Abstract:
A rotary orbital sander includes internal suction channels connecting with a suction housing connectable with a vacuum source for removing sanding waste during sanding. A dual weight balancing arrangement includes oppositely extending weights in planes spaced above a sanding pad to completely balance the eccentric rotary pad with the separately located weights.

Description:
FIELD OF THE INVENTION 
     This invention relates to a rotary orbital sander, and more particularly to a rotary orbital sander that is adapted for use with a vacuum source. 
     BACKGROUND OF THE INVENTION 
     It is known in the art relating to rotary orbital sanders to combine a sander and a vacuum to pick up particles of sanding waste that are loosened during the sanding process. Such prior art sanders, however, lack sufficient suction to draw particles from a significant distance from the vacuum (e.g. at the outer edge of the sander). Moreover, the vacuum simply blows internal particles rather than drawing them away from the sanding means and floor. 
     It is also known to balance orbital sanders using a counterbalance weight located in the plane of the unbalanced sanding rotor. However, placement of the balance weight requires a special design of sanding pad assembly. 
     SUMMARY OF THE INVENTION 
     The present invention provides a rotary orbital sander that solves the disadvantages of the prior art sanders by providing a suction housing that connects with a vacuum source such as a conventional shop vacuum. The suction housing is adjustably sealed to a unique sanding pad assembly having a plurality of radially extending suction channels connected with inner and outer annular channels. The suction channels draw air and sanding waste into the channels through holes in a sanding pad aligned with the annular channels so that loosened particles under the sanding disk are readily drawn through the channels into the suction housing and out a vacuum hose. The sanding pad assembly may also include side suction channels at the peripheral edge of the sanding pad to draw in sanding waste from beyond the sanding pad periphery. 
     Alternatively, the radial channels may be omitted and inner and/or outer annular channels can be fed through openings in a sanding disk. Sanding waste is carried from the annular channels through openings on the sanding pad directly to the suction housing which is enlarged to cover the outermost channel diameter. 
     The invention also provides a balancing assembly using a pair of balance weights oriented oppositely and spaced from the sanding pad to completely balance eccentric forces without requiring a complicated sanding pad assembly. This arrangement permits the sanding pad to be very large in diameter, greater than 8 inches. In fact, a 16 inch sanding pad has been successfully used in accordance with the invention. Moreover, the throw out, or radius of eccentricity that creates the orbital motion, of the present invention, exceeds 4 mm. 
     The rotary orbital sander of the present invention is adapted for use with pneumatic or electric tools. It is further suitable for coarse or the finest sanding. 
     These and other features and advantages of the invention will be more fully understood from the following detailed description of the invention taken together with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a perspective view of an electric rotary orbital sander according to the present invention; 
     FIG. 2 is a cross-sectional view of the rotary orbital sander of FIG. 1; 
     FIG. 3 is a perspective view of a drive head assembly coupled to a sanding pad assembly of the rotary orbital sander of FIG. 1; 
     FIG. 4 is an enlarged plan view of the drive head assembly of FIG. 3; 
     FIG. 5 is a side view of a drive head in the rotary orbital sander of FIG. 1; 
     FIG. 6 is a plan view of the suction housing and sanding pad assembly of the sander of FIG. 1; 
     FIG. 7 is a cross-sectional view of the suction housing from the line B-C of FIG. 6; 
     FIG. 8 is a partial lower perspective view of the sanding pad and pad assembly of the sander of FIG. 1; 
     FIG. 9 is a lower perspective view of the sanding pad of the sander of FIG. 1; 
     FIG. 10 is a perspective view of a second embodiment of a rotary orbital sander according to the present invention; and 
     FIG. 11 is a plan view of a third embodiment showing a pneumatic rotary orbital sander according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings in detail, numeral  10  generally indicates a first embodiment of a rotary orbital sander according to the present invention. Sander  10 , as shown in FIG. 1, includes an elongated handle  12  mounted to a drive motor  14 . The motor  14  is mounted to the upper surface of a suction housing  16  which receives a motor shaft  17  having an axis  18  as shown in FIG.  2 . The suction housing  16  is further adapted to connect with a vacuum source, for example, a hose  19  connectable to a conventional shop vacuum (not shown). 
     As shown in FIG. 2, the suction housing  16  includes an adjustable suction ring  20  that is clamped to the housing with a hose clamp  22 . Raising or lowering the suction ring  20 , decreases or increases the vacuum suction accordingly. The suction ring  20  lightly contacts or is spaced closely to a sanding pad assembly (shown generally as reference numeral  24 ) without interfering with the rotation of the sanding pad assembly  24 . 
     As best shown in FIG. 3, the sanding pad assembly  24  includes a pad backing  26  having a plurality of holes  28  formed therein and annularly spaced about a center axis  29  of the sanding pad assembly  24 . The suction housing  16  encloses the holes  28  which provide an outlet for loosened particles or sanding waste to be removed by the vacuum source. In a preferred embodiment, the pad backing  26  is made of a lightweight metal such as aluminum or strong, light, powerful plastic type material. 
     The pad backing  26  is mounted to a circular rubber sanding pad  30  as shown in FIG.  9 . As best illustrated in FIG. 6, sanding pad  30  includes a plurality of radially extending suction channels  32  connecting at their inner ends with an inner annular channel  34  open to the holes  28  of the pad backing  26 . At their outer ends, radial channels  32  connect with an outer annular channel  36  located near the periphery of the sanding pad  30 . 
     The sanding pad  30  may also include side channels  38  at the peripheral edge of the sanding pad  30 , connecting with outer annular channel  36 . Channels  32  and  36  draw air from the periphery of the sanding pad  30  and direct the air to channel  34  which also draws air from an inner portion of the pad  30 . When particles are loosened during the sanding process, they are drawn by the vacuum source into channels  36 ,  32  and/or  34 , up through holes  28  of the pad backing and out vacuum hose  19 . Side channels  38  provide additional paths for drawing air through the peripheral edge of the sanding pad  30  to the outer annular channel  36 . 
     Alternatively, a single annular channel may be provided which connects with a set of holes in the sanding disk, the annular channel also connects with holes in the pad backing, thereby eliminating the radial channels and the additional annular channel. In such an embodiment, the suction housing would be appropriately sized to enclose the holes of the pad backing which are aligned with the holes of the sanding pad. A second concentric annular channel and aligned rings of holes in the sanding pad and pad backing may also be provided, if desired. 
     As shown in FIG. 8, the sanding pad  30  is adapted to receive a piece of complimentary sized and shaped sand paper, such as a circular (or other suitably shaped) sanding disk  40 , having a plurality of annularly spaced holes  42  that are aligned in assembly with the inner channel  34  of the sanding pad  30  which in turn connects with the holes  28  of the pad backing  26 . Additional annularly spaced holes  43  are aligned with the outer annular channel  36 , which connects through radial channels  32  with the inner channel  34 . By providing at least one annular channel about the sanding pad which connects with holes in the pad which align with holes in the pad backing, it is not necessary for the user to precisely align the holes of the sand paper with holes in the pad backing. Suction from the vacuum will draw particles through the channel to the closet hole for elimination from the suction housing. To achieve this objective, the pad includes a central hole  44  which, when aligned with a central hole (not shown) in the sanding disk  40 , causes each of the holes of the sanding disk to become sufficiently aligned with the annular channels  34 ,  36  of the pad. 
     In operation, a vacuum source, such as a conventional shop vacuum, is connected to the suction housing  16 . In a preferred embodiment, the vacuum hose  19  is connected to a fitting  46 , attached to the suction housing  16 , shown in cross section in FIG. 7 along the line B-C of FIG.  6 . Fitting  46  connects the vacuum suction directly to the sanding pad assembly  24 . 
     The sander is contained within the suction housing  16  and operates in orbital fashion by means of an eccentric rotary drive head  50  rotatably driven about the axis  18  by the motor shaft  17  as shown in FIG.  2 . The drive head  50  includes an eccentric recess portion  52  off-set from the center line of the shaft  17 . Disposed in the recess  52  is a double ball bearing assembly  54  which supports a carrier  56  within the off-set portion  52  of the motor shaft  17 . The carrier  56  is mounted to the pad backing  26  and forms a part of the previously described sanding pad assembly  24 . 
     As shown in FIG. 2, the sanding pad assembly  24  is supported by the bearing assembly  54  for free rotation about an axis  58  that is radially offset from the motor shaft axis  18 . The sanding pad assembly  24  is, thus, driven by the motor  14  and drive head  50  in an orbital pattern around the motor shaft axis  18 . Assembly  24  is also free to rotate about the central axis  58  of the sanding pad assembly  24  and its carrier  56 . 
     In order to balance the eccentric mass of the sanding pad assembly  24  in its orbital rotation about the axis  18 , a combination of a first balance weight  60  and a counterbalance weight  62  are mounted on the drive head  50  above the center of gravity of rotation of the pad assembly  24 . The first balance weight is located uppermost on the drive head  50  and has a center of gravity of rotation offset from the axis  18  in the same direction as the rotational gravity center of the pad assembly  24 . The purpose of this first balance weight  60  is to raise the center of gravity of rotation of the drive head assembly, including the pad assembly  24 , to a level above the pad assembly  24 . The total rotational unbalance of the drive head assembly is then offset by locating the counterbalance weight with its center of gravity of rotation radially opposite to that of the total drive head assembly and providing an equal rotational mass. 
     The drive head assembly with its sanding pad assembly  24  and the two oppositely directed balance weights  60 ,  62  is thus perfectly balanced with both the eccentric masses and the bending couples applied to the motor shaft by the eccentric masses being completely offset. Accordingly, the first balance weight  60  is lighter than the counterbalance weight  62  and is located higher on the drive head  50  than the counterbalance weight  62 , thereby eliminating the tendency of the sanding pad to flap during rotation. The orbital sander thus runs smoothly without vibration and can be easily guided by the operator in a motion similar to floating over the surface being sanded. 
     The drive head and balance weights may be made in any desired manner and could be combined in an integral body. However, in the present embodiments, the first balance weight  60  and the counter balance weight  62  are both made with circular bores  64  fitted over a cylindrical portion  66  of the drive head  50 . The weights both have laterally extending arms  68 ,  70  that provide their eccentric masses, the rotational mass of the arm  68  of the first balance weight  60  being substantially less than that of the arm  70  of the counterbalance weight  62 . Both weights  60 ,  62  are retained on the drive head by locking screws  72 , which extend through their respective arms to engage the cylindrical portion  66  of the drive head  50 . Alternatively, weights  60 ,  62  may be permanently attached to the drive head  50 . 
     Where the surface to be sanded is particularly rough, weights may be added to the rotary orbital sander of the present invention. As shown in FIG. 10, elongated handle  12  is provided with a cross bar  74  having a center along the center line of the motor shaft  17 . As shown in FIG. 1, at each end of the cross bar  60  is an upstanding pin  76 . A third pin may be located at the center of the cross bar. Each pin  76  removably receives an appropriate weight  78 . When two weights are used, weights  64  of equal mass are equidistantly disposed on the pins  76  located on either side of the center line of the motor shaft  17 . A third weight may be added to the centrally located pin. 
     Of course, any suitable motor may be used to rotate the motor shaft  17 . By way of example, a first preferred embodiment of FIGS. 1,  2 ,  10  uses an electric motor. The motor shaft may also be pneumatically driven as illustrated in FIG.  11 . 
     Although the invention has been described by reference to a specific embodiment, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiment, but that it have the full scope defined by the language of the following claims.