GB1591376A - Taximeter apparatus - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO TAXIMETER APPARATUS (71) We, THE PLESSEY COMPANY LIMI TED, a British Company of 2/60 Vicarage Lane, Ilford, Essex, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to indicating devices and relates more especially to charge indicating devices such as taximeters.

In our Patent Specification No. 1570288 there is disclosed a charge indicating device in the form of a taximeter which includes direction sensing means for inhibiting operation of the device when reverse movement is sensed.

The direction sensing means that forms the basis of this co-pending application consists of a pair of angularly displaced transducers and the present invention relates to direction sensing means which requires only a single transducer.

According to the present invention there is provided taximeter apparatus which includes a taximeter; direction sensing means comprising a single sensing means and modulator means for effecting modulation of said sensing means, the sensing means and the modular means being rotatable relative to one another, the modulator means being operable for each relative revolution of the sensing means and the modulator means for effecting irregular modulation of the sensing means, the taximeter being provided with means for detecting the modulation of the sensing means to afford and indication of the direction of relative rotation of the sensing means and the modulator means.

In one arrangement for carrying out the invention, the sensing means may take the form of an optical sensor for receiving light from a light source, and the modulator means may take the form of a disc which is rotatable relative to the sensor between it and the light source, the disc being generally opaque and provided with a plurality of transparent portions or cut-outs which are irregularly spaced around the periphery of said disc, to cause the light received by the optical sensor to be modulated, means being provided operable on the output of the optical sensor for detecting the modulation and for affording an output indicative of direction.

In one arrangement for carrying out the invention the sensing means may take the form of a metal proximity detector and the modulator means may take the form of a metal disc which is rotatable relative to said detector such that the detector scans a circumferential path on said disc, the disc being provided with a plurality of unequally spaced cut-outs therein at points on the circumferential path which cause the output of the detector to be modulated in response to relative rotation of the disc and the detector, modulation detection means being provided for detecting the modulation and for affording an indication of the the relative direction of rotation of the disc.

By arranging that the disc is rotated in response to forwards or backwards movement of say, a taxi to which the taximeter is fitted, the output afforded by the modulation detection means may be used to indicate the direction of movement of the taxi.

Conveniently the unequally spaced angular cut-outs in the disc together with the "lands" therebetween may be arranged to switch the detector between logic '1' and logic '0' states.

The spacing and size of the cut-outs in the disc are chosen such that when the disc revolves in one direction the detector affords an output having a particular sequence of mark/space ratios, and when the disc is rotated in the other direction the sequence is reversed. Ideally, it should also be arranged that is is possible to detect the sequences even when the disc is accelerating or decelerating between specified limits.

Typically a disc may be provided having a 28.65mm diameter and thus a 90mm circumference, it being arranged that the periphery of the disc is provided with a first land of 6mm width, a first slot of 12mm width, a second land of 24mm width and a second slot of 48mm.

If the taximeter apparatus including such a disc and an associated proximity detector is fitted to a taxi which has a taximeter drive shaft rotation of 206.7 turns permile, then when the taxi is travelling at approximately 5 mph in a forwards direction, the periods between adjacent transitions in the pulse seqence afforded by the detector will be ....0.23, 0.46, 0.93, 1.86 etc. whereas with the taxi travelling at 5 mph in reverse direction, the periods between adjacent transitions will be ....1.86, 093, 0A6, 0.23 etc.

Thus by timing the period between adjacent transitions in the logic sequence, an indication can be obtained of the direction of movement of the taxi.

One method of making a decision on vehicle direction based on the above described form of system is to establish the differences between adjacent periods by subtracting a later period from the immediately preceding period. For any four consecutive periods, if two results are positive and one negative, the vehicle is travelling forwards, and if two results are negative and one positive, the vehicle is travelling in reverse direction.

The choice of a metal proximity detector in the above exemplary embodiment is given by way of example only as the principles described may be applied to other forms of transducer, e.g. optical, magnetic, inductive, capacitive etc.

as will be readily appreciated by a reasonably skilled person in order to obtain the required indication of direction.

WHAT WE CLAIM IS: 1. Taximeter apparatus which includes a taximeter; direction sensing means comprising a single sensing means and modulator means for effecting modulation of said sensing means, the sensing means and the modulator means being rotatable relative to one another, the modulator means being rotatable relative to one another, the modulator means being operable for each relative revolution of the sensing means and the modulator means for effecting irregular modu Ication of the sensing means, the taximeter being provided with means for detecting the modulation of the sensing means to afford an indication of the direction of relative rotation of the serving means and the modulator means.

2. Taximeter apparatus as claimed in Claim 1, in which the sensing means takes the form of an optical sensor for receiving light from a light source, and the modulator means takes the form of a disc which is rotatable relative to the sensor between it and the light source, the disc being generally opaque and provided with a plurality of transparent portions or cutouts which are irregularly spaced around the periphery of said disc, to cause the light received by the optical sensor to be modulated, means being provided operable on the output of the optical sensor for detecting the modulation and for affording an output indicative of direction.

3. Taximeter apparatus as claimed in Claim 1, in which the sensing means takes the form- of a metal proximity detector and the modulator means takes the form of a metal disc which is rotatable relative to said detector such that the detector scans a circumferential path on said disc, the disc being provided with a plurality of unequally spaced cut-outs therein at points on the circumferential path which cause the output of the detector to be modulated in response to relative rotation of the disc and the detector, modulation detection means being provided for detecting the modulation and for affording an indication of the relative direction of rotation of the disc.

4. Taximeter apparatus as claimed in Claim 3, in which the unequally spaced cut-outs together with the 'lands' therebetween are arranged to switch the detector between logic '1' and logic '0' states.

5. Taximeter apparatus as claimed in Claim 4 in which the spacing and size of the cut-outs in the disc are chosen such that when the disc revolves in one direction the detector affords an output having a particular sequence of mark/ space ratios, and when the disc is rotated in the other direction the sequence is reversed.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. at 5 mph in reverse direction, the periods between adjacent transitions will be ....1.86, 093, 0A6, 0.23 etc. Thus by timing the period between adjacent transitions in the logic sequence, an indication can be obtained of the direction of movement of the taxi. One method of making a decision on vehicle direction based on the above described form of system is to establish the differences between adjacent periods by subtracting a later period from the immediately preceding period. For any four consecutive periods, if two results are positive and one negative, the vehicle is travelling forwards, and if two results are negative and one positive, the vehicle is travelling in reverse direction. The choice of a metal proximity detector in the above exemplary embodiment is given by way of example only as the principles described may be applied to other forms of transducer, e.g. optical, magnetic, inductive, capacitive etc. as will be readily appreciated by a reasonably skilled person in order to obtain the required indication of direction. WHAT WE CLAIM IS:

1. Taximeter apparatus which includes a taximeter; direction sensing means comprising a single sensing means and modulator means for effecting modulation of said sensing means, the sensing means and the modulator means being rotatable relative to one another, the modulator means being rotatable relative to one another, the modulator means being operable for each relative revolution of the sensing means and the modulator means for effecting irregular modu Ication of the sensing means, the taximeter being provided with means for detecting the modulation of the sensing means to afford an indication of the direction of relative rotation of the serving means and the modulator means.

2. Taximeter apparatus as claimed in Claim 1, in which the sensing means takes the form of an optical sensor for receiving light from a light source, and the modulator means takes the form of a disc which is rotatable relative to the sensor between it and the light source, the disc being generally opaque and provided with a plurality of transparent portions or cutouts which are irregularly spaced around the periphery of said disc, to cause the light received by the optical sensor to be modulated, means being provided operable on the output of the optical sensor for detecting the modulation and for affording an output indicative of direction.

3. Taximeter apparatus as claimed in Claim 1, in which the sensing means takes the form- of a metal proximity detector and the modulator means takes the form of a metal disc which is rotatable relative to said detector such that the detector scans a circumferential path on said disc, the disc being provided with a plurality of unequally spaced cut-outs therein at points on the circumferential path which cause the output of the detector to be modulated in response to relative rotation of the disc and the detector, modulation detection means being provided for detecting the modulation and for affording an indication of the relative direction of rotation of the disc.

4. Taximeter apparatus as claimed in Claim 3, in which the unequally spaced cut-outs together with the 'lands' therebetween are arranged to switch the detector between logic '1' and logic '0' states.

5. Taximeter apparatus as claimed in Claim 4 in which the spacing and size of the cut-outs in the disc are chosen such that when the disc revolves in one direction the detector affords an output having a particular sequence of mark/ space ratios, and when the disc is rotated in the other direction the sequence is reversed.