Abstract:
An apparatus and method for efficiently generating a visible line of light on a surface such as a wall or a floor for the purpose of facilitating the layout process used in construction. Reference marking elements on the instrument correspond to the light beam&#39;s position. One or more level vials may be included for indicating vertical and horizontal, as well as a magnet for mounting and a reference bracket for a stud-finder instrument. In one embodiment the instrument is self-leveling on one axis only and is useful for projecting one or more orthogonal lines on a wall surface. The instrument, self-leveling or not, can be combined with a stud finder.

Description:
BACKGROUND OF THE INVENTION 
   This application is a continuation-in-part of application Ser. No. 10/338,764, filed Jan. 7, 2003, now abandoned, which was a continuation of application Ser. No. 09/684,696 filed Oct. 4, 2000, now U.S. Pat. No. 6,502,319. 

   This invention relates to hand tools, and in particular the invention is concerned with a hand tool for projecting a reference beam of visible light for precise alignment on floors and walls. 
   For some time laser beams have been used in construction for level references, vertical references and layout on floors and walls. Typically a construction worker marks the floor or walls indicating the location of walls, windows, or other building elements to be constructed. A chalk line is often used to permanently mark the walls or floors. This is a two man job with one man holding one end of the chalked string while the other snaps it, releasing chalk dust which makes the mark. 
   The most common prior laser device is a simple carpenter&#39;s level with level vials and with a laser beam projector attached. See  FIG. 1 . Many thousands of these are in use today. U.S. patents in this area include Genho U.S. Pat. No. 4,221,483, Rando U.S. Pat. No. 6,009,630 and others. Although indicating level, these levels do a poor job of projecting a beam on a floor or wall. The assignee of this invention has made a product for producing two beams of visible light on the floor for the purpose of laying out a 90° corner, described in U.S. Pat. No. 6,202,312, incorporated herein by reference. This instrument uses a collimated beam of light and an adjustable cylinder lens to convert the round beam into a fan of light and thus project a line on the surface. This is not a very efficient use of the laser diode light because of the natural divergence of the diode and cropping of the beam in collimation. Typically the laser diode beam divergence is 30° in one axis and 8° on the transverse axis. About half the light is lost in the collimation process. In addition, the line can be focused for only one distance. Such an optical system is shown in plan view in  FIG. 2  herein and in side view in  FIG. 3  herein, and is the present state of the art. Both the problems of efficient use of the laser light and focusing continuously along a line are solved by the current invention. 
   SUMMARY OF THE INVENTION 
   This invention allows the user to project a highly visible line on a surface. In addition it allows the line to be adjusted to true vertical or horizontal with the aid of a level vial when used on a vertical surface, e.g. a wall. An attachment to a stud-finder instrument is further provided. In some cases a magnet facilitates holding the unit to metal studs. The instrument is partially described in Disclosure Document No. 476310. 
   The simple, efficient optical system is an important feature of this invention. The instrument provides a highly visible line which can temporarily act as a chalk line for the purpose of marking points along the line, when requiring a more permanent mark, or for operations along the line with the laser line in place. Another important feature is embodied in a self-leveling laser instrument, with self-leveling along only one axis (in one plane), preferably via a type of pendulum in the instrument. The instrument can be put on a wall, will self-level in the only axis needed, and can project a single fan beam, or two 180° opposed fan beams, or even four fan beams in a cross configuration on the wall. These and other objects, advantages and features of the invention will be apparent from the following description of a preferred embodiment, considered along with the accompanying drawings. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view showing a prior art carpenter&#39;s level with projected laser beam. 
       FIGS. 2 and 3  are elevation and plan views showing a prior art laser line projector schematically using a cylinder lens. 
       FIGS. 4 and 5  are elevation and plan views illustrating the principle of line projection according to the invention. 
       FIGS. 6 and 7  are elevation and plan views similar to  FIGS. 4 and 5  but showing a different embodiment. 
       FIG. 8  is a schematic perspective view showing a laser instrument projecting a line on a surface in accordance with the principles of the invention. 
       FIG. 9  is a sectional elevation view schematically showing the instrument of  FIG. 8 , with some elements omitted for clarity. 
       FIGS. 10 and 11  are perspective views illustrating use of the instrument on a wall, to project a line which may be horizontal or vertical on the wall surface. 
       FIG. 12  is a perspective view showing the instrument used along with a stud finder, to project a vertical line indicating location of an entire stud. 
       FIGS. 13 ,  14  and  15  are schematic side views showing the components of the invention projecting a line on a surface and showing three different methods for utilizing the entire wide angle of the diverging beam along the long axis. 
       FIGS. 16 and 17  are schematic side views showing another form of the invention using cylindrical concave mirrors for focus in the narrow angle of the beam. 
       FIG. 18  is a schematic view showing a modified instrument which is self-leveling on one axis to achieve plumb and/or horizontal beams when the instrument is used against a wall. 
       FIG. 19  is a simplified sectional elevation view showing a single-axis self-leveling arrangement and an example of a part of the optics for the instrument of  FIG. 18 . 
       FIG. 20  is a simplified sectional elevation view of the  FIG. 19  instrument in profile. 
   

   DESCRIPTION OF PREFERRED EMBODIMENTS 
   An optical system is shown in  FIGS. 4 and 5 . A laser diode  2  is positioned above a surface  4  to be marked, with the wide divergence angle of the laser, i.e. the major or long axis, perpendicular to the surface. In other words, a plane which is longitudinal relative to the laser diode and which includes the long axis of the beam is perpendicular to the surface. Cylinder lenses  6 ,  8 ,  10  project a beam  11  from the laser diode  2  onto a continuous line  14 . The widths of the lenses are chosen to collect all the light from the narrow divergence angle (short axis) of the diode, substantially without cropping. The use of a plurality of lenses in the direction of the wide divergence (long axis) allows most of the light to be collected making the system efficient. The ability of each lens to be adjusted for a particular distance to produce a fine line is superior to the prior art; focus adjustment for distance can be done either by use of different focal length lenses or by adjustment of distance from the diode to each lens. The figures show how substantially all of the laser power in the wide and narrow divergence angles of the diode is projected into a tapering fan and into a line on a surface. 
   Another preferred embodiment of the optical system is shown in two views in  FIGS. 6 and 7 . A laser diode  14  projects a line  16  on a surface  18  using a single cylinder lens  20 . The lens is tipped to provide the best focus for the entire surface by varying continuously the distance between the lens and the diode along the wide angle or long axis of the diode&#39;s beam. This provides variation for best focus on the line  16  on the surface. The diode is located preferably about 25 mm to 125 mm above (or away from) the surface to provide the angle needed to distribute the light along the floor (or other surface on which the device is used). 
   A preferred embodiment of an instrument is indicated generally by  22  in  FIG. 8 . A housing  24  contains the projection system described above. A fan-shaped beam  26  is projected onto a surface  28  to form a line  30 . The housing has a battery door  32  and marking notches  34  and  36  which are in the same plane as the projected beam  26  and are used for positioning the line  30  and the instrument on marks on the floor during layout. An on-off switch  38  and sights  40  and  42  are in the plane of the beam  26  and may be used for sighting the instrument for desired alignment. Details of the internal construction of the instrument  22  are shown in  FIG. 9 . A battery  39  and wires  37  are included. 
   A slightly modified instrument  44  shown in  FIG. 10  is the same as  22  except for the addition of a horizontal indicating level vial  46 . A magnet  45  is provided to hold the instrument to a steel stud as may be necessary from time to time. The sights and switch of  FIGS. 8 and 9  have been removed for clarity in  FIG. 10 . The unit is positioned on a vertical wall  48 . A second level vial  50  for indicating vertical is also mounted to the line projector. In this figure a horizontal line  52  is projected on the wall. 
     FIG. 11  shows the instrument of  FIG. 10  positioned on the vertical wall projecting a vertical line  54  on the wall  48 . 
     FIG. 12  shows the instrument  44  of  FIGS. 10 and 11  on the vertical wall  48  with a bracket  56  attached to the instrument. The bracket holds a stud-finder  58  which indicates the location of a stud behind a wall with its indicator lights  60 . Using this combination instrument one location of the stud may be used to locate the entire length of a vertical stud. This eliminates the need to find the stud at several locations up and down the wall. 
   In another preferred embodiment the light in the wide angle divergence or long axis direction of the diode is used efficiently by employing one or more mirrors to reflect part of the light back onto the line as shown in  FIG. 13 . A laser diode  64  directs a beam of light  62  to a cylinder lens  66  to form a line  68 . A portion of the light  70  exiting the lens  66  strikes mirrors  72  and  73  and is directed onto the line  68  increasing its brightness, at the distant portion of the line where the line is weakest. A prism  74  can also be used to redirect the portion  70  back onto the line  68  as shown in  FIG. 14 .  FIG. 15  shows that a positive cylinder lens  76 , oriented transversely to the cylinder lens  66 , can be used to narrow the divergence of the diode laser beam as it reaches the cylinder lens  66  to efficiently use the power from the laser diode in this preferred embodiment. Instead of two separate cylinder lenses  66  and  76 , a hybrid lens could be fashioned to accomplish both functions. 
   In another preferred embodiment the light beam is focused in the narrow angle of divergence with a cylindrical mirror instead of a cylinder lens, achieving similar beam distribution and focus.  FIG. 16  shows the projector  80  comprising a laser diode  82  and cylindrical reflecting surface  84  projecting the beam, diverging in its wide angle as shown, from the laser diode into a fan of line  88  on a surface. The back-reflection arrangement shown allows the beam conveying element  84  to be placed at a proper angle of tilt to achieve optimum focus along the length of the line  88 , as shown with the lens in FIGS.  6  and  13 - 15 . The beam divergence in the wide angle can be further controlled by a lens  90  shown in  FIG. 17  which otherwise contains the same elements of  FIG. 16 . It is also possible to include the optical power of the lens  90  in the mirror  84 , by providing a mirror which curves concavely in the transverse direction, i.e. appearing arcuate and concave in side view, rather than linear as in  FIGS. 16 and 17 . This becomes an expensive optical element but is theoretically possible. In addition, the focus correction for a range of distance, as achieved by the tilted conveying element, could be realized using a concave cylinder reflecting surface that varies in radius of concavity along its length, to provide varying focal length for this narrow angle of divergence. 
   In another aspect of the present invention, an instrument is used to produce a plumb or level line on a wall, or several orthogonal lines on a wall, the instrument being self-leveling. In a preferred embodiment the instrument is self-leveling along only one axis, the axis which is horizontal and perpendicular to the wall; that is, the beam or beams are self-leveled in the plane of the wall surface, but not in the vertical plane which is perpendicular to the wall surface. In this way a simplified instrument can produce accurate level and/or plumb lines on a wall when the instrument is held against the wall in a position in which the housing of the instrument is flat against the wall but only roughly oriented with respect to level or plumb. 
     FIGS. 18-20  show, in schematic indications, such a tool for projecting a line or lines on a wall. In  FIG. 18  a laser projecting instrument  100  is shown engaged against a wall  102 . The instrument projects at least one fan beam  104 , seen in edge view in  FIG. 18 , and the fan beam produces a line ( 104 ) on the wall surface  102 . The instrument  100  can produce further beams if desired, such as an upward beam  106  in addition to the down beam  104 , and optionally, a horizontal beam  108  or even two opposed horizontal beams. These orthogonal fan-shaped beams, all seen in edge view in  FIG. 18 , are all self-leveled by a single-axis self-leveling device in the instrument  100 . 
   The optics described above can be used to produce a single fan-shaped beam  110  as seen in  FIGS. 19 and 20 . Those optics can be contained in an optics mounting assembly  112  which is suspended on a pendulum  114  within the housing  116  of the instrument. The pendulum  114  is suspended for self-leveling on a single axis, the axis being seen at  118  in  FIG. 19 . The axis  118  is perpendicular to the plane of the wall surface  102 , so that self-leveling is only in the plane of the wall surface, not in a vertical plane perpendicular to the wall surface. A ball bearing is shown at  120 , supporting the pendulum  115  for very low-friction rotation about the axis  118 . The optics described above can be contained in the optics assembly  112 , such that the fan-shaped beam  110  emanating from the assembly  112  is tilted somewhat toward the wall, i.e. toward the plane of a base side  122  of the instrument. If multiple beams are desired, the fan-shaped beam  110  can be reflected downwardly by a partially reflective/partially transmissive mirror  124  to produce the down beam  104  which will have the same fan-shaped characteristic and will incline toward the wall. The horizontal beam  108  can be produced by the transmitted portion of the beam  110 . Further, if an upward fan beam  106  is desired, the transmitted portion of the beam  110  can be partially reflected by another reflective/transmissive mirror  126 , so that a portion travels back to the left as seen in  FIG. 19  and then is fully reflected from a reflective back surface of the mirror optic  124 , to produce the upwardly-directed fan beam  106 .  FIG. 20  shows the up and down beams  106  and  104  in side view. 
   Alternatively, other optics can be used, involving full collimation of the laser beam. Multiple output beams can be produced, for example, using the optics of U.S. Pat. No. 6,542,304 which is incorporated herein by reference. That patent discloses use of a reflective pyramid device with a central hole, and this could provide three output beams in a single plane, generally as shown in  FIGS. 18 and 19 . Cylindrical lenses are then used to produce the fan beams, at the focus and at the desired aim. If four beams are desired, the optics of the above patent can be suspended from the same pendulum arrangement shown in  FIG. 19 , i.e. with the axis perpendicular to the wall, but with the laser directed parallel to the axis  118 . The beam can then be reflected off a four-faceted pyramid type reflector without a hole, so that four orthogonal beams are produced in one plane, two vertical and two horizontal, with the appropriate cylinder lenses also attached on the pendulum platform (arrangement not illustrated). 
   The instrument preferably includes reference markings as described above, to indicate on the housing the position of the fan beam or beams. The instrument may be retained on the wall in the ways described above, such as with a magnet in the case of metal studs in the wall, or the housing can include a mounting hole at or near the top for a small nail or pin to be driven or pushed into the wall, or a removable adhesive can be used, such as a gummy adhesive that can readily be removed when desired, without leaving residue. 
   The above described preferred embodiments are intended to illustrate the principles of the invention, but not to limit its scope. Other embodiments and variations to this preferred embodiment will be apparent to those skilled in the art and may be made without departing from the spirit and scope of the invention as defined in the following claims.