Crawler bushing and crawler link device

To provide a crawler bushing and a crawler link device that can maintain a sealing function stably on a long-term basis and permits easy maintenance for recovery of the sealing function. The bushing includes: crawler bushing body (31) including large-diameter cylindrical part (31a) defining an intermediate section along axis (O) and small-diameter cylindrical part (31b) which defines an end section along axis (O) and is smaller in diameter than large-diameter cylindrical part (31a); elastic ring (32) mounted to an outer periphery of small-diameter cylindrical part (31b); seal ring (33) which is formed with seal contact end face (37) at its outer end and coupled to small-diameter cylindrical part (31b) through elastic ring (32); reverse tapered surface (36) and mountain-shaped projection (35) for preventing outward movement of elastic ring (32) along axis (O) of small-diameter cylindrical part (31b); and tongue-shaped projection (39) and reverse tapered surface (40) for preventing outward movement of seal ring (33) along axis (O) of small-diameter cylindrical part (31b).

TECHNICAL FIELD

The present invention relates to a crawler bushing and a crawler link device that are suitable for use in a crawler belt mounted to a work vehicle such as a bulldozer or a hydraulic excavator.

BACKGROUND ART

A conventional sealing device for providing a seal between a crawler bushing and a crawler link of such a crawler belt is constructed of a seal contact end face of the crawler bushing and a seal member which is inserted in the crawler link to abut on the seal contact end face. This sealing device has its service life often determined by wear of the seal contact end face of the crawler bushing, rather than wear of the seal member. Thus, a measure against the wear of the seal contact end face of the crawler bushing needs to be taken to improve the seal service life.

An example of the crawler bushing having the seal contact end face with wear resistance is disclosed in patent document 1.

As shown inFIG. 10(a), plate102which underwent wear-resistant coating is attached to the seal contact end face of crawler bushing101of patent document 1with adhesive103. In crawler link device100equipped with this crawler bushing101, seal member105inserted in crawler link104makes contact with wear-resistant plate102, whereby the wear of the seal contact end face of crawler bushing101is suppressed.

However, this crawler link device100problematically faces time-consuming replacement of wear-resistant plate102which is attached to crawler bushing101with adhesive103.

As shown inFIG. 10(b), crawler bushing111of patent document 2is provided with annular recess112in its end face, and corrosion-resistant annular insert member114having corrosion resistance is inserted into this recess112via elastic ring113. In crawler link device110equipped with this crawler bushing111, seal member116inserted in crawler link115makes contact with corrosion-resistant annular insert member114, whereby the wear of the seal contact end face of crawler bushing111is suppressed. It is to be noted that when inserted into recess112, corrosion-resistant annular insert member114deforms elastic ring113by giving ring113a slight squeeze. For this reason, corrosion-resistant annular insert member114experiences resilience from elastic ring113in response to the squeeze and is thus urged in a sealing direction, that is, in the direction of arrow P pointing outward along an axis of crawler bushing111.

According to this crawler link device110, corrosion-resistant annular insert member114is simply squeezed into recess112of crawler bushing111via elastic ring113, so that insert member114can be replaced with ease.

However, the resilience of elastic ring113that is exerted on corrosion-resistant annular insert member114is strong in this crawler link device110. Accordingly, insert member114presses seal member116with excessive force. This causes damage and early wear to seal member116which as a result has an impaired sealing function. Consequently, oil leakage may problematically occur.

RELATED ART DOCUMENTS

Patent Documents

Patent Document 2:U.S. Patent Application Publication No. 2010/0090523

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

In view of the problems mentioned above, the present invention aims to provide a crawler bushing and a crawler link device that can maintain a sealing function stably on a long-term basis and permits easy maintenance for recovery of the sealing function.

Means for Solving the Problems

To achieve the above-object, a crawler bushing according to a first aspect of the present invention, having a seal contact end face to be in contact with a seal member disposed axially adjacent to the crawler bushing includes:

a crawler bushing body having a large-diameter cylindrical part defining an axially intermediate section of the crawler bushing body and a small-diameter cylindrical part having a smaller diameter than that of the large-diameter cylindrical part and defining an axially end section of the crawler bushing body;

an elastic ring mounted to an outer periphery of the small-diameter cylindrical part:

a seal ring attached to the small-diameter cylindrical part through the elastic ring, the seal ring being formed with the seal contact end face at an outer end thereof;

a first tapered surface on the outer periphery of the small-diameter cylindrical part, the first tapered surface spreading radially outward while extending axially outward; and

a second tapered surface on an inner periphery of the seal ring, the second tapered surface narrowing radially inward while extending axially inward.

According to a second aspect of the invention, it is preferable that the crawler bushing further includes a projection at an axially outer end of the first tapered surface, the projection projecting radially outward for locking the elastic ring.

According to a third aspect of the invention, it is preferable that the crawler bushing further includes a projection at an axially inner end of the seal ring, the projection being adjacent to the second tapered surface and projecting radially inward to be locked by the elastic ring.

According to a fourth aspect of the invention, it is preferable that the crawler bushing further includes a circumferentially extending groove formed in an inner end surface of the seal ring.

According to a fifth aspect of the invention, it is preferable that an outside diameter of the seal ring is substantially equal to an outside diameter of the large-diameter cylindrical part.

According to a sixth aspect of the invention, it is preferable that the elastic ring is disposed between the seal ring and the crawler bushing body and contacts the first tapered surface and the second tapered surface.

A crawler link device according to a seventh aspect of the invention is a crawler link device comprising:

crawler links overlapping each other at respective ends thereof and coupled to each other by means of a link pin and a crawler bushing that are disposed coaxially, and

a seal member inserted to be axially adjacent to the crawler bushing, wherein the crawler bushing according to first to sixth invention is adopted in the crawler link device.

Advantages of the Invention

In the crawler bushing of the first aspect of the invention, the first tapered surface prevents the elastic ring, which is mounted to the small-diameter cylindrical part of the crawler bushing body, from moving axially outward, and the second tapered surface prevents the seal ring, which is coupled to the small-diameter cylindrical part of the crawler bushing body through the elastic ring, from moving axially outward. Therefore, the seal ring, together with the elastic ring, is firmly secured to the crawler bushing body even when the seal ring experiences resilience from the elastic ring in response to a squeeze. For this reason, the seal member can maintain a stable sealing function on a long-term basis without being pressed by excessive force of the seal ring.

With regard to replacement of the seal ring, the seal ring can be removed easily from the crawler bushing body by detaching the seal ring from the crawler bushing body against locking force of the first tapered surface or the second tapered surface, and the seal ring can be mounted easily to the crawler bushing body by pushing the seal ring toward the crawler bushing against the resilience from the elastic ring in response to the squeeze. In this way, maintenance for recovery of the sealing function can be carried out with ease.

The crawler bushing of the first aspect of the invention can maintain the stable sealing function on a long-term basis and also enables easy maintenance for the recovery of the sealing function. Moreover, the crawler bushing is capable of preventing the axially outward movement of the elastic ring with its extremely simple structure.

The respective structures of the second and third aspects of the invention are extremely simple, and adopting these structures can prevent the axially outward movement of the seal ring.

Adopting the structure of the fourth aspect of the invention allows easy formation of the tapered surface and the projection which projects radially inward at the inner end of the seal ring to be locked by the elastic ring.

Adopting the respective structures of the fifth and sixth aspects of the invention permits simplification of the shape of the crawler bushing.

In the crawler link device of the seventh aspect of the invention, the crawler bushing of the first, second, third, fourth, fifth or sixth aspect of the invention is adopted as the crawler bushing on which the seal member is abutted, whereby the sealing function can be maintained stably on a long-term basis. Moreover, the crawler link device thus obtained allows the easy maintenance for the recovery of the sealing function.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Concrete exemplary embodiments of a crawler bushing and a crawler link device according to the present invention are demonstrated hereinafter with reference to the accompanying drawings.

The embodiments described below are examples in which the invention is applied to a crawler bushing and a crawler link device that are mounted to a bulldozer. However, it goes without saying that the invention is not limited to the bulldozer and is applicable to work vehicles in general, including a hydraulic excavator equipped with a crawler bushing and a crawler link device.

(Brief Description of a Bulldozer with Reference toFIG. 1)

Bulldozer1shown inFIG. 1includes vehicle body2. Right and left sides of vehicle body2are provided with respective crawler units3(only the left crawler unit is shown). In front of vehicle body2, blade device (front implement)4is disposed, while ripper device (rear implement)5is disposed at the back of vehicle body2. Blade device4of this bulldozer1performs dozing and earth carrying operations, while ripper device5performs breaking and digging operations.

(Brief Description of the Crawler Unit with Reference toFIG. 1)

Crawler unit3includes track frame6forming a framework of crawler unit3. Track frame6is disposed in front of sprocket7, which serves as a drive wheel supported at a rear part of vehicle body2, and extends back and forth. Idler8is rotatably mounted to a front part of track frame6to serve as an idler wheel. Crawler belt9serving as an endless track is wound around idler8and sprocket7in the form of an ellipse. Above track frame6, required carrier rollers10are provided to support from below crawler belt9, which moves in a direction from sprocket7to idler8or in a reverse direction, thereby preventing crawler belt9from hanging down under its own weight and meandering. Beneath track frame6, required track rollers11are provided to distribute the weight of the vehicle over crawler belt9as well as to prevent the meandering of crawler belt9.

(Brief Description of the Crawler Belt with Reference toFIG. 2)

Track chain12is constructed of a plurality of link assemblies13having their ends rotatably connected.

Track shoe14is fixed by bolting (not shown) to a ground contact surface of each link assembly13.

(Description of the Link Assembly with Reference toFIG. 2)

Crawler link assembly13is constructed of a pair of crawler links15facing each other across center line T of track chain12.

(Description of the Crawler Link with Reference toFIGS. 2 and 3)

As shown inFIG. 2, crawler link15is an offset link having one end offset in a direction away from center line T of track chain12relative to an opposite end.

As shown inFIG. 3, one of the crawler links15overlapping each other at their respective ends (i.e., outer crawler link15inFIG. 3) is formed with pin insertion hole16in its one end and inwardly opening counter bore17which surrounds pin insertion hole16to be concentric with pin insertion hole16.

The other one of the crawler links15overlapping each other at their respective ends (i.e., inner crawler link15inFIG. 3) is formed with bushing insertion hole18in its opposite end.

(Brief Description of a Crawler Link Device with Reference toFIG. 3)

Crawler link device20of the first embodiment is constructed by coupling crawler links15,15, which overlap each other at their respective ends, by means of link pin21and crawler bushing22that are disposed to share the same axis O and inserting seal member23into counter bore17of crawler link15so that seal member23is disposed adjacently along axis O.

(Description of Respective Interferences of the Link Pin and the Crawler Bushing Relative to the Crawler Link with Reference toFIG. 3)

Link pin21is press-fitted into pin insertion hole16of crawler link15. A relatively small interference is set between link pin21and pin insertion hole16, so that link pin21cannot easily be inserted into and extracted from pin insertion hole16.

Crawler bushing22is press-fitted into bushing insertion hole18of crawler link15. A relatively small interference is also set between crawler bushing22and bushing insertion hole18, so that crawler bushing22cannot easily be inserted into and extracted from bushing insertion hole18.

(Description of the Link Pin with Reference toFIG. 3)

Link pin21is centrally formed with lubricant reservoir21afor storing a lubricant. Also, link pin21is formed with continuous hole21bcommunicating between lubricant reservoir21aand an outer periphery of pin21. The lubricant stored in lubricant reservoir21ais delivered through continuous hole21bto the outer periphery of pin21for lubrication between the outer periphery of link pin21and an inner periphery of crawler bushing22.

Metal elastic ring24is interposed between an end of link pin21and a rim of pin insertion hole16, thereby preventing leakage of the lubricant from between link pin21and crawler link15.

(Description of the Seal Member with Reference toFIG. 4)

As shown inFIG. 4, seal member23is formed by providing seal framework ring25with load ring26and seal body27.

Seal framework ring25is formed of a metallic annular member having rigidity and is substantially L-shaped in section. This ring25includes cylindrical part25aand flange25bprojecting radially outward from cylindrical part25ato face crawler bushing22.

Load ring26is formed of an annular elastic body, such as rubber, which can come into close contact with a corner where a bottom surface and a peripheral surface of counter bore17meet, and abuts on cylindrical part25aof seal framework ring25.

Seal body27is formed of an annular elastic body, such as rubber, which can abut on seal contact end face37of seal ring33(described later), and is integrally joined to flange25bof seal framework ring25.

Spacer28is interposed between the bottom surface of counter bore17and crawler bushing22. This spacer28is formed of a ring-shaped member which has a predetermined thickness and can be mounted to the outer periphery of link pin21. Spacer28has the function of stably keeping a space for appropriate storage of seal member23in counter bore17by specifying the position of crawler bushing22with respect to counter bore17.

(Description of the Crawler Bushing with Reference toFIG. 3)

As shown inFIG. 3, crawler bushing22includes crawler bushing body31having a hollow part into which link pin21is inserted in a slidingly fit condition.

Crawler bushing body31includes large-diameter cylindrical part31adefining an intermediate section of body31along axis O and small-diameter cylindrical parts31bwhich are smaller in diameter than large-diameter cylindrical part31aand define respective ends of body31along axis O.

Elastic ring32is mounted to an outer periphery of small-diameter cylindrical part31bwhile butting against a radially extending end face of large-diameter cylindrical part31aat a border between large-diameter cylindrical part31aand small-diameter cylindrical part31b.

Seal ring33is coupled to the outer periphery of small-diameter cylindrical part31bthrough elastic ring32.

(Description of the Elastic Ring with Reference toFIG. 3)

Elastic Ring32is an annular packing having O-shaped or circular section and is made of an elastic member such as rubber, and what is called an O-ring is adopted as elastic ring32. This elastic ring32is inserted between small-diameter cylindrical part31bof crawler bushing body31and seal ring33in a moderately compressed state by being given a certain squeeze, thereby performing the function of preventing the lubricant from leaking out from between crawler busing body31and seal ring33.

(Description of the Small-Diameter Cylindrical Part of the Crawler Bushing Body with Reference toFIG. 4)

As shown inFIG. 4, a corner where the outer periphery and a leading end surface of small-diameter cylindrical part31bof crawler bushing body31meet is chamfered, thus forming tapered surface34anarrowing radially inward while extending outward along axis O. By pushing elastic ring32toward a base end of small-diameter cylindrical part31bwhile fitting ring32onto this tapered surface34aelastic ring32can more easily be mounted to small-diameter cylindrical part31b.

The outer periphery of small-diameter cylindrical part31bis provided with, in the axially inward direction (in the leftward direction inFIG. 4) starting from tapered surface34amountain-shaped projection35, reverse tapered surface (first tapered surface)36and round chamfer34bin this order.

Mountain-shaped projection35is formed adjacent to an axially inner edge of tapered surface34aand projects radially outward for locking elastic ring32.

Reverse tapered surface36is located axially internal to mountain-shaped projection35on the outer periphery of small-diameter cylindrical part31band spreads radially outward while extending outward along axis O. In other words, at a portion corresponding to reverse tapered surface36, the diameter of small-diameter cylindrical part31bincreases as it extends axially outward (rightward inFIG. 4).

To round a corner bordering large-diameter cylindrical part31around chamfer34bis formed at the axially innermost base end of small-diameter cylindrical part31b. Providing this round chamfer34ballows elastic ring32to fit perfectly to the base end of small-diameter cylindrical part31b.

(Description of First Locking Means with Reference toFIG. 4)

Mountain-shaped projection35and reverse tapered surface (first tapered surface)36that are provided to small-diameter cylindrical part31bof crawler bushing body31function as the first locking means which with their extremely simple structures, prevent elastic ring32from moving outward along axis O on small-diameter cylindrical part31b.

(Description of the Seal Ring with Reference toFIG. 4)

As shown inFIG. 4, seal ring33is formed of a ring-shaped member having substantially the same outside diameter as large-diameter cylindrical part31aof crawler bushing body31. Material for this seal ring33is preferably corrosion-resistant metallic material such as stainless steel.

An outer end surface of seal ring33is seal contact end face37making contact with seal body27of seal member23. It is preferable that this seal contact end face37is hardened by undergoing surface hardening such as carbonizing or induction hardening.

Seal ring33is formed with, at its outer end, flange38projecting radially inward to cover elastic ring32when viewed from outside the end face of crawler bushing22.

Seal ring33is formed with, at its inner end, tongue-shaped projection39projecting radially inward to be locked by elastic ring32.

Seal ring33has, at its inner periphery, reverse tapered surface (second tapered surface)40formed to connect with tongue-shaped projection39. This reverse tapered surface40narrows radially inward while extending axially inward to be locked by elastic ring32.

Seal ring33has circular groove41formed in its inner end surface.

(Description of Second Locking Means with Reference toFIG. 4)

Tongue-shaped projection39and reverse tapered surface40that are provided to seal ring33function as the second locking means which with their extremely simple structures, prevent seal ring33from moving outward along axis O. As mentioned earlier, elastic ring32is disposed between seal ring33and small-diameter cylindrical part31bof crawler bushing body31. Elastic ring32contacts axially inwardly located reverse tapered surface (second tapered surface)40of seal ring33as well as axially outwardly located reverse tapered surface (first tapered surface)36of small-diameter cylindrical part31b.

(Description of a Sealing Function with Reference toFIG. 4)

The abutting relationship between seal contact end face37of seal ring33and seal body27of seal member23provides a seal between crawler bushing22and crawler link15, thereby preventing the lubricant from leaking out.

(Description of a Method of Forming the Tongue-Shaped Projection and the Reverse Tapered Surface on the Seal Ring with Reference toFIG. 5)

FIG. 5(a) is a sectional view of an essential part of seal ring33before the press working is carried out.

Before the press working is carried out, groove41of seal ring33has, on its peripheral surface, tapered surface42narrowing radially inward at inclination angle θ1while extending inward along axis O.

FIG. 5(b) is a sectional view of an essential part of seal ring33which underwent the press working.

After the press working is carried out, groove41of seal ring33has, on its peripheral surface, tapered surface42′ narrowing radially inward at inclination angle θ2while extending inward along axis O. It is to be noted here that inclination angle θ2is greater than inclination angle θ1.

The press working involves the use of punch43. This punch43has engaging projection43afor engagement in groove41of seal ring33. Engaging projection43ahas tapered surface44narrowing radially inward at inclination angle θ3while extending inward along axis O. It is to be noted here that inclination angle θ3is greater than inclination angle θ2.

To form tongue-shaped projection39and reverse tapered surface40on seal ring33, as shown inFIG. 5(a), tapered surface44of engaging projection43aof punch43is first brought into contact with tapered surface42of groove41in seal ring33. Next, as shown inFIG. 5(h), punch43is moved outward along axis O at a specified feed rate through operation of a press machine (not shown), thereby pushing engaging projection43aof punch43into groove41of seal ring33. Accordingly, seal ring33is formed with tongue-shaped projection39which can be locked by elastic ring32at its inner end and reverse tapered surface40which can contact elastic ring32at predetermined inclination angle θ2-θ1.

Tongue-shaped projection39and reverse tapered surface40may be provided in continuous form along the circumference of seal ring33. Alternatively, tongue-shaped projections39and reverse tapered surfaces40may be provided in discontinuous form at a predetermined pitch along the circumference of seal ring33. In cases where tongue-shaped projections39and reverse tapered surfaces40are provided in discontinuous form at the predetermined pitch along the circumference of seal ring33, although a detailed explanation using a drawing is omitted, it goes without saying that engaging projections43aof punch43may be provided correspondingly in circumferentially discontinuous form at a predetermined pitch.

(Description of Effects of the First Embodiment with Reference toFIG. 4)

In crawler bushing22of the first embodiment, the outward movement of elastic ring32along axis O is prevented by reverse tapered surface36and mountain-shaped projection35of crawler busing body31. Moreover, the outward movement of seal ring33along axis O is prevented by reverse tapered surface40and tongue-shaped projection39of seal ring33. Therefore, seal ring33, together with elastic ring32, is firmly secured to crawler busing body31even when seal ring33experiences resilience from elastic ring32in response to the squeeze. For this reason, seal member23can maintain a stable sealing function on a long-term basis without being pressed by excessive force of seal ring33. When seal ring33experiences force (rightward force inFIG. 4) causing detachment of ring33from crawler bushing body31, the force is propagated from reverse tapered surface (second tapered surface)40of seal ring33through elastic ring32to reverse tapered surface (first tapered surface)36of small-diameter cylindrical part31b. In response, reactive force from reverse tapered surface36acts on seal ring33by way of the elastic ring, thereby securing seal ring33to crawler bushing body31. In this way, seal ring33is stably held to the crawler bushing when used in the crawler belt.

A sealing device constructed of seal member23and seal ring33has its service life often determined by wear of seal contact end face37of seal ring33, rather than wear of seal body27of seal member23. Thus, seal ring33needs replacement on an as needed basis or on a regular basis.

To effect the replacement of seal ring33, seal ring33can be removed easily from crawler bushing body31by detaching seal ring33from crawler bushing body31against locking force of reverse tapered surface36and mountain-shaped projection35of crawler bushing body31or locking force of reverse tapered surface40and tongue-shaped projection39of seal ring33or a resultant of these two locking forces. Also, seal ring33can be mounted easily to crawler bushing body31by pushing seal ring33toward crawler bushing body31against the resilience from elastic ring32in response to the squeeze. In this way, maintenance for recovery of the sealing function can be carried out with ease.

FIG. 6is a structural illustration of a crawler bushing and a crawler link device in accordance with the second exemplary embodiment of the present invention. It is to be noted that in the second embodiment described below, elements similar to those in the first embodiment have the same reference marks in the drawing, the detailed descriptions of those elements are omitted, and emphasis is placed on different features not seen in the first embodiment.

(Brief Description of a Rotary Crawler Bushing with Reference toFIG. 6)

Crawler link device20A of the second embodiment relates to an example in which the rotary crawler bushing is adopted in crawler link device20of the first embodiment.

In the second embodiment, crawler bushing50corresponding to crawler bushing22of the first embodiment is a combination of first crawler bushing51, which forms an intermediate section of crawler bushing50along axis O, and second crawler bushings52forming respective ends of crawler bushing50along axis O.

An established clearance is provided between bushing insertion hole18A of one of the crawler links15overlapping each other at their respective ends (i.e., inner crawler link15inFIG. 6) and first crawler bushing51. First crawler bushing51is rotatable relative to crawler link15and link pin21and is what is called the rotary crawler bushing.

As opposed to first crawler bushing51, second crawler bushing52is press-fitted into bushing insertion hole18A. A relatively small interference is set between bushing insertion hole18A and second crawler bushing52, so that second crawler bushing52cannot easily be inserted into and extracted from bushing insertion hole18A.

(Description of the First Crawler Bushing with Reference toFIG. 6)

First crawler bushing51includes crawler bushing body61similar to crawler bushing body31of the first embodiment.

Crawler bushing body61includes large-diameter cylindrical part61adefining an intermediate section of body61along axis O and small-diameter cylindrical parts61bwhich are smaller in diameter than large-diameter cylindrical part61aand define respective ends of body61along axis O.

Elastic ring62is mounted to an outer periphery of small-diameter cylindrical part61bwhile butting against a stepped surface at a border between large-diameter cylindrical part61aand small-diameter cylindrical part61b.

Seal ring63is coupled to the outer periphery of small-diameter cylindrical part61bthrough elastic ring62.

Description of the Second Crawler Bushing with Reference toFIG. 6)

Crawler bushing body71includes large-diameter cylindrical part71adefining an intermediate section along axis O and small-diameter cylindrical part71bwhich is smaller in diameter than large-diameter cylindrical part71aand defines an outer end of body71along axis O.

Counter bore17A is formed at an inner end of large-diameter cylindrical part71aof crawler bushing body71.

Elastic ring72is mounted to an outer periphery of small-diameter cylindrical part71bwhile butting against a stepped surface at a border between large-diameter cylindrical part71aand small-diameter cylindrical part71b.

Seal ring73is coupled to the outer periphery of small-diameter cylindrical part71bthrough elastic ring72.

Seal member23A is inserted into counter bore17A.

It is to be noted here that large-diameter cylindrical parts61a71a, small-diameter cylindrical parts61b71belastic rings62,72and seal rings63,73are similar to those (i.e., large-diameter cylindrical part31asmall-diameter cylindrical part31belastic ring32and seal ring33) in the first embodiment.

(Description of a Spacer Between the First and Second Crawler Bushings with Reference toFIG. 6)

Spacer28A is interposed between a bottom surface of counter bore17A of second crawler bushing52and first crawler bushing51. This spacer28A is formed of a ring-shaped member which has a predetermined thickness and can be mounted to an outer periphery of link pin21. Spacer28A has the function of stably keeping a space for appropriate storage of seal member23A in counter bore17A by specifying the position of first crawler bushing51with respect to counter bore17A.

(Description of Effects of the Second Embodiment with Reference toFIG. 6)

It goes without saying that the second embodiment provides the same effects as the first embodiment.

In addition, first crawler bushing51of the second embodiment is the rotary bushing, thereby advantageously reducing contact friction during engagement with sprocket7(seeFIG. 1).

FIG. 7is a structural illustration of a crawler bushing and a crawler link device in accordance with the third exemplary embodiment of the present invention. It is to be noted that in the third embodiment described below, elements similar to those in the first embodiment have the same reference marks in the drawing, the detailed descriptions of those elements are omitted, and emphasis is placed on different features not seen in the first embodiment.

(Description of a Cartridge Pin with Reference toFIG. 7)

Crawler link device20B of the third embodiment relates to an example in which the structure of the cartridge pin is adopted in crawler link device20of the first embodiment.

As shown in.FIG. 7, one of the crawler links15overlapping each other at their respective ends (i.e., outer crawler link15inFIG. 7) is formed with sleeve insertion hole74at its one end. Sleeve75is inserted into this sleeve insertion hole74.

Sleeve75is formed with pin insertion hole16B into which link pin21is inserted. Sleeve75is also formed with inwardly opening counter bore17B which surrounds pin insertion hole16B to be concentric with pin insertion hole16B. Pin insertion hole16B and counter bore17B of sleeve75correspond, respectively, to pin insertion hole16and counter bore17of crawler link15in the first embodiment.

Metal elastic ring24is interposed between an end of link pin21and a rim of pin insertion hole16B, thereby preventing leakage of a lubricant from between link pin21and sleeve75.

In the third embodiment, cartridge pin80B is constructed of link pin21, crawler bushing22, seal member23, metal elastic ring24, spacer28and sleeves75. This cartridge pin80B has the function of a connecting pin, the function of a bearing device and the function of a sealing device in combination.

(Description of Effects of the Third Embodiment with Reference toFIG. 7)

It goes without saying that the third embodiment provides the same effects as the first embodiment.

In the third embodiment, cartridge pin80B is adopted. Inserting and extracting cartridge pin80B correspond to inserting and extracting the connecting pin, the bearing device and the sealing device collectively. This provides an advantage that crawler belt9(seeFIGS. 1 and 2) is connected and disconnected more efficiently.

FIG. 8is a structural illustration of a crawler bushing and a crawler link device in accordance with the fourth exemplary embodiment of the present invention. It is to be noted that in the fourth embodiment described below, elements similar to those in each of the first, second and third embodiments have the same reference marks in the drawing, the detailed descriptions of those elements are omitted, and emphasis is placed on different features not seen in those embodiments,

(Description of a Cartridge Pin with Reference toFIG. 8)

Crawler link device20C of the fourth embodiment relates to an example in which the structure of the rotary crawler bushing and the structure of the cartridge pin are adopted by combining crawler link device20A of the second embodiment with the crawler link device of the third embodiment.

In the fourth embodiment, cartridge pin80C is constructed of link pin21, first crawler bushing51, second crawler bushing52, seal members23,23A, metal elastic ring24, spacers28,28A and sleeves75. This cartridge pin80C, too, has the function of a connecting pin, the function of a bearing device and the function of a sealing device in combination.

(Description of Effects of the Fourth Embodiment with Reference toFIG. 8)

It goes without saying that the fourth embodiment provides the same effects as the first embodiment.

In addition, the fourth embodiment provides a combination of the effects of the second and third embodiments. In other words, the fourth embodiment enables reduction of contact friction during engagement with sprocket7(seeFIG. 1) and can improve efficiency in connecting and disconnecting crawler belt9(seeFIGS. 1 and 2).

The embodiments of the crawler bushing and the crawler link device according to the present invention have been described above. However, the present invention is not limited to the structures described in the above embodiments and allows appropriate variations on each of the structures without departing from its spirit, such as, appropriately combining the structures of the foregoing embodiments.

(Description of a Variation with Reference toFIGS. 4 and 9)

The foregoing embodiments have given the example in which mountain-shaped projection35and reverse tapered surface36are adopted as the first locking means as shown inFIG.4. However, the present invention is not limited to this example and can adopt, for example, the following structure. As shown inFIG. 9, with only mountain-shaped projection35provided, flat surface81parallel to axis O is adopted, and an axially inner reverse tapered surface of mountain-shaped projection35functions as a first tapered surface.

Industrial Applicability

A crawler bushing and a crawler link device according to the present invention have the capability of maintaining a sealing function stably on a long-term basis as well as the capability of permitting easy maintenance for recovery of the sealing function and therefore, are suitable for use as components of a crawler belt mounted to a work vehicle such as a bulldozer or a hydraulic excavator.

Description of Reference Marks in the Drawings

20,20A,20B,20C crawler link devices

23,23A seal members

37seal contact end face