Note: Descriptions are shown in the official language in which they were submitted.
The present invent.ion relates generally to seals, ancl
more particular1y~ to seals adaptecl fox speciali~ed, severe
- serv.. ce app.lications.
One application for which there has been a large num~er
of seals proposed is that of the so-called track pins on
crawler tractor equipment. Crawler tractors usually include :
.. ...
a pair of tracks, and each track is in turn made up of inner
and outer chains of track links. A large plurality of links,
typically 30 to 40 links, are assembled into an endless chain,
and two such chains are then trained over the front idler rol-
ler an~ the rear sprocket final drive as well as over a number
::, .. ..
o~ suspension track rollers and track-carryin~ idler ro3.1ers.
The~inner and outer Iinks in each chain are held toye-ther by .:
track pins~and bushings which extend throuyh ope.nings at
. .
either end oE -the track links. Track shoes or ~rouser plates
extend transversely between the respective links on the inner ~.
and outer chains. These shoes or plates form the sur~ace
which rests on the earth and ultimately supports and forms the
traction for the vehicle. Thus, the right and le:Et hand vehi~
cle tracks each include a plurali.ty of plates, with the pla.tes
extend.ing between and joining the links in the inboard chain
to the links in the outboard chain.
Because track vehicles are particularly desi~ned for
us~ under severe conditions, narnely, mud, sand, ~rit/ ice and
snow, rocky terrain, etc., and ~ecause the track .is the por-tion
,: ~ .
~ the v~hicle ~hich comes into the mc.st direct and fre~luent
: ~ - ~ 1 '~
: 7,
con~act with these severe conditions, track pins and their
bushings are subject to rapid wear.
An ef~ective track pin seal should accommodate a r la~
tively great degree of axial dimensional variation, and even-
tual wear. Such a seal should have an axial spring rate
which is moderate and which will generate an initial axial
~orce which is sufficient to insure that the seal can success-
fully exclude water and grit and retain lube, even wnder condi
; tions of minimum load.
The seal of the present invention provides most ox all
of the advantages of expensive prior art seals and does so at
low initial cost. This seal uses structures and materials
which are different from the prior art and provides new oper~
ating characteristics and advantages.
The seal includes a generally annular secondary seal
and force applying member of a characteristic shape, and a
primary seal ring of a stiff, elastomeric material~ The pri-
mary ring has a generally L-shaped seat for receiving the
secondary member, and an axially directed end face portion
adapted to contact a part of the track pin mechanism to be
sealed, and a~so includes plura] passages extending hetween ~ ;
the axial ends of the primary seal ring to permit flow of
lubricant therethrough.
IN THE DR:P.WINGS:
FIG. 1 is a vertical sectional view, with portions
broken away, show:ing the track pin seal of the invention in
position of use;
FIG. 2 is a fragmentary vertical sectional view of the
seal of the invention prior to installation~ and showing the
axial lubricating passages on the inside diameter of the
primary seal ring;
- 2 -
FIG. 3 is an enlarged fragmentary front elevational
view of a portion of the seal of ;FIG. 2, taken along lines
- 3-3 thereof;
FIG~ 4 is a ~urther enlarged front view of the seal of
FIG. 1, taken along lines 4 4 thereo~; -
FIG. 5a is a vertical sectional view o~ a seal having
a modified cross sectional shape;
FIG. 5b is a vertical sectional view having a further
modified cross sectional shape;
FIG. 5c is a vertical sectional view having a still ~ -
further modified cross sectional shape;
~IG~ 6 is a fragment.ary, vertical sectional view of a ~;
modified form of seal made according to the invention and
showing the seal in a normal, installed position of use;
FIG. 7 is a ~ragmentary, vertical sectional view of
the form of seals shown in FIG. 7, showing the seal just prior
to complete installation thereof;
FIG. 8 is a vertical sectional view of the seal of the
invention showing the seal installed and positioned in a
lightly compresse~ position of use; and
FIG~ 9 is a vertical sectional view of the seal of
FIGS. 6-8 and showing the seal in the fully compressed position
~hereof.
In FIG. 1, the seal of the in~ention is designated 10
and is installed within a track link a~sen~ly designated 12.
A c~lindrical track pin 14 has an end cap 16 which is
secured along the interface 18 between an inner diameter of
the cap 16 and the outer diameter o~ the track pin 1~. These
parts do not undergo movernent relative to each other. The
end cap 16 typically constitutes the leading portion of one
traclc link, while the trailing portion of the same link is
press fit over a b~shing which i5 ~ree to rotate with respect
, . .
~ 3 ~ ; ~
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to the following track pin.
In FIG. 1, a counterpart end portion 22 of a preceding
track link is shown, with the link 22 having a radially
inwardly directed wall portion 24 defining an opening for
receiving the outer diameter 26 of a track pin bushing 28.
, .
A working clearance 30 exists between the inner diameter 32
of the track pin bushing 28 and the outer diameter 34 of the
track pin 14, the center line axis of which is shown at 20.
The link 22 and bushing 28 are pressed together, and .
therefore move as a unit with respect to the track pin 14.
The end ~ap 16 of the preceding link is ixed to the pin 14
:~ which permits the pin 14 to oscillate with respect to one end
o~ the track link.
The seal is rec~ived in a cavity 36 defined in part by
a mating surface 38 which is a radially extending, axially
directed face of the bushing 28. The outwardly directed face ~:
40 of a spacer ring 42, the radially extending end wall 44
and the axially extending wall 46 also define the cavity 36,
with walls 44, 46 defining a counterbore in the end cap 16.
The cavity 36 rece.ives the annular primary seal ring 48 which
: includes a slightly inclined end face surface 50 terminating
at an edge 52. The margine 54 lying radially inwardly of
the edge 52 will form the seal band or sealing surface which
actually engages t:he mating surface 38 on the bushing 28 to
create the primary seal. The inner diameter of the ring 48
comprises a plurality of serrations 56 (FIGS. 3, 4) which
have their :inner surfaces 58 snugly engaging the outer diameter ~ :
40 of the spacer 42. A seat for receiving a secondary sealing
member 60 is formed in the primary sealing ring by generally
axially and radially extending annular surfaces 62, 64. ~ .
The elastomeric secondary seal member 60 has a body ~ :
which is generally parallelogram shaped in cross section and
_ 4 _ !~
which includes xadially inner and ou~er axially ext~nding sur-
faces 66, 68 and generally inclined front and rear 3urfaces
70, 72. The sets of sur~aces 156, 68 and 70, 72 arP generally
parallel to each other in the unstressed or l~1loaded condition
of the seal. An outwardly and upwardly ext~nding flange 74
of small cross section is ~ormed around the radially outer
forward edge of the body of the secondary seal member 60.
This flange 74, is radially confined and deformed as shown
when the seal is i~stalled (FIG. l~.
The secondary seal ring 60 is preferably made from a
relatively soft synthetic rubber material, for example, a
nitrile rubber which tolerates temperature changes
well and which has a type "A" Durometer of about 50-60. Other
rubber compositions are also suitable.
The primary seal ring 48 is preferably made from a
touch, abrasion resistant elastomer such as a polyurethane
rubber, e.g. a material with a 90-9S Dur~meter (Shore A)
hardness. One example of such composition is a rubber de-
scribed as the reaction product o~ a polyether glycol such
as poly (l,4-oxbutylene) glycol with a stoichiometric excess
of a mixture of the 2,4- and 2,6- isomers of tolylene di-
isocyanate, ~ich forms a prepolymer having a molecular weight
of from about l'i00 to about 3000~ rrhis prepolymer is then
cured with a reactlve diamine such as methylene-bis-ortho-
chloroaniline. The cured elastomer has a 90-95 Durometer
(Shore A) hardness and a SpPci~ic ~ravity of about l.l6.
Other compositions may aliso be used.
During installation, the ring 60 is slipped over the
ring 48 with the oppositely directed surfaces 6Z, 66 on the
primary and secondary rings respectively engaging each other
with a moderately snug fit requiring a slight stretching of
, iq ~ ~
:, . . . ; . . .: . . ,
.
the secondary ring 60. These two parts are then placed into
the cavity 36, with the serrations 56 de~ining axial grooves
76 just spaced apart from or lightly engaging th~ outside
diameter 40 of the spacer 42. The flange 74 engages the sur-
face 46 upon initial installation to locate the secondary seal
ring 60 in the counterbore 46; the ring 60 is pushed fully
into the counterbore until the radially outer margin of the
surface 72 meets the end wall 44 of the cavity 36.
The radiused portion 78 of the ring 60 engages a radius
80 in the end cap 16. When no axial load is applied, the sur-
face 68 on the outside diameter oE *he ring 60 is spaced
slightly apart from or may lightly engaga the counterbore sur-
face 46; the flange 74 centers the ring 60 in the cavity.
The end cap 16, the track pin 14 and the spacer 42 are
assembled so that the pin 14 is received within the bushing
28. ~he edge 52 of the ring 48 then engages the end wall or
mating surface 38 of the bushing 28, slightly distorting the
margin 54 of the ri~g 48 so as to form a seal band 54 of a
measurable radial width. The extent to which the bushing 28
~0 mav move to ~lace an axial load on the seal assembly is deter-
mined by the axial width of the spacer 42. When the end sur- ;~
face 82 of the spacer engages the mating surf~ce 52 of the
bushing 28~ assembly i9 completeO
Axial compression of the seal unit torts the resilient
secondary seal ring 60. When it is axially compressed, the
seal ring 60 tends ^to bulge at its sidewalls 70, 7~ (FIG. 1)
and tends to become more flat and less frusto-conical, that
is, its axial extent is shortened and its cone angle is
rendered more planar. This greatly increases the radial
compressive load on the primary seal ring 48t and causes the
ring 48 to be tightly gripped by the ring 60. The ring 60 is
then capable of transmitting considerable torque.
. ..
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~ 6 - ~
.
In some respects, the action of -this seal is similar
to that of the seal described in United States Patent No.
3,241,843. However, in such prior seals, the primary sealing
ring was constructed from a stiff/ thick metal material capable
of accepting very high radial compressive loads without dis-
torting significantly. EIere, the primary seal ring 48 is made
from a m~lch harder, stiffer material than is the ring 60, but
he ring 48 is still made from an elastomer and in its free or
unsupported state cannot absorb compressive loads of the re-
quired order without deflecting inwardly to an undesirablygreat extent. Therefore, according to the present invention,
the inner diameter of the ring 48 in¢ludes the teeth 56 which
engage and rest upon a metal surface, namely, the spacer 42.
This supports the ring 48 against undue radial deflection.
; Before installation, the teeth 56 may be sharp (FIG. 3),
but the radial-compressive loaas distort the teeth 56 as shown
in FIG. 4. Nevertheless the passages 76 remain open, and a
substantial volume of oil may be kept within the sealed region.
The entire volume occupied by the passageways 76, and the
~ volume in the cavity 84, can receive oil, and so can the
clearance area 30.
The primaxy ring, made of a tough rubber, obtains
internal radial support fxom the spacer 42. The passages 76
permik all the o:il heId in the assembly to be used. I'he
secondary ring 60 is so~t and provides a low axial spring rat~
50 that the primary ring 48 can move without developing exces-
sive or insufficient axial loads. I~ the spring rate is too
highJ the seal wears out rapidly; if the forces are too low,
the unit will not: seal.
The rubber materials described provide proper spring
rates but other rubbers may also be used.
_
" . ~ . ,. . ,. ... ~ . . . .. ... . .. . .
q~
The rings 60 are frusto~conical rings having a general-
ly parallelogram-shaped cross-section. Some other equivalent
shapes may also function well; se~e FIGS. 5a and 5b. Rubber,
: when fully confined, is substantially imcompressible. The
secondary ring 60 will distort under load so as to place both
an axial seal load an a radial compressive load on the ring
48 in use.
The mounting flanges or so~-called l'barbs" 74 are pre-
ferred for installation but are not necessary.
In the present invention, the primary ring 4B is stiff
but elastomeric, and therefore, the portion of the ring 60
lying behind the intended seal band area 54 should be contacted
by a fillet or wedge-shaped portion of rubber from the ring 60,
even when the ring 60 is relaxed. ~ -
According to the invention, two pa~ls of rings 48, 60 .
may also be used within a single seal cavity in opposed series
or so-called "mirror image" foxm~ See United States Patent
No. 3,241,843.
In use, the spacer 42 limits the axial inward mo~ement
of the bushing 28, while a counterpart spacer 42 on the oppo-
site end of the track pin prevents undue axial movement in
the other direction. The radial force establishes a ~ir~
mechanical connect:ion between the end cap 16 and the ring ~8.
The ring 48 is supported hy the lubricated sur~ace 40 o.~ the
spacer 42. .
The end fac~ 50 of the ring 4~ is slightly angled so
that the entire surface is not in contact with the surface 38.
FIG. 5a shows a seal ring 28a with an inclined, radially
outwardly and rearwardly directed seating sur~ace 100. The
secondary ring 60a is of an O~ring configuration wh~n relaxed,
and is slightly toric or somewhat flattened in operation. A
':'' ' .
radially inwardly and forwardly directed seating surface 102
is formed in the end cap 16a.
The two oppositely directed surfaces 100, 102 form
frusto-conical ramps on which the O-ring secondary seal 60a
may move as radial and axial loads are placed on the ring.
The seal elements 48a, 60a function in essentially the same
manner as their counterparts in 7~IG5. 1-4 and the materials
from which these parts are made may be the same.
~`' FIG. 5b shows a primary seal ring 48b and a secondary
. ~ ,
seal ring 60b which is slightly different from the ring 60
in FIGS. 1 and 2. A plurality of deformable mounting spikes
or barbs 108 are provided to insure proper initial seating or '
positioning of the riny 60b. In use, the cross-section of ~,
the ring 60b deforms somewhat, and the ring 60b operates in ~ ,~
generally the same manner as the ring 60 in FIGS. 1-4.
FIG. 5c shows a ring 60c which includes small feet 110, - ',
~ 112 at the inner and outer radial ends respectively of the ,~
! ring 60c. Small notches 114, 116 appear to exist in the ring
~,~ 60c between the ends of the feet 110, 112 and the rest of the
ring 60c when the ring 60c is relaxedO As load is applied,
the ring 60c distorts so that most or all of the notches 114,
116 are closed up and the feet 110, 112 contact the ring 60c
in a snug relation.
The seal shown in FIG. 5c operates the same as the seal
of PIGS~ 1-4 and the materials are also the same.
FIGS. 6-9 show a modified form o~ seal of the invention. ,,
FIG. 6 shows the seal installed at a typically specified
"operating height:'l; FIG. 7 shows the seal being disposed in
the,counterbore just before installation is completed; FI~7. 8
shows the seal at maximum "operating height"; and FIG. 9 shows
the seal a~ minimum "operating height" or maximum compression.
..
_ g _
~ Track pin and like seals are referred to as having an
; "operating height" which indicates the degree to which the
seal assembly is compressed axial]y. Maximum operating height
occurs when the bottom o~ the counterbore is spaced axially
farthest from the portion of the primary seal ring member
which forms the seal band 54. ~inimum operating height cccurs
when the seal band~forming portion of the primary memb~r lies
closest to the bottom portiorl of the counterbore. A specified
or typical operating height lies between these two extremes,
and is a height which is sought to be, but is not always,
achieved in practice. The variations in operating height
occur because of the working clearances required to permit
operation of the machine, and the nee~ for reasonable manu-
facturing tolerances. The seal accommodates changes in working
height primarily by compression of the secondary riny or spring
member 60 and, to a much less extent, by deflection or compres- !
sion of portions of the primary seal memher 48.
If a seal is operated at more than the maximum opera-ting
height, it may fail to seal because the assembly is not com-
pressed enough to load the seal band axially. When the sealis compressed beyond the permissible minimum working height,
compression of the secondary member is at a maximum, and such
compression will create forces which extrude the film of
lubrication from between the parts and the seal will rapidly
fail in use because o~ excessive friction and high ~empera
tures.
PIGS. 6-9 show a modi~ied form of seal with a spacer
42d, a bushing 28d having an end face mating portion 38d and
a counterbore with a radial wall 44d and an axial wall ~6d.
The seal cavity 36d is defined by these thrce surfaces and by
the radially outwardly directed face 40d of the spacer 42d.
~ 10 - ~
,,: , . .
. ~'.. ,'`~ ',` ' ; ' '' , ', j , ,: , ~ , ,
When the seal assembly lOd is about to be installed
in the cavity 36d, the primary and secondary rings 48d, 60d
are positioned within the seal-receiving opening 36d. The
radially outwardly directed surface 68d and the radially
inwardly directed surface 66d are parallel to each other but
spaced by clearances "X" and "Y" respectively, from the
counterbore surface 46d and from the radially outwardly
facing surface 62d on the ring 48d.
These "X" and "Y" clearances are usually a few thou-
sandths of an inch. In one case, the clearanae "Y" is sub-
stantially æero or a light interference fit, while clearance
"X" is 0.020 - 0.060 inches. In such a case, the interference
fit between the surfaces 66d and 62d permits ~he rings 48d,
60d to be handled as a unit. When the seal is in this position,
the molded rubber parts 60d and 48d are relaxed and the end
~ace 38d is spaced from the seal ~an portion or edge 52d of
the primary ring 48d. In this condition, there is an angle
~ lying between a radial plane and the frusto-conical extent
.
of the secondary seal ring 60d. Such angle ~ might be 30,
e.g.
Installation occurs (FIG. 8) by moving the bushing 28d
and part 22d o~ the track link toward the cap 16d. The
bushing 28d then slides along the track pin 14d. When the edge
52d of the ring 48d engages the sur~ace 3ad on the bushing 28d
and is moved axially thereby, the ring 60d is moved so as to be
snugly seated, with the protion 78d thereof engaging the por-
tion 80d of the counterbore 36d. Further compression generates
an axial sealing load by distorting the secondary member 60d in
compression and s:Lightly reducing the angle ~, as to 20 or
25, e.g.
When the ring 60d is in the position o~ FIG. 8, the
553
`,
surfaces 70d, 72d are inclined with angle ~ but are parallel
to each other and not measurably bulged or distorted.
FIG. 6 shows the seal in a typical or "specification"
position of use with the surfaces 70d, 72d bulged somewhat.
FIG. 9 shows the seal at minimum height, with the front and
rear surfaces 70d and 72d bulged significantly. The entire
leading edge, which in the embodiment of ~IGS. 6-9 is a two-
element surface consisting of a radially inner, generally pla-
nar portion 200 and a radially outer, generally frusto-conical
portion 202, is inclined rearwardly and radially outwardly. ~- !
The inner, normally planar surface 202 is inclined radially
outwardly and toward the bottom of the counterbore, while
the frusto-conical surface portion 200 which terminates in
the sealing ed~e 52d is inclined somewhat less forwardly than
it would be under a lower axial load.
The axial extents or heights Hl, H2. H3, and ~ in
FIGS. 6-9, illustrate the maning of terms just used concerning
installed height or "working height~'. The dimension Hl, from
the edge 52d of the ring 48d to -the rear edge 78d of the ring
60d is the greatest height (FIG. 7). This is the height as
the unit is manufactured. H2 shows the maximum installed
height; which i9 sllghtly less than the manufactured height.
H3 is a typical specification or installed height, under a
.. . . .
moderate or intended working load~ H~ :is the shortest or
minimum installed height and is the height attained under
the highest permitted load.
rrhe articlllated or two~segment surface 200~ 202 on the
edge of the radial flange of the primary seal member 48d has
proved advantageous in use. This construction permits a
slightly greater effective angle to be achieved between the
surface 202 and the surfa~e 38d than ~an be achieved between
- 12 -
.
, .,, , .. ~ ... . .
countexpart surfaces 50 and 38 in the embodiment of FIGS.
1-5. Even when the seal operates through a range of low
working heights, including those shown in FIG. 9, the frusto-
conical portion 22 allows the angle between the surface 200
and the end face surface 38d of t.he bushing 28d to be sharp
enough to create a good seal.
Seals made according to the invention provide v~ry
extended life and great reliability in relation to their low
cost and can be used in most severe environments, including
track pin seal applications, to provide extended life of the
sealed parts and to provide a much quie~er track chain than
has been generally available previously. Several preferred
forms of the seal of the invention have been described in
detail. Other equivalent forms of su~h seal may also be made
which fall within the scope of the invention.
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