US20080090684A1

US20080090684A1 - Dart

Info

Publication number: US20080090684A1
Application number: US11/546,800
Authority: US
Inventors: Kelly M. Martinez
Original assignee: Great Lakes Dart Manufacturing Inc
Current assignee: Great Lakes Dart Manufacturing Inc
Priority date: 2006-10-12
Filing date: 2006-10-12
Publication date: 2008-04-17

Abstract

A dart barrel comprising a body, a surface on the body; and a coating deposited on the surface by physical vapor deposition, said coating comprising a layer of titanium, aluminum and nitride, whereby the dart barrel has improved hardness and wear resistance. The body is metal and the coating on the surface of the body has a thickness of between about 1.5 μm and about 5.0 μm. In one embodiment, the coating is a mono-layer coating. In another embodiment, the coating is a multi-layer coating.

Description

FIELD OF THE INVENTION

The invention relates generally to darts and specifically to an improved dart coating wherein the dart has increased durability and wear resistance.

BACKGROUND OF THE INVENTION

The game of darts has been played for centuries. Today, the game of darts is seen everywhere from pubs to organized competitive leagues. Since the origins of dart games in medieval times, the dart itself has undergone many changes. Darts were first crudely made from shortened arrows which were thrown at tree trunks or wine barrels. Today's darts consist generally of a dart barrel, a shaft, a tip and an end having flights (also known as fletchings). While these four basic features of darts remain relatively constant, numerous other factors determine the overall quality of a dart.
Several factors are critical in making a good dart. For instance, the composition of the dart barrel, weight of the barrel, overall balance, and the durability of the barrel are important features of a dart. A primary object of this invention focuses on increasing the durability of a dart. Many darts known in the art suffer from disadvantages related to durability. Dart barrels are typically coated; the nature of the coating determines whether the surface of the dart body will be prone to scratching, flaking and other signs of coating fatigue. Other darts have coatings that are known to decrease or mute the surface characteristics of the uncoated dart body. Darts known in the art have coatings that are susceptible to these disadvantages and, as such, have a shorter product life.
There is an ongoing search for a new and superior dart that has substantially improved life and increased wear resistance. It would be an improvement in the art to provide a new dart having a coating which gives the dart improved hardness and wear resistance.

OBJECTS OF THE INVENTION

It is an object of this invention, to provide a dart barrel having a coating with improved hardness and wear resistance.
Another object of the invention is to provide a dart having improved hardness and wear resistance.
A further object of the invention is to provide a dart having a surface with improved grip.
Another object of the invention is to provide a dart having a surface with accentuated surface characteristics.
Still another object of the invention is to provide a dart having an improved appearance.
It is yet another object of the invention to provide a dart having increased product life.

SUMMARY OF THE INVENTION

According to the invention, a dart barrel is disclosed having improved hardness and wear resistance. This dart barrel is characterized primarily by the elements:
a) a body;
b) a surface on the body; and
c) a coating deposited on the surface by physical vapor deposition, said coating comprising a layer of titanium, aluminum and nitride. The dart body is metal. Specifically, the dart body is one or more of tungsten, tungsten-copper, tungsten-nickel, tungsten-copper-nickel, tungsten-iron-nickel, brass, stainless steel and steel. In certain preferred embodiments, the coating is a mono-layer coating of Aluminum-Titanium-Nitride. In other highly preferred embodiments, the coating is a multi-layer coating of Titanium-Nitride and Titanium-Aluminum-Nitride.
The present invention also includes a dart having improved hardness and wear resistance.
Further details, advantages and features of this invention are given by the following description with reference to the enclosed drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a photograph of the inventive dart.

FIG. 2 shows a photograph including the inventive dart side-by-side to a competitor dart.

FIG. 3 shows a photograph of the dart barrels of the inventive dart and the competitor darts of FIG. 2.

FIG. 4 shows a dart barrel having a coating with improved hardness and wear resistance.

FIG. 5 is an overall view of a dart containing a dart body having a coating with improved hardness and wear resistance.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIG. 4, the invention comprises a dart barrel. The dart barrel 10, most broadly, comprises a body 20, a surface on the body 22 and a coating deposited on the surface by physical vapor deposition. The coating comprises a layer of titanium, aluminum and nitride whereby the dart barrel has improved hardness and wear resistance.
The body comprises metal. In preferred embodiments, the body comprises one or more of tungsten, tungsten-copper, tungsten-nickel, tungsten-copper-nickel, tungsten-iron-nickel, brass, stainless steel and steel.
In most highly preferred embodiments, the coating has a thickness of between about 1.5 μm and about 5.0 μm.
In one embodiment of the invention, the coating is a mono-layer coating. The mono-layer coating comprises a aluminum-titanium-nitride deposited simultaneously by physical vapor deposition. The mono-layer coating is commercially available through Guhring Inc., of Brookfield, Wis. under the product name Super-A. The hardness of the mono-layer coating is in excess of 3300 vickers. The mono-layer coating comprises about 33% titanium and about 67% aluminum. The mono-layer coating has a grey/black pigment.
Importantly, the inventive dart has improved hardness and wear resistance not only because of the titanium, aluminum, and nitride coatings but also because this improved coating is deposited through a process of physical vapor deposition (PVD). Generally, physical vapor deposition (PVD) is a group of vacuum coating techniques used to deposit thin films of various materials onto various surfaces by physical (mechanical) or thermodynamic means. More specifically, PVD is a vaporization coating process in which an atom by atom transfer of material from the solid phase to the vapor phase and back to the solid phase, gradually builds a film on the surface to be coated. The material to be deposited is called the “target.” The target is placed in an energetic, entropic environment, so that particles of material escape its surface. Facing the target is a cooler surface (the “substrate”) which draws energy from these particles as they arrive, allowing them to form a solid layer. The whole system is kept in a vacuum deposition chamber, to allow the particles to move as freely as possible. Because particles tend to follow a straight path, films deposited by PVD are commonly directional, rather than conformal.
The specific process used for application of the coating of the invention is a type of PVD using cathodic arc plasma (CAP) technology to provide a high deposition and ionization rate as well as a low-temperature of operation. Though CAP is very much a type of PVD technology it is important to note that CAP is energetic condensation from plasma ions, whereas standard PVD processes are known to be condensation of atoms from the vapor phase as described above. CAP are especially useful and impart particular benefits to dart coatings because CAPs are fully ionized with very energetic ions, creating adhesion and the formation of dense films.
In the CAP deposition process, part of the cathode is evaporated by the action of vacuum arcs. The basic components consist of a vacuum chamber, cathode assemblies, arc power supply systems, bias power supply, control panels, water-cooling system, compressed-air supply system and a vacuum-pumping system. The steps of the CAP deposition process are generally as follows:
First, the dart is subjected to a cleaning stage in which it undergoes vapor degreasing. The dart is cleaned with an aqueous soap solution and then rinsed in a deionzied bath. The dart is then placed into a tree-style rack which is designed to rotate during the coating process to ensure complete coating of the dart.
Next, the darts are placed into the PVD chamber. Mechanical pumps remove the oxygen from the environment so that the rest of the CAP process is carried out in a vacuum.
The darts are then heated. The optimal temperature for heating varies based upon the diameter of the dart and the size of the load to be coated. Temperatures used at Guhring, Inc. for the coatings process are about 450°, 570° or 480° C. (The known temperature for PVD is 500° C. for about 50 minutes.)
Next, begins the etching phase. This phase prepares the surface of the dart for receiving the coating. Argon gas is introduced into the chamber and applied to the dart surface by supplying a voltage to the dart. The etching phase takes a microscopic layer off of the surface of the metal dart. This marks the last preparation step to make the surface as clean as possible.
After the preparation steps are completed, the coating phase begins. There are cathodes in the machine that hold the targets, i.e. the coating layers to be deposited. The cathode is used to strike an arc on the face of the target which evaporates or pulls off the target into a vapor. Nitrogen is added as an electrically charged reactive gas to bind the target. The voltage plus the vapor attracts the atoms from the target. Finally, before removing the dart from the chamber, it is cooked under vacuum at 200° C.
In another preferred embodiment, the coating is a multi-layer coating. The multi-layer coating comprises six alternating layers. The first layer is titanium nitride or titanium aluminum. The multi-layer coating comprises a second layer of titanium-aluminum-nitride. This multi-layer coating is commercially available through Guhring Inc., of Brookfield, Wis. under the product name Fire-X. The multi-layer coating has a hardness of between about 3000 and about 3300 vickers. It comprises 40% titanium and 60% aluminum. The multi-layer coating has a gold/bronze pigment.
As shown in FIG. 5, the invention includes a dart 24 having improved hardness and wear resistance. Dart 24 and includes a point 26, a tail end 28, an elongated body 30 between point 26 and tail end 28 and a coating deposited on the body by physical vapor deposition. The coating is the same as that described above for both the mono-layer and multi-layer coating.
The dart shown in FIG. 1 shows the surface characteristics of the inventive dart. The photograph demonstrates the accentuated surface features. FIG. 4 is a competitor dart having a coating that mutes the surfaces features of the dart, as can be seen in the photograph.
As seen in FIGS. 1 through 3, the inventive dart barrel and, more generally, dart have a coating deposited on the surface of the dart 32. The coating provides improved hardness and wear resistance to the dart. Additionally, the inventive dart having the coating has an attractive appearance. FIGS. 2 and 3 particularly show the defined surface characteristics of the dart body are accentuated by deposition of the coating to the dart. A competitor dart 34 having a coating on the surface of the dart body is shown for comparison in FIGS. 2 and 3. Unlike darts known in the art, the inventive dart and dart barrel having the coating do not mute the surface characteristics of the body of the dart. This muting effect can be seen in competitor dart 34. Moreover, the improved dart having the coating applied by physical vapor deposition provides a dart with improved grip, even on smooth surfaces. Whether the surface of the dart body is smooth, grooved, or rough, for example, the improved dart having the coating retains the distinctive surface features of the dart.

Claims

1. A dart barrel comprising:

a body;

a surface on the body; and

a coating deposited on the surface by physical vapor deposition, said coating comprising a layer of titanium, aluminum and nitride,

whereby the dart barrel has improved hardness and wear-resistance.

2. The dart barrel of claim 1 wherein the body comprises metal.

3. The dart barrel of claim 2 wherein the body comprises one or more of tungsten, tungsten-copper, tungsten-nickel, tungsten-copper-nickel, tungsten-iron-nickel, brass, stainless steel and steel.

4. The dart barrel of claim 3 wherein the coating comprises a thickness of between about 1.5 μm and about 5.0 μm.

5. The dart barrel of claim 4 wherein the coating comprises a mono-layer coating.

6. The dart barrel of claim 5 wherein the mono-layer coating comprises Aluminum-Titanium-Nitride.

7. The dart barrel of claim 6 wherein the mono-layer coating has a hardness in excess of 3300 vickers.

8. The dart barrel of claim 7 wherein the mono-layer coating comprises about 33% titanium and about 67% aluminum.

9. The dart barrel of claim 4 wherein the coating comprises a multi-layer coating.

10. The dart barrel of claim 9 wherein the multi-layer coating comprises a first layer.

11. The dart barrel of claim 10 wherein said first layer comprises Titanium-Nitride.

12. The dart barrel of claim 10 wherein said first layer comprises Titanium-Aluminum.

13. The dart barrel of claim 10 wherein the multi-layer coating further comprises a second layer.

14. The dart barrel of claim 13 wherein the second layer comprises Titanium-Aluminum-Nitride.

15. The dart barrel of claim 14 wherein the multi-layer coating has a hardness of between about 3000 and about 3300 vickers.

16. The dart barrel of claim 15 wherein the multi-layer coating comprises about 40% Titanium and about 60% Aluminum.

17. A dart having improved hardness and wear resistance comprising:

a point;

a tail end;

an elongated body between the point and tail end;

a coating deposited on the body by physical vapor deposition, said coating comprising a layer of titanium, aluminum and nitride,

whereby the dart has improved hardness and wear-resistance.

18. The dart of claim 17 wherein the dart body comprises metal.

19. The dart of claim 18 wherein the dart body comprises one or more of tungsten, tungsten-copper, tungsten-nickel, tungsten-copper-nickel, tungsten-iron-nickel, brass, stainless steel and steel.

20. The dart barrel of claim 19 wherein the coating comprises a thickness of between about 1.5 μm and about 5.0 μm.

21. The dart of claim 20 wherein the coating comprises a mono-layer coating.

22. The dart of claim 21 wherein the mono-layer coating comprises Aluminum-Titanium-Nitride.

23. The dart of claim 22 wherein the mono-layer coating has a hardness in excess of about 3300 vickers.

24. The dart of claim 23 wherein the mono-layer coating comprises about 33% titanium and about 67% aluminum.

25. The dart of claim 20 wherein the coating comprises a multi-layer coating.

26. The dart of claim 25 wherein the multi-layer coating comprises a first layer.

27. The dart of claim 26 wherein said first layer comprises Titanium-Nitride.

28. The dart of claim 26 wherein said first layer comprises Titanium-Aluminum.

29. The dart of claim 26 wherein the multi-layer coating further comprises a second layer.

30. The dart of claim 29 wherein the second layer comprises Titanium-Aluminum-Nitride.

31. The dart of claim 30 wherein the multi-layer coating has a hardness of between about 3000 to about 3300 vickers.

32. The dart barrel of claim 31 wherein the multi-layer coating comprises about 40% Titanium and about 60% Aluminum.