Patent Publication Number: US-2022218451-A1

Title: Angle adjustment stage device for dental technique

Description:
TECHNICAL FIELD 
     The present invention relates to an angle adjustment stage device for dental technique, particular to, an angle adjustment stage device used in design of a hook and a base of a removable partial denture for replacement of missing teeth. 
     BACKGROUND ART 
       FIG. 8  is a perspective view of an example of a removable partial denture mounted on a plaster model. 
     As shown in  FIGS. 8(A) and 8(B) , the removable partial dentures  33  comprise artificial teeth  34  and clasps  36  engaged with clasped teeth  35  adjacent to the removable partial dentures  33 . 
     In manufacturing process of the removable partial denture  33 , firstly, a plaster model  37  is made by modeling target teeth and mucous membranes from a patient&#39;s mouth cavity, and the clasped teeth  35  for the removable partial dentures  33  are chosen from residual teeth of the plaster model  37 , and then the clasps  36  are designed and produced in such a way that they fit the curved surfaces of the clasped teeth  35 . 
     There are two types of clasps  36 , that is, a wire clasp which is made by bending a metal wire and a cast clasp which is made by casting alloys. 
     As shown in  FIG. 8(B) , the clasp  36  is composed of a clasp tang  38  embedded into the removable partial denture  33  so as to be integrated with the removable partial denture  33 , a clasp body  39  connected to the clasp tang  38  and engaging with an adjacent surface of the clasped tooth  35 , and a clasp arm  40  connected to the clasp body  39  and surrounding the clasped tooth  35  at an undercut area of the clasped teeth  35  (an area underside of a circumferential line (surveyor line) of the tooth). The clasp arm  40  is composed of an upper arm portion  40   a , a middle arm portion  40   b  and clasp tip  40   c  in order closest to the clasp body  39 . 
     When the removable partial denture  33  is mounted on a defective part of teeth, the clasp arm  40 , which extends from the removable partial denture  33  in such a manner that it surrounds the clasped tooth  35 , engages with the undercut area of the clasped tooth  35  so as to prevent the removable partial denture  33  from disengaging and wobbling. 
     In this case, the setting of the degree of bending of the clasp arm  40  is very important for design and production of the clasp  36 , and therefore, one of the important design items of the removable partial denture  33  because the amount of the clasp arm&#39;s bending into the undercut area has a huge effect on comfort and load on the clasped tooth  35  when wearing the removable partial denture  33 , and aesthetics of the removable partial denture  33 . 
     The inventor of the present invention has proposed “IBA Denture Design Method” as a wire clasp design method. 
     According to this method, as shown in  FIGS. 9(A) and 9(B) , a plaster model M is set on an initial setting position (see  FIG. 9(A) . a straight line D 1  indicates a vertical direction), and a baseline (circumferential line) L 1  is drawn on the plaster model M, and each time the plaster model M is rotated to buccal and lingual sides by a predetermined angle (usually 15 degrees), an inclined line (outline of clasp) L 2  is drawn on a side of the clasped tooth  35  (see  FIG. 9(B) . a straight line D 2  indicates a vertical direction). After that, the buccal and lingual sides balance between the baseline and the outline of clasp is checked, and when the balance is not good, the initial setting position of the plaster model M is changed (adjusted) and a new outline of clasp is drawn again. According to this method, the wire clasp is designed in a manner such that a whole of the clasp arm (the clasp tip, the middle arm portion and the upper arm portion) is located in the undercut area. 
     In “IBA Denture Design Method”, it is necessary to draw the line of clasp arm while tilting the plaster model from the initial setting position, and therefore, some of angle adjustment stage devices for supporting design of wire clasp according to this method have been proposed in the prior art. 
     As an angle adjustment stage device of this kind, for example, there is an angle adjustment stage device comprising a first rotary member attached to a support post on a base so as to be rotatable around a horizontal axis, and a second rotary member arranged in an interior space of the first rotary member so as to be rotatable around an axis perpendicular to the horizontal axis, the first rotary member being fixed to the support post at a desired rotational position, the second rotary member being fixed to the first rotary member at a desired rotational position. The angle adjustment stage device further comprises a universal joint mechanism attached to the second rotary member in a manner such that a rotational center of the universal joint mechanism is located on a vertical axis, a support rod connected to the second rotary member through the universal joint mechanism at lower end thereof, a stage connected to an upper end of the support rod, a means (third fixing means) for fixing the support rod at a desired tilt position, and a means (fourth fixing means) for fixing the support rod after rotating the support rod from the desired tilt position around an axis which is chosen from the horizontal axis and axes parallel to the horizontal axis and passes through the rotational center of the universal joint by a desired angle (see Patent Document 1). 
     According to this angle adjustment stage device, the number of both a rotary part and a part for fixing the rotational position is reduced so that the simplification of device, the reduction of manufacturing costs and the improved operability of the device can be achieved to some extent. 
     However, this angle adjustment stage device is still expensive and is not easy to maintain. In addition, it takes a long time to get familiar with the operation of the device. 
     That is to say, there is still plenty of room for simplification of the configuration and improvement of the operability in this angle adjustment stage device. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     Patent Document 1: JP 6150093 B 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     It is, therefore, an object of the present invention to provide an angle adjustment stage device with a simpler structure and excellent operability. 
     Means for Solving the Problems 
     In order to solve the object, the present invention provides an angle adjustment stage device for dental technique comprising: a base; a stage arranged above the base, a workpiece for dental technique being fixed on the stage; and a stage support mechanism provided on the base to support the stage in a manner such that a tilt angle of the stage is adjustable. The stage support mechanism includes a base shaft arranged in protruding manner on the base and having a magnet therein, and a rocking body magnetically coupled to the tip of the base shaft. The rocking body includes a square substrate, a sphere formed from ferromagnet, a sphere holder arranged at the center of the substrate so as to be rotatable around an axis which extends through the center of the substrate and perpendicular to the substrate, and a first stopper for fixing the sphere holder to the substrate at a desired rotational position, the sphere holder holding the sphere in a manner such that the sphere can be rotated around the center thereof and fixed at a desired rotational position while the center of the sphere is on the axis extending perpendicular to the substrate. The rocking body further includes a support rod extending radially outward form the sphere and connected to a lower surface of the stage at an upper end thereof, a lower portion of the sphere protruding from the underside of each of the sphere holder and the substrate, the rocking body being magnetically coupled to a receiving portion of the tip of the base shaft at a lower end of the sphere. The stage support mechanism further includes an elevating body fitted on the base shaft so as to vertically slide along the base shaft, and a second stopper attached to the elevating body and/or the base shaft for fixing the elevating body to the base shaft at a desired height. An upper surface of the elevating body forms a horizontal plane and has a recess for receiving the lower portion of the sphere, and a through hole is formed on a bottom surface of the recess to reach a lower surface of the elevating body, and the through hole has a diameter corresponding to a diameter of the base shaft so that the base shaft is inserted through the through hole. The rocking body takes a horizontal position when the elevating body is located at the highest point to contact a lower surface of the substrate of the rocking body at an upper surface thereof, while the rocking body takes a tilt position when one of four sides of the substrate is brought into contact with the upper surface of the elevating body after the elevating body is lowered from the highest point while separating the upper surface thereof from the lower surface of the substrate. The angle adjustment stage device for dental technique further comprises an angle display mechanism displaying a tilt angle at the tilt position of the rocking body depending on the height of the elevating body. 
     According to a preferred embodiment of the present invention, a first circular recess is formed at the center of the lower surface of the substrate of the rocking body, and a first circular opening whose diameter is larger than a diameter of the sphere is formed at the center of a bottom surface of the first circular recess to reach an upper surface of the substrate. The sphere holder of the rocking body comprises a holder body having a large diameter portion whose diameter is larger than the diameter of the first circular opening, and a small diameter portion connecting coaxially to a lower end surface of large diameter portion and having a thickness which corresponds to a depth of the first circular opening and a diameter which corresponds to the diameter of the first circular opening. A second circular recess whose diameter is larger than the diameter of the sphere is formed at the center of an upper end surface of the large diameter portion, and a second circular opening is formed at the center of a bottom surface of t he second circular recess to reach a lower end surface of the small diameter portion and having a diameter which is smaller than the diameter of the sphere. The sphere holder further comprises an annular member having a thickness which is smaller than a depth of the first circular recess, an outer diameter which is larger than the diameter of the first circular opening, but smaller than the diameter of the first circular recess and an inner diameter which corresponds to the diameter of the second circular opening. The annular member is combined coaxially with the lower end surface of the small diameter portion while the small diameter portion is fitted into the first circular opening of the substrate, and the holder body is attached to the substrate so as to be rotatable around the axis extending perpendicular to the substrate. The sphere holder further comprises an annular sphere holding member having an outer diameter which equals to the diameter of the first circular opening and an inner diameter which is smaller than the diameter of the sphere. First screw holes are formed at more than three positions which are spaced from each other in a circumferential direction of the sphere holding member so as to penetrate both end surfaces of the sphere holding member, while second screw holes are formed at positions corresponding to the first screw holes on a bottom surface of the second circular recess of the holder body. The sphere holding member further comprises fixing screws being screwed into the first and second screw holes, the fixing screws being screwed into the first and second screw holes from the outside of the sphere holding member with the sphere nipped between the bottom surface of the second circular recess of the holder body and the sphere holding member. 
     According to another preferred embodiment of the present invention, a plurality of recesses are formed on an outer peripheral surface of the small diameter portion of the holder body at equal distances, and at least one radial hole is formed at positions which correspond to the plurality of recesses on an inner wall of the first circular opening of the substrate and extends radially outward from the axis extending perpendicular to the substrate, and the first stopper consists of at least one ball plunger arranged in the at least one radial hole and elastically urged toward the outer peripheral surface of the small diameter portion to engage with the plurality of recesses of the small diameter portion. 
     According to further preferred embodiment of the present invention, the base shaft is rotatable around an axis thereof and has a flange at a lower portion thereof. The angle display mechanism includes a pair of fan-shaped plates are connected to each other so as to be rotatable around the center of each other. The tip of a radial side edge of a first fan-shaped plate of the pair of fan-shaped plates or an extension extending outward from the first fan-shaped plate along the radial side edge is attached to the flange of the base shaft so as to be rotatable around a horizontal axis. The tip of a radial side edge of a second fan-shaped plate of the pair of fan-shaped plates closer to the radial side edge of the first fun-shaped plate or an extension extending outward from the second fan-shaped plate along the radial side edge of the second fan-shaped plate is attached to a side wall of the elevating body so as to be rotatable around an axis parallel to the horizontal axis, so that the pair of fan-shaped plates rotate around the center of each other in a vertical plane as the elevating body moves up and down. An angle scale which corresponds to the tilt angle of the rocking body is attached on a peripheral wall of the first fan-shaped plate, and a zero point scale is attached on a peripheral wall of the second fan-shaped plate. 
     According to further preferred embodiment of the present invention, the base shaft is fixed to the base, and the angle display mechanism includes a pair of fan-shaped plates connected to each other so as to be rotatable around the center of each other. The tip of a radial side edge of a first fan-shaped plate of the pair of fan-shaped plates or an extension extending outward from the first fan-shaped plate along the radial side edge is attached to the base so as to be rotatable around a horizontal axis. The tip of a radial side edge of a second fan-shaped plate of the pair of fan-shaped plates closer to the radial side edge of the first fun-shaped plate or an extension extending outward from the second fan-shaped plate along the radial side edge of the second fan-shaped plate is attached to a side wall of the elevating body so as to be rotatable around an axis parallel to the horizontal axis, so that the pair of fan-shaped plates rotate around the center of each other in a vertical plane as the elevating body moves up and down. An angle scale which corresponds to the tilt angle of the rocking body is attached on a peripheral wall of the first fan-shaped plate, and a zero point scale is attached on a peripheral wall of the second fan-shaped plate. 
     According to further preferred embodiment of the present invention, the angle adjustment stage device for dental technique further comprises a marking unit attached to the base so as to draw a line for design on the workpiece for dental technique fixed on the stage. The marking unit includes a pole projected vertically on the base, an arm attached to the pole and extending radially from the pole and arranged on a plane perpendicular to the pole so as to be rotatable around an axis of the pole, a pen holder attached to the tip of the arm, and a pen held by the pen holder and extending downward from the pen holder and parallel to the pole. 
     Effect of the Invention 
     According to the present invention, compared with the conventional angle adjustment stage device, the number of parts which make up the angle adjustment stage device is reduced, and the device configuration becomes easier, thereby device manufacturing costs are significantly reduced and the device can be miniaturized and the maintenance of the device also becomes easier. 
     Furthermore, the number of parts to be operated for adjusting the angle of the stage is reduced and it is easy to operate those parts, and therefore, even beginners can master the operation of the device in a short period of time. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an angle adjustment stage device for dental technique according to an embodiment of the present invention. 
         FIG. 2  is a longitudinal section a stage support mechanism of the angle adjustment stage device for dental technique shown in  FIG. 1 . 
         FIG. 3  is a disassembled perspective view of a rocking body of the angle adjustment stage device for dental technique shown in  FIG. 1 . 
         FIG. 4  is a side view of the angle adjustment stage device for dental technique shown in  FIG. 1 . 
         FIG. 5  is a perspective view of a stage of the angle adjustment stage device for dental technique shown in  FIG. 1 , where a workpiece for dental technique is fixed on the stage. 
         FIG. 6  is a longitudinal section of a stage support mechanism of an angle adjustment stage device for dental technique of another embodiment of the present invention. 
         FIG. 7  is a side view of the angle adjustment stage device for dental technique shown in  FIG. 6 . 
         FIG. 8  is a perspective view illustrating a plaster model to which a removable partial denture is attached. 
         FIG. 9  is a view explaining how to design a wire clasp according to the IBA Denture Design Method, wherein (A) is a side view of a plaster model as viewed from the buccal side, (B) is a cross-sectional view taken along Dl of (A), and (C) is a plan view of the plaster model. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     A preferred embodiment of the present invention will be explained below with reference to accompanying drawings. 
       FIG. 1  is a perspective view of an angle adjustment stage device for dental technique according to an embodiment of the present invention, and  FIG. 2  is a longitudinal section a stage support mechanism of the angle adjustment stage device for dental technique shown in  FIG. 1 .  FIG. 3  is a disassembled perspective view of a rocking body of the angle adjustment stage device for dental technique shown in  FIG. 1 , and  FIG. 4  is a side view of the angle adjustment stage device for dental technique shown in  FIG. 1 . 
     Referring to  FIG. 1 , an angle adjustment stage device of the present invention comprises a base  1 , a stage  2  arranged above the base  1 , a workpiece W for dental technique being fixed on the stage  2 , and a stage support mechanism  3  provided on the base  1  to support the stage  2  in a manner such that a tilt angle of the stage  2  is adjustable, 
     In this embodiment, the base  1  has a rectangular plate shape, and rubber legs la are attached to four corners of the underside of the base  1 . 
     As shown in  FIG. 2 , the stage support mechanism  3  includes a base shaft  4  arranged in protruding manner on the base through a thrust bearing  5  to be rotatable around an axis of the base shaft  4 . 
     The base shaft  4  has a magnet  6  therein, and an upper end surface of the magnet  6  is exposed on a bottom surface of a receiving portion  4   a  which is formed at the tip of the base shaft  4  so as to receive a sphere  9  (described later). 
     The base shaft also has a flange  4   b  at a lower portion thereof. 
     The stage support mechanism  3  further includes a rocking body  7  magnetically coupled to the tip of the base shaft  4  (receiving portion  4   a ). 
     The rocking body  7  includes a square substrate  8 , a sphere  9  formed from ferromagnet, and a sphere holder  10  arranged at the center of the substrate  8  so as to be rotatable around an axis Z which extends through the center of the substrate  8  and perpendicular to the substrate  8 . 
     Referring to  FIGS. 2 and 3 , a first circular recess  8   b  is formed at the center of a lower surface of the substrate  8  and a first circular opening  8   a  whose diameter is larger than a diameter of the sphere  9  is formed at the center of a bottom surface of the first circular recess to reach an upper surface of the substrate  8 . 
     In this embodiment, the sphere holder  10  comprises an holder body  13  having a large diameter portion  11  whose diameter is larger than the diameter of the first circular opening  8   a , and a small diameter portion  12  connecting coaxially to a lower end surface of large diameter portion  11  and having a thickness which corresponds to a depth of the first circular opening  8   a  and a diameter which corresponds to the diameter of the first circular opening  8   a.    
     A second circular recess  11   a  whose diameter is larger than the diameter of the sphere  9  is formed at the center of an upper end surface of the large diameter portion  11 , and a second circular opening  12   a  is formed at the center of a bottom surface of the second circular recess  11   a  to reach a lower end surface of the small diameter portion  12  and having a diameter which is smaller than the diameter of the sphere  9 . 
     The sphere holder  10  further comprises an annular member  14  having a thickness which is smaller than a depth of the first circular recess  8   b , an outer diameter which is larger than the diameter of the first circular opening  8   a , but smaller than the diameter of the first circular recess  8   b  and an inner diameter which corresponds to the diameter of the second circular opening  12   a.    
     The annular member  14  is concentrically attached to the lower end surface of the small diameter portion  12  through screws, while the small diameter portion  12  of the holder body  13  is fitted into the first circular opening  8   a  of the substrate  12 , and thereby the holder body  13  is attached to the substrate  8  so as to be rotatable around the axis Z. 
     As can be seen from  FIG. 3 , a plurality of recesses (in this embodiment, four recesses)  12   b  are formed on an outer peripheral surface of the small diameter portion  12  at equal distances, and radial holes (not shown) are formed at positions corresponding to the plurality of recesses on an inner wall of the first circular opening  8   a  of the substrate  8  and extend radially outward from the axis Z of the substrate  8 . 
     A ball plunger  15  is arranged in each of the radial holes and always elastically urged toward the outer peripheral surface of the small diameter portion  12 . 
     The ball plungers  15  constitute a first stopper for fixing the sphere holder  10  to the substrate  8  of the rocking body  7  at a desired rotational position. 
     A configuration of the first stopper is not limited to this embodiment. 
     In this embodiment, although the ball plungers  15  engage with the recesses  12   b  of the small diameter portion  12  every time the sphere holder  10  rotates 90 degrees, the reference position of the workpiece W fixed on the stage  2  is defined by one rotational position at which the ball plungers  15  engage with the recesses  12   b  (this will be described later). 
     The sphere holder  10  also comprises an annular sphere holding member  16  having an outer diameter which equals to the diameter of the first circular opening  8   a  and an inner diameter which is smaller than the diameter of the sphere  9 . 
     First screw holes  17  are formed at more than three positions which are spaced from each other in a circumferential direction of the sphere holding member  16  so as to penetrate both end surfaces of the sphere holding member  16 , while second screw holes  18  are formed at positions corresponding to the first screw holes  17  on a bottom surface of the second circular recess  11   a  of the holder body  13 . 
     The sphere holder  10  further comprises fixing screws  19  being screwed into the first and second screw holes  17 ,  18 . 
     The fixing screws  19  are screwed into the first and second screw holes  17 ,  18  from the outside of the sphere holding member  16  while the sphere  9  whose center is on the axis Z extending perpendicular to the substrate  8  is nipped between the bottom surface of the second circular recess lla of the holder body  13  and the sphere holding member  16  with a lower portion of the sphere  9  protruding from the underside of each of the sphere holder  10  and the substrate  8 . 
     Thus the sphere  9  becomes rotatable while being magnetically coupled to the receiving portion  4   b  by loosening the fixing screws  19 , and the sphere  9  is fixed between the bottom surface of the second circular recess  11   a  of the holder body  13  and the sphere holding member  16  by tightening the fixing screws  19 . 
     The rocking body  7  further includes a support rod  20  extending radially outward form the sphere  9 . A lower surface of the stage  2  is connected to an upper end of the support rod  20 . 
     The rocking body  7  is magnetically coupled to the receiving portion  4   a  (magnet  6 ) of the tip of the base shaft  4  at a lower end of the sphere  9 . 
     In this case, the magnet  6  has a magnetic force which causes a magnetic coupling force large enough to maintain positional relationship of the sphere  9  with respect to the receiving portion  4   a.    
     The stage support mechanism  3  also includes an elevating body  21  fitted on the base shaft  4  so as to vertically slide along the base shaft  4 . 
     The elevating body  21  is composed of a rectangular (or square) flat upper portion  21   c  and a columnar lower portion  21   d  concentrically connecting to the center of the underside of the upper portion  21   c.    
     An upper surface of the upper portion  21   c  forms a horizontal plane, and an recess  21   a  for receiving the lower portion (portion protruding from the underside of each of the substrate  8  and the sphere holder  10 ) of the sphere  9  opens on the upper surface of the upper portion  21   c , and a through hole  21   b  is formed on a bottom surface of the recess  21   a  to reach the underside of elevating body  21 . The through hole  21   b  has a diameter corresponding to a diameter of the base shaft  4 . 
     A set collar  22  whose inner diameter corresponds to the through hole  21   b  is attached to the underside of the elevating body  21 , and the base shaft  4  is inserted through the through hole  21   b  and the set collar  22 . 
     Thus the elevating body  21  becomes slidably along the base shaft  4  by loosening a clamp screw  22   a , and the elevating body  21  is fixed to the base shaft  4  at a desired height by tightening the clamp screw  22   a.    
     The set collar  22  constitutes a second stopper for fixing the elevating body  21  to the base shaft  4  at a desired height. 
     A configuration of the second stopper is not limited to this embodiment. 
     In this way, the rocking body  7  takes a horizontal position when the elevating body  21  is located at the highest point to contact the lower surface of the substrate  8  of the rocking body  7  at an upper surface thereof (see  FIG. 2 ), while the rocking body  7  takes a tilt position when one of four sides of the substrate  8  is brought into contact with the upper surface of the elevating body  21  after the elevating body  21  is lowered from the highest point while separating the upper surface thereof from the lower surface of the substrate  8  (see  FIG. 4 ). 
     In this case, when the rocking body  7  is located at the horizontal position, the axis Z coincides with a vertical axis (axis perpendicular to the upper surface of the elevating body  21 ) (see  FIG. 2 ), wherein the stage  2  (support rod  20 )can be tilted through the sphere  9  by loosening fixing screws  19 , while the stage  2  (support rod  20 ) can be fixed at a desired tilt position by tightening the fixing screws  19 . 
     When the rocking body  7  is located at the tilt position while the stage  2  (support rod  20 ) is fixed at a desired tilt position, the stage  2  (support rod  20 ) can be rotated by the tilt angle of the rocking body  7  clockwise or counterclockwise around one of horizontal two axes (X-Y axes) which extend through the center of the sphere  9  and are orthogonal to each other on a vertical axis. 
     The angle adjustment stage device for dental technique of the present invention further comprises an angle display mechanism  23  displaying the tilt angle at the tilt position of the rocking body  7  depending on the height of the elevating body  21 . 
     As shown in  FIGS. 2 and 4 , in this embodiment, the angle display mechanism  23  includes a pair of fan-shaped plates  24 ,  25  connected to each other so as to be rotatable around the center of each other. 
     A first fan-shaped plate  24  of the pair of fan-shaped plates  24 ,  25  has an extension  24   b  extending outward from the first fan-shaped plate  24  along a radial side edge  24   a  of the first fan-shaped plate  24 , while a second fan-shaped plate  25  of the pair of fan-shaped plates  24 ,  25  has an extension  25   b  extending outward from the second fan-shaped plate  25  along a radial side edge  25   a  closer to the radial side edge  24   a  of the first fan-shaped plate  24 . 
     Then the tip of the extension  24   b  of the first fan-shaped plate  24  is attached to a mounting shaft  26  extending horizontally in a radial direction from a peripheral wall of the flange  4   b  of the base shaft  4  so as to be rotatable around an axis of the mounting shaft  26 , while the tip of the extension  25   b  of the second fan-shaped plate  25  is attached to a mounting shaft  27  extending radially from a side wall of the lower portion  21   d  of the elevating body  21  and parallel with the mounting shaft  26  so as to be rotatable around an axis of the mounting shaft  27 . 
     Thereby the pair of fan-shaped plates  24 ,  25  rotate around the center (connection point) of each other in a vertical plane as the elevating body  21  moves up and down. 
     Furthermore, an angle scale S 1  which corresponds to the tilt angle of the rocking body  7  is attached on a peripheral wall of the first fan-shaped plate  24 , and a zero point scale S 2  is attached on a peripheral wall of the second fan-shaped plate  25 . 
     The angle scale S 1  is pre-created as follows. 
     First, the elevating body  21  is fixed at the highest point thereof (the rocking body  7  takes the horizontal position), and a zero scale is assigned to a point of the angle scale S 1  which corresponds to the zero point scale S 2 . Secondly, the tilt angle of the tilt position of the rocking body is measured and the measured value is assigned to a point of the angle scale S 1  which corresponds to the zero point scale S 2  each time the height of the elevating body  21  is changed. 
     In this way, the elevating body  21  is fixed at a height at which the angle indicated by the zero point scale S 2  becomes a desired angle, and then one of four sides of the substrate  8  of the rocking body  7  is brought into contact with the upper surface of the elevating body  21 . Thereby, the stage  2  (support rod  20 ) is rotated by the desired angle clockwise or counterclockwise around one of the horizontal two axes (X-Y axes) which extend through the center of the sphere  9  and are orthogonal to each other on the vertical axis. 
     Although the pair of fan-shaped plates  24 ,  25  is the extension  24   b ,  25   b  in this embodiment, the pair of fan-shaped plates  24 ,  2 After 5  may be attached directly to the associated mounting shafts  26 ,  27  at the tips of radial side edges  24   a ,  25   a  thereof so as to be rotatable around the axes of the mounting shafts  26 ,  27  without the extensions  24   b ,  25   b.    
       FIG. 5  is a perspective view of the stage  2  with the workpiece for dental technique W fixed thereon. 
     AS shown in  FIG. 5 , the stage  2  is formed in a flat plate shape and has holes  2   a  evenly spaced in longitudinal and width directions of the stage  2 . A pair of receiving pins  2   b ,  2   b  and a tightening pin  2   c  provided with a clamping screw  2   d  are selectively fitted into any of these holes  2   a.    
     Then the workpiece W is fixed on the stage  2  by clamping the workpiece W between the pair of receiving pins  2   b ,  2   b  and the clamping screw  2   d.    
     In this embodiment, a marking unit  28  is provided to draw a line for design on the workpiece for dental technique W fixed on the stage  2 . 
     The marking unit  28  includes a pole  29  projected vertically on the base  1 , an arm  30  attached to the pole  29  and extending radially from the pole  29  and arranged on a plane perpendicular to the pole  29  so as to be rotatable around an axis of the pole  29 , a pen holder  31  attached to the tip of the arm  30 , and a pen  32  held by the pen holder  31  and extending downward from the pen holder  31  and parallel to the pole  29 . 
     In this embodiment, the marking unit  28  is provided to draw the surveyor line on the plaster model because the angle adjustment stage device is intended to use for design of the clasp and removable partial denture and therefore the plaster model is assumed as a workpiece for dental technique W, but the workpiece for dental technique W is not limited to the plaster model. When the workpiece for dental technique W should be cut or polished, a suitable cutting or polishing unit is provided instead of the marking unit  28 . 
     The angle adjustment stage device of the present invention may be used to locate an attachment and produce an implant stent and so on. 
     Next, a method of using the angle adjustment stage device of the present invention will be explained. 
     For example, when a surveyor line should be drawn on a plaster model for production of a removable partial denture, the plaster model as the workpiece for dental technique W is fixed on the stage  2 . At this time, the ball plungers  15  of the substrate  8  of the rocking body  7  engage with the recesses  12   b  of the sphere holder  10  so that the plaster model W is located at a reference position (shown in  FIG. 9(C) ). 
     Next, the elevating body  21  is fixed at a height (highest point) where the zero point scale S 2  of the angle display mechanism  23  coincides with the zero point of the angle scale S 1 . 
     Thereafter the fixing screws  19  of the rocking body  7  is loosen and the stage  2  (plaster model W) is tilted to the initial setting position while looking at the left and right balance of the plaster model W, and then the stage  2  is fixed at the initial setting position by tightening the fixing screws  19 . 
     At the initial setting position, a baseline (circumferential line) is drawn on the plaster model W by the marking unit  28  (pen  32 ) while rotating the stage  2 , the rocking body  7 , the elevating body  21  and the base shaft  4  together around the vertical axis (L 1  in  FIG. 9(A) ). 
     Thereafter, the clamp screw  22   a  of the set collar  22  is loosen, and the elevating body  21  is lowered until the zero point scale S 2  of the angle display mechanism  23  coincides with 15 degrees on the angle scale S 1 , and then the elevating body  21  is fixed at the height by tightening the clamp screw  22   a  again. 
     Next, the stage  2  is located at the tilt position so as to be tilted to the left and right of the plaster model W (the stage  2  is rotated clockwise and counterclockwise around the X axis shown in  FIG. 9(C) ), and in each case, an inclined line (outline of clasp) is drawn on buccal ang lingual sides of the clasped tooth  35  of the plaster model W by the pen  32 , while rotating the stage  2 , the rocking body  7 , the elevating body and the base shaft together around the vertical axis (L 2  in  FIG. 9(A) ). 
     After that, the buccal and lingual sides balance between the baseline L 1  and the outline of clasp L 2  is checked by contrasting those lines. The work is completed when the balance is good, but, when the balance is not good, it is necessary to change (adjust) the initial setting position of the stage  2  and draw a new outline of clasp again. 
     A method of change (adjustment) of the initial setting position is as follows. 
     (1) The change (adjustment) of the initial setting position around the X axis or the Y axis in  FIG. 9(C)   
     After the clamp screw  22   a  of the set collar  22  is loosen, the elevating body  21  is lowered to a desired angle while looking at the angle display mechanism  23 , and the elevating body  21  is fixed at the desired angle by tightening the clamp screw  22   a.    
     Thereafter the fixing screws  19  are loosen so that the fixation between the rocking body  7  and the sphere  9  is released. However, the inclination of the stage  2  is not changed because the sphere  9 , which supports the stage  2 , is magnetically coupled to the magnet  6  of the base shaft  4 . 
     Then the free rocking body  7  is adjusted to the desired tilt angle with respect to the X axis or the Y axis by bringing the associated one side of the substrate  8  of the rocking body  7  into contact with the upper surface of the elevating body  21 , and the sphere  9  is fixed to the rocking body  7  by the fixing screws  19 . Next, the clamp screw  22   a  of the set collar  22  is loosen and the elevating body  21  is raised until the zero point scale S 2  of the angle display mechanism  23  coincides with the zero point of the angle scale S 1 , so that the change (adjustment) of the initial setting position of the stage  2  is completed. 
     (2) The change (adjustment) of the initial setting position around an alpha (α) axis in  FIG. 9(C)   
     The sphere holder  10  is rotated until the alpha (α) axis coincides with the X axis or the Y axis while setting the stage  2  in the initial setting position. After that, the change (adjustment) is completed by operating in the same way as the case (1). 
     After the change (adjustment) of the initial setting position of the stage  2  is completed, a predetermined angle is set again with respect to the plaster model W based on the new initial setting position, and then the outline of clasp L 2  is drawn so that an ideal outline of clasp associated with a wire clasp. 
     According to the present invention, compared with the conventional angle adjustment stage device, the number of parts which make up the angle adjustment stage device is reduced, and the device configuration becomes easier, thereby device manufacturing costs are significantly reduced and the device can be miniaturized and the maintenance of the device also becomes easier. 
     In addition, the number of parts to be operated for adjusting the angle of the stage  2  is reduced and it is easy to operate those parts and therefore, even beginners can master the operation of the device in a short period of time. 
       FIG. 6  is a longitudinal section of a stage support mechanism of an angle adjustment stage device for dental technique of another embodiment of the present invention, and  FIG. 7  is a side view of the angle adjustment stage device for dental technique shown in  FIG. 6 . 
     The embodiment shown in  FIGS. 6 and 7  differs from the embodiment shown in  FIGS. 1 through 5  only in a mounting structure of the base shaft to the base and a mounting position of the angle display mechanism. Therefore, in  FIGS. 6 and 7 , the same elements as shown in  FIGS. 1 through 5  are identified with the same reference numerals as used in  FIGS. 1 through 5 , and the detailed explanation thereof will be omitted in what follows. 
     Referring to  FIGS. 6 and 7 , in this embodiment, a base shaft  4 ′ is fixed to the base  1  so as not to be rotatable around an axis thereof and has no flange. 
     The base shaft  4 ′ has the magnet  6  therein, and an upper end surface of the magnet  6  is exposed on a bottom surface of a receiving portion  4   a ′ which is formed at the tip of the base shaft  4 ′ so as to receive the sphere  9 . 
     Furthermore, the tip of the extension  25   b  of the second fan-shaped plate  25  of the angle display mechanism  23  is attached to the mounting shaft  27  of the elevating body  21  so as to be rotatable around the axis of the mounting shaft  27 , while the tip of the extension  24   b  of the first fan-shaped plate  24  is attached to a mounting shaft  26 ′, which is attached to the side of the base  1  and extends parallel to the mounting shaft  27 , so as to be rotatable around an axis of the mounting shaft  26 ′. 
     Thereby, the pair of fan-shaped plates  24 ,  25  rotate around the center (connection point) of each other in a vertical plane as the elevating body  21  moves up and down. 
     According to this embodiment, the rotation of the stage  2  around the vertical axis in the initial setting position is performed by rotating the stage  2  and the rocking body  7  together around an axis Z while bringing the lower surface of the substrate  8  of the rocking body  7  into contact with the upper surface of the elevating body  21 . 
     In addition, the rotation of the stage  2  around the vertical axis in the tilt position is performed by rotating the stage  2  and the rocking body  7  together around the receiving portion  4   a ′ of the base shaft  4 ′ as a pivot point while bringing the associated side of the substrate  8  into contact with the upper surface of the elevating body  21 . 
     Although a preferred embodiment of the present invention has been explained, the present invention is not limited to the above-mentioned embodiment and one skilled in the art can easily create a variety of modifications within the scope of the attached claims. 
     For example, the sphere holder  10  may have any configuration as far as the sphere holder  10  is arranged at the center of the substrate  8  so as to be rotatable around the axis Z which extends through the center of the substrate  8  and perpendicular to the substrate  8 . 
     For example, the angle display mechanism  23  may have any configuration as far as the angle display mechanism  23  displays a tilt angle at the tilt position of the rocking body depending on the height of the elevating body. 
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
           1  Base 
           1   a  Rubber leg 
           2  Stage 
           2   a  Hole 
           2   b  Receiving pin 
           2   c  Tightening pin 
           3  Stage support mechanism 
           4 ,  4 ′ Base shaft 
           4   a ,  4   a ′ Receiving portion 
           5  Thrust bearing 
           6  Magnet 
           7  Rocking body 
           8  Substrate 
           8   a  First circular opening 
           8   b  First circular recess 
           9  Sphere 
           10  Sphere holder 
           11  Large diameter portion 
           11   a  Second circular recess 
           12  Small diameter portion 
           12   a  Second circular opening 
           13  Holder body 
           14  Annular member 
           15  Ball plunger (first stopper) 
           16  Sphere holding member 
           17  First screw hole 
           18  Second screw hole 
           19  Fixing screw 
           20  Support rod 
           21  Elevating body 
           21   a  Recess 
           21   b  Through hole 
           21   c  Upper portion 
           21   d  Lower portion 
           22  Set collar (second stopper) 
           22   a  Clamp screw 
           23  Angle display mechanism 
           24  First fan-shaped plate 
           24   a  Radial side edge 
           24   b  Extension 
           25  Second fan-shaped plate 
           25   a  Radial side edge 
           25   b  Extension 
           26 ,  26 ′,  27  Mounting shaft 
           28  Marking unit 
           29  Pole 
           30  Arm 
           31  Pen holder 
           32  Pen 
           33  Removable partial denture 
           34  Artificial tooth 
           35  Clasped tooth 
           36  Clasp 
           37  Plaster model 
           38  Clasp tang 
           39  Clasp body 
           40  Clasp arm 
           40   a  Upper arm portion 
           40   b  Middle arm portion 
           40   c  Clasp tip 
         D 1  Initial setting direction 
         D 2  Tilt direction 
         L 1  Baseline (circumferential line) 
         L 2  Inclined line 
         M Plaster model 
         S 1  Angle scale 
         S 2  Zero point scale 
         W Workpiece for dental technique 
         Z Vertically extending axis