Track system for vehicles

A track suspension system for a vehicle having a frame and a continuous flexible track. A drive wheel is attached to the frame for engaging and driving the continuous flexible track. A leading idler arm is pivotally attached to the frame on each side thereof and a leading idler wheel is rotatably mounted for engagement with the track. A trailing idler arm is provided on each side of the vehicle and is pivotally attached to the frame and a trailing idler wheel engagement with the track is rotatably mounted to one end of each idler trailing arm. A leading mid-roller assembly engagement with the track is operably attached to the leading idler arm and a trailer mid-roller assembly is in engagement with the track and is attached to the trailing idler arm. A cushioning device interconnects the leading and trailer idler arms for providing shock absorbing function. A valve system is provided for releasing all of the pressure on the leading and trailing idler arms so that all of the weight of the tractor is on the mid-roller assembly, thereby facilitating easier turning. The valve system is also operable to put leading and trailing idler arms in either a cushioning mode for use in the fields or travel down the highway or into a non-cushioning mode for use in very soft fields.

TECHNICAL FIELD 
The present invention relates generally to a track system for vehicles and 
more particularly to a rubber track of a continuous type which can be 
attached to an agricultural tractor or other vehicle of a similar type 
which needs to traverse either soft or wet ground, or ground which should 
not be compacted any more than is necessary. 
BACKGROUND ART 
Track-type vehicles are commonly used for moving earth or the like in road 
construction and other earth moving tasks. While these track machines have 
on occasion been used for agricultural purposes, they are not in common 
usage in most parts of the country. These track systems are typically 
metal tracks of a continuous type. 
Agricultural tractors and other large agricultural implements, such as 
combines or the like, are quite heavy and because all this weight is 
distributed to a relatively small area on the tires of these vehicles, 
they cause a great deal of compaction of the earth. This is adverse to 
growing crops thereon, which typically needs loose soil. Furthermore, 
there are many times when fields are simply too wet for an ordinary 
agricultural tractor or agricultural implement, such as a combine, to 
enter the fields because they would merely become bogged down in the mud 
due to the fact that there is such a small area of the tire which is in 
contact with the ground. It is of course well known that the more the 
weight is distributed to a larger ground engaging structure the less 
likely it is to compact the earth or to get stuck in the mud. 
Consequently, there has been some development of track systems such as 
that shown in U.S. Pat. No. 4,953,919 to Langford. 
One particular need is for a track system which can be used on agricultural 
equipment as it is currently being produced rather than to design an 
entirely new track system for an agricultural tractor, combine, etc. 
Another need is for such a track system which provides a suspension which 
permits cushioning. Also, if such a conversion kit were to be placed on an 
agricultural tractor or the like, the advantage of having a large ground 
engaging portion thereon becomes a disadvantage when it is desired to turn 
the vehicle. Consequently there is a need to solve this particular 
problem. 
DISCLOSURE OF THE INVENTION 
The present invention relates generally to a track suspension system for a 
vehicle having a frame and a continuous flexible track. A drive wheel is 
attached to the frame for engaging and driving the continuous flexible 
track. A leading idler arm is pivotally attached to the frame on each side 
of the vehicle and a leading idler wheel is rotatably mounted thereon for 
engagement with the track. A trailing idler arm is provided on each side 
of the vehicle and is pivotally attached to the frame. A trailing idler 
wheel in engagement with the track is rotatably mounted to one end of each 
idler trailing arm. 
A leading mid-roller assembly in engagement with the track is operably 
attached to the leading idler arm and a trailer mid-roller assembly is in 
engagement with the track and is attached to the trailing idler arm. A 
cushioning device interconnects the leading and trailing idler arms for 
providing a shock absorbing function when the leading and trailing idler 
wheels move away from each other due to pivoting of the leading and 
trailing idler arms. 
A valve system is provided for releasing all of the pressure on the leading 
and trailing idler arms so that all of the weight of the tractor shifts to 
the mid-roller assembly, thereby facilitating easier turning. The valve 
system is also operable to put leading and trailing idler arms in either a 
cushioning mode for use in the fields or travel down the highway and also 
into a non-cushioning mode for use in very soft fields or to disconnect 
the hydraulic systems for repair. 
An object of the present invention is to provide an improved track system 
for vehicles. 
Another object of the present invention is to provide an improved 
suspension system for track vehicles. 
A further object of the present invention is to provide a suspension system 
which prevents and counteracts torque roll to maintain the idlers and 
mid-rollers from pivoting to the top of the drive wheel, thereby keeping 
them fully supporting the portion of the track which is engaging the 
earth. 
Another object of the present invention is to provide an improved 
suspension system with a cushioning and shock absorbing structure. 
A still further object of the invention is to provide such a track system 
which has the ability to release the leading and trailing arms so that 
their associated idler wheels move up to cause a smaller ground engagement 
portion, thereby making the vehicle easier to turn. 
Another object of the present invention is to provide a mid-roller assembly 
which permits the drive wheel to extend below and between it whereby a 
larger drive wheel can be used while the mid-wheel assembly can, at the 
same time, support a large area of the track thereunder.

BEST MODE FOR CARRYING OUT THE INVENTION 
Referring now to the drawings wherein like reference numerals designate 
identical or corresponding parts throughout the several views, FIG. 1 
shows an agricultural tractor (10) having the rubber track system (11) 
attached to the rear wheel assembly thereof and with the normal rubber 
tires removed therefrom. A drive wheel (12) is rotatably attached to the 
tractor (10) through an axle (13) to which it is rigidly affixed. The axle 
(13) is rotatably mounted by a beating (14) and is rotated in a 
conventional fashion through the tractor (10) by its engine and through a 
transmission which can vary the speeds and allow forward and reverse 
rotation. The bearing (14) is mounted by a bracket (15) to the frame (16) 
of the tractor (10). 
The drive wheel (12) has a plurality of drive projections (17) disposed 
thereon which engage depressions (18) in the rubber track (19). The frame 
(19) passes around the drive wheel (12) on each side of the tractor (10) 
as can readily be seen in FIG. 1. 
A leading trail arm (21) is pivotally attached to the frame (16) at pivot 
pin (22) and a trailing swing arm (31) is pivotally attached by a pivot 
pin (32) to the frame (16). The leading swing arm (21) has an idler roller 
(23) rotatably attached thereto through bearing structure (24). Similarly, 
the trailing swing arm (33) is mourned an axle or bearing structure (34). 
Rigidly attached to the leading swing arm (21) is a bracket (25) having 
another member (26) also rigidly attached thereto. A leading trolley 
assembly (27) is pivotally attached through a pin (28) so that the trolley 
(27) can pivot as needed. A total of four mid-rollers (29) are rotatably 
attached to the trolley (27) on each side of the tractor (10). These 
trolleys (29) are rotatably mounted about a pin (30). 
Similarly, on the trailing swing arm (31) is a bracket (35) having a member 
(36) attached thereto. A trolley assembly (37), which is identical to the 
trolley (27) of the leading swing arm, is pivotally attached through a pin 
(38). Mid-rollers (39) are rotatably attached by axles (40) to the trolley 
assembly (37). 
The top of the leading swing arm (21) has a hydraulic cylinder (41) 
pivotally attached thereto at pin (42). Similarly, the other end of the 
hydraulic cylinder (41) is pivotally to the hydraulic cylinder clevis (43) 
by a pin (44). The hydraulic cylinder has a vent port (45) on the shaft 
side of piston (46). A hydraulic supply port (47) extends into the 
cylinder (41) on the other side of the piston (46) for reasons which will 
be explained below. 
Referring now to FIG. 4, a schematic drawing is shown having a control 
system attached thereto for the hydraulic cylinders, of which there are 
two, one on each side of the right wheel (which are shown) and two which 
are on each side of the left assembly (11) (which are not shown in the 
schematic of FIG. 4). A pressure port (51) is shown going into a valve 
(52) which is controlled by computer (53). Also going into the valve (52) 
is a port (54) which leads to a sump (55). 
A hydraulic line (56) leads from the valve (52) to a solenoid valve (57) 
and to an accumulator (58). A line (59) leads to the high pressure side 
and port (47) of each of the hydraulic cylinders (41) on the right side 
assembly (11) and also to both of the hydraulic cylinders (41) on the left 
side assembly (11). 
A load sensor (60) is attached to only one of the hydraulic cylinders (41), 
although more sensors could be used on the other cylinders if desired. The 
one sensor (60) is adequate to sense the position of the leading and 
trailing idlers (23 and 33) based on the length that the hydraulic 
cylinder (41) has extended as shown in FIG. 2. The sensor (60) has a 
portion attached to the hydraulic cylinder barrel and has a shaft (61) 
extending therefrom which is attached to the clevis (43) by a member (62). 
Consequently, as the hydraulic cylinder (41) lengthens, so does the shaft 
(61) extend further from barrel portion (60) in which it reciprocates. 
Likewise when the cylinder (41) retracts, the shaft (61) will retract into 
the cylinder portion (60) of the load sensor. 
The load sensor (60) sends its information back through a 12-volt line (63) 
to the computer (53). Another 12-volt line (64) leads from the computer 
(53) to the electrically actuated solenoid valve (57) is spring biased to 
an open position but will move to a closed position thereof when the 
computer energizes the line (64) leading from the computer (53) to the 
solenoid (57). 
A switch (66) in the cab (67) of the tractor (10) is of the three position 
type. It will send a signal through line (68) from the cab of the tractor 
to the computer (53) depending upon which one of three modes is desired to 
be used. When the switch (66) is placed in the mode 1 position, the 
computer (53) will open the valve (52) to allow the pressure from port 
(51) of the tractor hydraulic system to enter line (56) and at the same 
time, the solenoid (57) will remain open so that the hydraulic cylinders 
(41) are pressurized and consequently lengthened to the position shown in 
FIG. 2, which is the optimum position for the idler rollers (23) for 
highway travel and also for travel in farm fields during normal 
conditions. In this position there is full load support on the entire 
distance shown on the bottom of the robber track as shown in FIG. 2. 
In mode 1, as the lead idler wheel (23) encounters obstructions, it may be 
forced upwardly. This will cause the cylinder (41) to retract slightly to 
compensate for that upward movement because the pressure can backup into 
the accumulator (58). The accumulator would typically be a tank having 
hydraulic oil therein which is charged on the top thereof with nitrogen 
gas, which will essentially act as a spring to hold the pressure high in 
the accumulator, but which will accommodate and absorb shocks during those 
times when the leading roller (23) hits an obstruction, such as a rock or 
the like, in a field. It is of course understood that if the tractor (10) 
is put into a reverse gear, the leading and trailing arms, idlers, etc. 
will essentially reverse. In any event, for the purposes of this 
description, the leading idler arm and leading idler will be referred to 
as if it were moving in a forward direction, which it will be doing a high 
percentage of the time. After the obstruction has been traversed, the 
pressure in the hydraulic lines will essentially force the idler arms (21) 
and (31) and respective idler rollers (23 and 33) back to the position 
shown in FIG. 2, after the shock of hitting the obstruction has passed. 
With the tractor in mode 1, it has been determined that while it is very 
desirable to have as much contact of the track with the ground or highway 
as possible, this becomes an impediment to turning the tractor when 
turning is needed. Consequently, when the user of the tractor (10) gets at 
the end of the row and wants to turn around to go in another direction, 
the switch (66) can be moved to mode 3 just for turning purposes only. 
When the switch (66) is moved to the mode 3 turning mode, solenoid (57) 
remains open but valve (52) is moved to drain and relieve pressure in the 
hydraulic line (56) to the sump (55) of the tractor. This essentially 
relieves the pressure on the high pressure side of each of the hydraulic 
cylinders (41), which will allow the cylinders to shorten to the FIG. 3 
position since they are vented to atmosphere on the other side of the 
piston. This puts all of the weight on the mid-roller assemblies (27 and 
37) on each side of the tractor and shortens the amount of the rubber 
track (19) which engages the ground or the road. There is no shock 
absorbing being done in the mode 3 configuration shown in FIG. 3. 
Consequently, it is not desired to leave it in this mode any longer than 
is necessary to complete a turn. After the turning is accomplished, the 
switch (66) is moved back to the mode 1 position where high pressure is 
returned to line (56). Because solenoid (57) is open, all of the hydraulic 
cylinders (41) will be moved back to the somewhat extended position 
desired as shown in FIG. 2. 
The load sensor (60) is essentially set for the optimum position shown in 
FIG. 2 and will tend to hold the hydraulic cylinders (41) in that 
pre-determined desired position shown in FIG. 2 assuming that the mode 1 
position of the switch (66) is maintained. The only thing that will cause 
it to move is if cushioning is needed due to some irregular condition 
encountered by the idler pulleys (23 and 33) transmitted to the leading 
and trailer idler arms (21 and 31). It is noted that the mode 3, FIG. 3, 
position can be used for turning either in the field or on the highway. 
Under very limited circumstances, the mode 2 position may be used. In the 
mode 2 position, the computer will energize the solenoid (57), thereby 
causing it to be closed. At the same time, it will completely close off 
the valve inlet line (51) so that hydraulic fluid from line (56) cannot 
move from line (51) to (56), nor can the pressure within (56) be in 
communication with line (54) and the sump of the tractor hydraulic system. 
By closing the line (56) entirely off and closing the solenoid valve (57), 
the cylinders (41) will be locked in the FIG. 2 position. Under these 
circumstances, there is no cushioning because the hydraulic cylinders are 
no longer in communication with the accumulator (58) and since hydraulic 
oil is essentially non-compressible. Mode 2 is used when the tractor is 
traversing very soft ground. The other time that mode 2 would be used 
would be when it is desired to change out some of the components of the 
system, such as the accumulator (58) or the hydraulic cylinders (41), or 
even if one of the hydraulic lines interconnecting the system needed to be 
replaced. 
Referring now to another embodiment (111) shown in FIGS. 8-11, it can be 
seen that the rubber track (19) is being moved by a larger drive wheel 
(112) which extends downwardly between and below mid-rollers (129) on 
mid-roller assembly (120). Each of the mid-rollers (129) are rotatably 
attached to the subframe (127) by short axles (130) which do not extend 
completely across the track and thereby permit the drive wheel (112) to 
extend downwardly between the stop shaft members (130). 
The subframe (127) on the mid-roller assembly (120) has an arm (126) 
rigidly attached to the subframe (127) and pivotally attached by pin (137) 
to bracket (135). The bracket (135) is rigidly attached to the trailing 
arm (31). Similarly, a bracket (125) rigidly attached to leading arm (21) 
is operably, pivotally attached to the other end of the subframe (127) by 
a link (126) which is pinned at the top thereof to member (127) and at the 
bottom thereof to the subframe (127) by a pin (128). Further structures 
can be used instead of the link (126) which can allow some lost motion 
between the arm (21) and the subframe (127). Also, of course, this link 
structure (126) could be on both ends of the subframe (127) or on the 
trailing end instead of the leading end in order to permit the idler arms 
(23) and (33) to move to the position shown in FIG. 11 and between the 
position shown in FIGS. 8 and 11 as is needed for proper operation of the 
device. Otherwise, the apparatus shown in FIGS. 8-10 works exactly like 
the embodiment shown in FIGS. 1-7, with the same control system being 
utilized. 
Accordingly, it will be appreciated that the preferred embodiment disclosed 
herein does indeed accomplish the aforementioned objects. Obviously many 
modifications and variations of the present invention are possible in 
light of the above teachings. For example, the hydraulic cylinder could be 
placed below the pivot pins (22 and 32) on the leading and trailing swing 
arms (21 and 31) instead of being up higher on extensions of the swing arm 
members where they are shown in FIGS. 2 and 3. It is therefore to be 
understood that, within the scope of the appended claims, the invention 
may be practiced otherwise than as specifically described.