US 3455244 A
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y 1969 K. BALLREICH ET AL 3,455,244
SHOCKPROOF PRIMER COVER Filed Sept. 22, 1967 INVENTORS KURT BALL REICH HELLMUT BENDLER HEINZ GAWLICK BY g ATTORNEYS 3,455,244 SHOCKPROOF PRIMER COVER Kurt Ballreich and Hellmut Bendler, Nuremberg, and Heinz Gawlick, Furth, Germany, assignors to Dynamit Nobel Aktiengesellschaft, Troisdorf, Germany Filed Sept. 22, 1967, Ser. No. 669,796 Int. Cl. F42c 19/08 US. Cl. 102-865 9 Claims ABSTRACT OF THE DISCLOSURE -A shockproof primer with the primer charge covered by a cup-shaped cover of synthetic material, preferably a thermoplastic such as polyethylene, where the cover has a central area resting flush upon the upper surface of the primer charge and has an oppositely extending annular portion projecting axially beyond the cup containing the primer charge so that the positive clamping effect will be upon this annular portion. The cup-shaped cover may have a central aperture covered by a foil of synthetic material, for example, or the like.
BACKGROUND OF THE INVENTION In firearms having a high breech mechanism speed and correspondingly high acceleration values in regard to introducing the cartridge into the cartridge chamber, the detonator or primer of the cartridge is exposed to very high stresses with respect to the so-called shock safety. Under these conditions, it is easy for the primer charge to crumble and fall out so that a premature firing can occur. In an attempt to avoid this unsafe situation, it has been the practice to compress the primer composition to a great extent and cover it by a metallic foil which has been coated with a more or less thick layer of lacquer or varnish to obtain good adhesion between the foil and the primer charge, as well as achieving a good rim seal. Experience has shown that a sufficient resistance against shock is not attained in every case with this known type of construction.
SUMMARY OF THE INVENTION It is an object of the present invention to provide a shockproof primer for insertion into a cartridge that will resist the high acceleration of the breech mechanism and other shocks, for purposes of safety and preventing misfiring.
According to the present invention, the primer charge is held within the primer cap by means of a cup-shaped cover of synthetic material, preferably a thermoplastic synthetic material, for example polyethylene. The cover is provided with a central area that rests flush on the upper surface of the primer composition and is held against the primer composition and primer cap by means of a substantially cylindrical rim or annular projection, which axially projects beyond the primer cap to receive the positive clamping effect when inserted in a cartridge.
The shockproof covering is also ensured when, according to a further variation of the present invention, the central area of the cover is provided with a central opening, when a cylindrical configuration is involved, and a thin cover foil of plastic, paper or the like is mounted between the cover and the primer charge to close the opening.
Further objects, features and advantages of the present invention will become more clear from the following detailed description of several preferred embodiments illustrated on an enlarged scale in the attached drawing.
3,455,244 Patented July 15, 1969 BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 illustrates an electric primer operating according to the aperture principle and having a cover held by the clamping effect according to the present invention;
FIGURE 2 illustrates a primer that is identical with the primer of FIGURE 1, except that the cover is differently constructed and is provided with a positive snap type of mounting with respect to the primer cap;
FIGURE 3 shows a substantially identical primer, but with an oflset stepwise mounting between the cover and the cap; and
FIGURE 4 shows a primer substantially identical to FIGURE 1, but with a central aperture in the cover and having a protective foil between the cover and primer composition.
DETAILED DESCRIPTION OF THE DRAWING The electric primer of FIGURE 1 is substantially symmetrical about an axis that is vertical with respect to the position in the figure. The primer employs an outer case 'that is tubular and has inwardly directed annular flanges at its opposite axial ends. Insulation 2 electrically isolates the pole piece 3 that forms a button to the case. The electrically connected primer composition 4 completes an electric circuit from the electrically conductive pole piece 3, through the primer composition 4, the intermediate electrically conductive ring 5 and to the electrically conductive case 1. The elements 1, 2, 3 and 5 form a primer composition receiving cup having an annular wall, bottom and a mouth axially opposite from the bottom.
Once the primer composition has been introduced into the receiving cup during assembly, the mouth of the cup is closed by means of the cover 6 that is substantially the same diameter as the intermediate ring 5, with allowance being made for the desirable interference fit between the slightly elastic material parts; thus, the primer composition is securely held within the receiving cup. The substantially cylindrical rim or annular projection 7 of the cup-shaped cover 6 axially extends outwardly beyond the receiving cup or case 1. When the primer is inserted into the bottom opening of a cartridge case to form a complete cartridge (the cartridge case not being shown), the clamping effect is upon the rim or projection 7 and correspondingly upon the primer charge 4 so that the primer charge cannot possibly crumble out or become dislodged even under extremely high stresses. This is true even though the cover 6 is only held in the intermediate ring 5 by means of a weak clamping efiect. Also, the elastic cover cap 6 acts as a shock absorber to buffer any jolts upon the pole piece 3 which could lead, under certain circumstances, to an accidental ignition of the primer composition 4.
The primer of FIGURE 2 is substantially identical to the primer of FIGURE 1 except for the connection between the cover 6 and the intermediate ring 5. The cover 6 and the intermediate ring 5 are positively locked together by means of a groove 8 in the internal surface of the ring 5 and an annular collar 9 projecting outwardly from the cover 7. The cross sectional complimentary configuration of the groove 8 and collar 9 provides a snap action during assembly so that the elastic cover 7 may be pushed into the ring 5 with the wedge or cam-shaped collar 9 being elastically deformed inwardly until it snaps into the groove 8 to form the positive interconnection. The support of the cover 7 is obtained by the clamping effect receiving annular rim 7 in the same manner as in the primer according to FIGURE 1.
The primer according to FIGURE 3 is similar to the primer of FIGURE 1, but employs a smaller charge of primer composition in a correspondingly stepped cover that has approximately the same sized rim for receiving theclampingforce. Thecover clamp 6 is tightly clamped.
into the intermediate ring by means of a force fit with its cylindrical rim 7. The primer according to FIGURE 3 differs from the primer of FIGURE 1 in that the cover rests with an additional, step-wise offset annular portion 10 and at its front face on the intermediate ring 5 and is thus accurately located in the desired position. As in the perceding variations, the cover 6 of FIGURE 3 projects axially beyond the case 1 with an approximately cylindrical,' annular or similarly formed projection 11 to receive the clamping force for transmission to the primer charge The covers 6 shown in FIGURE 1 and 2 have annular beads on their inside surface for reinforcement. The cover 6 of FIGURE 3 has an additional stepwise offset 12 at its bottom for purposes of reinforcement to increase the strength and rigidity of the composition engaging the bottom wall of the cup-shaped cover. Of course, the present invention may be broadly practiced with a cover that does not have reinforcements.
The primer receiving cap and primer composition 4 of FIGURE 4 is identical to the corresponding parts in FIGURE 1. The cover 6 of FIGURE 4 is provided with a central aperture 13 that is preferably cylindrical. A thin cover plate 14 of foil like material, preferably synthetic material, for example paper or the like, is provided between the cover 6 and the primer charge 4 to seal the aperture 13. With such a construction, the cap 6 may be constructed with relatively thick and rigid bottom wall without impairing the detonation of the propellant charge (not shown), because the ignition will be transferred through the aperture 13.
With reference to FIGURES 1-4, the broad aspects of the present invention may be practiced without the use of the intermediate ring 5, which could therefore be omitted with the primer charge 4 and the cover 6 directly engaging the case 1. In such a construction, the inwardly directed flange of the case 1 holding the intermediate ring 5 would similarly be omitted.
Although the specific aspects of the present invention have been illustrated with regard to electric primers, it is to be understood that the broad aspects of the present invention may be employed with other primers, for example percussion primers. If the teachings of the present invention are employed in percussion primers, a metallic case is not required and the primer composition receiving cup may be of a unitary single piece construction of synthetic plastic material, or the like.
Similarly, the broad aspects of the present invention may be practiced with covers of different shapes and materials. Preferably, thermoplastic and thermosetting synthetic materials are desired, depending upon their properties. It is particularly desirable to use readily meltable, flammable or combustible synthetic plastics so that, if at all possible, no undesirable residues will remain in the cartridge chamber or barrel of the weapon. Non-melting metallic covers are particularly undesirable because they may pass through the flash vent into the barrel of the weapon.
While several specific preferred embodiments of the present invention have been set forth in detail for purposes of illustration, it is to be understood from the above briefly mentioned variations that further variations, modifications and embodiments of the present invention are contemplated.
A We claim:
1. YA primer, comprising: a substantially cup-shaped v.primer receiving body having a generally tubular wall in the cup-shaped body against breech mechanism shocks and the like, said tubular projection being constructed of elastic synthetic material to constitute shock absorber means for elastically deforming in the axial direction to absorb shocks and impacts from axially applied forces and prevent unintentional ignition of said primer composition, and said cover further including a synthetic web portion completely sealing and homogeneously one piece with the end of said tubular projection adjacent said primer composition, said web portion being readily rupturable by ignition of said primer composition.
2. The primer of claim 1, wherein said cover is composed of thermoplastic polyethylene.
3. The primer of claim 1, wherein said tubular wall and said bottom wall are axially rigidly connected together; said tubular wall and said cover including means connecting them together for relatively easy axially movement of said cover toward said bottom wall to constitute said cover and tubular wall, piston and cylinder means for compressing said primer composition in response to a force received by said projection.
4. The primer of claim 1, wherein said tubular projection increases in radial thickness toward said primer composition for the majority of its axial length to provide greater elasticity at its end opposite from said primer composition.
5. The primer of claim 4, wherein said cover is composed of thermoplastic polyethylene.
6. The primer of claim 4, wherein saidcover is composed of a synthetic material readily meltable by the burning of said primer composition.
7. The primer of claim 4, wherein said cover is composed of a synthetic material readily combustible by the burning of said primer composition.
8. The primer of claim 1, wherein said cover is composed of a synthetic material readily meltable by the burning of said primer composition.
9. The primer of claim 1, wherein said cover is composed. of a synthetic material readily combustible by the burning of said primer composition.
References Cited UNITED STATES PATENTS 2,960,032 11/1960 Sahlin l02-46 3,090,310 5/1963 Peet et al 10286.5 X
3,363,565 1/1968 Walther 10286.5 X
I FOREIGN PATENTS 1,082,044 12/ 1954 France.
BENJAMIN A. BORCHELT, Primary Examiner GERALDH. GLANZMAN, Assistant Examiner