Patent Description:
Forestry machines are usually equipped with wide rubber tires. In some circumstances tracks are needed to provide better traction and climbing ability. Tracks decrease the surface pressure whereby damage to forest ground may also decrease. Special tracks have been designed for wet and marshy condition and for snow and ice. Such track should give good flotation together with good cleaning properties with ejection of snow and mud. Since tracks designed for traction may clog and jam in marshy or snowy conditions, they are not suitable for terrains where good flotation is needed. On the other hand, tracks that provide good flotation do not generally have good gripping properties. For these reasons each machine must have two sets of tracks if the machine if used in varying conditions and terrains, as they usually are. Investing for two set of tracks is of course a high financial burden.

The tracks for terrain vehicles equipped with rubber tires comprise a traction bar that extends over the width of the tire and has guide plates at each end. The guide plates reach over the edge of the tire and to the sides so that they hold the tire therebetween. This structure is typical for tracks designed for rubber tires as guide plates are needed for keeping the tracks on the tires. For this reason the tracks for rubber tires differ from tracks used for example in earth moving machines. The traction bars have also ears at their ends extending perpendicularly to the length of the traction bars. These ears have holes for chain links that join the traction bars together to form a complete track. In such a structure the wear is concentrated on the ears and chain links. When these parts are outworn, they have to be replaced by cutting them off from the traction bars. New parts can then be welded to replace the old ones. This repair method is quite time consuming, laborious and expensive.

Terrain going vehicles with tracks are described in documents <CIT> (which discloses the preamble of claim <NUM>, the corresponding features of claim <NUM>), <CIT> and <CIT>.

According to a first aspect of the present invention, there is provided a track assembly for a terrain going vehicle having tires, according to claim <NUM>.

According to a second aspect of the present invention, there is provided a track assembly for a terrain going vehicle having tires, according to claim <NUM>, the track assembly comprising at least two traction bars, each having a body that is dimensioned to extend over the width of the tire and have guide plates extending from the body so that they can be set to reach over the edge of the tire and to the sides of the tires, ears at each end of each traction bar, extending crosswise on relation to the length of the traction bar and on both sides of the body of the traction bar, the ears having each at least one hole for links that join the traction bars together to form a complete track, at least one link formed of a chain link and set to run through the holes of the ears to form a chain with the traction bars, at least one flotation bar placed between two parallel traction bars, the flotation bar having a longitudinal body and an attachment fork with at least one locking hole at each end of the longitudinal body, and a locking pin set through to each of the locking holes and connecting the attachment fork to the link between the two parallel traction bars.

In the present context, the term track assembly comprises full closed tracks and partial lengths of such tracks.

Lengthwise direction of the track assembly is the direction of the centreline of the longitudinal direction of the track.

Crosswise direction of the track assembly is crosswise to the lengthwise direction and same as length wise direction of the traction bars.

Forestry machines are usually equipped with wide rubber tires. In some circumstances tracks are needed to provide better traction and climbing ability. Different types of tracks are needed for different terrain conditions. One aspect of this invention is to provide a track assembly that can be accommodated to different terrain conditions simply by attaching accessories to the basic track. These parts may be designed to provide better flotation in marshy or snowy condition or better traction when it is needed or a combination of these properties. The idea of changing the properties of the track assembly by adding or removing accessories allows high flexibility and reduces cost as only one track with suitable accessories is needed instead of two or more tracks. Another feature of the invention is use of links and locking pins for making the track chain. By locking the rotation of the pins wear can be focused on easily changeable parts. Thus maintenance and repair of the track assembly is cost effective and fast compared to earlier methods.

<FIG> illustrates a set of tires equipped with a track assembly not in accordance with at least some embodiments of the present invention. The set of tires has in this example two tires <NUM>, which are in forestry machines usually rubber terrain tires set on metal spokes. The track assembly <NUM> comprises traction bars <NUM> that are perpendicular to length direction of the track assembly <NUM>. The purpose of the traction bars <NUM> is to provide good grip on the ground or any surface the vehicle is moving. The traction bars <NUM> are usually made of steel and various manufacturers have own specifications for the shape of the bar. The length of the traction bar <NUM> is set so that it extends over the width of a tire and depends thus of the dimension of the tires. The traction bars <NUM> have guide plates <NUM> at each end of the traction bar <NUM>. The purpose of the guide plates <NUM> is to keep the track assembly <NUM> on the tires <NUM>. As tires <NUM> don't have guide surfaces or grooves as wheels used with caterpillar tracks, the track assembly suitable for tires has to be guided at the edges of the tires <NUM> in order to keep the track assembly <NUM> on the tires even in difficult terrain conditions.

<FIG> and <FIG> illustrate the same track as in <FIG> but equipped with flotation bars <NUM>, in accordance with at least some embodiments of the present invention. The flotation bars <NUM> are set between two parallel traction bars <NUM>. Usually the flotation bars <NUM> are used in every gap between two parallel traction bars <NUM> but it can be contemplated that smaller number of flotation bars are used and some gaps are left empty. This way the balance between traction ability and surface pressure can be adjusted, if needed or desired.

The structure of the track assembly <NUM> is described in the following with reference to <FIG>. A track assembly <NUM> for a terrain going vehicle having tires <NUM> according to example in these figures comprises at least two traction bars <NUM>, each having a body <NUM> that is dimensioned to extend over the width of a tire <NUM>. The body <NUM> is curved so that it accommodates the outer shape of the tire <NUM> and provides an extension in crosswise direction of the rotation direction of the wheel. The crosswise extension and detailed shape of the body <NUM> may vary according to design preferences of the manufacturer. The body <NUM> has guide plates <NUM> extending from the body <NUM> so that they can be set to reach over the edge of the tire <NUM> and to the sides of the tires <NUM>. The guide plates <NUM> are flat plates that extend in an obtuse angle from the distal ends of the body <NUM> so that the body <NUM> and the guide plates <NUM> form an opening U-shape to accommodate the tire <NUM>. The shape of the guide plates <NUM> can be varied.

The body <NUM> comprises a set of four ears <NUM>, <NUM> at each end of each traction bar <NUM> extending crosswise on relation to the length of the traction bar <NUM>. The ears are set on both sides of the body <NUM> of the traction bar <NUM> so that a pair of ears <NUM>, <NUM> is on each opposite sides of the end of the body <NUM>. The ears <NUM>, <NUM> are directed to extend in the lengthwise direction of the track assembly. The set of ears comprise inner ears <NUM> set opposite each other on the body <NUM> and outer ears <NUM> set at a distance from the inner ears <NUM> towards the ends of the body <NUM>. The pair of inner ear <NUM> and outer ear form a slot <NUM> that is directed in the lengthwise direction of the track assembly <NUM>. The guide plates <NUM> may be joined with inner ears <NUM> or made as a separate structure.

The ears <NUM>, <NUM> have each at least one hole <NUM> for connecting to links <NUM> that join the traction bars <NUM> together to form a complete track assembly. The link11 has a link body <NUM> with a length and one connecting hole <NUM> at each opposite end of the link body <NUM>. The track assembly <NUM> is constructed by connecting traction bars <NUM> with links <NUM> and pins <NUM>. The pins <NUM> are set to run through a pair of one connecting hole <NUM> of the link body <NUM> and a hole <NUM> in inner ear <NUM> and outer ear <NUM> of the traction bar <NUM> in order to form a track chain. The pins <NUM> are locked in relation to the holes <NUM> of the ears <NUM>, <NUM> so that rotation of the pins <NUM> in the holes <NUM> is prevented. The locking of the pins <NUM> can be accomplishes simply by welding the pins to at least one of the ears <NUM>, <NUM>. Alternatively the locking may be accomplishes by using locking grooves and wedges or other shapes that prevent rotation of the pin <NUM> in the hole <NUM>.

The link <NUM> or more precisely the link body is made of single piece of material, for example steel. The link <NUM> is very simple an easy to manufacture. As can be seen from <FIG>, the link body <NUM> has two grooves <NUM>, <NUM> running crosswise to the length of the link body <NUM> in the middle of it length. Larger of the grooves is a positioning groove <NUM> and smaller is groove <NUM> for locking pin <NUM>. This shape facilitates mounting of flotation bars <NUM> on the links <NUM>.

The flotation bars <NUM> comprise a longitudinal body part <NUM> and an attachment fork <NUM> with at least one locking hole <NUM> at each end of the longitudinal body part <NUM>. The locking pin <NUM> is set through to the locking holes <NUM> to connect the attachment fork <NUM> to the link <NUM> between two parallel traction bars <NUM>. Usually at least at least one flotation bar <NUM> is placed between two parallel traction bars <NUM>. The longitudinal body part <NUM> can have various shapes depending of what kind of traction or flotation properties are needed. The opening v-shape shown in FIGURES provides good flotation and resists clogging of the track assembly. Protruding sawtooth shapes, spikes or gripping scoops may be used in circumstances where extreme traction and gripping power is needed. The possibility to use various shapes of flotation bars high flexibility without need of several specialized tracks.

One embodiment of the attachment fork <NUM> comprises two parallel extensions <NUM> having the locking holes <NUM> at their respective ends, the extensions <NUM> being placed at a distance from each other so that there is a gap <NUM> between the extensions <NUM>. The gap <NUM> is dimensioned to accommodate the link <NUM> so that a link placed in the gap <NUM> sets between locking pin <NUM> set in locking holes <NUM> and bottom of the gap <NUM>. Now the bottom of the gap <NUM> is on the positioning groove <NUM> that holds the attachment fork <NUM> and whole flotation bar <NUM> in place. The groove for locking pin <NUM> accommodates the locking pin <NUM>. Instead of a groove the link may comprise a hole for the locking pin <NUM>.

<FIG> illustrates a track assembly wherein the links are formed of chain links <NUM>. The ears of the traction bars <NUM> are loops <NUM> that are compatible to traditional chain links <NUM>. The chain links <NUM> are set to run through the holes of the loops <NUM> to form a chain with the traction bars <NUM>. Flotation bars <NUM> are mounted on the chain links <NUM> through attachment forks <NUM> and secured with locking pins <NUM>.

A method for repairing a track assembly comprises steps of removing locking of the pins <NUM>. For example, if pins <NUM> are secured by welding, welding is cut open, whereafter removing the pins <NUM> and links 11can be done simply by pulling the pins off from the holes. After this, the whole track assembly is disassembled. Assembly is done in opposite order by replacing the pins and links and securing the pins so that the rotation of the pins in the holes is prevented, for example by welding. If other securing system than welding is used, disassembly and assembly may involve opening bolts and nuts, securing rings or pins and such.

The assembly in <FIG> shows a track assembly with an alternative type of a flotation bar <NUM>. This flotation bar <NUM> comprises a longitudinal body part <NUM> and a similar attachment fork <NUM> as described above in one end. At the opposite end to the attachment fork <NUM> is a hook <NUM> formed of a hook body <NUM> and a notch <NUM> facing towards the attachment fork <NUM>. The notch <NUM> forms the hook <NUM> at the end of the hook body <NUM>.

The idea of the hook <NUM> is to simplify the structure and assembling of the track. Now the hook <NUM> can be placed around a link <NUM> or a chain link <NUM> ina tracxk assembly and the attachment fork <NUM> over the link <NUM> or a chain link <NUM> on the other side of the track assembly. Only one locking pin <NUM> is needed when this type of flotation bar is used. In <FIG> this type of flotation bar <NUM> is shown in a track assembly of <FIG> but would be suitable for track assemblies of <FIG> also or other type of track assemblies having links connecting the traction bars <NUM>.

Claim 1:
A track assembly (<NUM>) for a terrain going vehicle having tires (<NUM>), the track assembly (<NUM>) comprising:
- at least two traction bars (<NUM>), each having a body (<NUM>) that is dimensioned to extend over the width of a tire (<NUM>) and guide plates (<NUM>) extending from the body (<NUM>) so that they can be set to reach over the edge of the tire (<NUM>) and to the sides of the tires (<NUM>),
- ears (<NUM>, <NUM>) at each end of each traction bar (<NUM>), extending crosswise on relation to the length of the traction bar (<NUM>) and on both sides of the body (<NUM>) of the traction bar (<NUM>), the ears (<NUM>, <NUM>) having each at least one hole (<NUM>),
- at least one link (<NUM>) having a link body (<NUM>) with a length and one connecting hole (<NUM>) at each opposite end of the link body (<NUM>), and
- pins (<NUM>) set to run through a pair of one hole of the link body (<NUM>) and at least one hole of an ear (<NUM>, <NUM>) of the traction bar (<NUM>) in order to form a chain, wherein the pins (<NUM>) are locked in relation to the holes (<NUM>) of the ears (<NUM>, <NUM>) so that rotation of the pins (<NUM>) in the holes (<NUM>) is prevented,
characterized of
- at least one flotation bar (<NUM>) placed between two parallel traction bars (<NUM>), the flotation bar (<NUM>) having a longitudinal body part (<NUM>) and an attachment fork (<NUM>) with at least one locking hole (<NUM>) at least at one end of the longitudinal body part (<NUM>) and an attachment element in the opposite end of the longitudinal body part (<NUM>), and
- a locking pin (<NUM>) set through at least one of of the locking holes (<NUM>) and connecting the attachment fork (<NUM>) to the link (<NUM>) between the two parallel traction bars (<NUM>).