RU2117509C1 - Playing dart - Google Patents

Abstract

FIELD: sports equipment. SUBSTANCE: playing dart has collapsible body with needle and shank which are positioned within through opening of body. Feathering with wings is inserted into shank. Wings are positioned in symmetry in central portions of pylons arranged on feathering. Planes of wings are positioned at an acute angle to longitudinal axis of dart whose apex is directed to side opposite needle point. Needle is rigidly connected with shank and made in the form of rod positioned centrally for rotation in longitudinal body opening. Rod has beads engageable with surface of longitudinal body opening. EFFECT: improved quality and increased entertaining effect. 2 cl, 3 dwg

Description

 The invention relates to equipment for sports games such as "Darts", and more particularly, to a projectile designed for manual throwing at a target at short distances.

 Game darts for hand-throwing targets at close distances consist of an axisymmetric body, as a rule, of a heavy alloy located in front of it with a pointed tip (needle) with a diameter significantly smaller than the diameter of the body, and a shank, on which it is fixed in the grooves, as as a rule, a removable X-shaped plumage designed to stabilize the dart when flying to the target.

 The X-shaped plumage for a dart is known, consisting of four radial blades (wings) that provide aerodynamic stability of the dart and protect its shank from direct hit by another dart (US Pat. Nos. 4,583,745, CL 273 - 423, 1986 and Great Britain N 2166059, Cl. A 63 B 65/02, 1986).

 The plumage is made of lightweight elastic material and can be folded due to elasticity to reduce volume during transportation and storage. Since the plumage thickness is small and, as a rule, is 0.15-0.20 mm, it is obvious that when preparing the plumage before throwing a dart, it is difficult to ensure its geometrically ideal arrangement in two perpendicular planes intersecting at a given angle.

 In addition, due to the inaccuracy of the installation and manufacture of the plumage and shank, the line of intersection of the wings of the plumage is always located at a certain angle to the axis of the body of the tip and the shank of the dart.

 All this leads to the fact that in flight, after throwing a dart, he receives additional disturbances from the plumage that are not related to the inaccuracy of the throw, as a result of which an additional miss, independent of the player’s skill, appears.

 The plumage for a sports bow arrow is known to be rigidly mounted on a support blade that extends radially from the front of the boom body and is slightly bent in a spiral to twist the arrow in flight (US patent N 3756600, CL 273 - 106.5, 1973). The twist of the boom, as well as other unguided missile projectiles, provides averaging of the mass and aerodynamic asymmetries of the structure, which reduces their dispersion for reasons beyond the control of the player or missile device.

Such a solution for spinning the dart for the Darts game is unacceptable, since it increases the dimensions of the dart, shifts the center of its aerodynamic pressure forward, which reduces its aerodynamic stability. In addition, due to the small distance at which the dart is thrown in the Darts game (2 - 2.5 m), and the relatively large moment of inertia J _x with respect to the possible aerodynamic torque M _x from the spiral or oblique tail, the dart will have time to turn around its longitudinal axis.

 The design of the dart adopted for the prototype (US patent N 4101126, CL 273-95, 1978), consists of a housing and a rigidly attached shank with radial plumage, a spring-loaded needle with the possibility of deflection in radial planes. The deflecting needle is designed to reduce the likelihood of a javelin bouncing when it hits the target’s wire marking traditional for the Darts game: the needle, as it were, bends around the marking reinforcement, sliding over it, and penetrates the target.

 However, with a weak throw or with a throw at a large angle to the axis of the target, poor adhesion of the tip to the target is often observed, which can lead to insufficient penetration of the dart into the target and its fall.

 The deviating needle, due to its compliance, precisely at large angles of approach, can even worsen the penetration of the dart into the target, since part of its kinetic energy is spent on deformation of the spring holding the needle.

 The aim of the invention is to reduce that part of the miss when throwing a dart, which is due to an asymmetric plumage installation and deformation of the plumage wings, as well as an increase in its adhesion to the target due to the rotation of the tip during its introduction into the target.

 Both of these goals are achieved by the fact that constructive measures provide for repeated rotation around the own axis of the plumage and the needle during the flight to the target (from the moment the dart is thrown to its full penetration into the target), as a result of which the aerodynamic disturbing moment vector acting on the dart due to a defect the shape and inaccuracies of the plumage installation is averaged, and the dart needle goes deeper, as if it is screwed, as a rule, into the pliable pliable layer of the target, increasing the dart's adhesion to the latter.

, касательной к поверхности иглы и перпендикулярной вектору продольной скорости полета V, где

и r - угловая скорость вращения и средний радиус иглы соответственно. Векторное сложение продольной (основной) и тангенциальной (дополнительной) скоростей дает, что суммарная скорость внедрения иглы (скорость скольжения внешней поверхности иглы)

.An increase in the penetration depth of a rotating dart needle compared to a non-rotating one can be explained by the fact that the needle penetration rate increases due to the tangential component of the velocity

tangent to the surface of the needle and perpendicular to the vector of longitudinal flight speed V, where

and r is the angular velocity of rotation and the average radius of the needle, respectively. Vector addition of longitudinal (main) and tangential (additional) speeds gives that the total needle penetration rate (sliding speed of the outer surface of the needle)

.

The tip and plumage are rotated by installing the plumage wings at a certain angle δ to the longitudinal axis of the dart, which ensures the appearance of lift force in flight on the wings and, as a result, the aerodynamic torque M _x around the longitudinal axis of the dart.

, а угол проворота φ прямо пропорционален крутящему моменту M_x и обратно пропорционален моменту инерции J_x вращающейся части дротика относительно продольной оси, где ρ - плотность воздуха. С учетом небольшого (2 - 2,5 м) расстояния до мишени и специфики иглы скорость полета дротика V невелика и может меняться в зависимости от мастерства игрока в незначительных пределах, в то же время момент инерции J_x можно существенно уменьшить, вращая не весь дротик целиком, а возможно меньшую часть его и тем самым существенно увеличить угол поворота оперения φ .The value of M _{x is} directly proportional to the pressure head

, and the rotation angle φ is directly proportional to the torque M _x and inversely proportional to the moment of inertia J _{x of the} rotating part of the dart relative to the longitudinal axis, where ρ is the air density. Given the small (2 - 2.5 m) distance to the target and the specifics of the needle, the speed of the dart V is small and can vary slightly depending on the skill of the player, but at the same time, the moment of inertia J _x can be significantly reduced by not rotating the entire dart as a whole, and possibly a smaller part of it, and thereby significantly increase the angle of rotation of the plumage φ.

 In the present invention (Fig. 1), the rotating part of the dart is a needle 1 and a spindle 2, made in the form of a single rod, on which, for example, a shank 3 with a tail unit 4 is fastened with a thread. An axisymmetric through step hole is made in the housing 5 in which the specified rod is located. The contact of the rod and the housing is carried out through the inner surface of the hole and the side and end surfaces of the shoulders 6 and 7. To reduce the reactions, and therefore the friction moment acting on the rod from the side of the housing in flight, the collars are maximally (as far as the length of the housing allows) spaced . In order that the rod does not fall out of the body during throwing and in flight, the end openings have a diameter smaller than the diameter of the shoulders. Thus, the front end of the shoulder 6 prevents the movement of the rod relative to the housing forward, and the rear end of the shoulder 7 prevents it.

 To carry out the assembly of the dart, its body is made of two parts joined together, for example, using thread or friction.

In the proposed design, in order not to complicate the mounting unit of the plumage and not to increase the moment of inertia of the liner J _x , to create a torque, four plane wings of the tail of a trapezoidal, oval or other shape are centrally symmetrically mounted on four mutually perpendicular pylons of a triangular or trapezoidal shape, fixed, for example, in the cruciform slot of the shank, while the plane of each wing and the line of connection of its root chord with the adjacent pylon form a sharp dart with the longitudinal axis goal δ with a vertex facing the side opposite the needle tip (an isometric view of the plumage is shown in Fig. 2). It should be noted that, due to aerodynamic restrictions, the angle δ must not exceed the critical angle of attack α _kp , and in order for the plumage to minimize the obstruction of the target for the next dart, it must have a minimal projection onto the plane of the target. Due to these considerations, as well as due to the mass-inertial characteristics and design features used for playing darts, the rational value of the angle δ should lie in the range of 5 - 10 ^o .

(1/с) вращающейся части дротика.The proposed design of the dart makes it possible to provide at least two turns of the operation and the tip during the flight of the dart at a distance of ≈ 2 m at a throwing speed of 5 to 10 m / s. For the indicated distances and throwing speeds, as an example in FIG. Figure 3 shows the calculated dependences of the rotation angle φ (in radians) and the angular velocity on time t

(1 / s) of the rotating part of the dart.

The following parameters close to the parameters of sports darts were taken as initial data in the calculations:
rod length (needle with shank) - 150 mm;
rod diameter - 2 mm;
core material - steel;
plumage weight - 0.5 g;
the thickness of each of the four wings of the plumage - 0.2 mm;
the installation angle of each of the four wings δ = 5 ^o ;
wing shape (1: 1 scale) is shown in FIG. 3;
the distance from the aerodynamic focus of the wing to the shoulder 6 L ₆ = 70 mm and to shoulder 7 - L ₇ = 60 mm;
flange diameter - 2.8 mm;
the coefficient of friction of the surface of the beads and the surface of the housing - 0.15;
dart angle of attack α - 10 ^o ;
the movement of the dart in the speed-gaining section (in the hand) 0.5 m long - uniformly accelerated;
flight over a distance of 2 m with a constant speed V for a time t = 2 m / V;
wing lift coefficient C _y = 0.154;
atmospheric parameters are normal.

 As can be seen from the graph, a twofold increase in the speed of throwing a dart from 5 to 10 m / s leads to an increase in the rotation angle by about two times for the same flight time.

 Therefore, if we consider the angle of rotation as a function of the distance flown by the dart, then it is almost independent of the throwing speed.

 Thus, the proposed design of the dart allows, irrespective of the throwing speed, to reduce that part of the miss due to the natural asymmetric shape and the installation of an easily deformable plumage, as well as to increase the adhesion of the dart needle to the target due to its rotation during insertion into the latter, i.e. improve the performance of sports darts.

 Testing prototypes of darts of the described design confirmed their increased aerodynamic qualities and better adhesion to the target.

Claims (2)

 1. A game dart, in the through longitudinal hole of the assembly case of which, consisting of two coaxial parts rigidly interconnected, a needle and a shank are placed, into which a plumage is inserted, having wings, characterized in that pylons are made on the plumage, on which are centrally symmetrically mounted the said wings, and the plane of the wings are at an acute angle to the longitudinal axis of the dart, the apex of which is directed to the side opposite to the tip of the needle, the latter being rigidly connected to the shank and made in the form of a central rod mounted rotatably in said longitudinal opening of the housing, wherein the flange is made of flanges designed to interact with the surface of said longitudinal opening of the housing.  2. The dart according to claim 1, characterized in that the rod is installed with the possibility of interaction of the beads with a cylindrical and end surfaces that limit the through longitudinal hole of the housing.

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