US 3710723 A
A tracer projectile comprising a body having a rearwardly open recess with a pyrotechnic pack in the recess. The shell of the pack is located with radial clearance inside the recess. There are cooperating annular coned faces on the shell and in the recess. A threaded steel ring is screwed into the recess to the rear of the shell so that the axial thrust of the threaded ring on the shell will cause the pyrotechnic pack to be axially aligned by the cooperation of the annular coned faces. The threaded ring is provided with said radial slots on its side facing the shell.
Claims available in
Description (OCR text may contain errors)
rte States Patent 1 Muller et a1.
[ 51 Jan. 16,1973
 TRACER PROJECTILE Werkzeugmaschinenfabrik Oerlikon-Buhrle AG, Zurich, Switzerland  Filed: July 24, 1970 ] Appl. No.: 57,978
 Foreign Application Priority Data Aug. 5, 1969 Switzerland ..11860/69  References Cited UNITED STATES PATENTS 1/1960 Barker ..102/90X 4/1970 Grolly ..102/87X 3,272,126 9/1966 Edelman et al 102/90 X 3,473,472 10/1969 Bliss et al ...l02/87 X 1,875,985 9/1932 Brandt 1 ..102/90 1,105,849 8/1914 Semple... 102/56 3,532,056 10/1970 Irion ..102/56 3,176,617 6/1962 Brafford ....102/24 R 3,487,780 1/1970 Troen et a1. ...l02/87 X Primary Examiner-Benjamin A. Borchelt Assistant Examinerl-l. J. Tudor Attorney-Wenderoth, Lind & Ponack  ABSTRACT A tracer projectile comprising a body having a rearwardly open recess with a pyrotechnic pack in the recess. The shell of the pack is located with radial clearance inside the recess. There are cooperating annular coned faces on the shell and in the recess. A threaded steel ring is screwed into the recess to the rear of the shell so that the axial thrust of the threaded ring on the shell will cause the pyrotechnic pack to be axially aligned by the cooperation of the annular coned faces. The threaded ring is provided with said radial slots on its side facing the shell.
3 Claims, 1 Drawing Figure PATENTEDJAN 16 I975 3.710.723
I III l g I l2 5 iii l3 Attorneys TRACER PROJECTILE The invention relates to a tracer projectile comprising a projectile body which contains a rearwardly open recess for a pyrotechnic pack.
In a tracer projectile of the specified kind already known in the art the pyrotechnic pack is screwed into the rear end of the body of the projectile. The rear end of the shell of the pack has a flange-like enlargement of its external diameter that conforms with the caliber of the projectile. The enlargement extends the external contours of the projectile body. In this known tracer projectile the body of the projectile and the pyrotechnic pack must be exactly coaxial since otherwise difficulties would arise in fitting the cartridge to the projectile. By pressing the pyrotechnic charge into its shell the latter may be expanded, in which case the external threads on the pyrotechnic pack will no longer fit the internal threads in the body of the projectile. Since the body of the projectile and the pyrotechnic pack usually consist of different materials the screw connection also prevents thermal expansion between the two parts. Finally, the pyrotechnic pack may frac-' ture and splinter when exposed to the effect of the propellant gases when the tracer projectile is fired, and a muzzle velocity attachment on the barrel could also suffer damage.
It is the object of the present invention to eliminate the drawbacks of the prior art tracer projectile. Ac-' cording to the invention this is achieved by locating the pyrotechnic pack with radial clearance inside the recess, providing the pack and the recess with cooperating annular coned faces and by screwing a threaded ring into the open end of the recess to the rear of the pyrotechnic pack in such manner that the axial thrust of the threaded ring applied to the pyrotechnic pack will result in axial central alignment by virtue of the cooperation of the coned annular faces.
An embodiment of the proposed tracer projectile will be hereunder more particularly described with reference to the accompanying drawing.
A screw joint 2 connects the body 1 of a projectile to its cap 3. To the rear of the cap 3 the body 1 of the projectile is provided with' a cavity 4 which may contain, for instance, a blank charge. A recess 5 extending into the body of the projectile from the rear comprises a forward portion 5a and a relatively enlarged rear portion 5b. The transition between the two portions 5a and 5b is formed by a coned surface 6. The shell 7 of a pack containing a pyrotechnic charge 1 1 has external dimensions that substantially fit into the recess 5 but leave a small amount of clearance between the shell 7 and the inside wall of the recess 5. A coned face 8 on the shell 7 of the pack bears against a corresponding coned face 6 in the recess 5. The shell 7 is pushed axially forwards by a retaining element 9 in the form ofa screw ring which is insertable into the rear end of the projectile body 1.
This ensures contact between the coned face 6 in the recess and the coned face 8 of the shell which is thus axially aligned. The retaining element 9 has a central hole 16 and radial slots 10 on the side facing the shell 7. Pressed into the shell 7 is a pyrotechnic charge 11 com prising three stages. Behind the charge 11 is an initiating charge 12. Rearwardly the shell 7 is closed by a disc 13 which is held in place by a shim .14 and an interposed sealing ring 15.
The above described tracer projectile functions as follows:
The propellant gases WhlCh discharge the pro ectile punch a hole into the disc 13 and ignite the initiating charge 12 which in turn ignites the pyrotechnic charge 1 1. At the same time the propellant gases enter the gap between the pyrotechnic charge 11 and the inside wall of the shell 7. In order to prevent these gases from partly or completely ejecting the pyrotechnic charge the propellant gases are diverted through the radial slots 10 in the retaining ring 9 into the clearance gap between the body 1 of the projectile and the outside wall of the shell 7. This enables the pressure above the end of the shell 7 to be'fully equalized. If for any reason this pressure equalization should fail and the shell 7 should be fractured, allowing splinters to break away, these will still be prevented from falling out by the retaining ring 9.
The propellant gases are sealed by the cooperating coned faces 6 and 8. These two faces 6 and 8 also function to align the shell 7 centrally inside the recess 5. Consequently very close tolerances between the shell 7 of the pack and the recess 5 are not needed and the shell 7 has freedom to change its dimensions, as usually occurs after the case has been pressed into position. Moreover, that part of the shell 7 which extends forwards of the coned face 8 can freely move inside the bore 50 when it thermally expands under the heat of the burning pyrotechnic charge.
1. A tracer projectile comprising a body having a rearwardly open recess, a pyrotechnic pack in said recess having a shell located with radial clearance inside said recess, cooperating annular coned faces on said shell and in said recess, a threaded ring screwed into said recess to the rear of said shell so that the axial thrust of said threaded ring on said shell will cause said pyrotechnic pack to be axially aligned by the cooperation of said coned annular faces, radial slots provided between said threaded ring and said shell.
2. A tracer projectile according to claim 1 wherein said threaded ring is provided with said radial slots on its side facing said shell.
3. A tracer projectile according to claim 1 wherein said annular coned surface on said shell is provided at the rear end of said shell so that the major part of the shell extends freely into said recess.