Hammer drill

The present invention relates to a hammer drill in which motion mode can be switched between a hammering mode, a rotation mode, and a rotary hammering mode.

Generally, a hammer drill can transmit impact and rotation from a motor to a tool provided at its tip end by way of a hammering mechanism and a rotary driving mechanism, at the same time, or independently from each other, by operating an operating lever to rotate and selecting either of a hammering mode, a rotation mode and a rotary hammering mode.

In the above described hammer drill, selection of the motion mode is carried out by a mode switching mechanism. The motion mode switching mechanism is so constructed that the hammering mechanism and the rotary driving mechanism are respectively provided with clutches, thereby to connect or disconnect the rotating force from the motor to the hammering mechanism or the rotary driving mechanism.

Specifically, the mode switching mechanism which is so constructed that an intermediate shaft operatively coupled to the motor and a tool holding sleeve for holding the tip end tool are disposed in a housing in parallel with each other, and the tool holding sleeve can be operatively coupled to the hammering mechanism and the rotary driving mechanism by way of the intermediate shaft has been known. In this mechanism, the intermediate shaft is provided with two clutches, one of which transmits or interrupts a torque of the intermediate shaft to the hammering mechanism, and the other clutch transmits the torque to the rotary driving mechanism. The second clutch moves in an axial direction of the intermediate shaft thereby to be engaged with and disengaged from the driving gear which is provided on the tool holding sleeve. The above described mechanism is disclosed in U.S. Pat. No. 6,109,364.

In the above described mode switching mechanism, in the pure hammering mode, the second clutch moves in a direction separating from the driving gear along the intermediate shaft against an urge of a spring, and in the rotation mode, the second clutch returns to be engaged with the driving gear. Therefore, when the motion mode is switched from the pure hammering mode to the rotation mode, the gear of the second clutch which has been disengaged is moved by the urge of the spring to be reengaged with the driving gear. Accordingly, there is such anxiety that in case where the driving gear rotates, the gear may be damaged, because reengagement with the driving gear becomes difficult, or a sudden transmitting force by the reengagement is exerted on the driving gear.

One or more embodiments of the invention provide a hammer drill which can ensure smooth operation, with no problem of engagement between gears, even in case where motion mode is switched from a pure hammering mode to a rotation mode.

According to one or more embodiments of the invention, an intermediate shaft operatively coupled to a motor and a tool holding sleeve for holding a tip end tool are disposed in a housing in parallel with each other, a motion converting member for converting rotary motion to reciprocating motion thereby to operate the tip end tool to hammer is rotatably provided on the intermediate shaft, a first clutch is provided between the intermediate shaft and the motion converting member, a clutch sleeve coupled to the intermediate shaft by way of a rotation transmitting member and a second clutch which rotates integrally with the tool holding sleeve and can move in a longitudinal direction of the tool holding sleeve are arranged on an outer periphery of the tool holding sleeve, and the second clutch is provided so as to be engaged with and disengaged from the clutch sleeve.

In the above described hammer drill, the intermediate shaft and the tool holding sleeve are arranged in parallel, and operatively connected to each other by means of gears. The first clutch is provided at a side of the intermediate shaft, while the second clutch is provided at a side of the tool holding sleeve, and the rotation transmitting member and the clutch sleeve are interposed between the intermediate shaft and the second clutch. Therefore, rotation of the intermediate shaft is always transmitted to the clutch sleeve, and no problem of engagement occurs in this region.

Moreover, because the second clutch can rotate integrally with the tool holding sleeve, and can move along the longitudinal direction of the tool holding sleeve, the second clutch and the tool holding sleeve always rotate together in the engaged state, and no problem of engagement occurs.

Accordingly, it is possible to secure smooth operation irrespective of switching between the motion modes.

Moreover, the housing may be provided with a lock member capable of being engaged with the second clutch which has been disengaged from the clutch sleeve, and it is possible to urge this lock member so as to be engaged with the second clutch.

In this case, because the lock member is urged by a spring so as to be engaged, even when the second clutch is separated from the clutch sleeve, the second clutch is rapidly locked by the lock member, whereby the rotation of the tool holding sleeve can be reliably stopped.

Other aspects and advantages of the invention will be apparent from the following description, the drawings and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of an essential part of a hammer drill in rotary hammering mode.

FIG. 2 is a longitudinal sectional view of the essential part of the hammer drill in rotation mode.

FIG. 3 is a longitudinal sectional view of the essential part of the hammer drill in hammering mode.

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Rockshaft assembly with detachable hydraulic lift cylinder
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Hydraulic rotary percussive device of the drill type
Industry Class:
Tool driving or impacting

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