Abstract:
An elastic-bodied crawler, in which a ground pressure distribution is equalized and generation of local wear in use is prevented to provide for durability, and which is driven by drive power from driven projections provided on an inner peripheral surface of the crawler, comprises load propagating means embedded centrally of the crawler in a widthwise direction to extend over treads of rollers. The load propagating means causes pressing forces (ground pressure) of the rollers to act generally in the widthwise direction whereby a ground pressure distribution on a ground surface of the crawler is equalized, local wear in lug portions is eliminated to enhance durability of the crawler.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The invention mainly relates to an elastic-bodied crawler used for construction machines, such as crawler dump truck, hydraulic excavator and the like, and farm machines.  
           [0002]    Conventionally, an endless elastic-bodied crawler formed by covering a plurality of metal core members with an organic elastic material (for example, rubber) has been frequently used in crawler vehicles such as construction machines and farm machines. However, there is caused a problem that because of having metal core members, such elastic-bodied crawler is difficult to cut upon disposal after use, and so must be discarded as it is, which makes it difficult to dispose of the crawler as industrial waste. For such reasons, in recent years, an elastic-bodied crawler without metal core members has been adopted to facilitate cutting and disposal at the time of disposal. FIG. 7( a ) is a top plan view showing a concrete example of a conventional elastic-bodied crawler without metal core members and FIG. 7( b ) is a cross sectional view taken along the line a-a. The conventional elastic-bodied crawler  100  without metal core members is formed integral as shown in FIGS.  7 ( a ) and  7 ( b ) to comprise driven projections  105 , which are provided circumferentially at a predetermined pitch along a center line on an upper surface, and lug portions  102  having a lug  103  formed on an outer surface side (outer peripheral ground surface side) of an endless body  101  having a predetermined width and a predetermined thickness. The body  101  is structurally reinforced by arranging a multiplicity of reinforcement cables  106  near an inner surface of the body over an entire width of the body except ear portions  104  on both sides of the body and over an entire circumference of the body.  
           [0003]    The elastic-bodied crawler  100  thus structured is wound round a sprocket and an idler in a traveling section of a crawler vehicle (not shown) to be able to transmit power in a state, in which the driven projections  105  provided on an inner surface of the elastic-bodied crawler  100  at a predetermined pitch engage with engaging teeth provided on a circumferential surface of the sprocket, and a multiplicity of rollers provided between the sprocket and the idler hold a ground surface side of the elastic-bodied crawler  100  from above to be able to ensure a ground force. In addition, the elastic-bodied crawler  100  is so structured that outer peripheral surfaces of the sprocket and the idler bear flat surfaces  107 ,  107  on both sides of the driven projections  105 .  
           [0004]    Also, with the elastic-bodied crawler  100 , reaction forces during traveling are born by the plurality of rollers  110  provided for the purpose of ensuring a ground force during traveling and the flat surfaces  107 ,  107  on the both sides of the driven projections  105  provided along a center line on an inner surface of the body, as shown in FIG. 8. In addition, the rollers  110  are mounted on both side portions of a support shaft  112 , an intermediate portion of which is rotatably born by a bearing  115  provided and supported on a traveling body frame (not shown), and provided in a manner to contact on both sides thereof with the flat surfaces  107 ,  107  and to bridge areas where the driven projections  105  are provided.  
           [0005]    As described above, with the elastic-bodied crawler  100  wound round the traveling body, load from the rollers  110  is transmitted to a road surface immediately there below as it is. At this time, a ground pressure distribution is localized corresponding to projected surfaces of contact portions of the rollers  110 ,  110 , as shown in FIG. 8. As a result, the lug portions  102  on the elastic-bodied crawler  100  undergo local wear, as shown in FIG. 8. When such local wear is generated, there is caused a problem that not only outward appearance is markedly damaged but also the elastic-bodied crawler is consequently shortened in service life because durability of the elastic-bodied crawler  100  is determined by those portions thereof, which are worn violently.  
           [0006]    In this manner, the elastic-bodied crawler without metal core members involves a problem that the ground pressure distribution is inevitably localized because surfaces pressed by rollers for ensuring pressing forces toward the ground side in order to ensure ground pressure at the time of running drive are defined by flat surfaces on both sides bridging the positions of the driven projections by virtue of the structure, in which driven projections adapted to engage with the sprocket are formed in a central portion in a widthwise direction, and the crawler is formed by an elastic material (for example, rubber), which constitutes the crawler, and the reinforcement cables arranged circumferentially.  
           [0007]    The invention has been thought of in order to solve such problems, and has its object to provide an elastic-bodied crawler, by which the ground pressure distribution is equalized and in which generation of local wear in use is prevented to provide for durability.  
         SUMMARY OF THE INVENTION  
         [0008]    To attain the above object, the invention provides an elastic-bodied crawler driven by drive power from driven projections provided on an inner peripheral surface thereof, comprising load propagating means embedded centrally of the crawler in a widthwise direction to extend in projected areas of treads of rollers.  
           [0009]    According to the invention, since in addition to the reinforcement cables embedded in the body of the elastic-bodied crawler in a widthwise direction, the load propagating means is arranged centrally of the crawler in a widthwise direction to extend in projected areas of treads of rollers to produce a difference in rigidity of the elastic-bodied crawler between portions corresponding to treads of the rollers and the central portion thereof, pressing forces (ground pressure) of the rollers applied with portions, on which the driven projections are provided, therebetween make use of the difference in rigidity to act uniformly generally in the widthwise direction. As a result, there is given an effect that a ground pressure distribution on the ground surface of the crawler is equalized to eliminate local wear in the lug portions, and friction is equalized to enable enhancing durability of the crawler.  
           [0010]    The load propagating means is preferably arranged on a side of a reinforcement layer of main cables embedded in a body toward a portion formed with lugs (second invention). With such arrangement, the load propagating means as well as the reinforcement layer of main cables arranged in the body causes pressing forces applied by the rollers to be positively transmitted to flat portions, which bridge portions below and on both sides of the driven projections, that is, between right and left treads of the rollers in a widthwise direction, so that ground pressure is distributed over the central portion, on which load is not directly applied.  
           [0011]    The load propagating means is preferably formed by arranging and embedding a multiplicity of cables perpendicularly to a circumferential direction of the body or on the bias thereto (third invention). With such arrangement, load can be dispersed in a widthwise direction to act on the ground surface widely. Also, the load propagating means is preferably formed by embedding core bodies having a higher Young&#39;s modulus than that of an elastic material, which forms the body (fourth invention). With such arrangement, pressing forces applied on both sides of the driven projections by the rollers are transmitted generally in a widthwise direction by the core members, so that a ground pressure distribution is equalized to thereby enable preventing local wear of the crawler ground surface portion. In addition, it is preferable that the core bodies be formed from a material having a tensile strength and toughness. Used for the core bodies are high-hardness rubber, urethane resin, plastics (for example, phenol resin reinforced by a reinforcement material) having a high mechanical strength, aluminum, iron or the like.  
           [0012]    A circumferential pitch of the core bodies in the body is preferably 1/n (n: integer) times a pitch, in which the driven projections are provided (fifth invention). With such arrangement, the use of moldings for the core bodies provides an effect that determination of arrangement and positioning is facilitated, the function of maintaining a ground pressure distribution uniform after forming can be fulfilled, and the crawler can be easily cut at the time of disposal after use.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a view showing a hydraulic excavator with elastic-bodied crawlers, according to the invention, wound round a lower running body;  
         [0014]    [0014]FIG. 2 is a transverse cross section showing the elastic-bodied crawler according to a first embodiment;  
         [0015]    [0015]FIG. 3 is a view showing the relationship between the elastic-bodied crawler and rollers;  
         [0016]    [0016]FIG. 4 is a transverse cross section showing an elastic-bodied crawler according to a second embodiment;  
         [0017]    [0017]FIG. 5( a ) is a transverse cross sectional view showing an elastic-bodied crawler according to a third embodiment;  
         [0018]    [0018]FIG. 5( b ) is a longitudinal cross sectional view showing the elastic-bodied crawler of FIG. 5( a ) partially;  
         [0019]    [0019]FIG. 6( a ) is a transverse cross sectional view showing the elastic-bodied crawler of the third embodiment provided with additional means;  
         [0020]    [0020]FIG. 6( b ) is a transverse cross sectional view showing a modification of the elastic-bodied crawler of FIG. 6( a );  
         [0021]    [0021]FIG. 7( a ) is a top plan view showing a concrete example of a conventional elastic-bodied crawler without core metal members;  
         [0022]    [0022]FIG. 7( b ) is a cross sectional view taken along the line a-a in FIG. 7( a); and    
         [0023]    [0023]FIG. 8 is a view illustrating ground pressure distribution on portions of a conventional elastic-bodied crawler, which are pressed by rollers and a state, in which the elastic-bodied crawler is worn. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]    An explanation will be given below to concrete embodiments of an elastic-bodied crawler according to the invention with reference to the drawings.  
         [0025]    [0025]FIG. 1 is a view showing a hydraulic excavator with elastic-bodied crawlers according to the invention, wound round a lower running body, and FIG. 2 shows a cross section of an elastic-bodied crawler according to a first embodiment. FIG. 3 is a view illustrating the relationship between the elastic-bodied crawler and rollers.  
         [0026]    An elastic-bodied crawler  10  according to the embodiment is wound round a sprocket  4  and an idler  5 , as shown in FIG. 1, which are arranged on front and rear ends of a track frame  3  on a lower running body  2  of a crawler vehicle, for example, a hydraulic excavator  1 , and driven by engaging driven projections, which are provided in a predetermined pitch on an inner peripheral surface thereof, with drive teeth provided on the sprocket  4 . At the time of driving, a plurality of rollers  6  supported by shafts, which are rotatably born by bearings of brackets mounted on the track frame  3 , push the inner peripheral surface of the crawler to press the lug portions on the crawler against the ground surface. In addition, the reference numeral  7  denotes an upper revolving body, and  8  a working implement provided with a bucket.  
         [0027]    The elastic-bodied crawler  10  according to the first embodiment comprises, likewise the prior art with respect to an external appearance, driven projections  13  provided in a predetermined pitch on an inner peripheral surface  11   a  of an endless body  11 , which is formed from an elastic material (for example, rubber) to have a predetermined dimension, and lug portions  12  provided on an outer peripheral surface of the body to form a lug of a predetermined shape. As shown in FIG. 2, a multiplicity of reinforcement cables (main cables  15  (steel cables or cables of resin fiber)) are arranged and embedded circumferentially in positions near the inner peripheral surface  11   a  of the body  11 .  
         [0028]    Load propagating means  20  is provided in the body  11  to be disposed centrally in a widthwise direction and on a side of a reinforcement layer  15 A of the main cables  15  toward the ground side (side of the lug portions  12 ).  
         [0029]    The load propagating means  20  is provided in the body  11  to be disposed on a side of a reinforcement layer  15 A of the main cables  15  toward the ground side and comprises a reinforcement cable layer  21  comprised of a multiplicity of, for example, steel cables having a smaller dimension b than a widthwise dimension B of the body  11  and aligned in a row perpendicularly to a circumferential direction of the body  11  as shown in FIG. 2, the reinforcement cable layer bridging root portions of the driven projections  13  to extend on both sides thereof in a widthwise direction. In addition, the embodiment comprises, in addition to the reinforcement cable layer  21  arranged as the load propagating means  20 , an auxiliary cable layer  22  having a smaller dimension than that of the reinforcement cable layer and arranged on the ground side, thus the reinforcement cable layer and the auxiliary cable layer providing a two-layered structure. Also, the reinforcement cable layer  21  and the auxiliary cable layer  22  may be disposed to be aligned at suitable angles (within a range, in which bending is not impeded) relative to a circumferential direction of the body.  
         [0030]    With the elastic-bodied crawler  10  structured in this manner, the rollers  6 ,  6  press the inner peripheral surface  11   a  of the body  11  on both sides of the driven projections  13 , load applied on the reinforcement cable layer  21  in positions immediately below treads of the rollers  6 ,  6  is propagated to the respective reinforcement cables  21   a  to be applied on the central portion, on which load is not directly applied, by virtue of the structure, in which the reinforcement cable layer  21  arranged on the central portion in a widthwise direction of the body  11  and oriented in a direction intersecting the circumferential direction of the body is embedded in the body to lie below those surfaces, which are pressed by the rollers  6 ,  6 . As a result, the reinforcement cable layer  21  arranged widthwise enhances rigidity of the central portion in the widthwise direction of the body  11 , that is, the ground pressure distribution on the ground surface of the lug portion  12  is equalized generally in the widthwise direction.  
         [0031]    Since the reinforcement cable layer  21  fulfilling such function is arranged relative to the circumferential direction of the body  11  formed from an elastic material, for example, in a state, in which steel cables are oriented in the widthwise direction and aligned in one layer, the crawler is not prevented from bending and can be freely bent in the circumferential direction. However, rigidity of the respective steel cables (reinforcement cables  21   a ) fulfils the function of preventing bending in the widthwise direction. As a result, load applied through the rollers  6 ,  6  as described above is propagated to entire lengths of the reinforcement cables  21   a  to be applied to the lug portions  12  through that portion of the body  11 , in which the reinforcement cables  21   a  are embedded. In addition, the auxiliary cable layer  22  arranged as a second layer on the ground side serves to enhance rigidity there to assist in the propagation of load. In addition, the length b of steel cables constituting the reinforcement cable layer  21  will not develop the above function even in the case of being too large, and will lose the function of propagating load applied by the roller in the case of being too small. Accordingly, a ratio (approximately ½ of the width B of the body) shown in FIG. 2 is preferable in terms of economy or the like.  
         [0032]    [0032]FIG. 4 is a transverse, cross sectional view showing an elastic-bodied crawler according to a second embodiment. The elastic-bodied crawler  10 A according to the second embodiment is fundamentally the same in constitution as that according to the first embodiment, but is different therefrom partly in the structure of load propagating means embedded in the body  11 . Accordingly, except different portions of the load propagating means, the same reference numerals denote the same elements as those in the above embodiment, and a detailed explanation therefor is omitted.  
         [0033]    With the elastic-bodied crawler  10 A according to the second embodiment, reinforcement cable layers  23  as the load propagating means  20 A provided centrally in a widthwise direction and disposed on a side of the reinforcement layer  15 A of the main cables  15  embedded in the body  11  for the reinforcement purpose, toward the ground surface are centrally divided into halves, which lie in projected areas of root portions of the driven projections  13  to be arranged on portions corresponding to portions of treads of the rollers.  
         [0034]    The reinforcement cable layers  23 ,  23  serving as the load propagating means  20 A in the embodiment are arranged in a left-right symmetric manner in the widthwise direction in a state, in which steel cables are used and oriented in a direction intersecting a circumferential direction of the body in the same manner as in the first embodiment and a multiplicity of reinforcement cables are aligned circumferentially such that one ends thereof are disposed in projected areas of root portions of the driven projections  13  disposed centrally in the widthwise direction and the other ends thereof lie in portions immediately below treads of the rollers, and further reinforcement cable layers  23 ′ are arranged and embedded to be offset in positions further centrally than the reinforcement cable layers  23 , thereby enhancing rigidity in the central portion.  
         [0035]    With the elastic-bodied crawler  10 A structured in such manner, the load propagating means  20 A housed therein is constructed to be divided centrally in the widthwise direction, but the same function as that in the above embodiments can be fulfilled because the reinforcement cable layers  23 ,  23 ′ in two upper and lower layers cause load applied by the rollers to be propagated centrally from the reinforcement cable layers, which extend to portions immediately below the treads. In addition, the reinforcement cables in the present embodiment may be aligned at a predetermined angle relative to a circumferential axis. In this case, it is necessary to select an inclination of such magnitude that bending in a circumferential direction is not impeded. In this manner, although the reinforcement cable layers  23  ( 23 ′ ) are constructed to be divided centrally, there is given an effect that the central portion of the body  11  is further enhanced.  
         [0036]    [0036]FIG. 5( a ) is a transverse cross sectional view showing an elastic-bodied crawler according to a third embodiment, and FIG. 6( b ) is a longitudinal cross sectional view showing the elastic-bodied crawler partially. An elastic-bodied crawler  10 B according to the third embodiment is fundamentally the same in constitution as that in the first embodiment but is different therefrom in the constitution of load propagating means  20 B embedded in the body  11 . Accordingly, the same reference numerals denote the same or similar elements as those in the above embodiment except the load propagating means, and a detailed explanation therefor is omitted.  
         [0037]    With the elastic-bodied crawler  10 B according to the third embodiment, core bodies  25  are used as the load propagating means  20 B provided in the body  11 . In this load propagating means  20 B, the core bodies  25  are arranged circumferentially of the body  11  on a side of a layer  15 A of main cables  15  toward the ground in a pitch 1/n (n: integer) times a pitch P of the driven projections  13  in the same manner as the embodiment with the reinforcement cable layer  21  housed therein, the core bodies having a length b bridging projected areas of root portions of the driven projections  13  centrally of the body  11  in a widthwise direction and extending on both side of the projected areas, and a width L at least smaller than the pitch P of the driven projections  13 . In addition, that pitch, in which the core bodies  25  are arranged, is ½P. A thickness of the core bodies  25  can be set optionally in that range, in which they can be embedded in the body  11 , in accordance with a material forming them.  
         [0038]    Also, it is preferable that the core bodies  25  be formed from a material having a higher Young&#39;s modulus than that of an elastic material (rubber material), which forms the body  11  of the crawler. Thus flexibility of the crawler at the time of running can be maintained, and generation of local load in the ground surface portion can be prevented by causing load pressure applied on the treads by the rollers to be propagated generally to those portions, in which the core bodies are embedded, by the core bodies  25  in the same manner as in the above embodiment to enable uniformly distributing the load not only in the areas immediately below the treads of the rollers but also in the central portion in the circumferential direction. In particular, plate-shaped pieces are incorporated to be able to function as the load propagating means  20 B more markedly.  
         [0039]    In order to fulfill such function, it is preferable to use, for example, high-hardness rubber, urethane resin, plastics (for example, phenol resin reinforced by a reinforcement material) having a high mechanical strength, or metal such as aluminum, iron or the like for the core bodies  25 . In addition, organic materials among the above materials have an advantage that uniform resin molding scan be used. Also, inorganic materials can be made thin to attain the object. In addition, that pitch, at which the core bodies  25  are arranged, is made ½P relative to the pitch P of the driven projections  13 , whereby the function of equalizing a load distribution on the ground surface portions, the load being applied by the rollers, can be fulfilled without impeding bending of the body  11  in the circumferential direction.  
         [0040]    In the constitution, in which the core bodies  25  are used as the load propagating means  20 B, the core bodies  25  are formed centrally on one surface (surface toward the driven projections) thereof with a projection  26  as shown in FIG. 6( a ), whereby such projection can be used in determining positions, in which the core bodies  25  are embedded, at the time of forming of the crawler. Also, as shown in FIG. 6( b ), core bodies  25   a ,  25   a  as divided are arranged and embedded centrally in the widthwise direction of the body  11  to extend from projected areas of root portions of the driven projections  13  to both sides thereof, whereby load applied on positions immediately below the treads of the rollers are propagated to the central portion to enable equalizing the ground pressure distribution.  
         [0041]    As described above, the elastic-bodied crawler according to the invention has advantages that the load propagating means is arranged in the body centrally in the widthwise direction of the body  11  to enable equalizing the ground pressure distribution, and members incorporated as the load propagating means are embedded in a state, in which they are easy to separate in the circumferential direction, whereby at the time of disposal after use the members of the load propagating means being constructed to be circumferentially discontinuous can be simply cut for easy disposal when the main cables can be cut.