Combination low ground pressure, low turning resistance and self-cleaning track shoe

A combination low ground pressure, low turning resistance, and self-cleaning shoe for an articulated endless track used on track-type vehicles is disclosed. The shoe is formed as a rigid body having a sloping forward planar surface and a sloping rearward surface which each run the length of the shoe and which substantially converge toward each other. Projecting from between the forward and rearward surfaces is a third surface, or traction lug. High-floatation planar bearing surfaces are located on each end of the body and each have a portion adjacent to, and of the same width as the traction lug but increase in width with increasing distance from the lug.

BACKGROUND OF THE INVENTION 
This invention relates to the improvements in track shoes for track-type 
vehicles and particularly to low ground pressure shoes designed for use in 
medium-light or medium-wet soils. 
Modifications to track shoes have been proposed to improve the floatation 
and traction capabilities in light or very wet soils. For a given width 
and length of a track shoe, a number of these modifications involve 
varying the shape of the ground contact surface of the shoe. Such 
modifications usually incorporate a protuberant traction face which has a 
generally V-shaped or triangular face for engaging the ground. 
With some types of low ground pressure shoes, the V-shaped traction face is 
blunt enough or obtuse enough to provide good floatation in light soil, 
but suffers from not having sufficient projection depth to provide good 
traction. 
On the other hand, some type of low pressure shoes may have a projecting 
traction ridge running the length of the shoe to provide traction. 
However, with such designs the turning resistance is necessarily greater 
due to the projecting ridge which is in engagement with the soil. Further, 
the space between the ridge and other parts of the shoe and/or adjacent 
shoes can fill and become compacted with mud or soil to the extent that 
the effectiveness of the traction ridge is much reduced. 
It would be desirable to provide a low ground pressure shoe which, while 
presenting a large surface area to reduce ground pressure, would also 
incorporate a traction ridge member that provides a lower turning 
resistance as well as self-cleaning capability to prevent mud and soil 
from building up on the shoe and reducing the effectiveness of the design. 
It has been found that some types of V-shaped or triangular type low ground 
pressure shoes suffer from the disadvantage of imparting intermittent 
shock loading to the track support structure or portions thereof. This is 
due to the fact that triangular type shoes have a projecting apex which is 
the first portion of the shoe to come into contact with the ground. 
Obviously, a triangular type shoe that must initially support the weight 
of a vehicle on its apex is unstable and will tend to rotate to one side 
or the other of the apex as the shoe sequentially passes beneath, and 
bears the weight of, each track roller. This is especially true when the 
track is operating on a hard surface. 
The tendency of the shoe to rotate about the apex is, and must, be resisted 
by the particular members in the track (e.g., pins and links) to which the 
shoe is secured. During operation of the track, the shoes tend to rock 
about the apex so rapidly that the resulting moments and forces 
transferred to the track links and pins are actually in the nature of 
deleterious shock loadings. Such shock loadings can produce an undesirably 
high component wear rate. Thus, it would be desirable to provide a shoe 
which has the advantages of a triangular traction face yet does not 
generate high shock loads in the track components. 
SUMMARY OF THE INVENTION 
The track shoe of the present invention provides a traction face having a 
novel arrangement of protuberant surfaces which provide 1) a greatly 
increased surface area on the traction face to reduce ground pressure, 2) 
an integral traction lug for projecting into the light or wet soil but 
which is designed so that it also reduces greatly the turning resistance 
of the shoe and 3) a unique arrangement of smooth, planar surfaces with 
curved edges that function to effect self-cleaning of the shoe. 
More specifically, in the preferred embodiment, a substantially hollow, 
reinforced rigid body having a generally protuberant traction face is 
provided with a number of facets or surfaces. Most of the facets or 
surfaces are inclined or slanted with respect to a flat rectangular base 
by which the shoe is mounted on the track. 
In particular, a sloping forward planar surface and a sloping rearward 
planar surface run the length of shoe and substantially converge toward 
each other. An elongated traction lug, which projects from between the 
forward and rearward surfaces, is disposed above, and forward of, the 
center line of the base and midway between each end of the base. 
On each end of the shoe is a planar bearing surface between the forward and 
rearward surfaces which each have a portion adjacent to, and of the same 
width as, the traction lug. Each planar surface flares outwardly from the 
lug and increases in width with increasing distance from the lug. Further, 
each bearing surface is sloped away from the lug towards the base of the 
shoe. A slanting end surface on each end of the shoe marks the termination 
of the planar bearing surface, as well as the termination of the forward 
and rearward surfaces. 
With the multi-faceted protuberant traction face design of the present 
invention, a large overall surface area is presented which lowers the 
ground pressure. Further, the sloping nature of the many surfaces of the 
shoe affords little opportunity for soil or mud to build up on the shoe to 
an undesirable extent. Additionally, the slanting nature of the forward 
and rearward surfaces of the shoe afford little opportunity for mud or 
soil to stick or become compacted between adjacent shoes in the track. 
Moreover, the flared nature of the planar bearing surface provides a 
curved or elliptical edge at the top of the forward and rearward surfaces 
which provides a self-cleaning capability during turning operations. 
Also, since the projecting traction lug does not extend to the ends of the 
shoe, since it merges with the planar bearing surfaces, and since each 
planar bearing surface is sloped away from the lug towards the base of the 
shoe, the shoe turning resistance is greatly reduced. To the extent that 
both planar bearing surfaces on either side of the traction lug slope away 
from the lug (and hence upwardly and away from the ground), the contact of 
the shoe with the ground is similar to the curved surface contact of a 
sphere with the ground. Thus, as it is easier to turn a sphere about an 
axis perpendicular to the ground than a flat plate it is also easier to 
turn the shoe of the present invention about an axis perpendicular to the 
ground. 
To the extent that the planar bearing surfaces become wider at each end of 
the shoe, more stable support is provided as the shoe passes beneath, and 
bears the weight of, each track roller. This reduces any rocking tendency 
and substantially mitigates shock loadings on the track components. 
Numerous other advantages and features of the present invention will become 
readily apparent from the following detailed description of the invention 
and of one embodiment thereof, from the claims and from the accompanying 
drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
While this invention is susceptible of embodiment in many different forms, 
there is shown in the drawings and will herein be described in detail one 
specific embodiment, with the understanding that the present disclosure is 
to be considered as an exemplification of the principles of the invention 
and is not intended to limit the invention to the embodiment illustrated. 
The scope of the invention will be pointed out in the appended claims. 
For ease of description, the apparatus of the invention will be described 
in normal operating position, and terms such as upper, lower, horizontal, 
etc., will be used with reference to this normal operating position. It 
will be understood, however, that apparatus of the invention may be 
manufactured, stored, transported and sold in orientation other than the 
normal operation position described. 
The track shoe of the present invention is generally designated as 12 in 
FIG. 1. The track shoe may be solid but is preferably a substantially 
hollow, reinforced rigid body of steel or other suitable material and has 
a generally protuberant multi-faceted traction face rising from a base 16. 
The base 16 may be a solid plate extending across the bottom of the rigid 
body or may be merely defined by the termination of the perimetric walls 
that comprise the facets of the traction face. Preferably, reinforcing 
members 18 are provided to strengthen the hollow shoe 12. 
Within portions of the base 16, are apertures 20 for receiving bolts (not 
shown) by which the shoe is secured to the track links (not shown). To 
provide a greater surface area and to thus effect a lower ground pressure, 
the protuberant traction face of the shoe has a number of sloping facets 
or surfaces which intersect at generally obtuse angles. Two of these 
surfaces extend substantially the entire length of the shoe and slope 
upwardly from each side edge. One of these is a forward planar surface 22 
and the other is a rearward planar surface 24. Both surfaces 22 and 24 
rise from base 16 and substantially converge toward each other. 
Projecting from between the forward and rearward planar surfaces 22 and 24 
is an elongated track traction lug 28. The traction lug 28 is slightly 
forward of the center line of the base 16, as illustrated in the 
cross-sectional views of FIGS. 3 and 4, and is disposed midway between 
each end of the shoe as best illustrated in FIGS. 1 and 2. The projection 
of the traction lug beyond the forward and rearward surfaces 22 and 24 
obviously functions to dig further into the soft ground and provide a 
means of engagement of the shoe with the ground for withstanding the 
reaction thrust force as the vehicle moves forward. Though the traction 
lug 28 is shown as having a central flat surface, it could be curved or 
arched outwardly from the shoe. 
The traction lug 28 is uniquely designed to curve, or slope, near each end 
30 (as best illustrated in FIG. 2) and to, in a continuous, uninterrupted 
manner, merge with high-floatation planar bearing surfaces 34. The bearing 
surfaces 34 continue sloping down from the top of the lug 28 towards the 
base 16. Further, though a portion of each planar bearing surface 34 
adjacent the lug end 30 is the same width as the lug 28, each planar 
bearing surface 34 flares outwardly from the lug, increasing in width with 
increasing distance from the lug. Consequently, at the end of the shoe, 
the planar bearing surface 34 is considerably wider than the lug 28. The 
increased width of the planar bearing surfaces 34 provide a means for 
effecting reduced ground pressure and thereby provide a high-floatation 
effect. Also, the planar bearing surfaces provide more stable support of 
the shoe as it passes beneath, and bears the weight of, each track roller. 
This reduces the tendency of the shoe to rock and consequently reduces 
shock loading on the track components. It is important to note also that 
because the planar bearing surfaces slope towards the base 16 (hence, 
upwardly and away from the ground) on each side of the lug 28, the 
effectiveness of lug 28 as ground engaging traction device is not 
diminished. 
During turning operations, resistance to such turning is greatly reduced by 
the fact that the bearing surfaces are rising upwardly and away from the 
ground on each end of the shoe. Thus, the profile of ground contact of the 
shoe of the present invention is similar to that of the profile of a 
sphere in contact with the ground. In this respect, the resistance to 
rotation of the shoe about an axis perpendicular to the ground is reduced 
(with respect to a flat, non-sloping shoe) in much the same manner that 
the resistance to rotation of the sphere about an axis perpendicular to 
the ground is less when compared to a flat plate. 
Since each planar bearing surface 34 is formed, essentially, from a sloped 
plane that intersects the forward and rearward planar surfaces 22 and 24, 
curved edges 36 are necessarily formed at those intersections. The edges 
36, when combined with the sloping forward and rearward planar surfaces 22 
and 24, provide a self-cleaning capability. During vehicle turning 
operations, mud or compacted soil will have a tendency to slide along 
these sloping surfaces and the edges 36. Note also that there are no right 
angle corners or crevises in or between the surfaces of the shoe (except 
for the bolt hole areas) in which the mud or soil can build up, stick, or 
become compacted. 
Each end of the shoe 12 has an end surface 40 that terminates on one edge 
at the planar bearing surface 34, on two other edges at the forward and 
rearward planar surfaces 22 and 24, and on the bottom edge at the base 16. 
The end surface 40 preferably slants inwardly towards the center of the 
shoe with increasing shoe height. 
Owing to the slanted and sloping orientation of the surfaces of the track 
face, there is little opportunity for mud or soil to stick between or 
become compacted between adjacent shoes in a track. Thus, as the shoe is 
lifted away from ground contact and passes around the rear drive wheel of 
the track, mud or soil will easily tend to fall away from between the 
shoes. 
Though the surfaces of the protuberant traction face are illustrated as 
being sloping planar surfaces, gently curving surfaces may also be used 
with advantage. Of course, such surfaces would be somewhat more difficult 
to manufacture. 
From the foregoing, it will be observed that numerous variations and 
modifications may be effected without departing from the true spirit and 
scope of the novel concept of the invention. It is to be understood that 
no limitation with respect to the specific apparatus illustrated herein is 
intended or should be inferred. It is, of course, intended to cover by the 
appended claims all such modifications as fall within the scope of the 
claims.