Abstract:
A hand tool for deburring is provided, as well as a cutting blade to be inserted into the tool, the tool comprising a housing, and a rotatable holding device, the holding device being positioned in and being rotatable in the housing and having a chamber for releasably holding a cutting blade, the chamber running obliquely to the axis of rotation (z) of the holding device.

Description:
TECHNICAL FIELD OF THE INVENTION 
   This invention relates to a manual deburring tool, and a blade which can be inserted into it. 
   BACKGROUND OF THE INVENTION 
   Hand tools for deburring sharp corners, using rotating blades, are known in the art. Such hand tools consist of a handle and a cutting blade, which is made of round wire that has been bent into the form of a crank. The blade rotates in a longitudinal hole of the handle, and the cutting edge of said blade follows along the edge of a hole or straight line of a part to be deburred. Such hand tools are used mostly in the metalworking and plastics industries. 
     FIG. 1  shows a known deburring tool  10 . It consists of a handle  12  and a housing  14 . Housing  14  may be made in a single piece with handle  12 . Alternatively, handle  12  could be made as a separate part, which can be fastened removably to the housing. A blind hole  16  is drilled into the housing  14 , into which the round shaft  18  of a cutting blade  20  is inserted. This round shaft  18  has a groove  22 , into which a protrusion  24  enters, this protrusion being part of housing  14 . Protrusion  24  prevents axial movement of the cutting blade  20 , while still allowing free rotation of it in the housing. The cutting blade  20  has a cutting head  25  with a cutting edge  26 . This cutting head  25  is bent, so the cutting edge  26  runs along a line, which lies outside the axis of rotation of shaft  18 . 
     FIG. 2  shows an example of deburring the sharp edge of a hole  31  that was drilled into a workpiece  30 . The blade  20  with its cutting edge  26  is inserted into hole  31  and, while being held by handle  12 , a circular motion is performed, while exerting light pressure towards the workpiece. The blade  20  acts like a crank, so that its cutting edge  26  slides along the edge  32  of hole  31 , and thereby removes the burrs that were created during the drilling operation. During this operation, the cutting edge  26  will automatically adjust itself to the correct cutting angle. 
   A similar hand tool is described in German patent application no. DE OS 2 129 768. This tool also includes a blade with a round shank which acts as a shaft, rotating in a tool holder which acts as a bearing. This tool holder is held in the handle. A disadvantage of these known deburring tools is the fact that their blades are difficult to manufacture. In addition, sometimes it is necessary to lock the rotatability of the blade. It would be difficult to apply a mechanism for blocking this rotation directly to the small round shaft of the blade, and such a mechanism would make a smooth rotation problematic. 
   Another hand tool for deburring holes and edges is described in French patent No. 2759930. This hand tool consists of a handle and a holding unit. There the holding unit is made of a shaft, which at its outer end is formed into a blade-holder. As shown there in  FIG. 1  of French patent 2759930, the shaft  28  and the blade-holder  21  take the form of a crank. The shaft  28  rotates in bearing  25 , and at its end  32  a counterweight  31  is fastened. The purpose of this counterweight is to ensure that whenever a user takes the tool into his hands, the holding unit will point upwards. The blade-holder has a longitudinal hole into which a cutting blade can be inserted. It also has a threaded cross-hole through which the cutting blade can be fastened. 
   SUMMARY OF THE INVENTION 
   The present invention provides a hand tool that solves the above-mentioned problems, especially wear and tear of the shaft, thereby facilitating smooth rotation. 
   One of the basic ideas underlying this invention, is the introduction of a rotational mechanism, by which the cutting tool itself does not rotate in the housing, but is releasably held in a holding unit, which in turn rotates freely in a housing. The cutting blade is held in such a position, so that deburring can be performed successfully. 
   The present invention thus provides a hand tool for deburring which comprises a housing and a cutting tool, or blade, which freely rotates relative to this housing. A rotatable holding device is located inside this housing, for directly or indirectly retaining the cutting blade. 
   As the holding device is made to be the rotating member, instead of the shaft of the cutting blade itself, inaccuracies of the blade-shaft which would hinder smooth rotation, are now eliminated. The larger diameter of the holding device as compared to the cutting blade assures more even rotation, resulting in a better finish achieved, and longer life of the cutting blade. As mentioned above, known rotary blade deburring tools have their cutting edge located outside the axis of the blade&#39;s rotation. This feature enables the cutting edge to set itself at the correct cutting angle. In order to utilize this advantage also in the present invention, the interior of the holding device has a sloped chamber made to take the basically straight cutting blade. The centerline of this chamber forms an angle to the axis of rotation. 
   The cutting tool can be made in the form of a cutting blade, or with an indexable insert. In the case of the indexable insert, the cutting edge runs preferably along a straight line, not curved. 
   In order to simplify production of this hand-tool, and to reduce manufacturing costs, the housing and the handle are preferably made in one piece. Alternatively, the handle and the housing may be made in two pieces, and the housing would then be removably fastened to the handle. 
   In order to prevent axial movement of the holding device, it has a step at the end of its shaft, which fits into an appropriate hole in the handle, forming a thrust bearing. 
   For certain applications it may be necessary to have a tool with a non-rotating cutting blade. For this purpose, a locking device is provided, which blocks the rotation of the holding device in the housing. In a preferred design, this locking mechanism comprises a sleeve that is inserted between the housing and the holding device, plus a ball that can slide in a slot that has been cut into the holding device. Said sleeve has at least one internal recess into which the ball can slide. In the blocked position, the cutting blade holds said ball in the recess of the sleeve. Instead of one recess, the ring may have many such recesses, spaced along an internal step. This sleeve, which is referred to as a “locking ring”, makes it possible to block the rotation of the holding device in any rotational position. Said sleeve is pressed firmly into the housing and cannot rotate in it. Additional dowel pins may be provided, to assure that the rotating holding device would not be able to drive the sleeve with it. 
   The rotating holding device and its sloped chamber for accepting the cutting blade, allow the cutting blade to be made essentially straight, while still facilitating the self-adjusting feature as with the known blades, formed by bending, thereby offering ease of manufacture of the cutting blade. 
   As the cutting blade itself does not rotate, but is held in the rotating holding device, it can have, at least partially, a polygonal cross section. Such blades, without bends, are easier and more cost-effective to make than known blades having a bent head and a round shank. In addition, the chamber of the holding device has, at least near its opening, the form of a polygon, mating the form of the blade-shank. 
   In order to fasten the cutting blade releasably to the housing, a small notch is ground into it near the end of its shaft, and this notch snaps into a corresponding catch in the chamber when the blade is inserted into the chamber. Furthermore, inside the chamber is a spring, preferably a leaf spring, which presses the blade against said catch. To remove the blade from the chamber, the outer end of the blade is pressed against the spring pressure, until its notch is released from the catch. 
   As the section of the blade is essentially rectangular, it is possible to grind a locking notch also into the opposite side of the blade. This enables the user to turn the blade over, after one cutting edge is blunt. 
   The cutting blade usually has at its cutting end a small groove ground into it, in order to guide the blade, and avoid slipping. 
   In an alternative embodiment of deburring tool of the present invention, the cutting blade is not held directly in the chamber, but in a toolholder, the shaft of which is made to fit into the chamber, and the other end of which is formed into an elbow which runs at a predetermined angle to the shaft. At the outer end, this elbow is split into two parts, and between them a cutting tool can be fastened at a predetermined angle. The shaft of said toolholder has a polygonal section, and has at least one locking notch. Accordingly, a cutting blade is provided, which has a shaft and is essentially straight. At least the shaft of the cutting blade has a polygonal section. This cutting blade can be inserted into a rotatable toolholder. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Two embodiments of the hand tool of the present invention will be explained in detail with the aid of the drawings, in which: 
       FIG. 1  illustrates a known deburring tool, shown partly in sectional view; 
       FIG. 2  illustrates the use of the known deburring tool of  FIG. 1  to deburr a hole; 
       FIG. 3  illustrates a sectional view of the front part of a deburring tool according to the present invention; 
       FIG. 4  illustrates the holding device with inserted cutting blade, according to  FIG. 3 , inserted rotatably in a sleeve; 
       FIG. 5  illustrates the holding device with cutting blade according to  FIG. 3 , in which the holding device is prevented from rotating by the locking mechanism; 
       FIG. 6  illustrates the “locking ring” of the deburring tool of  FIGS. 3–5 ; 
       FIG. 7  illustrates the holding device, rotatable in a sleeve, according to  FIG. 3 , and a tool holder inserted into said holding device; and 
       FIG. 8  illustrates the holding device according to  FIG. 7 , deburring a hole. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 3  shows, in a partially sectional view, the front part of a deburring tool  40  of the present invention.  FIG. 3  shows housing  42  of deburring tool  40 , said housing  42  may become part of the handle. This housing  42  has a circular section and tapers at its end  42   a.  Inside housing  42  is a bore, preferably a blind bore  44 , which may reach into the handle of deburring tool  40 . Longitudinally, bore  44  has a stepped section. As shown in  FIG. 3 , the front part  44   a  of bore  44 , may be located at the front end  42   a  of housing  42 , whereas a second part,  44   b,  of bore  44 , may extend into the handle. The inside diameter of the front part of the bore,  44   a,  is larger than the inside diameter of the rear part  44   b,  of bore  44 . 
   A cylindrical sleeve  46  is pressed into the front part  44   a  of bore  44 . Sleeve  46  is shown in  FIG. 6 . This sleeve has at its front end a plain cylindrical bore  46   a,  and at its rear end a larger bore  46   b.  In the area of the step thus formed, are many recesses  48 , each having a half-round section, which are equally spaced around the bore. Recesses  48  form a so-called “locking ring”. The depth of each of these recesses is such that it leads into bore  46   a  without a step. The function of this locking ring will be explained later. 
   Into the bore  44  of housing  42  a round holding device  50  is inserted. Holding device  50  has a round head portion  52 , the diameter of which is made to form a sliding fit in front portion  46   a  of ring  46 . The length of said head portion  52  extends preferably over the whole length of sleeve  46 , and these two parts are assembled coaxially. The head of holding device  52  extends into a smaller diameter and forms a shaft  54 . At the rear end of shaft  54 , its diameter is reduced to form a shoulder  56 , which at its end has a threaded hole, into which a cap-screw  57  can be inserted, as shown in  FIG. 5 . This arrangement, in conjunction with a hole  45  in the handle, creates a thrust bearing, which prevents axial movement of the holding device  50 . 
   Inside the head portion  52  of holding device  50  is a chamber of such form, so a cutting blade  80  having a rectangular cross section, can be inserted into it at an oblique angle. In other words, between the centerline of the rectangular cutting blade and the centerline z of the holding device  50 , there is an acute angle. 
   The blade  80  has the form of an essentially rectangular bar. At one end, a cutting head  82  is formed, and on each of its two sides, a cutting edge is ground,  82   a  and  82   b.  These cutting edges may be curved at least partially. To the cutting head  82 , a shaft  84  is adjoined, which can be inserted into chamber  70  at least partially, as shown in  FIG. 3 . Two notches  86  are ground into the rear end of shaft  84 , on opposite sides of the cutting blade  80 . When the blade  80  is properly inserted into the chamber  70 , a corresponding protrusion, or catch  87 , built into the chamber will have snapped into said notch. 
   The chamber  70  has at its outer end a slightly larger profile than the shaft  84  of the cutting blade  80 . However, in its interior, there is a space, which allows a spring, preferably a leaf spring  90 , to be inserted into chamber  70  next to blade shaft  84 . Chamber  70  may be provided with a slot, into which one end of the leaf spring can be pressed and held. The other end of this leaf spring is free to move. As shown in  FIG. 3 , when shaft  84  is inserted into holding device  50 , spring  90  presses against it until the notch  86  snaps into the corresponding catch  87 . When blade  80  is in place, preloaded spring  90  will hold it in position. Whenever the blade  80  has to be removed, the blade head  82  is pressed in the direction of centerline z, until the catch  87  releases notch  86 . 
   As also shown in  FIG. 3 , the rear portion  52  of holding device  50 , has a slot  75  near portion  46   b  of sleeve  46 , which creates an opening into chamber  70 . Therefore, the shank  84  of cutting blade  80  enters partially into slot  75 , when inserted into the chamber  70 . The depth of slot  75  is about half the diameter of a steel ball  100 . The dimensions of slot  75  and of the adjacent diameter  46   b  of the locking ring  46  are such that the ball  100  can roll freely in slot  75  when no cutting blade is inserted. 
   The ball  100 , in conjunction with the locking portion  46   c  of locking ring  46 , creates a locking mechanism, by which the rotation of holding device  50  in sleeve  46  and the housing  42  can be arrested. This locking mechanism is described further with the aid of  FIGS. 4–6 . 
     FIG. 4  shows the deburring tool  40  without its housing  42 , in which the holding device  50  can freely rotate in sleeve  46 . As shown in  FIG. 4 , the shaft  84  of blade  80  enters into slot  75 , and holds the steel ball  100  away from the locking elements  46   c  of sleeve  46 . 
   In order to block the rotation of holding device  50 , the head  82  of blade  80  is pressed in the direction of the axis of rotation z. If the deburring tool  40  is now held in the appropriate position, the steel ball  100  is free to roll, by its own weight, into one of the locking recesses  48  of locking ring  46  ( FIG. 6 ). After releasing the pressure on blade  80 , spring  90  will press the blade back, so notch  86  of shaft  84  will again engage the catch  87  of the holding device. The ball is now held in one of the recesses  48  of locking ring  46 , as shown in  FIG. 5 , thereby blocking rotation of holding device  50  in sleeve  46 , and housing  42 . 
     FIG. 7  shows sleeve  46  and, inside it, holding device  50  of a second embodiment of the deburring tool of the present invention. Instead of the cutting blade  80 , the shaft  110  of a bladeholder  120  is now inserted into the front part  52  of holding device  50 . The shaft  110  is basically identical to shaft  84  of cutting blade  80 , therefore further explanations are not needed. Adjoining the outer end of shaft  110 , and at an obtuse angle to said shaft  110 , is a fork-like holding arm  130 . Between two sides  132  and  134  of this holding arm, a cutting blade  140  or an insertable insert can be fastened. Cutting edge  142  of blade  140  may be adjusted to any angle. 
     FIG. 8  shows schematically the front part of housing  42  of the deburring tool  40  with bladeholder  120 , as shown in  FIG. 7 , gripping the adjustable cutting blade  140 . To perform deburring, blade  140  with its cutting edge  142 , is inserted into hole  155  of a workpiece  150 , and a rotating motion, as shown by the arrow, is carried out.