Steering controls

Details Steering controls Steering controls

2001-06-21

2003-06-24

Morris, Lesley D. (Department: 3611)

Motor vehicles

Steering by driving

Combined with manual steering

C180S006200, C074S473280

Reexamination Certificate

active

06581704

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to structure for controlling the amount of effort required to actuate the steering levers of an earth moving vehicle, and more specifically, to a mechanism that increases or decreases the forces placed on the levers to allow an operator to more accurately steer the vehicle.
BACKGROUND OF THE INVENTION
Movement of vehicles of the type including skid-steer loaders is typically controlled by an operator's actuation of a pair of handles or levers located near the operator's seat in the vehicle. Each of the levers operating together control either forward or rearward motion of the vehicle, i.e., to move in a forward direction, an operator needs to push both levers forward at the same time and vice versa with regard to movement in the reverse direction. If an operator is moving in a forward or reverse direction and unexpectedly releases one of the levers, it may quickly return to its neutral and upright position without permitting an opportunity for the operator to regain its control. As a consequence, the vehicle will cease to move in the desired direction and often be abruptly jerked toward either a left hand turn if the left lever is released or a right hand turn if the right lever is released.
The above movement caused by actuation of either or both of these levers is permitted through their connection with a pair of rotating sleeves which are mounted to and which revolve around a steering shaft that extends therebetween. Connected with the sleeves are separate steering linkages which attach the sleeves to both a left and right pump for controlling movement of the vehicle towards either a left or right direction. The pumps are actuated by movement of the levers to release fluid to hydraulic motors which are driven or powered by the pumps. Each of these motors then drives a plurality of wheels or other traction device attached with the vehicle to propel it along the ground surface. Accordingly, upon movement of either one or both of the levers, the operator may cause the vehicle to travel in a desired direction as some effort or force is applied by the operator to reposition one or both of the levers either away from or towards the neutral position. In doing so, however, the operator will encounter a certain amount of resistance in moving the levers from the neutral position.
Resistance is a measure of the force applied to the levers when opposition to movement thereof is encountered. It is also that which determines the pace at which each lever returns to its neutral position after it has been moved therefrom. Resistance has been controlled by a separate mechanism mounted to and cooperating with the left pump and another with the right pump. Each mechanism has included a mounting plate attached to the left and right pump individually. This mounting plate has included a top and bottom portion with the bottom portion being mounted to the pump. On an interior of the top portion, a slide plate, the purpose of which is described below, has been secured thereto. With the top portion and slide plate secured together, the set has been thereafter mated with the bottom portion for movement on guide rails or pins that extend between the two portions so as to allow the set to glide therealong. Extending through a first side of the mounting plate, a bolt around which a spring has been placed has been used to provide resistance at each of the levers. To apply a desired amount of pre-load, and thus resistance at each of the levers, screws have been secured to the slide plate on a side thereof to allow an operator to set the amount of distance that exists between the slide plate/top portion of the mounting plate combination and the back portion of the mounting plate when each lever is in the neutral position. Setting of this distance has been made by the operator securing the slide plate relative to the first side of the mounting plate through the use of the screws so as to adjust the amount of pre-load described above.
To stroke the pumps and therefore allow hydraulic fluid to flow to each motor, each of the steering linkages has been connected to an arm extending from the left or right pump that has been used to permit the pumps to be stroked upon movement of the levers. Specifically, each arm has included a roller assembly on an end thereof that is positioned to initially contact the slide plate under the pre-load set above when a particular lever is in the neutral position and which further pushes against the slide plate when the arm is re-positioned by movement of the lever to either the forward or reverse direction. Further compression of the spring then takes place as the roller contacts its slide plate. This compression of the spring thereby increases the resistance at the effected lever(s). As a consequence of applying additional pressure against the slide plate in either the forward or reverse direction, movement of the arm strokes the pump and causes hydraulic fluid to flow to the respective left or right motor to allow the traction device of the vehicle to propel it in the desired direction.
Use of the above adjustment mechanism, however, carries with it at least five disadvantages. First, achieving the same resistance at each of the levers at the same time is problematic since there are two separate mechanisms used to obtain resistance at each of the left and right levers. Such a problem arises because each mechanism uses its own spring having a separate manufacturer's preset constant determinative of the force required to place the spring in either tension or compression. Because of this, an operator is left to judge and compensate for how much force should be used to actuate one or both of the levers. To have to do so is inconvenient and bothersome to those wanting a similar amount of effort or force to be required to move each lever out of its neutral position.
Second, since two mechanisms have been used to individually provide resistance at the levers, an operator may experience a higher degree of resistance when actuating one lever than when actuating the other. With different resistance at each lever, one lever often returns to the neutral position more quickly than would be expected if both levers were set at the same level of resistance. In this case, it is often more difficult for a lever that has been released from a forward or rearward position to gradually return to its neutral position so as to allow the operator an ability to obtain control thereof. Consequently, the vehicle is often caused to be jerked from its travel direction when one of the levers is unexpectedly released, as previously mentioned.
Third, it has been difficult to adjust the resistance of both levers simultaneously and not affect the vehicle's ability to maintain proper tracking. Tracking can be described as the ability of the vehicle to maintain a straight course when each lever is positioned in its furthest forward position so as to move the vehicle forwardly. Tracking has been set by adjusting the furthest distance the lever is permitted to move forwardly and rearwardly of its neutral position. Adjustment of the resistance has been made by either loosening or tightening the screws mentioned above to vary the distance that exists between the slide plates and the bottom portion of the mounting plates. Obtaining the same resistance setting at each of the levers has further been made difficult since maneuvering of the slide plates relative to the mounting plates has affected positioning of the pump arms. This affect occurs since each respective pump arm and its roller assembly is positioned between each slide plate and mounting plate and is therefore moved itself when an adjustment to the resistance at each of the levers is made. Consequently, adjustment of the resistance at each of the vehicle's levers has been difficult to do without affecting its tracking. This difficulty exists since the mechanism(s) used to adjust the resistance is/are connected with the steering linkage(s) connecting each of levers to the respective pump ar

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