US1838399A

US1838399A - Specific gravity indicator or recorder

Info

Publication number: US1838399A
Application number: US511827A
Authority: US
Inventors: Hodgson John Lawrence
Original assignee: George Kent Ltd
Current assignee: Elster Metering Holdings Ltd
Priority date: 1929-12-05
Filing date: 1931-01-28
Publication date: 1931-12-29
Anticipated expiration: 1948-12-29

Description

Dec. 29,1931. HOD SON 1,838,399

SPECIFIC GRAVITY INDICATOR OR RECORDER Filed Jan. 28, 1951 4 Sheets-Sheet 1 5 I I I a v I a i 1 Dec.29, 1931. 4 My HD SON 1,838,399

SPECIFIC GRAVITY INDICATOR OR RECORDER Filed Jan. 28, 1951 4 Sheets-Sheet 2 Dec. 29, 1931.

J. L. HODGSON SPECIFIC GRAVITY INDICATOR OR RECORDER Filed Jan. 28, 1931 4 Sheets-Sheet 3 Hill Dec. 29, 1931. J. HODGSON 1,838,399

SPECIFIC GRAVITY INDICATOR 0R RECORDER Filed Jan. 28, 1931 4 Sheets-Sheet 4 lllllll HIHIIIH Patented Dec. 29, 1931 UNITED ST TES PATEIAN OFFICE-Q1 1 .Ion v LAWRENCE HonGsoN; .oRLUTon, EnG-LANn'AssIGNoR r GEORGE, KENT,

" minimal or Lennon ENGLAND srncrrio GRAVITY InmoAT'oitoR REcoRnER ilpplication ma ianuar 28, 1931, Serial No. 511,827,".and in Great Britain. December 1929.

i The present inventionbrelates to devices suitable for indicating or ;recordmg variations in the specific gravity of a fluid passmg in a pipe.

. 5 ,The invention is illustrated-in.the accompanying drawings in which Figural is a vertical sectional elevation, Figure'2 a plan view partly in section with the top cover plate removed, Figure 3 an end sectional elevation and Figure 4 a front elevation. iFigure 5 is a diagrammatic viewf of a modification, and Figures G and 6*, to be jointlyconsidered, are left hand and right hand portions, respectively, of a sectional elevation of a further modification. .e c Referring more particularly to Figures 1-4,.1, 2 are displacers of widely different weights per unit volume, but of approximatelyequalweights, the displacer 1 being that d of smaller weightper nnit volume and being made hollow The displacers are secured to two opposite arms 3,,& forming a beam which is :pivotally mounted about aknifeedge 5v and whose positionis controlled by a pendulumweight 6. An adj usting weight 7 is provided which is so adjusted thattwhenthe displacers areimmers ed in:liquid of the mean specific gravity to. be indicated or recorded,

' there will be no deflection from the mean position, i. e. the pendulum. weight will hang vertically. If the liquid in which the displacers are immersed is now,replaced by a liquidoflower specific gravity, the arm-carrying the displacer 1 will descend, owingto as its greater loss of buoyancy, The amount that it willdescend will depend upon the size and the positionof the controlling'pen'dulum weight, so that a definite deflection will be obtainedfor each specific gravity of the liquid in which the beam carryingthe two displacers and the controlling weight isimmerse'd.

As "an apparatus constructe'd' aas above would show a deflection due to a fall in the specific gravity'of the liquid in which the displacers were immersed due to any rise-in tem- 9 is arrangedon the periphery of the circular perature, of that liquid, the following means are provided to render theindications of the 'apparatusunalfected by such changes of temperature. i i

Thehollfow displacer 1 is filled with liquid 6 of the-same coefficient, of-expansion as the liquid whosespecific gravity it is desired to indicate or record. The arm 3 carrying this dis'placer is als0 madehollow,and communir cates with a closed cylindrical chamber 8 wliose centre is at the centre'of' rotation of the knife edge- 5 which carries the beam with its two dis'p-lacersand pendulum control weight; The tubular arm carryingthe large 'displacer liis bent downwards into this closed cylindrical cavity which is partially filled with liquid so that the end of this tubular arm is always sealed by the liquid, the beam being adjusted for balance by means of the adjusting weights. A suitable filling plug chamber, so-Y long as the coeflicients of vexpansion ofthe liquids inside and outside the displacer are substantially equal, changes in the common temperatureof these liquids/will not appreciably affect the balancerof the beam as, an amountof liquid Whose weight is equal to, the lossof buoyancy, of the displacer 1 will expand into the centralcylindrical chamber 8 where itproduces no mo- *7 V -ment'about the knife edge since the pivot means 5 are at the volumetric or symmetrical j center of the vessel 8. The apparatus is therefore compensated for changes the specific gravity of the liquid inwhich thfe displacers are immersed, due to variations from thefmean temperature at which the zero of the beam was adjusted" bymeans of the ad justingweights. I 'f If theadjustingand controlling weights are made of different materials their expansions must be suitably compensated.

The error due totheiloss of buoyancy with fall of specific gravity with rise. of temperature'of the'liquid in which the controlling pendulum weight is immersed is a small fraction of 1 per cent over any reasonable range of temperature, and therefore it does not generally require compensation. A compensation can, however, be efiected by fitting above the pivotal axis of the arm 3 a volume the moment of whose buoyancy is equal to that of the controlling pendulum weight, but whose weight is much less.

The apparatus above described is located within a chamber in a casing 10 havinginlet and outlet connections 11, 12 for theliquid whose specific gravity is to be measured. Secured to the casing is a second casing 13 containing a chart 14 over which moves a pen 15. The pen is operated by the movement of the beam through a bracket 16 which is secured to the beam and to an extension 17 i of a frame 18 carrying the pen and having a knife edge pivot 19.

Battles

20, 21 are arranged in the chamber to enable the liquid therein to be continually exchanged without causing any deflection of the balance arm.

In the modification shown in Figure 5, the displacer 1, hollow arm 3 and central chamher 8' are completely filled with liquid, and in order to allow the temperature compensation to be obtained, the central chamber is extensible to accommodate an increase in volume of the liquid, due to temperature rise. To efiect this, one (or both) of the ends of the chamber is closed by concentric flexible tubes 22, 23 and an annular plate 24. Such an arrangement of temperature compensation is particularly suitable for use where the fluid whose specific gravity is being measured is under high pressure.

If the liquid is under pressure, the balance arm carrying the displacers must also be under pressure, and the motion of the arm is most suitably transmitted outside the pressure tight casing by means of a magnetic drive. Such an arrangement is illustrated in Figure 6 and consists of two

magnets

25, 26 operating through a window of nonmagnetic material, the magnet 25 being attached to the beam and the magnet 26 to the frame 18 carry the pen.

In this arrangement also the temperature compensation may be alternatively effected by forming the end walls of the displacer 1 by corrugated flexible plates 27 which allow the liquid freely to expand and contract on varia tion in temperature.

What I claim is 1. In apparatus for measuring the specific gravity of a fluid, the combination of a hol low displacer of 'fixed capacity which is adapted to move in response to variations in the specific gravity of the fluid to be measured, and is adapted to contain fluid, a sealed vessel, and means connectingsaid displacer and vessel and permitting fluid to pass between the displacer and the sealed vessel to compensate for variations in the specific gravity, due to variations in the temperature of the fluid to be measured, said vessel, displacer and means constituting a unit, and means fulcruming the unit on an axis passing through said vessel.

2. In apparatus for measuring the specific gravity of a fluid, the combination of a hollow displacer of fixed capacity which is adapted to contain fluid, a sealed vessel, and means connecting said displacer and vessel and permitting fluid to pass between the displacer and the sealed vessel to compensate for variations in the specific gravity, due to variations in the temperature of the fluid to be measured said vessel, displacer and means constituting a unit fulcrumed on an axis passing through the volumetric center of said vessel whereby the latter is located so that the movement of the displacer about said axis is unaffected by the contents of the vessel.

3. In apparatus for measuring the specific gravity of a fluid, the combination of a rocking beam, a pair of displacers supported on the rocking beam, one of the displacers being hollow, of fixed capacity, and adapted to contain fluid, a sealed vessel, and means permit ting fluid to pass between the hollow displacer and the sealed vessel to compensate for variations in the specific gravity, due to temperature variations of the fluid to be meas ured, said vessel, displacers, rocking beam and means constituting a unit fulcrumed on an axis passing through the volumetric center of the vessel whereby the latter is located so that the movement of the displacer about said axis is unaffected by the contents of the vessel.

4:. In apparatus for measuring the specific gravity of a fluid, a rocking arm, a hollow displacer supported by the arm and which is of fixed capacity and is adapted to move in response to variations in'the specific gravity of the fluid to be measured, a sealed flexible vessel, means placing the vessel in communication with the interior of the displacer and symmetrically disposed about a vertical plane passing through the pivotal axis of the arm, the displacer and flexible vessel being adapted to be filled with fluid and the flexible vessel permitting fluid to pass out of and into the displacer to compensate for variations in the specific gravity, due to variations in temperature of the fluid to be measured.

5. In apparatus for measuring the specific gravity of a liquid, a rocking arm, a hollow displacer carried by the rocking arm and of fixed capacity, the displacer being adapted to be filled with liquid and adapted to move in response to variations in the specific gravity ofthe liquidto be measured, and a sealed vessel means placing the vessel in communication with the interior of the displacer and partially filled with liquid so that the point of communication with the displacer is constantly under liquid seal, the vessel being so arranged that its contents are symmetrical about a vertical plane'passing t rough thepivotal axis of the arm so that liquid can pass between thedisplacer and vessel'to compensate for variations in the specific gravity, due to variations in temperature of the liquid to be measured. 1

' In testimony that I claim the foregoing as my invention I have signed my name this 14th day of January, 1931.

JOHN LAWRENCE HODGSO-N.