AU602793B2 - Method and apparatus for monitoring the specific gravity of a liquid - Google Patents

Description

i~s~i(i~ I 4 r AU-AI-22515/88 ~i~s~a PCT RLD? EL UA OPI ORGANIZATION INTERNATIONAL APPL T N P LISHED UNDER THE PATENT COOPERATION TREATY (PCT) (51) International Patent Classificatior International Publication Number: WO 89/ 01618 G01N 9/10 Al (43) International Publication Date: 23 February 1989 (23.02.89) (21) International Application Number: PCT/GB88/00653 (81) Designated States: AT, AT (European patent), AU, BB, BE (European patent), BG, BJ (OAPI patent), BR, (22) International Filing Date: 8 August 1988 (08.08,88) CF (OAPI patent), CG (OAPI patent), CH, CH (European patent), CM (OAPI patent), DE, DE (European patent), DK, FI, FR (European patent), GA (31) Priority Application Number: 8718733 (OAPI patent), GB, GB (European patent), HU, IT (Eu:opean patent), JP, KP, KR, LK, LU, LU (Euro- (32) Priority Date: 7 August 1987 (07.08.87) pean patent), MC, MG, ML (OAPI patent), MR (OA- PI patent), MW, NL, NL (European patent), NO, (33) Priority Country: GB RO, SD, SE, SE (European patent), SN (OAPI patent), SU, TD (OAPI patent), TG (OAPI patent), US.

(71) Applicant (for all designated States except US): PCA AS- t i I C)i SOCIATES (CONGLETON) LIMITED [GP/GBj; 19 Published Moody Street, Congleton, Cheshire CW12 4AN With internatiopal searctlihedir. m

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d c (72) Inventor; and Inventor/Applicant (for US only) DUTTON, John [GB/GB]; 411 London Road, Davenham, Northwich, 7 APR 19 Cheshire CW9 8HN 2 7 P 199 (74) Agent: ATKINSON, Pter, Birch; Marks Clerk, Suite

AUSIRALIAN

301, Sunlight House, Quay Steet, Manchester M3 3JY -9 1989 PAT'NT

OFFICE

(54) Title: METHOD AND APPARATUS FOR MONITORING THE SPECIFIC GRAVITY OF A LIQUID (57) Abstract Apparatus for monitoring the specific gravity of a liquid comprises a cantilevered load senring beam (24) on which is suspended a displacer The beam (24) is itself mounted on a support tube (19) extending from the wall of a vessel holding the liquid whereof the specific gravity is to be monitored, Deflection of the bean? which is measured by strain gauges provides a measure of any variation in specific gravity. The output of the strain gauges (27) is associated with processing means for providing information on specific gravity changes.

29 :a r 939 I I *Sl-"Lt H 9 1 METHOD AND APPARATUS FOR MONITORING THE SPECIFIC GRAVITY OF A LIQUID This invention relates to a method of and appara.tus for monLttciig the specific gravLty aE L, liquid, especially but not exclusively a fermenting liquid such as beer.

It is known that the specific gravity of a fermenting liquid such as beer decreases as sugars in the liquid are converted to alcohols and it is desirable that process workers operating the fermenting process be aware of such changes in specific gravity for efficient operation of the process.

It is therefore an object of the present invention to provide a simple and effective method of and apparatus for monitoring, continuously or intermittently, the specific gravity of a liquid, especially a fermenting liquid.

The p:esent invention has particular but not exclusive application to the brewing industry.

According to the present invention there is provided, apparatus for monitoring the specific gravity of a liquid comprising support means, a load sensing beam mounted as t, antilever on the end of said support means and b'eing associated with four strain gauges mounted ¢o the beam at the corners of a parallelogram for -,asauring deflection of the beam, and an elongate displacement body with a weight per uiit volume greater than that of the liquid to be monitored pivotally suspended from the beam whereby the apparatus is insertable through, and supported by, the wall of a vessel for holding said liquid.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:- Fig. 1 is a fragmentary part-sectional side "i ~VT C lilC( rltlC -II SUJJii31~3 uccliJ r PCT/GB 8 8 10 0 6 56 2 0 November 1989 2 elevation of a process receptacle, for example a fermenting vat, with the specific gravity monitoring apparatus; according to the present invention; Fig. 2 is a fragmentary side elevation of the specific gravity monitoring apparatus to an enlarged scale, but omitting details of the spray tube.

Fig. 3 is a detail of the load cell used in the apparatus of Fig. 1; Fig. 4 is a view on the line IV-IV of Fig.3; and Fig. 5 is a modification of the beam deflection limiting means shown in Figs. 3 and 4.

Referring to the drawings, a wall of the fermenting vat within which, for example, beer is being fermented is indicated at 10. The wall adjacent the bottom of the vat which may' be of considerable height, say 50 to 60 feet, is apertured at 11 and has an integral tubular port 12 flanged et 13.

The specific gravity monitoring apparatus of the present invention generally indicated at 14 is inserted through this port 12 into the vat and is partially ac.ommodated within the port 12.

The monitoring apparatus 14 comprises an elongate displacer 15 in the form of a closed tubular body of known volume and weight suspended within the beer contained in the vat. The displacer 15 has a weight per unit greater than that of the liquid to be monitored. This displacer 15 is sufficiently substantial so as to have a sufficiently high moment of inertia so as to be generally unaffected by the movement of bubbles and suspended solids in a fermenting liquid.

A bar or rod 16 is welded to one end of the displacer body 15 and is pivoted as indicated at 17 to one end of a load cell unit 18 (indicated in more detail in Fig. 3) from which the dispL.cer body 15 is suspended as aforesaid.

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6UBSTITUTE Si", dET UST Enited KngEdom Patent Ofce IPCT International ApplicationI

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IPCT/GB 8 8 06 2 0 November 1989 3 The load cell 18 is mounted on a support tube 19 welded to the load cell 18, the support tube 19 extending through, and out of, the port 12 and having a flange 20 whereby the tube 19 is bolted as indicated at 21 to the port flange 13. A sealing disc 22 or similar is sandwiched between the flanges 13, The signal cable of the load cell unit 18 is indicated at 23 and is housed in the support tube 19.

The cable 23 egresses from the support tube 19 externally of the vat as shown and is coupled to amplifying means (not shown) and thereafter to a signal processing means giving, for example, a readout in units of specific gravity, The support tube/load cel' arrangement 18, 19 is a sealed unit to prevent process product, for example, beer ingress, and it together with the displacer body and bar or rod 16 are made of stainless steel, for example 316 stainless steel, to prevent process product contamination and corrosion.

The connection or joint 13, 20 to 22 is leakproof due to the provision of the sealing disc 22, and is rigid with the port 12 and consequently the vat, Referring now to Figs. 3 and 4, the load cell unit 18 will be seen to comprise a load sensing beam 24 which is of rectangular cross-section and which has two generally circular cut-out 25 which open one into the other. Beam 24 is mounted as a cantilever on the end of support tube 19. Beam 24 is enclosed in bellows 26. A total of four strain gauges 27 are bonded by welding) to beam 24 and each positioned above or below a respective circular cut out 25 as shown. The use of four strain gauges (mounted at the corners of a parallelogram) on the beam 24 means that deficiencies in the machining of the beam 24 are compensated and that accurate Smeasurement of beam deflection is possible.

S Obviously the strain gauges are associated with the 0- SUBSTITUTE SIHEET United mi Patent Office SUBSTITUPCT International Application PCT/GB 8 8 0 a 6 o ovembar 9 Et, 4 necessary means for measuring the deformation of the beam.

A rod 28 is screwed at one end into a support 29 (at the end of beam 24) and its f,7ee end locates in an elongate aperture 30 in a circu1ir plate 31. Rod 28 serves to prevent excessive deflection of beam 24 (such as might occur by draining of the vat whilst leaving the displacer 15 freely suspended) by engaging against the ends of aperture 30 at a predetermined deflection of the beam.

A modification for rod 28 and aperture 30 is shown in Fig. 5 in which the rod (designated here as 291) has a tapered end. This taper allows for calibration of the over-range limit adjustment.

A platinum resistance thermometer 32 is bonded to beam 24 as shown.

A further feature of the apparatus is a spray tube 33 extending beneath, and parallel to, the support tube 19. This spray tube is for use in sparging the apparatus and for this purpose is connected to a supply of cleaning liquid water).

The apparatus is used as a continuous on-line monitor for the specific gravity of a liquid, particularly a fermenting liquid beer). The support tube 19 and displacer 16 are completely submerged in the liquid whereof the specific gravity is to be monitored. Ideally, the volume and/or weight of the displacer 15 is such that at the start of fermentation there is substantially no deflection of the beam 24. The load cell 18 detects apparent gains/losses in weight of the displacer body 15 due to changes in the specific gravity of the beer during fermentation. Signals generated by the load cell 18 are, as aforesaid, transmitted by the cable 23 to the amplifying means and the signal processing means to give the read-out in jpecific gravity units. The measurement is unaffected by bubbles and suspended 174 >1 ez-, r AJ SUBSTITUTE SHEEr United Kir2ndom Patent Offi it 1 IPC!" Intno. Applica on

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PCT/GB 88 0 0 6 2 0 Novemoer 1939 Polids which, as mentioned previously, do not cause movement of displacer Thus the specific gravity is continuously monitored to permit a process worker to check and Sdjust the process operation if necessary.

The platinum resistance thermometer 32 measures the temperature of the beer and allows a correction to be made for giving the specific gravity at a standard temperature, such as may be required for excise duty purposes.

Due to the pivot connection 17 between the displacer body 15 and the load cell 18 it is a simple matter to remove the specific gravity monitoring apparatus 14 through the port 12 after releasing the connection or joint 13, 20 to 22 for maintenance, repair or replacement purposes for example. Reinsertion, or insertion of a replacement apparatus, is equally simple.

Although the invention has been described with specific reference to a support tube 19 extending horizontally from the wall of the vessel, it is possible for the tube to be generally L-shaped with one vertical limb (supported above the vessel) and a horizontal limb on which the load sensing beam is mounted.

Tid CUBSTITUTE SHEET PCT ,da Anrn cao.o

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f %a 12J" Ca'IL C 171 o

Claims (12)

1. Apparatus for monitoring the specific gravity of a liquid comprising support means, a load Sensing beam mourited as a cantiLe.ver on the end of said support means and being associated with four strain gauges mounted on the beam at the corners of a parallelogram for measuring deflection of the beam, and an elongate displacement body with a weight per unit volume greater than that of the liquid to be monitored pivotally suspended from the beam whereby the apparatus is insertable through, and supported by, the wall of a vessel tor holding said liquid,

2. Apparatus as claimed in Claim wherein the beam is of rectangular cross-section and has two genrrally circular apertures in the plane of weight sens *ng deflection of the b(am, and two of said strain gauges are respectively mounted above and below one of said apertures and the other two strain gauges are respectively mounted above and below the other of said apertures.

3. Apparatus as claimed in Claim 1 or 2 provided with means for limiting the deflection of the beam.

4. Apparatus as claimed in Claim 3 wherein the means for limiting the deflection of the beam comprises a rod fixed at one end relative to deflection of the beam and locating at its other.end in a deflection limiting aperture provided adjacent the end of the beam from which the displacement body is suspended. Apnaratus an claimed in Claim 4 wherein the deflection limiting aperture is provided in a flange around said end the beam. 6 Apparatus as claimed in any one of Claims 1 to 5 provided with a platinum resistance thermometer.

7. Apparatus as claimed in Claim 6, wherein the thermometer is mounted on the beam. SUC3T1h7U7 1 'ci: rt:"O IET j 7

8. Apparatus as claimed in any one of Claims 1 LO 7 wherein the support means is an elongate support for insertion through, and support by, the wall of a vessel containing liquid. 9 Apparatus as claimed in claim 8 having a spray tube extending parallel to said elongate support, Apparatus as claimed in Claims 5 or 9 in which Ehe elongate support comprises a support tube connectible, at one end, to the vessel wall and having, at its other end, the load sensing beam.

11. A[:paratus as claimed in Claim 10 in which a signal-transmission cable from the means for measuring deflection of the beam is housed within the support tube,

12. Apparatus as claimed in Claims 10 or 11, in which the support tube is adapted to extend through and be f lange -connected to a port in the vessel wall.

13. Apparatus as claimed in Claim 12, in which the flange connection incorporates liquid sealing means.

14. Apparatus as claimed in Claim 11, 4,n which the signal transmission cable externally of the vessel and support tube is connected to signal-amplifying means and signal-processing means. Apparatus as claimed in Claim 14, in which the signal -processing means providi-s a read-out of the apparent body weight gains/losses in terms of specific gravity units,

16. Apparatus as claimed in any one of Claims 1 to 15 wherein the elongate body is a sealed hol.low tube of known weight and volume,

17. A vessel for holding a liquid and provided with apparatus as claimed in any one oi Claims 1 to 16. SU2CTI'TU72:~E