Outer pin seal

Abstract

A seal (200) of substantially wedge shaped cross section self adjusts and seals pivot joints (100) over a range of gap widths to be sealed.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a nationalization under 35 U.S.C. §371 of International Application No. PCT/US2008/005411, filed Apr. 25, 2008, titled “Outer Pin Seal,” which claims the benefit of U.S. Provisional Application Ser. No. 60/914,480, filed Apr. 27, 2007, the disclosures of which are expressly incorporated by reference herein.

FIELD OF THE INVENTION

The invention relates, generally, to seals for pivot joints used to look patiently connect mechanical parts and, more particularly, to outer seals for pins and bushings that rotation only connect linkages and work tools on work vehicles.

BACKGROUND OF THE INVENTION

Pivot joints used in the linkages of work vehicles such as, for example, loader backhoes and four wheel drive loaders include pins and bushings to allow relative rotation between connected parts. These pivot joints conventionally include seals between the pins and the bushings as barriers to debris. However, due to the harsh environments in which these vehicles are used, i.e., environments having significant amounts of dirt and debris, dirt and debris tend to get past these barriers and cause accelerated wear of the pivot joints.

Some manufacturers of work vehicles have sought to remedy the difficulties outlined above by forming pre-barriers, i.e., a first line of defense against debris, via o-rings located between outer surfaces of the connected portions of linkages and work tools as shown in FIGS. 6 and 6A. However, this approach has led to at least the following two difficulties: (1) the o-rings are typically round, allowing dirt and debris to eventually work past the o-ring and into the space between the pins and bushings; and (2) the o-rings wear and their eventual replacement requires disconnection of the rotationally connected parts, a substantial expense with respect to time and money.

SUMMARY OF THE INVENTION

Described herein is a device and method for sealing a pivot joint against dirt and debris that significantly reduces the difficulties addressed above. The rotationally connected parts of the pivot joint include a first member having an external surface with a substantially circular cross section in a plane perpendicular to the longitudinal axis of the pin and a second member having an external surface substantially orthogonal to the longitudinal axis. The seal has a cross section that is substantially wedge shaped. One corner of the wedge fits into a gap between the external cylindrical surface of the first member while the remaining corners span the gap between these surfaces. Each of the remaining corners spanning the gap may include lips for completing the sealing function of the device and for adjusting to variations in the size of the gap. The seal is split, having a first end and a second end such that when the first and second ends are joined, it, i.e., the seal, substantially forms a circle. At each end, the seal includes a connecting portion. In one embodiment, the connecting portion is on the seal's outer diameter and integral to the wedge. The first and second ends are generally joined via a connector such as, for example, a screw.

In practice, an accommodating portion of the external surface of the first member is shaped to conform to the shape and angle of one side of the wedge. Once the pivot joint is assembled, the seal is connected such that it fills a gap between the first member and the second member, where the one side of the wedge rides along the accommodating portion of the external surface of the first member and the lips of the seal ride along the external surface of the first member and the external surface of the second member. The seal is dimensioned to accommodate a relatively wide range of gaps in tension.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in detail, with references to the following figures, wherein:

FIG. 1 is a view of a work vehicle in which the invention may be used;

FIG. 2 is an oblique view of the front of the work vehicle illustrated in FIG. 1;

FIG. 3 is an oblique view of the outer pin seal;

FIG. 4 is another oblique view of the outer pin seal;

FIG. 5 is a cross-sectional view of the joint illustrated in FIG. 2 including the outer pin seals;

FIG. 6 is an oblique view of a conventional seal; and

FIG. 6A is a cross-sectional view of FIG. 6.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

FIG. 1 illustrates a work vehicle in which the invention may be used. The particular work vehicle illustrated is a four-wheel-drive loader 1 having a rear portion 20, a front portion 30, a pivot 35 between the rear portion 20 in the front portion 30, a cab 24, of boom 33, a bucket 34, and a pivot joint 100 rotationally connecting the boom 33 and the bucket 34.

While the outer pin seal, i.e., the invention, will work on practically any appropriately configured pivot joint, we will focus on the pivot joint 100 as illustrated in FIG. 2 which employs a greaseless bushing 140. FIGS. 3 and 4 provide oblique views of one embodiment of the invention which is first line defense seal 200. Greaseless style bushings require many levels of sealing to ensure bushing life. In this particular case, the first line defense seal 200 is the exterior seal at the boom to bucket joint, i.e., the pivot joint 100, which is exposed to abrasive chemicals and extreme environmental/operating conditions and is required to keep debris out of the joint. Due to manufacturing limitations, dimensional variations between parts require the seal to be effective over gaps of considerable range. In this particular instance the seal needs to span gaps ranging from, for example, 1 mm to 12 mm. Thus, the first line defense seal 200 is required to be adjustable, i.e., to effectively seal gaps of considerable range without falling into the pivot joint 100 during operation. The first line defense seal 200 is also required to last the life of the joint of 15,000 hours.

As illustrated in FIGS. 3 and 4, the first line defense seal 200 includes a first end 200a, a second end 200b, a first portion 201, a second portion 202 and a connector 203. The first line defense seal 200 may be constructed of any material of suitable flexibility and durability and may also contain self lubricating materials such as, for example molybdenum disulfide. The first line defense seal 200 be of the greaseless type as described above or may require the application of a lubricant.

FIG. 5 illustrates a cutaway view of one embodiment of the invention, i.e., first-line defense seal 200 as it is used to protect pivot joint 100 which includes a first member 110, a second member 120, a pin 130, and a bushing 140. As illustrated in FIGS. 3, 4, and 5, the first line defense seal 200 includes: a wedge shaped first portion 201 which includes lips 201a and 201b; a second portion 202; a first end 200a; a second end 200b; and a connector 203, comprising a bolt 203a, a nut 203b, and spacers 203c as required. As illustrated in FIG. 5, exemplarily, a first external surface 110a of the first member 110 substantially conforms to a first portion surface 201c of the first portion 201 of the first line defense seal 200. As illustrated, lip 201a contacts a second external surface 110b of the first member 110 and lip 201b seals a circular external surface 120a of the second member 120. The circular external surface 120a is substantially flat and orthogonal to the longitudinal axis 130a of the pin 130. The first external surface 110a is conical, i.e., at an angle that is oblique to the second external surface 110b. The second external surface 110b is cylindrical in shape.

In practice, the first line defense seal 200 is placed around the gap 100b as shown in FIG. 5 and connected via connector 203. Bolt 203a has an unthreaded length that provides a length L sufficiently short to close the first line defense seal 200 so as to provide an effective barrier to environmental contaminants and sufficiently long to avoid unduly distorting the seal 200 when tightened down.

Once the first line defense seal 200 is tightened down, the first portion surface 201c rides along the first external surface 110a while lip 201a contacts the second external surface 110b of the first member 110 and lip 201b contacts the circular external surface 120a of the second member 120. The first line defense seal 200 is always in some degree of tension in the sealed pivot joint 100. Due to the shape of the first member contacting surface 110a, which is, exemplarily, a chamfer in this case, the seal 200 will tend to seek a setting of the lease tension when it is connected as it will self adjust along the first member contacting surface 110a as dimensions of first member 110, the second member 120 and the gap 100b vary. As the gap 100b varies, the lips 201a, 201b aid in the self adjustment of the seal 200 as they tend to flex and relax as necessary to seal the gap 100b. As the outer diameters of the first external surface 110a and the second external surface 110b increase and decrease, the seal 200 tends to self adjust by positioning itself down and up along the first member contacting surface correspondingly.

Having described the illustrated embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.

Claims

1. A seal for a pivot joint, the pivot joint including a pivot pin and a bushing, the pivot joint rotationally connecting a first member and a second member, the first member having a longitudinal axis and a first external surface substantially conical in shape and substantially symmetrical about a first plane orthogonal to the longitudinal axis, the first external surface having a cross section that is substantially circular on the first plane orthogonal to the longitudinal axis, the second member having a circular external surface that is substantially flat and substantially orthogonal to the longitudinal axis, a gap being defined axially between the first external surface and the circular external surface, the seal comprising:

a first portion forming a circle in a second plane orthogonal to the longitudinal axis, the first portion having a cross sectional shape generally conforming to that of a triangle, an outer diameter of the circle formed by a first corner and a second corner of the triangle, a first lip at the first corner, a second lip at the second corner, an inner diameter of the circle formed by a third corner of the triangle, a first seal surface extending between the third corner and the first corner, a second seal surface extending between the third corner and the second corner, a majority of the first portion of the seal being positioned in the gap;

a second portion along an arc of the circle and positioned along the outer diameter, the second portion having the effect of thickening the seal along the arc, the second portion and the first portion being integral, the first and second portions being split in a plane parallel to the longitudinal axis such that the first portion has a first portion first end and a first portion second end and the second portion has a second portion first end and a second portion second end, a length of the second portion along the arc being greater than a width of the first portion; and

a fastener for connecting the first portion first end and the first portion second end and for connecting the second portion first end and the second portion second end.

2. The seal of claim 1, wherein the seal is connected over the gap between the first external surface and the circular external surface such that the gap is sealed, the seal fitting around a circumference of the first member external surface.

3. The seal of claim 2, wherein the first seal surface contacts the first external surface.

4. The seal of claim 3, wherein the second lip contacts the circular external surface.

5. The seal of claim 4, wherein the first lip contacts a second external surface of the first member.

6. A method of using a seal to seal a pivot joint, the pivot joint including a pivot pin and a bushing, the pivot joint rotationally connecting a first member and a second member, the first member having a longitudinal axis and a first external surface substantially conical in shape and substantially symmetrical about a first plane orthogonal to the longitudinal axis, the first external surface having a cross section that is substantially circular about the first plane orthogonal to the longitudinal axis, the second member having a circular external surface that is substantially flat and substantially orthogonal to the longitudinal axis, a gap being defined axially between the first external surface and the circular external surface,

the seal including:

a first portion forming a circle in a second plane orthogonal to the longitudinal axis, the first portion having a cross sectional shape generally conforming to that of a triangle, an outer diameter of the circle formed by a first corner and a second corner of the triangle, a first lip at the first corner, a second lip at the second corner, an inner diameter of the circle formed by a third corner of the triangle, a first seal surface extending between the third corner and the first corner, a second seal surface extending between the third corner and the second corner, and

a second portion along an arc of the circle and positioned along the outer diameter, the second portion having the effect of thickening the seal along the arc, a length of the second portion along the arc being greater than a width of the first portion,

the method comprising:

placing the seal of cross-sectional triangular shape across the gap between the first external surface and the circular external surface such that the first external surface contacts the first seal surface and the circular external surface contacts the second corner and such that a majority of the first portion of the seal is positioned in the gap.

7. The method of claim 6, wherein an outer surface of the seal extends between the first and second corners of the triangle and is substantially parallel to the longitudinal axis.

8. The method of claim 6, wherein the first member of the pivot joint includes a second external surface adjacent to the first external surface, and an outer surface of the seal is substantially parallel to the second external surface.

9. The seal of claim 1, wherein an outer surface of the seal extends between the first and second corners of the triangle and is substantially parallel to the longitudinal axis.

10. The seal of claim 1, wherein the first member of the pivot joint includes a second external surface adjacent the first external surface, and an outer surface of the seal is substantially parallel to the second external surface of the first member.