Abstract:
A sanding drum assembly in one embodiment includes at least one elastic friction member defining an outer perimeter, a plurality of feet located inwardly of the at least one elastic friction member, each of the plurality of feet including a movable portion movable between a first position whereat the plurality of feet define a first outermost circumference and a second position whereat the plurality of feet define a second outermost circumference, wherein the second outermost circumference is larger than the first outermost circumference, and an actuator, wherein the plurality of feet and the actuator are configured such that as the actuator and the plurality of feet change from a first configuration to a second configuration, the plurality of feet are forced from the first position to the second position.

Description:
FIELD OF THE INVENTION 
       [0001]    This patent relates generally to sanding drums which are driven by rotary tools. 
       BACKGROUND 
       [0002]    Rotary tools, including drills, grinders, and routers, include a tool retainer or holder that non-rotatably secures a rotary bit (e.g., a cutting tool such as a drill bit or a router bit) to a drive shaft that is rotated by the rotary tool. One bit that has been developed for use in such rotary tools is a sanding drum bit. A sanding drum bit includes one end portion adapted for engagement with the bit holder and a second end portion which is adapted to support a closed loop sanding belt. 
         [0003]    In order to mount the closed loop sanding belt on the sanding drum bit, the closed loop sanding belt must be somewhat larger in diameter than the mounting portion of the sanding drum bit. Configuring the closed loop sanding belt to fit onto the sanding drum bit in such a fashion, however, introduces the potential for the closed loop sanding belt to slip (radial relative movement) or creep (axial relative movement) on the sanding drum bit in use. Various approaches have been used to overcome this problem. 
         [0004]    One approach used to minimize slip and creep is to minimize the difference in diameter between the closed loop sanding belt and the sanding drum bit mounting portion. Of course, as the mismatch is reduced, the difficulty in mounting the closed loop sanding belt on the sanding drum bit increases. In another approach, the frictional force between the sanding drum mounting portion and the sanding belt is increased by selecting high friction materials. For example, in some sanding drum bits, the mounting portion of the bit is made from a rubber material. This increases the amount of friction that must be overcome before creep or slip is realized. At the same time, the increased friction makes mounting of the closed loop sanding belt on the sanding drum bit mounting portion more difficult. 
         [0005]    In some sanding drum bits, the mounting portion is configured to provide a variable diameter. In these devices, a rubber cylinder is compressed lengthwise, such as by using a screw and washer arrangement. As the length of the rubber cylinder is reduced, the diameter of the rubber cylinder is increased. Accordingly, a closed loop sanding belt can be mounted on the sanding drum bit with the rubber cylinder uncompressed. Once the closed loop sanding belt is mounted, the rubber cylinder is compressed to increase the friction between the closed loop sanding belt and the sanding drum bit. While effective, this approach can cause delay in changing between closed loop sanding belts. For example, a user must find a screwdriver to manipulate the screw and washer arrangement. Then, the screw and washer arrangement must be loosened to allow removal of a first closed loop sanding belt, and then tightened after a new closed loop sanding belt is positioned. 
         [0006]    In another approach, some sanding drums have been constructed with recessed inset areas into which a sanding belt is snugly fitted. This approach is a costly modification since the sanding drum and sandpaper must be made with complementary non-planar surfaces. In addition, seating of the belt must be exact, otherwise slippage will be exacerbated. 
         [0007]    What is needed is a sanding drum assembly that provides increased resistance to slip or creep. A further need exists for a sanding drum assembly that reduces the number of tools needed to replace sanding belts. Yet another need exists for a sanding drum assembly that allows for rapid replacement of sanding belts. 
         [0008]    Summary 
         [0009]    In accordance with one embodiment of the disclosure, a sanding drum assembly includes at least one elastic friction member defining an outer perimeter, a plurality of feet located inwardly of the at least one elastic friction member, each of the plurality of feet including a movable portion movable between a first position whereat the plurality of feet define a first outermost circumference and a second position whereat the plurality of feet define a second outermost circumference, wherein the second outermost circumference is larger than the first outermost circumference, and an actuator, wherein the plurality of feet and the actuator are configured such that as the actuator and the plurality of feet change from a first configuration to a second configuration, the plurality of feet are forced from the first position to the second position. 
         [0010]    In another embodiment, a sanding drum assembly includes a plurality of feet, the plurality of feet including a movable portion movable between a first configuration defining a first outermost circumference and a second configuration defining a second outermost circumference, wherein the second outermost circumference is larger than the first outermost circumference, at least one elastic friction member extending about the plurality of feet, the at least one elastic friction member expandable by the plurality of feet from a first outer perimeter to a second outer perimeter as the plurality of feet moves from the first configuration to the second configuration, and an actuator operably contacting an inner portion of the plurality of feet such that the actuator applies a force to the inner portion to force the plurality of feet from the first configuration to the second configuration. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  depicts a side plan view of rotary tool with a sanding drum assembly in accordance with principles of the present invention; 
           [0012]      FIG. 2  depicts a side plan view of the sanding drum assembly of  FIG. 1  aligned with the bit holder of the rotary tool of  FIG. 1 ; 
           [0013]      FIG. 3  depicts an exploded perspective view of the assembly of  FIG. 1 ; 
           [0014]      FIG. 4  depicts a side cross sectional view of the cylindrical elastic friction member of the sanding drum assembly of  FIG. 1 ; 
           [0015]      FIG. 5  depicts a side plan view of the actuator of the sanding drum assembly of  FIG. 1 ; 
           [0016]      FIG. 6  depicts a top plan view of the actuator of the sanding drum assembly of  FIG. 1 ; 
           [0017]      FIG. 7  depicts a side cross sectional view of the bushing member of the sanding drum assembly of  FIG. 1 ; 
           [0018]      FIG. 8  depicts a top plan view of the bushing member of the sanding drum assembly of  FIG. 1 ; 
           [0019]      FIG. 9  depicts a top cross sectional view of the bushing member of the sanding drum assembly of  FIG. 1  taken along the line A-A of  FIG. 7 ; 
           [0020]      FIG. 10  depicts a side cross sectional view of the sanding drum assembly of  FIG. 1  in the unlocked configuration; and 
           [0021]      FIG. 11  depicts a side cross sectional view of the sanding drum assembly of  FIG. 1  in the locked configuration without the elastic friction member but with the unlocked configuration of the elastic friction member depicted in shadow to show the increased diameter of the sanding drum assembly in the locked configuration. 
       
    
    
     DESCRIPTION 
       [0022]    For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and described in the following written specification. It is understood that no limitation to the scope of the invention is thereby intended. It is further understood that the invention includes any alterations and modifications to the illustrated embodiments and includes further applications of the principles of the invention as would normally occur to one skilled in the art to which this invention pertains. 
         [0023]      FIG. 1  depicts a rotary tool  100  including a bit holder  102 . A sanding drum assembly  104  is shown in  FIG. 1  mounted in the bit holder  102  while in  FIG. 2  the sanding drum assembly  104  is aligned with the bit holder  102 . As further shown in  FIG. 3 , the sanding drum assembly  104  includes an elastic friction member  106 , a mandrel  108 , a bushing  110 , a lock washer  112 , and a collar  114 . The elastic friction member  106 , shown in additional detail in  FIG. 4 , is cylindrical in shape and includes an outer wall  116 , an upper end portion  118 , and a lower end portion  120 . The elastic friction member  106  is hollow and includes a receiving area  122  defined by an inner wall  124 . An opening  126  extends from the receiving area  122  through the upper end portion  118  while an opening  128  extends from the receiving area  122  through the lower end portion  120   
         [0024]    The mandrel  108 , also shown in  FIGS. 5 and 6 , includes a shaft portion  130  and a head portion  134 . The shaft portion  130  includes a coupling portion  136  and a throat portion  138 . A notch  140  joins the coupling portion  136  and the throat portion  138 . The head portion  134  includes four tabs  142  which extend outwardly from a sidewall  144  of the head portion  134 . An upper rounded shoulder  146  extends between the side wall  144  and an upper surface  148  of the head portion  134  while a lower rounded shoulder  150  extends between the side wall  144  and a lower surface  152  of the head portion  134 . 
         [0025]    Referring now to  FIGS. 7-9 , the bushing  110  includes a base portion  160  and four feet  162 . A bore  164  extends through the base portion  160  from a lower surface  166  of the bushing  110  to an actuation chamber  168  generally defined by the feet  162 . Each of the feet  162  are joined to the base portion  160  by a hinge  170 . An inner portion  172  of each of the feet  162  includes a lower foot portion  174  that extends upwardly and inwardly from the hinge  170  to a neck portion  176 . The neck portions  176  define a reduced diameter portion of the actuation chamber  168 . Above the neck portion  176 , an upper foot portion  178  extends upwardly and outwardly from the neck portion  174  to an upper surface  180 . Each of the feet  162  are separated from adjacent feet  162  by guide slots  182 . 
         [0026]    Assembly of the sanding drum assembly  104  is described with reference to  FIGS. 5 and 7 . Initially, the coupling portion  136  of the mandrel  108  is aligned with the actuation chamber  168  and then inserting the coupling portion  136  through the actuation chamber  168  and the bore  164  in the base portion  160  of the bushing  110 . Continued movement of the mandrel  108  brings the head portion  134  adjacent to the upper foot portions  178  of the feet  162 . 
         [0027]    The head portion  134  is shaped complementary to the inner portion  172  in that both are generally circular. The head portion  134 , however, has a maximum diameter that is larger than the diameter of the portion of the actuation chamber  168  that is defined by the upper foot portions  178 . In one embodiment, the maximum diameter of the head portion  134  is about 7 millimeters (mm) while the diameter of the actuation chamber  168  at the upper surface  180  of the bushing  110  is about 6.29 mm. Accordingly, the head portion  134  comes into contact with the upper foot portions  178  as the mandrel  108  is moved through the actuation chamber  168 . The bushing  110 , however, is made of a plastic material. Accordingly, by aligning the tabs  142  with the guide slots  182  and applying pressure to the upper foot portions  178  with the head portion  134 , the feet  162  are pivoted about the hinges  170  in a radially outwardly direction, allowing the head portion  134  to enter into the actuation chamber  168  as the tabs  142  enter into a respective one of the guide slots  182 . Other materials which provide or can be modified to provide sufficient rigidity and flexibility for the functions described herein may be used. 
         [0028]    The neck portions  176  define a diameter of about 6.15 mm in a relaxed condition, while the lower foot portions  174  define at diameter of about 7.49 mm at a location adjacent to the base portion  160 . Accordingly, once the head portion  134  moves past the neck portions  176 , the feet  162  begin to move inwardly until they reach a relaxed position with the head portion  134  adjacent to the base portion  160 . At this point, the throat portion  138  of the mandrel  108 , which is about 4.4 mm in diameter, extends through the bore  164 , which is about 4.5 mm in diameter, and the tabs  142  are positioned within a respective one of the guide slots  182 . The guide slots  182  have a width of about  1 . 5  mm to accommodate the tabs  142  which have a width of about 1.4 mm. 
         [0029]    Next, the opening  126  in the elastic friction member  106  (see  FIG. 4 ) is aligned with the shaft portion  130  of the mandrel  108  and the coupling portion  136  of the mandrel  108  is inserted through the opening  126 , through the receiving area  122 , and out the opening  128 . The diameter of the coupling portion  136  in one embodiment is about 3.18 mm while the diameter of the opening  128  is about 3.1 mm. The elastic friction member  106 , however, is made of a rubber material and can be deformed so as to allow the coupling portion  136  through the opening  128 . Other materials such as elastomers or fluoroelastomers which provide or can be modified to provide sufficient elasticity and friction for the functions described herein may be used. 
         [0030]    Continued movement of the mandrel  108  through the elastic friction member  106  brings the upper end portion  118  of the elastic friction member  106  next to the lower surface  166  of the bushing  110 . The diameter of the base portion  160 , and of the feet  162  in a relaxed state, is about 10.25 mm while the diameter of the opening  126  is about 4.8 mm. Accordingly, the rubber material of the elastic friction member  106  must be stretched to allow the bushing  110  to move past the base portion  160  and along the feet  162 . Additionally, the opening  128  is further stretched to fit over the throat portion  138 . 
         [0031]    The bushing  110  is thus inserted into the receiving area  122 . The inner dimensions of the receiving area  122  prior to insertion of the bushing  110  into the receiving area  122  are about 8.4 mm in diameter and about 11.5 mm in height. The outer dimensions of the bushing  110  are about 10.25 mm in diameter and about 11.5 mm in height. Accordingly, the elastic friction member  106  is slightly extended, primarily in a radial direction, once the bushing  110  is inserted into the receiving area  122 . 
         [0032]    Assembly of the sanding drum assembly  104  is completed by insertion of the coupling portion  136  of the mandrel  108  through the lock washer  112  which is pushed up the coupling portion  136  until the lock washer  112  seats in the notch  140 . Then, the collar  114  is pushed along the coupling portion  136  until it receives the lock washer  112  in a hollow portion of the collar  114  thereby locking the collar  114  to the mandrel  108 . 
         [0033]    The resulting configuration of the sanding drum assembly  104  is as depicted in  FIG. 10 . In  FIG. 10 , the collar  114  is locked to the mandrel  108  by the locking washer  112 . The bushing  110  is located within the receiving area  122  with the head  134  of the mandrel  108  positioned within the actuation chamber  168  adjacent to the base portion  160 . Additionally, the throat portion  138  of the mandrel  108  extends through the bore  164  in the base portion  160  and through the opening  128  in the elastic friction member  106 . The coupling portion  136  may be coupled with the rotary tool  100  ( FIGS. 1 and 2 ) to prepare the sanding drum assembly  104  for use. 
         [0034]    In the configuration of  FIG. 10 , a sandpaper belt (not shown) can be quickly secured to the sanding drum assembly  104  by positioning the sandpaper belt around the elastic friction member  106 . Preferably, the sandpaper belt has an inner diameter that is either the same diameter as the assembled sanding drum assembly  104  or just slightly larger than the sanding drum assembly  104 . The guide slots  182  and hinges  170  allow for some amount of compression of the sanding drum assembly  104  to assist in positioning the sandpaper belt on the elastic friction member  106 . 
         [0035]    The sandpaper belt is then secured by applying force to the upper end portion  118  of the elastic friction member  106  as indicated by the arrow  190  of  FIG. 10 . The applied pressure is transferred to the upper surface  180  of the feet  162  of the bushing  110  forcing the bushing  110  in the direction of the arrow  190 . The downward force presses the lower foot portion  174  of the bushing  110  against the rounded upper shoulder  146  of the mandrel  108  resulting in a radially outward pressure on the feet  162  as indicated by the arrow  192 . Because the feet  162  are hingedly attached to the base portion  160  by the hinges  170 , the outward pressure causes each of the feet  162  to move radially outward away from an axis  196  defined by the mandrel  108 . The outward movement of the feet  162  increases the diameter of the actuation chamber  168 , thereby allowing the bushing  110 , the elastic friction member  106 , and the sandpaper belt (not shown) to move in the direction of the arrow  190 . 
         [0036]    The foregoing process continues until the elastic friction member  106  comes into contact with the collar  114  (see  FIG. 11 ). At this point, the sandpaper belt is securely held by the sanding drum assembly  104  as explained with continued reference to  FIG. 11 . In  FIG. 11 , the elastic friction member  106  is depicted in shadow in the size and shape of the elastic friction member  106  in the unlocked condition of  FIG. 10 . The rest of the sanding drum assembly  104  is depicted in the locked configuration which results from pressing the elastic friction member  106  in the direction of the arrow  190  as described above. 
         [0037]    In the locked condition, the head portion  134  of the mandrel  108  is located above the neck portion  176  of the bushing  110 . Accordingly, the relative slope between the upper foot portions  178  and the head portion  134  under the elastic pressure applied by the elastic friction member  106  tend to force the bushing  110  toward the collar  114 , thereby maintaining the elastic friction member  106  seated against the collar  114 . 
         [0038]    Additionally, because the diameter of the head portion  134  is larger than the diameter of the actuation chamber  168  defined by the upper foot portions  178  in a relaxed condition (see  FIG. 10 ), the feet  162  are maintained in a location that is radially outward of the location of the feet  162  in the unlocked position of  FIG. 10 . Thus, the outer circumference of the feet  162  defines a larger circumference in the locked condition of  FIG. 11 . This is evident by the movement of the upper portion of the feet  162  into the area formerly occupied by the elastic friction member  106  as depicted by the overlying portion of the feet  162  with the shadowed depiction of the elastic friction member  106  in 
         [0039]      FIG. 11 . The increased diameter of the sanding drum assembly  104  provides an increased frictional hold between the elastic friction member  106  and the sandpaper belt. 
         [0040]    The sanding drum assembly  104  may be easily unlocked by a user to facilitate replacement of a sandpaper belt simply by applying pressure at the base portion  160  of the bushing  110  so as to force the bushing  110  away from the collar  114 . This reverses the sequence described above, returning the sanding drum assembly  104  to the unlocked configuration of  FIG. 10 . 
         [0041]    The present invention has been described above with respect to a particular embodiment. In other embodiments, various dimensions may be modified for a particular application. Additionally, while the components where described with reference to a specific embodiment, various structural features of the sanding drum assembly  104  may be modified in other embodiments of the invention. By way of example, the elastic friction member was described above as being a single substantially cylindrical component. In other embodiments, an elastic friction member may be provided in the form of a band which fits around the feet. One such friction member is realized in the form of an o-ring. If desired, a number of band-like elastic friction members may be used. Furthermore, in some embodiments, the outer surface of the feet may be provided with a groove or similar indentation to receive the elastic friction member. 
         [0042]    Moreover, while the feet  162  were hingedly attached to a base portion  160  in the foregoing example, other forms of feet members may be used in a sanding drum assembly in accordance with the invention. In one embodiment, the feet are not connected to each other or to a base portion. In these embodiments, the elastic friction member(s) maintain the feet about the actuator. 
         [0043]    Consequently, while the invention has been illustrated and described in detail in the drawings and foregoing description, the same should be considered as illustrative and not restrictive in character. It is understood that only the preferred embodiments have been presented and that all changes, modifications and further applications that come within the spirit of the invention are desired to be protected.