NZ702607A - A method of forming a mounting or fixing device - Google Patents

Abstract

The present invention provides a method of processing an article configured for use as a mounting or fixing device, the article made of a malleable material and including at least one aperture and at least one substantially planar surface having a bulged region in a vicinity of the one or more apertures, wherein material in the bulged region extends above said planar surface, the method including pressing the bulged region using a press of sufficient capacity to deform and thereby distribute material in the bulged region so that substantially no material extends above the substantially planar surface in the vicinity of the one or more apertures. ures, wherein material in the bulged region extends above said planar surface, the method including pressing the bulged region using a press of sufficient capacity to deform and thereby distribute material in the bulged region so that substantially no material extends above the substantially planar surface in the vicinity of the one or more apertures.

Description

A METHOD OF FORMING A MOUNTING OR FIXING DEVICE FIELD OF THE INVENTION This invention relates to a method of forming a mounting or fixing device such as, for example, a ball mount that forms part of a trailer hitch assembly. This invention further relates to products such as ball mounts produced by the method of the invention and an apparatus for producing such mounting or fixing devices.

BACKGROUND TO THE INVENTION Towing lugs or ball mounts form part of trailer hitch assemblies which are used to tow or pull heavy loads. A typical trailer hitch assembly comprises a tow ball connected to a ball mount located on a towing vehicle and a coupler (or socket) located on a tongue of a trailer. The trailer coupler is capable of fitting over the vehicle tow ball in order to couple the trailer to the towing vehicle. A ball mount is essentially an extruded metallic bar comprising an aperture that is fixed to a towing vehicle. The tow ball typically comprises a shaft which is at least partially threaded to which a nut having a female thread is able to be attached. In order to fix the ball to the ball mount, the threaded shaft is inserted through the ball mount aperture and engaged by the nut which when tightened towards the mount bolts the ball in position. The ball is then able to be connected to the trailer by means of a coupler (or socket) located on the trailer that has an inner dimension similar to the outer dimension of the ball and is thus fitted and secured over the ball to thereby connect the trailer to the towing vehicle.

Various methods of forming apertures in metallic workpieces such as ball mounts include drilling, broaching and punching.

Drilling is a conventional process of forming apertures in a variety of objects including metal workpieces such as lugs. In order to drill a hole in a metal workpiece, a drill tool fitted with a driving tool attachment such a drill bit or drill head is pressed against the material to be drilled whilst the attachment (drill bit) is rotated thereby cutting and removing pieces of the material to form the aperture. A conventional drilling tool used in metal working is a drill press (or bench drill) which is a motor-driven, fixed style type of drill that is mounted on a stand or a workbench. In a drill press, the drill bit is moved up or down in a vertical direction and at right angles to the metal workpiece which is fixed or clamped in position. As described above, material from the workpiece is removed by the rotating action of the drill when pressed against and driven through the workpiece surface.

Broaching is an alternative metal working process that is used to form apertures in metal workpieces. The broaching process pushes (or pulls) a cutting tool called a broach through the surface of a metal workpiece to form an aperture. The broaching cutting tool generally comprises a series of cutting teeth extending along the broach length where each cutting tooth circumnavigates the broach shaft. Broaching is a high-volume, metal-removal process that is generally used to form apertures or holes in individual, or custom, parts or articles. The broaching process may be traced back to the mid-17 century in which early applications included cutting keyways in pulleys and gears. Broaching is a popular machining process as it may be used on any type of material including brass, bronze, copper alloys, aluminium, graphite and even harder materials such as mild steels and free machining steels. One of the more common uses of broaching includes the formation of apertures in ball mounts (or towing lugs) and the like. These apertures or holes may then accommodate the shaft of a tow ball for example.

Punching is another metal working process commonly used to form apertures in workpieces that typically uses a punch press to force a tool, called a punch, through the workpiece to create an aperture in the workpiece by a shearing action. The punch under the action of the punch press is forced through the workpiece into a die which accepts the cut away material known as a slug. Depending on the material being punched this slug may be recycled and reused or discarded. Punching is often the cheapest method for creating holes in metal in medium to high production volumes.

As broaching and drilling tend to be time consuming and are more expensive to perform compared to punching, the latter is usually adopted to form apertures in metal workpieces. The punching process, however, whilst lower in cost and higher in efficiency when compared to conventional drilling and broaching processes, tends to distort the metal workpiece in the vicinity of the aperture which as a result leads to regions of increased material thickness (or bulging) around the aperture. Such bulging prevents proper contact between planar abutting surfaces of the tow ball and the ball mount which can lead to regions of instability and wear on both the ball mount and tow ball surfaces ultimately leading to metal fatigue and device failure. In order to prevent or substantially eliminate such instability and wear of the ball mount and tow ball, machining, grinding, linishing and spot facing are processes that are typically adopted in order to ensure any regions of increased thickness or bulging around the formed aperture are removed.

Grinding and linishing processes tend to be imprecise due to manual operator skill and capability, and along with machining are quite time consuming. A need therefore exists for a method of reducing bulging in processed articles that eliminates or at least minimises some or all of these disadvantages.

SUMMARY OF THE INVENTION According to an aspect, the present invention provides a method of processing an article configured for use as a mounting or fixing device, the article made of a malleable material and including at least one aperture and at least one substantially planar surface having a bulged region in a vicinity of the one or more apertures, wherein material in the bulged region extends above said planar surface, the method including pressing the bulged region using a press of sufficient capacity to deform and thereby distribute material in the bulged region so that substantially no material extends above the substantially planar surface in the vicinity of the one or more apertures.

In an embodiment, the bulged region is pressed in a manner that results in a series of depressions. The depressions may be randomly positioned or positioned in a substantially regular pattern. In an embodiment, the depressions are in a substantially regular pattern wherein the ratio of depressed to non-depressed regions in the vicinity of the at least one aperture ranges from about 20:80 to about 60:40. In an embodiment, the depressed to non-depressed regions in the vicinity of the at least one aperture are in a 50:50 ratio.

The depressions may also be of any shape however regular shapes such as squares, circles or rectangles are preferred. In an embodiment, the shape of each depression is substantially rectangular wherein the depressions are arranged in a series of concentric circles and in a staggered pattern. In another embodiment, the depressions are circular and arranged in a series of concentric circles and in a staggered pattern.

It will be appreciated that when an aperture is formed in an extruded bar of malleable material such as a ball mount the bulged region in the planar surface of the bar in the vicinity of the aperture hinders stable abutment between the ball mount and the flange of the tow ball. This can lead to instability and movement between the ball mount and the tow ball which over time, leads to component wear and possible failure.

In order to provide a more stable abutment between the ball mount and tow ball flange, a substantially planar surface is required in the vicinity of the ball mount aperture that is in the region where the tow ball flange contacts and abuts the ball mount. As the method of the present invention results in a substantially planar surface in the vicinity of the aperture, more stable abutment between the ball mount and the flange of the tow ball is achieved.

In another aspect, the present invention provides a mounting device with at least one aperture having a pressed region with a series of depressions in the vicinity of the at least one aperture. The depressions may be randomly positioned or positioned in a substantially regular pattern. In an embodiment, the depressions are in a substantially regular pattern wherein the ratio of depressed to non-depressed regions in the vicinity of the at least one aperture ranges from about 20:80 to about 60:40. In an embodiment, the depressed to non-depressed regions in the vicinity of the at least one aperture are in a 50:50 ratio.

In another aspect, the present invention also provides a ball mount (or tongue) having a pressed region with a series of depressions in the vicinity of the aperture. The depressions may be randomly positioned or positioned in a substantially regular pattern. In an embodiment, the depressions are in a substantially regular pattern wherein the ratio of depressed to non-depressed regions in the vicinity of the at least one aperture ranges from about 20:80 to about 60:40. In an embodiment, the depressed to non-depressed regions in the vicinity of the at least one aperture are in a 50:50 ratio.

In another aspect, the present invention provides an apparatus operable to dispose a series of depressions on a mounting or fixing device made of a malleable material with at least one aperture and at least one substantially planar surface having a bulged region in the vicinity of the one or more apertures, wherein the apparatus presses the bulged region in order to deform and thereby distribute any bulged region so that substantially no material is raised above the substantially planar surface in the vicinity of the one or more apertures.

It should be noted that any one of the aspects mentioned above may include any of the features of any of the other aspects mentioned above and may include any of the features of any of the embodiments described throughout as appropriate.

Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated herein and constitute a part of this specification, illustrate various embodiments of the invention.

Figures 1a to 1c are directed to stepwise cross-sectional representations of a ball mount being subjected to a pressing or coining process in accordance with an embodiment of the present invention.

Figures 2a and 2b are cross sectional representations of a ball mount and tow ball attachment in which figure 2a depicts a ball mount that has not been pressed and in which figure 2b depicts a ball mount that has been subjected to the pressing method in accordance with an embodiment of the present invention.

Figure 3a is a plan view of a section of a ball mount with a pressed (coined) pattern in accordance with an embodiment of the present invention. Figure 3b is a cross-sectional view along section A-A of figure 3a.

Figures 4a and 4b are diagrammatic representations of a section of a pressed (or coined) ball mount in accordance with two alternative embodiments of the invention. Figure 4a is directed to a rectangular pressed pattern and Figure 4b is directed to a circular (or dimpled) pressed pattern on the substantially planar surface of a ball mount.

DETAILED DESCRIPTION OF EMBODIMENT(S) OF THE INVENTION Referring to figure 1, a stepwise depiction of the method in accordance with an embodiment of the present invention is shown. More specifically, figure 1a shows a ball mount 10 in cross sectional view having a first substantially planar side 12 and a second substantially planar side 14 with aperture 16 extending between the first substantially planar side 12 and the second substantially planar side 14.

Figure 1a also shows bulging regions 18 and 20 in which material is raised above substantially planar first and second sides 12 and 14.

Figure 1b shows ball mount 10 in cross sectional view whilst being subjected to a pressing step with press 22 acting on first and second substantially planar sides 12 and 14 in bulging regions 18 and 20 in the vicinity of aperture 16 extending between first and second substantially planar sides 12 and 14. It will be appreciated that whilst press 22 is shown acting on both first and second substantially planar sides 12 and 14 in this embodiment, in other embodiments only one side of the ball mount may be subjected to pressing with press 22.

Figure 1c shows ball mount 10 in cross sectional view after being subjected the method in accordance with an embodiment of the present invention. As can be seen from figure 1c, bulged regions 18 and 20 as shown in figures 1a and 1b, have been removed by the action of press 22 in accordance with an embodiment of the present invention. As a result of the processing step shown in figure 1b, any raised material above the substantially planar first and second sides 12 and 14 and in the vicinity of aperture 16 has been distributed and hence removed, thereby allowing more stable and secure abutment of a tow ball (as is shown and described in detail in respect of figure 2b). It will be appreciated in order to distribute and thereby remove any regions of bulging, the article to be processed in accordance with the method of the invention must be malleable. Typical examples of materials able to be processed in accordance with the method of the present invention include, but are not limited to, any mild steel from 250 to 350 MPa grades, aluminium, copper and any other malleable material.

The pressing step may be performed using any press machine that is known in the art and that is of sufficient capacity to perform the press and deform the malleable material of the mounting or fixing device. Pressing machines are characterised by their drive type and include, but are not limited to, flywheel drive presses, mechanical presses, hydraulic presses and turret presses.

The pressing action in a typical pressing machine is accomplished by a vertical moving ram that forces the press tool towards the article or workpiece thereby deforming the workpiece material. The press ram may be activated mechanically, or hydraulically. Whilst mechanical presses can operate faster than hydraulic punch presses, higher punching pressures are able to be achieved with hydraulic punch presses. Materials able to be pressed in accordance with the method of the invention are those that are able to be deformed and typically include, but are not limited to, any mild steel from 250 to 350 MPa grades, aluminium, copper and any other type of metal that is malleable and desired to be processed by a pressing or coining technique.

In order to press and thereby distribute a bulged region of material, a die set is used that comprises an upper part and a lower part. It will be appreciated that one or both sides of an article may be pressed in accordance with the method of the invention.

The upper part of the die set holds and supports a series of punch tools that are shaped and positioned in a corresponding pattern that is desired to be pressed into the malleable material. The lower part of the die set is an anvil on which the article or workpiece to be pressed is supported during the pressing operation. When only one side of the article is desired to be pressed, the anvil on which the workpiece rests has a substantially planar of flat surface. When both sides of the article are to be pressed, however, the anvil includes a series of projections, typically introduced by moulding the anvil, that correspond with the desired pattern. During a press operation, the lower part of the die set or anvil is fixed to a bottom plate of the press, whilst the upper part of the die set is allowed to slide up and down via axial bearing sets positioned in the corners of the die set. The entire die set is maintained as a complete unit that is mounted on the press machine.

The punch tools used to deform the workpiece material may be made of any material capable of withstanding the forces required to deform a workpiece material of a specific material grade and to a specific depth. High strength tool steels are used in punch components and are usually hardened by heat treating or cold working.

Standard steels used in the manufacture of punch tools typically used include, but are not limited to, high performance tool steels with 5% chrome, triple tempered high speed steel and triple tempered high vanadium, high carbon particle metal.

In an embodiment, the pressing operation is performed using a 200 tonne press with an operating speed of 1 second over a 200mm stroke (to press and retract the press/ram to the original position). The die set used to form the desired pattern comprises a cylindrical upper part approximately 80 mm in diameter that is fixed to the ram of the 200 tonne press. The cylindrical upper part serves to hold and support a series of punch tools each shaped and relatively positioned to achieve the desired press pattern on a top side of a workpiece. The lower part of the die set on which the workpiece rests during the pressing operation comprises a cylindrical anvil also of an approximate diameter of 80 mm comprising a series of moulded projections also shaped and positioned to form the desired pattern on the underside of the workpiece.

Figures 4a and 4b discussed further below illustrate desired patterns according to two different embodiments of the invention.

Referring now to figure 2 and more specifically figure 2a, tow ball 24 comprising collar 26 and shaft 28 is inserted through aperture 16 (as shown in figure 1) and fixed into position with washer 30 and nut 32. Due to bulging regions 18 and 20, collar 26 and washer 30 are unable to achieve stable abutment with ball mount 10 resulting in movement of tow ball 24 and shaft 28 within aperture 16 (see figure 1) of ball mount 10 ultimately resulting in component wear and possible failure. In figure 2b, however, as bulging regions 18 and 20 as shown in figure 2a have been removed by pressing in accordance with an embodiment of the invention, more secure and stable contact is able to be achieved between collar 26 and washer 30 with ball mount 10 thereby resulting in minimal or substantially no movement of tow ball 24 within ball mount 10.

Figure 3a shows a plan view of a ball mount 100 pressed in accordance with an embodiment of the invention. In this embodiment, a pressed pattern formed of discrete rectangular depressions 110 arranged in three concentric circles in a staggered configuration is shown. In this embodiment, the ratio of depressions 110 to non- depressed material 112 within the vicinity of aperture 115 is about 50:50. It will however be appreciated that other ratios of depressed to non-depressed material is possible, such as for example, 20:80 to 60:40. Figure 3b shows a cross-sectional view along section A-A of ball mount 100 shown in figure 3a. As can be seen from this cross- sectional view, the region in the vicinity of aperture 115 is substantially planar in which any bulged regions above the planar surface of either the first side 120 or second side 122 have been distributed and thereby removed due to the series of depressions 110 in a ratio of 50:50 (depressed : non-depressed material). As previously described in relation to figure 2b, the substantially planar configuration arising through the formation of depressions 110 results in more stable contact between the a tow ball collar and flange (not shown) and ball mount 100.

Referring now to figure 4, two different embodiments of articles processed in accordance with the methods of the present invention are shown. Figure 4a is directed to a perspective view of ball mount 100 previously described in relation to figure 3a with rectangular depressions 110 arranged in three concentric circles in a staggered pattern around an in the vicinity of aperture 115. Figure 4b shows a perspective view of an alternative embodiment of a pressed ball mount 200 processed in accordance with the methods of the present invention. In this embodiment, dimpled (or circular) depressions 210 also arranged in three concentric circles and in a staggered pattern are used to distribute and remove any bulging in the vicinity of aperture 215. This therefore results in ball mount 200 having a substantially planar surface so that close and stable abutment between a tow ball (not shown) and ball mount 200 is able to be achieved.

It will be appreciated that whilst the above embodiments are described in relation to the processing of ball mounts for fixing tow balls as part of trailer hitch assemblies, the method disclosed herein is suitable for use in the processing of any device in which bulging occurs through aperture formation and wherein stable and close abutment between two or more components is required. Examples of devices include, but are not limited to, holding cleats and parallel mounting or pivoting brackets.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims (17)

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A method of processing an article configured for use as a mounting or fixing device, the article made of a malleable material and including at least one aperture and at least one substantially planar surface having a bulged region in a vicinity of the one or more apertures, wherein material in the bulged region extends above said planar surface, the method including pressing the bulged region in a manner that results in a series of depressions using a press of sufficient capacity to deform and thereby distribute material in the bulged region so that substantially no material extends above the substantially planar surface in the vicinity of the one or more apertures.

2. A method according to claim 1 wherein the depressions are randomly positioned.

3. A method according to claim 1 where in the depressions are positioned in a substantially regular pattern.

4. A method according to claim 3 wherein the ratio of depressed to non-depressed regions in the vicinity of the at least one aperture ranges from about 20:80 to about 60:40.

5. A method according to claim 3 wherein the depressed to non-depressed regions in the vicinity of the at least one aperture are in a 50:50 ratio.

6. A method according to any one of the preceding claims wherein the depressions are selected from any one of a square, circle or rectangle.

7. A method according any one of the preceding claims wherein each depression is substantially rectangular and wherein the depressions are arranged in a series of concentric circles and in a staggered pattern.

8. A method according to any one of claims 1 to 7 wherein the depressions are circular and arranged in a series of concentric circles and in a staggered pattern.

9. A mounting device with at least one aperture having a pressed region with a series of depressions in the vicinity of the at least one aperture.

10. A mounting device according to claim 9 wherein the depressions are randomly positioned.

11. A mounting device according to claim 9 wherein the depressions are positioned in a substantially regular pattern.

12. A mounting device according to claim 11 wherein the depressions are positioned in a substantially regular pattern wherein the ratio of depressed to non-depressed regions in the vicinity of the at least one aperture ranges from about 20:80 to about 60:40.

13. A mounting device according to claim 11 wherein the depressed to non- depressed regions in the vicinity of the at least one aperture are in a 50:50 ratio.

14. A mounting device according any one of claims 9 to 13 wherein each depression is substantially rectangular and wherein the depressions are arranged in a series of concentric circles and in a staggered pattern.

15. A mounting device according to any one of claims 9 to 13 wherein the depressions are circular and arranged in a series of concentric circles and in a staggered pattern.

16. A mounting device according to any one of claims 9 to 15 wherein the mounting device is a ball mount.

17. An apparatus operable to dispose a series of depressions on a mounting or fixing device made of a malleable material with at least one aperture and at least one substantially planar surface having a bulged region in the vicinity of the one or more apertures, wherein the apparatus presses the bulged region in order to deform and thereby distribute any bulged region so that substantially no material is raised above the substantially planar surface in the vicinity of the one or more apertures.