Abstract:
A strong, durable, lightweight long gun stock comprising a rigid insert molded of reinforced thermoplastic material together with a foaming agent. The insert is over-molded with a thermoplastic material which provides the stock with the desired surface characteristics. The insert is dimensioned with respect to its over-molded surfaces to be smaller than the finished stock and is designed to give maximum strength to the stock. The insert is shaped to promote the flow of the over-mold material and to minimize shrinking, swelling or distortion of the insert. The over-mold material may be a hard, un-foamed material or a thermoplastic elastomer. The hard un-foamed over-mold material mechanically bonds with the insert and provides the stock with an extremely smooth, hard outer surface. The thermoplastic elastomer over-mold material is compatible with the material of the insert and bonds both mechanically and chemically with the insert, providing the stock with a soft, quiet, non-slip surface.

Description:
TECHNICAL FIELD 
     The invention relates to a stock for a long gun, and more particularly to such a stock comprising a molded, reinforced plastic insert over-molded with a material which provides the desired outer surface characteristics of the stock. 
     BACKGROUND ART 
     The invention is directed to improved stocks for long guns such as rifles, shotguns and the like. While not intended to be so limited, the invention will be described in its application to a rifle. It will be understood that the basic teachings of the present invention can be applied to stocks for other types of long guns. 
     Prior art workers have devised many types of rifle stocks to better hold and aim a rifle, to reduce recoil, and to improve the comfort and accuracy of a rifle. Heretofore, rifle stocks have been constructed from rigid materials such as wood or plastic. However, wood stocks are easily scratched and can be damaged by water and weather. Molded plastic stocks can be slippery and often have a poor finish due to foam filling. As a result, plastic stocks are frequently painted. 
     Another disadvantage of prior art molded plastic stocks lies in the fact that they produce a hollow, noisy sound when carried through brush or caused to contact some other object. This hollow sound is highly undesirable to hunters, law enforcement personnel, military snipers and the like. Finally, most rifles must be properly fit and bedded to conventional wood or synthetic stocks for maximum accuracy. This is usually a custom process that is sometimes difficult. 
     The present invention is based upon the discovery that a rifle stock, comprising an insert of reinforced thermoplastic material with an appropriate foaming agent, and an over-molded thermoplastic material which determines the characteristics of the stock&#39;s outer surface, can overcome the above-noted problems. When an un-foamed hard material is used as the over-mold material, an extremely hard stock is provided with an aesthetically pleasing, very smooth surface. When a thermoplastic elastomer (TPE) over-mold material is used, the stock is provided with a soft, comfortable, non-slip, and aesthetically attractive surface over the entirety of the stock. The thermoplastic elastomer also serves as a noise insulator which significantly reduces the noise of the stock when carried through brush and the like. The thermoplastic rubber material also reduces the action noise of the bolt which is highly desirable for hunting, police and military applications. 
     Rubberized elastomeric hand gun grips are old and well-known in the art. It will be understood, however, that rifles and hand guns are entirely different in both size and configuration. These differences pose many engineering and technical problems which had to be solved in order to produce the rifle stock of the present invention. These problems and their solution will be set forth hereinafter. 
     DISCLOSURE OF THE INVENTION 
     It is an object of the invention to provide a rifle stock which is both strong and durable, and at the same time is relatively lightweight. 
     It is an object of the invention to provide a stock with a finish superior to that which is possible to achieve in conventional rigid plastic stocks molded by conventional techniques. This is true of both the soft thermoplastic elastomer over-mold and the hard un-foamed material over-mold of the present invention. 
     It is an object of the present invention to provide a stock of exceptional aesthetic appearance. 
     It is an object of the invention to provide a stock which will allow for maximum accuracy by selectively providing adjustable means to free float or pressure bed the rifle barrel. The stock of the present invention may also be provided with hard bedding components strategically integrated into the stock. 
     It is an object of the present invention to provide a more comfortable and secure stock than is achievable with existing designs and conventional construction techniques. 
     It is an object of the present invention to provide a quiet stock which does not possess the noise problems with which conventional hard, synthetic, molded stocks are characterized. 
     Finally, it is an object of the invention to provide a cushioned rifle stock shaped to fit comfortably in the hands and arms of the user. 
     According to the invention there is provided a strong, durable, lightweight rifle stock. The stock comprises a rigid insert molded of reinforced plastic material, together with a foaming agent. The insert is over-molded with a thermoplastic material which provides the stock with the desired surface characteristics. 
     The insert is precisely dimensioned so that its over-molded areas are smaller than the finished stock. The insert is designed to give maximum strength to the stock and is shaped to promote the flow of the over-mold material to minimize joint and weld problems. The insert is designed to minimize shrinking, swelling or distortion of the insert, and to this end is provided with strategically located ribs and appropriate cored areas. 
     When the over-mold material is such as to provide a hard, un-foamed over-mold (such as nylon or the like), the over-mold material mechanically bonds with the insert and provides the stock with an extremely smooth, hard, aesthetically pleasing outer surface. 
     When thermoplastic material of the insert and the over-mold thermoplastic elastomer are both olefin based, the over-mold will bond both mechanically and chemically with the insert and will provide the stock with a soft, quiet, non-slip surface. The surface may be textured to further enhance the grip. Nevertheless, when the user relaxes his grip, the surface will allow manual mobility similar to that offered by a smooth stock. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of the insert of the present invention. 
     FIG. 2 is a top plan view of the insert of FIG.  1 . 
     FIG. 3 is a side elevational view of the complete over-molded stock of the present invention. 
     FIG. 4 is a top plan view of the stock of FIG.  3 . 
     FIG. 5 is a cross-sectional view taken along section line  5 — 5  of FIG.  4 . 
     FIG. 6 is a rear end view of the over-molded stock as seen from line  6 — 6  of FIG.  3 . 
     FIG. 7 is a cross-sectional view taken along section line  7 — 7  of FIG.  3 . 
     FIG. 8 is a cross-sectional view taken along section line  8 — 8  of FIG.  3 . 
     FIG. 9 is a cross-sectional view taken along section line  9 — 9  of FIG.  3 . 
     FIG. 10 is a cross-sectional view taken along section line  10 — 10  of FIG.  3 . 
     FIG. 11 is a cross-sectional view taken along section line  11 — 11  of FIG.  3 . 
     FIG. 12 is a end elevation of the forward end of the stock as viewed from line  12 — 12  of FIG.  3 . 
     FIG. 13 is a side elevational view of the stock of the present invention illustrating textured areas thereon. 
     FIG. 14 is a fragmentary plan view of the stock of the present invention illustrating lugs formed on the insert and serving as adjustable contact areas for adjusting the mounting of the barrel in the stock. 
     FIG. 15 illustrates a bedding block of the present invention. 
     FIG. 16 is a fragmentary view, partly in cross-section, illustrating the bedding block of FIG. 15 mounted within the stock. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     It will be understood by one skilled in the art that, for each type or model of long gun to which the stock of the present invention is to be applied, the finished stock, the insert and the molds must be appropriately designed in accordance with the teachings of the present invention. 
     The exemplary stock of FIGS. 3 and 4 is made of two major parts, the insert and the over-mold, in two steps. In some embodiments additional major parts may be used such as a bedding block, as will be described hereinafter. In the exemplary embodiment, the first step is the injection molding of the insert. The insert is best shown in FIGS. 1,  2  and  5 . The insert extends substantially the length of the finished stock and constitutes the skeleton of the stock. The insert is generally indicated at  1 . The forward portion  2  of the insert comprises a substantially channel-shaped portion adapted to receive the rifle barrel. The channel-shaped portion  2  is provided with a longitudinal rib  3  (see also FIG.  10 ), and a series of transverse ribs  4 ,  5 ,  6  and  7 . The forwardmost end of insert  1  terminates in an end wall  8  defining a curved notch  9  (see also FIG. 12) through which the rifle barrel extends. 
     At the rearward end of front portion  2  there is a planar platform  10  with at least one bore  11  extending therethrough. The purpose of bore  11  will be apparent hereinafter. 
     Rearwardly of interior platform  10  there is an opening  12  defined by a pair of sidewalls  13  and  14 . The walls  13  and  14  lead to the thick grip portion  15 . It will be understood by one skilled in the art that the opening  12  is adapted to receive the action of the rifle and the interior of the opening  12  will be precisely shaped for that purpose. The grip portion  15  leads to the shoulder abutting stock portion  16 . 
     Insert  1  is preferably molded of a strong, reinforced, synthetic material. Any appropriate synthetic material can be used when a hard un-foamed over-mold material is used. When a thermoplastic elastomer over-mold is used, an olefin base thermoplastic material is preferred for the insert because under these circumstances the over-mold material will bond chemically with the insert material. Excellent results have been achieved, for example, with both types of over-mold when the insert is molded of fiberglass reinforced polypropylene. An example of such material is manufactured by DSM Engineering Plastics, Inc. of Evansville, Ind., and sold under the trademark FIBERFIL® and designated J-60/30/E BK223. 
     The reinforced synthetic material is combined with an endothermic foaming agent. The foaming agent enables the molding of thick, lightweight portions of the insert without visible “sink” areas, gross warping, or the like. 
     In addition, the foaming agent helps to minimize or eliminate “joint” and “weld” problems. Welds, for example, are created when portions of molten plastic, traveling in different direction, meet in the mold and solidify. The insert mold must be designed in such a way to overcome this problem so that strong impact resulting from recoil or other forces will not cause a failure in the stock. A preferred way to overcome or minimize flow joints or flow welds is to introduce the material into the mold from one source through a single gate, when possible. On the other hand, the sheer size of the rifle stock, in accordance with conventional molding techniques, would dictate the provision of multiple sources of mold material and multiple gates to guarantee complete fill. Multiple sources and gates, however, potentially cause welds and joints. 
     In the embodiment illustrated in FIGS. 1 and 2, the joint and weld problems were overcome by using the above-noted endothermic foaming agent which, when activated, becomes solvent-like, thereby lowering the polymer viscosity during the injection molding process for the insert  1 . Because of the reduced melt viscosity, a mold could be made with a single gate resulting in the production of stocks free of polymer welds. Rubberized elastomeric hand gun grips are sufficiently small that joint and weld problems are not encountered. With other stock designs multiple gates may be desired or required. 
     The foaming agent also provides the critical advantage of reducing the inserts overall weight. At the same time, the foaming agent enhances the insert&#39;s overall strength by creating essentially a structural “honeycomb” within the insert itself. Excellent results have been achieved with a foaming agent sold by Reedy International of Keyport, N.J., under the trademark SAFOAM® and the designation PE-50. The foaming agent constitutes from 1% to 2% of the synthetic material-foaming agent combination. 
     The insert is designed to give maximum strength to the finished rifle stock. To this end, the insert is strategically ribbed in critical areas. With respect to the exemplary stock of FIGS. 1 and 2, the forward portion of the insert is provided with a longitudinal rib  3  and transverse ribs  4  through  7 . The number of ribs in this area may vary from rifle model to rifle model. The rather thin walls  13  and  14  at the opening  12  which receives the rifle mechanism may also reinforced by ribs. This is shown in FIG. 1 wherein the ribs  17 - 19  are illustrated on wall  13 . It will be understood that the wall  14  is similarly ribbed, one of which is shown at  17   a  in FIG.  2 . 
     In addition, the insert is cored out in critical or thick areas of the insert to reduce warping, excessive swelling or other deformation of the insert. It will be noted, for example, that the shoulder abutting portion  16  of the insert is cored out, as at  20  (see also FIGS. 5,  6  and  7 ). In addition, the grip portion  15  of the insert often constitutes a rather thick area. In some stock designs, to prevent deformation of this part of the insert, the insert may be provided with transverse holes extending inwardly from both sides toward but not through the middle. Such holes on the right side of the insert are shown in FIG. 1 at  21  through  24 . When the molding of insert  1  is completed, the holes  21 - 24  and their counterparts on the other side of the insert are plugged by cylindrical plugs  25  (see FIG.  2 ). 
     The insert  1  is provided with a protrusion  26  beneath the slightly enlarged transverse rib  7  of the forward insert portion  2 . In a similar fashion, a small protrusion  27  is located on the bottom of the shoulder abutting portion  16  of the insert. The mold is configured to provide each of these protrusions with an axial bore. The bores are intended to receive self-tapping sling swivel studs when the stock is completed. Such sling swivel studs are shown in FIGS. 3 and 13 at  28  and  29 . The insert is completed by the provision of two more bores  30  and  31  at the rearward end of the stock. These bores are clearly shown in FIGS. 5 and 6. The purpose of these bores will be apparent hereinafter. 
     As indicated above, the overall insert is precisely dimensioned so that its over-molded areas are smaller than the finished stock. The dimensions are chosen to minimize warpage of the insert and to allow for proper over-molding material flow and bonding. 
     Once the insert  1  has been molded, the next step is to mount the insert in a final mold and injection mold (over-mold) thereon the thermoplastic elastomer. As indicated above, the thermoplastic elastomer should be chemically compatible with the material from which the insert is molded so that a chemical bond occurs between the reinforced synthetic material of the insert and the thermoplastic elastomer of the over-mold. Excellent results have been achieved, for example, with a thermoplastic elastomer provided by Advanced Elastomer Systems of St. Louis, Mo., under the trademark SANTOPRENE®. 
     The side elevational view of FIG.  3  and the top plan view of FIG. 4 illustrate the over-molded insert, generally indicated at  1   a.  The same is true of the longitudinal cross-sectional view of FIG.  5 . FIG. 6 is a rear end view and FIG. 12 is a front end view of the over-molded insert. FIGS. 7,  8 ,  9 ,  10  and  11  are cross-sectional views taken along sections lines of the corresponding number in FIG.  3 . In these Figures, the thermoplastic rubber over-mold is generally indicated at  32 . The rearwardmost end of the stock is over-molded, as clearly shown in FIGS. 5 and 6. Generally, the entire exterior surface of insert  1  is over-molded. Only ribs  3 ,  4 ,  5 ,  6  and  7 , the platform  10  and the interior walls of the opening  12  are not over-molded. 
     It will be understood that distortion considerations due to shrinkage, warpage, outside forces and the like are unique with respect to the over-molded stock. The insert  1  is first molded and minimal shrinkage or warpage may occur and thereafter the insert  1  becomes stabilized. Next, the over-molding places a new thermoplastic material over the already stabilized insert creating stresses not found in single stage molded parts. Reference is made to FIG. 10, for example. The channel of the insert  1  through which the rifle barrel extends is made slightly narrower between the platform  10  and rib  4 , between rib  4  and rib  5 , between rib  5  and rib  6 , between rib  6  and rib  7  and between rib  7  and the end  8 . This initial dimension is shown in broken lines and is indicated at “x”. When the over-mold material  32  is applied to the insert with appropriate heat and pressure, and then is allowed to cool and stabilize, shrinkage of the thermoplastic rubber will tend to open the channel to the desired dimension “y”. It will be understood that the difference between dimensions “x” and “y” in FIG. 10 is exaggerated for purposes of explanation. Since the thermoplastic material of the insert and the thermoplastic rubber are compatible, the materials will chemically bond under the heat and pressure of the injection molding operation. 
     Again it is desirable to prevent unsightly weld and joint lines in the over-mold material. In the exemplary embodiment of FIGS. 3 and 4, it was possible to introduce the over-mold material into the mold through a single gate. The above-noted ribs  17 ,  18  and  19 , and their counterparts on the other side of the insert are designed and located to minimize the disturbance of the flow of the thermoplastic rubber. At the same time, the flow path of the rubber in the mold must be carefully designed to provide the most efficient rubber-to-insert bonding. 
     Insert  1  is also designed to provide a mechanical bond, wherever possible, between the thermoplastic rubber and the insert. In areas where delamination would be most likely to occur, such as at thin, fleeting edges of the insert, the insert is configured to cause the thermoplastic rubber to hook thereabout, forming a permanent melt seal. Such permanent melt seals are indicated at  33 ,  34 ,  35  and  36  in FIG. 9, which is a cross-sectional view through the walls  13  and  14 . 
     Because of the two-step injection molding process of the present invention, specific rheological analysis was made to ensure compatibility between the two processes and to provide critical data such as linear and transverse shrinkage ratios, as well as the impact of a foaming agent on the structural strength, shrinkage, warpage and weight of the rifle stock. 
     During the injection molding of the insert  1 , the reinforced synthetic material, combined with the foaming agent, was introduced into the mold at a point generally indicated in FIG. 1 at  38 . This, of course, created a sprue which had to be removed. The insert  1  was supported in the second mold primarily by means entering the opening  12 . Again, a single gate was used, the gate being located at a point generally indicated at  38   a  in FIG.  3 . Again, a sprue was created and removed. A bore  39  was formed in the stock and a plug  40 , bearing indicia was located in bore  39  (as shown in FIG.  5 ). 
     FIG. 13 illustrates the completed stock generally indicated at  41 . It will be noted that a butt pad  42  has been added to the rearward end of the stock. The butt pad  42  is affixed to the end of the stock by self-tapping screws (not shown) passing through the butt pad  42  and into the bores  30  and  31  of insert  1 . 
     It is within the scope of the invention to provide selected portions of the surface of the over-molded thermoplastic elastomer with a grip-enhancing texture. The texture may be of any appropriate and well known type. In FIG. 13, side gripping portions of the forward part of the stock and the side gripping portions behind the trigger are shown provided with textured areas  43  and  44 , respectively. The textured surface is of the stippled type which enables very firm gripping. At the same time, if the grip is relaxed, the stippled surface portions  43  and  44  allow the hand substantially the same mobility as a smooth stock. It will be understood that stippled areas corresponding to areas  43  and  44  will be located on the other side of rifle stock  41 . 
     As indicated above, a hard, un-foamed material such as nylon can also be used to over-mold the insert. This produces a very hard stock that is lightweight and superior in aesthetic appearance due to the absence of a foaming agent. Nylon will not form a chemical bond with the insert, but will form a mechanical bond. The procedure practiced with a hard, un-foamed over-mold is essentially the same as that practiced with the thermoplastic elastomer except for temperature, pressure and cooling times, determination of which is within the skill of the worker in the art and depends upon the over-mold material used. 
     As is well-known in the art, for maximum accuracy free floated rifle barrels are generally regarded as the best. In some long guns it is recommended to pressure bed the forward end of the barrel against the surface  9  of the stock. As indicated above, the stock of the present invention can be so constructed as to allow easy adjustment of the barrel bedding for maximum accuracy. 
     To this end, as shown in FIG. 14, the insert  1  may be provided with a pair of upstanding lugs  45  and  46 . When the action and barrel of the rifle are installed in the stock, by means of a bolt passing through bore  11 , the rifle barrel, at the surface  9  of the stock should be inspected to see if the barrel is free floating or pressure bedded. Less pressure bedding, or free floating if desired, is achieved by filing away some or all of lugs  45  and  46 . In an instance where more pressure bedding is required, shimming of lugs  45  and  46  will accomplish this purpose. 
     For rifles with larger and heavier barrels, usually encountered with center fire rifles, it may be desired to provide the stock with a bedding block. An exemplary bedding block is illustrated in FIG. 15 at  47 . The bedding block  47  is provided with an opening  48  corresponding to the opening  12  of FIG. 2, and adapted to receive the rifle action. The bedding block  47  is provided with a perforations  49  and  49   a  through which the action-attaching bolts pass. Bedding block  47  has a forward portion  50  forming the channel through which the barrel passes. Forward bedding block portion  50  may extend partway toward the forward end of the stock, or it may extend all the way to the forward end wall  8  of the stock. 
     When a stock of the present invention is to be provided with a bedding block such as bedding block  47 , the bedding block is molded into the insert. The over-mold also incorporates parts of the bedding block. FIG. 16 illustrates a stock  41  of the present invention provided with a bedding block  47 . The over-mold  32  is partially cut away so that the bedding block  47  may be easily seen in the Figure. The bedding block  47  may be made of metal, rigid plastic, or any other appropriate rigid material. Excellent results can be achieved with an aluminum bedding block. The bedding block makes the forward end of the stock inflexible and the action is provided with a very solid mount. 
     Modifications may be made in the invention without departing from the spirit of it.