Method for forming a track link bushing having a contoured opening

A method for extruding a track link bushing having a contoured opening and a generally cylindrical outer surface.

BACKGROUND OF THE INVENTION 
In the use of track link bushings, it was discovered that the life of the 
bushing could be markedly increased by tapering or contouring the end 
portions of the bushing openings to compensate for track link pin 
deflection under loaded conditions. The heretofore utilized methods of 
forming these double tapered bushings was by cutting or grinding the inner 
walls which required an undesirable amount of labor and time. 
This invention, therefore, resides in a method for forming a track link 
bushing by extrusion.

DETAILED DESCRIPTION OF THE INVENTION 
Referring to FIG. 1, a metal slug 10 of preselected configuration is 
positioned between a mandrel 11 and a first ring die 12 which sizes the 
outer surface of a tubular metal blank from the slug 10. The mandrel 11 
has an enlarged end 13 and a contoured double tapered or curved 14,15 
middle portion 16. 
Referring to FIG. 2, the mandrel 11 is urged against the metal slug 10 and 
through the first ring die 12 for extruding the metal slug 10 and forming 
a tubular metal blank 17 about the mandrel 11. 
During forming of the metal blank 17, metal flows about and along the outer 
surface of the mandrel 11 in the annulus between the mandrel 11 and the 
ring die 12. The configuration of the inner surface of the blank 17 is of 
the form of the middle portion 16 of the mandrel 11 which is of a 
preselected configuration. This configuration curves or tapers from a 
middle portion 18 of the blank outwardly toward the opposed ends 19,20 of 
the blank 17. The outer surface of the blank 17 is of a generally 
cylindrical configuration. The metal slug 10 is contacted by a ledge 
portion 30 of the mandrel 11 for forming the second end 20 of the blank 
17. 
Holding mean 21 or fingers positioned on the downstream side of the first 
ring die 12 move inwardly into contact with the second end 20 of the blank 
17 for maintaining the blank 17 and the mandrel 11 is thereafter moved 
through and from the blank 17. After removal of the mandrel 11, the 
elements 21 are retracted. 
Referring to FIGS. 2 and 3, as the mandrel 11 is passed through the blank 
17, the enlarged end portion 13 moves the walls and inside diameter 
outwardly, forms a generally cylindrical inside opening or surface 34, 
moves the outer walls or surface 33 of the blank 17 outwardly, and forms 
tapered blank outer surfaces of a preselected configuration, as shown by 
blank 23 of FIG. 3. This configuration curves or tapers from a middle 
portion 18 of the blank 13 inwardly toward opposed ends 19,20 of the blank 
23. 
Referring to FIG. 3, the second blank 23 is thereafter passed through a 
second ring die 22 for decreasing the outside diameter of the blank 23, 
forming a generally cylindrical outer surface, moving the inner walls 34 
of the blank 23 inwardly, and forming a third blank 24 having a blank 
opening 26 curving or tapering outwardly from the middle portion 18 of the 
blank 24 toward each end 19,20 of the blank 24. 
Each blank is preferably pushed through the second ring die 22 with a 
subsequently formed blank. Other elements, such as a push rod (not shown), 
can be used but the resultant production rate would be reduced by the 
additional steps of utilizing the other element. Also, by using a 
subsequently formed blank to contact the second end 20 of a previously 
formed blank and move said previously formed blank through the second ring 
die 22, the operation can be generally continuous. 
If desired, the metal slug can be heated to a preselected temperature prior 
to forming the blank. 
As is known in the metal extrusion art, the dimensions of the mandrel 11, 
ring dies 12,22 and the dimensions and configuration of the slug 10 are 
dependent upon the final dimensions of the resultant bushing 24. After the 
exact dimensions of the resultant bushing have been determined, one 
skilled in the art can readily determine the variables. 
On example track pin pushing that has proven to have increased wear 
properties is as follows: 
Length; 16 cm (6.28 in.) 
O.d.; 8.8 cm (3.81 in.) 
I.d. at ends (19,20); 5,791 cm (2.28 in.) 
I.d. at middle portion (18); 5.766 cm (2.27 in.) 
This bushing was formd with apparatus as follows: 
Slug (10); Alloy Steel, Carburizing Grade 
Configuration; Cylindrical 
Volume; 1065 cm.sup.3 
Mandrel (11); Double Linear Tapered 
Length; 45.7 cm (18 in.) 
Diameter, end (13); 5.817 cm (2.29 in.) 
Diameter, middle (16); 5.766 cm (2.27 in.) 
First Ring Die (12) 
Diameter; 9.67 cm (3.807 in.) 
Second Ring Die (22) 
Diameter; 9.52 cm (3.800 in.) 
Other aspects, objects, and advantages will become apparent from a study of 
the drawings, specification, and claims.