Track having rotatable bushing and link for the same

1. A track for use in a track-type vehicle comprising:

a track link having an alternate combination of external links and internal links, said external links and said internal links being interlinked right and left relative to a width direction of a track, said internal link being formed symmetrically with respect to the central longitudinal axial line when viewed from the front;

a coupler pin interlinking said external link and internal link,

a rotatable bushing being interposed between the right and left internal links, said rotatable bushing being supported rotatably on said coupler pin;

a coupler pin hole being provided through said external link, an end of said coupler pin being press fitted into said coupler pin hole;

a bushing hole being provided through said internal link; and

a fixed bushing, an outermost circumference of which being interfitted completely inside of said bushing hole;

wherein said bushing hole of said internal link being formed greater in thickness as viewed in the width direction than said coupler pin hole of said external link and having a uniform cylindrical structure.

2. The track as set forth in claim 1 , wherein a boss part having a raised portion around said bushing hole is provided on an outer surface area of said internal link.

3. The track as set forth in claim 2 , wherein an inner surface side circumferential area of said coupler pin hole of said external link is formed into a concave surface corresponding to an outer shape of said boss part of said internal link.

4. The track as set forth in claim 3 , wherein an outer surface side circumferential area of said coupler pin hole of said external link is formed into a raised shape.

5. A track for use in a track-type vehicle comprising:

a track link having a combination of external links and internal links, said external links and said internal links being interlinked right and left relative to a width direction of a track,

a coupler pin interlinking said external link and internal link,

a rotatable bushing being interposed between the right and left internal links, said rotatable bushing being supported rotatably on said coupler pin;

a coupler pin hole being provided through said external link, an end of said coupler pin being press fitted into said coupler pin hole;

a bushing hole being provided through said internal link; and

a fixed bushing being interfitted into the inside of said bushing hole;

wherein said bushing hole part of said internal link is 1.1 to 1.5 times greater in thickness as viewed in the width direction than said coupler pin hole part of said external link.

6. The track as set forth in claim 1 , wherein a seal ring, interposed between a fixed bushing which is interfittingly inserted into said bushing hole of said internal link and a rotatable bushing which is interposed between right and left internal links, is interfittingly disposed in the inside of said bushing hole.

7. The track as set forth in claim 1 , wherein a seal ring, interposed between a fixed bushing which is interfittingly inserted into said bushing hole of said internal link and said external link, is interfittingly disposed in the inside of said bushing hole.

8. A track for use in a track-type vehicle, comprising:

a track link having an alternate combination of external links and internal links, said external links and said internal links being interlinked right and left relative to a width direction of a track, said internal link being formed symmetrically with respect to the central longitudinal axial line when viewed from the front;

a coupler pin interlinking said external link and internal link;

a bushing including a pair of fixed bushing portions and a rotatable bushing portion disposed axially between the pair of fixed bushing portions, the rotatable bushing portion being interposed between the right and left internal links, said rotatable bushing portion being supported rotatably on said coupler pin;

a coupler pin hole being provided through said external link, an end of said coupler pin being press fitted into said coupler pin hole;

a bushing hole being provided through said internal link; and

an inner pair of sealing rings and an outer pair of sealing rings,

wherein a respective one of the pair of fixed bushing portions, a respective one of the pair of inner sealing rings and a respective one of the pair of outer sealing rings being completely disposed in the bushing hole of a respective one of the right and left internal links, the respective one of the pair of fixed bushing portions disposed between respective ones of the inner and outer sealing rings and being fixedly connected to a respective one of the right and left internal links inside the bushing hole,

wherein each one of the internal links having a flat inside internal link surface and an opposite outside internal link surface with an internal link boss part projecting from the outside internal link surface and surrounding the bushing hole,

wherein each one the external links having an inside external link surface and an outside external link surface, the inside external link surface having a concavely curved surface portion corresponding to and sized for receiving the internal link boss part, the external link boss part projecting from the outside external link surface and surrounding the coupler pin hole,

wherein the rotatable bushing portion being axially disposed between the pair of inner sealing rings with respective ones of the inner sealing rings being disposed between respective ones of the fixed bushing portions and the rotatable bushing portion, and

wherein said bushing hole of said internal link being formed greater in thickness as viewed in the width direction than said coupler pin hole of said external link.

9. A track according to claim 8 , wherein said bushing hole of said internal link is 1.1 to 1.5 times greater in thickness as viewed in the width direction than said coupler pin hole of said external link.