GB2102121A

GB2102121A - Improvements relating to distance measuring devices

Info

Publication number: GB2102121A
Application number: GB08217877A
Authority: GB
Inventors: Roy William Knott; Norman George Hammond
Original assignee: Sonic Tape Plc
Current assignee: Sonic Tape Plc
Priority date: 1981-06-20
Filing date: 1982-06-21
Publication date: 1983-01-26

Abstract

An extendable tape 2 carrying distance markings 3 and wound onto a spring loaded drum 4 is housed in a casing 1. An optical sensor 5 is disposed about the tape and is capable of reading the passage of the markings 3 as the tape 2 is withdrawn from the casing 1. The sensor 5 is powered from a battery 6 which also powers a printed circuitboard 7 incorporating a counter and memory device which will pass a signal to a numerical display device 8, to indicate the extent to which the tape 2 has been withdrawn. A keyboard 11 allows computations to be performed and displayed on the device 8. <IMAGE>

Description

SPECIFICATION Improvements relating to distance measuring devices This invention is concerned with device for measuring distance in the form of a so called "tape measure". Normally such a tape measure comprises a casing housing an extendable tape carrying markings indicating the distance being measured and the tape is either automatically or hand wound back into the casing when measuring has been completed. It should be noted that, where the term "tape" is used herein this is meant to include not only a basically flat strip but also, for example, a string, cable or wire which can be withdrawn from and returned to the casing.

It is an object of this invention to provide a tape measure which gives a very ready indication of the distance being measured at any time.

Accordingly this invention provides a distance measuring device comprising a measuring tape disposed within a housing but able to be withdrawn to a desired length from the housing, a reading device for determining the extent of withdrawal of the tape from the housing, and a display device for indicating the extent of withdrawal of the tape as determined by the reading device.

When using such a tape measure there is no need to examine the markings on a tape to calculate the precise distance measured nor indeed to add on any figure for the width of the casing itself. The display device gives a direct indication of the distance being measured so that very rapid and accurate measurements can be made and noted down. The reading device could just determine the length of the tape which has been pulled out from the casing or could automatically add on the width of the casing or a distance to a special mark or pointer on the casing which will be used to define one end of the distance being measured.

In the preferred embodiment the tape is wound onto a drum and ideally this drum is spring biased to cause the tape to be drawn into the housing although there could be a hand operated winding mechanism. With this particular arrangement the reading device could sense the extent of rotation of the drum. For example, the reading device could be an optical sensor provided to register the passage of markings or openings on the drum as the drum rotates. Alternatively the reading device could be a counter associated with a ratchet which follows the contours of teeth formed at or near the drum circumference.

Another method of determining the extent of withdrawal of the tape from the housing is to provide a reading device in the form of an optical sensor which will register the passage of markings or openings on the tape as the tape is withdrawn from the housing.

The display device ideally incorporates a numerical display provided by light emitting or liquid crystal diodes. It may well be of advantage to include a memory device for storing details of distance measured by the reading device. A calculator and keyboard could also be incorporated to enable calculations to be performed using details of distances stored in the memory device.

The invention may be performed in various ways and two preferred embodiments thereof will now be described with reference to the accompanying drawings, in which: Figure 1 illustrates diagrammatically the construction of the essential parts of one form of tape measure of this invention; and Figure 2 is a similar illustration of an alternative form of tape measure of the invention.

The tape measure shown in Figure 1 is housed in a casing 1 and incorporates an extendable tape 2 carrying distance markings 3 and wound onto a spring loaded drum 4. An optical sensor 5 is disposed about the tape near to the point where it leaves the casing and this sensor is capable of reading the passage of the markings 3 as the tape 2 is withdrawn from the casing 1. The sensor 5 is powered from a battery 6 which also powers a printed circuitboard 7 incorporating a counter and memory device which will pass a signal to a display device 8 incorporating a numerical display in the form of light emitting or liquid crystal diodes.

When the tape measure is to be used for measuring a distance the rear end 9 of the casing 1 will be placed at one end of the distance to be measured and the tape 2 will be withdrawn until tip 10 reaches the other end of the distance to be measured. The display device 8 will then indicate the precise distance (in imperial and/or metric units). If desired a keyboard 11 could be connected to the display device 8 and to the printed circuitboard 7 (which would include a calculator section) so that certain information could be stored and calculations performed on those figures, for example to calculate the volume of a room from the three necessary measurements which will have been made in sequence by the tape measure.

In the alternative form of tape measure shown in Figure 2, the difference is that an optical sensor 1 2 is provided to determine the extent of rotation of the drum 4. Thus the sensor 12 could read the passage of markings carried around the circumference of the drum or the sensor could be in the form of a light and photocell aligned with a sequence of holes through the drum as the drum rotates. As before, the sensor 2 would be linked to a printed circuitboard 7 and powered by a battery 6 so as to display an indication of the distance measured on a display device 8. In this case the tape itself need not carry any distance markings if that would be acceptable to the user. Indeed the tape 2 could be in the form of a continuous cable if no markings need to be applied to it. Where basically flat tape is employed, however, it is preferred that this should be constructed from steel or plastics material.

Where the tape to be read is provided with holes or other markings these could be encoded in a binary coded decimal coding. Also, as an alternative to optical reading, the tape could be a magnetic tape with coded signals thereon which will be read by a magnetic head in the place of the sensor 5.

Claims

1. A distance measuring device comprising a measuring tape disposed within a housing, but able to be withdrawn to a desired length from the housing, a reading device for determining the extent of withdrawal of the tape from the housing, and a display device for indicating the extent of withdrawal of the tape as determined by the reading device.

2. A measuring device according to claim 1, wherein the tape is wound on a drum.

3. A measuring device according to claim 2, wherein the drum is spring biased to cause the tape to be drawn into the housing.

4. A measuring device according to claim 2 or claim 3, wherein the reading device senses the extent of rotation of the drum.

5. A measuring device according to claim 4, wherein the reading device is an optical sensor provided to register the passage of markings or openings on the drum as the drum rotates.

6. A measuring device according to claim 4, wherein the reading device is a counter associated with a ratchet which follows the contrours of teeth formed at or near the drum circumference.

7. A measuring device according to any one of claim 1 to 3, wherein the reading device is an optical sensor provided to register the passage of markings or openings on the tape as the tape is withdrawn from the housing.

8. A measuring device according to any one of claims 1 to 3, wherein the reading device is a magnetic head which senses the passage of signals carried by the tape in the form of a magnetic tape.

9. A measuring device according to any one of claims 1 to 8, wherein the display device incorporates a numerical display provided by light emitting or liquid crystal diodes.

10. A measuring device according to any one of claims 1 to 9, including a memory device for storing details of distances measured by the reading device.

1 A measuring device according to claim 10, including a calculator and keyboard enabling calculations to be performed using details of distances stored in the memory device.

12. A device substantially as herein defined with reference to the accompanying drawings.