US 4,551,847 AGranted

Hand held digital measuring device

OwnerW. Kenneth Caldwellinventor

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Abstract

A hand-held tape measure is provided which includes a conveniently sized housing with an elongated measuring tape suitably coiled on a rotatable shaft mounted within said housing. A sprocket arranged to engage the surface of the tape without slippage is mounted within the housing and drivingly connected to an encoding disk whereby the rotation of the disk is directly proportional to the linear movement of the free end of the tape. The disk is divided into an equal number of alternating transparent and opaque segments and two energy sensitive coupler switches are mounted in conjunction with the disk to provide electrical outputs indicative of the adjacent disk segment to indicate the rotation of the disk. The switches are offset circumferentially to provide a phase differential which indicates whether the tape is extending or retracting with respect to the housing. The output from the switches is fed to an electronic circuit which counts and divides the output pulses with the result digitally displayed. A variable speed reversible motor which is powered by an internal power source can be drivingly connected to the tape to control its movement. A switch is provided on the housing for controlling the direction of the motor. This switch can also include a lock for holding the tape in the retracted position when the motor is deenergized.

Claims27

Dependent claims

A hand-held motorized measuring tape comprising:

(a) a housing means;
(b) a measuring tape means including an elongated thin and flexible tape having a predetermined length which is wound on a shaft which is rotatably mounted within said housing, the free end of said tape being arranged to extend outwardly from said housing through a suitable opening;
(c) reversible drive motor means mounted within said housing and connected to said tape rotating shaft by a suitable drive means;
(d) an electrical power source mounted in said housing, said power source including a switch mounted on the outer surface of said housing and electrically connected to said motor means to energize said motor means in either the forward or reverse direction so as to result in the extension or retraction of the free end of the measuring tape with respect to the housing;
(e) a digital output display means mounted on said housing and a sensing means positioned within said housing, said sensing means being arranged in conjunction with said measuring tape to accurately measure the lineal extension of said tape means and to provide an accurate digital output reading of the extended length of the tape on the display means;
said tape means having a series of equally spaced holes arranged along its central longitudinal axis and said sensor means includes a rotatably mounted sprocket which is arranged to mesh with the holes in said tape and to be rotated by the movement of said tape;
(f) an encoding disk;
(g) said sprocket means is drivingly connected to said ending disk whereby any rotation of the sprocket will be directly translated to similar rotation in the encoding disk, and switch means mounted in conjunction with said encoding disk to sense rotational movement of said disk and provide an output to the digital display means to accurately indicate the extended length of the tape means;
and
(h) said encoding disk is divided into alternating segments and the switch means includes at least two optical switches which are positioned around the circumference of said disk to provide electrical phase-related inputs to the electronic circuit for said display means which are indicative of the rotational direction of the adjacent disk segment.

7 more elements

A hand-held digital tape measure for providing accurate measurements of length, the tape measuring including:

(a) a housing means;
(b) an elongated measuring tape having a predetermined length which is attached at one end and wound on a shaft rotatably mounted within said housing means, the opposite free end of said tape being arranged to extend outwardly from said housing means through a suitable opening whereby the actual length of said tape extending from said housing can be used to provide an accurate dimensional measurment of an object;
(c) sensing means mounted within said housing means and arranged in conjunction with said tape to provide an output indicative of the actual lineal movement of the free end of said tape at it extends or retracts with respect to said housing means;
(d) digital display means mounted on said housing means and having an electronic circuit which receives the output from said tape sensing means whereby the actual length of said tape extending beyond the opening in said housing means will be accurately measured and indicated in the display means;
(e) said measuring tape has a series of small equally spaced holes extending along the central longitudinal axis;
(f) the sensing means includes a sprocket and encoding disk which are drivingly interconnected and rotatably mounted within said housing means, said sprocket being positioned to engage the holes provided in said tape so that as the tape moves lineally with respect to said housing, the encoding disk will rotate as a predetermined proportional rate;
and
(g) said encoding disk has a number of equally spaced alternating segments around its circumference and at least two optical coupler switches mounted with respect to said disk edge so as to sense the rotational movement of the disk whereby the switches will each produce an electrical output phase relation indicative of the adjacent segment which is fed to the electronic circuit means where it is processed to determine the display output for the measurement.

5 more elements

A hand-held tape measure for precisely measuring the length of an object and displaying this length digitally, the tape measure comprising:

(a) a housing;
(b) a source of electrical power mounted within said housing;
(c) a coiled elongated thin tape having a predetermined length which is coiled for storage on a rotatable shaft mounted within said nousing, the free end of said tape being arranged to extend tnrough a suitable opening in the side of said housing whereby the length of tape extending from said opening can be used to precisely measure the dimension of an object;
(d) said tape having a series of equally spaced apertures provided along its entire longitudinal axis and a sprocket rotatably mounted within said housing and arranged to engage the holes in said tape;
(e) an encoding disk rotatably mounted within said housing drivingly connected to said sprocket by a series of speed increasing gears whereby the rotational movement of said disk is directly proportional to the rotation of said sprocket which in turn is directly related to the linear movement of said tape;
(f) said encoding disk having alternating equally spaced transparent and opaque segments around its entire cirumference and at least two optical switches mounted so as to engage at least an edge of said disk and connected to said electrical power source whereby said optical switches will sense the phase of said segments and provide an electrical output depending upon its adjacent disk segment;
(g) digital display means mounted on said housing, said digital display means including electronic circuit means which is powered by the electrical power source and arranged to receive and process the output from said switches so that a digital output display will be provided in units of measurement which correspond to the total length of the free end of the tape which extends beyond the opening in said housing;
(h) reversible motor means suitably mounted within said housing and connected to said internal electrical power source, said reversible motor means is drivingly connected to the coiled tape measure means whereby the rotation of said motor will extend or retract the free end of said tape with respect to the housing;
and
(i) switch means mounted on said housing and electrically connected to said motor means, said switch means including variable control means whereby the actual rotational speed of said motor can be precisely varied to control the speed with which the tape is extended or retracted whereby precise measurements of length can be made.

7 more elements

A hand held digital measuring device for providing accurate measurements of length, the measuring device including:

(a) a housing means;
(b) an elongated measuring means having at least a straight portion and first and second ends with a predetermined length therebetween, said straight portion of said elongated measuring means being slidably mounted with respect to said housing means so that the first end will extend beyond one side of said housing means;
(c) sensing means mounted within said housing and arranged in conjunction with said measuring means to provide an output indicative of the actual lineal movement of the housing means from the first end as the housing means moves along said measuring means;
(d) digital display means mounted on said housing means and having an electronic circuit which receives the output from said tape sensing means whereby the actual length of the first end of said measuring means extending beyond the side of the housing means will be accurately measured and indicated by the display means;
(e) said measuring means having a series of small equally spaced holes extending along the central longitudinal axis;
(f) the sensing means includes a sprocket and encoding disk which are drivingly interconnected and rotatably mounted within said housing means, said sprocket being positioned to engage the holes provided in said measuring means so that as the measuring means moves with respect to said housing means the encoding disk will rotate at a predetermined rate;
and
(g) said encoding disk has a number of equally spaced alternating segments around its circumference and at least two optical coupler switches mounted with respect to said disk edge so as to sense the phase of said segments and the rotational movement of the disk whereby the switches will each produce an electrical output indicative of the adjacent segment which is fed to the electronic circuit means where it is processed to determined the display output for the actual measurement.

5 more elements

Dependencies are inferred from the claim text.