GB1570757A

GB1570757A - Temperature-compensating device

Info

Publication number: GB1570757A
Application number: GB13317/77A
Authority: GB
Original assignee: United Gas Industries Ltd
Current assignee: United Gas Industries Ltd
Priority date: 1977-03-30
Filing date: 1977-03-30
Publication date: 1980-07-09
Also published as: IT1101991B; FR2386103B1; FR2386103A1; IT7848615A0; DE2813433A1

Description

(54) TEMPERATURE-COMPENSATING DEVICE (71) We, UNITED GAS INDUSTRIES LIMITED of 3-4 Bentinck Street, London, Wl M 6DH, a British Company, 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 a temperaturecompensating device for use particularly but not exclusively in correcting the output of a gas meter for variations in temperature.

The invention provides a temperaturecompensating device comprising an infinitelyvariable ratio drive means, the ratio of which varies with a sensed temperature, said drive means comprising a pair of rotatable plates mounted separately but adjacent one another, rolling contact means sandwiched between the two plates to transfer drive between said plates, a first one of said plates being rotatably mounted on a first moveable lever whereby the centre point of said first plate may be adjusted to alter the radius at which the said rolling contact is made and the drive ratio between the plates varied, and temperature-sensitive means for adjusting the position of said lever.

Preferably said rolling contact means makes point contact with both plates, and may for instance be either a ball or a circular rim.

The second of said plates may be mounted on stationary structure and may also comprise a gear wheel forming part of a gear train for connection to the measurement being corrected. A corrected output may be taken from the rotation of said first plate, which receives a rotational drive from the second plate varied by the ratio obtaining.

The invention also extends to a gas meter having a temperature-compensating device as set forth previously.

In a gas meter which measures the volume of gas passing a temperature error occurs due to the operation of Charles' Law, according to which the volume of any definite weight of gas under constant pressure increases proportionately as the absolute temperature increases and vice versa.

This is expressed in the formula: V = volume (base corrected) V = C' where T = temperature (base) T C'= a constant Therefore: Vn = V ~ C' where Vn and Tn are the Tn T values at specific metering conditions other than the chosen base conditions.

Therefore: V = VnT Tn Therefore in order to correct Vn, the actually measured volume for the temperature variation Tn, a correction factor f is applied where: f = T Tn According to the invention the correction factor f is mechanically represented by the gear ratio obtaining in the infinitely variable gear.

The factor fin practice is found to vary be between 0.841 and 1.187 corresponding to ratios of 1.41:1 and 1:1 representing a temperature range of -30 C to 700 C.

Specific embodiments of the invention are shown in the drawings accompanying the Provisional Specification, in which: Figure 1 is a rear view of a compensator, Figure 2 is a side section through the compensator of Figure 1, Figure 3 is a front view of the compensator of Figure 1, Figure 4 is a section on the line A-A of Figure 1, Figure 5 is a rear view of a modified form of compensator, and Figure 6 is a diagrammatic representation of the drive from meter to index of the compensator of Figure 1, and in the accompanying drawing, in which: Figure 7 is a modification of the detail of Figure 4.

Referring first to Figures 1-3, the moveable operating pin 11 of a phial-operated temperaturesensing bellows assembly, shown only in part at 12, operates a lever 13 to pivot it about a fulcrum 14 at one end thereof. The other end of lever 13 carries a pivoted arm 15 which is also pivoted to a quadrant 16. This is mounted to be rotated about a generally central shaft 17, and has a quadrant gear 18 which meshes with a gear 19. A cam plate 21 is secured to the same shaft as gear 19 so that it rotates therewith. The movement of the bellows assembly in response to a temperature variation is therefore translated into an angular movement of the cam plate 21.

Cam plate 21 has a near-spiral shaped cam contour on which rests a follower 22 mounted for free rotation on ball bearings on the end of an arm 23. A spring (not shown) maintains follower 22 engaged with the cam. Arm 23 is in turn mounted at the lower end of a solid lever 25 which is pivoted at its top end about a shaft 26. A friction plate 27 having a plated hard bronze surface is mounted on a shaft journalled in lever 25 which shaft is rotatable with a gear 28.

The angular movement of cam plate 21 is thereby reproduced as an angular movement of the solid lever 25 about shaft 26, said movement also moving the centre point of plate 27 along an arc 38 centred on shaft 26.

Mounted separately from but adjacent friction plate 27 is a brass plate 30 and between the friction plate 27 and brass plate 30 engages a stainless steel 3/8" diameter ball 31. The ball is caged between a slot in fixed stainless steel bracket 32 and a ball bearing 33 mounted on a fixed arm, and frictionally engages the two plates 27 and 30 so as to transfer drive therebetween.

Brass plate 30 is also a gear wheel and engages at its circumference a train of gears (not shown) driven by the output of a gas meter e.g. of the rotary positive displacement type. The plate 30 drives an index 35 which gives a reading of the gas volume passed through the meter, uncorrected for temperature.

The ratio of the drive from plate 30 through ball 31 to the friction plate 27 depends on the radial position of the ball with respect to both plates. This position is fixed with respect to plate 30 but plate 27 is moveable as described previously about arc 38 so that the ratio is infinitely variable between certain limits, e.g.

from a centre point with a ratio of 1:1 to extremes of 1:1.19 in each direction which ratios effect corrections for temperature. The rotation of plate 27 is transferred to gear 28 and via a gear train 36 mounted on solid lever 25 to the corrected output shaft 26. From here a corrected index 37 is driven.

As described above the movement of the friction plate 27 along the arc 38 is caused by the movements of the bellows assembly and adjusts the gear ratio by an amount which alters the meter output to adjust it for the temperature variation. The cam contour for cam plate 21 is nearly spiral, requiring only minor variations therefrom to adjust for relatively minor linkage errors in the device, and for any non-linearity in the response of the bellows assembly to temperature variations.

The front of the device (Figure 3) shows both the corrected and the uncorrected indexes and also an ambient temperature scale 40. This scale co-operates with a moving index 41, on the end of a lever which is moved by a linkage 42 from shaft 17, in a ratio such that the index 41 shows the temperature being sensed by the bellows assembly 12.

The bellows assembly 12 is liable to manufacturing variations which affect its line of action and its length of movement. These are allowed for by the means for applying the bellows movement to the lever 13 which are seen in section in Figure 4. The operating pin 11 engages in a trunnion device 44 which has a bearing 45, pivotally supported from the lever 13 at 49. Movement of the trunnion about the bearing allows for variations in the line of action of pin 11. The distances between the fulcrum 14 and pin 11 and between pin 11 and the lever 15 are both independently variable as shown in Figure 1 by slotted connections 46 and 47, and by screw 48, rotation of which adjusts the position of the lever with respect to the fulcrum 14. The amount of movement transmitted to lever 15 can therefore be corrected for variations in the length of movement of pin 11.

The action of the ball 31 in transmitting infinitely variable drive from plate 30 to plate 27 is by rotation on both surfaces, the ball having point contact on both surfaces. When the plate 27 moves in response to a variation in temperature, the ball remains held by the caging devices (32, 33) and slides sideways with respect to the plate. The point contact allows this sideways sliding movement with a minimum of resistance.

The embodiment shown in Figure 5 is generally similar to Figure 1, but has a different method of driving from plate 30 to friction plate 27. An adjustable L-shaped bracket 50 has a shaft 51 secured to it. Ball bearings on the shaft support a cylinder 52 of bearing quality stainless steel, having at one end a driving rim 53 of increased diameter. The rim is shaped to a radiused point to contact both the plate 30 and friction plate 27 at points on either side thereof. Plate 27 in this embodiment has a hard chromium plated surface. The ball bearing support allows the rim to rotate freely. Otherwise this embodiment operates in a similar manner to that described with reference to Figure 1.

In use on a rotary displacement gas meter, the phial of the temperature-sensitive device is mounted in the stream of gas. The corrector is mounted on the body of the meter with the gear train leading to plate 30 connected to the rotational output of the meter, the speed of rotation being the measure of volumetric flow through the meter. Figure 6 shows diagrammatically the meter 55, gear train 56, uncorrected index 35, friction plates 27, 30 and ball 31, and corrected index 37. The bellows assembly 12 is also shown operating on quadrant 16 and cam plate 21.

The modification shown in Figure 7 has a trunnion device 44' of a different form from that shown in Figure 4. This device has two vertically spaced bearings 45', 45" through which it engages the lever 13'. The lower bearing 45' carries a pin 60 which slides vertically in a slot in stationary support structure 61. This modification gives the trunnion more stability and reduces unwanted freedoms, while still allowing for manufacturing variations in the line of action of the bellows assembly.

WHAT WE CLAIM IS: 1. A temperature-compensating device comprising an infinitely-variable ratio drive means, the ratio of which varies with a sensed temperature, said drive means comprising a pair of rotatable plates mounted separately but adjacent one another, rolling contact means sandwiched between the two plates to transfer drive between said plates, a first one of said plates having a rotational mounting carried on a first moveable lever whereby the rotational mounting may be moved relative to the rolling contact means so as to alter the radius at which said rolling contact is made and thereby to vary the drive ratio between said plates, and temperature-sensitive means for adjusting the position of said lever.

2. A temperature-compensating device as claimed in Claim 1, wherein said rolling contact means makes substantially point contact with both plates.

3. A temperature-compensating device as claimed in Claim 2, wherein said rolling contact means is a ball.

4. A temperature-compensating device as claimed in Claim 3, wherein said first plate has a plated hard bronze surface.

5. A temperature-compensating device as claimed in Claim 2, wherein said rolling contact means is a cylinder having a contact rim.

6. A temperature-compensating device as claimed in Claim 5, wherein said first plate has a hard chromium plated surface.

7. A temperature-compensating device as claimed in any of Claims 1 to 6, wherein said first lever is pivoted to stationary structure at one point and at another point has the rotational mounting for the said first plate, whereby angular movement of said lever about said one point moves the said rotational mounting along an arc, whereby the radius at which the rolling contact means engages with the first plate is varied.

8. A temperature-compensating device as claimed in Claim 7, wherein the position of engagement of said rolling contact means is maintained on a fixed radius with respect to the second plate.

9. A temperature-compensating device as claimed in Claim 7 or Claim 8, wherein the temperature-sensitive means comprises a phialoperated bellows which operates on a second lever which imparts movements of the bellows through a lever system to said first lever..

10. A temperature-compensating device as claimed in Claim 9, wherein said second lever incorporates length adjustments to adjust for manufacturing variations in bellows performance.

11. A temperature-compensating device as claimed in Claim 9 or Claim 10, wherein the bellows movement is transferred to said second lever through a trunnion device allowing for variations in the line of action of the bellows.

12. A temperature-compensating device as claimed in any of Claims 9 to 11, wherein said lever system comprises a pivoted arm which rotates a quadrant gear meshing with a gear operating a cam plate, said first lever carrying a follower which rides on said cam plate.

13. A temperature-compensating device as claimed in Claim 12, wherein said cam plate has a near-spiral contour.

14. A temperature-compensating device as claimed in any of Claims 7 to 13, wherein said first lever carries an output gear train driven from said first plate at a temperaturecorrected drive rate and said second plate is connected to be driven from an input gear train at an uncorrected drive rate.

15. A temperature-compensating device as claimed in Claim 8, wherein said rolling contact means is caged between a fixed bracket and a ball bearing.

16. A temperature-compensating device as claimed in Claim 8, wherein said rolling contact means is rotatable on a shaft secured to a bracket.

17. A temperature-compensating device substantially as described hereinbefore with reference to the drawings accompanying the Provisional Specification or to these drawings as modified by reference to the accompanying drawing.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. 27. An adjustable L-shaped bracket 50 has a shaft 51 secured to it. Ball bearings on the shaft support a cylinder 52 of bearing quality stainless steel, having at one end a driving rim 53 of increased diameter. The rim is shaped to a radiused point to contact both the plate 30 and friction plate 27 at points on either side thereof. Plate 27 in this embodiment has a hard chromium plated surface. The ball bearing support allows the rim to rotate freely. Otherwise this embodiment operates in a similar manner to that described with reference to Figure 1. In use on a rotary displacement gas meter, the phial of the temperature-sensitive device is mounted in the stream of gas. The corrector is mounted on the body of the meter with the gear train leading to plate 30 connected to the rotational output of the meter, the speed of rotation being the measure of volumetric flow through the meter. Figure 6 shows diagrammatically the meter 55, gear train 56, uncorrected index 35, friction plates 27, 30 and ball 31, and corrected index 37. The bellows assembly 12 is also shown operating on quadrant 16 and cam plate 21. The modification shown in Figure 7 has a trunnion device 44' of a different form from that shown in Figure 4. This device has two vertically spaced bearings 45', 45" through which it engages the lever 13'. The lower bearing 45' carries a pin 60 which slides vertically in a slot in stationary support structure 61. This modification gives the trunnion more stability and reduces unwanted freedoms, while still allowing for manufacturing variations in the line of action of the bellows assembly. WHAT WE CLAIM IS:

1. A temperature-compensating device comprising an infinitely-variable ratio drive means, the ratio of which varies with a sensed temperature, said drive means comprising a pair of rotatable plates mounted separately but adjacent one another, rolling contact means sandwiched between the two plates to transfer drive between said plates, a first one of said plates having a rotational mounting carried on a first moveable lever whereby the rotational mounting may be moved relative to the rolling contact means so as to alter the radius at which said rolling contact is made and thereby to vary the drive ratio between said plates, and temperature-sensitive means for adjusting the position of said lever.

18. A gas meter including a temperature

compensating device as claimed in any of Claims 1 to 17, connected to correct the measurements of the meter.

19. A rotary displacement gas meter including a temperature-compensating device as claimed in any of Claims 1 to 17, connected to provide a temperature-corrected rotational output of the meter.