Abstract:
A traction band with improved ground-engaging lugs is disclosed. The traction band generally comprises an endless body extending along the longitudinal axis of the traction band. The body comprises an outer ground-engaging surface and an inner sprocket wheel engaging surface. The inner sprocket wheel engaging surface can comprise rows of drive lugs cooperating with the sprocket wheel. The outer ground-engaging surface comprises a series ground-engaging lugs which, according to the present invention, have a generally H-shape, I-shape, C-shape, O-shape or a rectangular shape when viewed from the top.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to an endless traction band or track that is used to propel track laying vehicles. More particularly, the present invention relates to a traction band with improved ground-engaging lugs.  
       BACKGROUND OF THE INVENTION  
       [0002]     Traction band for use on snowmobile, wheel-replacement traction kit, skid-steer and other well known track laying equipments and vehicles are known in the art and their uses increase with each passing year. The use of these traction bands allow track-laying vehicles to travel over soft, muddy, snowy, sandy and other similar terrain.  
         [0003]     In the case of traction bands for snowmobile, numerous improvements have been done throughout the years to enhanced the performance, the resistance, the rigidity, the noise profile and other characteristics of these bands.  
         [0004]     Nowadays, traction bands, especially for snowmobiles, are known to comprise transverse reinforcing rods or stiffeners to rigidify the band, specific clip and/or holes patterns to reduce the noise generated by the band, adapted drive lugs and corresponding sprocket wheels to improve the transmission of power between the motor and the band. Even the material of the bands themselves, far from being only rubber, now comprises steel cords, fabrics, Kevlar™ and other composite reinforcing material.  
         [0005]     Nevertheless, the transmission of the power of the motor to the ground ultimately depends on the ground-engaging lugs which effectively contact the ground. Some improvements have been proposed in recent years. For example, the Applicants proposed, in co-pending U.S. patent application Ser. No. 10/414,557, a snowmobile traction band which comprises ground-engaging or traction lugs with specific profiles to reduce the wear of the traction band and improve the handling of the vehicle.  
         [0006]     In U.S. Pat. Nos. 6,505,896 and 6,609,771, we can see two different traction lugs configurations which are respectively designed to be higher and bulkier. These traction bands provide a better traction but with a corresponding increase in the weight of the track.  
         [0007]     U.S. Pat. No. 6,626,258, granted to Forbes, is probably the closest prior art of the present invention. The traction lugs of Forbes comprise rigidifying portions which are generally transverse with respect to the lugs.  
         [0008]     However, in the prior art, in order to improve the rigidity and the resistance of the traction lugs, the usual method was to enlarge the lugs and to make them higher. The net results were indeed stronger lugs but also a heavier traction band which, in the end, is more costly and less efficient.  
         [0009]     There is therefore a need to improve the design of the ground-engaging lugs of traction bands to enhance the resistance and the rigidity of these lugs without increasing their size and thus the weight of the band.  
       OBJECTS OF THE INVENTION  
       [0010]     Accordingly, an object of the present invention is to provide a traction band with improved ground-engaging lugs that obviate the above-mentioned disadvantages.  
         [0011]     Another object of the present invention is to provide a traction band which comprises more rigid ground-engaging lugs.  
         [0012]     Still another object of the present invention is to provide a traction band which comprises more resistant ground-engaging lugs.  
         [0013]     A further object of the present invention is to provide a traction band which is generally not heavier than a standard prior art traction band.  
         [0014]     Other and further objects and advantages of the present invention will be obvious upon an understanding of the illustrative embodiments about to be described or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.  
       SUMMARY OF THE INVENTION  
       [0015]     According to one aspect of the present invention, a traction band with improved ground-engaging lugs is provided. The traction band comprises an endless body which extends along the longitudinal axis of the band. The body comprises an inner surface and an outer surface. The inner surface preferably comprises rows of drive lugs which cooperate with the sprocket wheel to transfer the power from the motor to the band. The inner surface can also comprises rows of holes wherein each two consecutives holes define a clip area which generally support a clip. The outer surface comprises a plurality of ground-engaging lugs which are generally transversely disposed along the longitudinal axis of the band.  
         [0016]     According to a preferred embodiment of the present invention, the material forming the ground-engaging lugs is generally partially longitudinally displaced. In a preferred embodiment, the lug is formed in a I or H shape when viewed from the top. As a result, the ground-engaging lugs are more resistant, more rigid and improve the traction capabilities of the band without adding more lug material and thus, without increasing the weight of the band. The lugs, according to the present invention therefore generally improve the weight/rigidity ratio of the lugs. Similar results have also been obtained with lugs having a C-shape, O-shape or square shape. Other shapes which shall be described below have also shown similar performances.  
         [0017]     According to a preferred embodiment, when the ground-engaging lug is viewed from the top, the bulk of the material that composes the lug is generally displaced in generally two longitudinally offset portions, joined by a connecting portion, in order to preferably obtain an “I” or “H” shaped lug.  
         [0018]     Generally speaking, when viewed from the top, such lug has a shape reminiscent of the shape of a section of a steel I-beam.  
         [0019]     When the lugs are in use, their base (the portion of the lug which is contact with the traction band) is subjected to extreme traction and compression forces. Overtime, the prior art lugs will break or at least be partially destroyed. By longitudinally displacing lug material away from the general center of the lug, where the forces are the lowest, to the outer edges, where the traction and compression forces are the highest, the resistance and rigidity of the lug are greatly improved without adding new material. Since each lug is more rigid, it has a lesser tendency to bend under the strain of the friction between the ground and the lug. This, in return, improves the traction capability of the band.  
         [0020]     All these advantages are obtained without the addition of supplemental material and without generally altering the height and/or size of the lugs. This is achieved by displacing a portion of the lug material located generally in the center of the lug, where the forces are lesser to where the forces are the greatest, that is, away from the general center of the lug.  
         [0021]     The invention accordingly comprises the furthers of construction, combination of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     For a fuller understanding of the nature and object of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings in which:  
         [0023]      FIG. 1  is a partial top view of the traction band comprising a first embodiment of the ground-engaging lugs.  
         [0024]      FIG. 2  is a partial side view of the traction band shown in  FIG. 1 .  
         [0025]      FIG. 3  is a close-up top view of a portion of the traction band shown in  FIG. 1 .  
         [0026]      FIG. 4  is an enlarged side view of the first embodiment of the lug of the present invention.  
         [0027]      FIG. 5  is a close-up top view of a second embodiment of the present invention.  
         [0028]      FIG. 6  is a close-up top view of a third embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0029]     With reference to the annexed drawings, the preferred embodiments of the present invention will be herein described for indicative purposes and by no means as of limitation.  
         [0030]     The following description will be made with respect to a traction band for a snowmobile. However, it is to be understood that traction bands used on other track-laying vehicles shall comprise characteristics which can differ from the one set forth here. Still, the ground-engaging lugs of the present invention can be used on other types of traction bands without departing from the scope of the invention which will be defined in the appended claims.  
         [0031]     Referring now to  FIGS. 1 and 2 , we can see partial top and side views of a traction band  10  which comprises a sprocket engaging surface  12  and a ground-engaging surface  14 . The sprocket engaging surface  12  preferably comprises rows of drive lugs  20  which are adapted to cooperate with the sprocket wheel (not shown) of the vehicle in order to transmit power from the motor (not shown) to the traction band  10 .  
         [0032]     The traction band  10  also preferably comprises a plurality of stiffeners or reinforcing rods  30  (shown in dotted lines), transversely embedded into the band  10  and generally evenly spaced. The stiffeners  30  are generally longitudinally aligned with the drive lugs  20 . The space between two consecutive stiffeners and thus, drive lugs, generally defines the pitch  21  of the traction band.  
         [0033]     The outer or ground-engaging surface  14  of the band  10  comprises a plurality of ground-engaging lugs  40  and  140  which are generally transversely disposed. The lugs  40  and  140  are generally and preferably disposed above the embedded stiffeners  30 . Each two consecutive lug zones  22  are generally separated by a generally flat and lug-less zone  23 . The choice of the pattern of the traction lugs  40  and  140  is important and has an impact on the performance of the traction band. However, the pattern of the traction lugs  40  and  140  is not the object of the present invention and the pattern shown in  FIGS. 1-3  is for illustrative purpose only and in no way limitative in nature.  
         [0034]     The preferred embodiment of the lug of the present invention is generally indicated as  140 . Lugs  140  are best viewed in  FIG. 3  where they have been enlarged for better clarity. The zone  22  where the lugs  140  are disposed comprises a generally central lateral axis  141  which divides the zone  22  into two sides  143  and  145  (see also  FIG. 4 ). The skilled addressee will understand that even though it is preferred that the lugs  140  (and  40 ) be placed over the stiffeners  30 , this is not an absolute requirement. Therefore, the central lateral axis  141  is to be used to clarify the description and not as a limitation.  
         [0035]     According to the present invention, the lugs  140  comprises a first portion  150 , longitudinally displaced with respect with the central axis  141  and extending generally laterally. The first portion  150  also comprises a central longitudinal axis  151  generally located at the middle of the portion  150 .  
         [0036]     As used herein, the term “central longitudinal axis” refers to an longitudinal (in relation to the traction band) axis passing through the center of a structure.  
         [0037]     The lugs  140  also comprise a second portion  160  longitudinally displaced with respect to the central axis  141 . The second portion also generally extends laterally. As for first portion  150 , second portion  160  also comprises a central longitudinal axis  161  located in its middle.  
         [0038]     Whereas the first portion  150  is longitudinally displaced on first side  143 , second portion  160  is longitudinally displaced on second side  145 .  
         [0039]     Finally, the first portion  150  and second portion  160  are joined by a third portion  170  which is located between and adjacent to first and second portions  150  and  160  and which overlaps the axis  141 . The third portion thus longitudinally extends on both sides of the axis  141 . The third portion also comprises a central longitudinal axis  171 .  
         [0040]     As best seen in  FIG. 3 , the width  155  of the first portion  150  and the width  165  of the second portion  160  are greater that the width  175  of the third portion  170 . Also, the skilled addressee will observe that first portion  150  and second portion  160  are generally larger than the third portion  170 . Still, the width  155  of the first portion  150  need not to be equal to the width  165  of the second portion  160 . In fact, it could be possible to find, on the same track  10 , some lugs  140  with portions  150  and  160  of equal width and some other lugs  140  with portions  150  and  160  of different width.  
         [0041]     In order to obtain the best results, it is preferable to provide lugs  140  with a generally I-shape or H-shape when viewed from the top. Therefore, the central longitudinal axis  151 ,  161  and  171  should preferably be substantially aligned. However, depending on the exact shape of each portions, lugs  140 , wherein the axis  151 ,  161  and  171 , of the first portion  150 , second portion  160  and third portion  170  respectively, are not perfectly aligned or are offset, could be contemplated without departing from the scope of the invention. Indeed, a variant wherein the axes are not aligned shall be described below.  
         [0042]     Moreover, should it be required, a plurality of third portions  170  could be used to join first portion  150  and second portion  160 . Each of the plurality of portions  170  would understandably be generally laterally spaced from each other. For example, a fourth portion (not shown), similar to the third portion  170  but laterally offset could be added to the lug  140 . This variant would generally have a square (or rectangle) shape, an oval shape or an O-shape.  
         [0043]     The reason for this novel design is that when traction lugs  140  are in use, they are subjected to flexion strain which will tend to bend the lugs  140 . As they bend, traction forces and compression forces are applied to the base of the lugs  140  and principally at the outer edges  147  and  149  ( FIG. 4 ). However, almost no force is applied to the central portion  153  of the lug  140 .  
         [0044]     The lug material located on the central portion  153  is thus less strained.  
         [0045]     The lugs  140  have the particularity that the bulk of the lug material (first portion  150  and second portion  160 ) is displaced at the outer edges  147  and  149  where the compression and traction forces are the highest. In the center portion  153 , where less forces are applied, the lugs  140  comprises less lugs material (third portion  170 ). This particular shape of lugs  140  therefore provides a better rigidity to weight ratio since the lugs  140  are more rigid without being larger. Lug material has in fact be allocated to where the forces are the highest.  
         [0046]     Even though a preferred embodiment has just been described, it is to be understood that the concept of displacing lug material to where the forces are highest can be generalized and embodied in multiple variants. Such variants are shown in  FIGS. 5 and 6 .  
         [0047]     In  FIG. 5 , the lug  240  is generally divided in two by a lateral axis  241 . The axis  241  defines a first side  243  and a second side  245 . The lug  240  comprises a first portion  250 , generally located on the first side  243 , a second portion  260 , generally located on the second side  245  and a third portion  270 , generally located in the center and overlapping the axis  241 . The third portion  270  generally connects the first portion  250  and the second portion  260 . However, the skilled addressee will understand that in lug  240 , the third portion  270  could be removed and the first  250  and second  260  portions made to contact each other directly near the axis  241 . A fourth portion  290  could be added, as shown in  FIG. 5  but is not absolutely necessary.  
         [0048]     In  FIG. 5 , the first portion  250  and second portion  260  have generally triangular shape when viewed from the top. These portions are thus different than the ones shown in  FIG. 3  which are generally laterally extending. In fact, in the embodiment of  FIG. 5 , the displacement of lug material away from the center is more gradual than in the embodiment of  FIG. 3 . However, the bulk of lug material is still substantially away from the axis  241 .  
         [0049]     The embodiment shown in  FIG. 6  is slightly different. This embodiment  340  is also divided in two by a lateral axis  341  which defines a first side  343  and a second side  345 . The lug  340  comprises a first portion  350  located on the first side  343 , a second portion  360 , located on the second side  345  and a third portion  370  located generally in the center, overlapping the axis  341 . The third portion  370  is located between and adjacent to first portion  350  and second portion  360 . Whereas in the embodiment  140  of  FIG. 3 , the first portion  150 , the second portion  160  and the third portion  170  were generally aligned, in this lug  340 , the first portion  350 , the second portion  360  and the third portion  370  are generally laterally offset.  
         [0050]     Furthermore, it is contemplated, as best shown in  FIG. 6 , to add a fourth portion  390  and a fifth portion  380 . The fourth portion  390  is generally located on the first side. As for the fifth portion  380 , it acts as the third portion  370 , in linking the second portion  360  to the fourth portion  390 . As for portions  350 ,  360  and  370 , portions  360 ,  380  and  390  are generally offset. In  FIG. 6 , the lug  340  therefore generally defines a “V” shape.  
         [0051]     Yet, with or without portions  380  and  390 , the lug  340  expresses the same concept of lug material displacement. Indeed, first portion  350  and second portion  360  are generally located away from the axis  341  and are larger than central portion  370 . Thus, the lug material is allocated where the forces are the highest as in the first and second embodiment.  
         [0052]     Although the present traction band has been described with a certain degree of particularity it is to be understood that the disclosure has been made by way of example only and that the present invention is not limited to the features of the embodiment(s) described and illustrated herein, but includes all variations and modifications within the scope and spirit of the invention as hereinafter claimed.