GB2309084A - Electronic cord/tape measure - Google Patents

Abstract

The cord/tape 20 includes a housing 12A, 12B which accommodates electronic circuit board means 53 for measuring and displaying the length of the cord/tape 20. Toothed/splined pinch rollers 39A, 39B allow extension/retraction of the cord/tape 20 without slippage. A pinch roller is connected with a code wheel 50 and then by capacitive coupling to a stator (87, see block diagram) which produces a combined voltage sum signal processed by a decoder (83) to represent rotation of the rotor 50 and thus linear movement of cord/tape 20 which is fed to display 70.

Description

TITLE : EXTENDING MEASURE DESCRIPTION This invention relates to extending measures.

Extending measures are well known for use by such as builders, handymen, carpenters and other tradesmen. One typical such measure has a coiled strip of spring steel extensible from a housing having a retractor mechanism adapted to withdraw the strip back into the housing after use. Usually, the spring steel strip is transversely bowed to extend with a degree of form-sustaining stiffness, often effective over a metre or more; and is retractable automatically. This type of measure allows its extending metal strip to be pulled out of the housing against a bias provided by a spring of the retractor mechanism. It is popular in sizes up to a few metres of extending strip, but tends to became quite heavy and bulky, and increasingly inq?ractical, at sizes of five or more metre lengths.

Another, often even bulkier, type of extending measure tends to be used for much longer lengths of extending strip normally of flexible textile material. and often with a simple manually operated retractor mechanism. For these types of extending measure, the steel or textile strip carries graduated markings of length to enable use of the strip in making direct measurements.

A further proposal is also known from published Patent Specification G8-A-2217459 for a tape measure comprising a housing associated with a measuring strip having measuring indicia marked thereon, means for retracting the measuring strip into the housing, means for determining the length of strip extended from the housing, and an associated display arrangement for a numerical value equal to or calculated from the marked length of strip extended from the housing.

It is an object of this invention to provide a compact and versatile extending measure.

According to one aspect of this invention, there is provided an extending measure utilising a pull-out cord- or tape-like extending element (generally of much smaller sectional size and/or more flexible than prior strip-type tapes) in a housing further accommodating electronic means for measuring and displaying the length of the extending element extended from holding and progressive release means therefor.

Such use of a cord or tape along with clear but indirect indication of length or distance leads to a low overall size and weight of measuring device, much lower than can be provided for conventional strip types of the same or similar measuring capability. Indeed, it is envisaged that preferred embodiments hereof will provide for measuring up to thirty metres or more using a housing as small or smaller than hitherto normal for a steel strip measure for up to a two or three metres only.

Use of light-weight flexible cord or tape can be further advantageous relative to prior metal or textile strips, by way at least of being less likely to be disturbed by wind when used out of doors, not presenting any sharp edges, and being readily applied to following curved or irregular surfaces or bodies virtually regardless of sharpness of corners or radii of curvature. Use of nonmetallic, thus non-rusting, and electrically non-conducting material can be further advantageous; as can general high resistance to degrading as readily available from synthetic plastics materials of appropriate flexibility and inextensibility in normal conditions of use.

Ideally, despite intendedly long maximum extension from a small housing, bias-type resistance to such extension should be as nearly constant as reasonably achievable over the full extension range, likewise applied retraction force. Preferred bias spring provisions involve a gear coupling system using intermediate or planetary wheels meshing with a central or sun wheel or spindle and with an outer ring, say of a spring housing. Conveniently the spring is a reverse wound spiral coil effectively acting between the housing and a cord or tape spool turning with the central or sun wheel.

Such substantially constant force retraction and/or bias spring provisions are applicable to systems other than the extending measure of the first aspect of this invention, including to a relatively short spring steel strip measure, and generally constitutes a second aspect of this invention.

At least for a cord-type measure hereof, a preferred exit (and return, of course) of the cord from the device housing is through splined spindles or rolls/wheels preferably further with mutually engaging teeth to ensure rotation together and the cord gripped by the splining to assure slip-free conversion of its linear movement into rotation of one of the splined spindles/rolls relative to which electronic measurement is made, conveniently by way of a code wheel rotating with one of them.

In order to avoid need for extreme accuracy of parts, particularly splined spindles/rolls etc, maybe also cord or tape spool provision, it is further preferred and advantageous to make calibration provisions, thereby assuring results of acceptable accuracy without expense inevitably otherwise associated with tight tolerance machining of parts. A micro-controller may be programmed to assert a relationship between rotations of a pinch roller and a standard length of cord or tape drawn out of the device and/or derive a correction factor relative to a nominal such relationship, and make such comparison and calibration for each device produced, conveniently storing results in non-volatile storage of or associated with such said microcontroller.

For a tape-type measure hereof, preferred out- and infeed makes use of spaced holes along the tape, typically at accurately equal spacings, conveniently in-line medially of width of the tape. Highly positive feed is readily applied using toothed roll means, typically one toothed roll over most if not substantially all teeth of which the tape passes with successive sets of its holes engaged and another roll that may or may not be toothed and via which the tape is entrant and exit the measure.

It will be appreciated that a portable hand-held measure as envisaged herein with electronic development and display of distance or length concerned necessitates a measure device that is battery powered. Even with ubiquity of battery powered units of all kinds, there is advantage in maximising battery life and intervals between required replacement, both in relation to initial perceived appeal as a purchase and for longer term acceptability in use. In this connection and as a third aspect of this invention, there is provided an extending measure with electronic development and display of length or distance concerned, wherein conversion from rotary motion into electrical signals and development of same into what is displayed involves reliance on electrical capacitance.Typically such provision can rely on a rotor and a stator with conductive pads or patterns and modifications ot stator energisation according to capacitive coupling with the rotor moving with the cord or tape.

Specific implementation for this invention is now described in more detail by way of example with reference to the accompanying diagrammatic drawings, in which Figure 1 is an exploded view of one extending measure device and its parts generally, specifically shown as of cord-type; Figure 2 shows a spring/gear sub-assembly for assoc iation with cord (or tape) spool and exit provisions; Figures 3A and 3B are fragmentary views showing more detail of specifically cord exit and return provision; Figures 4A,B,C,D are fragmentary views showing detail for an otherwise generally similar measure device of extending tape type, specifically regarding such tape and its exit and return provisions; Figures 5A,B,C are interior side, sectional and other side views for the assembled device;; Figures 6A,B,C are side, end and other side views of the device in its outer housing; and Figure 7 is a schematic electronic circuit diagram.

In the drawings, the specifically cord-type measure device 10 comprises an outer housing shown as a two-part casing 12A,B assembled as two generally similar side halves to be joined in any suitable way, indicated as being along the thickness of the device 10. Each side half 12A,B and the device 10 as a whole extends to a point 14A,B from a generally circular main formation 16A,B, and one (12A) has an associated belt clip 13. There is an exit 18 adjacent the point 14 for the cord 20, shown as being of lightweight flat shape and attached at its free end to a claw 19 also serving as a closure of the cord exit 18.

Inside, the casing or housing 12A,B B are generally circular components including a cord spool 21, a spring housing 23 to fit within the cord spool 21, and a reverse wound spiral coil spring 25 to fit into one side of its housing 23. The spring housing 23 has an annular partition 27 with the spring 25 to one side adjacent a spring cover 25C and a gear mounting plate 29 within. The gear mounting plate 29 carries a central axle 30 for a toothed central or sun wheel 31 that turns with the cord spool 21, preferably is integrally moulded therewith; and has stub axle mounts 33A,B,C taking planetary toothed wheels 35A,B,C that mesh both with interiorly toothed rim 37 of the spring housing 23 and with the central or sun wheel 31 of the cord spool 21.

The spring and gear sub-assembly 23 - 37 is best seen in Figure 2, further showing arrows for rotations associated with extending the cord 20 and also indicating the relationship to be achieved with the cord spool 21 via the central or sun wheel 31. Figure 2 also gives a good view of toothed and splined pinch rollers 39A,B that mesh by teeth and through splining of which the cord 20 is gripped as withdrawn for extension and measurement and retracted afterwards, in each case with protection against slippage by serpentine passage through and gripping between the splining of the rollers 39A,B, feasibly with increase in surface contact by the cord 20 compared the drawing.

The pinch rollers 39A,B fit rotatably between stub formations of two spaced chassis parts 40A and 40B shown extending into the pointed part of the device sides formations, i.e. towards the cord exit 18. One (40A) of the chassis parts affords a battery mounting position 41 (see also batteries 41B, and related spring 41S and cover 41C); also accommodation 42 for a cord lock as a shaped lever 43 pivoted at 43T with a jamming action lock nose 43L and a plate 43P with a button 45 to push for its release.

The button 45 is shown accessible through a hole 46 in the casing half 12A. The other (40B) of the chassis parts will also contribute to pivot mounting of the cord lock lever 43; and is apertured at 47 for passing and interference fitting of a code wheel 50 to and to rotate with one (39A) of the pinch rollers.

The code wheel 50 is shown on the other side of an aperture 51 in a printed circuit board 53 conveniently fitting between the cord spool 21 and the nearest casing side half 12B, actually onto a stub axle formation 55 and into a shallow rotation well formation 57 seating against a low friction washer 59, for example of PTFZ. Also located between the side case half 12B and the circuit board 53 is a key mat 60 which may be of silicone rubber and has parts 61A,B1C and 63, 65 accessible through corresponding apertures in the case half 12B.The key mat 60 will cooperate with push switch or key pad provisions of or associated with the circuit board 53 for various required or desired function, including ON/OFF (65), conveniently also zeroing; selection of System Units (63), typically inches or centimetres/millimetres; etc (61A,B,C), for example storage, sum or square or cube calculations, plus or minus casing dimension.

Turning to Figures 4A-D, alternative pinch rolls 139A and 139B serve for flat tape 120 (rather than narrower/ thicker cord 20) having in-line equally spaced medial holes 138E along its length. The roll (139B) first encountered by tape 120 from tape spool 121 (similar in other respects to the cord spool 21) is shown with correspondingly equally spaced peripheral teeth 138T all shown engaged by the tape 120. The other roll (139A) is shown also engaged by the tape 120 over more than half its circumference towards exit 118 from the measure.Typical tape 120 may be a laminate comprising two outer films, say of suitable synthetic plastics material over a core of fibrous reinforcement, say single fibres extending transversely of the tape 120 at least to each side of positions of its holes 13 so. Such tape is conveniently made by coextrusion with heat sealing adhesive at confronting surfaces of the films, which may well be of polyester, say about 10-25 micro-metre thickness for fibres of about 10-20 micrometre nominal diameter. At least the upper film surface as leaving the measure could be printed with indicia, say with a one-metre repeat.

Further concerning mechanical features, the two halves of the casing are indicated as secured together by screw members 74 and 76 that further serve to afford axes of rotation for the cord spool 21 and related gearing relative to the spring 25 and for the code wheel 50, respectively.

Also shown associated with at least one of the casing halves 12A,B is a 90' bracket formation 80. Further associated with the circuit board 60 and the two casing halves 12A,B is a suitable display 70 shown as being of liquid crystal type and located in cooperating formations 71A,B in the casing halves 12A,B in their thicknesses.

Turning to Figure 6, the printed circuit board 53 may carry control electronics in the form of a micro-controller 81, which will be of semiconductor integrated circuit (chip) type, shown communicating with a decoder 83, which may also be of chip type, conveniently over line 82 by serial interfacing. The micro-controller 81 is also connected at 84 and 85 with liquid crystal display 70 and non-volatile storage 86, respectively. The printed circuit board 53 further carries a stator 87 with plural capacitive plate segments (or suitable capacitor plate patterns on the board itself), and the rotor or code wheel 50 also has capacitive plate segments to cooperate with the plate segments of the stator 87 and/or be apertured as indicated in Figure 1.Suitable energisation of the plate segments of the stator 87 over connection 88, say each at a voltage with its own different phase relationship with a reference signal, will be influenced by capacitive coupling determined by the rotor 50, typically across a small air gap between stator 87 and rotor 50, or through some other dielectric. Representation of such capacitive influence of the rotor 50 on the stator 87 can be by way of signals to the decoder 83 over connection 89, say from a common segment of the stator 87, typically circular and operative to produce a combined voltage sum signal processed by the decoder 83 to represent angular movement/rotation of the rotor 50, thus linear movement of the cord 20.

It is convenient for the decoder 83 to deliver to the micro-processor 81, over 89, a measure of rotations and part rotations for conversion into linear extension of the cord 20 and feeding to the display 70. These operations will, of course, be controlled by programs, whether in permanent or at least non-volatile storage, such as ROM or EPROM, of the micro-processor 81 itself, or as represented by the associated storage 86 in Figure 6. Multiplication involved in this conversion can be by way of a multiplier or multipliers generated individually for each device 10, or by a device-dependent modifier or modifiers relative to a nominal multiplier or multipliers. In either case device dependent data can be generated and stored into the storage 86 at manufacture or after replacement of parts by program routine(s) activated relative to withdrawal of a definite standard length of the cord 20.

Claims (16)

1. Extending measure device utilising a pull-out cord- or tape-like extending element, wherein a housing accomm odating holding and progressive release means for said extending element further accommodates electronic means for measuring and displaying extended length of said element.

2. Extending measure device according to claim 1, wherein exit provision for said extending element from said housing is of splined or toothed spindle or roll/wheel type for substantially slip-free relationship between linear and rotary movements of said element and said exit provision, respectively.

3. Extending measure device according to claim 2, wherein at least one splined or toothed rotary part of said exit provision is associated with a code wheel serving as transducer means for said electronic measuring means.

4. Extendingmeasure device according to any preceding claim, wherein said electronic means includes provision for calibration to take account at least of permitted tolerance variations of mainly mechanical parts associated with said electronic means.

5. Extending measure device according to claim 4. wherein said calibration provision includes programmable means whereby a particular relationship between rotations of a or said rotary part of extendible element housing exit means and a standard length of extended said element.

6. Extending measure device according to claim 4 or claim 5, wherein said calibration provision includes prog rammable means whereby relative to a nominal relation- ship between rotations of a or said rotary part of extendible element housing exit means and a standard length of extended said element a correction factor is derived that may differ as between different actual said devices.

7. Extending measure device according to claim 5 or claim 6, wherein said programmable means is associated with non-volatile storage for data representing said part icular relationship or correction factor.

8. Extending measure device according to any one of claims 4 to 7, wherein said calibration means includes a solid-state integrated circuit semiconductor micro controller.

9. Extending measure device according to any preceding claim, wherein conversion from rotary motion into electrical signals and development of same into what is displayed is by means involving reliance on elec trical capacitance.

10. Extending measure device according to claim 9, wherein the electrical capacitance reliant conversion and development means includes a rotor and a stator with conductive pads or patterns and modifications of stator energisation according to capacitive coupling with the rotor as moving with the extending element.

11. Extending measure device according to any preceding claim, wherein said extending element also carries extended length indicating indicia.

12. Extending measure device according to any preceding claim, wherein said extending element has associated bias-type resistance means operative through its full extension/retraction range.

13. Extending measure device according to any preceding claim, wherein said extending element has associated bias-type resistance means comprising spring means of a gear coupling system using intermediate or planetary wheels meshing with a central or sun wheel or spindle and with an outer ring.

14. Extending measure device according to claim 13, wherein said outer ring is of a part that houses said bias spring.

15. Extending measure device according to claim 13 or claim 14, wherein said spring is of reverse wound spiral coil type effectively acting between the spring housing and a cord or tape spool turning with the central or sun wheel.

16. Extending measure device arranged and adapted to operate substantially as herein described with reference to and as shown in the accompanying drawings.