Electronic digital tape-rule

Claim 1

An electronic digital tape. rule consisting of a housing, a rotatable tape reel encased within said housing and having a flexible and extensible measuring tape, a power source for supplying electric power to the electronic circuit, an actuator acting as a switch means for selecting a forwarding or backwarding count of a counter, a detector for sensing the number of revolutions of a disc as the tape is extended and for generating a signal in response thereto, a counter responsive to the signal generated by said detector for accumulating a count representative of the length of said tape, a display for displaying the count accumulated by said counter, a brake for stopping and releasing said tape and a power switch; characterized by that said actuator comprising: a friction roll rotatably mounted on a shaft fixed at an inner wall of said housing; a disc disposed on the upper end of said roll and rotatable by the friction of the roll; a plate fixed on the upper end of said roll and having a hole with a pair of contact plates attached on the two side walls thereof; a spring mounted between said disc and said plate for constantly pressing the disc against said roll; and an actuating rod disposed upright on the upper side of said disc and being arranged in such a manner that its upper end passes through the hole of said plate and is able to contact one of said two contact plates depending on the rotating direction of said disc.