ELASTIC CRAWLER

An elastic crawler with excellent durability is provided. The elastic crawler of the present disclosure includes a crawler body (2) made of an elastic material, and a plurality of protrusions (3) arranged on an inner circumferential surface (21) of the crawler body (2). The protrusions (3) each include an elastic material portion (31) and a resin member (32). The resin member (32) includes a crawler widthwise side face portion (321). The side face portion (321) has a crawler thicknesswise end face (325A) configured to form a boundary surface (BS) with the elastic material portion (31). The end face (325A) has a concave or convex shape in a crawler widthwise view.

TECHNICAL FIELD

The present disclosure relates to an elastic crawler.

BACKGROUND

As conventional elastic crawlers, there are rubber crawlers in which mountain-shaped resin members made of polyketone resin are disposed on rubber protrusions provided on an inner circumferential surface of a crawler body, in order to produce great effects on rubbing of rolling wheels and rubbing with drive pins (refer to, for example, Patent Literature (PTL) 1). According to such elastic crawlers, wear and the like of the rubber protrusions are suppressed, which enables to provide elastic crawlers with high durability.

CITATION LIST

Patent Literature

SUMMARY

Technical Problem

However, rubber and resin are different materials. Accordingly, in the conventional elastic crawlers, when a resin member is subjected to large force, stress concentrates at a boundary surface between rubber and resin or in the vicinity of the boundary surface, which may affect durability in adhesion between a rubber protrusion and the resin member. Therefore, the conventional elastic crawlers described above have room for further improvement in terms of durability.

It would be helpful to provide an elastic crawler with excellent durability.

Solution to Problem

An elastic crawler according to the present disclosure includes: a crawler body formed in the shape of an endless band and made of an elastic material; and a plurality of protrusions arranged at intervals on an inner circumferential surface of the crawler body, wherein the protrusions each include an elastic material portion and a resin member, the resin member includes a crawler widthwise side face portion, the crawler widthwise side face portion has a crawler thicknesswise end face configured to form a boundary surface with the elastic material portion, and the crawler thicknesswise end face has a concave or convex shape in a crawler widthwise view. The elastic crawler according to the present disclosure has excellent durability.

In the elastic crawler according to the present disclosure, the concave or convex shape is preferably, in the crawler widthwise view, a shape of an arc or mountain convex from the crawler thicknesswise end face to another crawler thicknesswise end face. In this case, the durability is further improved.

In the elastic crawler according to the present disclosure, a crawler widthwise outer corner of the crawler thicknesswise end face of the crawler widthwise side face portion is preferably, in a crawler widthwise cross-sectional view, in a rounded shape from an outer surface of the crawler widthwise side face portion toward an inner surface of the crawler widthwise side face portion. In this case, the durability is further improved.

In the elastic crawler according to the present disclosure, the crawler thicknesswise end face of the crawler widthwise side face portion preferably has a flat portion configured to continue to the crawler widthwise outer corner and to flatly extend toward the inner surface of the crawler widthwise side face portion, in the crawler widthwise cross-sectional view. In this case, the durability is further improved.

In the elastic crawler according to the present disclosure, a crawler widthwise inner corner of the crawler thicknesswise end face of the crawler widthwise side face portion is preferably, in the crawler widthwise cross-sectional view, in a rounded shape from the inner surface of the crawler widthwise side face portion toward the outer surface of the crawler widthwise side face portion. In this case, the durability is further improved.

In the elastic crawler according to the present disclosure, the resin member preferably includes two of the crawler widthwise side face portions arranged so as to face each other in a crawler width direction, and the resin member preferably further includes at least one connection portion configured to connect the two crawler widthwise side face portions. In this case, the durability is further improved.

In the elastic crawler according to the present disclosure, the crawler widthwise side face portion is preferably exposed from a side face of the elastic material portion in a crawler width direction. In this case, the durability is further improved.

Advantageous Effect

According to the present disclosure, it is possible to provide the elastic crawler with excellent durability.

DETAILED DESCRIPTION

An elastic crawler according to an embodiment of the present disclosure will be described below with reference to the drawings. In this document, a “crawler width direction”, a “crawler thickness direction”, and a “crawler circumferential direction” refer to directions with respect to a crawler body (here, synonymous with the “elastic crawler”). In the drawings, the crawler width direction is indicated by the arrow WD, the crawler thickness direction is indicated by the arrow TD, and the crawler circumferential direction is indicated by the arrow CD. In this document, a “crawler inner circumferential side” and a “crawler outer circumferential side” also refer to an “inner circumferential side” and an “outer circumferential side” with respect to the crawler body (here, synonymous with the “elastic crawler”), respectively. Furthermore, in this document, a “crawler thicknesswise outer circumferential side” refers to a crawler outer circumferential side of both sides in the crawler thickness direction, and is also simply referred to as a “lower side”. In this document, a “crawler thicknesswise inner circumferential side” refers to a crawler inner circumferential side of both sides in the crawler thickness direction, and is also simply referred to as an “upper side”.

FIG. 1is a side view schematically illustrating an example of a crawler traveling apparatus to which an elastic crawler1according to the embodiment of the present disclosure can be applied.

InFIG. 1, the reference numeral100indicates a crawler traveling apparatus to which the elastic crawler1can be applied. The crawler traveling apparatus100can be used, for example, for traveling of vehicles such as agricultural machines (tractors, combine harvesters, and the like) and construction machines (mini excavators, and the like). In this example, the crawler traveling apparatus100is configured as a traveling apparatus for a tractor.

In the example ofFIG. 1, the crawler traveling apparatus100includes a drive wheel110, driven wheels120, and rolling wheels130. These wheels are mounted on a fuselage of a vehicle (not illustrated). The drive wheel110is a cage-type sprocket. The cage-type sprocket has a plurality of pins110P arranged with a constant pitch around a rotation axis O (inFIG. 1, only one of the pins is exemplarily indicated with the reference numeral). In this example, the crawler traveling apparatus100has one of the drive wheel110, two of the driven wheels120, and three of the rolling wheels130. However, the numbers of the drive wheel110, the driven wheels120, and the rolling wheels130can be changed according to the configuration of the crawler traveling apparatus100. Also, in this example, the pins110P are each configured in the shape of a cylinder extending in the crawler width direction, but the configuration of the pins110P can be changed as appropriate.

The elastic crawler1is looped on the drive wheel110, the driven wheels120, and the rolling wheels130.

The elastic crawler1has a crawler body2that is formed in the shape of an endless band and made of an elastic material.

The elastic crawler1has, on an inner circumferential surface21of the crawler body2, a plurality of protrusions3(inFIG. 1, only one of the protrusions3is exemplarily indicated with the reference numeral) that are arranged at intervals in the crawler circumferential direction and crawler width direction.

As illustrated inFIG. 1, the plurality of protrusions3each protrude from the inner circumferential surface21of the crawler body2to the crawler inner circumferential side. The plurality of protrusions3are arranged at regular intervals from each other in the crawler circumferential direction. In the present embodiment, an inner circumferential surface11of the elastic crawler1is constituted of the inner circumferential surface21of the crawler body2and outer surfaces F3o(refer toFIG. 3) of the protrusions3.

Furthermore, with reference toFIG. 1, the elastic crawler1of the present embodiment has a plurality of lugs4(inFIG. 1, only one of the lugs4is exemplarily indicated with the reference numeral) that are arranged on an outer circumferential surface22of the crawler body2at intervals. The plurality of lugs4each protrude from the outer circumferential surface22of the crawler body2to the crawler outer circumferential side. The shape and arrangement of the lugs4are not limited to those illustrated in each drawing, and any shape and arrangement can be adopted. In the present embodiment, an outer circumferential surface12of the elastic crawler1is constituted of the outer circumferential surface22of the crawler body2and outer surfaces of the lugs4. The lugs4are made of an elastic material. In this example, the elastic material is rubber. The lugs4may be integrally molded together with the crawler body2, or may be vulcanized and bonded to the crawler body2.

As illustrated by the arrow D inFIG. 1, when the drive wheel110rotates about the rotation axis O, the pins110P come in contact with the protrusions3of the elastic crawler1, which correspond to the respective pins110P, in turn. The protrusions3have the function of transmitting driving force from the pins110P to the crawler body2when the pins110P of the drive wheel110contact the protrusions3.

FIG. 2Ais a cross-sectional view taken on the line A-A ofFIG. 1.FIG. 2Ais a cross-sectional view of the crawler traveling apparatus100in cross section in the crawler width direction.

The elastic crawler1in the present embodiment is a coreless rubber crawler. As illustrated inFIG. 2A, in the present embodiment, the protrusion3is located in the center of the crawler width direction.

In the present embodiment, the crawler body2includes a steel cord layer5and one or more layers (three layers in the example of the drawing) of reinforcing plies6, which are buried in the crawler body2. The steel cord layer5is constituted of a plurality of steel cords5a(inFIG. 2A, only one of the steel cords5ais exemplarily indicated with the reference numeral). Each of the reinforcing plies6is disposed on the crawler thicknesswise outer circumferential side relative to the steel cord layer5. Each of the reinforcing plies6includes, for example, a plurality of cords6a(inFIG. 2A, only one of the cords6ais exemplarily indicated with the reference numeral) that are inclined with respect to the crawler circumferential direction. However, the reinforcing plies6may be omitted.

As exemplarily illustrated in the protrusion3ofFIG. 2A, the plurality of protrusions3each include an elastic material portion31and a resin member32.

In the present embodiment, as illustrated inFIG. 2A, the protrusion3consists of only two parts: the elastic material portion31and the resin member32.

In the present embodiment, the elastic material portion31is an elastic protrusion provided on the inner circumferential surface21of the crawler body2. The elastic material portion31absorbs shock from outside, while having strength against contact with the pin110P. In the present embodiment, the elastic material portion31protrudes from the inner circumferential surface21of the crawler body2to the crawler thicknesswise inner circumferential side, as part of the protrusion3. In the present embodiment, the elastic material portions31, as part of the protrusions3, are arranged in the center of the crawler width direction at regular intervals from each other in the crawler circumferential direction. The elastic material portion31is made of an elastic material. In this example, the elastic material is rubber, as with the lug4.

The resin member32is a coating member that covers the elastic material portion31. The resin member32suppresses wear and tear of the elastic material portion31and also reinforces the elastic material portion31. In the present embodiment, the resin member32is formed of polyketone resin. In the present embodiment, the resin member32is embedded in the elastic material portion31. In the present embodiment, part of the resin member32is exposed from the elastic material portion31. The reference numeral F31oindicates an outer surface of the elastic material portion31. The reference numeral F32oindicates an outer surface of the resin member32. In the present embodiment, the outer surface F3oof the protrusion3is formed with the outer surface F31oof the elastic material portion31and the outer surface F32oof the resin member32. The remaining part of the resin member32, excluding the exposed part (outer surface F32o) of the resin member32, is embedded in the elastic material portion31. The outer surface F31oof the elastic material portion31and the outer surface F32oof the resin member32constitute the outer surface F3oof the protrusion3. In the present embodiment, there is no step between the outer surface F31oof the elastic material portion31and the outer surface F32oof the resin member32, and the outer surface F3oof the protrusion3is formed smoothly. In other words, the outer surface F3oof the protrusion3is in the same plane (coplanar) constituted of the outer surface F31oof the elastic material portion31and the outer surface F32oof the resin member32. However, there may be a step between the outer surface F31oof the elastic material portion31and the outer surface F32oof the resin member32. For example, the outer surface F32oof the resin member32may protrude outward from the outer surface F31oof the elastic material portion31to create a step in the outer surface F3oof the protrusion3.

The protrusion3may be molded, for example, of unvulcanized rubber together with the elastic material portion31, for example, with the resin member32as an insert. Alternatively, the protrusion3may be formed, for example, by bonding the resin member32onto the elastic material portion31. In these cases, the protrusion3may be vulcanized and bonded onto the crawler body2. Alternatively, the protrusion3may be molded, for example, of unvulcanized rubber together with the elastic material portion31and the crawler body2, with the resin member32as an insert. That is, the protrusion3may be formed by chemically or physically bonding the elastic material portion31and the resin member32.

In the present embodiment, the resin member32is provided with two of the crawler widthwise side face portions321arranged so as to face each other in the crawler width direction. In the present embodiment, each of the two crawler widthwise side face portions321is formed from a thin plate panel.

In the present embodiment, the resin member32has at least one connection portion322that connects the two crawler widthwise side face portions321. In the present embodiment, the resin member32includes one of the connection portion322. That is, in the present embodiment, the two crawler widthwise side face portions321are connected by the one connection portion322. In the present embodiment, the connection portion322of the resin member32is connected to crawler thicknesswise inner circumferential ends (upper ends) of the crawler widthwise side face portions321. As illustrated inFIG. 3A, in the present embodiment, the connection portion322is also formed of a thin plate panel.

With reference toFIG. 3B, the reference numeral325indicates an end face of the crawler widthwise side face portion321. The end face325is a face that forms the contour of the crawler widthwise side face portion321in a crawler widthwise view viewed from outside in the crawler width direction. In the present embodiment, the end face325of the crawler widthwise side face portion321, as a crawler thicknesswise end face, has a crawler thicknesswise outer circumferential end face325A and a crawler thicknesswise inner circumferential end face325B. In addition, in the present embodiment, the end face325of the crawler widthwise side face portion321has two crawler circumferential end faces325C, as crawler circumferential end faces. In the present embodiment, the contour of the crawler widthwise side face portion321is formed with the crawler thicknesswise outer circumferential end face325A, the crawler thicknesswise inner circumferential end face325B, and the two crawler circumferential end faces325C.

The crawler widthwise side face portion321has a crawler thicknesswise end face that forms a boundary surface BS with the elastic material portion31.

With reference toFIG. 2A, in the present embodiment, the crawler thicknesswise outer circumferential end face325A forms the boundary surface BS between the elastic material portion31and the crawler widthwise side face portion321when the crawler widthwise side face portion321is embedded in the elastic material portion31.

The crawler thicknesswise end face325includes a concave or convex shape in the crawler widthwise view.

With reference toFIG. 3B, in the present embodiment, the crawler thicknesswise outer circumferential end face325A is in the shape of an arc convex from the crawler thicknesswise outer circumferential end face325A toward the crawler thicknesswise inner circumferential end face325B (the other crawler thicknesswise end face) in the crawler widthwise view. In the present embodiment, the crawler thicknesswise outer circumferential end face325A is formed with only one arc-shaped portion325A3in the crawler widthwise view. Specifically, the crawler thicknesswise outer circumferential end face325A is formed with the arc-shaped portion325A3formed with a radius of curvature R1.

Here, inFIG. 3B, a crawler thicknesswise outer circumferential end face325D, in which the crawler thicknesswise outer circumferential end face of the crawler widthwise side face portion321of the resin member32is made flat in crawler widthwise view, is illustrated by the dashed line, as a comparative example.

In the case of the crawler thicknesswise outer circumferential end face325D as the comparative example, as illustrated by the dashed line inFIG. 3B, when the resin member32receives driving force, the resin member32is easily subjected to force in the direction of peeling off from the elastic material portion31along the crawler thicknesswise outer circumferential end face325D. In contrast, in the present embodiment, at the crawler widthwise side face portion321of the resin member32, the crawler thicknesswise outer circumferential end face325A of the crawler widthwise side face portion321is formed with the arc-shaped portion325A3, as illustrated by the solid line inFIG. 3B. In this case, when the resin member32receives the driving force, the resin member32is hardly subjected to the force in the direction of peeling off from the elastic material portion31along the crawler thicknesswise outer circumferential end face325A.

Thus, the elastic crawler1of the present embodiment can prevent the peeling of the resin member32from the elastic material portion31and the progress thereof, which results in excellent durability.

In the present embodiment, the concave or convex shape is made with the arc-shaped portion325A3that is convex from the crawler thicknesswise outer circumferential end face325A toward the crawler thicknesswise inner circumferential end face325B, in the crawler widthwise view. In this case, since the crawler thicknesswise outer circumferential end face325A is formed into the shape of an arc, the crawler thicknesswise outer circumferential end face325A does not have a complex shape, which results in the elastic crawler1of simple configuration with excellent durability.

The concave or convex shape may be in the shape of a mountain.

FIG. 4Ais a side view that illustrates a variation of the crawler widthwise side face portion321of the resin member32illustrated inFIG. 3A, viewed from outside in the crawler width direction.

With reference toFIG. 4A, in the present embodiment, the crawler thicknesswise outer circumferential end face325A is in the shape of a mountain that is convex from the crawler thicknesswise outer circumferential end face325A toward the crawler thicknesswise inner circumferential end face325B (the other crawler thicknesswise end face), in the crawler widthwise view. In the present embodiment, the crawler thicknesswise outer circumferential end face325A is formed with only one mountain shape in the crawler widthwise view. Specifically, the crawler thicknesswise outer circumferential end face325A is formed into the shape of a mountain constituted of two inclined faces, inclined faces325A1and325A2. More specifically, the angle between the inclined face325A1and the inclined face325A2is an angle α. In the present embodiment, the intersection of the inclined face325A1and the inclined face325A2is a point at which two straight lines intersect in the crawler widthwise view. However, according to the present disclosure, the intersection of the inclined face325A1and the inclined face325A2may be a point of intersection with a curve with a radius of curvature r325, in the crawler widthwise view.

Here, also inFIG. 4A, a crawler thicknesswise outer circumferential end face325D, in which the crawler thicknesswise outer circumferential end face of the crawler widthwise side face portion321of the resin member32is made flat in crawler widthwise view, is illustrated by the dashed line, as a comparative example.

With reference toFIG. 4A, in this example, in the crawler widthwise side face portion321of the resin member32, the crawler thicknesswise outer circumferential end face325A of the crawler widthwise side face portion321is formed into the shape of a mountain, as illustrated by the solid line inFIG. 4A. In this case also, when the resin member32receives driving force, the resin member32is hardly subjected to force in the direction of peeling off from the elastic material portion31along the crawler thicknesswise outer circumferential end face325A. Therefore, in the case of this example, it is possible to prevent the peeling of the resin member32from the elastic material portion31and the progress thereof, which results in excellent durability.

In this example, the concave or convex shape is the shape of a mountain that is convex from the crawler thicknesswise outer circumferential end face325A toward the crawler thicknesswise inner circumferential end face325B, in the crawler widthwise view. In this case, since the crawler thicknesswise outer circumferential end face325A is formed into the shape of a mountain, the crawler thicknesswise outer circumferential end face325A does not have a complex shape, which results in the elastic crawler1of simple configuration with excellent durability.

The concave or convex shape may include a plurality of concave or convex shapes. The concave or convex shape may include, for example, a plurality of arc shapes. The concave or convex shape may be, for example, a plurality of mountain shapes. The concave or convex shape may be, for example, a shape that includes at least one combination of an arc shape and a mountain shape.

FIG. 4Bis a side view of a variation of the crawler widthwise side face portion of the resin member32illustrated inFIG. 4A, viewed from outside in the crawler width direction.

In the variation illustrated inFIG. 4B, in the crawler widthwise side face portion321of the resin member32, the crawler thicknesswise outer circumferential end face325A of the crawler widthwise side face portion321is formed with a plurality (three, in this example) of mountain shapes. In this example, the crawler thicknesswise outer circumferential intersection of the inclined face325A1and the inclined face325A2is a point of intersection with a curve with a radius of curvature rc, in the crawler widthwise view. However, according to the present disclosure, the intersection of the inclined face325A1and the inclined face325A2may be a point at which two straight lines intersect, in the crawler widthwise view.

FIG. 4Cis a side view of another variation of the crawler widthwise side face portion321of the resin member32illustrated inFIG. 3A, viewed from outside in the crawler width direction.

In the variation illustrated inFIG. 4C, in the crawler widthwise side face portion321of the resin member32, the crawler thicknesswise outer circumferential end face325A of the crawler widthwise side face portion321is formed with a plurality (five, in this example) of arc shapes. In particular, in this example, the crawler thicknesswise outer circumferential end face325A includes three arc-shaped portions325A31that are convex from the crawler thicknesswise outer circumferential end face325A toward the crawler thicknesswise inner circumferential end face325B (the other crawler thicknesswise end face). In this example, these three arc shapes are formed with a radius of curvature r2. Also, in this example, the crawler thicknesswise outer circumferential end face325A includes two arc-shaped portions325A32that are convex from the crawler thicknesswise inner circumferential end face325B to the crawler thicknesswise outer circumferential end face325A (the other crawler thicknesswise end face). In this example, these two arc-shaped portions325A32are formed with a radius of curvature r3. In this example, the radii r2and r3of curvature are centered on the crawler thicknesswise outer circumferential end face325D, which is illustrated by the dashed line as a comparative example.

As illustrated inFIGS. 4B and 4C, when there is a plurality of the above-described concave or convex shapes, the elastic crawler1has more excellent durability.

With reference toFIG. 2A, the reference numeral3eindicates a crawler thicknesswise outer circumferential end of the protrusion3. The crawler thicknesswise outer circumferential end3eof the protrusion3is a boundary surface between the protrusion3and the crawler body2. That is, the crawler thicknesswise outer circumferential end3eof the protrusion3is a lowest end of the protrusion3. In the present embodiment, the crawler thicknesswise outer circumferential end3eof the protrusion3coincides with the inner circumferential surface21of the crawler body2. Also, in the present embodiment, the crawler thicknesswise outer circumferential end3eof the protrusion3is a virtual bonding surface to the crawler body2.

With reference toFIG. 2A, in the present embodiment, the height H of the protrusion3is a height in the crawler thickness direction. In the present embodiment, the height H of the protrusion3is a height from the crawler thicknesswise outer circumferential end3eof the protrusion3to a top face F3tof the protrusion3. In the present embodiment, in the crawler thicknesswise outer circumferential end face325A of the crawler widthwise side face portion321, the crawler thicknesswise outer circumferential end face325A, as a lowest end of the resin member32, is located at a height h (>0) from the crawler thicknesswise outer circumferential end3eof the protrusion3. The height h is a height in the crawler thickness direction. The height h can be set as appropriate according to various requirements such as the dimensions, shape, and required performances of an elastic crawler1A. For example, in the present embodiment, the height h is set higher than the thickness of a rubber portion133(refer toFIG. 2) in the crawler thickness direction, so that the resin member32is prevented from directly contacting the rubber portion133of the rolling wheel130, on which the elastic crawler1A can be mounted.

In the present embodiment, the resin member32is embedded in the elastic material portion31so that the crawler thicknesswise outer circumferential end face325A of the crawler widthwise side face portion321is located on the crawler thicknesswise inner circumferential side (upper side) relative to the crawler thicknesswise outer circumferential end3eof the protrusion3. In this case, the crawler thicknesswise outer circumferential end3eof the protrusion3is originally a portion at which strain tends to concentrate due to contact with the rolling wheel130and the like. Accordingly, when the crawler thicknesswise outer circumferential end face325A of the crawler widthwise side face portion321of the resin member32reaches the crawler thicknesswise outer circumferential end3eof the protrusion3, strain generated in the vicinity of the crawler thicknesswise outer circumferential end3eof the protrusion3further increases due to difference in rigidity occurring at the boundary surface BS between the resin member32and the elastic material portion31. However, locating the crawler thicknesswise outer circumferential end face325A of the crawler widthwise side face portion321of the resin member32at a higher position than the crawler thicknesswise outer circumferential end3eof the protrusion3prevents the generation of strain at the crawler thicknesswise outer circumferential end3eof the protrusion3and in the vicinity of the crawler thicknesswise outer circumferential end3e, thus further improving durability.

Here,FIG. 2Bis an enlarged cross-sectional view of a region X ofFIG. 2A.

As illustrated inFIG. 2B, in the present embodiment, the crawler thicknesswise outer circumferential end face325A is constituted of a crawler widthwise outer corner325athat continues to an outer surface F321oof the crawler widthwise side face portion321in a crawler widthwise cross-sectional view, a crawler widthwise inner corner325bthat continues to an inner surface F321iof the crawler widthwise side face portion321, and a middle portion325cthat continues to the crawler widthwise outer corner325aand the crawler widthwise inner corner325b.

As illustrated inFIG. 2B, the crawler widthwise outer corner325aof the crawler thicknesswise outer circumferential end face325A is in a rounded (fillet) shape from the outer surface F321oof the crawler widthwise side face portion321toward the inner surface F321iof the crawler widthwise side face portion321, in the crawler widthwise cross-sectional view.

As illustrated inFIG. 2B, in the present embodiment, the crawler widthwise outer corner325aof the crawler thicknesswise outer circumferential end face325A is contoured by an arc with a radius of curvature Ra, in the crawler widthwise cross-sectional view. Thus, in the present embodiment, the crawler widthwise outer corner325aof the crawler thicknesswise outer circumferential end face325A is filleted with a radius of curvature Ra along an extending direction of the crawler thicknesswise outer circumferential end face325A. The fillet can be formed, for example, by R machining.

Also, as illustrated inFIG. 2B, in the present embodiment, the crawler thicknesswise outer circumferential end face325A of the crawler widthwise side face portion321has a flat portion that continues to the crawler widthwise outer corner325aand flatly extends to the inner surface F321iof the crawler widthwise side face portion321, in the crawler widthwise cross-sectional view. In the present embodiment, the flat portion is the middle portion325cof the crawler thicknesswise outer circumferential end face325A of the crawler widthwise side face portion321. In the present embodiment, the flat portion extends along the crawler width direction.

Also, as illustrated inFIG. 2B, in the present embodiment, the crawler widthwise inner corner325bof the crawler thicknesswise outer circumferential end face325A of the crawler widthwise side face portion321is formed into a rounded (fillet) shape from the inner surface F321iof the crawler widthwise side face portion321toward the outer surface F321oof the crawler widthwise side face portion321, in the crawler widthwise cross-sectional view. As illustrated inFIG. 2B, in the present embodiment, the crawler widthwise inner corner325bof the crawler thicknesswise outer circumferential end face325A of the crawler widthwise side face portion321is contoured by an arc with a radius of curvature Rb, in the crawler widthwise cross-sectional view. As described above, in the present embodiment, the crawler widthwise inner corner325bof the crawler thicknesswise outer circumferential end face325A is filleted with a radius of curvature Rb along the extending direction of the crawler thicknesswise outer circumferential end face325A. The fillet can also be formed, for example, by R machining. It is preferable that the radius of curvature Ra is set to be larger than the radius of curvature Rb. In the present embodiment, the radius of curvature Ra is set to be larger than the radius of curvature Rb. However, according to the present disclosure, the radius of curvature Ra may be set to be equal to or smaller than the radius of curvature Rb.

By the way, as illustrated inFIG. 2A, in the crawler traveling apparatus100of this example, the rolling wheel130includes two rolling wheel bodies131spaced apart in the crawler width direction, and a connecting shaft132that connects the rolling wheel bodies131. Furthermore, in this example, an outer circumferential surface of each of the rolling wheel bodies131is covered with the rubber portion133. In the crawler traveling apparatus100of this example, the rolling wheels130are configured to each roll on a rolling wheel passing surface11a. That is, the elastic crawler1according to the present embodiment is configured to pass over the rolling wheels130when traveling.

In the crawler traveling apparatus100of this example, the protrusions3of the elastic crawler1are configured to be each located inside the two rolling wheel bodies131in the crawler width direction. The protrusions3have the function of guiding the rolling wheels130in the crawler width direction by crawler widthwise side faces F3wof the protrusions3. This prevents the elastic crawler1A from falling off (i.e., the elastic crawler1A coming off the rotating body such as the rolling wheels130). In this example, the driven wheels120are also configured in the same way as the rolling wheels130. This also prevents the elastic crawler1A from falling off the driven wheels120.

In the elastic crawler according to the present disclosure, the crawler widthwise side face portion321is exposed from a crawler widthwise side face F31wo(refer toFIG. 2B) of the elastic material portion31. In this case, the crawler widthwise side face portions321of the resin member32protect the elastic material portion31, thus suppressing wear, deformation, and the like of the protrusion3, which results in further improvement in durability.

With reference toFIG. 2B, in the present embodiment, the outer surface F321oof the crawler widthwise side face portion321is exposed from the crawler widthwise side face F31woof the elastic material portion31, as part of the resin member32, and constitutes the crawler widthwise side face F3wof the protrusion3. In this case, the protrusion3can be protected by the crawler widthwise side face portions321of the resin member32. The resin member32is formed of a resin material having a lower coefficient of friction than rubber. Therefore, the protrusions3each constituted of the elastic material portion31and the resin member32, as in the present embodiment, prevent the elastic crawler1from being falling off the protrusions3, because even if the rotating body such as the rolling wheel130tries to ride up on the protrusion3, the rotating body slides down.

On the other hand, in a case in which the protrusion3is constituted of the elastic material portion31and the resin member32, there is difference in rigidity, due to difference in materials, based on the boundary surface BS formed between the elastic material portion31and the resin member32. For this reason, when strain concentrates at the boundary surface BS between the elastic material portion31and the resin member32or in the vicinity of the boundary surface BS, there is a concern that the elastic material portion31may crack.

On the other hand, with reference toFIG. 2B, in the present embodiment, in the crawler widthwise side face portion321of the resin member32, the crawler widthwise outer corner325aof the crawler thicknesswise outer circumferential end face325A is formed into a rounded shape from the outer surface F321oof the crawler widthwise side face portion321toward the inner surface F321i. In the present embodiment, the boundary surface BS between the elastic material portion31and the resin member32is in a rounded chamfered shape. In this case, even when a large load is applied to the crawler widthwise side face portion321of the resin member32toward inside in the crawler width direction, strain does not concentrate at the boundary surface BS between the elastic material portion31and the resin member32or in the vicinity of the boundary surface BS, in particular, at the boundary surface BS between the crawler widthwise outer corner325aof the crawler thicknesswise outer circumferential end face325A of the crawler widthwise side face portion321and the elastic material portion31or in the vicinity of the boundary surface BS toward the inside in the crawler width direction, and therefore the generation of strain at the boundary surface BS between the crawler widthwise outer corner325aand the elastic material portion31or in the vicinity of the boundary surface BS is reduced. Therefore, according to the present embodiment, the generation of a crack from the boundary surface BS between the elastic material portion31and the crawler thicknesswise outer circumferential end face325A of the crawler widthwise side face portion321of the resin member32or the vicinity of the boundary surface BS toward inside in the crawler width direction is prevented. In this case, the direction of shear force generated in the elastic material portion31is, as illustrated by an arrow inFIG. 2B, in the direction of coming around the inside of the crawler widthwise side face portion321of the resin member32along the rounded shape, which forms the crawler widthwise outer corner325aof the crawler thicknesswise outer circumferential end face325A. Therefore, according to the present embodiment, even if a crack toward the inside in the crawler width direction is generated, the propagation of the crack is prevented.

In the present embodiment, the middle portion325cof the crawler thicknesswise outer circumferential end face325A is a flat portion that continues to the crawler widthwise outer corner325aand extends flatly toward the inner surface F321iof the crawler widthwise side face portion321. In this case, leaving the flat portion between the crawler widthwise outer corner325aof the crawler thicknesswise outer circumferential end face325A and the crawler widthwise inner corner325bfurther prevents the generation of a crack and the propagation of the crack, which further improves durability.

In the present embodiment, the inner corner325bof the crawler thicknesswise outer circumferential end face325A of the crawler widthwise side face portion321of the resin member32is in a rounded shape from the inner surface F321iof the crawler widthwise side face portion321toward the outer surface F321o. In this case, compared to a case in which the crawler widthwise inner corner325bof the crawler thicknesswise outer circumferential end face325A of the crawler widthwise side face portion321is not formed in the above-described rounded shape, the generation of a crack and the propagation of the crack are more prevented, thereby further improving durability.

As illustrated inFIG. 3B, in the present embodiment, in the crawler widthwise side face portion321of the resin member32, the crawler thicknesswise outer circumferential end face325A continues to the two crawler circumferential end faces325C. Also in the two crawler circumferential end faces325C, as illustrated inFIG. 2B, the crawler widthwise outer corner325aand the crawler widthwise inner corner325bare in a rounded (fillet) shape, and the middle portion325cis flat.

In the present embodiment, the crawler widthwise side face portions321of the resin member32are connected in a cantilevered state on the crawler thicknesswise inner circumferential side (upper side) via the connection portion322. In this case, the crawler widthwise side face portions321of the resin member32move easily against the connection portion322based on the crawler thicknesswise inner circumferential side. Accordingly, in the protrusion3, strain easily concentrates at the boundary surface BS between the crawler thicknesswise outer circumferential end face325A of the crawler widthwise side face portion321and the elastic material portion31and in the vicinity of the boundary surface BS, due to contact with the rolling wheels13and the like.

In contrast, in the present embodiment, in at least the crawler thicknesswise outer circumferential end face325A of the resin member32, the crawler widthwise outer corner325aand the crawler widthwise inner corner325bare in a rounded (fillet) shape, and the middle portion325cis flat, the generation of a crack and the propagation of the crack are more prevented, which further improves durability.

Also with reference toFIG. 3A, in the present embodiment, the resin member32includes the two crawler widthwise side face portions321that are arranged so as to face each other in the crawler width direction, and the at least one connection portion322that connects the two crawler widthwise side face portions321. In this case, in the resin member32, the two crawler widthwise side face portions321are connected by the connection portion322, as one rigid body, thereby improving the rigidity of the entire resin member32, which further improves durability. In this case, a portion of the protrusion3excluding the two crawler widthwise side face portions321and the connection portion322of the resin member32is formed with the elastic material portion31, so a large adhesion area between the resin member32and the elastic material portion31is secured. Therefore, the resin member32and the elastic material portion31are bonded more firmly. Accordingly, in this case, the durability of the entire protrusion3is improved, and the durability is further enhanced.

By the way, in the present embodiment, the resin member32is configured as a thin plate member. In the present embodiment, the resin member32is integrally formed as one component by injection molding using thermoplastic resin or the like. In the present embodiment, as illustrated inFIG. 3B, the length of the connection portion322in the crawler circumferential direction is shorter than the length of the crawler widthwise side face portion321of the resin member32in the crawler circumferential direction. The connection portion322of the resin member32is connected to upper ends of the crawler widthwise side face portions321of the resin member32. Accordingly, as illustrated inFIG. 3A, the resin member32has a region R that accommodates (contains) the elastic material portion31constituting the protrusion3, between the crawler widthwise side face portions321and the connection portion322. In this case, a large embedded surface F of the resin member32, which contacts the elastic material portion31, is secured, and hence a large adhesion area between the elastic material portion31and the resin member32is secured. As a result, according to the present embodiment, the durability of the protrusion3and, in turn, the durability of the elastic crawler1A can be further improved.

In the present embodiment, the resin member32preferably has at least one of a concave portion and a convex portion in a part contacting the elastic material portion31, that is, the embedded surface F. In this case, the large embedded surface F of the resin member32, which contacts the elastic material portion31, is secured, and thus a large adhesion area between the elastic material portion31and the resin member32is secured. As a result, bonding force between the elastic material portion31and the resin member32is increased, and the durability of the protrusion3, and, in turn, the durability of the elastic crawler1A can be further improved.

With reference toFIGS. 3A and 3B, the embedded surface F of the resin member32includes the crawler widthwise side face portions321and the connection portion322of the resin member32. The above-described concave portion or the convex portion includes a single convex portion, embossing, grain, or the like. In the present embodiment, the entire embedded surface F may be provided with a concave or convex portion, such as embossing. This improves adhesion between the elastic material portion31and the resin member32. In particular, when the elastic material portion31is rubber, adhesion with the resin member32is improved. On the other hand, the outer surface F32oof the resin member32preferably has reduced frictional resistance, in consideration of contact with the rolling wheels130and the like. For this reason, it is preferable that the outer surface F32oof the resin member32is not subjected to surface roughness processing, such as provision of the above-described convex portion. According to the present disclosure, the end faces325of the resin member32may also be included in the embedded surface F. The embedded surface F may also include a reinforcing portion324.

FIG. 5is a plan perspective view schematically illustrating a resin member32constituting part of a protrusion3of an elastic crawler1B. In the present embodiment, the resin member32includes two of the connection portions322that connect the two crawler widthwise side face portions321. In this case, since the rigidity of the entire resin member32is improved, the durability of the protrusion3of the elastic crawler1B and, in turn, the durability of the elastic crawler1B can be further improved. Also, in the present embodiment, a gap S is formed between the two connection portions322. In the present embodiment, as well as the region R of the resin member32according to the first embodiment, the gap S functions as the region R, and part of the elastic material portion31is accommodated in the gap S. In this case, a large embedded surface F of the resin member32, which contacts the elastic material portion31, is secured, and thus a large adhesion area between the elastic material portion31and the resin member32is secured. Therefore, the durability against adhesion between the elastic material portion31and the resin member32is increased, and as a result, the durability of the protrusion3of the elastic crawler1B and, in turn, the durability of the elastic crawler1B can be improved.

The foregoing disclosure discloses only a few embodiments of the present disclosure, and various modifications are possible in accordance with the claims. For example, according to the present disclosure, the resin member32may be constituted of only the crawler widthwise side face portions321. In this case, of the end faces325of the crawler widthwise side face portion321of the resin member32, at least one of the crawler thicknesswise outer circumferential end face and/or the crawler thicknesswise inner circumferential end face may be shaped as described above.

Some or other parts of the resin member32may be separated. In the present embodiment, in the resin member32, the crawler widthwise side face portions321and the connection portion322are integrated into one unit, but may be configured as separate members. The connection portion322of the resin member32may be integral with the elastic material portion31. In this case, the connection portion322of the resin member32is not exposed from the elastic material portion31. The various configurations employed in each of the above-described embodiments may be used in combination with each other. Also, the various configurations employed in each of the above-described embodiments can be replaced with each other as appropriate.

REFERENCE SIGNS LIST