Abstract:
An electric-powered cutting machine includes a reciprocable plunger held by and protruding outward from a housing; an operation member capable of being pivoted on the housing; and a blade holding mechanism disposed at a tip end portion of the plunger, the blade holding mechanism causing a blade to be detachably attached to the plunger. The operation member includes an operation portion and an abutting portion, wherein a distance from the operation portion to a rotating fulcrum is longer than a distance from the abutting portion to the rotating fulcrum. The blade holding mechanism is biased and is capable of swinging, and the blade holding mechanism includes a rotating member capable of being pressed against a side of the blade, wherein the abutting portion abuts against the rotating member when the operating member swings, and wherein the blade is detachably attached to the plunger by swinging of the rotating member.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a Continuation of U.S. application Ser. No. 10/419,169, filed on Apr. 21, 2003 now U.S. Pat. No. 7,216,434. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a jigsaw type electric-power cutting machine having a blade holding mechanism. 
     2. Background Art 
     A conventional electric-powered cutting machine will be described with reference to  FIGS. 1 and 18 , taking a jigsaw as an example. 
     As shown in  FIG. 1 , a jigsaw includes: a housing  2  which has a switch  4  and a handle  3 , in which a base  5  that serves as a guiding member during a cutting operation is attached to a lower side, and which houses an electric motor  100  as is known in the art and that is schematically shown in  FIG. 1 ; and a plunger  1  which reciprocates in the vertical directions in the figure by a turning force of the electric motor  100 . In the illustrated jigsaw, the plunger  1  is covered by a cover  6  which is formed by a transparent member. An upper portion of the plunger  1  is reciprocatively held inside the housing  2 , and a lower portion protrudes to the outside from the housing  2 . A blade  7  is detachably held by the lower portion of the plunger  1 . 
     As shown in  FIG. 18 , the conventional jigsaw has a configuration in which a locking screw  28  that presses against a flat face of the blade  7 , and a support member  29  that supports a flat face of the blade  7  on the side opposite in the pressing direction are attached to the tip end of the plunger  1 . When the blade  7  is inserted into the plunger  1 , the blade  7  can be fixed to the plunger  1  by fastening the locking screw  28 . 
     However, the above-mentioned configuration has the inconvenience that it is necessary to use a tool for operating the locking screw  28  during a work of replacing the blade  7 . Apparently, the fastening force acting on the locking screw  28  is variously changed depending on the worker, thereby causing a problem in that, when the fastening force is excessively large, the blade  7  is deformed. 
     As a jigsaw for solving the problem, European Patent Nos. 722,802 and 855,239 disclose a configuration in which a work of replacing a blade can be conducted without using a tool or the like. 
     SUMMARY OF THE INVENTION 
     Among the conventional jigsaws, the jigsaw disclosed in European Patent No. 722,802 is configured in the following manner. When a lever disposed on the tip end of a plunger is operated without using a tool, two projections. for preventing a blade from slipping off are engaged with a wall face which is perpendicular to a tip end face of the plunger, whereby the blade can be fixed easily and irrespective of a force exerted by the worker. 
     Since the lever having a relatively large size is disposed on the tip end of the plunger, the plunger is heavy. Therefore, the jigsaw has a disadvantage that, during a cutting work, the plunger largely vibrates. In the plunger, an opening for inserting a blade is not clearly formed. In a work of inserting a blade into the plunger, therefore, the blade may be erroneously inserted with being inclined. In this case, there is the possibility that the blade is fixed while maintaining the inclined state. Such an inclined blade greatly affects the cutting accuracy. 
     The jigsaw disclosed in European Patent No. 855,239 has a configuration which can solve the problem in the blade fixing method by screwing, in the same manner as that disclosed in European Patent No. 722,802, and in which the problem discussed with respect to that disclosed in European Patent No. 722,802 is solved by disposing a clear opening for inserting a blade, and by performing the fixation through a remote operation using a lever that is disposed in a place different from the plunger. 
     In the configuration, a spring pressing a moving member must be designed so that the spring can be placed in a gap formed between the moving member and an outer hull, while the gap is narrowed by the remote operation using the lever. When the lever is released and the moving member is moved to a position where the member presses the blade, the spring is stretched to some extent and the pressing force is lost. In order to compensate the pressing force, therefore, a number springs must be placed in the gap. As a result, the total weight of the plunger is increased. In a jigsaw in which a plunger reciprocates at a high speed, the increased weight tends to adversely affect vibrations of the main unit of the jigsaw. 
     It is an object of the invention to provide a jigsaw which can eliminate the above-discussed disadvantages, and in which, without increasing the weight of a plunger, vibrations during a cutting work can be suppressed and blade replacement can be conducted easily and in a short time. 
     The object can be attained by configuring a blade holding mechanism so as to comprise: a blade receiving face including a groove having a shape which is substantially identical with a shape of an attachment portion of a blade including projections; a swinging member having: one end which has a swing fulcrum that elongates in a direction substantially identical with a longitudinal direction of a plunger, and a blade pressing portion that can be placed in a place opposed to the groove; and another end which elongates to separate from the plunger; and a pressing member which presses the one end of the swinging member toward the groove of the plunger. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention may be more readily described with reference to the accompanying drawings: 
         FIG. 1  is a perspective view showing an embodiment of the electric-powered cutting machine of the invention. 
         FIG. 2  is an enlarged bottom view of main portions showing the embodiment of the electric-powered cutting machine of the invention. 
         FIG. 3  is a section view taken along the line A-A in  FIG. 2 . 
         FIG. 4  is a section view taken along the line B-B in  FIG. 3 . 
         FIG. 5  (views  a  and  b ) shows an enlarged front view of main portions and a side view showing an example of a blade. 
         FIG. 6  is a section view taken along the line C-C in  FIG. 3 . 
         FIG. 7  is an enlarged bottom view of main portions showing an operation state of the electric-powered cutting machine of the invention. 
         FIG. 8  is an enlarged bottom view of main portions showing an operation state of the electric-powered cutting machine of the invention. 
         FIG. 9  is an enlarged bottom view of main portions showing an operation state of the electric-powered cutting machine of the invention. 
         FIG. 10  is an enlarged bottom view of main portions showing an operation state of the electric-powered cutting machine of the invention. 
         FIG. 11  is an enlarged bottom view of main portions showing another embodiment of the electric-powered cutting machine of the invention. 
         FIG. 12  is an enlarged bottom view of main portions of  FIG. 11  showing an operation state of the other embodiment of the electric-powered cutting machine of the invention. 
         FIG. 13  is an enlarged bottom view of main portions of  FIG. 11  showing an operation state of the other embodiment of the electric-powered cutting machine of the invention. 
         FIG. 14  is an enlarged bottom view of main portions of  FIG. 11  showing an operation state of the other embodiment of the electric-powered cutting machine of the invention. 
         FIG. 15  is a section view taken along the line D-D in  FIG. 11  showing the other embodiment of the electric-powered cutting machine of the invention. 
         FIG. 16  is an enlarged bottom view of main portions of  FIG. 15 . 
         FIG. 17  is a section view taken along the line D-D in  FIG. 11  showing an operation state of the other embodiment of the electric-powered cutting machine of the invention. 
         FIG. 18  shows an enlarged front view of main portions and a side view showing an example of a conventional electric-powered cutting machine. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of the jigsaw of the invention will be described with reference to  FIGS. 1 to 10 .  FIG. 1  is a perspective view showing a state where the blade  7  is attached to a tip end portion of the plunger  1 ,  FIG. 2  is an enlarged bottom view of main portions showing a blade holding mechanism,  FIG. 3  is a section view taken along the line A-A in  FIG. 2 , and  FIG. 4  is a section view taken along the line B-B in  FIG. 3 . 
     As shown in  FIG. 5 , the blade  7  which can be attached to and detached from the jigsaw of the invention has an attachment portion  7   a  including a pair of projections  7   b  which elongate perpendicular to the longitudinal direction of the blade  7 . 
     A blade holding portion  8  is disposed in the tip end of the plunger  1  as shown in the figures. A bottom face  9  which extends perpendicular to the longitudinal direction of the plunger  1 , and in which a hole  9   a  is formed, is disposed on the blade holding portion  8  on the side of the base  5 . The hole  9   a  has a thickness (see  FIG. 2 ) which is smaller than the width T of the attachment portion  7   a  of the blade  7 , and a dimension L which is larger than a dimension V between the projections  7   b . The dimension V is the maximum width of the attachment portion  7   a  of the blade  7 . The blade holding portion  8  has an upper face  10  which extends in parallel with the bottom face  9 , and which is positioned in the vicinity of the lower end face of the plunger  1 . A blade receiving face  11  which extends substantially parallel to the longitudinal direction of the plunger  1  is positioned between the bottom face  9  and the upper face  10  and in the vicinity of the middle of the plunger  1 . 
     As shown in  FIG. 3 , a groove  11   a  having a shape which is substantially identical with that of the attachment portion  7   a  of the blade  7  is formed in the blade receiving face  11 . The hole  9   a  of the bottom face  9  communicates with the groove  11   a.    
     A pin  12  which is held by the upper face  10  and the bottom face  9  of the blade holding portion  8  is disposed between the upper face  10  and the bottom face  9 . A swinging member  13  which uses the pin  12  as a swing fulcrum is held by the blade holding portion  8 . 
     As shown in  FIG. 4 , the swinging member  13  has an approximately V-like shape, and is attached so that the pin  12  serving as a swing fulcrum is positioned in a substantially middle portion of the member. One end  13   a  of the member is always pressed toward the blade receiving face  11  by a spring  14  which is a pressing member for pressing an end portion of the member. The one end  13   a  of the swinging member  13  has a shape which can be placed substantially parallel to the blade receiving face  11 , and has a hemispherical convex portion  13   c  in a place corresponding to the middle portion of the groove  11   a . The convex portion protrudes toward the groove  11   a  to serve as a blade pressing portion. The center position of the pin  12  is located substantially on an extended line of the blade receiving face  11 , whereby the one end  13   a  of the swinging member  13  is allowed to be easily placed substantially parallel to the blade receiving face  11  as described above. 
     Although the one end  13   a  of the swinging member  13  is positioned between the upper face  10  and the bottom face  9  of the blade holding portion  8 , the other end  13   b  is not positioned between the upper face  10  and the bottom face  9 , and has a shape which elongates so as to separate from the blade receiving face  11  or radially outwardly separate from the plunger  1 . 
     As shown in  FIGS. 4 and 6 , a hole  1   a  having an inner wall face which is substantially flush with the face of the groove  11   a  is formed in the plunger  1 . When the blade  7  is attached, an end of the attachment portion  7   a  of the blade is positioned in the hole  1   a  of the plunger  1 . 
     In the housing  2 , a lever  15  which serves as an operation member, and which has a swing fulcrum  15   c  that elongates in a direction substantially identical with the longitudinal direction of the plunger  1  is disposed on the housing  2  so as to cover the blade holding portion  8 . In the lever  15 , an abutting portion  15   b  which can abut against the other end  13   b  of the swinging member  13  is disposed at a position close to the swing fulcrum  15   c , and an operation portion  15   a  is formed in a place which is remote from the abutting portion  15   b.    
     The lever  15  is pressed by a pressing member such as a torsion spring which is not shown, so as to be located at the position shown in  FIG. 2 . The lever can be swung with using the swing fulcrum  15   c  as a fulcrum, by operating the operation portion  15   a.    
     When the lever  15  is swung, as shown in  FIG. 7 , the abutting portion abuts against the other end  13   b  of the swinging member  13 . When the lever  15  is further swung, the shape of the abutting portion  15   b  causes the swinging member  13  to be swung so that the other end  13   b  of the swinging member  13  is moved toward the blade receiving face  11  against the pressing force of the spring  14 . 
     When the operation of swinging the lever  15  is cancelled in the state of  FIG. 7 , the lever  15  is returned to the state shown in  FIG. 2  by the pressing member (not shown). As previously described, the pressing member can be formed by a torsion spring. In accordance with this returning operation, the swinging member  13  is swung by the urging force of the spring  14  so that the one end  13   a  is moved toward the blade receiving face  11 , and the other end  13   b  is moved to radially outwardly separate from the plunger  1 , with the result that also the swinging member  13  is returned to the state shown in  FIG. 2 . 
     Next, the operation to be performed. when the blade  7  is attached to the blade holding portion  8  will be described. 
     First, the lever  15  is swung against the pressing member as described above to cause the swinging member  13  to swing against the pressing force of the spring  14 . The lever  15  is then held to the state shown in  FIG. 7 . 
     In this state, the attachment portion  7   a  of the blade  7  is inserted into the blade holding portion  8  via the hole  9   a  of the bottom face  9  of the blade holding portion  8 . The attachment portion  7   a  of the blade  7  is then engaged with the groove  11   a  of the blade receiving face  11 , and the holding of the lever  15  is cancelled. As shown in  FIG. 8 , therefore, the lever  15  is returned to the state shown in  FIG. 2 , and also the swinging member  13  is returned to the state shown in  FIG. 2 . This causes the convex portion  13   c  on the one end  13   a  of the swinging member  13  to press the flat face of the attachment portion  7   a  of the blade  7  engaged with the groove  11   a . As a result, the work of attaching the blade  7  to the blade holding portion  8  is ended. 
     The blade  7  attached to the blade holding portion  8  is prevented from downward slipping off, by the projections  7   b  of the blade  7  and the groove  11   a  opposed to the projections  7   b . The upward movement of the blade  7  is. restricted by butting of the upper faces of the projections  7   b  of the blade  7  against the inner wall face of the upper face of the blade holding portion  8 . 
     In the jigsaw of the embodiment, as shown in  FIG. 10 , the abutting portion  15   b  of the lever  15  has a shape which elongates in a direction substantially identical with the longitudinal direction of the plunger  1 . This configuration is employed because of the following reason. Even when the blade holding portion  8 , i.e., the other end  13   b  of the swinging member  13  against which the abutting portion  15   b  abuts is at any position in the reciprocal motion range of the plunger  1 , the abutting portion  15   b  of the lever  15  can abut against the other end  13   b  of the swinging member  13  to enable the blade  7  to be attached or detached. 
     The jigsaw of the embodiment is configured so that, as shown in  FIG. 2 , a through hole  11   b  which communicates with the groove  11   a  is formed in the blade receiving face  11 . A projecting portion  13   d  is capable of being inserted into the through hole  11   b  to protrude into the groove  11   a . The projecting portion  13   d  is disposed on the other end  13   b  of the swinging member  13 . According to the configuration, when the lever  15  is swung in the work of detaching the blade  7 , the projecting portion  13   d  functions to cause the blade  7  to automatically slip off from the blade holding portion  8 , whereby the workability of the replacement of the blade  7  is improved. 
     The jigsaw of the embodiment is configured so that the plunger  1  is rockable in the cutting direction. The jigsaw has a roller  16  for abutting against a face of the blade  7 . The face is a rear face with respect to the cutting direction. The pin  12  which serves as the swing fulcrum of the swinging member  13  is positioned more rearward in the cutting direction than the center of the plunger  1  in order that, during an operation of attaching or detaching the blade  7 , the plunger  1  can rock in a direction along which the plunger separates from the roller  16 , i.e., toward the forward side in the cutting direction as shown in  FIG. 10 . When the abutting portion  15   b  of the lever  15  abuts against the other end  13   b  of the swinging member  13 , a moving force acts toward the forward side in the cutting direction. According to the configuration, the work of replacing the blade  7  can be conducted without being hindered by the roller  16 , whereby the workability can be improved. 
     As described above, the pressing force of the spring  14  serving as the pressing member acts on the vicinity of the end portion of the one end  13   a  of the swinging member  13  having the swing fulcrum. According to the principle of the lever, therefore, a greater pressing force can be given to the blade  7  via the convex portion  13   c . In other words, it is not necessary to dispose plural springs  14  or the spring  14  of a larger size in order to obtain a pressing force which is required at minimum. Therefore, the weight of the blade holding portion  8  can be relatively reduced, so that vibrations. which are caused during reciprocal motion of the plunger  1  can be suppressed. As shown in  FIG. 2 , the pin  12  which serves as the swing fulcrum of the swinging member  13  is placed at a position which is separated from the outer periphery of the plunger  1 , and the place where the spring  14  presses the one end of the swinging member  13  is set to the vicinity of the end portion of the one end  13   a , whereby the pressing force of the convex portion  13   c  acting on the blade  7  can be further enhanced. A convex portion  13   e  which is disposed on the one end  13   a  of the swinging member  13  so as to protrude toward the spring  14 , and a pin  17  attached to the blade holding portion  8  prevent the spring  14  from slipping off from the blade holding portion  8 . 
     As described above, the convex portion  13   c  is disposed on the one end  13   a  of the swinging member  13  as a pressing member with a hemispherical shape. The convex portion  13   c  presses the flat face of the blade  7  engaged with the groove  11   a  of the blade receiving face  11 . Even when another blade  7  having a different width is inserted, therefore, the pressing force of the spring  14  acts on a substantially middle portion of the blade  7  via the convex portion  13   c.    
     In the jigsaw of the embodiment, after the blade  7  is inserted into the blade holding portion  8  through the hole  9   a  of the bottom face  9 , the blade  7  must be moved in the direction perpendicular to the longitudinal direction to cause the attachment portion  7   a  of the blade  7  to be engaged with the groove  11   a  of the blade receiving face  11 . In the configuration of the embodiment, when the operation of the lever  15  is cancelled in the state where the blade  7  is inserted into the blade holding portion  8 , the blade is guided by the convex portion  13   c  of the swinging member  13  to be engaged with the groove  11   a . At this time, because the convex portion  13   c  has a hemispherical shape as described above, the convex portion  13   c  presses a substantially middle portion of the blade  7 , and hence the blade  7  is stably guided into the groove  11   a.    
     As described above, in the blade holding portion  8 , the blade  7  must be moved in the direction perpendicular to the longitudinal direction. Therefore, the widths of the hole  1   a  of the plunger  1  and the hole  9   a  of the bottom face  9  of the blade holding portion  8  are set to have dimensions which enable the above-mentioned movement of the blade  7 . 
     In the embodiment, the upper face  10  of the blade holding portion  8  is positioned at the upper end of the groove  11   a . When the blade  7  is moved as described above in the state where the upper faces of the projections  7   b  of the blade  7  abut against the inner wall face of the upper face  10  of the blade holding portion  8 , therefore, the attachment portion  7   a  of the blade  7  is engaged with the groove  11   a . As a result, the movement of the blade  7  caused by the convex portion  13   c  of the swinging member  13  is performed more stably, and the position of the blade  7  is set when the blade  7  is inserted into the blade holding portion  8 , so that the work of attaching the blade can be easily conducted. 
     In the embodiment, the blade holding portion  8  is formed as a member which is different from the plunger  1 . Alternatively, the blade holding portion may be formed integrally with the plunger  1 . 
     Next, another embodiment of the jigsaw of the invention will be described with reference to  FIGS. 11 to 14 . The components similar to those of the above-described embodiment are denoted by the same reference numerals, and their description is omitted. 
     The embodiment has a feature in the shape of the convex portion  13   c  which is disposed on the one end  13   a  of the swinging member  13  to function as the blade pressing portion. 
     As shown in the figures, a convex portion  13   c ′ which is disposed on the one end  13   a  of the swinging member  13 , and which presses the flat face of the blade  7  has a width which is slightly smaller than the illustrated width of the groove  11   a , and has a shape which can be placed substantially parallel to the groove  11   a , so that, when the blade  7  of a width which is more frequently used is engaged with the groove  11   a , the convex portion can substantially come into surface contact with the flat face of the blade  7 . 
     In the case of the hemispherical convex portion  13   c  in the embodiment described above, the flat face of the blade  7  and the convex portion  13   c  make a point contact, and there is the possibility that the blade  7  is inclined with using the convex portion  13   c  as a fulcrum. By contrast, according to the above-mentioned configuration, even when the blade  7  of a different width is inserted and butting between the flat face of the blade  7  and the convex portion  13   c ′ is formed by a point contact, the face of a portion of the convex portion  13   c ′ which is not in contact with the flat face functions to suppress the inclination, with the result that the inclination of the blade  7  can be suppressed. 
       FIG. 12  is an enlarged view of main portions showing a state where the blade  7  of a thickness which is more frequently used is attached,  FIG. 13  is an enlarged view of main portions showing a state where a blade  7 ′ of a thickness which is smaller than that of the blade  7  of  FIG. 12  is attached, and  FIG. 14  is an enlarged view of main portions showing a state where a blade  7 ″ of a thickness which is larger than that of the blade  7  of  FIG. 12  is attached. 
     In the state shown in  FIG. 12 , the convex portion  13   c ′ and the flat face of the blade  7  are substantially in surface contact. The blade  7  can be almost completely prevented from being inclined to escape from the groove  11   a  in the illustrated state. By contrast, in the state shown in  FIG. 13  or  14 , the convex portion  13   c ′ and the flat face of the blade  7 ′ or  7 ″ make a point contact, but the allowable range of the inclination of the blade  7 ′ or  7 ″ is restricted by a portion other than the convex portion  13   c ′ which is in contact with the flat face of the blade  7 ′ or  7 ″. Therefore, it can be seen that the inclination of the blade  7 ′ or  7 ″ can be suppressed to a small degree (approximately the degree of a or b shown in the figures). 
     Next, a further embodiment of the jigsaw of the invention will be described with reference to  FIGS. 15 to 17 . The components similar to those of the above-described embodiments are denoted by the same reference numerals, and their description is omitted. 
     The embodiment has a feature in the shape of the slot  1   a  formed in the plunger  1 ′, into which the end portion of the attachment portion  7   a  of the blade  7  is to be inserted. 
     As shown in the figures, the slot  1   a  of the plunger  1 ′, has: a first inner wall face  1   b  which is flush with the groove  11   a  of the blade receiving face  11 ; a second inner wall face  1   c  which is placed to be opposed to the first inner wall face  1   b ; and a third inner wall face  1   d  which is opposed to the end face of the blade  7 . 
     The width of the third inner wall face  1   d  is substantially equal to the maximum width of the blade  7  which can be used. The second inner wall face  1   c  is formed as an inclined face which is continuous with a portion (an upper portion in the figures) of the third inner wall face  1   d  that is opposite to the first inner wall face  1   b , and which extends to the upper face  10  of the blade holding portion  8 . 
     As described above, to engage the attachment portion  7   a  of the blade  7  with the groove  11   a , the attachment portion  7   a  must be moved by a distance corresponding to the depth of the groove  11   a . Therefore, the slot  1   a  of the plunger  1 ′ must be formed so as to allow the movement of the blade  7 . Consequently, the width of the slot  1   a  of the plunger  1 ′ cannot be set to be substantially equal to that of the blade  7 . As a result, there is the possibility that, when a load is applied to the vicinity of the lower end of the blade  7 , the blade is inclined so as to rotate around the convex portion  13   c  or  13   c ′ pressing the flat face of the blade  7 . The movement of the blade  7  is enabled by forming the second inner wall face  1   c  as an inclined face. The inclination of the blade  7  can be suppressed by setting the width of the third inner wall face  1   d  to be slightly larger than the thickness of the blade  7 . 
       FIGS. 16 and 17  are section views of main portions showing a state where the blade  7  of a width which is more frequently used is attached. As shown in  FIG. 16 , the width of the third inner wall face  1   d  is slightly different from that of the blade  7 . As shown in  FIG. 17 , even when a load in the direction F shown in the figure is applied to the vicinity of the lower end (the left side in the figure) of the blade  7 , the end face of the blade  7  on the side of the attachment portion  7   a  abuts against the second inner wall face  1   c , whereby the inclination of the blade  7  is restricted. Therefore, it can be seen that the inclination of the blade  7  can be suppressed to a small degree (approximately the degree of about c shown in the figure). 
     In the embodiment, the work of attaching the blade  7  can be conducted in the following manner. When the blade  7  is to be inserted into the blade holding portion  8 , the blade  7  is inserted with being inclined. with respect to the longitudinal direction of the plunger  1 ′. The blade  7  is inserted until the end face is substantially contacted with the third inner wall face  1   d  of the slot  1   a  of the plunger  1 ′. Thereafter, the attachment portion  7   a  of the blade  7  is engaged with the groove  11   a  by a manual operation or pressing by the convex portion  13   c  or  13   c ′ of the swinging member  13 . 
     As described above, according to the invention, it is possible to provide a jigsaw in which, without increasing the weight of a plunger, vibrations during a cutting work can be suppressed and blade replacement can be conducted easily and in a short time.