US 3243112 A
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Description (OCR text may contain errors)
Filed Sept. 16, 1963 2 Sheets-Sheet 1 JJI r. P2 z 1 J OUTPUT Temperature Differential Pressure Transmitter PI'GSSUII'G Transmitter T m I I 17 FLOW 2+ 17/ o, P T.
ORIFICE INVENTOR March 29, 1966 J. SORTEBERG WEIGHBEAM SYSTEM Filed Sept. 16, 1963 2 Sheets-Sheet z Fol l Kessaru; $15M. ccNvezsro I gwmx 5 Pmx Pmax max Emu- Fmt TEMFEKATUZE $(GNAL com 5am fanf= max Plane? ARALLELOGRAM or FOR6ES 5" K P CREATED BY KNEE Bki Kil' w United States Patent 3,243,112 WEIGHBEAM SYSTEM Johannes Sorteberg, Darien, Conn. (540 Connecticut Ave., South Nor-walk, Conn.) Filed Sept. 16, 1963, Ser. No. 309,061 3 Claims. (Cl. 235-200) The object of my present invention is to devise a novel control system or means for expressing mechanically the formula for a straight line, y=Kx+C (in a right angle coordinate system with x and y being the coordinates).
A further object of the invention is to use it as an auxiliary device in gas flow measurements when it is desired to compensate such measurements for absolute temperature and/ or pressure. A further object of the invention is to devise a novel construtcion and arrangement of the component parts to obtain'the results herein set forth.
For the purpose of illustrating the invention, I have shown in the accompanying drawings a preferred embodiment of it which I have found in practice to give satisfactory and reliable results; It is, howeyer,'to.beunderstood that the various instrumentalities of which the invention consists can be variously arranged and organized and the invention is not limited, except by the scope of the appended claims to the exact arrangement and organization of these instrumentalities as herein set forth.
FIGURE 1 is a diagrammatic view of a weighbeam system embodying my invention. 7
FIGURE 2 is an enlarged sectional view showing more clearly, the construction and arrangement of the kneebracket and its cooperating parts.
FIGURE 3 is an exploded view of the parts seen in FIGURE 2.
FIGURE 4 is a diagram of transmitter signal (s) plotted against pressure (p) showing the relationship be tween the output signal from a hypothetical absolute pressure transmitter represented by line Z M and the output signal from transmitter 17 represented by the line 0M.
- FIGURE 5 is a diagram of transmitter signal (s) plotted against temperature (t) showing the relationship between the output signal from a hypothetical absolute temperature transmitter represented by line Z M and the output signalfrom transmitter 16, represented by line 0M. I
. FIGURE 6 is a'diagram showing the principle of the parallelogram of forces applied. to both pressure and temperature signal conversion.
Similar numerals of parts. g
Referring to the drawings:
Referring fiISLtoFIGURE 1. This figure shows .a mechanical embodiment of the invention as used in combination with a Force Bridge in a measuring circuit. Only the principal elements of the Force Bridge are shown.
Refer to Patent No. 2,643,055 for complete details. F is the main frame of the Bridge. W and W are the weighbeams. R and R are the rollers which provide the movable fulcrums F and F A, B, C and D are the four forces automatically kept in balance in accordance with the Force Bridge formula A C=B D, or
D C- XB I and II are similar load cells, each consisting of bellows 1 in a housing 2, mounted on a base 3, which in turn is mounted on a bracket 4 supported on a frame F. Thrust rod 5 freely mounted in a tapered hole in a kneebracket 6, and bearing against a ball 6 transmits the force created by the load cell to said kneebracket supporting a shaft 7 reference indicate corresponding 1 and bearing 8, the rim of which rests against a rotatable plane 9 which is journalled in bracket 4. A second thrust rod 10 fixed in the other arm of kneebracket 6, transmits the force originating in the load cell but modified by means of the plane and bearing in accordance with principle of parallelogram of forces (see FIGURE 6). A spring 11 creates a force which is transmitted to rod 10 through washer 12 and is adjustable by means of Washer 13, said washer 13 being provided with a clearance from the kneebracket 6. This force is independent of the force orginating in the load cell. Together these forces create force A and/or B which are transmitted to the weighbeam. Load cells III and IV-consist only of parts similar to 1, 2, 3, and 5. Their thrust rods 5 act directly on weighbeam W A pipeline 14 has an orifice 15. A temperature transmitter 16 with range T to T transmits signals 0 to scorresponding respectively to T and T to load cell I. A pressure transmitter 17 with a range P to P transmits signals 0 to Sp to load cell II. A differential pressure transmitter 18 with range d to d transmits signals 0 to s to load cell IV. Load cell III transmits the compensated output signal of the Force Bridge to its point of use. 1
With further reference to FIGURE 4 it should be noted that:
P =lower limit for pressure transmitter 17 P =upper limit for pressure transmitter 17.,
K =tan QP= L u angle between OTI and (TE a =angle between WI andfil s =maximum signal from transmitter 17 a='constant=K P 1: any given pressure within the range of transmitter 17 7 pl: p
With further reference to FIGURE S it should be noted that:
T =lower limit for temperature transmitter 16 'T =upper limit for temperature transmitter 16 Briefly the system operates as follows:
Air is supplied to nozzles NL and NR which oppose weighbeam extensions, baffles 19 and 20. The back pressure from nozzle NL is transmitted through tube 21 to air motor AM which positions fulcrum rollers R and R The back pressure from nozzle NR is transmitted through tube 22 to load cell III and the output tube. Assume that both weighbeams are in balance, i.e., A a=B b and D a=C b. If now, for instance, force A increases, bafiie 19 will move towards NL, increasing the back pressure and the air motor will move the fulcrum rollers to the left until W is again in balance. This movement of the rollers will have the effect of unbalancin-g W in such a way as to move bafiie 20 away from nozzle NR and dropping the back pressure, but this will decrease force C until W is again in equilibrium or balance.
A typical example of the usefulness of the invention is in connection with gas flow measurements. The general formula for gas flow is:
wherein The above formula can also be written Q =c /E where P 1: d d
The Force Bridge is used to solve the formula P l: d d
with A representing T, B representing P, D representing d and C representing d l. The force created by a load cell is equal to the signal value multiplied by the effective area of the bellows, and I will, in order'to simplify matters, assume the effective area of each load cell to be 1. Thus, I can substitute signal values for forces in the formula, which can now be written In order to make temperature compensation for the gas volume in accordance with formula it is necessary to produce a signal proportionate to the absolute temperature values in the interval considered. This can be done in two ways: a
(1) Employ an absolute temperature transmitter pro? ducing an output signal at Z (absolute zero tempera-v ture) and a signal sTmax at T transmitting directly to a load cell similar to cells III or IV engaging the weighbeams directly, or:
(2) Use a converter such as this invention covers in combination with transmitter 16 to produce the absolute temperature signals in the temperature span considered, T1 to T Similar consideration applies to the pressure compensation.
By referring to FIGURE 4 it is evident that the signal values representing the absolute pressure at any point P PP+ and similarly, by reference to FIGURE 5 the signal value representing the absolute temperature at any point T isi In my construction the constants a and b are produced by the spring 11 and the variables are produced by respective load cells in combination with their knee-brackets. (See FIGURE 6.)
In these equations:
I Should be n e t b urning h p an a tmnd the bearing axis, constants K and K; can be made to have any value between 0 and 00. It should further be noted h the above qu t ns $=KBV+ and =KTt+b oth represent straight lines, a general form of which is =K in a. right angle coor nate stem With x and y as coordinates. K and C are constants,
Having thus described my invention, what I claim as new and wish to secur y Letters Patent is:
1. A device for generating a variable function com.- prising, means e c i i a a ab e si na a d scavening it to a force, means for applying said force to, a paralr lelogram me h c ran eme t c m ri n n; n u
thrust member receiving said force, an output member,
a circular bearing articulated to said members and servin a a u r the or a a P ne u ac m u ted for adjustment tangentially to said circular bearing, said plane serving to modify the force input at the input member to produce an output at said output member proportionate to the tangent of the angle between the input member and a perpendicular to said plane surface and means for applying a further adjustable force to said output member.
2. A device according to claim 1 wherein the first force applied to said output thrust member represents the product of the input force and the tangent of the afore: said angle and wherein said further force is added t9 said product, 1 a
3. A device according to claim lwherein said input and output thrust members are in a perpendicular rela tionship'to each other.
References Cited by the Examiner UNITED STATES PATENTS 2,643,055
LEO SMILOW, Pr'imary Examiner. I
T. J. ANDERSON, Assistant Examiner.