Abstract:
According to one embodiment, a throttle adjustment device, for a brush cutter in which an engine is mounted at one end of a handle pipe and in which a throttle adjustment wire extends from a throttle of the engine, include: a throttle lever having an operation portion to be operated by the user; a sub lever having a holding portion to be connected with an extending end of the throttle adjustment wire; a case to be fixed to the handle pipe, the throttle lever and the sub lever being rotatably mounted in the case; and a connecting member configured to bring the throttle lever and the sub lever into: an interlocked state where the throttle is adjustable in accordance with an operation amount of the throttle lever; or an un-interlocked state where the throttle is not adjustable regardless of the operation amount of the throttle lever.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This application claims priorities from Japanese Patent Application No. 2011-014809 filed on Jan. 27, 2011, the entire contents of which are herein incorporated by reference. 
       FIELD 
       [0002]    The present invention relates to a throttle adjustment device for a brush cutter or the like. For example, a brush cutter may include: a handle pipe accommodating a driving shaft thereinside; an engine disposed at one end of the handle pipe; and rotary blades disposed at the other end of the handle pipe to be driven by the engine through the driving shaft. The present invention relates specifically to a throttle adjustment device for adjusting rotation of the engine in such brush cutter. 
       BACKGROUND 
       [0003]    Generally, a brush cutter has an engine driven by using gasoline as fuel, at the rear of a handle pip. And, rotary blades at the front of the handle pipe driven by the engine through a centrifugal clutch mechanism. In such blush cutter, the user is allowed to control the output (rotation) of the engine by operating a throttle lever with their finger while holding the grip of the handle pipe, as necessary. 
         [0004]    For example, JP-4211959-B proposes a throttle adjustment device (lever device) for a brush cutter, as shown in  FIG. 13 . In the throttle adjustment device, a throttle adjustment wire  53  (Bowden wire) is extended from an engine (not shown), and a drum  54  is provided at an end of the throttle adjustment wire  53 . The throttle adjustment device includes a throttle lever  57  having a drum holding portion  55  for holding the drum  54  and an engagement wall  59 , and a sub lever  58  having a regulating member  60  to be faced to the engagement wall  59 . The throttle lever  57  and the sub lever  58  are rotatably disposed in a case  52  fixed to a handle pipe  51 . The rotation range of the throttle lever  57  is adjusted by the sub lever  58  through a contact between the regulating member  60  and the engagement wall  59 . 
         [0005]    A rotary shaft  61  of the throttle lever  57  is inserted into a guide hole  62  of the case  52 . The guide hole  62  guides the rotary shaft  61  such that the throttle lever  57  rotates about a contacting point of the engagement wall  59  and the regulating member  60  as a fulcrum. A turn spring  63  is provided to minimize the stroke of the throttle adjustment wire  53  and to press the grip portion of the throttle lever  57  away from the handle pipe  51 . Further, a locking lever  64  is provided opposite to the throttle lever  57  to be engaged/disengaged with respect to the throttle lever  57  at the initial position. The locking lever  64  has an engagement hook  65  to be engaged/disengaged with respect to the drum holding portion  55 , and is kept pressed to be normally engaged with the throttle lever  57 . 
         [0006]    It is assumed that the sub lever  58  is in the position as shown in  FIG. 13  (where the sub lever  58  has been frictionally rotated counterclockwise to the maximum). In this state, when the engagement hook  65  of the locking lever  64  is disengaged from the drum holding portion  55  and the throttle lever  57  is strongly gripped, the throttle lever  57  can be maximally rotated until the engagement wall  59  contacts the regulating member  60 . As a result, the throttle adjustment wire  53  is drawn out to the maximum, the throttle opening degree is increased to the maximum, and the rotation speed of the engine increases to the maximum. The throttle opening degree can be set to the medium or the minimum by frictionally rotating the sub lever  58  such that the engagement wall  59  contacts the regulating member  60  at a corresponding position. 
         [0007]    In the above-mentioned throttle adjustment device, once the sub lever  58  has been frictionally rotated, the throttle opening degree (rotation speed of the engine) can be constantly maintained by simply strongly holding the throttle lever  57 , without finely adjusting the holding force. Thus, it is superior in the operability and workability. Moreover, the throttle lever  57  can be locked at the initial position by the locking lever  64  as shown in  FIG. 13 . Thus, in the non-working time, the engine can be prevented from being unintentionally driven. 
         [0008]    However, in the above-mentioned throttle adjustment device, once the throttle lever  57  is locked at the initial position by the locking lever  64  as shown in  FIG. 13 , the throttle lever  57  can not be moved from the initial position even if a shock, for example, due to the brush cutter falling down is applied thereto. If such shock is applied to the throttle lever  57  being locked, components for locking, such as the throttle lever  57 , the drum  54 , the drum holding portion  55  and the locking lever  64 , may be broken or damaged. 
       SUMMARY 
       [0009]    One object of the present invention is to provide a throttle adjustment device in which, even when large load is applied to a throttle lever being locked, components for locking is prevented from being broken or damaged. 
         [0010]    According to an aspect of the present invention, there is provided a throttle adjustment device for a brush cutter in which an engine is mounted at one end of a handle pipe and in which a throttle adjustment wire extends from a throttle of the engine, including: a throttle lever having an operation portion to be operated by the user; a sub lever having a holding portion to be connected with an extending end of the throttle adjustment wire; a case to be fixed to the handle pipe, the throttle lever and the sub lever being rotatably mounted in the case; and a connecting member configured to bring the throttle lever and the sub lever into: an interlocked state where the throttle is adjustable in accordance with an operation amount of the throttle lever; or an un-interlocked state where the throttle is not adjustable regardless of the operation amount of the throttle lever. 
         [0011]    According to another aspect of the present invention, there may be provided, based on the above-mentioned structure, the throttle adjustment, wherein, in the case, the throttle lever and the sub lever are rotatably supported by a support shaft in common, the sub lever being rotatably supported at an end thereof opposite to the holding portion, wherein a concavo-convex fitting hole is formed in the sub lever at a position between the support shaft and the holding portion, a convex fitting portion being formed in the concavo-convex fitting hole, and wherein the connecting member is slidable in a direction parallel to the support shaft, the connecting member being lockable with the concavo-convex fitting hole upon being slid. 
         [0012]    According to still another aspect of the present invention, there may be provided, based on the above-mentioned structure, the throttle adjustment, wherein the connecting member is a pin member slidable in a direction parallel to a support shaft rotatably supporting the throttle lever and the sub lever, the pin member including: a shank portion to be inserted into a concavo-convex fitting hole formed in the sub lever; and a concave fitting portion formed in the shank portion to be lockable with a convex fitting portion in the concavo-convex fitting hole, wherein a spring is provided to outwardly urge the pin member, and wherein a retaining pin is provided to maintain the pin member at a non-operation position against the spring. 
         [0013]    According to the above configurations, the throttle lever to be operated and a sub lever to be connected to the throttle adjustment wire are concentrically and rotatably mounted in the case which is fixed to the handle pipe. The throttle lever and sub lever can be maintained in an un-interlocked state in a normal state by a connecting member provided for interlocking or un-interlocking the throttle lever and the sub lever. As a result, in the normal state, even when the throttle lever is unintentionally rotated with an excessive force, while the engine output is prevented from being increased, the throttle lever is allowed to idly rotate to thereby prevent the components from being broken or damaged by the applied force. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0014]      FIG. 1  is a front view of a throttle adjustment device of an embodiment. 
           [0015]      FIG. 2  is a right side view of the throttle adjustment device. 
           [0016]      FIG. 3  is a cross-sectional view taken along the line A-A of  FIG. 2 . 
           [0017]      FIGS. 4A to 4C  illustrate a throttle lever, in which  FIG. 4A  is a front view,  FIG. 4B  is a side view, and  FIG. 4C  is a rear view. 
           [0018]      FIGS. 5A to 5D  illustrate a sub lever, in which  FIG. 5A  is a front view,  FIG. 5B  is a side view,  FIG. 5C  is a rear view, and  FIG. 5D  is a perspective view. 
           [0019]      FIGS. 6A to 6C  illustrate a connecting member (locking pin), in which  FIG. 6A  is a front view,  FIG. 6B  is a side view, and  FIG. 6C  is a perspective view. 
           [0020]      FIG. 7  illustrates a normal state. 
           [0021]      FIG. 8  illustrates a first action state where the connecting member is pressed from the normal state ( FIG. 7 ). 
           [0022]      FIG. 9  illustrates a second action state whether the throttle lever is rotated (the throttle opening degree is increased) following the first action state ( FIG. 8 ). 
           [0023]      FIG. 10  illustrates the second action state ( FIG. 9 ), correspondingly with the cross-sectional view of  FIG. 3   
           [0024]      FIG. 11  illustrates an idling state where the throttle lever is rotated without pressing the connecting member from the normal state ( FIG. 7 ). 
           [0025]      FIG. 12  illustrates the idling state ( FIG. 11 ), correspondingly with the cross-sectional view of  FIG. 3 . 
           [0026]      FIG. 13  illustrates a related-art throttle adjustment device. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]      FIGS. 1 to 12  illustrate a throttle adjustment device according to the embodiment. The throttle adjustment device includes a handle pipe  1 , a fixing band and a case  3 . The handle pipe  1  has a grip portion for holding a brush cutter. And, the case  3  has a substantially reversed U-shaped cross-section to be detachably mounted on the handle pipe  1  by the fixing band  2 . The case  3  has an introduction portion  5  for a throttle adjustment wire  4 . The throttle adjustment wire  4  is composed of an outer wire  4 - 1  and an inner wire  4 - 2 , and a drum  6  is formed at the end of the inner wire  4 - 2 . The throttle opening degree is increased by drawing out the inner wire  4 - 2  together with the drum  6 , thereby increasing the rotation speed of an engine. 
         [0028]    The case  3  houses a throttle lever  7  and a sub lever  8 . The throttle lever  7  has an operating portion. The sub lever  8  has a holding portion  8 - 1  for the drum  6  formed at the end of the throttle adjustment wire  4 . Both of the throttle lever  7  and the sub lever  8  are rotatably mounted to the case  3  by a support shaft  9  in common. As shown in  FIGS. 4A to 4C , the throttle lever  7  includes an operating portion  7 - 1 , a mounting hole  7 - 2  for the support shaft  9 , and a slide hole  7 - 3  for a connecting member (locking pin)  10 . The mounting hole  7 - 2  and the slide hole  7 - 3  are formed at one end of the operating portion  7 - 1 . The connecting member (locking pin)  10  to be inserted into the slide hole  7 - 3  is used for interlocking or un-interlocking the throttle lever  7  and the sub lever  8 . 
         [0029]    As shown in  FIGS. 5A to 5D , the sub lever  8  includes the holding portion  8 - 1  for the drum  6  at one end, and a mounting hole  8 - 2  for the support shaft  9  at the other end. Both ends of the sub lever  8  extend perpendicularly with each other. The sub lever  8  also includes a concavo-convex fitting hole  8 - 3  and a convex fitting portion  8 - 4 , for the connecting member  10 . The concavo-convex fitting hole  8 - 3  is formed between the holding portion  8 - 1  and the mounting hole  8 - 2 . The connecting member  10  is slidingly insertable into the concavo-convex fitting hole  8 - 3  by being pressed in a direction parallel to the support shaft  9  which is inserted into the mounting hole  8 - 2 . The convex fitting portion  8 - 4  is formed at the end of the concavo-convex fitting hole  8 - 3 . 
         [0030]    As shown in  FIGS. 6A to 6C , the connecting member  10  includes a head portion  10 - 1  and a shank portion  10 - 2 . The connecting member  10  further includes a convex portion  10 - 3  to be concavo-convexly fitted to the convex fitting portion  8 - 4 , and a guide slot  10 - 4  for receiving a retaining pin  14 . While the head portion  10 - 1  is formed at one end of the shank portion  10 - 2 , the convex portion  10 - 3  is formed at the other end of the shank portion  10 - 2 . And, the guide slot  10 - 4  is formed at the middle portion of the shank portion  10 - 2 . 
         [0031]    The throttle lever  7  and the sub lever  8  are rotatably mounted in the case  3  by the support shaft  9  and a nut  11 , such that the support shaft  9  penetrates through the case  3 , the mounting hole  7 - 2  of the throttle lever  7  and the mounting hole  8 - 2  of the sub lever  8 . A return spring  12  is mounted on the outer circumference of the mounting hole  7 - 2  to urge the throttle lever  7  toward the initial position as shown in  FIGS. 1 to 3 . The connecting member  10  is slidably inserted into the slide hole  7 - 3  of the throttle lever  7 . A return spring  13  is mounted between the throttle lever  7  and the head  10 - 1  to outwardly urge the connecting member  10 . While the connecting member  10  is urged by the return spring  13  toward the initial position, the connecting member  10  is slidingly insertable into the concavo-convex fitting hole  8 - 3  by being pressed. A retaining pin  14  is mounted to the throttle lever  7  while being inserted into the guide slot  10 - 4  to thereby maintain the connecting member  10  at a non-operation position. 
         [0032]    Next, the operation of the above-mentioned throttle adjustment device will be described. In the normal state as shown in  FIGS. 3 and 7 , the head  10 - 1  side end of the connecting member  10  is outwardly urged by the return spring  13  to protrude from the slide hole  7 - 3  of the throttle lever  7 , and the opposite end of the connecting member  10  is not inserted into the concavo-convex fitting hole  8 - 3  of the sub lever  8 . Thus, the throttle lever  7  and the sub lever  8  are remained in the un-interlocked state. In this state, even when the throttle lever  7  is rotated toward the handle pipe  1 , as shown in  FIGS. 11 and 12 , the sub lever  8  is not rotated, and therefore, the inner wire  4 - 2  of the throttle adjustment wire  4  is not drawn out. As a result, the engine remains idling, and the rotary blades (not shown) mounted on the front of the handle pipe  1  do not rotate. 
         [0033]    By pressing the connecting member  10  against the return spring  13  from the normal state (initial position) of  FIG. 7 , the concave fitting portion  10 - 3  of the connecting member  10  is concavo-convexly fitted to the convex fitting portion  8 - 4  of the sub lever  8  as shown in  FIG. 8 . After that, by slightly rotating the throttle lever  7  in the direction of arrow B ( FIG. 10 ) from the state of  FIG. 8 , the throttle lever  7  and the sub lever  8  are brought into the interlocked state. By further rotating the throttle lever  7 , the sub lever  8  moves interlockedly with the throttle lever  7  through the connecting member  10  as shown in  FIGS. 9 and 10 , thereby drawing out the inner wire  4 - 2  of the throttle adjustment wire  4  and increasing the throttle opening degree. 
         [0034]    In this state, in a range where the throttle opening degree is sufficiently large, the connecting member  10  does not return to the initial position because of the locking between the sub lever  8  and the connecting member  10 , even when the pressing of the connecting member  10  is released (free state). When the throttle lever  7  is released, the throttle lever  7  and the sub lever  8  are rotated in the direction of arrow C ( FIG. 10 ) from the above state by the return spring  12 , and the throttle lever  7  and the sub lever  8  return to their initial positions. Then, the locking between the sub lever  8  and the connecting member  10  is released, and the connecting member  10  returns to the initial position by the return spring  13 . Thus, the throttle lever  7  and the sub lever  8  return to the un-interlocked state as shown in  FIG. 7 . In this state, even when the user carelessly contacts the throttle lever  7 , the throttle lever  7  is merely idly rotated toward the handle pipe  1 , and throttle-up does not occur. Further, even when the connecting member  10  is pressed in a state where the throttle lever  7  is idly rotated against the return spring  12 , since the connecting member  10  and the sub lever  8  are not concavo-convexly fitted with each other ( FIG. 11 ), throttle-up does not occur. 
         [0035]    As described above, in the throttle adjustment device of the embodiment, when the throttle lever  7  is rotated toward the handle pipe  1  against the return spring  12  after the connecting member  10  is pressed, the throttle lever  7  and the sub lever  8  are brought into the interlocked state by the connecting member  10 , and the inner wire  4 - 2  of the throttle adjustment wire  4  is drawn out to increase the throttle opening degree. And, when the throttle lever  7  is released, the throttle lever  7  and the sub lever  8  return to their initial positions by the return spring  12 , and the connecting member  10  also returns to the initial position by the return spring  13 . Thus, the throttle lever  7  and the sub lever  8  return into the un-interlocked state. In this state, even when the throttle lever  7  is unintentionally operated, although the throttle lever  7  merely idly rotates, the inner wire  4 - 2  of the throttle adjustment wire  4  is not drawn out. Thus, throttle-up does not occur, and the engine output is not increased. Further, since the throttle lever is allowed to idly rotate, the components of the throttle adjustment device are prevented from being broken or damaged even when an excessive force is applied to the throttle lever  7 . 
         [0036]    Although a throttle adjustment device for a brush cutter is exemplified, the embodiment may be applied to a throttle adjustment device for controlling the rotation speed of other types of engines. 
         [0037]    The throttle adjustment device of the embodiment has a throttle lever to be operated and a sub lever to be connected to the throttle adjustment wire, and the throttle lever and the sub lever are concentrically and rotatably mounted in a case which is fixed to a handle pipe. Further, there is provided a connecting member for not only maintaining the throttle lever and sub lever in the un-interlocked state in a normal state, bus also for bringing them into the interlocked state upon being operated. As a result, according to the throttle adjustment device of the embodiment, in the normal state, even when the throttle lever is unintentionally rotated with an excessive force, while the engine output is prevented from being increased, the throttle lever is allowed to idly rotate to thereby prevent the components from being broken or damaged by the applied force.