Abstract:
A family of spacers of various sizes for securing a standardized terminating electrical protection device (such as one of the “snap-cap” type) to an electrical energy power source (i.e., a lithium electrochemical cell) is described. The terminating protection device is mounted on a header for an electrochemical cell and contains a circuit board provided with electrical components, such as diodes and fuses. The function of the circuit board is generally to protect the cell from being overcharged or too rapidly discharged, and the like. The spacers are sized to take up the space between the edge of the cell and the edge of the terminating protection device. That way, only variously sized spacers need to be stocked. The spacers are relatively simple to manufacture and inexpensive to stock. For example, the same terminating protection device sized for a “C” sized cell can be used on any larger size cell, for example, a “D” sized cell, by providing a spacer taking up the space between the edge of the larger cell and the terminating protection device.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims priority from provisional application Ser. No. 60/422,199, filed Oct. 30, 2002. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to devices for protecting an electrical component, and more particularly to a protection device for a circuit board connected to an electrochemical cell or battery. 
     Protection devices are known for protecting an electrical component, such as a fuse and diode assembly, mounted on an electrochemical cell. According to the present invention, a protection device housing a circuit board mounted on an end of the cell is provided with a cylindrical spacer ring. The spacer ring surrounds and captures the protective device so that a standard shrink-wrap material is suitable for securing the spacer and, consequently, the protective device to the cell. By providing spacers rings in various sizes for variously sized cells, the protection device is standardized. Examples of protection devices, sometimes referred to as snap-cap devices, for an electrical component connected to an electrochemical cell are found in U.S. Pat. Nos. 6,205,034, 6,317,335 6,426,867, and 6,437,239, all to Zayatz, and U.S. Pat. Nos. 6,617,953 and 6,618,273, both to Zayatz et al., the disclosures of which are hereby incorporated by reference. 
     SUMMARY OF THE INVENTION 
     The present invention provides a relatively inexpensive family of spacers of various sizes for securing a standardized terminating electrical protection device (such as one of the “snap-cap” type) to an electrical energy power source (i.e., a lithium electrochemical cell). The terminating protection device is mounted on the cell header and contains a circuit board provided with electrical components, such as diodes and fuses. The function of the circuit board is generally to protect the cell from being overcharged or too rapidly discharged, and the like. 
     Conventional practice is to provide the terminating protection device sized for a particular sized cell. However, this means that separate devices must be manufactured and stocked for each cell size. The present spacers eliminate this stocking problem. The spacers are sized to take up the space between the edge of the cell and the edge of the terminating protection device. That way, only variously sized spacers need to be stocked. The spacers are relatively simple to manufacture and inexpensive to stock. For example, the same terminating protection device sized for a “C” sized cell can be used on a “D” sized cell, and larger, by providing a spacer taking up the space between the edge of the larger cell and the terminating protection device. 
     These and other aspects and advantages of the present invention will become increasingly more apparent to those skilled in the art by reference to the following description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded view of a protective housing  36  including a terminal cap  68  mounted on a cell  10 . 
     FIG. 2 is a perspective view of the protective housing  36  mounted on the cell casing  12  shown in FIG.  1 . 
     FIG. 3 is a side elevational view of the protective housing  36  shown in FIG. 1 mounted on an oversized cell casing  12 A with the aid of a spacer ring  78  according to the present invention. 
     FIG. 4 is an enlarged view of the indicated area in FIG.  3 . 
     FIG. 5A is a top plan view of the spacer ring  78  shown in FIGS. 3 and 4. 
     FIG. 5B is a side elevational view of the spacer ring  78 . 
     FIG. 5C is a bottom plan view of the spacer ring  78 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, FIG. 1 is an exploded view of an electrochemical cell  10  comprising a casing  12  closed by a lid or header  14  to house the electrochemical components therein. The cell comprises an anode active material  15 A and a cathode active material  15 B segregated from each other by a separator  15 C and activated with an electrolyte (not shown). The cell is not intended to be limited to any particular chemistry, and can comprise a solid anode/solid cathode type or a solid anode/liquid depolarizer type. The cell can be of either a primary or a secondary chemistry. Exemplary chemistries include lithium/iodine, lithium/silver vanadium oxide, Li-ion cells, and the like. 
     In any event, the cell is typically built in a case-negative configuration having the anode electrically connected to the casing  12  and header  14  as the negative terminal and the cathode electrically connected to a terminal pin  16 . The terminal pin  16  is electrically isolated from the casing  12  and header  14  by an insulating glass  18  forming a glass-to-metal seal. The cell can also be built in a case-positive configuration having the cathode connected to the casing and header and the anode connected to the terminal pin. 
     A circuit board  20  having any one of a number of electrical components, such as a fuse  22  and diode  24 , is mounted on the cell header  14 . The exact electrical components and their configuration are not necessarily part of the present invention and depend on the intended application of the cell  10 . The present invention is, however, directed to protecting the electrical components of the current board  20  from shock and vibration conditions, and the like, regardless of their exact function and configuration. 
     The fuse  22  and diode  24  are supported on a substrate  26  of an insulating material. The substrate  26  has an aperture  28  sized to receive the terminal pin  16  when the circuit board  20  is mounted on the cell header. In this position, the terminal pin  16  is connected to a first lead  30  having one of its ends disposed immediately adjacent to the aperture  28  perimeter. That way, when the circuit board  20  is supported on the cell header with the terminal pin  16  extending through the aperture  28 , a weld is used to connect the first lead  30  to the terminal pin  16 . The other end of the lead  30  is connected to an electrical trace (not shown) embedded in or provided on the substrate  26 . 
     A second lead  32  has its proximal end connected to the substrate  26 . The distal end of this lead is for connecting to the cell header serving as the negative terminal for the case-negative cell  10 . Similarly, a third lead  34  is provided with its proximal end connected to an electrical trace (not shown) embedded in or provided on the substrate  26 . The distal end of this lead is for connecting to a terminal for the terminal pin  16 , as will be described in detail hereinafter. 
     In order to protect the circuit board  20  from damage, for example, if the cell is used to power a downhole tool in an oil well logging or drilling operation, a protective housing  36  is provided. A material that is suitable for the protective housing  36  is a polyamide sold by E. I. du Pont de Nemours and Company under the trademark ZYTELO (Nylon 6/6) 70G33L. Other suitable materials include VICTREX® (PEEK) 450-G manufactured by Victrex USA Inc. of Westchester, Pa., a polyamide-imide available from DSM Engineering Plastic Products, Inc. of Reading, Pa., as TORLON® 4203 PAI, a material marketed under the name KETRON® PEEK 1000 by DSM Engineering Plastic Products, Inc., and a liquid crystal polymer market as ZENITEe by E. I. du Pont de Nemours and Company. 
     In the embodiment shown in FIGS. 1 and 2, the protective housing  36  has a base  38  of a size and shape that substantially matches that of the cell header  14 . Since the exemplary cell is housed in a cylindrical casing  12 , the base  38  is circular with a centrally located aperture  40  therethrough. However, it is within the scope of the present invention that the base  38  can have other multi-sided shapes, such as square, rectangular, octagonal, and the like. The shape of the base  38  need not necessarily match that of the cell header. 
     The base  38  supports a plurality of arcuate projecting shoulders  42  spaced at intervals about the periphery thereof. The projecting shoulders  42  comprise an outer wall  44  and an inner wall  46 , both extending upwardly to an upper surface  48 . The plane of the upper surface  48  is substantially parallel to the plane of the base  38 . The plurality of outer walls  44  are spaced inwardly from the outer periphery of the base  38  to provide a ledge  50 , the purpose of which will be described hereinafter. 
     Upwardly extending retaining clips  52  are supported on the base  38  between each pair of adjacent projecting shoulders  42 . The retaining clips  52  comprise an outer wall  54  and an inner wall  56 , each wall extending upwardly to an inwardly projecting hook portion  58 . The hook portion  58  comprises an angled wall  60  that slopes downwardly and inwardly toward the base aperture  40  to terminate at a planar bottom wall  62 . The plane of the bottom wall  62  is substantially parallel to the plane of the base  38  and spaced above the upper planar surfaces  48  of the projecting shoulders  42 . The junction where the angled wall  60  meets the bottom wall  62  of each retaining clip  52  is spaced somewhat outwardly toward the base perimeter in relation to the inner wall  46  of the projecting shoulders  42 . The plurality of outer walls  44 ,  54  of the respective projecting shoulders  42  and retaining clips  52  are substantially at an equal radius from the base aperture  40 . 
     To facilitate manufacturing the retaining clips  52 , for example by injection molding, molding orifices  64  are preferably provided in the base  38 . The molding orifices  64  allow a portion of a mold to extend through the base  38  to form the bottom wall  62  of the retaining clips  52 . Once the retaining clips  52  are formed, the mold is withdrawn through the molding orifices  64 . 
     The protective housing  36  is mounted on the cell header  14  with the terminal pin  16  received in the base aperture  40 . The circuit board  20  is supported on the base  38  of the housing  36  with the terminal pin received in the aperture  28  thereof. 
     A compressible pad  66  and terminal cap  68  complete the protective housing. The compressible pad is preferably a silicone-based material capable of withstanding temperatures up to at least about 200° C. A silicone based material suitable for the compressible pad 66 is available from Furon Company of New Haven, Conn. as product number R10470 and referred to by the trademark COHRLASTIC®. 
     The pad  66  is sized to fit snuggly inside the inner wall  46  of the projecting shoulders  42  with a thickness from the upper surface of the circuit board  20  to the retaining clips  52 . The terminal cap  68  is shaped to match the shape of the inner walls  56  of the retaining clips  52 . The outer peripheral edge of the terminal cap  68  is sized to extend beyond the inner walls  46  of the projecting shoulders  42  to contact the inner walls  56  of the retaining clips  52  in a close-fitting, releasable relationship. 
     After the compressible pad  66  is positioned inside the protective housing  36  resting on the circuit board  20 , the terminal cap  68  is inserted into the protective housing  36  over the pad to rest on the upper surface  48  of the projecting shoulders  42 . Since the retaining clips  52  are of a resilient material, they flex backwardly enough to accommodate this movement, and then snap back into their original position to capture the terminal cap  68  confined between the projecting shoulders  42  and the retaining clips  52 . The terminal cap  68  can be removed without damage to the protective housing  36 , if necessary. 
     The terminal cap  68  is preferably of a conductive material, such as stainless steel or nickel, and includes an upwardly projecting boss  70 . The previously described third lead  34  from the circuit board is bent to curl up and over the top of the terminal cap  68  and welded, soldered, or otherwise secured thereto. This electrically connects the terminal cap  68  to the cell&#39;s terminal pin 
     As shown in FIG. 1, the cell header  14  is provided with a projection  72  spaced from the terminal pin  16 . The projection  72  is received in a second aperture  74  (shown in dashed lines) in the base  38  of the protective housing  36 . This further prevents rotational movement of the protective housing  36  relative to the cell  10  and header  14 . Furthermore, a thin NOMEX® disc (not shown) with double sided high temperature adhesive may be used to secure the protective housing  36  to the header  14 . 
     FIG. 2 is a perspective view of the protective housing  36  including the terminal cap  68  mounted on the cell header  14 . As shown, the outer peripheral edge of the base  38  of the protective housing  36  is substantially equal to the size of the cell header  14 . The ledge  50  formed between the plurality of outer walls  44 ,  54  of the respective projecting shoulders  42  and the retaining clips  52  provides a structure for securing the protective housing  36  to the cell  10 . While not shown in the drawings, a cylindrically shaped piece of shrink-wrap polymeric material is positioned over the casing sidewall to extend upwardly beyond the ledge  50 . The shrink-wrap is then heated, such as by a hot-air gun. This causes the shrink-wrap material to become semi-liquid and then shrink down onto the cell and protective housing, lying over the ledge  50  as it cools. In this position, the deformed shrink wrap locks the protective housing  36  down onto the cell header  14 . 
     It is a primary aspect of the present invention to standardize the shape of the protective housing  36 , compressible pad  66 , terminal cap  68  and circuit board  20 . That way, the same size parts can be used regardless of the size of the cell. For example, while FIG. 2 shows a cell  10  that has substantially the same peripheral size as the protective housing  36 , that is not necessary. FIGS. 3 and 4 show a cell  10 A comprising a cylindrical casing  12 A having a peripheral size substantially larger than the periphery of the protective housing  36 . In these figures, the circuit board, compressible pad, terminal cap, and projecting shoulders of the protective housing  36  are not shown for the sake of simplicity. The cell  10 A can be of a similar or different chemistry as the cell  10  shown in FIGS. 1 and 2. 
     In order to secure the undersized protective housing  36  to the header  14 A for cell  10 A, a spacer  78  is provided. As shown in FIGS. 5A to  5 C, the spacer  78  is generally a ring shaped member having a circular outer wall  80  and a circular inner wall  82 . The coaxial outer and inner walls  80 ,  82  extend to a planar upper surface  84 . The junction of the outer wall  80  and a lower surface  86  forms a step  88 . A ledge  90  is provided at the junction of the inner wall  82  and the planar bottom surface  86 . With the protective housing  36  resting on the cell header  14 A having the cell terminal pin  16 A received in the base aperture  40  of the protective housing  36 , the ledge  90  is sized to surround and capture the step  50  of the protective housing. The step  88  of the spacer  78  is disposed adjacent to the periphery of the cell header  14 A. Then, when the previously described shrink-wrap polymeric material is heat-shrunk down and onto the spacer  78  and its step  88 , the spacer is secured to the cell. The spacer, in turn, helps secure the protective housing  36  to the cell. 
     Thus, it can be seen that cells of a wide variety of sizes can be provided with a stock protective housing  36 , compressible pad  66 , terminal cap  68  and circuit board  20 . The spacer  78  is provided in a variety of sizes to take up the space between the step  50  of the protective housing  36  and the peripheral edge of the cell. That way, there only needs to be a variety of spacer sizes kept in stock and not a variety of protective housings, compressible pads, terminal caps and circuit boards. This greatly facilitates economy of assembly, as less different sized parts are needed to build cells of different sizes to meet customer requirements. 
     It is appreciated that various modifications to the inventive concepts described herein may be apparent to those skilled in the art without departing from the spirit and the scope of the present invention defined by the hereinafter appended claims.