GB1595474A - Electronic counting device - Google Patents

Description

(54) AN ELECTRONIC COUNTING DEVICE (71) We, VDO ADOLF SCHINDLING AG, of 103 Grafstrasse, Frankfurt/Main, Germany, a body corporate organized according to the laws of Germany, 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:- The present invention relates to an electronic counting device, in particular a distance counter for motor vehicles, having an electronic display system, which is controlled by a binary counter fed with counting pulses.

Known counter devices of this type have the disadvantage that on switching off the value written into the meter is cancelled. As long as these counting devices are employed only for adding-up of counting pulses within short time intervals, this disadvantage does not arise. However, the position is different if the counting devices add up counting pulses over a long period of time, e.g. months or years, such as is in the case with counting devices which are to be employed as distance counters for motor vehicles.

It is already known to overcome this disadvantage by associating with the counter a structure store of a periodic re-generating store, In the case of structure stores, the operating voltage can be switched off for a long time or may collapse without the stored value being lost. It is disadvantageous that this store is extremely expensive and is, therefore, not suitable for distance counters for motor vehicles. Periodically regenerating stores are substantially less expensive but the operating voltage must not be switched off for periods of time exceeding several hours, since the stored value is cancelled. Since in the case of a distance or a time counter operational voltage switch-offs of several days or weeks are possible, these stores are unsuitable for use in motor vehicles.Furthermore, the known stores occupy a considerable volume which is disadvantageous when they are used in motor vehicles.

It is an object of the invention to provide an electronic counting device, in particular a distance counter for motor vehicles, wherein the cancellation of the particular value stored is not lost in the event of switching off of the operational voltage.

According to the present invention there is provided an electronic counting device having a binary counter fed with pulses to be counted, decoding means, and an electrochromatic liquid crystal display system operated from the decoded output of the binary counter, wherein means are provided for determining the numerical state of the display system when the counting device is restarted having been switched off, and for reading into the counter the numerical value previously displayed.

Such display systems have the property that the energy required for transcription or cancellation of individual numbers or numerical segments depends on whether the numerals or the numeral segment had or had not been previously stimulated. If the numeral or the numeral segment had been stimulated, then for cancellation or transcription, a higher energy must be employed than in the case of a numeral which is not excited or a non-excited numeral segment. Thereby, the possibility exists, that on cancelling the indication when the counting device is switched on, to ascertain the numerical state by reason of the required cancelling energy per numerical segment and, on the basis of this result, to read into the binary counter a number of counting pulses corresponding to this numerical state.

The present invention will now be described in greater detail by way of example with reference to accompanying drawing wherein the sole figure is a block diagram of one preferred form of electronic counting device.

The counting device comprises a binary counter 1 into which distance-dependent pulses per time unit are read-in via a line 1'.

The information is built up in the particular selected binary code at the output of the counter I according to the distance travelled and is converted in a decoding device 2 so that the segments corresponding to the numerical value of the numerical indication in an electro-chromatic liquid crystal display system 3 light up.

After switching-off the counting device.

the last numerical indication is retained in the electrochromic liquid crystal display system 3 since a higher energy is needed to reenergize a segment which was previously illuminated than one not previously illuminated.

On rc-switching on the counter device. the numerical indication is cancelled by means of a cancellation device 4. The cancelling information in the form of different energy levels according whether a particular segment was illuminated or not occurs at the output of the cancellation device 4 and is supplied to a plurality of one terminal of a comparator 5. The output from the decoding device 2 is supplied to a plurality of the other terminal of the comparator 5. When the display is cancelled, a pulse generator 6 is started and the counter I counts up from its zero position until the information supplied to both sets of terminals of the comparator 5 are equal at which instant the pulse generator 6 is stopped.The counter content now available in the counter I corresponds to that previously displayed by the display system 3 prior to switching off of the counter device.

Once the comparator 5 has stopped the pulse generator 6, the counter control current circuit comprising the cancellation device 4, the comparator 5 and the pulse generator 6 is rendered inoperative.

In the case where the counting device is used to determine the distance travelled by a motor vehicle, the pulses to be counted are fed to the counter I from a tachometer device driven by the road wheels of the vehicle.

Alternatively, in the case where it is desired to determine the time ofajourney or the time that the engine is running, the pulses are fed to the counter I at a constant frequency during the period that the engine is running.

WHAT WE CLAIM IS: 1. An electronic counting device having a binary counter fed with pulses to be counted, decoding means, and an electrochromatic liquid crystal display system operated from the decoded output of the binary counter, wherein means are provided, for determining the numerical state of the display system when the counting device is restarted having been switched off, and for reading into the counter the numerical value previously displayed.

2. An electronic counting device according to claim 1, wherein said means includes a cancellation device, a comparator and a pulse generator, which are put into operation when the counting device is restarted, the pulse generator feeding pulses to the counter, the comparator comparing the decoded value of the pulses with the value provided by the cancellation device on cancelling the display system and stopping the pulse generator when the two values are equal, this value also being fed to the display system.

3. An electronic counting device according to claim I or 2, for counting the distance travelled or journey time of a motor vehicle, the pulses being supplied to the counter either in accordance with distance travelled or at a constant frequency respectively.

4. An electronic counting device constructed and arranged to operate substantially as herein described with reference to and as illustrated in the accompanying drawing.

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

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. system 3 light up. After switching-off the counting device. the last numerical indication is retained in the electrochromic liquid crystal display system 3 since a higher energy is needed to reenergize a segment which was previously illuminated than one not previously illuminated. On rc-switching on the counter device. the numerical indication is cancelled by means of a cancellation device 4. The cancelling information in the form of different energy levels according whether a particular segment was illuminated or not occurs at the output of the cancellation device 4 and is supplied to a plurality of one terminal of a comparator 5. The output from the decoding device 2 is supplied to a plurality of the other terminal of the comparator 5. When the display is cancelled, a pulse generator 6 is started and the counter I counts up from its zero position until the information supplied to both sets of terminals of the comparator 5 are equal at which instant the pulse generator 6 is stopped.The counter content now available in the counter I corresponds to that previously displayed by the display system 3 prior to switching off of the counter device. Once the comparator 5 has stopped the pulse generator 6, the counter control current circuit comprising the cancellation device 4, the comparator 5 and the pulse generator 6 is rendered inoperative. In the case where the counting device is used to determine the distance travelled by a motor vehicle, the pulses to be counted are fed to the counter I from a tachometer device driven by the road wheels of the vehicle. Alternatively, in the case where it is desired to determine the time ofajourney or the time that the engine is running, the pulses are fed to the counter I at a constant frequency during the period that the engine is running. WHAT WE CLAIM IS:

1. An electronic counting device having a binary counter fed with pulses to be counted, decoding means, and an electrochromatic liquid crystal display system operated from the decoded output of the binary counter, wherein means are provided, for determining the numerical state of the display system when the counting device is restarted having been switched off, and for reading into the counter the numerical value previously displayed.

2. An electronic counting device according to claim 1, wherein said means includes a cancellation device, a comparator and a pulse generator, which are put into operation when the counting device is restarted, the pulse generator feeding pulses to the counter, the comparator comparing the decoded value of the pulses with the value provided by the cancellation device on cancelling the display system and stopping the pulse generator when the two values are equal, this value also being fed to the display system.

3. An electronic counting device according to claim I or 2, for counting the distance travelled or journey time of a motor vehicle, the pulses being supplied to the counter either in accordance with distance travelled or at a constant frequency respectively.

4. An electronic counting device constructed and arranged to operate substantially as herein described with reference to and as illustrated in the accompanying drawing.