US2578276A - Circuit closer for high-low alarms - Google Patents

Description

Dec- 11, D. R. YARNALL ET AL CIRCUIT CLOSER FOR HIGH-LOW ALARMS Filed June 20, 1947 5 Sheets-Sheet 1 I INVENTOR6 1953 D. R. YARNALL ET AL CIRCUIT CLOSER FOR HIGH-LOW ALARMS 5 Sheets-Sheet 2 Filed June 20, 1947 INVENTORS 5; @2706? Dec. 11, .1951 D Y RN E 2,578,276

CIRCUIT CLOSER FOR'HIGH-LOW ALARMS Filed June 20, 1947 5 Sheets-Sheet 3 A TTORNEYfi 1951 D. R. YARNALL ETAL 72,573,276

CIRCUIT CLOSER FOR HIGH-LOW ALARMS Filed June 20, 1947 5 Sheets-Sheet 4 jig le log INVENTORS Dec. 11, 1951 D. R. YARNALL ET AL 2,578,275

CIRCUIT CLOSER FOR HIGH-LOW ALARMS Filed June 20, 1947 5 Sheets-Sheet 5 INVENTORS Patented Dec. 11, 1951 UNITED STATES PATENT .O.ZFF-.I.CIE

CIRCUIT CLOSEREOR HIGH-LOWALARMS David *Robert arnall, Philadelphia, and James --W. Williams,- .31 d,-Ambler, Pa., assignors' to Yarznallewaringtflomnany, Philadelphia,iPa., a cor- .pora inn efsBennsylv nia Application'June' 20, 1947, Serial N 0.1553980 'zzflla m l Our invention relates to high-low alarms of the typeused-on boilersancl the like, to=circuit closers therefor, -and' to processes of circuit closmg.

A purpose of ourinventionis to reducethe reaction on a primaryindicator shaft-of .ahighlow alarm carrying a circuit closing magnet due 'to operation of asensitive magnetic. switch.

A further purpose is to build uptheiclosing *force exerted by the magnet on the magnetic switch very gradually, obtaining smooth -,:opera- 'tion and gradual development of a slightreaction on the primary indicator.

A further purpose is to close a sensitivemag- :neticswitch by-abar=magnet, one pole of which is maintained remote from the switch :and the other pole of which :is swung close' toithe switch, so that thepercentage change in reluctancemi' the magnetic path with unit movement of the proximate pole will be: slight.

A further purpose is tolextendttheabarmagnet transverse totthe' axis of the :supportingiprimary indicator shaft, preferably equally '-in opposite directions to balance the magnetpand preferably also-to curve the poles about the. axis.

A further purpose is to employ widezbarznagnet poles, extending preferably. over. morer-thanBO degrees :of arcand preferably less IthflllZBO-LGG- grees of arc; the most :desirable span ebeing .ap-

proximately 45 degrees .of arc, .softhat 'thegeffect of the magnetic field --will' be; gra'duallyiapplied.

Aiurther purpose is to-support magneticisensi- -tive switches preferably two :in number, .on; adjustment arms individual to each switch, ;.and

preferably pivoted on an adjustment pivot i-in prolongation of :the primary indicatoraxis, so that the switches can be swung aroundithe arcuate .path' of movement of the "poles.

Further purposes appear in the specification and in the claims.

'Inthe drawings wethave chosen to illustrate a few only of theembodiments which our .invention may appear, choosing the forms: :shown from the standpoints .of iconvenience intilluswtration, clarity :in explanation and :satisfactory aoperation.

.Figure 1' is vafront'elevation of thezcircuit closer of; our invention.

Figure .2 is a sideelevation of the circuitjcloser.

'Figures 3 and '4 are detail diagrammatic front --elevations showing theswitches-in diflferentad- ..justment positions.

Figure.Sisaperspective of the primary inclicator .shaft and circuit closing magnet.

.FIE'igure 6 is a perspectivev similar to :Iigure ashowingla variation-in the, magnet.

Figure 7 is a iront elevation partly in central longitudinal section, of one --'form' of sensitive magnetic switch.

Figure 8 is a right side elevation ofcliigure 7 partly in central 1 longitudinal section.

Figures 7a. and-8 are views corresponding to Figures 7 and 8 respectively showing \a .variant iorm of :magnetic switch.

Figure 9 I is. a diagram: ofthe .alarmcircuits.

Figure "10 is: a central vertical section .through I 1 one viorm ofv primary indicator.

sboiler.

Figure :l-iis .a diagrammatic central. ,ryertical section :of a variant :primary iindicator.

' Like numerals :refer to .like .parts throughout. v.In the. operation ;of boilers. .and.other=pressure vessels, it is=c0mn11on-to:.employ. s.o.called ihighlow alarms .to :warn the .operator. gofremergency conditionsregarding liquid llevel. :.;-Many. .of :the

most satisfactory primary;indicatorsgwhichmove a shaft at a point of indicationinresponseto "liquid level .cr zthezlike, are.capablerof exerting very .little .force .on the, primary, indicator. shaft without l ss in: 1 130310 reliabi ty of th .in-

dication. This is :true -for. example of the ,mag

netizable spiral as; described; and claimed ini-fthe Un d :St t smat t applica ns ,o ,-.llia g- J- .I, Iin. 'na S ri l-No. 5,177 24 le i .l nn ryqfi,

1944, ew Pat nt No-2.50&.644 ,M@i2;30, 1.95. ni0 D n ia Bressure au e. a .e. i 1 0- 7l3.03 file -Nor b rl a 46 ..fo Me e :"Ih

:us eu ie ineswitc s i hi he se m a e e o t 1 w uit v fo e eratie sby the m te fec iv p imar -ind cat r We h i estigate h i ssi il ao $16,111-

closing, using the well-known horseshoemagnets- Wefin theti he w tch gl s i nt stantial reaction on thefprimary in icator.

. h co se. o ouri v sti t fdn f e.-@nr9 avoid substantial reaction onthe primary I indicator andeliminate 'abruptness in, action lug-litedesigning the mechanism.

W fin t at it .isvery;impo en it remp ey. a bar magnet, in which thepoles are divergingand remote, rather than a horseshoemagnet, inopereti alo athe maenet ty e sw t .iQneipg only of the bar magnet, mounted on the primary indicator shaft, is brought close to a magnetic switch while the other pole is remote so that the change in the reluctance of the magnetic path due to the presence of the armature of the magnetic switchis gradual, and, for a given unit of magnetic motion, represents only a fraction of the change which occurs in a horseshoe magnet, with its short return path. Thus the reaction on the shaft of the primary indicator is much reduced, and the indicator does not jump or deflect and low liquid level as later explained. The

shaft supports an indicator pointer 22 and on one end, transverse to the axis, supports a bar magnet 23 of any suitable permanent magnet 25 preferably curved as shown on an are about the shaft axis, and suitably fiat in the axial direction. The poles extend for a substantial distance around the circumference, preferably from .alloy. The bar magnet has diverging poles 24,

30 to 90 degrees of arc, and most desirably about 45 degrees.

It will be understood that the bar magnet is preferably not straight, but the midlines of the poles make an angle 26 which is between 45 and 315 degrees, and preferably of the order of 90 to 120 degrees. In the preferred form (Figures 1 to 5 inclusive) there is thus a recess 21 at one'side in line with the axis, and the magnet is mounted on the shaft 20 by a U-clip 28 and a screw 29 passing through holes in the arms of the clip into the end of the shaft. in the alternate form of Figure 6, the bar magnet 23 is bored at 29' to receive the screw 29.

Arranged at adjustable positions around the magnet 23 are sensitive magnetic switches 36 and 3|, desirably of the hermetically sealed type, held by clips 32 on arms 33 and 34 pivoted at 35 on the axis of shaft 20 in prolongation of the shaft. The adjustment pivot is supported on a base plate 36 mounted on the housing 31. the clip 32 is mounted on a portion 38 beyond the pivot 35 from an adjustment extension 39 which rides over a scale 40 under-a clamp guide 4| and is limited in travel by screws 42. On arm 34 the On arm 33 adjustment extension 43 under guide 4| is on the' same side of the pivot as the clip-supporting portion 44. Adjustment extensions 39 and 43 are recessed at 45 and permit movement half-way up or down on scale 40.

By swinging the adjustment extensions to dif-'*- ferent positions, the switches 30 and 3| respectively operating on low and high liquid level, are moved to positions corresponding to different liquid levels, as shown in Figures 3 and 4. Figure 3 corresponds to a relatively low high-level alarm position and a relatively high low-level alarm position, while Figure 4 corresponds to a relatively high high-level alarm position and a relatively low low-level alarm position. Of

course the arms 33 and 34 can be adjusted independently when screws 42 are loosened, and

4 will stay in adjusted position due to the clamping action of bar 4| when screws 42 are tightened.

Figures 7 and 8 show the construction of the magnetic mercury switches, which represent one of the types of sensitive magnetic switches well suited to the present invention. These comprise casings 46 of glass or other insulation sealed and containing inert gas on the interior at 41. A cavity at the bottom holds a mercury pool 48, connected by a lead 49 to a terminal 50 passing through the casing. The opposite terminal 5|, passing through the casing, supports an electrically conducting spiral spring 52 at its center from the outer end of which extends downward a movable contact 53, offset at .54, and having a contact end which in open position (solid lines in Figure 7) is above and to one side of the mercury pool 48 and in closed position (dot-and-dash lines in Figure 7 enters the mercury pool 48. A magnetically susceptible armature 56 on the movable contact 53 near the side wall of the cas-.

ing, moves between the positions shown in Figure 7 to close the switch (dot-and-dash position) against the action of the spring. A support 51 on the terminal 5| carries an eye 58 which guides the offset portion 54 of the movable contact 53.

Figures '7 and 8 show a hermetically sealed inert gas filled sensitive magnetic switch, which employs a fixed solid metallic contact 48 connected to the terminal similarly to the connection of the mercury pool in Figures 7 and 8, and cooperating With a relatively movable solid metallic contact 55 supported on the spiral spring 52 already described. A magnetizable armature 56 is positioned on the movable element. An extension 54' from the movable element is guided in motion by the eye 58, already described.

It will thus be evident that as the magnet pole approaches the armature 56 of one of the switches, force is gradually built up by the magnet on the armature against the spring, until the switch closes.

The operation of the primary indicator is not itself part of the present invention, but may conform to Walter J. Kinderman United States patent applications Serial No. 517,242, filed January 6, 1944, supra for Differential Pressure Gauge, and Serial No. 713,035, filed November 29, 1946, supra for Meter. In these devices angular motion from a primary indicator shaft is transmitted without substantial frictional loss from a closed space in response to pressure differential or the like within the space.

A housing 66 of the indicator, as best seen in Figures 10 and 11, comprises a body 6| and a cover 62 united by bolts 63 and sealed by annular packing 64 on opposite sides of a diaphragm support 65 apertured at 66. The diaphragm support is recessed at 6'! on the side toward the body 6| in order to permit a well, later to be described, to fit into. the recess. The housing is mounted in any suitable position, such as vertical, by a bolt entering a threaded opening 68. On the side toward the cover, the diaphragm support is recessed at 69 to permit collapse into this space of an annular transversely free flexible diaphragm portion 16 of a diaphragm. The diaphragm is held at its upper edge by the packing 64 which protects against leakage between the support and the cover. At the center the diaphragm is stiffened by diaphragm plates 12 which are united by threaded members '13, 14 recessed at 15 to receive a thrust pin 76 engaging in a conical socket H and extending through an opening 18 in the threaded member 1.4. The, pin I6. carries a collar I9 to prevent accidental removal of its end from the space I5.

The diaphragm H is subjected to differential pressures on opposite sides through nipples 80 and 8|. The pressure upon thev inner face at, 8| is a standard pressure in liquid level devices, which should be equal to or greater than the pressure obtained due to the highestv level of liquid indicated.

At the opposite end the thrust pin I6 engages Within a cavity ,82 of a thimble 8:3 which is mounted as by peening at 84 on a leaf spring 85. The spring provides. a convenient support for an indicator horseshoe magnet 86, and retards the movement of the magnet. The horseshoe magnet 86 is conveniently mounted on the spring by extending a plate 81 over the magnet and thimble and bolting through the plate, magnet and spring at 88. The thimble may conveniently be peened over at 89 to unite to the plate.

The motion of the magnet is transmitted to, the primary indicator shaft 23 through a pressure wall or well 98 of suitable nonmagnetic material, which surrounds a magnetically susceptible rotatable armature 9| of spiral formation which is external of the housing 60 in the sense that it is not subjected to the pressure of the housing. The magnetic transmission is based upon the change of reluctance of the magnetic path with movement of the magnet at right angles to its .flux along the axis of the armature, accompanied by rotary reaction of the armatureto the magnet movement to reestablish the reluctance of the magnetic circuit at a balance position.

The magnet 86 is preferably a permanent magnet of highly magnetic alloy havin curved poles 92, 93 which effectively surrounds the well 90, with suitable clearance to permit movement longitudinally of the well.

Both the permanent magnet 23 and the permanent magnet 86 may suitably be made of Alnico (24 to 30% nickel, 9 to 13% aluminum, balance iron) as well known in the art.

The well is threaded at 94 into the housing and internally threaded at 95 to receive the mounting of one bearing 2|, the opposite. bearing 2| being in the end of the well.

The armature 9i, like the armature. 56, may preferably be of soft iron or long carbon steel, such as Swedish iron or "core iron. Silicon bronze is satisfactory for the well. The relation of the spiral pitch to themagnet thickness should be relatively high. A 4 to 1* ratio gives good results, and a 3 to 1 ratio is acceptable.

Provision is made for adjustment of the fulcrum of spring 85. Movement of the fulcrum edge normal to the plane of the spring controls the zero setting, while movement of the fulcrum edge along the surface of the spring parallel to the spring length changes theunsupported spring length and, therefore, changes the deflection characteristics. This is equivalent to calibration for range of liquid level travel.

The spring is desirably supported at its rear end between a transverse block 96 and its cap 31, both held together by bolts 98. If the supporting spring were of the same thickness and width throughout its length, the possible adjustment in range of movement due to fulcrum adjustment would be relatively small. To increase the effect of change in fulcrum, the spring can be varied in thickness or, as is more convenient in production, can be varied in width where it is: bent. The spring is, accordingly made wide and is slotted at 99 adjacent the. supporting end I00, and, the walls adjacent the bifurcationqare tapered oppositely at to.- The outer walls are tapered inwardly and upwardly toward the upper end at I02.

Although the spring is at all times supported by the block and the cap, the effective length of the spring, is determined by an adjustable fulcrum in the form of a bar I03 having a knife edge I04 extending across the spring. The bar I03 is movable transversely of the length of the knife edge. The bar I33 is slotted transversely at I05 from the back so as to permit it to he slid from the left in Figure 10 upon a barrel I06 of a spool IBI having flanges I08. The spool is rigid with a screw I09 threaded into the housingv 6B and into the block 96. The screw is accessible for turning through an opening I I0 closed by a closure bolt III. A disc H2 on the screw I I3 mounted in the housing behind bar H13 moves the bar to the left or right in Figure 10 and correspondingly moves the fulcrum. Access to the screw I I3 is provided through an opening I I4 closed by a closure bolt I I5. Since the setting of the zero point of the indicator is dependent upon the position of the magnet to the right or left in Figure 10, the zero point can be adjusted by advancing or retracting the disc II2. A set screw II6 prevents lowering of the bar I33 beyond the limit of adjustment.

In operation, the device of Figures 10 to 12 is controlled by motion of the diaphragm under differential pressure which causes the pin 16 to move the horseshoe magnet 86 against the retardation of the spring 85. Movement of the horseshoe magnet surrounding the well causes the armature BI to rotate and thus turn the primary indicator shaft 20.

In Figure 13 the mechanism is shown applied to a steam drum and water column by which water level differences are indicated by difference in pressure on the indicator. The steam drum (boiler) II! is connected by pipes H8, H9, one reliably above and one below the water level. with the water column I20 from which pipes I2I, I22, again one reliably above and one reliably below the water level, connect with pressure pots I23, I24. From these pressure pots pipes I25, I26 lead through valves I21 to opposite, sides of the diaphragm "II as shown in Figure 10.

In this form the pipe connection I26 carrying varying pressure communicates with the nipple 80 at the left hand side of Figure 10. The pipe I25 communicates with the nipple 8I on the opposite side of the diaphragm in Figure 10. As the variant water level communicating with the lower pressure pot I24 drops, the pressure difference with respect to the constant level in pressure pot I23 increases and the magnet is shifted along the well toward the pointer, that is, outward along the armature, so as to give progressively lower indication for variant water level.

In Figure 14 the invention is applied to a plain float I28 within a boiler or other chamber under pressure but with indication outside. The float follows the level I29 of the liquid I30. The float arm or rod I 3I is rigidly fastened to a magnet 86 so that each forms one arm of a crank pivoted at I32. The magnet thus swings angularly to the same extent as the float arm or rod. The compartment I 33 is formed conveniently by a fitting I34 attached by flanges I35 and bolts I36 to a side of the boiler I31. The compartment communicates with the boiler through a casing opening I38. The magnet can be of the same character as magnet 86 except that for a considerable angle of swing of the magnet the poles desirably are opposite parallel surfaces. The well 90 and the armature 91 may be as in Figures and 11.

It will be evident that the advantages of the invention in minimizing reaction on the primary indicator shaft from the magnetic mercury switches and obtaining smooth action, can be obtained with any of a wide variety of alarm circuits. For example, in Figure 9 we illustrate a low level alarm I39 such as an electric bell or lamp, in circuit with switch 30 across electric power lines I40. Similarly a high level alarm I4! is in circuit with a switch 31 across the lines I40. Other suitable alarm circuits may be used.

In view of our invention and disclosure variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art, to obtain all or part of the benefits of our invention without copying the structure shown, and we, therefore, claim all such insofar as they fall within the reasonable spirit and scope of our claims.

Having thus described our invention what we claim as new and desire to secure by Letters Patent is:

1. In a liquid indicator, a primary indicator including a shaft turning in response to high and low quantities to be indicated, a single divergent U-shaped permanent magnet positioned centrally on the shaft with the plane or" the U transverse to the shaft, an adjustment pivot in prolongation of the axis of the shaft, an adjustment arm on the adjustment pivot having a plurality of angular adjustment positions, a switch mounted on the adjustment arm remote from the pivot and having a relatively fixed contact element, a swingable contact element adapted to contact the relatively fixed contact element when the switch is closed, having a spring urging the contact elements into open position and having a magnetizable armature on the movable contact element located at one side of the shaft generally in prolongation of a radius of the orbit of turning of the magnet, the armature being swingable about a point located on a line generally transverse to the said radius at a position remote from the radius, and the armature adapted to be magnetically influenced to move the movable contact for closing the switch, the switch in closed position having one magnet pole adjacent the armature and the other magnet pole remote therefrom and the magnet pole adjacent the armature being the only magnet pole adjacent thereto.

2. In 'a liquid indicator, a primary indicator including a shaft turning in response to high and low quantities to be indicated, a single divergent U-shaped permanent magnet centrally positioned on the shaft'with the plane of the U transverse to the shaft, the magnet having radially outwardly directed arcuate poles each covering 30 to 90 of the arc of turning of the magnet, an adjustment pivot in prolongation of the axis of the shaft, a'pair of adjustment arms on the adjustment pivot extending in divergent directions, switches each mounted on one of the adjustment arms remote from the pivot and each having a relatively fixed contact element, a movable contact element adapted to contact the relatively fixed contact element when the switch is closed, a spring urging the contact elements into open position, and a magnetizable armature on the movable contact element located at one side of the shaft generally in prolongation of a radius of turning of the magnet and swingable about a point located on a line generally transverse to said radius and remote therefrom, the armature being adapted to be magnetically influenced to move the movable contact element of the switch to close the switch, each switch in closed position having one pole adjacent the armature and the other pole remote from the armature of the switch when closed and the pole adjacent the armature of the closed switch being the only magnet pole adjacent such armature.

DAVID ROBERT YARNALL. JAMES W. WILLIAMS, 3RD.

REFERENCES CITED The following references are of record'in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,529,470 Dowd Mar. 10, 1925 2,109,953 Bates Mar. 1, 1938 2,245,596 Lindberg June 17, 1941 2,307,304 Rudd Jan. 5, 1943 2,319,010 McLeod May 11, 1943 2,419,942 Brewer May 6, 1947 2,459,930 Fink Jan. 25, 1949 FOREIGN PATENTS Number Country Date 576,685 Germany May 12, 1933 720,957 France Dec. 12, 1931

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