Abstract:
A power tool including a housing with an electric motor in the housing. The motor has a stator and an armature, the stator having field coils and the armature having an armature shaft on which a commutator is affixed. A pair of brush boxes are located in the housing on opposite sides of the commutator. An orbit mechanism coupled to the armature shaft and a platen is coupled to the orbit mechanism. The field coils comprise a first field coil facing a front of the sander and a second field coil facing a rear of the sander and the brush boxes are rotationally offset from the field coils with respect to a vertical axis of the sander.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 13/548,327 filed Jul. 13, 2012, and application Ser. No. 12/040,971 filed on Mar. 3, 2008, and issued on Jul. 31, 2012 as U.S. Pat. No. 8,231,437. The entire disclosure of the above applications are incorporated herein by reference. 
     
    
     FIELD 
       [0002]    The present disclosure relates to electric sanders, and more particularly, to a low height quarter sheet electric sander. 
       BACKGROUND 
       [0003]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0004]    An electric quarter sheet sander is a type of orbital sander having an electric motor that drives an orbit mechanism that moves a platen in an orbital pattern. A sheet of sandpaper is removably fastened to the platen. When the platen with the sandpaper fastened thereto is applied to a work surface, such as to wood, the orbital motion of the platen moves the sandpaper in an orbital motion against the work surface to sand it. Since a full sheet of sandpaper is 9″×11″ and the sheet of sandpaper fastened to the platen is 4½″×5½″, or ¼ of a full sheet of sandpaper, sanders of this type are commonly known as ¼ sheet sanders. 
         [0005]    One disadvantage ¼ sheet electric sanders have suffered is due to the height of the sander. If the user grasps the sander by placing the palm of the user&#39;s hand over the top of the sander, the user&#39;s hand is sufficiently far from the work that the user is sanding to cause more fatigue than is the case with pneumatic orbital or random orbital sanders where the user can grasp the sander close to the work piece. This often leads to user&#39;s grasping electric ¼ sheet sanders on the side of the sander. This tends to be awkward compared to grasping the top of the housing. Also, the greater height of the ¼ sheet electric sander causes more wobble compared to the lower height pneumatic orbital sander. 
         [0006]      FIGS. 1 ,  3   5 , and  7  show a prior art Black &amp; Decker QS800 series and KA171 ¼ sheet electric sander  100 . Sander  100  has a housing  102  that includes first and second clamshell halves  104 ,  106  mated together. An upper portion of housing  102  is formed as a handle  108 . An on-off switch  110  is disposed in front end  109  of handle  108  of housing  102 . An electric motor  300  ( FIGS. 3 and 5 ) is disposed in housing  102 . Electric motor  300  is a universal AC motor having a field or stator  302  and an armature  308 . Stator  302  includes a lamination stack  304  having field coils  306  wound in slots (not shown) therein. Motor  300  is a two-pole motor and stator  302  includes two field coils  306 . Armature  308  extends through lamination stack  304  of stator  302 . Armature  308  has an armature shaft  310  extending through and affixed to a lamination stack  312 . Lamination stack  312  includes slots (not shown) in which armature coils (not shown) are wound. Portions of armature shaft  310  generally at upper end  316  and lower end  318  ( FIG. 7 ) thereof (as oriented in the drawings) are entrained in upper bearing  320  and lower bearing  322  ( FIG. 7 ) (as oriented in the drawings). Upper and lower bearings  320 ,  322  are received in bearing holders  324 ,  326  formed in clamshell halves  104 ,  106  of housing  102 . A commutator  314  is affixed to armature shaft  310  toward upper end  316  thereof. 
         [0007]    A fan  328  is affixed to armature shaft  310  toward a lower end of armature shaft  310  and an orbit mechanism  330  ( FIG. 5 ) is coupled to the lower end  318  of armature shaft  310 . Fan  328  is illustratively disposed in housing  102  and at least a portion of orbit mechanism  330  ( FIG. 5 ) extends below a bottom  111  of housing  102 . A platen  112  is coupled to orbit mechanism  330 . A ¼ sheet of sandpaper  114  is removably secured to platen  112 . 
         [0008]    Clamshell housing halves  104 ,  106  each include a plurality of screw bosses, illustratively six, for receiving screws (not shown) that hold clamshell halves  104 ,  106  together. The screw bosses may illustratively be threaded screw bosses in one of clamshell halves  104 ,  106  and through holes in the other of clamshell halves  104 ,  106 . The screw bosses of each clamshell housing half include a pair of upper screw bosses  336  generally at opposite sides of upper bearing  320 , a pair of lower screw bosses  338  generally at and slightly above opposite sides of lower bearing  322 , and a pair of screw bosses  340  ( FIG. 5 ) at an upper back end of handle  108  of housing  102  generally where a cordset  116  enters housing  102  and connects to a terminal block  341  ( FIG. 3 ). When clamshell halves  104 ,  106  are mated together, the screw bosses extend across housing  102  from one clamshell half  104  to the other clamshell half  106 . Switch  110  and terminal block  341  are disposed in a horizontal elevation (when sander  100  is upright) above a horizontal elevation of brush boxes  332 . 
         [0009]    Two brush boxes  332  are disposed on opposite sides of commutator  314  in respective brush box retainers  334  formed in clamshell halves  104 ,  106  of housing  102 . Brush boxes  332  are located in housing  102  so that they bridge across clamshell halves  104 ,  106  of housing  102 . Stator  302  of electric motor  300  is located in housing  102  so that one field coil  306  is disposed in clamshell half  104  and the other field coil  306  is disposed in clamshell half  106  and are generally parallel to each other. Each field coil  306  thus extends across the respective clamshell half  104 ,  106  in which it lies and not toward the other clamshell half  104 ,  106 . When clamshell halves  104 ,  106  are mated, edge  344  of clamshell half  104  and edge  346  ( FIG. 5 ) of clamshell half define a vertical plane  352  (when sander  100  is upright). A horizontal (when sander  100  is upright) centerline  348  ( FIG. 7 ) of brush boxes  332  (a line that extends through the centers of the brush boxes  332 ) lies in that vertical plane  352  and a horizontal centerline  350  ( FIG. 7 ) of field coils  306  (a line that extends through the centers of field coils  306 ) lies in a vertical plane  354  that is rotated ninety degrees with respect to plane  352 . Centerline  348  ( FIG. 7 ) of brush boxes  332  and centerline  350  ( FIG. 7 ) of field coils  306  are thus rotated ninety degrees with respect to each other. 
         [0010]    As best shown in  FIG. 5 , field coils  306  are sufficiently wide so that they bridge across lower screw bosses  338  and housing  102  must thus have sufficient height so that lower ends  342  of field coils  306  are above lower screw bosses  338 . As best shown in  FIG. 3 , switch  110  and terminal block  341  are disposed above brush boxes  332 . 
         [0011]    Sander  100  has a height, the distance from the top of handle  108  to the bottom of platen  112 , of 155 mm. Lamination stack  304  of stator  302  of electric motor  300  has a height of 25 mm and commutator  314  has a height of 15 mm. Electric motor  300  is illustratively a 230 volt, 50 Hz, 200 watt, 15,000 RPM (no load speed) motor or a 120 volt, 60 Hz, 2 amp, 15,000 RPM (no load speed) motor. 
       SUMMARY 
       [0012]    A reduced height quarter sheet sander has a housing having first and second halves mated together. An upper portion of the housing provides a handle. An electric motor is disposed in the housing. The electric motor has a stator and an armature. The stator has field coils and the armature has an armature shaft on which a commutator is affixed. A pair of brush boxes is disposed in the housing on opposite sides of the commutator. An orbit mechanism is coupled to the armature shaft and a platen is coupled to the orbit mechanism. In an aspect, a switch disposed in the handle of the housing and a terminal block (at which a cordset that enters the housing terminates) disposed in the handle of the housing have generally the same horizontal elevation as the brush boxes (when the sander is upright). In an aspect, first and second halves of the housing have lower screw bosses generally on opposite sides of the electric motor that extend across the housing from one half to the other half, the stator disposed in the housing so that the field coils extend across the housing from one housing half to the other housing half and outside the lower screw bosses wherein bottoms of the field coils are horizontally adjacent or below the lower screw bosses. 
         [0013]    In an aspect, edges of the halves of the housing define a vertical plane when the housing halves are mated together and the sander is upright, and a horizontal centerline of the brush boxes is perpendicular to that vertical plane. In an aspect, a horizontal centerline of the field coils lies in the vertical plane defined by the edges of the housing halves and the horizontal centerline of the brush boxes is perpendicular to the centerline of the field coils. 
         [0014]    In an aspect, top and bottom portions of the field coils are bent outwardly and toward each other. 
         [0015]    In an aspect, the sander has a vertical height of that does not exceed 135 mm. In an aspect, the sander has a vertical height that does not exceed 130 mm. In an aspect, the sander has a vertical height that does not exceed about 125 mm. 
         [0016]    Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0017]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0018]      FIG. 1  is side perspective view of a prior art ¼ sheet electric sander; 
           [0019]      FIG. 2  is a side perspective view of a reduced height ¼ sheet electric sander in accordance with an aspect of the present disclosure; 
           [0020]      FIG. 3  is a side perspective view, partially cut away, of the sander of  FIG. 1 ; 
           [0021]      FIG. 4  is a side perspective view, partially cut away, of the sander of  FIG. 2 ; 
           [0022]      FIG. 5  is a side sectional view of the sander of  FIG. 1 ; 
           [0023]      FIG. 6  is a side sectional view of the sander of  FIG. 2 ; 
           [0024]      FIG. 7  is a side perspective view of an electric motor and brush boxes of the sander of  FIG. 1 ; and 
           [0025]      FIG. 8  is a side perspective view of an electric motor and brush boxes of the sander of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
         [0027]    With reference to  FIGS. 2 ,  4 ,  6 , and  8 , a reduced profile ¼ sheet sander  200  is shown. Sander  200  has a housing  202  having first and second clamshell halves  204 ,  206  mated together. Housing  202  and first and second clamshell halves  204 ,  206  are similar to housing  102  and first and second clamshell halves  104 ,  106  of sander  100 , but having a reduced height as discussed below. An upper end of housing  202  is formed as a handle  208 . On-off switch  110  is disposed in a front end  209  of handle  208  of housing  202 . An electric motor  400  ( FIGS. 4 and 6 ) is disposed in housing  202 . Electric motor  400  is a universal AC motor having a field or stator  402  and an armature  408 . Stator  402  includes a lamination stack  404  having field coils  406  wound in slots (not shown) therein. Motor  400  may illustratively be a two-pole motor and stator  402  includes two field coils  406 . Armature  408  extends through lamination stack  404  of stator  402 . Armature  408  has an armature shaft  410  extending through and affixed to a lamination stack  412  ( FIG. 6 ). Lamination stack  412  includes slots (not shown) in which armature coils (not shown) are wound. Portions of armature shaft  410  generally at upper end  416  and lower end  418  ( FIG. 6 ) thereof (as oriented in the drawings) are entrained in upper bearing  420  and lower bearing  422  ( FIG. 6 ) (as oriented in the drawings). Upper and lower bearings  420 ,  422  are received in bearing holders  424 ,  426  formed in clamshell halves  204 ,  206  of housing  202 . A commutator  414  is affixed to armature shaft  410  toward upper end  416 . Electric motor  400  may illustratively be a 230 volt, 50 Hz, 200 watt, 16,000 RPM (no load speed) motor or a 120 volt, 60 Hz, 2 amp, 16,000 RPM (no load speed) motor. 
         [0028]    A fan  428  is affixed to armature shaft  410  toward lower end of  418  of armature shaft  410  and an orbit mechanism  430  is coupled to the lower end  418  of armature shaft  410 . Fan  428  is illustratively disposed in housing  202  and at least a portion of orbit mechanism  430  ( FIG. 6 ) extends below a bottom  211  of housing  202 . A platen  112  is coupled to orbit mechanism  430 . A ¼ sheet of sandpaper  114  is removably secured to the bottom of platen  112 . 
         [0029]    Clamshell housing halves  204 ,  206  each include a plurality of screw bosses, illustratively six, for receiving screws (such as screws  458  in  FIG. 4 ) that hold clamshell halves  204 ,  206  together. The screw bosses may illustratively be threaded screw bosses in one of clamshell halves  204 ,  206  and through holes in the other of clamshell halves  204 ,  206 . The screw bosses of each clamshell housing half include a pair of upper screw bosses  436  generally at opposite sides of upper bearing  420 , a pair of lower screw bosses  438  generally at and slightly above opposite sides of lower bearing  422 , and a pair of screw bosses  440  at an upper back end of handle  208  of housing  202  generally where a cordset  116  enters housing  402  and connects to a terminal block  441 . When clamshell halves  204 ,  206  are mated together, the screw bosses extend across housing  202  from one clamshell half  204  to the other clamshell half  206 . 
         [0030]    Electric motor  400  is similar to electric motor  300  of sander  100 , but with the following differences. The height of lamination stack  404  of stator  402  is shorter than the height of lamination stack  304  of stator  302 , illustratively by about twenty percent. In an aspect, the height of lamination stack  404  of stator  402  is about 20 mm compared with the 25 mm height of lamination stack  304  of stator  302 . The height of lamination stack  412  of armature  408  is correspondingly reduced. The height of commutator  414  of armature  408  of electric motor  400  is shorter than the height of commutator  314  of armature  308  of electric motor  300 , illustratively by about 4 mm. In an aspect, the height of commutator  414  is about 11 mm compared with the 15 mm height of commutator  314  of armature  308 . This allows the height of sander  200  to be reduced compared to the height of sander  100  as the overall height of electric motor  400  is shorter compared to the height of electric motor  300  of sander  100 , and the height of sander  200  is so reduced. 
         [0031]    Sander  200  includes two brush boxes  432  affixed to a brush ring  433 . The brush ring  433  may illustratively be secured in housing  202  with screws (not shown) that pass through holes in lamination stack  404  of stator  402 . Brush ring  433  is secured in housing  202  with brush boxes  432  disposed on opposite sides of commutator  414  so that one brush box  432  is disposed in clamshell half  204  and the other brush box  432  is disposed in clamshell half  206 . Stator  402  of electric motor  400  is located in housing  202  so that the two field coils  406  bridge across clamshell halves  204 ,  206 . When clamshell halves  204 ,  206  are mated, edge  444  of clamshell half  204  and edge  446  of clamshell half  206  define a vertical plane  452  ( FIG. 4 ) (when sander  200  is upright). A horizontal (when sander  200  is upright) centerline  450  ( FIG. 8 ) of field coils  406  lies in vertical plane  452  and a horizontal centerline  448  ( FIG. 8 ) of brush boxes  432  lies in a plane  454  that is rotated ninety degrees with respect to plane  452 . Centerline  448  of brush boxes  432  and centerline  450  of field coils  406  are thus rotated ninety degrees with each other. In sander  200 , brush boxes  432  and field coils  406  are rotated (about a vertical axis when sander  200  is upright) ninety degrees in housing  202  compared with brush boxes  332  and field coils  306  of sander  100 . 
         [0032]    By rotating brush boxes  432  in housing  202  of sander  200  compared with brush boxes  332  in housing  102  of sander  100 , switch  110  and terminal block  441  can be located in the space occupied by brush boxes  332  of sander  100  and in generally the same horizontal elevation (when sander  200  is upright) as brush boxes  432 . In this regard, as can be seen from  FIGS. 4 and 6 , switch  110  and terminal block  441  are disposed on opposite sides of commutator  414 . Switch  110  is thus disposed on its side of commutator  414  between brush boxes  442  and terminal block  441  is thus disposed on its side of commutator  414  between brush boxes  442 . Thus, as can be seen in  FIG. 4 , vertical plane  452  defined by the edges  444 ,  446  of housing halves  204 ,  206  intersects switch  110  and terminal block  441 , but not brush boxes  442 . 
         [0033]    In contrast, switch  110  and terminal block  341  of sander  100  are located in housing  102  a horizontal elevation (when sander  100  is upright) that is above the horizontal elevation in which brush boxes  332  of sander  100 . This also allows the height of sander  200  to be reduced compared to the height of sander  100 , and the height of sander  200  is so reduced. 
         [0034]    By rotating field coils  406  of stator  402  ninety degrees compared with field coils  306  of stator  302 , the field coils  406  are disposed outside of lower screw bosses  438  and lower ends  442  of field coils  406  can be horizontally adjacent (when sander  200  is upright), or even below, lower screw bosses  438 . This allows stator  402  and armature  408  of electric motor  400  to be moved down compared to stator  302  and armature  308  of electric motor  300  of sander  200 . This also allows the height of sander  200  to be reduced compared to the height of sander  100 , and the height of sander is so reduced. Field coils  406  are also bent over to reduce the overall height of field coils  406 . As shown in  FIGS. 4 ,  6  and  8 , upper ends  456  and lower ends  442  of field coils  406  are bent outwardly and toward each other. This also allows the height of sander  200  to be reduced compared to the height of sander  100 , and the height of sander  200  is so reduced. 
         [0035]    To further reduce the height of sander  200 , electrical creepage and electrical inaccessibility dimensions may be minimized consistent with UL or other similar requirements. 
         [0036]    In an aspect, sander  200  illustratively has a vertical height, the height from the top of housing  202  to the bottom of platen  112 , of 135 mm or less. In an aspect, sander  200  illustratively has a vertical height of 130 mm or less. In an aspect, sander  200  illustratively has a vertical height that does not exceed about 125 mm (i.e., 125 mm+/−3 mm). In an aspect, sander  200  has a vertical height that is about 125 mm.