Lock-out mechanisms for lockable power switches are known in the art. These mechanisms are intended to unlock the locked power switch or trigger of a motor driven tool or machine in order to allow the actuation of the motor by the power switch. The power switch of many power tools such as circular saws, table saws of various sorts, hedge trimmers and the like is provided with a lock mechanism in order to prevent unintended operation of a power tool or machine through inadvertent actuation of the power switch prior to operation of the power tool or machine. The user is required to actuate the lock-out mechanism in order to bring the lock mechanism of the power switch in an unlocked position in which the power switch can be depressed and, accordingly, the motor can be actuated.
In an electrically powered miter saw, for instance, used here for example only and not by way of limitation, a motor is used to power a circular saw blade mounted on an cantilevered arm. A platform including guides is also provided. The blade has a housing which covers the unused area of the blade. In this example, as in many power tools, a handle is attached to extend above or besides the blade for convenient operation of the saw, and on the handle is installed a power lever or switch which can be of the trigger-switch variety.
When using the saw, the user is often required to hold the item to be sawed with one hand, and to subsequently raise and lower the saw blade with the other hand. For example, in order to make a mitered cut in a length of wood trim, the user first positions the wood on a platform located below the blade. The user then turns the machine power on by grasping the handle and squeezing or depressing the power lever switch. Without removing the hand from the handle, the user then lowers the saw blade down onto the trim while holding the work piece on the platform with the other hand in order to make the desired cuts. Once cutting is complete, without removing the hand from the handle, the user raises the handle and turns off the saw by releasing the power switch. After release the power switch moves back to its rest position in which the motor is inactuated.
In many power tools including saws, the power switch will be locked by lock means as soon as it comes into its rest position for security reasons. If locked, the power switch cannot be moved into the actuation position in which the motor starts turning. To operate the tool or machine, the user has to actuate the lock-out means first in order to release the power switch.
Many of the prior art lock-out mechanisms, however, are designed for the right-handed individual. In an embodiment with a grip handle arranged in a substantially horizontal manner the lock-out mechanism is positioned left to the power switch. In this case the mechanisms involve intended movement of the right thumb in order to actuate the lock-out mechanism. Left-handed operators, however, must either use both hands for unlocking and depressing the power switch, or they must inconveniently use their right hand for operation of the saw. Thus, left-handed operators are unable to realize the same ergonomic benefits from the lock-out mechanisms as do right-handed operators.