Patent Publication Number: US-2005123830-A1

Title: Parallel rib battery cover

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
      This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/527,400 filed on Dec. 5, 2003, entitled “PARALLEL RIB BATTERY COVER,” herein incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION  
      This invention relates in general to a battery cover, and deals more particularly with a battery cover having parallel ribs formed on the underside thereof, thus providing greater structural rigidity and integrity.  
     BACKGROUND OF THE INVENTION  
      Over the past 25 years, containers for lead-acid batteries have come to be made chiefly of polypropylene. As a structural material, polypropylene exhibits the desired chemical resistance and strength over the temperature ranges in which motive-power and automotive batteries normally operate. Moreover, the use of polypropylene material is economically viable in the large-scale production of battery containers.  
      The covers utilized with polypropylene battery containers are typically attached to the body of the battery jar via hot-plate welding operation or the like. Prior to the use of polypropylene, hard rubber was utilized for lead-acid battery containers, and their covers were attached and sealed with asphalt. Asphalt seals, however, were not as strong or as durable as welded polypropylene seals.  
      Despite these drawbacks, one benefit of containers and covers made from hard rubber is that they exhibit a higher stiffness modulus than does polypropylene. Covers are preferably stiff in the area surrounding the filling hole, as it is undesirable for this area to become depressed by forces exerted during the filling process. Any such depression in this area may promote the collection of acid, water and contaminates which may get inside the battery and thus lead to possible catastrophic failure of the battery as a whole.  
      It is also desirable that the peripheral area surrounding the filling hole remains substantially flat so that a gasket disposed between the filling hole and a filler cap will seal well.  
      Given the desire in the art for stiff battery covers, stiffening in the area surrounding the filling hole has been previously addressed by several differing techniques. One technique involves providing a cylindrical skirt  10  that depends from the periphery of the filling hole, together with radially extending gussets  12  between the skirt and the underside of the top of the cover, as shown in  FIGS. 1-3 . These measures have been adequate for hard-rubber covers, but have been found to be somewhat lacking in stiffness, in certain situations, when utilized with covers made from polypropylene.  
      Another known technique involves simply making the battery cover thicker. Although marginally effective, such a technique increases material use and hence directly affects cost. Moreover, thicker battery covers would also indirectly affect the cost of each cover as a result of the longer cooling times inherently required during/after the molding process.  
      With the forgoing problems and concerns in mind, it is the general object of the present invention to provide a battery cover which overcomes the above-described drawbacks while providing greater structural rigidity and integrity.  
     SUMMARY OF THE INVENTION  
      It is an object of the present invention to provide a battery cover.  
      It is another object of the present invention to provide a battery cover that provides greater structural rigidity and integrity.  
      It is another object of the present invention to provide a battery cover that provides greater structural rigidity and integrity without substantially increasing molding time and cost.  
      It is another object of the present invention to provide a battery cover having parallel ribs formed on the underside thereof, thus providing greater structural rigidity and integrity.  
      According, therefore, to one embodiment of the present invention, a battery cover includes a planar section and an aperture formed through the planar section. A rib extends outwardly from the planar section and is substantially tangential to the aperture.  
      These and other objectives of the present invention, and their preferred embodiments, shall become clear by consideration of the specification, claims and drawings taken as a whole. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a top plan view of a known battery cover.  
       FIG. 2  is a bottom plan view of a known battery cover.  
       FIG. 3  is a cross-sectional view is of the battery cover shown in  FIGS. 1 and 2 .  
       FIG. 4  illustrates a perspective view of a battery cover according to one embodiment of the present invention.  
       FIG. 5  illustrates a top plan view of the battery cover shown in  FIG. 4 .  
       FIG. 6  illustrates a bottom plan view of the battery cover shown in  FIG. 4 .  
       FIG. 7  illustrates a perspective view of the bottom of the cover shown in  FIG. 4 .  
       FIG. 8  illustrates a cross-section view of the cover shown in  FIG. 4 .  
       FIG. 9  illustrates a finite element analysis of the force-deflection relationship of the cover design of the present invention compared with that of a known design.  
       FIG. 10  illustrates a cover according to another embodiment of the present invention.  
       FIGS. 11-14  illustrate a cover according to another embodiment of the present invention.  
       FIGS. 15 and 16  illustrate a top plan view and a bottom plan view, respectively, of a battery cover  20 , according to another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       FIGS. 4 and 5  illustrate a perspective and a top plan view, respectively, of a planar battery cover  20 , according to one embodiment of the present invention. As shown in  FIGS. 4 and 5 , a plurality of filling apertures for posts may be formed in the cover  20 , with a filling hole  22  typically defined in the middle thereof.  
       FIG. 6  illustrates a bottom plan view of the battery cover  20 . As shown in  FIG. 6 , the cover  20  includes two, preferably parallel, strengthening and stiffening ribs  24  provided on the underside of the cover  20 . The ribs  24  run from adjacent one side of the cover  20  to adjacent the other side of the cover  20 . In the preferred embodiment of the present invention, the ribs  24  are tangential to the skirt  26  and blend into the material of the cylindrical skirt  26  which depends downwardly from the cover  20 . A pair of venting slots  28  are provided in the cylindrical skirt  26  for gas venting through the cap that covers the filing hole  22 .  FIG. 7  illustrates a perspective view of the cover  20  and the ribs  24  shown in  FIG. 6 .  FIG. 8  illustrates a cross-section view of the cover  20  and the ribs  24  shown in  FIG. 6 .  
      Returning to  FIG. 6 , the ribs  24  are preferably straight and continuous and run substantially through the center of the cover  20 . It is important to note, however, that in the preferred embodiment of the present invention, the ribs  24  do not extend all the way to the edges of the cover  20 , thereby allowing a passage for any extraneous gasses to migrate around their ends to the pair of venting slots  28 , typically formed in the cylindrical skirt  26 , as mentioned previously, and as shown in phantom in  FIG. 7 .  
      It is therefore an important aspect of the present invention that the ribs  24  in conjunction with the cylindrical skirt  26  provide a cover  20  that is stronger and stiffer than known battery covers which utilize known radially extending gussets (best seen in  FIG. 2 ). These radially extending gussets are not efficient in reducing deflection around the filling hole primarily because the cylindrical skirt to which the radially extending gussets are attached can deflect radially.  
       FIG. 9  illustrates a finite element analysis of the force-deflection relationship of the cover design of the present invention compared with that of a known design, illustrating that a cover having the ribs  24  in accordance with the present invention is significantly stronger and stiffer than the known radially extending gusset design.  
      As shown in  FIG. 9 , two plate cover designs were examined, both formed from polypropylene. A cover formed with the ribs  24  in accordance with the present invention, termed a ‘thin step edge cover’ in  FIG. 9 , was formed with a thickness of 0.095 inches, while a cover with the known radially extending gusset design, termed a ‘standard step edge cover’ in  FIG. 9 , was formed with a thickness of 0.140 inches.  
      As shown in  FIG. 9 , the parallel rib design of the present invention deflected 16% less than did the known radially extending gusset cover design, even though the thickness of the parallel rib design was 32% less.  
      It will be readily appreciated that the present invention therefore increases strength and stiffness while also reducing material cost, and molding and cooling time.  
       FIG. 10  illustrates another embodiment of the present invention where the parallel ribs  30  may be formed to a height which is substantially equal to the depth of the downwardly extending cylindrical skirt  26 . A proportional increase in the strength and stiffness of the embodiment shown in  FIG. 10  over that exhibited by the design shown in  FIGS. 4-9  will be readily appreciated.  
      Further increases in both strength and stiffness can also be accommodated without making the ribs  26  extend deeper into the battery cell by alternatively providing a raised area  32  across the area of the filling hole  22 , as shown in  FIGS. 11-14 . As best shown in  FIGS. 13 and 14 , the raised area  32  is defined by a pair of raised ribs  33  which extend outwardly and upwardly from the planar cover  20 . As will be appreciated, these ribs  33  are preferably tangential to the filling hole  22  and substantially define the edges of the raised area  32 .  
       FIGS. 15 and 16  illustrate a top plan view and a bottom plan view, respectively, of a battery cover  20 , according to another embodiment of the present invention. As shown in  FIGS. 15 and 16 , covers for six-post battery cells typically have the filling hole  22  located between the four posts at one end of the cover  20 . In this embodiment, the ribs  24  may be provided for the filling hole, while additional ribs may also be provided between the four posts at the other end of the cover as well.  
      As will be appreciated by a review of the drawing figures, the ribs  24  are preferably aligned so as to be substantially orthogonal to the elongated edges of the cover  20 . That is, in the preferred embodiment of the present invention, the ribs  24  are oriented to be substantially orthogonal to the two, longest opposing edges of the cover  20 , for maximum effect.  
      While the invention has been described with reference to the preferred embodiments, it will be understood by those skilled in the art that various obvious changes may be made, and equivalents may be substituted for elements thereof, without departing from the essential scope of the present invention. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention includes all equivalent embodiments.