GB2444776A - Electronic measuring device - Google Patents

Abstract

An electronic measuring device 2 comprising a tape 20, a source of light 4 and at least one photosensitive component 22 is disclosed. The photosensitive component is disposed on one side of said tape and the light disposed on the other side and orientated such that the light is directed onto the tape and towards the photosensitive component. The invention is characterised in that the tape is at least partially transparent and of laminar construction wherein at least one of the laminae is woven such that the light casts a shadow of the weaving pattern onto the photosensitive component, such being coupled with processing electronics adapted to repeatedly capture the image thereon at a predetermined frequency and, by means of comparison with a formerly captured image, make a determination of the extent to which the tape has been displaced over the frequency period. In a most preferred arrangement, the electronic measuring device is incorporated in an electronic tape measure comprising a housing in which a spool of the tape is mounted, said housing having an opening through which one end of the tape extends and can be subsequently withdrawn.

Description

Electronic measuring device This application relates to an electronic

measuring device, and more specifically to an electronic measuring device which incorporates a tape which can be withdrawn from the device in the manner of a conventional tape measure, and which also includes electronics which facilitate the determination of the length of tape which has been nthdrawn.

BACKGROUND

Electronic Measuring devices are now well known. Such devices are generally provided to overcome the errors commonly occurring during the manual identification and transcription of lengths measured using a conventional tape measure from which a tape on which a series of evenly spaced, numerically marked gradations is printed. Simply, the fundamental problem with conventional tape measures Is that they require some degree of memory on the part of the user. Imperfect recollection on the part of the user will inevitably result in a generally serious and possibly costly shortage or excess of the artide which is to be fitted according to the measured distance.

EP0740126 discloses a digital measuring device induding a housing from which a tape can be withdrawn in conventional manner to measure a distance, and further discloses a comprehensive system for manipulating and/or recording the measurement data received from the device. In terms of the device, the tape is provided with a series of evenly spaced apertures therein indicative of predetermined lengths, and a sensor is provided internally of the device and comprises a series of evenly spaced light emitting diodes (LEDs) on one side of the tape, and a series of photosensitive detectors disposed on the alternate side of the tape such that light from the LEDs can impinge thereon when the apertures in the tape are aligned therewith. There are two important disadvantages of this type of arrangement. Firstly, the provision of evenly spaced apertures in a tape with any great accuracy is not a simple matter, and secondly, the electronic device is only capable of determining distances to an accuracy defined by the spacing between the apertures. For instance if the apertures in the tape are spaced 2mm apart, then only measurements of 2mm, 4mm, 6mm, 8mm etc. can be taken. Such accuracy is inadequate for some purposes.

p. ip, , _*_ GB-A-2023290 discloses a tape measure with a tape housing incorporating an electronic calculator, a tape exit opening, and an internal take-up spindle for the tape which Is driven by a motor and provided with an optical device co-operating with a series of holes in a disk rotated by movement of the tape for sensing the length by which the tape has been extended or further extended.

US-A-4575944 discloses an electronic digital tape rule consisting of a housing, a tape reel having an extendible and flexible measuring tape, a battery case, an actuator, a detector, a counter, a display and a brake. The actuator comprises a friction roll rotatably mounted on a shaft fixed at an inner wall of the housing, a disc disposed on the upper end of the roll and rotatable by the friction of the roll, a plate fixed on the upper end of the roll and having a hole with a pair of contact plates attached on the two side walls of the hole, a spring mounted between the disc and the plate for constantly the disc against the roll and an actuating rod disposed upright on the upper side of the disc and having its upper end engaging with the hole.

EP-A-0103216 discloses a portable measuring device for measuring wood by hand comprising calipers for the diameter measurement, on the displaceable measuring leg of which a length measuring device with a pull-out measuring tape is arranged. The calipers and the length measuring device are each assigned an automatically operating pick-up device for the production of an electric diameter or length signal. The distance pick-up device comprises a Wiegand strip inside the guide tube of the callipers and an associated Wiegand sensor on the movable measuring leg of the callipers. The length pick-up device comprises a measuring wheel which is surrounded by the steel measuring tape and on which the measuring tape, as a result of an axial magnetic potarisation of the measuring 10 wheel on its circumference, adheres free of slip. The rotary movement of the measuring wheel corresponding to the pull-out movement of the measuring tape is detected by a shaft-angle encoder which comprises permanent magnets on the measuring wheel and associated magnetic field sensors on the movable measuring leg.

All the devices described above are beset with problems of accuracy and the footprint of the electronics required inside the device to achieve a reasonable electronic measuring function.

It is an object of this invention to provide an improved electronic measuring device including a withdrawable tape which precludes the need to punch, perforate or mark the tape, and also precludes the need to provide any additional mechanical components inside the housing whose motion is measured as being indicative of the extent to which the tape is withdrawn.

It is a further object of this invention to provide an electronic measuring device which is nevertheless far more accurate than the devices already known.

BRIEF SUMMARY OF THE DISCLOSURE

According to the invention there is provided an electronic measuring device comprising a tape, a source of light and at least one photosensitive component disposed on either side of said tape and orientated such that the light is directed onto the tape and towards the photosensitive component on the alternate side thereof, characterised in that the tape is at least partially transparent and of laminar construction wherein at least one of the Iamjnae Is woven such that the light casts a shadow of the weaving pattern onto the photosensitive component, such being coupled with processing electronics adapted to repeatedly capture the image thereon at a predetermined frequency and by means of comparison with a formerly captured image, make a determination of the extent to which the tape has been displaced over the frequency period.

Most preferably, the electronic measuring device is embodied in an electronic tape measure comprising a housing in Which a spool of the tape is mounted, said housing having an opening through which one end of the tape extends and can be subsequently withdrawn, said light source and said photosensitive component being mounted inside the housing on either side of the portion of the tape which extends tangentially away from the periphery of the spool and the opening.

Preferably, the electronic tape measure indudes a source of power.

In a preferred arrangement, a tape regulating component (TRC) is additionally provided inside the housing comprising upper and lower members between which the tape is arranged to travel, at least one of said upper and lower members providing an opening through which light from the source can pass onto the tape, the alternate member also having an opening within or between respective portions of said member to permit light having passed through the tape to impinge on the photosensitive element disposed proximately thereabove or therebelow.

Preferably, the TRC is comprised of two elongate members being upper and lower in orientation which are proximately disposed and have a rebated profile so that together, they define a cavity therebetween,.said upper and lower portions having apertures through their faces which are substantially concentric with the corresponding opening in the alternate member.

Further preferably, at least one of the elongate members of the TRC is provided with tape contacting nibs, one at either end, and with which the tape is caused to frictionally engage by virtue of the reaction of said at least one member against the other member.

Preferably at least one of the upper and lower members is springingly biased against the other, and further preferably, both upper and lower members are provided with tape contacting nibs at either end so that a tension is maintained in the tape between respective pairs of nibs. In this manner, the tautness of the tape in the measuring area is maintained, and thus measurement accuracy is guaranteed.

In a preferred arrangement, the upper member is rigidly mounted whereas the lower member is spnngingly mounted so as to be biased against the upper member.

Preferably the upper member is of unitary or solid construction.

In one embodiment, the lower member is a multi-part construction consisting of a central portion in which the aperture is provided, and two pivotally connected nib portions, said lower member being springingly mounted in the nib portions.

In a further embodiment, the lower member consists of two independent nib portions springingly mounted so as to be biased against corresponding nib portions of the upper member.

Most preferably, the tape comprises three laminae, a middle woven layer sandwiched between upper and lower translucent flexible plastics material layers. Preferably the woven layer is encapsulated between the upper and tower plastics layers.

The invention provides as its primary advantage an increase in the accuracy of measurement down to the thickness of the individual filaments or fibres in each warp or weft of the weave. Also the invention precludes the need for tapes to be accurately printed or perforated as previously.

A specific embodiment of the Invention will now be provided by way of example with reference to the accompanying drawings wherein

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a schematic sectional view of a first embodiment of an electronic measuring device according to the invention, Figure 2 shows both sectional and schematic plan views of the tape used in the invention, Figures 3-8 show different configurations and embodiments of the invention, and Figure 9 shows an electronic tape measure in which the electronic measuring device may be housed.

DETAILED DESCRIPTION

Referring firstly to Figure 1 there is shown the essential components of an electronic measuring device 2 according to the invention. Specifically, a light emithng diode (LED) 4 is disposed in an aperture 6 provided in one upper member 8 of a tape regulating component. The upper member 8 is of elongate unitary construction and provided with a pair of tape contacting nibs 10 at either end. A corresponding lower member 12 is of similar construction in that it is provided with corresponding aperture 14 concentrically aligned with aperture 6 and nibs 16 arranged in opposition to the nibs 6. The upper and lower members 8, 12 are rebated on their facing surfaces so as to define a cavity 18 through which a flexible tape 20 passes after being fed through the slits defined between each pair of nibs 10, 16. To the underside of the lower member 12 there is provided a photosensitive device such as a charge coupled device (CCD) or photodiode in communication with a processing device and associated memory 24.

The arrangement shown in Figure 1 and subsequent figures is intended to be suitably mounted and positioned inside a housing provided with a source of power for both LED 4 and processor 22, and additionally means are provided for the transfer and/or display of tape displacement data. For instance, in a self-contained electronic tape measure, a small display may be incorporated in the housing for display of measurement data, or in an alternative arrangement, the device may be in communication with a suitably programmed PC, either through wired or wireless means.

Refemng to figure 2, according to the invention, the tape is of laminar construction in that it consists of three laminae being a pair of encapsulating plastics material outer laminae between which is sandwiched a third lamina 30 being of woven construction.

The plastics laminae may be bonded to the woven lamina by suitable means. This lamina may be woven from any of a number of different natural or synthetic fibres 32 in a warp and weft pattern such that together the fibres of the warp and weft define apertures 34 through which light from the LED 4 can shine during use.

In this regard, the capability of the device in accurately measuring tape displacement therethrough depends on the tightness of the weave and the thickness of the fibres, WhICh can vary quite considerably. Accordingly, each device may require calibration before being used in a production environment. During use, the tape is drawn through the device as a user attempts to measure a specific distance. The photosensitive device and processor are adapted to capture Images at a suffidently high frequency so that regardless of the speed of tape travel (which will only ever be effected manually and therefore be limited), each captured image of the shadow pattern cast by the LED as it shines through the tape onto the photosensitive device can be compared to the previously captured image and have some degree of correlation or similarity therewith.

More specifically, if the frequency of image capture is high enough, any captured image will always have some portion Which is present in the previously captured image and therefore a processor calculation of displacement for that period can be obtained.

The patterns of warp and weft arranged fibres together with light and dark areas created within the tape 20 increases the image detail captured by the processor. In this way the resolution and accuracy of the devise is greatly enhanced.

Although the arrangement of components shown in Figure 1 may be generally satisfactory, the problems of tape sag and ruffle within the cavity are demonstrated in Figures 3 and 4. It will be immediately appreciated that such problems necessanly affect the measurement accuracy, and further that such can be overcome be ensuring that the tape 20 remains taut between the respective pairs of nibs 10, 16 of upper 8 and tower 12 members.

Referring to Figure 5 there is shown a further embodiment of the invention wherein the lower member is replaced by two independently springingly mounted nibs 40,42.

Springs 44,46 effectively bias these nibs 40,42 into gentle contact with the tape 20 and react against the corresponding nibs 10 of the upper member 8. A component 50 is provided with aperture 48 and effectively restricts the light impinging on the photosensitive device 22 in a similar manner to the aperture 14 in the lower member 8 in Figure 1.

In a further alternative embodiment shown in Figure 6, an alternate form of lower member 50 may be provided as a unitary elongate member which is spnngingly mounted at either end 44, 46 so as to be biased and react against the upper member 8 thus bringing nib portions 50, 52 into contact with the tape 20. Figure 7 shows a torsionally biased spool 54 from which the tape 20 is unwound as it is pulled through the device 2 in the direction 56. The torsion spring providing the spool torsion bias effectively provides a slight resistance to the unwinding of the tape, and therefore tension can be maintained in the tape throughout any measuring process. In a preferred embodiment, the torsion spring in the spool is chosen so that it can not overcome the frictional resistance of the tape to moving between corresponding nibs 10, 40/42, or 10, 50/52. In this manner, the frictional resistance of the tape to moving between the nibs acts as a damp on the tape until, by virtue of mechanical, user applicable means provided on the exterior of the housing in which the device is mounted, the spring bias is reduced on at least one of the nibs, e.g. at 60, whereupon the tape automatically winds back onto the spool 54 as shown at 58.

In Figure 8 there is shown a yet further embodiment of the invention wherein the lower member 12 is comprised of a central apertured portion 80 to which nib arms 82, 84, are pivotafly connected at 86,88. Spring mountings 90, 92 are provided for nibs 94, 96 such that they react against corresponding nibs 10 of the upper member 8 as previously described.

Refemrig finally to Figure 9, there is shown one embodiment of an electronic tape measure 100 incorporating an electronic measuring device as previously described. The tape measure 100 includes a housing 102 from which the tape 20 can be withdrawn to provide a measurement function. The free end of the tape terminates in a plastic tab 104 which prevents the tape from disappearing completely inside the housing under the torsional bias of the spool (not shown) disposed therein, and also provides a clear tine 106 against which the desired measurement can be taken.

One or more control buttons 108. 110 may be provided to cause the processor to capture a measurement and/or clamp or release the tape in at a particular extension. For instance, once the tape has been withdrawn by a desired extent in the act of measurement, the pressing of one of the buttons may cause both the crystallisation of that particular measurement and furthermore the transmission of the measurement data directly to a PDA. laptop or desktop computer using wires, Infra-red, blue tooth or other wireless technology.

In an alternative embodiment, the user may push one of the buttons to inform the processor that a measurement is about to be taken, subsequently extend the tape over the measured article or person and when appropriate push the button again to capture the measurement and transmit the relevant data to the computer. In a preferred embodiment, the tape measure is provided with two red lines, one on the tab 104 of the tape 20 at 106, and one on the housing at 112 between which measurements can be accurately defined.

In a preferred arrangement, the device is also programmed to be capable of taking continuous measurements and therefore saving time on the user having to return the tape to its fully retracted position for each measurement. This ability also allows for the taking of sequential measurements, which is prevalent in the urnade to measure clothing industry.

in this regard, this invention also covers the relevant computer program permitting the device to function in this manner.

An LED display 114 providing the user with information about the pre set order of Ihe measurements that need to be taken may be provided. The LED also offers other coding information which may be transmitted from the computer to the device.

Claims (14)

1. An electronic measuring device comprising a tape, a source of light and at least one photosensitive component disposed on either side of said tape and orientated such that the light is directed onto the tape and towards the photosensitive component on the alternate side thereof, characterised in that the tape is at least partially transparent and of laminar construction wherein at least one of the Iaminae is woven such that the light casts a shadow of the weaving pattern onto the photosensitive component, such being coupled with processing electronics adapted to repeatedly capture the image thereon at a predetermined frequency and by means of comparison with a formeily captured image, make a determination of the extent to which the tape has been displaced over the frequency period.

2. A device according to claim 1 including a source of power.

3. A device according to any preceding claim wherein a tape regulating component (TRC) is additionally provided comprising upper and lower members between which the tape is arranged to travel, at least one of said upper and lower members providing an opening through which light from the source can pass onto the tape, the alternate member also having an opening within or between respective portions of said member to permit light having passed through the tape to impinge on the photosensitive element disposed proximately thereabove or therebelow.

4. A device according to claim 3 wherein the TRC is comprised of two elongate members being upper and lower in orientation which are proximately disposed and have a rebated profile so that together, they define a cavity therebetween, said upper and lower portions having apertures through their faces which are substantially concentric with the corresponding opening in the alternate member.

5. A device according to claim 3 or 4 wherein at least one of the elongate members of the TRC is provided with tape contacting nibs, one at either end, and with which the tape is caused to frictionally engage by virtue of the reaction of said at least one member against the other member.

6. A device according to any of claims 3-5 wherein at least one of the upper and lower members is springingly biased against the other.

7. A device according to claim 5 or 6 wherein both upper and lower members are provided with tape contacting nibs at either end so that a tension is maintained in the tape between respective pairs of nibs.

8. A device according to any of daims 3-7 wherein the upper member is rigidly mounted whereas the lower member is springingly mounted so as to be biased against the upper member.

9. A device according to claims 3-8 wherein the upper member is of unitary or solid construction.

10. A device according to claims 3-9 wherein the lower member is a multi-part construction consisting of a central portion in which the aperture is provided, and two pivotally connected nib portions, said lower member being spnngingly mounted in the nib portions.

11. A device according to claims 3 or any of claims 5-10 when dependent thereon wherein the lower member consists of two independent nib portions spnngingly mounted so as to be biased against corresponding nib portions of the upper member.

12. A device according to any preceding claim wherein the tape comprises three laminae, a middle woven layer sandwiched between upper and lower translucent flexible plastics material layers.

13. A device according to claim 12 wherein the woven layer is encapsulated between the upper and lower plastics layers.

14. A device according to any preceding claim when included in an electronic tape measure comprising a housing in which a spool of the tape is mounted, said housing having an opening through which one end of the tape extends and can be subsequently withdrawn, said light source and said photosensitive component being mounted inside the housing on either side of the portion of the tape which extends tangentially away from the periphery of the spool and the opening.