GB2068755A - Dart shafts - Google Patents

Abstract

A dart shaft has at one end a portion (12) provided with a cruciform slot (13) forming a dart flight holder and at the other end a portion (14) having means, usually a screw thread (15), for connecting it to one end of a dart barrel, the two portions (12 and 14) being interconnected by a central shaft portion (11) of smaller diameter, wherein at least one of the portions (11, 12 or 14) is composed of magnesium or an alloy thereof containing at least 50% magnesium. If the end portions (12 and 14) are formed integrally with the central shaft portion (11), the shaft may be formed by a cold heading or cold forming process, such as rolling, and composed of the same or another metal or alloy. <IMAGE>

Description

SPECIFICATION Dart shafts This invention relates to dart shafts which form part of the construction of a dart used for playing the game of darts, and is concerned, more particularly, with dart shafts of the type having at one end a portion provided with a cruciform slot forming a dart flight holder and at the other end a portion having means, usually a screw thread, for connecting it to one end of a barrel having at its other end a dart point, the two end portions being interconnected by a central shaft portion of smaller diameter.

It is an object of the present invention to provide an improved dart shaft.

The present invention consists in a dart shaft of bthe type indicated, wherein at least one of the portions is composed of magnesium or an alloy thereof containing at least 50% magnesium.

- The invention further consists in a dart shaft having a smaller diameter central shaft portion formed integrally with enlarged portions at each end, one portion serving as a flight holder and the other portion having means for connecting the shaft to a dart barrel, wherein the shaft is composed of metal and formed by a cold heading or cold forming process such as rolling.

In carrying the invention into effect according to one convenient mode by way of example, the accompanying drawing shows a dart shaft having a smaller diameter central portion 11, say between .07 and .09 inches in diameter, formed integrally with enlarged portions at each end, say between .2 and .3 inches in diameter, one portion 12 having a cruciform slot 13 to form a flight holder and the other portion 14 having a screw thread 15 by means of which the shaft may be connected to a dart barrel (not shown).

The shaft is composed of magnesium or an alloy containing at least 50% magnesium. The shaft is manufactured from a length of stock material by means of a cold heading process in which axial pressure is applied to wire to cause its ends to be increased to the desired diameter and shape, the enlarged end portion 12 then being slitto provide the cruciform slot 13. Using such a process the grain structure more closely follows the profile of the shaft resulting in increased strength in the finished shafts.

Also the forming process causes work-hardening of the metal and this effect is greatest at the ends where most needed. Alternatively, the shaft may be manufactured by rolling a thicker wire to reduce its diameter to give the final desired shape.

The enlarged end portion 14 is provided with a screw thread 15, such as a 2BA or 14ft BSF thread. It is customary to provide an undercut adjacent to the shoulder at the base of the thread washer which provides a retaining effect when the shaft is screwed into the barrel. However, this creates a stress con centration in the shoulder region, which can prom ote local fracture, and it is preferred to dispense with the undercut.The thread is preferably formed by rol ling between hardened thread rolls or fiat dies instead of being cut, so that a stronger and smoother thread is produced in which the grain structure fol lows the profile, and the threaded portion is slit lon- gitudinallythrough its axis, as at 16, the two parts thus created being forced slightly apart by means of a wedge so asto exert radial pressure when screwed into the barrel thereby providing a self-jamming or locking effect to give a secure fixing.

Itis preferredthatthe shaft should be work- hardened or further work-hardened, for example by ball-burnishing.

Various modifications may be made within the scope of the present invention.

For example, one or both of the enlarged end portions may be connected to the central shaft portion instead of being formed integrally with it, in which case it may be of advantage to form only one or two ofthethree portions from magnesium or magnesium alloy, the other portion or portions being composed, for example, ofanother metal or plastics.

Alternatively, where the three portions are formed integrally by a cold heading or cold forming process, a metal other than magnesium or magnesium alloy may be used, such as aluminium or an aluminium alloy.

1. A dart shaft of the type indicated, wherein at least one of the portions is composed of magnesium or an alloy thereof containing at least 50% magnesium.

2. A dart shaft as claimed in claim 1, wherein the end portions are formed integrally with the central shaft portion.

3. A dart shaft having a smaller diameter central shaft portion formed integrally with enlarged portions at each end, one portion serving as a flight holder and the other having means for connecting the shaft to a dart barrel, wherein the shaft is composed of metal and formed by a cold heading or cold forming process.

4. A dart shaft as claimed in claim 3, wherein the said metal is magnesium organ alloy thereof containing at least 50% magnesium.

5. A dart shaft as claimed in any one of claims 1 to 4, wherein the shaft is work-hardened or further work-hardened.

6. A dart shaft as claimed in any one of claims 1 to 5, wherein the means for connecting the shaft to a shaft barrel includesathreaded portion having longitudinal slits.

7. A dart shaft substantially as described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Dart shafts This invention relates to dart shafts which form part of the construction of a dart used for playing the game of darts, and is concerned, more particularly, with dart shafts of the type having at one end a portion provided with a cruciform slot forming a dart flight holder and at the other end a portion having means, usually a screw thread, for connecting it to one end of a barrel having at its other end a dart point, the two end portions being interconnected by a central shaft portion of smaller diameter. It is an object of the present invention to provide an improved dart shaft. The present invention consists in a dart shaft of bthe type indicated, wherein at least one of the portions is composed of magnesium or an alloy thereof containing at least 50% magnesium. - The invention further consists in a dart shaft having a smaller diameter central shaft portion formed integrally with enlarged portions at each end, one portion serving as a flight holder and the other portion having means for connecting the shaft to a dart barrel, wherein the shaft is composed of metal and formed by a cold heading or cold forming process such as rolling. In carrying the invention into effect according to one convenient mode by way of example, the accompanying drawing shows a dart shaft having a smaller diameter central portion 11, say between .07 and .09 inches in diameter, formed integrally with enlarged portions at each end, say between .2 and .3 inches in diameter, one portion 12 having a cruciform slot 13 to form a flight holder and the other portion 14 having a screw thread 15 by means of which the shaft may be connected to a dart barrel (not shown). The shaft is composed of magnesium or an alloy containing at least 50% magnesium. The shaft is manufactured from a length of stock material by means of a cold heading process in which axial pressure is applied to wire to cause its ends to be increased to the desired diameter and shape, the enlarged end portion 12 then being slitto provide the cruciform slot 13. Using such a process the grain structure more closely follows the profile of the shaft resulting in increased strength in the finished shafts. Also the forming process causes work-hardening of the metal and this effect is greatest at the ends where most needed. Alternatively, the shaft may be manufactured by rolling a thicker wire to reduce its diameter to give the final desired shape. The enlarged end portion 14 is provided with a screw thread 15, such as a 2BA or 14ft BSF thread. It is customary to provide an undercut adjacent to the shoulder at the base of the thread washer which provides a retaining effect when the shaft is screwed into the barrel. However, this creates a stress con centration in the shoulder region, which can prom ote local fracture, and it is preferred to dispense with the undercut.The thread is preferably formed by rol ling between hardened thread rolls or fiat dies instead of being cut, so that a stronger and smoother thread is produced in which the grain structure fol lows the profile, and the threaded portion is slit lon- gitudinallythrough its axis, as at 16, the two parts thus created being forced slightly apart by means of a wedge so asto exert radial pressure when screwed into the barrel thereby providing a self-jamming or locking effect to give a secure fixing. Itis preferredthatthe shaft should be work- hardened or further work-hardened, for example by ball-burnishing. Various modifications may be made within the scope of the present invention. For example, one or both of the enlarged end portions may be connected to the central shaft portion instead of being formed integrally with it, in which case it may be of advantage to form only one or two ofthethree portions from magnesium or magnesium alloy, the other portion or portions being composed, for example, ofanother metal or plastics. Alternatively, where the three portions are formed integrally by a cold heading or cold forming process, a metal other than magnesium or magnesium alloy may be used, such as aluminium or an aluminium alloy. CLAIMS

1. A dart shaft of the type indicated, wherein at least one of the portions is composed of magnesium or an alloy thereof containing at least 50% magnesium.

2. A dart shaft as claimed in claim 1, wherein the end portions are formed integrally with the central shaft portion.

3. A dart shaft having a smaller diameter central shaft portion formed integrally with enlarged portions at each end, one portion serving as a flight holder and the other having means for connecting the shaft to a dart barrel, wherein the shaft is composed of metal and formed by a cold heading or cold forming process.

4. A dart shaft as claimed in claim 3, wherein the said metal is magnesium organ alloy thereof containing at least 50% magnesium.

5. A dart shaft as claimed in any one of claims 1 to 4, wherein the shaft is work-hardened or further work-hardened.

6. A dart shaft as claimed in any one of claims 1 to 5, wherein the means for connecting the shaft to a shaft barrel includesathreaded portion having longitudinal slits.

7. A dart shaft substantially as described with reference to the accompanying drawings.