Electronic read out tape measure

Claim 1

A tape measure device incorporating a flexible tape mounted on a spring-biased rotatable reel in a housing, said housing enclosing an electric calculator connected to an electronic digital display unit, with said calculator connected to means to sense the length of tape extended out of said housing in terms of a total of discrete units, and with said calculator incorporating means to cause the electronic digital display unit to display the said total of discrete units, said tape fabricated of joined individual links, with each link perforated by a through hole of a size to fit over a tooth of a sprocket wheel rotatably mounted in said housing, with the links of said tape engaged about the sprocket wheel so as to cause the sprocket wheel to rotate in direct proportion to the travel of said tape into or out of said housing, said sprocket wheel rotatably linked to switching means which transmit pulses of electrical current to said calculator in response to the rotation of said sprocket wheels, the number of said pulses being directly proportional to the degree of rotation of the sprocket wheel and the polarity of said pulses being responsive to the direction of rotation of said sprocket wheel, such that the calculator controls the electronic digital display unit to display a numeral representing a length of tape extended out of the housing, said numeral being the sum of pulses of a first polarity minus the sum of pulses of the reverse polarity.