US2911992A - Controller - Google Patents

Description

Nov. 10, 1959 R. B. WATROUS CONTROLLER Filed Dec. 13, 1957 FlG.l l3,

2 Sheets-Sheet 1 coun 28W-- WEIGHT IN VEN TOR.

ROBERT B. WAT ROUS W/VW ATTORNEY.

Nov. 10, 1959 Filed D80. 13, 1957 INVENTOR ROBERT B. WATROUS ATTORNEY.

United States Patent CONTROLLER Robert B. Watrous, Philadelphia, Pa., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application December 13, 1957, Serial No. 702,642

9 Claims. (Cl. 137-86) This invention relates to means operated by the pressure of an elastic fluid for producing an output which varies as the square root of an input. More specifically, these means include: a valve controlling the pressure of an elastic output fluid, such as compressed air; input means operating said valve and thereby varying the pressure of said output fluid in one sense; a pair of flat, flexible diaphragms equal in area and connected to each other at their perimeters and at their centers and free to move at their centers relative to their perimeters; means applying said output fluid to two, oppositely-acting, variably-effective faces of said diaphragms; one of the relatively movable portions of said diaphragms being movable with said valve and operating said valve and therefore the pressure of said output fluid in the sense opposite to the sense in which said valve is operated by said input means; and elastic-fluidpressure-operated means responsive to the pressure of said output fluid and providing an output which varies as the square root of said force exerted by said input means.

Means such as those described in the preceding paragraph are disclosed as the prior invention of Robert B.

Watrous and Robert E. Ochs, Jr., in application Serial No. 461,084; filed October 8, 1954, now Patent Number 2,874,713.

The device of the prior invention is entirely satisfactory in practical operation. However, under certain circumstances, it is desirable to provide the two diaphr'agms with a greater range of movement than is possible under the prior invention.

This invention, therefore, discloses four ways in which the two diaphragms may be given a greater range of movement. Essentially, this is done by providing, in addition to the pair of diaphragms recited above, an additional elastic-pressure-fluid-operated means, such as a flexible bellows, which acts to vary the valve and therefore the pressure of the output fluid in the opposite direction to that in which it is operated by said input means.

More specifically, two of the modifications disclosed herein attain the additional range of motion of the two diaphragms by making both the relatively movable parts of the valve, hereinafter referred to as the flapper and the nozzle, respectively, movable.

Another way in which this additional range of movement of the two diaphragms is secured is to cause the pair of diaphragms, above referred to, and the additional elastic-fluid-pressure-operated means to act in series with one another on the valve and to therefore increase the range of movement of the two diaphragms.

Accordingly, the general object of the present invention is to provide elastic-fluid-pressure-operated means for providing an output which varies as the square root of the input and which includes two diaphragms having an increased range of movement over those heretofore used.

A better understanding of the present invention may be had from the following detailed description when read in connection with the accompanying drawings, in which:

Fig. 1 is a diagrammatic or schematic representation 2,911,992 Patented Nov. 10, 1959 ice Of ne embodiment of the device with parts shown in vertical cross section;

Fig. 2 is a similar view of a modification;

Fig. 3 is a'similar view of a second modification; and

Fig. 4 is a similar view of a third modification.

In the form of the invention illustrated in Fig. 1, by way of example, 1 designates a rigid, stationary casing forming the body portion or outer wall of error compensating diaphragm mechanism comprising error compensating diaphragm sheets or membranes 2 and 3 which are equal to each other in size. Diaphragms 3 and 2 have their peripheral edges secured to'the casing 1. The centers of diaphragms 2 and 3 have similar, rigid, central, disc elements 5 and 6, respectively, which are intergrally connected by a shaft 7 within and coaxial with the cylindrical space in the casing 1 in which the diaphragms 2 and 3 V are "mounted. The area of one of the disc elements 5 or 6 is less than three percent of the area of one of the dia-' phragms 2 ori3. Diaphragms 2 and 3 are normally in the form of slack membranes which bend but do not stretch and which bulge towards or away from one another when fluid under pressure, for example, compressed air, is applied to the outer sides of the diaphragms or fills the chamber 8 enclosed by the diaphragms and the annular wall of easing 1. Chamber 8 is an error compensating chamber. Shaft 7 comprises one, relatively-movable element, hereinafter called the flapper, of a valve. The other element of this valve is constituted by a hollow nozzle9 which is connected by a conduit 10 to the motor chamber of a pilot valve or relay 11. Such a pilot valve or relay 11 is a well known, commercially available article, such as'is disclosed in US. Patent 2,125,081; patented July 26, 1938; to C. B. Moore. Pilot valve or relay 11 is connected to a supply of elastic fluid under pressure, such as a filtered air supply, marked F.A.S. in the drawing. A conduit 12 connects this supply of air to the pilot valve or relay 1 1.

If desired, the pilot valve or relay may be omitted, in some cases, and the nozzle of the valve constituted by the flapper'7 and the nozzle 9 connected directly to the source F.A'.S. through a restriction of reduced cross section (not shown). Pilot valve or relay '11, or if the pilot valve or relay 1-1 is omitted, the nozzle 9, is connected to an output pipe 13 adapted to provide a supply of output pressure herein referred to as P(out). Pressure P(out) is conducted to an elas'tic-fluid-pressure-operated output element 14 such as a meter, recorder or controller.

Output pipe 13 is also connected, by a branch pipe '15, to the space 30 between a pair of bellows 16 and 17. Bellows 16 and 17 each have one end attached to casing 1 and the other end free to move. The nozzle 9 is mounted on the free or movable end of bellows 16 and 17. A cantilever spring 18 is fixed at one end and bears, at its free or movable end, a manually adjustable screw 19 which contacts with the free end of the movable bellows 16 and 17 and thus serves to adjust the position of nozzle'9.

Output pipe '13 is connected by a second branch pipe 22 to the space 8 between the diaphragms '2 and 3. The nozzle 9 discharges into space 29 which communicates with the atmosphere through an opening 21 in casing 1.

In this embodiment of the invention, the input device is in the form of an input pressure P(in) which is applied by means of a conduit 23 to a bellows 24 having one end fixed to ground or a stationary element and its upper end 25 movable. The free or movable end 25 of bellows 24 engages lever 26 which is mounted on a pivot;27. Pivot 27 is adjustable horizontally, as shown in Fig. 1, and thus provides adjustment of the span of the device.

To one end of lever 26 is connected one 'end of a spring 28, which is connected at its other end to casing 1. Spring 28 is adjustable to serve as a suppression 3 spring. The opposite end of lever 26 is connected by a w link 31 with the flapper 7.

Operation The input pressure P(in) is a liquid or fluid pressure proportional to the square of the variable being measured. It may be furnished directly by a measuring element or the measuring element may operate a pilot valve or relay which converts the changes in the variable being measured to changes in elastic-fluid-pressure. Assuming that the instrument has been properly installed and calibrated and is at balance, a change in the input pressure P(in) in bellows 24 causes lever 26 to rock about its pivot 27 and thus causes link 31 to move flapper 7 relative to nozzle 9 and varies the output fluid pressure P(out) in conduit 13. The pressure of this output fluid P(out) operates the indicator, recorder or controller 14.

This output pressure P(out) in conduit 13 passes through branch conduit 15 to the chamber 30 between bellows 16 and 17 and thereby varies the pressure in this chamber. This variation of the output pressure P(out) in the chamber 30 causes nozzle 9 to move against the pressure of cantilever spring 18 in such a way as to operate the valve so as to vary the output pressure P(out) in the sense opposite to the sense in which the valve was caused to operate by the change in the input pressure P(in).

The change in pressure of the output fluid P(out) in pipe 13 is also fed by means of branch conduit 22 to the space 8 between the diaphragms 2 and 3. The way in which diaphragms 2 and 3 act is as follows. The output pressure P(out) applied to the chamber 8 causes the diaphragms 2 and 3 to bridge or bow away from each other. This output pressure P(out) applies a biasing force which causes the diaphragms 2 and 3 to assume a normal or zero position in which the biasing force equals the loading force. If the loading force varies, the central portions of the diaphragms 2 and 3 and the flapper 7 attached thereto will move linearly, i.e. by increments which are substantially directly proportional to the changes in loading force. As the central portions of the diaphragms 2 and 3 move away from their normal or zero position, for example, down as seen in Fig. l, the active area of diaphragm 3 increases and the effective area of diaphragm 2 decreases producing a net area on which the diflerent pressures acting on the opposite sides of the diaphrgams 2 and 3 and, consequently, on this net area, produce a restoring force which is analogous to the force of a spring. This restoring force is in opposition to the loading force no matter in which direction the loading force is applied. Since the efiective area of the diaphragms 2 and 3 varies and since the pressure applied to the chamber 8 varies, these two variations may be suitably proportioned so as to cause the output pressure P(out) to vary as the square root of the input force, in this case, the input pressure P(in).

For a detailed explanation of the operation of the pneumatic spring constituted by easing 1, diaphragms 2 and 3 and flapper 7, reference may be had to applicants prior co-pending, joint application Serial No. 461,084, Patent No. 2,874,713 mentioned above.

The mathematical basis for this invention is as follows:

These equations apply to Fig. 2. Let

A equal the net area of diaphragms 2 and 3 A equal the efliective area of input bellows 24 A; equal the effective area between the nozzle-position ing bellows 16 and 17 K equal the gradient of the cantilever spring 18.

X equal the motion of flapper 7 relative to stationary casing.

Y equal the distance between flapper 7 and nozzle 9.

C, C C C C equal constants From the foregoing it will be seen that (1) A.=C +C'X multiplied by at a condition of force balance P m (0111;) by substituting (1), (2), (3), into (4) we get 1 CO2 W +P wes-00+;

which can be written in out) out This is the desired square root equation where D, E, and F are constants.

Modification of Fig. 2

Fig. 2 shows a modification in which all the bellows or diaphragms which actuate the valve (constituted by the nozzle 7 and the flapper 9) have a common axis or center and are stacked or mounted in casing 1.

Casing 1 has within it a chamber 33 which communicates with the atmosphere through a hole 34. The nozzle-positioning spring 18A is a compression spring and acts on the upper or free end of the bellows 16 and 17 which define a chamber 30 between them.

Nozzle 9 is mounted on the free ends of bellows 16 and 17 and communicates by means of pipe 10 with a pilot valve or relay 11 having an output conduit 13 communicating with an indicator, recorder or controller 14. Pipe 13 also communicates by means of branch conduit 15 with chamber 30 and, by means of branch conduit 22, with chamber 8 between diaphragms 2 and 3. The outer face of diaphragm 2 is exposed to the atmospheric pressure in chamber 31 by means of hole 32.

In this modification, the lever 26 is omitted since the flapper 7 is mounted directly on the free end 25 of an input element formed of bellows 24 and additional bellows 24A, which define a chamber 24C between them. Conduit 23 conducts the input pressure P(in) to the chamber 24C.

Suppression of the device is attained by means of a weight 28W mounted on the flapper 7. This requires that the device be mounted with the axis of the flapper 7 and nozzle 9 vertical.

The operation of this modification of the invention is the same as the operation of that of Fig. 1.

Modification of Fig. 3

Fig. 3 shows a modification in which the increased movement of the two diaphragms 2 and 3 is attained by mounting the first feedback bellows 16A and the second feedback means constituted by the diaphragms 2 and 3 so that the forces which they each exert on the value constituted by the flapper 7 and the nozzle 9 are applied in series with each other.

In this modification, the input means for operating the valve 7-9 is illustrated by an arrow to which the legend F (in) is applied. The input force P(in) is applied directly to the flapper 7B which is mounted on a suitable pivot 7A on a stationary support 76. Flapper 7B cooperates with a stationary nozzle 9 connected by a conduit 10 to a pilot valve or relay 11 whose output conduit 13 is connected to a meter, recorder, or controller 14.

Pipe 13 is also connected by means of branch pipe 15 with the interior 30 of a first feedback element constituted by a bellows 16A and mounted on a stationary support 29. The free or movable end of bellows 16A carries a rigid cup 35 on it. Cup 35 supports the perimeters of the diaphragms 2 and 3 so that the diaphragms 2 and 3 define a chamber 8 between them. Flapper 7 is connected to the center of diaphragms 2 and 3 and bears on pivoted flapper 7B. Beneath the outer face of diaphragm 3 is a chamber 20 vented to atmosphere through opening 21.

The operation of this modification of this invention is as follows. Starting from a balanced or steady state condition, if the input force F(in) changes, the pivoted flapper 7B is moved toward or away from the stationary nozzle 9. This causes the output pressure P(out) from pilot valve or relay 11 to change. This change in pressure of output fluid P(out) actuates the indicator, recorder or controller 14. The output pressure P(out) is also fed through branch conduit 15 to the chamber 30 and causes the bellows 16A to move away from or toward the flapper 7. The output pressure P(out) is also fed through branch conduit 22 to the chamber 8 between the diaphragms 2 and 3. This change in the pressure in chamber 8' also causes flapper 7 to act in series with the movable end of bellows 16A to apply a force to the pivoted flapper 7B in such a way as to vary the output pressure P(out) in a sense opposite to that in which the output pressure was varied by the input force F(in). By suitably proportionin'g the change in effective area of the diaphragms 2 and 3 and the change in the pressure of the output fluid P(out) applied to the chamber 8, the flapper 7 can be made to move in such a way as to compensate for the non-linear character of the change in input force F(in). The change in pressure of the fluid applied to chamber 30 causes the two diaphragms 2 and 3 to move further than they otherwise would.

Modification of Fig. '4

The construction and mode of operation of this modification of the present invention are very similar to those of the modification shown in Fig. 3. The'difference is that the relative position of the bellows 16A and of the diaphragms 2 and 3 is reversed. However, the forces exerted by the bellows 16A and by the diaphragms 2 and 3 on the valve constituted by the flapper 7 and the nozzle 9 is the same, that is to say, the force exerted by the bellows 16A and the force exerted by the diaphragms 2 and 3 are in series.

What is claimed is:

1. Means for producing an output which varies as the square root of an input, including: a valve controlling the pressure of an output fluid; input means operating said valve and thereby varying the pressure of said output fluid in one sense; first means responsive to the pressure of said output fluid and tending to operate said valve and therefore to vary the pressure of said output fluid in the opposite sense to the sense in which the pressure of said output fluid is varied by said input means; second means having movable operating surfaces each acting opposite to the other and of equal areas and of varying eifective areas responsive to the pressure of said output fluid, the product of said effective area and of the pressure of said output fluid varying as the square of the variation in the pressure of said output fluid, said second means tending to operate said valve so that the pressure of said output fluid varies in the sense opposite to the sense in which the pressure of said output fluid is varied by said input means; and fluid-pressure-operated means responsive to the pressure of said output fluid and providing an output which varies as the square root of the force exerted by said input means.

2. Means according to claim 1 in which said second means act in series with said first means on said valve and to vary the force of said first means and of said second means on said valve.

3. Means according to claim 1 in which said first means is a flexible bellows having a portion thereof movable by the pressure of said output fluid.

4. Means for producing an output which varies as the square root of an input, including: a valve controlling the pressure of an output fluid; input means operating said valve and thereby varying the pressure of said output fluid in one sense; first means responsive to the pressure of said output fluid and tending to operate said valve and therefore to vary the pressure of said output fluid in the opposite sense to the sense in which the pressure of said output fluid is varied by said input means; a pair of slack, flexible diaphragms equal in area and connected to each other at their perimeters and at their centers and free to move at their centers relative to their perimeters; means to apply the pressure of said output fluid to two, oppositely-acting, variably-effective faces of said diaphragms; one of said relatively movable portions of said diaphragms being movable in response to the pressure of said output fluid and operating said valve and there'- fore varying the pressure of said output fluid in said opposite sense; and fluid-pressure-operated means responsive to the pressure of said output fluid and providing an output which varies ,as the square root of the force exerted by said input means.

5. Means for producing an output which varies as the square root of an input, including: a valve controlling the pressure of an output fluid; input means operating said valve and thereby varying the pressure of said output fluid in one sense; first means having a movable portion responsive to the pressure of said output fluid and tending to operate said valve and therefore to vary the pressure of said output fluid in the opposite sense to the sense in which the pressure of said output fluid is varied by said input means; a pair of slack, flexible diaphragms equal in area and connected to each other at their perimeters. and at their centers and free to move at their centers relative to their perimeters; means to apply the pressure of said output fluid to two, oppositely-acting, variably-effective faces of said diaphragms; one of the relatively movable portions of said diaphragms being movable with the movable portion of said first means and the other of the relatively movable portions of said diaphragms being movable with said valve and operating said valve and therefore varying the pressure of said output fluid in said opposite sense, said diaphragms transmitting the force of said first means to operate said valve; and fluid-pressure-operated means responsive to the pressure of said output fluid and providing an output which varies as the square root of the force exerted by said input means.

6. A force-to-pressure transducer producing an output air pressure which varies as the square root of an input force, including: a valve comprising a relatively movable flapper and nozzle connected to a supply of air under pressure and varying the pressure of output air; input means operating said valve in one sense and thereby varying the pressure of said output air in one sense; a flexible bellows having a portion thereof movable by the pressure of said output air and tending to operate said valve in the opposite sense; a rigid cup mounted on the movable portion of said bellows; a spring opposing the movement of the movable portion of said bellows and tending to operate said valve in said one sense, the changes in the force exerted by said spring upon movement thereof being much greater than the changes in the pressure of said output air; a pair of slack, flexible diaphragms equal in area and connected to each other at their perimeters and at their centers and free to move at their centers relative to their perimeters; means to apply the pressure of said output air to two, oppositely-acting, variably-efiective faces of said diaphragms; one of the relatively movable portions of said diaphrgams being movable with said cup and the other of the relatively movable portions of said diaphragms being movable with said valve and operating said valve in the opposite sense, said diaphragms transmitting the force of the movable portion of said bellows to operate said valve; a pilot valve controlled by said flapper-nozzle valve and varying the pressure or" said output air; and airpressure-operated output means responsive to the pres sure of said output air and providing an output which "7 varies as the square root of the force exerted by said input means. i

7. An elastic-fiuid-pressure-operated square root extraction, including, an input means to which is applied an input force, an output bellows to which is applied an output pressure varied in consequence of said input force, a pair of error-compensating diaphragms to which is applied said output pressure and having an effective area which varies as said output pressure varies, and a valve adapted for movement in one direction by said input member and in the opposite direction by said output bellows and by said error-compensating diaphragms, said member causing said output pressure to vary as the square root of said input force.

8. An elastic-fiuid-pressure-operated square root extractor, including, an input chamber having a movable wall to which an input pressure is applied, an output chamber having a movable wall to which the output pressure is applied, a pivotally mounted lever, connections between said lever and said movable members whereby said movable members move said lever in opposite directions, a flapper-and-nozzle valve actuated by said lever so as to control said output pressure by varying the flow of air through said valve, a pilot valve connected under the control of said flapper-and-nozzle valve so as to be actuated by the escape of air therethrough, the output of said pilot valve forming said output pressure, a conduit connecting said pilot valve to said output chamber to conduct the output pressure of said pilot valve to said chamber so that the pressure in said outlet chamber varies, an error-compensating chamber having a pair of oppositely acting movable walls, 'a conduit connecting said pilot valve to said error-compensating chamber to conduct the output pres sure thereto, and a spring connecting said lever to ground to actuate said lever in the opposite direction to said input pressure, said output chamber and said error-compensating chamber having movable connection with said flapperand-nozzle valve so as to actuate said valve in the direction opposite to that in which said valve is operated by said input chamber.

9. In a meter for continuously measuring the square root of a measured variable, an input member means to move said input member a distance proportional to the variations in the variable being measured, valve means for transforming the movement of said input member into variations in a fluid pressure, and means co-acting with said input member to modify the movement of said input member to cause it to follow the true, substantially square root relation of said measured variable and comprising means to apply said variations in the fluid pressure to move said input member with a linearly varying motion in the direction opposite to its movement by said input member, and second means to move said input member with a non-linearly varying motion in the direction opposite to its movement by said input member.

References Cited in the file of this patent UNITED STATES PATENTS 2,672,151 Newbold Mar. 16, 1951 2,698,023 Eckman Dec. 28, 1954 2,834,363 Pessen May 13, 1958

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