Patent Publication Number: US-2007107573-A1

Title: Light beam alignment system

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a saw having a light source alignment system that does not require internal batteries to power the light source.  
      2. Background Art  
      Miter saws, portable circular saws, radial arm saws, chop saws, and compound saws are used to precisely cut wood and other materials. For example, miter saws and compound saws are used to cut baseboards, crown moldings, cove moldings, and a wide variety of trim pieces and structural members to exact dimensions. Such circular saws generally have a blade that is rotated at a high rate of speed to cut workpieces. The blade is guarded by a retractable blade guard that covers the saw blade but is retracted as the blade is brought into contact with a workpiece. The workpiece is retained on a base and a turntable that, in conjunction with a fence, are used to position the workpiece to be cut by the saw.  
      Before cutting, workpieces are generally marked with a pencil at the intended cut location according to precise measurements to assure accuracy. A common problem with these types of saws is that it takes considerable skill and attention to consistently align the workpiece with the saw blade so that the edge of the saw blade cuts the workpiece at the desired location. With prior art saws, it has not been possible to know if the saw alignment is proper until the saw begins to cut the material. The workpiece may be ruined if it is not set up at the correct orientation when the saw blade contacts the workpiece.  
      A laser arbor for a circular saw has been proposed in U.S. Pat. No. 5,862,727 to Kelly. The Kelly patent discloses the use of a semiconductor laser arbor for a circular saw that is actuated by a centrifugal switch and directs a line of laser beam on a workpiece. The Kelly patent discloses a battery powered laser light source. One problem with reliance upon batteries is that the semiconductor laser light source draws substantial power from the batteries to illuminate the laser, resulting in limited battery life and requiring frequent battery changes. Similarly, U.S. Pat. No. 6,035,757 to Caluori et al. discloses a similar semiconductor laser light beam alignment device for a circular saw having a focusing lens that causes the laser beam to be directed to the blade cut line. The Caluori patent likewise relies upon a battery power source that is carried by the laser arbor. This system has the same problem of limited battery life as the Kelly patent.  
      The assignee of this application has marketed a battery power laser alignment device which is described in copending U.S. patent application Ser. No. 09/860,898 entitled “Miter Saw Having a Light Beam Alignment System” which is incorporated by reference herein for general background purposes.  
      Applicants have solved the battery life problem by their development of a laser alignment system that utilizes a power source external to the laser arbor.  
     SUMMARY OF THE INVENTION  
      According to one aspect of the present invention, a miter saw (or other circular saw) is provided that includes a motor with a spindle to which a blade is secured and rotated by the motor to cut a workpiece that is disposed on a turntable or saw table. The motor is part of a saw head assembly that is supported relative to the table by an arm. A laser or other directed light source (hereinafter referred to as “laser” or “light source”) is mounted in a laser arbor housing that is secured to the spindle and rotated by the motor along with the blade. The light source emits a narrow beam of light from the housing to a location adjacent to the blade for checking the alignment of the blade with the workpiece. Power for the light source is provided by a source located outside the laser arbor housing.  
      The invention may also be defined as a laser arbor for a circular saw having a spindle that rotates the saw blade relative to a non-rotating portion of the saw. The laser arbor comprises a LED laser light and a circuit connected to the laser for providing power to the laser. The circuit provides power from a voltage source that includes a portion secured to the non-rotating portion of the saw.  
      According to another aspect of the invention, the circuit of the laser arbor for a circular saw may further comprise a generator having a rotor associated with the spindle and a stator associated with the non-rotating portion of the saw. Electrical energy is generated as the spindle rotates the rotor relative to the stator.  
      According to another aspect of the invention, the laser arbor for a circular saw may have an inductively coupled power source. The inductive power source may comprise a first induction coil inside the laser arbor that rotates with the arbor and a second induction coil mounted near the arbor that induces voltage in the first coil. The first induction coil is electrically connected to a power conditioning circuit that provides power directly to the light source. According to another aspect of the invention, the light source may be a LED laser.  
      Alternatively, the circuit may comprise a power source electrically connected by slip ring contacts that establish electrical contact between the power source and the circuit. The slip ring contacts may comprise a first set of contacts that rotate with the spindle and a second set of contacts that are stationary and contact the first set of contacts. The circuit further comprises a power conditioning circuit that provides power within a predetermined voltage range to the laser.  
      These and other aspects of the invention and advantages of the invention over the prior art will be better understood in view of the attached drawings and following detailed description provided below.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective view of a sliding compound miter saw having a laser arbor including a power generator for powering the laser;  
       FIG. 2  is a schematic fragmentary view of a circular saw blade, laser arbor and blade guard to which a stator for a generator is secured;  
       FIG. 3  is an exploded perspective view of a laser arbor including a fixed induction coil secured to the blade guard and a rotatable induction coil secured within the laser arbor;  
       FIG. 4  is an exploded perspective view of a laser arbor including a generator having a permanent magnet stator connected to the blade guard and a arcuate coil section secured within the laser arbor; and  
       FIG. 5  is a diagrammatic view of a laser arbor having slip ring contacts for providing power to the laser. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Referring now to  FIG. 1 , a saw  10  having a circular saw blade  12  is shown. The saw  10  also includes a base  13  and a turntable  14  that together comprise a supporting table generally referred to by reference numeral  15 . A fence  16  is provided on the supporting table  15 . A workpiece  18  is placed on the supporting table  15  and held against the fence  16  as the workpiece  18  is cut by the saw  10 . An arm  20  connects the motor assembly  22  to the turntable  14 . The motor assembly  22  forms a part of the saw head assembly, generally indicated by reference numeral  24 . The motor assembly  22  drives the saw blade  12 . The saw blade  12  is shielded by a fixed guard  28  and a retractable shield  30 . A handle  32  is provided for manipulating the saw head assembly  24 .  
      The saw  10  shown in the illustrated embodiment is a sliding compound miter saw having a miter angle adjustment mechanism  38  and a tilt adjustment mechanism  40 . While the illustrated embodiment is of a sliding compound miter saw, the invention is equally applicable to other types of circular saws such as a simple miter saw, a compound miter saw, a chop saw, portable circular saw, or radial arm saw. The saw head assembly  24  is pivotally connected to the arm  20  and includes a spring (not shown) for biasing the saw head assembly  24  normally out of engagement with the workpiece  18 .  
      When an operator is ready to make a cut with the saw  10 , the operator grips the handle  32 , depresses the trigger causing the circular saw blade  12  to rotate, and pulls it down toward the workpiece  18 . The miter angle adjustment mechanism  38  permits the turntable  14  to rotate relative to the base  13  to change the miter angle of cut. The tilt adjustment mechanism  40  allows the saw head assembly  24  to be pivoted to adjust the inclination of the blade  12  relative to the supporting table  15 .  
      Referring now to  FIG. 2 , a saw  10  having a laser arbor  42  is illustrated. The laser arbor  42  is mounted adjacent the saw blade  12  on the same spindle  44  as the saw blade. The laser arbor  42  directs a laser beam  48  outwardly from the laser arbor  42  as it is rotated by the spindle  44 . The light beam is slightly angled toward the blade preferably at the top surface of the work piece where the blade cuts the work piece. While the light source is described as a laser, another light source such as a light emitting diode (LED) laser, focused electric light bulb based system or other small light could be used with the saw  10 .  
      Referring now to both  FIGS. 1 and 2 , a stator  50  is secured to the fixed guard  28  near the laser arbor  42 . The stator  50  may include an electrical magnet or permanent magnet that creates magnetic flux through which the laser arbor  42  is rotated to generate electricity, as will be more fully described below.  
      Referring now to  FIG. 3 , one alternative embodiment of the invention is shown wherein a stationary induction coil  52  is included as part of the stator  50  that is mounted on the fixed guard  28 . A housing  54  for the laser arbor encloses a rotating induction coil  56 . The housing  54  and rotary induction coil  56  are assembled to a laser arbor washer  58  that supports a LED laser module  60 . The laser module  60  directs a beam of light through a slot  62  formed on the washer  58 . Electricity induced in the coil  56  is conditioned by a conventional inductively coupled power supply circuit of the type commonly used in electric toothbrushes or the like in order to power laser module  60 . Stationary induction coil  52  is powered by an AC power source or a pulsed reversing polarity or on-off DC source that induces a corresponding current through the rotating induction coil  56  which is located within the magnetic field of coil  52 .  
      Referring now to  FIG. 4 , another alternative embodiment is shown wherein a permanent magnet  64  is secured to the fixed guard  28 . The permanent magnet  64  is preferably formed by a plurality of arcuate segments (not shown) of a ceramic permanent magnet formed of ferrite or other well-known magnetic ceramic material. A housing  66  is secured to a laser arbor washer  68 . An arcuate coil  70  is mounted on the laser arbor washer  68 . The coil  70  is rotated with the laser arbor module through the alternating polarity (N-S-N) flux created by permanent magnet  64  thereby generating electricity that is provided to the laser arbor module  72 . Laser light is emitted through a slot  74  formed in the laser arbor washer  68 .  
      Referring now to  FIG. 5 , yet another alternative embodiment is provided wherein a first set of contacts comprising contacts  80  that are provided on a hub  81  of a laser arbor washer  82  of a laser arbor  84 . A housing  85  is provided for enclosing the component parts of the laser arbor  84 . Contacts  86  are provided on the spindle  88  that maintain contact with the contacts  80 . A pair of slip ring contacts  90  are provided on the spindle  88  at a location spaced from the laser arbor  84 . The slip ring contacts  90  connect to contacts  91  and are electrically connected to the contacts  86 . The laser module  92  is supported by a laser arbor washer  82  and directs a laser beam through a slot  94  formed in the laser arbor washer  82 .  
      In each of the embodiments described above with reference to  FIGS. 3-5 , no batteries are required to provide power to the laser modules.  
      A power conditioning circuit may be provided by a circuit board  96  secured to the washer or could be built-in as part of laser modules. In  FIG. 3 , an AC pulse reversing circuit  98  is illustrated that may be provided as part of the power circuit.  
      While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.