Abstract:
A hand lever apparatus is mountable on a working machine for controlling operation of the working machine. The hand lever apparatus includes a main lever and a magnitude-magnifying mechanism. The magnitude-magnifying mechanism includes a pivot pin, a lever member pivotal about the pivot pin, a pulley, and a connecting cable. The lever member has a shorter arm portion and a longer arm portion, which opposes the shorter arm portion and is operatively connected to a throttle cable of a throttle valve of the working machine. The shorter arm portion is operatively connected to the main lever via the connecting cable so that actuation of the finger-manipulable portion pivots the lever member about the pivot pin and causes the longer arm portion to pull the throttle cable away from the throttle valve and open the throttle valve of the working machine from a minimum-opening idling state. The hand lever apparatus also includes a position-adjust mechanism cooperatively associated with the pulley to cause translational movement of the pulley axis to control the speed of a driven member of the working machine.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a hand lever apparatus for manipulating through cable means various driven members such as a throttle valve of an internal combustion engine, and in particular to a hand lever apparatus which is adapted to be mounted in the vicinity of grip portion of a handle in a portable working machine such as a hedge trimmer or a bush cutter and which is suited for manipulating the opening and closing of the throttle valve by means of a throttle cable. 
     In a portable working machine such as a hedge trimmer or a bush cutter, a hand lever apparatus for adjusting the opening degree of a throttle valve of an internal combustion engine is attached to a portion of a U-shaped handle or a bar handle which is in the vicinity of grip portion of these handles for controlling the output of the internal combustion engine by hand. 
     This hand lever apparatus is usually provided with a throttle trigger (a throttle lever) that can be manipulated with fingers of an operator, so that the opening degree of the throttle valve can be adjusted by turning this throttle lever. The throttle valve is usually biased in the direction of minimum opening degree (idling opening degree) so that the throttle valve is retained at this idling opening degree in a free condition. However, when the throttle cable is pulled beyond a predetermined distance thus losing a predetermined looseness, the opening of the throttle valve is shifted from the idling opening degree to a high speed revolution side. 
     As for the construction of the handle lever apparatus for adjusting the opening degree of the throttle valve as explained above, there are known two types, i.e. an idling opening degree automatic reset type wherein the throttle lever can be automatically returned together with the throttle valve to the original position (idling opening degree) when the throttle lever is released from the state of revolution manipulation; and an opening degree-fixed type wherein the throttle lever can be kept immobilized at a desired revolution manipulation position even if fingers are released from the throttle lever (see Japanese Utility Model Publication S/57-19944). 
     According to the handle lever apparatus of idling opening degree automatic reset type, the engine can be automatically returned to the idling condition whenever the throttle lever is released from the operating fingers, so that if the portable working machine is of the type where the rotational driving force of the engine is transmitted via a centrifugal clutch to a working portion such as a cutting blade, the centrifugal clutch is turned into a cut-off condition thus preventing the rotational driving force from reaching the working portion. Therefore, if any accident happens to occur, the movement of the working portion can be immediately stopped by immediately rendering the throttle valve to return to the idling opening degree, which is an advantage in terms of enhancing the operational safety. However, there are problems in this handle lever apparatus of idling opening degree automatic reset type that the throttle lever is required to be held always with fingers so as to keep the throttle lever at a desired revolution position, thus making it cumbersome in operating the throttle lever at an intermediate opening degree, thus giving a fatigue to the operating fingers, and making it difficult to keep the magnitude of manipulation (revolution speed) constant. 
     When easiness of use is taken into account, it is generally desired that the revolution manipulation lever that will be manipulated with fingers such as a throttle lever should be constructed such that it takes only two positions, i.e. a released position and a set position (grasping position) without requiring to take an intermediate opening degree. In other words, it is considered preferable in view of manipulability that the adjustment of the throttle valve to an intermediate opening (a partial opening) and to a full opening (WOT) should be effected by setting the throttle lever to the same revolution manipulation position (the set position). 
     On the other hand, a hand lever apparatus of the aforementioned opening degree-fixing type is free from the aforementioned problems accompanied with the handle lever apparatus of idling opening degree automatic reset type, i.e. the throttle lever can be kept in an immobilized state at a desired revolution manipulation position even if fingers are released from the throttle lever, thus allowing the fingers to become free so as to easily perform the working. In spite of these advantages however, if any accident happens to occur, the throttle lever position-retaining function of the hand lever apparatus is required to be canceled by way of a separate manipulation, i.e. it is impossible to immediately stop the movement of the working member, thus rendering the hand lever apparatus of opening degree-fixing type inferior in terms of safety as compared with the hand lever apparatus of idling opening degree automatic reset type. 
     In any of the idling opening degree automatic reset type or the opening degree-fixing type, it is required to readjust the revolution manipulation position of the throttle valve if the throttle valve is to be returned to the previous opening degree in resuming the work after the throttle lever is once left free for temporarily suspending the work (this kind of manipulation is frequently experienced in the case of the bush cutter). However, this readjustment operation is troublesome so that there is still left room for improvement in terms of manipulability. 
     With a view to overcome the aforementioned problems or to solve the subject matter involved in the conventional hand lever apparatus, the present assignee has proposed as set forth in Japanese patent application H/7-108340 a hand lever apparatus, which is provided with a main lever and a sub-lever both being adapted to be rotationally manipulated. According to this hand lever apparatus, the cable connected to a driven member is adapted to be pulled by the sub-lever through a turning member such as a movable pulley, and the turning member is adapted to be shifted by the main lever. 
     According to this hand lever apparatus, the opening degree of the throttle valve constituting a driven member can be adjusted by way of the cable and at the same time easily retained at a desired opening degree. Additionally, this hand lever apparatus is advantageous in that it is possible to immediately put the throttle valve back to the minimum opening degree (the idling opening degree) whereby assuring a high safety, that it is possible to avoid fingers from being tired in short time, and that it is possible to dispense with the readjustment of opening degree of the throttle valve when the throttle valve is desired to be set to the previous opening degree which has been set in advance before the throttle valve is returned to the idling opening degree. 
     However, since the length of a cable to be pulled by the main lever corresponds with the rotational angle of the main lever of the hand lever apparatus, a relatively large rotational manipulation angle of the main lever is required for pulling a sufficient length of the cable, thus making the hand lever apparatus disadvantageous in this respect. In order to assure this large rotational manipulation angle of the main lever, a relatively large space for allowing the rotation of the main lever is required between the grip portion of the handle and the main lever, resulting in an enlargement in size and an increase in weight of the apparatus. In particular, when the main lever protrudes outward from the handle to a large extent, the main lever frequently becomes an obstacle at the time of use or even at the time of non-use, whereby deteriorating the workability and manipulability of the hand lever apparatus. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention has been made under the circumstances mentioned above, and therefore an object of the present invention is to provide a hand lever apparatus which is capable of adjusting the opening degree of the throttle valve constituting a driven member by making use of a cable, capable of easily retaining the throttle valve at a desired opening degree, capable of immediately putting the throttle valve back to the minimum opening degree (idling opening degree) whereby assuring a high degree of safety, capable of avoiding fingers from being tired in short time, capable of dispensing with the readjustment of opening degree of the throttle valve when the throttle valve is desired to be set back to the previous opening degree which has been set in advance before the throttle valve is returned to the idling opening degree, capable of minimizing the size and lightening the weight of the apparatus, and capable of improving the workability and manipulability of the apparatus. 
     With a view to realize the aforementioned objects, the hand lever apparatus according to the present invention is featured in that it is fundamentally provided with a main lever which is adapted to be rotationally manipulated so as to pull a cable connected to a driven member, and with a pulling magnitude-magnifying mechanism for magnifying a pulling magnitude of the cable by the main lever, the pulling magnitude-magnifying mechanism being interposed between the main lever and the cable. 
     According to a preferred embodiment of the present invention, the hand lever apparatus is additionally provided with a position-adjustment mechanism wherein the main lever is adapted to be manipulated to pull the cable connected to the driven member through a turning member and the turning member is adapted to be shifted to and retained at a desired position. 
     As for an example of the pulling magnitude-magnifying mechanism, one employing a lever or a gear may be used. 
     As a preferable example of the position-adjustment mechanism, one provided with a sub-lever adapted to be rotationally manipulated and with a turning member which is attached to a position which is dislocated from the rotational axis of a sub-lever may be employed. In this case, the sub-lever should preferably be mounted in such a manner that it can be retained in an immobilized state at a desired operating position. 
     As a typical but non-limitative use of the hand lever apparatus according to this invention, it may be employed for adjusting the opening degree of a throttle valve of an internal combustion engine. As a preferable specific example of such use, the following embodiment may be mentioned. 
     Namely, there is proposed a hand lever apparatus which is disposed near the grip portion of a handle in a working machine wherein the aforementioned throttle valve is usually energized in the direction of idling opening degree and when a throttle cable is pulled beyond a predetermined extent thus losing a predetermined looseness, the throttle valve begins to open from the idling opening degree so as to render an internal combustion engine provided with the throttle valve to actuate a working member such as a cutting blade. This hand lever apparatus is featured in that the throttle cable is adapted to be pulled through the aforementioned pulling magnitude-magnifying mechanism and the aforementioned turning member by the main lever thereby losing a predetermined looseness, and at the same time the turning member is forcibly shifted in the direction of pulling the throttle cable by the position-adjustment mechanism, thereby adjusting the opening degree of the throttle valve. 
     According to a preferable embodiment of the hand lever according to this invention, when the main lever is rotationally moved up to a set position which is close to the grip portion of the handle, the throttle cable is pulled by the pulling magnitude-magnifying mechanism employing a lever for instance as well as through the turning member comprising a pulley for instance to a predetermined extent, thereby to lose the aforementioned looseness. 
     In this case, the magnitude of pulling (the magnitude of displacement) of the cable by the main lever can be enlarged by the pulling magnitude-magnifying mechanism, so that the rotational angle of the main lever that is required for pulling the cable at a predetermined required distance can be minimized as compared with that required in the conventional hand lever apparatus. Accordingly, the space for allowing the main lever to rotate between the grip portion of the handle and the main lever can be minimized, resulting in a miniaturization and lightening of the apparatus and hence the workability and operability of the hand lever apparatus can be improved. 
     When a manipulation member mounted on the position-adjustment mechanism such as a sub-lever is moved to a desired position while keeping the main lever maintained at the aforementioned set position, the turning member is forced to move in the throttle cable-pulling direction, and hence the throttle cable is further pulled via the pulling magnitude-magnifying mechanism and the turning member, thus moving the throttle valve from the minimum opening degree (the idling opening degree) to a desired opening degree thereby to adjust the opening degree. 
     In this case, since the throttle cable is pulled by the turning member while being wound around the turning member, the throttle cable will be pulled twice as much distance as that of the moving distance of the turning member (which is the same as the increase in magnitude of displacement by a movable pulley). As a result, the magnitude for manipulating the position-adjustment mechanism which is required for adjusting the opening degree of the throttle valve, i.e. the moving distance of the turning member can be minimized, thus further enhancing the miniaturization and lightening of the apparatus. 
     In this case, even if the manipulation member such as the sub-lever is left free, the manipulation member can be kept as it is in an immobilized state at the previous manipulation position due to the effect by a position-holding means attached to the manipulation member, so that the pre-adjusted opening degree (the set opening degree) of the throttle valve can be maintained. Because of this, a burden on the fingers can be reduced. 
     When any accident happens to occur at the occasion where the opening degree of the throttle valve is set at a desired degree so as to necessitate a prompt and drastic reduction of revolutional speed of the engine, the main lever is released thereby allowing the main lever to be pulled in the reverse direction to return together with the pulling magnitude-magnifying mechanism to the original positions, since the throttle cable is always energized in a direction to close the throttle valve. As a result, the throttle cable is returned to the manipulation-free state, and the throttle valve is allowed to return to the idling opening degree, thus rendering the engine to take an idling state. 
     In this case, when this hand lever apparatus is applied to a working machine whose rotational driving force is adapted to be transmitted via a centrifugal clutch to a working member such as a cutting blade, the centrifugal clutch is turned into a cut-off condition, thus cutting the transmission of driving force to the working member thereby making it possible to immediately stopped the movement of the working member such as a cutting blade. 
     When the main lever is rotated again up to the set position close to the grip portion after the main lever is once released as mentioned above, the looseness of the throttle cable becomes zero and, since the sub-lever provided with the position-adjustment mechanism is kept remained in the previous operational position, the throttle valve is put back to the previous opening degree which has been set before the main lever is released, thus making the re-adjustment of the sub-lever unnecessary. 
     As explained above, according to the hand lever apparatus of the present invention, the opening degree of the throttle valve constituting a driven member can be controlled by means of a cable and at the same time easily retained at a desired opening degree. Additionally, the throttle valve can be immediately put back to the minimum opening degree (the idling opening degree) thus ensuring a high operational safety, and at the same time it is possible to avoid the fingers from becoming tired in short time. Furthermore, when the throttle valve is desired to be put back to the previous opening degree which has been set before the throttle valve is turned into the idling opening degree, it can be achieved without requiring the re-adjustment of the sub-lever. Moreover, according to the hand lever apparatus of the present invention, it is possible to effectively miniaturize and lighten the apparatus, and hence the workability and operability of the hand lever apparatus can be further improved. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     FIG. 1 is a perspective view showing one example of a bush cutter which is provided with one embodiment of the hand lever apparatus according to the present invention; 
     FIG. 2 is a left side view illustrating one embodiment of the hand lever apparatus according to the present invention; 
     FIG. 3 is a plan view illustrating one embodiment of the hand lever apparatus according to the present invention; 
     FIG. 4 is a right side view illustrating one embodiment of the hand lever apparatus according to the present invention; 
     FIG. 5 is a partially sectioned enlarged left side view illustrating a state where a left side cover case of the hand lever apparatus shown in FIG. 2 is dismantled; 
     FIG. 6 is a sectional view taken along the line VI—VI of FIG. 5; 
     FIG. 7 is a sectional view taken along the line VII—VII of FIG. 5; 
     FIG. 8 is a schematic perspective view showing the pulling magnitude-magnifying mechanism of the hand lever apparatus shown in FIG. 2 together with the relevant portion thereof; 
     FIG. 9 is a perspective view showing an intermediate cover case of the hand lever apparatus shown in FIG. 2; 
     FIG. 10 is an enlarged sectional view taken along the line X—X of FIG. 2; 
     FIG. 11 is a cross-sectional view illustrating a state where a right side cover case, an intermediate cover case and a left side cover case of the hand lever apparatus shown in FIG. 6 are dismantled from the handle; and 
     FIG. 12 is a partially sectioned left side view illustrating another example of the hand lever apparatus of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will be further explained with reference to the drawings depicting various embodiments of this invention. 
     FIG. 1 shows one example of a bush cutter which is provided with one embodiment of the hand lever apparatus according to the present invention. This bush cutter  1  shown in FIG. 1 comprises a cylindrical bar handle  7  provided with a pair of grip portions  11  and  12  which are spaced apart from each other by a predetermined distance; an operation portion  3  comprising a cutting blade  13  and a safety cover  14  which are mounted on the distal end portion of the bar handle  7 ; and an internal combustion engine (a small air-cooled two-cycle gasoline engine)  2  mounted on the proximal end portion of the bar handle  7  and functioning as a power source for driving the cutting blade  13  by way of a drive shaft (not shown) coaxially inserted in the bar handle  7 . This internal combustion engine  2  is accompanied with a recoil starter  6  and a fuel tank  4 , and provided with a carburetor (not shown) having a throttle valve CV and also with an ignition plug  5 . 
     In this embodiment, the throttle valve CV is usually energized in the direction of the minimum opening (idle opening) so that when a throttle (inner) cable  17  (see FIG. 5) which is connected to the throttle valve CV and will be explained hereinafter is pulled beyond a predetermined distance from the non-operation state, the looseness is taken away and the throttle valve CV begins to open from the minimum opening degree. 
     For the purpose of adjusting the opening degree of the throttle valve CV, a hand lever apparatus  10  according to this embodiment is attached to a portion of the bar handle  7  which is adjacent to the rear grip portion  11  (rather than the fore grip portion  12 ) and adapted to be grasped usually by the right hand. 
     As shown in FIGS. 2 to  4 , the hand lever apparatus  10  comprises a case  20  which is externally fitted over and in close to the rear grip portion  11  of the bar handle  7 , and a main lever  30  which is pivotally attached to the case  20  for pulling the throttle cable  17  inserted in an outer tube  16  of a Bowden cable  15  which is connected to the throttle valve CV. 
     As clearly shown in FIGS. 6 and 7, the case  20  is formed of a three-block construction consisting of a right cover case  21 , an intermediate cover case  22  and a left cover case  23 , all being made of a plastic material. 
     As clearly shown in FIG.  2  and FIG. 10 showing an enlarged sectional view taken along the line X—X of FIG. 2, the right cover case  21  and the left cover case  23  each having a rectangular tray-like shape in outer appearance are provided, at four portions thereof i.e. upper two portions and lower two portions, with tapped holes  21   a  and  21   b  and insertion holes  23   a  and  23   b.  A screw  24  is screwed in each of the tapped holes  21   a  and insertion holes  23   a  which are disposed at the upper portion, and a screw  25  is screwed in each of the tapped holes  21   b  and insertion holes  23   b  which are disposed at the lower portion. 
     The right cover case  21  and the left cover case  23  are fastened with the intermediate cover case  22  being interposed therebetween in such a manner that the contacting surfaces  21 A and  22 A of the fore and rear end portions thereof each having a semi-circular cross-section are contacted with the outer peripheral surface of the bar handle  7  so as to hold the bar handle  7  therebetween. 
     As clearly shown in FIG. 10, FIG. 5 where the left side cover case  23  is dismantled and FIG. 9 illustrating the single body of the intermediate cover case  22 , the intermediate cover case  22  which is interposed between the right cover case  21  and the left cover case  23  is provided with insertion holes  22   b  which are coaxially interposed between the lower tapped holes  21   b  and the lower insertion holes  23   b  so as to allow the screw  25  to be inserted therethrough. In addition to that, the intermediate cover case  22  is provided with a contacting surface  22 A having a semi-circular cross-section which is adapted to be contacted with the lower right portion of the outer periphery of the bar handle  7 , and with insertion holes  22   c  in the vicinity of upper fore and rear end portions of the contacting surface  22 A, which are adapted to be inserted by a fastening screw  26  to be screwed in tapped holes  21   c  formed in the vicinity of central fore and rear end portions of the right cover case  21 , so that the intermediate cover case  22  can be firmly attached to the right cover case  21  by means of the screws  26 . 
     The contacting surface  22 A of the intermediate cover case  22  is provided with a locking protrusion  29  which is adapted to be engaged with a circular concave  9  (i.e. not a through-hole) formed in the vicinity of the center portion of the right outer peripheral surface of the cylindrical handle  7  (see FIG.  6 ). 
     As clearly seen from FIGS. 5 to  8 , the main lever  30  which is rotatably attached to the case  20  comprises a straight manipulation portion  31  which is adapted to be rotated by the fingers so as to come close to a lever receiver  11   a  formed on the lower end portion of the rear grip portion  11 , a cylindrical portion  32  loosely fitted over a supporting shaft  35 , and a curved portion  33  linked via the proximal end portion thereof to the cylindrical portion  32  and being slightly twisted slantwise in a rightward and upward direction. The right end portion of the supporting shaft  35  is press-fitted in an insertion hole  21   d  which is formed in the vicinity of the lower corner portion of the rear end of the right cover case  21 , while the left end portion of the supporting shaft  35  is press-fitted in an insertion hole  22   d  formed in the intermediate cover case  22  and at the same time loosely inserted in an insertion hole  23   d  formed in the left cover case  23  (see FIG.  6 ). 
     In this structure, the throttle cable  17  is adapted to be pulled by the main lever  30  constructed as mentioned above via a pulling magnitude-magnifying mechanism  40  and a pulley  45  constituting a turning member. 
     As clearly seen from FIGS. 7 and 8, the pulling magnitude-magnifying mechanism  40  comprises a lever  41  which is rotatably fitted over a supporting shaft  42  whose both end portions are held by a bearing hole  21   g  formed at the lower forward portion of the right cover case  21 , by an axis-supporting portion  21   f  provided near the central portion of the right cover case  21  and by an axis-supporting portion  22   f  formed on the intermediate cover case  22 . Thus, as shown in FIG. 8, the terminal metal fitting  19 ″ of the throttle cable  17  attaches to the longer arm portion (or second arm portion)  41 A at a second-arm-portion connection position which, although not numbered, corresponds to the position of the terminal metal fitting  19 ″ of the throttle cable  17 . A second distance d 2  separates the supporting shaft  42  from the second-arm-portion connection position. A terminal metal fitting  19  attached to the distal end portion of the throttle cable  17  is fitted in the distal end portion (left end portion) of a longer arm portion  41 A of the lever  41 . 
     By the way, the distal end portion of the outer tube  16  of the Bowden cable  15  in which the throttle cable  17  is inserted is fastened at a fastening portion  22   i  formed on the intermediate cover case  22 , and the throttle cable  17  is extended from a slit  22   j  formed at the fore end portion of the fastening portion  22   i  (see FIG. 9) toward the longer arm portion  41 A of the lever  41  and linked thereto as mentioned above. 
     A cable  18  is wound around a pulley  45  constituting a turning member so that the running direction of the cable  18  is reversed by the pulley  45 , and both end portions of the cable  18  are attached respectively with a metal fitting  19 ′ or  19 ″, one of which being connected to the distal end portion (right side portion) of the shorter arm portion  41 B of the lever  41 , the other being connected to the cylindrical distal end portion  33   a  of the curved portion  33  of the main lever  30 . Thus, the terminal metal fitting  19 ′ of the cable  18  attaches to the shorter arm portion (or first arm portion)  41 B at a first-arm-portion connection position which, although not numbered, corresponds to the position of the terminal metal fitting  19 ′ of the cable  18 . A first distance d 1  separates the supporting shaft  42  from the first-arm-portion connection position. As seen from FIG. 8, the first distance d 1  of the shorter arm portion  41 B is smaller than the second distance d 2  of the longer arm portion  41 A. 
     As clearly seen from FIG. 8, when the main lever  30  (or the manipulating portion  31  thereof) having the structure as mentioned above is manipulated to rotate in the direction to come close to the rear grip portion  11 , the shorter arm portion  41 B of the lever  41  is pulled backward by means of the cable  18  thereby causing the lever  41  to rotate clockwise direction (in the plan view), and hence the throttle cable  17  is drawn out forward by way of the longer arm portion  41 A of the lever  41 . In this case, due to the lever ratio of the lever  41 , the pulling distance of the throttle cable  17  by the main lever is magnified. 
     According to this embodiment, a position-adjustment mechanism  50  is provided for forcibly shifting the pulley  45  in the direction of pulling the throttle cable  17  (the rearward direction) so as to retain the pulley  45  at a desired position in an immobilized state. 
     As clearly seen from FIGS. 4 to  7 , this position-adjustment mechanism  50  comprises a rotatable axis  60  provided with a housing portion  64  for housing the pulley  45 , and a sub-lever  51  provided with a serration  52  to be engaged with a serrated shaft  62  disposed on the right end portion of the rotatable axis  60  and secured by means of screw  55  to the right end portion of the rotatable axis  60 . 
     The left end portion of the rotatable axis  60  is axially supported by a bearing portion  22   e  disposed on the right side of the intermediate cover case  22 , while the right end portion of the rotatable axis  60  is axially supported by a bearing portion  21   e  formed in the right cover case  21 . The pulley  45  disposed inside the housing portion  64  is rotatably mounted on a pin  46 . In this case, the central axial line O′ of the pin  46  supporting the pulley  45  is offset upward by a predetermined distance of E from the rotation axis O of the sub-lever  51  (the central axial line of the rotational axis  60 ), so that when the sub-lever  51  is allowed to rotate in the rearward direction, the pulley  45  is caused to move in the direction of pulling the throttle cable  17  (or in the rearward direction). 
     A cylindrical push button  53  having an opened bottom is fitted in the upper portion of the sub-lever  51  in such a manner that it can be slid upward and downward. In this push button  53  is slide-fitted a bottomed sleeve  57  which is normally biased by a coil spring  56  in the downward direction and mounted in such a manner that the bottom portion of the bottomed sleeve  57  is downwardly protruded so as to contact with and slidable in the forward or rearward direction on the right shoulder portion of the right cover case  21 . 
     A serrated movable gear  58  is disposed facing upward at the lower left end portion of the push button  53 . On the other hand, as clearly shown in FIGS. 3 and 4, a serrated fixed gear  28  engaging with the serrated movable gear  58  is disposed at the upper portion of the right cover case  21  in such a manner that the serrated fixed gear  28  depicts a circular arc facing downward and extending in the forward and rearward direction with the center of curvature being at the rotation axis line O of the sub-lever  51 . 
     When the push button  53  is pressed in the structure of this position-adjustment mechanism  50 , the serrated movable gear  58  is disengaged from the serrated fixed gear  28 , so that when the push button  53  is pulled to a desired rearward position while keeping the pressing of the push button  53 , the sub-lever  51  is caused to swing rearward, and at the same time the pulley  45  is caused to move in the direction of pulling the throttle cable  17  (the rearward direction). When the pressing of the push button  53  is released under this condition, the serrated movable gear  58  is caused to engaged with the serrated fixed gear  28  again, and the states of the sub-lever  51  and the pulley  45  are kept remained at that rotational manipulation position. 
     A slide type stop switch  67  for short-circuiting the passage of electric current to the ignition plug  5  of the internal combustion engine  2  so as to stop the engine  2  is mounted in such a manner as to be interposed between rectangular cut portions  21   k  and  23   k,  which are formed at the upper central portions of the right cover case  21  and the left cover case  23  respectively (see FIG.  6 ). 
     The attachment of the hand lever apparatus  10  constructed according to this embodiment to the bar handle  7  can be performed as follows. Namely, first of all, the movable members such as the main lever  30 , the pulling magnitude-magnifying mechanism  40 , the pulley  45 , the position-adjustment mechanism  50 , etc. are assembled and housed by making use of the right cover case  21  and the intermediate cover case  22 , and at the same time the intermediate cover case  22  is fastened onto the right cover case  21  by making use of a couple of screws  26  (see FIGS. 5,  10  and  11 ). 
     Then, the assembled body comprising the mobile members such as the main lever  30 , the pulling magnitude-magnifying mechanism  40 , the pulley  45 , the position-adjustment mechanism  50 , etc. which are housed in the right cover case  21  and the intermediate cover case  22  is attached to the bar handle  7  in such a manner that the bar handle  7  is sandwiched between and enclosed by this assembled body and the left cover case  23 . In this case, the positioning of the assembled body to the bar handle  7  can be performed by fitting the locking protrusion  29  formed on the intermediate cover case  22  in the concave portion  9  formed in the bar handle  7  (see FIG.  11 ). Thereafter, all of the right cover case  21 , the intermediate cover case  22  and the left cover case  23  are fastened together by making use of four pieces of bolts  24  and  25 . 
     As a result, the case member  20  constituted by the right cover case  21 , the intermediate cover case  22  and the left cover case  23  is externally fitted over a predetermined position of the bar handle  7 . 
     The dismantling of the hand lever apparatus  10  of this embodiment from the bar handle  7  can be performed by disassembling the left cover case  23  from the right cover case  21  and from the intermediate cover case  22  which has been assembled with the right cover case  21 . 
     Even if the case member  20  constituted by the right cover case  21 , the intermediate cover case  22  and the left cover case  23  is dismantled from the bar handle  7  and disintegrated, in other words, even before the hand lever apparatus  10  is assembled with the handle  7  or even at the occasion of maintenance service, the movable members such as the main lever  30 , the pulling magnitude-magnifying mechanism  40 , the pulley  45 , the position-adjustment mechanism  50 , etc. can be kept in an assembled state in association with only the right cover case  21  and the intermediate cover case  22  as shown in FIG.  11 . 
     Due to this construction, it is possible with the hand lever apparatus  10  of this embodiment to more easily perform the assembling work and maintenance service as compared with the conventional hand lever apparatus of two-pieces divided type where the movable members can be hardly kept in an assembled state in association with the case member (one of the pair). 
     Furthermore, the bar handle  7  is provided with the concave portion  9 , while the intermediate cover case  22  is provided with the locking protrusion  29  to be engaged with the aforementioned concave portion  9 . Therefore, it is possible, when the case member  20  is externally fitted over the bar handle  7  by fitting the locking protrusion  29  in the concave portion  9 , to prevent the case member  20  from being rotated around the bar handle  7  or from being moved in the longitudinal direction due to the effect of engagement between the locking protrusion  29  and the concave portion  9 . 
     Therefore, it is possible to obtain a constantly stabilized manipulability without accompanying a dislocation of the distal tip of the throttle cable  17  so that the distance of pulling of the throttle cable  17  in relative to the magnitude of manipulating the main lever  30  and the position-adjustment mechanism  50  will become constant, thus making it possible to accurately control the opening degree of the throttle valve CV. 
     When the main lever  30  is manipulated to be rotated up to the set position in close to the rear grip portion  11  of the bar handle  7  in the hand lever apparatus  10  of this embodiment constructed as explained above, the throttle cable  17  is pulled up to a predetermined distance via the pulling magnitude-magnifying mechanism  40  employing the lever  41  and via the pulley  45  constituting the turning member thereby taking the looseness away. 
     In this case, the magnitude of pulling (displacement) of the cable  17  by the main lever  30  is magnified by the pulling magnitude-magnifying mechanism  40 , so that the turning angle a of the main lever  30  which is required for pulling the cable  17  in a sufficient degree can be minimized as compared with that required in the conventional hand lever apparatus (see FIG.  2 ). Accordingly, the space for allowing the main lever  30  to rotate between the grip portion  11  of the bar handle  7  and the main lever  30  can be minimized, resulting in a miniaturization and lightening of the apparatus and hence the workability and operability of the hand lever apparatus  10  can be improved. 
     When the push button  53  mounted on the position-adjustment mechanism  50  is pushed so as to move the sub-lever  51  to a desired rearward position while keeping the main lever  30  maintained at the aforementioned set position, the pulley  45  is forced to move in the direction of pulling the throttle cable  17 , and hence the throttle cable  17  is further pulled via the pulling magnitude-magnifying mechanism  40  and the pulley  45 , thus moving the throttle valve CV from the minimum opening degree (the idling opening degree) to a desired opening degree thereby to control the opening degree. 
     In this case, since the throttle cable  17  is pulled by the pulley  45  while being wound around the pulley  45 , the throttle cable  17  will be pulled twice as much distance as that of the moving distance of the pulley  45 . As a result, the magnitude for manipulating the sub-lever  51  of the position-adjustment mechanism  50  which is required for adjusting the opening degree of the throttle valve CV, i.e. the moving distance of the pulley  45  can be minimized, thus further promoting the miniaturization and lightening of the apparatus. 
     In this case, even if the sub-lever  51  is leased, the sub-lever  51  can be kept as it is in an immobilized state at the previous manipulation position due to the engagement between the serrated movable gear  58  and the serrated fixed gear  28 , so that the pre-adjusted opening degree (the set opening degree) of the throttle valve CV can be maintained. Because of this, a burden on the operator&#39;s fingers can be also reduced. 
     When any accident happens to occur under a condition where the opening degree of the throttle valve CV has been set at a desired degree so as to necessitate a prompt and prominent reduction of rotational speed of the engine  2 , the main lever  30  is released thereby allowing the main lever  30  to be pulled in the reverse direction to return together with the lever  41  of the pulling magnitude-magnifying mechanism  40  to the original positions, since the throttle cable  17  is always energized in a direction to close the throttle valve CV. As a result, the throttle cable  17  is returned to the manipulation-free state, and the throttle valve CV is allowed to return to the idling opening degree, thus rendering the engine  2  to take an idling state. 
     In this case, when this hand lever apparatus  10  is applied to a working machine  1  whose rotational driving force is adapted to be transmitted via a centrifugal clutch to a working member  3  such as a cutting blade  13 , the centrifugal clutch is turned into a cut-off condition, thus cutting the transmission of driving force to the working member  3  thereby making it possible to immediately stop the movement of the working member  3  such as the cutting blade  13 . 
     When the main lever  30  is rotated again up to the set position in close to the grip portion  11  after the main lever  30  is once released as mentioned above, the looseness of the throttle cable  17  becomes zero and, since the sub-lever  51  provided in the position-adjustment mechanism  50  is kept remained in the previous operational position, the throttle valve CV is put back to the previous opening degree which has been set before the main lever  30  is released, thus making the re-adjustment of the sub-lever  51  unnecessary. 
     As explained above, according to the hand lever apparatus  10  of the present invention, the opening degree of throttle valve CV constituting a driven member can be controlled by the cable  17  and at the same time easily retained at a desired opening degree. Additionally, the throttle valve CV can be immediately put back to the minimum opening degree (the idling opening degree) thus ensuring a high operational safety, and at the same time it is possible to avoid the fingers from becoming tired in short time. Furthermore, when the throttle valve CV is desired to be put back to the previous opening degree which has been set before the throttle valve CV is returned into the idling opening degree, it can be achieved without requiring the re-adjustment of the sub-lever  51 . Moreover, according to the hand lever apparatus  10  of the present invention, it is possible to effectively miniaturize and lighten the apparatus, and hence the workability and operability of the hand lever apparatus can be further improved. 
     While one embodiment of the present invention has been explained in details for the purpose of illustration in the foregoing, it will be understood that the construction of the device can be varied without departing from the spirit and scope of the present invention. 
     For example, the pulling magnitude-magnifying mechanism is not limited to those having a lever  41  as explained above, but may be constructed as shown in FIG.  12 . Namely, in this embodiment, the main lever  70  is provided with a manipulation portion  71 , with a cylindrical portion  72  externally fitted around a supporting shaft  35  and with a first sector gear  73  having a larger diameter which is integrally formed on the cylindrical portion  72 . The support shaft  35  has a first axis (unnumbered) about which the manipulation portion  71  is pivotal. On the other hand, a second sector gear  77  having a smaller diameter is rotatably fitted around a supporting shaft  75  so as to be engaged with the first sector gear  73 . A distal end portion of the throttle cable  17  is connected with the distal end portion of a tension lever  78 , so that the throttle cable  17  can be pulled by the tension lever  78  via a guide member  79  and the pulley  45  which is rotable about a second axis. In this case, the first sector gear  73 , the second sector gear  77  and the tension lever  78  function to magnify the magnitude of pulling the throttle cable  17  by the main lever  70 . 
     While the foregoing embodiments have been illustrated centering on the case where the hand lever apparatus of the present invention is applied to the internal combustion engine  2  for controlling the opening degree of the throttle valve CV, the hand lever apparatus of this invention is not confined to the aforementioned embodiments but is applicable to various kinds of devices other than for controlling the opening degree of the throttle valve CV. 
     Furthermore, the hand lever apparatus  10  may be mounted on a U-shaped handle other than the aforementioned bar handle. 
     As would be clear from the foregoing explanations, it is possible according to the hand lever apparatus of the present invention to control the opening degree of throttle valve constituting a driven member by making use of a cable and at the same time the opening degree of the throttle valve can be easily retained at a desired degree. Additionally, the throttle valve can be immediately put back to the minimum opening degree (the idling opening degree) thus ensuring a high operational safety, and at the same time it is possible to avoid the fingers from becoming tired in short time. Furthermore, when the throttle valve is desired to be put back to the previous opening degree which has been set before the throttle valve is returned into the idling opening degree, it can be achieved without requiring any re-adjustment of the valve. Moreover, according to the hand lever apparatus of the present invention, it is possible to effectively miniaturize and lighten the apparatus, and hence the workability and operability of the hand lever apparatus can be further improved.