Metal treatment – Process of modifying or maintaining internal physical... – Heating or cooling of solid metal
Reexamination Certificate
2000-01-05
2002-02-19
Yee, Deborah (Department: 1742)
Metal treatment
Process of modifying or maintaining internal physical...
Heating or cooling of solid metal
C148S649000, C148S654000
Reexamination Certificate
active
06348112
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a trailer hitch assembly for use with a truck and a method for making the same and, more particularly, relates to a trailer hitch assembly comprising bainitic parts and a method for making the same.
BACKGROUND ART
Trailer hitch assemblies for connecting a vehicle, such as a truck with a trailer are well known. Trailer hitches connect automobiles, trucks and other vehicles to items such as campers, small boats, and other loads. The trailer hitch assembly is usually attached to the frame of the vehicle.
Because the loads on the trailer are usually items which are relatively heavy, such as boats and the like, the trailer hitch assembly must be able to withstand compressive and tensile loads according to SAE test method J684. Typically, a trailer hitch assembly must be capable of pulling a load equal to at least one and one-half times the weight of the trailer. A common problem associated with trailer hitch assemblies is that potholes and uneven road surfaces create a great deal of wear and tear on the trailer hitch assembly, which could result in eventual fracture of the trailer hitch.
Conventional trailer hitch assemblies comprise a horizontally extending crossbar disposed between a pair of side brackets. The side brackets mount to the frame of the vehicle. The crossbar is coupled with a receiver which operates to couple the trailer to the hitch assembly.
Conventional trailer hitch assemblies have been made by cold formed steel square tubes having a uniform cross-section. The steel used for the crossbar has conventionally been SAE 1010 or SAE 1020 steel which consists essentially of iron, carbon, silicon, manganese, phosphorus, sulfur and chromium. The side brackets of a conventional trailer hitch assembly are also made of conventional SAE 1010 or SAE 1020 steel. The side brackets are welded to opposite ends of the crossbar.
These conventional cold formed tube trailer hitch assemblies are limited to a specific geometric configuration. Moreover, the process requires that these cold formed tube trailer hitch assemblies have a uniform cross-sectional width. Also, the microstructure of these trailer hitch assemblies is primarily ferrite.
It would be desirable to provide a trailer hitch assembly which is lighter and less expensive than the conventional trailer hitch assemblies without foregoing any of the structural strength of the trailer hitch assembly, i.e., still having a capability of withstanding the typical compressive and tensile loads required of trailer hitch assemblies. It would also be desirable to provide a trailer hitch assembly which is able to have varied cross-sections. Furthermore, it would be desirable to have a process that allows for the steel to be formed in a variety of geometric configurations and uses less starting material.
DISCLOSURE OF INVENTION
Accordingly, it is an object of the present invention to provide a method of making trailer hitches that while, using lesser starting material, produces a product at least as strong as conventionally manufactured trailer hitches.
It is a further object of the present invention to provide a trailer hitch assembly which is lighter than conventional trailer hitch assemblies without sacrificing any of the structural strength of the trailer hitch assembly, i.e., still having a capability of withstanding compressive and tensile loads as specified by SAE test method J684.
It is yet a further object of the present invention to provide a trailer hitch assembly which is able to have varied cross-sectional dimensions to provide strength where maximally needed.
The above and other objects of the present invention are met by providing a trailer hitch assembly that comprises a crossbeam assembly, and a pair of side brackets disposed on opposite ends of the cross-beam assembly. The crossbeam assembly and the side brackets are made of boron steel having a bainitic microstructure.
In another aspect of the present invention, a method of making a trailer hitch assembly for use with a vehicle is provided. The trailer hitch assembly comprises a plurality of trailer hitch parts comprising a crossbeam assembly and a pair of side brackets disposed on opposite ends of the crossbeam assembly. Each of the trailer hitch parts are made by preheating ultra-high-strength boron steel to the austenite range, forming the preheated steel while in its austenite range to the shape of the desired trailer hitch assembly part, and quenching the formed part to yield a part having a bainitic microstructure.
In yet another aspect of the present invention, a method is provided for manufacturing a trailer hitch assembly comprising a crossbeam assembly and a pair of side brackets disposed on opposite horizontal ends of the crossbeam assembly. The method comprises preheating a first blank of boron steel to the austenite range. The blank, while in the austenite range, is then formed into a horizontally extending U-shaped member. The horizontally extending U-shaped member is then quenched to its bainitic microstructure. A second blank of boron steel is preheated to its austenite phase. The second blank of boron steel, while in the austenite range, is formed into a reinforcing bar. The reinforcing bar is then quenched to its bainitic microstructure. The reinforcing bar is then secured to the channel to form a crossbar assembly. A third blank of boron steel is preheated to the austenite range. The third blank, while in the austenite range, is formed into at least one side bracket. The side bracket is quenched to its bainitic microstructure. The first side bracket and a second side bracket are then secured to opposite ends of the crossbeam assembly.
REFERENCES:
patent: 6010142 (2000-01-01), McCoy et al.
Bewick Mark Lawrence
Hildreth Brian S.
Shelton Larry I.
Visteon Global Technologies Inc.
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