Retainer for slip sleeve liners

A telescopic drive line includes an inner square drive shaft and an outer drive tube having a square bore at one end. A thin-walled liner in the bore has an inner surface providing a low-friction axial bearing for the drive shaft. The considerably greater coefficient of friction between the outer body of the liner and the bore of the drive tube secures the liner axially in the bore irrespective of the radial force applied to the liner. Only supplementary securement is provided by a key fitted in a keyway. The several liners fit between inward projections of the key. An outward projection fitting a recess in the drive tube secures the key axially. Deflection of the exposed end of the key allows the projecting tab to be disengaged from the recess for insertion and withdrawal of the key along with the several sleeves.

BACKGROUND OF THE INVENTION 
The axial bearings of a telescoping drive line such as for agricultural 
implements have generally been of the lubricated type. Anti-friction 
bearings have been used in drive lines for agricultural implements but 
have generally been found to be unduly expensive and requiring too 
frequent maintenance. A recently developed glass filament reinforced 
resin-bodied thin-walled liner having a Teflon fabric inner face has been 
found to provide the low break-away force required of telescopic drive 
lines and to withstand the pulsating loads applied thereto. The unique 
capability of the particular liners referred to in essentially providing 
their own securement within the bore of the outer drive tube is the 
subject of the co-pending application Ser. No. 593,132 filed July 3, 1975 
by Fritz A. Callies for TELESCOPING DRIVE LINE, now Pat. No. 4,020,659 
.The telescoping drive line of said application includes a readily 
replacable liner requiring at most nominal endwise securement for assembly 
purposes. It is an object of the present invention to provide a simple, 
rugged, inexpensive retainer which may be readily inserted along with the 
liners in their assembly. It may also be desireable to be able to remove 
damaged or worn liners readily in the field under such adverse 
circumstances as may there by encountered and with no more than a simple 
tool such as a screwdriver or possibly a pocket-knife. 
SUMMARY OF THE INVENTION 
The outer drive tube of a telescopic drive line is provided with a square 
bore and a keyway parallel to the bore and centrally of one of the flat 
sides of the bore. A recess at the exposed end of the keyway receives the 
outwardly extending projection of a key. Portions of the key project into 
the bore and engage the opposite ends of a single liner or several liners 
to secure them axially in the bore. When the projection is retracted, the 
key is slidably disposed in the keyway so that the liner or liners are 
also slidable in the bore. For that purpose, the key is of a resilient or 
plastic material and the radial dimension of the key diminishes toward the 
outer end of the key so that the outer end may be deflected radially 
inwardly to retract the projection and allow the key to be slidably 
positioned in the keyway or withdrawn therefrom. The square shaft when 
slidably supported in the liner or liners prevents the projection from 
leaving the recess under any circumstances. 
If the liners, when worn and requiring replacement, have become tight in 
the bore, the liners may have to be destructively removed; the similar 
removal of the key may then be convenient or also required. In any case, 
the key is of nominal cost and the invention optimally includes the 
provision and use of a new key with the replacement liners.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The telescoping drive line shown in the drawing includes the universal 
joints 11 and 12, the square inner shaft 13 and the tubular outer shaft 
14. Shaft 13 is of solid steel construction and should have 
corrosion-resistant, smooth sliding surfaces. One end of shaft 13 is 
welded to the hub 11a of universal joint 11. Shaft 13 is not exactly 
square for what is called phasing purposes, as will be described. 
The outer shaft 14 comprises the seamed or seamless tube 15, the sleeve 16 
and the liner assembly which will be described. Sleeve 16 is of solid 
steel round stock and end 16a of sleeve 16 is welded to one end of the 
tube 15; the other end of tube 15 is welded to the hub 12a of universal 
joint 12. 
The liner assembly consists of the two identical liners 18 and 19 and the 
retainer or key 20. 
The square bore 16b of sleeve 16 extends the length thereof and is of a 
size which allows liners 18 and 19 to be inserted endwise with a slip-fit 
or a slide fit. Each liner is in the form of a square tube having a wall 
thickness of about 4mm and is typically 38mm long. Their length is 
important to providing adequate bearing areas for shaft 13 and their 
over-all spacing or length is also important in supporting the drive line. 
For phasing purposes, liners 18 and 19 can be inserted endwise in bore 16b 
as shown or in a position turned 180.degree. about their axis; shaft 13 
can similarly be inserted in the liners as shown or when turned 
180.degree.. These limitations are due to the fact that the sections of 
shaft 13, the liners 18 and 19 and bore 16b are nearly square but actually 
rectangular. Accordingly shafts 13 and 14 can be assembled in either of 
only two different rotational positions which are 180.degree. apart so 
that the phase relationship of universal joints 11 and 12 is maintained. 
Each liner 18 and 19 is of a composite construction and the liners are 
preferably identical. Each liner has, of course, adequate compressive 
strength and impact resistance; the inner facing of each liner has good 
wear resistance and self-lubricating properties, a low coefficient of 
friction and a low breakaway force. In the presently preferred embodiment 
of the invention, the body of liners 18 and 19 are of a glass filament 
reinforced resin and their inner facing is of Teflon woven fabric which is 
embedded in the resin of the body. The coefficient of friction of the 
outer surface of each liner with the steel sleeve 16 is in the order of 
0.3 whereas the coefficient of friction of the inner surface of each liner 
with the steel square inner shaft 13 is less than 0.1. The latter 
coefficient of friction is, of course, in the order of that which is 
required so that typically, a 1500 pounds of axial thrust is not exceeded 
at the maximum torque loads for which this limit is applicable. 
Accordingly, the relative coefficients of friction are of such an order 
that only normal securement of the liners 18 and 19 in bore 16b of sleeve 
16 is required. The present invention provides such securement by means of 
the key 20 which may be fitted in either of grooves 16c formed in sleeves 
16. Grooves 16c are oppositely disposed and adjoin the bore 16b. The 
portions of liners 18 and 19 which span the grooves are unsupported but 
are mid-way between the load-bearing portions of the liners which adjoin 
their corners. Two grooves 16c are provided mainly for a balance in the 
broaching operation by which the grooves are formed; they also allow the 
use of two keys 20 if desired. However, a single key has been found to 
provide the entirely adequate securement of the liners. 
The key 20 of the present invention consists of a single molded device of 
uniform width and is of a size so that it has a sliding fit in either 
groove 16c and extends generally the length thereof. Nylon is a suitable 
material for key 20. The radial dimensions of key 20 (having reference to 
the axis of sleeve 16) are such that it is convenient to describe the key 
as having five sections 20-25 of different configurations and functions. 
The outer and inner connecting sections 22 and 24 fit entirely within 
groove 16c and respectively extend alongside liners 18 and 19. The locking 
end 21, the intermediate section 23 and the inner end 25 extend to but do 
not contact the shaft 13. Section 23 thus extends between liners 18 and 19 
and spaces them; the inner end 25 forms an abutment which limits the 
relative inward axial movement of liner 19. That is, liner 19 fits between 
section 23 and end 25; liner 18 similarly fits between the spacing section 
23 and the locking end 21. 
In order that key 20 may function to position liners 18 and 19 axially in 
bore 16b of sleeve 16, key 20 must itself be positioned axially in groove 
16c by means which also allows its removal when desired. For that purpose, 
sleeve 16 is internally machined to provide an annular slot having a 
bottom radius preferably less than the distance from the sleeve center to 
the corners of bore 16b. Such machining in effect provides opposite slots 
16d which respectively intersect grooves 16c and two intermediate slots 
16e. Slots 16e have no function other than to allow machining slots 16d in 
a simple single lathe operation of low cost. In the same operation the end 
16f of sleeve 16 may also be chamfered as shown to provide a lead-in for 
shaft 13. 
Each slot 16d forms a recess at the outer end of groove 16c and end 21 of 
key 20 includes a projection 27 which extends into the recess. While 
projection 27 normally prevents endwise movement of key 20 in groove 16c, 
the endwise insertion and removal of key 20 from either groove 16c 
requires that the projection 27 be permitted to pass over or by that 
portion of sleeve 16 which forms the ledge 16g between slot 16d and the 
open end of sleeve 16. The means therefor and by which key 20 may be so 
engaged and disengaged depends merely on two dimensional features of key 
20; one is that the radial dimension of connecting section 22 of key 20 is 
tapered or diminishes toward locking end 21 so that a clearance 20c is 
normally provided between liner 18 and section 22; the other feature is 
that locking end 21 of key 20 is provided with an exposed cross-wise slot 
20s. 
It is important to note that the assembly and disassembly of liners 18 and 
19 in and from sleeve 16 with key 20 can only be accomplished with shaft 
13 removed from shaft 14. For assembly, key 20 is disposed with its 
section 24 laid against one side of liner 19 so that they may be inserted 
together, respectively in bore 16b and either groove 16c. While section 23 
is still partially extending from sleeve 16, liner 18 is similarly placed 
against section 22 and key 20 and liners 18 and 19 are further inserted 
into sleeve 16. 
When projection 27 reaches ledge 16g, the section 21 of key 20 is pushed 
toward the sleeve axis, this motion being allowed by the clearance 20c 
provided. That is, key 20 is deflected to allow projection 27 to clear the 
ledge 16g of sleeve 16. If end face 16f of sleeve 16 is chamfered, a ramp 
is provided projection 27. Such a ramp can effect the deflection of key 
20. However, if a sleeve, not shown, does not have such a lead-in, the 
deflection is readily effected manually. When liners 18 and 19 and key 20 
are positioned in sleeve 16, the resilience of the material of key 20 
causes the key to straighten to its normal condition and projection 27 is 
thereby inserted and retained in slot 16d. Further, of course, shaft 13 
upon assembly in liners 18 and 19 then and thereafter secures projection 
27 in slot 16d. That is, key 20 also cannot be removed except after 
removal of shaft 13. 
In considering the nondestructive removal of key 20, it is assumed that no 
ambient material has accummulated in recess 20c. If recess 20c is 
adequately clear, and liners 18 and 19 are not tight in bore 16b, removal 
of key 20 and liners 18 and 19 is readily effected by lifting projection 
27 out of slot 16d and pulling the key 20 from slot 16c and liners 18 and 
19 from bore 16b. Any of several common tools may be employed, e.g. pliers 
(not shown) may be used to grasp section 21 of key 20 and to pull the key. 
As shown, the end of the screwdriver 40 may be inserted in slot 20s and 
pivoted against the end of sleeve 16 to bend and unlock key 20 and then 
effect its removal. Normally, if key 20 may be removed as described, it 
may also be reused. However, the destructive removal of key 20 may be more 
convenient. The pending application for patent above referred to describes 
as a normal and desireable possibility the incrustation of liners 18 and 
19 by accumulating rust. Even though the drive line is regularly enclosed 
for personnel safety, the conditions of use in agricultural machinery 
makes such incrustation a normal expectation applicable equally to the 
nylon key 20. Accordingly and according to the present invention, the 
normal complement of replacement liners 18 and 19 would include, as well, 
a replacement key 20. Thus, the nominal cost of key 20 and its replacement 
is of especial significance. 
The destructive removal of key 20 and that of liners 18 and 19 which are 
worn-out inside and tightly encrusted in bore 16 is not shown in the 
drawings. After removal of shaft 13, screwdriver 40 can be inserted in the 
groove 16c opposite that in which key 20 is fixed and the liners may be 
pried and broken loose from bore 16b. The removal of key 20 may be 
effected in a similar manner. That is, section 21 may be broken from 
section 22 or sections 21 and 22 may be freed in groove 16c sufficiently 
to be wedged between key 20 and the bottom of the groove and then pried 
loose. 
ALTERNATE EMBODIMENTS OF THE INVENTION 
Liners 18 and 19 may be combined to comprise a single liner, not shown, and 
key 20 would then not include the projecting section 23. 
It is preferred that the key 20 be formed of a resilient material. However, 
the key could be merely flexible. In that case, the key would be removable 
in the same manner as described, but to secure the key in groove 16c, the 
outer end would have to be depressed radially outwardly in order to cause 
projection 27 to become engaged in recess 16d. 
The following CLAIMS particularly point out and distinctly claim the 
subject matter which the applicants (inventors) regard as their invention 
and are intended to include all alternate embodiments of the invention 
which are and are not presently contemplated by the inventors but are 
within the scope of the following CLAIMS.