Metal deforming – Process – Tube making or reshaping
Reexamination Certificate
1999-10-19
2001-05-15
Tolan, Ed (Department: 3725)
Metal deforming
Process
Tube making or reshaping
C072S342100, C072S342960, C072S370250, C072S260000, C029S897200
Reexamination Certificate
active
06230540
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an axle for heavy vehicle applications, and more particularly to forming an integral bearing shoulder in a tubular axle.
As a part of the production of axles, a shoulder is required as a back-up for the bearings which are assembled to the axle. The bearing shoulder is a stepped-up section of the spindle and is typically formed intermediate the spindle and axle diameter. The bearing fits onto the spindle at each end of the axle and the shoulder supports the bearing.
There are several known methods to produce this shoulder. One method is to manufacture an axle from a solid bar of steel. The entire axle, spindle and shoulder are directly produced from the steel bar. Other methods manufacture the axle as a tube with spindles welded to each end. These spindles also have a shoulder forged into them to provide the bearing support.
Yet another method is to form the spindle onto the end of the tubing and weld a collar onto the formed spindle to produce the bearing shoulder. This has proven to be an effective method for the production of semi-trailer axles. However, a machined component and a welding operation are required. Although practical, this does increase the finished axle cost.
Attempts to form the shoulder directly from axle tubing have required the use of temperatures in excess of 2000 degrees Fahrenheit in a localized area. This temperature is above the transition temperature of steel which has previously not allowed the use of heat treated tubing. The non-heat treated tube must be subjected to a quench and temper operation after forming to provide a tube having the desired strength for an axle. This increases the manufacturing complexity and also increases the finished axle cost.
Accordingly, it is desirable to provide an economical method for forming a tubular axle having the bearing shoulder directly formed into the tubing.
SUMMARY OF THE INVENTION
The method according to the present invention provides a tubular axle having the bearing shoulder directly formed into heat-treated tubing. The method generally includes a heating operation, a preform operation and an upset forming operation.
The first operation in forming the tubular axle is the heating of a length of the tubular blank. The first length is heated to a temperature less than 1500 degrees Fahrenheit, and preferably to a temperature of approximately 1250 degrees Fahrenheit. By heating the tubular blank to a temperature less than the transformation temperature of steel (which occurs at approximately 1500 degrees Fahrenheit) the present invention allows the use of heat treated steel without loss of the heat treated properties.
The next operation includes forcing a preform die assembly onto the end of the tubular blank by a machine such as a double-ended hydraulic press having a two-stage die holder. Preferably, the tubular blank is held stationary as the machine simultaneously forces the die assemblies onto both ends of the tubular blank. By using a lubricant and by performing a two stage forming operation, a mandrel is not required to be inserted into the tubular axle blank during the forming. This eliminates the possibility of a mandrel being wedged into the tubular blank and the resultant scrap.
The preform die assembly is forced onto the tubular blank, and the original diameter is reduced to a second diameter. As the preform die assembly is forced further onto the tubular blank an intermediate section is formed between the original diameter and the second diameter. The intermediate section is preferably formed as a first ramped section and a second ramped section.
The final operation includes forcing an upset die assembly onto the end of the tubular blank to form the final bearing shoulder and spindle configuration. The upset die assembly forms a gathered material section that is preferably a substantially stepped section formed intermediate the first ramped section and the second ramped section.
The second diameter provides a pre-machined diameter for the final axle spindle and the gathered material area provides a pre-machined area for the integral bearing shoulder. The axle of the present invention does not require a machined collar to be welded onto the spindle which results in a manufacturing cost savings. Further, a fatigue life improvement in the axle is obtained as the high stress area at the heat effected zone of the collar weld is eliminated.
REFERENCES:
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patent: 5205464 (1993-04-01), Simon
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patent: 5517843 (1996-05-01), Winship
patent: 640414 (1995-03-01), None
patent: 59-215221 (1984-12-01), None
patent: 61-279328 (1986-12-01), None
patent: 1375391 (1988-02-01), None
Bhalla Vipan Kumar
Wilch John Wayne
Carlson Gaskey & Olds P.C.
Meritor Heavy Vehicle Systems LLC
Tolan Ed
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