Patent Publication Number: US-2011056084-A1

Title: Electric Cutting Tool

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application relates to subject matter contained in Japanese Patent Application No. 2009-208109, filed on Sep. 9, 2009, and Japanese Patent Application No. 2010-142507, filed on Jun. 23, 2010, all of which are expressly incorporated herein by reference in their entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electric cutting tool, and particularly, the present invention relates to an electric cutting tool in which a cutting depth (depth of cut) or an inclination angle of a circular saw blade is displayed at a position viewable for an operator. 
     2. Description of the Related Art 
     Heretofore, an electric cutting tool, including a surface plate, a body portion tiltably mounted on this surface plate and a circular saw blade rotatably provided by driving power from a driver included in the body portion, is known (for example, see Japanese Patent Application Publication No. 8-142001; hereinafter, referred to as “Patent Literature 1”). In a conventional electric cutting tool illustrated in Patent Literature 1, an indicator scale has generally been provided so that a cutting depth of the circular saw blade can be confirmed during an operation. However, since an operator has to confirm this indicator scale by sight, the indicator scale has a problem that it lacks in accuracy. Further, the indicator scale included in the conventional electric cutting tool must convert a circular motion, that is, a rotary motion of the circular saw blade into a linear dimension, that is, a cutting depth. For that reason, intervals of scale marks (measurements) necessarily become imbalanced like the indicator scale disclosed in Patent Literature 1. Therefore, it is hard for the operator to view and confirm the conventional indicator scale, and it is easy to generate an error. 
     On the other hand, Japanese Patent Application Publication No. 9-268516 (hereinafter, referred to as “Patent Literature 2”) discloses a technique for displaying a cutting depth with high accuracy. Patent Literature 2 discloses a concrete cutter with a display device capable of displaying the cutting depth of a blade. However, this concrete cutter with the cutting depth display device detects movement amounts of two members including an up-and-down arm and a frame, each of which carries out a circular motion, by means of a rack and a pinion; converts an amount of rotation of the pinion into an up-and-down amount of a mounting shaft of the blade; and thereby displays a cutting depth of the blade. 
     However, the technique disclosed in Patent Literature 2 mentioned above obtains the movement amount of the blade on the basis of the two members including the up-and-down arm and the frame, each of which carries out the circular motion. Thus, such a technique includes a structural problem that an error occurs inevitably. Therefore, even if the conventional techniques disclosed in Patent Literatures 1 and 2 mentioned above are combined, it is impossible to obtain an electric cutting tool capable of displaying a cutting depth and/or an inclination angle of a circular saw blade with high accuracy. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in order to solve the problem described above, and it is an object of the present invention to provide a new electric cutting tool capable of calculating a cutting depth and an inclination angle of a circular saw blade with high accuracy, and of displaying its calculation result by means of a display section arranged at a position viewable for an operator. 
     Hereinafter, the present invention will be described. In this regard, reference numerals of the appending drawings are added in parenthesis in order to facilitate understanding of the present invention. However, this does not cause the present invention to be limited in the illustrated forms. 
     In order to achieve the above object, the present invention is directed to an electric cutting tool. The electric cutting tool ( 10 μ,  10 ′) according to the present invention includes: a surface plate ( 11 ); a body portion ( 21 ) tiltably provided on the surface plate ( 11 ); and a circular saw blade ( 41 ) capable of rotating by means of driving power from a driver ( 25 ) provided in the body portion ( 21 ). The electric cutting tool ( 10 ,  10 ′) also includes a movement amount measuring section ( 50 ,  50 ′,  50 ″,  80 ,  90 ) for measuring a movement amount of the body portion ( 21 ) with respect to the surface plate ( 11 ) in response to a tilting action. The electric cutting tool ( 10 ,  10 ′) also includes a calculating section ( 61 ) for calculating a cutting depth of the circular saw blade ( 41 ) or an inclination angle of the body portion ( 21 ) on the basis of the movement amount measured by the movement amount measuring section ( 50 ,  50 ′,  50 ″,  80 ,  90 ). The electric cutting tool ( 10 ,  10 ′) also includes a display section ( 62 ) for displaying the cutting depth or the inclination angle of the body portion ( 21 ) calculated by the calculating section ( 61 ). 
     In the electric cutting tool ( 10 ) according to the present invention, it is preferable that the movement amount measuring section ( 50 ,  50 ′,  50 ″,  80 ) includes: a scale section ( 51 ,  51 ′,  51 ″,  81 ) installed on any one of the surface plate ( 11 ) and the body portion ( 21 ), the scale section including scale marks provided at predetermined intervals; and a scale detecting section ( 52 ,  52 ′,  52 ″,  82 ) for detecting the scale marks included in the scale section ( 51 ,  51 ′,  51 ″,  81 ), the scale detecting section being installed on the other of the surface plate ( 11 ) and the body portion ( 21 ). 
     Further, in the electric cutting tool ( 10 ) according to the present invention, it is preferable that the scale section is a magnetic scale ( 51 ,  51 ′,  51 ″) in which the scale marks are recorded as magnetic patterns, and that the scale detecting section is a magnetic detecting head ( 52 ,  52 ′,  52 ″) for measuring the movement amount of the body portion ( 21 ) with respect to the surface plate ( 11 ) in response to the tilting action by reading out the scale marks from the magnetic scale and converting a read-out result into an electrical signal. 
     Further, in the electric cutting tool ( 10 ) according to the present invention, it is preferable that the scale section is a rack ( 81 ) in which teeth for the scale marks are cut at predetermined intervals, and the scale detecting section is a pinion ( 82 ) for measuring the movement amount of the body portion ( 21 ) with respect to the surface plate ( 11 ) in response to the tilting action by causing the pinion to carry out a rotary motion while engaging with the rack ( 81 ) and detecting an amount of rotary motion. 
     Moreover, in the electric cutting tool ( 10 ) according to the present invention, it is preferable that the body portion ( 21 ) includes: a gripper ( 28 ) used when a tilting operation of the body portion ( 21 ) is carried out; and a cover portion ( 27 ) that covers an outer circumference of the circular saw blade ( 41 ), wherein the display section ( 62 ) is installed at a region between the gripper ( 28 ) and the cover portion ( 27 ). 
     Furthermore, in the electric cutting tool ( 10 ,  10 ′) according to the present invention, it is preferable that the body portion ( 21 ) is configured so that the circular saw blade ( 41 ) can be tilted in a direction to be tilted to a side surface of the electric cutting tool, and that the calculating section ( 61 ) calculates the cutting depth of the circular saw blade ( 41 ) by carrying out correction in accordance with a tilt angle in a direction in which the circular saw blade ( 41 ) is to be tilted to the side surface. 
     Furthermore, in the electric cutting tool ( 10 ′) according to the present invention, it is preferable that the movement amount measuring section ( 90 ), the calculating section ( 61 ) and the display section ( 62 ) are integrally installed by means of a casing ( 64 ). 
     Further, in the electric cutting tool according to the present invention ( 10 ′), it is preferable that the calculating section ( 61 ), the display section ( 62 ) and the casing ( 64 ) are arranged so as not to protrude from an outline of the body portion ( 21 ). 
     Moreover, in the electric cutting tool ( 10 ′) according to the present invention, it is preferable that the electric cutting tool ( 10 ′) further includes: a link member ( 13 ) for linking the surface plate ( 11 ) to the body portion ( 21 ), the link member ( 13 ) extending along a tilt direction of the body portion ( 21 ) from an upper surface of the surface plate ( 11 ), that the movement amount measuring section includes an angle sensor ( 90 ) for detecting an inclination angle of the link member ( 13 ) with respect to the surface plate ( 11 ), and that the calculating section ( 61 ) calculates the cutting depth of the circular saw blade ( 41 ) or the inclination angle of the body portion ( 21 ) on the basis of the inclination angle detected by the angle sensor ( 90 ). 
     Furthermore, in the electric cutting tool ( 10 ′) according to the present invention, it is preferable that the body portion ( 21 ) includes a cover portion ( 27 ) that covers an outer circumference of the circular saw blade ( 41 ), the cover portion ( 27 ) capable of tilting with respect to the surface plate ( 11 ) together with the circular saw blade ( 41 ), that the movement amount measuring section includes an angle sensor ( 90 ) for detecting an inclination angle of the cover portion ( 27 ) with respect to the surface plate ( 11 ), and that the calculating section ( 61 ) calculates the cutting depth of the circular saw blade ( 41 ) or the inclination angle of the body portion ( 21 ) on the basis of the inclination angle detected by the angle sensor ( 90 ). 
     According to the present invention, it is possible to provide a new electric cutting tool capable of calculating a cutting depth or an inclination angle of a circular saw blade with high accuracy, and of displaying its calculation result by means of a display section arranged at a position viewable for an operator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other objects, features and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments of the present invention that proceed with reference to the appending drawings: 
         FIG. 1  is an external front view of an electric cutting tool according to the present invention; 
         FIG. 2  is an external back view of the electric cutting tool according to the present invention; 
         FIG. 3  is an external right side view of the electric cutting tool according to the present invention; 
         FIG. 4  is an external left side view of the electric cutting tool according to the present invention; 
         FIG. 5  is a cross-sectional view for explaining an internal configuration of the electric cutting tool according to the present invention, and shows a cross-sectional view taken along the line A-A in  FIG. 4 ; 
         FIG. 6  is a partially broken-out top view of the electric cutting tool according to the present invention; 
         FIG. 7  is a schematic right side view in which a part of the members is omitted for explaining an operation of the electric cutting tool according to the present invention, and particularly shows a state when a body portion is in the closest position to a surface plate; 
         FIG. 8  is a schematic right side view in which a part of the members is omitted for explaining an operation of the electric cutting tool according to the present invention, and particularly shows a state when the body portion is tilted upward with respect to the surface plate; 
         FIG. 9  is a block diagram for explaining a main configuration of the electric cutting tool according to the present invention; 
         FIG. 10  is a view illustrating a modified form that a movement amount measuring section according to the present invention can take; 
         FIG. 11  is a view illustrating another modified form that the movement amount measuring section according to the present invention can take; 
         FIG. 12  is a view illustrating still another modified form that the movement amount measuring section according to the present invention can take; 
         FIG. 13  is a schematic right side view for illustrating another embodiment of the movement amount measuring section according to the present invention; 
         FIG. 14  is a partially broken-out top view illustrating another embodiment of the movement amount measuring section according to the present invention; 
         FIG. 15  is a view illustrating a modified form of the electric cutting tool according to the present invention shown in  FIG. 7 ; 
         FIG. 16  is an external left side view of the electric cutting tool according to a modified form that the present invention can take; 
         FIG. 17  is a partially broken-out top view of the electric cutting tool according to the modified form; 
         FIG. 18  is an enlarged cross-sectional view of a main part of  FIG. 17 ; 
         FIG. 19  is a view illustrating another modified form that a pivot and an angle sensor shown in  FIG. 18  can take; 
         FIG. 20  is a view illustrating still another modified form that the pivot and the angle sensor shown in  FIG. 18  can take; 
         FIG. 21  is a view illustrating a modified form of the electric cutting tool according to the present invention shown in  FIG. 1 ; 
         FIG. 22  is a view illustrating a modified form of the electric cutting tool according to the present invention shown in  FIG. 2 ; 
         FIG. 23  is a schematic view showing a state where the cutting depth in a perpendicular direction to a processed material changes when the circular saw blade is inclined in a horizontal direction; 
         FIG. 24  is a view showing a desktop type sliding circular saw to which the present invention can be applied; and 
         FIG. 25  is a view for explaining a method of adjusting a cutting depth in the desktop type sliding circular saw shown in  FIG. 24 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, preferred embodiments for implementing the present invention will be described with reference to the appending drawings. In this regard, the embodiments described below do not tend to limit the invention as claimed in each of the claims described below. Further, it is not always true that all of combinations of the features explained in the embodiments are essential for elements of the present invention. 
     A basic structure of an electric cutting tool according to the present invention will first be described with reference to  FIG. 1  to  FIG. 8 . Here,  FIG. 1  is an external front view of the electric cutting tool according to the present invention.  FIG. 2  is an external back view of the electric cutting tool according to the present invention.  FIG. 3  is an external right side view of the electric cutting tool according to the present invention.  FIG. 4  is an external left side view of the electric cutting tool according to the present invention. Further,  FIG. 5  is a cross-sectional view for explaining an internal configuration of the electric cutting tool according to the present invention, and shows a cross-sectional view taken along the line A-A in  FIG. 4 . Moreover,  FIG. 6  is a partially broken-out top view of the electric cutting tool according to the present invention.  FIG. 7  and  FIG. 8  are schematic right side views in each of which a part of the members is omitted for explaining an operation of the electric cutting tool according to the present invention. In particular,  FIG. 7  shows a state when the body portion  21  is in the closest position to the surface plate  11 .  FIG. 8  shows a state when the body portion  21  is tilted upward with respect to the surface plate  11 . In this regard, the case where the electric cutting tool  10  according to the present invention is configured as a handheld radial arm saw is illustrated. Further, directions defined in the present specification match those expressed in “brief description of the drawings” described above, but these directions are defined so as to fit with directions when viewed from an operator who operates an electric cutting tool  10 . 
     The electric cutting tool  10  according to the present invention is configured so as to include: a surface plate  11  mounted on a processed material; a body portion  21  tiltably provided on this surface plate  11 ; and a circular saw blade  41  capable of rotating by means of driving power from a driver such as a motor  25  provided in the body portion  21 . 
     The surface plate  11  is a member on which the body portion  21  is installed. The surface plate  11  is configured so as to have a substantially rectangular shape when viewed from the above (see  FIG. 6 ). Further, a bottom surface of the surface plate  11  is formed as a flat and smooth surface so that the electric cutting tool  10  can stably be mounted on a processed material. By operating the electric cutting tool  10  while causing the bottom surface of the surface plate  11  to slide on the processed material, a stable cutting operation can be made. 
     An opening portion  12  is formed in this surface plate  11 . The opening portion  12  allows the circular saw blade  41  included in the body portion  21  to move up and down. An operator can specify a cutting position of a processed material by viewing the processed material from this opening portion  12 . In this regard, although it is not shown in the drawings, a mark or the like, which becomes alignment for cutting, is formed in the vicinity of the opening portion  12  on an upper surface of the surface plate  11 . Accurate processing can be made by carrying out the cutting processing while aligning this mark with an ink line drawn on a processed material. 
     Further, a safety cover  42  (to be described later) passes through the opening portion  12 . The safety cover  42  is provided for a lower circumference of the circular saw blade  41 . For that reason, the opening portion  12  having a shape based on shapes of the circular saw blade  41 , the safety cover  42  and the like is adopted. In particular, swarf generated from a processed material by means of the rotating circular saw blade  41  is rolled up when cutting processing is carried out. However, since the opening portion  12  is formed so as to be narrowed to a minimum necessary opening range, it is possible to effectively prevent swarf from depositing on the surface plate  11 . 
     The body portion  21  is installed above the surface plate  11  described above in a tiltable state in an up-and-down (vertical) direction (that is, a direction along a rotational direction of a circular saw blade  41 ) and a right-and-left (horizontal) direction (that is, a direction in which the circular saw blade  41  is to be tilted to the side surface). A connecting structure between the surface plate  11  and the body portion  21  for achieving such an action will be described. At a front side of the electric cutting tool  10 , the body portion  21  is rotatably connected to the surface plate  11  via a pivot  22 . The body portion  21  is configured so that a back side of the body portion  21  can be tilted to the vertical direction with respect to the surface plate  11  using this pivot  22  as the center of rotation. Therefore, the operator is allowed to tilt the back side of the body portion  21  to the vertical direction with respect to the surface plate  11 , and to move the circular saw blade  41  to a direction along the rotational direction of the circular saw blade  41  by causing the circular saw blade  41  to protrude or retract from the opening portion  12  of the surface plate  11 . The operator can thus carry out cutting processing by means of the circular saw blade  41 . Further, it is possible to adjust a cutting depth (depth of cut) by adjusting an amount of protrusion of the circular saw blade  41 . 
     In order to fix the body portion  21  described above to a desired tilt position, a link member  13  is installed at the upper surface in the back side direction of the surface plate  11  (see  FIG. 7  and the like). This link member  13  is a member formed so as to extend along a tilt direction of the body portion  21  from the upper surface of the surface plate  11 . A connecting end to the surface plate  11  is tiltably linked to the body portion  21  via the shaft member  14 . Further, a guide hole  13   a  is formed in a body of the link member  13 . This guide hole  13   a  is formed as an opening with a step as shown in  FIG. 7 . An engaging nut  23  is fitted into a step portion of the guide hole  13   a . A lever  23   a  with a screw shaft is attached to the engaging nut  23  by screwing together so as to sandwich the step portion of the guide hole  13   a  between the engaging nut  23  and the lever  23   a . Fastening and loosening of the engaging nut  23  can be carried out by operating the lever  23   a . Namely, by operating the lever  23   a  to loosen fastening of the engaging nut  23  against the guide hole  13   a  of the link member  13 , it becomes possible to tilt the body portion  21  to a desired tilt position. Moreover, by operating the lever  23   a  at a desired position to carry out fastening of the engaging nut  23  against the guide hole  13   a  of the link member  13 , it becomes possible to fix the body portion  21  with a desired tilt position. 
     On the other hand, as shown in  FIG. 1  and  FIG. 2 , the surface plate  11  is connected to the body portion  21  by means of shaft members  15   a ,  15   b  even on its front surface and back surface. By using the shaft members  15   a ,  15   b  as the center of tilt, it is possible to tilt the body portion  21  in the horizontal direction (that is, a direction in which the circular saw blade  41  is to be tilted to the side surface). Further, guide holes  16   a ,  16   b  for defining a tilting range in the horizontal direction of the body portion  21  are formed on both the front side and the back side of the surface plate  11 . Fixing screws  24   a ,  24   b  included in the body portion  21  pass through and are installed in the two guide holes  16   a ,  16   b . A tilt angle of the circular saw blade  41  in the direction to be tilted to the side surface is adjusted by causing the body portion  21  to be tilted in the horizontal direction with respect to the surface plate  11 , and the fixing screws  24   a ,  24   b  are then fastened to the guide holes  16   a ,  16   b , whereby the body portion  21  is fixed. For that reason, the body portion  21  can be fixed at a desired right or left tilt position. Namely, it is possible to set up a desired tilt angle of the circular saw blade  41  in the direction to be tilted to the side surface with respect to the circular saw blade  41 . 
     The body portion  21  includes: a housing  26  for receiving (or housing) the motor  25  that is a driving source; a cover portion  27  that covers an upper portion of the circular saw blade  41 ; and a handle  28  as a gripper (gripping section), which is formed on an upper portion of the housing  26  for operating the electric cutting tool  10 . 
     A switch lever  28   a  for driving rotation of the circular saw blade  41  is provided in the handle  28 . When the operator presses the switch lever  28   a , the motor  25  is driven. Thus, the cutting processing can be implemented by transmitting rotary driving power to the circular saw blade  41 . 
     Further, as shown in  FIG. 3 , an opening  29  is provided at the back of the cover portion  27 . This opening  29  allows swarf generated by a cutting motion of the circular saw blade  41  when the electric cutting tool  10  is used to be discharged to the outside of the cover portion  27 . 
     Moreover, a lower half of the circular saw blade  41  is covered by the safety cover  42 . The safety cover  42  is configured so as to be tilted and stored in the inside of the cover portion  27  that covers the circular saw blade  41  by being pressed by means of a processed material when the processed material is cut. This makes it possible to ensure safety for the operator while the cutting motion is not inhibited. 
     As shown in  FIG. 5 , the motor  25  that is a driving source and a plurality of gear groups for transmitting rotary driving power of the motor  25  to the circular saw blade  41  as a rotary driving power transmitter are housed (or stored) in the inside of the housing  26 . 
     A fan  25   b  is fixed at a front side of a motor shaft  25   a  included in the motor  25 . The fan  25   b  is rotated when the motor  25  is driven, whereby cooled wind is introduced into the housing  26 . Therefore, the motor  25  and the like that become a heat generating source are cooled suitably, and the electric cutting tool  10  can be operated suitably. 
     Further, both ends of the motor shaft  25   a  included in the motor  25  are supported by bearings  31 ,  32 , respectively. A start gear  25   c  is formed at an end portion of the front side of the motor shaft  25   a . On the other hand, a saw blade shaft  41   a  in which the circular saw blade  41  is installed via the plurality of gear groups is installed under the start gear  25   c . The saw blade shaft  41   a  is supported to the inside of the housing  26  via bearings  33 ,  34 . Such a configuration causes a substantially lower half of the circular saw blade  41  to protrude downward from a lower end of the housing  26  via the opening portion  12  of the surface plate  11 . In this regard, an end gear  41   b  is fixed at a tip portion of the saw blade shaft  41   a  that enters the housing  26 . 
     As shown in  FIG. 5 , the gear groups for connecting the start gear  25   c  to the end gear  41   b  are constructed by a first gear  35   a  and a second gear  35   b  that become intermediate gears. The first gear  35   a  and the second gear  35   b  are aligned on the same shaft in series and are fixed on the shaft. 
     In the electric cutting tool  10  according to the present invention having such a configuration, the rotary driving power of the motor  25  is transmitted from the start gear  25   c  of the motor shaft  25   a  to the end gear  41   b  via the first gear  35   a  and the second gear  35   b , and is finally transmitted to the saw blade shaft  41   a . As a result, the circular saw blade  41  is configured to be rotatively driven. 
     The electric cutting tool  10  according to the present invention has a basic configuration explained above. Moreover, the electric cutting tool  10  also has a significant configuration in which a cutting depth and/or an inclination angle of the circular saw blade  41  can be calculated with high accuracy and its calculation result can be displayed at a place arranged at a position viewable for the operator. Now, significant features that the electric cutting tool  10  according to the present invention has will be described using  FIG. 5  to  FIG. 8  and adding  FIG. 9  thereto as a new reference drawing. In this regard,  FIG. 9  is a block diagram for explaining a main configuration of the electric cutting tool  10  according to the present invention. 
     The electric cutting tool  10  according to the present invention includes a movement amount measuring section  50  for measuring a movement amount (distance) of the body portion  21  with respect to the surface plate  11  in response to a tilting action. This movement amount measuring section  50  is configured as an incremental type of encoder that is a conventional technique. Namely, the movement amount measuring section  50  according to the present embodiment is configured by a magnetic scale  51  and a magnetic detecting head  52 . The magnetic scale  51  is installed on the link member  13  included in the surface plate  11 . The magnetic detecting head  52  is installed within the cover portion  27  included in the body portion  21 . 
     The magnetic scale  51  is a member configured as a scale section including scale marks (measurements) arranged at predetermined intervals. More specifically, minute magnetic patterns are recorded in a magnet material, and are utilized as scale marks of a scale (or ruler). The magnetic scale  51  is attached onto the upper side of the link member  13  formed so as to extend along a tilt direction of the body portion  21 . 
     On the other hand, the magnetic detecting head  52  is a member configured as a scale detecting section for detecting the scale marks included in the magnetic scale  51  configured as a scale section. More specifically, the magnetic detecting head  52  is one for measuring a movement amount (distance) of the body portion  21  with respect to the surface plate  11  in response to a tilting action by reading out scale marks of the magnetic scale  51  and converting a read-out result into an electrical signal. 
     In this regard, the magnetic detecting head  52  is swingably attached so as to have a shaft member  52   a  and move along the magnetic scale  51  attached onto the upper side of the link member  13 . For example, when a state of the body portion  21  is shifted from a state where the body portion  21  is held up (or lifted) upward as shown in  FIG. 8  to a state where the body portion  21  is depressed downward as shown in  FIG. 7 , the magnetic detecting head  52  relatively slides on the magnetic scale  51  along a surface of the magnetic scale  51  above the link member  13 , and they can fulfill the function as the movement amount measuring section  50  suitably. 
     On the other hand, a calculation and display section  60  is installed between the handle  28  as the gripper included in the body portion  21  and the cover portion  27  (see  FIG. 5  and  FIG. 6 ). This calculation and display section  60  includes: at least a calculating section  61  as a CPU (Central Processing Unit) used to calculate a cutting depth of the circular saw blade  41  or an inclination angle of the body portion  21  on the basis of a movement amount (distance) obtained by the movement amount measuring section  50  described above; and a display section  62  as a digital liquid crystal screen used to display the cutting depth or the inclination angle of the body portion  21  calculated by the calculating section  61 . Moreover, in the present embodiment, the calculation and display section  60  is configured so as to include a storage section  63  as a HDD (Hard disk drive). Data calculated by the calculating section  61 , basic data and arithmetic expressions of the electric cutting tool  10  used for calculation are stored in the storage section  63 . 
     In this regard, an installed position of the calculation and display section  60  is provided between the handle  28  and the cover portion  27  as shown in  FIG. 2 ,  FIG. 5  and  FIG. 6 . For this reason, it becomes an installed position remarkably viewable for the operator. Further, as shown in  FIG. 5  particularly, the electric cutting tool  10  is configured so that a height of the calculation and display section  60  is lower than a virtual line α connecting an uppermost position of the handle  28  and an uppermost position of the cover portion  27  when the A-A cross section is viewed, and the height of the calculation and display section  60  is further lower than a virtual line β connecting a lowermost position of the switch lever  28   a  included in the handle  28  and the uppermost position of the cover portion  27 . Such a configuration fulfills a suitable effect that it is easy for the operator to view the calculation and display section  60  and it does not disturb the operator who grips the handle  28 . A form and an arrangement of the calculation and display section  60  are adopted in view of operability of the electric cutting tool  10 . Moreover, by making the installed position of the calculation and display section  60  lower than the virtual line α, it is possible to avoid contact of an object with the calculation and display section  60  and application of impact force even though the electric cutting tool  10  is hit with the object or dropped on the ground. Therefore, it is possible to reduce the possibility that the calculation and display section  60  is damaged or broken down. 
     In the present embodiment, when the body portion  21  is operated, the magnetic detecting head  52  sliding on the magnetic scale  51  measures a movement amount (distance) of the body portion  21  with respect to the surface plate  11  in response to a tilting action. Data obtained by the measurement are transmitted (or sent) from the magnetic detecting head  52  that is the scale detecting section to the calculating section  61 . The calculating section  61  obtaining measured data on the movement amount (distance) of the body portion  21  converts the measured data into a cutting depth of the circular saw blade  41 . On this conversion, the calculating section  61  reads out calculation conditions, in which a conversion expression based on a shape of the electric cutting tool  10  stored in the storage section  63 , a diameter of the circular saw blade  41  and the like are set up in advance, from the storage section  63 , and calculates the cutting depth and/or the inclination angle of the circular saw blade  41 . A calculation result obtained by the calculating section  61  is transmitted to the display section  62 , and is instantly displayed on the digital liquid crystal screen included in the display section  62 . 
     In this regard, the display section  62  allows a desired display form to be selected from various display forms. For example, a display unit of the cutting depth can be converted into any of various units such as “inch” based on the Imperial system and “Cun (=3.03 centimeters)” based on the Japanese measuring system in addition to “millimeter (mm)” based on the SI system of unit, and a converted unit can be displayed. In such a conversion and display process, when the operator pushes a unit switching button (not shown in the drawings), a unit switching command by an electrical signal is transmitted from the display section  62  to the calculating section  61 , and the calculating section  61  receiving this command again transmits a display command by a new unit to the display section  62 . This makes it possible to achieve selection of the display form. 
     The movement amount measuring section according to the present embodiment can measure not only a movement amount of the body portion  21  in response to a tilting action in a vertical direction (that is, a direction along a rotational direction of the circular saw blade  41 ), but also a movement amount by a tilting action in a horizontal direction (that is, a direction in which the circular saw blade  41  is to be tilted to the side surface). For example, as shown in  FIG. 1  and  FIG. 6 , a magnetic scale  51 ′ is attached to an upper surface of a member in which the guide hole  16   a  for defining the tilting range of the body portion  21  in the horizontal direction is formed, and a magnetic detecting head  52 ′ is installed at a side of the body portion  21 , which faces this magnetic scale  51 ′. Thus, a movement amount measuring section  50 ′ capable of fulfilling a function similar to that of the movement amount measuring section  50  described above can be configured. In the case of the movement amount measuring section  50 ′, the calculating section  61  calculates measured data of the movement amount (distance) obtained by the magnetic detecting head  52 ′ as the inclination angle of the body portion  21  with similar processing to the above processing. The inclination angle of the body portion  21  thus obtained is instantly displayed on the digital liquid crystal screen included in the display section  62 . However, even in this case, any display form can be selected. For example, the display form can be changed into desired representation such as representation by “prime (′)” and “radian (rad)” in addition to “degree (°)”. 
     In this regard, the movement amount measuring sections  50 ,  50 ′ described above are configured as the incremental type of encoder that is a known art. Although explanation of its principle of operation is omitted, it is noted that an operation to carry out zero point adjustment and the like are required for every measurement. 
     As described above, the suitable embodiment of the present invention has been explained, but a technical scope of the present invention is not limited to the scope described in the above embodiment. A variety of changes and modifications can be added to the above embodiment. 
     For example, although a tip saw has been used as the circular saw blade  41  according to the embodiment described above, the present invention can be applied to any form of circular saw blade such as a diamond plate and a cutter for digging a groove. 
     Further, for example, in the embodiment described above, as shown in  FIG. 7 , the magnetic detecting head  52  was swingably attached via the shaft member  52   a  so as to move along the magnetic scale  51  attached onto the upper side of the link member  13 . However, means for attaching the magnetic detecting head  52  in a swingable state is not limited to one in which the shaft member  52   a  is used. As a concrete modified example, as shown in  FIG. 10 , a configuration in which a magnetic detecting head  52  is connected to an inner surface of a cover portion  27  via a tiltable link arm  71  and a torsion coil spring  72  is installed on this link arm  71  can be adopted. According to such a configuration, elastic force of the torsion coil spring  72  is always exerted on the magnetic detecting head  52  via the link arm  71 , and the magnetic detecting head  52  is always pressed to the magnetic scale  51 . For that reason, it is possible to maintain a suitable measurement state. In this regard, by providing packing members  73 ,  73  made of an elastic member such as a rubber plate in the vicinity of contact points of the magnetic detecting head  52  with the magnetic scale  51 , it is possible to prevent refuse such as swarf and dust from entering between the magnetic scale  51  and the magnetic detecting head  52 . Thus, it is preferable. 
     Further, for example, as shown in  FIG. 11 , means capable of always pressing the magnetic detecting head  52  toward the magnetic scale  51  suitably can be realized by providing a compression coil spring  74  between the magnetic detecting head  52  and the inner surface of the cover portion  27 . By using the compression coil spring  74  illustrated in  FIG. 11 , operations and effects similar to those realized by the link arm  71  and the torsion coil spring  72  can also be obtained. 
     Further, an arrangement position of the magnetic scale  51  and the magnetic detecting head  52  that construct the movement amount measuring section  50  is not limited to the embodiment described above. Any modified form can be adopted within a range capable of fulfilling the similar function. In the embodiment described above, as shown in  FIG. 7  and the like, the magnetic scale  51  and the magnetic detecting head  52  are arranged so as to face each other in the vertical direction. However, for example, as shown in  FIG. 12 , a magnetic scale  51 ″ and a magnetic detecting head  52 ″ that construct a movement amount measuring section  50 ″ can be arranged so as to face each other in the horizontal direction. In this case, as a member in which the magnetic scale  51 ″ and the magnetic detecting head  52 ″ are installed, any form arbitrarily changed depending upon a condition of the arrangement place can be adopted. For example, as shown in  FIG. 12 , by using a link member  13 ″ including a flange-like shape, the magnetic scale  51 ″ can be arranged at a stable place on which maintenance or the like is easily carried out. 
     Further, although the case where each of the movement amount measuring sections  50 ,  50 ′,  50 ″ according to the present embodiment described above is configured as an incremental type of encoder has been illustrated, the movement amount measuring section of the present invention can be configured as a capacitive absolute encoder. By adopting an absolute encoder as the movement amount measuring section, it is not required to carry out zero point adjustment for every measurement. This makes it possible to improve handleability thereof dramatically. 
     Further, the scale section and the scale detecting section constructing the movement amount measuring section according to the present invention are not limited to the magnetic scales  51 ,  51 ′,  51 ″ and the magnetic detecting heads  52 ,  52 ′,  52 ″ as described above, respectively. For example,  FIG. 13  and  FIG. 14  are views for illustrating another embodiment of the movement amount measuring section according to the present invention. As shown in  FIG. 13  and  FIG. 14 , the scale section can be configured as a rack  81  in which teeth for scale marks are cut at predetermined intervals, and the scale detecting section can be configured as a pinion  82  for measuring a movement amount (distance) of the body portion  21  with respect to the surface plate  11  in response to a tilting action by causing the pinion  82  to carry out a rotary motion while engaging with the rack  81  and detecting an amount of rotary motion. By constructing a movement amount measuring section  80  by the rack  81  and the pinion  82  in this manner and obtaining the amount of rotation of the pinion  82  by means of the calculating section  61 , the movement amount (distance) of the body portion  21  with respect to the surface plate  11  can be grasped. Therefore, the cutting depth of the circular saw blade  41  can be calculated on the basis of the measured data, and the calculation result can be displayed on the display section  62 . 
     Further, the storage section  63  included in the calculation and display section  60  according to the present embodiment as described above can be omitted. Namely, in the case where a configuration in which the calculation process is carried out using the calculating section  61  and the calculation result and the like are not stored is selected, it is possible to obtain a reduction effect of production costs by omitting the storage section  63 . 
     Further, each of the movement amount measuring sections  50 ,  50 ′,  50 ″ according to the present embodiment described above is one that detects a moving distance of a member. However, values detected by the movement amount measuring section of the present invention are not limited to the moving distance data. For example, the movement amount measuring section of the present invention can be configured so as to detect a movement amount as inclination angle data. 
     More specifically, as the electric cutting tool  10 ′ shown in  FIG. 15 , which illustrates a modified form of the electric cutting tool  10  according to the present invention shown in  FIG. 7 , an angle sensor  90  as the movement amount measuring section is provided at a position of a shaft member ( 14 ) for tiltably linking the link member  13  to the surface plate  11 , and a tilt angle of the link member  13  with respect to the surface plate  11  is measured. This makes it possible to obtain a cutting depth or an inclination angle of the circular saw blade  41  with high accuracy. The angle sensor  90  installed at the portion of the shaft member ( 14 ) detects the movement amount as inclination angle data. Such a configuration can also be adopted suitably as the movement amount measuring section of the present invention. 
     In this regard, as shown in  FIG. 15 , the angle sensor  90  can also be installed at a portion of a pivot ( 22 ) for rotatably connecting the body portion  21  to the surface plate  11  in addition to the portion of the shaft member ( 14 ). A cutting depth and/or an inclination angle of the circular saw blade  41  can also be obtained with high accuracy by measuring a tilt angle of the body portion  21  with respect to the surface plate  11 . In this regard, two angle sensors  90  have been illustrated at two portions including the portion of the shaft member ( 14 ) and the portion of the pivot ( 22 ) in  FIG. 15 . This is drawn for illustrating installable portions of the angle sensor  90 . So long as the angle sensor  90  is provided at any one portion, it is possible to suitably fulfill the function as the movement amount measuring section according to the present invention (of course, a plurality of angle sensors  90  each of which fulfills the same function may be provided at a plurality of portions). 
     Here, a concrete example of the case where the angle sensor  90  is provided at the portion of the pivot ( 22 ) will be described with reference to  FIG. 16  to  FIG. 18 . Here,  FIG. 16  is an external left side view of the electric cutting tool  10 ′ according to the modified form that the present invention can take.  FIG. 17  is a partially broken-out top view of the electric cutting tool  10 ′ according to the modified form. Further,  FIG. 18  is an enlarged cross-sectional view of a main part of  FIG. 17 . 
     In the electric cutting tool  10 ′ shown in  FIG. 16  to  FIG. 18 , the pivot  22  is installed fixedly to a supporting member  101  installed fixedly to the surface plate  11 . Moreover, the cover portion  27  included in the body portion  21  is tiltably connected to this pivot  22  (see  FIG. 18 , particularly). 
     A flange portion  22   a  is formed in the vicinity of a shaft end of the pivot  22  at a left side. The angle sensor  90  and a casing for installing a display section (display section installing casing)  64  are installed at a portion of a further left shaft end of the flange portion  22   a  in this order toward the shaft end. 
     The flange portion  22   a  is a member formed integrally with the pivot  22 . A dust-proof packing  22   b  made of an O-ring is installed at an outer circumference of the flange portion  22   a . The dust-proof packing  22   b  is installed between the flange portion  22   a  and the display section installing casing  64 . Therefore, it is possible to surely prevent refuse such as swarf and liquid from scattering or invading (or breaking) into the angle sensor  90  that is precision mechanical equipment. Installation of the dust-proof packing  22   b  allows a prevention effect of damage and a false operation of the angle sensor  90  to be obtained suitably. 
     The display section installing casing  64  becomes a state where the display section installing casing  64  can be tilted with respect to the pivot  22  integrally with the body portion  21  including the cover portion  27 . Further, the calculation and display section  60  including the display section  62  is integrally installed on the display section installing casing  64 . Moreover, a battery  65 , which becomes a power source for the calculation and display section  60 , is installed within the display section installing casing  64 . This installation position of the battery  65  is a left side of the electric cutting tool  10 ′ and no impeditive member exists on its front surface. For that reason, the electric cutting tool  10 ′ has a configuration by which maintenance such as replacement of the battery  65  can be carried out very easily. 
     Further, although the battery  65  is installed at an installation portion of a lid member  64   a  that is opened and closed when the battery  65  is replaced, a dust-proof packing (not shown in the drawings) is installed between the lid member  64   a  and the display section installing casing  64 . For that reason, a configuration is adopted in which it is possible to surely prevent refuse and liquid from invading into the inside of the display section installing casing  64  from a space between the lid member  64   a  and the display section installing casing  64 . 
     The angle sensor  90  is installed at the position sandwiched between the flange portion  22   a  and the display section installing casing  64  described above. The angle sensor  90  included in the electric cutting tool  10 ′ is constructed from a first substrate  90   a  fixed to the display section installing casing  64  and a second substrate  90   b  fixed to the flange portion  22   a . Since the first substrate  90   a  is fixed to the display section installing casing  64 , the first substrate  90   a  carries out a rotary motion with a tilting action when the body portion  21  carries out the tilting action using the pivot  22  as the center of rotation. On the other hand, since the second substrate  90   b  is fixed to the flange portion  22   a  that is fixed and not rotated, the second substrate  90   b  always maintains a fixed state. Therefore, when a tilting action for the body portion  21  is carried out, the first substrate  90   a  carries out the rotary motion with respect to the fixed second substrate  90   b . It is possible to grasp an amount of change of an angle of the tilting action for the body portion  21  by detecting an amount of change of the rotary motion. As a result, it is possible to measure a cutting depth of the circular saw blade  41  or the like. 
     In this regard, in the modified form example shown in  FIG. 16  to  FIG. 18 , a configuration in which two members including the calculation and display section  60  and the angle sensor  90  are installed to the display section installing casing  64  provided with the battery  65  that is a power source is adopted. Thus, there are advantages that no wiring is required and the configuration has good assemblability compared with another embodiment and is excellent in a dust-proof function. Moreover, as is apparent from  FIG. 16 , the display section installing casing  64  and the calculation and display section  60  are arranged so as not to protrude from an outline of the body portion  21  including the cover portion  27 . For this reason, even when the electric cutting tool  10 ′ is mounted in any posture, the display section installing casing  64  and the calculation and display section  60  are hardly in contact with the ground, and thus, troubles such as breakage never occur. 
     As described above, although the suitable modified form examples that the present invention can take have been explained, a further modified form can be adopted for the pivot  22  and the angle sensor  90 . For example, the pivot  22  of the electric cutting tool  10 ′ shown in  FIG. 18  in detail penetrates through the display section installing casing  64 . However, as shown in  FIG. 19 , a configuration in which a shaft tip of the pivot  22  at the left side surface becomes a flange portion  22   a , the angle sensor  90  and the display section installing casing  64  are installed at the outside of the flange portion  22   a , and the pivot  22  is not directly in contact with the display section installing casing  64  can be adopted. Further, for example, the pivot  22  and the flange portion  22   a  of the electric cutting tool  10 ′ shown in  FIG. 18  in detail are integrally configured. However, as shown in  FIG. 20 , a configuration in which a flange portion  22   a  is divided from a pivot  22  and each of the pivot  22  and the flange portion  22   a  is installed fixedly to the supporting member  101  can be adopted. In this regard, in the case of the configuration shown in  FIG. 19  and  FIG. 20 , the pivot  22  does not penetrate through and protrude out of the display section installing casing  64  unlike the configuration shown in  FIG. 18 . Therefore, it is advantageous that refuse and liquid can be surely prevented from invading into the inside of the display section installing casing  64  (that is, the angle sensor  90 ). 
     Namely, as the forms of the members constructing the electric cutting tool according to the present invention, various kinds of modified forms can be adopted within a range capable of fulfilling the operations and effects of the present invention as described above. 
     Moreover, as shown in  FIG. 21  and  FIG. 22 , the movement amount measuring section (angle sensor  90 ) for detecting a movement amount as inclination angle data can be installed to the shaft members ( 15   a ,  15   b ), which become the center of a tilting action, in the horizontal direction of the body portion  21  with respect to the surface plate  11  (that is, a direction in which the circular saw blade  41  is to be tilted to the side surface). In this case, so long as the angle sensor  90  is installed to any one of the shaft members ( 15   a ,  15   b ), an object of measuring the movement amount as the inclination angle data is achieved. The angle sensor  90  installed in such a configuration allows the operator to obtain an inclination angle in the horizontal direction of the circular saw blade  41  with high accuracy. In addition, as shown in  FIG. 18  and the like, one having a form configured by two members including the first substrate  90   a  and the second substrate  90   b  can also be adopted as the movement amount measuring section (angle sensor  90 ) for detecting a movement amount as inclination angle data. 
     In this regard, in the case where the circular saw blade  41  is tilted in the horizontal direction, as shown in  FIG. 23 , a cutting depth in a perpendicular direction to a processed material W changes. Namely, in the case where an inclination angle of the circular saw blade  41  in the horizontal direction is not set, a cutting depth of the processed material W in the perpendicular direction is defined as a cutting depth D 1 . In the case where an inclination angle of the circular saw blade  41  in the horizontal direction is set, a cutting depth of the processed material W in the perpendicular direction is defined as a cutting depth D 2 . A relationship between the cutting depth D 1  and the cutting depth D 2  of course meets D 1 &gt;D 2 . Therefore, in order to display a correct cutting depth on the display section  62 , the movement amount measuring section is caused to detect an inclination angle of the circular saw blade  41  in the horizontal direction, and the calculating section  61  is required to carry out a correction process according to this tilt angle on the basis of the detected data. As the movement amount measuring section in this case, it is necessary to use both the movement amount measuring section for measuring the inclination angle data, such as the movement amount measuring section  50 ′ constructed by the magnetic scale  51 ′ and magnetic detecting head  52 ′, or the angle sensor  90 , and the movement amount measuring section for measuring the moving distance data, such as the movement amount measuring section  50  constructed by the magnetic scale  51  and the magnetic detecting head  52 , in combination. Adoption of such a configuration allows the cutting depth of the circular saw blade  41  to be obtained with high accuracy. 
     However, installation of both the movement amount measuring section ( 50 ′,  90  and the like) for measuring the inclination angle data and the movement amount measuring section ( 50  and the like) for measuring the moving distance data to the electric cutting tool is not a necessary requirement for the present invention. Any one of the movement amount measuring sections may be provided, or both of the movement amount measuring sections may be provided. Thus, any combination can be adopted. For example, in the case of the electric cutting tool in which only the movement amount measuring section for measuring moving distance data is installed, the cutting depth D 2  of the circular saw blade  41  in the perpendicular direction to the processed material W cannot be grasped when the circular saw blade  41  is tilted in the horizontal direction. However, a cutting depth in an oblique direction can be grasped. Namely, in the electric cutting tool according to the present invention, it is preferable to select a configuration of the movement amount measuring section and the like described above in accordance with various specific conditions such as use application of the electric cutting tool and a production cost. 
     Further, the case where the electric cutting tool  10  according to the present invention described above is configured as a handheld radial arm saw has been illustrated. However, the present invention can be applied to any other type of electric cutting tool within a range capable of fulfilling the similar operation and effect to the embodiments described above and various modified forms. 
     For example, the present invention can also be applied to a desktop type sliding circular saw  110  as shown in  FIG. 24 . In the case of this sliding circular saw  110 , a table  111  and a tilt supporting section  112  correspond to the surface plate of the present invention, and a cutting machine body  113  corresponds to the body portion of the present invention. However, the cutting machine body  113  is installed to the tilt supporting section  112  attached to the table  111  in a tiltable state. The tilt supporting section  112  is connected to the cutting machine body  113  by means of a pivot  114 . By attaching the calculation and display section  60  with the display section installing casing  64  or the angle sensor  90  to a portion of this pivot  114 , it becomes possible to grasp a tilt movement amount of the cutting machine body  113 , that is, a cutting depth of the circular saw blade  41 . 
     In this regard, by providing an adjusting screw  115  as a lower limit stopper and a stopper abutting section  116  between the tilt supporting section  112  and the cutting machine body  113  to the sliding circular saw  110  shown in  FIG. 24 , it is possible to adjust a lower limit position of a tilting action of the cutting machine body  113 . As for a method of adjusting the lower limit position, an amount of protrusion of the adjusting screw  115  can be adjusted in advance, or the lower limit position can be adjusted while viewing the display section  62  of the calculation and display section  60  in a state where the adjusting screw  115  abuts upon the stopper abutting section  116 . 
     Moreover, as a method of adjusting a cutting depth of the desktop type sliding circular saw  110  shown in  FIG. 24 , as shown in  FIG. 25 , when the operator wants to grasp a cutting depth (A) with respect to a processed material W, an (a) surface, which is an upper surface of the processed material W, may be set as a point of origin (zero point). Further, when the operator wants to grasp a height (B) with respect to a base surface of the table  111 , a (b) surface, which is the base surface of the table  111 , may be set as a point of origin (zero point). Thus, compared with the desktop type sliding circular saw  110  in which the point of origin (zero point) must be adjusted in accordance with use application or an object of cutting, by providing the angle sensor  90  as the movement amount measuring section of the present invention, it is possible to realize an electric cutting tool with nonconventional high operability or improved processing accuracy. 
     It is apparent from the following claims that embodiments to which such changes and modifications are added can be included in a technical scope of the present invention.