Abstract:
A bush cutting apparatus has a first rotational shaft mounted for undergoing rotation and a cutter blade connected to the first rotational shaft for rotation therewith. A clutch mechanism has a rotational member, at least one clutch moving member mounted on the rotational member for undergoing movement along a radial direction of the rotational member, a clutch drum mounted on the first rotational shaft for sliding movement therealong to engage the clutch moving member, and a clutch resilient member for biasing the clutch moving member toward an axial centerline of the rotational member. A brake mechanism has a brake shoe formed at an end portion of the clutch drum, a brake pad disposed opposite to and confronting the brake shoe, and a braking resilient member for biasing the brake shoe into pressure contact with the brake pad. A drive source has a second rotational shaft for selectively rotating the rotational member of the clutch mechanism at rotational speeds higher or lower than a preselected rotational speed. The second rotational shaft is axially spaced from and operatively connected to the first rotational shaft via the clutch mechanism and the brake mechanism for rotationally driving the first rotational shaft.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to a bush cutting apparatus, and more particularly to an improved brake mechanism for stopping rotation of a cutter blade of a bush cutting apparatus. 
     BACKGROUND OF THE INVENTION 
     Brake mechanisms of bush cutting apparatuses are known, for example, from Japanese Utility Model Laid-Open Publication Nos. 51-53248 and 51-99039. The first-mentioned 51-53248 publication discloses a bush cutting apparatus which includes brake shoes and cam plates for moving the brake shoes into and out of engagement with a driven shaft. As a human operator releases a brake bar, the cam plates are caused, via springs, to pivot to press the brake shoes against the driven shaft, so that there is automatically produced a braking force to stop rotation of the rotary cutter. 
     The second-mentioned 51-99039 publication discloses a bush cutting apparatus which includes a brake lining provided along the outer periphery of a clutch drum. As a human operator releases a lever, the brake lining comes into engagement with the outer periphery of the clutch drum and a signal is generated from a movable contact to deactivate a prime mover or drive source, so that a rotary cutter can be caused to stop its rotation. 
     With the structure disclosed in the 51-53248 publication, it would take a considerable deal of time and labor to deactivate the rotary cutter because the human operator is required to manually manipulate the brake lever. Further, the disclosed structure requires a great number of component parts, such as the brake lever, wires and the like and hence add to production costs. 
     Also, with the structure disclosed in the 51-99039 publication, it would take a considerable deal of time and labor to deactivate the drive source and rotary cutter because the human operator is required to manually manipulate the lever, which leads to a poor operability. Further, in the disclosed bush cutting apparatus, a control rod coupled to one end of a connecting wire extends through a hole formed in a clutch housing, and measures for maximizing dust-tightness and water-tightness must be taken in relation to the hole in the clutch housing. Furthermore, extra operations are necessary for checking and adjusting the tension of the connecting wire coupled at the other end to the lever, which would require an extra time and labor. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, it is an object of the present invention to provide an improved bush cutting apparatus which can achieve an enhanced operability and enhanced dust-tightness and water-tightness and which can be manufactured at reduced costs. 
     According to one embodiment of the present invention, there is provided an improved bush cutting apparatus of the type which includes a cutter-blade driving shaft having a cutter blade attached thereto and a drive source having an output shaft operatively connected with the cutter-blade driving shaft for rotating the cutter-blade driving shaft via a clutch mechanism and a brake mechanism. The clutch mechanism in the bush cutting apparatus of the invention comprises: a rotating member mounted on the output shaft of the drive source; a clutch moving member mounted on the rotating member for sliding movement along a radial direction of the rotating member, the clutch moving member having a tapered outer side surface; a clutch drum mounted on the cutter-blade driving shaft for axial movement therealong and having a tapered portion with an inner surface corresponding in contour to the tapered outer side surface of the clutch moving member; and a clutch resilient member for normally pulling the clutch moving member toward an axial centerline of the rotating member. The brake mechanism comprises: a brake shoe formed at a tip of an open end portion of the clutch drum that constitutes a greatest diameter region of the tapered portion in the clutch drum; a brake pad secured to a non-rotating fixed housing in opposed relation to the brake shoe; and a braking resilient member for normally pressing the brake shoe against the brake pad. When the rotating member is not rotated by the drive source at more than a predetermined rotation speed, the clutch moving member is kept disengaged from the clutch drum due to pulling force of the clutch resilient member so that the brake shoe is pressed against the brake pad to apply the brakes. But, when the rotating member is rotated by the drive source at more than a predetermined rotation speed, the clutch moving member is moved radially outward to press the clutch drum by centrifugal force in such a manner that the clutch drum is caused, by the tapered outer side surface of the clutch moving member, to slide to a non-braking position. 
     When the rotation of the rotating member and hence of the cutter blade has fallen below the predetermined rotation speed, the brake mechanism is automatically activated to terminate the rotation of the cutter blade. Namely, when the number of rotations of the drive source and hence of the clutch mechanism has fallen below a predetermined value, the moving member in the clutch mechanism is disengaged from the clutch drum, and thus the clutch drum is freed and resiliently slid, by the brake mechanism, back to a predetermined braking position where the brake shoe is pressed against the brake pad to apply the brakes; namely, in this case, the brake mechanism causes the brake shoe to be pressed against the brake pad via the braking resilient member. As a result, the clutch drum having the brake shoe as well as the cutter-blade driving shaft and the cutter blade is caused to stop rotating. Because the brake mechanism is thus automatically activated in accordance with a variation in the number of rotations of the drive source, the present invention can eliminate the need for a human operator to manually manipulate a brake lever or the like, and thus allows the human operator to manipulate the bush cutting apparatus with a significantly enhanced operability. 
     On the other hand, when the number of rotations of the drive source and hence of the clutch mechanism has increased above a predetermined value, the clutch moving member in the clutch mechanism is caused to slide radially outward along the rotating member in such a manner that the clutch moving member slides the clutch drum to the non-braking position against the bias of the braking resilient member while transmitting the rotational force from the rotating member to the clutch drum by means of the tapered outer side surface, so that the brake shoe formed on the clutch drum is disengaged from the brake pad to release the brakes. 
     With such arrangements, the present invention can dispense with a lever and wire for braking operation by the human operator and eliminate a need for an apparatus housing to have a hole for passing component parts, such as a wire and rod, through the housing. As a result, the present invention can achieve enhanced dust-tightness and water-tightness of the bush cutting apparatus. Further, because the parts, such as the brake lever and wire, can be dispensed with, the bush cutting apparatus of the present invention can be manufactured at reduced costs. 
     According to another embodiment of the present invention, there is provided another improved bush cutting apparatus of the type including a cutter-blade driving shaft having a cutter blade attached thereto and a drive source having an output shaft operatively connected with the cutter-blade driving shaft for rotating the cutter-blade driving shaft via a clutch mechanism and brake mechanism. In this bush cutting apparatus, the clutch mechanism comprises: a rotating member mounted on the output shaft of the drive source; a clutch moving member mounted on the rotating member for movement along radial and axial directions of the rotating member; a clutch drum mounted on the cutter-blade driving shaft for axial movement therealong; and a clutch resilient member for normally pulling the clutch moving member toward an axial centerline of the rotating member. The brake mechanism comprises: a brake shoe formed at a tip of an open end portion of the clutch drum; a brake pad secured to a non-rotating fixed housing in opposed relation to the brake shoe; and a braking resilient member for normally pressing the brake shoe against the brake pad. When the rotating member is not rotated by the drive source at more than a predetermined rotation speed, the clutch moving member is kept disengaged from the clutch drum due to pulling force of the clutch resilient member in such a manner that the brake shoe is pressed against the brake pad to apply the brakes, while when the rotating member is rotated by the drive source at more than a predetermined rotation speed, the clutch moving member is moved radially outward and axially to press and slide the clutch drum in a direction where the brake shoe is disengaged from the brake pad. 
     When the number of rotations of the drive source and hence of the clutch mechanism has fallen below a predetermined value in the other embodiment, the moving member in the clutch mechanism is disengaged from the clutch drum, and thus the clutch drum is freed and resiliently slid, by the brake mechanism, back to a predetermined braking position where the brake shoe is pressed against the brake pad to apply the brakes; namely, the brake mechanism causes the brake shoe to be pressed against the brake pad via the braking resilient member. As a result, the clutch drum having the brake shoe as well as the cutter-blade driving shaft and the cutter blade is caused to stop rotating. Because the brake mechanism is thus automatically activated in accordance with a variation in the number of rotations of the drive source, the present invention can eliminate the need for a human operator to manually manipulate a brake lever or the like, and thus allows the human operator to manipulate the bush cutting apparatus with a significantly enhanced operability. 
     On the other hand, when the number of rotations of the drive source and hence of the clutch mechanism has increased above a predetermined value, the clutch moving member in the clutch mechanism is caused not only to slide radially outward along the rotating member but also move in the axial direction away from the brake pad. Such movement of the clutch moving member causes the brake shoe of the clutch drum to disengage from the brake drum, thereby releasing the brakes. 
     With such arrangements, the present invention can dispense with a lever and wire for braking operation by the human operator and eliminate a need for an apparatus housing to have a hole for passing component parts, such as a wire and rod, through the housing. As a result, the present invention can achieve enhanced dust-tightness and water-tightness of the bush cutting apparatus. 
     In a preferred embodiment of the present invention, a plurality of the clutch moving members are provided symmetrically with each other about the axial centerline of the rotating member. The symmetrical arrangement can distribute the weights of the moving members and thus can reliably prevent unbalance during the rotation. Further, the symmetrical arrangement permits synchronization between the two moving members and thereby allows the clutch mechanism and brake mechanism to operate smoothly, so that reliable brake performance can be accomplished. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Certain preferred embodiments of the present invention will hereinafter be described in detail, by way of example only, with reference to the accompanying drawings, in which: 
     FIG. 1 is a view showing a manner in which a human operator cuts bushes using a bush cutting apparatus in accordance with a first embodiment of the present invention; 
     FIG. 2 is a partly-sectional front view of a body section of the cutting apparatus shown in FIG. 1; 
     FIG. 3 is a sectional view of the bush cutting apparatus taken along the  3 — 3  line of FIG. 2; 
     FIGS. 4A and 4B are views explanatory of behavior of the bush cutting apparatus shown in FIG. 2; 
     FIG. 5 is a sectional view of a bush cutting apparatus in accordance with a second embodiment of the present invention; and 
     FIGS. 6A and 6B are views explanatory of behavior of the bush cutting apparatus shown in FIG.  5 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a view showing a manner in which a human operator cuts bushes using a bush cutting apparatus in accordance with a first embodiment of the present invention. Namely, the human operator is shown here as carrying the bush cutting apparatus  10  with a belt  11  suspended from one of operator&#39;s shoulders and gripping a handling portion  12  of the cutting apparatus  10  with one of his or her hands. The bush cutting apparatus  10  includes a rotary cutting blade  13  and various other components as will be described in detail hereinbelow. 
     FIG. 2 is a partly-sectional front view of a body section of the cutting apparatus  10  circled at  2  in FIG.  1 . As shown, the bush cutting apparatus  10  includes a prime mover or drive source  21 , a clutch mechanism  23  and brake mechanism  24  connected to a crankshaft  22  of the drive source  21 , and a cutter-blade driving shaft  25  connected to the clutch mechanism  23 . 
     The clutch mechanism  23  includes a rotating member  41  mounted on the crankshaft  22  functioning as an output shaft of the drive source  21 . The clutch mechanism  23  also includes two moving members  45  each having, on its outer side (i.e., the side remote from the crankshaft  22 ), a tapered surface  44  tapering in a direction away from the drive source  21 , and the moving members  45  are mounted on the rotating member  41  for sliding movement along radial directions of the rotating member  41  as denoted by arrow {circle around (2)}. The clutch mechanism  23  further includes a clutch drum  31  that is mounted on the cutter-blade driving shaft  25  for movement along the axial direction (denoted by arrow {circle around (1)}) of the shaft  25  and that has a tapered portion  43  with an inner surface corresponding in contour to the tapered outer side surfaces  44  of the moving members  45 . The clutch mechanism  23  further includes resilient members  46  (FIG. 3) that normally pulls the moving members  45  toward each other, i.e. toward the centerline C of the rotating member  41 . 
     Brake mechanism  24  includes a brake shoe  33  formed at the tip of an open end portion  32 , closer to the drive source  21 , of the clutch drum  31  which constitutes a greatest-diameter portion of the tapered portion  43 , brake pads  35  secured to a non-rotating fixed housing  34  in axially-opposed relation to the brake shoe  33 , and a braking resilient member  36  for normally pressing the brake shoe  33  against the brake pads  35 . 
     The prime mover or drive source  21  includes a cylinder  51 , a piston  52 , the above-mentioned crankshaft  22 , and a sparking plug  63 . Reference numeral  54  in FIG. 2 represents a fuel tank,  55  an oil tank, and  56  a starting device. 
     The tapered clutch drum  31  has the brake shoe  33  of the brake mechanism  24  formed, as a kind of radial flange, at the tip of the open end portion (right end portion in FIG. 2)  32  having the greatest diameter D, and a disk-shaped connecting portion  61  at its bottom end portion (left end portion in FIG. 2) having a smallest diameter. Connecting shaft  62  is coupled to the connecting portion  61  and has serrations  62   a  in its axial middle portion for coupling with the cutter-blade driving shaft  25 . For this purpose, the cutter-blade driving shaft  25  has, in its end portion closer to the clutch drum  31 , serrations  25   a  meshing with the serrations  62   a  by a given axial length L 1 . 
     The housing  34  has a bearing portion  65  centrally on its body  64 , and pad mounting portions  67  at its open end closer to the drive source  21 . The brake pads  35  are each fixed to a corresponding one of the pad mounting portions  67  via a rug  68 . Bearing unit  71  is fitted in the bearing portion  65 , and a collar  72  is snugly fitted between the bearing unit  71  and the connecting shaft  62 . The braking resilient member  36  abuts at its one end against the collar  72  and at the other end against the connecting portion  61  of the clutch drum  31 . The collar  72  is made, for example, of white metal and constructed to function as sliding bearings. Further, the braking resilient member  36  comprises, for example, a dish-shaped spring. 
     The rotating member  41  has a central mounting portion  73  projecting axially toward the drive source  21  and coupled to the crankshaft  22 , and guide portions  74  projecting laterally from a base of the central mounting portion  73  in opposite directions for guiding respective ones of the moving members  45  of the clutch mechanism  23 . Each of the clutch moving members  45 , having the tapered outer side surface  44 , has an inner protrusion  75  slidably fitted in the corresponding guide section  74 . Each of the clutch moving members  45  also has an engaging portion  76  (FIG. 3) adjacent the inner protrusion  75  for engaging corresponding ends of the resilient members  46  (FIG. 3) of the clutch mechanism  23 . 
     FIG. 3 is a sectional view of the bush cutting apparatus taken along the  3 — 3  line of FIG.  2 . As seen in FIG. 3, the two clutch moving members  45  are positioned symmetrically with (diametrically opposed to) each other about the centerline C of the rotating member  41  and radially slidable along the guide portions  74  as denoted by arrow {circle around (2)}. Also, it is seen in FIG. 3 that the diametrically-opposed clutch moving members  45  are engaged by the resilient members  46  and the clutch drum  31  has the tapered portion  43  to be acted on or pressed by the clutch moving members  45 . As also clearly seen in FIG. 3, the brake shoe  33  of the brake mechanism  24  is formed integrally on the open end portion  32  of the clutch drum  31 , and the brake pads  35  are secured to the housing  34  in opposed relation to the brake shoe  33 . Reference numeral  77  in FIG. 3 represents a key interconnecting the rotating member  41  and the crankshaft  22 . 
     The following paragraphs describe behavior of the bush cutting apparatus  10  in accordance with the first embodiment of the invention constructed as above, with primary reference to FIGS. 4A and 4B. 
     In the brake mechanism  24  of the bush cutting apparatus  10 , as shown in FIG. 4A, the brake shoe  33  is normally pressed against the brake pads  35  as denoted by arrow {circle around (3)}. To initiate bush cutting operations in this state, the drive source  21  is first activated, and then the rotating speed, i.e. the number of rotations, of the drive source  21  is caused to increase progressively. 
     Then, when the rotating speed of the drive source  21  has been increased to such an extent as to cause the rotating member  41  of the clutch mechanism  23  to rotate at more than a predetermined rotation speed, i.e. exceed a predetermined number of rotations, with the brake shoe  33  sliding along the surface of brake pads  35 , the clutch moving members  45  slide radially outward, away from each other, by centrifugal force as denoted by arrow {circle around (2)} and thereby press the inner surface of the tapered portion  43  of the clutch drum  31  so that the tapered outer surfaces  44  of the moving members  45  cause the clutch drum  31  to axially slide to a non-braking position, as denoted by arrow {circle around (4)}, against the bias of the braking resilient member  36 . Thus, the brake shoe  33  is moved away or disengaged from the brake pads  35  by a distance Y. As a result, the number of rotations can be further increased to allow the cutter-blade driving shaft  25  to rotate at a corresponding rate as denoted by arrow {circle around (5)}. 
     Conversely, when the rotating speed of the drive source  21  has been reduced to such an extent as to cause the rotating member  41  of the clutch mechanism  23  to rotate at less than a predetermined rotation speed, i.e. fall below a predetermined number of rotations, the moving members  45  are disengaged from the clutch drum  31  and resiliently moved radially inward away from the clutch drum  31 , as denoted by arrow {circle around (6)} in FIG. 4A, by pulling force F 1  exerted by the resilient members  46 . Thus, the clutch drum  31  resiliently moves back to the original position by force F 2  exerted by the braking resilient member  36 , where the brake shoe  33  is again pressed against the brake pads  35  to thereby apply the brakes such that the rotation of the clutch drum  31  and hence the rotation of the cutter-blade driving shaft  25  is terminated instantaneously. 
     Namely, with the rotating member  41  of the clutch mechanism  23  rotating at less than the predetermined rotation speed, the clutch moving members  45  are resiliently slid away from the clutch drum  31  by pulling force F 1  of the resilient members  46 , while the brake shoe  33  of the brake mechanism  24  is resiliently brought back into abutment against the brake pads  35  to automatically apply the brakes. Such arrangements can eliminate the need for the human operator to perform manual braking operation to stop the rotation of the cutter-blade driving shaft  25 , and thereby can enhance the operability of the bush cutting apparatus  10 . 
     Further, in the instant embodiment where the brake mechanism  24  is composed of the brake shoe  33  formed on the clutch drum  31 , brake pads  35  provided on the housing  34  and braking resilient member  36  for normally pressing the brake shoe  33  against the brake pads  35 , there is no need for the housing  34  to have a hole for passing component parts, such as a wire and rod, through the housing  34 , so that enhanced dust-tightness and water-tightness can be achieved. Furthermore, because the brake mechanism  24  is arranged to automatically apply the brakes when the predetermined number of rotations is not reached, it is possible to dispense with component parts to be used for manual braking operation, such as a handling lever and wire, and thus the manufacturing costs of the bush cutting apparatus can be reduced considerably. 
     In addition, with the two moving members  45  of the clutch mechanism  23  provided symmetrically with each other about the centerline C of the rotating member  41 , the weights of the component parts can be distributed uniformly to the center axis of the rotation, which can reliably prevent unwanted unbalance during the rotation. Further, the symmetrical arrangement permits synchronization between the two clutch moving members  45  and thereby allows the clutch mechanism  23  and brake mechanism  24  to operate smoothly, so that reliable brakes can be assured. 
     Furthermore, because the collar  72  is mounted on the connecting shaft  62  of the clutch drum  31  and also fitted in the bearing unit  71 , the collar  72  can support the connecting shaft  62  with a reduced friction coefficient, so that the connecting shaft  62  and hence the brake shoe  33  can be readily slid to the non-braking position (in the arrow {circle around (4)} direction of FIG.  4 B). Furthermore, because the serrations  25   a  of the cutter-blade driving shaft  25  mesh with the serrations  62   a  of the connecting shaft  62  by the axial length L 1 , the connecting shaft  62  allows the brake shoe  33  to slide to the non-braking position (in the arrow {circle around (4)} direction of FIG. 4B) while transmitting the rotational force. 
     Next, a description will be made about a bush cutting apparatus in accordance with a second embodiment of the present invention. FIG. 5 is a sectional view of the bush cutting apparatus, in which the elements of the same structures and functions as those in FIG. 2 are represented by the same reference characters. 
     Clutch mechanism  23 B includes a rotating member  84  mounted on a crankshaft  22  functioning as an output shaft of a drive source  21 , and clutch moving members  85  mounted on the rotating member  84  for movement both along the radially outward directions of the rotating member  84  as denoted by arrow {circle around (2)} and along the axial direction of the crankshaft  22  as denoted by arrow {circle around (1)}. The clutch mechanism  23  further includes a clutch drum  81  that is mounted on a cutter-blade driving shaft  25  for movement along the axial direction (arrow {circle around (1)} direction) of the driving shaft  25 , and clutch resilient members  46  (FIG. 6) that normally pulls the moving members  85  toward each other, i.e. toward the centerline C of the rotating member  84 . 
     Brake mechanism  24 B includes a brake shoe  83  formed, as a kind of radial flange, at the tip of its open end portion (right end portion in FIG. 5)  82  of the clutch drum  81 , brake pads  35  secured to a non-rotating fixed housing  34  in axially-opposed relation to the brake shoe  83 , and a braking resilient member  36  for normally pressing the brake shoe  83  against the brake pads  35 . The clutch drum  81  has the brake shoe  83  of the brake mechanism  24 B formed at the tip of its cylindrical portion  86 , and a disk-shaped connecting portion  61  at its bottom end portion (left end portion in FIG.  5 ). Connecting shaft  62  is coupled to the connecting portion  61  of the clutch drum  81 . Each of the clutch moving members  45  has a tapered outer side surface  87 , and it has an inner protrusion  88  having an orthogonal portion  88   a  and a slanted portion  88   b . Each of the clutch moving members  85  also has an engaging portion  76  (see FIG. 3) adjacent the inner protrusion  88  for engaging corresponding ends of the resilient members  46  of the clutch mechanism  23 B. 
     The following paragraphs describe behavior of the bush cutting apparatus  10  in accordance with the second embodiment of the invention constructed as above, with primary reference to FIGS. 6A and 6B. 
     In the brake mechanism  24 B of the bush cutting apparatus  10 , as shown in FIG. 6A, the brake shoe  83  is normally pressed against the brake pads  35  as denoted by arrow ( 3 . To initiate bush cutting operations in this state, the drive source  21  is first activated, and the rotating speed of the drive source  21  is caused to increase progressively. 
     Then, when the rotation speed of the drive source  21  has been increased to such an extent as to cause the rotating member  84  of the clutch mechanism  23 B to rotate at more than a predetermined rotation speed, i.e. exceed a predetermined number of rotations, the clutch moving members  85  slide radially outward away from the rotating member  84  by centrifugal force as denoted by arrow {circle around (2)}. Once respective bottom outer corners  89  of the clutch moving members  85  contact the inner surface of the clutch drum  81 , the clutch moving members  85  move (almost tumble) in a direction away from the brake pads  35  (arrow {circle around (7)}) direction) because each of the clutch moving members  85  has its center of gravity G displaced or offset from the bottom outer corner due to the provision of the tapered outer side surface  87 . Simultaneously, the clutch moving members  85  causes the clutch drum  81  to slide in the arrow {circle around (7)} direction, against the bias of the braking resilient member  36 , so that the brake shoe  83  is moved away from the brake pads  35  by a distance Y. As a consequence, the number of rotations can be further increased to allow the cutter-blade driving shaft  25  to rotate at a corresponding rate as denoted by arrow {circle around (5)}. 
     Conversely, when the rotating speed of the drive source  21  has been reduced to such an extent as to cause the rotating member  84  of the clutch mechanism  23 B to rotate at less than a predetermined rotation speed, i.e. fall below a predetermined number of rotations, the moving members  85  are resiliently retracted away from the clutch drum  81 , as denoted by arrow {circle around (6)} in FIG. 6A, by pulling force F 1  exerted by the clutch resilient members  46 . Thus, the clutch drum  81  resiliently moves back to the original position by force F 2  exerted by the braking resilient member  36 , where the brake shoe  83  again abuts against the brake pads  35  to thereby apply the brakes, so that the rotation of the clutch drum  81  and hence of the cutter-blade driving shaft  25  is terminated instantaneously. 
     Because the rotating member  84  of the clutch mechanism  23 B rotating at less than the predetermined rotation speed allows the brake mechanism  24 B to automatically apply the brakes, it is possible to eliminate the need for manual braking operation to stop the rotation of the cutter-blade driving shaft  25  and thereby enhance the operability of the bush cutting apparatus  10 . Also note that the brake mechanism  24 B in the second embodiment can attain the same results as the brake mechanism  24  in the first embodiment. 
     It should also be appreciated that any suitable number of the clutch moving members may be employed in the present invention rather than being limited to just two. Further, the embodiments of the present invention have been described in relation to the case where the clutch moving members are caused to press the clutch drum by centrifugal force and slide the clutch drum axially to the non-braking position with their tapered outer side surfaces in an alternative, there may be provided a separate mechanism for axially sliding the clutch drum to the non-braking position. Furthermore, although the embodiments of the present invention have been described as employing two brake pads, three or more brake pads may be provided. 
     In summary, according to the present invention, when the rotating member is not rotated by the drive source at more than a predetermined rotation speed, the clutch moving member is kept disengaged from the clutch drum due to the pulling force of the clutch resilient members so that the brake shoe is normally pressed against the brake pad to apply the brakes. Such arrangements can eliminate the need for the human operator to manually manipulate a brake lever or the like, and thus allows the human operator to manipulate the bush cutting apparatus with a significantly enhanced operability. On the other hand, when the rotating member is rotated by the drive source at more than a predetermined rotation speed, the clutch moving member is moved, against the bias of the clutch resilient members, radially outward to press the clutch drum by centrifugal force in such a manner that the clutch drum is caused, by the tapered outer side surface of the clutch moving member, to axially slide to the non-braking position to allow the cutter blade to be rotated via the cutter-blade driving shaft. 
     Thus, the present invention can dispense with a lever and wire for braking operation by the human operator and eliminate the need for the apparatus housing to have a hole for passing component parts, such as a wire and rod, through the housing. As a result, the present invention can achieve enhanced dust-tightness and water-tightness of the bush cutting apparatus. Further, because the parts, such as the brake lever and wire, can be dispensed with, the bush cutting apparatus of the present invention can be manufactured at reduced costs. 
     In the case where a plurality of the clutch moving members are provided symmetrically with each other about the axial centerline of the rotating member, the weights of the moving members can be distributed uniformly to the center axis of the rotation and thus can reliably prevent unbalance during the rotation. Further, the symmetrical arrangement permits accurate synchronization between the two moving members and thereby allows the clutch mechanism and brake mechanism to operate smoothly, so that reliable brake performance can be accomplished. 
     The present disclosure relates to the subject matter of Japanese Patent Application No. 2001-014069, filed Jan. 23, 2001, the disclosure of which is expressly incorporated herein by reference in its entirety.