Patent Publication Number: US-10328545-B2

Title: Bell shaped rotary sander

Description:
TECHNICAL FIELD 
     This disclosure relates generally to power tools, and, more particularly, to powered sander tools. 
     BACKGROUND 
     A sander is a power tool used to smooth surfaces or abrade away a surface layer of material or a coating on a surface. Sanders generally include an attachment point for attaching an abrasive material such as sand paper, and a drive mechanism that drives the attachment point into motion. Both the abrasive material and the drive mechanism can have many different forms. A drum sander, in particular a portable drum sander, generally includes a drive mechanism that drives the rotation of an output spindle, and a drum that includes an abrasive material. The abrasive material can be integral with the drum, or can be a separate piece that is mounted on the drum. The drum is mounted to and rotated by the output spindle, and the resulting rotation of the abrasive material forms a three-dimensional friction region that can be applied to a workpiece. Drum sanders are adapted for a wide variety of applications, such as sanding tight or hard to reach places. 
     Drums are generally tubular in shape. While drums having a shape that is somewhat varied from a generally tubular shape have been made, such as drums with a frustum or ellipsoid shape, the high rate of rotation generally limits that shapes that drums can take. As a result, one disadvantage with drum sanders is that drum sanders are generally not adapted to sanding surfaces with a complex contour. The generally tubular shape of the drum may not align with the complex contour, resulting in a flattening out of the features of the surface and a generally poor finish of the workpiece. As a result, drum sanders generally do not perform well when used on surfaces with a shape that varies along an extent of the surface. 
     Advances have been made in order to address some of these deficiencies. A flap-wheel drum includes a central drum and a plurality of flaps of abrasive material radiating outward from the central drum. The flaps are configured to flex, so that the diameter of the flap-wheel drum can effectively change in order to accommodate a changing surface shape. Flap-wheel drums, however, still exhibit the same type of flattening behavior as other drums when applied to a surface with a complex contour. 
     Therefore, a drum for a drum sander that can be applied to surfaces with a complex contour without flattening out the complex contour would be beneficial. 
     SUMMARY 
     In order to facilitate sanding of surfaces having a complex contour, an attachment for a sanding tool includes a first portion and a second portion. The first portion has a generally tubular shape that defines a mounting end portion for mounting the attachment on the sanding tool. The second portion defines a distal end portion of the attachment and a plurality of slits. The slits extend along an axial direction of the attachment, such that portions of second portion between adjacent slits each form a respective flap configured to axial flex and define a contoured sanding surface along the axial direction. 
     In an embodiment, at least the outer surface of the second portion includes an abrasive material. 
     In an embodiment, the second portion is integral with the first portion. 
     In another embodiment, the second portion is separate piece from the first portion, and is configured to be removably mounted to the first portion so as to rotate with the first portion. 
     In a further embodiment, the plurality of slits extends to the distal end portion of the second portion, such that the distal end portion is formed by separate ends of the plurality of flaps. 
     In an embodiment, in a flexed position of the plurality of flaps, the second portion has a substantially bell-like shape. 
     In another embodiment, the flaps formed by the plurality of slits are joined together at the distal end portion of the second portion. 
     In one embodiment, in a flexed position of the plurality of flaps, the second portion has a substantially ellipsoid or hyperboloid shape. 
     In a further embodiment, the attachment further includes a flexure device that is selectively operable to flex the plurality of flaps toward different flexed positions to define different contoured sanding surfaces along the axial direction. 
     In an embodiment, the flexure device includes a shaft and a nut. The shaft passes through the second portion along the axial direction, and the nut is threaded onto a portion of the shaft extending out from the distal end portion of the second portion and engaged with the distal end portion of the second portion such that rotation of the nut causes the distal end portion to move and flex the plurality of flaps toward different flexed positions. 
     In one embodiment, the nut is integral with the distal end portion, such that the distal end portion rotates with the nut and causes the plurality of flaps to twist. 
     In another embodiment, the nut is separate from the distal end portion, such that as the nut is threaded along the shaft in the axial direction, the distal end portion moves axially with the nut. 
     In a further embodiment, the flexure device includes an actuator configured to act on the second portion to selectively flex the plurality of flaps into different flexed positions, and a controller configured to electronically operate the actuator. 
     In one embodiment, the flaps are configured to flex in response to rotation of the attachment. 
     In another embodiment, the flaps are configured to exert a pressure on a workpiece in directions normal to the contoured sanding surface. 
     This summary is intended only to introduce subject matter pertaining to a bushing service tool which is discussed in more detail in the detailed description, the drawings, and the claims, and is not intended to limit the scope of this disclosure in any way. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing aspects and other features of the present disclosure are explained in the following description, taken in connection with the accompanying drawings. 
         FIG. 1  is a side view of an exemplary embodiment of an attachment for a sanding tool according to this disclosure. 
         FIG. 2  is a side view of the attachment of  FIG. 1  in a flexed position. 
         FIGS. 3 and 4  are side views of the attachment of  FIG. 1  in use on different surfaces. 
         FIG. 5  is a side view of another exemplary embodiment of an attachment for a sanding tool according to this disclosure. 
         FIG. 6  is a side view of the attachment of  FIG. 5  in use on a surface. 
         FIG. 7  is a perspective image of the attachment of  FIG. 5   
         FIG. 8  is a perspective image of the attachment of  FIG. 5  in use on a surface. 
         FIG. 9  is a perspective image of another exemplary embodiment of an attachment for a sanding tool according to this disclosure. 
         FIG. 10  is a perspective image of the attachment of  FIG. 9  in a flexed position. 
         FIG. 11  is a perspective image of different exemplary embodiments of attachments for a sanding tool according to this disclosure. 
         FIGS. 12 and 13  are side views of different exemplary embodiments of attachments for a sanding tool according to this disclosure. 
         FIG. 14  is a side view of the attachment of  FIG. 13  in a flexed position. 
     
    
    
     DETAILED DESCRIPTION 
     For the purposes of promoting an understanding of the principles of the embodiments described herein, reference is now made to the drawings and descriptions in the following written specification. No limitation to the scope of the subject matter is intended by the references. This disclosure also includes any alterations and modifications to the illustrated embodiments and includes further applications of the principles of the described embodiments as would normally occur to one skilled in the art to which this document pertains. 
       FIG. 1  is a side view of an exemplary embodiment of an attachment  100  for a sanding tool. The attachment  100  includes a first portion  102  and a second portion  104 . 
     The first portion  102  has a generally tubular shape  106 . In other words, in this embodiment the first portion  102  is substantially a hollow cylinder. In other embodiments, first portions  102  of other shapes are also contemplated. The tubular shape generally defines an axis of rotation  112  for the attachment  100 . As used herein, the “axial direction” means directions parallel to the axis of rotation  112  and is also identified with the numeral  112 . The first portion  102  defines a mounting end portion  108  at a first end portion  110  of the tubular shape  106 . The mounting end portion  108  is configured to mount the attachment  100  onto an attachment point of a sanding tool, such as an output spindle, in order to rotate the attachment  100  about the axial direction  112 . 
     The second portion  104  extends axially from the first portion  102 . As illustrated in  FIG. 1 , in this embodiment, the second portion  104  is integral with the first portion  102 . The second portion  104  defines a distal end portion  114  of the attachment  100  that is opposite the mounting end portion  108 . The second portion  104  also defines a plurality of slits  116  that extend substantially parallel to the axial direction  112 . The slits  116  divide at least a portion of the second portion  104  into a plurality of flaps  120 . In the embodiment illustrated in  FIG. 1 , the slits  116  increase in width in a direction toward the distal end portion  114 . In other embodiments, slits of other shapes are also contemplated, such as linear slits, slits that taper in a direction toward the distal end portion  114 , and slits of other regular and irregular shapes. 
     Each flap  120  is configured to axially flex. As used herein, an element “axially” flexing means that the element flexes such that at least a portion of the element moves along the axial direction  112 . In a flexed position, the flaps  102  together with a remainder of the outer surface  118  of the second portion  104  define a contoured sanding surface along the axial direction  112 . 
       FIG. 2  is a side view of the attachment  100  with the flaps  120  in a flexed position relative to the position illustrated in  FIG. 1 . In this embodiment, the slits  116  extend to the distal end portion  114  of the attachment  100 , such that the distal end portion  114  is formed by separate end portions  124  of the plurality of flaps  120 . Thus, in the flexed position of the flaps  120 , the distal end portion  114  expands outwards in a radial direction  126  relative to the un-flexed position of the flaps  120  illustrated in  FIG. 1 . As illustrated in  FIG. 2 , in this embodiment, the flexed position of the flaps  120  results in the second portion  104  being in the form of a substantially bell-like shape. Other shapes for the second portion  104  in a flexed position are also contemplated, such as a frustum shape, conical shape, etc. 
     In this embodiment, the flaps  120  are configured to flex in response to the rotation of the attachment  100  about the axial direction  116 . Other techniques for flexing the flaps  120  are also contemplated in other embodiments, such as those discussed in further detail below. From a rotational perspective of the attachment  100 , rotation of the attachment  100  about the axial direction  112  results in a centrifugal force acting on the flaps  120  of the second portion  104  outwards away from the axial direction  116  in the radial direction  126 . The flaps  120 , enabled to flex away from the outer surface  118  via the slits  116 , are flexed outwards to form a contoured surface. 
       FIG. 3  is a side view of the attachment  100  of  FIG. 1  in use with a sanding tool  130  being applied to a surface  140 . The first portion  102  of the attachment  100  is mounted on an output spindle  132  of the tool  130 , which is driving a rotation  134  of the attachment  100  about the axial direction  112 . As a result of the rotation  134 , the flaps  120  of the second portion  104  of the attachment  100  are in the flexed position forming the contoured surface  122 . 
     The surface  140  has a contoured shape  142 . In this embodiment, the contoured shape  142  substantially corresponds to the contoured surface  122  formed by the flaps  120 . To apply the attachment  100  to the surface  140  in order to perform a sanding operation, the contoured surface  122  is brought into contact with the contoured shape  142  of the surface  140 . The contoured surface  122  frictionally engages with the contoured shape  142  in order to sand the surface  140 . Since the contoured shape  142  substantially corresponds to the contoured surface  122 , the friction applied by the contoured surface  122  is applied substantially tangentially along the contoured shape  142  of the surface, so that the contoured shape  142  is not flattened out during the sanding operation. 
       FIG. 4  is a side view of the attachment  100  in use with another surface  240 . In this embodiment, the surface  240  has a contoured shape  242  that differs from the contoured surface  122  formed by the flaps  120 . As the contoured surface  122  is brought into contact with the contoured shape  242  of the surface  240 , portions  244  of the surface  240  that interfere with the shape of the contoured surface  122  engage with the flaps  120  so that the flaps  120  flex inwards toward the axial direction  112  along the radial direction  126 . The resulting modified contoured shape  222  illustrated in  FIG. 4  is not symmetrical, since the flaps  120  engaged with the surface  240  are flexed relative to the flaps  120  that are not engaged with the surface  240 . As a result, the portion of the modified contoured shape  222  in contact with the surface  240  generally corresponds with the shape  242  of the surface  240 . Additionally, as a result of the centrifugal force acting on the flaps  120  in the outwards away from the axial direction  116  along the radial direction  126 , the flaps  120  exert a centrifugal pressure  250  on the portions  244  of the surface  240  acting on the flaps  120 . 
     When using a conventional drum in a sanding operation, engagement between the drum and a surface being sanded is normal only to the axial direction. In other words, contoured portions of a surface being sanded are not acted on in a direction normal to the contoured shape of that surface since the normal direction of the drum is not aligned with the normal direction of the contoured portions of the surface. This can decrease the quality of the finish due to the sanding operation. Additionally, since a conventional drum generally cannot be reshaped to accommodate a particular shape of a surface, the shape of a conventional drum may not align with the shape of the surface. In other words, some portions of the contoured surface may be out of contact with the drum, while other portions are frictionally engaged and are being sanded. As a result of the foregoing, the contoured portions of the surface experience significant flattening. In contrast, the centrifugal pressure  250  acts in a direction normal to the contoured shape  242  of the surface  240 , and facilitates the frictional engagement of the attachment  100  with the surface  240 . Since the pressure  250  acts in the direction normal to the contoured shape  242 , the finish formed by the sanding operation is not deformed. Additionally, since the flaps  120  can flex in response to differences between the surface  240  and the contoured surface  122 , the attachment  100  is able to engage the surface  240  without leaving gaps. As a result, flattening out of the contoured shape  242  during the sanding operation is reduced. 
       FIG. 5  is a side view of another exemplary embodiment of an attachment  300  according to this disclosure in use with a sanding tool, and  FIG. 6  is a side view of the attachment  300  in use with the tool  130  in a sanding operation of a surface  340  having a contoured shape  342 . In this embodiment, the second portion  304  is a separate piece from the first portion  302 . The first portion  302  defines a substantially cylindrical outer surface  306 . The second portion  304  in this embodiment includes a connecting region  308  opposite the distal end portion  314 . The connecting region  308  has a substantially hollow cylindrical shape configured to form a removable press fit with the outer surface  306  of the first portion  304 . Other techniques for mounting a second portion onto a first portion are also contemplated in other embodiments. 
     In this embodiment, the second portion  304  is formed from an abrasive material, such as sand paper. In other embodiments, the second portion can additionally include other materials disposed inside of an abrasive material that forms the outer surface  316  of the second portion. For example, a core of the second portion can be formed from a rubber, plastic, steel, etc., and can include an exterior layer or coating of abrasive material. The first portion  302  can include any acceptable material. In this embodiment, the first portion  302  is formed from a rubber material. 
       FIG. 7  is a perspective image of the attachment  300  mounted onto an output spindle  132  of a sanding tool  130 , and  FIG. 8  is a perspective image of the sanding tool  130  with the attachment  300  in use sanding a surface  340  that has a contoured shape  342 . As illustrated in  FIG. 8 , the contoured sanding surface  322  enables the attachment  300  to sand the surface  340  without flattening out the contoured shape  342 . 
       FIG. 9  is a perspective image of another exemplary embodiment of an attachment  400  for a sanding tool according to this disclosure. A first portion of the attachment  400  is not shown in order to show other elements, but a first portion similar to the first portion  302  illustrated in  FIGS. 5 and 6  can be used. In this embodiment, the plurality of flaps  420  in the second portion  404  are formed by slits  416  that are joined together at a distal end portion  414  of the second portion  404 . In other words, the slits  416  do not extend through the distal end portion  414  or the mounting end portion  408  of the attachment  400 . As a result, a diameter  450  of the attachment  400  changes as the flaps  420  axially flex. In this embodiment, the second portion  404  has a substantially ellipsoid shape, whereby flexure of the flaps  420  inversely changes a diameter  450  of second portion  404  transverse to the axial direction  412  and a length  452  of the second portion  404  along the axial direction  412 .  FIG. 10  illustrates the attachment  400  from  FIG. 7  where the flaps  420  are in a flexed position such that the diameter  450  has increased and the length  452  has deceased. 
     In other embodiments, other shapes for the second portion are also contemplated.  FIG. 11  illustrates different exemplary embodiments of an attachment  500   a ,  500   b , and  500   c  having different shapes. 
     The attachment  500   a  has a dual bell shape, with a first bell shape  504   a  and a symmetrical second bell shape  505   a  joined together at a common maximum diameter  550 . In this embodiment, the bell shapes  504   a  and  505   a  have a concave exterior  522   a , but convex exteriors, linear exteriors, and combinations thereof are also contemplated in other embodiments. The attachment  500   b  has a pill shape  522   b  with a substantially cylindrical middle portion  505   b  between tapered end portions  508   b  and  514   b . In this embodiment, the end portions  508   b  and  514   b  taper via a convex curve, but concave curves, linear tapers, and combinations thereof are also contemplated in other embodiments. The attachment  500   c  has a middle region  505   c  with a substantially hyperboloid shape disposed between tapered end portions  508   c  and  514   c.    
     In these embodiments, slits  526   a - c  are linear and are disposed substantially symmetrically, such that the shape of the attachments  500   a - c  and the flexure of the flaps  520   a - c  are substantially symmetrical. In other embodiments, the slits may be disposed at different distances from the distal end portions  514   a - c  than from the mounting end portions  508   a - c , or the slits  526   a - c  may change in width along the axial directions  512   a - c.    
     Embodiments where the flaps join together at the distal end portion enable a wide variety of flexure behaviors in order to form a wide variety of contoured sanding surfaces. For example, attachments  500   a  and  500   b  enable sanding of an internal surface, such as the inside of a tube or other space. In particular, attachment  500   b  enables sanding of an inside surface surrounding an inner side of an opening. 
     The embodiments  500   a - c  described above are configured to flex in response to rotation in a manner similar to the attachment  100  discussed above. Such embodiments are thus also configured such that the flaps  520   a - c  exert a pressure on a work surface that is normal to the work surface. 
     In some applications, it may be beneficial to enable precise control over the flexure of the attachment.  FIG. 12  is a cross-section view of the attachment  600  that has a shape similar to the attachment  500   c  in  FIG. 11 , and that also includes a flexure device  660 . The flexure device  660  is selectively operable to flex the plurality of flaps  620  toward different flexed positions to define different contoured sanding surfaces along the axial direction  612 . In this embodiment, the flexure device  660  includes a shaft  662 , and a nut  664 , where the nut  664  is separate from the distal end portion  614  of the second portion  604 . In this embodiment, the shaft  662  defines the first portion  602  and the mounting end portion  608  of the attachment  600 . 
     The shaft  662  further defines a stop portion  666  and passes through the second portion  604  via a hole  668  in the connecting region  607  and a hole  670  in the distal end portion  614 . At least a portion of the shaft  662  defines a threaded surface  672  that extends out from the distal end portion  614 . The nut  664  is threaded onto the threaded surface  672  of the shaft  662  so as to engage with the distal end portion  614 . Rotation of the nut  664  moves the nut  664  axially along the threaded surface  672 . When the nut  664  is moved toward the stop portion  666 , the nut  664  pushes against the distal end portion  614  such that the second portion  604  is compressed between the nut  664  and the stop portion  666 , resulting in flexure of the flaps  620 . When the nut  664  is moved away from the stop portion  666 , a resilience of the second portion  604  acts to de-flex the flaps  620  and move the distal end portion  614  away from the stop portion  666 . By selectively rotating the nut  664  to move the nut  664  to different axial locations along the threaded surface  672 , the flaps  620  of the second portion  604  can be flexed to different flexed positions to form a variety of contoured sanding surfaces. 
       FIG. 13  is a cross-section of another exemplary embodiment of an attachment  700 . In this embodiment, the nut  764  is integral with the distal end portion  714  of the second portion  704 . As a result, when the nut  764  is rotated on the threaded surface  772 , the distal end portion  714  rotates along with the nut  764 . The rotation of the distal end portion  714  causes the flaps  720  to twist.  FIG. 14  illustrates the attachment  700  in a twisted position. 
     It may also be beneficial to enable electronic control of the shape of an attachment. In one embodiment, the nut  664 ,  674  is configured to electronically actuate. In another embodiment, the shaft  662 ,  762  includes a linear actuator (not shown) configured to increase and decrease a length of the shaft  662 ,  762 . Any other acceptable actuating technique can also be used, and any acceptable technique can be used to operate such actuator(s), such as an onboard controller integrated into the nut  664 ,  674 , or a receiver configured to receive instructions from a remote device. In one embodiment, a sensing device is configured to determine a contour of a work surface, such as via optical or infra-red sensing, and transmit an instruction to a controller configured to operate at least one of the actuatable shaft and nut in order to form a contoured sanding surface that corresponds to the determined contour. 
     It will be appreciated that variants of the above-described and other features and functions, or alternatives thereof, may be desirably combined into many other different systems, applications or methods. Various presently unforeseen or unanticipated alternatives, modifications, variations or improvements may be subsequently made by those skilled in the art that are also intended to be encompassed by the disclosure.