U.S. patent number RE34,909 [Application Number 07/807,347] was granted by the patent office on 1995-04-18 for wheel for a track laying vehicle.
This patent grant is currently assigned to Motor Wheel Corporation. Invention is credited to Leslie M. Kindel, Iqbal S. Rai.
United States Patent |
RE34,909 |
Kindel , et al. |
April 18, 1995 |
Wheel for a track laying vehicle
Abstract
A road wheel for a track laying vehicle comprising a metallic
disc and rim part wherein the rim portion of the part is of
toroidal geometry. An elastomeric tire .[.tread.]. .Iadd.part
.Iaddend.is bonded to the outer surface of the rim part and has a
.Iadd.tread with .Iaddend.a cylindrical outer face adapted for
engagement with the track treads of the track laying vehicle. The
cross sectional thickness of the metallic disc and rim part is
substantially uniform throughout the same. The rim portion has a
radially in-turned flange at the free end thereof extending at an
acute angle to the axis of the road wheel. The disc portion merges
with the rim portion integrally through a bend portion and extends
radially inwardly a given distance to provide a track lug wear
surface. The disc portion also has a reverse bend offset axially
toward the outer free edge of the rim portion to provide clearance
for track guide lugs in the operation of said wheel. The rim
portion has a radius of curvature taken in radial cross section in
a plane including the wheel axis generally equal to the radius of
the disc-rim wheel part measured in a plane at right angles to the
wheel axis from the wheel axis to the other curved surface of the
rim part. The tire .[.tread.]. has axially opposite sloping side
walls inclined in a radially inward divergent relationship to one
another. A method of making the road wheel is also disclosed.
Inventors: |
Kindel; Leslie M. (Holt,
MI), Rai; Iqbal S. (Akron, OH) |
Assignee: |
Motor Wheel Corporation
(Lansing, MI)
|
Family
ID: |
27019830 |
Appl.
No.: |
07/807,347 |
Filed: |
December 16, 1991 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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869388 |
May 30, 1986 |
|
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Reissue of: |
407274 |
Sep 14, 1989 |
04950030 |
Aug 21, 1990 |
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Current U.S.
Class: |
305/129; 152/12;
305/193 |
Current CPC
Class: |
B60B
3/005 (20130101); B62D 55/14 (20130101); B60B
3/02 (20130101); B60B 3/008 (20130101); B60B
3/007 (20130101); B60B 2360/50 (20130101); B60B
2310/206 (20130101); B60B 2900/321 (20130101); B60B
2310/212 (20130101); B60B 2310/321 (20130101); B60B
2310/56 (20130101); B60B 2900/111 (20130101); B60B
2310/228 (20130101); Y02T 10/86 (20130101); B60Y
2200/254 (20130101); B60B 2360/102 (20130101) |
Current International
Class: |
B60B
3/00 (20060101); B60B 3/02 (20060101); B60B
19/00 (20060101); B62D 55/14 (20060101); B62D
055/00 () |
Field of
Search: |
;305/23,24,28,21,56,57
;301/95 ;152/1,11,12,323 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0199911 |
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Nov 1986 |
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EP |
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6143 |
|
Jan 1906 |
|
FR |
|
364323 |
|
Jan 1906 |
|
FR |
|
367529 |
|
Jan 1906 |
|
FR |
|
2564040 |
|
Nov 1985 |
|
FR |
|
Primary Examiner: Stormer; Russell D.
Attorney, Agent or Firm: Barnes, Kisselle, Raisch, Choate,
Whittemore & Hulbert
Parent Case Text
This is a continuation Ser. No. 06/869,388, filed on 05/30/86 now
abandoned .
Claims
We claim:
1. A support wheel for a vehicle comprising a disc .[.part.]. and
.[.a.]. rim part .[., said rim part.]. having a rim portion of
toroidal geometry, said rim portion toroidal geometry being defined
by a radially outermost surface of said rim portion having a
uniform radius of curvature taken in radial cross section in a
plane including the axis of rotation of said wheel and being
symmetrical about a radially outermost apex of said toroidal rim
portion, said rim portion being joined to and extending generally
axially from the radially outermost portion of .[.said.]. .Iadd.a
.Iaddend.disc .Iadd.portion of said .Iaddend.part and having .[.at
least.]. .Iadd.only .Iaddend.one free end portion spaced axially of
.[.si.]. .Iadd.said .Iaddend.wheel remote from said radially
outermost .Iadd.portion of said .Iaddend.disc portion, and a
non-pneumatic elastomeric tire .[.tread.]. .Iadd.part
.Iaddend.having a curved inner surface complimentarily matching and
being bonded to said outermost surface of .[.the.]. .Iadd.said
.Iaddend.rim portion and centered on .[.ad.]. .Iadd.and
.Iaddend.also being symmetrical about the apex of said toroidal rim
portion, said tire .Iadd.comprising a .Iaddend.tread having a
smooth circumferentially continuous cylindrical .Iadd.tread
.Iaddend.outer face adapted for engagement with a hard, flat
supporting surface for the vehicle.
2. A wheel as set forth in claim 1 wherein the cross sectional
thickness of said rim portion is substantially uniform throughout
the same.
3. A wheel as set forth in claim 2 wherein said rim portion has a
radially in-turned flange at said one free end thereof extending
convergently toward said disc portion at an acute angle to the axis
of the road wheel.
4. A wheel as set forth in claim 3 wherein said radially in-turned
flange angle ranges between about 35.degree. to 55.degree..
5. A wheel as set forth in claim 4 for use as a road wheel with a
track laying vehicle having track treads which define the hard flat
supporting surface for the vehicle, said tire tread being adapted
for engagement with the track laying vehicle track treads, and
wherein said disc portion merges with said rim portion integrally
through a bend portion and extends radially inwardly a given
distance to provide a track lug wear surface, said disc portion
having a reverse bend portion merging with said wear surface
portion and being offset axially toward the outer free edge of the
rim portion to provide clearance for track guide lugs in the
operation of said wheel, said reverse bend portion also merging
with a wheel hug mounting portion in the central area of said disc
.[.part.]., said wheel hub mounting portion being offset axially
farther from the free end of said rim .[.port.]. .Iadd.portion
.Iaddend.than said radially extending disc wear surface
portion.
6. A road wheel as set forth in claim 5 wherein said tire
.[.tread.]. has axially opposite sloping side walls inclined in a
radially inward divergent relationship to one another.
7. A road wheel as set forth in claim 6 wherein the one of said
tire .[.tread.]. side walls closest to the wheel hub mounting
.Iadd.portion of .Iaddend.said disc-rim part terminates at its
radially inwardly edge with a slight axially outward offset from
the junction of the rim portion with the disc portion of said
.Iadd.disc and rim .Iaddend.part.
8. A road wheel as set forth in claim 6 wherein said side walls
slope at an angle to the axis of the wheel ranging from about
3.degree. to 7.degree..
9. A wheel as set forth in claim 2 wherein said radius of curvature
is generally equal to the radius of the disc-rim wheel part
measured in a plane at right angles to the wheel axis from the
wheel axis to said outer curved surface of said rim portion.
10. The wheel as set forth in claim 2 wherein said tire .[.tread.].
has axially opposite side walls extending radially inwardly from
said tread outer face to respective junctions with said rim portion
outermost surface, and wherein the ratio of the minimum thickness
of said tire .[.tread.]. radially of the wheel to the maximum
radial dimension of said .[.tread.]. .Iadd.tire .Iaddend.measured
from said cylindrical outer face of the tread to the junction of
the side walls of the .[.tread.]. .Iadd.tire .Iaddend.with the rim
portion of the disc-rim part is approximately 1.2.
11. A wheel as set forth in claim 10 wherein the ratio of the
uniform radius of curvature of said radially outermost surface of
said rim portion of the maximum axial dimension of said tire tread
is in the range of about 11.12:6.81 to about 4.35:3.66.
12. A wheel as set forth in claim 4 wherein said wheel is adapted
for use as a road wheel on a track laying vehicle having track
treads which define the supporting surface for the vehicle, said
tire .[.tread.]. being adapted for engagement with the track treads
of the track laying vehicle and said cylindrical outer face of said
tire tread is adapted for engagement with the treads of the track
of the track laying vehicle.
13. The wheel as set forth in claim 12 wherein said tire tread has
axially opposite side walls extending radially inwardly from said
tread outer face to respective junctions with said rim outermost
surface, wherein the ratio of the minimum thickness of said tire
.[.tread.]. radially of the wheel to a maximum radial dimension of
said .[.tread.]. .Iadd.tire .Iaddend.measured from said cylindrical
outer face of the tread to the junction of the side walls of the
.[.tread wit.]. .Iadd.tire with .Iaddend.the rim portion of the
disc-rim part is approximately 1:2 and wherein the ratio of the
uniform radius of curvature of said radially outermost surface of
said rim portion to the maximum axial dimension of said tire
.[.tread.]. is in the range of about 11.12:6.81 to about
4.35:3.66.
14. The wheel as set forth in claim 13 wherein said radius of
curvature is generally equal to the radius of the disc-rim wheel
part measured in a plane at right angles to the wheel axis from the
wheel axis to said outer curved surface of said rim portion.
15. The wheel as set forth in claim 13 wherein said tire
.[.tread.]. side walls are inclined in a radially inward divergent
relationship to one another.
16. The wheel as set forth in claim 11 wherein said disc and rim
parts are formed integrally as one piece from sheet metal, said rim
portion extending generally axially in only one direction from the
radially outermost portion of said disc part to said one free end
portion so as to be cantilevered from said disc part.
17. The wheel as set forth in claim 13 wherein said disc and rim
parts are formed integrally as one piece from sheet metal, said rim
portion extending generally axially in only one direction from the
radially outermost portion of said disc part to said one free end
portion so as to be cantilivered from said disc part.
18. The wheel as set forth in claim 15 wherein said disc and rim
parts are formed integrally as one piece from sheet metal, said rim
portion extending generally axially in only one direction from the
radially outermost portion of said disc part to said one free end
portion so as to be cantilivered from said disc part. .Iadd.
19. A one piece metal support wheel for a vehicle comprising a
metallic disc and rim part having a vehicle mounting disc portion
and a non-pneumatic tire mounting rim portion of toroidal geometry,
said rim portion toroidal geometry being defined by a radially
outermost convex surface of said rim portion having a generally
uniform radius of curvature taken in radial cross section in a
plane including the axis of rotation of said wheel, said outermost
surface of said rim portion extending generally axially from the
radially outermost portion of said disc portion of said disc and
rim part to a radially in-turned free end flange portion of said
rim portion spaced axially of said wheel remote from said disc
portion, said rim portion extending generally axially in only one
direction from the radially outermost portion of said disc portion
to said free end flange portion so as to be cantilevered from said
disc portion, said disc portion merging with said rim portion
integrally through a bend portion in said radially outermost
portion of said disc portion and extending radially inwardly
therefrom to define a bolt circle mounting portion of said disc
portion adapted for removable mounting of said wheel via wheel
fastener means to a vehicle wheel mounting part, said rim portion
outermost surface being disposed radially outwardly of said bend
portion and adapted to receive thereon by bonding thereto a
non-pneumatic tire having a tread defining an outer peripheral
surface adapted for engagement with a supporting surface for the
vehicle. .Iaddend. .Iadd.20. A wheel as set forth in claim 19
wherein said radially in-turned flange portion extends convergently
toward said disc portion at an acute angle to the
axis of the road wheel. .Iaddend. .Iadd.21. A wheel as set forth in
claim 20 wherein said radially in-turned flange portion acute angle
ranges between about 35.degree. to about 55.degree.. .Iaddend.
.Iadd.22. A wheel as set forth in claims 20 and 21 wherein said
wheel is formed from sheet metal such that the cross sectional
thickness of said rim portion is substantially uniform throughout
at least a major portion of the same. .Iaddend. .Iadd.23. A wheel
as set forth in claim 21 for use with a track laying vehicle having
track treads which define a hard flat supporting surface for the
vehicle, said wheel further including a tire part having a tread
defining an outer peripheral surface adapted for engagement with
the track laying vehicle track treads, said tire having an inner
surface complimentarily matching and being bonded to said outermost
surface of said rim portion. .Iaddend. .Iadd.24. A wheel as set
forth in claim 23 wherein said disc portion extends radially
inwardly a given distance from said bend portion to provide a track
lug wear surface, said disc portion having a reverse bend portion
merging with said wear surface portion and being offset axially
toward the outer free edge of the rim portion to provide clearance
for track guide lugs in the operation of said wheel, said reverse
bend portion also merging with said wheel mounting portion in the
central area of said disc and rim part, said wheel hub mounting
portion being offset axially farther from the free end of said rim
portion than said radially extending disc wear surface portion.
.Iaddend. .Iadd.25. A wheel as set forth in claim 23 wherein said
tire has axially opposite sloping side walls inclined in a radially
inward divergent relationship to one another. .Iaddend. .Iadd.26. A
wheel as set forth in claim 25 wherein the one of said tire side
walls closest to the vehicle wheel mounting part terminates at its
radially inwardly edge with a slight axially outward offset from
the junction of the rim portion with the disc portion of said disc
and rim part. .Iaddend. .Iadd.27. A wheel as set forth in claim 25
wherein said side walls slope at an angle to the axis of the wheel
ranging from about 3.degree. to 7.degree.. .Iaddend. .Iadd.28. A
wheel as set forth in claim 23 wherein said outer peripheral
surface of said tire tread is cylindrical, and wherein the radio of
the minimum thickness of said tire radially of the wheel to the
maximum radial dimension of said tire measured from said
cylindrical outer tread face to the junction of side walls of the
tire with said rim portion of said disc
and rim part is approximately 1:2. .Iaddend. .Iadd.29. A wheel as
set forth in claim 23 wherein the ratio of the uniform radius of
curvature of said radially outermost surface of said rim portion to
the maximum axial dimension of said tire is in the range of about
11.12:6.81 to about 4.35:3.66. .Iaddend. .Iadd.30. A wheel as set
forth in claim 19 wherein said radius of curvature is generally
equal to the radius of said disc and rim part measured in a plane
at right angles to the wheel axis from the wheel axis to said outer
curved surface of said rim portion. .Iaddend. .Iadd.31. A wheel as
set forth in claim 20 further including a non-pneumatic elastomeric
tire part having an inner surface complimentary matching and being
bonded to said outermost surface of the rim portion and having an
outer tread surface adapted for engagement with a supporting
surface for the vehicle. .Iaddend. .Iadd.32. A wheel as set forth
in claim 31 wherein said tire tread outer surface comprises a
generally cylindrical outer tread face adapted for engagement with
the supporting surface for the vehicle. .Iaddend. .Iadd.33. A wheel
as set forth in claim 31 wherein said rim portion convex surface is
generally symmetrical about an apex of
the arch of said toroidal rim portion. .Iaddend. .Iadd.34. The
wheel as set forth in claim 33 wherein said radially in-turned
flange portion acute angle ranges between about 55.degree. to about
35.degree.. .Iaddend. .Iadd.35. The wheel as set forth in claim 33
wherein said tire is generally centered on and also generally
symmetrical about the apex of said toroidal rim portion. .Iadd.36.
The wheel as set forth in claim 35 wherein said wheel is formed
from sheet metal such that the cross sectional thickness of said
rim portion is substantially uniform throughout at least as major
portion of the same.
Description
The present invention relates to wheels for track laying vehicles
and, more particularly, to improvements in road wheels for military
tanks and other heavy track laying vehicles.
In track assemblies of crawler-type vehicles a plurality of wheels
are provided in a tandem row on each side of the vehicle to contact
and run upon the associated track and carry the vehicle weight
through the associated suspension systems. One type of known track
or bogie wheel assembly comprises a dual wheel set in which two
wheels, each having a mounting disc or body and a peripheral rim,
are mounted back-to-back onto a hub or spindle, and solid
elastomeric .[.treads.]. .Iadd.tires .Iaddend.are secured to the
outer faces of the dual rims to ride upon the track shoes or
cleats. The mutually facing edges of the dual rims are spaced apart
axially of the wheel to provide clearance for the usual upwardly
protruding track guides of the track shoes as the wheels roll along
the track. In this art, it is common to find special wheel designs
which are characteristically custom made, heavy and expensive.
Some typical examples of such prior art tank or track vehicle road
wheels are disclosed in U.S. Pat. Nos. 3,263,315 and 3,997,217.
Also of interest for their showing of tank idler wheels are U.S.
Pat. Nos. 2,789,438 and 3,013,843.
The previous art of tank road wheel design and manufacture
typically comprised a substantially flat (cylindrical) rim base to
which the rubber tire was bonded. Often the axial edges were curved
inwardly to reinforce the edges and as a concession to the economic
production of such rims. These flat rims were subject to loads
imposed by the tire due to the road forces being absorbed. The flat
rim, having a small thickness in the direction of the major
resultant of the forces and thus a low section modules or beam
strength, was subject to high deformation and stresses.
A further problem in the art arises due to wider rims (axially of
the wheel) being used to allow smaller diameter wheels (a function
of the carrying capacity of the tires) for greater suspension
travel so as to increase mobility over rough terrain. These wider
rims accentuate the deflection and thus the required reinforcement
for the same. Such reinforcement has been accomplished in a variety
of ways, including thicker rim stock, rings attached to the
interior of the tire rim, and location of the wheel disc near the
high deflection point. All of these methods are aimed at reducing
the span between support points to thereby lower overall deflection
and stresses. They also add weight and cost.
Another problem in such road wheels for track laying vehicles
resides in the high stress levels and stress concentrations in the
molded rubber tire affixed to the rim of the wheel. Hysteresis heat
generation in the tread rubber due to high loads and speeds
contributes to premature rubber and rubber-to-metal bond failures.
Also, high compressive and tensile stress concentrations have been
found to exist at the bonded edges of such tires. This is where
most failures have been seen to initiate in current road wheel tire
designs, such as those used on the M1 U.S. military tank. Thus,
despite the use of a relatively thick rubber section in the tire,
which adds weight and cost to the wheel, tire life has not been as
satisfactory as desired in such heavy duty military track laying
vehicle applications.
Accordingly, it is an object of the present invention to provide an
improved road wheel for a track laying vehicle which is constructed
to have a more even distribution of imposed loadings to hereby
reduce deflection stresses of the wheel and tire, thus lowering
overall stresses on the part and allowing either greater life or a
reduction in stock thickness and weight for the same life with
respect to both the wheel and tire.
Another object of the present invention is to provide an improved
method of manufacturing the aforementioned novel wheel of the
invention.
Other objects, as well as features and advantages of the present
invention will become apparent from the following detailed
description and when taken in conjunction with the accompanying
scale drawings, wherein:
FIG. 1 is a side elevational view of one embodiment of a tank road
wheel constructed in accordance with the present invention as
viewed from the hub mounting side of the wheel;
FIG. 2 is a fragmentary cross sectional view taken on the line 2--2
of FIG. 1;
FIG. 3 is a fragmentary composite diagrammatic layout view
illustrating certain progressive steps in the formation of the
wheel of FIGS. 1 and 2 pursuant to one embodiment of the method of
the invention;
FIG. 4 is a fragmentary view of the wheel of FIGS. 1 and 2
sectioned as in FIG. 2, but without the tire thereon illustrating
its mode of deflection under typical load applications;
FIG. 5 is a fragmentary side elevational view of another embodiment
of a tank road wheel constructed in accordance with the present
invention viewed from the hub-mounting side of the wheel;
FIG. 6 is a radial cross sectional view taken on the line 6--6 of
FIG. 5; and
FIG. 7 is a fragmentary view of the wheel of FIGS. 5 and 6,
sectioned as in FIG. 6, but without the tire thereon, illustrating
its mode of deflection under typical load applications.
Referring to FIGS. 1 and 2, one embodiment of a tank road wheel 20
constructed in accordance with the present invention comprises as
one-piece stamped steel disc and rim part 22 including a disc or
"backbone" portion 24 having a hub mounting portion 26 provided
with a center opening 28 and a circular row of mounting holes 30
for receiving suitable wheel mounting fasteners therethrough for
attachment of the wheel to an associated hub or axle spindle. Disc
portion 24 also has a reversely curved portion 32 extending
radially outwardly from mounting portion 26 which merges with a
radially extending outer peripheral margin portion 36, which in
turn is integrally joined through a right angle bend 38 to a rim
portion 40. Rim 40 extends generally axially of the wheel away from
disc portion 24 and merges through a return bend portion 42 at its
outboard edge with an in-turned flange portion 44.
Road wheel 20 also includes a solid rubber tire 50 bonded to the
outer peripheral surface of rim 40 to form a circumferentially
continuous tire surface for the wheel. Tire 50 has a cylindrical
outer periphery which forms a track engaging .Iadd.tread
.Iaddend.surface 52, and laterally opposite sloping side surfaces
54 and 56 which preferably are tapered to diverge radially inwardly
relative to the wheel center axis 58 to accommodate the difference
between the required narrower width of tread face 52 (axially of
the wheel) and the preferred wider axial dimension of rim 40. The
inner peripheral surface 60 of tire 50 exactly matches the exterior
contour of the outer surface 62 of rim portion 40, a match up which
occurs automatically when tire 50 is molded in situ to rim 40.
Preferably side surface 54 terminated tangentially with the
curvature of return bend 42, whereas inboard tire surface 56 is
axially offset in an outboard direction to intersect bend 38 so as
to be slightly spaced axially outwardly from the plane of the
exterior surface of disc margin 36.
The disc-rim part 22 is preferably manufactured in accordance with
the procedure indicated diagrammatically in FIG. 3. In the first
stage of this method a flat sheet stock of suitable metal, such as
SAE 950 HSLA steel modified to meet hardenability requirements and
having a minimum thickness of, for example, 0.300", , is blanked to
form a circular blank of appropriate starting diameter. Preferably
sequentially in the same die set an initial draw stamping operation
is performed to work the blank into a perform having the contour
indicated at 70 in FIG. 3. In the next stage of stamping and
ironing operation is performed to reshape preform 70 into the
configuration illustrated in phantom at 72 in FIG. 3. In a third
operation the upper edge portion 74 of the formed edge flange is
machined off or otherwise edge conditioned to provide an edge 75 of
uniform height and free of burrs, etc. Next, the upright flange
portion is bent inwardly to an angle of approximately 45.degree.
with the blank axis 58 to thereby tip the flange inwardly to the
position shown at 76 in FIG. 3. The final rim forming opertion
curls flange 76 to the position shown at 78 in FIG. 3 so that the
resultant flange 44 will have its final inclination (approximately
55.degree. to axis 58) as shown in FIG. 2. Center hole 28 and bolt
mounting holes 30, if not already integrated in a previous
operation, can then be pierced and/or punched in the disc-rim part
22 while the same is held fixtured by its rim portion 40 to insure
concentricity of the center and bolt holes, 28, 30 with the axis of
rim portion 40. It is to be understood that the residual stresses
in part 22 resulting from the aforementioned drawing and forming
operations are intentionally concentrated primarily in the
tipped-in flange 44 as well as in the central portion of rim 40,
and are beneficial relative to part geometry and design load
application inasmuch as they tend to prevent yielding under load.
That is, work hardening in the finished disc-rim part resulting
from the above-described draw forming and die shaping sequence of
steps is sufficient to increase the yield strength of the part
material in the areas of highest stress so that the stress levels
present will not initiate yielding in the part even under
theoretical overloads.
Preferably, the radially extending margin portion 36 is surface
hardened to Brinell 287- 461 and to a minimum depth of 0.120", ,
the hardening method as per MIL-STD-12515 or using interrupted
quench after induction hardening, with the part to be 400.degree.
F. to 500.degree. F. after quench.
In accordance with one principle feature of the present invention,
the forming of the disc-rim part 22 is predesigned to produce a rim
section 40 having the shape of an arch as viewed in cross section
in FIG. 2. This rim arch preferably has a substantially uniform
radius of curvature in the plane of the drawing (perpendicular to
the radius of curvature of rim section 40 about the axis 58). The
arch of the rim 40 spans from the outermost edge 38 of the disc
portion 24 to the junction of the rim 40 with the return bend 42.
Rim 40 is thus of convex configuration looking in the direction of
the applied load in service. It will thus be understood that the
geometry of rim 40 provides the strength of the classic arch, which
is one of the strongest architectural forms known to man.
In addition, the arch radius of curvature of rim 40 in the
aforementioned axial plane may be substantially equal to the radius
of curvature of rim 40 about the wheel axis 58. Thus, in three
dimensional terms, the curvature of rim portion 40 forms a section
of a sphere and is thus spheroidal, another elemental structure of
great strength. Design and structural analysis may require
different radii of the arch of the rim 40 versus the outside radius
about the wheel axis 58, resulting in a substantially toroidal
surface. Nevertheless, if consistent with other design
specifications and limitations for a given vehicle, such as overall
wheel width and wheel diameter, equal radii of rim curvature and
wheel are preferred, i.e., a truly spherical rim geometry. Thus, as
used herein "toroidal" may be defined as spherical plus or minus
the reqeuired deviation in rim arch radius from such equality to
meet the vehicle wheel envelope specifications. This toroidal
surface may be optimized to minimize stress concentrations due to
imposed loadings, thereby causing the entire surface of the toroid
to support those loads, thereby distributing stresses and keeping
any maximum stress relatively low. Due to this configuration of rim
portion 40, in accordance with the present invention, deflection of
the rim portion is kept to a minimum, thus lowering overall
stresses in the part which in turn results in either greater life,
or a reduction in stock thickness and weight for the same life.
Referring to FIG. 4, the aforementioned improvement in uniformity
of stress distribution can be seen in the manner in which the
disc-rim part 22 deflects under normal service loading as the tank
road wheel rolls on its track under the weight of the vehicle
loading. Compare the solid line position in the unloaded free state
of wheel disc-rim part 22 with the phantom line showing of the part
which shows typical part deflection at its maximum rated loading.
Note that maximum deflection occurs in the displacement of the
in-turned outer edge flange 44. Note also that very little change
occurs in the curvature of the rim portion 40 between unloaded and
maximum deflection positions. It thus will be seen that rim 40, due
to its toroidal section, has the strength to carry the loading out
to the outer rim edge 44, which, due to its C-shaped channel
section, has a strong section modulus relative to the rim portion
40. Relatively even stress distribution thus results so that the
strength of the material is utilized with maximum efficiency.
It has also been found that the angle of the in-turned flange 44
relative to axis 58, or alternatively to the radial plane of the
wheel perpendicular to this axis, affects the desired optimum
stress loading of the part. In the case of the wheel geometry of
the embodiment of FIGS. 1-4 )M1 wheel geometry), an angle of
approximately 55.degree. relative to the radial plane has been
found to be optimal for this effect. In addition, it has been found
that the effect of just changing from the prior art "flat" rim to a
toroidal rim, without changing from the usual radial flange, is
sufficient to reduce the maximum stress by approximately 16% in
this embodiment (design). The rubber thickness of tire 50 and the
rim toroidal diameters are also parameters which are variables in
optimizing the wheel design. Generally speaking, lower stresses can
be obtained utilizing larger toroidal diameters.
Another feature of the design shown in FIGS. 1-4 is the "reverse
backbone" at portion 32. This reverse backbone is located at the
track lug wear surface-disc interface to provide an open wear
surface along disc portion 38. Without this reverse curvature, the
wheel would be susceptible to being "notched" as the track guide
lugs wore against the disc wear surface. Moreover, it has been
found that the provision of the reverse backbone in the disc is not
detrimental or significant to the resulting desired reduction in
the stress levels in the wheel.
Another important feature of the present invention, and presently
believed to be a significant contributor to synergistically
improved results obtained thereby, resides in the configuration of
the molded rubber tire .[.tread.]. .Iadd.part .Iaddend.50 which is
vulcanized to rim section 40. Because of the arched and toroidal
configuration of the interface between .[.tread.]. .Iadd.tire
.Iaddend.50 and rim portion 40, the stresses in the molded rubber
tire 50 are also significantly reduced, thereby reducing stress
crack initiation and retarding growth of the same so as to improve
the rubber life of the tire .[.tread.]. 50. Basically it has been
found that a toroidal supporting surface for the tire
.[.tread.].whether it be an arch or toroidal section such as rim
portion 40 or some other section geometry providing this contour of
outer supporting surface, will cause a reduction in maximum stress
in the road wheel rubber due to a more uniform stress distribution
of loads in and through the rubber .[.tread.]. .Iadd.tire
.Iaddend.50.
Prior art track laying wheels and associated rubber .Iadd.tire and
.Iaddend.tread designs, such as those used in the M1 tank road
wheel tire, have been analyzed and found to indicate high
compressive and tensile stress concentrations at the bonded corner
where most failures have been seen to initiate. However, with the
toroidal supporting surface provided by the rim section 40 of the
present invention, much more uniform stress distribution has been
obtained, thereby increasing the .[.tread.]. .Iadd.tire
.Iaddend.strength-to-weight ratio and allowing greater life for the
.[.tread.]. .Iadd.tire .Iaddend.in addition to that of the wheel
steel or, due to such greater strength-to-weight ratio, a reduction
in thickness of the radial dimension of the tire .[.tread.]. 50
with a concomitant reduction in the weight thereof as well as the
wheel. For example, by providing a toroidal support for the tire
.[.tread.]. 50 in accordance with the present invention, stress
concentrations at the bonded corners of the tire .[.tread.]. are
eliminated, tensile stresses on the lateral face of the tire
.[.tread.]. are decreased, up to 7.3% less rubber is used in the
.[.tread.]. .Iadd.tire .Iaddend., and the .[.tread.]. .Iadd.tire
.Iaddend.retains a stiffness within 5% of prior art designs.
Because of the elimination of stress concentrations and reduction
in tensile stresses, a more durable product is obtained. By
following the aforesaid novel .[.tread.]. .Iadd.tire
.Iaddend.geometry, it is also believed that the use of a higher
than normal modulus rubber compound would further improve
performance of the tire .[.tread.]. and overall performance of the
wheel. In the embodiment of FIGS 1-4, it has been found that the
preferred .[.tread.]. .Iadd.tire .Iaddend.geometry may be expressed
as a ratio of the minimum thickness of tire .[.tread.]. 50 taken
radially of wheel 20 to the maximum radial dimension of .[.tread.].
.Iadd.tire .Iaddend.50 measured from the cylinder defined by the
outer face 52 of .[.tread.]. .Iadd.tire .Iaddend.50 to the junction
of the side walls 54 and 56 of .[.tread.]. .Iadd.tire .Iaddend.50
with the .[.tim.]. .Iadd.rim .Iaddend.portion 38, 40,42 of the
disc-rim part 22, this ratio being approximately 1:2.
FIGS. 5, 6, and 7 illustrate another embodiment of a road wheel 100
for a track laying vehicle constructed in accordance with the
present invention, with those elements corresponding to like
elements in wheel 20 designated by reference numerals with a prime
suffix. Different wheel design specifications have resulted in a
variation of the evolution of the wheel geometry of the present
invention while adhering to the aforementioned general principles
thereof. The wheel 100 of FIGS. 5, 6 and 7 is designed to employ
HSLA steel and the dimensional specifications for an armored combat
earthmover. It will be seen from viewing these Figures that the
toroidal rim concept of the invention is again applied, and weight
reduction, which, of course, is desirable, is also obtained. Thus,
wheel 100 again consists of a disc-rim part 102 with a molded
rubber tire tread 104 having a cross-sectional contour of the
present invention and vulcanized to the outer periphery of the rim.
Flange 44' has a somewhat smaller inner diameter than that of
embodiment 20 due to the different parameters of wheel diameter and
loading in this design. As compared to the prior art present wheel
configuration used for the aforementioned armored combat
earthmover, the embodiment of FIGS. 5 and 6 may be characterized by
way of distinction as having a toroidal rim section 40' and the
reverse in-turned flange 44' (FIG. 6), preferably having an angle
of incidence with the axis 58' of the wheel of 35.degree.. Wheel
100 also has a shallower dish portion 106 than that of the previous
prior art design geometry, i.e., a larger radius of curvature and
less offset axially relative to the mounting hub portion 26' of the
disc-rim part 102.
It has been found that the highest stress location is at the outer
flange 44'. The effect of changing the angle of incidence of flange
44' relative to the axis 58' from 0.degree. to the aforementioned
35.degree. is to shift the point of maximum stress from the tip
(free edge) of the flange back along the outer side edge of the
flange, i.e. toward the return bend portion 42' of the flange.
Again, wheel 100 with the disc-rim part 102 may be formed pursuant
to the procedure described previously in conjunction with FIG. 3.
Likewise, the maximum stress which might be calculated or expected
in the wheel embodiment 100 in the steel portion 102 may be
mitigated by the residual forming stresses developed in shaping the
part 102 according to the method sequence described previously in
conjunction with FIG. 3. The resulting work hardening in the part
is expected to be sufficient to increase the yield strength so that
the stress levels present will not initiate yielding in the
material. In addition, weight savings are obtained in this design,
mainly from the change in the disc backbone or dish 24'.
Again, it has been found, in accordance with the principle feature
of the present invention, that the presence of the toroidal rim 40'
is beneficial in that the same strength could not be maintained
without it at the same stock thickness. As illustrated in the free
state versus loaded conditions in FIG. 7, the presence of the
toroidal rim contour prevents the rim section from deflecting
inwardly radially under load. Again the toroidal rim 40' of wheel
100 cooperates with the cross-sectional contour of the rubber tire
.[.tread.]. 104 as shown in FIG. 6 to improve the performance of
tire 104 by reducing high shear stresses present at the bonded
corners of the .[.tread.]. .Iadd.tire .Iaddend.and by reducing both
maximum and minimum principal stresses along the lateral rim
surface. Although tire .[.tread.]. 104 of wheel embodiment 100 is
relatively thick radially of the wheel as compared with embodiment
20, thinning of this .[.tread.]. .Iadd.tire .Iaddend.section would
provide increased tire life, but not necessarily improve the
performance of the metal disc-rim part 102.
From the foregoing description it will now be appreciated that the
improved road wheel for a track laying vehicle of the present
invention provides several advantages over prior commercial and
military road wheels. The toroidal support of the tire .[.treads.].
significantly reduces the maximum stress concentrations in the
rubber tire, and the toroidal shape of the rim section likewise
minimizes maximum stress concentrations and improves the strength
to weight ratio of the metal part of the wheel. Overall reduction
in weight or an improvement in strength to weight ratio is thus
obtained by the present invention in a very economical fashion.
Although the present invention is particularly designed and adapted
for use with military-type armored or heavy track laying vehicles,
it should be understood that the invention may be used with other
types of crawler vehicles, such as those utilized in earth moving
operations.
In one working example of the present invention constructed in
accordance with FIGS. 1 through 4 of the drawings, wheel embodiment
20 is made to the following specifications:
EMBODIMENT SPECIFICATIONS
______________________________________ Embodiment Specifications
______________________________________ Overall wheel diameter
25.00" Radius of rim 40 measured to its 11.81" outer surface apex
Radius of curvature of toroidal rim section 11.12" 40 in the axial
plane of the drawing Angle of flange 44 relative to axis 58
55.degree. of the wheel Minimum radial thickness of .[.tread.].
.Iadd.tire.Iaddend. 50 .94" Maximum axial dimension of .[.tread.].
.Iadd.tire.Iaddend. 50 6.81" Axial dimension of flat
.Iadd.tread.Iaddend. surface 52 5.73" .[.tread.].
.Iadd.tire.Iaddend. 50 Composition of tread 50 per MIL-W-3100 or
equivalent ______________________________________
EMBODIMENT SPECIFICATIONS ______________________________________
Embodiment Specifications ______________________________________
Material specification of disc-rim part 22 SAE 950 HSLA Mod. Radius
of curvature of bend 42 1.06" Radius of curvature of bend 38 1.06"
Radius of curvature of reverse backbone 32 1.20" Thickness of steel
stock in disc-rim part 22 .300 min"
______________________________________
In accordance with another working example of the wheel constructed
in accordance with the present invention pursuant to the alternate
wheel embodiment 100 of FIGS. 5, 6,and 7, the following
specifications were employed:
EMBODIMENT SPECIFICATIONS ______________________________________
Embodiment Specification ______________________________________
Overall wheel diameter 28" Radius of rim 40' measured to its 12.95"
outer surface apex Radius of curvature of toroidal rim 4.35"
section 40' in the axial plane of the drawing Radius of curvature
of bend 42' .735" Angle of flange 44' relative to axis 58
35.degree. of the wheel ______________________________________
EMBODIMENT SPECIFICATIONS ______________________________________
Minimum radial thickness of .[.tread.]. .Iadd.tire.Iaddend. 104
(28"-25.90") Maximum axial dimension of .[.tread.].
.Iadd.tire.Iaddend. 104 3.66" Axial dimension of flat
.Iadd.tread.Iaddend. surface 108 3.25" of .[.tread.].
.Iadd.tire.Iaddend. 104 Composition of .[.tread.].
.Iadd.tire.Iaddend. 104 per MIL-W-3100 or equiv Material
specification of disc-rim part 102 SAE 950 HSLA modified Radius of
curvature of bend 38' .59" Radius of curvature of reverse backbone
106 1.46" Thickness of steel stock in disc-rim part 102 .229" min
______________________________________
It will also be understood that, although the foregoing description
and drawings describe and illustrate in detail successful working
embodiments of the present invention, to those skilled in the art
to which the present invention relates the present disclosure will
suggest many modifications in construction as well as widely
differing embodiments and applications without hereby departing
from the spirit and scope of the invention. The present invention,
therefore, is intended to be limited only by the scope of the
appended claims and the applicable prior art.
* * * * *