Track roller suspension apparatus for a track-type vehicle

A track roller suspension apparatus for a track-type vehicle having a track frame and a track assembly mounted on the track frame, which includes a shaft rotatably mounted on the track frame, a first arm rotatably mounted on the shaft, a second arm rotatably mounted on the shaft, the first and second arms being arranged crossing each other, and a pair of track rollers each mounted on the respective arms. Resilient pads are disposed between the first and second arms to absorb shock loads.

BACKGROUND OF THE INVENTION 
This invention relates to a track roller suspension apparatus for a 
track-type vehicle. 
In a conventional system, it is well known to provide track rollers in 
rolling contact with the inner periphery of a track of a track-type 
vehicle, such track rollers making up part of an overall vehicle 
suspension system. In general, such track rollers define channels in their 
outer peripheries which engage with inwardly protruding portions of the 
track, so that the track tends to be laterally positioned relative to 
track rollers as the track moves relative to the track rollers. 
An improved track roller suspension apparatus is disclosed in U.S. Pat. No. 
4,097, 093, in which track rollers are flexibly or resiliently mounted on 
a track frame, allowing the loads from the track to be reduced or absorbed 
efficiently. While the apparatus of the above patent has proved relatively 
effective in operation, it is to be understood that under certain 
conditions loads reducing rate of the apparatus is not high enough for 
flexible mounting. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a track 
roller suspension apparatus for a track-type vehicle which can effectively 
reduce loads or shock loads from a track of the vehicle even if such loads 
are imposed entirely on one of a pair of track rollers. 
Another object of the present invention is to provide an improved track 
roller suspension apparatus for a track-type vehicle which can enhance 
operability of the vehicle. 
In accordance with an aspect of the present invention, a track roller 
suspension apparatus is provided for a track-type vehicle having a track 
frame and a track assembly mounted on the track frame, said apparatus 
comprising: shaft means rotatably mounted on said track frame; first arm 
means rotatably mounted on said shaft means, said first arm means having a 
roller mounting lower section and an upper section; second arm means 
rotatably mounted on said shaft means, said second arm means having a 
roller mounting lower section and an upper section, said first and second 
arm means being arranged crossing each other; first roller means rotatably 
mounted on the roller mounting lower section of said first arm means; and 
second roller means rotatably mounted on the roller mounting lower section 
of said second arm means. 
The above and other objects, features and advantages of the present 
invention will be readily apparent from the following description taken in 
conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention will now be described in detail with reference to the 
accompanying drawings. Before describing the present invention, however, 
the prior art systems will first be described with reference to the 
accompanying drawings since further description of the prior art system in 
considered essential for the better understanding of the features and 
advantages of the present invention. 
FIG. 1 shows schematically the system disclosed in U.S. Pat. No. 4,097,093 
which comprises an arm O adapted to pivot about a fulcrum P and having a 
leg member Q pivotally mounted thereto, said leg member Q having rollers R 
and S rotatably carried at both ends thereof, and a spring V resiliently 
connected between the arm O and a track frame. 
In the first case, when a load F is exerted uniformly on the rollers R and 
S as shown in FIG. 1, the following relative equation is applicable. 
EQU F=kx (k:spring constant, x: stroke) 
In the second case, when the load F is exerted only on the roller R as 
shown in FIG. 2, the following relative equation is aplicable. 
EQU F=(a/b).sup.2 kx 
In the third case, when the load F is exerted only on the roller S as shown 
in FIG. 3, the following equation is applicable. 
EQU F=(a/c).sup.2 kx 
As can be seen from FIGS. 2 and 3, in the case where the balance effect is 
unavailable, or only one roller is subjected to a load, the load reduction 
rate varies because of difference in sring constant. In the case of the 
arrangement shown in FIG. 2, if the spring constant "k" is set at a proper 
value to achieve a sufficient load reduction, it will be too small for the 
other two cases thereby giving a bad influence on the operability of the 
vehicle. 
The quantitative explanation of the foregoing will now be made hereinbelow. 
1. Load F exerted only on roller S as shown in FIG. 3 (wich is referred to 
as "case 3" below.) 
A prior art rigid suspension system is shown in FIG. 4, while flexible 
suspension systems are shown in FIGS. 5A, 5B and 5C. 
##EQU1## 
The variables k.sub.o and F.sub.o are a spring constant and a load, 
respectively, in the case of the rigid suspension system. The variables k' 
and F' are a spring constant and a load, respectively, in the case of the 
flexible suspension system. E is an impact energy. The suspension system 
of FIG. 5A is equivalent to these of FIGS. 5B and 5C. The spring constant 
in the arrangement of FIG. 5C is k' which is the spring constant of the 
flexible suspension system. 
The following equation is obtained from FIGS. 5B and 5C. 
##EQU2## 
From the equation 1 , the following equation can be derived. 
##EQU3## 
.alpha. is a load reduction rate of the flexible suspension relative to the 
rigid suspension. 
##EQU4## 
Substitution of .alpha.=0.7 which is a load reduction rate considered to be 
enough from the empirical rule in the above equation gives the following 
equation. 
##EQU5## 
2. Load F exerted only on roller R as shown in FIG. 2 (which is referred to 
as "case 2" below.) 
A rigid suspension system is shown in FIG. 6, while flexible suspension 
systems are shown in FIGS. 7A, 7B and 7C. 
##EQU6## 
The variables k" and F" are a spring constant and a load, respectively, in 
the case of the flexible suspension system. The suspension system of FIG. 
7A is equivalent to those of FIGS. 7B and 7C. 
From FIGS. 7B and 7C, the following equation is obtained. 
##EQU7## 
Substitution of the equation 2 in the above equation gives the following 
equation. 
EQU F"=0.947F.sub.o 
3. Load F exerted uniformly on rollers R and S as shown in FIG. 1 (which is 
referred to as "case 1" below.) 
A rigid suspension system is shown in FIG. 8, while flexible suspension 
systems are shown in FIGS. 9A and 9B. 
##EQU8## 
The variables k'" and F'" are a spring constant and a load, respectively, 
in the case of the flexible suspension system. 
Since the suspension system of FIG. 9A can be set to be equivalent to that 
of FIG. 9B, the following equation is obtained. 
##EQU9## 
Substitution of the equation 2 in the above equation gives the following 
equation. 
EQU F'"=0.827 F.sub.o 
Therefore, the load exerted on either one of the rollers R and S will be as 
follows. 
EQU f=0.413 F.sub.o 
Referring now to FIGS. 10 to 14 which show a lower track roller suspension 
system according to the present invention, reference numeral 1 denotes a 
track frame, the lower surface of which has a bearing member 2 fixedly 
secured thereto by means of bolts 2a, the bearing member 2 having a shaft 
pin 3 rotatably mounted thereto. 
Arm members 4 and 5 are attached to the shaft pin 3 so that they can 
oscillate. The arm member 4 has a roller mounting portion 6 formed in one 
end thereof and an upper carrier portion 7 formed in the other end 
thereof. The arm member 4 has an opening 8 formed in the approximately 
central part thereof. 
The arm member 5 has an upper carrier portion 9 formed in one end thereof 
and a roller mounting portion 10 formed in the other end thereof. 
The carrier portion 9 of the arm member 5 extends through the opening 8 of 
the arm member 4 and is located above the roller mounting portion 6 
thereof. The carrier portion 7 of the arm member 4 is located above the 
roller mounting portion 10 of the arm member 5. 
The roller mounting portions 6 and 10 of the arm members 4 and 5 have 
rollers 11 and 12 rotatably mounted thereto. 
Fixedly secured to the carrier portion 7 of the arm member 4 is a rubber 
pad 13, while fixedly secured to the upper surface of the roller mounting 
portion 10 of the arm member 5 is a rubber pad 14. The rubber pads 13 and 
14 abut against each other and form a resilient member A. 
Fixedly secured to the carrier portion 9 of the arm member 5 is a rubber 
pad 15, while fixedly secured to the upper surface of the roller mounting 
portion 6 of the arm member 4 is a rubber pad 16. The rubber pads 15 and 
16 abut each other and form a resilient member B. 
Fixedly secured to the track frame 1 are stoppers 20 and 21. The 
arrangement is made such that, when only one of the track rollers 11, 12 
which is in rolling contact with the track frame 1 is subjected to the 
load, the corresponding arm's carrier portion 7 or 9 will strike against 
the stopper 20 or 21. 
The roller suspension systems thus constructed and including resilient 
members A and B having a spring constant K are schematically shown in 
FIGS. 15 to 17. 
In the case the load F is exerted uniformly on the rollers 11 and 12, the 
following relative equation is applicable. 
EQU F=8kx (k: spring constant, x: stroke) 
In the case the load F is exerted only on the roller 11 as shown in FIG. 
16, the following relative equation is applicable. 
EQU F=2kx 
Similarly, when the load F is exerted only on the roller 12 as shown in 
FIG. 17, the following relative equation is applicable. 
EQU F=2kx 
In view of the foregoing, where only one roller is subjected to the load F, 
an equivalent load reduction effect can be obtained because of having a 
symmetrical configuration and an equal spring constant. 
Further, if the spring constant k is set at a value to achieve a sufficient 
load reduction when only one roller is subjected to the load F, the spring 
constant will not reduce appreciably even when the two rollers are 
subjected to the load, thereby giving little influence on the operability 
of the vehicle. 
The quantitative explanation of the foregoing will now be made hereinbelow. 
5. Load exerted uniformly on the (which are referred to as "case 2" and 
"case 3" below.) 
A rigid suspension system is shown in FIG. 18, while flexible suspension 
systems are shown in FIGS. 19A, 19B and 19C. 
In the similar manner as in the aforementioned case, the following equation 
is obtained. 
##EQU10## 
Where k.sub.o and F.sub.o are a spring constant and a load, respectively, 
in the case of the rigid suspension, while K' and F' are a spring constant 
and a load, respectively, in the case of the flexible suspension, and E is 
an impact energy. 
The suspension system of FIG. 19A can be set to be equivalent to those of 
FIGS. 19B and 19C. The spring constant in the arrangement of FIG. 19C is 
k' which is the spring constant of the flexible suspension system. 
From FIGS. 19B and 19C, the following equation is obtained. 
##EQU11## 
Substitution of the equation 5 in the above equation gives the following 
equation. 
##EQU12## 
.alpha. is a load reduction rate of the flexible susension relative to the 
rigid suspension. 
##EQU13## 
If, in the similar manner as in the case of the prior art system, 
substitution of .alpha.=0.7 in the above equation gives the following 
equation. 
##EQU14## 
5. Load exerted uniformly on the two rollers 11 and 12 (which is referred 
to as "case 1" below.) 
A rigid suspension system is shown in FIG. 20, while flexible suspension 
systems are shown in FIGS. 21A, 21B and 21C. 
##EQU15## 
Where k" and F" are a spring constant and a load, respectively, in the case 
of the flexible suspension system. 
Since the suspension system of FIG. 21A can be set to be equivalent to 
those of FIGS. 21B and 21C, the following equation is obtained. 
##EQU16## 
Substitution of the equation 6 in the above equation gives the following 
equation. 
##EQU17## 
A comparison of the load exerted on the roller in the prior art roller 
suspension system with that in the roller suspension system of the present 
invention is given in the table below. 
TABLE 1 
______________________________________ 
Rigid Prior Art Suspension 
suspension suspension system of the 
system system present invention 
______________________________________ 
Case 1 F.sub.o 0.413 F.sub.o 
0.445 F.sub.o 
Case 2 F.sub.o 0.947 F.sub.o 
0.7 F.sub.o 
Case 3 F.sub.o 0.7 F.sub.o 
0.7 F.sub.o 
______________________________________ 
This table indicates that the suspension system of the present invention is 
superior to that of the prior art suspension system in the case of "Case 
2". 
It is to be understood that the foregoing description is merely 
illustrative of a preferred embodiment of the present invention, and that 
the scope of the invention is not to be limited thereto, but is to be 
determined by the scope of the appended claims.