US2296969A - Liquid responsive system - Google Patents

Description

Sept. 29, 1942. R. A. WITTMANN' LIQUID RESPONSIVE SYSTEM Filed July 18, 1938 2 Sheets-Sheet l Sept. 29, 1942.

R. A. WITTMANN 2,296,969 LIQUID RESPONSIVE SYSTEM Filed July 18, 1938 2 Sheets-Sheet 2 2 fig. 2.

Patented 'Sept. 29, 1942 LIQUID RESPONSIVE SYSTEM Robert A. Wittmann, Chicago, Ill., assignor to Chicago By-Products Corporation, a corporation of Illinois Application July 18, 1938, Serial No. 219,935

14 Claims.

My invention relates, generally, to systems responsive to the absence and presence of liquids, and it has particular relation to such systems in which Curie point metal is the responsiv element.

My invention can be used in conjunction with boilers, autoclaves, pressure and vacuum kettles, evaporators, stills, condensers, cooling and heating coils, and similar devices where a check on the absence or presence of liquid is required.

Because of its freedom from moving parts ex-v posed to the liquids in which it may be disposed for operation, it is a marked improvementover similar systems used heretofore. Since it can be made resistant to or protected from corrosive liquids and vapors it has a wide application in the chemical and related industries. Also it can be designed to operate under substantially all temperatures encountered in practice.

Accordingly, one object of my invention is to provide a system responsive to the absence and presence of liquids wherein there are no moving parts exposed to the liquids and hence eliminating frequent safety inspections.

Another object of my invention is to provide a system responsive to the absence and presence of liquids which will operate satisfactorily for long periods under both continuous and intermittent operating conditions.

Another object of my invention is to provide a system responsive to the absence and presence of liquid which can be readily installed in new or existing equipment.

Other objects of my invention will, in part, be obvious and in part appear hereinafter. I

Accordingly, my invention is disclosed in the embodiments shown in the accompanying drawings, and it comprises the features of construction, combination of parts, and arrangementof elements which will be exemplified in the constructions hereinafter set forth and the scope of the application of which will be indicated in the appended claims.

- For a more complete understanding of the nature and scope of my invention, reference may be had to the following detailed description, taken in conjunction with the accompanying drawings in which:

Figure 1 illustrates diagrammatically one embodiment of my liquid responsive system applied to a steam jacketed kettle; I

Figure 2 illustrates diagrammatically another embodiment of my liquid responsive system applied to a boiler;

Figure 3 illustrates diagrammatically another embodiment of my liquid responsive system applied to a boiler; and

Figure 4 illustrates diagrammatically still another embodiment of my liquid responsive system applied to what may be either a cooling or heating coil.

Referring to Figure l of the drawings, it will be observed that the reference character 5 designates a'kettle the bottom portion of which is surrounded by a steam jacket 6. For example, this might be a kettle in which a liquid is evaporated to remove a desired amount of water. The steam jacket 6 may be supplied with steam through the pipe Hi from a steam main through a shut-oil valve shown, generally, at l2. For accurate control of the steam supply, a needle valve I3 may be provided in the pipe. The shutoiT valve, I2 is provided with an electric motor II for closing it. A hand wheel I5 is provided to manually open and close the valve l2. The manner in which the motor I4 is operated will be described in detail hereinafter.

. With a view to limiting the level to which a liquid in the kettle 5 can be evaporated, a liquid level responsive system shown, generally, at 20 is provided. The liquid level responsive system 20 comprises a permanent horseshoe magnet II with two pole extension members 22 and 23 extending from the poles thereof. If desired, the permanent horseshoe magnet 2| can be replaced by some other shaped permanent magnet or by an electromagnet. A non-magnetic plate 24 may be inserted into the side wall of the kettle 5 with the pole extension members 22 and 23 passing therethrough as shown. Electrically insulated,

liquid and vapor-proofed, heating coils 25 are wrapped around the pole extension members 22 and 23 as shown, and connected in series circuit relationship with the terminal leads extending through insulating bushings 28 and 21. A magneticallyoperated switch shown, generally, at,

the-bottom of the glass container 3|, where, inv

a suitably formed depression or the container 3|, there is deposited a pool of mercury 35 in which the conductor. 34 is at all times immersed. The inlead 32 is connected to a coil spring conductor 36 which normally holds the lower contact end 3? in the pool of mercury 35. This coil spring conductor 36 carries a magnetic armature 8B which, when attracted towards the adjacent wall of thecontainer 35, causes the lower contact end 31 to leave the mercury pool 35 and thereby break electrical contact with it to open the circuit between the inleads 32 and The magnetic control switch 3@ is so positioned that the magnetic armature 38 is opposite the air gap 39 between the ends of the pole extension members 22 and 23.

With a view to furnishing a source of electrical energy for operating the motor l6 and the heating coils 25, a pair of energized conductors Gil and M are provided. For example, this source may be the ordinary 110 volt alternating current source. The terminal ends ofthe heating coils 25 may be connected by the conductors (l2 and 38 to the energized conductors (it and (it. A switch it is provided in the conductor 53 for controlling the energization of the heating coils 25 as desired. The inlead 32 of control switch as can be connected to the energized conductor 6i! by the conductor 35. Inlead 33 is connected by means of conductor (it to one terminal of the motor M. The other terminal of the motor M3 is connected to the energized conductor M by the conductor (Hi. It will be seen that the control switch 3b is in series circuit relationship with the motor i l.

The pole extension members 22 and 23 are of Curie point metal which, when below their Curie point, are ferromagneticand, when above it, are nonmagnetic. Since there is a large variety of Curie point metals with dii'lerent Curie points or transition temperatures, it is possible to make a selection for diflerent operating conditions as desired. When the heating coils 25 are energized they will heat the pole extension members 22 and 23. However, when the pole extension members 22 and 23 are surroundedby liquid, the heat will betransferred away to such an extent that they will not rise above their Curie point and become nonmagnetic. If however the'pole extension members 22 and 23 are not surrounded by a liquid medium, but instead a gaseous medium, the heat from the heating coils 25'will not be dissipated so rapidly and the pole extension members 22 and 23 will become nonmagnetic.

It will be seen that when the pole extension members 22 and 23 are below their Curie point and therefore ferromagnetic nearly all of the flux from the permanent horseshoe magnet M will flow across the air gap 39 between the ends of the pole extension members 22 and 23. The flux density will then be sufilcient to attract the magnetic armature 38 against the force of the coil spring conductor 36 and cause the lower contact end 31 to leavethe mercury pool 35. thereby opening the circuit between the inleads 32 and 33. However, when the pole extension members 22 and 23 are heated above their Curie point and are therefore nonmagnetic, the flux density in the air gap 39 will decrease to such an extent that the magnetic armature 88 will no longer be attracted to an extent .suflicient to maintain the control switch 30 in the open positon.

In operation, assume that the kettle is filled close.

jacket 6. Also, the switch 341 is closed to complete the circuit through the heating coils 25. The liquid surrounding the heating coils 25 will conduct the heat away at such a rate-that the pole extension members 22 and 23 of the Curie point metal will not be heated above their Curie point and therefore the control switch 38 will be in the open position. After a time the liquid level in the kettle 5 will gradually fall partially or wholly below the permanent magnet 2i as illutrated. When this occurs, the pole extension members 22 and 23 will no longer be surrounded by liquid but they will be surrounded by the gases above the liuid. As the heat from the heating coils '25 cannot now be so rapidly dissipated, the pole extension members 22 and 23 will be heated above their Curie point and become nonmagnetic. When this happens the flux density in the air gap 39 will decrease causing the control switch to to Upon closing of the control switch 3d, the circuit to the motor ill will be completed. The motor i l on energization operates the shut-oft valve 52 to the closed position, thereby shutting oi? the steam supply to the steam jacket 6. The operator may now draw off the concentrated batch and refill the kettle 5. The foregoing cycle of operation can thenbe repeated. The responsive switches herein disclosed may optionally be normally open or normally closed with appropriate closed or open circuits, respectively, accordingly. It is well known that before a liquid can 'go into vapor, the temperature must first be raised to the boiling point, and then the so called latent heat of vaporization must be supplied to it. In the case of water, the latent heat of vaporization is a very large quantity. In brief, with a high specific heat to begin with, and with a large latent heat of vaporization required to vaporize the liquid after it reaches the boiling point, a body of liquid is capable of receiving a large amount oi heat, and of keeping its temperature at no higher than the boiling point even though considerable amounts of heat be conducted to it.

y In the present case, thermal contact of the Curie point material with the liquid keeps said material from increasing its temperature above the boiling point of the liquid, no matter how much heat is supplied to the body by the electric heaters 25 or 86 or I00, in Figure l or 3 or 4, or the gas heater 52 in Figure 2. {The Curie point of the magnetic element is selected to lie above the boiling point of the liquid. Hence the present device cannot operate so long as liquid remains in thermal contact with the body of Curie point material. That means that the present device. provides a sensitive and stable means for detecting liquid level, or the presence of liquid in a given position, which is peculiarly reliable and durable.

If desired, my liquid level responsive system can be disposed entirely within the kettle 5 and the magnetic control switch 30 can be replaced by some other type of magnetic switch. When with a definite quantity of a liquid to be evaporated to a certain degree and that the quantity is such that when it isevaporated down to the level of the permanent magnet 2|, the desired quantity of water willhave been removed. After the batch has been put into the kettle 5, the shut-oil valve I2 is opened and the needlevalve i3 is adjusted allowing steam to pass through to the steam heated. In order to take care of. this requirement the pole extension members" and 23 may shown, generally, at 62.

be selected so that they will become nonmagnetic below this maximum allowable temperature so that the heat supply may be shut off even though the liquid is not evaporated to the desired extent. Such an installation will respond to either of the aforesaid conditions, namely, it will respond to dropping of the liquid level below the selected minimum height, or the liquid leaving the locus of thermal contact between the liquid and. the element; and, second, it will respond if the liquid is heated to a temperature inexcess of a certain fixed value even if the level of the liquid be above the selected minimum, or be in position to make the aforesaid thermal contact.

It will be seen that there are many other applications or" my liquid level responsive system illustrated in Figure 1. For example, it may be used equally well to operate shut-off valves in steam, hot oil or gas mains. Another important application is its use in maintaining a definite liquid level. In this case the magnetic control switch can be connected in series with the motor of an electric pump which supplies liquidtoa tank. When the liquid surrounds the heating coils 25, the heat will be dissipated and the magnetic control switch will be opened, thereby shutting off the motor which operates the pump. lli, however, the liquid level should fall below the pole extension members, the heat from the heating coils 25 will not be dissipated to the former extent and the magnetic control switch will be closed thereby starting the electric motor which drives the pump supplying liquid to the tank. The pump will continue to operate until the liquid again surrounds the pole extension members and the heat of the heating coils 25 is once more dissipated allowing the magnetic control switch to open and to stop the electric motor. Also, the

permanent magnet 2! may be located in a tank at the lowervwater level point and the magnetic control switch 30 may be connected to an alarm in such manner that, once the liquid falls below this lower limit, the magnetic control switch 30 will close. thereby causing the alarm tobe sounded.

Referring now to Figure 2 of the drawings, another construction of a liquid level responsive system shown, generally, at 56, is applied to a boiler shown, generally, at 5i, for operation therewith. The boiler 51 may be heated by a gas burner 52 positioned at the bottom of the combustionchamber 53. The combustion chamber 53 is formed by the boiler top 54 and the water leg 55.; Gas is supplied to the has burner 52 through a supply line 55 containing a solenoid operated valve 5|. Electric current for opening the solenoid valve 51 is supplied thereto from a pair of nergized conductors 58 through conductors 55 and 60'. The conductor 60 contains in series circuit relation a thermostat 6i and a switch The switch 82 consists of a stationary contact 53 and a movable contact 64.

The liquid level responsive System50 has as its responsive element a bar of Curie point metal 65 extending through th water leg 55 into the combustion chamber 53. The bar 55 is positioned at the lowest safe operating water level of the boiler 5|. A rod 65 is adapted to move up and down in a hole provided therefor in the outer end of the bar 85. lower end a permanent horseshoe magnet 61. An extension 68 of the rod 66 is provided as support means therefor having 'a diameter greater than that of the hole through which the rod 68 is suspended. The extension 68 is provided with The rod 66 carries from its heat is conducted therethrough to its outer end under which the magnet 61 is suspended. So

long as the bar 65 is surrounded by water in the leg suflicient heat will be dissipated therefrom so that the outer end will remain below its Curie point and thus will be ferromagnetic. When the outer end is below its Curie point and ferromagnetic the magnet ill will be attratcted to it and the switch 62 will be closed. If now the thermostat Gl is calling for heat the circuit to the solenoid valve 51 will be completed and the valve will be opened allowing gas to flow to the burner 52. Now if the water in the water leg 55 falls below the bar heat will not be dissipated from it sufiiciently and the outer end will rise above its Curie point and become non-magnetic allowing the magnet hi to drop and thereby opening the switch 62 and shutting oil the solenoid valve til.

Thus it will be impossible for gas to be supplied to the burner 52 unless the water in the water leg 55 is at a level above that of the bar of Gurie point metal 65. It will be understood that the boiler 52 might be heated by oil or coal and the liquid level responsive system 59 could be adapted to close the oil supply valve or stop a Stoker if a low water level should occur.

With a view to providing a liquid level responsive system in which the responsive element is a body of Curie point metal, which is electrically heated and which will only be heated when heat is being supplied to the installation to be protected, I have provided the system illustrated in Figure 3 of the drawings. In this figure a section' of a boiler 15 may be provided which is supply line 18 containing a solenoid operated valve l7. Electric current may be supplied for operating the solenoid valve ill from a pair of energized conductors 18 through conductors 1.9 and 80. The conductor has in series circuit relation therewith a thermostat 8i and a switch 82. A member 83 of Curie point metal is provided as the responsive element being disposed partly within and partly outside the boiler 15. One section of the member 83 is heated by an electric resistance coil 84 which may be supplied with electric energy from the energized conductors i8 and is in series circuit relation with the thermostat 8!. A horizontal section 85 of the member 83 is provided adjacent to and below the switch 82, beneath which a permanent magnet 86 carried on a rod 81 is supported. The permanent magnet 86 operates just as the permanent ma net 61, Figure 2, operates. The rod 81 carries a member 85 of insulating material which is adapted to move the movable contact 89 of the switch 82 to the open position.

In operation gas can be supplied to the burner heating the boiler 15 only when the thermostat aaaaaeo its safety protection is desired. If when the:

thermostat 8I is calling for heatand when the burner is heating the boiler I5, the water level should drop so that the Curie point member 88 is no longer surrounded by water, the heat supplied to the Curie point member 83 by the heating coil 84 will not be dissipated sufliciently and the horizontal section 85 thereof will be heated above its Curie point and will become nonmagnetic. Upon this occurrence the permanent magnet 88 will no longer be attracted to the underside of the horizontal section 88 and it will drop causing the switch 82 to be opened as shown in the drawing. When the switch 82 is opened the circuit to the solenoid valve 11 will be broken and the gas supply to the gas burner will be shut oil, preventing damage to the boiler I5 due to low water level therein. It will thus be seen that a very reliable and economical safety system is eiIected.

Failure of the cooling water supply to cooling coils employed in various installations may easily result in serious damage. .Thus in the case where large transformers are. kept from overheating by cooling coils therein the failure of the cooling water supply in such instances may cause the destruction of the transformer. In order to provide against such and similar destruction I have provided a system responsive to the presence and absence of liquid as shown in Figure 4 of the drawings. A cooling coil shown, generally, at 9.", may be taken as representative. of one that might be used in a transformer, condenser or other installationfln the outlet pipe 98 of the cooling coil 95 a pipe fitting 91 is interposed through which a member 98 of Curie point metal extends.

A hole 99 in the member 98 allows cooling water to flow therethrough. The projection of the member 98 extending to the left of the pipe fitting 91 is heated by an electric heating coil I88 which is supplied with current from a pair of energized conductors I8I. "the heating coil I88 so that the projection of the Sufficient heat is supplied by member 98 extending to the right of the pipe fitting 91 is heated above its Curie pbint and becomes non-magnetic when cooling water is not flowing through the pipe fitting 91 and conducting heat away from the member 98. When cooling water is flowing, unless its temperature the energized conductors IM to an electric operating device I81. In the case where the cooling c il 95 is used .in connection with a transformer this electric operating device I81 might be adapted to operate a switch permitting the transformer to be put in or out of service. Thus in operation assume that the cooling coil 95 is disposed in a transformer and that the proper supply of cooling water is flowing thereto. In this condition the right hand projection of the Curie point member 98 will be cooled below its Curie point andthe magnet I82 will be attracted'to it closing the contacts I85 and I 88 and thereby allowing the electric operating device I8I to put the transformer in service. Now if the cooling water 75 supply shouldfail for some reason the member 98 will become heated above its Curie point and become non-magnetic allowing the magnet I82 to drop and thus opening the circuit to the electric operating device I81, thereby causing the transformer to be taken out of service and preventing damage thereto.

- The Curie point metal may be selected to respond at such a value thatif the liquid itself becomes too warm, the control circuit will be switched, without reference to the separate heat input means I88. Or the Curie point metal may be responsive to the combined effect of the electrical heat input and the temperature of the I cooling or condensing medium.

The level control herein disclosed may be employed for high level as well as for low level by causing the liquid at high level to effect an abstraction of heat to produce a response of the switch. A I

In the disclosure herein where the heat of electric current flow is relied upon the heater may burn out.

The circuit may optionally be arranged to rely upon the current carrying properties of the heater wire to maintain the system in operation. That is to say, the heater wire may serve as a fuse to shut off the current; from the rest of the system. Alternatively, a relay in circuit with the heater may operate upon the current supply or it may control one or more circuits to take the system outof operation or. perform any other safety or emergency operation such as shutting down the system or a part of the-same. Thus, forexample, it may cut out the burner or the motor or the like.

It will be understood that wherever permanent horseshoe magnets have been used they may he s replaced by electro-magnets and permanent magnets in other shapes.

Since certain further changes can be made in the foregoing construction, and different embodiments of the invention may be made without de-" parting from the scope thereof, it is intended that all-matter shown in the accompanying drawings or described hereinbefore shall be interpreted as illustrative and not in a limiting-sense.

I claim as my invention:

1. In a system responsive to the-presence and 59 absence of liquid independently of the temperature of the liquid, in combination, a responsive element of Curie point metal, means independent of said liquid for heating said responsive element above its Curie point to render the-element nonmagnetic, a container for liquid associated with said element and adapted to bring liquid into thermal contact therewith, thermal contact of.

liquid in said container with the element serving to dissipate the heat of said heater and to cool the elementbelow its Curie point whereby it becomes magnetic, a source of flux interacting with said responsive element, and means external to the container controlled by interaction of said responsive element and said source of flux.

' 2. In a system responsive to the presence and absence ofliquid independently of the temperature of'the liquid, in combination, a responsive element of Curie point metal, means adapted to contain liquid in which the element is adapted to be immersed, means independent of the liquid for-heating said responsive element above its Curie point when it is not suiliciently cooled by being immersed in said-liquid, a source of. flux interacting with saidresponsive element as a function of its magnetic condition, and means .external to the liquid containing means, said last named means being controlled by the interaction of said source of flux and said responsive element.

3, In a liquid level responsive system, in combination, a source of flux, spaced apart extension means including a responsive element of Curie point metal extending from the opposite magnetic poles of said source of flux, means for heating said responsive element above its Curie liquid container adapted to contain liquid the level of which may fluctuate above and below a predetermined level, said element being subject to thermal contact with the liquid when the level magnetic poles of said source of flux and adapted to be operated when said responsive element is not immersed in liquid.

4. In a liquid level responsive system, in com bination, a source of flux, spaced apart responsive elements of Curie point metal extending from the opposite magnetic poles or said source of flux, heating elements disposed to heat said spaced apart responsive elements to raise them above the Curie point, whereby the said elements become substantially non-magnetic, a container for liquid, the level oiwhich liquid varies in respect to a predetermined level, said liquid upon attaining said predetermined level coming in thermal contact withsaid elements and cooling the same below the Curie point whereby they become magnetic, a circuit means connecting said heating elements and a current source, and a magnetic switch disposed adjacent to the ends Curie point.

7, In a liquid level responsive system, in combination, a responsive element of Curie point metal, means for heating said responsive element, a magnet adapted to be attracted to said responll) sive element when i Lis ferromagnetic, said point to render the element non-magnetic, a

switch means operated by said magnet, said element comprising a plurality of sections, a heating coil for heating one section or said responsive element, means for immersing another section thereof in liquid, and another section thereof of the liquid rises to or above said predetermined attracting said magnet when ferromagnetic, electric current being supplied to said heating coil only when the liquid level responsive system is in operation 8. In a system responsive to the presence and absence oi fluid flow, in combination, a responsive element of Curie point metal comprising a plurality of sections, one section of which is positioned in a path of fluid flow, means for continggg uously heating another section or said responsive element, magnet meam adapted to be attracted to another section or said responsive element when said last named section is at a temperature below its Curie point due to the presence of fluid 39 in thermal contact with said first named section,

and switch means operated by said magnet means.

9. A device responsive to the presence of a body of liquid independently or the temperature of the liquid, comprising a body of Curie point ad material the Curie point or which lies above the boiling point oi the liquid, heating means independent of the liquid in thermal conductive relation to at least a part of said body to heat said body when the body is out oi thermal contact Of Said Spaced apart responsive elements 9-Way lit with the liquid to a temperature above the Curie from the opposite magnetic poles of said source or magnetic flux and adapted to be operated when said spaced apart responsive elements are not cooled by said liquid.

5. In a liquid level responsive system, in combination, a permanent horseshoe magnet, spaced apart responsive elements of Curie point metal extending from the opposite magnetic poles or 1 said horseshoe magnet, a container for liquid, the level or which varies in'respect to av predetermined level, said liquid upon attaining said predetermined level coming in thermal contact with said elements and cooling the same below the Curie point whereby they become magnetic, heating coils surrounding said responsive elements for heating them above their Curie point when not cooled by said liquid, circuit means for interconnecting said heating coils and a current source, and a magnetic switch disposed adjacent responsive element when it is at a temperature below its Curie point, and switch means operated by said magnet, one section of said responpoint which will render a selected part of the same non-magnetic, and liquid containing means r in winch/a body or liquid may be brought into thermal contact with said body to abstract sumcient heat from the body to bring said selected part below the Curie point and to render the same magnetic, and control means responsive to the magnetic or non-magnetic condition of said selected part of the body.

iii; A device sensitive to contact with a liquid comprising heating means, a vessel adapted to contain a liquid, a body of Curie point material in thermal contact with the heating means and adapted to be contacted with liquid When the 55. same occupies a predetermined position in said vessel, the heating means being adapted to raise the temperature of the Curie point material to the Surie point to render the same non-magnetic when said material is out of thermal contact with go the liquid, thermal contact of the liquid dissipating the heat added by said heating means to the extent or cooling 9. selected part of the same below the Curie point and thereby rendering the same magnetic, and control means including an electric switch responsive to the magnetic or nonmagnetic condition of said selected part of the body.

11. In combination, a permanent magnet, a body ot-Curie point material, means including a 7 0 switch responsive to extension of the field of the magnet through the body of Curie point material when the same is diamagnetic, heating means for heating the Curie point material when the same is out of thermal contact with a body sive element being exposed to said heating means, of liquid to the Curie point whereupon it becomes paramagnetic, and means adapted to cpntain liquid which when in thermal contact with the body conducts away heat fast enough to keep the body below the Curie point.

12. Means responsive to :the presence or absence of liquid-in a predetermined space comprising in combination a body of Curie point material having a Curie point above the boiling point of the liquid, means apted to confine liquid in'thermal contact with a portion of,

said body for-the purpose of limiting the temperature of said portion to a value-below the Curie point or the material, means independent oi. the liquid for continuously adding heat to said body, said means being capable in the absence ot-heat removal by said liquid of raising the temperature'oi said body above the Curie controlled by the interaction of said body and I liquid contact with said body which liquid is adapted to carry heat away from: said body so long as the liquid is in thermal contact with the body to keep said. body below the Curie point, a source or magnetic flux interacting with said body hr one manner when the body is below its Curie point, and in a diflerent manner when the body is at or above the Curie point, and means,

said source of flux.

14. In combination, a vessel in which liquid is,

adapted to be contained above a certain level, a body oi. Curie point material in thermal contact with liquid above said level, the Curie point of said material being above the boiling point of said liquid, heating means in'thermal conductive relation to said body, for supplying heat to the body at a rate faster than said body can dissipate the min the absence or thermal contact with; I}

said liquid, a source oi. magnetic flux interacting with said body, and means controlled by inter- 7 action of said body and said source of flux,

' ROBERTA.WI'ITMANI V.

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