Note: Descriptions are shown in the official language in which they were submitted.
~7~
This invention relates to a tape rule.
The provision of an electronic tape rule in which a
digital readout of tape position is combined with an
ability to perform calculations using tape position as an
input is described in Japanese Utility Model No. SH0 Sl-
71937, US Patent Nos 4161781 (Hildebrandt), 4181959
(Tateishi), 4181960 (Tateishi et al), 4316081 (Washizuka)
and V~ Patent Specifications Nos 2102121 (Souic Tapei) and
2052745 (Wine~). However the above references require the
user to carry out two key operations to display the result
of a calculation based on a previous tape position and do
not provide for updating the result continuously based on
current tape position.
In one aspect the invention provides a tape rule
comprising a tape that may be extended from a housing and
that carries a position track therealong, reading means in
the housing past which the position track travels during
movement of the tape, first processor mean~ electrically
connected to the reading means for receiving electrical
~ignals therefrom and gen'erating an output state
indicating an extension of the tape, visual readout rneans
for providing a visual display of tape axten~ion and
second prooes~or ~eans electrically connected to the
vi~al readout means and to ~he fir~t proces~or means for
communication of the output state and arranged in a first
operative state to pa~s a signal signiflcant of real tape
extension to the visual readout means and res~onsive to
selector means to pass to a second operative state in
which subsequent real tape exten~ions are operated on
using an earlier ex~ension value ~tored in memory and a
result is passed to the visual readout means.
The ability to execute arithmetical calculations in
real time depending upon a current position of the tape
enables a "tab" function to be provided in which a flag
portion of the display i9 illuminated when the tape has
been pulled out a distance which is at or close to a
multiple of a previous distance.
In a further aspect the inven~ion provides a tape
rule comprising a tape that may be extended from a housing
and that carrie~ a po~ition track therealong, reading
means in the housing past which the position track travels
during movement of the tape, first processor means
eleetrically connected to the reading means for receiving
electrical signals therefrom and generating an output
state indica~ing an extension of the tape, visual readout
means, and econd proces~or means electrically connected
to the vi~ual readout means ~nd to th~ firat processor
means for communication o~ the output ~tate and ar~anged
to respond to operation of seleetor m~ans ~o store a then
e~i~ting real ~ape e~tension in memory ~nd sub~equently to
determine whether a subsequent real tape exten~ion differs
from an integer times the stored tape extension by no more
than a predetermined permis~ible di~tance, and to indicate
,
the existence of such a relatlonship on the vi~ual reado~lt
means.
In a yet further function which is preferably
included, on ac~uation of further selector means second
processor means divides the real tape extension by two and
outputs the result to the visual readout means.
In a yet further aspect the invention provides a
tape rule compri~ing a ~ape that may be extended from a
hou~ing and that carries a position track therealong,
reading means in the housing past which the po~i~ion track
travels during movement of the tape and processor means
electrically connected to the reading means for receiving
electrical signal~ therefrom and generating an output
stage indicating an extension of the tape and visual
15 readout mean~ for providing a visual display of tape
e~tension in accordance with the output state, wherein a
datum position is provided on a side o~ the housing froln
which the tape extends and either the processor means
corrects the information read from the tape when
generating the output Ytate by allowing for an offset
between the ~ensors ~and th~ datum po~ition or the
effective s~art of the po~i tion tracX i3 of fR*~: Erom the
~tar~ of the tape.
An embodim~n~ of the invention will now be
25 described, by way of example only, with ref~rence to the
accompanying drawing~, in which:-
Figure 1 iY a block diagram of a tape rule according
to the inven~ion;
Figure 2 is a flowchart illu~trating routines held
as firmware in a micro~roces30r forming part of the tape
rule of Pigure l;
Figure 3 is a diagram illustrating succe~sive states
of a display formin~ part of the tape rule of Fi~ure l;
and
Figure ~ is a diagrammatic 3ide view of a ca3.ing of
a tape rule according to the invention.
In the drawings, there i.~ ~hown a steel tape rule
that incorporates an electronic system tha~ can give a
digital reading-o~ length, mea~ured in either metric or
imperial unit~. In use the tape operate~ in a ~imilar
manner to a conventional ~eel rule but can include
additional features to a~sist the user, for example,
automatic correction of reading for reveal mea~urement,
taking the tape b~dy width into account.
The proposed mea~urement method i~ described below
in conjunction with Figure 1. A tape 1 of steel or other
~0 inexten ible material i-~ used as in a conventional tape
rule controll~d by a tensator ~pring i but is printed with
a pair of ~patial encoder track~ 3, 4 in addition to the
usual visually readable distance scale~ 2. Internal ~o a
casing~ 6 of the product, the tape 1 i~ illuminated by
~S mean~ of a li~h~-~mitting diode 31 and an image of the
encoder tracXs 3, 4 i9 ormed usin~ a lens 7 on a
photosen~or array 30 which i3 arranged ~o have four
i
sensitive areas in grouped pairs corresponding to the
naired encoder tracks 3, 4. ~ach sensitive area views a
s~all part of its encoder track. The pairs of sensors in
array 30 are aligned with ~he tracks 3, 4 which are
defined by ~ark and space or black and white areas of
varying widths, printed on the tape 1 and imaged at the
photosensors. Movement of the tape 1 causes the light
level at each photos~nsor to vary as the area of the tape
1 corresponding to an individual pho~osensitive area
changes between black and white. By suitable analogue
processing, four binary ~ignals, one for each
photosensitive area are derived from the photo~ensor
outputs. The two states of the signals represent black or
white at the areas on the tape 1 corresponding to each of
the photosensors.- Movement of ~he tape 1 causes the
binary signals ~o change as the encoder ~rack~ 3, 4 move
past the photosensor 30.
The pat~ern of the encoder track3 3, 4 and ~he
spacing of the photosen~ors 30 are arranged ~o ~hat for
every position on the tape 1, incremental movemen~ of the
tape 1 cause only one of the o~pu~s to change ~tat~ at a
ti~e. Sequence~ of states fulfilling thi~ criterion are
known a~ Gray codes. Additionally, it can b~ arranged
that the direction of movement c~n, ~t ~ ime~, be
deduced from ~he change in output state~. The ~equences
of ~tate~ produced by ~ensing the marXings preferably
deine one or other of al~ernate paths that may be
- .
,
,
- . ~ . .
,
' ' : ' ' ' :.
:
recognised by a local state decoder as a logical 1 or a
logical n element of an m-sequence of pseu~o-random
elements o~ ab~olute position code (APC) laid down along
the tape, the sequence having the "window" pro~)erty that
any group of m quccessive element~ occurs once only in the
sequence. Thus a recognised group of m APC elements
defines a unique po~ition on the tape, as described and
claimed in Canadian natel._ Applica~ion No. 523,681 filed 2a
November 1986r An advantage of using such an absolute
position code is that damage to part of the tape does not
bring about inutility of the whole tape beyond the damaged
region.
As is apparent from Figure 1, the ou~put of sensor
array 30 i~ fed o an analogue processing circuit 8 and
then to CMOS digital processing logic 9 which are
implemented in a single application-speci~ied integrated
circuit (ASIC) 10 that provides po~ition data at input
port 11 of a 4-bit CMOS mask-programmed microprocessor 12
and receive~ information and commands through an output
port 13. The digital processing logic 9 of ~he ASIC 10
inc~udes a local state decode~ and an APC binary sequence
decoder that are both implemented a~ hard wired logic and
h~nce can run much more rapidly than the microproeessor 1 2
80 that the code tracks 3, 4 can be followed even during
25 rapid tape movementO The architecture of the
microproce~sor 12 i3 similar to a conventional calculator-
~ype microprocessor and the ports 11, 13 communicate via a
,
.~ ' . .
~7~3~
4-bit bus 15 with an ALU 16, accumulator 17, display RAM
18 an general purpose ~AM l9 which may be of 2-4 K size,
under the control of firmware ROM 14. A ~eypad 21
communicates with the bu~ 15 through input port 20 that
S may read up to 12 keys. The output value to be displayed
is fed from display RAM 18 to a display driver 22 that
may conveniently drive a display of up to 64 segments and
is shown on a liquid crystal display 23.
The working position 70 of optical sensor 30 is
inevitably located behind a datum position 71 defined by a
flat front face 72 of the casing 6 from which the tape 1
is withdrawn or a cursor piece in front of the casing,
from which measurement is to be made. In determining the
value to be displayed the microprocessor 12 must allow for
lS this offset 73 in normal measurement mode, as it would do
in an alternative "case include" mode. It is particularly
important to do so when the tape carries an absolute
position code. Alternatively the start of the encoder
tracks 3, 4 may be offset from the start of distance
scales 2 by a distance corresponding to offset 73.
Re~erring to Figure 2, ~he firmware in ROM 14 wlll
from a start-up state 35 clear ~tored data from RA~ l9 at
step 36 and then return. It then reads data significant
of current tape po~ition at 37, calculates a tape position
in imperial or metric unit~ to be displayed on display 23
at ~tep 38, taXing account of the offset 73 between the
sensor po~ition and the datum position at the front of the
.
.
casing 6 and in a normal operation or default mode outputs
at step 39 that position to display ~ 18 and ret~rns.
The invention provides a con~inuous.summation mode
which supports length measurement where the length to be
mea~red i8 greater than the leng~h of the tape. On
entering the ~ummation mode, the di-~play 23 3hows the
current tape exten~ion which will have been loaded into
RAI~l 18 at ~tep 39 of the default mode. The value in RAM
18 is maintained until either a predetermined time has
passed or until new tape position data determined by the
ASIC chip 10 differs by a predetermined amount from the
value when key 41 ha~ been pre~sed~ Pressing the
summation key 41 causes a value significant of tape
extension to be stored in RAM 19 at step 42 after which
15 new position da~a from the ASIC 10 i8 read at 43. A tape
position is calculated at step 44 as the sum of the new
posi~ion from the ASIC and the extension value stored in
RAM 19, a check i~ made at step 46 whe~her a clear key 48
has been pressed, and assuming tha~ this has not happened
the accumulator ~ub-routin~ output~ at 49 the result to
di~play R~M 18 and returns to' step 43. The stored value
in thé relevant r~gis~er of RAM 19 will hav~ been set to 0
at switch-on and at each subses~uent actuation of summation
key 41 the contents of that regl~ter will be incremented
with the e~ten8ion value ob~ain~d from ASIC 10 00 that a
cumulative ~um of ~everal measurements i a obtained
including the current tape po~ition a~ latest measurement,
:
,
.
,
. ~
~.a.~
whieh sum is displayed on display 23. On passing the CLR
key 48 the firmware brings about a return to step 36 and
the value in RAM 19 is cleared, after which ~he machine
return to the default mode.
The el'fect on the display 23 is illustrated
diagrammatically in Figure 3. At the top 1 ine the tape
rule is opera~ing in default mode and the display 23 shows
current tape position. At the second line, key 41 has
been pressed, the value on display 23 is frozen and an
indicator area S0 of the di play is active. At line 3 the
tape has been return~d from an initial 5 metra extension
- to an extension of 4.437 metres, this moYement exceeding a
predetarmined di~tance that the tap~ has to travel before
display RAM 18 i~ freed. The sum of the ~tored and real
15 tape e~t~nsion values is now placed in RAM 18 at ~tep 49
and th~ display reads 9.437 metres.
A further key 51 cause~ the firmwar~ in ROM 14 to
cause the microproceA~or 12 to opera~e in a TAB mod~. The
tape extenRion ~alculated at st~p 38 i~ loas~ed at step S2
into RAM 19, ~nd 3ubsequent operations of key 51 will
:cause th~ previous value to b~cleared and a new value to
be entered. A tab ~elected indicatox 62 of ~he display 23
i~ then activated a~ step 53. The microproces~or 12 then
enters a rou$inQ where data i& re~d from ASIC chip 10 at
step 54, a current tape eXtension i~ caleula~d at step 55
and the current extension i8 divided at s~ep 56 by the
stored exten~ion. If the result i8 an integer or differs
from an in~eger by no more than defined limits when tested
at step 57, a tab indicator 63 of display 23 is activated
at step 58, and the position is ou~put a~ st~p 59. The
microprocessor checks at 60 whether cl~ar key 48 has been
pressed and as~uming tha~ this is not the case returns to
step 54. The re~u lt is that tape extension is
continuously shown on the di~play 23 and the tab indicator
63 is aetivated whenever the exten~lon is a multiple of a
stored tab value, so that it is easy e.g. to mark a wall
101 at 0.15metre intervals for attachment of battens at that
spacing. On depre~sion of CLR key 48 the firmware returns
at 61 to step 36 and clears the relevant part of RAM 19,
and indicator 62 i~ deactivated.
The accumulator and tab routines are preferably not
: 20 mutually e~lu~ive but may be run concurrently by the
firmware in ROM 14.
A yet further mode of operation of mieroprocessor 12
provides a "cen~re" function. On depre~ion of key 65 the
current po~ition value i~ halved at step 66 and the result
25 i8 output at 67 to display RAM 18. The firmware continues
to monitor tape po~ition at 68 and maintains the value in
RAM 18 and on display 23 until the tape ha~ moved a preset
distance ~9, after which the firm~are returns to ~tep 37.
,
:
