DESCRIPTION

POWER TOOL

Technical Field

The present invention relates to a power tool and, more particularly, a power tool having a vibration isolating handle.

Background Art

In the prior art, a power tool having a vibration isolating handle has been proposed. For example, such a power tool is disclosed that an elastic means is interposed between one end portion of a main handle and a main body portion and the main handle is provided to turn around the other end portion in the direction from the main body portion to one end portion. See Patent Literature 1 JP-A-2005-74573 , for example. Also, another has been proposed that a main handle and a main body portion both being coupled mutually are provided and also an electric motor and a reciprocating motion converting portion for converting a rotational motion of the electric motor into a reciprocating motion are installed in the main body portion. Also, a tip tool being driven by the reciprocating motion of the

reciprocating motion converting portion is fitted to a top end of the main body portion.

The main handle has one end portion positioned on its upper side and the other end portion positioned on its lower side. One end portion and the other end portion are connected to a rear portion of the main body portion respectively. An elastic means is interposed between one end portion and the main body portion. A shaft is provided to the other end portion, and the main handle is provided to turn around the shaft in the direction from the main body portion to one end portion. The elastic means is constructed by a first elastic supporting member, a second elastic supporting member, and a coil spring. The first elastic supporting member is fixed to the main body portion, and a first groove and a second groove being communicated with the first groove are formed on the first elastic supporting member. The first groove is formed to extend in the longitudinal direction. The second groove is positioned on the rear side of the first groove, has a width narrower than the first groove, and is opened to the back of the first elastic supporting member.

The second elastic supporting member is fixed to one end portion of the main handle. A column portion and a semicircular column portion are provided to the second

elastic supporting member. The column portion extends from the rear portion of the second elastic supporting member to the front portion, and passes through the second groove. The semicircular column portion is provided to a top end of the column portion, has a width wider than a width of the second groove, and is arranged in the first groove to slide/move with respect to the first elastic supporting member. The coil spring is arranged in the first groove such that it is interposed between the first elastic supporting member and the semicircular column portion. One end portion of the main handle is energized by the coil spring in the direction from the main body- portion to one end portion.

In the above power tool, the coil spring can absorb a low vibration when an initial load of the coil spring, i.e., a load applied to the coil spring in its non-operation state, is set smaller. Therefore, it is desirable that the initial load of the coil spring should be set small . However, when there is an attempt to render the initial load of the coil spring small (render a free length short) , sometimes a wobbliness of the coil spring is caused owing to an error in precision. Conversely, when there is an attempt to eliminate the wobbliness of the coil spring, the initial load had to be set large. Therefore, the initial load of the coil spring is set

large in its initial state, and as a result the coil spring small cannot satisfactorily absorb the vibration in a low vibration range of the power tool and also a workability of the coil spring small is lowered.

Disclosure of Invention

Therefore, it is an object of the present invention to provide a power tool capable of reducing an initial load applied to a spring in an initial state, and absorbing effectively a vibration in a low vibration range .

In order to attain the above object, the present invention provides a power tool, which includes a housing; a main handle arranged on a rear side of the housing; a sub handle connected to the housing via a swing shaft, which is directed substantially perpendicularly to a longitudinal direction of the housing, to swing around the swing shaft as a fulcrum; and an energizing means for giving a resistance force in a direction to counter the swing of the sub handle.

Since the energizing means for giving a resistance force in a direction to counter the swing of the sub handle is provided, the vibration generated in the housing can be buffered. Therefore, it can be suppressed that the vibration generated in the housing is transmitted to the

sub handle, and a workability of the power tool can be improved .

Here, it is preferable that a fitted portion is provided to an outer periphery of the housing, a fitting portion is fitted to the fitted portion such that a fitting position is changed in a circumferential direction of the fitted portion, and the sub handle is connected to the fitting portion.

The fitted portion is provided to an outer periphery of the housing, the fitting portion is fitted to the fitted portion such that the fitting position is changed in the circumferential direction of the fitted portion, and the sub handle is connected to the fitting portion. Therefore, the power tool can be used while changing the position of the sub handle in the circumferential direction of the fitted portion by changing the fitting position of the fitted portion.

Also, it is preferable that a fitted portion is provided to an outer periphery of the housing, and a fitting portion is fitted to the fitted portion, and the sub handle is connected to the fitting portion such that an initial position is changed with respect to the fitting portion in a swinging direction around the swing shaft, and the sub handle is swung against the resistance force of the energizing means on a basis of the initial

position .

The fitted portion is provided to an outer periphery of the housing, and the fitting portion is fitted to the fitted portion, and the sub handle is connected to the fitting portion such that the initial position is changed with respect to the fitting portion in the swinging direction around the swing shaft, and the sub handle is swung against the resistance force of the energizing means on a basis of the initial position. Therefore, the power tool canbe used while changing the initial position to the desired position in the swinging direction around the swing shaft.

Also, it is preferable that the fitting portion has a clamp which surrounds the fitted portion and to which the sub handle is fixed, and a clamp tightening mechanism is provided to the sub handle and, when the clamp is tightened by the clamp tightening mechanism, a fitting position is fixed in a circumferential direction of the fitted portion and the sub handle is positioned in a desired initial position in the swinging direction around the swing shaft with respect to the fitted portion.

The fitting portion has the clamp which surrounds the fitted portion and to which the sub handle is fixed, and the clamp tightening mechanism is provided to the sub handle. Therefore, when the clamp is tightened by

the clamp tightening mechanism, the fitting position can be fixed in a circumferential direction of the fitted portion and the sub handle can be positioned in the desired initial position in the swinging direction around the swing shaft with respect to the fitted portion.

Also, it is preferable that the energizing means has a nitrohite spring. Since that the energizing means has the nitrohite spring, a spring load applied in its initial state can be set small . Therefore, the vibration generated in the housing at the initial stage of the impacting action can be buffered effectively, and a workability of the power tool can be improved.

Here, it is preferable that the nitrohite spring has a substantially cylindrical outer frame portion whose outer shape is a substantially polygonal column shape and which is fixed to the fitting portion, circular column rubber rods whose axes are directed in parallel with the swing shaft and which are arranged at corner portions of the outer frame portion on an inner peripheral surface side respectively, and a polygonal column portion whose axis coincides with the swing shaft and whose corner portions are arranged between adjacent rubber rods respectively, and the nitrohite spring has a coupling portion that couples the sub handle and the polygonal column portion to swing together.

Also, it is preferable that the coupling portion has polygonal column notched portions provided to an end portion of the polygonal column portion in an axial direction, and notched portions provided a portion of the sub handle opposing to the polygonal column notched portions as a part of the sub handle to engage with the polygonal column notched portions .

Also, it is preferable that the swing shaft is constructed by a volt that functions as the coupling portion, the bolt has a shaft portion, a polygonal shape portion which is provided to the shaft portion and whose sectional shape when taken perpendicularly to an axis direction of the bolt is formed as a polygonal shape, and a polygonal head portion, the polygonal shape portion passes through the polygonal column portion and engages/disengages with/from the polygonal column portion, and is turned together with the polygonal column portion when the polygonal shape portion engages with the polygonal column portion, the head portion engages/disengages with/from the sub handle, and is turned together with the sub handle when the head portion engages with the sub handle, and the polygonal shape portion of the bolt engages with the polygonal column portion when the head portion of the bolt engages with the sub handle.

Also, it is preferable that the swing shaft is constructed by a shaft portion and a head portion, the nitrohite spring has a polygonal concave portion forming portion formed on an open end on one end of a through hole, which is formed in the sub handle and through which the bolt passes through, to define a polygonal concave portion that releasably holds the head portion therein, circular column rubber rods whose axes are directed in parallel with the swing shaft and which are arranged at corner portions of the polygonal concave portion on an inner peripheral surface side respectively, and a polygonal head portion whose corner portions are arranged between adjacent rubber rods respectively, and the bolt is fixed not to turn with respect to the fitting portion when the head portion of the bolt engages with the polygonal concave portion via the rubber rods.

Also, it is preferable that the present invention provides the power tool, which further includes a motor contained in the housing; a tip tool fitted to a top end side of the housing; and a reciprocating motion converting portion for converting a rotation of the motor into a reciprocating motion; wherein the reciprocating motion converting portion has a cylinder, a piston provided on an inner periphery of the cylinder to slide, a motion converting portion for converting a

rotating/driving power of the motor into the reciprocating motion of the piston, and an impacting piece driven by the reciprocating motion of the piston, and the tip tool is driven by the reciprocating motion of the reciprocating motion converting portion.

The power tool further includes a motor contained in the housing; a tip tool fitted to a top end side of the housing; and a reciprocating motion converting portion for converting a rotation of the motor into a reciprocating motion; wherein the reciprocating motion converting portion has a cylinder, a piston provided on an inner periphery of the cylinder to slide, a motion converting portion for converting a rotating/driving power of the motor into the reciprocating motion of the piston, and an impacting piece driven by the reciprocating motion of the piston, and the tip tool is driven by the reciprocating motion of the reciprocating motion converting portion. Therefore, the vibration generated in the housing at the initial stage of the impacting action can be buffered effectively, and a workability of the power tool can be improved.

Also, it is preferable that the main handle is connected to the housing via the elastic means. According to this configuration, the vibration applied to the worker can be reduced more effectively.

Also, it is preferable that the elastic means has the nitrohite spring. According to this configuration, the vibration applied to the worker can be reduced more effectively . With the above, the present invention can provide the power tool that is capable of reducing the initial load applied to the spring in the initial state, and absorbing effectively the vibration in the low vibration range .

Brief Description of the Drawings

FIG.l is a perspective exterior view of a first embodiment in which a power tool of the present invention is applied to an impacting tool. FIG.2 is a sectional view of the first embodiment in which the power tool of the present invention is applied to the impacting tool.

FIG.3 is a partial sectional view of the rear side of a main body portion and a main handle in a non-operating state of the impacting tool shown in FIG.2.

FIG.4 is a sectional view of an elastic means shown in FIG.3.

FIG.5 is a sectional view of a turning/energizing means shown in FIG.3. FIG.6 is a pertinent sectional view showing a

fitting portion and a sub handle of the first embodiment in which the power tool of the present invention is applied to the impacting tool.

FIG.7 is a pertinent sectional view showing a sub handle and an energizing means of the first embodiment in which the power tool of the present invention is applied to the impacting tool.

FIG.8 is an exploded perspective view showing the energizing means of the first embodiment in which the power tool of the present invention is applied to the impacting tool.

FIG.9 is a plan view showing a sub handle of a second embodiment in which a power tool of the present invention is applied to an impacting tool. FIG.10 is a pertinent sectional view showing a fitting portion and a sub handle of the second embodiment in which the power tool of the present invention is applied to the impacting tool.

FIG.11 is a pertinent sectional view showing a fitting portion and a sub handle of a third embodiment in which a power tool of the present invention is applied to an impacting tool.

FIG.12 is a plan view showing an energizing means of a fourth embodiment in which a power tool of the present invention is applied to an impacting tool.

FIG.13 is a pertinent partial sectional view showing a fitting portion and a sub handle of a fifth embodiment in which a power tool of the present invention is applied to an impacting tool.

Best Mode for Carrying out of the Invention

A first embodiment in which a power tool of the present invention is applied to an impacting tool will be explained with reference to FIG.l and FIG.8 hereunder . Explanation will be made in a situation that, in FIG.l and FIG.2, the left side is assumed as the front end side of an impacting tool 1 and the right side is assumed as the rear end side of the impacting tool 1. The impacting tool 1 contains a main handle 10, a sub handle 110, and a main body portion 60 consisting of a motor housing 20 and a gear housing 30. The motor housing 20 and the gear housing 30 correspond to the housing.

As shown in FIG.2, the main handle 10 is provided to the rear end of the housing, i.e., the right end in FIG.2, and the main handle 10 is equipped with a power supply cable 11 and a switching mechanism 12 is built in the main handle 10. A trigger 13 that is operable by a user is connected mechanically to the switching mechanism 12. The power supply cable 11 connects the switching mechanism to an external power supply (not

shown) such that, when the user operates the trigger 13, connection and disconnection between an electric motor 21 described later and the external power supply can be switched. Also, the main handle 10 has a grip portion 14 that the user grips when such user uses the impacting tool 1.

Also, the main handle 10 has one end portion 1OA positioned on the upper side, and the other end portion 1OB positioned on the lower side. One end portion 1OA is connected to a rear portion of a motion converting housing 31 described later. An elastic means 50 is interposed between one end portion 1OA and the motion converting housing 31. The other end portion 1OB is connected to a rear portion of the motor housing 20. A turning/energizing means 80 is interposed between the other end portion 1OB and the motor housing 20.

The elastic means 50 and the turning/energizing means 80 will be explained with reference to FIG.3 to FIG.5 hereunder. As shown in FIG.4, the elastic means 50 is constructed by a transitory unit consisting of a first elastic supporting member 51, a second elastic supporting member 52, and four rod-like rubber elastic bodies 53. The first elastic supporting member 51 is fixed to the motion converting housing 31, and a longitudinal first groove 51a and a second groove 51b

that is in communication with the first groove 51a are formed in the first elastic supporting member 51. The first groove 51a is formed to extend in the longitudinal direction. The second groove 51b is positioned at the back of the first groove 51a and has a narrower width than the first groove 51a, and is opened from the rear surface of the first elastic supporting member 51. Also, a first inclined surface 51C is formed on both side walls of the first elastic supporting member 51. The second elastic supporting member 52 is fixed to one end portion 1OA of the main handle 10 with bolts 54. A column portion 52A and a circular column portion 52B are provided to the second elastic supporting member 52. The column portion 52A extends forward from the rear portion of the second elastic supporting member 52, and passes through the second groove 51b. The circular column portion 52B is provided to a top end of the column portion 52A, and has a diameter that is longer than a width of the second groove 51b. The circular column portion 52B is arranged in the first groove 51a such that it can be slid with respect to the first elastic supporting member 51. Therefore, one end portion 1OA can go away from and come close to the motion converting housing 31. Also, since a diameter of the circular column portion 52B is longer than a width of the second

groove 51b, disengagement of the circular column portion 52B from the first groove 51a and the second groove 51b can be prevented and a separation of the main handle 10 from the motion converting housing 31 at a predetermined distance or more can restricted.

Also, the second inclined surface 52C that extends in parallel with the first inclined surface 51C and is separated from the first inclined surface 51C at a predetermined distance is formed on an inner wall of the second elastic supporting member 52. Four elastic bodies 53 are interposed between the first inclined surface 51C and the second inclined surface 52C. Therefore, the main handle 10 and the motion converting housing 31 are connected via four elastic bodies 53. Also, the elastic bodies 53 is 'subjected to the rolling friction between the second inclined surface 52C and the first inclined surface 51C when the second elastic supporting member 52 moves toward the first elastic supporting member 51 side. As a result, the elastic means 50 shows the nonlinear characteristic.

As shown in FIG.3 and FIG.5, the turning/energizing means 80 is constructed by a nitrohite spring consisting of an outer frame 81, a shaft 82, a rotating member 83 having a substantially square sectional shape, and four rubber rods 84. The turning/ energizing means 80

corresponds to the elastic means. The outer frame 81 defines an internal space 81a having a substantially square sectional shape, and is fixed to the motor housing 20. The shaft 82 passes through the internal space 81a, and is fixed to the other end portion 1OB of the main handle 10 by bolts 85. The main handle 10 is provided to turn on the shaft 82. The rotating member 83 is fixed to the shaft 82 in the internal space 81a, and is provided to turn together with the shaft 82. Therefore, when the main handle 10 is turned, the shaft 82 turns and also the rotating member 83 turns. Also, four rubber rods 84 are interposed between the outer frame 81 and the rotating member 83 in the internal space 81a.

As shown in FIG.l, the sub handle 110 is provided to the fitted portion that constitutes the top end portion of the gear housing 30 and is shaped into a substantially circular cylindrical shape. The sub handle 110 has a clamping portion 111, and the clamping portion 111 is connected to the top end portion of the gear housing 30 via a fitting portion 120 having an annular portion 121. More concretely, as shown in FIG.l, the sub handle 110 has an almost ^λλ π "-shaped form that is constructed by connecting four rod portions consisting of a upper portion 112, a lower portion 113, a right portion 114, and a left portion 115. A part of the left portion 115

in FIG.l constitutes a notched portion shown in FIG.7. As shown in FIG.7, a notchedportion 115B on which notches are formed in a radial fashion around a through hole 110a described later is provided to a pair of notched surfaces 115A, 115A, which are opposed mutually to define a notched portion, respectively. In FIG.7, only one notched portion 115B is illustrated.

Also, the through hole 110a extending in the extending direction of the left portion 115, i.e., the vertical direction in FIG.l and FIG.6, is formed in the left portion 115. Abolt 116 is inserted into the through hole 110a. An upper end of the through hole 110a is shaped into a concave opening portion 110b having a hexagon, and a hexagonal head portion of the bolt 116 engages with the upper end. A thread fastening portion 117 is provided to a lower end of the left portion 115, and is screwed into a top end of the bolt 116. A through hole 117a that is screwed onto the top end of the bolt 116 protruded from the lower end of the left portion 115 is formed in the thread fastening portion 117. The thread fastening portion 117 corresponds to a clamp tightening mechanism.

As shown in FIG.7, an energizing means 130 is provided between a pair of notched surfaces 115A, 115A of the left portion 115. As shown in FIG.8, the

energizing means 130 is the nitrohite spring that consists of a cylindrical outer frame portion 131 whose outer shape is a substantially square column shape, four circular rubber rods 132, 132, 132, 132 arranged on the inner peripheral side of the outer frame portion 131, and a square column portion 133. Four rubber rods 132 are arranged in four corner positions on an inner peripheral surface of the outer frame portion 131 such that their longitudinal direction coincides with the longitudinal direction of the outer frame portion 131. As shown in FIG.8, the square column portion 133 is positioned such that its four corners are positioned between the rubber rod 132 and the rubber rod 132 respectively and its longitudinal direction coincides with the longitudinal direction of the rubber rods 132. A through hole 133a is formed in an axial center position of the square column portion 133 and, as shown in FIG.6, the bolt 116 passes through the through hole 133a. The square column portion 133 corresponds to a polygonal column portion.

A square column notched portion 133A on which the notch is formed radially from a center of the through hole 133a is provided around the through hole 133a respectively. The square column notched portions 133A, 133A engage with the notched portions 115B, 115B provided

on the notched surfaces 115A, 115A of the left portion 115 of the clamping portion 111. The square column notched portions 133A, 133A and the notched portions 115B, 115B correspond to a coupling portion. In this case, in FIG.7 and FIG.8, only one square column notched portion 133A is illustrated. When the square column portion 133 is put between the notched portions of the left portion 115 and then fastened by turning the thread fastening portion 117, the square column notched portions 133A and the notched portions 115B are always engaged with each other. Therefore, the clamping portion 111 cannot be turned relatively to the square column portion 133, and thus an initial position of the clamping portion 111 to the fitting portion 120 is decided in the swinging direction around the bolt 116 as the swing shaft. However, because of the presence of the energizing means 130, the clamping portion 111 can be swung slightly from the initial position in the swinging direction around the bolt 116 as the swing shaft, and the clamping portion 111 is brought into its vibration absorbing state as described above.

When the clamping of the square column portion 133 between the notched portions of the left portion 115 is loosened by turning the thread fastening portion 117, the convex portions of the notched portions 115B can run

up onto the convex portions of the square column notched portions 133A. Therefore, the square column notched portions 133A can turn relatively to the notched portions 115B, and thus the clamping portion 111 can turn relatively to the square column portion 133 and the outer frame portion 131. As a result, the initial position of the clamping portion 111 in the swinging direction on the bolt 116 can be changed.

As shown in FIG.6, the annular portion 121 of the fitting portion 120 is fixed to the outer frame portion 131 to surround the whole side surface. Annular housing fitting ring portions 122 whose shaft center is directed perpendicularly to the axis direction of the bolt 116 are connected to the annular portion 121. The housing fitting ring portions 122 constitute a split structure in the diameter direction such that one half ring portion can turn around the connection position with respect to the other half ring portion. Respective portions of the ring portions 122 in positions opposing to the connecting position in the diameter direction can be connected mutually with a screw 123. When respective portions are not connected mutually with the screw 123, one portion of the housing fitting ring portions 122 is turned with respect to the other portion and is opened. Then, one portion of the housing fitting ring portions 122 is turned

P2008/051989

from the other portion while bringing the top end portion of the gear housing 30 into contact with the inner peripheral surface of the housing fitting ring portion 122, so that the split structure is closed to constitute the ring form, as shown in FIG.6. Then, the turning position of the fitting portion 120 in the circumferential direction of the gear housing 30 around a shaft of a tip tool 16 described later can be fixed by connecting respective portions mutually with the screw 123.

As shown in FIG.6, the axial center of the housing fitting ring portion 122 and the axial direction of the bolt 116 are positioned perpendicularly to each other, and thus the sub handle 110 can swing on the bolt 116. Therefore, the sub handle 110 cannot swing in other directions, e.g., in the circumferential direction of the gear housing 30. Also, the nitrohite spring is interposed between the sub handle 110 and the fitting portion 120. Therefore, when the user tries to turn the sub handle 110 from the initial position around the bolt 116 as the swing shaft, the side surfaces of the square column portion 133 of the sub handle 110 that is positioned in its initial position push the rubber rods' 132 respectively. Thus, the fitting portion 120 and the outer frame portion 131 being fixed to the gear housing

30 receive an energizing force from the rubber rods 132 and are subjected to the rolling friction. In other words, the energizing force is applied in the direction to counter the swing of the sub handle 110, and the energizing means 130 shows the nonlinear characteristic and can absorb effectively the vibration caused by the gear housing 30 and the fitting portion 120.

As shown in FIG.2, the motor housing 20 is provided to the lower portion of the main handle 10 on the top end side. The electric motor 21 is installed in the motor housing 20. The electric motor 21 has an output shaft

22 that outputs a rotating/driving force. A pinion gear

23 is provided to a top end of the output shaft 22, and is positioned in the gear housing 30. The gear housing 30 has the motion converting housing 31 and an impacting housing 32. The motion converting housing 31 is positioned over the motor housing 20. The impacting housing 32 is positioned on the top end side of the motion converting housing 31. . A crankshaft 34 extended in parallel with the output shaft 22 is supported rotatably on the rear end side of the pinion gear 23 in the motion converting housing 31. A first gear 35 that engages with the pinion gear 23 is fixed coaxially to a lower end of the crankshaft 34. A motion converting mechanism 36 is provided to an upper

end portion of the crankshaft 34. The motion converting mechanism 36 has a crank weight 37, a crank pin 38, and a connecting rod 39. The crank weight 37 is fixed to an upper end of the crankshaft 34. The crank pin 38 is fixed to an end portion of the crank weight 37. The crank pin 38 is inserted into the rear end of the connecting rod 39.

A cylinder 40 extending in the direction that intersects orthogonally with the output shaft 22 is provided in the impacting housing 32. A center shaft of the cylinder 40 and a rotating shaft of the output shaft 22 are positioned on the same plane. Also, a rear end portion of the cylinder 40 opposes to the electric motor 21. A tool holding portion 15 is provided on the top end side of the cylinder 40, and the tip tool 16 (FIG.l) is detachably attached to the tool holding portion 15. An axis direction of the tip tool 16 coincides with the longitudinal direction of the housing. Also, a piston 43 is provided in the cylinder 40 such that it can slide on its inner periphery. The piston 43 has a piston pin 43A, and this piston pin 43A is inserted into the top end of the connecting rod 39. An impacting piece 44 is provided to the top end side in the cylinder 40 such that it can slide on its inner periphery of the cylinder 40. An air chamber 45 is defined between the piston 43 and

the impacting piece 44 in the cylinder 40. Also, an intermediate piece 46 is provided on the top end side of the impacting piece 44 such that it can slide in the longitudinal direction in the cylinder 40. A counter weight mechanism 70 is arranged in the portion opposing to the main handle 10 in the motion converting housing 31. The counter weight mechanism 70 is equipped with two weight holding portion supporting portions 71, 72, a weight holding portion 73, and a counter weight 74. The weight holding portion supporting portions 71, 72 are arranged in the direction orthogonal to the direction of a reciprocating motion of the piston 43 to put the counter weight 74 between them. Next, an operation of the impacting tool 1 according to the first embodiment will be explained hereunder. The user pushes the tip tool 16 against the workpiece material

(not shown) while clamping the main handle 10 by hand.

Then, the user pulls the trigger 13 to supply an electric power to the electric motor 21 and turn/drive it. This turning/driving force is transferred to the crankshaft 34 via the pinion gear 23 and the first gear 35. A rotation of the crankshaft 34 is converted into a reciprocating motion of the piston 43 in the cylinder 40 via the motion converting mechanism 36 (the crank

weight 37, the crank pin 38, and the connecting rod 39) . An air pressure of in the air chamber 45 is increased and decreased repeatedly in response to the reciprocating motion of the piston 43 and applies a hitting force to the impacting piece 44. The impacting piece 44 moves forward to run into the rear end of the intermediate piece 46, so that the hitting force is transmitted to the tip tool 16 via the intermediate piece 46. This hitting force is applied to the tip tool 16 and the workpiece material is crushed.

At a time of operating the above impacting tool 1, vibration is produced due to the reciprocating motion of the impacting piece 44 in the main body portion 60 at a substantially predetermined period. Since the rubber rods 84 are interposed between the outer frame 81 fixed to the motor housing 20 and the rotating member 83 fixed to the other end portion 1OA and also the elastic bodies 53 are interposed between the first elastic supporting member 51 fixed to the motion converting housing 31 and the second elastic supporting member 52 fixed to one end portion 1OA, the vibration generated in the main body portion 60 can be buffered by the rubber rods 84 (the turning/ energizing means 80) and the elastic bodies 53 (the elastic means 50) . Therefore, it can be suppressed that the vibration generated in the main body

portion 60 is transmitted to the main handle 10, and thus a workability of the impacting tool 1 can be improved.

Also, since the rubber rods 132 are interposed between the outer frame portion 131 and the square column portion 133, the rubber rods 132 give a resistance force in the direction to counter the swing of the sub handle 110, and thus the vibration generated in the main body portion 60 can be buffered. Therefore, it can be suppressed that the vibration generated in the main body portion 60 is transmitted to the sub handle 110, and thus a workability of the power tool 1 can be improved. Also, since the spring loads of the rubber rods 84 and the rubber rods 132 are small in an initial state, the vibration generated in the main body portion 60 in the low vibration area at an initial stage of the hitting operation can be buffered more effectively by the rubber rods 84 and the rubber rods 132, and thus a workability of the impacting tool 1 can be improved.

Also, the vibration generated in the main body portion 60 is transmitted to the weight holding portion supporting portion 71, 72 via the motion converting housing 31. The vibration being transmitted to the weight holding portion supporting portion 71, 72 is transmitted to the weight holding portion 73 and the counter weight 74. Thus, the counter weight 74 vibrates

in the same direction as the direction of the reciprocating motion of the piston 43. The vibration of the impacting tool 1 caused by the impacting can be reduced by this configuration. Next, a second embodiment in which a power tool of the present invention is applied to an impacting tool will be explained hereunder. This second embodiment is different from the first embodiment in that the square column notched portion 133A and the notched portions 115B are not provided and the notched surfaces 115A, 115A of the left portion 115 of the clamping portion 111 contact end surfaces of a square column portion 1133 in a flat plane. Also, this second embodiment is different from the first embodiment in that a bolt 1116 cannot be turned with respect to the square column portion 133 but can be moved in the axial direction. Also, as shown in FIG .9, this second embodiment is different from the first embodiment in that a head portion of the bolt 1116 is not shaped into a hexagonal shape but an octagonal shape and also a concave opening portion 1110b of the left portion 115 of the clamping portion 111 is formed in a similar shape. Remaining structures are identical to those in the first embodiment. Only portions in these different points will be explained hereunder, and the same reference symbols are affixed to the same members

in explanation.

A through hole 1133a of the square column portion 1133 is formed as a polygonal column shape whose sectional shape is a square column shape, or the like when taken along the perpendicular direction to its axial direction. Except the head portion of the bolt 1116, a portion of the bolt 1116 passing through the through hole 1133a and an upper portion of the bolt 1116 than that portion are formed to have the substantially same sectional shape as the through hole 1133a. A sectional shape of a lower portion than the portion of the square column in FIG.10 is formed as a circular shape, like the first embodiment. Therefore, as shown in FIG.10, because the square column portion of the bolt 1116 engages with the through hole 1133a, the square column portion 1133 cannot turn around the bolt 1116.

Also, a portion of a through hole 1110a of the left portion 115 positioned upper than an upper end of the square column portion 1133 is expanded larger in diameter than the square column portion of the bolt 1116, and the left portion 115 can turn around the shaft of the bolt 1116. Therefore, when the bolt 1116 is loosened and is moved in the upper direction in FIG.10 as the axial direction to disengage the head portion of the bolt 1116 from the concave opening portion 1110b, the left portion

115 and the clamping portion 111 can be swung with respect to the bolt 1116, the square column portion 1133 and the fitti-ng portion around the bolt 1116 as the swing shaft. In setting the initial position of the clamping portion 111 in a desired position, first the bolt 1116 is moved in the releasing direction by turning the thread fastening portion 117. Thus, the octagonal head portion of the bolt 1116 is brought into its disengaged state from the concave opening portion 1110b of the left portion 115 of the clamping portion 111. Then, the clamping portion 111 is swung around the bolt 1116 in a desired position at a 45 ° segment such as 45°, 90°, and the like. Then, the octagonal head portion of the bolt 1116 is engaged with the concave opening portion 1110b of the left portion 115 of the clamping portion 111 by moving the bolt 1116 in the axial direction in that position. Then, the bolt 1116 is tightened by turning the thread fastening portion 117, and thus the octagonal head portion of the bolt 1116 is brought into its engaged state with the concave opening portion 1110b of the left portion 115 of the clamping portion 111. As a result, the initial position of the clamping portion 111 can be set in the desired position.

Here, the initial position of the clamping portion 111 can be changed at a 45 ° segment by shaping the head

portion of the bolt 1116 and the concave opening portion 1110b of the clamping portion 111 into the octagonal shape respectively. In this case, when a polygonal shape whose polygonal number is larger than the octagon is employed, the initial position can be changed at a smaller angular segment .

Next, a third embodiment in which a power tool of the present invention is applied to an impacting tool will be explained hereunder. The third embodiment is different from the first embodiment in that a fitting portion 2120 is constructed by a housing fitting annular portion 2122 formed of the thin ring plate member in which one mitre is formed as an open portion, and an annular portion 2121 consisting of an annular portion upper portion 2121A connected to one piece of the mitre to surround an upper half of the outer frame portion 131 in FIG.11 and an annular portion lower portion 2121B connected to the other piece of the mitre to surround a lower half of the outer frame portion 131 in FIG.11, whereby the annular portion 2121 surrounds the square column portion 133 and the overall fitting portion 2120 constitutes the clamp. Remaining structures are identical to those in the first embodiment. In this case, the same reference symbols are affixed to the same members in explanation.

In setting the initial position of the clamping portion 111 in a desired position, first the annular portion upper portion 2121A and the annular portion lower portion 2121B are put between the notched portions of the left portion 115 and fastened by turning the thread fastening portion 117, and also the square column portion 133 is put between them and fastened. According to this, the square column notched portion 133A (FIG.8) and the notched portion 115B (FIG.7) are always engaged with each other, and the initial position of the clamping portion 111 is decided in the swinging direction around the bolt 115 as the swing shaft. Also, the fitting portion 2120 is set temporarily in its unturned state around the gear housing 30 by fastening the top end of the gear housing 30 by the housing fitting annular portion 2122, and thus the fitting portion 2120 can be positioned in the circumferential direction of the gear housing 30.

Next, a fourth embodiment in which a power tool of the present invention is applied to an impacting tool will be explained hereunder. The fourth embodiment is different from the first embodiment in that the square column portion 133, the outer frame portion 131, and four rubber rods 132 are not provided, a solid annular portion in a center of which a square through hole, through which a bolt 3116 can pass, is formed is provided instead of

the substantially cylindrical annular portion 121, the bolt 3116 is shaped into a square column portion 3116A from the middle portion like the second embodiment, the square column portion 3116A can engage with the hexagonal through hole of the solid annular portion, and the bolt 3116 cannot be turned with respect to the fitting portion 120. Also, the fourth embodiment is different from the first embodiment in that the nitrohite spring as an energizing means 3130 is provided to a concave opening portion 3110b (FIG.12) of the left portion 115 of the clamping portion 111. Remaining structures are identical to those in the first embodiment. Only portions in these different points will be explained hereunder, and the same reference symbols are affixed to the same members in explanation.

As shown in FIG.12, the concave opening portion 3110b of the left portion 115 of the clamping portion 111 (FIG.l, etc. ) is shaped into a hexagonal shape larger than the head portion of the bolt 3116, and six rubber rods 132 are arranged in total at corner portions on the inner peripheral surface of the concave opening portion 3110b respectively. A portion of the sub handle 110 defining the concave opening portion 3110b corresponds to a polygonal concave portion forming portion, and the concave opening portion 3110b corresponds to the

polygonal concave portion. The corner portion of the head portion of the bolt 3116 is arranged between the adjacent rubber rods 132. The head portion and the shaft portion of the bolt 3116 are constructed separately and, as shown in FIG .12 , the head portion and the shaft portion are fixed integrally by inserting the square column portion 3116A provided to the shaft portion into a through hole 3116a formed in the head portion.

In setting the initial position of the clamping portion 111 in a desired position, first the bolt 3116 is loosened by turning the thread fastening portion 117 (FIG.6, etc.) and is moved in the axial direction. Thus, the hexagonal head of the bolt 3116 is disengaged from the rubber rods 132, and the clamping portion 111 is swung around the bolt 3116 in a desired position. Then, the bolt 3116 is moved in the axial direction in that position to insert the hexagonal head portion into the concave opening portion 3110b, and is brought into contact with the rubber rods 132. The bolt 3116 is tightened by turning the thread fastening portion 117 such that the hexagonal head portion of the bolt 3116 is always be brought into contact with the rubber rods 132. Thus, the initial position of the clamping portion 111 can be set in the desired position. In the sub handle 110 whose initial position is

positioned, the hexagonal sides of the head portion of the bolt 3116 push the rubber rods 132 respectively, and thus the fitting portion 120 and the bolt 3116 fixed to the gear housing 30 receives the energizing force from the rubber rods 132 and are subjected to the rolling friction. Therefore, the energizing means 3110 shows the nonlinear characteristic and can absorb effectively the vibration given from the gear housing 30 and the fitting portion 120. Next, a fifth embodiment in which a power tool of the present invention is applied to an impacting tool will be explained with reference to FIG.13 hereunder. The fifth embodiment is different from the first embodiment in that a clamping portion 4111 has a bar shape. Remaining structures are identical to those in the first embodiment. In this case, the same reference symbols are affixed to the same members in explanation.

A sub handle 4110 has a square column holding portion 4112 shaped into an almost ^λλ =t " shape by a pair of side walls 4113, 4114 and a bottom wall 4115 connected to one ends of these side walls, and the bar-like clamping portion 4111 one end of which is connected to the bottom wall 4115. The square column portion 133, the outer frame portion 131, the rubber rods 132 (FIG.8), and the annular portion 121 are sandwiched by a pair of side walls

4113, 4114 of the square column holding portion 4112. A through hole 4110a is formed in portions of a pair of side walls 4113, 4114 of the square column holding portion 4112 on the other end portion, and the bolt 116 is inserted into the through hole 4110a. A concave opening portion 4110b is formed in an upper end of the through hole 4110a in FIG.13, and the head portion of the bolt 116 engages with the concave opening portion 4110b. The other end of the bolt 116 is protruded downward in FIG.13 from the through hole 4110a in the side walls 4113, 4114 of the square column holding portion 4112, and the thread fastening portion 117 is screwed onto a protruded portion, like the first embodiment. The setting and change of the initial position of the sub handle 4110 and the change and fixing of the position of the gear housing 30 of the fitting portion 120 in the circumferential direction are made by turning the thread fastening portion 117, as in the first embodiment.

The power tool according to the present invention is not limited to the above embodiments, and various variations and improvements can be applied within a scope set forth in claims. For example, the power tool is not limited to the impacting tool. For example, the power tool may be applied to the grinder, and a circular disk grindstone may be used as the tip tool. The present

invention can be applied to various power tools such as the driver, the drill, and the like.

Also, the nitrohite spring has the square column portion 133 in the first to third, fifth embodiments, and the nitrohite spring has the hexagonal head of the bolt 3116 in the fourth embodiment. But the head portion is not limited to such square column shape, or such hexagonal shape. Other polygonal shapes may be employed, and an involute shape may be employed.