Tool driving or impacting – Drive adjustable to completely change kind of drive – Adjustable to impacting device
Reexamination Certificate
2000-08-25
2001-02-27
Smith, Scott A. (Department: 3721)
Tool driving or impacting
Drive adjustable to completely change kind of drive
Adjustable to impacting device
C173S109000, C173S201000
Reexamination Certificate
active
06192996
ABSTRACT:
This application claims priority on Japanese Patent Application No. 11-240114 filed on Aug. 26, 1999, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to hammer drills. More particularly, the present invention relates to a type of hammer drill with selectable hammer and rotary operation modes.
2. Description of the Related Art
A certain type of hammer drill includes a clutch mechanism provided on an intermediate shaft which is disposed between the output shaft of the motor and the tool holder of a hammer drill. The clutch mechanism is capable of placing the hammer drill in different operating modes. Japan Published Unexamined Patent Application No. 6-262413 discloses one such clutch mechanism which includes a rotation transmitting member, Such as a gear, mounted on an intermediate shaft for transmitting rotation of a motor to a tool holder, and a strike transmitting member, such as a boss, also freely rotatably mounted on the intermediate shaft and having a piston arm for transmitting hammer blows to a bit held in the tool holder. The clutch mechanism further includes a clutch member which has clutch claws on both axial ends thereof and is disposed between the rotation transmitting member and the strike transmitting member. Additionally the clutch member is slidably disposed on the intermediate shaft so as also to be integrally rotatable with this shaft. By operating an external switch lever to change the axial position of the clutch member, an operator of this tool can place the tool into one of three operating modes: a rotation-only mode in which the clutch member engages the rotation transmitting member only; a rotation-plus-hammer mode in which the clutch member engages both the rotation transmitting member and the strike transmitting member; and a hammer-only mode in which the clutch member engages the strike transmitting member only.
While the foregoing switch mechanism achieves its intended objective, it is not free from certain problems and inconveniences. Generally, when a chisel, which is often used at a desired rotational angle, is attached to a hammer drill, it would be preferable if the drill were to permit adjustment of the rotational angle of the attached chisel or similar tool bit. In the foregoing hammer drill, however, when the tool is in the hammer-only mode, in which the clutch member engages the strike transmitting member only, the rotation transmitting member is disengaged from the clutch member so as to be freely rotatable. As the tool holder is in permanent engagement with the rotation transmitting member, the tool holder, and thus the attached bit, cannot be rotated to and secured at a new rotational angle. It is possible to provide the hammer drill with a function to fix the rotational angle of the bit by adding a separate mechanism which may include a locking device for preventing the rotation of the tool holder and the rotation transmitting member in the hammer-only mode. This not only contributes to increased cost of the tool, but it also reduces the overall operability of the tool, as such additional mechanism makes the operation of the tool all the more complicated.
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 a simple structure that permits mode selection from the aforementioned three operating modes and adjustment of the rotational angle of the tool bit.
Another object of the present invention is to provide a hammer drill that realizes higher ease of operation at a low cost.
The above objects and other related objects are realized by the invention, which provides a hammer drill having a plurality of selectable operating modes. The hammer drill includes: a motor; a housing; an intermediate shaft having a longitudinal axis and supported within the housing for being rotated upon activation of the motor; and a rotation transmitting member freely rotatably provided on the intermediate shaft and slidable along the longitudinal axis of the intermediate shaft. The rotation transmitting member, when rotated, transmits rotation of the motor to a tool bit attached to the hammer drill. The hammer drill further includes a strike transmitting member freely rotatably provided on the intermediate shaft, and a clutch member integrally rotatable with the intermediate shaft and slidable along the longitudinal axis of the intermediate shaft between the rotation transmitting member and the strike transmitting member. The strike transmitting member, when rotated, converts the rotation of the motor into hammer blows and transmitting the hammer blows to the tool bit, whereas the clutch member, when sliding, are capable of engaging, and integrally rotating with, at least one of the rotation transmitting member and the strike transmitting member. The hammer drill additionally includes a first switchover device for being externally operable to slide at least one of the clutch member and the rotation transmitting member, and a second switchover device interlocked with the first switchover device to slide whichever is not slid by the first switchover device of the clutch member and the rotation transmitting member. According to this hammer drill, the engagement status of the clutch member with the rotation transmitting member and with the strike transmitting member is changeable by operation of the first switchover device so as to select the operation mode of the hammer drill from a rotation-only mode, a rotation-plus-hammer mode, and a hammer-only mode. Particularly, in the hammer-only mode, the rotation transmitting member is movable between a free-rotation position in which the rotation transmitting member is permitted to rotate and a lockup position in which the rotation transmitting member is prevented from rotation by one of the first and second switchover devices.
The rotation transmitting member is adapted to be slidable in the axial direction, whereas the first switchover device allows selection of the three operating modes of the drill while providing, in the hammer-only mode, both a lockup position, in which the rotation transmitting member is prevented from rotation and a free-rotation or neutral position, in which the rotation transmitting member is not locked up, but is freely rotatable to allow the tool bit to be rotated to desired angles. This bit angle adjusting mechanism is realized merely by the addition of the second switchover device and the slide of the rotation transmitting member, thereby contributing to simplification of the overall structure and to cost reduction. The selectability of all three operating modes and the neutral position merely by means of the first switchover device ensures high operability of the hammer drill.
According to one aspect of the present invention, the first switchover device is a rotary lever that permits manual operation to selectively place the hammer drill in the three modes. Moreover, when the hammer drill is in the hammer-only mode, the first switchover device can be operated to slide the rotation transmitting member along the longitudinal axis between the lockup position, in which a first stopper provided in the rotation transmitting member engages the second switchover device so as to prevent rotation of the rotation transmitting member, and the free-rotation position.
According to another aspect of the present invention, the second switchover device is a clutch plate having a second stopper that engages the first stopper of the rotation transmitting member when the rotation transmitting member is in the lockup position and disengages from the first stopper of the rotation transmitting member when the rotation transmitting member is in the free-rotation position.
According to still another aspect of the present invention, the first switchover device, when operated to place the hammer drill in the hammer-only mode from the rotation-plus-hammer mode, slides the rotation transmitting member to disengage this member from th
Sakaguchi Takahiro
Shimma Yasutoshi
Lahive & Cockfield LLP
Makita Corporation
Smith Scott A.
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