Abstract:
An apparatus and method for securing and aligning level indicators such as bubble vials includes the use of a spring structure with a screw adjuster. In some embodiments, multiple spring structures are positioned perpendicular to one another to allow precise adjustment in different planes. The spring structure is economical to manufacture, and allows accurate adjustment of levels placed in equipment having imprecisely bored holes.

Description:
CLAIM OF PRIORITY 
     The present application claims priority to U.S. Provisional Patent Application Ser. No. 60/205,845, entitled “Method and Apparatus for Securing and Aligning Bubble Vials”, filed on May 19, 2000. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates broadly to the field of leveling devices used in, by way of example only, the construction industry. More particularly, the present invention relates to an improvement in the assembly of leveling devices that allows for precise adjustment or calibration of the leveling device, using economical manufacturing methods. 
     2. Description of the Related Art 
     In construction leveling devices, as well as other leveling devices, a small plastic or glass bubble vial is often used for a direct indication of level. The vial is mounted in the leveling device, such as a rail or other piece of equipment. A user identifies a level line by manipulating the leveling device until a small bubble in the vial is centered between two marks. Bubble vials have a range of features including specific sensitivity and accuracy. Multiple vials may be used to indicate level in multiple planes or particular set angles, such as 45 degrees. 
     In the manufacture and assembly of bubble vial leveling devices, the bubble vial is precisely aligned with respect to a gauging surface, to ensure accuracy of the device. Manufacturers typically employ one of three approaches for aligning bubble vials: (a) press fitting, (b) fixture positioning and gluing, or (c) providing for user adjustment. 
     In press fitting, manufacturers press fit plastic vials into a drilled or reamed hole. The hole is precisely bored with respect to the gauging surface, and does not allow for subsequent adjustment of the vial&#39;s angle. In some instances, manufacturers use epoxy or glue to secure the vial&#39;s fit. 
     In fixture positioning, manufacturers employ a mounting fixture to position a bubble vial in a bored holding cavity. In this approach, the holding cavity is less precisely bored than in press fitting. Once the vial is correctly positioned, the manufacturer secures the vial with glue or epoxy and removes the fixture. 
     As a third approach, manufacturers may fix the vial in a separate holder, such as a die-cast aluminum tray. The holder is then fixed with screws and springs. This allows users to adjust or calibrate the vial. If adjustment is desired in two planes, then a more complex holder is needed. The disadvantage of this method of creating adjustable vials is its extra cost of manufacturing, size, and complexity. 
     Alternatively, manufacturers may mount a vial in a machined hole having an oval slot on each end with counter-locking screws mounted on axes perpendicular to each other. This allows independent calibration in two planes. This arrangement, however, is difficult to machine in the practical configurations of a leveling device&#39;s rail. 
     SUMMARY OF THE INVENTION 
     The invention described herein relates to a leveling device having an adjustable level indicator. Embodiments of the present invention provide for economical manufacture of adjustable levels by allowing a vial, or other level indicator, to be fitted into a loose extruded or imprecisely bored hole. The vial, or other level indicator, is then calibrated or adjusted to ensure operational accuracy. 
     One embodiment of the present invention includes a spring structure for securing a level indicator and a screw for adjusting the indicator&#39;s position. The spring structure is mounted in a cavity in a leveling device. The spring structure includes two flexible elongated members that are deflected by the cavity&#39;s walls. The elongated members place a resultant force on the level indicator to secure the indicator&#39;s position in the cavity. 
     The screw extends into the cavity to apply an adjustment force to the level indicator. The adjustment force directs the level indicator to a position that results in a level indication when the leveling device is placed on a gauging surface. In one embodiment, the adjustment force is applied to align the level indicator&#39;s centerline with the cavity&#39;s centerline. The use of the spring structure and screw avoids the need to precisely extrude the cavity for holding the level indicator. 
     In one embodiment, multiple combinations of a spring structure and screw are employed to provide for adjustments in multiple planes. A first spring structure and screw secure a first end of a bubble vial and a second spring structure and screw secure a second end of the bubble vial. In one such embodiment, the first spring structure and second spring structure are positioned perpendicular to each other within the leveling device bore. This provides for the level indicator to be adjusted in two independent orthogonal planes—allowing precise calibration and operational accuracy of the leveling device with regard to all sides of the rail. 
     These and other objects and advantages of the present invention will appear more clearly from the following description in which the preferred embodiment of the invention has been set forth in conjunction with the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 a  shows one embodiment of a spring structure in accordance with the present invention. 
     FIG. 1 b  shows an end representation of the spring structure of FIG. 1 a.    
     FIGS. 1 c  and  1   d  show cross-sectional representations of a pair of spring structure and screw combinations holding a level indicator in place. 
     FIG. 2 shows an alternate embodiment of a spring structure in accordance with the present invention. 
     FIG. 3 shows yet another embodiment of a spring structure in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 a  illustrates one embodiment of a spring structure in accordance with the present invention. Spring structure  10  is substantially rigid, but has some degree of planar flexibility and elasticity. In one embodiment, spring structure  10  is fabricated from sheet metal using conventional laser cutting or die tooling methods. Spring structure  10  can also be manufactured from other materials that exhibit flexibility and elasticity and still remain within the spirit and scope of the invention. For example, a wire form can be employed instead of sheet metal. 
     Spring structure  10  includes elongated members  1  and  2 , each extending symmetrically from base  3 . In one embodiment, elongated members  1  and  2  extend from base  3  at an acute angle. As explained above for spring structure  10 , elongated members  1  and  2  are manufactured to be substantially rigid, but to have a degree of planar flexibility. Two smaller tab-like members also branch off base  3 : retaining tab  4  pointing inwards toward the center of spring structure  10 , and fixing tab  5  pointing outwards away from spring structure  10 . 
     FIG. 1 b  shows an end view of spring structure  10  in use in one embodiment of the present invention. FIG. 1 b  shows extruded hole  7 , which forms a cavity in a leveling device for mounting level indicator  6 . In one embodiment, level indicator  6  is a bubble vial. Spring structure  10  is manufactured for insertion into hole  7  to secure vial  6 . 
     Base  3  contacts the interior surface of hole  7 . Elongated members  1  and  2  press against the interior surface of hole  7  and are deflected from their original state. Bubble vial  6  is placed between elongated members  1  and  2 . As a result, elongated members  1  and  2  take on a bowed shape. In one embodiment, hole  7  is circular with a diameter of 12 millimeters (“mm”), and vial  6  measures 9 mm in diameter. 
     Elongated members  1  and  2  of spring structure  10  produce uniform forces against vial  6 . The forces keep vial  6  securely positioned in hole  7  and minimize undesired movement. The force from member  1 , represented by vector  22 , includes a component directed along the y-axis in a positive direction and a component directed along the x-axis in a positive direction. The force from member  2 , represented by vector  24 , includes a component directed along the y-axis in a positive direction and a component directed along the x-axis in a negative direction. In one embodiment, the forces from members  1  and  2  create a resultant force on vial  6  directed to keep vial  6  pressed against the interior wall of hole  7 . As a result, the center of vial  6  aligns with centerline  12  of hole  7 . 
     Retaining tab  4  is sized to allow bubble vial  6  to pass through spring structure  10  during an insertion process. Once vial  6  is properly aligned in hole  7 , retaining tab  4  prevents vial  6  from sliding through elongated members  1  and  2 . Further details about retaining tab  4  will be explained below with reference to FIGS. 1 c  and  1   d.    
     Fixing tab  5  is inserted into notch  11  in the interior surface of hole  7  to register spring structure  10 . As a result, spring structure  10  is fixed in place and prevented from slipping from side-to-side or around bubble vial  6 . 
     FIGS. 1 c  and  1   d  show one embodiment of the present invention in which two spring structures are employed in a leveling device to secure a bubble vial, or other level indicator. Vial  6  is located in hole  7  of a leveling device. FIG. 1 c  shows a cross-section of one end of vial  6  in hole  7  in the x-y plane. FIG. 1 d  shows a cross-section of the opposite end of vial  6  in hole  7  in the x-y plane. Spring structures  30  and  32  in FIGS. 1 c  and  1   d  are the same as spring structure  10  in FIG. 1 b  and include the same reference numbers. 
     The leveling device shown in FIGS. 1 c  and  1   d  also includes screw  8  (FIG. 1 c ) and screw  9  (FIG. 1 d ). Screws  8  and  9  extend through the interior wall of hole  7  and are used to adjust the alignment of vial  6 . Screw  8  extends into hole  7  to contact vial  6  and apply a force in opposition to the force applied by spring structure  30 . Screw  9  extends into hole  7  to contact vial  6  and apply a force in opposition to the force applied by spring structure  32 . In one embodiment, screw  8  provides a force normal to base  3  of spring  30 , and screw  9  provides a force normal to base  3  of spring  32 . In other embodiments of the invention, the forces supplied by screws  8  and  9  are not normal to the spring structure bases. 
     When making the leveling device shown in FIGS. 1 c  and  1   d , a manufacturer places spring structures  30  and  32  at opposite ends of hole  7 . Fixing tab  5  on spring  30  is inserted through notch  11   a  in the interior wall of hole  7  to register spring structure  30 . Fixing tab  5  on spring  32  is inserted through notch  11   b  in the interior wall of hole  7  to register spring structure  32 . The manufacturer inserts bubble vial  6  between elongated members  1  and  2  of spring structure  30  (FIG. 1 c ) and between elongated members  1  and  2  of spring structure  32  (FIG. 1 d ). 
     Vial  6  is longer than the distance between spring  32  and the end of spring  30  that faces spring  32 . During vial insertion, a manufacturer first slides vial  6  between members  1  and  2  of spring  30 —beginning from the end of spring  30  closest to spring  32 . In doing this, a first end of vial  6  passes through an opening formed by the interior wall of hole  7  and member  1 , member  2 , and retaining tab  4  of spring  30 . retaining tab  4  of spring  30  is designed to allow for such clearance when screw  8  is retracted into the interior wall of hole  7 . Retaining tab  4  in spring  32  is similarly designed for operation with screw  9 . 
     Next, the manufacturer drops vial  6  completely into hole  7 —sliding a second end of vial  6  between members  1  and  2  of spring  32  and retracting the first end of vial  6  back past retaining tab  4  of spring  30 . Alternatively, a manufacturer can first insert vial  6  between member  1 , member  2 , and retaining tab  4  of spring  32 . 
     In one embodiment, spring  30  is aligned orthogonal to spring  32 . In such an embodiment, springs  30  and  32  are positioned so that base  3  of spring  30  is perpendicular to base  3  of spring  32 . The resultant force applied to vial  6  by spring  30  is perpendicular to the resultant force applied to vial  6  by spring  32 . The forces from springs  30  and  32  press respective portions of vial  6  against the interior wall of hole  7 , as described above with reference to FIG. 1 b.    
     The manufacturer employs screws  8  and  9  to provide adjustment forces against the forces from springs  30  and  32 , respectively. The adjustment forces move vial  6  into a calibrated position in hole  7 . When vial  6  is in a calibrated position, the vial provides a level indication when the leveling device is placed on a gauging surface. In one such embodiment, screws  8  and  9  position vial  6  toward the center of hole  7 . 
     Retaining tab  4  on spring  30  is sized to prevent vial  6  from sliding between elongated members  1  and  2  on spring  30  when screw  8  forces vial  6  toward the center of hole  7 . Retaining tab  4  on spring  32  is sized to prevent vial  6  from sliding between elongated members  1  and  2  on spring  32  when screw  9  forces vial  6  toward the center of hole  7 . 
     Once vial  6  is in the calibrated position, the ends of vial  6  are potted in one embodiment of the present invention. The ends of vial  6  are potted in a silicone or similar Room Temperature Vulcanization compound. Potting the assembly in this manner provides stabilization from shock and vibration. Even when fully set, the potting compound remains flexible, so subsequent adjustment is possible using screws  8  and  9 . Other potting materials can be used and be within the spirit and scope of the invention. 
     FIGS. 2 and 3 illustrate spring structures in alternate embodiments of the present invention. Spring structures  40  and  50  in FIGS. 2 and 3 do not include either retaining tab  4  or fixing tab  5 . As explained above with reference to spring structure  10 , spring structures  40  and  50  are substantially rigid with some degree of planar flexibility and elasticity. 
     Spring structure  40  in FIG. 2 includes base  43  and flexible elongated members  41  and  42  extending symmetrically from base  43  at acute angles. Tab  45  extends from the end of member  41 , and tab  46  extends from the end of member  42 . Tabs  45  and  46  hold spring structure  40  in place. In operation, tabs  45  and  46  rest against the exterior of a hole in a leveling device, such as hole  7  in FIGS. 1 b-d.    
     In FIG. 3, spring structure  50  includes flexible elongated members  51  and  52  extending symmetrically from base  53  at acute angles. A manufacturer mounts spring  50  in a leveling device hole, such as hole  7  in FIGS. 1 b - 1   d . Since spring  50  does not include a retaining tab, the manufacturer may place caps at the ends of hole  7  to prevent a vial from sliding through members  51  and  52 . 
     Industrial Applicability: Accordingly, embodiments of the present invention provide a spring structure that accurately and reliably positions a bubble vial or similar type of level indicator in a leveling device or its like. 
     The foregoing detailed description of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. The described embodiments were chosen in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.