CA1101009A

CA1101009A - Dart with resiliently mounted tip member

Info

Publication number: CA1101009A
Application number: CA262,708A
Authority: CA
Inventors: Kent Sj'gren
Original assignee: Individual
Current assignee: Individual
Priority date: 1976-05-07
Filing date: 1976-10-05
Publication date: 1981-05-12
Also published as: AU1774776A; JPS6036306B2; DE2642962A1; AU501191B2; DE2642962C2; JPS537999A

Abstract

ABSTRACT OF THE DISCLOSURE

A dart comprising an elongate body portion, a bore extending axially in said body portion, and a tip arranged for axial movement in said bore between first and second limit positions The tip is encircled by a spring arranged in the elongate body portion. Flights are fitted to the end of the body remote from said tip and means may be provided for ejecting the flights of the dart upon axial movement of the tip to its first limit position. Preferably the tip is able to move radially in the bore between preferred limits. The advantage afforded by such a dart is that the number of rebounds occurring should the dart strike a wire of a dartboard are greatly reduced in comparison with a standard dart.

Description

Ot9 The game of darts is normaliy played with a set of three darts, which are intended to be thrown against a - target for the purpose of amassing a s-tipulated score.
The target norma]ly has the form of a circular dart-board divided into 20 segments, numbered from 1 to 20 in a predetermined order. Extending around the perimeter of the board are two wires arranged relatively close together, these two wires being intersected by wires defining the aforementioned 20 segments. The portion of the target 0 defined by the perimeter wlres and -two adjacent intersectingj wires represents twice the number allotted to that particular portion, thus if the segment in question has the value 20, dart in said defined portion would score 40.
Siml]arily, two further wires are arranged in closely adjacent circles at a distance radially inwardly of the perimeter wires~ These further wires, toge-ther with the intersecting wires, define areas in which the number ~ ~ allotted to a particular segment is trebled. An area of 1 the board encircling the centre of the circle is given the value 50, while a further area encircling said centre , area is given the value 25.

Although relatively thin and flexible, the wires defining the various target areas of the dart board also present an obstacle to a dart aimed at one of the areas. For example, it often happens that the point of a dart will strike a defining wire~ causing the dart to .

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lO~ 9 rebound, i.e. to bounce away Prom the board and fall to the floor, which means that at times not all of the darts thrown score thereby placing the thrower at a disadvantage in relation -to his competitor.
It is therefore a primary object of the present invention to provide a dart having the-ability, should it strike a wire in the manner explained above, to "sidestep" it and stick in an adjacent region of the board, such a feature being heretofore unknown in this art.
lQ Accordingly, the invention, as herein broadly claimed, is a-dart including: a hollow elongate body; a tip member axially slidable within this body and having a pointed end projecting from one end of the body; stop means for limiting movement of the tip member towards the said one endi and resilient means provided within the body and arranged resiliently to resist movement of the part of the tip member located within the body away from this one end of the body, the tip member being arranged for radial movement in said body, and the combina-tion of said resilient means and said radial movement being such that a reduction in the likelyhood in dart bounce is achieved.
The resilient means preferably involves a spring effective to take up~recoil forces acting on the tip when the ~ ~ tip strikes an obstacle, such as a wire defining two adjacent :~ target areas. ~-The elongate body preferably comprises two halves, which can be screwed together or which can be joined together by some other suitable means.
The body is bored and the bore in one of said halves ma~ be conveniently enlarged to form a chamber for recelving the spring and the portion of the tip membex Iocated in said chamber may be provided with the stop means including a raised portion effective to ]imit the axial movement of the tip relative .

- ~alo~oos to the elongate body at least in one direction of the said relative movement.
Suitabl~, the chamber has a first wall deflning a ;

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first predetermined position and a second wall defining a second predetermined position. Alternatively the second pre-determined position may be defined by the end o the flight stem adjacent the end of the tip. In this latter case, said end of said flight stem will be provided with a reinforcing member, so as to prevent damage to said end upon impact with said tip , end as the tip rebounds. - , Conveniently the diameter of the bore is such as to enable the tip to move radially therein.
Ejection means may be arranged between the end of the tip adjacent the flights and said flights such that axial movement of the tip towards the flights causes them to be ~ r eiected. Alternatively, the tip may be of such length as to - eject the flights when moved axially thereagainst.
- The aforementioned primary object as well as other -ancillary ob~acts of the invention will be more readily 1~ , ' . ' : .

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' understood and optional features thereof made apparent7 exemplary embodiments of the invention will now be described with reference to the accompanying schematic drawing, in which :-Flgure 1 is a sectional` view of a dart constructed I in accordance wlth the invention; and j Figure 2 is a cross-s~ectional view taken on the line A-B in Figure 1.
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, The illustrated dart comprises an elongate body portion, shown generally at 1, which in turn comprises two halves~2 and 3. Extending through the body portion ~ `
1 is a bore 4. In the half 2, the bore 4 is widened to form a chamber 5.
Arranged in the bore 4 and extending through chamber S is an elongate tip 7. That part of the tlp 7 located within the chamber 5 is provided with a shoulder 8 against which, in the assembled state of the dart, one ~f~ end of a spring 10 may be brought to bear. This spring is~effective to absorb recoil forces acting~axially on ; ~ 20 ~ ~the tip 7 towards the flights of the darts, as will be described more in detail hereinafter.
The flights (not shown) have a stem~portion~, part of which is shown~at 11~ which is adapted to be flrmly - received in one end of the body half 2.
The tip 7 of the illustrated dart lS contlnuous and i~ forms an eJeCtor pin, as shown at 12, w~ich ~ermlna~es at~

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~10~ 9 a dista~ce a from the end 13 of the flight stern 11.. The .l di.stance between the mutually facing ends of the flight stem 11 and the ejector pin 12 is such as to permit sufficient penetration of the tip 7 into the target and to permit the flight to be ejected from -the bore 4 upon relative axial movement of the body portion 1 with the - . tip 7. Although, when the tip 7 strikes the target, the l ~ body 1 will be slightly decelerated thls deceleration is ¦ ~ not appreciable and the body l will continue to move :. :
I0 ` towards the target. When the body 1 hàs moved the distance relative to the~pin 7 equal to the dis~tance a, the e~ector pin port.ion 12 of the tip 7 will engage the flight stem . 11, whereupon further relative mQvement of the body 1 with the tip 7 will cause the flights to be ejected.
Clearly the length~of tip protruding beyond the j leading face of the half 3 shall be sufficient to permi.t the tip 7 to enter the target and to permit the flights r to be ejected upon said relative movement between the body portion 1 and the tip 7.
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: 20 Although the bore 4 has been shown to extend : ;
completely through the elongate body 1, the bore need ; only extend through part of said body with the remainder of the body solld,~provision being made at one end of ~sa~d~
. body for receivinq the~flight stem~ll. In this: case, no . .
provision is made for ejecting the fliqhts and the tlp 7 ~ will extend partly inlo the chamber 5? the part of the ¦ stem located within the chamber beiny encircled :~1 . - ~

,' ' ', ~ ' ' ,': ' ' ' , ' ' ' ~ .' by the sprlng 10. Alternatively, the elongate body ¦ portion need not be provided with a chamber 5 for the spring 10, but the spring may be contained within the ' bore 4 and means may be provided for limiting the axial ! 5 movement of the -tip 7 between the beforementioned I predetermined limit positions.
! Normally~ the flights of a dart are made of a I plastics material and, in the case of a dart in which-i ~ .
! ~ ~ the second predetermined position is defined by the end ¦ 10 oE the flight stem entering the elongate-body, the flight stem is liable to become damaged as a result of impact between it and a bouncing lip.
To prevent this, this end of the flic3ht tip may be pl~ViC~
~ with an insert of hard material able to wi-thstand repeated ¦ 15 blows by the dart stem as it bounces within the elongate ¦ body portion. Such an insert is indicated at 13a.
With regard -to the rebound frequency of a dart f~ constructed in accordance with the-invention, in whicll the tip is axially moveable rela~ive to the elongate body ¦~ 20 portion against the force of a spring, it has been found that such a dart will rebound less frequen~ly than will a dart with a fixed tip, i.e. a dart in which the , .
tip is not free to move axially.
' Although it is not fully understood why this is so, one reason could be as follows~ rhe velocity of a thrown dart can be resolved into three components, l .

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- a component ln the Z direction, a component in the X
direction~ ac-ting vertically between the 20 and the 3 on a standard board, and a component Y acting at right angles to the X component.
The wires of a dart board are relatively thin and somewhat resilient and the board on which the wires are a'rranged comprises a material which is soft compared with the wires and the tip of the dart. The wires will therefore not remain at rest when struc]c by a dart but will move sllghtly in the direction of at--least any~one 'I of the three components of velocity. The energy required for this movement is taken from the kinetic energy of the dart, thereby reducing sai~d k:inetic energy. Whether -the-direction in which the dart is moving is lS changed or notland the extent of any such change,depends on the angle at which the dart strikes the wire. If a ` dart having a rigidly moun~ted tip strlkes the central-I ~ zone of a wire, as seen in relation to the longitudinal axis of the wire, the dart will loose a great part of 20~ its kinetic energy and its directlon of movement is~
~ mainly reversed. The dart will then~move away from the I ~ dart-board and~will fall to the ground without scoring.
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If such a dart strikes areas of the wire ad~ja~cent said centra] zone the dart will loose less kinetic energy than ~- - 25 when it strikes said central zone. Furthermore, the change in the three components of velocity will be considerable. Iiowever the dart veloclty after the bounce is not of such magnitude and direction as to enable the dart to enter the board. When , -' ~ ' ' ' ~ , .
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., a dart having a rigidly mounted point strikes the peripheral areas of the wire, however, the dart will loose but little energy as a result of striking the wire and the main component of velocity will then be the X or -the Y component.
This will cause lhe tip of the dart to slide around the wire and to enter the dart-board. Generally speaking, the transfer of kinetic energy from a moving body hitting a body at rest to said body at rest depends on the velocity ¦ ~ of the moving body and the weight of the two bodies.
I 10 When the dart tip is rigidly mounted, the--transfer of energy depends on the weight of the dart and on the resilience of the wire. If, on the~other hand, the tip of the dart is moveably mounted, as in accordance with the invention, this transfer of energy will depend upon the weight of the dart tip and on the resilience of the wire, unless the spring is completely compressed as the I .
dart strikes the wire. When a moveable tip hits a wire, the amount of energy lost by the dart as a whole is there-fore small cornpared with the amount of energy lost when I ~ 20 the tip is rigidly mounted. Consequently enough kinetic energy remalns to enable the dart to enter the board so as to score.
When a dart constructed in accordance with the ¦ ~ invention hits the central zone of a wire, the bounce of the tip will leave the velocity of the dart body almost unchangcd. The direction of movement of the tip however will be reversedO During the initial bounce, the spring .: , . .
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will slightly reduce the velocity of the elongate body and greatly reduce the velocity of the tip. Subsequently, the spring itself or the spring together with an internal bounce o~ the tip against the body will reverse the direction of movement of the tip. Whether or not there is internal bounce between the body and the tip depends on the spring force and the welght of the body and the tip. The tip will then strike the surface of ~l ~ the wire again at the same place as it did the first time, `~ 10 or at a point adjacent said first place. After bouncing ¦ two or more times, possibly with internal bounces of the tip, the velocity of the body will be lost and the dart will not enter the board.
¦ When a dart constructed in accordance with the ~1 15 present lnventlon strikes the wire in areas adjacerit said central zone, the course of events will be similar to those when striking said central zone. Ilowever, due to tlle angle between the velocity component in the Z direction and the surface of the wire, the transfer ¦ 20 of energy and tip bounce etc. will cause the main velocity of the dart to be changed to the X or Y component. The point at which the tip strikes the wire will be Eurther from the central zone than the point at which the tip first struck the wlre. The angle between the Z component and the surface of the wire wilI be greater than it was - when tile tip first struck the wire, and the components of velocity in the X or Y directions will be greater than -: ~ ' ,, :

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the component in the Z direction~ Owing to the low loss of ~inetic energy after each bounce, suffic~ent energy remains to enable the tip to enter the board, provided that it passes the wire. There is a tendency of the tip to slide o-Ef or around the wire due to the successive, varying points at which the tip strikes the wireO This tendency is increased when the point is able to move radially.
¦ ~ ~ Experiments have shown that the rebound frequency ~ ~o of a dart constructed in accordance with~the invention ¦ is influenced by the weight of the elongate body, the weight of the tip, the maximum axial relative movement ~i o~ a tip with a body, the speed at which the dart is thrown and the rating of the spring. Although no general 3 15 limits regarding the spring rating can be given, the spring sllall preferably be able to store the rebound energy of the tip before the tip contacts its rearward ( movement-limitillg surface, but shaLl be unable to cause `i the elongate body to be slowed to an extent such that the res;dual velocity of the dart is insufficient for the I tip to enter the board. It has been found that the ` rating of the spring shall suitably lie between 100 N/m and 1000 N/m with a dart weighing, for example, between 24 grams and 30 grams. Suitably, the spring has a rating lying between 200 and 600 N/m.
Tests have s}~own that t~e axial movement of the tip in the elongate body should lie betweell 4.5 and 20 mm, ,. . :` 3 ~?

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'~ ' . ' ' preferably between 10 and 15 mm. The radial movement of the tip rnay lie between 0.1 and 1 mm, preferably between ~ . .
0.2 and 0.7 mm.
A number of tests has been carried out with darts i 5 ~ of different weight. The results of these tests are shown in the table below. ~ach dart was thrown 500 times at a calculated average speed of 5 m~s. The test board comprised a base member of fibrous material and a plurality of wires arranged in grid form on the base member. The io vertical wires of the grid were spaced 4mm apart and had-a length of 16 cm and a diameter of 1.65 mm~ The transverse wires of the grid were spaced 5 mm apart and had a diameter of 1.5 mm. The wires covered - approximately 55% of the area of the test board. The darts were dropped or thrown against the test board from a distance of ~.5 metres at the beforementioned calculated ~ average speed of 5 m/s.
i ( ~ Tests A1 and A2 were carried out with darts (weight 24 grams) in which no spring was fitted but in which the tip could move radia]ly a distance of 0~7 mm.
The rebound frequency of these darts was recorded to `` be 9.8% and ~.6% respectively. Tests A3 - A6 were carried ; out with darts in which respective tips were able to move axially against the force of a spring, the rating of which was 600 ~m. A marked improvement in rebound frequency was recorded, tlle best result being obtained - - with the dart used in test A6, the tip of which could _., .

, move aY~lally 1~,S rnm.
I Test A7 was carried out wi.th a clart in which nospriny was ~i.tted but in which the t.ip could move axially 1 6 mrn. Til,e bounce ~requency was recorded as belnc~ 9.0%, 'de,spite tlle ability o~ the tip to move axially.
The test;s show t:hat -the rebound irequency o~ a dart ls rnarkedly reduced when the tip is able to move axially against the ~orce of a spring. A lower rebouncl ~requency ls also,obtained when the tip is able to move '10 ' radlally in the bore. A su:itable rneasurernent of such , radial rnovement ls 0.2 - 0.8 mm.
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,, Althouc~h the invention has been described with ' ref~rence to specific embodirnent~ thereo~, itis not restricted thereto~ but can be modified wlthin the ~5 scope o~ the ~ollowing C.laims.
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`~ TABL,E

Extent of axial movement of tlp Test Dart Radial against force of Spring Rebound , No. weight movement spring strength frequency ~ , .. , . . I
gram mm mm N/m %
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Al 24 0.7 0* 00* 9.8 A2 24, 0.7 0~ 00~ 8.6 A3 24 0.65 4.5 - 600 5.
A4 24 0~7 8.5 600 5.2 A5 24 0.7 9.5 600 3 ~ 4 A6 24 0.7 14.5 600 2.8 A7 28 On3 6.0 0 9.0 A~ 30 Oal 8.5 600 = 9.4 A9 30 O ~ 3 . 10 ~ O . 600 1.9 A10 30 O ~ 3 ~` 7.5 - 600 0.6 The weight o~ the tip was, in each case, approximately 1.5 grm ' "'"

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

l. A dart including: a hollow elongate body; a tip member axially slidable within said body and having a pointed end projecting from one end of said body; stop means for limiting movement of said tip member towards said one end; and resilient means provided within said body and arranged resiliently to resist movement of the part of the tip member located within said body away from said one end of said body, the tip member being arranged for radial movement in said body and the combina-tion of said resilient means and said radial movement being such that a reduction in likelihood of dart bounce is achieved.
2. A dart according to claim l, wherein a flight assembly is provided at said other end of said body.
3. A dart as claimed in claim l, wherein the resilient means includes a spring whose rating is between 100 N/m and 1000 N/m.
4. A dart as claimed in claim 3, wherein the rating of the spring is between 200 and 600 N/m.
5. A dart as claimed in claim l, in which the extent of axial relative movement of the tip member with the elongate body lies between 4.5 and 20 mm.
6. A dart as claimed in claim 5, wherein said extent of axial relative movement lies between 10 and 15 mm.
7. A dart as claimed in claim l, wherein said hollow body defines a bore in Which said tip member is slidable and the radial movement of the tip member lies between 0.1 and 1 mm in relation to the centre axis of the bore.
8. A dart as claimed in claim 7, wherein the extent of radial movement lies between 0.2 and 0.7 mm.
9. A dart as claimed in claim 1, wherein the elongate body comprises two halves, each of which is provided with means for joining said halves together.
10. A dart as claimed in claim 9 , wherein the body defines a bore in which the tip member is slidable and the bore in one of said halves is enlarged to form a chamber for receiving a spring as part of said resilient means.
11. A dart as claimed in claim 10, wherein the portion of the tip member located in said chamber is provided with a raised portion as part of the resilient means, this raised portion being effected to limit the axial relative movement of the tip member with the elongate body toward said one end.
12. A dart as claimed in claim 2, wherein flight-ejection means are arranged between the end of the tip member adjacent the flight assembly and said assembly, such that axial movement of the tip towards the flight assembly will cause the flights thereof to be ejected.
13. A dart as claimed in claim 12, wherein said ejection means comprises part of the the member.
14. A dart as claimed in claim 1, wherein the end of the tip member entering the elongate body is provided with a reinforcing member.
15. A dart as claimed in claim 8, wherein the end of the tip member entering the elongate body is provided with a reinforcing member.
16. A dart as claimed in claim 12, wherein the end of the tip member entering the elongate body is provided with a reinforcing member.
17. A dart comprising: an elongate hollow body portion defining a bore extending coaxially therein, flights having means for attaching them to one end of said body: a tip member adapted to be received in the end of said bore remote from said one end of said body, said tip member having a pointed end projecting from said bore remote end and arranged for limited relative axial movement with said body between first and second predetermined positions; stop means for limiting movement of said tip member toward said remote end whereby to allow movement of said pointed end solely between said positions; and resilient means provided within said body and arranged resiliently to resist movement of the part of said tip member located within said body away from said remote end, the tip member being arranged for radial movement in said body and the combination of said resilient means and said radial movement being such that a reduction in likelihood of dart bounce is achieved.
18. A dart as claimed in claim 17, wherein the bore is enlarged to form a chamber for receiving a spring of said resilient means and the part of the tip member located in said chamber is provided with an abutment surface against which one end of the spring bears, said abutment surface forming part of said stop means.
19. A dart including: a hollow longitudinally extending body; a tip member axially slidable within said body and having a pointed end projecting from one end of said body;
stop means for limiting movement of said tip member towards said one end; and a spring located within said body and adapted to urge the part of the tip member located within said body towards said one end of said body, the tip member being arranged for radial movement in said body and the combination of said spring and said radial movement being such that a reduction in likelihood of dart bounce is achieved.
20. A dart comprising, in combination: an elongated body having a longitudinally exending bore which opens through at least the forward end of said body;
an elongated tip member disposed in said bore and protruding forwardly from said body, said tip member being movable longitudinally relative to said body; and means for reducing the likelihood of dart bounce when the tip member encounters an obstruction having the characteristics of a target-defining wire on the surface of a dart board, said means for reducing the likelihood of dart bounce including:
cooperating movement limiting means carried by said body and said tip member for limiting relative axial movement of said body and said tip member between a first position in which said tip member projects forwardly from said body to its utmost extent and a second position in which said tip member is partially retracted but still projects forwardly from said body sufficiently to penetrate and remain stuck in a dart board, said limiting means including stop means for limiting movement of said tip member toward said forward end and resilient means engaged between said body and said tip member for biasing said tip member forwardly towards said first position; the tip member being arranged for radial movement in said body and the combina-tion of said resilient means and said radial movement being such that a reduction in likelihood of dart bounce is achieved;

said resilient means exerting on said tip member a biasing force such that, upon impact of the dart on a dart board with attendant deceleration of said tip member, said body can move forwardly relative to said tip member until said tip member occupies said second position, said biasing force and the distance between said first and second positions being such that said tip member may penetrate a dart board even when the tip member encounters an obstruction having the characteristics of a target-defining wire on the surface of the dart board.
21. A dart as claimed in claim 11, wherein said chamber defines a first radial wall away from said one end and a second radial wall toward said one end, said walls being spaced from one another axially of said chamber, and wherein said spring is mounted about said tip member between said first wall and said raised portion to bias said tip member toward said second wall.
22. A dart as claimed in claim 1, including further stop means restricting movement of said tip member away from said one end.
23. A dart as claimed in claim 22, wherein said body defines a bore in which the tip member is slidable, and wherein said bore is enlarged to form a chamber having a first radial wall away from said one end and a second radial wall towards said one end, said walls being spaced from one another axially of said chamber and acting as said first mentioned and said further stop means.
24. A dart as claimed in claim 23, wherein said resilient means comprises: a raised portion on, and solid with, said tip member and a spring mounted about said tip member between said first wall and said raised portion to bias said tip member towards said second wall.