Tool driving or impacting – Drive adjustable to completely change kind of drive – Adjustable to impacting device
Reexamination Certificate
1999-09-14
2001-01-23
Vo, Peter (Department: 3721)
Tool driving or impacting
Drive adjustable to completely change kind of drive
Adjustable to impacting device
C173S029000
Reexamination Certificate
active
06176321
ABSTRACT:
This application claims priority on Japanese Patent Application No. 10-261891 filed on Sept. 16, 1998, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a hammer drill. More particularly, the present invention relates to a hammer drill having a rotation transmission mechanism which is provided between a motor and a tool bit attached to the top of a drill housing and which rotates the bit, and having a impact transmission mechanism provided also between the motor and the tool bit for transmitting hammer blows to the tool bit.
2. Description of the Related Art
It is a common practice in the art to which the present invention pertains to provide a change-over device for the rotation transmission mechanism and for the impact transmission mechanism for switching between transmission and disconnection of drive power from the motor, thus changing the operation mode of the hammer drill. The Applicant disclosed in Japan Published Unexamined Patent Application No. 9-57650 a large hammer drill which incorporates a crank mechanism, the contents of which are incorporated herein by reference. The hammer drill includes a sleeve which functions as a first change-over device for selectively transmitting rotation from the motor to the tool bit when slid to one position and disconnecting the motor rotation when slid to another position. The hammer drill additionally includes a link which functions as a second change-over device for selectively transmitting reciprocating motion of the piston to the tool bit when slid to one position and disconnecting the reciprocating motion when slid to another position. Moreover, a rotary selector knob is provided in this tool for allowing the operator to simultaneously select a combination of the slide positions of the two change-over devices, i.e., one of the three possible operation modes of the hammer drill. When a rotation-plus-hammer mode is selected, both rotation and hammer blows are transmitted to the tool holder. In a hammer-only mode, only hammer blows are transmitted to the tool holder. In a neutral mode, the tool bit is manually freely rotatable in either direction, thus allowing the operator to change the rotational angle of the tool bit.
From a viewpoint of convenience, it would be preferable to have such a large hammer drill with a crank mechanism as described above be able to operate in a rotation-only mode in addition to a rotation-plus-hammer mode and a hammer-only mode. The structure of the selector knob renders implementation of a rotation-only mode in the hammer drill very difficult. Significant changes in the design and thus increase in the manufacturing cost would be inevitable if these three modes are to be realized without altering the basic structures of the impact transmission mechanism and the rotation transmission mechanism. One possible means to achieve this goal is to provide two separate operating members for independently operating a sleeve provided for transmission of rotation separate and a link provided for transmission of hammer blows. One drawback of this configuration is that since each operating member has a position in which rotation or hammer blows are disconnected (an “off” state), the operator may unintentionally and inconveniently place the hammer drill in an off-off state, in which neither rotation nor hammer blows are transmitted to the tool bit, thus rendering the tool inoperative.
SUMMARY OF THE INVENTION
In view of the above-identified problems, an important object of the present invention is to provide a hammer drill with improved operability that allows change-over between three operating modes with two switching devices, such as levers, without inducing an “off-off” operational state.
The above object and other related objects are realized by the invention, which provides a hammer drill, comprising: a tool bit attached to a front end of the hammer drill; a motor for providing drive power for the tool bit; a rotation transmission mechanism provided between the tool bit and the motor for transmitting rotation of the motor to the tool bit; an impact transmission mechanism provided between the tool bit and the motor for transmitting hammer blows generated by the motor to the tool bit; a first change-over member associated with the rotation transmission mechanism for selectively enabling and disabling the rotation transmission mechanism to transmit the rotation of the motor to the tool bit; a second change-over member associated with the impact transmission mechanism for selectively enabling and disabling the impact transmission mechanism to transmit the hammer blows generated by the motor to the tool bit; a manually operable first operating member movable between operative and inoperative positions, wherein the first operating member, when in the operative position, operates the first change-over member so as to enable the rotation transmission mechanism and, when in the inoperative position, operates the first change-over member to disable the rotation transmission mechanism; a manually operable second operating member movable between operative and inoperative positions, wherein the second operating member, when in the operative position, operates the second change-over member so as to enable the impact transmission mechanism and, when in the inoperative position, operates the second change-over member to disable the impact transmission mechanism; and a lock means for, when one of the first and second operating members is in its inoperative position, coordinating with the other operating member so as to prohibit the other operating member from moving to its inoperative position, thus avoiding induction of an operating state of the hammer drill in which neither rotation nor hammer blows of the tool bit are available.
According to one aspect of the present invention, one of the first and second operating members is a circular rotary lever and the other operating member is a slide lever slidable tangentially to the rotary lever. Additionally, the lock means includes a cut-out formed in an edge of the slide lever for fitting the circumferential edge of the rotary lever so as to prevent the slide lever to slide when the slide lever is in its operative position, and a chamfer formed on a portion of the circumferential edge of the rotary lever such that when the rotary lever is rotated to the operative position, the chamfer is positioned adjacent the slide lever so as to allow the slide lever to slide, and when the rotary lever is rotated to the operative position and the slide lever is in its inoperative position, the chamfer closely opposes an edge of the slide lever so as to prohibit rotation of the rotary lever.
According to another aspect of the present invention, the first operating member is the rotary lever and the second operating member is the slide lever. Moreover, the rotary lever and the slide lever are disposed on a line parallel to a longitudinal axis of the tool bit, with the rotary lever interposed between the tool bit and the slide lever.
According to still another aspect of the present invention, the slide lever has a generally rectangular shape and is slidable on the rotary lever and perpendicularly to the parallel line between its operative and inoperative positions.
According to yet another aspect of the present invention, the rotary lever is rotated 180 degrees around a second axis from its inoperative position to its operative position, the second axis intersecting and oriented perpendicularly to the parallel line.
In accordance with another aspect of the present invention, the cut-out is formed in a portion of the long side of the slide lever which is adjacent to the rotary lever, leaving a portion of the long side intact where the cut-out is not formed. The intact side edge closely opposes the chamfer of the rotary lever when the rotary lever is in its operative position and the slide lever is in the inoperative position such that the rotary lever cannot be rotated back to its inoperati
Arakawa Takuo
Hirayama Toshiro
Nakamura Shin
Calve Jim
Foley Hoag & Eliot LLP
Makita Corporation
Vo Peter
LandOfFree
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