GB2296450A - A dart - Google Patents

Abstract

A dart for use in the game of darts, which dart provides a retractable point (3) which may retract inside a bore (9, 10, 11) provided in the body portion (1) of the dart, the resistive force against that retraction being determined by the frictional force between a radially expandable member (8) and the bore (9, 10, 11), the characteristics of the bore (9, 10, 11) and the radially expandable member (8) determining the force exerted by the dart in various phases of its impact with the dartboard, so that in a first phase there is frictional resistance, in a second phase there is substantially no resistance and in a third phase a direct connection hammers the point into the target. The member (8) may be a split ring. <IMAGE>

Description

A DART The present invention relates to a projectile for impacting a target, and has particular reference to a dart for use in the game of darts.

A well known failing of conventional darts is that, during a game of darts, occasionally a dart thrown by one of the players rebounds from the dartboard. This presents a number of problems. Firstly, the player will not score with that throw. Secondly, the rebounding dart may injure the player himself, other players or a spectator. Thirdly, the dart may be damaged by its impact with the ground.

Much effort has been expended in attempting to provide a dart which is better adapted to penetrate and be retained in a dartboard than a conventional dart, and which, in the event of a rebound, will rebound a shorter distance from the dartboard than a conventional dart.

The problem of a conventional dart failing to penetrate a dartboard is more acute when a dartboard has become worn. In this case, wear and tear on the dartboard results in the outermost part of the bristles which make up the dartboard being worn away, leaving a hard compacted mass for the dart to penetrate. A high proportion of conventional darts thrown at such a target do not penetrate it to any degree, and hence fall away from the dartboard soon after impact. These throws do not count towards a player's score and may result in the darts being damaged or falling to a position from which they are difficult to retrieve.

Another problem which commonly arises occurs when a dart thrown by a player strikes one of the wires which define the scoring areas on the dartboard, or one of the staples which holds these wires in place. Commonly, the resilience of the wire or staple is sufficient to result in the rebound of the dart from the board at a similar speed to that at which it approached the board. In that case, the player scores no points for that throw. In addition, the rebounding dart may injure that player, another player, a spectator or a bystander.

Yet another problem presented by conventional darts is that a dart thrown at the dartboard may be deflected from its intended trajectory by a collision with a dart that is already stuck in the dartboard. In this circumstance the likelihood of the darts thrown by a player being grouped closely together is reduced. Since the high scoring areas of the dartboard present a small area to incoming darts, this difficulty in grouping the darts can seriously reduce a player's score and hence cause that player to lose an entire darts match.

In relation to a conventional dart, it will be appreciated that the flight carried by the dart already stuck in the board presents a relatively large crosssectional area to an incoming dart in comparison with the cross-sectional area presented by the remainder of the dart. Therefore, if deflections off the flight of a previously thrown dart can be avoided then the above problem is substantially overcome.

Each of the above problems relating to conventional darts is well known and a number of different dart constructions have been suggested which attempt to overcome some or all of those problems. However, none of these dart constructions are entirely satisfactory and, as a result, the majority of players still use conventional darts.

An early attempt to provide an improved dart is described in United Kingdom Patent No. 1593047. This patent discloses a dart which is of a conventional design except that the point is retractable against the action of a spring. In order to construct this dart, it is necessary to provide a bore right through the barrel of the dart.

Those skilled in the art will realise that this requires precise manufacturing techniques and hence tends to lead to an increase in the cost of the dart. Furthermore, it will be realised that the function of a spring is to store energy rather than dissipate it and hence that such a dart will not rebound a significantly shorter distance from a dartboard than a conventional dart. A further disadvantage of the dart is that the flight carried by the dart is not adapted to yield when struck by an incoming dart.

United Kingdom Patent Application No. 2180461 discloses a dart having a barrel with a bore extending part way into the barrel. The point of the dart is carried in the bore which defines a clearance fit for the point. Although this construction allows the remainder of the dart to rotate relative to the point, it does not provide a dart having a decreased chance of rebounding from the dartboard.

Another dart commercially available under the trade name "The ELKAPOINT", has a bore extending part way into the barrel which bore has a circumferential groove machined in to the sides of the bore at a position intermediate its ends. An O-ring is carried in this groove. The point of the dart comprises a shaft portion which is pointed at its forward end and carries a brass plunger at its rearward end. This point is retractable in the bore from an extended position to a retracted position, the brass plunger lying rearwardly of the 0ring in both those positions. On impact with the board, the shaft of the point is pushed back through the O-ring, the energy of the impact being dissipated partly by overcoming the friction between the shaft portion and the O-ring, and partly by the compression of the air initially lying rearwardly of the brass plunger in the bore.When the brass plunger reaches the rear of the bore, the barrel of the dart directly engages the plunger and drives the point further into the dartboard.

However, there are a number of disadvantages presented by the design of tThe ELKAPOINT". Firstly, the machining of the circumferential groove to carry the O-ring and the placing of the O-ring in that groove are relatively difficult manufacturing operations which lead to an increase in the unit production cost of the dart.

Secondly, the friction between the point and the O-ring means that the point is unable to rotate relative to the remainder of the dart. As stated above, this leads to a difficulty in closely grouping the darts and results in a reduced score. Thirdly, no clear indication is given to the player as to whether the point is in its fully extended position when he throws the dart. Owing to the parabolic trajectory followed by a dart when thrown at a dartboard, a dart with a relatively long point will tend to impact the dartboard at a higher position than a similar dart with a relatively short point. Hence, the lack of any indication of how far the point is extended leads to an uncertainty as to the length by which the point extends from the barrel of the dart, which in turn leads to an uncertainty in the point of impact with the dartboard.This uncertainty in the point of impact may have an adverse effect on a players score.

United Kingdom Patent Application No. 2039755 discloses six different designs for a dart with a point retractable into a bore provided in the barrel of the dart. All these embodiments have the feature that the point does not retract until a predetermined force is exerted on it by the dartboard and furthermore that the resistive force against retraction of the point into the barrel is maintained or even increased as the point moves towards its retracted position. In addition, in each of the six embodiments described in the above application, there is a significant frictional force against relative rotation of the point of the barrel when the point is in its retracted position. Hence, even after the dart has impacted the board (thereby moving the point to its retracted position) the remainder of the dart is substantially unable to rotate relative to the point.

Since each of the described darts carries a conventional flight holder, this frictional force between the point and the barrel reduces the ability of the flight of a dart already retained in the dartboard to rotate when struck by an incoming dart, and, as discussed above, may reduce a players score.

United Kingdom Patent Application No. 2192804 discloses a dart which has a bore extending part way into the barrel, that bore having an internal thread towards its outer end. The dart further comprises an end cap which has an external thread which is adapted to engage the internal thread on the bore. The end cap is further provided with a relatively narrow bore, and carries a tapering point, the front end of which point projects forwardly from the end cap and the rearward end of which point is of too great a diameter to pass through the bore in the end cap. In use, the point is pulled outwards from the end cap as far as the taper will allow.

The distance by which the point of the dart extends from the barrel is highly dependant on the respective shapes of the taper and the point. The taper and the point must therefore be manufactured to a very high tolerance in order to avoid an unpredictability in the projecting length of the point of the dart, which (as discussed in relation to "The ELKAPOINT") leads to an unpredictability in the point of impact of the dart and hence reduces a players score. The necessity for the point to be manufactured to a high tolerance results in an increase in the unit production cost of the dart. This problem is compounded by the further problem that, when the point has been pulled outwards from the end cap to return it to its extended position, no positive indication is given that the point has been returned to its extended position.

International Application No. WO86/01418 also discloses a dart with a retractable point. That dart has a barrel with a bore extending right through the barrel.

A circumferential groove is machined around that bore at a position intermediate its ends, and this groove carries an O-ring. The bore itself comprises a narrow bore extending right through the barrel of the dart and a wider counterbore extending from the rearward end of the barrel to a position close to the front end of the barrel. The wide counterbore is plugged towards its rearward end by an insert member. The point of the dart is provided by an elongate shaft pointed at its forward end and having an enlarged head at its rearward end. The diameter of that enlarged head is greater than the diameter of the narrow bore. The point extends forwardly through the narrow bore, the enlarged head being located in the wide counterbore.The point is thus constrained to move between an extended position (in which the enlarged head portion lies in front of the O-ring) and a retracted position (in which the enlarged head of the point lies rearwardly of the O-ring).

On impact, the application of a predetermined force to the point may result in the enlarged head moving backwards past the O-ring whereafter there is no further resistance to the retraction until the enlarged head strikes the end of the bore. Again, the difficulty of manufacturing the circumferential groove around the bore and placing the O-ring therein leads to an increase in the unit production cost of the dart.

Therefore, there is a need for a dart which is simple to manufacture, and which overcomes some or all of the above problems.

According to the present invention there is provided a projectile comprising: a body portion provided with a bore; an impact member retractable in said bore from an extended position to a retracted position; said bore having first and second widths at respective first and second positions spaced along its length said second width being greater than said first width and said second position lying further in the direction of retraction than said first position; and a resilient engaging means attached to said impact member which, when said impact member is in said extended position, is compressed between said impact member and the surface of said bore at said first position; the arrangement being such that on impact with the target the impact member is maintained in said extended position until the frictional force between the engaging means and the surface of the bore at said first position is overcome, whereupon said impact member moves towards said retracted position, and, on said engaging means reaching said second position, said frictional force on the engaging means is less than the frictional force in said first position.

In a preferred application, said projectile is a dart, said impact member is a point means of said dart, and the target is a dartboard.

Preferably, the bore has a width narrower than said first width at a forward position, said forward position lying in front of said first position in the direction of retraction, and a seating means being provided by the widening of the bore between said forward position and said first position in the direction of retraction, the impact member having an enlarged portion and a shaft portion, wherein in the extended position, a shoulder formed between the enlarged portion and the shaft portion engages the seating means. Thus, as a user of the dart pulls the point forward towards its extended position, he will first feel an increase in the friction against that extension as the engaging means moves from said second position towards said first position and will accordingly increase the force he exerts on the point.

Once the increased frictional force is overcome, the point will move until the shoulder engages the seating means. A skilled person will realise that this will result in the point "clicking" into its extended position. Thus, a positive indication is given that the point has been moved into its extended position.

Preferably, the bore has a width greater than said first width at a rearward position, and the resilient engaging means is located at that rearward position in the bore when the impact member is in its retracted position. This has the result that when the impact means is in its retracted position there is substantially no compression of the engaging means and hence there is substantially no friction against relative rotation of the impact member and the projectile body. Thus, when a dart has impacted the dartboard (thereby moving the point to its retracted position), the remainder of the dart is able to rotate relative to the point of the dart which may be held against rotation by its contact with the dartboard.Therefore, if an incoming dart strikes the flight of the dart already retained in the dartboard, then that flight will be able to rotate together with the barrel of the flight holder of the dart around the point of the dart. Hence, the incoming dart will not be substantially deflected from its original trajectory and the grouping of the darts in the dartboard may be improved.

Advantageously, the body portion of the projectile directly engages the impact member of the projectile when the impact member is in its fully retracted position.

This has the result that a large impulsive force is delivered to the impact member thereby tending to hammer it into the target.

Preferably, the bore comprises a first bore, and first and second counterbores, said seating means thereby being provided by the seat defined at the boundary of the bore and the first counterbore, the first portion of said bore being provided by said second counterbore, said second position being provided at the base of said bore.

This arrangement may be simply manufactured, and also allows the dart to be manufactured so that the distance that the point projects in its extended position may be easily kept within a desired tolerance.

Advantageously the projectile body comprises a first body portion and a second body portion, wherein at least said bore and said first counterbore are provided in said first body portion. This has the result that it is not necessary to provide a bore running right through the dart body and enables the dart to be more cheaply and easily manufactured.

Preferably, the first body portion may be provided by a sleeve means, said sleeve means subsequently being inserted into a bore provided in the second body portion.

Usefully, the second body portion can be provided by a conventional dart barrel and the sleeve can be provided with such an outer diameter that it is press-fittable into a conventional dart barrel. This arrangement also facilitates the replacement of the sleeve means and impact member.

The reduction in the resistive force against the retraction of the point means as the engaging means moves from said first position to said second position gives the advantage that on striking a wire on the dartboard the dart is less likely to rebound from the dartboard.

In this circumstance, the wire is pushed into the board by the point means until the initial frictional force between the engaging means at said first position and said bore is overcome, whereafter the reduction in the resistive force results in the point being catapulted towards its retracted position. This in turn results in a rapid alteration in the length of the dart and, depending on the trajectory of the dart, may result in the subsequent point of impact with the dartboard being at a different position from the initial impact. It will therefore be seen how a dart according to the present invention may be less likely to rebound from a wire on the dartboard.

In one embodiment, the sleeve means may alternatively be threadingly engaged with the outer body portion. In addition to releasably attaching the sleeve means to the outer body portion, this feature also provides the advantage of enabling the distance retracted by the point to be adjustable.

Furthermore, this embodiment may be adapted so that the rotation of the point means with respect of the sleeve may alter the characteristic variation in the force exerted by the connection means or indeed determine whether the point is retractable or not.

The invention will now be described further with reference to and as illustrated in the accompanying drawing in which the single figure is a cross-sectional view of the front end of a dart according to a specific embodiment of the present invention.

It will be realised that a conventional dart has a point at its front end which is typically press-fitted into a bore in the front end of a cylindrical barrel which barrel is in turn is adapted to accept a flight carrying shaft at its rearward end, that flight carrying shaft itself carrying a flight at the rear of the dart.

Turning now to Figure 1, it will be seen that the front end of the dart of the specific embodiment of the present invention comprises a dart barrel (1), a hollow sleeve (2), and a point (3). It is to be appreciated that the dart is of a conventional construction rearward of the front end of the dart illustrated in Figure 1.

Turning firstly to the point (3), this is an elongate solid of generally circular cross-section. At a first end, it has a relatively wide head portion (4) which tapers inwardly to a central portion (5) whose length is eight or nine times as great as the length of the head portion. The central portion (5) is terminated by a tapered portion (6) where the diameter of the point (3) is reduced to a point on the longitudal axis of the point (3).

A circumferential groove (7) is machined into the head portion at a distance about three-quarters of its length away from the first end of the point (3). The central portion (5) is provided with a shallow neck (20) adjacent the tapered portion (6). A split ring (8) is located in the groove (7).

Turning now to the sleeve (2), this is provided by a hollow cylinder (2) whose length is approximately one third of the length of the point (3). The entire length of the cylinder (2) has a narrow bore (9) provided along its longitudal axis. A concentric intermediate counterbore (10) extends into the cylinder to about twofifths of its length and a concentric wide counterbore (11) extends into the cylinder to about one fifth of the length of the cylinder (2). The two counterbores (10,11) define a first shoulder (16) and a second shoulder (17).

The narrow bore (9) is of a diameter to allow the central portion (5) of the point (3) to slide therein. The intermediate counterbore (10) is of a diameter to provide an interference fit with the split ring (8) resting in the groove (7) of the point (3), and the wide counterbore (11) is of a sufficient diameter to provide negligible resistance to the passage of the split ring (8) along the bore (11).

The dart barrel (1) is provided by a conventional dart barrel which is provided with a bore (12) which is concentric with the longitudal axis of the barrel and which extends into the barrel to a depth equal to the length of the sleeve (2). The size of the bore (12) is such as to allow the sleeve (2) to be press-fitted therein.

The split ring may be manufactured of any suitable material such as metal, nylon, rubber or plastic.

It will be seen that, to assemble the dart, the tapered portion (6) of the point (3) may be inserted into the rearward end of the sleeve (2) until the head portion (4) of the point (3) enters the intermediate bore (10) in the sleeve (2). The head portion (4) may then be pulled into the intermediate bore (10) against the resistive force provided by the interference of the split ring (8) with that bore by gripping the shallow neck (20) of the point (3). Once this has been achieved, the sleeve (2) may be press-fitted into the bore (12) provided in the dart barrel (1), and remain fixed owing to the interference fit thus produced.

In operation, it will be seen that when the point (3) of the dart strikes the target (not shown) and the force exerted on the point by the target is sufficient to overcome the frictional force provided by the interference fit of the split ring (8) in the intermediate counterbore (10), then the point (3) will retract inside the bore (10). In this retraction, the static friction presented by the contact of the split ring (8) and the bore (10) and then the dynamic friction as the point moves backwards relative to the bore (10) will need to be overcome. Once the split ring (8) has reached the shoulder (17), the resistance to the retraction of the dart then becomes negligible.Clearly, although some of the kinetic energy of the dart will have been lost in overcoming the friction between the bore (10) and the split ring (8), the dart barrel (1) may still have some kinetic energy, the continued motion of the dart barrel (1) towards the target resulting in the base of the bore (12) in the dart barrel (1) striking the head portion (4) of the point (3) and hence providing an impulsive force tending to drive the point (3) into the target (not shown).

It will therefore be seen how the specific embodiment of this invention will increase the likelihood of a dart penetrating and sticking into a worn and compacted dartboard.

Once the player has finished his turn, the point (3) may be restored to its original fully extended position by pulling on the shallow neck (20) provided in the centre portion (5) to bring the head portion (4) back into the intermediate counterbore (10). It will be realised that the engagement of the split ring (8) and the intermediate counterbore will be felt by the player who will then have to exert a greater force on the point until he feels the head portion (4) engage the first shoulder (16). This increased resistance to the extension of the point and subsequent engagement of the head portion (4) and the first shoulder (16) provides a positive indication that the point has been returned to its fully extended position.

Furthermore, it will be seen that when the point (3) of the dart strikes a wire on the dartboard, then the wire will initially be pushed into the board until the force exerted on the point by the wire exceeds the static friction presented between the split ring (8) and the counterbore (10) whereupon the point (3) will begin to retract along the counterbore (10). The dynamic friction provided by this contact will then continue to slow the dart until the split ring (8) passes into the wide counterbore (11) when the resistance to that retraction will become negligible. The removal of the resistive force will result in the wire on the dartboard recovering (i.e. moving back towards its original position before it was struck by the dart).Provided that the frictional force between the split ring (8) and the counterbore (10) is of a sufficient magnitude, the energy stored by the wire and subsequently released will be sufficient to catapult the point away from the target. However, the point will subsequently reach its fully retracted position in which the head portion (4) is in contact with the base of the bore (12) in the dart barrel (1), whereupon the effective collision of the dart barrel (1) and the point (3) will result in the point again moving towards the target. It will be appreciated that in the time which elapses as the point (3) retracts to the base of the bore (12) the dart as a whole will have moved downwards slightly and therefore that the second impact of the dart will be at a position below the wire that was originally struck.

It will therefore be appreciated how the above described dart is less likely to rebound from a wire on the dart board.

It will further be appreciated that the work done in overcoming the resistive force presented between the split ring and the counterbore (10) will reduce the kinetic energy of the dart and hence reduce the velocity of the dart if it were to rebound from the dartboard.

Claims (16)

1. A dart or similar projectile comprising: a body portion; a point means projecting from said body portion and adapted to penetrate a target; and a connection means resistively connecting the point means to the body portion in a manner which allows retraction of the point means against a resistive force between the body portion and the point means; said body portion having a mass so chosen in relation to the resistive force that the projectile will have sufficient energy to continue in motion when the point retracts against said resistive force.

2. A dart or similar projectile according to claim 1 wherein: said body portion is arranged to engage said point means directly when said point means is fully retracted so that an impulsive force is delivered to the point means in a final phase of impact and the point means is thereby hammered into the target.

3. A dart or similar projectile according to claim 1 or claim 2 wherein: said resistive connection so relates to the mass of the body portion that when the point means hits a wire of a dartboard the point means will retract and be moved forward again under the influence of said body portion as the body portion continues in motion.

4. A dart or similar projectile according to Claim 2 or Claim 3 wherein: said connection means defines a resistive connection between the point means and the body portion which in a first phase of movement provides a frictional resistive force, in a second phase of movement provides substantially no resistance to movement, and in a third phase provides a direct connection between the point means and the body portion.

5. A dart or similar projectile according to any preceding claim wherein said body portion comprises: a sleeve means; and an outer body portion; said outer body portion defining a bore into which said sleeve is inserted, thereby facilitating the replacement of the sleeve means and the point means.

6. A dart or similar projectile according to claim 5 wherein: said sleeve means threadingly engages said outer body portion.

7. A dart or similar projectile according to claim 4 wherein: said point means has a first end and a second end in the form of a pointed tip; said bore extends part way into said body portion, the depth of said bore being less than the length of the point means; thereby resulting in the base of the bore being engaged directly by said first end of the point means when said point means is fully retracted.

8. A dart or similar projectile according to any preceding claim wherein: said connection means comprises an outwardly expandable member: the arrangement being such that the retraction of the point means involves a variation in the dimensions of the outwardly expandable member, which in turn results in a variation in the frictional force between the point means and the body portion, this variation in the frictional force providing a variation in the resistive force exerted by the connection means.

9. A dart or similar projectile according to claim 8 wherein: a circumferential groove is provided around said point means; and the outwardly expandable member is provided by a radially expandable member.

10. A dart or similar projectile according to claim 9 wherein said radially expandable member is provided by a ring carried by said groove.

11. A dart or similar projectile according to claim 10 wherein said ring is provided by a split ring.

12. A dart or similar projectile according to claim 9 or 10 wherein: a first portion of said bore provides an interference fit with said radially expandable member; a second portion of said bore disposed inwardly of said portion is of such a width as not to interfere with the retraction of the point means; and the resistive force exerted by the connection means is arranged to decrease from an initial value provided by said first portion to a substantially negligible value provided by said second portion, so that part of the energy of the body portion is utilised during retraction of the point means and the remainder of said energy is lost in the direct application of force from the first end of the point means to the base of the bore.

13. A dart or similar projectile according to claim 7 wherein the first end of the point means is of an enlarged dimension, thereby adapting said point means to withstand the impact of the body portion.

14. A dart or similar projectile according to any preceding claim wherein the point means may be returned to its extended position by pulling it outwardly from the body portion by hand.

15. A dart or similar projectile according to claim 13 wherein the point means is so shaped to facilitate it being so extended.

16. A dart or similar projectile substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.