Brake/differential lock pedal linkage

A brake/differential lock pedal linkage includes a two-stage manual control that may lock a differential before progressively engaging a brake. The manual control may be a foot pedal or hand lever. The linkage may include a brake cam lever that pivots on a brake cam shaft in response to movement of the manual control, a differential lock link connected between the brake cam lever and an actuator that can move a differential lock shaft to lock the differential, and a lost motion coupling between the brake cam lever and the actuator allowing the brake cam lever to pivot to a differential lock position in which the actuator moves the differential lock shaft sufficiently to lock the differential, before the brake cam lever pivots further to progressively engage the brake.

FIELD OF THE INVENTION

The present invention relates generally to differential locks for work vehicles such as agricultural and industrial tractors, and specifically to linkages between the tractor brake and differential lock.

BACKGROUND

Work vehicles such as agricultural and industrial tractors are sometimes equipped with a single internal brake. These work vehicles also may be provided with a differential lock for the primary drive axle. To make both drive wheels lock when the brake foot pedal is depressed, the differential lock must be engaged prior to actuating the brakes. Tractors commonly have a brake foot pedal and a separate differential lock foot pedal to lock the differential. For example, many tractors have a heel-actuated differential lock foot pedal.

It is desirable to simplify the operator's station of a work vehicle by reducing the number of controls and pedals. It also is desirable to provide a differential lock that can be engaged and disengaged quickly and easily by the operator.

SUMMARY OF THE INVENTION

A brake/differential lock pedal linkage includes a two-stage manual control that can be moved between a disengaged position, a differential lock position, and a brake engagement position. The two-stage manual control may be a foot pedal or hand lever, for example. In the first stage, the foot pedal or hand lever may be moved from the disengaged position to the differential lock position. In the second stage, the foot pedal or hand lever moves from the differential lock position progressively to the brake engagement position. A lost motion coupling may be provided between a brake cam lever and the differential lock shaft.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In one embodiment, the brake/differential lock pedal linkage is provided for a vehicle having a single internal brake. The brake/differential lock pedal linkage provides a two-stage control for the differential lock and brake. In a first stage of movement, the control moves to the differential lock position. During the second stage of movement, after the differential is locked, the control may be moved to progressively engage the brake. The two-stage manual control may be a foot pedal, hand lever, or other manually operated control.

In one embodiment, the two-stage manual control may be foot pedal11. In a first stage of movement, foot pedal11may be depressed to move from a disengaged position to a differential lock position. In a second stage, after the differential is locked, foot pedal11may be depressed further to progressively engage the brake. Eliminating a separate differential lock control lever reduces the number of controls, simplifies the operator's station, and allows the operator to more quickly and easily lock the differential before applying the brake.

FIG. 1of the drawings shows transmission assembly50of a work vehicle, such as a tractor, including left and right axle housings51. In one embodiment, brake/differential lock pedal linkage10may include foot pedal11pivotably mounted to shaft13attached to transmission assembly50. Pedal return spring12may bias the foot pedal toward the disengaged position. Upper link15may be pivotably attached to one end of the pedal, and turnbuckle17may connect upper link15to lower link16. The lower link may be pivotably attached to a first lobe of brake cam lever19mounted on shaft20. As the operator moves foot pedal11from the disengaged position toward the differential lock position, the pedal pulls the upper and lower links forward, causing brake cam lever19to pivot on shaft20. This is the first stage of pedal movement.

In the embodiment shown inFIGS. 2 and 3, during the first stage of movement of foot pedal11, from the disengaged position toward the differential lock position, brake cam lever19pivots on shaft20and pulls down on differential lock link46. Differential lock link46is connected between a second lobe of brake cam lever19and guide45in lost motion coupling43. Pulling down on differential lock link46moves lost motion coupling43down and pivots actuator33, which may be a plunger, lever or other device, that is pivotably attached to mounting bracket34. Actuator33pivots against the end of differential lock shaft29, which may have an annular seal ring47thereon. Differential lock spring30biases the differential lock shaft to the unlocked position, but in the first stage as the foot pedal is moved to the differential lock position, actuator33may exert sufficient force on differential lock shaft29to compress differential lock spring30, and move the shaft on its longitudinal axis in an internal passage in transmission housing50.

In an alternative embodiment, during the first stage, the actuator may rotate the differential lock shaft to engage the differential lock. In another alternative embodiment, during the first stage, foot pedal11or other control may cause engagement of the differential lock electrically or hydraulically.

In one embodiment, differential lock fork36, which is attached to differential lock shaft29, moves together with the differential lock shaft. As differential lock fork36moves toward differential assembly37, it pushes pins38extending from plate53into slots in spider gear35, to lock the differential. During the first stage of movement, to reach the differential lock position, differential lock shaft29may move along its longitudinal axis until reaching a stop in the transmission housing.

In one embodiment, the first stage may require a relatively small movement of foot pedal11to engage the differential lock. Moving foot pedal11to the differential lock position pivots brake cam lever19until differential lock shaft reaches a stop. The second stage of movement may occur after reaching the differential lock position. Moving foot pedal11past the differential lock position begins actuating the brakes. The additional movement of foot pedal11from the differential lock position toward the brake engagement position causes brake cam lever19to continue pivoting on shaft20. As brake cam lever19continues to pivot, it pulls down on differential lock link46attached to guide45, compressing spring44in lost motion coupling43. Spring44has sufficient stiffness so that it does not compress until the rear differential is locked and differential lock shaft29has reached a stop in the transmission housing.

In one embodiment, spring44does not compress until the second stage of movement, after foot pedal11has moved to the differential lock position. Spring44acts as a rigid link in coupling43during the first stage, until the differential is locked and the differential lock shaft has reached a stop. Spring44may have higher stiffness than differential lock spring30. As a result of the high stiffness of spring44, greater force is required to depress foot pedal11during the second stage to progressively engage the brake, than was required to depress the pedal during the first stage to lock the differential. As a result, spring44may provide a two-stage feel for operation of the foot pedal.

In one embodiment, pivoting of brake cam lever19from the differential lock position to the brake engagement position rotates brake cam shaft20and moves brake cam lobe40into engagement with brake actuating disk49. Engagement of the brake cam shaft with the brake actuating disk actuates the vehicle brakes by causing steel balls to move up ramps between brake quill39and brake actuating disk49, moving brake plates41and compressing brake pads between the plates. Brake cam lever19engages the brakes after differential lock shaft29has reached a stop and the differential is locked.

In one embodiment, the two-stage control may be park brake handle22. The park brake handle may be used to lock the differential during a first stage of movement, and engage the brake during a second stage. Park brake handle22may pivot on pin23, to pull upper link25attached to lower link26with turnbuckle27. The lower link may be connected to a third lobe of brake cam lever19, and may include lost motion device28so that actuation of foot pedal11does not move the park brake handle. The park brake lever may include a ratcheting mechanism to lock the park brake handle in the differential lock position or a brake lock position.