Battery Terminal and Case Structure

1. Field of the Invention

The present invention relates generally to electrochemical devices and, more particularly, to terminal connector assemblies for a device such as a battery. Specifically, the present invention relates to improved terminal assemblies for electrochemical devices, such as batteries, which assembly structures reduce the transmission of mechanical loads to the sealing mechanism thereof. In addition, the present invention further relates to electrochemical cell casing structures adapted to contain such improved terminal assemblies as well as to provide substantial gripping handles for the battery.

2. Description of the Prior Art

A major concern in the manufacture and use of sealed electrochemical devices, such as batteries, is that of leakage of electrolyte and/or gas from the battery container. Under normal conditions, such leakage generally occurs at the site where a battery terminal exits the battery container or casing thus providing a path for leakage. Optimally, a battery terminal should be capable of complete sealing against leakage of electrolyte and/or gases contained within the battery during the lifetime of the battery.

Numerous approaches to resolving this problem have been developed in the past. Such past approaches have included the use of elastic bushings, grommets, press-fit ferrule structures, and the like. A particularly successful battery terminal arrangement is disclosed in U.S. Pat. No. 4,859,547, the contents of which are hereby incorporated herein by reference. This particular arrangement includes a battery terminal post which passes through an opening in a resilient casing, and a pair of ferrules or bushings inserted about the terminal post and press-fit into the opening within the casing wall. In this manner, a much more efficient seal is effected between the terminal post and the plastic casing at the terminal interface without failure due to electrolyte or gas seepage.

Nonetheless, battery terminal structures utilized in existing starved electrolyte recombination batteries do not generally provide adequate gas and electrolyte sealing for a long-life, sealed cell, especially where the terminals are subjected to vibrational stresses. Typically, the battery as designed does provide adequate sealing. However, when mechanical loads, such as torques and pullouts, are applied to the exterior terminal connectors, such mechanical loads are transmitted to the sealing area and tend to loosen the seal. When a seal fails, the life of the battery is diminished through the loss of electrolyte and the ingress of oxygen, as well as through the corrosion of the battery terminal post and the connectors.

In another battery terminal design as taught in U.S. Pat. No. 3,704,173, the seal used in a sealed recombination cell has a terminal seal which prevents the leakage of gas and electrolyte between the lead and plastic parts. This seal depends on an expanding body, that is a rivet, to create and maintain the seal. The external terminal connector of the cell is of a different material from the lead post and also depends on intimate contact between the rivet and the post to obtain a path through which current can flow. An alternate design for the terminals, as disclosed in U.S. Pat. No. 3,964,934, includes the use of a threaded stud which is cast into the post during the post manufacturing. This design depends on the drawing of the stud into the plastic post cavity via a nut to obtain its seal. Both of these designs require non-lead parts to create the electrolyte and gas seal. Additionally, should a corrosion occur between the lead post and the expansion body, that is the rivet or the stud, the electrical contact between the rivet or stud and the lead port can be seriously degraded or lost, thus making the cell unusable. For high-current applications, the dissimilar metals contact creates an area which is susceptible to heating due to contact resistance. This can result in weakening of the seal area and also promotes oxidation of the contact surfaces which can further increase the contact resistance.

The terminal seal taught by U.S. Pat. No. 4,859,547 overcomes some of the aforementioned problems. This particular design permits the use of all lead parts and a terminal configuration without sacrificing seal performance, manufacturing ease or manufacturing costs. Under the design of this particular U.S. Patent, the plastic seal area is molded into the battery lid. However, under vibrational loads and/or high external mechanical stresses, the seal can nonetheless be damaged. Damage can also result to the terminal seal when the battery lid moves relative to the battery elements and the battery case or when the outer terminal moves relative to the sealing components in the battery lid. Thus, there still remains a need for a battery terminal design which provides long-term sealing capability against leakage despite mechanical loading on the battery and which overcomes the other aforementioned problems.

Accordingly , it is one object of the present invention to provide an improved terminal connector structure for electrochemical batteries.

It is another object of the present invention to provide a terminal structure for electrochemical devices which provide sealing capability against electrolyte leakage even under high mechanical load stress conditions.

It is yet another object of the present invention to provide an improved electrochemical battery design having enlarged handle portions for carrying the battery.

Still another object of the present invention is to provide an improved terminal connector design for batteries wherein the sealing mechanism which prevents electrolyte leakage is remote from the external terminal member of the battery.

To achieve the foregoing and other objects and in accordance with a purpose of the present invention as embodied and broadly described herein, a terminal connector assembly is disclosed. The terminal connector assembly conducts electric current from an electrolytic device through the wall of a case containing the device while preventing leakage of the electrolyte from the case. The terminal connector assembly includes a terminal insert mounted within the case wall. The insert includes a first end portion which projects through the wall and forms an exterior connection member, and a second end portion laterally spaced from the first end portion within the case and which forms an interior connection member remote from the exterior connection member. A mechanism is provided for substantially reducing the transmittal of mechanical loads from the first end portion to the second end portion. Moreover, a member electrically interconnects the interior connection member with the electrolytic device within the case. Finally, a mechanism is provide for sealing the connection between the electrically interconnecting member and the interior connection member to prevent leakage of electrolyte from the device.

These and other objects of the present invention will become apparent to those skilled in the art from the following detailed description, showing the contemplated novel construction, combination, and elements as herein described, and more particularly defined by the appended claims, it being understood that changes in the precise embodiments of the herein disclosed invention are meant to be included as coming within the scope of the claims, except insofar as they may be precluded by the prior art.

The accompanying drawings together with the description illustrate complete preferred embodiments and serve to explain the principles of the invention according to the best modes presently devised for the practical application of the principles thereof, and in which:

FIG. 1 is front perspective view of a battery constructed in accordance with the present invention;

FIG. 2 is top plan view of the battery of FIG. 1 with the cover member removed therefrom;

FIG. 3 is a partial sectional view taken generally along line 3--3 of FIG. 2; and

FIG. 4 is an exploded view of the components of a terminal insert member constructed in accordance with the present invention.

Referring first to FIG. 1, an electrochemical device or battery 10 is illustrated and includes a case 12 having body side portions 14 and a bottom portion 16 integrally molded together. Preferably, the case 12 is made from an electrically nonconductive, resilient material such as plastic and the like. In one preferred form, polypropylene is utilized to form case 12, with the cell walls of case 12 are approximately 1/8th inch thick. The body 14 is divided into a plurality of chambers 18, six being illustrated, which are sized and shaped to receive individual electrochemical cells as is known in the art, and described below and, for example in U.S. Pat. No. 4,780,379. An upper flange member 20 is a substantially rectangular in shape is integral with, and forms the upper portion of case 12. A cover 22 is also substantially rectangular in shape and is sized and shaped to fit over flange 20 and provide a cover for battery 10. Terminal connectors 24, 26 are provided at each end of battery 10 and are configured to accept connection to a user's battery cables. In addition, flange 20 provides two ledge portions 28, 30 at either end of battery 10 proximate terminal connectors 24, 26. The ledges 28, 30 function as handles in order to lift and grasp battery 10 in easy fashion.

Referring now with more particularity to FIGS. 2-4, a plurality of individual electrochemical cells or elements 32, 34, 36, 38, 40 and 42 are disposed within chambers 18 of battery 10. As shown, elements 32, 34, 36, 38, 40 and 42 are shown to be, and are preferably cylindrical in form and are deposited within cylindrical chambers 18 (FIG. 1). The cylindrical cells provide for tight compression which results in improved cell life. In one preferred form, the electrochemical elements or cells 32, 34, 36, 38, 40 and 42 are arranged in two substantially parallel rows with cells, 32, 34 and 36 in one row, and cells 38, 40 and 42 in a second adjacent row. As can be seen from FIGS. 1 and 2, the first row of cells 32-36 are aligned in an offset fashion relative to the second row of cells 38-42 so that the cells 38-42 nest in the areas 44 between cells 32, 34 and 36. In this manner, cells 32, 34, 36, 38, 40 and 42 are positioned in closer proximity to each other as compared to prior art cells wherein the rows of cells are aligned immediately next to each other in mirror image. In addition, the design of the present invention enables more electrolyte and active material a to be placed within the same case volume and reduces empty space between the cells and the battery cover, thus providing a more effective use of space. Finally, this offset arrangement of cells 32, 34, 36, 38, 40 and 42 also enables the creation of ledges 28 and 30 which serve a dual function, as described below.

The cells 32, 34, 36, 38, 40 and 42 are interconnected in electrical series by electrically conducting strap members 46. Moreover, terminals 24, 26 are electrically interconnected to cells 32, 34, 36, 38, 40 and 42 by end-straps 48 and 50. The construction of straps 46, 48 and 50 and elements 32, 34, 36, 38, 40 and 42 are well known in the art and disclosed in the U.S. Pat. No. 4,859,547 and U.S. Pat. No. 4,780,379, the contents of which are hereby incorporated by reference, as though set forth in their entirety, and details with respect to their construction and function will not be repeated herein.

The terminal connector design of the present invention will be described with respect to terminal connector 24 and ledge 28. However, it should be noted that the terminal connector 26 and ledge 30 are essentially mirror images of external connector 24 and ledge 28 and are thus formed and function in a similar manner. Moreover, while the preferred embodiment of the terminal connector 24 is described in detail below, any terminal configuration may be utilized wherein the interior connection is laterally spaced from the exterior connection in accordance with the present invention.

Referring to FIGS. 3 and 4, in one preferred form, terminal connector 24 includes an insert member 52 which is mounted in and preferably molded into casing wall 54 of ledge portion 28. The insert member 52 includes an elongated body portion 56 having a first end portion in the form of a terminal post 58. The terminal post 58 projects angularly from body 56 and preferably at right angles to body 56. The terminal post 58 preferably includes an upper collar 60 which provides a shoulder for engagement with cover 22. A terminal stud 62 projects axially outwardly from the end of post 58 to form an exterior terminal connector member 24.

Disposed at the opposite end of body member 56 is a second end portion preferably a in the form of a pin 64 which also projects angularly upwardly and preferably at right angles a from body 56, and substantially parallel to post 58. In preferred form, pin 64 includes an annular collar 66 located at the base thereof proximate body member 56 to form a shoulder 68. As shown in FIG. 4, body member 56 and collar 66 are embedded within case wall 54 similar to post 58. However, pin 64, projects outwardly into the center of case 12 and is exposed to the interior space 94 of battery 10. The case wall 54 is sized and shaped so as to form an annular portion 70 immediately surrounding collar 66.

The above arrangement for insert 52 permits the exterior terminal connection member 62 to be remotely located within the ledge 28 relative to the interior connection member which is in the form of pin 64, as clearly illustrated in FIGS. 2 and 3. This spacing between the external terminal connection member 62 and the interior connection member 64, which in turn is connected directly to cell 38 by way of end strap 48, reduces the transmission of any mechanical loads which may be imposed on external connector member 62 to internal connection 64. Thus, torque loads imposed on external connection member 62 as well as loads imposed by outward pulling are resisted by case wall 54 and are not transmitted to the internal connection member 64. In order to further assist in the reduction of transmission of mechanical loads, a plurality of ribs or tabs 72 are preferably provided along exterior surface of post 58. The tabs 72 enhance the surface area engagement between case wall 54 and post 58 to assist in enabling cell wall 54 to carry rotational or torque loads imposed on exterior connector member 62. Likewise, foot portions 74, 76 are provided at the base of post 54 and pin 64, respectively. The foot portions 74, 76 are in the form of flanges which extend laterally outwardly from body member 56 so as to provide additional surface area engagement with case wall 54. These foot portions 74, 76 likewise enhance the feature of mechanical loads being resisted and carried by case wall 54 rather than being transmitted to interior connection member 64.

In order to interconnect pin 64 to electrochemical cells 32, 34, 36, 38, 40 and 42, which are connected in series as previously described, end strap 48 includes an aperture 78 which is adapted to receive pin 64. In order to ensure that terminal connector 24 is sealed to prevent the leakage of gas or electrolyte from the case 12, a ferrule or bushing 80 is provided having a collar or flange portion 82, as shown in FIG. 4. The ferrule 80 is sized and shaped so that its internal opening 84 will receive pin 64 therein. The aperture 78 in end strap 48 is sized and shaped to receive exterior surface 86 of ferrule 80. The pin 64 and the ferrule 80 are tapered in form so that as end strap 48 is forced down about outer surface 86 of ferrule 80 which in turn is seated around pin 64, ferrule 80 is compressed tightly between the pin 64 and the end strap 48 so as to have a fluid tight press fit relationship between the three components. To this end, ferrule 80 is preferably constructed from lead so as to provide excellent electrical conductance while also being pliable. Due to the arrangement of insert member 52, end strap 48 is significantly higher, say about one inch, than body portion 56. This permits sealing ferrule 80 to be embedded in battery 10. In addition, this construction prevents extra space between cover 22 and the top of cells 32, 34, 36, 38, 40 and 42 as compared to the existing design as illustrated in U.S. Pat. No. 4,780,379. This arrangement reduces the volume available to collect hydrogen gases and thus reduces the danger of explosion.

Referring in particular to FIG. 3, annular member 70 surrounding collar 66 at the base of pin 64 includes an annular upraised portion 88 in the form of a sealing ring. The sealing ring 88 functions to engage and press into the bottom surface of the collar 82 of ferrule 80 as the ferrule 80 is pressed down about pin 64. In addition, annular portion 70 further includes an annular groove 90 into which a resilient O-ring 92 is placed. The combination of O-ring 92 and sealing ring 88 which engage collar 82 of ferrule 80 ensure against seepage of gas or electrolyte fluids from within interior 94 of battery 10 past the internal electrical connection.

Since good wear resistance and hardness are highly desired characteristics of the terminal, it is preferred that exterior terminal member 62 be constructed from a lead alloy which is much harder than pure lead. One preferred alloy is antimony (2%-8%)/lead alloy or an antimony/tin/lead alloy. Other alloy combination well known to the art may also be used. As previously indicated, it is preferred that the sealing ferrule 80 be constructed from pure lead. The end strap 48 is preferably also a lead alloy so as to provide a harder material as compared to sealing ferrule 80. To complete the construction of the interior connection with end strap 48, a fusion weld 96 is completed between pin 64, sealing ferrule 80 and end strap 48. This burn or fusion weld 96 ensures sound and firm mechanical attachment and electrical contact between these three components.

To assemble the battery arrangement of the present invention, the preferably cylindrical battery elements 32, 34, 36, 38, 40 and 42, constructed in accordance with known technology, are placed into the appropriate cavities 18 in battery case 12 and partially pressed into place. As previously discussed, cavities 18 are arranged in two rows in offset fashion. The battery cell interconnection straps 46 are then cast onto cell tabs 98 along with end straps 48, 50, which are configured to fit over the interior terminal end pin 64 and sealing ferrule 80. The cells 32, 34, 36, 38, 40 and 42 with these straps 46 are then fully pressed into case 12, and end straps 48, 50 are then pressed over terminal pin 64 and sealing ferrule 80 of terminals 24 and 26. The end strap, terminal pin and sealing ferrule are then all burned together to form a good electrical path through the fusion weld 96. At the appropriate time in the assembly sequence, battery lid or cover 22 is joined to the battery case 12, thus completely sealing the battery from the external environment.

The offset arrangement of battery cells 32, 34, 36, 38, 40 and 42 allow for the creation of ledges 28 and 30, and permit insert member 56 to be integrally molded within case wall 54 at ledge 28 while providing the spaced apart relationship between the external battery connector 62 and the internal connecting member 64. As previously discussed, this spaced apart relationship as well as other features of inset member 52 provide the significant advantage of the present invention by reducing the transmittal of mechanical loads to the sealing area of the internal connecting member. In this manner, the seal is less likely to be broken as in prior designs since it is not exposed to the mechanical stresses that have caused failure of prior art sealing designs.

As can be seen from the above, the present invention provides several significant advantages over the prior art. The present invention provides a battery design which, due to its offset sequencing of cells, permits more electrolyte and active material to be placed within the same volume as compared to prior art designs. This enhances the life and power of the battery. Moreover, the present invention also provides handles at each end of the battery of significant size to permit full grasping of the battery with the user's hands rather than fingertip control as is the case of many prior art battery designs. Inasmuch as these batteries tend to be quite heavy, prior art designs permitting only fingertip lifting of the batteries created inconvenience and safety concerns. The present invention overcomes these problems by providing substantial, full hand-hold members to pick up and carry the battery of the present invention. Moreover, the present invention provides a terminal connector arrangement whereby mechanical loads imposed on the external terminal connectors are not transmitted to the internal connection area which carries the seal which in turn prevents the leakage of electrolyte and gas from the interior of the battery. By preventing the transfer or transmittal of mechanical loads to the seal area, the present invention substantially a reduces the likelihood of such seals being broken over time due to vibration or handling of the battery. Thus, the present invention provides for longer life due to less likelihood of electrolyte seepage.

The foregoing description and the illustrative embodiments of the present invention have been described in detail in varying modifications and alternate embodiments. It should be understood, however, that the foregoing description of the present invention is exemplary only, and that the scope of the present invention is to be limited to the claims as interpreted in view of the prior art.