Slip spline sealing plug

A slip spline assembly includes a splined stub shaft slidably received in a splined bore of a yoke member. A sealing plug is provided at one end of the yoke bore to maintain lubricant on the splines and prevent ingress of foreign matter. A plurality of resilient fingers on the plug snap into an annular groove formed in the yoke bore to positively retain the plug. A vent opening in the plug relieves pressure in the closed end of the yoke when the splined shaft slides toward the yoke closed end.

BACKGROUND OF THE INVENTION 
This invention relates to couplings in general and is particularly directed 
to a sealing plug for use in a torque transmitting slip spline assembly. 
Slip spline assemblies of the type to which the invention relates typically 
comprises a yoke having a splined bore for slidably receiving a splined 
portion of a stub shaft. In these applications it is necessary to provide 
lubrication between the mating sliding splines. The spline connection may 
be lubricated for life at assembly, or the yoke may have a lubrication 
fitting for periodically replenishing lubricant. Usually, the body end of 
the slip yoke is sealed with a plug to retain the spline lubricant. The 
plug may be either solid or vented. The method of sealing employed for a 
spline connection generally depends on its specific design as well as its 
application. For example, in an internally splined slip yoke used at the 
transmission output shaft of a vehicle, a solid plug is used at the body 
end and a boot type seal is provided at the hub end of the slip yoke to 
protect the splines from dust, dirt, and other foreign matter. In this 
type of application, it is common practice to remove one of the spline 
teeth to facilitate the back and forth flow of lubricant during stroking. 
In applications having a seal retained on the slip yoke hub end in direct 
sealing contact with the stub shaft, a vented plug is used to maintain 
lubricant on the splines and prevent a pressure build-up when the stub 
shaft slides towards the closed end of the slip yoke. 
In the past, numerous methods have been disclosed for retaining sealing 
plugs in slip yoke bores. The plugs also have taken many shapes. The more 
conventional types include a Welch plug, which consists of a flat annular 
disc, and a cup-shaped plug. In each case, the plug is pressed into the 
hub end of the slip yoke bore and retained in place by welding, staking, 
or a suitable epoxy cement. 
While plugs of the above type function satisfactorily, they require 
additional operations after being pressed in place for positive retention 
in the slip yoke bore. 
SUMMARY OF THE INVENTION 
The present invention is a cup-shaped sealing plug for a slip spline 
assembly comprising a flexible section having a radial shoulder which 
snaps and locks into an annular radial groove provided in the slip yoke 
bore when the plug is pressed in place. The locking connection achieved by 
the cooperating radial shoulder and groove eliminates the need for 
providing additional welds, staking or special bonding cement to secure 
the plug after it has been pressed into the slip yoke bore.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, a slip spline assembly is shown generally at 10 
including a slip yoke 12 and a mating slip stub shaft 14. Slip yoke 12 has 
an internally splined bore 16 for sliding connection with an externally 
splined portion 18 on stub shaft 14. Slip yoke 12 comprises a body portion 
20 at one end formed with opposed ears 22. Bearing cross holes 24 are 
provided in the ears 22 for mounting a journal cross (not shown) for 
connection to a conventional end yoke (not shown). The opposite end of 
slip yoke 12 comprises an axially elongated tubular hub portion 26 which 
surrounds the stub shaft splined portion 18. An annular seal 28 is 
attached by a seal retainer 30 to the outer end of hub portion 26 to 
slidably and sealingly engage the cylindrical surface on stub shaft 14. 
The outer end of stub shaft 14 comprises a pilot portion 32 for attachment 
to a driveline member (not shown). 
In the preferred embodiment, the body end of slip yoke 12 is constructed 
with an annular counterbored recess 34 for receiving a cup-shaped sealing 
plug 36. The plug 36 retains lubricant on mating splines 16 and 18 and 
prevent ingress of foreign matter. Plug 36 comprises a flat end wall 38 
and an integral axially inwardly extending cylindrical side wall 40. A 
breather or bleed opening 41 is provided in end wall 38 to prevent a 
pressure build-up in yoke bore 34 when stub shaft 14 slides toward the 
closed end of slip yoke 12. 
Thus, in viewing FIG. 1, it will be seen that splined bore 16 extends 
completely through slip yoke 12 thereby defining first and second openings 
on opposite sides of splined bore 16, i.e. at the inner body end and outer 
hub end. 
Cooperating fastening means are provided on the open or axially inner end 
of plug side wall 40 and in slip yoke recessed bore 34 for securing plug 
36 in place. The fastening portion on plug 36, as seen best in FIGS. 2 and 
3, comprises an annular raised shoulder 42 having a plurality of equally 
spaced notches 44 extending axially inwardly from the end of plug side 
wall 40. Notches 44 serve to divide shoulder 42 and thereby the open end 
of the side wall 40 into a plurality of flexible portions 46. As most 
clearly seen in FIGS. 2 and 3, flexible portions 46 comprises equally 
spaced arcuately shaped axially extending tab sections. 
Referring to FIGS. 1 and 4, the fastening portion on slip yoke 12 comprises 
an annular groove 48 in recessed bore 34 for cooperating with shoulder 42 
on plug flexible locking portions 46. In assembly, initial pressure 
applied to the outer face of plug end wall 38 by a conventional assembly 
tool (not shown) will result in tab sections or locking portions 46 being 
flexed radially inwardly as shoulder 42 initially contacts the outer edge 
of yoke bore 34. Further pressure applied to plug 36 forces it deeper into 
yoke bore 34 until shoulder 42 aligns with annular groove 48. At this 
point the flexibility of locking portions 46 permits shoulder 42 to snap 
outwardly into locking engagement with bore groove 48 thus serving to 
positively lock plug 36 in yoke bore 34 without requiring any additional 
means or operation to secure plug 36 in place. 
Referring specifically to FIG. 4, it will be seen that yoke bore groove 48 
defines inner and outer radial walls 50 and 52 respectively which are 
disposed at right angles to the groove bottom. In the preferred 
embodiment, for clearance purposes, plug shoulder 42 has its outer 
peripheral portion constructed with a diameter which is less than the 
inner diameter of the groove bottom and greater than the outer diameter of 
plug side wall 40 thereby defining inner and outer radial walls 54 and 56 
respectively on shoulder 42. The axial length of shoulder 42, i.e., the 
distance between shoulder walls 54 and 56, is slightly less than the axial 
distance between groove walls 50 and 52. For assembly purposes, the 
radially outer edge of inner shoulder wall 56 has a chamfer 58 which 
serves as a camming means for flexing section 46 inwardly as plug 36 is 
initially pressed into yoke bore 34. The respective mating outer walls 50 
and 54 in bore groove 48 and on shoulder 42 are constructed so that when 
sections 46 snap into place, shoulder outer wall 54 engages bore groove 
outer wall 50 thereby serving to positively lock plug 36 in yoke bore 34. 
A slight chamfer is provided on shoulder outer wall 54 to allow shoulder 42 
to be cammed into bore groove 48 when alignment occurs between shoulder 42 
and bore groove 48. If desired, outer wall 54 may be constructed parallel 
to mating inner groove wall 50 so that when locked in place they will be 
flush. 
While the present invention is disclosed in combination with slip spline 
assemblies that is designed for periodic replenishing of lubricant, it may 
also be used in assemblies that are lubricated for life. In such 
assemblies, bleed opening 41 (see FIGS. 2 and 3) would be eliminated and a 
boot type seal would be employed in place of seal 28 and retainer 30. In 
typical applications of this type, one of the spline teeth is removed to 
prevent pressure build-up and facilitate back and forth flow of lubricant 
during stroking. 
Also, the flexibility of locking portions 46 may be reduced by reducing the 
number of notches 44 which extend from the end of plug side wall 40 or 
increased by increasing the number of notches. 
Sealing plug 36 may be a stamped metal part which is finished machined or, 
alternatively, a one piece molded part made from a suitable plastic 
material such as nylon or a nylon/glass filled combination. 
From the foregoing description it is apparent that the advantages of the 
present invention result from the combined relationship of the flexible 
locking portions of the sealing plug and its cooperation with the annular 
locking groove in the yoke bore. The arrangement provides a positive and 
economical way of retaining a sealing plug in the splined bore of a slip 
spline assembly that eliminates the need for providing additional welds, 
staking, or the use of a special bonding cement to secure the plug in 
place at assembly. 
Having thus described the preferred embodiment of the present invention, it 
should be understood that the invention is not to be limited to the 
specific construction and arrangement shown. It will be apparent to those 
skilled in the art that modifications or alterations may be made without 
departing from the spirit and scope of the present invention as set forth 
in the claims.