Patent Abstract:
An electrically powered belt sander comprising a housing, a dust flow path defined by the housing, a motor mounted in the housing at a first location and having an output shaft, a fan connectable to the motor output shaft and rotateably mounted in the housing at a second location a distance from the motor output shaft, a belt connectable between the motor output shaft and the fan whereby the rotation of the motor output shaft drives the rotation of the fan, and a damper located in the dust flow path and operable for blocking the dust flow path.

Full Description:
FIELD OF THE INVENTION 
       [0001]    The present invention generally relates to electric powered portable sanders having a dust collection system. More particularly it relates to portable belt sanding power tools. 
       BACKGROUND OF THE INVENTION 
       [0002]    All sanding tools create a large amount of dust. In particular, a belt sander creates large quantities of wood dust both in the air and on the surface of the workpiece. Because of this most electric sanders employ some sort of dust collection system. These dust collection systems typically use a fan driven directly by the motor to create a suction for the dust collection system. The dust collection fan may be half of a two-sided or double sided fan (the other half cooling the motor) or it may be mounted on one end of a motor opposite to the other end bearing a motor cooling fan. In either case, dust laden air is deliberately routed past the motor and dust leakage into the motor is aggravated. 
         [0003]    Furthermore, these systems tend to clog due to the tortuous flow path though and around narrow channels, small chokes, and tight corners. Clogging of the dust removal flow path not only degrades or stops dust collection, it can also foul the dust fan, load down the motor, and reduce cooling air to the sander motor, which may damage the motor. Another drawback of those systems employing a main motor fan to collect dust is that, when the user would prefer to work without dust collection, such systems cannot be deliberately shut off, because of the need to cool the motor. Simply leaving off the dust receptacle is often impractical since a stream of dust laden air would then exhaust at or near the user. 
         [0004]    In some sanders such as the Black &amp; Decker model 4028, a second, separately controllable electric motor and fan is provided for the dust collection system. The inclusion of a separate dust collection motor, however, drives up the size, weight, and cost of the sander. 
         [0005]    Accordingly, it is an object of the present invention to provide an improved sander that provides a dust collection system wherein an obstruction of the dust removal path does not reduce cooling air flow to the motor. It is another object of the present invention to provide a sander dust collection system that allows for operation of the sander with the dust collection airflow deliberately blocked or stopped. 
         [0006]    Another problem with current sander designs is the common use of so called “flag bag” dust receptacles. Flag bag receptacles are fabric dust bags usually suspended from a support over the top of the sander or set off to one side. The height of the bag and the location create problems with tool access to and with user vision of the workpiece. As the bag fills with dust the added weight can unbalance a type of portable tool that is often already top heavy. Furthermore, as it fills the bag will often droop down into dragging contact with the workpiece, which can damage the bag or pull the sander from the intended track. 
         [0007]    Accordingly it is another objective of the present invention to provide a dust receptacle that will not droop or sag when loaded and which can be securely mounted low down and behind the main body of the belt sander. 
         [0008]    Still another problem with current sanders is that the inlet of the dust receptacle and the dust outlet of the tool usually rely on a simple friction or taper fit to hold the two conical or tubular components together. Without a positive locking mechanism to hold the two parts together, it is possible for the two parts to separate during use, resulting in dust laden air blowing out of the suddenly exposed dust outlet. 
         [0009]    Accordingly it is still another objective of the present invention to provide a secure mechanical engagement between the improved dust receptacle and to provide a positive locking mechanism to prevent the inadvertent disengagement of the dust receptacle from the sander. 
       SUMMARY OF THE INVENTION 
       [0010]    In one preferred form, the present invention provides a sander with a separate dust collection fan driven off the main motor, but not directly connected to it. This dust fan can be located away from the motor for a more compact tool and improved dust removal airflow. Moreover it can be spun at a speed independent of the motor armature and more efficient for dust collection. In a preferred embodiment the dust fan is powered from the main motor by means of a belt drive, but a gear train could also be used. 
         [0011]    The separate fan system can be turned off by either of two convenient methods. A user operable damper may be provided in the dust flow path to interrupt the airflow even though the fan continues to spin. Unlike the single motor single fan designs, this will have no adverse effect on cooling the motor. Alternatively, the dust fan can be disconnected from the motor, thus permanently disabling the dust collection system, unloading the motor, and decreasing tool noise. 
         [0012]    In another preferred embodiment, the sander is provided with a semi-rigid dust cassette that is mounted low and rearward of the sander. Thus located, it reduces tool access and user vision problems. Moreover, the dust fan does not have to blow dust upward into a fabric sack that is held open only by the air pressure within. Additionally, so located and constructed the preferred dust receptacle/cassette reduces the access, vision, and balance problems associated with the “flag bag” type receptacles. 
         [0013]    In the preferred embodiment, the dust receptacle comprises a flexible part of rubber like material. Thus constructed, the flexible part of the dust receptacle can be deformed in order to facilitate alignment and engagement of the dust receptacle when mounting it to the sander, 
         [0014]    In another aspect of the preferred embodiment, secure engagement is further enhanced by the provision of a positive locking mechanism for holding together the dust outlet of the sander housing and the inlet of the dust receptacle. The locking mechanism comprising a movable collar on the outlet duct of the housing which lockably engages tabs on the inlet nozzle of the dust receptacle. 
         [0015]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, white indicating a preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    A sander according to the present invention will now be described by way of example, with reference to the accompanying drawings in which; 
           [0017]      FIG. 1  is an elevation view of a belt sander; according to the present invention, and with part of the exterior housing removed. 
           [0018]      FIG. 2  is a simplified exploded view of the belt sander of  FIG. 1 . 
           [0019]      FIG. 3  is another simplified exploded view of the belt sander of  FIG. 1 . 
           [0020]      FIG. 4  is another simplified exploded view of the belt sander of  FIG. 1 . 
           [0021]      FIG. 5  is a right side elevation view of the gear case of the belt sander of  FIG. 1 . 
           [0022]      FIG. 6  is a left side elevation view of the gear case of  FIG. 5 , 
           [0023]      FIG. 7  is another side elevation view of the gear case of  FIG. 5 . 
           [0024]      FIG. 8  is a perspective view of the gear case of the belt sander of  FIG. 1 . 
           [0025]      FIG. 9  is a close up perspective view of portions of the gear case of  FIG. 8 . 
           [0026]      FIG. 10  is a partial cutaway and close-up perspective view of details of the dust fan of the belt sander of  FIG. 9 . 
           [0027]      FIG. 11  is a cutaway elevation view of the dust fan of  FIG. 10 . 
           [0028]      FIG. 12  is a further cutaway perspective view of the dust fan of  FIG. 10 . 
           [0029]      FIG. 13  is a cutaway elevation view of the dust fan of  FIG. 12 . 
           [0030]      FIG. 14  is a cross section elevation view of the dust fan of  FIG. 13 . 
           [0031]      FIG. 15  is a simplified elevation view of portions of the belt sander of  FIG. 1  with the addition of elements of the dust receptacle. 
           [0032]      FIG. 16  is a perspective view of the belt sander and dust receptacle of  FIG. 15  with additional elements added. 
           [0033]      FIG. 17  is a perspective view of the dust fan enclosure and collar assembly of the  FIG. 15 . 
           [0034]      FIG. 18  is a rear end elevation view of the fan enclosure and collar assembly of  FIG. 17 . 
           [0035]      FIG. 19  is an alternative perspective view of the fan enclosure and collar assembly of  FIG. 17 . 
           [0036]      FIG. 20  is an exploded perspective view of the dust receptacle of the belt sander of  FIG. 16 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0037]    With reference to the accompanying  FIGS. 1 ,  2 ,  3 , and  47  motor assembly  10  is transversely mounted between the rearwardly located drive roller  9  and the front roller assembly  8 . The motor output shaft, which extends through an opening in gear case cover  4 , ends in drive pulley  12 . 
         [0038]    Drive pulley  12  pulls drive belt  14 . Drive belt  14  turns driven pulley  16 . Driven pulley  16 , through gearing not shown, turns rear drive roller  9 . A second portion of driven pulley  16  pulls dust collection fan belt  18 , which powers a dust collection fan  20  that is located on an upper portion of -ear case cover  4 . In the preferred embodiment shown, fan belt  18  is an o-ring. 
         [0039]    With particular reference to  FIGS. 24 , the left-hand/outward side of the gear case cover  4  is covered by belt cover/housing  6 , which encloses the pulleys  12  and  16  and belts  14  and  18 . Completing the frame/superstructure of the sander is the right side housing  3 . 
         [0040]    With additional reference to  FIGS. 5-7 , the suction created by dust fan  20  pulls an air flow (indicated by arrows in  FIG. 5 ) from the vicinity of drive wheel  9  through an air passage  22  cast into the right housing  3  and gear case  4 . Upper portions of both the right housing  3  and gear case  4  define an inlet or suction chamber  24 . The upper portion of gear case  4  also defines suction openings  26  in a trefoil arrangement. Rotatably mounted to the upper exterior portion of gear case  4  is an inlet or suction damper  28 . Damper  28  has trefoil openings and a user operable switch or damper  29  for rotating the damper  28  between an open or “ON” position, wherein the suction openings  26  and damper openings are aligned, and a closed or suction “OFF” position, wherein the damper is unaligned and blocks the suction openings  26 . 
         [0041]    With further reference to  FIGS. 8-14 , on the exterior side of the gear case  4 , dust fan  20  is rotatably and coaxially mounted with damper  28  and suction openings  26 . Dust fan  20  includes a pulley portion  23 , to which fan belt  18  is drivingly connected. Dust fan  20  is a radial type fan. That is, rotation of dust fan  20  creates a suction at its center and a pressure around its periphery, so that airflow is from the center radially outward through the fan vanes  21  to the periphery. 
         [0042]    Mounted to the exterior of gear case  4  is fan enclosure  30  with fan  20  sandwiched in between. Fan enclosure  30  and gear case  4  define between them a fan chamber  31 . Fan  20  divides fan chamber  31  into a radially inward suction/inlet chamber  32  and a radially outward discharge/outlet chamber  33 . Fan enclosure  30  also defines a slot  34 , through which damper switch  29  projects, and an opening  35 , through which pulley portion  23  of fan  20  projects. 
         [0043]    Referring now to  FIG. 15 , air and dust pulled through dust fan  20  exits discharge/outlet chamber  33  through outlet duct  36 , which in the preferred embodiment is an integral portion of fan enclosure  30 . The downstream end of duct  36  connects to the dust cassette  60  by means of a locking collar assembly  40 . In the preferred embodiment, locking collar assembly  40  comprises a collar  42  movably mounted to the exterior of duct  36 . Collar  4 A is movable between a first locked position, wherein it secures the inlet  61  of the dust cassette  60  to the outlet of the duct  36 , and a second unlocked position, wherein the dust cassette is detachable from the outlet duct  36 . 
         [0044]    The operation of the dust collection system will now be summarised. Motor  10  drives driven pulley  12  via drive belt  14 . In turn, driven pulley  16  drives dust fan  20  via fan belt is. Rotation of dust fan  20  creates a suction that pulls air and dust from the vicinity of rear drive wheel  9  through air passage  22  and into chamber  34 . With damper  28  in the “ON” position, the air and dust is drawn through openings  26  and damper  28  and across fan  20 . The air and dust is exhausted from the fan  20  through duct  36  and locking collar assembly  40  into the dust cassette  60 . In the dust cassette  60  the dust is trapped while the air is filtered and exhausted across the air permeable sides. 
         [0045]    If it is desired to disable the dust collection system, for example during outdoor use, this may be accomplished in two ways. First, the user may rotate the suction damper  28  to the “OFF” position. In the OFF position the dust fan  20  will continue to turn, but will not produce a suction in the vicinity of the rear drive wheel  9 . Alternatively, the user may temporarily remove belt cover  6  from gear case  4 , thus exposing the belts  14  and  18 . Fan belt  18  may be removed from driven pulley  16  and pulley portion  23  of dust fan  20 . With fan belt  18  removed, the dust fan  20  will not be turned and no airflow will be produced in any portion of the dust collection path. 
         [0046]    For cost effective and practical assembly, dust fan enclosure  30  mounts to the gear case  4  over the suction damper  28 . Between the enclosure  30  and damper  28  is a seal member  27 . In the preferred embodiment shown in  FIG. 14  seal member  27  is in the form of a flexible overmold bonded to the damper  28 . The seal overmold  27  provides a sufficiently tight fit between enclosure  30  an damper  28  so as to limit air in leakage to the suction side of fan  20 , while permitting relative rotation between damper and enclosure. 
         [0047]    With reference to  FIGS. 15 and 16 , in the preferred embodiment dust cassette  60  comprises a first part  62  and a second part  64 . First part  62  is substantially funnel shaped as it expands from a small upstream/inlet end  61 , connected to the exhaust duct  36  by means of the collar assembly  40 , to a larger rectangular shaped downstream end  63 . First part  62  is preferably semi-rigid, that is slightly flexible, so that it may be deformed for ease of installation and connection. In one preferred embodiment, first part  62  may be made of Santoprene® or another rubber-like material. Second pan  64  is an air permeable fabric skin over a rigid frame  80 . 
         [0048]    Air and dust from the dust fan  20  flows through the exhaust duct  36  into the first part  62  of dust cassette  60  and then into the second part  64  Dust is trapped inside the dust cassette  60 , but the air is filtered through the air permeable sides of second part  64  and thus exhausted. When the dust cassette  60  is substantially full of dust it can be quickly emptied by breaking the connection  66  between the first part  62  and the second part  64 . Depending on the circumstances, it may first be necessary to disconnect the entire dust cassette  60  from the sander at the collar assembly  40 . 
         [0049]    With particular reference to  FIGS. 15-20 , the connection between the dust cassette  60  and the sander will be described in further detail. First part  62  of cassette  60  comprises a flexible clip  67  and an inlet end  61 . To attach the dust cassette  60  to the sander, flexible clip  67  hooks onto and grips a flange  7  located on the rearward end of belt cover  6 . Simultaneously, inlet end  61  is inserted into the locking collar assembly  40 . The simultaneous alignment of the clip  67 , flange  7 , inlet end  6 . 1 , and locking collar assembly  40  is made easier by the flexible material of first part  62 , which the user can deform in order to make the two connections. 
         [0050]    Inlet end  61  includes two protruding ribs  69 . With collar  42  in the second/unlocked position, inlet end  61  is fit into the collar assembly  40  so that ribs  69  are inserted through and past cutouts  43  in collar  42  and fit into recesses  38  defined in the outlet end flange  37  of the outlet duct  36 . Collar  42 , which slidably engages end flange  37 , can then be slid down to its first position, wherein collar  42  traps ribs  69  within recesses  38 , thus locking inlet end  61  in collar assembly  40 . Mating detent structures  39  on flange  37  and  46  on the collar  42  restrain the collar in either of the locked or unlocked position, unless overcome by the force of the user deliberately moving the collar. 
         [0051]    With particular reference to  FIG. 20  (wherein the dust cassette is shown inverted from its attached/in-use orientation), the construction of the dust cassette  60  will be described in greater detail. The second part  64  of the dust cassette  60  is a dust bag/box constructed as an air permeable fabric stretched over a rigid frame  80  in the known way. In the preferred embodiment second pant  64  is substantially a rectangular solid and open at one side  65 . At open end  65  frame  80  defines opposed slots  82  on opposite sides of the open end and an upper lip  84 . 
         [0052]    The downstream end  63  of first part  62  (shown in the facing view  20 A) includes a flange  70  and flexible tabs  72 . A hook  74  is pivotably attached to first part  62  proximate to the downstream end. 
         [0053]    To connect the parts of the dust cassette  60 , the flange  70  of first part  62  is slid into slots  82  of frame  80  of the second part  64  until open side  65  of the second part is aligned with the downstream end  63  of the first part. When so aligned, flexible tabs  72  on first part  62  will detent underneath lip  84  of the second part  64  to secure the first part and second part together. Additional security is provided by the hook  74  on first part  62 , which can be pivoted to engage a latch  86  on the second part  64 . 
         [0054]    Disconnecting of the two parts  62  and  64  is made easier by the flexible construction of the first part. After unlatching hook  74 , the user can squeeze and deform first part  62  so as to undo the detent between tabs  72  and lip  84 . Then flange  70  may be readily slid out of slots  82 . 
         [0055]    While the invention has been described it the specification and illustrated in the drawings with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention as defined in the claims. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment illustrated by the drawings and described in the specification as the best mode presently contemplated for carrying out this invention, but that the invention will include any embodiments falling within the foregoing description and the appended claims.

Technology Classification (CPC): 1