ELASTIC ENDLESS CRAWLER

Abstract: An elastic endless crawler, wherein cord projected parts at each end of a crawler main body are divided into some groups according to the projected length and, as viewed from vertical direction relative to a blet surface, the entire cord projected part at one end of the crawler main body can present a male-shape and the entire cord projected part at the other end of the crawler main body can present a female-shape, as viewed from a vertical direction relative to the belt surface, a line connecting the tips of the cord projected parts at the ends of the crawler main body to each other can be formed in a terrace, stepped, or serrated shape and, as viewed in the vertical direction relative to the blet surface, an overlapped part includes two outlines separated from each other in the longitudinal direction of a belt and both outlines can be formed of bent lines, whereby, because a difference in rigidity between a crawler mian body part including the overlapped part of steel cords and the other part can be reduced as much as possible, vibration and noise can be suppressed effectively from occurring, and because a boundary between a highly rigid part of the rubber crawler and the other part is formed distinguishingly, the possibility of occurence of bending and buckling of the rubber crawler is reduced to provide the rubber crawler excellent in durability and relability.

Description: The present invention relates to a ring-shaped elastic endless crawler which comprises an elongate belt-shaped elastic crawler body, and a plurality of cords disposed in array and embedded in the crawler body so as to extend in a longitudinal direction of the crawler body, in which each of cord protruding portions projecting out from one end of the crawler body and a corresponding cord protruding portion projecting out from another end of the crawler body are made to overlap each other, and the cord protruding portions are entirely subjected to vulcanization processing to thereby form an integrally connected structure. A conventional rubber crawler 1 will be hereinafter described with reference to Figs. 1 to 4, of the accompanying drawings. In a manufacturing process of the rubber crawler 1, first, as illustrated in Fig. 3, a semi-manufactured product is formed in which steel cords 3 are made to project out from each of one end 1a of a crawler body and another end 1b of the crawler body by the same length. Next, as illustrated in Fig. 4, each of cord protruding portions 3a at the one end 1a of the crawler body, and corresponding cord protruding portions 3b at the other end 1b of the crawler body are disposed so as to overlap each other. Lines A0 - A0, and B0 - B0 each connecting opposite ends of cord protruding portions, are arranged in parallel in a transverse direction of a belt and extend transversely of an entire width of the belt. For the purpose of facilitating understanding, in Fig. 4, a portion in which cord protruding portions overlap each other is indicated exaggeratively by a thick line. Due to the cord protruding portions 3a and 3b being entirely subjected to vulcanization processing (heating and filling unvulcanized rubber), an integrated rubber crawler as shown in Figs. 1 and 2 is completed. However, the rigidity of the rubber crawler 1 depends on the steel cords 3, and a portion of the crawler body including a region in which steel cords 3 overlap each other necessarily becomes higher in rigidity (becomes very hard) than a portion of the crawler body not including the region in which the steel cords 3 overlap each other. Accordingly, when the rubber crawler 1 is used in a state of being fitted around a sprocket or an idler (which are not shown), a state is caused in which a hard portion and a non-hard portion of the rubber crawler 1 are intermittently engaged with each other. As a result, vibration or noise may be unavoidably generated. Further, the lines A0 - A0 and B0 - B0 which form the boundary between a high-rigidity (hard) portion and a nonrigid portion of the rubber crawler 1 are straight lines each extending transversely of an entire width of the crawler body (that is, the belt). Therefore, the rubber crawler 1 may easily considerably bend with the lines A0 - A0 and B0-B0 substantially as the center. Attention is also drawn to the disclosures of JP-U-53-011135, which discloses a crawler according to the preamble of claim 1, DE-A-4340159 and JP-A-53-126136. One object of the present invention is to provide a structure by which a difference in rigidity between a portion of a crawler body including a region in which steel cords overlap each other, and a portion of the crawler body not including said region, can be reduced as far as possible, thereby preventing generation of vibration or noise. Further, another object of the present invention is to provide a rubber crawler having excellent durability and reliability, in which a boundary between a high-rigidity portion and a non rigid portion of the rubber crawler is formed characteristically to alleviate occurrence of bending or buckling of the rubber crawler. The present invention provides a ring-shaped elastic endless crawler comprising an elongate belt-shaped elastic crawler body, and a plurality of cords disposed in array and embedded in the crawler body so as to extend in a longitudinal direction of the crawler body, in which each of cord protruding portions projecting out from one end of the crawler body and corresponding cord protruding portions projecting out from the other end of the crawler body are made to overlap each other, and thereafter are entirely subjected to vulcanization processing to thereby form an integrally connected structure, wherein cord protruding portions at each of the ends of the crawler body are divided into groups such that each group has a protruding length different from those of other groups, characterized in that a length of protrusion of cords in a central group relative to a transverse direction of the crawler body at one end of the crawler body is longer than that of cords in each of groups located at both sides of the central group, and a length of protrusion of cords in a central group relative to a transverse direction of the crawler body at the other end of the crawler body is shorter than that of cords in each of groups located at both sides of the central group; in that the endless crawler further comprises a plurality of elastic protrusions for driving the endless crawler that are formed at predetermined intervals in the crawler body longitudinal direction on an inner peripheral surface of the crawler; and in that cords are embedded into the crawler body so that the ends of cord protruding portions are located at positions in which said ends and the driving protrusions overlap each other. In one preferred aspect according to the present invention, the entire cord protruding portions at the one end of the crawler body when seen from a direction perpendicular to a crawler (belt) surface are formed so as to present a male configuration, and the entire cord protruding portions at the other end of the crawler body are formed so as to present a female configuration. In another preferred aspect according to the present invention, lines each connecting ends of facing cord protruding portions at the ends of the crawler body are disposed so as to have a configuration that is one of terraced, tiered, and crenellated when seen from a direction perpendicular to a crawler (belt) surface. In a further preferred aspect according to the present invention, when seen from a direction perpendicular to a crawler (belt) surface, a portion in which cord protruding portions overlap each other includes two outlines separated from each other in a longitudinal direction of a crawler (belt), and each outline includes a belt line. The invention will be further described with reference to the accompanying drawings, wherein: Fig. 1 is a cross-sectional side view which shows a connecting portion in a conventional rubber crawler; Fig. 2 is a plan view of the rubber crawler shown in Fig. 1; Fig. 3 is a plan view which shows cord protruding portions at each of ends of a crawler body in a connecting process of the rubber crawler shown in Fig. 1; Fig. 4 is a plan view which shows a state in which each of the cord protruding portions shown in Fig. 3 and corresponding cord protruding portions are made to overlap each other; Fig. 5 is a cross-sectional side view which shows a connecting portion in a rubber crawler according to a first embodiment of the present invention; Fig. 6 is a plan view of the rubber crawler shown in Fig. 5; Fig. 7 is a plan view which shows cord protruding portions at each of ends of a crawler body in a connecting process of the rubber crawler shown in Fig. 5; Fig. 8 is a plan view which shows a state in which each of the cord protruding portions shown in Fig. 7 and corresponding cord protruding portions are made to overlap each other; Fig. 9 is a plan view of a rubber crawler according to a second embodiment of the present invention; Fig. 10 is a plan view which shows cord protruding portions at each of ends of a crawler body in a connecting process of the rubber crawler shown in Fig. 9; and Fig. 11 is a plan view which shows a state in which each of the cord protruding portions shown in Fig. 10 and corresponding cord protruding portions are made to overlap each other. Referring now to the drawings, the present invention will be hereinafter described in conjunction with a plurality of embodiments. It should be understood that the present invention should not be limited to the embodiments. For example, a rubber crawler according to these embodiments is a so-called internal driving type rubber crawler, but the present invention is not limited to the same. A first embodiment of the present invention will be described with reference to Figs. 5 to 8. As shown in Figs. 5 and 6, a rubber crawler 11 of the first embodiment includes an elongate belt-shaped elastic crawler body, and a plurality of cords 13 made of, for example, steel, which are disposed in array and embedded in the crawler body so as to extend in a longitudinal direction of the crawler body. A plurality of protrusions 17 for driving the rubber crawler are formed at an underside of the rubber crawler (belt), that is on an inner peripheral surface of the crawler. As shown in Fig. 7, in a rubber crawler manufacturing process (in a connecting process), a semi-manufactured product is prepared in which cords 13 (13a and 13b) are respectively made to project out from one end 11 a of the crawler body and the other end 11b of the crawler body, and the cords are disposed so as to face each other. Subsequently, as shown in Fig. 8, each of cord protruding portions 13a at the one end 11a of the crawler body and corresponding cord protruding portions 13b at the other end 11b of the crawler body are disposed so as to overlap each other. For the purpose of facilitating understanding, portions in which corresponding cord protruding portions overlap each other are indicated exaggeratively by thick lines. Due to the cord protruding portions 13a and 13b being entirely subjected to vulcanization processing (heating and filling unvulcanized rubber), a rubber crawler product having an integrally connected structure as shown in Figs. 5 and 6 is completed. A structural feature of the present embodiment is that, as shown in Fig. 7, the cord protruding portions 13a and 13b at the ends 11a and 11b of the crawler body are divided into groups such that each group has a protruding length different from those of other groups. Specifically, when seen from a direction perpendicular to a belt surface, the cord protruding portions at the one end 11a of the crawler body have, as a whole, a convex configuration (a male configuration), and the cord protruding portions at the other end 11b of the crawler body have, as a whole, a concave configuration (a female configuration). In other words, the lines which each connect ends of facing cord protruding portions at the ends of the crawler body are disposed so as to have one of terraced; tiered, and crenellated configurations. As can be seen from Fig. 8 which shows the overlapping state, the cord overlapping portion includes outline (A1-A1'-A1) and outline (B1-B1'-B1). The above-described outlines are separated from each other in a longitudinal direction of the belt (that is, a longitudinal direction of the crawler body). Each outline is comprised of a bent line, not one straight line. Due to the above-described structural feature of the present embodiment, the difference in rigidity between a portion of the crawler body including the overlapping portion, and a portion thereof not including the overlapping portion becomes small as compared with the conventional rubber crawler 1. Namely, the portion of the crawler body including the overlapping portion is not so hard. Accordingly, a problem of high noise or high vibration generated in the conventional rubber crawler is overcome. It is considered that this is because the overlapping portion in which high rigidity may be caused is partially offset (dispersed) in the longitudinal direction of the belt. Further, the outline (A1-A1'-A1) and the outline (B1-B1'-B1), which form the boundary between the high-rigidity portion and the non rigid portion of the rubber crawler 11 are not a straight line. Therefore, as compared with the conventional rubber crawler, bending of the rubber crawler 11 with the above-described outlines substantially as the center only occurs with defficulty. Referring again to Figs. 6 and 8, a dimension H between position B1 and an intermediate position of position A1' and position B1' (which intermediate position is position P1) in the longitudinal direction of the belt is preferably 10 mm or greater, and more preferably 20 mm or greater. When the dimension H is less than 10 mm or 0 mm, buckling is apt to occur very often in an intermediate portion of the rubber crawler including the overlapping portion. Next, a description will be given, with reference to Figs. 9 to 11, of a rubber crawler 21 according to a second embodiment of the present invention, mainly in respect of which the second embodiment differs from the first embodiment. In the second embodiment, as can be seen from Fig. 11 which shows the overlapping state, a portion in which cord protruding portions 23a and 23b overlap each other, includes outline (A2-A2'-A2"-A2'-A2) and outline (B2-B2'-B2"-B2'-B2). The above-described outlines are separated from each other in the longitudinal direction of the belt, and each outline is comprised of a bent line, not one straight line. In other words, the lines which each connect ends of facing cord protruding portions at ends 21a and 21b of the crawler body are disposed so as to have one of terraced, tiered, and crenellated configurations. Due to the above-described structural feature of the second embodiment, the same effect as that of the first embodiment, or an improved effect can be obtained. That is, a portion of the crawler body including the overlapping portion does not become hard, and bending of the rubber crawler with the outlines substantially as the center only occurs with difficulty. Referring again to Fig. 11, from the standpoint of preventing occurrence of buckling, it is preferable that the intermediate position between position A2" and position B2" in the longitudinal direction of the belt does not coincide with position B2 or position B2'. In each of the first and second embodiments, when the rubber crawler is used, there is a risk of ends of cord protruding portions (at position B1' of Fig. 6 and position B" of Fig. 9) projecting out from the crawler body made of rubber. Accordingly, cords are embedded into the crawler body so that the ends of cord protruding portions be located at positions in which the ends and the driving rubber protrusion 17 and 27 overlap each other. As a result, the above-described drawback can be avoided. Further, any of the cord protruding portions at the ends of the crawler body may be positioned at the side of the inner periphery (or outer periphery) of the rubber crawler. As described above, according to the present invention, the difference in rigidity between a connecting portion of the crawler body and a portion thereof not including the connecting portion can be lessened, and occurrence of bending or buckling in the connecting portion can be prevented. As a result, a rubber crawler having excellent durability and reliability can be provided.

Claims: A ring-shaped elastic endless crawler (11;21) comprising an elongate belt-shaped elastic crawler body, and a plurality of cords (13;23) disposed in array and embedded in the crawler body so as to extend in a longitudinal direction of the crawler body, in which each of cord protruding portions ( 13a;23a) projecting out from one end (11a;21a) of the crawler body and corresponding cord protruding portions (13b;23b) projecting out from the other end (11b;21b) of the crawler body are made to overlap each other, and thereafter are entirely subjected to vulcanization processing to thereby form an integrally connected structure, wherein cord protruding portions at each of the ends of the crawler body are divided into groups such that each group has a protruding length different from those of other groups, characterized in that a length of protrusion of cords in a central group relative to a transverse direction of the crawler body at one end of the crawler body is longer than that of cords in each of groups located at both sides of the central group, and a length of protrusion of cords in a central group relative to a transverse direction of the crawler body at the other end of the crawler body is shorter than that of cords in each of groups located at both sides of the central group; in that the endless crawler further comprises a plurality of elastic protrusions (17;27) for driving the endless crawler that are formed at predetermined intervals in the crawler body longitudinal direction on an inner peripheral surface of the crawler; and in that cords are embedded into the crawler body so that the ends of cord protruding portions are located at positions in which said ends and the driving protrusions (17;27) overlap each other. An elastic endless crawler as claimed in claim 1, characterized in that a configuration of cord protruding portions (13a;23a) at one end (11a;21a) of the crawler body and a configuration of cord protruding portions (13b;23b) at the other end (11b;21b) of the crawler body are complementary to each other. An elastic endless crawler as claimed in claim 1, characterized in that a configuration of cord protruding portions (13a,13b;23a,23b) at each of the ends (11a,11b;21a,21b) of the crawler body is symmetrical relative to a longitudinal center line extending in the longitudinal direction of the crawler belt at a transversely-central portion thereof. An elastic endless crawler as claimed in any of claims 1 to 3, characterized in that the crawler body is made of rubber. An elastic endless crawler as claimed in any of claims 1 to 4, characterized in that each of the cords (13;23) is made of steel. An elastic endless crawler as claimed in any of claims 1 to 5, characterized in that the entire cord protruding portions (13a;23a) at the one end (11a;21a) of the crawler body when seen from a direction perpendicular to a crawler surface are formed so as to present a male configuration; and the entire cord protruding portions (13b;23b) at the other end (11b;21b) of the crawler body are formed so as to present a female configuration. An elastic endless crawler as claimed in any of claims 1 to 6, characterized in that lines each connecting ends of facing cord protruding portions (13a,13b;23a,23b) at the ends (11a,11b;21a,21b) of the crawler body are disposed so as to form a configuration that is one of terraced, tiered, and crenellated when seen from a direction perpendicular to a crawler surface. An elastic endless crawler as claimed in any of claims 1 to 7, characterized in that when seen from a direction perpendicular to a crawler surface, a portion in which cord protruding portions (13a,13b;23a,23b) overlap each other includes two outlines separated from each other in a longitudinal direction of the crawler and each outline includes a bent line.

Inventors: MATSUO SHUICHI, MATSUO, SHUICHI, MATSUO, Shuichi, Bridgestone Corporation
Applicants: BRIDGESTONE CORP, BRIDGESTONE CORPORATION
Application year: 2000
Main classification: B62D55
IPC codes: B62D55