Motor vehicles – Steering by driving
Reexamination Certificate
1999-10-05
2001-03-06
Johnson, Brian L. (Department: 3618)
Motor vehicles
Steering by driving
C180S006440, C180S006660, C477S001000, C475S019000, C475S023000, C074S473170
Reexamination Certificate
active
06196342
ABSTRACT:
BACKGROUND OF THE INVENTION
It is known to provide a vehicle transmission that allows the vehicle to execute zero radius turns and spin turns. Military tank vehicles and other tracked vehicles have been provided with a dual differential type of transmission capable of zero radius turns and spin turns. This type of drive and steer transmission is described in the articles entitled Tanks And Dozers Turn On A Dime With New All-Gear Steering, and Tank-Steering Mechanisms. The transmission includes a driving portion having a driving differential which receives rotational power from the vehicle power source for propelling the vehicle during operation. The driving portion includes a drive input control which can be operatively engaged by the operator for varying the speed and forward/reverse direction of the vehicle. The transmission also includes a steering portion having a steering differential. The steering portion includes a steering input control that can be operatively engaged by the operator for executing turns. The steering portion engages the driving portion such that as the steering input control is engaged by the operator to execute a turn the steering portion increases the speed of the track on one side of the vehicle and proportionately decreases the speed of the track on the other side of the vehicle. In this manner the vehicle executes a turn. When the vehicle is stationary, the operator can engage the steering input control, which will cause the tracks on one side of the vehicle to be driven forwardly, and the tracks on the other side of the vehicle to be driven rearwardly at the corresponding speed. This causes the vehicle to execute a spin turn.
As described in the article entitled Tank-Steering Mechanisms, a different transmission having planetary gear arrangements functions in a manner similar to the dual differential drive and steer transmission described above. This type of transmission also includes a driving portion having a driving input control, and a steering portion having a steering input control. The steering portion interacts with the driving portion to increase the speed of the tracks on one side of the vehicle and correspondingly decrease the speed of the tracks on the other side of the vehicle.
These types of drive and steer transmissions allow the vehicle to be highly maneuverable, and allow the vehicle to execute zero radius turns and spin turns. These drive and steer transmissions are typically provided on heavy duty vehicles such as military tanks, bulldozers, and other large tracked vehicles.
If these types of transmissions were controlled by a conventional steering wheel, the vehicle would execute turns in the direction that the steering wheel is turned when traveling in the forward direction of vehicle travel. However, when travelling in the reverse direction, some of these drive and steer transmissions would cause the vehicle to execute a turn to the seated operator's left if a steering wheel were to be turned to the right when driving in the reverse direction of travel, and would execute a turn to the seated operator's right if a steering wheel were to be turned to the left when driving in the reverse direction of travel. These steering characteristics are generally unfamiliar to the general public, who are generally more comfortable and familiar with the steering characteristics of automobiles. Automobiles execute turns to the left when the operator turns the steering wheel to the left when driving in reverse, and execute turns to the right when the operator turns the steering wheel to the right when driving in reverse.
It would therefore be desirable to provide drive and steer transmissions with a mechanism that alters the steering characteristics in reverse so that the transmission steers the vehicle in a manner similar to an automobile. If steering in reverse were to be similar to the steering of an automobile, then more of the general public would be comfortable and familiar with the handling of such a vehicle. This would help allow a drive and steer transmissions to be utilized on vehicles other than large tracked vehicle, such as relatively small residential lawn tractors. Such a vehicle would be highly maneuverable and would steer in directions the direction that the operator turns a steering wheel in a fashion that is familiar to most operators. No special driving skill would be required of the operator.
SUMMARY OF THE INVENTION
The present invention provides a mechanism adapted for use with a dual differential type of drive and steer transmission that is steered by turning a steering wheel. The mechanism interacts with the transmission for causing the transmission to execute vehicle turns in the direction that the steering wheel is turned when operating in the forward or reverse directions.
The present invention provides a linkage extending between the steering wheel and a steering control input of the steering portion of the transmission. The linkage includes a cam member pivotable about a pivot axis. The cam member includes an arcuate slot. Within the slot is received a front end portion of an elongate member or rod. The rear end portion of the elongate member is coupled with an arm that is fixed with the pivotable steering control input of the transmission. As the steering wheel is turned by the operator the cam swings about its pivot axis. During forward vehicle travel the elongate member is positioned in the upper end of the slot and above the cam pivot axis. Therefore as the cam swings in response to turning of the steering wheel, the elongate member will shift fore or aft depending on the direction the steering wheel is turned. Fore or aft shifting of the elongate member causes the arm and steering control input to pivot, thereby causing the transmission to initiate a vehicle turn. During reverse vehicle travel the elongate member is positioned in the lower end of the slot and beneath the cam pivot axis. Therefore as the cam swings in response to turning of the steering wheel when driving in reverse, the elongate member will shift in the opposite direction that it would have if the elongate member were in the upper end of the slot during forward travel. The steering in reverse is therefore corrected such that the vehicle will execute a turn in the direction the steering wheel is turned regardless of whether the vehicle is travelling in forward or reverse direction of travel.
In one embodiment an actuating device is provided that engages the cam member for shifting the elongate member between its various positions. The actuating device includes an actuating member having a slot or cam surface. The actuating member is coupled with a forward and reverse foot pedals. The actuating member pivots in one direction when the forward pedal is depressed by the operator and pivots in the other direction when the reverse pedal is depressed. A cam follower is positioned within the slot of the actuating member and is operatively coupled with the elongate member. As the actuating member pivots in response to one of the foot pedals being depressed, the cam follower is shifted within the slot. This causes the elongate member to shift to the appropriate end of the slot formed in the cam member.
When the operator is not depressing either foot pedal, the elongate member is positioned within the central portion of the slot and in general alignment with the cam member pivot axis. Therefore, if an operator turns the wheel while neither pedal is depressed the cam member will pivot but the elongate member will not shift fore or aft. This generally prevents the vehicle from turning or executing a spin turn as an operator standing next to the vehicle turns the steering wheel. The foot pedals must be engaged in order for the steering to become operative. A slot is formed in the drive linkage between the foot pedals and the drive control input of the transmission. This slot establishes a delay in the drive linkage that, as the forward foot pedal is depressed, allows the actuating member to shift the elongate member to the appropriate end of th
Goebert Barry Joseph
Hayes Eugene Gary
Hutchinson Wayne Robert
Marchese David Lewis
Teal Richard Donald
Deere & Company
Johnson Brian L.
Lerner Avraham H.
LandOfFree
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