Abstract:
A reserve battery including a dual-purpose fill port member that also operates as a battery activation mechanism. The reserve battery includes a frangible barrier positioned inside a case. The frangible barrier divides the case into a first compartment holding cell electrodes and a second compartment capable of holding an electrolyte in isolation from the first compartment. Positioned in the second compartment proximate to the frangible barrier is a fill port member that is movable in response to an applied force for rupturing the frangible barrier. The fill port member also has a fluid passageway for use in transferring an amount of the electrolyte to the second compartment. The dual purpose of the fill port member is that it efficiently uses the available space and permits the design and production of a more compact reserve battery for use in space-limited applications, such as artillery shells.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention relates generally to reserve batteries, and more particularly, to reserve batteries with set back activation mechanisms.  
       BACKGROUND OF THE INVENTION  
       [0002]     Reserve batteries represent reliable sources of portable electrical power following long periods of storage and are designed to be activated very quickly with little degradation in performance over time. In some applications, the reserve battery must have a prolonged shelf life even at extreme temperatures. Once activated, the reserve battery electrically powers a circuit for a few seconds to a few minutes. No maintenance is required for the reserve battery during storage prior to use, permitting it to be permanently installed in equipment.  
         [0003]     One reserve battery construction, widely used as a source of in-flight electrical power for components of artillery projectiles, physically separates a reservoir filled with electrolyte and cell electrodes with a frangible barrier. The battery cells are stored in a dry condition and are wetted during flight of the projectile with electrolyte. In artillery projectiles, the reserve battery should have a shelf life exceeding twenty years while stored at temperatures ranging from −40° F. to +145° F. When the artillery shell is loaded into a weapon and the weapon is fired, the set back force applied by the artillery projectile to the reserve battery precipitates rupture of the frangible barrier.  
         [0004]     Electrolyte flows from the reservoir through the breach in the frangible barrier and wets the cell electrodes, which activates the reserve battery for powering a circuit in the artillery projectile such as electronics of a proximity fuse or electronics of a self-destruct mechanism.  
         [0005]     Conventional reserve batteries include, as distinct components, a fill port and a breaking device. The fill port is used to introduce electrolyte into the reservoir inside the reserve battery and may be sealed using a ball seal with an interference fit.  
         [0006]     The breaking device operates to rupture the frangible barrier when the weapon is fired, so that the electrolyte can wet the cell electrodes. In small conventional reserve batteries, the fill port and the breaking device collectively occupy a significant volume of the reservoir that could otherwise be used to store electrolyte, which represents a significant disadvantage.  
         [0007]     It would be desirable, therefore, to provide a compact reserve battery with improved space utilization.  
       SUMMARY  
       [0008]     In one embodiment of the invention, a reserve battery includes a case and a frangible barrier positioned inside the case. The frangible barrier divides the case into a first compartment and a second compartment capable of holding an electrolyte in isolation from the first compartment. The reserve battery further includes a plurality of cell electrodes positioned in the first compartment and a fill port member positioned in the second compartment proximate to the frangible barrier. The fill port member is movable in response to an applied force for rupturing the frangible barrier. The fill port member also has a fluid passageway for transferring an amount of the electrolyte to the second compartment.  
         [0009]     The reserve battery of the invention improves upon conventional reserve batteries. More specifically, the reserve battery of the invention has a fill port member that operates as a filling port for introducing electrolyte and that also operates as an activation mechanism or ram capable of rupturing the frangible barrier separating the electrolyte from the battery cells. The dual purpose of the fill port member is that it efficiently uses the available space and permits the design and production of a more compact reserve battery for use in space-limited applications, such as artillery shells.  
         [0010]     These and other objects and advantages of the present invention shall become more apparent from the accompanying drawings and description thereof. 
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0011]     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the principles of the invention.  
         [0012]      FIG. 1  is a partial cross-sectional view of a reserve battery in accordance with the invention;  
         [0013]      FIG. 2  is a view of the reserve battery of  FIG. 1  coupled with a nozzle that fills the reserve battery with electrolyte;  
         [0014]      FIG. 3  is a view of the reserve battery of  FIG. 2  after filled with electrolyte and before the fill port is plugged with the sealing member; and  
         [0015]      FIG. 4  is a view of the reserve battery of  FIG. 1  during activation.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]     With reference to  FIG. 1 , a reserve battery  10  includes a sealed battery case  12  having an interior that is partitioned by a breakable or frangible barrier  14  into one sealed cavity or compartment  16  defining a reservoir filled with an electrolyte  18  and another sealed cavity or compartment  20  enclosing a plurality of cell electrodes  22 . The battery case  12  may be formed in a variety of shapes, but typically is cylindrical. The frangible barrier  14  provides a fluid-tight hermetic seal that isolates and physically separates the electrolyte  18  from the cell electrodes  22 . The cell electrodes  22 , which are maintained in a dry and inactive state, are activated to generate power only when exposed to electrolyte  18 .  
         [0017]     An annular cell cover  27  is joined about its outer periphery with the battery case  12  for sealing compartment  20 . A terminal pin  25  is positioned inside the inner bore of annular cell cover  27  and is electrically insulated from the cell cover  27  by an intervening ring  29  of insulating material. Terminal pin  25  electrically couples the cell electrodes  22  with a circuit (not shown) external to the battery case  12 . An exposed portion of the terminal pin  25  outside of the sealed battery case  12  is available for establishing an electrical connection with the cell electrodes  22 . An annular disk  31  of insulating material, which has a central bore receiving a portion of the terminal pin  25 , electrically insolates the cell cover  27  from the cell electrodes  22  and is coaxial with the cell cover  27 .  
         [0018]     The battery case  12  may be formed from any suitable material resistant to any corrosive effects of a typical electrolyte  18 , including but not limited to Kovar (i.e., ASTM F15 Ni/Fe/Co alloy) and stainless steels. In one embodiment of the invention, the case  12  is cylindrical with a diameter of about 0.25″ and a height of about 0.3″. The frangible barrier  14  may be formed from a continuous, solid disk of any suitable material, such as a brittle glass, and thickness that is stable for extended periods of time when exposed to the electrolyte  18 , that is susceptible to fracture or rupture when exposed to an applied force of a magnitude determined by the specific application for reserve battery  10 , and that is sturdy enough to resist premature rupture or fracture due to, for example, handling of the device in which the reserve battery  10  is installed. If the device is an artillery shell, for example, the frangible barrier  14  may be formed of a type of material and a thickness of material selected to rupture only if the reserve battery  10  is exposed to a predetermined acceleration for a predetermined time. The outer perimeter of the frangible barrier  14  is sealed with the inward-facing surface of the battery case  12  by a conventional method, such as an oxide glass to metal compression seal.  
         [0019]     Cell electrodes  22  represent an assembly comprising a stacked spirally-wound arrangement of anodes, which may be formed from any suitable material (e.g., lithium), series-connected current collectors or cathodes, which are formed from an electrical conductor (e.g., high surface area carbon), and separators of electrically-insulating material between adjacent pairs of anodes and cathodes. The anodes of the cell electrodes  22  may include lithium deposited on thin nickel substrates and the current collectors may be high surface area carbon on a chemically etched thin nickel substrate. The invention contemplates that the cell electrodes  22  may have any conventional arrangement as understood by persons of ordinary skill in the art. The electrolyte  18  may be any suitable electrolyte, such as thionyl chloride or sufuryl chloride (SO 2 Cl 2 ) which is commonly used in conjunction with lithium anodes. Excess electrolyte  18  may be housed inside compartment  16  to insure rapid and complete battery activation.  
         [0020]     The electrolyte reservoir defined by sealed compartment  16  is closed on one end by the frangible barrier  14  and on the opposite end by a reservoir cover  24  including a rolling diaphragm  26 . The rolling diaphragm  26  may be formed, for example, by a flexible annular nickel membrane having a thickness of about 0.002″. The outer peripheral edge of rolling diaphragm  26  is sealed with the battery case  12 .  
         [0021]     Reservoir cover  24  further includes a fill port member  28  having a threaded fill port or fluid passageway  30  used for filling the reservoir of compartment  16  with the electrolyte  18 , as explained below. An exposed first end face  32  of the fill port member  28  is sealed with an inner peripheral edge of rolling diaphragm  26 . An opposite end face  34  of the fill port member  28  is positioned in compartment  16  proximate to the frangible barrier  14 . The separation between the end face  34  and the nearby surface of the frangible barrier  14  is selected to minimize the likelihood that the reservoir cover  24  will inadvertently move, during handling and transportation, by an amount sufficient to rupture the frangible barrier  14  and activate the reserve battery  10 . A portion of terminal pin  25  located inside compartment  20  is generally aligned with the end face  34 , although the invention is not so limited, and may cooperate with fill port member  28  in rupturing the frangible barrier  14 . The fill port member  28  may be formed from the same material as the battery case  12 .  
         [0022]     A closure element or insert  36 , illustrated as a spherical stainless steel member or ball, is positioned in the fluid passageway  30  proximate to the second end face  34  and forms a sealing contact with a seat  40  defined inside the fluid passageway  30  proximate to end face  34 . As described below, after the reservoir of compartment  16  is filled with electrolyte  18 , the insert  36  is inserted with a frictional or interference fit into the fluid passageway  30 . An outer circumferential surface of the insert  36  has a sealing contact that creates a hermetic seal for preventing electrolyte leakage.  
         [0023]     With reference to  FIGS. 1-3 , a filling procedure for the reserve battery  10  will be described. As shown in  FIG. 2 , a fill tool  38  is coupled with a length of the fluid passageway  30  and the reservoir of compartment  16  is evacuated through an open lumen of fill tool  38 . Then, a volume of the electrolyte  18  is introduced into the reservoir of compartment  16  through the open lumen of fill tool  38 . While the fill tool  38  remains engaged with the fluid passageway  30  to stabilize and prevent unwanted movement of the fill port member  28 , the insert  36  is inserted into the fluid passageway  30 , as shown in  FIG. 3 , and forcefully driven into an interference fit with the seat  40 . After installation, the insert  36  may project beyond the end face  34  or, alternatively, may be recessed inside fluid passageway  30  beneath the plane of the end face  34 . The assembled reserve battery  10  is depicted in  FIG. 1 .  
         [0024]     With reference to  FIGS. 1 and 4 , the activation of the reserve battery  10  will be described. The reserve battery  10  is incorporated as a component of a device, such as an artillery projectile, having an activation projection  42  and is free to move relative to the device. The reserve battery  10  is positioned in the device with the end face  32  of the fill port member  28  proximate to the activation projection  42 . End face  32  may have a contacting relationship with the activation projection  42  or may be spaced a short distance from the activation projection  42  with a non-contacting relationship.  
         [0025]     A circuit inside the device is electrically coupled with the battery case  12 , which constitutes one connection point (i.e., a positive electrode) to the reserve battery  10 , and with the terminal pin  25 , which supplies the other connection point (i.e., negative electrode) with the reserve battery  10 . In the condition shown in  FIG. 1 , the reserve battery  10  is dormant and voltage is not generated as the frangible barrier  14  isolates the electrolyte  18  from the cell electrodes  22 . The reserve battery  10  is stored in this dormant state for an indefinite period until intentionally activated.  
         [0026]     The reserve battery  10  is oriented inside the device such that when the device is subject to heavy acceleration, such as the set back force experienced when a weapon fires an artillery projectile, the entire reserve battery  10  moves in the direction of arrow  50  toward the activation projection  42 . The applied force moving the reserve battery  10  toward the activation projection  42  is dependent upon the weight of the reserve battery  10 . If the applied force is sufficient, contact between the end face  32  of fill port member  28  and the activation projection  42  precipitates dynamic displacement of the end face  34  of fill port member  28  toward frangible barrier  14 . The rolling diaphragm  26 , which yields or rolls as the fill port member  28  moves, facilitates the displacement.  
         [0027]     The moving fill port member  28  effectively operates as a ram against the frangible barrier  14 . As a result, either the end face  34  of the fill port member  28  or a portion of the insert  36  projecting beyond the plane of the end face  34  is driven into the frangible barrier  14  and, in cooperation with the terminal pin  25 , causes rupture of the frangible barrier  14 . Rupturing the frangible barrier  14  releases the electrolyte  18  inside compartment  16  from its confinement for rapid flow into compartment  20 . Remnants or fragments  14   a  of the frangible barrier  14  are present in the electrolyte  18  but do not affect battery operation. The electrolyte  18  wets the cell electrodes  22  residing in compartment  20  and, thereby, activates the reserve battery  10  to generate electric current that energizes the circuit of the device coupled with battery  10 . The capacity of the reserve battery  10  is specified by the application. For example, the reserve battery  10  should have a capacity adequate to at least permit in-flight operation of circuitry in an artillery projectile.  
         [0028]     While the present invention has been illustrated by a description of various embodiments and while these embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicant&#39;s general inventive concept. The scope of the invention itself should only be defined by the appended claims, wherein I claim: