Abstract:
A stock of a firearm, which can be warmed or cooled, in order to generate a comfortable temperature in designated portions. A warm or cool gunstock helps a shooter or hunter to stay outdoors longer in cold or hot circumstances and enables he or she to perform better triggering of the firearm with a reliable triggering hand. Warming or cooling is made with a separate thermal element, which can be inserted into a firearm.

Description:
TECHNICAL FIELD 
       [0001]    The purpose of the invention is to produce a device and a method to warm up or cool outer surfaces of a firearm to be touched or handled. Another feature in the present invention is related to an energy source to warm up or cool a firearm. 
       BACKGROUND OF THE INVENTION 
       [0002]    Most sport hunting seasons are conducted during cold weather. While shooting or hunting game in cold weather, shooters or hunters often need to remain hidden, quiet and nearly motionless in blinds or in stands or are often walking in open areas and are exposed to wind and cold. 
         [0003]    Also during the hunting season there is occasionally a need to check a zeroing of the firearm, so that a point of impact of bullets, slugs or pellets are close enough to a line of sight. Consequently, a hunter in cold weather is confronted with the alternatives of wearing heavy gloves or shooting bare handed with cold, stiff fingers. Both alternatives will limit the hunters&#39; ability to operate the firearm safely and effectively. A hunter with heavily gloved or cold, numb fingers is more likely to misfire or leave a safety off when it is thought to be engaged. Accordingly, for reasons of safety and comfort, there exists a continuing need for a simple, reliable device that locally heats a selected portion of the firearm stock surface so that a hunter using the firearm can operate it more comfortably and effectively with a warm, reliable triggering hand. 
         [0004]    Most hunting firearms are equipped with a stock, which is made traditionally of walnut, beech, maple, ebony, birch etc. There is also available firearms, in which the stock is of composite, plastic, fibreglass, rubber or something else related artificial material or a combination of previously mentioned ones, which is typically fed into a mold to produce a gunstock or a blank to be finished a one. There are also solutions in which the stock or part of it is coated with an insulating or comfortable material to prevent a direct contact of a cold surface of a firearm next to a hunter&#39;s hands or cheeks. 
         [0005]    No matter whether the firearm stock is of natural or artificial material, it will feed cold to a hunter&#39;s wrists, palms, fingers or a cheek during any longer duration of hunt in cold circumstances. On the other hand, there are is also a need for hot conditions to cool down surfaces to be touched with a bare hand or skin. 
         [0006]    A heated firearm stock is known to exist in the prior art. For example, Miller in U.S. Pat. No. 6,164,003 describes a firearm stock for a long firearm having a pistol grip. This specification teaches warming the pistol grip using electrical current which is conducted in to a volume below to an area to be warmed. 
         [0007]    In order to increase the amount of energy available there is a possibility to increase the mass of batteries, which will affect the unwanted weight of the firearm. 
         [0008]    Usually a point of balance is designed to in the area of receiver (in over/under or side by side shotguns to the proximity of a hinge pin, around which barrels are turned to open or close the receiver or action). This is done in order to get a specific feeling of the firearm for shooting, so called “between the hands”. 
         [0009]    In order to support this feeling as well, the most weight of a firearm is usually located close to the receiver in order to decrease a moment of inertia to help handling and pointing the firearm. 
         [0010]    Miller places the batteries inside the stock quite close to the buttplate, which will affect both the point of balance and the moment of inertia to point the firearm. To overcome the problem of point of balance can be compensated by decreasing the weight in the area of butt or by increasing the weight in forepart of the firearm, in barrels. Both these remedies will affect to the moment of inertia of the firearm. 
         [0011]    In Miller&#39;s solution energy is transferred from the batteries to areas to be heated by a electrical circuit. 
       SUMMARY OF THE INVENTION 
       [0012]    The invention relates to a stock for a firearm, and more particularly to such a stock which is adapted to be heated or cooled in handling portions of the stock. The invention is directed to improved stocks for long firearms 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 or a shotgun. It will be understood that the basic teachings of the present invention can be applied to stocks for other types of firearms, like revolvers, pistols, sniper firearms, law enforcement firearms, military firearms etc. 
         [0013]    The present invention relates to a device for heating a portion of the surface of a firearm stock and specifically pertains to warming the fingers of the shooting hand of a hunter in cold conditions to improve his or her comfort, and markmanship as well as to improve his or her ability to safely operate the trigger and safety mechanism of the firearm. 
         [0014]    It is an objective of the invention to provide a lightweight gunstock with an excellent balance and ergonomics when combined with other parts of the firearm in order to build up a whole firearm, which fulfils requirements of easy and fast handling firearm with excellent pointability. 
         [0015]    It is an other objective of the invention to provide a gunstock with a reliable and economic way to change the temperature of those parts of the stock to be in touch with a hunter&#39;s body, more specifically fingers, palms, wrists and a cheek. 
         [0016]    A further objective of the invention to provide a gunstock, which is warmed or cooled in those parts to be touched by a human body and the warming or cooling method is robust to mechanical shocks, moisture and water. 
         [0017]    These and other advantageous objectives are fulfilled by providing a thermal element that can be inserted into the stock of the firearm. 
         [0018]    According to an aspect of the invention there is provided an aesthetic gunstock, which can be warmed or cooled without any significant difference in appearance to recognise it from a firearm that has not a capability to be warmed or cooled. If wanted, it is also possible to provide the gunstock with a visible mark or logo to show its capability to be warmed or cooled. 
         [0019]    According to an aspect of the invention there is provided a gunstock, which can loaded with a separate thermal element. 
         [0020]    According to an aspect of the invention there is provided a gunstock, which can be loaded with several thermal elements. 
         [0021]    According to an aspect of the invention there is provided a thermal element, which can be inserted in a gunstock. 
         [0022]    Also, according to an aspect of the invention there is provided a recyclable or rechargeable thermal element, which can be inserted in a gunstock. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    The following detailed description refers to the attached drawings in which: 
           [0024]      FIG. 1  is a side view of a gunstock according to the invention. 
           [0025]      FIG. 2A  is a side view of the thermal element. 
           [0026]      FIG. 2B  is a cross-sectional view of the thermal element. 
           [0027]      FIG. 3  is a cross-sectional view of the thermal element to be placed in the stock. 
           [0028]      FIG. 4  is a cross-sectional view of the thermal element mounted within the stock. 
           [0029]      FIGS. 5A ,  5 B,  5 C are bottom views of the pistol grip, illustrating a valve to connect ON/OFF the thermal energy into wanted or unwanted surfaces. 
           [0030]      FIG. 6  is a partial view of a gunstock according to the invention illustrating a valve to connect the thermal energy onto surfaces of pistol grip. 
           [0031]      FIG. 7  is a partial view of a gunstock according to the invention illustrating a valve to connect the thermal energy onto surfaces of cheekpiece. 
           [0032]      FIG. 8  is a partial view of a gunstock according to the invention illustrating a valve to connect the thermal energy onto both surfaces of pistol grip and cheekpiece. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0033]    Symbols and numbers used in the description:
         1 —firearm     2 —stock     3 —pistolgrip     4 —buttplate     5 —forestock     6 —trigger guard     7 —trigger assembly     8 —receiver     9 —barrel     10 —thermal element     11 —cavity     12 —release     13 —hatch     14 —band     15 —valve     16 —thermal conductive material     17 —spring     18 —thermally conductive sector     19 —thermally conductive sector     20 —thermally conductive sector     21 —checkering     22 —comb     23 —cheekpiece     30 —material storing or generating energy   p—thermal conductive material, connected to pistol grip   c—thermal conductive material, connected to cheekpiece       
 
         [0060]    It will be understood by one skilled in the art that, for each type or model of long firearm to which the stock of the present invention is to be applied, the stock and the thermal element must be appropriately designed with each other in accordance with the teachings of the present invention. 
         [0061]    The firearm stock  2  of  FIG. 1  is a traditional type of stock for a repeating hunting rifle. The major distinguishable sections of the stock are a buttplate  4 , a heel, a comb  22 , a checkering  21 , a pistol grip  3 , a bedding area for a receiver  8  and a forestock  5  including a barrel channel. In front of the pistol grip  3  there is typically a space reserved for a trigger and trigger guard  6 . According to the first embodiment of the invention, the pistol grip  3  is designed to have an empty, openable and closable cavity  11 , in which a separate thermal element  10  can be inserted. The thermal element  10  may create thermal energy by a chemical process or by storing and releasing the accumulated heat or energy. The thermal energy is transferred from the thermal element  10  to the stock  2  by thermal conduction and therefore the cavity  11  inside the pistol grip  3  is among the preferable embodiments. It directly warms or cools the operators hand intended to use the trigger and the safety catch. 
         [0062]    There are also firearm models, in which a distinguishable pistol grip is missing and the area behind the trigger guard is straight extending as a straight line from the trigger guard to the heel. This stock model is called “English stock”, typically used in side by side shotguns. There is also a stock model between a one with a pistol grip and a “English stock”, in which the pistol grip area is something in between these two extremes and forms only a little hump in the lower contouring line between the trigger guard and the heel. This stock model is called a half or a quarter pistol grip or a “Prince of Wales” grip. These models may also be adapted to receive a thermal element inside the gripping portion of the stock. 
         [0063]    A pistol grip is typically curved down forming a comfortable and ergonomic grip to grasp. In the tip of the pistol grip there is usually a plane or rounded plate, which is often used also for decorative purposes. These parts may be utilized to create an aesthetic appearance of the invention. They may also be utilized to conceal the openable cavity inside the pistol grip. 
         [0064]    The above mentioned features can also be utilized with other embodiments of the invention. 
         [0065]    The thermal element  10 , illustrated in  FIGS. 2A and 2B , may create thermal energy by a suitable chemical process or by storing and releasing the accumulated heat or energy. A principle of generating the energy in the thermal element  10  may be based on a chemical reaction or a physical phenomenon. For example, for warming purposes two (or more) chemicals are brought together for reacting and mixing with each other supplying some extra energy. One possible way is also to preheat the thermal element before use by boiling it for a while in a water pot or heat the thermal element  10  in a microwave oven. The thermal element  10  may also be utilized in cooling the stock  2  in very hot climate. In case of cooling, the thermal element is binding energy from the stock  2  with a chemical reaction or a physical phenomenon.  FIG. 2A  illustrates a thermal element  10  as a cylinder as an example. Cross-section of a thermal element  10  could be a square or polygonal as well.  FIG. 2B  illustrates a cross-section of a thermal element revealing a container inside of it. It may contain energy storing or generating material  30 , any chemical or mixture of chemicals in a internal cavity or in cavities divided by a partition (not shown). For example, to initiate the thermal element to transfer energy, a shock or bending could be enough to break the partition and start mixing of chemicals. 
         [0066]    In case of warming, it is also possible to utilize electrical energy in the form of a battery or an accumulator. These could be chargeable or non-chargeable ones. In a very simple way to do this is to use a commercial, cheap, easily available batteries for example in standard sizes, like A, AA or AAA sizes. A single or multiple ones can be used. Use of batteries or accumulators requires a simple electrical circuit to connect the poles of the battery or accumulator to each other to generate a short circuit. Once connected the battery will start heating up, while it has a proper resistance in it. The electrical circuit may comprise also a potentiometer to adjust the heating ratio. Commercial batteries have a metal cover on them, which also transfers the warming energy further. 
         [0067]    In general a thermal element can inserted into any designated cavity. However, it is preferred to have a cavity, which can be opened and closed by a hatch to keep the thermal element safely in its position and also to conduct the heat to the right places in the stock—not to waste the heat to the open air. It is preferred to insulate metal parts—barrel, receiver and trigger assembly—from a thermal energy. It would be waste of energy and also warping metal parts would harm the accuracy of the firearm. These metal parts can be insulated with insulative material. In order to have a good conduction of heat, the mechanical clearance between the cavity and the thermal element is preferred to be quite tight. The mechanical clearance may be arranged so that the fitting between the cavity and the thermal element allows extraction any time, regardless of any thermal expansion. This rather tight clearance enables to have fast response in warming up the stock. Soon after the thermal element is inserted into the cavity, energy of the element starts warming up the designated portions of the stock and it can be felt as a comforting feeling on hands and on a cheek, if the firearm is raised to point. 
         [0068]    According one embodiment of the invention the pistol grip  3  is designed to have an empty cavity  11 , in which a separate thermal element  10  can be inserted. This is shown in  FIGS. 3 and 4 . The cavity  11  can be opened and closed with a hatch  13 . The hatch  13  may have a hinge and the hatch will be lifted up to open the cavity. Another possibility to open the hatch  13  is to use a pivot, in which is the hatch  13  is attached and the hatch  13  is turned sideways to open the cavity  11 . A third alternative is to slide the hatch  13  along a dovetail joint to open the cavity  11 . It is preferable to have the hatch  13  attached to the stock  2  all the time, so it does not have a chance to get lost, especially in the woods. When the hatch  13  is closed, it is locked into its position with a tight fitting, a spring loaded pin, a locking device or a release  12 . The hatch  13  may contain a sign or logo revealing the thermal feature. It is also possible that the hatch  13  or the stock  2  may contain a gauge or meter to show temperature or capacity of thermal energy, which is still available. 
         [0069]    An alternative to opening and closing the cavity is to use a hatch with bayonet joint and the opening and closing can be made fast, reliable and easy. 
         [0070]    In one embodiment, surfaces of the cavity facing an inserted thermal element are covered with a material, which has a good conductivity of thermal energy. This kind of preferred materials are metals such as light metals, aluminium, titanium, zinc, etc. Copper or steel may be used in thin layers, carbon fiber has also suitable conductivity. These are only examples among many suitable materials for this purpose of thermal connection. 
         [0071]    Extraction of the thermal element out of the cavity can be made for example, by pulling an end of a flat band  14 , which is fitted to be on a loop between the cavity  11  and the thermal element  10  when inserting the thermal element  10 . An alternative to this embodiment is a cage, in which the thermal element is inserted and then the cage together with the thermal element is inserted to the stock. It is also possible to equip the thermal element itself with a strap of string at the outer end, by which it can drawn out. Yet another alternative is to have a spring  17  at the bottom of the cavity or on the inner end of the thermal element so that when the hatch is opened, the spring  17  pushes the thermal element  10  partly out. 
         [0072]    It is the second embodiment of the invention that feeds the thermal element into the stock by arranging an entrance to the cavity from rear. This embodiment is suitable especially for “English stock”. The hatch can built in the proximity of the buttplate  4 . The hatch  13  could be integrated in the buttplate  4 , or the buttplate  4  could be the hatch  13  itself. It is also possible to have the entrance on the side of the stock  2  between the pistol grip  3  and the buttplate  4 . Another position of entrance is on the lower edge of the stock  2  behind the triggerguard  6 . This feature is preferred in case of an English stock, which usually has a quite slender cross-section of stock behind the triggerguard  6 . Rather than feeding the thermal element  10  directly into a straight pistol grip area, it is inserted into the cavity  11  in a stock  2  behind the pistol grip. Thermal effect can be directed from the thermal element  10  to the pistol grip  3  area with thermally conductive material  16 , as it is explained later. Thermally conductive material  16  can be used also to strengthen the pistol grip  3  area. Opening, closing and locking of the hatch  13  can be similarly, as explained in case of the hatch  13  in the pistol grip  3 . 
         [0073]    It is the third embodiment of the invention that inserts the thermal element  10  into the forestock  5  of the firearm  1 . The cavity  11  can be opened and closed for example with an aid of a hatch  13 , which could be hinged in its front, rear or side edge. Another embodiment of opening and closing the cavity  11  for a thermal element  10  is to have a sliding chest, which has a specific cavity  11  in it. The chest can be pushed sideways from the forestock to open an access to the cavity  11 . The thermal element  10  can be inserted in a cavity  11 , the chest pushed sideways back to its position inside of the stock. In order to increase the aesthetic appearance of the stock  2  and fade the joint of the chest and the stock  2 , the sliding surfaces of the chest may join the outer edges of the checkering  21 , or some inner lines of the checkering  21 . It is also possible to manufacture the chest and the stock  2  of different materials, and emphasize difference of appearance between the chest and the stock  2 . For example, the stock  2  can be made of a composite and the chest can be made of rubber, or only the outer sidepanels of the chest can be covered with a rubber. The chest can be locked in its working position with a locking device to prevent premature or unwanted opening. An alternative to set the thermal element  10  in a stock  2  is to build the forestock  5  of two or several pieces, and the thermal element  10  can be placed between them. A releasable portion of the forestock  5  can be fixed to the stock  2  with a screw, a release  12  or with any other of the methods described earlier to close the cavity  11  in the area of the triggering hand. 
         [0074]    It is the fourth embodiment of the invention that conducts warming energy to the most wanted directions through thermally conductive materials  16 . This can made by using metal inserts with sophisticated cross-sectional profiles. Material to be used is for example steel, copper or any light weight alloyed metal, which is the preferred option in this embodiment. Another possibility is to use an insert portion which is made of a thermally insulating material which prevents most of generated energy from transferring into the remainder of firearm stock  2  where it would dissipate and be wasted. 
         [0075]    It is the fifth embodiment of the invention that directs the thermal energy to most efficiently to wanted areas. It is possible to have a specific thermal conduction valve  15  on a path from the thermal element  10  to the wanted area or volume to be warmed or cooled. A possibility to perform this is to have a layer or a piece of thermally conductive material  16  starting from the thermal element  10  to the valve  15  and continuing from the valve  15  to the area or volume to be warmed or cooled. For example, a hunter may select the warming effect only to the pistol grip by turning the valve  15 . If desired, the warming can be selected to warm also a comb  22  or a cheekpiece  23  of the stock  2  in order to give comfort of the warmth also to the cheek of a hunter. 
         [0076]    The thermal conduction valve  15  can be manufactured as a rotating cylinder, which has a thermal conducting path through it when turned “ON”. The valve can also be rotated to position “OFF” and the conductive path is closed between the paths of thermally conductive material  16  to the valve  15  and further from it. The preferred location of the valve  15  is close to a thermal element  10  to avoid unnecessary loss of energy in a case when the valve  15  is closed. 
         [0077]    The thermal conductive valve  15  can also surround the thermal element  10 , as in  FIGS. 5A ,  5 B and  5 C. The Figures show situation when the thermal element  10  is inserted into the cavity  11  and the hatch  13  is open. The thermal conductive valve has multiple thermally conductive sectors  18 , 19 , 20 , through which the thermal energy is transferred to thermally conductive material  16  and further to selected parts of the stock  2 . Selective transfer is based on an idea that sectors  18 , 19 , 20  in the valve are divided differently than those sectors of thermally conductive material p,c. 
         [0078]    In  FIG. 5A , an indicator (a dot) for the user is in position PG. Sector  18  is in contact with thermally conductive material p. The energy of the thermal element  10  is connected to pistol grip  3  and energy is transferred to a hand on a pistol grip. In  FIG. 5B , the indicator (a dot) for the user is in position CH. Sector  18  is in contact with thermally conductive material c. The energy of the thermal element  10  is connected to cheekpiece  23  and energy is transferred to a cheek on a cheekpiece. In  FIG. 5C , an indicator (a dot) for the user is in position PG+CH. Sector  20  is in contact with thermally conductive material p. Sector  19  is in contact with thermally conductive material c. The energy of the thermal element  10  is connected to pistol grip  3  and also to cheekpiece  23  and energy is transferred to a hand on a pistol grip and to a cheek on a cheekpiece. Sector  18  is not in contact of thermally conductive material  16  in this very position. 
         [0079]    FIGS.  6 , 7  and  8  clearly demonstrate the thermal connection from the thermal element  10  through the thermal conductive valve  15  to the thermally conductive material p and c, with those sectors in the proximity of the valve  15 . Thermal connection is continuous in a way that “p” is connected thermal conductive material  16  ending to pistol grip  3  and “c” is connected to thermal conductive material  16  ending to cheekpiece  23 . 
         [0080]    Another alternative of a selective device as a fifth embodiment for thermal conductivity is a piston, which can pushed in a designated position to give a desired effect for areas to be warmed or cooled. There may be several designated positions in the piston to give combinations of warmed or cooled areas in the stock for a firearm. For example, the piston can be placed behind the pistol grip and it can be moved sideways. Conductive layers in the stock added with conductive layers in the piston will generate a combination chart, which can be presented for example, in a Boolean table. 
         [0081]    A stock may comprise a single or multiple cavities for a single or multiple thermal elements. So a hand and/or hands and/or a cheek can be warmed or cooled during handling of the firearm. On the other hand, also a single thermal element can be used to warm or cool hands and cheek. In order to give highest efficiency of the energy and comfort, different models can be delivered to right hand or left hand shooters. 
         [0082]    To activate or charge or store energy in a thermal element can be done in various ways based on a physical or chemical phenomenon. 
         [0083]    A method to activate the element is to pre-heat it in a microwave oven or in boiling water. Another method is to use two component system, which are in separate containers in the thermal element. A mechanical shock or stress may break the internal containers in order to create a mixture, causing a release of energy based on a chemical process. It is a matter of optimization to pick up proper combination of chemicals involved. The optimization can focus on maximum temperature, duration of warming, warming rate to reach the maximum temperature, maximum content of energy, slow rate to cool down from the maximum temperature, safe handling of chemicals, recycleability, etc. 
         [0084]    The thermal element can be rewarmable, rechargeable and/or recyclable. 
         [0085]    It is also possible to have the hatch integrated in a thermal element and the cavity is closed when the thermal element is inserted in a gunstock. 
         [0086]    An arrangement according to the invention is capable of generating energy and transferring it reliably to an area to be warmed or cooled. Reliability of the invention is better, if compared for instance to an arrangement, in which energy is transferred through an electrical circuit. 
         [0087]    An arrangement according to the invention is a lightweight construction and requires only a modest volume inside of the gunstock. The arrangement for the thermal element is practically not affecting the point of balance nor the moment of inertia of the firearm. 
         [0088]    An arrangement according to the invention is capable of producing energy for warming or cooling on extended duration, depending on the chemical or physical characteristics of the thermal element (combination of materials, dimensions etc.). The capability of the thermal element to produce warming (or cooling) energy is not affected by the surrounding temperature. For example, batteries have a tendency to weaken or loose their charge in cold temperatures. 
         [0089]    Electrical circuits in general are sensitive to mechanical shocks, which will occur e.g. if a hunter falls down in the woods and the firearm is exposed to a mechanical shock. The severest shocks will be caused by a recoil of the firearm. Any mechanical shock might impart the conductivity of the electrical circuit of warming arrangement. The invention according the thermal element is robust against mechanical shocks. 
         [0090]    Reliability of the invention is better also against problems of moisture, which is known to be critical as long the electrical circuits are concerned. During hunting season there is typically moisture or water available more often than wanted. The firearm stock will be exposed to rain, snow and fog. A hunter&#39;s own warmth and perspiration will generate some moisture which might condensate on the surface of the stock. The condensate will attack on the firearm stock at the latest, when hunter returns with his or her firearm from cold hunting grounds back to indoors. 
         [0091]    As it is easily understood the thermal characteristics of a thermal element can be utilized to also cool down the gunstock in a hot environment. A proper combination of materials and dimensioning in a cooling element and/or gunstock may have to be picked up in order to avoid possible problems of thermal expansion or conductivity to make sure of a satisfying performance. 
         [0092]    As can be seen from the foregoing, warmed or cooled firearm stock accomplishes the objectives of the invention. A warmed or cooled firearm stock can look very much like an ordinary firearm stock, yet includes a simple and robust means for locally warming or cooling a selected portion of the firearm stock. A hunter may use warmed firearm stock without resorting to any specialized equipment or processes and a hunter using warmed firearm stock will experience the comfort and safety enhancing advantages of aiming and firing with a warm and comfortable trigger hand. In case of cooling, shooters hands are not so easily prone to sweat, and handling of the gun is safer. 
         [0093]    The skilled reader, in view of this specification may envision numerous modifications and variations. It is possible to build combinations of explained embodiments. These modifications and variations may be in the invention without departing from the spirit of it. 
         [0094]    While there have been shown and described and pointed out fundamental novel features of the invention as applied to preferred embodiments thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices and methods described may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto. Furthermore, in the claims means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures.