GB2203536A

GB2203536A - Length measuring device

Info

Publication number: GB2203536A
Application number: GB08709243A
Authority: GB
Inventors: Roger Howard Thornton
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-04-16
Filing date: 1987-04-16
Publication date: 1988-10-19
Also published as: GB8709243D0

Abstract

A measuring device comprising a flexible, non-stretchable line 1 normally housed in a reservoir 2 which may be a rotatable drum, which is spring-biased to allow the line 1 to automatically retract into the drum 2. In one embodiment, the line 1 passes between a feed roller 3 and a measuring roller 4 on which is mounted a graduated disc 5 rotatable with the measuring roller. Graduations on the disc 5 are opaque whilst the remainder of the disc 5 allows light to be transmitted therethrough from a light source 6 to a detector device (7). Electrical signals from the detector (7) are processed for display on a display device which provides an indication of the length of the line 1 fed from the reservoir 2. The non-stretchable line may be a cord, chain or wire or a tape of metal or other material. <IMAGE>

Description

MEASURING DEVICE This invention relates to a measuring device.

Existing tape measures can be awkward to read accurately and are difficult to use in some situations such as measuring a length in three mutually perpendicular directions where errors are likely to arise.

It is an object of the present invention to provide a measuring device which can have its measurements displayed in an easily read form.

According to this invention there is provided a measuring device having a flexible measuring member, a reservoir for the latter, means for feeding the measuring member out of, and back into, the reservoir, said measuring member being arranged to co-operate with means for detecting the length of the measuring member which has been fed from the reservoir, means for converting said length into an electrical signal value, and means for displaying said electrical signal value as an indication of said length.

Preferably said measuring member comprises a line enabling ready measurement of a length in three mutually perpendicular directions.

Preferably, means are provided for storing said electrical signal value, for performing simple calculations on said signal value and for displaying the results of the calculations.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Fig. 1 is a cross-sectional view of part of a measuring device embodying this invention; Fig. 2 is an end view of the device shown in Fig. 1; Fig. 3 is a block circuit diagram of one form of circuit arrangement which can be used in the device shown in Figs. 1 and 2, and Fig. 4 is a flow chart illustrating the operation of the circuit arrangement shown in Fig. 3.

Referring to Figs. 1 and 2, a measuring device comprises a line 1 and a line reservoir 2 which in this case takes the form of a rotatable drum which is spring-biased so that the line 1 can be automatically fed back into the reservoir 2. There are of course alternative known methods of feeding line into the reservoir such as by means of a crank handle. The line 1 passes between two rollers 3 and 4 and is in close frictional contact with both rollers so that any longitudinal movement of the line causes both rollers to rotate.

In this embodiment, the roller 4 is merely a feed roller and the roller 3 is a measuring roller having a graduated disc 5 attached to it so as to turn with the roller 3. The position of the disc 5 can be seen clearly from Fig. 2.

At least the edge portion of the disc 5 is made of a light transmitting material with graduated lines which are opaque. Light sources 6 are arranged to direct light beams through the disc 5 on to light sensors 7 which convert the light signal to an electrical one.

The direction of movement of the graduations is determined by having a plurality of light sources 6 and a plurality of light sensors at 7 which are of such a size that they fit between any adjacent two of the graduations. Thus, after a clear signal is given from all sensors, the next signal will either be obscure from the RHS sensor or group of sensors (depending on the width of the graduation line) and clear from the LHS sensor(s) signalling a right to left movement or will be obscure from the LHS sensor(s) and clear from the RHS sensor(s) signalling a left to right movement.

The line could alternatively be shaped so as to fit between indentations in the rollers to give a positive grip rather than relying on friction alone.

The graduations on disc 5, the movement of which indicates movement of the line 1, could be positioned on the rollers 3,4 themselves, possibly etched into the rollers, so that the light sensors 7 would be arranged to detect light reflected from the etchings rather than directly transmitted light. Alternatively, the rollers 3,4 could be dispensed with completely and the light sensors could be used to detect graduations on the line itself, thereby simplifying the mechanical structure of the device.

The electrical signals generated by the sensors are fed into a processing portion of the circuit arrangement shown in Fig. 3.

The circuit arrangement comprises a processor 20 with a programme store 21 and random access store 22 and the processor has connections to a keyboard 23 directly and via a multiplexer arrangement 24 via which the processor is also connected to a display 25.

In operation, firstly the digital display is reset to zero.

When the line 1 is fed out, the number of passing graduations is counted and labelled as increments or decrements, corresponding respectively to a movement of the line 1 in or out of the reservoir 2. The resulting counted signal is then translated to the metric or imperial standard and displayed.

There are many possibilities for introducing various calculating facilities in the electrical circuit arrangement of the device which would facilitate certain operations requiring measurement. For example, one calculating function could be the automatic subdivision of the measured length in order to place brackets at equal distances without resorting to separate calculations.

While the measuring member described above preferably comprises a line in the form of a cord, chain or wire of substantially non-stretchable material, it could also comprise a tape of metal or other substantially non-stretchable material.

Claims

CLAIMS:

1. A measuring device having a flexible measuring member, a reservoir for the latter, means for feeding the measuring member out of, and, back into, the reservoir, said measuring member being arranged to cooperate with means for detecting the length of a measuring member which has been fed from the reservoir, means for converting said length into an electrical signal value, and means for displaying said electrical signal value, as an indication of said length.

2. A measuring device as claimed in claim 1, wherein said flexible measuring member comprises a line of substantially non-stretchable material and said reservoir comprises a rotatable drum which is spring-biased to allow the line to be automatically retracted back into the reservoir.

3. A measuring device as claimed in claim 1, wherein said reservoir comprises a rotatable drum provided with a crank handle to allow the measuring member to be retracted back into the reservoir.

4. A measuring device as claimed in claim 1, wherein said flexible measuring member comprises a line of substantially non-stretchable material, a plurality of graduations being provided on the line or on means arranged to move with the line and detection means for sensing the passage therepast of said graduations and to produce electrical signals indicative thereof.

5. A measuring device as claimed in claim 4, wherein said line is arranged to pass between a pair of rollers, one of which is provided with a graduated disc arranged to rotate therewith, said disc being of light transmitting material and said graduations being opaque, and being arranged to pass between a light transmitting sources and light detecting devices such as to produce a plurality of signals corresponding in number to the number of graduations passing the detecting devices as the disc is rotated therepast thereby providing an electrical indication of the length of the line fed from the reservoir.

6. A measuring device as claimed in claim 4, wherein said line is arranged to pass between a pair of rollers, at least one of which is provided with a plurality of graduations arranged to pass between a light source and detector means as the line is fed from the reservoir, such that light reflected from the graduations is detected to provide electrical signals whose number provides an electrical indication of the length of the line fed from the reservoir.

7. A measuring device as claimed in claim 4, wherein the line is provided with a plurality of graduations arranged to pass between a light source and detector means as the line is fed from the reservoir such as to provide an electrical indication of the length of line fed from the reservoir.

8. A measuring device as claimed in any of claims 1 to 7, wherein the electrical signals produced as the line is fed from the reservoir are supplied to a circuit including a processor, a random access storage device and a processor storage device, the processor being connected to a keyboard for supplying input material to the processor, and to a digital display device via a multiplexer unit such as to provide a digital display of the length of the line fed from the reservoir.

9. A measuring device as claimed in claim 1, wherein electrical signals generated by said detecting means are supplied to signal processing means and means included in said signal processing means for introducing calculating facilities therein to facilitate measurement operations, e.g. the automatic subdivision of a measured length in order to place brackets at equal distances.

10. A measuring device as claimed in claim 4, wherein electrical signals generated by said detecting means are supplied to signal processing means, means for providing the algebraic sum of the increments and decrements of the graduations according to the direction of movement of the line into or out of the reservoir, means for converting signal indicative of said algebraic sum into metric or imperial standard of measurement and for displaying the converted signals on said display means.

11. A measuring device substantially as hereinbefore described and as shown in Figures 1 and 2 of the accompanying drawings.

12. A measuring device including means for processing electrical signals obtained therefrom and substantially as hereinbefore described with reference to Figures 3 or 4 of the accompanying drawings.