 . As shown in  FIG. 34 , the bore  366  is a through bore and the pin  367  can extend out either end of the bore  366  depending upon the locking condition of the coupler. As illustrated in  FIG. 34 , the coupler is in the locked position with the locked condition visual indicator  262  visible on the exposed end of the locking pin  367 . As shown, the unlocked condition visual indicator  260  is contained within the bore  366 . When the locking pin  367  is pushed in the opposite direction of that shown, the locking pin  367  would be moved to an unlocked position in which the unlocked condition visual indictor  260  is exposed through the right end of the bore  366  while the locking position visual indicator  262  would be contained within the bore  366 . 
     It should be understood that the instructions provided in  FIGS. 30-31  can also be provided on the embodiments of  FIGS. 32-34 . 
     Although the invention has be described in detail with reference to certain preferred independent embodiments, variations and modifications exist within the scope and spirit of one or more independent aspects of the invention as described above. It should be understood that independent features disclosed in the application (e.g., splined connection, joint locking assembly, the locking indicia, etc.) may be employed alone or in combination with one or more additional disclosed features. 
     It should also be understood that, while the detailed description was provided with reference to a tractor and an implement, in other embodiments, independent features of the invention can be used between a vehicle and another accessory or within a single vehicle. For example, the disclosed splined connection, joint locking assembly, and/or the locking indicia can be used between a vehicle and another accessory or within a single vehicle to connect one shaft to another. 
     One or more independent features and independent advantages of the invention may be set forth in the claims.