Abstract:
A Seebeck active cooling device for use in conjunction with a weapon to cool the barrel, in order to reduce its weight, to remove the need for a second barrel, and to prolong its useful life. In particular, the cooling device employs a plurality of thermoelectric devices that convert the energy from the heat produced by the hot barrel during the operation to an electric current. The electric current powers a series of electric fans, which in turn, cool the barrel.

Description:
GOVERNMENTAL INTEREST 
     The invention described herein may be manufactured and used by, or for the Government of the United States for governmental purposes without the payment of any royalties thereon. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates in general to the field of munitions. More specifically, this invention relates to an improved means of cooling the barrel of a weapon, which offers the potential to reduce its weight, to remove the need for a second barrel, and to improve its barrel life. In particular, the present invention uses a thermoelectric device to convert the energy from the heat produced by a hot barrel during operation, to power a fan that cools the barrel. 
     BACKGROUND OF THE INVENTION 
     The weight reduction of small arms weapons is a significant concern for a soldier. A significant portion of the weight of individual and crew served weapons is in the barrel of the weapon. Much of the additional weight is necessary, not only to withstand the pressure of firing the cartridge, but also as a heat sink to absorb the thermal energy of firing the weapon. 
     In fact, machine guns typically have a removable, secondary barrel for the purpose of replacing the barrel after firing for a short time, in order to allow the primary barrel to cool. This additional barrel adds weight and complexity to the weapon. 
     What is therefore needed is a device for cooling the weapon barrel with significant weight reduction. In other terms, it would be desirable to solve the cooling problem and to remove the redundant weight associated with the need for a second barrel. Furthermore, since the barrel life is primarily a function of the barrel temperature, barrels fired at lower temperatures last significantly longer. As a result, it would be desirable to extend the life of the barrel by reducing its operation temperature. Prior to the advent of the present invention, the need for such a cooling means has heretofore remained unsatisfied. 
     SUMMARY OF THE INVENTION 
     The present invention satisfies this need, and describes a barrel cooling device and method (collectively referred to as “the present device,” “the present method”, or “the present system”). The present device captures the energy from the heat produced by a hot barrel during operation, and converts the captured energy into electric power that energizes one or more thermoelectric fans to cool the barrel. 
     Barrel cooling typically occurs through natural convection of the airflow around the barrel. Generally, forced air convection can result in significant improvement of cooling compared to natural convection. The barrel cooling device of the present device uses the heat of the barrel during firing as a means to cool the barrel. 
     The barrel cooling device uses a thermoelectric generator that is mounted to the barrel, which produces electricity as the barrel heats up from firing. The generated electrical current drives a series of electric fans to cool the barrel. 
     The thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice-versa. A thermoelectric device creates a voltage when there is a difference in temperature on opposite sides of semiconductors to produce electrical energy. 
     To this end, when the thermoelectric device is placed on a hot barrel it uses the recaptured heat energy to power a series of thermoelectric fans. This effect accelerates the air cooling of the barrel. A cooler barrel increases the lifespan of the barrel, and allows the weight of the barrel to be reduced because less material is required for a heat sink. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features of the present invention and the manner of attaining them, will become apparent, and the invention itself will be best understood, by reference to the following description and the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of an exemplary machine gun provided with a cooling device that is mounted onto the machine gun barrel according to the present invention; 
         FIG. 2  is an exploded view of the machine gun barrel of  FIG. 1 , illustrating the cooling device of  FIG. 1 , as including a plurality of thermoelectric fans that are automatically powered by the heat emanating from the barrel, to cool the barrel according to the present invention; 
         FIG. 3  is an enlarged schematic view of a thermoelectric fan according to a preferred embodiment of the present invention; 
         FIG. 4  is an enlarged schematic view of a thermoelectric fan according to another preferred embodiment of the present invention; 
         FIG. 5  is an enlarged, exploded, schematic view of a thermoelectric fan according to still another preferred embodiment of the present invention; 
         FIG. 6  is an enlarged, exploded, schematic view of a thermoelectric fan according to yet another preferred embodiment of the present invention; 
         FIG. 7  is a computer simulation chart of the temperature at selected areas of the machine gun barrel, underneath the thermoelectric fans of any of  FIGS. 3 through 6 , with the fans turned ON and then OFF; and 
         FIG. 8  is a perspective, exploded view of the machine gun barrel of  FIG. 1 , provided with a cooling assembly that includes bladeless thermoelectric fans, according to the present invention. 
     
    
    
     Similar numerals refer to similar elements in the drawings. It should be understood that the sizes of the different components in the figures are not necessarily in exact proportion or to scale, and are shown for visual clarity and for the purpose of explanation. 
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  illustrates an exemplary machine gun  10  that is provided with a thermoelectric cooling device  100 . In this exemplary preferred embodiment of the present invention, the thermoelectric cooling device  100  is mounted onto the machine gun barrel  15 . The cooling device  100  includes a plurality of thermoelectric fans  200 ,  205 ,  210 ,  215 . 
     While four thermoelectric fans  200 ,  205 ,  210 ,  215  are shown in  FIG. 1 , it should be clear that a different number of thermoelectric fans and corresponding devices could be used. In addition, while the present invention will be described in connection with the machine gun  10 , it should be clearly understood that the present invention may be used with other weapons and weapon systems, including but not limited to rifles. 
     In one embodiment, the thermoelectric fans include three thermoelectric fans  205 ,  210 ,  215  that are generally equally spaced between the gas block and the chamber, and a fourth thermoelectric fan  200  that is located between the gas block and the front sight of the machine gun. 
     As used herein, thermoelectric fans are electric fans that are powered by the thermoelectric effect. The thermoelectric effect is also referred to as the Seebeck effect, and is used to generate electricity. Generally, the thermoelectric effect encompasses three separately identified effects: the Seebeck effect, the Peltier effect, and the Thomson effect. 
     In general, a thermoelectric device includes one or a series of p-type semiconductor elements and one or a series of n-type semiconductor elements that are electrically connected. When the two dissimilar elements are subjected to different temperatures, the Seebeck effect causes a voltage to be generated across the junctions between the p-type and n-type semiconductor elements. 
     With further reference to  FIGS. 2 and 3 , the thermoelectric cooling device  100  includes the thermoelectric fans  200 ,  205 ,  210 ,  215 . In  FIG. 3 , one thermoelectric fan  200  is shown in more detail for clarity of illustration, with the understanding that the other thermoelectric fans  205 ,  210 ,  215  are generally similar in construction and design to the thermoelectric fan  200 . 
     In  FIG. 1 , the thermoelectric fan  200  is secured to the barrel  15 , and generally comprises an electric fan  300  and a thermoelectric device  310 . The thermoelectric fan  205  generally comprises an electric fan  301  and a thermoelectric device  312 . The thermoelectric fan  210  generally comprises an electric fan  302  and a thermoelectric device  314 . The thermoelectric fan  215  generally comprises an electric fan  303  and a thermoelectric device  316 . 
     As more clearly illustrated in  FIG. 2 , the thermoelectric device  310  may be formed of a plurality of modules, such as three modules  315 . The modules  315  straddle the barrel  15  in order to absorb the optimal amount of heat emanating from the barrel  15 . 
     The modules  315  are electrically connected to the electric fan  300 , to supply it with the desired energy. As illustrated in  FIG. 3 , an electrically conductive wire or trace  320  connects the thermoelectric device  310  to the electric fan  300 . 
     The electric fan  300  has an open end that is secured to the barrel  15 , by means of a mechanical device, such as a clamp or a similar device, to form a cooling chamber  331  therewith. As shown in  FIG. 1 , the thermoelectric device  310  may be secured to the barrel  15  and is disposed next to the electric fan  300 . 
     In the preferred embodiment of  FIG. 3 , the electric fan  300  includes a flat bottom  307  that matches the geometry of the modules  315  of the thermoelectric device  310 . Each module  315  is made of a generally rectangularly shaped, flat, ribbon. 
     While  FIG. 3  illustrates the electric fan  300  as a bladed fan, it should be clear that a bladeless fan or any other available and suitable electric fan might be used instead. 
     The thermoelectric device  310  may be comprised of any available or suitable thermoelectric modules, such as the HZ-2 thermoelectric modules from Hi-Z Technology, Inc. Quantum well and lead telluride modules or other available thermoelectric devices may be used. 
     The electric fan model PSD1204PBB1-A from SUNON, or any other suitable or available electric fan may be used. The electric fan  300  may, for example, be approximately 40 mm×40 mm×24 mm in dimensions, and can produce approximately 21.6 CFM of airflow. 
     The wire  320  may for example be nickel plated copper insulated with mica tape and a fiberglass jacket. It should be noted that other suitable conductors may alternatively be used. 
     When the thermoelectric device  310  is placed in contact with the hot barrel  15 , it uses the recaptured heat energy to power the electric fan  300 , which will accelerate the air circulation within the cooling chamber  331 , to cool the barrel  15 . This increases the lifespan of the barrel  15 , and has the potential to reduce the weight of the barrel  15  because less material is required for a heat sink. 
       FIG. 4  illustrates another thermoelectric fan, i.e.,  205  according to the present invention. The thermoelectric fan  205  is generally similar in construction and function to the thermoelectric fan  200  of  FIG. 3 , but allows for the bottom of the components to be curved in order to better fit around the barrel  15 . The thermoelectric fan  205  is secured to the barrel  15 , and generally comprises an electric fan  400  and a thermoelectric device  410 . An electrically conductive wire or trace  420  connects the thermoelectric device  410  to the electric fan  400 . 
     The electric fan  400  has an open end that is secured to the thermoelectric device  410  to form a cooling chamber  431  therewith. In turn, the thermoelectric device  410  is secured to the barrel  15 , and is disposed next to the electric fan  400 . 
     Alternatively, the electric fan  400  is secured to the barrel  15  by means of a mechanical device, such as a clamp or a similar device, with the thermoelectric device  410  sandwiched therebetween. 
     In a preferred embodiment, the electric fan  400  includes a curved bottom  407  that matches the shapes of both the barrel  15  and the thermoelectric device  410 . The thermoelectric device  410  is made of a generally rectangularly shaped, curved, ribbon that is adhered or glued onto the curved bottom surface  407  of the electric fan  400 . 
     With reference to  FIG. 5 , the thermoelectric fan (i.e.,  210 ) is generally comprised of an electric fan  500 , a support structure  505 , and a thermoelectric device  510 . An electrically conductive wire or trace  520  connects the thermoelectric device  510  to the electric fan  500 . 
     The support structure  505  retains the electric fan  500  a predetermined, optimal distance above the barrel  15  and forms a cooling chamber  531  therewith. The support structure  505  is open at both ends. 
     In the embodiment of  FIG. 5 , the support structure  505  includes a flat bottom  507 . The thermoelectric device  510  is made of a generally rectangularly shaped, flat strip  512  that can be adhered to, or glued onto the flat bottom  507  of the support structure  505 . Alternatively, the thermoelectric device  510  can be secured to the barrel  15 , and disposed next to the electric fan  500 . 
     With reference to  FIG. 6 , the thermoelectric fan (i.e.,  215 ) is generally similar in construction and function to the thermoelectric fan  210  of  FIG. 5 , but is different in design. The thermoelectric fan  215  generally comprises an electric fan  600 , a support structure  605 , and a thermoelectric device  610 . An electrically conductive wire or trace  620  connects the thermoelectric device  610  to the electric fan  600 . 
     The support structure  605  includes a curved bottom  607  that matches the shapes of both the barrel  15  and the thermoelectric device  610 . The thermoelectric device  610  is made of a generally rectangularly shaped, curved strip  612  that can be adhered to, or glued onto the curved bottom  607  of the support structure  605 . Alternatively, the thermoelectric device  610  can be secured to the barrel  15 , and disposed next to the electric fan  600 . 
     In use, as the barrel  15  heats up during operation, it generates heat energy that is captured by any of the thermoelectric devices  310 ,  410 ,  510 ,  610 . In turn, as explained earlier, the thermoelectric device, e.g.,  310  automatically converts the captured heat energy into an electric current that is transmitted to the electric fan, e.g.,  300 , via the conductor  320 . The electric fan  300  provides the desired cooling effect to the barrel  15 . 
     In summary, the electric fan, e.g.,  300  is automatically powered by the heat emanating from the barrel  15 , to cool the barrel  15 . It should be understood that the other thermoelectric fans  205 ,  210 ,  215  that form the cooling device  100  operate similarly to the thermoelectric fan  200  to respectively cool adjacent sections of the barrel  15 . It should also be understood that the different thermoelectric fans  200 ,  205 ,  210 ,  215  are included here to illustrate several different potential fan configurations, and that a single configuration may be used for all thermoelectric fans in the device. 
     Experimentally, and with further reference to  FIG. 7 , the thermoelectric devices  310 ,  410 ,  510 ,  610  provide sufficient power to a reasonable configuration of electric fans  300 ,  400 ,  500 ,  600 , respectively. A computer simulation was done of a barrel  15  firing 100 rounds per minute, with four similar thermoelectric fans  200  both ON and OFF. The fan configuration chosen was four fans over the barrel  15 , which would produce a total of about 85 CFM of airflow over the barrel  15 . 
     Each one of the thermoelectric fans  200  requires approximately 6 Watts of power at 12 Volts, which can be achieved using 3 to 4 thermoelectric devices per electric fan. 
     With reference to  FIG. 8 , it illustrates another preferred embodiment of the present invention, and shows a thermoelectric cooling assembly  800  to be mounted onto the machine gun barrel  15 , as explained earlier in connection with the thermoelectric cooling devices of  FIGS. 3 through 6 . The cooling assembly  800  includes at least one bladeless thermoelectric fan (also referred to as Dyson fan). 
     It should be understood that other modifications might be made to the present design without departing from the spirit and scope of the invention.