U.S. patent number RE29,723 [Application Number 05/801,717] was granted by the patent office on 1978-08-08 for resilient mid-pitch lug for an endless track.
This patent grant is currently assigned to Caterpillar Tractor Co.. Invention is credited to Glenn M. Haslett, Harold L. Reinsma.
United States Patent |
RE29,723 |
Haslett , et al. |
August 8, 1978 |
Resilient mid-pitch lug for an endless track
Abstract
An endless track assembly for use with a track-type vehicle
having a notched drive sprocket is provided with link elements
having a resilient mid-pitch impact lug located midway between the
track link bushings. The resilient mid-pitch lug reduces track
noise and wear due to metal-to-metal impact of the track against
the sprocket and idler by having a topmost portion of greater
height than adjacent bushings whereby initial contact is made by
the lug so that impact energy is thereby absorbed prior to
engagement of the track bushings.
Inventors: |
Haslett; Glenn M. (Peoria,
IL), Reinsma; Harold L. (Dunlap, IL) |
Assignee: |
Caterpillar Tractor Co.
(Peoria, IL)
|
Family
ID: |
23667583 |
Appl.
No.: |
05/801,717 |
Filed: |
May 31, 1977 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
420720 |
Nov 30, 1973 |
03887244 |
Jun 3, 1975 |
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Current U.S.
Class: |
305/197 |
Current CPC
Class: |
B62D
55/096 (20130101); B62D 55/202 (20130101) |
Current International
Class: |
B62D
55/20 (20060101); B62D 55/096 (20060101); B62D
55/08 (20060101); B62D 055/08 () |
Field of
Search: |
;305/57,35R,54,53,36,37,38 ;74/216.5,245R,245C,247 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Reeves; Robert B.
Assistant Examiner: Shannon; John P.
Attorney, Agent or Firm: Muir; Robert E.
Claims
What is claimed is:
1. In an endless track assembly of the type used on a vehicle
provided with a drive sprocket having teeth and notches alternately
disposed about the circumference of the sprocket, said track
assembly comprising a pair of laterally upstanding link elements;
parallel pin and bushing elements secured to and interconnecting
respectively opposite ends of the links; a track shoe secured to
the bottoms of said links; the improvement comprising a resilient
impact lug reinforced by reinforcing means including a wear
resistant material secured to the contact end of said impact lug,
said lug being releasably secured to the shoe midway between the
bushing elements, said impact lug having a topmost portion of
greater height from the track shoe than the topmost portion of the
adjacent bushings whereby initial contact is made by said lug so
that impact energy is absorbed by the lug prior to engagement of an
adjacent bushing.
2. The invention of claim 1 wherein the impact lug comprises a
solid body of natural rubber.
3. The invention of claim 2, wherein said solid body further
includes at least one protrusion extending laterally therefrom and
adapted to underlie the edge of an adjacent track shoe.
4. The invention of claim 2, wherein said solid body is provided
with a tapered contact end.
5. The invention of claim 4, wherein said tapered contact end is
provided with a metal tip.
6. In an endless track assembly of the type used on a vehicle
provided with a drive sprocket having teeth and notches alternately
disposed about the circumference of the sprocket, said track
assembly comprising a pair of laterally upstanding link elements;
parallel pin and bushing elements secured to and interconnecting
respectively opposite ends of the links; a track shoe secured to
the bottoms of said links; the improvement comprising a resilient
impact lug in the form of a hollow, generally tubular body .[.of
synthetic plastic material substantially harder than natural
rubber.]. releasably secured to the shoe midway between the bushing
elements, said hollow, generally tubular body being reinforced by
reinforcing means including a reinforcement ply imbedded therein,
comprising a steel wire reinforcement ply circumferentially
imbedded in said hollow, generally tubular body, said impact lug
having a topmost portion of greater height from the track shoe than
the topmost portion of the adjacent bushings whereby initial
contact is made by said lug so that impact energy is absorbed by
the lug prior to engagement of an adjacent bushing.
7. .[.The invention of claim 6, wherein said reinforcement ply
comprises.]. .Iadd.In an endless track assembly of the type used on
a vehicle provided with a drive sprocket having teeth and notches
alternately disposed about the circumference of the sprocket, said
track assembly comprising a pair of laterally upstanding link
elements; parallel pin and bushing elements secured to and
interconnecting respectively opposite ends of the links; a track
shoe secured to the bottoms of said links; the improvement
comprising a resilient impact lug in the form of a hollow,
generally tubular body releasably secured to the shoe midway
between the bushing elements, said hollow, generally tubular body
being reinforced by reinforcing means including a reinforcement ply
imbedded therein, comprising .Iaddend.a fabric reinforcement ply
circumferentially imbedded in said hollow, generally tubular body
.Iadd., said impact lug having a topmost portion of greater height
from the track shoe than the topmost portion of the adjacent
bushings whereby initial contact is made by said lug so that impact
energy is absorbed by the lug prior to engagement of an adjacent
bushing.Iaddend..
8. The invention of claim 6, .Iadd.including a mounting strip
disposed internally of the tubular body, and .Iaddend.wherein the
impact lug is secured to the track shoe by at least one bolt
.[.threadably engaging the body of said lug.]. .Iadd.extending
.Iaddend.between said shoe and .[.a.]. .Iadd.the .Iaddend.mounting
strip. .[.
9. In an endless track assembly of the type used on a vehicle
provided with a drive sprocket having teeth and notches alternately
disposed about the circumference of the sprocket, said track
assembly comprising a pair of laterally upstanding link elements;
parallel pin and bushing elements secured to and interconnecting
respectively opposite ends of the links; a track shoe secured to
the bottoms of said links; the improvement comprising a resilient
impact lug in the form of a hollow, generally tubular body of
synthetic plastic material substantially harder than natural rubber
releasably secured to the shoe midway between the bushing elements,
said tubular body being provided with capping means at the contact
end thereof and contains therewithin spring means biased between a
pair of pressure plates secured within the body at opposite ends
thereof, said impact lug having a topmost portion of greater height
from the track shoe than the topmost portion of the adjacent
bushings of the adjacent bushings whereby initial contact is made
by said lugs so that impact energy is absorbed by the lug prior to
engagement of an adjacent bushing..]. .[.10. The invention of claim
9, wherein said capping means comprises a steel cap..]. .[.11. The
invention of claim 10, wherein said spring means comprises a
plurality of Belleville washers..].
Description
.Iadd.CROSS-REFERENCE
This is a reissue in division for purposes of conversion of letters
patent No. 3,887,244, granted on June 3, 1975. .Iaddend.
BACKGROUND OF THE INVENTION
This invention relates to track assemblies for track-type vehicles.
In particular, this invention relates to an improved impact lug for
such assemblies which minimizes metal-to-metal contact between the
track and frame elements thereof during operation of the vehicle,
and imparts improved wear and operating characteristics to the
assembly.
Conventional endless tracks for use with track-type vehicles such
as crawler tractors comprise a series of track links interconnected
by pins fitted with an external bushing. In such a construction,
the track links have an inner rail surface upon which the track
rollers and idler wheels roll. The pin and bushing connections of
these conventional prior art structures provide a drive means for
coaction with a chain-driving sprocket whereby the track is
forcibly driven by rotational movement of the sprocket.
Although such a track construction has gained wide acceptance, it
is subject to several shortcomings, such as noise created by the
bushings impacting upon the drive sprocket, and the rail surfaces
impacting on the idler. Such conventional structures are also
subjected to a high rate of wear and power losses due to these
impactions and due also to the scrubbing action of the bushings
against the sprocket as the track is driven.
A recent development in the art of endless tracks for track-type
vehicles is the provision of a drive lug located on the track shoes
intermediate the pin and bushing connections to assist the bushings
in driving the track. Although these mid-pitch drive lugs have been
somewhat effective in substantially eliminating a number of the
disadvantages associated with conventional endless tracks, other
disadvantages, such as high noise and wear levels, have not been
satisfactorily overcome. Exemplary of prior art attempts to reduce
noise, wear and other shortcomings of endless track assemblies
include the mid-pitch drive lugs described in U.S. Pat. Nos.
3,563,614; 3,567,294; and 3,680,929; the cushioned assembly and
related components described in U.S. Pat. Nos. 2,338,817 and
3,504,562; and the miscellaneous improvements described in U.S.
Pat. Nos. 3,486,574 and 3,504,951.
Cross reference is made to U.S. application Ser. No. 416,828, to
Boggs et al, filed Nov. 19, 1973, .Iadd.now Pat. No. 3,889,550
.Iaddend.which illustrates another solution to solve the
problem.
Typically, these and other endless track assemblies presently in
use fail to meet the stringent noise limitations for track-type
vehicles imposed by Federal legislation.
SUMMARY AND OBJECTS OF THE INVENTION
Accordingly, the present invention provides an improved impact lug
for an endless track assembly comprising a resilient mid-pitch lug
which minimizes metal-to-metal impact between the track and the
idler and sprocket of a track-type vehicle. The resilient lug
minimizes the customary impact through the absorption of impact
energy by deflection of the resilient lugs prior to engagement of
the track with the sprocket and idler.
The minimization of such metal-to-metal impact by the resilient
impact lug concurrently reduces noise associated with operation of
the vehicle, and increases the wear life of the related track
assembly components. Alternate embodiments of the invention include
resilient drive lugs having improved wear life, lower manufacturing
costs, improved mounting means, sprocket-cleaning means, higher
resiliency quotients for use with relatively larger vehicles, and
alternate means for improved noise reduction.
It is therefore an object of the invention to provide an improved
track assembly for track-type vehicles which minimizes vehicle
noise production during operation and improves the wear life of
assembly components.
It is another object of this invention to provide a resilient
mid-pitch impact lug for endless track assemblies for track-type
vehicles which reduce track noise and wear resulting from customary
metal-to-metal impact of the track against the sprocket and
idler.
It is another object of this invention to provide a resilient
mid-pitch impact lug for endless track assemblies having relatively
high wear resistance and relatively low manufacturing costs.
It is an additional object of this invention to provide a resilient
mid-pitch impact lug for endless track assemblies having improved
means for mounting the lug on the track assembly.
It is a further object of this invention to provide a resilient
mid-pitch impact lug having a sprocket cleaning means.
It is a further object of this invention to provide a resilient
mid-pitch impact lug for endless track assemblies having increased
resiliency for use in conjunction with relatively large track-type
vehicles.
It is yet a further object of this invention to provide a resilient
mid-pitch impact lug for endless track assemblies which reduces
track noise resulting from metal-to-metal impact of track elements
during back flexing of the track.
Other objects and advantages of the invention will be apparent from
the following description and claims and the accompanying drawings
which, by way of illustration, show preferred embodiments of the
present invention and the principles thereof and what are now
considered to be the best modes of applying these principles. Other
embodiments of the invention embodying the same or equivalent
principles may be used, and structural changes may be made as
desired by those skilled in the art without departing from the
scope of the present invention or the purview of the appended
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevation of a track-type vehicle including a
track assembly incorporating a preferred embodiment of the
resilient impact lug of this invention;
FIG. 2 is a fragmentary top plan view of the track assembly of FIG.
1;
FIG. 3 is a fragmentary front elevation view in partial cross
section of the track assembly taken along the lines III--III of
FIG. 2;
FIG. 4 is a fragmentary side elevation view in partial cross
section of the track assembly of FIG. 1 illustrating in detail the
resilient impact lug of this invention; and
FIGS. .[.5-8.]. .Iadd.5-7 .Iaddend.illustrate in detail alternate
embodiments of the invention in partial cross section.
DETAILED DESCRIPTION
With particular reference to FIGS. 1 through 5, a track-type
vehicle such as a crawler tractor generally indicated at 10 is
illustrated, conventionally including an operator station shown
generally at 11 and an engine 12 mounted on a main frame .[.14.].
.Iadd.13.Iaddend.. The main frame 13 is supported by a pair of
laterally spaced track roller frames, one of which is shown at 14.
Each of the track roller frames 14 includes a drive sprocket 16
having a plurality of notches 17 formed therearound, and an idler
wheel 18 having a rim 19 with a raised center portion 21. An
endless track 22 is rotatably mounted around the sprocket 16 and
the idler 18 for driving the tractor 10. The endless track 22 is
constructed from a plurality of articulately connected track link
assemblies, one of which is generally indicated at 23 (FIGS. 2 and
3). The track link assembly 23 includes a pair of links 24 which
are retained in spaced relationship by a pair of track bushings 26
fitted about the outer diameter of a pair of track pins 27, which
are received in a pair of bores 28 of the track links 24. A track
shoe 29 having an inner surface 31 toward the links 24 is secured
to each of the links by a plurality of fasteners such as bolts 32.
As best shown in FIG. 3, the track links 24 include an inner rail
surface 33 upon which the track wheels, such as the idler 18, are
adapted to roll. The endless track 22 is driven by the engagement
of the bushings 26 with the sprocket 16. As will be recognized, the
foregoing is representative of a conventional track-type vehicle
provided with an endless track assembly.
The conventional track assembly described above is shown provided
with the preferred resilient mid-pitch impact lug of this
invention, generally indicated at 34. As best shown in FIG. 2, the
lug 34 is disposed at a central location midway between each of the
bushings 26, and, as best shown in FIGS. 3 and 4, includes a
generally tubular body 36 of an elastomeric material. In the
preferred embodiment of the invention illustrated in FIGS. 1-4, the
elastomeric material is preferably a synthetic plastic having a
hardness substantially greater than natural rubber, e.g.
polyurethane, for better wear- and abrasion-resistance of the lug
34. Also, in the preferred embodiment, the generally tubular body
36 is hollow, reducing the amount of material necessary to form the
lug 34, thereby reducing the manufacturing costs thereof.
Advantageously, a fabric or metal, for example steel, reinforcing
ply 37 may be circumferentially imbedded in the body 36 for
additional strength, or other reinforcing means may be used.
The lug 34 may be formed by conventional means. For example, the
lug 34 reinforced by the ply 37 may be formed by extruding the
material and subsequently cutting it to the proper dimensions.
Alternatively, if the ply 37 is not used, the body 36 may be formed
by injection molding, a preferred method for minimizing
manufacturing costs.
The lug 34 is attached to the inner surface 31 of the track shoe 29
by fastening means such as a pair of bolts 38, as shown in FIG. 3.
The bolts 38 are disposed through the shoe 29 and the wall of the
tubular body 36, and threadably engage a mounting strip 39. A pair
of cylindrical spacers 40 are preferably disposed around the bolts
38 so that a sufficiently torque may be applied to the bolts to
prevent loosening during operations of the vehicle, while avoiding
the exertion of undue compressive force on the lug 34. As shown in
FIG. 4, a shim 41 may be placed under each lug 34 after a
predetermined amount of wear has occurred in the lug, to extend its
useful life.
In the alternate embodiment of the invention shown in FIG. 5, a
resilient drive lug 34a comprises a natural rubber body 36a. Since
the natural rubber is softer than the synthetic plastic material
comprising the lug 34, the body 36a is solid rather than hollow to
provide it with a comparable resiliency or spring rate. The body
36a also includes a mounting strip 39a bonded thereto, which is
threadably engaged by the mounting bolts 38. A particular advantage
of the lug 34a is that, in the event the track 22 jumps the
sprocket 16, the natural rubber body 36a is sufficiently flexible
to be deflected sideways with little or no injurious effects.
In the alternate embodiment shown in FIG. 6, a resilient drive lug
34b includes a solid natural rubber body 36b having a wedge-shaped
tapered end 42. The tapered end 42 forces mud or other
accumulations from the sprocket notches 17 during operation of the
vehicle to prevent the mud from building up therein. Preferably, a
hard tip 43 of steel or other wear-resistant material is bonded or
otherwise secured to the tapered end 42 to provide increased wear
resistance of the lug 34b.
.[.In the embodiment illustrated in FIG. 7, a resilient lug 34c
includes a hollow tubular body 36c having cap means 44 disposed
over one of the open ends thereof and bonded thereto for imparting
increased wear-resistance to the body 36c. The material comprising
the cap means 44 has sufficiently high wear resistant qualities to
increase the wear life of the lug 34c, while at the same time being
sufficiently low in mass to avoid having an appreciably detrimental
effect on the noise abating qualities of the lug. Steel cap means
of low mass may be advantageously used..].
.[.The resilient lug of this invention may be used in conjunction
with additional spring means as illustrated in FIG. 7 to provide a
lug having a greater spring rate, for use for example in
conjunction with relatively large vehicles. As shown, a pair of
spaced pressure plates 46 and 47 are disposed within the hollow
body 34c, and secured thereto, as by bonding. Spring means
comprising two stacks of opposing Belleville spring washers 48,
separated by a spacer 49, are disposed between the pressure plates
46 and 47. A hold-down bolt 51 having a shoulder 52 to limit
compression of the lug 34c cooperates with a nut 53 to secure the
lug to the track shoe 29. The bolt 51 is provided with an enlarged
head 54 which engages the pressure plate 46 for preloading the
washers 48..].
In the alternate embodiment illustrated in FIG. .[.8.].
.Iadd.7.Iaddend., a resilient impact lug 34d includes a solid
rubber body 36d, and a pair of lateral protrusions 56 extending
laterally from the opposite sides thereof. One of the protrusions
56 is disposed adjacent an underlying edge 57 of the adjoining
track shoe 29a to provide a cushion between the adjacent track
shoes 29 and 29a, and the track shoe 29a and the corresponding
track link 24a to reduce metal-to-metal contact customarily
encountered between grouser 58 and the shoe 29 during back-flexing
of the track assembly 22. Although one protrusion 56 is sufficient
to this purpose, two are preferably provided to make the lug 34d
reversible and thereby extend its useful life.
In operation, as the track assembly 22 advances around the track
roller frame 14, each of the individual link sections 24
successively comes into engagement with the idler 18 and the
sprocket 16. On conventional track structures, the initial contact
of such engagement is accompanied by a severe impact between the
bushings 26 at the sprocket and the rail surfaces 33 at the idler.
However, with the present track structure employing the resilient
lug 34, which is dimensioned to be of greater height from the track
shoe inner surface 31 than the topmost portion of the adjacent
bushings 26, such initial contact is made by the lug, as in the
notches 17 of the sprocket and the raised center portion 21 of the
idler, so that the impact energy is absorbed by the lugs prior to
the metal-to-metal engagement of the track with the idler and
sprocket. Therefore, the noise and wear associated with such
metal-to-metal impact is greatly reduced.
As the track is driven clockwise around the sprocket, as best shown
in FIG. 4, the driving tension in each track link section 23
becomes sucessively less, which permits the energy stored in the
lugs 34 to progressively lift the bushings 26 out of engagement
with the sprocket notches 17 to eliminate the scrubbing which
normally occurs therebetween as the track chain leaves at the top
of the sprocket. Thus, the lug 34 eliminates another major source
of wear of the bushings 26 and the sprocket notches 17.
Still another source of track noise is produced from the
metal-to-metal impact between adjoining track shoes, which occurs
when the track is back-flexed, as when the track runs over a rock
or other similar object. The noise produced by such back-bending is
reduced by the utilization of the protrusions 56 provided on the
lug 34d shown in FIG. 8, which contacts the underlying edge 57 of
the adjacent track shoe prior to the metal-to-metal contact of the
edge of one track shoe with the grouser 58 of the following track
shoe. Therefore, the noise is reduced in a manner similar to the
way in which the main body 36d reduces the noise between the track
and the idler and sprocket, as described earlier, by the absorption
of the impact energy the the lug. The protrusions 56 are provided
on both sides of the lug 34d to make the lug reversible.
Although the invention has been hereinbefore described and
illustrated in the accompanying drawings with respect to specific
embodiments, various modifications and changes may be made therein
without departing from the true spirit and scope of the invention,
and thus it is not intended to limit the invention except by the
terms of the appended claims.
* * * * *