U.S. patent number RE32,442 [Application Number 06/832,546] was granted by the patent office on 1987-06-23 for belt tensioning mechanism.
This patent grant is currently assigned to Caterpillar Inc.. Invention is credited to Ronald L. Satzler.
United States Patent |
RE32,442 |
Satzler |
June 23, 1987 |
Belt tensioning mechanism
Abstract
A belt tensioning mechanism is provided for use with a vehicle
having an axle pivotably connected to a frame of the vehicle with
inextensible belts entrained about wheel assemblies mounted on
either side of the vehicle for transmitting tractive effort to the
earth. Some systems provide tensioning of belts by producing a
separating force between only the wheel assemblies on one side of
the vehicle independent from the tensioning of the other side while
others provide tensioning of track having sprocket driving members
by using bulky complicated mechanisms for providing the tensioning
of the track and to provide relative motion of the front axle from
one side to the other. In the subject arrangement, an axle is
connected to a frame by a swivel bearing being slidably disposed on
a pin, such that, the axle moves longitudinally relative to the
frame while still being able to swivel about the pin. Furthermore,
an adjusting mechanism is provided to produce the force necessary
to sufficiently tension the belts to provide frictional drive
between the belts and the drive wheel assemblies. In one of the
embodiments, the adjusting mechanism includes a force generating
mechanism responsive to fluid pressure transmitted thereto from a
pump. This arrangement allows the axle to move relative to the
frame in the longitudinal direction in the event that a foreign
object passes between one of the belts and its respective wheel
assembly without requiring a large bulky mechanism that would be
impractical for use on large industrial vehicles.
Inventors: |
Satzler; Ronald L.
(Princeville, IL) |
Assignee: |
Caterpillar Inc. (Peoria,
IL)
|
Family
ID: |
27073369 |
Appl.
No.: |
06/832,546 |
Filed: |
February 24, 1986 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
563719 |
Dec 20, 1983 |
04537267 |
Aug 27, 1985 |
|
|
Current U.S.
Class: |
180/9.1;
305/154 |
Current CPC
Class: |
B62D
55/30 (20130101) |
Current International
Class: |
B62D
55/30 (20060101); B62D 55/08 (20060101); B62D
055/08 () |
Field of
Search: |
;180/9.1,9.5
;305/10,22,29,30,31,32 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Pekar; John A.
Attorney, Agent or Firm: Burrows; J. W.
Claims
I claim:
1. A belt tensioning mechanism for use on a vehicle having a frame
defining a plane aligned along its longitudinal axis, an axle
connected to the frame at one end of the vehicle and extending
thereacross through said plane, a first pair of wheel assemblies
rotatably mounted on opposite ends of the axle independent of said
frame, a second pair of wheel assemblies drivably mounted on
opposite sides of the frame at the other end of the vehicle, and
first and second inextensible belts respectively entrained about
the wheel assemblies on each side of the vehicle, comprising:
means for .[.universally.]. .Iadd.permitting universal
.Iaddend.swiveling .Iadd.of .Iaddend.said axle relative to said
frame and said centrally disposed plane and for .Iadd.permitting
.Iaddend.sliding .Iadd.of .Iaddend.said axle longitudinally
relative to said frame and said centrally disposed plane; and
.[.means for adjusting the position of said axle relative to said
frame to maintain at least a predetermined tension in said first
and second belts while permitting said universal swiveling and
longitudinal movements of said axle.].
.Iadd.a controllable force generating mechanism connected at one
end directly to the frame and connected at the other end directly
to the axle only between the first pair of rotatably mounted wheel
assemblies, and the controllable force generating mechanism being
adapted to apply and maintain at least a predetermined tension in
the first and second belts while permitting universal swiveling and
longitudinal movements of the axle relative to the
frame.Iaddend..
2. The mechanism, as set forth in claim .[.1.]. .Iadd.16,
.Iaddend.wherein the .[.connecting means.]. .Iadd.means for
universally swiveling .Iaddend.includes a pin and a universally
swiveling bearing slidably mounted on the pin, one of said pin and
swivel bearing being secured to said axle at a point midway between
the ends of the axle and the other of said pin and swivel bearing
being secured to said frame at the one end of the vehicle along
said centrally disposed plane. .[.3. The mechanism, as set forth in
claim 2, wherein the adjusting means includes a force generating
mechanism connected between the frame and the axle and being
adapted to move the axle relative to the frame to establish the
predetermined tension in the first and second belts..]. 4. The
mechanism, as set forth in claim .[.3.]. .Iadd.2.Iaddend., wherein
the force generating mechanism includes a jack mechanism pivotably
and operatively connected at one end to said frame along said
centrally disposed plane and a force transfer mechanism connected
to opposite ends of the axle and
operatively connected to the other end of said jack mechanism. 5.
The mechanism, as set forth in claim 4, wherein the jack mechanism
includes a pivot pin connected to the frame along the centrally
disposed plane longitudinally remote from and in axial alignment
with said pin, a force transmitting member pivotably mounted on
said pivot pin, and a pair of jack assemblies each respectively
connected between opposite ends of the
force transmitting member and the force transfer mechanism. 6. The
mechanism, as set forth in claim 5, wherein the force transfer
mechanism includes a pair of force transmitting arms each connected
between one of
the jack assemblies and one of the ends of the axle. 7. The
mechanism, as set forth in claim 6, wherein each of the jack
assemblies includes a rod end portion and a head end portion with
one of the end portions of the jack assemblies being connected to
the opposite ends of the force transmitting member and the other of
the end portions of the jack
assemblies being connected to the respective force transmitting
arms. 8. The mechanism, as set forth in claim 7, wherein each of
said jack assemblies is adapted to generate at least a
predetermined force on the axle for tensioning said first and
second inextensible belts and is independently movable in response
to one end of the axle moving longitudinally relative to said frame
while maintaining at least said
predetermined tension on said first and second belts. 9. The
mechanism, as set forth in claim 8, wherein the force generating
mechanism includes means for aligning each of said first pair of
wheel assemblies relative to said belt so that said wheel
assemblies are maintained in alignment with
said belt. 10. The mechanism, as set forth in claim 9, wherein each
of said force transmitting arms is pivotably connected to the axle
by a pin joint and said aligning means includes a pair of spindles
respectively pivotably connected to each end of the axle and having
the respective wheel assemblies rotatably mounted on one end of
each spindle, and a pair of adjusting assemblies respectively
connected between each spindle and
the respective force transmitting arms. 11. The mechanism, as set
forth in claim 10, wherein each of said spindles is connected to
the axle at the respective pin joint and each of said adjusting
assemblies are connected
to the other end of the spindles. 12. The mechanism, as set forth
in claim 10, wherein said pair of jack assemblies are operative to
selectively retract said axle and said first pair of wheel
assemblies relative to said second pair of wheel assemblies so that
said first and second belts may be
changed. 13. The mechanism, as set forth in claim 12, wherein said
pin is attached to the frame and said swivel bearing is attached to
said axle.
.Iadd.14. A belt tensioning mechanism for use on a vehicle having a
frame defining a plane aligned along its longitudinal axis, an axle
connected to the frame at one end of the vehicle and extending
thereacross, a first pair of rotatably mounted wheel assemblies
connected to opposite ends of the axle independent of the frame, a
second pair of rotatably mounted wheel assemblies driveably
connected to opposite sides of the frame at the other end of the
vehicle, and first and second inextensible belts respectively
entrained about the wheel assemblies on each side of the vehicle,
comprising:
means for connecting the axle to the frame only between the mid
portion of said axle and said frame at substantially the point of
intersection between said mid portion and said centrally disposed
plane so that said axle is permitted to universally swivel relative
to said frame and said centrally disposed plane and said axle is
permitted to move longitudinally relative to said frame; and
a controllable force generating mechanism connected at one end
directly to the frame and connected at the other end directly to
the axle only between the first pair of wheel assemblies, said axle
being movable longitudinally relative to the frame, and the
controllable force generating mechanism being adapted to apply and
maintain at least a predetermined tension in the first and second
belts and selectively to release the tension for
removal of the belts..Iaddend. .Iadd.15. The mechanism, as set
forth in claim 14, wherein the first and second inextensible belts
frictionally engage the respective wheel assembly of the second
pair of wheel assemblies to provide a frictional driving force
therebetween, said predetermined tension in said belts generated by
the controllable force generating mechanism is sufficient to
maintain said frictional driving
force. .Iaddend. .Iadd.16. The mechanism, as set forth in claim 1,
wherein the first and second inextensible belts frictionally engage
the respective wheel assembly of the second pair of wheel
assemblies to provide a frictional driving force therebetween, said
predetermined tension in said belts generated by the controllable
force generating mechanism is sufficient to maintain said
frictional driving force. .Iaddend.
Description
DESCRIPTION
1. Technical Field
This invention relates to crawler-type vehicles, tractors or
equipment using track as opposed to wheels for providing both
ground support and tractive effort, and more particularly, to
vehicles having an axle extending across the vehicle with a belt
tensioning mechanism provided for tensioning the belts.
2. Background Art
Work vehicles as opposed to vehicles for personnel transport are
generally intended to push or pull other equipment or earth, or
carry a load. Consequently, these vehicles require high tractive
forces between the vehicle and the terrain that is being travelled.
When using a belted track to increase tractive force, a high load
must be generated in the belt in order to minimize slippage between
the belted track and the drive wheels. Various types of tensioning
mechanisms have been suggested for use on track-type vehicles and
on belt-type vehicles to tension each track independently. However,
these vehicles do not use a single axle extending across the
vehicle.
Vehicles using a track tensioning mechanism in conjunction with a
single axle extending across are illustrated in U.S. Pat. No.
1,401,625 issued Dec. 27, 1921 to J. Mader. The vehicle illustrated
in this patent is a small garden tractor and includes a sprocket
drive which does not rely on friction to provide belt drive, but
utilizes a complex and bulky mechanism to provide tensioning of the
track and further provide recoil when objects pass between the
sprocket drive and the track. When attempting to utilize apparatus
of this type in large industrial vehicles, the components would be
unreasonably large and bulky thus prohibiting their practical
use.
The present invention is directed to overcoming one or more of the
problems as set forth above.
DISCLOSURE OF THE INVENTION
In one aspect of the present invention a belt tensioning mechanism
is provided for use on a vehicle having a frame defining a plane
aligned along its longitudinal axis. An axle is connected to the
frame at one end of the vehicle and extends thereacross through the
plane. A first pair of wheel assemblies are rotatably mounted on
opposite ends of the axle and a second pair of wheel assemblies are
driveably rotatably mounted on opposite sides of the frame at the
other end of the vehicle. First and second inextensible belts are
respectively entrained about the wheel assemblies on each side of
the vehicle. A means is provided for connecting the axle to the
frame so that the axle is free to swivel and to slide
longitudinally relative to the frame and the centrally disposed
plane. Also, a means is provided for adjusting the position of the
axle relative to the frame to maintain at least a predetermined
tension in the first and second belts while permitting the
swiveling and longitudinal movements of the axle.
The present invention provides a tensioning mechanism which allows
the axle to swivel about a locus relative to the frame and further
allows the axle to move longitudinally relative to the frame for
absorbing any motions created by one end of the axle moving in a
longitudinal direction. Furthermore, the tensioning mechanism is
compact while still having the ability to produce high forces for
tensioning the belts. The entire mechanism utilized for tensioning
and swiveling of the axle is relatively simple in construction and
does not require large bulky components. This arrangement provides
the high forces necessary for tensioning the belts while still
allowing the axle to move relative to the frame whenever an object
such as a rock, limb or board passes between the belt and the
wheels.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevational view of a vehicle utilizing the
embodiments of the present invention;
FIG. 2 is a front elevational view of the vehicle illustrated in
FIG. 1; and
FIG. 3 is a plan view showing a portion of the vehicle encompassing
an embodiment of the present invention taken generally along the
line III--III in FIG. 2.
BEST MODE FOR CARRYING OUT THE INVENTION
Referring now to the drawings and more particularly to FIGS. 1 and
2, a work vehicle 10 is shown having a chassis 12 and a frame 14
which constitutes a portion of the chassis 12. The frame defines a
longitudinal axis 16 and a plane 18 centrally disposed along the
longitudinal axis 16.
The vehicle includes an axle 20 connected to a front portion of the
frame 14 and has a first pair of wheel assemblies 22,22' rotatably
connected to opposite ends of the axle 20. A second pair of wheel
assemblies 24,24' are respectively connected to opposite sides of a
rear portion of the frame 14. First and second inextensible belts
26,28 are respectively entrained about the wheel assemblies
22,24,22',24' on each side of the vehicle 10. A bogie system 30 is
rotatably connected to the frame 14 on each side of the vehicle 10
and in load sharing contact with the respective belts 26,28 to
share the loads being placed on the belts from the load of the
vehicle as it negotiates the terrain.
Referring now to FIG. 3, a belt tensioning mechanism 31 is
illustrated which more clearly shows an embodiment of the present
invention. A means 32 is provided for connecting the axle 20 to the
frame 14 so that the axle 20 is free to swivel and to slide
longitudinally relative to the frame. The connecting means 32
includes a pin 34 connected to the frame 14 parallel to the
longitudinal axis 16 and along the centrally disposed plane 18. The
connecting means 32 also includes a swivel bearing 36 connected to
the axle 20 and slidably disposed on the pin 34. The swivel bearing
36 includes a race 37 secured to the axle 20 by a snap ring 38 and
a spherical bearing member 39 defining a bore 40 adapted to
slidably mount on the pin 34.
A means 42 is provided for adjusting the axle 20 relative to the
frame 14 to maintain at least a predetermined tension on the first
and second belts 26,28, while permitting the swiveling and
longitudinal movements of the axle 20. The adjusting means 42
includes a force generating mechanism 44 connected between the
frame 14 and the axle 20.
The force generating mechanism 44 includes a jack mechanism 45
pivotably connected at one end to the frame 14 along the centrally
disposed plane 18. The jack mechanism 45 includes a pivot pin 46,
such as a bolt, dowell, etc., connected to the frame 14 along the
centrally disposed plane 18 longitudinally remote from and in axial
alignment with the pin 34. The jack mechanism 45 also includes a
force transmitting member 48 pivotably mounted on the pivot pin 46
and a pair of jack assemblies 50.
Each of the jack assemblies 50 has a rod end portion 52 and a head
end portion 54. Each of the jack assemblies 50 further includes a
housing 56 and a rod 58 connected to a piston 60 which is slidably
disposed in the housing 56. The head end portion 54 is generally
defined by the housing 56 while the rod end portion 52 is generally
defined by the rod 58. The housing 56 of each jack assembly 50
defines first and second ports 62,64 respectively in communication
with head and rod end pressure chambers 66,68 which are separated
by the piston 60. The housing 56 of each jack assembly is connected
to opposite ends of the force transmitting member 48 while the rod
58 of each jack assembly 50 slidably extends through the force
transmitting member 48 at the location of the connection with the
housing 56.
The force generating mechanism 44 also includes a force transfer
mechanism 69, such as, a pair of force transmitting arms 70 each
respectively connected to opposite ends of the axle 20 by
respective pin joints, one shown at 72. The other end of each of
the force transmitting arms 70 is connected to the rod 58 of each
of the jack assemblies 50 by locking nuts 73 in a known manner. The
arms 70 each respectively has a surface 74 in sliding contact with
the opposite ends of the force transmitting member 48. A plurality
of retainers 76 are secured to the member 48 and adapted to
maintain the sliding and alignment relationship between the surface
74 of the arms 70 and the opposite ends of the member 48.
Additionally, the force generating mechanism 44 includes a means 78
for aligning each of the first pair of wheel assemblies 22,22'
relative to the belts 26,28. The alignment means 78 includes a pair
of spindles 80 each pivotally connected to the opposite ends of the
axle 20 at the respective pin joint 72 and a pair of adjusting
assemblies 82 each being connected between the respective spindle
80 and the associated one of the force transmitting arms 70. The
adjusting assembly 82 includes a first bracket 84 secured to the
other end of the spindle 80 and a second bracket 86 secured to the
arm 70 with an adjustable fastener member 88 connected between the
brackets 84,86. As shown, the fastener member 88 is a bolt and nut,
but it is recognized that the fastener member 88 could be replaced
with other known adjustable fastening means. Each of the spindles
80 has the respective wheel assembly 22/22' rotatably connected to
one end thereof.
The force generating mechanism 44 additionally includes a source of
pressurized fluid, such as a pump 90, which draws fluid from a tank
92 in a conventional manner and delivers presssurized fluid to a
switching valve 94 through a conduit 96. A pair of conduits 98,100
respectively connect the switching valve 94 to the inlet ports
64,62 of the jack assemblies 50. The switching valve 94 is
connected to the tank 92 in a conventional manner by a conduit 102
and may be actuated either manually, electrically or hydraulically.
A relief valve 104 is connected to the conduit 96 and adapted to
control the pressure in the conduit 96 to a predetermined maximum
level.
From a review of the Figs. and the above description, it is readily
apparent that numerous modifications and/or combination of elements
could be combined without departing from the essence of the
invention. For example, various forms of hydraulic circuits could
be utilized to extend and/or retract the cylinder disclosed herein
without departing from the essence of the invention.
INDUSTRIAL APPLICABILITY
In the use of work vehicles of this type, the belt tensioning
mechanism 31 as shown in the various embodiments herein is
necessary to provide the high tensions in the belt to prevent
slippage between the drive wheels 24,24' and the first and second
belts 26,28. The tensioning mechanism 31 must generate sufficient
tension in each of the belts 26,28 so that there is a satisfactory
frictional driving force between the drive wheels 24,24' and the
respective belt 26/28. For example, in one vehicle having a gross
weight of 115.7 kN (26,000 lbs.) and a belt width of 61 cm (25
inches), an initial tension of 44.5 kN (10,000 lbs.) in each of the
belts operated successfully. It is recognized that different size
belts would vary in total force needed in the belt to maintain the
frictional driving force between the belts 26,28 and the respective
wheel assemblies. Furthermore, it is necessary to provide recoil of
one side of the axle 20 in the event an object such as a rock,
limb, board, etc. passes between one of the belts 26/28 and the
respective wheel assembly 22/24,22'/24'.
Referring more specifically to the operation of the embodiment
shown in FIG. 3, fluid pressure from the pump 90 is directed to the
pressure chambers 68 of the jack assemblies 50 generating a force
on the piston 60 which is transferred through the rod 58 and the
arms 70 to the axle 20. The bore 40 of the spherical bearing member
39 allows the axle 20 to slide relative to the pin 34.
Consequently, the force transmitted to the axle 20 is further
transferred through the spindles 80 to the pair of wheel assemblies
22,22' and tensions the first and second belts 26,28. The relief
valve 104 controls the maximum pressure in the pressure chambers 68
and consequently controls the tension in the belts 26,28.
When a foreign object passes between, for example, the belt 28 and
the wheel assembly 22', the spindle 80 that is connected to the
wheel assembly 22' moves towards the second wheel assembly 24'. It
is recognized that if pneumatic tires are being used in the wheel
assembly 22' that the tires will take a portion of the recoil and
in many cases will be sufficient to absorb all of the recoil
needed. In the event that the spindle 80 which is connected to the
axle 20 moves towards the second wheel assembly 24', the axle 20
pivots about the other wheel assembly 22 and slides relative to the
pin 34 without inducing any bending moments in the axle 20.
Simultaneously therewith the arm 70 slides along the surface 74
relative to one end of the force transmitting member 48 causing
extension of the rod 58 relative to the housing 56 against the bias
of the pressure in the pressure chamber 68. The fluid displaced in
the pressure chamber 68 as a result of the movement of the rod 58
is forced out the port 64 to the tank 92 through the conduit 98,
the switching valve 94 and the relief valve 104. Since the setting
of the pressure relief valve 104 has not changed, the force on the
axle 20 through the arm 70 does not change with the above-noted
movement. As the foreign object moves out from between the belt and
wheel assembly, the axle 20 returns to its original position by
fluid under pressure entering the pressure chamber 68 causing
movement of the piston 68, rod 58, arm 70, and axle 20.
The swivel bearing 36 further allows the axle 20 to pivot about the
pin 34 in the event one of the wheel assemblies 22,22' runs over a
raised object on the ground. The force transmitting member 48
pivots about the pivot pin 46 thus allowing the jack assemblies 50
and arms 70 to pivot simultaneously with any pivoting movement of
the axle 20 about the pin 34.
In the event that tensioning of the belts 26,28 cause relative
misalignment of the rotating axis of the wheel assemblies 22,22',
the adjusting assemblies 82 are adjusted in order to move the wheel
assembly 22/22' about the pivot point 72 to realign the respective
wheel assembly 22/22'.
If it is desirable to change one or both of the belts 26,28, the
switching valve 94 is moved to its other position thus directing
pressurized fluid to the pressure chambers 66 of the jack
assemblies 50. The pistons 60 and associated rods 58 resulting in
the axle 20 moving along the pin 34 towards the second pair of
wheel assemblies 24,24'. After the new belt(s) have been installed,
the switching valve 94 is returned to the original position thus
directing the pressurized fluid into the pressure chambers 68 of
the jack assemblies 50 to tension the belts as previously
described.
In view of the foregoing, it is readily apparent that the belt
tensioning mechanism 31 shown and described in the various
embodiments provides a simple mechanism having the ability to
provide high tensioning forces in the belts 26,28 while still
allowing the axle 20 of the vehicle 10 to swivel and slide in a
longitudinal direction relative to the frame 14 of the vehicle 10
to compensate for recoil action of one of the wheel assemblies
22,22' relative to the other.
Other aspects, objects and advantages of this invention can be
obtained from a study of the drawings, the disclosure and the
appended claims.
* * * * *