Patent Publication Number: US-2004056637-A1

Title: Minimizing battery-to device contact resistance stemming from insulating contaminant layer on same

Description:
RELATED APPLICATION  
     [0001] The present application is related to the following commonly owned U.S. patent application:  
     [0002] U.S. patent application entitled “BATTERY ARRANGEMENT FOR REDUCING BATTERY TERMINAL CONTACT RESISTANCE STEMMING FROM INSULATING CONTAMINANT LAYER ON SAME,” naming as inventor Larry E. Maple. 
    
    
     
       BACKGROUND OF THE INVENTION  
       [0003] 1. Field of the Invention  
       [0004] The present invention relates generally to batteries and, more particularly, to decreasing battery terminal contact resistance attributable to the presence of an insulating contaminant layer on the battery terminals.  
       [0005] 2. Related Art  
       [0006] Electrical devices commonly derive their power by way of one or more batteries that are housed within a compartment associated with the electrical device. The battery compartment typically is integral with the electrical device. Alternatively, the battery compartment can be provided remotely from the electrical device with a connection thereto via conductor elements such as electrical wires.  
       [0007] There are numerous types of primary (non-rechargeable) and secondary (rechargeable) batteries. Dry cell batteries are commercially available in a number of well-known sizes and configurations such as the standardized AAA, AA, C, and D battery sizes. Miniature batteries, also referred to as watch, disc, dish, and button batteries, are also available in standard sizes and are commonly used in hearing aids, electric wristwatches and other devices.  
       [0008] Dry cell battery compartments have a positive contact, commonly in the form of a planar tab or a conical coiled spring, for electrically contacting the negative terminal of an installed dry cell battery. A negative contact, commonly in the form of a planar tab, is provided in the compartment for electrically contacting the positive terminal of an installed dry cell battery. Planar and dimpled tabular contacts are commonly used in miniature battery compartments. When one or more batteries are installed in such battery compartments, the device serves as an electrical load placed across the terminals of the installed batteries.  
       [0009] In compartments that require more than one dry cell battery, the batteries are housed in a series or parallel arrangement. In a series arrangement, the batteries are positioned “head to tail” with the planar surface of the positive terminal button abutting the negative terminal surface of the forward adjacent battery, with the batteries having parallel or coexistent longitudinal axes; that is, the batteries form a straight line. As a result, batteries arranged in this manner are said to be “linearly aligned”.  
       [0010] A well-documented problem with standard dry-cell, miniature and other types of batteries is the oxidation and sulfidation of the battery terminals. Oxide and sulfide layers often develop with time such as from when the batteries are manufactured to when they are ultimately used. In addition, galvanic corrosion of the battery terminals can occur in certain circumstances and environments. These oxide, sulfide and corrosive films are surface contaminants that insulate the battery terminal. Of particular relevance to the present invention is the increased battery contact resistance caused by this insulating contaminant layer. Contact resistance is the electrical resistance in the battery circuit attributable to the physical contact between adjacent batteries and between the batteries and the device. In circumstances in which the terminals have an insulting contaminant layer, the contact resistance can be significant, consuming valuable battery power, particularly in high current applications. This results in the rapid depletion of the installed batteries, decreasing device availability and increasing the rate at which the batteries need to be replaced or recharged. Furthermore, such a high contact resistance decreases the maximum current available from the installed batteries, making certain battery arrangements unsuitable for use in high current devices.  
       [0011] For example, two 1.2-volt dry cell batteries arranged in series provide 2.4 volts. In a high current application of 5 amperes, the batteries deliver 12 watts of power. If the contact resistance increases from a nominal 0.06 ohms to 0.2 ohms due the presence of an insulating contaminant layer on one or more of the battery terminals, the power consumed overcoming the contact resistance increases from 1.5 to 5 watts. In other words, 40% of the available power is consumed by the contact resistance. This reduces the power and current available to the device. In addition, the lost power essentially heats the battery terminals and/or device contacts. This can damage or degrade the batteries, damage the battery compartment and increase the risk of fire.  
       [0012] One traditional approach to solving this problem has been to provide the operator with a separate dimpled piece of sheet metal to insert between neighboring linearly aligned batteries. This approach has some drawbacks. For example, the additional part increases product cost. It also adds complexity, making it difficult for the user to install quickly and easily the batteries. The user must install a first battery, position the sheet metal intermediate contact in the proper position, and then insert the second battery while retaining the sheet metal in its proper position. Thus, such supplemental parts are often used improperly or misplaced or lost and not used at all.  
       [0013] An insulating contaminant layer on the battery terminal also increases the contact resistance between the batteries and device. For example, the first battery in a series battery arrangement is positioned with the planar surface of its positive terminal button parallel to and in contact with a planar negative tab contact of the device. The last battery in the series battery arrangement is positioned such that its planar negative terminal surface is parallel to and in contact with a planar conical coiled spring winding or contact tab. Conventional conical coiled spring contacts have a series of helical windings, with the upper winding residing in a plane substantially parallel to and in contact with the negative battery terminal surface. Similarly, in parallel arrangements, the batteries are each positioned with their positive and negative terminals contacting the opposing polarity contacts of the battery compartment in a similar manner. The planar tab and planar conical coiled spring winding can not penetrate the insulating contaminate layer coating the battery terminals.  
       SUMMARY OF THE INVENTION  
       [0014] The present invention is directed to a conical coiled spring battery contact for use in a battery compartment that ruptures an insulating contaminant layer on a terminal of a battery installed in the battery compartment. Such a conical coiled spring contact minimizes the contact resistance between the conical coiled spring contact and the battery terminal due to the presence of such an insulating contaminant layer. This in turn increases the amount of battery power and current available for the implementing device.  
       [0015] A number of aspects of the invention are summarized below, along with different embodiments that may be implemented for each of the summarized aspects. It should be understood that the embodiments are not necessarily inclusive or exclusive of each other and may be combined in any manner that is non-conflicting and otherwise possible regardless of which aspect of the invention they are presented in connection with. It should also be understood that these summarized aspects of the invention are exemplary only and are considered to be non-limiting.  
       [0016] In one aspect of the invention, a conical coiled spring contact for use in a battery compartment is disclosed. The coiled spring contact is constructed and arranged such that only a battery terminal contact point contacts an abutting a terminal of a battery installed in the battery compartment, wherein said contact point is defined by a minimal surface area of an upper end turn of the coiled spring contact.  
       [0017] In another aspect of the invention, a conical coiled spring contact for use in a battery compartment to contact a terminal of a battery installed in the battery compartment is disclosed. The conical coiled spring contact is constructed and arranged with an upper end turn configured such that a minimum surface area of the upper end turn comes into contact with the installed battery.  
       [0018] In a still further aspect of the invention, a battery compartment is disclosed. The battery compartment includes a housing configured to receive one or more batteries; and a conical coiled spring contact. The conical coiled spring contact has a lower end turn secured to an interior surface of the housing, an upper end turn for contacting a terminal of an installed battery, and a plurality of concentric windings disposed between the upper and lower end turns. The upper end turn forms a forward-most eccentric terminal contact point to contact a terminal of a battery installed in the housing.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0019] The foregoing and other features and advantages of the present invention will be understood more clearly from the following detailed description and from the accompanying figures. This description is given by way of example only and in no way restricts the scope of the invention. In the drawings, like reference numerals indicate identical or functionally similar elements. Additionally, the left most one or two digits of a reference numeral identify the drawing in which the reference numeral first appears. In the figures:  
     [0020]FIGS. 1A and 1B are schematic side views of two prior art dry cell batteries that can be arranged in accordance with embodiments of the present invention.  
     [0021]FIGS. 2A and 2B are schematic side views of two prior art miniature batteries that can be arranged in accordance with embodiments of the present invention.  
     [0022]FIG. 3 is a schematic diagram of two dry cell batteries in a serially-aligned arrangement with their respective longitudinal axes intersecting in accordance with one embodiment of the present invention.  
     [0023]FIG. 4 is a schematic diagram of two miniature batteries in a serially aligned arrangement with their respective longitudinal axes intersecting in accordance with one embodiment of the present invention.  
     [0024]FIG. 5 is an illustration of a device contact tab in accordance with one aspect of the present invention.  
     [0025]FIG. 6 includes a top, front and side views of a conical coiled spring device contact with an eccentric contact point in accordance with one embodiment of the present invention.  
     [0026]FIG. 7A includes a top, front and side views of a conical coiled spring device contact with an eccentric contact point in accordance with an alternative embodiment of the present invention.  
     [0027]FIG. 7B is an isometric view of a conical coiled spring device contact with more than one eccentric contact point in accordance with an alternative embodiment of the present invention.  
     [0028]FIG. 8 is an illustration of a dry cell battery compartment that retains the batteries in a serially-aligned, intersecting longitudinal axis arrangement in accordance with one embodiment of the present invention.  
     [0029]FIG. 9 is an illustration of a dry cell battery compartment that retains the batteries in a serially-aligned, intersecting longitudinal axis arrangement in accordance with one embodiment of the present invention.  
     [0030]FIG. 10 is an illustration of a dry cell battery compartment that retains the batteries in a serially-aligned, intersecting longitudinal axis arrangement in accordance with one embodiment of the present invention.  
     [0031]FIG. 11A is an illustration of a battery compartment for miniature batteries that retains the batteries in a serially-aligned, intersecting longitudinal axis arrangement in accordance with one embodiment of the present invention.  
     [0032]FIG. 11B is an illustration of a battery compartment for miniature batteries that retains the batteries in a serially-aligned, intersecting longitudinal axis arrangement in accordance with an alternative embodiment of the present invention.  
     [0033]FIG. 12 is a schematic block diagram of a hand-held scanner having a battery compartment in accordance with one embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION  
     [0034] I. Introduction  
     [0035] The present invention is directed to methods and apparatus that minimize battery-to-battery and battery-to-device contact resistance by rupturing or removing an insulating contaminant layer disposed on the portions of the battery terminals that contact each other or that contact the contacts of a battery compartment. Specifically, the present invention arranges standard dry cell and miniature batteries such that a minimum surface area of the terminals contacts of an adjacent battery terminal or device contact. A given compression force applied to the serially-aligned batteries in the battery compartment results in a maximum contact pressure sufficient to rupture the insulating contaminant layer disposed on the surface of the abutting battery terminals and/or abutting battery terminal and device contact. Preferably, a relative lateral motion is imparted between adjacent batteries and/or a battery and device contact when the batteries are installed in the battery compartment to facilitate the penetration of the insulating contaminant layer.  
     [0036] The disclosed embodiments of the present invention are directed to a battery arrangement for two or more standard dry cell or miniature batteries with their respective longitudinal axes intersecting at an angle which causes the batteries to contact each other with a minimal accessible surface area of at least one of the terminals, such as the edge of a positive terminal button of a dry cell battery or an edge of the positive casing of a miniature battery. Providing battery-to-battery and battery-to-device contact at only this terminal edge region minimizes the contact surface area and maximizes the localized contact pressure. This ruptures the insulating contaminant layer on the contacting terminal regions thereby reducing contact resistance attributable thereto. Importantly, the resulting decrease in contact resistance is achieved without reconfiguring the batteries; that is, standard, commercially available batteries are used, and without using additional components such as springs or dimple sheets.  
     [0037] The present invention is also directed to a conical coiled spring battery contact for use in a battery compartment. The conical coiled spring contact is configured with an upper end turn that is bent to form one or more terminal contact regions having a minimal surface area for contacting a terminal of an abutting battery. The contact region(s) each provide, for a given compression force, a contact point that imparts a pressure sufficient to rupture an insulating contaminant layer on the abutting battery terminals. Preferably, the conical coiled spring contact has an axis of rotation defined by the windings with the terminal contact point(s) laterally offset from the axis. This causes regions of the windings in this lateral direction to compress more that other regions of the windings in response to an axial compression force applied by an abutting battery. This in turn causes the terminal contact point(s) to shift further in the lateral direction as the contact spring is compressed. As this occurs, the terminal contact point(s) scrape against the terminal of the installed battery, removing substantially any insulating contaminant layer disposed on the battery terminal.  
     [0038] II. Battery Description  
     [0039] A battery, sometimes referred to as an electric cell, is a device that converts chemical energy into electricity. As used herein, a battery can consist of one cell alone as well as two or more cells connected in series or parallel within a single casing. Each cell consists of a liquid, paste or solid electrolyte, a positive electrode and a negative electrode. The electrolyte serves as an ionic conductor; one of the electrodes reacts with the electrolyte to produce electrons while the other electrode accepts the electrons. When connected across a load, such as when installed in a device battery compartment, this reaction causes current to flow from the battery and power to be consumed. Although the present invention can be applied to and operate with many types of rechargeable and non-rechargeable batteries, the present invention, solely for the ease of understanding, will be discussed in connection with two of the more common types of batteries, dry cell batteries and miniature batteries. Such batteries have different chemistries such as Lithium Ion, Nickel Cadmium, Nickel Metal Hydride, rechargeable alkaline, and others.  
     [0040] A. Dry Cell Batteries  
     [0041] A perspective view of two commonly available, standard dry cell batteries is provided in FIGS. 1A and 1B. Dry cell batteries  100 A and  100 B are collectively and generally referred to as dry cell batteries  100  or, simply, battery or batteries  100 . Dry cell batteries  100  can be either primary or secondary batteries. Primary batteries are batteries in which the electrolytes cannot be reconstituted into their original form once the energy stored in the battery has been converted into a current; that is, they are non-rechargeable. Primary battery cells were originally referred to as a Leclanche cell in honor of its inventor, French chemist Georges Leclanché who invented the dry cell battery in the 1860&#39;s. Other names given to this type of battery include, for example, a flashlight battery, a voltaic battery, an alkaline battery, etc. Dry cell batteries  100  can also be secondary batteries. Secondary batteries can be recharged by reversing the chemical reaction in the battery; that is, they are rechargeable. Such a battery was invented in 1859 by the French physicist Gaston Planté. The chemical composition of rechargeable and non-rechargeable dry cell batteries  100 , some of which are noted above, are well known and not described further herein.  
     [0042] The size and configuration of primary dry cell batteries and, more recently, secondary dry cell batteries are specified by ANSI standards, and are commercially available in the standardized AAA, AA, C, and D battery sizes. As such, a common feature of all such dry cell batteries  100  is its configuration. FIGS. 1A and 1B are side views of two prior art dry cell batteries  100 A and  100 B that satisfy the specifications for a “C” size dry cell battery. Dry cell batteries  100  includes a cylindrical shell or casing  108  defining a head region  102  and a tail region  104 . A positive terminal  106  is disposed at head region  102  while a negative terminal  108  is disposed at tail region  104 . The internal configuration and chemistry of dry cell batteries  100  varies, and is well known in the art. However, in all cases, positive terminal  106  is a formed cylindrical protrusion extending from casing  110 , commonly referred to as a button. Terminal button  106  has a curved or parabolic edge  112  while the top surface  114  of positive terminal button  106  is substantially planar. A longitudinal axis  118  extends through batteries  100  from negative terminal  108  to positive terminal  106 . Planar surfaces  116  and  114  are orthogonal to longitudinal axis  118 . The height or thickness  120  of positive terminal button  106  varies, as shown by the two illustrative batteries  100 A and  100 B.  
     [0043] Examples of the above batteries are available from Duracell, Inc., and Eveready Battery Company, Inc. DURACELL® batteries are described in detail at www.duracell.com, while the EVEREADY® batteries are described in detail at www.eveready.com. (DURACELL is a registered trademark of Duracell Inc., a division of The Gillette Company. EVEREADY is a registered trademark of the Eveready Battery Company, Inc.) Because the dimensions of these and other dry cell batteries have been standardized and are specified by ANSI standards, the dimensions of such batteries will be substantially the same, within the specified tolerances, regardless of manufacturer.  
     [0044] B. Miniature Batteries  
     [0045]FIGS. 2A and 2B are top and side views of two embodiments of another common battery in use today, referred to herein as a miniature batteries  200  (collectively and generally referred to as miniature battery  200  or, simply battery or batteries  200 ). Miniature battery  200  is also referred to as a watch, coin, button, disc, dish and mercury battery. Today, miniature battery  200  is commonly available in chemistries such as mercury, lithium and manganese dioxide, silver oxide, and others.  
     [0046] Miniature batteries  200  are made in the shape of a small flat disk for use in, for example, hearing aids, photoelectric cells and electric wristwatches. A miniature battery  200  includes a disc-shaped shell or casing  210  defining a head region  202  and a tail region  204 . A positive terminal  206  is located at tail region  204  while a negative terminal  208  is located at head region  202 . The internal configuration of miniature batteries is considered to be well known in the art and is not described further herein. The height or thickness  220  of miniature batteries  200  varies, as shown by the two illustrative batteries  200 A and  200 B. Negative terminal  208  may be a small cylindrical raised surface, as shown on battery  200 A, or it may be flush with the surface, as in battery  200 B. In battery  200 B, negative terminal  208  does not extend to the periphery of battery casing  210 . As shown in the top view, it is a substantially circular region with a diameter slightly less than the diameter of battery casing  210 . As with dry cell batteries  100 , the top surface  216  of negative terminal  208  and the surface  214  of positive terminal  206  are substantially planar. Each battery  200  has an axis  218  through its center, extending from positive terminal  206  to negative terminal  208 . Planar surfaces  214 ,  216  are substantially orthogonal to longitudinal axis  218 .  
     [0047] III. Battery Arrangements  
     [0048] Battery compartments currently available today hold one or more batteries either in a laterally adjacent or a serially aligned manner. In the laterally-adjacent arrangement, the batteries are each electrically connected to a positive and negative device contact, while in the serially-aligned arrangement, the batteries are aligned with their longitudinal axes parallel or coextensive with each other. Batteries in this latter conventional arrangement are referred to herein as being “linearly aligned” with each other; that is, they form a straight line. In both arrangements, the longitudinal axes of an installed battery is also parallel or coextensive with a central axis of the conical coiled spring contact and an orthogonal surface vector of the device tab contact. Such arrangements dictate that conventional dry cell batteries  100  and miniature batteries  200  have planar surfaces  114 ,  116 ,  214 ,  216  that abut each other and/or a planar coil winding or tab device contact. As noted, the contact resistance between such linearly-aligned batteries can be significant due to the presence of an insulating contaminant layer that is disposed on the battery terminals. A similar phenomenon also occurs between the battery terminals and device contacts. Conventional approaches such as those noted above typically retrofit such existing battery compartments with additional parts that are designed to decrease contact resistance between the adjacent, linearly-aligned dry cell batteries. As noted, such supplemental parts add to the complexity of the battery compartment, and are often used improperly or not at all.  
     [0049] In contrast to such approaches, the present invention includes a battery compartment in which one or more batteries are arranged so that a minimal surface area of their respective terminals contacts each other. Specifically, the inventor has observed that existing dry cell batteries  100  and miniature batteries  200  have an edge on at least one of their terminals that is accessible by a planar, opposing-polarity terminal of an adjacent battery. Specifically, referring again to FIGS. 1A and 1B, positive terminals  106  of dry cell batteries  100  have, as noted, a curved or parabolic edge surface  112  around the periphery of planar positive terminal surface  114 . Since positive terminal button  106  is raised from head portion  102  and the remainder of the positive terminal surface, edge  112  is accessible by a planar, opposing-polarity battery terminal or device contact that is nonparallel to the planar surface  114  of positive terminal  106 . Referring again to FIGS. 2A and 2B, positive terminal  206  of miniature batteries  200  includes a casing with an accessible edge  212 . Edge  212  is, as noted, a curved or parabolic surface around the periphery of planar positive terminal surface  214 . Because edge  212  is on the periphery of the battery casing, edge  212  is a region of the positive terminal surface that is accessible by a planar, opposing-polarity battery terminal or device contact that is nonparallel to the planar surface  214  of positive terminal  206 .  
     [0050] Battery compartments configured in accordance with the present invention arrange the installed batteries with terminal edges  112 ,  212  being the only point of contact between positive battery terminals  106 ,  206  and corresponding negative terminals  108 ,  208 . By taking advantage of terminal edge  112 ,  212 , the present invention reduces the area of contact between neighboring batteries as compared to the planar contacting surfaces  114  and  116 , and provides a significant localized contact pressure between neighboring batteries  100 ,  200 . This contact pressure is significantly greater that the contact pressure provided by conventional battery arrangements subject to the same compression force. The high pressure contact point ruptures an insulating contaminant layer on terminals  106 ,  108 ,  206  and  208 . This, in turn, decreases the contact resistance between neighboring batteries installed in a battery compartment of the present invention. In certain embodiments, the contact resistance between the installed batteries and the device contacts is also reduced in a similar manner.  
     [0051]FIGS. 3 and 4 are illustrations of two dry cell batteries and two miniature batteries, respectively, arranged in accordance with various embodiments of the present invention. FIG. 5 is a schematic diagram of a device contact and a dry cell battery arranged in accordance with another embodiment of the invention. Referring to FIG. 3, two dry cell batteries  100 , labeled for ease of reference as batteries  302 A and  302 B in FIG. 3, are arranged in accordance with the present invention. Specifically, dry cell battery  302 A is positioned in front of dry cell battery  302 B. A terminal contact point  304  is the only point of contact between positive terminal  106  of battery  302 B and negative terminal  108  of battery  302 A. Terminal contact point  304  is that region of positive terminal edge  112  that contacts planar surface  16  of negative terminal  108 . To achieve this, dry cell batteries  302  are arranged such that their longitudinal axes  118 A and  118 B intersect each other at a predetermined angle  308 . Angle  308  ranges from an angle greater than that at which planar surfaces  114 ,  116  are parallel with each other, as in conventional arrangements (that is, zero degrees), and an angle less than that at which casings  110  contact each other and cause the separation of terminals  106 ,  108  (which varies with the dimensions of dry cell batteries  100 ).  
     [0052] Similarly, referring to the miniature battery arrangement illustrated in FIG. 4, two miniature batteries  200 , labeled for ease of reference as batteries  402 A and  402 B in FIG. 4, are arranged in accordance with the present invention. Specifically, miniature battery  402 A is positioned in front of miniature battery  402 B. A terminal contact point  404  is the only point of contact between positive terminal  206  of battery  402 B and negative terminal  208  of battery  402 A. Terminal contact point  404  is that region of positive terminal edge  212  that contacts planar surface  216  of negative terminal  208 . To achieve this, miniature batteries  402  are arranged such that their longitudinal axes  218 A and  218 B intersect each other at a predetermined angle  408 . Angle  408  ranges from an angle greater than that at which planar surfaces  214 ,  216  are parallel with each other (that is, zero degrees), and an angle less than 90 degrees.  
     [0053] As will be described in detail below, battery compartments of the present invention also impart a relative lateral movement between adjacent battery terminals and/or between a battery terminal and device contact when the terminals and/or contacts come into contact with each other, preferably while under some compression force. This is illustrated with arrows in FIGS. 3 and 4. Referring to FIG. 3, one battery  302  can move in the direction of arrow  310  or  312  while the other battery  302  remains stationary or moves in the opposing direction  310 ,  312 . In such aspects of the invention, the insulating contaminant layer disposed on the terminals is broken or otherwise penetrated by the resulting contact wiping action. Such a battery compartment is configured such that the batteries are serially-aligned and the device contacts are on opposing ends of the installed batteries. The distance between the opposing polarity device contacts is less than that of the total length of batteries that are installed therebetween. When the batteries are installed in the battery compartment, the batteries are pressed against the device contacts. The device contacts undergo elastic deformation providing the space necessary to enable the batteries to be installed in the battery compartment. Thereafter, the device contacts apply a spring force along the longitudinal axis of the batteries when the batteries are in their installed position in the battery compartment. This spring force compresses the batteries against each other, insuring the terminal-to-terminal and the terminal-to-device contacts are maintained. Such a relative lateral movement can be invoked during installation or at other subsequent times, such as in response to the activation of a mechanical switch, depending on the embodiment and application.  
     [0054]FIG. 5 is a schematic diagram of a contact tab configured in accordance with the present invention illustrating one implementation to reduce battery-to-device contact resistance. Referring to FIG. 5, in a dry cell battery compartment  500  configured in accordance with the present invention, a negative contact tab  502  is arranged so as not to be parallel with the surface  114  of positive battery terminal  106 . Rather, device terminal tab  502  is positioned so as to contact only positive terminal edge  112  of an installed battery  100 . This provides a contact point  304  between positive battery terminal  106  and negative device terminal  502  that imparts a greater contact pressure than would otherwise be imparted in conventional arrangements. The relative angles and other configuration details can be easily determined by those of ordinary skill in the art given the dimensions of battery  100 .  
     [0055] IV. Conical Coiled Spring Contacts  
     [0056]FIG. 6 includes side, top and front views of a conical coiled spring contact in accordance with one aspect of the present invention. Conical coiled spring contact  600  reduces or eliminates contact resistance between a battery terminal and conical coiled spring contact  600  by providing a high pressure contact point and, preferably, a contact wiping action that ruptures, scrapes or otherwise removes an insulting contaminant layer on an abutting battery terminal.  
     [0057] A conical coiled spring contact  600  of the present invention has a series of windings or convolutions  602 . In the embodiment shown in FIG. 6, windings  602  each has a diameter that is greater toward a lower end turn  614  and smaller toward an upper end turn  608 . As a result, the coiled spring contact  600  is approximately conical in shape. In alternative embodiments, the diameter of each winding  602  does not vary substantially or varies differently than that shown in FIG. 6. As shown in FIG. 6, the windings have a central axis of rotation  604 . The axis of the conical coiled spring is preferably parallel to or coextensive with axis  118 ,  218  of the abutting battery  100 ,  200 .  
     [0058] Lower end turn  614  defines a bottom face  612  while upper end turn  608  defines top face  606  of conical coiled spring contact  600 . Typically, bottom face  612  is secured to a region of an implementing battery compartment or circuit board while top face  606  contacts a battery  100 ,  200  installed therein. In contrast to conventional conical coiled spring contacts that, when compressed, maintains a flush contact between the surface along the length of the upper winding and the terminal surface, conical coiled spring contact  600  is configured with an upper end turn  608  that is bent to form a terminal contact region  610  for contacting negative terminal  108 ,  208  of dry cell batteries  100  or miniature batteries  200 . Contact region  610  provides, for a given compression force, a contact point that imparts a pressure sufficient to rupture an insulating contaminant layer on the abutting battery terminals.  
     [0059] Furthermore, contact point  610  is eccentric; that is, contact point  610  is spaced laterally from axis  604  of conical coiled spring  600 . As a result, as a battery  100 ,  200  compresses conical coiled spring contact  600 , contact point  610  shifts laterally from its shown position in the direction of eccentricity  616 . This imparts a lateral sliding motion against the abutting battery terminal that scrapes away a substantial portion of any existing insulating contaminant layer. In addition, as noted, contact point  610  thereafter provides a contact point that imparts a pressure sufficient to rupture any remaining insulating contaminant layer.  
     [0060] Conical coiled spring contact  600  is preferably formed of a highly conductive material, and is preferably unitary. In accordance with one aspect of the invention, a lead (not shown) is attached to distal end  620  of conical coiled spring contact  600  in any well-known manner. For example, a standard crimp-on connector is used in one embodiment. In another embodiment, the lead is soldered onto conical coiled spring  600  using any of a myriad of known techniques. In a further embodiment, an electrically conductive sleeve is securely connected to conical coiled spring  600 . The sleeve has an interior diameter sufficient to receive and retain the lead.  
     [0061] This is in contrast to conventional techniques that connect the lead to the opposite end of the conical coiled spring contact; that is, to lower end turn  614 . This conventional approach has been universally implemented because the lower end turn  614  is the portion of conventional spring contacts that is connected to the printed circuit board or battery compartment. In contrast, the present invention reduces substantially the significant bulk resistance of conical coiled spring contacts. For example, a typical conical coiled spring contact of a AA battery compartment uses 140-150 mm in length of 0.81 mm diameter wire. The resistance of such a coiled spring contact is approximately 0.211 ohms, 0.527 ohms, 0.337 ohms and 0.039 ohms when the spring contact material is 302 stainless steel, music wire, Be-Cu C 17200 and Phosphor Bronze 521, respectively. The present invention reduces the length of the coiled spring contact through which current travels from the approximate 140-150 mm to approximately 4 mm by connecting the lead to distal end  620 . This, in turn, reduces the bulk resistance of the conical coiled spring contact, for each of the noted materials, to 0.0055 ohms, 0.0139 ohms, 0.0044 ohms and 0.001 ohms, respectively. Furthermore, the conical coiled spring contact implementing this feature of the present invention can be used in place of conventional tab or leaf spring battery contacts due to the reduced bulk resistance. Such an application is cost effective because coiled spring contacts are significantly less expensive to manufacture than traditional dimpled leaf springs commonly used in conventional battery compartments. For example, the equipment to manufacture the conical coiled spring contact is significantly less expensive than the sheet metal die and related equipment to make the leaf springs. In addition, there is minimal material waste generated during the manufacturing process. Further, less material is used for each type of contact.  
     [0062]FIG. 7A includes a side, top and front view of a conical coiled spring contact in accordance with an alternative embodiment of the present invention. As with conical coiled spring  600 , conical coiled spring contact  700  reduces or eliminates contact resistance between an abutting battery terminal and conical coiled spring contact  700  by providing a high pressure contact point that ruptures, scrapes or otherwise removes an insulting contaminant layer on the contact  700  and abutting battery terminal.  
     [0063] Conical coiled spring contact  700  has a series of windings or convolutions  702 . In the embodiment shown in FIG. 7A, conical coiled spring contact  700  is conical in shape although it can have other configurations. As shown in FIG. 7A, the windings  702  have a central axis of rotation  704 .  
     [0064] A lower end turn  714  defines a bottom face  712  designed to be secured to a region of an implementing battery compartment while an upper end turn  708  defines top face  706  that contacts a battery  100 ,  200 . Conical coiled spring contact  700  is configured with an upper end turn  708  that is bent to form an eccentric terminal contact point  710  for contacting negative terminal  108 ,  208  of dry cell batteries  100  or miniature batteries  200 . Eccentric contact point  710  shifts laterally in the direction of eccentricity  716  as spring  700  is compressed, providing a lateral sliding motion against the abutting battery terminal and, thereafter, providing a high pressure contact point that can rupture an insulating contaminant layer on the abutting battery terminal.  
     [0065] Referring back to FIG. 6, contact point  610  of conical coiled spring contact  600  is formed with a hairpin upper end turn  608 . As shown, distal end  620  of coil  600  is directed toward bottom face  612  along axis  604 . Coiled spring contact  700  (FIG. 7) shows an alternative embodiment. Contact point  710  of conical coiled spring contact  700  is formed with a slight bend in upper end turn  708 . The apex of this bend forms contact point  710 . It should become apparent to those of ordinary skill in the art that in alternative embodiments, conical coiled spring contact can have other configurations that provide an eccentric contact point at top face  606 ,  706 .  
     [0066]FIG. 7B is an isometric view of a conical coiled spring contact with more than one eccentric contact point in accordance with an alternative embodiment of the coiled spring contact of the present invention. Conical coiled spring contact  750  reduces or eliminates contact resistance between an abutting battery terminal and conical coiled spring contact  750  by providing multiple high pressure contact points  752  each of which ruptures, and preferably scrapes, an insulting contaminant layer on contact point  752  and abutting battery terminal.  
     [0067] Conical coiled spring contact  750  is constructed similarly to contacts  600  and  700 .  
     [0068] Accordingly, the similar details are not described further herein. However, in contrast to contacts  600  and  700 , conical coiled spring contact  750  is configured with an upper end turn  756  with bends that form three eccentric terminal contact regions  752 A- 752 C on upper face  754  for contacting an abutting battery terminal. The relative location on upper end turn  756  of each terminal contact point  752  can be selected to prevent or induce the lateral shift noted above with reference to contacts  600  and  700 .  
     [0069] V. Battery Compartments  
     [0070] A. Battery Compartments for Dry Cells  
     [0071] As noted, in a dry cell battery compartment of the present invention the dry cell batteries are aligned with the longitudinal axes of neighboring batteries intersecting at an angle that results in the high pressure contact point of the positive terminal edge contacting the planar negative terminal of the neighboring battery. Such a battery compartment can have a number of configurations, some of which are described below.  
     [0072]FIG. 8 is an illustration of a dry cell battery compartment in accordance with one embodiment of the present invention. Battery compartment  800  includes a housing  802  configured to receive two dry cell batteries  814 A and  814 B in a serially aligned arrangement. Dry cell battery  814 A is in a forward position of compartment  800  while dry cell battery  814 B is in a rear position. Housing  802  includes a housing base  804  with a housing door  806  together defining an interior region of compartment  800 .  
     [0073] Housing base  804  includes a base floor  812  with an integral rear sidewall  808  and forward sidewall  810 . Secured to rear sidewall  808  is a conical coiled spring  600 . Conical coiled spring  600  contacts negative terminal  104  of battery  814 B. Attached to conical coiled spring contact  600  is an electrical lead  828 . Forward sidewall  810  has secured to it a fixed domed contact  820  for electrically contacting positive terminal  106  of forward battery  814 A. A lead  826  is electrically connected to contact  820 . Together, leads  828  and  826  provide current to the hosting device. Fixed domed contact  820  preferably has multiple contact domes each with a small radius to provide low contact resistance. In one embodiment, the domes are spaced closely and have a lead-in angle that prevents positive terminal  106  from being inadvertently retained within housing base  804 . Conical coiled spring  600  has the structure and performs the functions as those noted above, while fixed domed contact is conventional. It should be understood, however, that both fixed domed contact  820  and conical coiled spring contact  600  can be replaced with contacts having other configurations.  
     [0074] In the embodiment illustrated in FIG. 8, batteries  814  are shown in the fully installed position, with the angle  308  between their longitudinal axes  118  (FIG. 1) being approximately  7  degrees. It should be understood, however, that this angle is by way of example only and that batteries  814  can be arranged such that the angle  308  between their longitudinal axes is some other angle. In this illustrative embodiment, this angle is maintained by securing the batteries  814  against a floor having different slopes. As shown, housing floor  812  has one region with a surface that supports battery  814 A and a second region with a surface that supports battery  814 B. The surface of housing floor  812  in each of these regions has a relative angle and configuration to maintain the batteries  814  with their longitudinal axes at the desired intersecting arrangement.  
     [0075] Housing floor  812  includes resilient supports  816 A and  816 B for supporting batteries  814 A, and  814 B, respectively. Resilient supports  816 A and  816 B reside in channel  830 A and  830 B, respectively. In an uncompressed state, supports  816  have a height slightly greater than the depth of the respective channel  830 , extending above the surface of housing floor  812 . Resilient supports  816  are made of an elastomeric or other flexible supporting material. Initially, batteries  814  are placed in housing base  804  loosely. First, battery  814 A is installed against fixed contact  820 . When installed, battery  814 A rests on resilient support  816 A, elevated temporarily off of the surface of housing floor  812 . Forward sidewall  810  includes a cantilevered overhang  818  that extends over the location at which battery  814 A is to be located. Overhang  818  provides the operator with a guiding surface for installing battery  814 A. Then, battery  814 B is installed against conical coiled spring  600  with its positive terminal  106  resting against negative terminal  104  of battery  814 A. In this position, battery  814 B rests on resilient support  816 B, elevated temporarily off of floor  812 .  
     [0076] In an alternative embodiment, resilient supports  816  are replaced with flat springs having a dome that extends through an aperture in housing floor  812  approximately at the location of channels  830  shown in FIG. 8. In such embodiments, the spring can be heat staked or otherwise secured to the exterior surface of housing base  804 . Preferably, such a spring either is made of a plastic or coated with a non-electrically conductive coating. When implemented as springs, resilient supports  816  should not contact each other to prevent the springs from providing a conductive path should installed batteries  814  have a hole or other defect.  
     [0077] Housing door  806  includes a rigid structure  822  to which a battery compression member  822  is secured. Battery compression member  824  is configured to apply a compression force against batteries  814  when door  806  is closed. As door  806  is closed, battery  814 A is pushed against housing floor  812 , compressing resilient support  816 A. In addition, battery  814 A is pressed further against fixed contact  820 . This causes a relative lateral movement between positive terminal  106  of battery  814 A and fixed contact  820 . As noted, when this is performed while under a force against contact  820 , contact  820  ruptures substantially any insulating contaminant layer disposed on positive terminal  106 . The disclosed embodiment of compression member  824  is nonconductive since it contacts simultaneously both installed batteries  814 . In an alternative embodiment, springs or other flexible elements could be used. It should be understood, however, that if a conductive material is used, it should be implemented as two elements each of which contacts one battery  814  to prevent the establishment of a conductive path between the two battery casings.  
     [0078] Similarly, as door  806  is closed, battery compression member  824  applies a compression force against battery  814 B, pushing battery  814 B against conical coiled spring  600  and against resilient support  816 B to ultimately rest on housing floor  812 . Due to the axial force exerted by conical coiled spring  600 , positive terminal  106  of battery  814 B scrapes against the surface of negative terminal  104  of battery  814 A as battery  814 B travels toward floor  812 . This causes a relative lateral movement between positive terminal  106  of battery  814 B and negative terminal  104  of battery  814 A, as well as between negative terminal  104  of battery  814 B and conical coiled spring contact  600 . As noted, this wipes or scrapes a significant portion of any insulating contaminant layer disposed on positive terminal  106  and negative terminal  104  of battery  814 B.  
     [0079] As shown in FIG. 8, the points at which such a compression force is applied is at the head and tail regions of batteries  814 . As one of ordinary skill in the art would find apparent, the locations at which such a compression force is applied, the sequence in which the force is applied as door  806  is closed, and similar operational features is a function of a number of factors. These factors include, for example, the number of batteries  814  in battery compartment  800 , the configuration of the installed batteries, the manner in which housing door  806  engages housing base  804 , etc. In one particular embodiment, housing door  806  is hinged to housing base  804  and includes a latch for securing one to the other. It should be understood that housing door  806  is sufficiently rigid such that when it is in its closed position, door  806  forces batteries  814  into housing base  804  as described above regardless of variations in battery tolerances.  
     [0080]FIG. 9 is a side view of an alternative embodiment of a battery compartment of the present invention. Battery compartment  900  has a curved housing  902  that holds two dry cell batteries  100  in a linearly-aligned, intersecting axis arrangement. A domed contact  908  is mounted on latched door  904  so as to contact positive terminal  106  of a battery  100  in position  914 A when door  904  is latched to housing  902 . A conical coiled spring contact  600  is mounted on the distal interior surface of housing  902  to contact negative terminal  104  of dry cell  100  in a position  914 B. Leads  910  and  912  are connected to conical coiled spring contact  600  and domed contact  908 , respectively.  
     [0081] Compartment housing  902  is curved such that batteries  100  contact each other as illustrated in FIG. 3 and described above. As door  904  is closed and dry cell  914 A is forced against dry cell  914 B, a spring  906  or other deformable material located in housing  902  causes a relative lateral movement of dry cells  914 . Under the initial compression force, spring  906  deforms, allowing dry cell  914 A to travel further into housing  902 . Dry cell  914 A then slides downward in the direction of arrow  916 . This causes a relative lateral movement to occur between batteries  914 A and  914 B. Such a lateral movement causes edge  112  of dry cell  914 B to scrape through the insulating contaminant layer on negative terminal  104  of dry cell  914 A.  
     [0082] It should be appreciated that other mechanisms can be implemented with curved housing  902  to effect a desired relative lateral motion between batteries  914 A and  914 B. For example, in one alternative embodiment, a slide switch is mounted on housing  902  adjacent to tail region  104  of battery  914 A. The slide switch travels in a slot substantially parallel with the longitudinal axes of batteries  914 . A top portion of the slide switch is disposed on the exterior of housing  902  for manual access and control. A beveled protrusion of the slide switch is disposed in the interior of housing  902  adjacent to battery  914 A. As the slide switch travels along the slot from a forward position (toward latched door  904 ) to a rear position (toward conical coiled spring contact  600 ), a larger portion of the beveled region becomes interposed between tail region  104  of battery  914 A and the interior surface of housing  902 . This results in a downward force in the direction of arrow  916 , repositioning battery  914 A in a downward direction. This causes a relative lateral movement between the two batteries  914 A and  914 B to occur. As noted, such a lateral movement causes edge  112  to scrape through a substantial portion of the insulating contaminant layer. Preferably, the slide switch is made of one or more non-conductive materials to prevent the sliding switch from breaking through the insulation on the battery case and causing a short.  
     [0083]FIG. 10 is a side view of another embodiment of a battery compartment of the present invention. Battery compartment  1000  includes a clamshell housing  1002 . Housing  1002  is separated longitudinally into two halves: a bottom half  1002  for receiving batteries  914  and a top half  1006  hingedly connected to bottom half  1004 . In this embodiment, a relative lateral movement is imposed on the installed batteries through the operation of the clamshell housing  1002 . Bottom housing half  1004  receives batteries  914  in a partially installed position. Top half  1006  includes non-conductive extensions  1010  such as rubber posts, extending from the its interior surface toward bottom half  1004 . As top housing half  1004  is rotated about hinges  1008  from an open position to a closed position, extensions  1010  come into contact with batteries  914 , imparting a force on batteries  914  in direction  916 . This force pushes battery  914 B bottom half  1004  and into conical coiled spring  600 . As conical coiled spring  600  is compressed, dry cell  914 B rotates slightly, causing edge  112  of positive terminal  106  of dry cell  914 B to forcibly travel against the surface of negative terminal  104  of dry cell  914 A under a force applied by conical coiled spring contact  600 .  
     [0084] B. Battery Compartments for Miniature Batteries  
     [0085]FIG. 11A is a schematic illustration of a battery compartment  1100  for miniature batteries in accordance with one embodiment of the present invention. In this particular embodiment, housing  1102  is configured to receive three miniature batteries  1104 A- 1104 C. As shown, batteries  1104  are arranged such that edges  212  of batteries  1104 B and  1104 C provide a high pressure contact point against surfaces  216  of miniature battery  1104 A and  1104 C, respectively. This novel arrangement was introduced and described above with reference to FIG. 4.  
     [0086] It should be appreciated that the space provided in housing  1102  for each battery  1104  is sufficient to allow for maximum size of one battery and the minimum size of a neighboring battery. As such, the edges  212  may contact surface  216  at different locations depending on the particular batteries installed. To provide for minor adjustments to accommodate such variations in batteries  1104 , housing  1102  provides a corner  1108  against which miniature battery  1104 B pivots. In addition, space is provided between batteries  1104  and interior surface of housing  1102 .  
     [0087] In the embodiment shown in FIG. 11A, a device domed contact  1104 A is mounted in battery compartment  1100  to contact positive terminal  206  of miniature battery  1102 A. As miniature battery  1104 B pivots against corner  1108  the point at which it contacts surface  216  of miniature battery  104 A will vary. Accordingly, domed contact  1104 A is preferably a contact with widely spaced domes to insure that battery  1102 A is maintained against battery  1102 B. Another domed contact  1106 B is provided in compartment  1100  to contact negative terminal  208  of miniature battery  1104 C. Domed contact  1106 B also should be of sufficient size to insure proper electrical contact between it and adjacent battery  1104 C regardless of the size variations of all installed batteries  1104 . It should also be appreciated that either or both domed contacts  1106  can be replaced by a conical coiled spring contact  600 ,  700  of the present invention, as described above.  
     [0088]FIG. 11B is an illustration of a battery compartment  1150  for miniature batteries in accordance with an alternative embodiment of the present invention. As shown, batteries  1154  are arranged such that edges  212  provide a high pressure contact point against surfaces  216  of an adjacent miniature battery. In this particular embodiment, housing  1152  is configured to receive five miniature batteries  1154 . In this arrangement, a repetitive pattern is developed, with batteries  1154 A and  1154 B having the same relative position as batteries  1154 C and  1154 D, and batteries  1154 B and  1154 C having the same relative position as batteries  1154 D and  1154 E. A fixed domed contact  1156 B is provided at one end of the arrangement while a flexible domed contact  1156 A is provided at the other to maintain the batteries  1154  in contact with each other. Four pivot corners  1108  are provided to allow for minor adjustments and variations in battery sizes. It should be appreciated that the repetitive arrangement can be extended to include any number of batteries  1154 .  
     [0089] VI. Exemplary Device Application  
     [0090] The battery compartment of the present invention can be implemented in any battery-powered device now or later developed. Any battery-powered device can benefit from the present invention. As noted, those devices that are most adversely effected by the noted contact resistance are high current devices. Examples include devices that have light attachments such as cameras, scanners, flash lights and VCRs; power tools such as power screw drivers, power drills, hedge trimmers, electric razors, and the like; and other types of battery-powered devices. It should be understood that this is not by limitation and that the present invention can be implemented on numerous other battery-powered devices. One such device, a scanner, is described below with reference to FIG. 12. FIG. 12 is a schematic block diagram a hand-held scanner implementing the battery compartment of the present invention. Scanner  1200  is any scanner such as the hand-held optical scanners available from Hewlett-Packard Company.  
     [0091] Scanner  1200  has a bell-shaped housing  1202  with a flat bottom surface  1216 . Housing  1202  is designed to be easily grasped by a user. Generally, the user will hold housing  102  and manually drag scanner  1200  over a paper  1204  to scan to printed information presented thereon. Scanner  1200  includes a CCD  1206  with navigational illumination lights  1214 . Navigation illumination devices  1214  are high power drainage devices that generate infrared light that is used by an image processing and data storage device  1208  to track the location of scanner  1200  on paper  1204 . CCD  1206  picks up the information on the page  1204  and image processor  1208  reconstructs the image on the paper. A battery compartment  1212  is configured to receive two 1.2 volt, AA dry cell batteries. Power supply  1210  coverts the 2.4 DC voltage to a 5 and 12 volts DC for use by scanner  1200 .  
     [0092] Due to the high power consumption of navigation illumination devices  1214 , scanner  1200  draws approximately 5 amps. Without the present invention, scanner  1200  can deplete the two 1.2 volt batteries in 0.25-0.30 hours. A significant contributing factor to this rate of depletion is that the contact resistance between the two batteries is on the order of 0.2 ohms due to the presence of an insulating contaminant layer over the battery terminals. As such, 5 watts or 40% of the available 12 watts of power can be consumed overcoming the contact resistance. Implementing the present invention, however, reduces the contact resistance between abutting batteries to approximately 0.06 ohms; thereby reducing the power consumed overcoming the contact resistance to 1.5 watts. Similar scanners that operate at 2.5 amperes reduce the power losses at the terminal contacts from 1.25 watts to 0.38 watts, illustrating that devices with lower current requirements also benefit substantially from the present invention.  
     [0093] The present invention is related to commonly owned U.S. patent application “BATTERY ARRANGEMENT FOR REDUCING BATTERY TERMINAL CONTACT RESISTANCE STEMMING FROM INSULATING CONTAMINANT LAYER ON SAME,” naming as inventor Larry E. Maple, filed concurrently herewith, which is hereby incorporated by reference herein.  
     [0094] While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. For example, it should also be appreciated that although the noted dry cell and miniature batteries are described as being primary batteries, the present invention can also be used with secondary, or rechargeable batteries having the same or similar configuration. In the embodiments disclosed herein, the longitudinal axes of neighboring batteries both lie in the same imaginary plane. However, this need not be the case. That is, the longitudinal axes may not reside in the same plane. In other words, the longitudinal axes of the neighboring batteries may not only intersect at an angle in one plane or axis, but may also intersect at an angle in a second or third plane or axis. It should also be clear that the number of batteries is not restricted to those disclosed herein. For example, any number of dry cell batteries  100  can be serially aligned, each having the relative arrangement with its neighbor as noted above. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.