US2145508A - Bladed projectile - Google Patents

Description

. Jan. 31, 193.9.r lPTE. J. DENolx 2,145,508 l BLADED'PROJECTILE .Fired Dee. 27,. 1957 Patented Jan. 3l, 1939 D STTES PATENT orifice amplio raoJao'rrLE Application December 27, 1937, Serial No. 181,973 In Switzerland `anuary 4, 1937 3 Claims.

This invention relates to bladed projectiles of all types. intended to be discharged from a launching device, or dropped from a certain height to fall on the ground, as is the case with aerial bombs.

It has already been proposed to provide such projectiles with oblique, preferably helical, blading, with a view to imparting a gyratory motion about their longitudinal axis, during the trajectory, for the purpose of attaining a high rotational velocity and of adding the eiect of gyroscopic stabilization to that of feathering.

The present invention contemplates making the pitch of the screw, or equivalent surface, in relation to the axis ofthe elongated projectile suilclently slight to render the increased resistance of the preferably helicoidal blading negligible by comparison with that of straight blading, and by the gyroscopic eect having a stabilizing action which is almost nil.

Experience shows that the eiTect of the low rate of gyration thus imparted to the projectile is to counteract any asymmetry of the latter and, in the particular case of a projectile propelled by a reaction fuse, to nullify the adverse effects resulting from any divergence there may be between the direction of impulse of the propulsive fuse and the geometrical axis of the projectile. A notable improvement in precision results.

Owing to the low pitch angle of the blades forming the screw, thedragisgpractically the same as with straight blades, so that, the braking effect due to the curvature being almost nil, the range is not reduced in comparison with that of a projectile feathered with straight blades.

Finally, the angular velocity is sufficiently low to allow the bladesl to continue to play their part as aerodynamic stabilizers, without the gyroscoplc effect produced interfering therewith and a'ecting the stability during ight.

Further features and advantages of the invention will appear from the following description taken in conjunction with the accompanying drawing which illustrates diagrammatically and by way of example two embodiments thereof and in which:-

Figs. land 2 are, respectively, a section and an elevation of one embodiment provided with a propulsive fuse or jet propulsive device in its forward portion;

Fig. 3 is a rear elevation of the bieding;

Fig. 4 is a projection, on a horizontal plane, of the trajectory of a self-propelling projectile with straight blading, on ,which-as is almost inevitable-the manufacturing tolerances and the slight (Cl. IGZ-32) imperfections in machining or assembling, may produce an asymmetrical effect causing a systematic deviation of the projectile in relation to the line of iire;

Fig. 5 shows the trajectory of the same projectile equipped with blading in accordance with the invention, and in which the same asymmetric effect would exist.

In the case of Fig. 4, the deviation of the trajectory in relationfto the line of fire is evident, whilst in the case of Fig. 5 a sinusoidal trajectory is maintained along the line of lre as a result of the rotation.

Fig. 6 is a ection through a further embodiment, in whic the propulsive fuse is in the rear.

Fig. 7 is a known curve, giving the value of the drag effect of the blading as a function of the pitch angle of the screw.

I'he elongated projectile shown in Figs. 1 and 2 comprises a body, the forward portion I of which accommodates a propulsive reaction charge 2 intendedto escape into the atmosphere through l vents 3, whilst the rear portion 4, separated from the front portion I by a partition 5, contains the ciensive charge 6, which is explosive or of any other nature. 'l denotes the driving bands, of known type, which are provided on the projectile when it is fired from a smooth-bore gun.

According to the present invention, the projectile is provided, on the rear end, with incurved or helical blading or vanes 8. 'I'he pitch angle is exaggerated inl the drawing, for the sake of clearness. It is preferably below 4 degrees.

When the resultant of the reactive thrusts of the gases issuing from the vents 3 does not coincide with the axis :zz-ag the projectile would, if tted with straight blading, tend to deviate from the line of re F, in the manner shown by the line Y in Fig. 4.y

With blading in accordance with the invention the trajectory however assumes the general form y of a spiral, as shown by the line Y' in Fig. 5,

which represents the projection of said spiral on a horizontal plane. The projectile oscillates on both sides of the trajectory corresponding to a perfect projectile, but maintains its general initial -larity in their discharge.

The projectile shown in Fig. 6 is similar to that described with reference to Figs. 1 to 3 except that the vent 3a is located between the blades of the f feathering 8 and is supplied by a propulsive charge housed in the rear compartment 9.

'Ihe slight Obliquity of the blades 8 in relation to the axis z--rc of the projectile, checks the forfward movement to only an insignicant extent, as is evident from Fig. 7, which shows, that for an angle of incidence of 2, the drag of a symmetrical profile is increased by only 10% by comparison with a zero angle of incidence.

Moreover, the gyrational velocity imparted to the projectile by its blading remains too slight to cause it to deviate from the tangent to its trajectory through gyroscopic action, as is the case when, the pitch angle being too great, the ratio between the gyrational velocity and the velocity of translation of the bladed projectile becomes excessive.

The invention applies especially to projectiles red from smooth-bore weapons, mortars, bomb throwers and the like, with or without a propulsive fuse. It also vapplies to aerial bombs, whether propelled, or not, by a fuse.

The invention enables the effect of manufacturing tolerances to be lessened, the action of the blading serving to correct the asymmetries or irregularities which may exist, between one projectile and another, in the distribution ofthe masses, and in the conformation and ilnish of the outer surface, and, in the case of projectiles with a propulsive fuse, in the centering of the vents and in the intensity of their discharge.

It is obvious that Avarious. modifications and alterations can be made in the invention without departing from the scope thereof as dened by the appended claims.

I claim:

1. An elongated projectile having a body and stabilizing varies ixed at the rear part of said body, said vanes being inclined by an angle below 4 degrees in relation to the longitudinal axis of the projectile.

2. An elongated projectile having a body, stabilizing Vanes fixed at the rear part of said body, said vanes being inclined by an angle below 4 degrees in relation to the longitudinal axis of the projectile, and a jet propulsion device in said projectile.

3. An elongated projectile having a. body and helicoidal stabilizing Vanes fixed at the rear part of said body, said vanes being inclined by an angle below 4 degrees in relation to the longitudinal axis f the projectile.

PAUL JOSEPH DENOIX.

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