CA1279474C - Electronic tape rule - Google Patents

Abstract

ELECTRONIC TAPE RULE OF THE DISCLSOURE: An electronic extension tape for linear measurement has a tape portion extensible from the housing thereof, the housing containing a position track with electronic reading means adjacent thereto, connected with an electrical processer providing output to a visual readout representing real tape extension, in a first operative state; and in a pre-selected second state utilizing a pre-programmed processer and memory to provide readouts as desired functions of real extension. The processor enables a tab function to be used, in which multiples of a pull-out value are flagged. The processor also permits division of an output value by an integer, so as to read a half value for a real tape extension. The memory also provides an additive function for sequential tape extension values.

Description

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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 - .

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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 , .~ ' . .

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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 .
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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, :

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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.

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Claims (10)

CLAIMS:

1. A tape rule comprising a housing a tape that may be extended from the housing and which carries a position track therealong reading means in the housing past which the position track travels during movement of the tape first processor means electrically connected to the reading meaans for receiving electrical signals therefrom and generating an output indicating the extent of extension of the tape visual readout means for providing a visual display indicative of the extent of tape extension second processor means electrically connected to the visual readout means and to the first processor means and selection means for specifying a choice of alternative preprogrammed calculations said second processor means being operative in a first operative state to pass a signal indicating the extent of real tape extension to the visual readout means and responsive to said selector means to co-operate in operative state in which subsequent signals indicative of the extent of current tape extensions are processed using an earlier extension value stored in memory and a continuously processed result is passed to the visual readout means.

2. A tape rule according to claim 1 wherein in the second operative state the output of the first processor indicative of an earlier extension value is stored in memory; and said output is incremented by the then existing signals indicative of the extent of current tape extension value; and the sum thereof is passed to the visual readout means.

3. A tape rule according to claim 1 wherein the position track is encoded to define absolute positions along the tape and the position track is formed by markings defining a sequence in which groups of m elements occur once, and the first processor means determines the tape extension by gathering values corresponding to m successive elements and determining their position in the sequence.

4. A tape rule according to claim 1, wherein the first processor means employs hard wired logic to generate the output and wherein the second processor means is a microprocessor having firmware instructions defining said operative states.

5. A tape rule comprising a housing, a tape that may be extended from the housing and which carries a position track therealong, reading means in the housing past which the position track travels during movement of the tape, first processor means electrically connected to the reading means for receiving electrical signals therefrom and generating an output state indicating the extent to which the tape has been extended, visual readout means, second processor means electrically connected to the visual readout means and selector means, said second processor means also being electrically connected to the first processor means for communication of the output state and arranged to respond to operation of the selector means to store a then existing real tape extension in memory and subsequently to determine whether a subsequent real tape extension differs from an integer times the stored tape extension by no more than a predetermined permissible distance, and to indicate the existence of such a relationship on the visual readout means.

6. A tape rule according to claim 5, wherein the second processor means sends a signal signifying real tape extension to the visual readout means.

7. A tape rule according to claim 5, wherein upon a further actuation of the selector means the second processor means divides the real tape extension value by two and outputs the result to the visual readout means.

8. A tape rule according to claim 5, wherein, upon actuation of the selector means, the second processor means maintains a current extension value sent to the visual readout means until the second processor means has determined that the tape has been displaced by at least a predetermined interval from that extension.

9. A tape rule according to claim 1, wherein a datum position is provided on a side of the housing from which the tape extends and either the processor means corrects the information read from the tape when generating the output state by allowing for an offset between the sensors and the datum position or the start of the position track is offset from the start of the tape.

10. A tape rule according to claim 9, wherein the position track is encoded to define absolute position along the tape.