Patent Publication Number: US-2013247386-A1

Title: Shoulder-Hanging Type Grass Cutter

Description:
TECHNICAL FIELD 
     The present invention relates to a portable grass cutter that is used in a state of being hung on the shoulder. 
     BACKGROUND ART 
     Conventionally, a commonly used shoulder-hanging type grass cutter  10  is supposed to be used in a state in which the grass cutter body  100  thereof is hung on the shoulder with a shoulder-hanging strap  5  as shown in  FIG. 12 . The grass cutter body  100  includes a rotation drive section  1 , an operation section  2  having a cutter  21 , a rod section  3  for connecting the rotation drive section  1  to operation section  2 , and a handle  4 . The rod section  3  has a straight shape from the rotation drive section  1  to the operation section  2 . Furthermore, the operator grips the handle  4  and operates the grass cutter body  100  to control the height and angle of the operation section  2 .
     Patent Document 1: JP-A-2008-142072   Patent Document 2: JP-A-2006-340628   

     DISCLOSURE OF THE INVENTION 
     Problem to be Solved by the Invention 
     In the shoulder-hanging type grass cutter  10  having the above-mentioned configuration, when the operator releases his/her hands from the handle  4 , the gravity center of the handle  4  itself is likely to be positioned downward from the axis of the rod section  3 , whereby a rotation moment is exerted by the handle  4  to the rod section  3  around the axis thereof and there is a fear that the grass cutter body  100  may be rotated 90 degrees as shown in  FIG. 13  or rotated 180 degrees as shown in  FIG. 14  around the axis of the rod section  3 . For this reason, if the operator releases his/her hands from the handle  4  in the case that the operator slips, falls, or loses physical balance on an inclined ground or the like during work, for example, the cutter  21  is oriented vertically, thereby shaving ground or bouncing back onto trees or the like. As a result, the operation section  2  becomes inoperable and there is a fear that the operator himself/herself and persons around the operator may be in danger. Hence, various countermeasures for solving this problem have been proposed conventionally. 
     The present invention is intended to provide a shoulder-hanging type grass cutter capable of preventing the danger described above from occurring. 
     Solution to the Problem 
     The present invention is characterized in that there is provided a shoulder-hanging type grass cutter including a grass cutter body and a shoulder-hanging strap for supporting the grass cutter body so that the grass cutter body is hung on the shoulder, the grass cutter body equipped with a rotation drive section for generating a rotation force; an operation section for generating a rotation force; an operation section for performing cutting work by using a cutter that is rotated by receiving the rotation force; a rod section for connecting the rotation drive section to the operation section and for transmitting the rotation force generated by the rotation drive section to the operation section; and a handle secured to the rod section, wherein the shoulder-hanging strap is attached to the rod section on the side of the rotation drive section from the gravity center of the grass cutter body and on the side of the rotation drive section from the handle, the portion of the rod section on the side of the rotation drive section from the handle is curved in one direction, and the above-mentioned one direction is downward in the vertical plane including the rod section and the rotation shaft of the cutter in a state in which the grass cutter body is hung on the shoulder so as to be operable. 
     Effects of the Invention 
     According to the present invention, since the rod section is balanced like a “balancing toy” with the attachment position of the shoulder-hanging strap serving as a fulcrum, even if the operator releases his/her hands from the handle during work, the rotation moment exerted by the handle to the rod section around the axis thereof can be suppressed, and the rotation of the rod section around the axis thereof can be suppressed. As a result, it is possible to prevent the rod section from rotating arbitrarily and to prevent the occurrence of danger. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view showing a state in which a shoulder-hanging type grass cutter according to the present invention is used; 
         FIG. 2  is a perspective view showing a handle of a two-hand grip type; 
         FIG. 3  is a vertical cross-sectional view showing a rod section; 
         FIG. 4  is a cross-sectional view taken on line IV-IV of  FIG. 3 ; 
         FIG. 5  is a side view showing the grass cutter and includes an enlarged cross-sectional view showing an operation section; 
         FIG. 6  is an exploded perspective view showing the internal components of another example of the rod section; 
         FIG. 7  is a vertical cross-sectional view showing the example shown in  FIG. 6 ; 
         FIG. 8  is a perspective view showing another example of the handle; 
         FIG. 9  is a perspective view showing still another example of the handle; 
         FIG. 10  is a perspective view showing yet still another example of the handle; 
         FIG. 11  is a side view showing another curved state of the rod section; 
         FIG. 12  is a side view showing a state in which the conventional shoulder-hanging type grass cutter is used; 
         FIG. 13  is a side view showing a state in which the grass cutter shown in  FIG. 12  is rotated 90 degrees around the axis of the rod section; 
         FIG. 14  is a side view showing a state in which the grass cutter shown in  FIG. 12  is rotated 180 degrees around the axis of the rod section; and 
         FIG. 15  is a cross-sectional view showing the rod section of the grass cutter shown in  FIG. 12 . 
     
    
    
     DESCRIPTION OF THE REFERENCE NUMERALS 
     
         
         
           
               1  rotation drive section 
               2  operation section 
               21  cutter 
               3  rod section 
               30 A,  30 B,  30 C portions 
               31  outer pipe 
               32  flexible shaft liner 
               33  flexible shaft 
               321  convex section 
               4  handle 
               5  shoulder-hanging strap 
               10  shoulder-hanging type grass cutter 
               100  grass cutter body 
           
         
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
       FIG. 1  is a side view showing a state in which a shoulder-hanging type grass cutter  10  according to the present invention is used. This grass cutter  10  includes a grass cutter body  100  and a shoulder-hanging strap  5 . The shoulder-hanging strap  5  is provided to support the grass cutter body  100  so that the grass cutter body  100  is hung on the shoulder. 
     The grass cutter body  100  has a rotation drive section  1 , an operation section  2 , a rod section  3 , and a handle  4 . The rotation drive section  1  generates a rotation force. The operation section  2  receives the rotation force generated by the rotation drive section  1 , thereby rotating a cutter  21  to perform cutting work. The rod section  3  connects the rotation drive section  1  to the operation section  2  and transmits the rotation force generated by the rotation drive section  1  to the operation section  2 . The handle  4  is secured to the rod section  3 .  FIG. 2  is a perspective view showing the handle  4  of a two-hand grip type. The handle  4  has grip sections  41  at both end sections thereof. The operator grips the handle  4  and operates the grass cutter body  100  to adjust the height and angle of the operation section  2 . 
     The shoulder-hanging strap  5  is attached to the rod section  3  on the side of the rotation drive section  1  from the gravity center of the grass cutter body  100  and on the side of the rotation drive section  1  from the handle  4 . 
     The shoulder-hanging strap  5  is attached to the rod section  3  so as to be rotatable around the axis of the rod section  3 . Hence, the operator can grip the handle  4  and perform operation so that the grass cutter body  100  is rotated around the axis of the rod section  3 . In other words, the operator can change the inclination of the cutter  21  as desired depending on the inclination of the ground. 
       FIG. 3  is a vertical cross-sectional view showing the rod section  3 .  FIG. 4  is a cross-sectional view taken on line IV-IV of  FIG. 3 . The rod section  3  has a triple structure including an outer pipe  31 , a flexible shaft liner  32 , and a flexible shaft  33 . The flexible shaft  33  is configured to rotate and transmit the rotation force. The flexible shaft  33  is inserted into the flexible shaft liner  32  so as to be rotatable. The flexible shaft liner  32  is made of resin and has five convex sections  321  on the outer surface thereof. However, the number of the convex sections  321  is not limited to five but should only be three or more. The convex sections  321  are positioned at equal intervals in the circumferential direction and have the same protrusion height. In addition, the tip ends of the convex sections  321  make contact with the inner wall of the outer pipe  31 , whereby the flexible shaft liner  32  is fitted in the outer pipe  31 . One end of the flexible shaft  33  is connected to the output shaft (not shown) of the rotation drive section  1 , and the other end thereof is connected to the operation section  2 . 
       FIG. 5  is a side view showing the grass cutter  10  and includes an enlarged cross-sectional view showing the operation section  2 . The rotation shaft  22  of the cutter  21  is in a vertical state in the case that the face  211  of the cutter  21  is in a horizontal state. A bevel gear  221  is secured to the upper end of the rotation shaft  22 . On the other hand, a bevel gear  331  is secured to the other end of the flexible shaft  33 . In addition, the bevel gear  331  is engaged with the bevel gear  221 , whereby the rotation of the flexible shaft  33  is transmitted to the cutter  21 . The angle α formed by the center axis A of the bevel gear  331  and the center axis B of the bevel gear  221  is 120 degrees. 
     Furthermore, in the present invention, the portion  30 A of the rod section  3  on the side of the rotation drive section  1  from the attachment position X of the shoulder-hanging strap  5  is curved in one direction (in the direction indicated by arrow Y). The portion  30 B of the rod section  3  on the side of the operation section  2  from the attachment position X of the shoulder-hanging strap  5  has a straight shape. The above-mentioned one direction is downward in the vertical plane  300  including the rod section  3  and the rotation shaft  22  of the cutter  21  in a state in which the grass cutter body  100  is hung on the shoulder so as to be operable. Furthermore, the curved angle β of the portion  30 A with respect to the portion  30 B is 30 degrees. Hence, the portion  30 A and the portion  30 B are balanced with each other like a “balancing toy” in the vertical plane  300  with the attachment position X of the shoulder-hanging strap  5  serving as a fulcrum in the state shown in  FIG. 5 . The angle α is related to the angle β; since the angle β is 30 degrees, the angle α is 120 degrees. Hence, general-purpose bevel gears can be used as the bevel gears  221  and  331 . However, the angle β is not limited to 30 degrees but should only be in the range from 10 to 90 degrees. This is because, in the case that the angle β is in the range from 10 to 90 degrees, the portion  30 A and the portion  30 B can be balanced with each other like a “balancing toy” in the vertical plane  300  with the attachment position X serving as a fulcrum. 
     In the grass cutter  10  having the above-mentioned configuration, when the rotation drive section  1  is started in the state that the grass cutter body  100  is hung on the shoulder of the operator with the shoulder-hanging strap  5  as shown in  FIG. 1 , the rotation force thereof is transmitted to the cutter  21  via the flexible shaft  33 , and the grass cutter  10  performs cutting work by using the cutter  21 . At the time, the operator grips the handle  4  and rotates the rod section  3  around the axis thereof, whereby the operator can perform operation so that the face  211  of the cutter  21  is aligned with the inclination of the ground. 
     Furthermore, in the grass cutter  10  having the above-mentioned configuration, since the portion  30 A and the portion  30 B of the rod section  3  are balanced with each other like a “balancing toy” in the vertical plane  300  with the attachment position X serving as a fulcrum, even if the operator releases his/her hands from the handle  4  during work, the rotation moment exerted by the handle  4  to the rod section  3  around the axis thereof is suppressed, whereby the rotation around the axis of the rod section  3  is suppressed. As a result, in the grass cutter  10  having the above-mentioned configuration, even if the operator releases his/her hands from the handle  4  during work, the grass cutter body  100  can be prevented from being rotated 90 degrees as shown in  FIG. 13  or 180 degrees as shown in  FIG. 14  around the axis of the rod section  3 . Hence, it is possible to prevent the occurrence of danger to the operator himself/herself and persons around the operator. 
     Moreover, in the grass cutter  10  having the above-mentioned configuration, the flexible shaft liner  32  can be prevented from being rotated together with the flexible shaft  33  without providing any particular configuration. In other words, in the grass cutter  10  including the rod section  3  having the straight shape shown in  FIG. 12  throughout the entire length, convex sections  311  with which the tip end sections of convex sections  321  of the flexible shaft liner  32  make contact in the circumferential direction are formed on the inner wall of the outer pipe  31  as shown in  FIG. 15  to prevent the flexible shaft liner  32  from being rotated together with the flexible shaft  33 . However, in the grass cutter  10  having the above-mentioned configuration according to the present invention, since the rod section  3  is curved, the rotation of the flexible shaft liner  32  is suppressed. As a result, in the grass cutter  10  having the above-mentioned configuration, the flexible shaft liner  32  can be prevented from being rotated together with the flexible shaft  33  without providing any particular configuration. 
     The rod section  3  may have an inner structure shown in  FIGS. 6 and 7 . In this example, the flexible shaft liner  32  is fitted in the outer pipe  31  via rubber bushings  35  and  36  that are fitted on the flexible shaft liner  32 . The rubber bushings  35  and  36  have a function to dampen the vibration caused by the rotation of the flexible shaft  33 . The convex sections  321 , four in number, are provided and positioned at equal intervals in the circumferential direction and protrude by the same height. The height has a dimension so that the convex sections  321  do not make contact with the inner wall of the outer pipe  31 . In the convex sections  321  used as a pair and disposed in opposite directions, cutouts  322  are formed at predetermined intervals in the longitudinal direction. The rubber bushings  35  and  36  are fitted on at the positions of the cutouts  322 . At the time, the convex sections  321  which are used as a pair and in which the cutouts  322  are not formed are fitted in grooves  351  and  361  formed in the inner faces of the rubber bushings  35  and  36 . The rubber bushing  35  has peripheral face sections  353  separated by grooves  352  on the outer face thereof, and the peripheral face sections  353  make contact with the inner wall of the outer pipe  31 , whereby the rubber bushing  35  is fitted in the outer pipe  31 . The rubber bushing  36  has a plurality (eight in this figure) of protruding convex sections  362  inclined in one direction of the circumferential direction, and the tip ends of the convex sections  362  make contact with the inner wall of the outer pipe  31 , whereby the rubber bushing  36  is fitted in the outer pipe  31 . Also in the case of the rod section  3 , since the rod section  3  is curved, the rotation of the flexible shaft liner  32  is suppressed. As a result, also in the grass cutter  10  in which the rod section  3  is used, the flexible shaft liner  32  can be prevented from being rotated together with the flexible shaft  33  without providing any particular configuration. 
     What&#39;s more, for the grass cutter  10  having the above-mentioned configuration, a looped handle  4  shown in  FIG. 8 , a U-shaped handle  4  shown in  FIG. 9 , or a cantilever handle  4  shown in  FIG. 10  may also be adopted, for example. 
     Still further, in the grass cutter  10  having the above-mentioned configuration, although the portion  30 A of the rod section  3  on the side of the rotation drive section  1  from the attachment position X of the shoulder-hanging strap  5  is curved, the portion  30 C of the rod section  3  on the side of the rotation drive section  1  from the handle  4  may also be curved as shown in  FIG. 11 . 
     INDUSTRIAL APPLICABILITY 
     The shoulder-hanging type grass cutter according to the present invention can prevent the rod section thereof from rotating arbitrarily and prevent the occurrence of danger, thereby being high in industrial applicability.