Cold-forged hitch receiver and method of making the same
A method for reinforcing an end of a metal tube, and a resultant receiver tube for a motor vehicle trailer hitch assembly, wherein the method and resultant tube does not require creating a fold in the metal tube to create a reinforcing lip. The integral lip is formed by the plastic deforming a length of the first end of the tube extending beyond the die wherein the deformable length is less than or equal to two times the wall thickness of the tube.
The present invention relates in general to reinforcing the end of a metal tube, and in particular, to the novel manufacture of a component for a motor vehicle trailer hitch assembly and resultant receiver tube component having an integral, reinforced lip created through plastic deformation of tube stock.
BACKGROUND So as to provide towing capability, vehicles are often fitted with hitch assemblies capable of connection with a trailer for hauling boats, travel trailers, utility trailers, etc. Typical hitch assemblies, as shown in
As illustrated in
There are two manners of construction known in the art for manufacturing a receiver tube having a reinforcing ring; a) welding a separate reinforcing ring on one end of the tube stock, or b) folding an end portion of the tube stock upon itself to create a resultant reinforcing ring. There are several disadvantages to each manner of construction.
As explained in greater detail below, welding a reinforcing ring over one end of the receiver tube end has numerous disadvantages. First, the weld beads joining the receiver tube and the reinforcing ring are a prime area for the generation of corrosion, thus possibly leading to a reduction in weld strength and creating an undesirable appearance when a trailer is not connected thereto. Further, because the reinforcing ring is fitted to the receiver tube with separation gaps therebetween, water, dirt, and contaminants can be trapped therein leading to further corrosion problems effecting the strength and appearance of the receiving tube. Also significant is the fact that the multi-piece construction of the separate retainer ring construction requires two components to be separately manufactured, transported, handled, and welded in order to manufacture the receiver tube.
Likewise, there are several disadvantages with creating a receiver tube having a reinforcing ring by folding an end portion of the tube stock upon itself to create the resultant reinforcing ring. First, there is generally a need to heat the tube end to an elevated temperature to promote folding of the tube stock onto itself. Also, by folding the tube stock a gap is created that is capable of retaining water, dirt, and contaminants within the fold. Such contaminants collecting in the fold can cause rusting and corrosion that, as indicated above, can affect the strength and appearance of the receiver tube. Further, because there is a tight fit between the receiver tube and the hitch bar, such contaminant collection in the fold could prevent the proper insertion of the hitch bar.
The present invention addresses each of these disadvantages and more to provide an improved manufacturing method and resultant receiver tube.
The present invention will be more fully described in the following written description with reference to the accompanying drawings.
SUMMARY OF THE INVENTIONThe present invention provides an improved method for integrally reinforcing an end of a metal tube, and a resultant receiver tube for a motor vehicle trailer hitch assembly, wherein the method and resultant tube does not require creating a fold in the metal tube to create an integral reinforcing lip. The integral lip is formed by plastically deforming a length of the first end of the tube extending beyond the die. Preferably, the deformable length of the tube is less than or equal to two times the wall thickness of the tube.
The resulting trailer hitch receiver tube has a much-improved appearance having no weld beads or rough metal edges visible. The integral construction also eliminates pockets for contaminant collection caused by folding and welding and provides exceptional reinforcement for the tube seam weld. The absence of folds or welds provides a smooth surface for the hitch bar may slidably enter into the receiver tube. Further, the interior of the receiver tube can be radiused to allow easy entrance of the hitch bar and locates the load point away from the edge of the reinforcing ring, increasing its strength. Receiver tubes produced according to this invention further reduce manpower and assembly requirements, thus providing efficient production capabilities.
A further advantage of the present invention is that the cycle time for producing the tubes is reduced by removing the need for heating and, subsequently, cooling the tubes and for removing the deposits of any carburization that may take place. Further, the metal forming the tube is not weakened due to any molecular effects resulting from the heating step used in the folding method. Thus, the present invention provides a process for cold forming the ends of tubes so as to provide a reinforced portion. By omitting the need for heating the tube prior to the forming step, the various problems discussed previously are avoided. However, it is clear that the present invention is still applicable and productive even if the tube is heated.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
FIGS. 5 to 8 are cross-sectional views of the present method for manufacturing receiver tubes wherein a first end portion of the tube is not folded upon itself, but plastically deformed to create the integral reinforcing ring.
A trailer hitch assembly according to the prior art, generally designated by reference number 10, is shown in
With continued reference to
As indicated above, because conventional tube stock includes a weld seam 32 that can affect the strength of the end portion of the tube, reinforcement is needed to strengthen the tube end. Such reinforcement is provided through the use of a reinforcing ring. As described above, there are two modes of construction known in the art for manufacturing a receiver tube having a reinforcing ring; a) welding a separate reinforcing ring on one end of the tube stock, or b) folding an end portion of the tube stock upon itself to create a resultant reinforcing ring.
The second manner of construction for a conventional receiver tube 12 having a reinforcing ring, as illustrated with reference to
As further shown in
As illustrated in
Again, there are several disadvantages with constructing a receiver tube with reinforcing ring by means of folding an end portion of the tube stock upon itself to create the resultant reinforcing ring. First, there is generally a need to heat the tube end to an elevated temperature to promote folding of the tube stock onto itself. Further, given the gap created by folding, there is an increased chance that water, dirt, and contaminants can be lodged within the fold to promote corrosion, which, as indicated above, can affect the strength and appearance of the receiver tube.
Now with reference to
The method for cold forging metal tubes of the present invention, preferably receiver tubes for trailer hitch assemblies, is illustrated in
As shown in
As illustrated in
During the construction method, stop 82 prevents the tube from moving relative to die 68. In addition to forming the reinforcing lip 66, mandrel 74 also partially extrudes the inside corners of the tube 62. The portion of the mandrel 74 that fits inside the tube 62 has small radius corners that deform the inside of the tube to a sharp corner further providing an tight-fitting slidable entry for the hitch bar. After the cold forging process described above, apertures are punched in the receiver tube so as to receive the receiver hitch-locking pin. Afterwards, the receiving tube is shot blasted to remove any burrs and residual coating.
The invention has been described with reference to the preferred embodiment. Obviously, modifications and alternations will occur to others upon a reading and understanding of this specification. The claims as follows are intended to include all modifications and alterations insofar as they come within the scope of the claim or the equivalent thereof.
Claims
1. A method for reinforcing an end of a metal tube, said method comprising the steps of:
- a) providing an elongated tube having a substantially uniform wall thickness, said tube having inner and outer surfaces and first and second ends;
- b) providing a die defining a cavity conforming to the outer surface of said tube;
- c) placing said tube in said die cavity such that a length of said first end extends beyond said die cavity;
- d) preventing movement of the tube longitudinally with respect to said die cavity;
- e) providing a mandrel having a first portion adapted to fit within said tube through said first end and a second portion extending radially from said mandrel first portion having a tube deforming recess surface adapted to impinge upon said first end;
- f) inserting said mandrel first portion into said first end until said tube deforming surface contacts said first end; and
- g) advancing said mandrel under pressure thereby causing cold deformation of said first end, without creating a fold therein, and plastically deforming said first end within said mandrel recess thereby creating an integral, reinforced lip at said first end.
2. The method of claim 1, wherein during step c, said length of said first end extending beyond said die cavity is less than or equal to two times the wall thickness of said tube.
3. The method of claim 2 wherein said mandrel first portion conforms to the inner surface of said tube.
4. The method of claim 2 wherein said tube has a circular cross section.
5. The method of claim 2 wherein said tube has a rectangular cross section.
6. The method of claim 2 wherein said tube comprises a hitch bar receiver tube.
7. A method for forming an elongated receiver tube for a motor vehicle trailer hitch assembly of the type wherein said receiver tube has a hollow interior passage that receives a hitch bar, said method comprising the steps of:
- a) providing an elongated tube having a substantially uniform wall thickness, said tube having inner and outer surfaces and first and second ends;
- b) providing a die defining a cavity conforming to the outer surface of said tube;
- c) placing said tube in said die cavity such that a length of said first end extends beyond said die cavity, said length being less than or equal to two times the wall thickness of said tube;
- d) preventing movement of the tube longitudinally with respect to said die cavity;
- e) providing a mandrel having a first portion adapted to fit within said tube through said first end and a second portion extending radially from said mandrel first portion having a tube deforming recess surface adapted to impinge upon said first end;
- f) inserting said mandrel first portion into said first end until said tube deforming surface contacts said first end; and
- g) advancing said mandrel under pressure thereby causing cold deformation of said first end, without creating a fold therein, and plastically deforming said first end within said mandrel recess thereby creating an integral, reinforced lip at said first end.
8. The method of claim 7 wherein said mandrel first portion conforms to the inner surface of said tube.
9. The method of claim 7 wherein said tube has a circular cross section.
10. The method of claim 7 wherein said tube has a rectangular cross section.
11. An elongated receiver tube for a motor vehicle trailer hitch assembly, said receiver tube comprising:
- a) an elongated hollow tube having first and second ends and a substantially uniform wall thickness; and
- b) a lip extending radially-outwardly from said first end, said lip integrally formed with said hollow tube without folding said first end.
12. The receiver tube of claim 11, wherein said lip is integrally formed with said tube through the plastic deformation of a length of said first end wherein said deformable length is less than or equal to two times the wall thickness of said tube.
13. The receiver tube of claim 11, wherein said elongated hollow tube has a circular cross-section.
14. The receiver tube of claim 11, wherein said elongated hollow tube has a rectangular cross-section.
Type: Application
Filed: Jul 10, 2003
Publication Date: Jan 13, 2005
Inventors: Robert Greczanik (Canton, OH), Murali Bhupatiraju (Clinton TWP, MI), Joel Edwards (North Canton, OH)
Application Number: 10/616,825