Access plate for an axle of a differentially steered vehicle

Motor vehicles – Transmission mechanism – Gear transmission relationship to frame or axle

Reexamination Certificate

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Details

C180S378000, C180S009440, C180S006660

Reexamination Certificate

active

06286620

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to a differentially steered axle having an access plate to which the steering motor and some of the steering components are mounted.
2. Description of the Prior Art
Differentially steered work vehicles are well known. Differential steering uses changes in wheel speed on the left and right sides of the vehicle to steer. This steering system can be used on tracked and wheeled vehicles. One system that has been used in the prior art is a planetary system having two planetary gear sets. The main drive input from the vehicle transmission drives the sun gear of both planetary gear sets and a steering motor is used to drive the ring gears of both planetary sets. The final drives driving the wheel hubs are coupled to the planetary carriers. Whenever the steering motor increases the speed in one planetary set, the same amount of speed is subtracted from the other planetary set. For example if the speed on one side is increased by three miles per hour, the speed on the other side is decreased three miles per hour. At very slow speeds or when the vehicle is stopped the vehicle can be spin steered. That is the vehicle can be turned on its vertical axis. Typically the steering motor is coupled to the ring gears of the planetary sets by a beveled pinion gear that meshes with the beveled ring gear. An example of this steering system is disclosed in U.S. Pat. No. 4,718,508.
Spur gears have also been used to provide the steering input to the planetary gear sets. If spur gears are used a reverser mechanism is required to provide a rotational change in direction between the planetary sets by the steering motor input. In one example, the main drive input from the vehicle transmission is directed to the planetary carriers of both planetary sets and the steering input is directed to the sun gear of both planetary sets. The steering input is applied to a steering shaft that is parallel to the drive axle. One end of the steering shaft drives a first spur gear which is operatively coupled to the first planetary set. The other end of the steering shaft drives a reverser gear that in turn drives a second spur gear which is operatively coupled to the second planetary gear. The final drives for the wheel hubs are coupled to the ring gear, see U.S. Pat. No. 5,921,335.
SUMMARY
It is an object of the present invention to provide a differentially steered drive axle having an access plate that provides easy access to the steering mechanism in the axle.
The axle is provided with an axle housing that is secured to the work vehicle. A steering mechanism for differentially steering the work vehicle is located inside the axle housing. A main drive rotational input from the transmission of the work vehicle is directed into the axle housing for driving the final drive units of the vehicle. The final drive units in turn drive the wheel hubs of the vehicle. The steering mechanism comprises first and second planetary gear sets which receive the main rotational input from the main drive input and directs this input to the first and second final drives. An access plate for covering an access opening in the axle housing is provided with an exterior side and an interior side. A steering motor mount is provided in the access plate for receiving a steering motor and directing its steering input to a steering shaft rotatively mounted to the interior side of the access plate. The steering motor is mounted on the exterior side of the access plate. A first spur gear is also rotatively mounted to the interior side of the access plate and drivingly engages the rotatable shaft. In addition, the first spur gear operatively engages the first planetary gear set. A reverser gear is rotatively mounted on a pin mounted to the interior side of the access plate and drivingly engages the rotatable shaft. In addition, the reverser gear operatively engages a second spur gear. The second spur gear is also rotatively mounted to the interior side of the access plate and operatively engages the second planetary gear set.
The steering motor is a hydraulic motor that can be driven in a clockwise or counterclockwise direction. When the steering motor is driven in a clockwise direction, it rotates the steering shaft in a counterclockwise direction. The steering shaft applies this counterclockwise input to the first spur gear and the reverser gear driving them both in a clockwise direction. This clockwise input is applied to the first planetary gear set by the first spur gear driving the first ring gear of the first planetary gear set in a counterclockwise direction. Similarly, the reverser gear is driven in a clockwise direction by the steering shaft and thereby drives the second spur gear in a counterclockwise direction. The second spur gear, in turn drives the second ring gear of the second planetary set in a clockwise direction. In this way the vehicle is differentially steered by adding speed to one side of the vehicle and subtracting the same amount of speed from the other side of the vehicle.


REFERENCES:
patent: 3530741 (1970-09-01), Charest
patent: 4506772 (1985-03-01), Sommer
patent: 4611505 (1986-09-01), Cronin et al.
patent: 4718508 (1988-01-01), Tervola
patent: 4882947 (1989-11-01), Barnard
patent: 5004060 (1991-04-01), Barbagli et al.
patent: 5390751 (1995-02-01), Puetz et al.
patent: 5423235 (1995-06-01), Botterill et al.
patent: 5558174 (1996-09-01), Avitan et al.
patent: 5871413 (1999-02-01), Tar et al.
patent: 5873800 (1999-02-01), Maslow et al.
patent: 5921335 (1999-07-01), Straeker

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