Patent Publication Number: US-2009229484-A1

Title: Safety cap for small arms cartridge

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to small arms cartridges, and more particularly to a safety device for a small arms cartridge. 
     2. Description of Related Art 
     Even though there has been efforts to educate gun owners regarding the safety issues that arise when a gun may unintentionally be handled by a child, there are occasional accidents that continue to occur. Because even one tragic accidental death or injury is one accident too many there is a need for additional safety devices for small caliber weapons such as shotguns, sporting rifles, handguns and the like. 
     Some approaches to this safety issue have been developed but involve rendering a firearm almost so inoperative that it may be unavailable for self-defense or protection when needed. Additional safety techniques that have been proposed may be effective but can damage firearm in which they are used. Thus, there remains the need for a system that can prevent unwanted firing of ammunition in a weapon but performs in such a way that does not damage the weapon nor make it awkward or impossible to use when needed. 
     In large caliber explosive shells such as those used by the military, it is recognized that the firing cap, or primer, can be a source of unwanted explosion. Thus, there are special boxes and shipping containers that have been developed which allow storing and transporting of these explosive shells in a way that prevents unwanted ignition of the primer. Furthermore, in some instances, the primers are stored separately from the shells in which they will eventually be installed. In this way, the primers can be packed separately and will not cause an unwanted explosion of a shell. However, neither separating the primer from the cartridge nor providing a separate safety container for each round is an economical or viable solution for small arms cartridges such as those used by sport shooters and hunters. Thus there remains the need for an effective, safe, convenient, and economical method to prevent unwanted firing of small caliber cartridges from firearms. 
     BRIEF SUMMARY OF THE INVENTION 
     Embodiments of the present invention relate to a safety cap for a small arms cartridge that fits over the primer end of the cartridge casing and includes a cushioning material and a rigid material. The cap holds the two materials over the primer and prevents a firing pin from igniting the primer; thereby, rendering the cartridge safe. Furthermore, the added circumference around the end of the cartridge will, in most cases, prevent the cartridge from fitting in a magazine or being chambered in the weapon for which it is sized. 
     It is understood that other embodiments of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein it is shown and described only various embodiments of the invention by way of illustration. As will be realized, the invention is capable of other and different embodiments and its several details are capable of modification in various other respects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  depicts an exploded view of a safety cap designed according to the principles of the present invention. 
         FIG. 2  depicts a view of a small caliber cartridge assembled with a safety cap in accordance with the principles of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
     The detailed description set forth below in connection with the appended drawings is intended as a description of various embodiments of the invention and is not intended to represent the only embodiments in which the invention may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without these specific details. In some instances, well known structures and components are shown in block diagram form in order to avoid obscuring the concepts of the invention. 
       FIG. 1  illustrates an exploded view of a small arms or small caliber cartridge having a safety cap designed in accordance with the principles of the present invention. The terms “small arms” or “small caliber” as used herein are intended to pertain to those cartridges that are legally available to sport shooters, home defenders and hunters. They can include, for example, rim-fire cartridges such as .22LR, shotgun shells in a range of gauges, handgun rounds for both semi-automatic pistols and revolvers, and also center-fire rifle cartridges in a range of calibers (e.g., .223 to .50 cal). Unlike high caliber shells like the military uses, these small arms cartridges are manufactured in very high volumes and any safety device must not add significantly to the cost of a single cartridge or it will be difficult to sell. One difference in some of the different cartridges identified above is that the casing in many rifle cartridges taper from the primer end towards the bullet end while, in contrast, the casing of shot shells and many handgun cartridges have relative straight sides along its entire length. The safety cap described herein in accordance with the principles of the present invention is designed to work effectively with either type cartridge. 
     In  FIG. 1 , there is a rifle cartridge  100  that includes a casing  102  and a bullet  104 . The shape of the casing  102  and its material is unimportant to the practice of the present invention. Similarly, the shape and material of the bullet  104  is unimportant to the practice of the present invention. At the bottom, or primer end  106 , there is a center-fire primer  108 . As mentioned previously, the safety cap described herein will also operate with a rim-fire cartridge as well. In such an instance, the primer  108  is around the outside circumference of the primer end  106 . 
     In operation, a firing pin strikes the primer  108  causing it to ignite which operates to ignite the powder (not shown) within the casing  102 . This second explosion is what provides the motive force which propels the bullet  104  out of the muzzle of a weapon. 
     If the primer  108  can be protected from a firing pin, then the cartridge  100  can be prevented from being fired. Thus, the safety cap  110  is provided to serve this purpose. The cap  110  slides onto the primer end  106  of the cartridge  102  holding a cushion  114  and a rigid portion  116  against the end  106  of the cartridge  100 . The cushion  114  and the rigid portion  116  are preferably circular, or disc-like, in construction and are sized to match the diameter of the primer end  106  of the cartridge  100 . 
     The cushion material  114  may, for example, be similar to a sponge or other water-liking material. It serves a dual purpose, first it provides a cushioning effect if a firing pin were to hit the cap  110 . Thus, it provides an added layer that prevents the primer from being struck and it softens the impact on the firing pin itself which helps protect the weapon as well. Furthermore, a sponge-like material will retain moisture and be in contact with the primer end  106  of the casing  102 . Thus, when the cap  110  and the sponge  114  are removed from the cartridge  100 , rust will likely be present if any moisture entered the cap  110  sometime in the past. Knowing that a cartridge has been exposed to moisture is important so that the cartridge  100  can be discarded thereby preventing a misfire or dry fire in a critical situation. As for thickness, the sponge  114  may be around ⅛ th  inch thick. Depending on the resiliency of the material and how much shock absorption it provides, different thickness may be utilized as well. 
     The rigid portion  116  is preferably a metal such as aluminum or steel. This material provides the main protection against the firing pin striking the primer  108 . Other metals and even composite materials may be used but the cost and strength must be balanced so that the safety cap can be provided in an effective yet economically viable manner. As for thickness, 1/16 th  inch thick steel would be effective and inexpensive. One of ordinary skill, however, will readily recognize that different materials and different thicknesses may be used without departing from the scope of the present invention. 
     Holding the cushion  114  and the rigid portion  116  against the cartridge  100  is the safety cap  110 . This material is preferably a plastic that has some resiliency such that it is deformable to fit over the cartridge and yet fit snuggly as well. This will allow the safety cap  110  not only to hold the components which prevent unintentional firing of the cartridge  100  but will also provide a barrier against moisture reaching the primer  108 . Because cartridges  100  may be stored for a long time in environmental conditions that can sometimes be harsh, the material of the cap  110  must be such as not to easily degrade. Many plastics, vinyls, synthetic rubbers are available for this purpose, and can be selected from, in order to construct the cap  110 . The color of the cap  110  may vary as well. If it is colored to closely match the color of the casing  102 , then a child may not even be aware that the safety cap  110  is present (and, therefore, will not think of it as something to remove). Alternatively, the safety cap  110  may be brightly colored or distinguishably colored so that a user will quickly recognize that the cartridge will not fire without the safety cap  110  being removed. 
     As for the length of the cap  110 , it preferably fits about a third of the way up the cartridge casing  102 . This amount of length provides a firm grip on the cartridge casing  102  thereby preventing the cap  110  from accidentally slipping off while utilizing material economically so as not to make the cap  110  overly long with no additional benefit. 
     The cartridge  100  is manufactured in a conventional manner; thus, the safety cap  110  does not interfere or change the normal manufacturing process of the cartridge maker. The cap  110  and the other portions  114 ,  116  may be manufactured separately and then the two combined in a later manufacturing step. For example, a completed cartridge may be forced into the cap  110  in an assembly line fashion as the last step in manufacturing. To aid such insertion, the cap  110  may be warmed so that it is more pliable and will shrink to a tight fit when it cools. Also, the cap  110  may be lightly lubricated on the inside to aid in insertion of the cartridge  102  (the cartridge may be lubricated as well for this purpose.) Although it is possible to heat the plastic cap  110  to help it shrink fit to the casing  102 , this should be done with caution so as not to inadvertently ignite the primer  108 . 
     Alternatively, the sponge  114  and rigid portion  116  may be lightly tacked in place on the end of the cartridge  100  which is then dipped into a liquid plastic. When the coated cartridge is then removed, the liquid plastic will form a hardened shell that serves as the cap  110 . 
     The safety cap  110  (along with the cushion  114  and rigid portion  116 ) may also be sold separately to users who can then retrofit conventional cartridges that they purchase separately. The user would simply force the cartridge into the safety cap  110  to take advantage of its benefits. 
       FIG. 2  illustrates a completely assembled cartridge  200  having an installed safety cap  110 . This cartridge  200  will have a length and circumference at the primer end that is slightly larger than that of the conventional cartridge  100 . Thus, it will be nearly impossible for the cartridge  200  to be chambered in a weapon it is sized for or even fit within a magazine sized for its caliber. While it is possible for a small round (e.g., .22LR) that has the safety cap  110  installed to be chambered in a bigger caliber weapon (e.g., .38 Special), the rigid portion and sponge will still continue to prevent the firing pin from striking the primer of the cartridge. 
     In order to successfully fire a protected cartridge  200 , the safety cap  110  must be removed. While it is possible to use a plastic that will easily tear without assistance, a pull tab  112  along with perforations is preferably manufactured into the safety cap  110 . The user, then, would simply pull on the tab  112  which would rip along the perforations to allow the cap  110  to be removed along with the cushion  114  and rigid portion  116 . Once these are removed, the cartridge will function as intended. The perforation can extend the entire length of the cap  110  or just a significant portion of its length so as to allow the cap  110  to be easily removed. 
     The previous description is provided to enable any person skilled in the art to practice the various embodiments described herein. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments. Thus, the claims are not intended to be limited to the embodiments shown herein, but are to be accorded the full scope consistent with each claim&#39;s language, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” All structural and functional equivalents to the elements of the various embodiments described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. §112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for.”