Abstract:
A bush cutting machine has a relay member mounted to undergo movement by actuation of a throttle lever to adjust the opening degree of a throttle valve and to release a brake unit from a braking condition. A first wire has first and second ends each connected to a respective one of the throttle lever and a first portion of the relay member so that pivotal movement of the throttle lever pulls the second end of the first wire in a pulling direction from a standby condition to an operative condition. A first end of each of second and third wires is connected to a respective one of the throttle valve and the brake unit.

Description:
FIELD OF THE INVENTION 
     This invention relates to a bush cutting machine having a lever with improved operability in performing throttle adjustment and braking a cutter blade and brake releasing of the latter. 
     BACKGROUND OF THE INVENTION 
     There have been known various bush cutting machines which include a throttle adjustment unit mounted in a prime mover for adjusting the rotational speed of a cutter blade, and a brake unit provided in a drive power transmission path between the cutter blade and the prime mover for applying the brakes to the cutter blade. Typical examples of such bush cutting machines are disclosed in Japanese Utility Model Laid-Open Publication No. SHO-51-53248 and Japanese Patent Laid-Open Publication No. SHO-52-145135. 
     The bush cutting machine disclosed in SHO-51-53248 comprises a rotary cutter or blade connected to the prime mover via a clutch and a driven shaft, and a handle carrying a brake lever connected via a wire to a brake shoe of the brake unit. When the brake lever is released from a gripped state, the brake shoe is urged against an outer circumferential periphery of the driven shaft to apply the brakes to the rotary cutter. 
     In the thus-arranged bush cutting machine, for adjusting the rotational speed of the rotary cutter using the throttle lever, an operator is required to perform respective operations of the throttle lever and the brake lever in a well-timed fashion during a bush cutting operation, for example, by operating the throttle lever in such a manner as to gradually increase the rotational speed of the rotary cutter while gripping the brake lever to gradually release the brakes from the rotary cutter, thus requiring the operator to have a skill in operating the levers. Further, since the operator needs not only to perform a lever operation with his hand but also to maintain an attitude of the bush cutting machine during work, the levers must be desirably operated in a possible simplest way with a view to improve workability and minimize operator&#39;s fatigue. 
     The bush cutting machine disclosed in SHO-52-145135 comprises a cutter blade connected to the prime mover via a rotary shaft, a handle rod mounted to an operation rod through which the rotary shaft passes, a brake lever and a throttle lever both mounted to the handle rod, a brake lever connected via a wire to a brake section for braking the cutter blade, a throttle lever connected to a throttle valve mechanism via a wire, and a control box provided midway of the wires for linking the wires to one another. The control box includes a control body rotatably secured to a pivot shaft. The wires are connected to respective ends of the control body. 
     In the bush cutting machine of SHO-52-145135, the brake section and the throttle valve mechanism are interlinked to each other through operation of the brake lever. However, the presence of the control box provided midways of the wires makes the structure complicated with a resultant difficulty compelled in assemblage of the control box and the wires. Further, in the bush cutting machine, since an outer tube between the control box and the throttle lever and the outer tube between the control box and the throttle valve mechanism warp largely and return to their original positions upon operation of the throttle lever, the outer tubes interfere with an operator and disturb his work. Moreover, the control box has component parts, provided at the pivot shaft, the control body and the respective ends of the control body, for mounting the wires, thereby increasing the number of component parts. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a bush cutting machine which has a lever with improved operability in adjusting the opening degree of a throttle valve and braking and unbraking a cutter blade, and which is simplified in structure to provide improved workability and assemblage efficiency. 
     According to an aspect of the present invention, there is provided a bush cutting machine which comprises: an operation rod; a cutter blade mounted to a front end of the operation rod; a prime mover mounted to a rear part of the operation rod for driving the cutter blade; a throttle lever for adjusting a throttle of the prime mover; a brake unit for stopping rotation of the cutter blade driven by the prime mover; and a link mechanism actuated by operation of the throttle lever to adjust the degree of opening of the throttle and to release the brake unit from a braking condition. 
     In the bush cutting machine thus arranged, by operating the throttle lever, adjustment of the opening degree of the throttle and actuation of the brake unit and releasing of the brakes can be effected for thereby improving the operability of the bush cutting machine and the workability of the latter. Also, the presence of the relay member, serving as a link mechanism, located in close proximity to the prime mover, that is, the presence of the link mechanism mounted to a cover of the brake unit adjacent the prime mover, allows the single piece of main cable to be located between the handle and the link mechanism closer to the prime mover when the throttle lever is mounted to the throttle lever, resulting in a simplified structure around the handle. 
     Desirably, the link mechanism includes a delay mechanism to be actuated by operation of the throttle lever such that the throttle opens with a time delay from the releasing of the brakes. As a result, operation of the throttle lever alone causes the brake unit to be released from a braking condition and then the throttle to open. This sequence of operations can be performed smoothly. 
     In a specific form, the link mechanism is housed in an operating lever unit, which serves as a grip of the handle mounted to the operation rod. This arrangement makes the bush cutting machine compact in structure. 
     Preferably, the bush cutting machine further comprises a single piece of throttle cable extending between the throttle lever and the brake unit. The link mechanism may be provided midway of the single throttle cable so that both the opening degree adjustment of the throttle and the releasing of the brake unit from the braking condition can be achieved by the single throttle cable. This results in reduction of the number of cables, thereby providing a simplified structure around the handle. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Certain preferred embodiments of the present invention will be described in more detail below, by way of example only, with reference to the accompanying drawings, in which: 
     FIG. 1 is a side view illustrating one example of a bush cutting machine according to the present invention in practical use; 
     FIG. 2 is an enlarged view of a front portion of an engine, illustrating an example arrangement wherein a relay member serving as a link mechanism is mounted inside a cover of a brake unit of the bush cutting machine according to a first preferred embodiment of the present invention; 
     FIG. 3 is a partial view, as seen in the direction of arrow  3  of FIG. 2, illustrating a relationship between a throttle wire and a throttle arm; 
     FIG. 4 is a top plan view illustrating the vicinity of a clutch case with a relay member shown in FIG. 2; 
     FIGS. 5A and 5B are schematic views illustrating a manner of assemblage of the relay member shown in FIG.  4  and the relationship between the main wire, the throttle wire and the brake wire; 
     FIG. 6 is an enlarged cross sectional view taken along line  6 — 6  of FIG. 4, illustrating a brake unit; 
     FIG. 7 is a cross sectional view illustrating details of an operating lever unit shown in FIG. 1; 
     FIGS. 8A and 8B are views illustrating an operation of the operating lever unit shown in FIG. 7; 
     FIG. 9 is a schematic view illustrating an operation of the relay member with the throttle lever gripped and rotated an angle up to midway as shown in FIG. 8B; 
     FIG. 10 is a schematic view illustrating an operational state wherein a brake shoe is removed from an outer periphery of a drum to unbrake by pulling a brake wire as shown in FIG. 9; 
     FIG. 11 is a view illustrating an operation of the operating lever unit with the throttle lever further deeply gripped from a state of FIG. 8B; 
     FIG. 12 is a view illustrating an operation of the relay member with the relay member further moved from the position of FIG. 9 to cause the throttle wire to be pulled; 
     FIG. 13 is a view illustrating an operation wherein the throttle wire is pulled to rotate the throttle arm to cause a throttle valve to be brought into an open condition; 
     FIG. 14 is a partial cross sectional view of a bush cutting machine according to a second preferred embodiment of the present invention, wherein single piece of throttle cable allows the opening degree of the throttle to be adjusted and the brakes to be released, illustrating a carburetor, the brake unit and the throttle cable; 
     FIG. 15 is a view illustrating a relationship between the throttle cable and the carburetor as viewed in the direction of arrow  15  of FIG. 14; 
     FIG. 16 is a view illustrating a relationship between the throttle cable and the carburetor as viewed in the direction of arrow  16  of FIG. 14; 
     FIG. 17 is a partial cross sectional view taken along line  17 — 17  of FIG. 14, illustrating a relationship between the throttle wire and the brake unit; 
     FIG. 18A is a view illustrating a relationship between the throttle wire and the throttle arm upon gripping movement of the throttle lever up to midway to pull the throttle wire, and 
     FIG. 18B is a view illustrating the movement of the brake unit in such relationship; 
     FIG. 19 is a view illustrating a condition wherein the throttle valve is opened by the throttle wire when the throttle lever is fully gripped; 
     FIG. 20 is a modified form of the bush cutting machine according to the first and second embodiments, which has an operation rod with a U-shaped handle and an operating lever unit mounted to the grip of the handle; 
     FIG. 21 is an enlarged cross sectional view of the operating lever unit shown in FIG. 20; 
     FIG. 22 is a cross sectional view of the operating lever unit employed in a bush cutting machine according to a third embodiment, as one of grids of the handle shown in FIG. 20, illustrating a relay member serving as a link mechanism housed in the operating lever unit; 
     FIG. 23 is a cross sectional view taken along line  23 — 23  of FIG. 22; 
     FIG. 24 is a cross sectional view taken along line  24 — 24  of FIG. 22; 
     FIG. 25 is a cross sectional view of the brake unit with the relay member of FIG. 2 removed; 
     FIG. 26 is a view as seen in the direction of arrow  26  of FIG. 25, illustrating a relationship between the throttle wire and the throttle arm; 
     FIG. 27 is a cross sectional view taken along line  27 — 27  of FIG. 25, illustrating the brake unit; 
     FIGS. 28A and 28B illustrate an operation of the operating lever unit according to the third embodiment; 
     FIG. 29 is a view illustrating an operation of the brake unit which is released when the throttle lever shown in FIG. 28B is rotated an angle up to midway of the throttle lever to pull the throttle wire; 
     FIG. 30A is a view illustrating an operation of the operating lever unit with the throttle lever fully gripped at its extreme position, and FIG. 30B is a view illustrating an operation with the throttle wire pulled and the throttle valve opened; 
     FIG. 31 illustrates an operation of the operating lever unit with the throttle lever locked with the throttle lever; and 
     FIG. 32 is a view illustrating a modified form of the third preferred embodiment, with a relay member as a link mechanism incorporated in the operating lever unit of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description is merely exemplary in nature and is in no way intended to limit the invention, its application or uses. 
     When in use as shown in FIG. 1, a bush cutting machine  11  according to a first preferred embodiment of the present invention is suspended from a shoulder of an operator  10  via a shoulder strap  12  with an operating lever unit  14 , mounted to the bush cutting machine  11 , held by a right hand  13  of the operator  10  while a handle  16  is held by a left hand  15  of the operator  10  for carrying out bush cutting work. 
     The bush cutting machine  11  includes an engine  21  serving as a prime mover, a cutter blade  22  driven by the engine  21 , a transmission shaft  23  for transmitting drive power from the engine  21  to the cutter blade  22 , an operation rod  24  interposed between the engine  21  and the cutter blade  22  for accommodating therein the transmission shaft  23 , the operating lever unit  14  mounted to the operation rod  24  adjacent the engine  21 , and a loop shaped handle  16  mounted to the operation rod  24  at a location remote from the operating lever unit  14  in a direction toward the cutter blade  22 . A reference numeral  26  designates a gear case which is interposed between a distal end of the operation rod  24  and the cutter blade  22 . In order to protect the operator  10  at his feet during cutting operation of weeds  28 , the cutter blade  22  is partially concealed with a cover  27 . 
     In FIG. 2, a centrifugal clutch  51  is mounted to a front portion of the engine  21 . The centrifugal clutch  51  connects or disconnects a power delivery path from the engine  21  to the transmission shaft  23 . The centrifugal clutch  51  is incorporated in a clutch case  52  mounted to the front portion of the engine  21 . The operation rod  24  is mounted to a front portion of the clutch case  52 . A carburetor  53  is mounted to a side portion of the engine  21 . One end of a throttle cable  54  is connected to the carburetor  53 . The other end of the throttle cable  54  is connected to a relay member  55 . One end of a main cable  56 , which extends from the operating lever  14  shown in FIG. 1, is connected to the relay member  55 . A brake shoe  61 , which forms a part of a brake unit  65 , is mounted to a pivot shaft  58  which is rotatably mounted to a lower portion of the clutch case  52 . 
     The centrifugal clutch  51  includes a weight  21   b  fixed to the output shaft  21   a  of the engine  21 , and a cup shaped drum  63  with which the weight  21   b , swinging due to a centrifugal force exerted when the output shaft  21   a  exceeds a given rotational speed, is brought into engagement. Mounted to a bottom portion of the drum  63  is an end of the transmission shaft  23 . The brake unit  65  compels the brake shoe  61 . to be urged against an outer periphery  63   a  of the drum  63  to apply a brake to the rotation of the drum  63  for thereby braking the rotations of the transmission shaft  23  and the cutter blade  22  shown in FIG.  1 . The clutch case  52  also serves as a cover for concealing the brake unit  65 . The end of the transmission shaft  23  is rotatably supported with the clutch case  52  via a bearing  67 , and the other end of the transmission shaft  23  is rotatably supported in the gear case  26  of FIG.  1 . 
     FIG. 3 shows the relationship between the carburetor  53  and the throttle cable  54 . 
     In FIG. 3, the carburetor  53  includes a case  71 , a throttle valve  72   a  for opening or closing an air intake passage formed in the case  71 , a throttle shaft  72  to which the throttle valve  72   a  is mounted, a throttle arm  73  fixed to the throttle shaft  72 , a strut shaped wire mount portion  74  rotatably mounted to an end of the throttle arm  73 , a stopper portion  75  which permits the throttle valve  2   a  to be retained at a fully open position when the throttle arm  73  is rotated counterclockwise about a center of the throttle shaft  72 , a screw  76  whose distal end is held in abutting contact with the end of the throttle arm  73  to enable adjustment of a fully closed position of the throttle valve  72   a.    
     The wire mount portion  74  has a transverse bore  78  formed in a direction perpendicular to an axis of the strut and extending from a side of the strut, and a transverse recess  82  formed in an upper surface  81  of the wire mount portion  74  in parallel with the transverse bore  78 . The transverse bore  78  and the transverse recess  82  are connected to one another. A width of the transverse recess  82  is smaller in size than the inner diameter of the transverse bore  78  but is larger than a diameter of the throttle wire  54   b.    
     The throttle cable  54  includes a throttle tube  54   a , the throttle wire  54   b  moveably inserted through the throttle tube  54   a , a cylindrical member  54   c  mounted to a distal end of the throttle wire  54   b , and a throttle tube terminal member  54   d  which allows one end of the throttle tube  54   a  to be mounted to a bracket  84  formed on the engine  21  shown in FIG.  2 . 
     To connect the throttle wire  54   b  to the sire mount portion  74  of the carburetor  53 , the throttle wire  54   b  is inserted through the transverse bore  78  via the transverse recess  82  and, then, the cylindrical member  54   c , mounted to the distal end of the throttle wire  54   b , is inserted through the transverse bore  78  to allow the cylindrical member  54   c  to engage the wire mount portion  74 . 
     In order to adjust the tension of the throttle wire  54   b , nuts  85 ,  85 , which are screwed onto a male thread formed on the throttle tube terminal member  54   d , are rotated and loosened, permitting the throttle tube terminal member  54   d  to be longitudinally moved by a given distance and subsequently allowing the nuts  85 ,  85  to be tightened. 
     FIG. 4 shows the relay member  55  which serves as a link mechanism that interconnects the main cable  56 , and the throttle cable  54  and the brake cable  87 . The relay member  55  is mounted to an upper area of the clutch case  52  by bolts  86 ,  86 . The main cable  56  is connected to one side, closer to the operation rod  24 , of the relay member  55 . The brake cable  87 , which serves as the throttle cable  54  and a brake release cable, is connected to the other side, closer to the engine  21  (see FIG.  2 ), of the relay member  55 . 
     The main cable  56  has a main wire  56   b  moveably inserted through a main tube  56   a . The main wire  56   b  has a distal end formed with a main wire terminal member  56   c . The main tube  56   a  has a distal end formed with a main tube terminal member  56   d . An end portion of the main wire  56   b  protrudes outward from the main tube terminal member  56   d.    
     The throttle wire  54   b  of the throttle cable  54  has a distal end formed with a throttle wire terminal member  54   e . The throttle tube  54   a  has a distal end formed with a throttle tube terminal member  56   f.    
     The brake cable  87  has a brake wire  87   b  moveably inserted through a brake tube  87   a . The brake wire  87   b  has a distal end formed with a brake wire terminal member  87   c . The brake tube  87   a  has a distal end formed with a brake tube terminal member  87   d.    
     The relay member  55  includes a case  91 , and a wire connecting member  92  received in the case  91 . The main tube terminal member  56   d  is mounted to a side wall  91   a , closer to the operation rod  24 , of the case  91 . The throttle tube terminal member  54   f  and the brake tube terminal member  87   d  are mounted to a side wall  91   b , closer to the engine  21 , of the case  91 . The wire connecting member  92  has a U-shape configuration in cross section as shown in FIG.  2 . The main wire terminal member  56   c  engages a first upright portion  92   a , closer to the operation rod  24 , of the wire connecting member  92 . The throttle wire terminal member  54   e  and the brake wire terminal member  87   c  engage a second upright portion  92   b , closer to the engine, of the wire connecting member  92 . 
     As shown in FIG. 4, the amount of protrusion of the throttle wire  54   b  extending from the throttle tube  54  is settled to have a greater value than that of the brake wire  87   b  extending from the brake tube  87   a . In addition, the brake wire terminal member  87   c  is brought into abutting engagement with the second upright portion  92   b  of the wire connecting member  92 , letting the throttle wire terminal member  54   e  to be separated from the second upright portion  92   b . Here, it is supposed that there is a difference D between the distance between the throttle wire terminal member  54   e  and the second upright portion  92   b  and the distance between the brake wire terminal member  87   c  and second upright portion  92   b.    
     Thus, the presence of the relay member  55  of the preferred embodiment, with the throttle wire terminal member  54   e  which remains further away from the second upright portion  92   b  with respect to the brake wire terminal member  87   c , allows a delay mechanism  93  to be provided for causing the throttle wire  54   b  to be pulled later than the brake wire  87   b  when the main wire  56   b  is pulled to shift the wire connecting member  92 . 
     FIGS. 5A and 5B show outlines how the main cable  56 , the throttle cable  54  and the brake cable  87  are coupled to the relay member discussed above. 
     First, in FIG. 5A, the main wire terminal member  56   c  is inserted through a through-bore  91   c  formed in one side wall  91   a  of the case  91  of the relay member until the main tube terminal member  56   d  is brought into abutting engagement with the one side wall  91   a . Next, the throttle wire terminal member  54   e  is inserted through a through-bore  91   d  formed in the other side wall  91   b  of the case  91  of the relay member until the throttle tube terminal member  54   f  is brought into abutting engagement with the other side wall  91   b . Further, the brake wire terminal member  87   e  is inserted through a through-bore  91   e  formed in the other side wall  91   b  of the case  91  of the relay member until the tube terminal member  87   d  is brought into abutting engagement with the other side wall  91   b.    
     Subsequently, in FIG. 5B, the main wire  56   b  is inserted through a recess  92   c  formed in the first upright portion  92   a , at one side, of the wire connecting member  92 . The throttle wire  54   b  is inserted through a recess  92   d  formed in the second upright portion  92   b , and the brake wire  87   b  is inserted through a recess  92   e  formed in the second upright portion  92   b  at the other side. And, in FIG. 4, fixing a lid over the case  91  completes an assembly of the relay member  55 . Since the wire connecting member  92  is accommodated in the case  91  as shown in FIG. 2 not to move in upward or downward directions, the main wire  56   b , the throttle wire  54   b  and the brake wire  87   b  are precluded from disengaging the recesses  92   c ,  92   d  and  92   e  formed in the wire connecting member  92  shown in FIG. 5B even during weed-cutting operation. 
     FIG. 6 shows the brake unit  65 . The brake unit  65  includes the brake cable  87  shown in FIG. 4, a cable fastening fixture  95  for fixedly securing a distal end of the brake tube  87   a  to the clutch case  52 , a brake arm  96  connected to a distal end of the brake wire  87   b  protruding from a distal end of the cable fastening fixture  95 , a pivot shaft  58  mounted to the brake arm  96 , a brake shoe  61  mounted to the pivot shaft  58 , the drum  63  adapted to be urged by the brake shoe  61  for applying a brake to the transmission shaft  23 , and a tension coil spring  97  which urges the brake shoe  61  against the drum  63 . The brake wire  87  is connected to the brake arm  96  via the wire terminal member  87   e.    
     The brake shoe  61  shown in FIG. 6 remains in an urged state against the drum  63  due to the tension force of the tension coil spring  97 , with the drum  63  being held in a braked condition. 
     The cable fastening fixture  95  has a distal end formed with a male thread portion  95   a . Formed in the clutch case  52  is an upright wall  101  which has a recessed portion  101   a . Inserting the male thread portion  95   a  into the recessed portion  101   a  and tightening nuts  102 ,  102  at both sides of the upright wall  101  cause the cable fastening fixture  95  to be fixed to the clutch case  52 . 
     One end of the tension coil spring  97  is hooked to a spring hook portion  103 , with the other end being hooked to a pin  104  fixed to the clutch case  52 . 
     Although the cable fastening fixture  95  and the brake arm  96   a  located outside the clutch case  52 , these component parts are concealed with a case cover  105  shown in FIG. 2 to be precluded from being exposed to the outside. 
     Adjustment of the tension of the brake wire  87   b  is performed by loosening the nuts  102 ,  102  to move the cable fastening fixture  95  in an axial direction and subsequently tightening the nuts  102 ,  102 . 
     FIG. 7 shows the operating lever unit  14 . The operating lever unit includes a handle case  106 , a throttle lever  107  swingably mounted to the handle case  106  for adjusting the rotational speed of the engine  21  shown in FIG. 2, a lock lever  108  swingably mounted to the handle case  106  for temporarily fixing the throttle lever  107 , and a kill switch  111  for shutting off the operation of the engine  21 . 
     The handle case  106  is composed of two case halves by which the operation rod  24  is sandwiched from its both sides. 
     One end of the handle case  106  has protruding segments  106   a ,  106   a , protruding from the two case halves, respectively, which are tightened with a bolt  112 , with the other end of the handle case  106  being fixedly secured to the operation rod  24  with tightened bolt (not shown). 
     The throttle lever  107  is comprised of an operating section  107   a  to allow a finger to engage therewith for operation, a wire arm connecting arm  107   b  connected to the main wire  56   b  of the main cable  56 , and a bearing portion  107   c  which supports a pivot shaft  106   b  mounted to the handle case  106 . 
     The lock lever  108  functions as a member to restrict the operation of the throttle lever  107  during braking operation of the cutter blade  22  at an idling condition of the engine  21  shown in FIG.  1 . The lock lever  108  is comprised of a palm restraining portion  108   a , an arm engagement portion  108   b  which is able to disengage from a distal end of the wire connecting arm  107   b  of the throttle lever  107 , and a bearing portion  108   c  receiving a pivot shaft  106   c  mounted to the handle case  106 . 
     Reference numeral  56   e  designates a wire terminal member fixed to a base end of the main wire  56   b . Reference numeral  56   f  designates a case mount member secured to the main tube  56   a  for fixing a proximity base end of the main cable  56  to the handle case  106 . Reference numeral  114  designates a twisted coil spring for urging the throttle lever  107  in a clockwise direction about the center of the pivot shaft  106   b . Reference numeral  115  designates a twisted coil spring for urging the lock lever  108  in a counterclockwise direction about the center of the pivot shaft  106   c.    
     Adjustment of the tension of the main wire  56   b  is performed by loosening the nuts  116 ,  116 , screwed onto a male thread formed on the case mount member  56   f  to move the case mount member  56   f  in an axial direction by a given distance and subsequently tightening the nuts  116 ,  116 . 
     Now, the operation of the bush cutting machine of the first preferred embodiment is described below with reference to FIGS. 8A to  13 . 
     First, the engine is start up into an idling state. When this occurs, since the rotational speed of the engine is below the given value, the centrifugal clutch  51  remains in its off state as explained with reference to FIG. 2, and, also, the brake shoe  61  is held in pressured contact with the drum  63 , rendering the cutter blade inoperative. 
     Under such an idling state, as shown in FIG. 8A, the lock lever  108  is pressed with the palm of the hand in a direction as shown by an arrow a while gripping the handle case  106 . When this takes place, the arm engagement portion  108   b  of the lock lever  108  is brought out of engagement with the distal end of the wire connecting arm  107   b  of the throttle lever  107 , thereby releasing the throttle lever  107  from its locked state. Consequently, the throttle lever  107  is rendered operative. 
     In FIG. 8B, manipulating the operating section  107   a  of the throttle lever  107  with the finger and rotating the throttle lever  107  to the halfway as shown by an arrow b cause the main wire  56   b  to be pulled in a direction as shown by an arrow c. 
     When gripping the throttle lever  107  in such a manner described above, the main wire  56   b  is pulled in the direction as shown by the arrow c as viewed in FIG. 9, compelling the wire connecting member  92  to pull the brake wire  87   b  in a direction as shown by an arrow d concurrently with the movement of the main wire  56   b.    
     As the brake wire  87   b  is pulled in the direction as shown by the arrow d, the brake arm  96  is rotated in a direction as shown by an arrow e about the center of the pivot shaft  58  as shown in FIG.  10 . When this occurs, the brake shoe  61 , which is integral with the brake arm  96 , is caused to swing in a direction as shown by an arrow f against the tension force of the tension coil spring  97 , compelling the brake shoe  61  to disengage from the drum  63  for thereby releasing the brake effect. 
     When gripping the throttle lever  107  further strongly in a direction as shown by an arrow g as shown in FIG. 11, the main wire  56   b  is further pulled in a direction of arrow h. 
     In FIG. 12, when the main wire  56   b  is further pulled in the direction as shown by the arrow h, the brake wire  87   b  is further pulled in a direction as shown by an arrow j via the wire connecting member  92  and, at the same time, the throttle wire  54   b , which is not yet pulled as viewed in FIG. 9, is initiated to be pulled in a direction as shown by arrow k. By the foregoing operation, the distal ends of the main wire  56   b , brake wire  87   b  and throttle wire  54   b  are pulled in the directions shown by arrows h, j, k, respectively, which correspond to the same pulling direction. 
     In FIG. 13, as the throttle wire  54   b  is pulled in the direction as shown by the arrow k, the throttle arm  73  of the carburetor  53  is rotated in a direction as shown by an arrow m about the center of the throttle shaft  72 . 
     As a consequence, the throttle valve  72   a  mounted to the throttle shaft  72  is brought into an open state, with a resultant increase in the volume of air and fuel to be supplied to the engine to increase the engine speed. As the engine speed exceeds the given value, in FIG. 2, the centrifugal clutch  51  is coupled to transmit drive power from the engine  21  to the cutter blade which in turn is rotated. 
     As described above with reference to FIGS. 3 and 4, FIGS. 5A and 5B and FIG. 6, the first preferred embodiment of the present invention firstly features the provision of the bush cutting machine, having the throttle lever  107  for adjusting the opening degree of the throttle valve  72   a  of the engine  21  shown in FIG.  1  and the brake unit  65  for braking the rotation of the cutter blade  22  driven with the engine  21 , which includes the main cable  56  connected at the one end with the throttle lever  107 , the relay member  55  serving as the link mechanism interconnected with the other end of the main cable  56  and mounted to the clutch case  52  located in close proximity to the engine  21 , the throttle cable  54  connected between the relay member  55  and the throttle arm  73  mounted to the throttle shaft  72  of the throttle valve  72   a , and the brake cable  87  connected between the relay ember  55  and the brake arm  96  which releases the operation of the brake unit  65 . 
     Operating the throttle lever  107  enables the opening degree of the throttle valve  72   a  to be adjusted and the brake unit to be actuated or released, with a resultant improvement in operability and workability of the bush cutting machine. 
     Also, since the relay member  55  is mounted to the clutch case  52  disposed adjacent the engine  21 , for example, when assembling the throttle lever  107  to the handle  16  shown in FIG. 1, a single piece of main cable  56  should be merely located between the handle  16  and the relay member  55  close to the engine  21 , enabling a structure around the handle  16  to be simplified in construction while enabling the operability of the bush cutting machine  11  to be highly improved. 
     As described above with reference to FIG. 4, the first preferred embodiment of the present invention secondly concerns the presence of the relay member  55  which includes the delay mechanism  93  which is arranged to cause the throttle wire  54   b  to be delayed in movement from that of the brake inner wire  87   b  when operating the throttle lever  107 , shown in FIG. 6, to pull the main wire  56   b . As a result, operating the throttle lever  107  enables the brake unit  65 , shown in FIG. 6, to be actuated or released and the opening degree of the throttle valve  72   a , shown in FIG. 3, to be adjusted in a sequence of movements in a smooth fashion. Since, further, the relay member  55  is composed of a minimum number of component parts which are simple in structure, an assembling efficiency is highly improved in a reduced cost. 
     Now, a bush cutting machine according to a second preferred embodiment of the present invention is described below. Also, the same components parts as those used in the first embodiment bear the same reference numerals as those used therein and a description of these component parts is herein omitted. The bush cutting machine of the second preferred embodiment has no relay member, serving as the link mechanism, which has been shown in the first preferred embodiment with reference to FIGS. 2 and 4. 
     The throttle cable  254  shown in FIG. 14 extends between the operating lever unit  14  shown in FIG.  1  and the brake unit which will be described later. The throttle cable  25  is connected at its midway to the carburetor  53  mounted at the side area of the engine  21 . 
     The connection between the throttle cable  254  and the carburetor  53  is shown in FIGS. 15 and 16. 
     Referring to FIG. 15, the throttle cable  254  is shown having a first throttle tube  254   a , a second throttle tube  254   b , a throttle wire  254   c  and a throttle-arm actuating member  277 . One end of the first throttle tube  254   a  is connected to the operating lever unit  14  shown in FIG. 1, and the other end is connected to a first bracket  84   a  extending from an external wall of the engine  21  shown in FIG.  14 . One end of the throttle tube  254   b  is connected to a second bracket  64   b  extending from the external wall of the engine  21 , and the other end extends around the upper area of the engine  21  and is connected to the brake unit  65 . The throttle wire  254   c  is moveably inserted through the first and second throttle tubes  254   a ,  254   b . One end of the throttle wire  254   c  is connected to the operating lever unit  14 , and the other end is connected to the brake unit  65 . The throttle-arm actuating member  277  is disposed in the midway of the throttle wire  254   c  and has an expanded portion which is larger in diameter than the throttle wire  254   c.    
     Reference numeral  254   d  designates a first tube terminal member disposed at the other end of the first throttle tube  254   a , and reference numeral  254   e  designates a second tube terminal member disposed at the one end of the second throttle tube  254   b.    
     In FIG. 16, the wire mount portion  74  has an upper surface  81  formed with the transverse recess  82 . The traverse recess  82  has a width slightly larger in size than the diameter of the throttle wire  254   c . The throttle wire  254   c  is moveably disposed in the transverse recess  82  along the longitudinal direction thereof. 
     The throttle-arm actuating member  277  is located at a position displaced from the wire mount portion  74  by a distance D and closer to the second tube terminal member  254   e . Reference numeral  283  designates an adjusting nut which is brought into abutting engagement with the throttle arm  73  for adjustably rotating the throttle arm  73  with a view to adjusting the fully closed position of the throttle valve. 
     FIG. 17 shows a brake unit of a bush cutting machine of a second preferred embodiment. The brake unit  65  has at its one end a brake arm  96 . The other end of the throttle wire  254  is connected to the other end of the brake arm  96  via the first wire terminal member  254   g  disposed at the distal end of the throttle wire  254 . The brake shoe  61  is mounted to the pivot shaft  58 . Urging the brake shoe  61  against the drum  63  applies the brake to the rotation of the transmission shaft  23 . The tension coil spring  97  urges the brake shoe  61  against the drum  63  at all times. Reference numeral  254   f  is a third tube terminal member fixed to the end of the second throttle tube  254   b  shown in FIG. 15 for mounting the throttle cable  254  to the clutch case  52 . The third tube terminal member  254   f  has a distal end formed with a male thread portion  254   h.    
     The operating lever unit  14  of the bush cutting machine according to the second preferred embodiment has the same structure as that shown in FIG. 7 as the first preferred embodiment, and the throttle lever  107  and the lock lever  108  operate in the same manner as those shown in FIGS. 8A and 8B. For this reason, a description of the operating lever unit  14  of the second preferred embodiment is omitted. 
     In FIG. 18A, when pulling the throttle wire  254   c  of the throttle cable  254  in the direction as shown by the arrow d, the throttle-arm actuating member  277 , disposed at the midway of the throttle wire  254   c , moves with the throttle wire  254   c  toward the wire mount portion  74  of the throttle arm  73 . When this occurs, since the throttle-arm actuating member  277  and the wire mount portion  74  are still spaced from one another by the distance D 1 , the wire mount portion  74  remains stationary and the throttle valve  72   a  remains in a substantially closed condition. 
     In FIG. 18B, when pulling the throttle wire  254   c  in the direction as shown by the arrow d as described with reference to FIG. 18A, the brake arm  96  rotates clockwise about the center of the pivot shaft  58  as shown by the arrow e. Since the brake unit  61  is integral with the brake arm  96 , the brake shoe  61  rotates against the force of the tension coil spring  97  in the same direction as the brake arm  96  and is displaced from the drum  63  to be brought into the brake-released condition. 
     Like in the first preferred embodiment shown in FIG. 11, when fully gripping the throttle lever  107  and pulling the throttle wire  254   c  in the direction as shown by the arrow h in FIG. 11, the throttle-arm actuating member  277  is brought into abutting contact with the wire mount portion  74  as shown in FIG.  19 . When this takes place, the throttle arm  73  rotates counterclockwise about the center of the throttle shaft  72  as shown by the arrow j, thereby rendering the throttle valve  72   a , mounted to the throttle shaft  72 , to be brought into an open condition. This causes the amount of intake air and fuel to increase, with a resultant increase in the engine speed. When the engine speed exceeds the given value, in FIG. 14, the centrifugal clutch  51  is coupled such that the drive power is transmitted from the engine  21  to the cutter blade which is consequently rotated. 
     As described above with reference to FIGS. 14,  16  and  17 , the bush cutting machine according to the second preferred embodiment features the provision of the throttle lever  107  for adjusting the opening degree of the throttle valve  72   a  of the engine and the brake unit  65  which applies the brake to the rotation of the cutter blade  22 , shown in FIG. 1, which is driven with the engine  21 , with the end of the throttle cable  254  being connected to the throttle lever  107  while the other end of the throttle cable  254  is coupled to the brake arm  96  for releasing the brake or applying the brake with the brake unit  65  and with the throttle-arm actuating member  277  being disposed at the midway of the throttle cable  254  to act as the link mechanism for rotating the throttle arm  73  to open or close the throttle valve  72   a  when operating the throttle valve  107 . 
     Thus, the presence of the single piece of throttle cable  254  acting to perform both the operation of the brake unit  65  and the operation of the throttle valve  72   a  enables the number of cables to be reduced for thereby reducing the cost of the component parts. 
     Further, according to the second preferred embodiment, a single piece of throttle cable  254  may be located between the handle  16  and the engine  21  shown in FIG. 1, with a structure around the handle  16  being simplified while improving the operability of the bush cutting machine  11 . 
     With such a bush cutting machine according to the second preferred embodiment, the throttle-arm actuating member  277  is located near the brake unit and spaced from the throttle arm  73  by the distance D, providing the delay function to achieve the opening and closing operations of the throttle valve  72   a  with a delay in timing from the releasing operation of the brake unit  65 . That is, when pulling the throttle cable  254  by operating the throttle lever  107 , first, the brake arm  96  is actuated to release the brake unit  65  and, then, the throttle-arm actuating member  277  is brought into abutting contact with the throttle arm  73  to compel these to be interlinked to one another, thereby providing an ability for achieving the opening movement of the throttle valve  72   a  with a time delay from the releasing operation of the brake. 
     Also, when letting the throttle cable  254  to be returned, on the contrary, the brake operation is performed after the closing movement of the throttle valve  72   a , resulting in a capability of smoothly carrying out both the releasing operation of the brake or applying the brake and the adjusting operation for the opening degree of the throttle valve  72   a  in a sequence of operation of the throttle lever  107 . 
     FIGS. 20 and 21 show a modified form of the first and second preferred embodiments wherein a bush cutting machine  120  of the modified form, as shown in FIG. 20, has the operation rod  24  mounted with a U-shaped handle  221  whose right handle component is mounted with an operating lever unit  222  while a left handle component is mounted with a grip  223 . When in use, the operator  10  grips and operates the operating lever unit  222  with right hand  13  while holding the grip  223  with left hand  15 . Other component parts are similar to those shown in FIG. 1 and a description of the same is omitted. 
     FIG. 21 shows the operating lever unit  222 , mounted to the right handle component shown in FIG. 20, in cross section. 
     The operating lever unit  222  according to the modified form shown in FIG. 21 includes a handle case  225 , a throttle lever  226  swingably mounted to the handle case  222  for adjusting the rotational speed of the engine  21  shown in FIG. 20, a lock lever  227  swingably mounted to the handle case  225  for temporarily fixing the throttle lever  226 , and a kill switch  228  for stopping the engine  21 . 
     The handle case  225  is comprised of two case halves, which are fixed to the handle  221  with screws which are not shown. 
     The throttle lever  226  is comprised of an operating section  226   a , a wire arm connecting arm  226   b  connected to the main wire  56   b  of the main cable  56  or the throttle wire  254   c  of the throttle cable  254 , and a bearing portion  226   c  which supports a pivot shaft  225   a  mounted to the handle case  225 . 
     The lock lever  227  is comprised of a pressure section  227   a  which is pressed with the palm of the hand, an arm engagement segment  227   b  which engages or disengages from the wire connecting arm  226   b  of the throttle lever  226 , and a bearing portion  227   c  which supports a pivot shaft  225   b  mounted to the handle case  225 . 
     The throttle lever  226  and the lock lever  227  operate in the same manner as the throttle lever  10  and the lock lever  108  shown in FIG.  7  and FIGS. 8A and 8B in conjunction with the first preferred embodiment and detailed description of the same is herein omitted. 
     Reference numeral  225   c  designates a tube mount portion formed in the handle case  225  for mounting a distal end of the main tube  56   a  of the main cable  56 , or a distal end of the throttle tube  254   a  of the throttle cable  254  to the handle case  225 . Reference numeral  231  designates a twisted coil spring which urges the throttle lever  226  such that the throttle lever  226  can be rotated clockwise about the center of the pivot shaft  225   a . Reference numeral  232  designates a twisted coil spring which urges the lock lever  227  such that the lock lever  227  can be rotated counterclockwise about the center of the pivot shaft  225   b.    
     Now, a bush cutting machine of a third preferred embodiment is described below. The bush cutting machine according the third preferred embodiment features the provision of a link mechanism composed of a relay member, described in conjunction with the first preferred embodiment, which is located in the operating lever unit  222  which acts as one of the grips of the U-shaped handle  221  shown in FIG. 20. A description is given below about an operating lever unit  222 , which acts as one of the grips of the U-shaped handle  221  shown in FIG. 20, a throttle actuating mechanism and a brake unit with reference to FIGS. 22 to  31 . Also, the same component parts as those of the bush cutting machine shown in the first preferred embodiment bear the same reference numerals and a detailed description of the same is herein omitted. 
     Referring now to FIG. 22, the operating lever unit  314  includes a handle case  331 , a throttle lever  332  swingably mounted to the handle case  331  for adjusting the rotational speed of the engine shown in FIG. 20, a lock lever  333  swingably mounted to the handle case  331  for locking the swinging movement of the throttle lever  332 , a twisted coil spring  334  which provides a rotational force to the throttle lever  332  in a clockwise direction, a twisted coil spring  335  for applying a rotational force to the lock lever in a counterclockwise direction, and a kill switch  336  for stopping the engine  21 . 
     The handle case  331  is comprised of two case halves by which the handle  221  shown in FIG. 20 is sandwiched, with two case halves being fixed to the handle  221  by screws which are not shown. Further, the handle case  331  includes a throttle lever stopper segment  331   a  for restricting the clockwise swinging movement of the throttle lever  332 , a lock lever stopper segment  331   b  for restricting a counterclockwise swinging movement of the lock lever  333 , a spring hook portion  331   c  engaging one end of a twisted coil spring  335 , and a grip portion  331   d  which is gripped with the hand. 
     The throttle lever  332  is comprised of an operating section  332   a  with which fingers (for, example, a forefinger, a middle finger, etc.) are hooked, a wire connecting arm  332   b  connected to a main wire  338 , a bearing portion  332   c , a projecting portion  332   d  which protrudes toward the lock lever  333  ,and a spring inserting portion  332   e  which allows one end of a twisted coil spring  334  to be inserted. Also, reference numeral  332   f  designates a side wall of the projecting portion  332   d.    
     The lock lever  333  is comprised of a swing stopper arm  333   b  for restricting the swinging movement of the throttle lever  332  by compelling at to move toward the projecting portion  332   d  of the throttle lever  332 , a bearing portion  333   c  which supports a pivot shaft  331   f  mounted to the handle case  331 , and a spring inserting portion  333   d  through which the other end of the twisted coil spring  335  is inserted. Also, reference numeral  333   e  designates a sidewise protrusion which protrudes from an end portion of the stopper arm  333   b  toward a side thereof (corresponding to the front surface of the drawing), and reference numeral  333   f  designates a circular arc wall of the sidewise protrusion  333   e.    
     The operating lever unit  314  incorporates therein a relay member  345 , which acts as a link mechanism, for interlinking the main wire  338  and the throttle cable  343 , which extends to the carburetor to be described later, and interlinking the main wire  338  and a brake cable  344 , which acts as a brake releasing cable, extending to the brake unit which will be described later. 
     One end of the main wire  338  has a wire terminal member  338   a , which is larger in diameter than the main wire  338 , and is connected to a relay member  345 . The other end of the main wire  338  is connected to the wire connecting arm  332   b  of the throttle lever  332  via the wire terminal member  338   b.    
     The throttle cable  343  is comprised of a throttle tube  343   a , a throttle wire  343   b  moveably disposed in the throttle tube  343   a , the wire terminal member  343   c  fixed to one end of the throttle wire  343   b , and a tube terminal member  343   d  mounted to one end of the throttle tube  343   b.    
     The brake cable  344  includes a brake tube  344   a , a brake wire  344   b  moveably inserted through the brake tube  344   a , a wire terminal member  344   c  mounted to one end of the brake wire  344   b , and a tube terminal member  344   d  mounted to one end of the brake tube  344   a . Also, reference numeral  331   g  designates a cable support portion formed in the handle case  331  for supporting the tube terminal members  343   d ,  344   d.    
     The relay member  345  includes a C-shape, in cross section, which has one end formed with a first upright portion  345   a  with which the wire terminal member  338   a  of the main wire  338  is engageable and the other end formed with a second upright portion  345   b  with which wire terminal member  343   c  of the throttle cable  343  and the wire terminal member  344   c  of the brake cable  344  are engageable. 
     In a normal use wherein the throttle lever  332  is not gripped, the amount of protrusion of the throttle wire  343   b  extending from the throttle tube  343   a  of the throttle wire  343   b  is selected to be greater than that of the brake wire  344   b  from the brake tube  344   a . And, the wire terminal member  344   c  of the brake cable  344  is held in abutting engagement with the second upright portion  345   b  of the relay member  345 , and the wire terminal member  343   c  of the throttle cable  343  is spaced from the second upright portion  345   b . That is, a distance between the wire terminal member  343   c  and the second upright portion  345   b  is determined to be greater than that between the wire terminal member  344   c  and the second upright portion  345   b.    
     Thus, the relay member  345  according to the third preferred embodiment has a function as a delay mechanism  347  wherein the presence of the wire terminal member  343   c  of the throttle wire  343   b  is spaced from the wire terminal member  344   c  of the brake wire  344  enables the throttle wire  343   b  to be pulled with a time delay from the movement of the brake wire  344   b  when the main wire  338  is pulled to move the relay member  345 . 
     As shown in FIG. 23, the handle case  331  is composed of first and second case halves  331   j ,  331   k . A pivot shaft  331   e  is formed in the first case half  331   j , and a pivot shaft  331   m  is formed in the second case half  331   k , with the pivot shafts  331   e ,  331   m  being received in a bearing portion  332   c . the wire connecting arm  332   b  extends from the bearing portion  332   c  whose distal end engages the wire terminal member  338   b  of the main wire  338  shown in FIG.  22 . Reference numeral  348  designates a screw by which the first and second case halves  331   j ,  331   k  are coupled to one another. 
     In FIG. 24, the first case half  331   j  has a pivot shaft  331   f , and the second case half  331   k  has a pivot shaft  331   n . These pivot shafts  331   f ,  331   n  are received by a bearing portion  333   c . A swing stopper arm  333   b  extends from the bearing portion  333   c . A side projecting portion  333   e , which is a distal end of the swing stopper arm  333   b , is close to a projecting portion  332   d  of the throttle lever  332 . 
     FIG. 25 is a view which corresponds to the cross sectional view of the front portion of the engine of the bush cutting machine shown in FIG. 14 in conjunction with the second preferred embodiment. The throttle cable  343  and the throttle arm  73  are similar in structure and in operation to those shown in FIG. 3 in conjunction with FIG. 3, and a detailed description is herein omitted. Reference numeral  343   e  shown in FIG. 26 designates a cylindrical member which corresponds to the cylindrical member  54   c  shown in FIG. 3, and reference numeral  343   f  designates a tube terminal member which corresponds to the tube terminal member  54   d  shown in FIG.  3 . 
     FIG. 27 shows the brake unit  65  according to the third preferred embodiment. Reference numeral  344   e  designates a wire terminal member located at the distal end of the brake wire  344   b  for connecting the brake wire  344   b  to the brake arm  96 . The brake unit according to such preferred embodiment is similar in structure and operates in the same manner as the brake unit  65  shown in FIG. 6 in conjunction with the first preferred embodiment, with like parts bearing the same reference numerals as those used in FIG. 6 to omit a description of the same parts. 
     Now, an operation of the operating lever unit  314  according to the third preferred embodiment and the engine are described below with reference to FIGS. 28A to  31 . 
     First, the engine is started up and brought into an idling state. 
     When this occurs, the centrifugal clutch  51  shown in FIG. 25 remains in an uncoupled state due to the rotational speed of the engine being below the given value. Also, since the drum  63  shown in FIG. 27 is urged with the brake shoe  61 , the cutter blade  22  shown in FIG. 20 remains inoperative. 
     Under such a condition, in FIG. 8A, the palm restraining portion  333   a  of the lock lever  333  is pressed in the clockwise direction with the palm of the hand as shown by the arrow a and the lock lever  333  is rotated while the grip portion  331   d  of the handle case  331  is gripped. This compels the swing stopper arm  333   b  of the lock lever  333  to be rotated in the direction as shown by the arrow a, causing the swing stopper arm  333   b  and the projecting portion  332   d  of the throttle lever  332  to be brought into disengagement from one another such that the lock condition of the throttle lever  32  is released to enable the operation of the throttle lever  32 . 
     In FIG. 28B, the operating section  332   a  of the throttle lever  332  is rotated counterclockwise with the finger up to the midway of the fully movable range of the throttle lever  332  in the direction as shown by the arrow b. Then, the main wire  338  is pulled in the direction as shown by the arrow c, thereby shifting the relay member  345  in the direction as shown by the arrow c. 
     Due to such shifting movement, the brake wire  344   b  of the brake cable  344  is pulled in a substantially concurrent movement of the main wire  338  in the direction as shown by the arrow d. When this takes place, since there is a clearance CL between the wire terminal member  344   c  of the throttle cable  343  and the second upright portion  345   b  of the relay member  345 , the throttle wire  343   b  is not pulled. 
     When the brake wire  344   b  is pulled in the direction as shown by the arrow d, the brake arm  96  rotates about the center of the pivot shaft  58  in the direction as shown by the arrow e. The brake shoe  61 , which is integral with the brake arm  96 , rotates in the direction as shown by the arrow f against the force of the tension coil spring  87 , compelling the brake shoe  61  to be displaced from the drum  63  for thereby releasing the brake. 
     As shown in FIG. 30A, when gripping the throttle lever  332  further deeply in the direction as shown by the arrow g to rotate the same, the main wire  338  is further pulled in the direction as shown by the arrow h such that the relay member  345  is further moved upward. When this takes place, the brake wire  344   b  is further moved in the direction as shown by the arrow j, allowing the throttle wire  343   b , which has not been pulled as shown in FIG. 28B, to be pulled in the direction as shown by arrow k. 
     When the throttle wire  343   b  is pulled in the direction as shown by the arrow k, the throttle arm  73  of the carburetor  53  rotates about the center of the throttle shaft  72  in the direction as shown by the arrow m as shown in FIG.  30 B. Due to such rotation, the throttle valve  72   a  mounted to the throttle shaft  72  is released, with a resultant increase in engine speed. If the engine speed exceeds the given value, the centrifugal clutch  51  shown in FIG. 25 is brought into a coupled condition to allow the drive power from the engine  21  to be transmitted to the cutter blade which in turn is rotated. 
     When removing the palm of the hand from the lock lever  333  while gripping the handle case  331 , the lock lever  333  is caused to swing in the direction as shown by the arrow n as shown in FIG. 31 due to repulsive power of the tension coil spring  335 . As a result, the circular arc wall  333   f  of the sidewise protrusion  333   e  of the lock lever  333  and the side wall  332   f  of the protruding section  332   d  of the throttle lever  332  are brought into engaging contact with one another such that, even when the finger is removed from the operating section  332   a  of the throttle lever  332 , the throttle lever  332  is enabled to remain stationary due to the frictional force between the circular arc wall  333   f  and the side wall  332   f.    
     Regardless of the position of the throttle lever  332  shown in the drawings, if the circular arc wall  333   f  and the side wall  332   f  are located in a position to be held in engaging contact with one another, it is possible for the finger to be removed from the throttle lever  332  for thereby eliminating the load for operating the lever. 
     As previously discussed above, with the bush cutting machine according to the third preferred embodiment, manipulating only the throttle lever  332  compels both the throttle shaft  72 , connected to the throttle cable  343 , and the brake arm  96 , connected to the brake cable  44 , to be operated via the relay member  345  which serves as the link member, providing an ease of carrying out the adjustment for the opening degree of the throttle valve, and the actuation or releasing operation of the brake unit. 
     Next, a modified form of the third preferred embodiment, i.e. an example wherein a relay member serving as a link mechanism is located in the operating lever  14  (corresponding to a component part  421  in the presently filed modification) which is contained in the bush cutting machine of the first preferred embodiment shown in FIG. 1, is described below with reference to FIG.  32 . Also, the same component parts as those of the operating lever unit  314  of the third preferred embodiment shown in FIG. 22 bear the same reference numerals as those used therein and detailed description of the same is herein omitted. 
     In FIG. 32, the operating lever unit  421  includes a handle case  426 , a throttle lever  427  swingably mounted to the handle case  426  for adjusting the rotational speed of the engine shown in FIG. 1, a lock lever  428  swingably mounted to the handle case  426  for locking the swinging movement of the throttle lever  427 , and a kill switch  431  for stopping the engine  21 . Reference numeral  424  designates a twisted coil spring for urging the throttle lever  427  in a clockwise direction at all times, and reference numeral  435  designates a twisted coil spring for urging the lock lever  428  counterclockwise at all times. 
     The handle case  426  is composed of two case halves which sandwiches the operation rod  24 . A longitudinal one end of the handle case  426  is formed with projecting segments  426   a ,  426   a , protruding from the two case halves, respectively, (with one of the projecting segments  426   a  being not shown) which are tightened with a bolt  437 , with the other longitudinal end being tightened with a bolt (not shown) to fixedly secure the handle case  426  to the operation rod  24 . 
     The throttle lever  427  is comprised of an operating section  427   a  with which fingers are hooked, a wire connecting arm  427   b  connected to the main wire  338 , a bearing portion  427   c  which supports a pivot shaft  426   b  mounted to the handle case  426 . 
     The lock lever  428  serves as a member for restricting the operation of the throttle lever  427  when the brake is applied to the cutter blade  22  under the idling condition of the engine  21  shown in FIG.  1 . The throttle lever  428  is comprised of an arm engaging segment  428   b  engaging the wire connecting arm  427   b  of the throttle lever  427  and a bearing portion  428   c  which supports a pivot shaft  426   c  mounted to the handle case  426 . 
     The operating lever unit  421  incorporates therein a link mechanism for interlinking the movement of the main wire  338  with the throttle cable  343  and the brake cable  344 . More particularly, the operating lever unit  421  incorporates therein a relay member  438  which serves as the ink mechanism which interlinks the main wire  338  and the throttle cable  343  extending to the carburetor  53  shown in FIG.  25  and also interlinks the main wire  338  and the brake cable  344  extending to the brake unit  65 . 
     The wire terminal member  338  formed at the one end of the main wire  338  is connected to the relay member  438 , with the wire terminal member  338 b formed at the other end of the main wire  338  being connected to the wire connecting arm  427   b  of the throttle lever  427 . 
     The handle case  438  includes a cable support portion  426   d  for supporting the throttle tube  343   a  of the throttle cable  343 , and a cable support portion  426   e  for supporting the brake tube  344   a  of the brake cable  344 . 
     The relay member  438  includes a circular arc member which has a C-shape, in cross section taken in a direction along the axis of the operation rod  24 , and which copes, in cross section perpendicular to the axis of the operation rod  24 , with the outer circumferential periphery of the operation rod  24 . The wire terminal member  338   a  of the main wire  338  engages a first upright portion  438   a  formed at one end of the relay member  438 , whose other end is formed with a second upright portion  438   b  to which the wire terminal member  343   c  of the throttle cable  343  and the wire terminal member  344   c  of the brake cable  344  are hooked. 
     In FIG. 32, the amount of protrusion of the throttle wire  343   b  extending from the throttle tube  343   a  is selected to be greater than that of the brake wire  344   b  extending from the brake tube  344   a . Also, the wire terminal member  344   c  of the brake cable  344  is held in substantially abutting engagement with the second upright portion  438   b  of the relay member  438 , and the wire terminal member  343   c  of the throttle cable  343  is spaced from the second upright portion  438   b . That is, a distance between the wire terminal member  343   c  and the second upright portion  438   bb  is determined to be greater than that between the wire terminal member  344   c  and the second upright portion  438   b.    
     Thus, the relay member  438  according to the present modification has a function as a delay mechanism  441  wherein the presence of the wire terminal member  343   c  of the throttle wire  343   b  is spaced from the wire terminal member  344   c  of the brake wire  344  enables the throttle wire  343   b  to be pulled with a time delay from the movement of the brake wire  344   b  when the main wire  338  is pulled to move the relay member  345 . 
     The relay member  438  according to the modification described above has the same function as the relay member  345  shown in FIG. 22, and a description of the same is herein omitted. 
     The degree of tension of the throttle wire  343   b  may be adjusted by loosening the nuts  443 ,  443  screwed to the male thread formed on the case mount member  343   g  formed at the end of the throttle tube  343   a  and tightening the nuts  443 ,  443  subsequent to the case mount member  443   g  being adjusted in a longitudinal axis thereof. 
     The degree of tension of the brake wire  344   b  may be adjusted in the same manner as described above by loosening the nuts  443 ,  443  screwed to the male thread formed on the case mount member  344   g  formed at the end of the brake tube  344   a  and tightening the nuts  443 ,  443  subsequent to the case mount member  344   g  being adjusted in a longitudinal axis thereof. 
     The present disclosure relates to the subject matters of Japanese Patent Application No. 2001-004233, filed Jan. 11, 2001, Japanese Patent Application No. 2001-006314, filed Jan. 15, 2001, and Japanese Patent Application No. 2001-006352, filed Jan. 15, 2001, the disclosures of which are expressly incorporated herein by reference in their entireties.