US 5,842,527 AGranted

Hammer drill with a mode change-over mechanism

AssigneeMakita Corporation

InventorsTakuo Arakawa, Masao Miwa

Life of this patent

Estimating the term…

Loading patent…

Abstract

A hammer drill has a mode change-over mechanism including a change link with a horizontally elongated slot, an eccentric pin projecting from a mode selector switch and penetrating the slot. The change link is moved vertically by rotating the mode selector switch, which in turn vertically moves a pair of change keys secured to a holder of the change link, thus either engaging or disengaging the change keys with or from a sleeve provided in a rotation transmission mechanism for transmitting the rotation of a motor to the tool holder. In the engagement position, the rotation of the motor of the hammer drill is transmitted to a tool holder while in the disengagement position, the rotation of the motor is not transmitted. Also, the eccentric pin is engaged with a square recess formed in a lock ring which is fitted around the tool holder and urged backward by a compression spring. The eccentric pin is horizontally moved by rotating the mode selector switch, which in turn moves the lock ring in the axial direction, thereby couple or de-couple the lock ring to or from the tool holder.

A hammer drill, comprising:

a motor for providing drive power for the hammer drill;
a cylinder fixed in a housing;
a rotatable tool holder for receiving and integrally rotating a tool bit therewith, the tool holder being provided with an engagement member;
a rotation transmission mechanism for transmitting the rotation of the motor to the tool holder, the rotation transmission mechanism provided between the tool holder and the motor;
transmission switching means included in the rotation transmission mechanism for, by the movement thereof, selecting one of two operational states in one state of which the rotation of the motor is transmitted to the tool holder and in the other state of which the rotation of the motor is not transmitted to the tool holder;
a locking member movable between a position in which the locking member is engaged with the engagement member of the tool holder and another position in which the locking member is disengaged from the engagement member;
and
mode change-over means for moving the transmission switching means and the locking member, the mode change-over means connecting the transmission switching means with the locking member;
whereby the operation mode of the hammer drill can be selected by operating the mode change-over means from:
a rotation plus hammer mode in which the transmission switching means is moved to a position where the transmission switching means is able to transmit the rotation of the motor to the tool holder and the locking member is moved to a position where the locking member is disengaged from the engagement member of the tool holder;
a neutral mode in which the transmission switching means is moved to a position where the transmission switching means is unable to transmit the rotation of the motor to the tool holder and the locking member is moved to a position where the locking member is disengaged from the engagement member of the tool holder;
and
a tool holder lock-up mode in which the transmission switching means is moved to a position where the transmission switching means is unable to transmit the rotation of the motor to the tool holder and the locking member is moved to a position where the locking member is engaged with the engagement member of the tool holder.

10 more elements

Abstract

Claims9