Automatic Track Drive Tensioner

A system and method for automatically adjusting the tension of a track on a snow machine, or other track-driven vehicle, is disclosed. The system includes an axle mounted in slotted adjustment holes with an axle bolt or other means to fix the axle to the track guide of the track-driven machine. The system also includes one or more biasing members to exert a force on the axle. When an axle bolt is loosened, the axle moves forward or backward in the adjustment slots to achieve the proper tension on the track. The axle bolt can then be tightened to fix the location of the axle in the adjustment slots at the location that provides proper tension for the track. The system obviates the need to use complicated tools and procedures to properly tension the track.

BACKGROUND

Snow machining is a popular winter sport. Snow machines have evolved from basic winter transportation used in remote areas to a fully developed motorsport. Long travel suspensions and powerful engines have enabled ski machines to compete in arenas formerly occupied only by motorcycles and bicycles. Events involving ski machines include ski machine motocross, free-style jumping, and cross country racing, among other things.

Snow machines, snow cats, snow bikes, and other vehicles often use track drives. The tracks can be attached to the engine in a similar manner to that used for military track drives, such as on tanks and half-tracks. The tracks are wide and offer a lower surface pressure than a standard wheel, for example, to help prevent sinking in snow, sand, or other loose material. The tracks can be equipped with different “tread” patterns to handle different conditions. The tracks may be equipped with deep paddles, for example, for use in mud or deep snow.

DETAILED DESCRIPTION

As mentioned above, there are a number of vehicles that use track drives. Snow machines and snow bikes, for example, often use wide, flexible tracks with a variety of tread features depending on what type of terrain and conditions will be encountered. Snow machine tracks were originally manufactured from steel reinforced rubber, similar to a car tire. Modern tracks tend to comprise composite materials, however, such as Kevlar®.

Regardless of their composition, however, the tracks stretch over time. In addition, due in part to their large width, they may also stretch in a slightly nonlinear manner. In other words, due to the layup of materials and/or belts inside the track, manufacturing tolerances, drive systems, and other factors, the track may stretch slightly more in the middle than on the sides (or vice-versa), or may stretch more on one side than the other. As a result, tensioning the track can be a time consuming and tedious process.

In many cases, the vehicle must be run to bring the track up to operating temperature and then the vehicle must be supported on a jack, stand, or lift such that the track is off the ground. The adjusters, axle bolts, or other fasteners securing the axle for the track are then loosened and a weight is hung from a predetermined location on the vehicle's swingarm. The adjusters are then tightened and the vehicle is ridden again to bring the track back up to temperature. The vehicle is then placed back on the stand or lift to recheck the tension of the track. The process can take an experienced mechanic 30 minutes or more. Obviously, a novice may take considerably longer.

To this end, examples of the present disclosure can comprise a system for automatically tensioning the track of a track-driven vehicle, such as a snow machine or a snow bike. The system can enable the user to simply loosen the fixing mechanism (e.g., the axle) on the vehicle. When loose, one or more biasing elements can provide the necessary tension in an even manner such that, when then adjusters are tightened, no further adjustment or checks are necessary. The system can also eliminate specialized tools such as weights, track tension gauges, and adjusters, which are required when using conventional track adjustment mechanisms.

As shown inFIGS. 1 and 2, the system100can comprise a track guide102for guiding a track (not shown) on a track-driven vehicle. The track guide102can include frame members104and one or more cross members106. One or more of the cross members106can also act as a roller, or guide108for the track. The system100can also include an axle110, one or more idlers112, and one or more biasing members114.

As shown, in some examples, the frame members104and cross members106can provide the basic framework for the track guide102. The frame members104can comprise a suitably light, strong material such as, for example, steel, plastic, carbon fiber, plastic, or other composite material. The frame members104are preferably aluminum. In some examples, the cross members106can comprise one or more spacers116aand one or more bolts116b.In this manner, the cross members106can set the spacing and provide rigidity to the track guide102. In some examples, the cross members106can also comprise one or more guides108, or rollers, to promote proper alignment of the track and to reduce friction between the track and the system100.

In some examples, the frame members104can also comprise one or more wear guards118. As the name implies, the wear guards118can be disposed in an overlying manner to the surfaces of the frame members104that come in contact with the track. In this manner, the wear guards118can be sacrificial (i.e., the wear guards118can act as a wear surface) to prevent damage to the frame members104caused by the friction of the track over the frame members104. In some examples, the wear guards118can also provide a lower coefficient of friction between the frame members104and the track. In this configuration, the wear guards118can comprise a material that is very hard, contains inherent lubricity, or otherwise lowers the friction between the track and the wear guards118.

In some examples, the wear guards can comprise a hard plastic or composite such as, for example, ultra-high molecular weight (UHMW) polyethylene (e.g., TIVAR®), Kevlar®, or nylon. In some examples, the wear guards118can be detachably coupled to the frame members104to facilitate their replacement when sufficiently worn. The wear guards118can be, for example, slid over a channel on the frame members104and/or bolted, screwed, clipped, or otherwise secured to the frame members104.

As mentioned above, tracks stretch over time. Thus, when it is new, a track is at its minimum length (and the axle110is in the forward most position). As the track wears, the overall length of the track increases, necessitating adjustment to maintain the same track tension. When the track has reached a maximum predetermined length (i.e., the axle110has reached the limit of its rearward adjustment), the track is considered to be worn out and needs to be replaced. Failure to do so can result in the track breaking and/or slipping on the drive due to a lack of tension. The tension can be adjusted by moving the axle110rearward in adjustment slots120in the frame members104to increase the tension of the idlers112on the track.

The idlers112can comprise a suitably hard, yet resilient material to enable them to contact and tension the track. In some examples, the idlers112can comprise rubber tires, plastic wheels, or rollers in contact with the track. In some examples, the idlers112can also comprise teeth, or other means, to engage with the track. In other examples, the idlers112can also comprise a groove, similar to the groove shown in the guide108, to maintain the alignment of the track. In this configuration, the idlers112can not only tension the track, but also maintain the alignment of the track. In some examples, the idler112can also comprise a continuous roller, or spool, spanning a majority of the axle110.

As mentioned above, in some examples, the frame members104can define one or more adjustment slots120to enable the axle110to move forward and backward in the frame members104. This enables the idlers112to move backward and forward to tension the track. The axle110can be affixed to the system100using one or more axle bolts122, or similar. In this manner, when the axle bolt122is tightened to a predetermined tightening torque, the axle110is substantially fixed to the frame members104in the adjustment slots120. When the axle bolt122is loosened, on the other hand, the axle110is free to move back and forth in the adjustment slots120to affect adjustment of the track tension.

The system100can also include one or more adjustment collars124. In some examples, the biasing members114can comprise a first end114aand a second end114b. The first ends114aof the biasing members114can be pivotally coupled to the frame member104or a cross member106. The second ends114bof the biasing members114can be pivotally coupled to the adjustment collars124. This can enable the biasing members114to transmit the adjusting force to the axle110, though the movement of the axle110in the adjustment slots120and the force provided by the biasing members114may not be parallel. In some examples, as shown, the axle110can be disposed through, or attached to, the adjustment collars124.

In some examples, as shown, the axle bolt122can comprise a single through-bolt that passes through the adjustment collars124, axle110, and adjustment slots120. The axle bolt122can also comprise one or more washers and/or nuts to secure the axle bolt to the track guide202. In some examples, the axle bolt122can comprise a stud with nuts and washers threadably engaged on both ends. In still other embodiments, the ends of the axle110or adjustment collars124can be threaded and the axle bolt122can comprise two bolts threaded into the axle110or adjustment collars124from the outside of the frame members104.

The biasing members114can comprise units suitable to provide the proper tension to the track. In some examples, the biasing members114can comprise, for example, hydraulic cylinders or springs suitable to provide this tensioning force. In other examples, the biasing members114can comprise pneumatic shocks similar to those used for hood and hatch struts on vehicles.

The track tension can vary from machine to machine based on horsepower, torque, track length, track width, swingarm length, and track material and tread pattern, among other things. To this end, the gas and/or hydraulic pressure and piston size of the biasing members114can enable the biasing members114to be designed and/or adjusted to provide the proper tension for different tracks. In some examples, the biasing members114can also comprise Schrader valves, or similar, to enable adjustment of the tension via pressurized gas (e.g., air or nitrogen). In this manner, a single biasing member114, or set of biasing members114, can be used with a variety of different types of tracks. In other examples, different biasing members114can be designed for each vehicle or based on type of track, tread pattern, engine size, etc.

In some examples, the biasing members114can be sized and shaped such that they provide substantially consistent tension throughout the range of motion of the axle110. In some examples, this can be achieved by using an appropriately sized piston and body for the biasing member114. In other examples, the range of adjustment of the adjustment slot120can be suitably small (i.e., short) in comparison to the stroke of the biasing member114such that any changes in the force exerted by the biasing members114from the forward most position to the rear most position are negligible. In still other examples, the biasing members114can employ pulleys, eccentrics, levers, or other means to maintain a constant force on the axle110throughout its travel.

In addition to requiring periodic adjustment to track tension, the track may also have a range of allowable tensions (e.g., tension to between 20-25 ft./lbs.). To this end, in some examples, the biasing members114can be configured to provide the maximum allowable tension when the track is new (i.e., axle forward) and the minimum allowable tension when the track reaches its maximum allowable length (i.e., axle rearward). In this manner, though the tension decreases slightly as the track stretches and the axle110moves rearward, the tension of the track is nonetheless maintained within allowable limits.

As shown inFIG. 3, the biasing members114can exert a force, FB, on the axle110via the adjustment collars124(or other suitable means). FB, in turn, can cause the axle110to move rearward in the adjustment slots120of the frame members104. As discussed above, the biasing members114can be designed such that FBprovides the desired tension to a track302mounted on the track guide102. The biasing members114can be hydraulic, pneumatic, or spring-actuated, for example, to provide the desired force, FB. In some examples, FBcan be adjusted by adjusting, for example, the spring pre-load or air pressure in the biasing members114.

As shown, the biasing members114can be pivotally coupled to the frame members104and the axle110to enable them to move through the range of motion of the axle110without binding. In some cases, the biasing members114can be mounted parallel to the adjustment slots120, such that FBis substantially parallel to the direction of adjustment for the axle110. In other example, as shown, the biasing members114can be disposed at an angle to the adjustment slots120. This may be more convenient from a packaging perspective, for example.

As discussed below with respect toFIG. 4, to adjust the track302tension, the user need only loosen the axle bolt122, allow the axle110to move rearward in the adjustment slots120. When the resistance from the tension on the track302equals FB(i.e., the two forces equalize), the axle110will stop, and the user can re-tighten the axle bolt122. In this manner, the tension of the track302can be adjusted automatically with no special tools and/or skills required.

As mentioned above, in some examples, the track302may stretch unevenly across its width. This may be due to slight manufacturing defects or variances in the track302material. Regardless, in some examples, the system100can comprise at least two biasing members114disposed on opposite sides of the axle110. In this manner, when the axle bolt122is loosened, the biasing members114can apply equal force to each side of the axle110. This enables the track302to be evenly tensioned despite any slight differences in wear on the track302. It is possible, of course, that the axle110may become slightly skewed, but this slight misalignment is immaterial to the operation of the machine. More importantly, evenly tensioning the track302increases the life of the track302and also reduces wear on other drivetrain components (e.g., the idlers112and guides108).

The use of the biasing members114obviates the need to use complicated tensioning procedures to ensure the track302is properly tensioned. As shown inFIG. 4, the process400is vastly simplified over conventional tensioning techniques that often require special weights or gauges to properly tension the track302. At402, the user can ride the machine until the track302has reached operating temperature. As with most driveline components, the temperature of the track302increases slightly with use, eventually normalizing to a standard operating temperature. Thus, the track302may elongate slightly as it warms to operating temperature. In addition, the track302may become more flexible enabling it to be properly tensioned.

At404, the user can lift the snow machine, or at least the rear of the snow machine, off the ground such that the rear swingarm and track302is unloaded. In some examples, this can be achieved using a floor jack or stand. In other examples, the user may lift the entire vehicle off the ground with a hydraulic or pneumatic lift for this purpose—e.g., similar to an automotive lift.

At406, the user can loosen the axle bolt122(or other axle retainer, as applicable). In this manner, the axle110is free to move backward and forward in the adjustment slots120. In addition, when the axle bolt122is loosened, the biasing members114are free to act on the axle110via the adjustment collars124(or other suitable means). Thus, if the track302is too loose, the force provided by the biasing members114, FB, will overcome the tension of the track302and the axle110will move rearward in the adjustment slots120, and vice versa. Of course, because tracks302tend to stretch over time and not shrink, the opposite would likely only be true if the track302has somehow been manually over tightened, for example.

At408, because the biasing members114evenly and automatically tension the track302to the proper tension, once equalized, the user need only tighten the axle bolt116b. Due to the design of the biasing members114, the axle110is automatically moved to the proper location in the adjustment slots120to provide proper tension on the track302. In addition, when two or more tensioning members114disposed evenly on the axle110are incorporated, the track302tension is also set from side to side. Properly and evenly tensioning the track302increases the life of the track302and the related components (e.g., the idlers112and the guides108). As mentioned above, if the track302has worn unevenly, this may result in the axle110being slightly skewed. This is immaterial to the functioning of the track302, however.

At410, the user can then simply lower the machine back onto the ground. There is no need for special tools or weights to properly tension the track302. There is also no need to ride the machine and then recheck the tension. The system100greatly reduces the complexity of adjusting the tension of the track302. The system100also reduces the time required to adjust the tension. In addition, properly and evenly adjusting the tension of the track302increases the life of the track302and associated components.

The terms “snow machine” and “track” are used herein to simplify the disclosure. These terms are not intended to limit the disclosure. As used herein, the term snow machine could also refer to other track-driven vehicles such as, for example, snow bikes, snow cats, tanks, bulldozers, and bobcats. Similarly, the term “track” is used to describe a continuous, flexible track with a tread pattern as is commonly found on a snow machine. The system could also be used on other machines with belts such as, for example, drive belts, fan belts, and accessory belts, among other things.

The specific configurations, choice of materials, and the size and shape of various elements can be varied according to particular design specifications or constraints requiring a device, system, or method constructed according to the principles of this disclosure. Such changes are intended to be embraced within the scope of this disclosure. The presently disclosed examples, therefore, are considered in all respects to be illustrative and not restrictive. The scope of the disclosure is indicated by the appended claims, rather than the foregoing description, and all changes that come within the meaning and range of equivalents thereof are intended to be embraced therein.