GB2168862A - Commodity meters - Google Patents

Abstract

A gas or other commodity meter has a mechanical counter mechanism comprising a plurality of rotating indicators which can be read visually. In order to allow the reading to be read at a distant location or by a computer an electrical coded representation of the reading is set up. Associated with each rotating indicator is a rotating slider, which slides on a stationary printed circuit board (11, Figure 5) having on its face a pattern of four concentric rings of spaced contact strips, arranged in the Gray code. As the slider passes over the strips it energises them in a pattern unique to the decimal digit shown by the rotating indicator. Multicore cable (21) is connected to each of the strips and leads to a reading device at which the pattern of energisation is decoded. Figure 3 shows an alternative pattern of contact strips. <IMAGE>

Description

SPECIFICATION Commodity meters This invention relates to commodity meters, in which a mechanical counter mechanism sets up an analogue ofthe metered quantity, and more particularly to means for reading the analogue metered quantity at a location remote from the meter.

Our earlier Patent Specification No. 1,213,125 describes one way of changing a mechanical counter reading into an electrical representation which can be transmitted over electrical. wires to a remote reading device. This comprises having separate electrical contacts for each digit and a separate electrical output wire from each contact. This arrangement has problems when changing from one contact to the next, since instantaneous changeover from one contact to another cannot be practically achieved. This invention provides means for meeting the changeover problem.

The invention provides a commodity meter having a mechanical counter mechanism comprising a plurality of rotating indicators, each representing one digit of a decimal number, each indicator having associated therewith a stationary pattern of electrical contact strips and electrical conducting means rotating with the indicator and sliding over said contact strips to energise selected ones in arrangements unique to each number from 0-9 indicated by the indicator, and electrical output lines whereby the energisation of the contact strips can be detected and the counted number read, the contact strips being arranged so that each strip overlaps one or more others, whereby no instantaneous change from one contact to another occurs, there being logic means for determining the number represented by the arrangement of the energisation of the contact strips.

One pattern for the contact strips comprises two rings of spaced strips, each strip overlapping another strip in the other ring, the logic means resolving the ambiguity which results by reference to the reading of an adjacent indicator.

Another pattern for the contacts comprises an adaptation of the Gray code in which there are five concentric rings of spaced strips, the change from one number to the next being achieved by a single connection or disconnection, the logic means comparing the arrangement of energisation with a memory.

Specific embodiments of the invention are shown in the accompanying drawings, in which: Figure 1 is a front view of a digit-displaying counter of a meter index, Figure 2 is a side view of part of the counter of Figure 1, Figure 3 is a diagrammatic representation of the layout of a first form of printed circuit contact board for use in the counter of Figure 2, Figure 4 is a diagrammatic representation of the layout of a second form of printed circuit board for use in the counter of Figure 2, Figure 5 is a perspective view of a contact board using the layout of Figure 4, Figure 6 is a diagrammatic representation of the electrical circuit of the counter, Figure 7 is a perspective view of a digit-displaying drum of a meter index, Figure 8 is a side view of part of a meter index incorporating the drum of Figure 7, and Figure 9 is a diagrammatic representation of a gas meter incorporating the meter index of Figure 2, in a particular location.

A dry gas meter measures the flow of gas therethrough by counting the reciprocations of a flexible diaphragm. The reciprocations are translated into rotational movements of a shaft driving an input drive dog (30) of a digital counter (31) shown in Figures 1 and 2. The counter has a series of gear wheels and pinions, shown only partially in Figure 2, which drive a series of six indicators (33), each geared down at a rate of 10:1 from the previous one, so that each represents a single digit of a decimal number making up a counted quantity of gas.

Stationary index markings (34) provide a visual read-out of digits 0-9 against which the indicators (33) can be read.

Each indicator is mounted to rotate with a shaft (35) (Figure 2) carrying a pinion (36) driven through a gear wheel (37). Although the reading can be read visually it is desired to provide means whereby the read-out can be transferred to a location remote from the meter to be read either visually or electronically, e.g. for computer use. For this purpose each indicator (33) has associated with it a respective stationary printed circuit board (11), having on its face a pattern of electrically conducting strips. The pattern may be as shown in Figures 3 or 4 as described hereinafter and is designed to provide an electrical code denoting the displayed digit of the adjacent indicator.

Each indicator shaft (35) carries adjacent its printed circuit board a conducting bridge (12) secured to rotate with the shaft, and in rotating to slide over the pattern on the circuit board. Thus the displayed number from 0-9 is coded as a unique combination of contacts of the bridge (12) with the pattern on the printed circuit board.

One suitable pattern is shown in Figure 3 and comprises an unbroken central ring (13) surrounded by two concentric broken rings (14, 15).

The board is considered as being divided into ten segments, each segment corresponding to a digit from 0-9 as indicated, the pattern of the two broken rings being related to these segments so as to provide a unique electrical contact for each digit.

As shown, the central ring (14) comprises separate annular contact strips extending fully across the segments relating to digits 1, 3, 5, 7 and 9, each strip also extending at each end a short distance into the adjacent segments. The outer ring (15) comprises separate annular strips extending fully across the segments relating to digits 0, 2, 4, 6 and 8, each strip also extending a short distance into the adjacent segments. Thus, as seen in the drawing, each of the strips overlaps the adjacent strips of the adjacent ring by a few degrees, e.g. about 1"-5" of arc.

Each of the strips has a separate electrical outlet connection (not shown in Figure 3). The unbroken central ring (13) has a permanent electrical inlet connection, and is thus permanently live when energised. In use bridge (12) extends across the paths of all three rings, so is permanently in contact with central ring (13) and intermittently energises one of the strips of the two outer broken rings (14) and (15) as it passes over them. Thus the outlet connections, amounting to ten separate conductors, are energised one by one, each connection representing a different digit from 0-9. The outlet and inlet connections may be led to a distant location at which a logic circuit (e.g; a microchip) reads the pattern of energisation and translates it into a number which may be displayed to be read or used directly in a computerised billing device.

When the bridge (12) comes to the end of one strip it will for a short time overlap the next strip, so that two successive outlet connections will be energised together. The microchip circuitry includes logic for determining which of these two possible digits is correct on the following basis: The circuitry checks what digit the next succeeding lower indicator in the series is indicating. If this digit is more than 5 then the circuit takes the lower number of the two possibles. If this digit is less than 5, then the circuit takes the higher number of the two possibles. A consideration of the way in which the indicators rotate continuously as they count the gays volume flow provides the basis for this logic. Taking a specific example, there is an overlap which may extend from a reading of say 2.8 to 3.2.Over this area both the connection for 2 and the connection for3 are energised. If, therefore, the logic circuit looks at the next indicator in the series to see if it is showing something of the order of .8 or something of the order of .2, it can judge whether it is the 2 or the 3 reading it should take. Thus the ambiguity is resolved.

Previously, as in our prior Patent No. 1,213,125, there has been a problem with a contact moving from one contact strip to another, since it is hardly possible for the manufacturing tolerances to be good enough for the changeover to be made si- multaneously. Thus at the changeover point there is either a brief point at which no contact is made, or an overlap. Either way there is insufficient information for a reading means to determine what is meant. Patent No. 1,213,125 provides a mechanical device for making the contact jump over the changeover point, but such a device is expensive and noisy. By means of this invention the device is not needed, no very special manufacturing tolerances are required for locating the ends of the strips, and a simple electronic logic device resolves the deliberately caused ambiguity.

The pattern of strips shown in Figure 3 requires ten output electrical lines and one input line, thus requiring a multiwire electrical cable. By the use of a more sophisticated coding pattern shown in Figure 4, the number of wires can be reduced to 5 output lines and one input. As shown, the pattern comprises a continuous inner circle (16) and four broken outer circles (17, 18, 19 and 20). The outer circle (20) comprises a single strip extending across the segments corresponding to digits 5, 6, 7, 8 and 9. The next inner circle (19) has a single strip extending across the segments corresponding to digits 3 4, 5 and 6. The next inner circle (18) has two strips, one corresponding to digits 1, 2 and 3, the other to digits 6, and 7. The next inner circle (17) has a single strip corresponding to digits 9, 0 and 1.Each strip, as before, has separate electrical connections, but instead of each being at least nominally separately energised, a coding pattern has been set up whereby each decimal digit corresponds to a unique code of energisation of the strips, each strip taking part in the coded energisation corresponding to more than one digit The particular code shown is an adaptation of the Gray code. As described in relation to Figure 3, an electrically conducting bridge (12) spans all the circles, energising them. Inspection of Figure 4 will show that each digit segment has a unique combination of strips across it and thus a unique combination of energisation of-the output lines. It will be seen that this coding allows every strip to overlap one or more strips in others of the circles.As the coded number changes, each step comprises only a disconnection or a connection to a strip, the requirement for simultaneous connection and disconnection never occurring.

The logic circuit (not shown) to which the output lines lead matches the pattern of energisation of output lines to a memory which contains the coding, thereby determining the digit being indicated.

The input and output lines may lead some distance from the gas meter, for instance to an outside access point for a meter reader. In this case the logic circuit sets up another visual display for the meter reader to read. The logic circuit may operate continuously, maintaining the display updated. Alternatively, it may only interrogate the meter when operated by the meter reader, providing a pulse of energy on the input line and detecting the corresponding pulses on the output lines.

The electrical lines may alternatively lead to an interface unit for supplying information when interrogated over telephone lines or over electrical mains lines.

Figures 5, 6, 7 and 8 show an alternative form of counter in which the rotational movement of a shaft drives the first of a series of parallel decimal digit-displaying drums (1), of which one is shown in Figure 7 and three are shown with their mechanical connections in Figure 8. The index mechanically counts by each drum driving the next through a transfer tooth (9) which engages a pinion wheel (70) driving teeth (8) on the next wheel, once in each revolution. The operation of a mechanical counter and visual display of this kind is described in detail in our U.K. Patent Specification No. 1,213,125 Each drum is numbered 0-9 around its circumference, that number which is located at a real or notional reading position being the cor- rect number in the counted quantity.

Each drum has associated with it a respective stationary printed circuit board (11) similar to those described with reference to Figures 1 to 4, and an electrical bridge (12) rotating with the drum and sliding over the surface of the circuit board. As seen in Figure 5, the strips are connected through to the back of the board to edge connectors and thus to an output cable (21). Figure 6 shows diagrammatically the electrical circuit made from the input circle (16) through the bridge (12) to the selected outputs.

It will be seen that a sliding contact rotating on a printed circuit provides a unique coded output for each of ten sectors of the rotation, the changeover between one sector and the next being either the making of a new contact or the breaking of an existing contact, never the change from one contact to another. The counter may, as described, have visual indicators comprising either pointers associated with indices or drums carrying numerals, but it is within the invention to provide no visual readout but only the electrical code described.

Using a remote reading device as described above, it becomes possible to locate a gas or other commodity meter in less accessible locations. As shown in Figure 9, a gas meter (22) may be made of relatively impervious material, e.g. of a polyethylene plastics material which is buried directly in the ground (23), i.e. not in a sealed chamber but in contact with the soil. As shown, a small access pipe (24) allows a rod (25) to be inserted in order to operate a main valve (26). A tube (28) allows a governor (27) to breathe. The cable (21) carries the reading from the meter either to a reading location or there may be a visual display at the entrance to the pipe (24).

While the means for providing a remote reading have been described in relation to a gas meter, it is clear that similar means may be used for transferring the reading of any device having a mechanical counting device.

Claims (10)

1. A commodity meter having a mechanical counter mechanism comprising a plurality of rotating members each successive arc of rotation of which represents a digit of a decimal number, each rotating member having associated therewith a stationary pattern of concentric rings of spaced contact strips and electrically conducting slider means rotating with said member and sliding over said contact strips so as to energise selected strips in pattern each providing an electrically coded representation of the digit represented by the respective arc, the contact strips being arranged so that the pattern change from one arc to the next never requires connection to one strip and disconnection from another strip to occur at the same time.

2. A commodity meter as claimed in claim 1, wherein each strip in a ring overlaps a strip in another ring, there being also reading means including logic means to resolve the ambiguity which results by reference to the value of the next succeeding lower digit in the decimal number.

3. A commodity meter as claimed in claim 2, wherein said contact strips are arranged in two concentric circles, each circle comprising five equally spaced strips.

4. A commodity meter as claimed in claim 3, comprising also an unbroken contact ring slidingly engaged by said slider to provide an electrical supply thereto.

5. A commodity meter as claimed in claim 3 or claim 4, wherein there are separate electrical connections from each of said contact strips to said reading means, which determine the correct indicated digital number.

6. A commodity meter as claimed in claim 1, wherein said contact strips are arranged in four concentric circles, the strips providing a physical adaptation of the Gray code, wherein no strip starts or finishes on the same radial line as any other, and each arc representing a digit has a different pattern of energisation.

7. A commodity meter as claimed in claim 6, wherein there are five strips, and separate electrical connections from each strip to reading means wherein the pattern of energisation is compared with a memory whereby the indicated decimal number is deduced.

8. A commodity meter as claimed in claim 6 or claim 7, comprising also an unbroken contact ring slidingly engaged by said slider to provide an electrical supply thereto.

9. A commodity meter as claimed in any of claims 2 to 5, or 7, wherein said reading means is arranged to interrogate the meter at intervals.

10. A commodity meter substantially as described hereinbefore with reference to any of Figures 2, 3, 4, 5, 6, 7, 8 or 9 of the accompanying drawings.