US2053885A - Pressure-actuated control apparatus - Google Patents

Description

Sept 8, 1936. s. s. WEEKS 2,053,885-

PRESSURE ACTUATED CONTROL APPARATUS` Filed Dec. 13, 1934 Patented Sept. 8, 1936 UNITED STATES PATENT oEFlcE PRESSURE-ACTUATED CONTROL APPARATUS 2 Claims.

This invention relates to improvements in pressure-actuated control apparatus. It is herein particularly described in its application to a boiler installation where it is desired to exercise automatic control of the agencies affecting the fire' conditions by means responsive to changes in the steam pressure of the boiler. In its broader aspects the invention is adaptable to the control of any fluid subject to pressure changes.

An object of the invention is to provide irnproved apparatus of the so-called step action type having the advantageous exactitude of adjustment of re controlling factors characteristic of such step action, but having further the capacity of employing as many steps as may be desired with exceedingly small increments between consecutive steps, thus making possible much closer regulation than heretofore. This improved result is obtained, according to my invention, by apparatus of marked simplicity, small size and long life, easy to install and adjust.

It is a feature of the invention that the change of pressure which actuates the control is imposed upon a diaphragm normally in balance, as it were, or subjected to equal forces on both sides. This enables a highly sensitive element to be employed and insures alertly responsive action to a relatively small change in pressure. Moreover, the apparatus is so constructed and arranged that Whenever the diaphragm is flexed the resulting operation promptly reestablishes the balance of forces acting on the diaphragm, thus enabling it to resume its unflexed or most sensitive position. And this is so regardless of the particular step in the range of action whereat the apparatus is awaiting a change of pressure. The enhanced sensitivity, the provision for exact and nice adjustment, and the exceptional simplicity of the mechanism, result in control apparatus capable of rendering a most satisfactory performance.

The accompanying drawing shows the best modein which I have contemplated applying the principles of my invention, but these are to be taken as merely illustrative because it is intended that the patent shall cover by suitable expression in the appended claims whatever features of patentable novelty exist in the invention as a whole.

In the accompanying drawing:

Figure 1 is a plan, partly in section as on line I-I of Figure 2, of apparatus illustrative of my invention;

Figure 2 is a side elevation, viewed as on line 2--2 of Figure 1; and

Figure 3 is an elevation of a detail.

.Referring more particularly to the drawing,

the actuating pressure is conducted by a pipe I from a source such as the boiler system of a power plant to a chamber 2 where it is applied to a diaphragm 3. The latter may be made of highly sensitive material since, as will presently appear, the forces acting upon its opposite sides are normally in balance, and its responsive flexures are occasioned by comparatively small deviations from the normal counterbalanced condition. The edge of the diaphragm is tightly clamped between a suitably shaped frame member 4 and a cover 5, and its center is secured to a stem 6 between a backing plate 'I and a face plate 8 by nuts 9. A coiled spring I6 seats at one end on the backing plate 'I and at its other end seats against a collar II which in turn rests upon a hollow adjusting screw I2 threaded into a portion 4a of the frame member 4. The stem 6 passes freely through both the collar and the adjusting screw and beyond them is provided with a reduced threaded portion Ba to which, by means of nuts I3,'is secured an arm I4 preferably made up of two strips I4a and I4bof resilient material.

The separated ends of these strips carry a short threaded rod I5 on which are provided adjusting nuts I6, I6 each of which is arranged to engage respectively an operating plunger I'I, I'I of a sensitive electric switch I8, I8 such as a Burgess micro switch. A movement of only a few thousandths of an inch will alter the setting of such switches. They are here indicated diagrammatically as of the type tending to remain open and each is electrically connected in series with a similar sensitive switch I9, I9 which normally stands closed. Both sets of switches control an electric circuit, represented diagrammatically by dot-and-dash lines 20, 2|, 22, 23, 24, 25 and 26, which connect the power lines Z and switches with a reversible motor 2l. This motor, by suitable gearing, 28, 29, 30, 3I and 32, also shown somewhat diagrammatically, is connected to a gear on what is hereinafter termed a control shaft 34. This shaft carries an element 35 which may be connected by any suitable means (not shown) with the dampers governing the air flow through a boiler system and with valves or other agencies which regulate the feed of fuel to the combustion chamber.

Mounted on the control shaft 34 is a cam element 36 comprising a hub and a series of adjustable cam faces disposed therearound. Each such cam face is herein shown as a roller 3l mounted on a sort of crank shaft 38a (see Figure 3) which is provided eccentrically on a main shaft CII or shank 38. These shanks are inserted in radially disposed sockets 36a distributed around the hub circumferentially and disposed progressively along the hub, that is, axially or longitudinally thereof, to dene a helix around the hub'. Each roller may be adjusted axially with respect to the axis of the hub, or the shaft 34, by merely rotating its supporting shaft 38 in its socket in the hub and when positioned as desired each shaft l may be locked by a set screw 39 against inadvertent displacement. Each roller, of which there is here shown a series numbered 31a, 311), 31e, 31d, 31e, 31] and 31g, represents one step of the step acl tion control and since each roller is individually. adjustable, the apparatus can be nicely adjusted'V at each step without altering or disturbing the adjustment of any other step.

As the cam element revolves .with the control shaft 34 the several adjustable rollers .successively engage an arcuate arm 48 on the endof a'.V bar M Carriedby a pair Vof .levers 42,43 pivotallyv mounted on the irarnelt. One of ,these leversA has a Pair of shortarmsgd Which bear on a sleeve.

paratus letitbe` assumed that the normal steam pressure to be carriedon the boiler system is to besubstantially 10 0 po und s per square inch. Assumeiurthenfor example, that the effective area of the diaphragmis twelve square inches. Under such-assumptions thetotal pressure or force eX- erted on the right side of the diaphragm is 1200 pounds. To initially adjust theapparatus for this pressure, ,the ha nd switch 48 is .'lrst thrown out and2 with ,the `Y a1.n element 36. preferably Asot as shownin Figure' ;1, .that is, withthe median roller ldoi ,theseries in eontact withthe arcuate 4j), the springs Ill and .41 are adjusted toestablish a .balanced condition of forces acting on the dia- Phlagm..

,The larger. shrine. lil Should bo. of.'A Cons.i ion=1}l51r Strength Sonnet ,when its ,foroo is imposed upon the lett side of the diaphragm the greater pornonni, the ootnatinaprossuro will bo opposed.-

Flor exampleslet the adjusting screw 2 be turned until ,Spring .1415 oxortineonproximatoly a .foros of r11,1()` pounds on the. backing plate 1. The sleeve nut 4,8 is nextfturned until the forceexertedby spring 41 counterbalances ,the remainder o f the actuatingpressure, The total force now acting on thelleftside Vof the diaphragm is equal and in opposition to the pressure on itsright side. Thus thehorfnal counterbalanced condition is establishedwiththe diaphragm. unlexed and in its most sensitive position as shown' Figure 1'.

u The nutsl3 on the reduced portion `ci the diavphra'gm stem m ay now be adjusted to position the arm |14 so that its resilient ends |411, |412 are midway between the plungers l1 and. l1 of the sensitive switches I8 and I8 respectively. The nuts I6.,..|6.'..1nay be Autilized for the renement of this adjustment.. TheY manual switch 48 is now closed andethe apparatus. is ready to assume automatic controlof the fireaffecting-agencies it being understood, ofcourse, that with the roller 31d in contact with the arm 4Q, the position of element 35 and the corresponding settings of the air and fuel regulating agencies are such as to maintain a steam pressure of pounds so long as the dcmand on the boiler remains unchanged.

If this demand should increase, however, the resulting eiiect will be a drop in the steam pressure. Since the forces acting on the diaphragm are in balance, a relatively small reduction in the steam prcssureiorexample a half pound or evenl less, will be sufficient tolaect an response by the diaphragm. The latter will flex to the right a slight amount but still sufcient to cause the resilient end |41) of the arm i4 to move plunger I1 a. ewthdusahdths of an inch and thereby close switch i8. This establishes the circuit through wire ,28,g switch, I9 (normally closed) wire 2l, switch l8',"wli"e"22, motor 21 and wire 26. The motor is. accordingly rotated and causes rotation of gear ,33 and shaft 34 in the direction indicated 'by' the a'r'row A. This will open up the fuel regulators and dampers and bring about. an' increase in the re conditions to .produce additional steam to satisfy the increased demand.

As the.shaft 34. rotates, roller.3'1d rides along the arm 40 and ci its tapered end'lla, thus allowing the arm t'o m'ove toward the rightand into engagement' with roller .31e. Simultaneously withV the movement of. the bar 4l,A lever 42L is swung clockwise. The leftwise swing of' its short arms 42a releases the compression on spring 41 and correspondingly decreases the force exerted by this spring on the diaphragm If this reducticnis suiiicient to odset the reduction in steam plessure .caused by the increased demandl on the boilenthe diaphragm is again under balanced conditions andr will return' to .its unilexed positicn. This will move arm i4 and its; end: |4b so as to permit switch 13" to` open and thus break' the circuit through themotor. The latter willv promptly stop, such slight overrun as may occur being negligible inasmuch as theroller thenin contact with the arm 40, canV roll along its flat face.

I f` the reducticn in foi'ceof ,the spring 41 is not enoughto eiect acounterbalanced condition on' the diaphragm, the latter remains exed, until the (step oi the apparatus is reachedat which Vthe .opposing forces acting on the diaphraern'are brought into balance. Thereupon, as already de-` scribedthe diaphragm is restored to its initial unflexedccndition withtheiorces acting upon it in balanced relation. To prevent yany damageto the apparatus, as where an extreme reductionin steam pressuremight occun; a cam 49 is provided`V on Shaft ,Si which. .in duo course engages a resilient arm andforces `it against plunger 5l of switch i8 to cause the latter toopen and break tno. enereiznaoirouit through the motor.` This stops further operation of the apparatus in this direction butstill leaves all the elements inposi'fV tion to respond in the reverse .direction upon rostoration of the steampressure withinthe operative .range of thedevine-V Incidentally, no Aharm is done to the sensitive diaphragm Since the enjd of itsstern 6 brings up against the cover 5 after a very v short movement.

34 likewise revolves, roller 31e will engage the tapered end 40a of arm 40 and cause the latter to shift to the left, thus swinging lever 42 counterclockwise to increase the compression of spring 41. If the force thus added to the left side of the diaphragm is sulcient to counterbalance the slight increase of steam pressure which caused the ilexing of the diaphragm, the latter will be restored to its unlexed position, switch i8 will be opened and the action of the controller arrested. If the corresponding new setting of the re affecting agencies is such as to make the steam production correspond with the reduced demand, no further change occurs. But otherwise, the controller continues through its successive steps until the desired balance is attained. Here again, to prevent undue operation of the apparatus, another cam 52 on shaft 34 coacts with resilient arm 53 to depress plunger 54 and open switch I9 to stop the motor. In this instance the backing plate l bottoms on the internal shoulder of the frame member 4 and saves the diaphragm from any excessive rlexure. But the elements are still in position to respond in a reverse direction to a restoration of the pressure within the range of the apparatus.

It will be noted that the pressure responsive element, the diaphragm 3, is normally in its unilexed position where it is most sensitive to pressure changes. When flexed in response to some change, the apparatus at once goes into operation and promptly restores the diaphragm to its original position. And since it is normallyr acted upon by counterbalanced forces, it is alertly responsive to a pressure change and this continues true and to the same degree regardless of what the actual pressure condition is within the range of the apparatus.

While the disclosure has assumed an operative pressure of pounds, it is, of course, understood that any pressure may be accommodated by selecting springs of the proper characteristics. And although particularly described in its application to a boiler installation the use of the improved apparatus is not so limited because it may readily be adapted for controlling the pressure in gas making plants, annealing or blast furnaces, and other instances Where the fluid whose pressure is to be controlled may be applied to the responsive element of the apparatus.

I claim:

1. Pressure actuated control apparatus comprising, in combination, a diaphragm subjected on one side to an actuating pressure; an adjustably mounted spring arranged to exert a force on the opposite side of said diaphragm to counterbalance the greater portion of said pressure force; a stem connected to said diaphragm; a movable arm associated with said stem so as to be moved thereby in accordance with the movement of said stem due to the flexing of said diaphragm upon change of said actuating pressure; an electric switch arranged to be closed by movement of said arm; an electric circuit controlled by said switch; an electric motor connected to said circuit; a rotatable cam connected to said motor so that upon energization of the motor said cam is rotated; a lever arranged to be swung by rotation of said cam; a second spring arranged to be flexed by said lever and to exert a force against the actuating pressure on the diaphragm; the aforesaid elements being constructed and organized so that upon a change in the actuating pressure said stem is moved to eiect closure of the switch and energization of the motor, thereby causing rotation of the cam and a consequent change in the eiective force of said second spring to counterbalance said pressure change and thereby return said stem to its initial position to bring about the opening of said switch.

2. Pressure actuated control apparatus comprising, in combination, a pressure responsive element subjected on one side to an actuating pressure; a spring arranged to exert a force against the opposite side of said element to counterbalance the greater portion of said pressure force; a second spring arranged to exert a force against the said opposite side of said element to counterbalance the remainder of said pressure force; an arm arranged to move in accordance with the movement of said element in response to changes of said pressure; a pair of electric Switches arranged to be actuated selectively by movement of said arm; electric circuits controlled by said switches; a reversible electric motor connected with said circuits, and adapted to be rotated in one direction upon the actuation of one of said switches and in the other direction by actuation of the other of said switches; a rotatable cam connected with said motor and arranged to be rotated in accordance with the rotation of the motor; and a lever arranged to be swung by said cam and thereby alter the eiective force of said second spring; the said elements being organized so that upon an increase in the actuating pressure on said pressure responsive element, the arm moves to eiect closure of the switch which brings about an increase in the effective force of the second spring to counterbalance the increase of pressure, and so that upon a decrease in said pressure the arm moves to eiect closure of the switch which brings about a decrease in the effective force of said second spring to counterbalance the decrease in said pressure; the said arm being moved by the said i SHIRLEY S. WEEKS.

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