Endless traction band support apparatus

A vehicle supporting endless traction band including an endless resilient band of concavo-convex transverse shape and a pair of assemblies for supporting and protecting opposite sides of the band. The assemblies are similar to conventional roller chains except that the inner support links (those adjacent the sides of the band) are configured to pivot on the chain studs and to define slots into which the side margins of the band are received. A plurality of tension resistant members obliquely span the space between the roller chain assemblies on the concave side of the band to prevent the band from buckling when subjected to concentrated loads.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to vehicle traction apparatus of the type including 
an endless concavo-convex band or loop wheel and more particularly to 
apparatus for supporting the band on a vehicle to improve its load 
supporting characteristics and to improve its longevity. 
2. Description of the Prior Art 
Italian Pat. No. 438,805 and U.S. Pat. No. 2,055,932 disclose structures 
that incorporate an endless band of concavo-convex configuration for use 
as a traction member on a vehicle. Because neither of the prior art 
structures includes mechanism for supporting the side edges of the endless 
band their load capabilities are extremely low and their longevity is 
poor. 
Commonly owned U.S. patent application Ser. No. 867,428, filed Jan. 6, 1978 
by Wolfgang Trautwein discloses an endless traction band and edge support 
structure therefor that is far superior to the systems disclosed in the 
references noted in the preceding paragraph. The band disclosed in the 
Trautwein application is retained in positive sprocket engagement by means 
of transversely extending stud bands having at opposite ends threaded 
studs which are installed coaxially with roller chain rollers disposed at 
opposite side edges of the endless band. Although such system has good 
load supporting characteristics, its longevity is reduced because of the 
flexure of the bands and studs that are experienced during operation. 
SUMMARY OF THE INVENTION 
According to the present invention there is an endless roller chain 
supported at each edge of the endless band. The links on the outer side of 
the roller chain remote from the endless band are substantially 
conventional but the links on the inner side adjacent the band are formed 
to perform two functions: to constitute a part of the chain in resisting 
tension loads applied thereto and to engage and protect the edge margins 
of the endless band. The studs that extend through the rollers and retain 
the links and rollers in assembled relation have at the inner end a 
spherical enlargement with which correspondingly shaped sockets in the 
links adjacent the endless band cooperate to afford limited pivotal 
movement. Accordingly, as the endless band flexes in response to loads or 
in response to movement around the sprockets that support the structure, 
the pivotal movement avoids overstressing any of the parts. 
The loads that can be supported by a traction system of the type under 
consideration is limited by the resistance to buckling possessed by the 
endless band. In operation over smooth surfaces substantial loads can be 
supported, but on terrain where sharp protrusions are likely to be 
encountered, contact with such protrusion imparts a concentrated force on 
the band which can cause it to buckle. According to the present invention, 
there is provided in spanning relation to the endless band on the concave 
side thereof a plurality of tension resistant members which retain the 
band in a curved, load supporting configuration even in the presence of 
concentrated forces thereon that result from contact with a sharp 
protrusion. The modified inner links of the roller chain, referred to 
above, are adapted for engaging opposite ends of the tension resistant 
members. 
To facilitate movement of a track according to the invention around the 
sprockets disposed at opposite ends thereof, the above mentioned tension 
resistant members extend diagonally or obliquely of the direction of 
movement of the band. Accordingly one end of each tension resistant member 
moves around the sprocket ahead of or behind the other end of such member. 
The objects, features, and advantages of the present invention will be more 
apparent after referring to the following specification and the 
accompanying drawings.

DETAIL DESCRIPTION OF A PREFERRED EMBODIMENT 
The supporting and driving mechanism for an endless traction band embodying 
the invention is equivalent to that shown in commonly owned U.S. patent 
application Ser. No. 867,428, filed Jan. 6, 1978 and entitled IMPROVED 
LOOP TRACK MOBILITY SYSTEM; the disclosure of the support and drive system 
from the above cited co-pending application is incorporated herein by this 
reference. Referring more particularly to the drawings, an endless band 12 
is formed of two resilient cores 14 and 16 which, as disclosed in the 
above cited co-pending application, are formed of a plurality of filaments 
adhered to one another to form the cores in a concavo-convex shape as seen 
in FIG. 1. Surrounding the cores and extending therebetween is a body 18 
of flexible material such as rubber which can be reinforced with fibers or 
cords. As can be seen in FIG. 1, the exterior surface of rubber body 18 is 
also of concavo-convex configuration. To the convex surface of rubber body 
18 a hard rubber tread 20 is bonded, the rubber tread constituting the 
exterior and ground contacting portion of the endless traction band. 
Opposite side margins of band 12 are supported by assemblies designated 
generally at 22 and 24 in FIG. 1. Assemblies 22 and 24 include roller 
chains which are engaged in sprockets, not shown herein, but disclosed in 
the above cited co-pending application. Also as disclosed in the 
co-pending application, the endless band 12 is formed of resilient 
material which normally resides in the concavo-convex shape shown in FIG. 
1. Such material is sufficiently flexible however, that it can be deformed 
to a substantially flat condition as it moves around the sprockets which 
support and drive the roller chain. The strength of cores 14 and 16 
determines the load carrying capability of a given structure. 
Because side margin support assemblies 22 and 23 are substantially 
identical to one another, a description of one will suffice as a 
description of both. Referring to FIGS. 3 and 4, edge support assembly 22 
includes a roller chain having a plurality of rollers 24 which are 
supported for rotation on studs 26, the distance between adjacent studs 
being uniform throughout the length of the roller chain and determining 
the pitch thereof. On the outer side of the roller chain remote from 
endless band 12 there is a series of more or less conventional outer links 
28 which alternate with a series of more or less conventional inner links 
30, the links having holes in their opposite ends to accommodate studs 26. 
On the inner side of the roller chain adjacent endless band 12 are inner 
support links 32 and outer support links 34. Support links 32 and 34 
perform several functions, one of which is to cooperate with links 28 and 
30 to complete the roller chain assembly. 
Outer support link 34 has an elongate body portion 36, the opposite ends of 
which define holes 38 which are spaced on centers equal to the pitch of 
the roller chain. As can be seen most clearly in FIG. 4, holes 38 have a 
spherical configuration of the same radius of curvature as a spherical 
enlargement 40 which is mounted on the end of each stud 26 and there 
retained by a flat head 41. Body portion 36 of outer support link 34 has a 
thickness less than the radius so that a portion of spherical enlargement 
40 extends beyond, i.e. to the right as viewed in FIG. 4, body portion 36. 
Inner support link 32 has a similarly dimensioned elongate body portion 42 
which defines spherical holes 44 spaced from one another by a distance 
equal to the pitch of the roller chain. Holes 44 engage the portion of 
spherical enlargement 40 that extends beyond body portion 36. 
Extending inward from the body portions of support links 32 and 34 are 
substantially identical upper flanges 46 and lower flanges 48 which are 
vertically spaced from one another by an amount corresponding to the 
thickness of band 12 so as to provide a slot that receives the side margin 
of the band therebetween and supports and protects the same. As can be 
seen in FIG. 4, the slot between the flanges is slightly narrower at the 
inner or left-hand extremity thereof so as to assure frictional engagement 
between the side margins of band 12 and the inner surfaces of the flanges. 
Such frictional engagement transfers the force imparted to the roller 
chain to the endless band 12. As can be seen in FIG. 3, there is a gap 
between the edges of adjacent flanges so as to permit the roller chain to 
flex as it passes over the sprockets. 
Extending outward from the respective body portions of support links 32 and 
34 is a chain protector plate 49 which overlies rollers 24, studs 26 and 
links 28 and 30 to exclude dirt and the like therefrom. Chain protector 
plate 49 can be provided with one or more strengthening ribs 50 as seen in 
FIG. 4. 
On the inner portion of support link 34 (i.e. the portion remote from tread 
20) there is an integral boss 51 for receiving and retaining the ends of 
tension resistant members 52. An exemplary structure for retaining the 
ends of the tension resistant members is a ball fitting 54 which is 
crimped onto the end of the tension members, boss 51 having a wall 56 that 
defines a slot 58 having a cross-sectional shape corresponding to that of 
the tension resistant member. A relieved volume 60 interior of wall 56 
accommodates ball 54 so that the ends of tension resistant members 52 are 
retained while under tension to outer support links 34. 
As can be seen in FIG. 2, tension resistant members 52 extend diagonally or 
obliquely so that one end of each tension member 52 leads the opposite end 
of the same tension member in order to assure that when the assembly moves 
over the relatively small diameter sprockets, deformation of band 12 into 
a substantially flat transverse shape is made possible. In one structure 
designed in accordance wih the invention the angle between tension members 
52 and the direction of movement of the band is about 55.degree. , an 
angle in the range of about 40.degree. to about 70.degree. being 
considered the approximate preferred range. It will be appreciated that 
the specific angle depends on the chain pitch, the diameter of the 
sprockets, the overall width of the endless track, and like parameters. 
Before a description of the assembly and operation of an endless traction 
band embodying the invention, it should be noted in FIG. 4 that there are 
resilient compression washers 62, 64 and 66 on stud 26 and between the 
parts carried on the stud. Such compression washers are stressed by 
appropriate adjustment of a nut 68 threaded on the protruding end of stud 
26, a retainer 70 being provided to lock the nut in place after it is 
tightened. Compression washers 62, 64 and 66 and elastic seal 67 serve to 
prevent contamination of the lubricated internal bearing surfaces during 
operation. 
In assemblying the support structure of the invention, support links 32 are 
installed onto the edge of the band 12. Next, a spherical enlargement 40 
is placed on a stud 26 and such is introduced through hole 38 in each end 
of outer support link 34. The support link is then pressed onto the side 
margin of band 12 so that the edge of the band retains the enlargement and 
the stud in place within hole 38 of support link 34 and hole 44 of support 
links 32. Finally, rollers 24, links 28 and 30, compression washers 62, 64 
and 66, seal 67 and nut 68 are installed and assembly is completed. Next 
tension resistant members 52 are installed in a crisscross pattern as 
shown in FIG. 2 and are dimensioned such as to slightly stress band 12 
into a somewhat more curved position than it would assume if unloaded. 
When the assembled apparatus is installed under load rollers and engaged 
in sprockets as disclosed in the aforecited co-pending application the 
system is ready for operation. As the tread 20 encounters small 
protuberances, substantial localized loads are imposed on band 12, the 
magnitude of such loads at high speeds exceeding at times the buckling 
strength of cores 14 and 16. The presence of tension resistant members 52, 
however, prevents endless band 12 from buckling even under such high 
concentrated loads because the tension resistant members limit the outward 
movement of the edges of the endless band to prevent such buckling. 
Consequently the inclusion of tension resistant members 52 significantly 
improves the load carrying capability of a given structure without 
materially adding to the weight thereof. 
It is desirable to exclude dirt, small stones and the like from entry 
between tension resistant members 52 and the concave surface of band 12. 
For this purpose (see FIG. 1) the space between the concave surface of 
endless band 12 and tension resistant members 52 is filled with foam 
rubber or like closed cell material indicated at 72, and a fabric 
reinforced elastomer cover sheet is adhesively secured over the tension 
resistant members and bosses 50 so as to exclude dirt and the like. 
Because foam material 72 and cover sheet 74 are extremely light weight, 
they do not add materially to the overall weight of the structure. 
Band 12 experiences almost continuous flexure as it moves over irregular 
ground surfaces and as it moves around the relatively small diameter of 
the sprockets that support the roller chains. Because of the presence of 
spherical enlargement 40 and the spherical surfaces of holes 38 and 44, a 
sufficient degree of pivotal movement is afforded so that the flexure of 
the band does not cause undue wear to the supporting mechanism. 
Thus it will be seen that the present invention provides an improved 
endless traction band support and drive system which is capable of 
supporting greater loads, which has far better longevity than known prior 
art devices, and which can be embodied without significant increase in 
weight. Although one embodiment of the invention has been shown and 
described it will be obvious that other adaptations and modifications can 
be made without departing from the true spirit and scope of the invention.