Note: Descriptions are shown in the official language in which they were submitted.
WO 93/04:~93 ~ 1 1 6 0 1 ~i PCI/US91/05958
Ç~
BEARING WITH LUBRICATING ~ND NON-LUBRICATING
SPACERS
Teçhnical Field
This inven~ion relates to self-lubricating
bearings of the type in which the roller elements are
lubricated by lubricant transfer from spacers containing
lubricants.
Bac~round of the Invention
U.S. Patent No. 4,906,110 discloses an improved
solid lubricant roller bearing in which the rollers are
separated by floating lubricating spacers. ~he present
invention aims to increase the life and stability of this
type of bearing.
Summa~y of the ~ent~Qn
In accordance with the present invention,
lubricating and n~n-lubricating spacer elements are
positioned between the rollers to provide solid lubricant
and stability, re-~pectively, ~or the rollers. The non-
lubricating spacer elemen~s primarily have only a spacing
function, although they may be of a material which has
favorable an~i-frictiQn characteristics. The lubricating
elements are floating and the non-lu~ricatin~ elements may
be floating or part o~ a cage. When provided as floating
elements the non-lubricating elements are preferably
alternated with the lubricating spacer elements in an
arrangement placing each non-lubricating spacer element
opposite a lubricating spacer element so that the race
engaging portion of the rollers is lubricated by direct
contact with the lubricating spacer elements as the
rollers turn. The non-lubricating spacers assist in
spreading the lubricant on the rollers and provide roller
stability to the extent not provided by the lubricating
W093/04293 PCT/US91~059~X
211601S
spacers. In an arrangement whereon the non-lubricating
spacers are floating elements it is preferred to provide a
pair of non-lubricating end spacers adjacent the ends at
one side of each roller and a central n~n-lubricating
spacer opposite its o~her side. When a ~age proYides the
non-lubricating spacers a substantial central portion of
each roller is opposed on opposite sides by lubricating
spacer elements.
Brief Description of the Drawinas
Figure 1 is an exterior side view of a typical
assembly of spacer and roller elements ~o which the
invention is applicable;
Figure 2 is an end view of the assembly with an
annular end ring removed;
Figure 3 is a d~tailed end view taken as in
Figure 2;
Figure ~ is an isometric exploded view of a
portion of a bearing constructed in accordance with the
present invention;
Figure 5 is an exploded isometric view of a
preferred spacer and roller configuration;
Figure 6 is an alternate embodiment of a spacer
for use with the rollers.
Figure 7 is a fragmentary plan view of a second
embodiment of the invention utilizing a cage;
Figure 8 is a transverse sectional view taken as
shown by lines 8-8 in Figure 7; and
Figure 9 is a fragmentary end view of the second
embodiment.
Detailed Description of the Invention
Referring to Figures 1-2, floating spacers
having a solid lubricant composition separate an equal
number of rolling needle elements 2. Each spacer 1 is
preferably machined or molded to provide concave opposite
sides 3, 5 with a curvature similar to the outer surface 4
W093/04293 2116 01 S PCT/US91/0~958
of the needle rolling elements 2 to provide a relatively
large initial contact area for solid lubricant transfer
thereto. The outer and inner surfaces 6, 7 of the spacers
1 may be molded or machined with a convex curvature to
S conform, respectively, to that of the inner and outer
raceways, as determined by diameters 8, 9, or the surfaces
6, 7 may be planar and have two-line contact along t~e
longitudinal edges of outer surface 6 with the outer
raceway and single-line tangential contact with the inner
raceway midway between the longitudinal side edges of
inner surface 7. End lubrication of the rolling elements
2 may be accomplished, for example, by annular rings loo
of solid lubricant material positioned adjacent the ends
of the rollers 2 and spacers 1, or by end caps of solid
lubricant material mounted on the ends of the rollers, or
by end portions of the spacers arranged to overlap the
ends of the rollers.
For cost economy it is preferred to form the
spacers 1 by a high-pressure compaction and secondary
sintering procedure precluding a need for follow-up
machining. The joints at the meeting ends of adjoining
spacer elements at opposite sides of each roller may be
staggered endwise of the roller, so that each portion of
the roller circumference will directly contact a spacer
element during each roller rotation. This end can be
accomplished, for example, by beveling the adjoining ends
~f the spacers to provide sloped end fac~s. By this
arrangement the joint lines between respective spacer
- elements at opposîte sides of a roller are staggered
relative to one another along the roller.
Referring to ~igure 3, a recess 10 with angle 11
is preferably provided in the spacer elements along a
plane 12 passing through t~e center axis of the adjoining
rolling elements 2. This recess angle 11, as measured
with respect to a plane 13 passing through the rotary axis
of the bearing and the rotary axis of the adjoining
rolling element, typically has a value of 30 degrees and
W093/04293 PCT/US91tO5958
211~1S
will ensure that wear particles separated from the spacer
are of minimum size 8C as not to interfere with the smooth
operation of the bearing. The recess also serves to
recapture small, loose wear particles of transfer
lubricant and consolidate the particles back into the body
of the spacer under the compressive action occurring
between the rolling elements and the spacer with respect
to the apex of the recess angle 11.
In an alternate embodiment of the spacer element
lo 10, shown in Figure -6, the recesses 10~ are relieved so as
to be substantially concave. This modification encourages
wear particles to be captured in the recesses 10' rather
than becoming entrapped between relative moving surfaces
of the assembly~
In accordance with the present invention, non-
lubricating spacers are also provided. It is preferred to
alternate spacer elements containing solid lubricant
substances ~"lubricating spacer elementsU) with spacer
elements which do not have lubrication as their principal
20 function ("non-lubricating spacer elements"~ and
preferably are more resistant to wear from roller contact.
If both the lubricating and non-lubricating spacer
elements are floating, they preferably are alternated in
both the axial roller direction and circumferential
direction of rotation of the entire bearing a~sembly.
This arrangement maintains proper alignment and spacing of
the roller elements by way of the non-lubricating spacers
as the lubrica~ing spacer ~egments are consumed. In this
r~gard the initial clearances can be such that only the
lubricating spacers contact the rollers until a preset
amount of wear of the lubricating spacers has occurred.
Preferred materials for the "non-lubricating"
spacer elements include, but are not limited to such hard
wearing materials as ceramic materials, non-lubricated
polymide materials, steel, silver impregnated bronze,
phenolic materials, nylon, etc. The "non-lubricating"
spacer elements may also be made from relatively soft
W093/04293 211 6 0 1 S PCT/US91/05958
materials such as Teflon~, phenolic materials, nylon, etc.
for low load conditions.
A basic arrangement of lubricating and non-
lubricating spacer elements denote~ 101 and 102,
respectively, is shown in Figure 4 for adjacent spacers.
Spacer la, for example, has a pair of lubricating spacer
elements 101 separated by a non-lubricating spacer element
102, whereas spacer lb has a pair of non-lubricating
spacer elemen~s 102' separated by a lubricating spacer
element 101'. Each of the lubricating spacer elements are
preferably longer than the non-lubricating spacer elements
so that the full length of the related roller will always
be in contact with lubricating spacer elements. However,
this arrangement is not essential because the lubricant
spreads across the races and rollers responsive to
rotation of the roll~rs.
The illustrated arrangement of alternating
lubricating and non-lubricating spacers in Figure 4
provides each roller (roller 2~, for example) with two
non-lubricating roller elements 102' adjacent its ends at
one side of the roller, and with a central non-lubricating
roller 102 at the other side of the roller. This assures
stability to the rollers by the non-lubricating spacers.
- Referring to Figure 5, the spacer lc can provide
end lubrication for ~he roller ~ by having the spacer ends
cover the ends of the cavi~y with which the rollers
interfit. Also, the rollers ~ can comprise a series of
roller elements 2a placed end-~o-end. As in the Figure 4
example, non-lubricating spacer elements are alternated
with lubricating spacer elements. At one side of the
roller 2 spacer lc has a pair of l~bricating spacer
elements 101'' which are opposed by a shorter pair of non-
lubricating spacer elements 102'' in spacer ld at the
other sideO ~urther, in spacer ld center lubricating
spacer element 101''' opposes a central non-lubricating
spacer 102''' in spacer lc.
W093/04293 PCT/US91/059~8
211601~
In the embodiments shown in Figures 4 and 5, the
spacers la-ld have been shown as each ~onsisting of three
spacer elements. It will be understood that there can be
a greater number of spacer elements in each spacer~
preferably an odd number of elements in each which are
arranged so that (a) lubricating spacer elements alternate
with non-lubricating elements in each spacer, and
(b) lubricating spacer elements in each spacer are
positioned opposite a non-lubricating spacer element in
the adjacent spacers.
The lubricating spacer elements may be macle from
Vespel~ SP-21 polymide, a commercially available product
produced by the DuPont Company having U.S. Military
Specification R46198. This product does not soften and is
thermally resistant such that it can carry loads at
temperatures beyond the reach of most plastic materials
and do so while exhibiting very low creep. For example,
when the product is subjected for 100 hours to loads of
2,500 psi at 572-F, the total deformation is only 1.2%.
At the end of 600 hours under these load and temperature
conditions the total deformation only increases to 1.6%.
Vespel~ SP-21 has a polymide matrix containing a
dispersion of various solid lubricant su~stances such as
graphite and Teflon~. The lubricating spacer elements are
~ade by high-pressure compaction of Vespel~ powder and
s~condary sintering. The highest s~rength and lowest
thermal exæan~ion are usually found in the direction
perpendicular to the pressing direction. Vespel~ SP-21
may be used for spacer elements to be used at lower
temperatures. Initially there may be less tolerance
pr~vided between the lubricating spacer elements and the
rollers than between the non-lubricating spacers and the
rollers. After use has commenced, the lubricant from the
lubricating spacer elements spreads over the rollers and
the non-lubricating spacer elements.
Referring to Figures 7-9, the non-lubricating
spacers may be provided by a cage 200 having end rings
W093/04293 2 1 1 6 ~ 1 5 PCT/US91/05958
200a, 200b from which non-lubricating spacer elements 202
project inwardly parallel to ~he axis of the bearing.
Roller elements 2 have their opposite end portions
positioned between circumferentially adjoining of the
elements 202 and floating lubricating spacer elements 201
are located between the roller elements 2 and between the
en~s of the non-lubricating spacer elements 202. To tie
the end rings 200a, 200b together some of the elements 202
at opposite sides are connected by connecting elements
203. These connecting elements 203 may be alternated
circumferentially of the bearing with the lubricating
spacer elements 201, or the connecting elements 203 can be
at less intervals so that more lubricating spacer elements
are provided. Needle roller elements are normally
lS slightly tapered inwardly slightly toward the ends and so
the race engaging portion of the roller elements is
normally a central part of the length. Accordingly, the
lubricating spacer elements 201 concentrate application of
lubricant to the "working" part of the roller elements
while the non-lubricating sp2cer elements 202 maintain the
roller elements in proper alignment. However, durinq
operation lubricant from the lubricating spacer elements
normally migrates over the entire length of the roller
elements.
Normally the cage 200 will be constructed of two
halves which initially are flat. T~e roller elements and
lubricating sparer elements can be loaded into the cage
halves while they are flat, and then the cages are each
bent into a semi-cylindrical shape. The cross-sectional
shape of the transverse non-lubricating spacer elements of
the cage can be made such as to retain the end portions of
the roller elements after the cage halves have been bent
into their final shape. The cage may be made of silver
impregnated bronze or other suitable materials.
Although it is preferred to maximize the initial
roller contact surface of the lubricating spacer elements,
this is not essential. Accordingly, the lubricating
W093/04293 PCT/US9l/05958
2116015
spacer elements could have a square or trap~zoidal
transverse cross-section for example.
Although I have shown and described specific
embodiments of my invention, it will be apparent that many
minor changes of structure and operation could be made
without departing from the spirit of the invention as
defined by the scope of the appended claims.
3S
