Abstract:
A level including an elongate hollow frame with two sidewalls and a topwall extending therebetween. A central vial is within a topnotch formed by removal of a topwall section and adjacent sections of sidewalls including notch-defining bottom and side edges. An integral inner vertical wall extends between the top and bottom walls thereby reinforcing the frame along the frame length. The inventive level further preferably includes an external brace reinforcing a central frame portion weakened by forming the topnotch. The external brace includes first and second plate members each against one of the sidewalls about the notch-defining bottom and side edges and each substantially spanning a respective one of the sidewalls. A fastening member extending through the sidewalls and pulling the plate members toward each other to sandwich the sidewalls therebetween, thereby reinforcing a central frame portion weakened by forming the topnotch.

Description:
RELATED APPLICATION 
       [0001]    This application is based in part on U.S. Provisional Application No. 61/256,264, filed Oct. 29, 2009, the contents of which are incorporated herein by reference, and on U.S. Provisional Application No. 61/259,038, filed Nov. 6, 2009, the contents of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to levels and, more particularly, to structures for reinforcement of the level frame. 
       BACKGROUND OF THE INVENTION 
       [0003]    In heavy-duty levels it is important that the frame of the level maintains stability for accurate measurement readings. It is also important that levels, which are used in professional construction on types of jobs when a level may be dropped from a substantial height and be subjected to various stresses, sustain the impact with minimal or no damage. 
         [0004]    Many box levels have a central vial positioned into a notch which is formed by removing a section of a top wall and adjacent portions of each side wall, as seen in  FIG. 1 . 
         [0005]    Because material is removed from the center of the extruded frame, a central frame section becomes the weakest portion of the extrusion. Tests have shown that in prior levels  10 , the central region  11  of a frame  12  with the cut-out notch portion  20  for the central vial is substantially weak.  FIG. 2  shows that in such prior levels  10  a bottom  21  of the notch  20  is the weakest region. Portions  22  of sidewalls  13  which surround the central-vial notch  20  are also substantially weak regions  22 A which extend to weakened areas  22 B. 
         [0006]    It is further seen in  FIG. 2  that there is also a substantial weakness in top-wall regions  23  adjacent to hand holes from which material is also removed from the level frame  12 . There is a need for an improved level with a strong stable frame. 
       OBJECTS OF THE INVENTION 
       [0007]    It is an object of the invention to provide an improved level which overcomes some of the problems and shortcomings of the prior art, including those referred to above. 
         [0008]    Another object of this invention is to provide a level with a strong stable frame even in areas of material removal. 
         [0009]    Another object of the invention is to provide a level with a reinforcement of the central region of the level frame. 
         [0010]    How these and other objects are accomplished will become apparent from the following descriptions and the drawings. 
       SUMMARY OF THE INVENTION 
       [0011]    This invention, which will be described in detail below, is an improvement in levels of the type including an elongate hollow frame with two sidewalls and top and bottom walls which extend between the sidewalls and define top and bottom measuring surfaces. A topnotch is formed by removal of a topwall section and adjacent sections of sidewalls including notch-defining bottom and side edges. A central vial is within the topnotch. 
         [0012]    The inventive level includes an external brace which has first and second plate members each against one of the sidewalls about the notch-defining bottom and side edges and each substantially spanning a respective one of the sidewalls. It is preferred that a fastening member extends through the sidewalls and pulls the plate members toward each other to sandwich the sidewalls therebetween, thereby reinforcing a central frame portion weakened by forming the topnotch. The fastening member secures the plate members through the sidewalls with threaded fasteners extending through apertures in the first plate member and engaging aligned threaded channels protruding inwardly from the second plate member. 
         [0013]    Each sidewall includes top and bottom outmost wall-portions joined with a recessed major wall-portion by top and bottom inclined wall-portions. The external brace preferably includes top and bottom ends each positioned against a respective one of the inclined wall-portions such that the brace is substantially recessed with respect to the outmost wall-portions. 
         [0014]    It is preferred that the fastening member secure the plate members through the sidewalls with threaded fasteners extending through apertures in the first plate member and engaging aligned threaded channels protruding inwardly from the second plate member. 
         [0015]    The hollow frame is preferably an extrusion including an inner horizontal wall extending between the sidewalls at the notch-defining bottom edges thereby reinforcing the frame weakened by the removal of the topwall section. The extrusion further preferably includes an integral inner vertical wall extending between the top and bottom walls thereby reinforcing the frame along the frame length. 
         [0016]    Another aspect of this invention is a method for manufacturing a reinforced level including (a) an elongate hollow frame with two sidewalls and top and bottom walls each between the sidewalls and (b) a central-vial receiving topnotch formed by removal of a topwall section and adjacent sections of sidewalls including notch-defining bottom and side edges. The method includes the steps of providing an external brace including a pair of plate members each configured to substantially span one of the sidewalls about the notch-defining edges; positioning each plate member against a respective one of the sidewalls about the notch-defining edges; and securing the external brace to the frame with a fastening member extending through the sidewalls and pulling the plate members toward each other to sandwich the sidewalls therebetween, thereby reinforcing a central frame portion weakened by the topnotch. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a fragmentary perspective view of a prior level showing a top-notch material removal. 
           [0018]      FIG. 2  is a fragmentary perspective view of a prior level frame showing weak regions around material removal for central-vial top notch and hand-hold holes. 
           [0019]      FIG. 3  is a perspective view of the frame of the inventive level showing inner walls. 
           [0020]      FIG. 4  is a fragmentary perspective end view of the frame of the level of  FIG. 3  showing material removal for central-vial top notch and hand-hold holes. 
           [0021]      FIG. 5  is a fragmentary perspective side view of the level frame of  FIG. 5 , showing strengthening of the weak regions around material removal. 
           [0022]      FIG. 6  is a comparison table reflecting test results showing increase in frame strength in the inventive level frame of  FIG. 5 . 
           [0023]      FIG. 7  is a fragmentary perspective view of the inventive level frame showing precisely parallel surfaces for a calibration-free installation of the central vial. 
           [0024]      FIG. 8  is an exploded fragmentary perspective view showing one version of the calibration-free installation of the central vial to the level frame of  FIG. 7 . 
           [0025]      FIGS. 9-12  are exploded fragmentary perspective views of the inventive box level showing different stages of calibration-free installation of the central vial and exterior strengthening of the central region of the level frame. 
           [0026]      FIGS. 13 and 15  are fragmentary perspective views of the central region of the inventive level assembled as shown in  FIGS. 9-12 . 
           [0027]      FIG. 14  is a fragmentary perspective view of the central region of the inventive level and showing precise callibration-free installation of the central vial. 
           [0028]      FIG. 16  is a fragmentary perspective view of the central region of the inventive level of  FIG. 15  in more detail. 
           [0029]      FIG. 17  is a fragmentary perspective view of the central region of partially-assembled inventive level showing strengthening by the external reinforcement of the central region. 
           [0030]      FIG. 18  is a comparison table reflecting test results for increase in frame strengthening in the inventive level frame of  FIG. 5  compared to the inventive level frame of  FIG. 17  and to a prior art level. 
           [0031]      FIG. 19  is a fragmentary perspective view of the end-vial region of the inventive level, and showing calibration-free installation of the end vial. 
           [0032]      FIG. 20  is a fragmentary perspective view of the end-vial region of the inventive level showing an improved-visibility plumb vial. 
           [0033]      FIG. 20A  is an exploded view of the end-vial structure of the inventive level of  FIG. 20 . 
           [0034]      FIG. 20B  is cross-sectional view of the inventive plumb-vial assembly along a horizontal section plane. 
           [0035]      FIGS. 21 and 22  are fragmentary perspective views of the inventive level and illustrating high-visibility plumb vial aspect of the present invention. 
           [0036]      FIG. 23  is a detailed fragmentary perspective view of the end-vial region of the inventive level showing an improved-visibility plumb vial and an improved end cap. 
           [0037]      FIG. 24  is an end view of the inventive level, showing a gripping extension of the plumb-vial assembly. 
           [0038]      FIG. 25  is a fragmentary perspective view showing details of the improved end cap. 
           [0039]      FIG. 26  is a front perspective views of the inventive level shown in resting position against a vertical surface. 
           [0040]      FIGS. 27  is a side perspective views of the inventive level shown in resting position against a vertical surface. 
           [0041]      FIGS. 28 and 29  are fragmentary perspective views showing an improved hand grip of the inventive level. 
           [0042]      FIG. 30  is a perspective view of the inventive level. 
           [0043]      FIG. 31  is a front elevation of the inventive level. 
           [0044]      FIG. 32  is a cross-section of the inventive level taken along a horizontal plane. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0045]      FIGS. 3-5 ,  7 - 17  and  19 - 32  illustrate an inventive level  100  which includes an elongate hollow frame  120  with two sidewalls  180 , a top wall  130  and a bottom wall  140  which extend between sidewalls  180  and define top and bottom measuring surfaces. A topnotch  20  is formed by removal of a topwall section and adjacent sections of sidewalls including notch-defining bottom and side edges. A central vial  50  is within topnotch  20 . 
         [0046]    In inventive box level  100 , level frame  120  includes an internal horizontal wall  30 . As seen in  FIGS. 3 and 4 , such internal horizontal wall  30  is substantially parallel to top wall  130  and is spaced from top wall  130  for a distance  31  necessary for installation of a cental vial  50 .  FIG. 4  shows that this internal horizontal wall  30  is entirely removed in portions of level frame  120  to form hand-holes  150  and in areas  160  for installation of end vials such as plumb vials  40 . 
         [0047]    Because of its specific location along bottom  21  of central-vial notch  20 , internal horizontal wall  30  significantly strengthens the central region  170  of frame  120  which has been weakened by the material removal. 
         [0048]      FIGS. 3 and 4  further show that frame  120  of inventive box level  100  further includes an internal vertical wall  35 . Such vertical internal wall  35  adds rigidity to entire frame  120  and strengthens areas with material removal and where horizontal wall  30  is not present, including around hand holes  150  and plumb-vial holes  160 , as seen in  FIG. 4 . 
         [0049]      FIG. 5  shows that in inventive box level  100  the weakness of the central-vial notch region  20  is reduced to much lesser degree, i.e., to green in previously notch-bottom red areas  21 , light blue in previously green areas  22 A and to no weakness in previously light blue areas  22 B. In fact, a table of  FIG. 6 , which includes data from finite element analysis of prior-level frame  12  and the improved frame  120  of level  100  of this invention, shows that the improved frame  120  is 180% stronger then prior frame  12  without the internal horizontal and vertical walls  30  and  35 . 
         [0050]    As seen in  FIGS. 3 and 4 , internal horizontal and vertical walls  30  and  35  form a quad-box structure of a superior strength. It should be noted that during manufacturing of the inventive level  100 , the thickness of the frame-forming walls has been reduced. Surprisingly, despite such thinning of the walls, the strength of the frame increased. This was partially explained by decrease in the overall weight of the frame  120  which resulted in static improvement and the frame impact performance. In addition to the improved level performance characteristics, such thinning of the walls provides reduction in material used which translates in lower product cost. 
         [0051]    It is also important to note that specific positioning of the internal horizontal wall  30  at bottom  21  of central-vial notch  20  is important for achieving such improved strength. 
         [0052]    Another important aspect of the present invention is that such positioned internal horizontal wall  30  serves for accurate secure installation of the central vial  50 . During manufacturing of the level frame  120 , top and bottom measuring walls  130  and  140  and an upper surface  32  of internal horizontal wall  30  within central-vial notch  20  all simultaneously undergo a milling by a computer-numerical control machine (CNC). The CNC milling during a single operation ensures that all three surfaces are parallel to each other. Thus, upper surface  32  of internal horizontal wall  30  is parallel to top and bottom measuring walls  130  and  140 , as seen in  FIG. 7 . 
         [0053]    Such accurately machined upper surface  32  of the internal horizontal wall  30  forms a reference shelf  33  for precise installation of central vial  50  along vertical axis  53 . As shown in  FIGS. 8-11 , vial  50  is placed in a cradle  51  and mechanically mounted to upper surface  32  of reference shelf  33  with mechanical fasteners such as screws  52 . 
         [0054]    Because of the accuracy in machining of reference shelf  33 , there is no need for manual calibration or adjustment in the positioning of central vial  50  with respect to measuring surfaces  130  and  140 . Such advance in the central-vial installation provides great improvement in manufacturing processes by substantially reducing manual labor. In prior levels, each vial was secured to frame  12  by using an epoxy-based locking system. Each such vial was individually calibrated and only then permanently secured to frame  12 . A number of problems is associated with such prior method of vial installation. One is that the need for calibration of the vial prior to permanent securement involves manual labor which increases costs for manufacturing and requires special quality-control procedures. Another problem is that over time due to variations in temperature or humidity adhesives tend to change its characteristics which may contribute to changes in positioning of the vial as well as in weakening of the vial attachment to the frame. In inventive level  100 , vial  50  is accurately secured to frame  120  without any glue, but only with mechanical fastening against precisely machined reference surface  33  which does not change overtime. 
         [0055]    Such mechanical securement of central vial  50  also involves an external brace  60  which is secured over central region  170  of level frame  120 , as seen in  FIGS. 9-15 . External brace  60  includes two plates  61  each of which spans the entire surface of the respective vertical side wall  180 . External brace CO is preferably made from cast aluminum and is mechanically secured to the frame with screws  62  which extend through apertures  63  in sidewalls  180  and internal vertical wall  35 . 
         [0056]    Such external brace  60  completes mechanical fastening of the central vial  50  to frame  120  by an additional fixing of vial  50  in a horizontal plane  54 . As best seen in  FIGS. 12-16 , brace sandwiches a flange  55  of a vial frame  56  such that vial  50  is securely held in front-to-back, up-and-down and left-to-right directions. 
         [0057]    Furthermore, external brace  60  provides an additional reinforcement of central region  170 . In fact, the sandwiching of the central region by external brace  60  substantially eliminates the weakness in that area. Indeed,  FIG. 17  illustrates that tests showed that previously weakest (red) areas in bottom  21  of notch  20 , as seen in  FIG. 2  showing prior level  10 , are just slightly weakened (light blue) in improved level  100  which includes external brace  60 . The areas, which in prior level  10  were substantially weak (green) or weakened (light blue), in improved level  100  (seen in  FIG. 17 ) exhibit similar strength as the strongest areas of frame  120  where no material removal occurred. 
         [0058]    Moreover, the table of  FIG. 18 , which includes data from testing of prior level  10  and improved level  100 , shows that improved level  100  is 300% stronger then prior level  10 . 
         [0059]    The manufacturing of the improved inventive level  100  also includes CNC milling of openings  160  for plumb vials  40 . While entirely removing internal horizontal wall  30  in regions  160  of frame  120 , such CNC milling forms precise positioning references  36  in internal vertical wall  35  for installation of plumb vials  40 , as seen in  FIGS. 19 and 20A . This process allows for adhesive-free installation of plumb vials and ensures precise positioning when the vials are secured within frame  120  without any calibration or adjustment required. This is a great improvement over manufacturing of many prior box levels which required calibration and adjustment of plumb vials. This process further eliminates quality and longevity concerns associated with the use of adhesive, as already discussed above. Vials installed within frame  120  according to the inventive method will remain in their precise position for accurate reading over time. 
         [0060]      FIGS. 20 ,  20 A and  20 B show that, in inventive box level  100 , plumb vials  40  are encased in a plumb-vial structure  41  made of a high-quality and durability Xenoy* alloy which is a blend of semi-crystalline polyester (typically polybutylene terephthalate, PBT, or polyethylene terephthalate, PET) and polycarbonate (PC). The Xenoy* alloy offers great impact resistance even at low temperatures, heat resistance, and outstanding aesthetic characteristics. Xenoy alloys further offer outstanding performance in applications that are exposed to harsh conditions, or that require a high degree of toughness such as applications for professional-construction levels. Furthermore, Xenoy iQ* resins are created with polybutylene terephthalate (PBT)-based polymers derived from 85% post-consumer plastic waste, consuming less energy and yielding less carbon dioxide (CO2) in their manufacturing than traditional resins. It is seen that the use of Xenoy* alloys present many advantages over standard acrylics often used in plumb-vial casings. 
         [0061]    In levels of substantial lengths such as forty-eight inches and greater, plumb vials are positioned at substantial distance from user&#39;s eyes.  FIG. 21  shows how in some prior levels plumb-vial mounting structures may block the view for reading of the plumb vial. 
         [0062]      FIGS. 19-23  illustrate another aspect of the present invention which provides improved visibility of plumb vial  40 . Such improved visibility is achieved by an inventive configuration of plumb-vial mounting structure  41  includes an elongate inclined ramp  42  sloping from about the side-wall surface at a reduced angle toward a plumb-vial window  43 . Plumb-vial structure  41  has a viewing-end region  47 A and an opposite-end region  47 B, the viewing-end region  47 A including elongate ramp  42  sloping along a level-longitudinal axis  101  toward plumb vial  40  with an inclination angle  400  permitting vial viewing from shallow angles  401 . Such reduced angle  400  of inclination facilitates user&#39;s viewing of plumb vial  40  from about central region  170  of level  100  or even from farther distance, as&#39;seen in  FIG. 30 .  FIG. 20B  best shows angle  400  being 8.65° and as little as 5°. Vial opening  43  also has an elongate configuration of an inner portion  44  on the side of the level central region  170 . Such elongation allows spacing of vial  40  away from ramp  42 . As further seen in  FIGS. 22 and 30 , such spacing in cooperation with elongate inclined ramp  42  compensates for the extended viewing distance and provides improved visibility of vial  40  for the necessary measurement readings. 
         [0063]    The term “shallow,” as referred to the viewing angle  401 , means that such angle is closer to the 0° plane (of the major level sidewall surface) than to the 90° plane (perpendicular to the level sidewalls). Angles  401  are preferably slightly above sidewall surfaces such that the vial becomes visible at a little over angle  400  of sloping ramp  42  shown in  FIGS. 20B and 32 . 
         [0064]    Plumb-vial window  43  includes lenses  48  made of “bullet proof” Lexan* material. Such lenses provide further durability and impact resistance of improved level  100 . 
         [0065]      FIGS. 20A and 20B  show that plumb-vial structure  41  includes first and second side portions  411  and  412 . Each side portion  411  and  412  is positioned along one of level sidewalls  180 . First side portion  411  includes a high-friction region  46  extending from first side portion  411  outwardly beyond an outmost sidewall portion  190 , as best seen in  FIG. 24 , for gripping a work surface. High-friction region  46  is preferably made of rubber molded over the Xenoy* alloy. Rubber portions  46  extend beyond the outmost vertical side surface  190  of that side of level  100  to allow gripping of a work surface against which level  100  is positioned for measurements. 
         [0066]      FIG. 23  further shows an improved end cap  70  which is made with an ABS material on the inside and an outside rubber coating over the ABS material. The rubber coating provides an improved shock absorption even if the level  100  is dropped from a substantial height. As seen in  FIGS. 23 and 25 , outside rubber coating of end cap  70  includes a slightly raised section  71 . While raised section  71  does not extend beyond the outmost vertical side surface  190  of that side of level  100 , such raised rubber section  71  facilitates gripping of a vertical surface against which level  100  may be leaned against during a break between jobs, as seen in  FIGS. 26 and 27 . 
         [0067]    As further seen in  FIG. 25 , end cap  70  is held to frame  120  with two cast aluminum mounting plates  72  which are mechanically secured to frame  120  with screws  73 . Such secure screw attachment also permits end caps  70  to be removed by simple disengagement of screws  73 . While the removal of end caps  70  requires use of additional tools such as screw driver, when necessary, this removable end-cap assembly accommodates precise marking of the work surface even along corners. Each end cap  70  also has an enlarged hang hole  74  which allows for quick hanging of level  100  on the job site. 
         [0068]    As with the plumb-vial casing, a hand grip  80  seen in  FIG. 28  is also made from Xenoy iQ* alloy which is a material used in car bumpers and is very strong in all temperatures, chemical resistant and UV stable. As seen in  FIG. 29 , hand grips  80  are made with an enlarged hole  81  to accommodate gloved hands and to reduce fatigue.