U.S. patent application number 13/266283 was filed with the patent office on 2012-11-22 for track shoe assembly for continuous track vehicles.
This patent application is currently assigned to BLEEDING EDGE ENSYS, LLC. Invention is credited to George R. Sturmon.
Application Number | 20120292983 13/266283 |
Document ID | / |
Family ID | 42991475 |
Filed Date | 2012-11-22 |
United States Patent
Application |
20120292983 |
Kind Code |
A1 |
Sturmon; George R. |
November 22, 2012 |
TRACK SHOE ASSEMBLY FOR CONTINUOUS TRACK VEHICLES
Abstract
An improved track shoe assembly (13) for a continuous track
vehicle (1). The track shoe assembly comprises a pin (17) which is
rotatable relative to the shoe assembly (13). The shoe assembly
comprises an elastomeric tube (31) through which the pin extends,
the elastomeric tube being rotatable with respect to one of the pin
and the shoe assembly and being fixed with respect to the other of
the pin and the shoe assembly.
Inventors: |
Sturmon; George R.; (St.
Charles, MO) |
Assignee: |
BLEEDING EDGE ENSYS, LLC
Dixon
MO
|
Family ID: |
42991475 |
Appl. No.: |
13/266283 |
Filed: |
April 26, 2010 |
PCT Filed: |
April 26, 2010 |
PCT NO: |
PCT/US10/32368 |
371 Date: |
October 26, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61172755 |
Apr 26, 2009 |
|
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Current U.S.
Class: |
305/162 ;
305/160 |
Current CPC
Class: |
B62D 55/211 20130101;
Y10T 29/49952 20150115; B62D 55/26 20130101 |
Class at
Publication: |
305/162 ;
305/160 |
International
Class: |
B62D 55/20 20060101
B62D055/20; B62D 55/21 20060101 B62D055/21 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 30, 2009 |
US |
12650296 |
Claims
1-10. (canceled)
11. An improved track shoe assembly for a continuous track vehicle,
the track shoe assembly comprising a road pad formed of
polyurethane having good abrasion and puncture resistance and
having a Shore hardness of about 90 A to about 95 A.
12. The shoe assembly of claim 11 wherein the pad provides longer
life, in use on a vehicle having a weight in excess of twenty-five
tons, than a conventional rubber pad having superior hysteresis
characteristics.
13. The shoe assembly of claim 11 wherein the shoe assembly
comprises at least one shoe, the shoe comprising a shoe body, the
road pad being attached to a lower face of the shoe body.
14. The shoe assembly of claim 13 wherein the shoe body is a
casting.
15. The shoe assembly of claim 13 wherein the road pad is bolted to
the shoe body.
16. The shoe assembly of claim 13 wherein a road wheel pad is
attached to an upper face of the shoe body.
17. The shoe assembly of claim 16 wherein the road wheel pad is
bonded to the shoe body.
18. The shoe assembly of claim 13 wherein the road wheel pad is
formed of polyurethane.
19. The shoe assembly of claim 18 wherein the road wheel pad has a
Shore hardness of 95 A to 105 A.
20. The shoe assembly of claim 13 wherein the track shoe assembly
comprises two shoes, each shoe having a shoe body and a road pad
attached to the shoe body, each road pad being made of polyurethane
having a Shore hardness of about 90 A to about 95 A.
21. A continuous track vehicle having a track composed of shoe
assemblies of claim 11.
22. The vehicle of claim 21 wherein the vehicle has a weight in
excess of about twenty-five tons.
23. The vehicle of claim 22 wherein the vehicle has a weight in
excess of about fifty tons.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is related to, and claims priority from,
United States Provisional Application Serial No. 61/172,755, filed
26 Apr. 2009, and U.S. application Ser. No. 12/650,296, filed 30
Dec. 2009, the disclosures of which are hereby incorporated by
reference.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
[0002] Not Applicable.
BACKGROUND OF THE INVENTION
[0003] Continuous track vehicles (also known as "track laying"
vehicles) are well known and widely used. The present invention
relates to such vehicles and has particular applicability to
military tanks. The construction of military tanks and their tracks
is well known and is described for example in Cory, U.S. Pat. No.
4,765,694, Kent, U.S. Pat. No. 6,080,493, Soucy et al, U.S. Pat.
No. 7,416,266, Gonzalez, U.S. Pat. No. 7,445,299, and Touchet et
al, U.S. Pat. No. 5,264,290, the disclosures of all of which are
hereby incorporated by reference.
[0004] Briefly, a military tank typically includes two tracks, one
on each side of the vehicle. Each track has a road-engaging side
and an inner side which engages a set of road wheels, as well as a
drive sprocket at the forward or rearward end of the vehicle, an
idler wheel at the other end of the vehicle, and support rollers
along an upper reach of the track above the road wheels. The track
itself is formed of track shoe assemblies. Each assembly typically
includes two track shoes, spaced laterally from each other and
separated by a center guide which guides the track around the road
wheels, drive sprocket, idler wheel and support rollers. Each track
shoe carries an elastomeric inwardly-facing road wheel pad bonded
to its inner face and an elastomeric outwardly-facing road pad
removably mounted to its outer face. The pads are generally rubber,
although composite pads have also been proposed for the road
pad.
[0005] Each track shoe assembly also includes two pin assemblies
extending laterally across and beyond the track shoe assembly. The
pin assemblies hold the two track shoes of each shoe assembly
together in alignment with each other, and the ends of pin
assemblies of adjacent shoe assemblies are connected by end
connectors. In one modern arrangement, the center guide is mounted
on the pin assemblies of adjacent shoe assemblies, so that a
projection part of the center guide straddles adjacent shoe
assemblies, rather than being centered between the track shoes of a
single shoe assembly. Although metal bushings have been used in
tractor-type continuous track vehicles, as described for example by
Wright, U.S. Pat. No. 3,313,578, large continuous track vehicles,
such as military tanks, have used rubber bushings.
[0006] In a military tank or the like, each pin assembly includes a
hollow pin in the form of a steel shaft drilled out to reduce its
weight. Multiple rubber bushings are bonded to the exterior of the
pin. Bonding is typically produced by injection molding the rubber
onto the pin, and then vulcanizing the rubber. The number of
bushings shown in the patent literature is generally two: one for
each track shoe. In practice, seven rubber "donuts" are bonded to
the pin for each track shoe, giving fourteen rubber bushings for
each pin assembly, in an arrangement similar to Krotz, U.S. Pat.
No. 2,430,573. This arrangement allows the rubber to compress and
spread laterally (axially of the pin) when the pin assembly is
forced into the shoe assembly. The rubber conventionally has a
nominal hardness of about 75 A on the Shore hardness scale before
it is compressed by about forty percent when pushed into the sleeve
of the track shoe assembly. The force required to push the pin into
the shoe assembly requires a thirty- to fifty-ton press. For many
years, the art has taught that, "Such compression must be
sufficient so that there is no rotation between the bushing and the
outer sleeve portions or the pin upon bending of the track during
use." (Cory, U.S. Pat. No. 4,840,438 at col. 2, lines 9-12). This
arrangement insures that "relative rotation therebetween [between
the pin and the track shoe] along the length of the pin assembly is
controlled by elastic deformation of the resilient bushing." (Id.
at col. 13, lines 41-43). Because the rubber bushings are bonded to
the pin, there has been no need to machine the pin to close
tolerances, and the pin may have a variation in diameter of as much
as 0.5 mm (0.020'') and may deviate substantially from being
linear. Conventional pin assemblies incorporating compressed
bushings are disclosed in Knox et al, U.S. Pat. No. 1,955,751,
Lamb, U.S. Pat. No. 1,973,214, Knox et al, U.S. Pat. No. 2,089,210,
Knox, U.S. Pat. No. 2,301,954, Saurer et al U.S. Pat. No.
2,332,976, Krotz, U.S. Pat. No. 2,430,573, Reynolds et al, U.S.
Pat. No. 3,357,750, Huhne et al, U.S. Pat. No. 4,139,241, Fix, U.S.
Pat. No. 4,165,906, Ruddell, U.S. Pat. No. 4,195,887, and Wiesner,
U.S. Pat. No. 5,749,634, the disclosures of all of which are hereby
incorporated by reference.
[0007] Cory, U.S. Pat. No. 4,840,438, discloses that the extreme
compression required by the conventional compressed bushings
creates assembly problems and also "results in a greater resistance
to the required bending during use and a consequent greater power
requirement for driving of the associated vehicle." To solve this
problem, Cory molds and bonds the rubber bushing in situ to the pin
and to a pair of sleeve sections having a positioning flange which
fits into a groove in the associated track shoe when the bushing is
compressed about 5% and pressed into the shoe assembly. The flange
and groove prevent rotation of the pin assembly with respect to the
shoe assembly, thereby insuring any relative rotation of the pin
and shoe is controlled by elastic deformation of the rubber. Cory's
arrangement, however, adds considerable complexity and additional
manufacturing requirements, thereby substantially increasing the
cost of the track.
[0008] Particularly with heavy continuous track vehicles, such as
military tanks, the lifetime of the track is very short, frequently
a few hundred miles of use. When the track fails, the vehicle may
become unusable. The failure of tank tracks creates a huge
financial cost and may cause logistical issues and personnel safety
issues. The problem is particularly acute with tanks of the size of
a Bradley Fighting Vehicle having a weight of greater than about
twenty-five tons, an M-60 battle tank having a weight greater than
about fifty tons, or an Abrams M-1 battle tank having a weight
greater than about fifty tons to about seventy-five tons or more.
The problem has long been known, as witnessed for example by
Ruddell, U.S. Pat. No. 4,195,887, filed 1978 ("The compressive and
shear loads placed on the elastomeric bushings far exceed the
capabilities of present elastomers to withstand these loads and the
elastomeric bushings wear out and must be replaced."), Cory, U.S.
Pat. No. 4,840,438, effectively filed 1985 ("The constantly
increasing weight and speed of track laying vehicles has resulted
in a decrease in the track life and a constant increasing need for
track maintenance by either repair or replacement."), or Kent, U.S.
Pat. No. 6,080,493, filed 1998 ("A complete set of tracks for a
U.S. Army M-1 Abrams tank can cost as much as $100,000.00 and may
only last from 300 to 2000 miles.").
[0009] The problems with track life are two-fold. Although the
inner road wheel pads apparently exhibit little wear, the outer
road pads are subject to substantial wear and to hazards such as
puncturing. They are therefore made to be field replaceable.
Second, and more seriously, the rubber bushings rapidly fail. In
practice, the bushings generally fail before the road pads, so the
entire track is frequently replaced before the road pads can be
field replaced. Replacing the entire track requires removing the
tank to a repair facility via a tank carrier vehicle.
BRIEF SUMMARY OF THE INVENTION
[0010] Briefly stated, the present invention provides an improved
track shoe assembly for a continuous track vehicle.
[0011] In accordance with an embodiment of the invention, the track
shoe assembly includes a pin which is rotatable relative to a shoe
of the track shoe assembly. The preferred track shoe assembly
includes two bushings; each bushing has a metal sleeve and an
elastomeric tube bonded to the interior of the sleeve. Each sleeve
is force-fit into a shoe of the track shoe assembly. The pin is
pushed through the elastomeric tubes and in use rotates freely with
respect to the elastomeric tube. The elastomeric tube is preferably
formed of polyurethane. The polyurethane in some embodiments has a
Shore hardness of at least 60 D; in other embodiments, the Shore
hardness is between about 65 D and about 70 D; in yet other
embodiments the Shore hardness is between about 95 A and 110 A.
Generally, the polyurethane is chosen to have excellent hysteresis
properties, that is, it does not build up substantial heat as it is
stressed and released. In some embodiments, the sleeve is a DOM
(drawn over mandrel) steel tube and has a wall thickness of about
0.76 mm to about 2.5 mm (about 0.030'' to about 0.100''); in other
embodiments the sleeve has a wall thickness of 1.5 mm
(0.06'').+-.20%. In an illustrative embodiment, the sleeve has a
diameter of 50.8 mm (2.00''). In some embodiments, the elastomeric
tube has a wall thickness of about 2.5 mm to about 6.4 mm (about
0.1'' to about 0.25''); in other embodiments, the elastomeric tube
has a wall thickness of 5.1 mm (0.2'').+-.15%.
[0012] Because polyurethane, unlike rubber, internally relieves
stresses, because the polyurethane is not prestressed by forcing
the bushing into the track shoe, because the bearing area of the
polyurethane elastomer is greatly increased as compared with
conventional rubber donuts, and because the polyurethane does not
control the rotation of the pin with respect to the shoes by
elastic deformation, the bushings of the present invention will
greatly outwear conventional rubber bushings. The decrease in
differential stress produced by the shoe assemblies of the present
invention extends not only to the bushings but to the pins and
other components of the tracked vehicle, thereby increasing both
performance and durability.
[0013] Because they do not limit rotation of the pin with respect
to the shoe, the bushings of the present invention are also
expected to reduce the energy required to propel the vehicle,
thereby increasing performance and efficiency. The improvements
produced by the present invention are more remarkable in light of
the long-standing belief that bonding of the bushings to prevent
rotation with respect to both the pin and the shoe of the track is
essential to operation of the track. The success of the present
bushings also belies the belief that rotatable mounting of the pins
would lead to standing waves in the upper reaches of the continuous
track and early failure of the track.
[0014] In accordance with another embodiment of the invention, the
pin is machined, preferably centerless ground, to a tolerance of
0.0254 mm (0.001''), thereby permitting the pin to be inserted into
the bushings mounted in the shoes of the track shoe assembly with
the use of a hand-held mallet or sledge. The pin is preferably made
of 4340 steel, heat treated and shot peened for hardness, then
drilled out to reduce its weight.
[0015] The bushing of the present invention is related to the
bushings described in my prior patents, U.S. Pat. Nos. 4,840,395
and 5,988,614, the disclosures of which are hereby incorporated by
reference. The modified bushing of the present invention, however,
has heretofore been considered by those skilled in the art as
unusable in a track shoe assembly of a heavy endless track
vehicle.
[0016] In accordance with another embodiment of the invention, the
road pad of the shoe is formed of polyurethane having good abrasion
and puncture resistance and having a Shore hardness of about 90 A
to 95 A. This pad provides far longer life than the rubber pad,
despite having inferior hysteresis characteristics. The hysteresis
test is currently relied upon as the chief indicator of pad
life.
[0017] In accordance with another embodiment of the invention, the
road wheel pad is made of polyurethane having a Shore hardness of
95 A to 105 A, having good hysteresis characteristics, heat
resistance, and puncture resistance.
[0018] The foregoing and other objects, features, and advantages of
the invention as well as presently preferred embodiments thereof
will become more apparent from the reading of the following
description in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0019] In the accompanying drawings which form part of the
specification:
[0020] FIG. 1 is a view in side elevation of a conventional pin
assembly for use in the continuous track of an M-1 tank.
[0021] FIG. 2 is a view in side elevation of a pin and bushings of
the present invention for use in the continuous track of an M-1
tank.
[0022] FIG. 3 is a view in upper side perspective of two adjacent
shoe assemblies of the present invention.
[0023] FIG. 4 is a top plan view of two adjacent shoe assemblies of
the present invention showing their inner, road wheel pads.
[0024] FIG. 5 is a perspective view of a blank for a bushing for
use with the pin and track shoe assemblies of FIGS. 2-4.
[0025] FIGS. 6A and 6B are perspective and end views, respectively,
of a cast and machined-steel track shoe for use in the present
invention, before bonding of a road wheel pad to its top,
installation of a road pad to its bottom, and installation of
bushings.
[0026] FIG. 7 is a perspective view of a road pad of the present
invention.
[0027] FIGS. 8A and 8B are views in side elevation of an M-1 tank
and an M-60 tank, respectively, in which embodiments of the present
invention may be used.
[0028] Corresponding reference numerals indicate corresponding
parts throughout the several figures of the drawings.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0029] The following detailed description illustrates the invention
by way of example and not by way of limitation. The description
clearly enables one skilled in the art to make and use the
invention, describes several embodiments, adaptations, variations,
alternatives, and uses of the invention, including what is
presently believed to be the best mode of carrying out the
invention.
[0030] As shown in FIG. 8A, an Abrams M-1 tank 1 includes, on each
side, road wheels 3, a drive sprocket 5 at the rear of the vehicle,
an idler wheel 7 at the front of the vehicle, and support rollers 9
along an upper reach of the track above the road wheels. A
continuous track 11 passes around these wheels, sprockets and
rollers and drives the tank 1. The M-60 tank 1' shown in FIG. 8B is
similar, but has six road wheels 3' and has its drive sprocket 5'
at its forward end. Because the M-60 tank lacks the side armor of
the M-1 tank, its support rollers 9' are visible.
[0031] The track 11 is made up of track shoe assemblies 13. Each
shoe assembly 13 includes two shoes 15 mounted side by side on pins
17.
[0032] In this embodiment, the pins 17 are about sixty-five cm
(25.5'') long and 38.1 mm (1.5'') in diameter. The pins are
provided with flats 19 near their ends to accommodate standard
track shoe assembly end connectors 21. Each pin is formed of a
steel shaft drilled out to reduce its weight.
[0033] A center guide 23 is mounted on the pins of adjacent shoe
assemblies, so that a projection part 25 of the center guide
straddles adjacent shoe assemblies, rather than being centered
between the track shoes of a single shoe assembly.
[0034] As thus far described, the construction is that of a
standard military tank, well known in the art for many years.
[0035] In the prior art construction shown in FIG. 1, a pin
assembly includes a steel pin 17' with fourteen rubber donut
bushings 27 bonded to the pin 17'. In accordance with the present
invention, the pin assembly which has heretofore been pressed into
the track shoes is replaced with bushings 31 pressed into the track
shoes and a modified pin 17 which is pushed through the bushings
and rotates freely with respect to the bushings during operation of
the tank.
[0036] Each bushing 31 is formed of an outer sleeve 33 and a
polyurethane tube 35 bonded to the inside of the sleeve 33. In some
embodiments, in which side load is expected, the end of the sleeve
33 may be turned inward sufficiently to prevent or restrain
movement of the polyurethane axially beyond the end of the sleeve
33. The sleeve 33 is a DOM (drawn over mandrel) low carbon steel
tube. The sleeve 33 has a length of 22.9 cm (9'') and has a wall
thickness of 1.9 mm (0.075'') and an outer diameter of 50.80 mm
(2.000''). Although the wall thickness of the sleeve 33 is not
critical, the outer diameter of the sleeve 33 is chosen to give a
line-to-line fit with a tubular opening in the shoes 15 as
described below. The polyurethane tube 35 is formed and bonded to
the sleeve 33 by sand-blasting the inner surface of the tube,
applying a bonding agent, and pouring liquid polyurethane into the
sleeve, around a central mandrel. The central opening in the
polyurethane tube is then bored out to 38.10 mm (1.500'') diameter.
The polyurethane material is chosen to have low hysteresis (low
internal heating with repeated stresses and releases) and an
unstressed hardness of Shore 60 D to 70 D. A suitable material is
sold by ITWC, Inc., Malcom, Iowa, 50157, US, and is identified as
ATRO PL07, having a hardness of 65 D. Another suitable material is
sold by UET, LLC, Peoria, Ariz., 85345, as its 8001-A-82%, having a
hardness of 62 D. The PLOT material has been shown to have a
load-deflection curve similar to that of the rubber conventionally
used in tank track bushings.
[0037] The track shoe 15 is conventionally made of a cast steel
shoe body 37 having a lower face to which a road pad is bolted and
an upper face to which a road wheel pad is bonded. The body 37
includes a bolt hole 39 for accepting a bolt of the road pad and
two cylindrical openings 41 which accept and hold the pin
assemblies of a conventional shoe assembly. The track shoe 15 of
the invention is modified by boring out the openings 41 to give
them a true and uniform diameter of 5.090 cm (2.004''). Because the
openings 41 and bushings are 22.9 cm (9'') long, the fit between
them is tight, requiring on the order of ten to twenty tons of
pressure to install them and providing no rotation between the
bushing and the shoe 15.
[0038] The modified pin 17 is made of 4340 steel, heat treated and
shot peened for hardness, and drilled out to reduce its weight. The
outside diameter of the pin 17 is machined by centerless grinding,
to exactly 38.1 mm (1.5'') in diameter with a tolerance of about
0.0254 mm (0.001''), thereby permitting the pin to be inserted into
the bushings mounted in the shoes 15 of the track shoe assembly 13
with the use of a hand-held mallet or sledge. The pin 17 is
conventionally 64.8 cm (25.5'') long and has flats 19 ground near
each end, to accept conventional connectors 21 which assemble the
track.
[0039] The removable road pad 51 bolted to each shoe 15 is formed
to the same dimensions as a conventional rubber road pad, but is
formed of polyurethane having good abrasion and puncture resistance
and having a Shore hardness of about 92 A. This pad provides far
longer life than the rubber pad, despite having inferior hysteresis
characteristics. The hysteresis test is currently relied upon as
the chief indicator of pad life.
[0040] The road wheel pad 53 bonded to each shoe 15 is made of
polyurethane having a Shore hardness of 95 A to 105 A, having good
hysteresis characteristics, heat resistance, and puncture
resistance.
[0041] Numerous variations in the track shoe assemblies, bushings,
pads, and pins of the present invention, within the scope of the
appended claims, will occur to those skilled in the art. Merely by
way of example, the elastomeric tube 35 could be bonded directly to
the opening 41 of the shoe and the sleeve 33 omitted. This
arrangement would require more aggressive removal of the elastomer,
as by boring or burning, in order to rehabilitate the bushing, but
would permit the wall of the opening 41 to be made thicker if
desired. The shoe 15 may be slightly enlarged, or the diameter of
the pin 17 may be slightly reduced in order to increase the
thickness of the opening 41, of the elastomeric tube 35, or of the
sleeve 33.
[0042] For use with track laying vehicles such as the Bradley
Fighting Vehicle System in which the pin is conventionally
non-circular, the elastomeric tube 35 can be bonded to the pin and
made rotatable with respect to the sleeve 33. Alternatively, an
enlarged circular-cross section can be provided on the central part
of the pin, as by utilizing a modified pin or fitting a sleeve over
the central part of the conventional pin.
[0043] As various other changes could be made in the above
constructions without departing from the scope of the invention, it
is intended that all matter contained in the above description or
shown in the accompanying drawings shall be interpreted as
illustrative and not in a limiting sense.
[0044] All patents and patent applications mentioned herein are
hereby incorporated by reference.
* * * * *