Patent Publication Number: US-7717772-B2

Title: Polishing tool

Description:
BACKGROUND OF THE INVENTION 
   I. Technical Field 
   The present invention relates to a hand-held polishing tool by which a user performs polishing operation. More particularly, the present invention relates to a polishing tool having an oscillating shaft and a polishing member attached to the oscillating shaft, wherein the oscillating shaft is oscillated by means of a motor within a predetermined angular range about an axis of the shaft, whereby the polishing member performs polishing operation. 
   II. Description of Related Art 
   Conventionally, a polishing member used in such a polishing tool is generally thin and triangular in shape so that it is possible to easily polish a surface in a narrow portion such as a corner portion of the inner bottom surface of a box-shaped casing. A surface in such a narrow portion is polished by means of a corner portion of the triangular shape (Japanese Unexamined Utility Model Registration Application Publication No. 6-63284). In this case, a polishing tool body is often inclined such that a polishing surface in the corner portion of the polishing member firmly contacts with a to-be-polished surface in a corner portion and the like, and thus the polishing surface in the corner portion of the polishing member is often urged against the to-be-polished surface. Therefore, the polishing surface in the corner portion of the polishing member wears faster than other portions. Thus, the whole of the polishing member needs to be replaced even though the central portion of the polishing member can still be used, resulting in diseconomy. 
   Further, Japanese Patent No. 2607056 discloses a polishing tool in which the side portion of the triangular polishing member is arc-shaped in order to prevent the oscillating polishing member from hitting hard against a linearly extending side wall of the above-mentioned casing when polishing the inner bottom surface of the box-shaped casing at a portion adjacent to the side wall in a state in which the side portion of the triangular polishing member is adjacent to the side wall. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to enable a polishing surface of a polishing member to be in surface contact with a to-be-polished surface in not only the corner portion but also a wide area of the polishing surface even if a user inclines the polishing tool when polishing a surface in the above-described narrow portion. 
   It is another object of the present invention to reduce an impact of the polishing member caused when the oscillating polishing member hits against the side wall or the like adjacent to the to-be-polished portion. 
   The present invention provides a polishing tool including an oscillating shaft configured to oscillate about an axis thereof within a predetermined angular range, a plate-shaped polishing member including a polishing surface on one side thereof, and an oscillation transmitting member connecting the polishing member and the oscillating shaft and transmitting oscillation of the oscillating shaft to the polishing member in a state in which the polishing surface is in contact with a surface to be polished. The oscillation transmitting member includes a base secured to the oscillating shaft, and a plate-shaped polishing member holding portions each connected to the base through a connecting portion and extending radially outwardly with respect the oscillating shaft. The polishing member has cushioning properties and an edge portion positioned radially outside a radially outer edge of the polishing member holding portion with respect to the oscillating shaft. 
   In this polishing tool, the polishing member has the edge portion extending outwardly beyond the radially outer edge of the polishing member holding portion with respect to the oscillating shaft. Therefore, for example, even if the polishing member hits against a side wall of a casing when polishing the bottom surface of the casing, the polishing member absorbs the impact, whereby it is possible to properly perform polishing operation. 
   In the above polishing tool, since the connecting portions have elasticity, the oscillating shaft can be inclined with respect to the polishing member in a state in which the whole of the polishing surface of the polishing member is in contact with the surface to be polished. Therefore, for example, in order to polish a surface in a narrow portion such as a corner portion of the inner bottom surface of a box-shaped casing, the oscillating shaft can be inclined with respect to the polishing member in a state in which the polishing surface of the polishing member is in surface contact with the to-be-polished surface, whereby it is possible to exerts a large pressure on the polishing surface. Thus, it is possible to efficiently perform polishing operation. 
   Specifically, the polishing member may have a plate-shaped pad attached to the polishing member holding portion and having a first surface fixed to one surface of the polishing member holding portion and a second surface opposite to the first surface, and a polishing sheet fixed to the second surface of the pad to form the polishing surface. 
   Preferably, the pad should be made of rubber. 
   Further, it is preferable that the edge portion of the polishing member positioned radially outside a radially outer edge of the polishing member holding portion with respect to the oscillating shaft have at least one corner having an angle of less than 90 degrees so that it is possible to easily polish a corner portion of a housing and the like. 
   Specifically, the polishing member may be, as a whole, triangular in shape such that three corners ar e formed on a periphery of the polishing member. 
   As a specific example, three polishing member holding portions are spaced in an equal angle to each other about the oscillating shaft, and the polishing member is composed of three polishing pieces attached to the polishing member holding portions and arranged so as to form the above-mentioned three corners. 
   More specifically, a base may be triangular in shape and has three sides and a fixing hole at the center thereof into which the oscillating shaft is securely fitted; the polishing member holding portions each may have a base portion connected to a corresponding one of the three sides of the base through the connecting portion and extend in a triangular shape from the base portion. 
   Further, a surface of the polishing member on which the polishing surface is provided is apart from the triangular base in an axial direction of the oscillating shaft, and the connecting portion is inclined from a portion connecting with the triangular base toward the polishing member holding portion. 
   In the polishing tool according to the present invention, even if the polishing member hits against a side wall of a casing when polishing the bottom surface of the casing, for example, the polishing member absorbs the impact, whereby it is possible to properly perform polishing operation. Further, the connecting portion has elasticity. Therefore, for example, in order to polish a surface in a narrow portion such as a corner portion of the inner bottom surface of a box-shaped casing, the oscillating shaft can be inclined with respect to the polishing member in a state in which the polishing surface of the polishing member is in surface contact with the to-be-polished surface, whereby it is possible to exerts a large pressure on the polishing surface. Thus, it is possible to efficiently perform polishing operation. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a partially sectional view showing a body of a polishing tool and a state in which a polishing member is fitted and fixed to an oscillating shaft of the body. 
       FIG. 2  is a plan view of the polishing member. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   An embodiment of a polishing tool according to the present invention will now be described with reference to the accompanying drawings. 
   A polishing tool  10  according to the present invention has an oscillating shaft  12 , a body  14  having a motor  13  for oscillating the oscillating shaft  12 , and a polishing member  18  attached to the oscillating shaft  12 . 
   The polishing member  18  has a generally triangular shape in which each apex angle is 60 degrees ( FIG. 2 ). Three polishing pieces  20  are arranged about an axis  12 - 1  of the oscillating shaft  12  at a constant interval so as to form the apexes. 
   The polishing pieces  20  are attached to an oscillation transmitting member  30  made of a generally triangular plate-like spring member which is secured to the oscillating shaft  12 . The oscillation transmitting member  30  has a triangular base  24  having at the center thereof a fixing hole  22  into which the oscillating shaft  12  is fitted and fixed, triangular polishing member holding portions  26  each extending from each side of the triangular base  24 , and connecting portions  28  elastically connecting the polishing member holding portions  26  and the triangular base  24 . The connecting portion  28  is inclined from a portion connecting with the triangular base  24  toward the polishing member holding portion  26  such that the polishing member holding portion  26  is positioned apart from the triangular base  24  in an axial direction of the oscillating shaft  12 . The polishing pieces  20  are each composed of a thin plate-like cushion member, i.e. a pad  32 , attached to the polishing member holding portion  26 , and a polishing sheet  36  detachably attached to the pad  32  by means of removable adhesive or the like and forming the polishing surface  34  of the polishing member  18 . As shown in the figure, each polishing piece  20  has an edge portion  20 - 1  extending radially outwardly beyond the radially outer edge  26 - 1  of the polishing member holding portion  26  with respect to the oscillating shaft  12 . The pad  32  is made of a cushioning material such as rubber, soft synthetic resin, or the like. The polishing piece  20  is not necessarily composed of the pad  32  and the polishing sheet  36 . For example, the polishing piece may be made of a cushioning material such as rubber, and then abrasive may be mixed in one surface of the polishing piece to form a polishing surface. 
   The oscillation transmitting member  30  is formed such that the oscillating shaft  12  can be inclined with respect to one polishing piece  20  and oscillation of the oscillating shaft is transmitted to the polishing member  18  in a state in which the polishing piece  20  is in surface contact with the to-be-polished surface. 
   In the illustrated example, the polishing member  18  is arranged such that one polishing piece  20  is disposed with projecting forward (leftward in  FIG. 1 ) from the tool body  14 , while the other two polishing pieces  20  are disposed rearward of the one polishing piece  20  on both sides of the tool body  14 . When the wear amount of the one polishing piece  20  reaches or exceeds a predetermined amount, a fixing bolt  38  is loosened to rotate the polishing member  18  by 120 degrees about the oscillating shaft and then tightened to fix the polishing member  18 , which allows continuous use of the polishing member  18 . Further, particle sizes of the three polishing pieces  20  may differ from each other in order to enable polishing operation from rough finishing to fine finishing by rotating the polishing member  18  about the oscillating shaft. 
   In polishing operation, a user grasps the body  14  of the polishing tool  10 . When polishing, for example, a narrow portion such as a corner portion of the inner bottom surface of a box-shaped casing, the user urges the polishing piece  20  which is positioned forward of the body  14  against the narrow portion. In this case, even if the user inclines the polishing tool body, it is possible to perform polishing operation in a state in which the polishing surface  34  is kept in surface contact with the to-be-polished surface by means of the connecting portions  28  of the oscillation transmitting member  30  made of a spring member. Therefore, it is possible to prevent partial wear of the polishing sheet  36  forming the polishing surface  34  as well as to perform efficient polishing operation. 
   Further, the polishing piece  20  having cushioning properties has an edge portion  20 - 1  extending radially outwardly beyond the radially outer edge  26 - 1  of the polishing member holding portion  26  with respect to the oscillating shaft  12 . Therefore, even if the polishing piece  20  hits against a side wall around the to-be-polished surface in polishing operation, it is possible to absorb the impact to smoothly continue polishing operation.