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Description  |
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BACKGROUND OF THE INVENTION
The present invention relates to an electronic digital taperule and, more
particularly, to an actuating device for the electronic digital tape
measure.
A conventional electronic digital tape measure was disclosed, for example,
in U.S. Pat. Nos. 4,031,360 to Soule, and 4,316,081 to Washizuka. In the
former reference, a measuring tape was formed of links fitted to each
other, with each link perforated by a through hole, that is, the measuring
tape had a considerably large volume and the housing of the tape measure
was not compact. Furthermore, since the conventional measuring tape was
not flexible per se, it was impossible to determine the length of curves
such as the circumferential length of a tube or cylinder. The conventional
measuring tape was also apt to damage fingers, etc. because of its sharp
edges.
In order to eliminate such drawbacks in U.S. Pat. No. 4,031,360, U.S. Pat.
No. 4,316,081 provides a compact electronic digital tape measure having an
improved flexible measuring tape structure capable of measuring both the
length of straight line and curves. In this patent, there is disclosed a
flexible measuring tape constituted by allocating a number of magnetic
balls in predetermined space from each other and by locating a number of
non-magnetic balls to provide the space therebetween. The chain of the
magnetic balls and the non-magnetic balls is buried within a flexible tape
generally made from synthetic resin and the like. Due to the complicated
special structure of the flexible tape, it is difficult to manufacture
such a tape and the manufacturing cost is considerable high. U.S. Pat. No.
4,031,360 also provides a common flexible measuring tape which has no
special structure similar to the above-mentioned flexible tape. An
electronic actuating and detecting device comprising a photoelectric
sensor, a rotatable disc having slits, a counter, a display and a pressure
roller is provided within the housing and its arrangement is such that the
detecting device may detect the measuring tape pulled out from the housing
through said pressure roller and disc, and generate a series of signals to
the counter to display the corresponding length of the tape in digit form
through an electronic circuit. According to the above-said known digital
tape measure, the disclosure relates to the basic arrangement and
principle of the assembly only and does not account for a detail in
constitution and relation in the components, especially, the actuating
device which is very important to a tape measure. Therefore, there exists
many problems in the manufacture or work-out of the known tape measure,
and even in making the invention a practical use.
SUMMARY OF THE INVENTION
Accordingly, it is the primary object of the invention to provide a
practical construction of an actuating device for electronic digital
tape-rule having superior operability.
It is a further object of the invention to provide an actuating device
which in cooperation with the friction rolls can accomplish the switching
action corresponding to the directions of rotation of the friction rolls.
Other objects and further features of the present invention will become
apparent from the following detailed description taken in connection with
the accompanying drawings wherein:
FIG. 1 is a perspective view of an electronic digital taperule according to
the invention;
FIG. 2 is a cross-sectional view of the electronic digital tape-rule of
FIG. 1, showing the arrangement of the components within a housing;
FIG. 3 is a block diagram of a detector and display according to the
invention; and
FIG. 4 is a cross-sectional view of an actuating device in cooperation with
the detector in accordance with the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIGS. 1 and 2, in accordance with the invention an electronic
digital tape-rule 01 comprises a housing 1, a tape reel 2 having a
flexible measuring tape 21 therein, a battery case 3 receiving at least
one dry cell 31 therein, an actuator 4, a detector 5, a forward-backward
counter 6, a display 7, a brake 8 and a power switch 9.
The structure and arrangement of tape reel 2 with an extensible measuring
tape 21 therein and a brake 8 for stopping the tape 21 from moving are
basically similar to those of the conventional tape measure, i.e., a
non-electronic tape measure; however, in the embodiment described herein,
there is ample space provided for battery case 3, actuator 4, detector 5,
counter 6, display 7 and power switch 9 within housing 1.
The flexible measuring tape 21 has its free end being led out from the
spring-biased tape reel 2 to a lead-out slit 11 provided at one corner of
housing 1 via actuator 4 and detector 5.
According to the present invention, the improvement is chiefly in the
constitution of actuator 4 and detector 5, the latter working in
cooperation with the former.
FIG. 4 illustrates an arrangement of actuator 4 and detector 5 of the
electronic digital tape rule, in which the actuator 4 comprises a shaft 41
fixed at one of the two main walls 1a, 1b of housing 1, for example, at
wall 1a, with its upper end portion 41a being formed of a polygonal
section and the rest portion a cylindrical section, and the upper end
being fastened to the other wall 1b by a screw 42 passing through the
latter. A friction or pressure roll 43, which is generally a resilient
rubber roll, is rotatably mounted on shaft 41 by means of a bearing 44,
and a rotatable disc 45 is mounted coaxially on the upper side of the roll
43 and rotatable therewith by friction. A fixed plate 46 is disposed on
the upper end portion 41a of shaft 41 by fitting a polygonal hole 46a
provided thereon onto the same polygonal shaft portion 41a, and has a
further hole 46b which is generally in sector shape and is provided with
two contact plates 461, 462 being located on both side walls thereof. A
compression spring 47 is mounted between a disc 45 and plate 46 for
biasing the disc 45 constantly against the upper surface of friction roll
43, whereas an actuating rod 48 is disposed with its one end fixed on the
upper surface of rotatable disc 45 and the other end engaging sector hole
46b.
The detector 5 comprises a shaft 51 fixed at the wall 1a of the housing in
the same manner as shaft 41 and screwed by a screw 52 passing through wall
1b to the shaft 51. A friction or pressure roll 53, which is generally a
resilient rubber roll, is rotatably disposed on shaft 51 by means of a
bearing 54; a rotating disc 55 is fixedly and coaxially mounted on the
upper end of the roll 53 having a positioning pin 531 inserted in a hole
551 provided on the disc. The diameter of disc 55 is larger than that of
roll 53 so that its outer periphery protrudes out radially from and is
rotatable with roll 53, which includes a plurality of slits 55a arranged
in a circle on the outer peripheral portion thereof. A sensor assembly 57
is mounted on a supporting member 58 which is protruded upwardly from wall
1a and a shield plate 56 which has a slit 56a is located between sensor
assembly 57 and disc 55.
The light emitter 57a and photo sensor 57b of the sensor assembly 57, the
slit 56a of shield plate 56 and one of slits 55a are generally located in
a straight line so that the rotation of the roll 53 will cause rotating
disc 55 to rotate together with roll 53 and will be sensed by the sensor
assembly 57.
The brake 8 comprises a rod 81 being provided within the housing 1 and
having a friction pad 82 attached on its lower end, a coil spring 83
constantly biasing on the upper end of rod 81 for pressing pad 82 on the
free end portion of tape 21 and a push button 84 having a pin 85
engageable in a hole 86 of the rod 81 to keep pad 82 pressing on tape
portion 21 and releasable by pushing button 84.
FIG. 3 illustrates a block diagram of the electronic connection of the tape
rule according to the invention, wherein the electronic circuit of
batteries 8, switch 9, counter 6, actuator 4, detector 5 and display 7 is
shown.
In the application of the electronic digital tape rule in a linear
measurement, switch 9 is first turned on, whereby all the components of
the tape rule as shown in FIG. 3 will be placed in an workable state. The
free end of measure tape 21 is then pulled outwardly against the spring
force of tape reel 2 and pressure force of friction pad 82. At this
moment, the two friction rolls 43, 53 driven by a friction force from tape
21 which is now being tightly held therebetween, are moved to rotate
synchronously in a direction indicated by the arrow A. As such, disc 45
against the force of spring 47 is also moved to rotate along with roll 43
by the friction force and so also rod 48 on the top of disc 45, which
rotates together with the disc till the upper end thereof touches contact
plate 461 of hole 46b when rotation of the rod 48 stops. Due to the
contact of contact plate 461 and rod 48 a signal is immediately given off
and sent to forward-backward counter 6 for operation of forward counting
by the latter. On the other hand, as roll 53 drives rotating disc 55 to
rotate together therewith, sensor assembly 57 having the light emitted by
light emitter 54a, which passes through slit 56a of shield plate 56 and
slit 55a of the disc 55 and which is next received by photo sensor 54b,
sends off pulse signals to be delivered to forward-backward counter 6. The
counter 6 next begins counting the number of slits 55a of disc 55 that
have passed over the disc, that is, the number of revolutions of disc 55,
and signals undergo conversion to become the linear length of tape 21
corresponding to that number of revolutions, which is then shown on
display 7. This length in digital form can readily be read from that
display 7.
If however, the tape that has been pulled out exceeds the length in measure
and needs to be adjusted, it is necessary only to press button 84 of brake
8. Upon application of pressure on button 84, rod 81 in counteracting the
force of spring 83 is lifted upward by a very slight distance, thereby
permitting pad 82 to release tape 21 which, in a subsequent action, is
rewound back into tape reel 2 under the immediate resilient action of a
rewinding spring located therein. In so doing, the pulled-out end portion
of tape 21 is being gradually shortened and until when it comes close to
and is in the vicinity of the required length, press button 84 is released
and biased by the force of spring 83, rod 81 pushes downward enabling pad
82 to press against tape 21 again so that the latter will not move any
longer.
During its withdrawing and shrinking towards the inside of housing 1, tape
21 with friction force moves rolls 43, 53 to rotate in a direction
opposite that described above, that is, in a direction counter the one
shown by arrow A. Therefore, as rod 48 carried by disc 45 rotates together
with the disc, this rod 48 is released from contact with contact plate 461
and comes into contact with the other contact plate 462. A signal is thus
generated at this contact, which is transmitted to forward-backward
counter 6 for operation of backward counting by the latter. On the other
hand, roll 53, as described before, rotates together with roll 43 thereby
driving rotating disc 55 to rotate in a direction opposite that described
above. Sensor assembly 57, in a like manner as described before, starts
counting down now the number of revolutions of disc 55 and after
subtracting the length of tape 21 that has been withdrawn, the remaining
length of the tape is shown in digital form on display 7. In this way, the
extended tape can be pulled out to the required length or the length of
the extended tape that has been pulled out in excess can be withdrawn by
controlling brake 8 till the required length has reached, and the length
of the extended tape can then be adjusted into the length of an object to
be measured and this length can next be read out from display 7.
If the tape is not in use and is to be rewound back into housing 1, it is
necessary only to press down button 8 whereby the extended tape will be
withdrawn into tape reel 2 by a spring force and at this time, the digital
unit will be returned to indicate zero on display 7. Finally, switch 9 is
turned off to cut off the power source.
From the above, it is possible therefore to indicate the length of an
object to be measured on display 7 by pulling out the tape from or
withdrawing the tape into tape reel 2. However, it is to be contemplated
that when the tape is pulled out or withdrawn into tape reel 2, during the
brief period before rod 48 has been shifted from one contact point and
come into contact with the other point, counter 6 will not have assumed
any operation yet. Still, as the tape has already been in movement,
therefore, before counter 6 has begun any counting, at the free end
portion of the tape where extension or withdrawal is carried out there
will be a length of the tape which has not been calculated in counter 6.
Because this un-calculated length is so short, generally within the
permissible range of error for a measurable length by a typical flexible
rule, the length can thus be neglected from calculation. To remove such
error from a measurement, it can also be contemplated that the
uncalculated length be added before to the value of counting pulses
started in counter 6 for calculation so that the concern for an error in
initial counting can be avoided.
As described above, the present invention has for its purpose to provide a
most practically applicable construction of an electronic digital tape
rule.
While a preferred embodiment of the invention has been shown and described,
it will be apparent to those skilled in the art that various changes and
modifications may be made therein without departing from the spirit and
scope of the invention as claimed.
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