Abstract:
A refillable pyrophoric lighter having an outer casing with a hinged cover and having an inside unit that is received inside the casing by a frictional fit that is enhanced by at least one transverse rib integrally formed on the outside of the housing of the inside unit.

Description:
This application claims benefit of provisional Application No. 60/193,026 filed Mar. 29, 2000. 
    
    
     FIELD OF INVENTION 
     The present invention relates generally to lighters, and more particularly to a fit-up rib for improving the fit between the inside unit and the outer case of a lighter. 
     BACKGROUND OF THE INVENTION 
     The design of some reusable lighters incorporates a case having a hinged top and a removable insert. The insert contains the functioning mechanism of the lighter. Some lighters have removable inside units for refilling the inside unit with liquid fuel, whereas some lighters have permanent inside units with refill ports on the bottom or side of the lighter for refilling the liquid fuel reservoir in the inside unit. For removable inside units, the optimal fit between the inside unit and the case is when the inside unit can easily be extracted and reinserted by hand, without the use of tools. The fit of the inside unit to the case should not allow the inside unit to move inside the case during normal operation of the lighter. One method for ensuring this fit is to manually spread the sides of the inside unit at the bottom. After spreading the sides of the inside unit, this fit-up operation requires insertion of the inside unit into the case to check for fit. If the fit is not correct, the spreading step is repeated, and the process starts again until the fit is correct. 
     There have been many designs directed to the fit between the inside unit and the case for lighters. 
     U.S. Pat. No. 1,006,557 discloses a leaf-type spring (reference “o” in FIG. 1) attached to the inner wall of the outer case for securing the inside unit in the case. 
     U.S. Pat. No. 2,541,111 also discloses a leaf spring attached to the inside wall of the outer case for positioning and retaining the inside unit. 
     U.S. Pat. No. 2,571,435 discloses an inner container that is held in position by screws and therefore is not manually removable. Referring to FIG. 1, four structural members hold the corners of the container  2 , and a bottom plate  19  that is held in position by a screw  21 , holds the container  2  in position. 
     U.S. Pat. No. 4,133,450 discloses a table lighter arrangement where a disposable lighter is held firmly in the base by upstanding flexible fingers with ribs disposed thereon. When the lighter is inserted the upstanding fingers function as springs to apply a force to the lighter to hold it in position. 
     U.S. Pat. No. 4,625,861 also discloses a case for a lighter. As shown in FIG. 4, the case is designed to be smaller than the lighter such that a tight fit is achieved. 
     U.S. Pat. No. 4,901,848 also discloses an outer case for a lighter. The case provides a snug fit as shown in FIG. 5 or a living hinge as shown in FIG.  6 . 
     U.S. Pat. No. 5,740,905 discloses a set of notched flaps at the top of the outer shell that deflect inward when the lighter is inserted and maintain a force against the lighter body to hold it in position. 
     The above-described patents provide solutions for the fit between the inside unit and the case that are generally expensive, difficult to manufacture, and subject to failure when exposed to repeated removal of the inside unit from the case. What is needed is a relatively simple, durable device for establishing and maintaining the proper fit between the inside unit and the case for a liquid refillable lighter with a removable inside unit. 
     SUMMARY OF THE INVENTION 
     The present invention meets the above-described need by providing a rib that is formed in the side or sides of the inside unit shell. The rib is a narrow form that extends horizontally. The rib starts at the side corners of the inside unit shell and gradually increases in thickness toward the center of the shell. The shape may contain a single radius or may comprise a composite of multiple radii and cords. The rib preferably has a varying thickness that blends in at the corners of the inside unit shell and extends out the farthest at the center of the shell where the outer case is most flexible. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is illustrated in the drawings in which like reference characters designate the same or similar parts throughout the figures of which: 
     FIG. 1 is a side elevation view of a lighter of the present invention; 
     FIG. 2 is a partial top plan view of the lighter illustrating the position of the inside unit with respect to the outer case; 
     FIG. 3 is a side elevation view of the inside unit of the present invention; and, 
     FIG. 4 is a partial top plan view of the inside unit illustrating a preferred embodiment of the fit-up rib of the present invention. 
     FIG. 5A is a cross-sectional view taken along line  5 A— 5 A of FIG. 3; and, 
     FIG. 5B is an alternate embodiment of the rib of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring generally to FIGS. 1-4, a lighter  10  of the present invention includes an inside unit body  13  and an outer case  16 . The outer case  16  has a cover  19  attached by means of a hinge  20 . The inside unit body  13  and the outer case  16  are both hollow and formed out of sheet metal. The outer case  16  has two side walls  22 ,  23 ; two end walls  24 ,  25 ; and a bottom wall  26 . The case is open at the top. The hinge  20  attaches the cover  19  to the case  16  at the top of end wall  25 . 
     The inside unit  13  is preferably formed as a sheet metal casing  28  with an open lower end  62 , and is provided with a wick (not shown) that extends downwardly in a central location to the lower end of the body  13 . A filling of suitable absorbent material (not shown), which may be of cotton, surrounds the wick and fills the space within the metal casing  28 . 
     The inside unit  13  carries as part of its mechanism a striker wheel  31 , a flint  60 , and a spring biased cover-control lever  37 . The inside unit  13  has a hollow housing  28  defined by a first side wall  42  disposed in spaced apart relation from a second side wall  44 . A first end wall  46  is disposed in spaced apart relation to a second end wall  48  and a top plate  50 . The first and second side walls  42 ,  44  extend above the top plate  50  and are formed to provide a wind screen  52  and a front and rear pair of lugs  54 ,  56 . The inside unit  13  has a lever  37  mounted between the rear pair of lugs  56  and a spring-biased plunger (not shown) for biasing the lever  37  against the cross member  58  when the cover  19  is closed. The inside unit  13  has a flint wheel  31  mounted in the front pair of lugs  54 . The flint wheel  31  is disposed adjacent to the flint  60  and to the wick extending from a fuel reservoir defined inside the housing  28 . The workings and arrangement of these parts are disclosed in greater detail in U.S. Pat. No. 2,032,695, which is incorporated herein by reference. 
     The inside unit body  13  is disposed inside the outer case  16  by means of a snug frictional fit. The frictional fit has to be snug enough so that the inside unit  13  does not move inside the outer case  16 , yet is loose enough such that it can be removed for refilling. In order to refill the lighter  10 , the inside unit  13  is removed and lighter fuel is added through the bottom of the inside unit  13 . A resilient barrier (not shown) covering the absorbent cotton material is removed manually, and the lighter fuel is added to the absorbent cotton material until a charge of fluid has been delivered. Next, the inside unit  13  is frictionally fit back into the outer case  16  such that the open end  62  of the inside unit  13  slides down into engagement with the closed bottom of the outer case  16  to form a fuel storage area that is sealed against leaking by the snug fit. 
     The optimal fit between the inside unit  13  and the case  16  is when the unit  13  can be easily extracted and reinserted by hand, without the use of tools. The proper fit of the inside unit  13  to the case  16  should not allow the inside unit  13  to move inside the case  16  under normal operation of the lighter  10 . 
     In order to provide for a snug frictional fit, the inside unit  13  of the present invention is provided with a horizontal form or rib  70  that preferably extends across the entire width of the inside unit  13 . The rib  70  is integrally formed in the sheet metal housing of the inside unit  13  such that the inside unit  13  fits snugly into the outer case  16 . The horizontal rib  70  extends from one corner  80  where a side wall  22  meets an end wall  24  to the opposite corner  82  where the side wall  22  meets the opposite end wall  25 . 
     The rib  70  is preferably narrower adjacent to the corners. The corners  90 ,  92  of the outer case  16  correspond to the corners  80 ,  82  of the inside unit  13  when the inside unit  13  is inserted into the case  16 . The construction of the case  16  is strongest and has the least amount of flexibility in the corners  90 ,  92  where the side wall  22  meets the end walls  24 ,  25 . The outer case  16  becomes more flexible toward the center of the side walls  22  where the maximum flexibility is provided. 
     Accordingly, the thickness of the rib  70  preferably varies roughly according to the flexibility of the side wall  22 . In the corners  90 ,  92  where the outer case  16  is relatively rigid, the rib  70  is provided with its minimum thickness. At the center of the side wall  22  where the case  16  is most flexible, the rib  70  is provided with its maximum thickness. 
     The cross-sectional shape of the rib  70  may take several forms including a single radius (FIG. 5A) or multiple radii and/or cords (FIG.  5 B). 
     The rib  70  provides several advantages including minimizing single point contact between the inside unit  13  and the case  16  both during removal and insertion of the inside unit  13  and during normal use. By increasing the contact area between the sides of the inside unit  13  and the case  16 , the rib  70  distributes the load over a larger area and therefore provides better wear characteristics. The rib  70  also provides a more consistent fit between the inside unit  13  and the case  16 . 
     While the invention has been described in connection with certain preferred embodiments, it is not intended to limit the scope of the invention to the particular forms set forth, but, on the contrary, it is intended to cover such alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.