Crawler belt apparatus

A crawler belt apparatus includes a drive wheel having engaging teeth, a crawler belt having engaging projections engageable with the engaging teeth, and a plurality of discharge passages formed between root bottoms defined by the engaging projections, and top ends of the engaging teeth, for discharging foreign substances such as dirt and sand entered between the root bottoms and the top ends. The foreign substances passing through the discharge passages are not compressed by the drive wheel and hence do not become a solid mass.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to an improvement in a crawler belt 
apparatus and more particularly to a crawler belt apparatus adapted to 
discharge foreign substances such as dirt and sand stuck between engaging 
projections of a crawler belt and engaging teeth of drive wheels thereof. 
2. Description of the Related Art 
Normally, transport vehicles for use on rough terrain employ a crawler belt 
apparatus as shown in FIG. 9A to FIG. 9C hereof. 
FIG. 9A is a sectional view taken transversely of a crawler belt and 
illustrating the engaging relationship between the belt and a drive wheel. 
FIG. 9B is a cross-sectional view taken along line IXB--IXB of FIG. 9A. 
FIG. 9C is illustrates the operation of the crawler belt and the drive 
wheel. 
Crawler belt apparatus 100 is comprised of a drive wheel 101 having on an 
outer periphery thereof a plurality of engaging teeth 102, and a crawler 
belt 105 having on an inner periphery thereof two rows of longitudinally 
spaced engaging projections 106 for engagement with the engaging teeth 
102. The crawler belt 105 is a rubber belt (without any reinforcing core 
cords). As the crawler belt apparatus 100 is used on rough terrain, 
foreign substances 108 such as dirt and sand often get caught between the 
engaging teeth 102 and the engaging projections 106. If the foreign 
substances 108 grow larger and turn into a solid mass, this strongly 
presses on the belt 105, whereby a tension applied to the crawler belt 105 
becomes significantly large compared to a belt tension set upon assemblage 
of the crawler belt apparatus 100. This excessive tension shortens the 
life of the crawler belt 105 and hence is undesirable. 
Moreover, if the foreign substances 108 are compressed and get stuck, it 
becomes difficult for the crawler belt 105 to deform vertically (in a 
direction of the thickness of the belt). As a result, influences of an 
uneven road surface are reflected directly upon a crawler body, thus 
deteriorating the drivability of a crawler vehicle. 
SUMMARY OF THE INVENTION 
With a view to overcome the foregoing problems, there is provided according 
to the present invention a crawler belt apparatus having a drive wheel and 
a crawler belt engageable with the drive wheel, comprising a plurality of 
engaging teeth disposed on an outer periphery of the drive wheel, a 
plurality of engaging projections disposed on an inner periphery of the 
crawler belt along the length thereof and being engageable with the 
engaging teeth, and a plurality of discharge passages formed between root 
bottoms defined by adjacent two of the engaging projections and top ends 
of the engaging teeth, for discharging foreign substances. 
In the crawler belt apparatus thus arranged, foreign substances such as 
dirt and sand entered between the engaging projections of the crawler belt 
and the engaging teeth of the drive wheel can be discharged easily through 
the discharge passages formed between the top ends of the engaging teeth 
and the root bottoms defined by two adjacent engaging projections. 
Consequently, foreign substances can be prevented from growing in amount 
and getting caught between the top ends of the engaging teeth and the 
inner peripheral surface of the crawler belt to become a solid mass. As a 
result, it becomes possible to keep a tension applied to the crawler belt 
substantially constant and maintain the engagement between the drive wheel 
and the crawler belt in a desired condition. Moreover, because no foreign 
substances get caught and become a solid mass, the crawler belt is 
rendered capable of deforming in accordance with a rugged road surface and 
absorbing shocks resulted from running on the rugged road surface. The 
crawler belt apparatus thus achieves stable crawler running. 
In one preferred form, the drive wheel has an increased diameter portion 
provided centrally of an outer periphery thereof and reduced diameter 
portions provided on both sides of the increased diameter portion while 
the reduced diameter portions and the root bottoms jointly define spaces 
therebetween for serving as the discharge passages for discharging foreign 
substances. That is, the increased diameter portion is provided on a 
widthwise center of the outer periphery of the drive wheel to thereby 
provide the discharge passages of equal length on both sides of the 
increased diameter portion. As a result, foreign substances can be 
discharged uniformly through the discharge passages on both sides of the 
increased diameter portion. Further, since only the increased diameter 
portion of the drive wheel is abutted against the inner periphery of the 
crawler belt, least force is applied to compress the foreign substances 
against the inner periphery of the crawler belt. As a result, the 
engagement relationship between the drive wheel and the crawler belt is 
not adversely influenced by the foreign substances and can be maintained 
in a good condition. 
In another preferred form, the engaging projections of the crawler belt 
have a height larger than a height of the engaging teeth of the drive 
wheel while the top ends of the engaging projections are abutted against 
surfaces of the root bottoms of the engaging teeth to thereby provide the 
discharge passages. The discharge passages pass through the belt 
transversely thereof, whereby the foreign substances can be discharged 
smoothly. Additionally, these discharge passages are simple in 
construction. 
In yet another preferred form, the engaging projections of the crawler belt 
have a height larger than a height of the engaging teeth of the drive 
wheel while the engaging teeth are fitted between adjacent two engaging 
projections in a wedge-like fashion to thereby provide the discharge 
passages. These discharge passages pass through the belt transversely 
thereof, as in the foregoing arrangement, and can discharge foreign 
substances smoothly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The following description is merely exemplary in nature and is in no way 
intended to limit the invention or its application or uses. 
Referring to FIG. 1, a transportation crawler vehicle 1 is comprised of two 
groups of crawler belt apparatuses 3, 3 (only one shown) disposed on right 
and left (front-rear of the sheet) sides of a body frame 2, a bed 4 
mounted to an upper part of the body frame for supporting loads thereon, 
an engine 5 with a transmission 5a mounted to a rear part of the body 
frame 2, and a handle 6 extending obliquely upwardly rearwardly from the 
body frame 2. 
Each crawler belt apparatus 3 is comprised of a drive wheel 10 mounted to a 
rear part of the body frame 2, an idling wheel 20 mounted to a frontal 
part of the body frame 2, and a crawler belt 30 disposed between the drive 
wheel 10 and the idling wheel 20. 
Reference numeral 6a denotes a handle grip. Designated by reference numeral 
7 is a clutch lever. Reference numerals 8, 9 designate a brake lever and a 
shift lever, respectively. Reference numerals 29, 29 denote tensioning 
rollers. 
Turning to FIG. 2, an integral part of the crawler belt 30 according to the 
present invention is shown schematically. The drive wheel 10 comprises a 
boss portion 13, a rim 14, a plurality of arms 15 connecting the boss 
portion 13 and the rim 14, and a plurality of engaging teeth 16 projecting 
from both sides of the rim 14, which are molded integrally. The engaging 
teeth 16 are provided on an outer periphery of the drive wheel 10 at a 
predetermined pitch and take the form of bars extending transversely of 
the drive wheel. 
The crawler belt 30 is made from a resilient material such as rubber and 
comprises a looped belt body 31, a plurality of engaging projections 32 
rising from an inner peripheral surface of the belt body 31, and a 
plurality of treads 33 of a given pattern disposed on the outer peripheral 
surface of the belt body 31, which are all formed integrally. The engaging 
projections 32 are provided at a predetermined pitch in two rows. 
Reference is now had to FIG. 3 showing a drive shaft 11 with a hub 12 
mounted thereto and the boss portion 13 mounted to the hub 12. 
The rim 14 is positioned transversely centrally of the wheel and has an 
increased diameter portion 14a of narrow width at an outer periphery 
thereof. On both sides of the increased diameter portion 14a, there are 
provided reduced diameter portions 14b, 14b of generally convex cross 
section. The increased diameter portion 14a is in contact with the inner 
peripheral surface of the belt body 31. The rim 14 is fitted between 
adjacent two of the engaging projections 32, 32 arranged in two rows along 
the length of the belt and thus restricted of its swinging movement in a 
transverse direction (right-left direction in the figure). 
The engaging teeth 16 have radial top ends 16a (hereinafter simply called 
"top ends 16a") which are flush with the reduced diameter portions 14b and 
extend in a transverse direction (right-left direction in FIG. 3) relative 
to the drive wheel 10. Hereinafter, the term "reduced diameter portions 
14b" should be construed as including the "top ends 16a" of the engaging 
teeth 16. 
Referring now to FIG. 4, the engaging portions 32 take the form of 
projections having a cross section of generally involute gear as seen in a 
longitudinal direction (right-left direction in the figure). 
The engaging teeth 16 are of substantially triangular cross section with 
the top ends 16a being circular as seen laterally so that they can be 
fitted into root bottoms 34 defined between two adjacent engaging 
projections 32, 32. It is desirable that the engaging teeth 16 are fitted 
between the adjacent two engaging projections 32, 32 in a wedge-like 
fashion. 
A discharge passage for discharging foreign substances such as dirt is 
formed between the top ends 16a of the engaging teeth 16 (reduced diameter 
portions 14b) and surfaces of the root bottoms 34 defined between the two 
adjacent engaging projections 32, 32 (inner peripheral surface of the 
crawler belt 30). 
Specifically, the discharge passage comprises a space S defined between the 
reduced diameter portions 14b of the rim 14 (top ends 16a of the engaging 
teeth 16) and the surfaces of the root bottoms 34. The engaging 
projections 32 have a height larger than a height of the engaging teeth 
16. 
Returning to FIG. 3, the belt body 31 has a plurality of reinforcing core 
cords 35 embedded therein at a predetermined pitch along the length 
thereof and extending transversely of the belt (in a right-left direction 
in the figure). The core cords 35 have a length substantially equal to a 
dimension between end surfaces of the right and left engaging teeth 16, 16 
(a width dimension of an idling wheel 20 to be described below). That is, 
the crawler belt 30 is reinforced by the core cords 35 only at a 
transverse center thereof. As a result, the center can hardly deform 
transversely. Therefore, the crawler belt 30 can hardly deform on a rugged 
surface of rough terrain, whereby the space (discharge passage) S for 
discharging foreign substances can be maintained in its normal state. 
Turning now to FIG. 5, the idling wheel 20 has a generally bobbin-like 
configuration. The idling wheel 20 is comprised of a boss portion 23 
rotatably disposed on a driven shaft 21 by means of bearings 22, 22, and 
wheel portions 24, 24 of dish-like cross section disposed on transverse 
(right and left) ends of the boss portion 23. 
The right and left wheel portions 24, 24 are spaced from each other such 
that they surround from sideways the engaging projections 32 arranged in 
two rows longitudinally of the belt. Since there is no member fitted in 
the root bottoms 34 (see FIG. 4) formed between the adjacent two engaging 
projections 32, 32, it is therefore not necessary to provide the idling 
wheel 20 with a discharge passage for discharging foreign substances. 
Next, having reference to FIG. 6A and FIG. 6B, discussion will be made as 
to the operation of the crawler belt apparatus 3 arranged as explained 
above. 
In FIGS. 6A and 6B, a space (discharge passage) S designated by hatchings 
is opened in longitudinal and transverse directions relative to the belt. 
Therefore, foreign substances such as dirt and sand moving near the 
bottoms 34 formed between the adjacent two engaging projections 32, 32, 
and the top ends 16a of the engaging teeth 16 (reduced diameter portions 
14b) can get out freely through the space S. As a result, it becomes 
possible to prevent the foreign substances from getting caught between the 
top ends 16a of the engaging teeth 16 and inner peripheral surface of the 
crawler belt 30 and from growing larger and becoming a solid mass. Since 
the foreign substances do not get caught and become a solid mass, a 
tension applied to the crawler belt 30 remains unchanged. 
Since only the increased diameter portion 14a of the drive wheel 10 is 
brought into abutment against the inner peripheral surface of the crawler 
belt 30, the drive wheel 10 as a whole does not compress the foreign 
substances against the inner peripheral surface of the crawler belt 30, 
whereby the foreign substance compressing force can be reduced. 
Due to the reasons explained above, the engagement relations between the 
drive wheel 10 and the crawler belt 30 are held in a desirable condition. 
With the increased diameter portion 14a being positioned transversely 
centrally of the drive wheel 10, the spaces (discharge passages) S at both 
sides of the increased diameter portion 14a are equidistantly spaced from 
each other. Thus, the foreign substances entered into the spaces S can be 
discharged generally uniformly. 
Since the foreign substances entered between the top ends 16a of the 
engaging teeth 16 and the inner peripheral surface of the crawler belt 30 
do not stay there as a solid mass, the crawler belt 30 can deform in 
accordance with bumpy road surfaces to thereby absorb shocks or vibrations 
resulting from running a crawler on such road surfaces. 
In the embodiment just described, the crawler belt apparatus 3 is featured 
in the discharge passages provided between the top ends 16a of the 
engaging teeth 16 and the surfaces of the root bottoms 34 formed between 
the adjacent two engaging projections 32, 32 for discharging foreign 
substances. As can be readily appreciated by those skilled in the art, 
alterations of the apparatus 3 are possible. For example, the apparatus 3 
may be arranged as shown in FIGS. 7A and 7B or FIGS. 8A and 8B. 
In FIGS. 7A, 7B, 8A and 8B, like reference numerals are used for 
corresponding parts shown in FIGS. 1-6 and their detailed discussion will 
therefore be omitted. 
Shown in FIGS. 7A and 7B is a first alteration of the crawler belt 
apparatus 3. More specifically, FIG. 7A is a transverse cross-sectional 
view illustrating an engagement relationship between a crawler belt 30 and 
a drive wheel 10 while FIG. 7B is a cross-sectional view taken along line 
VIIB--VIIB of FIG. 7A. 
The crawler belt apparatus 3 according to the first alteration includes a 
plurality of engaging projections 32 having a height larger than a height 
of engaging teeth 16 of a drive wheel 10. Top ends 32a of the engaging 
projections 32 are brought into abutting engagement with tooth bottoms 16b 
formed between adjacent two engaging teeth 16, 16 to thereby provide 
spaces (discharge passages) S. 
Specifically, the engaging teeth 16 are interconnected at radially proximal 
ends thereof by means of an annular member 17. An outer peripheral surface 
of the annular member 17 acts as tooth bottoms 16b of the engaging teeth 
16. In this case, the increased diameter portion 14a of the rim 14 (see 
FIG. 3) is not required. 
As explained above, in the first alteration, spaces (discharge passages) S 
extending transversely of the belt are formed between the top ends 16a of 
the engaging teeth 16 and the root bottoms 34 defined by the adjacent two 
engaging projections 32, 32. As a result, foreign substance discharge 
efficiency can be increased, because the foreign substances can be 
discharged quickly through the spaces S. 
FIG. 8A and FIG. 8B illustrate a second alteration of the crawler belt 
apparatus 3. Specifically, FIG. 8A is a transverse sectional view showing 
a mode of engagement of a crawler belt 30 and a drive wheel 10 whilst FIG. 
8B is a cross-sectional view taken along line VIIIB--VIIIB of FIG. 8A. 
The crawler belt apparatus 3 according to the second alteration includes a 
plurality of engaging projections 32 having a height larger than a height 
of engaging teeth 16 of a drive wheel 10. The engaging teeth 16 are fitted 
in a wedge-like fashion between adjacent two engaging projections 32, 32 
to thereby provide spaces (discharge passages) S. 
Specifically, the engaging teeth 16 are fitted in a wedge-like fashion 
between adjacent two engaging teeth 32, 32 to thereby provide spaces S 
between top ends 16a of the engaging teeth 16 and the surfaces of the root 
bottoms 34. In this case, the increased diameter portion 14a of the rim 14 
(see FIG. 3) is not required. 
In the second alteration, spaces (discharge passages) S extending 
transversely of the belt are formed between the top ends 16a of the 
engaging teeth 16 and the bottoms 34 defined by the adjacent two engaging 
projections 32, 32. As a result, foreign substance can be discharged 
smoothly via the spaces S. 
As thus far explained in detail, the crawler belt apparatus according to 
the present invention has the discharge passages disposed between the top 
ends of the engaging teeth of the drive wheel and the root bottoms formed 
between the two adjacent engaging projections for discharging foreign 
substances such as dirt and sand. Thus, the foreign substances entered 
between the engaging projections of the crawler belt and the engaging 
teeth of the drive wheel can be discharged easily through the discharge 
passages. Consequently, it becomes possible to avoid such instances where 
foreign substances get caught between the top ends of the engaging teeth 
and the inner peripheral surface of the crawler belt and grow larger to 
become a solid mass. As a result, a tension applied to the crawler belt 
remains unchanged and the engagement between the drive wheel and the 
crawler belt is maintained in a good condition. 
Further, since foreign substances do not get caught in the discharge 
passages, the crawler belt can deform in accordance with a rugged road 
surface, thus absorbing vibrations resulting from running the crawler on 
such a road surface. As a result, the crawler belt apparatus achieves 
stable crawler running. 
The foregoing discussion discloses and describes merely exemplary 
embodiments of the present invention. One skilled in the art will readily 
recognize from such discussion, and from the accompanying drawings and 
claims, that various changes, modifications and variations can be made 
therein without departing from the spirit and scope of the invention as 
defined in the following claims.