Belt tensioning mechanism

Abstract

A belt tensioning mechanism is provided for use with a vehicle having an axle pivotably connected to a frame of the vehicle with inextensible belts entrained about wheel assemblies mounted on either side of the vehicle for transmitting tractive effort to the earth. Some systems provide tensioning of belts by producing a separating force between only the wheel assemblies on one side of the vehicle independent from the tensioning of the other side while others provide tensioning of track having sprocket driving members by using bulky complicated mechanisms for providing the tensioning of the track and to provide relative motion of the front axle from one side to the other. In the subject arrangement, an axle is connected to a frame by a swivel bearing being slidably disposed on a pin, such that, the axle moves longitudinally relative to the frame while still being able to swivel about the pin. Furthermore, an adjusting mechanism is provided to produce the force necessary to sufficiently tension the belts to provide frictional drive between the belts and the drive wheel assemblies. In one of the embodiments, the adjusting mechanism includes a force generating mechanism responsive to fluid pressure transmitted thereto from a pump. This arrangement allows the axle to move relative to the frame in the longitudinal direction in the event that a foreign object passes between one of the belts and its respective wheel assembly without requiring a large bulky mechanism that would be impractical for use on large industrial vehicles.

I claim: 
     
       1. A belt tensioning mechanism for use on a vehicle having a frame defining a plane aligned along its longitudinal axis, an axle connected to the frame at one end of the vehicle and extending thereacross through said plane, a first pair of wheel assemblies rotatably mounted on opposite ends of the axle independent of said frame, a second pair of wheel assemblies drivably mounted on opposite sides of the frame at the other end of the vehicle, and first and second inextensible belts respectively entrained about the wheel assemblies on each side of the vehicle, comprising: means for .[.universally.]. .Iadd.permitting universal .Iaddend.swiveling .Iadd.of .Iaddend.said axle relative to said frame and said centrally disposed plane and for .Iadd.permitting .Iaddend.sliding .Iadd.of .Iaddend.said axle longitudinally relative to said frame and said centrally disposed plane; and   .[.means for adjusting the position of said axle relative to said frame to maintain at least a predetermined tension in said first and second belts while permitting said universal swiveling and longitudinal movements of said axle.].   .Iadd.a controllable force generating mechanism connected at one end directly to the frame and connected at the other end directly to the axle only between the first pair of rotatably mounted wheel assemblies, and the controllable force generating mechanism being adapted to apply and maintain at least a predetermined tension in the first and second belts while permitting universal swiveling and longitudinal movements of the axle relative to the frame.Iaddend..   
     
     
       2. The mechanism, as set forth in claim .[.1.]. .Iadd.16, .Iaddend.wherein the .[.connecting means.]. .Iadd.means for universally swiveling .Iaddend.includes a pin and a universally swiveling bearing slidably mounted on the pin, one of said pin and swivel bearing being secured to said axle at a point midway between the ends of the axle and the other of said pin and swivel bearing being secured to said frame at the one end of the vehicle along said centrally disposed plane. .[.3. The mechanism, as set forth in claim 2, wherein the adjusting means includes a force generating mechanism connected between the frame and the axle and being adapted to move the axle relative to the frame to establish the 
     
     
        predetermined tension in the first and second belts..]. 4. The mechanism, as set forth in claim .[.3.]. .Iadd.2.Iaddend., wherein the force generating mechanism includes a jack mechanism pivotably and operatively connected at one end to said frame along said centrally disposed plane and a force transfer mechanism connected to opposite ends of the axle and 
     
     
        operatively connected to the other end of said jack mechanism. 5. The mechanism, as set forth in claim 4, wherein the jack mechanism includes a pivot pin connected to the frame along the centrally disposed plane longitudinally remote from and in axial alignment with said pin, a force transmitting member pivotably mounted on said pivot pin, and a pair of jack assemblies each respectively connected between opposite ends of the 
     
     
        force transmitting member and the force transfer mechanism. 6. The mechanism, as set forth in claim 5, wherein the force transfer mechanism includes a pair of force transmitting arms each connected between one of 
     
     
        the jack assemblies and one of the ends of the axle. 7. The mechanism, as set forth in claim 6, wherein each of the jack assemblies includes a rod end portion and a head end portion with one of the end portions of the jack assemblies being connected to the opposite ends of the force transmitting member and the other of the end portions of the jack 
     
     
        assemblies being connected to the respective force transmitting arms. 8. The mechanism, as set forth in claim 7, wherein each of said jack assemblies is adapted to generate at least a predetermined force on the axle for tensioning said first and second inextensible belts and is independently movable in response to one end of the axle moving longitudinally relative to said frame while maintaining at least said 
     
     
        predetermined tension on said first and second belts. 9. The mechanism, as set forth in claim 8, wherein the force generating mechanism includes means for aligning each of said first pair of wheel assemblies relative to said belt so that said wheel assemblies are maintained in alignment with 
     
     
        said belt. 10. The mechanism, as set forth in claim 9, wherein each of said force transmitting arms is pivotably connected to the axle by a pin joint and said aligning means includes a pair of spindles respectively pivotably connected to each end of the axle and having the respective wheel assemblies rotatably mounted on one end of each spindle, and a pair of adjusting assemblies respectively connected between each spindle and 
     
     
        the respective force transmitting arms. 11. The mechanism, as set forth in claim 10, wherein each of said spindles is connected to the axle at the respective pin joint and each of said adjusting assemblies are connected 
     
     
        to the other end of the spindles. 12. The mechanism, as set forth in claim 10, wherein said pair of jack assemblies are operative to selectively retract said axle and said first pair of wheel assemblies relative to said second pair of wheel assemblies so that said first and second belts may be 
     
     
        changed. 13. The mechanism, as set forth in claim 12, wherein said pin is attached to the frame and said swivel bearing is attached to said axle. 
     
     
        .Iadd.14.  A belt tensioning mechanism for use on a vehicle having a frame defining a plane aligned along its longitudinal axis, an axle connected to the frame at one end of the vehicle and extending thereacross, a first pair of rotatably mounted wheel assemblies connected to opposite ends of the axle independent of the frame, a second pair of rotatably mounted wheel assemblies driveably connected to opposite sides of the frame at the other end of the vehicle, and first and second inextensible belts respectively entrained about the wheel assemblies on each side of the vehicle, comprising: means for connecting the axle to the frame only between the mid portion of said axle and said frame at substantially the point of intersection between said mid portion and said centrally disposed plane so that said axle is permitted to universally swivel relative to said frame and said centrally disposed plane and said axle is permitted to move longitudinally relative to said frame; and   a controllable force generating mechanism connected at one end directly to the frame and connected at the other end directly to the axle only between the first pair of wheel assemblies, said axle being movable longitudinally relative to the frame, and the controllable force generating mechanism being adapted to apply and maintain at least a predetermined tension in the first and second belts and selectively to release the tension for   
     
     
        removal of the belts..Iaddend. .Iadd.15.  The mechanism, as set forth in claim 14, wherein the first and second inextensible belts frictionally engage the respective wheel assembly of the second pair of wheel assemblies to provide a frictional driving force therebetween, said predetermined tension in said belts generated by the controllable force generating mechanism is sufficient to maintain said frictional driving 
     
     
        force. .Iaddend. .Iadd.16.  The mechanism, as set forth in claim 1, wherein the first and second inextensible belts frictionally engage the respective wheel assembly of the second pair of wheel assemblies to provide a frictional driving force therebetween, said predetermined tension in said belts generated by the controllable force generating mechanism is sufficient to maintain said frictional driving force. .Iaddend.