US1683071A

US1683071A - Liquid conductor heater and method op operating same

Info

Publication number: US1683071A
Authority: US
Publication date: 1928-09-04
Anticipated expiration: 1945-09-04

Description

Sept. 4, 1928.

M. w. HANKs E'r-AL LIQUID CONDUCTOR HEATER AND METHOD 0F OPERATING SAME Sept. 4, 1928. 1,683,071

M. w. HANKs Er AL LIQUID CONDUCTOR HEATER AND METHOD OF OPERATING SAME Filed .J'an.`12, 1925 4 sheets-sheet 2 sept. 4, 192s.

M.- W. HANKS ET AL LIQUID CONDUCTOR HEATER AND METHOD OF OPERATING SAME 4 sheets-'sheet 3 Filed Jan. 12, 1925 sept. t4, 192s. 1,683,071

' M. W. HANKS ET'AL LIQUID CONDUCTOR HEATER AND METHOD OF OPERATING SAME Filed Jan. l2, 1925 4 Sheets-Sheet 4 i 15 liqIuIild disappears.

Patented' Sept. '4, 1928.

UNITED STATES PATENT- oFFi'cs.

W. BANKS AND MAX MASON, OFl MADISON, WISCONSIN, ASSGNORS'TQ y ANKSCRAFT COMPANY, A.'OORPOBATION 0F WISCONSIN.

LIQUID-CONDUCTOR nnarnn. AND mamon or OPERATING sum.

Application led January 12, 1925. Serial No. 1,7 84.

This invention relates to liquid conductor heating devices in which a measured or re determined quantity of liquid is vaporize by the passage therethrough of an electric curl rent which is automatically shut oi to stop the operation of the device when the liquid becomes completely vaporized Devices of this type may be employed, for example, for

. cooking eggs, warming milk bottles, or performing other tasks having a desired definite period or duration., or requiring a fixed amount of' heat for their consummation, the cooking or heating being el'ected by the vapor ofthe liquid and being consummated when the the operation of these devices, itis de sirable to maintain a substantially constant current and a uniform rate of vaporization throughout the period of o ration and to secure a relatively rapid or a rupt termination of the operation of the device at the end of that period, inorder that the effects and durations of successive operations of the device 'will be uniform and in order that the device may beavailable for a succeeding task after a definite and predetermined period of operation. To obtain these results, one of the diii`iculties to be overcome is that arising-from the variations in the conductivity of the liquid 3" dueto the bubble formation produced by the passage therethrough ofa, current suiicient to:va riz'eit. The vapor, so produced, forms in bu bleswhich may permeate the'. whole or a part of the liquid carrying the current,

thereby tending to force the liquid away from the electrodes and to transform the original homogeneous liquid body into a cellular structure having a .greatly reduced electrical conductivity per unit of volume, so that the cur- 5I give rise to objectionable i'ictuationsy in 'the current which are patricularly troublesome` where the electrodes are mounted one above the other in horizontal position, because the bubbles collect between the electrodes and increase insize until their volume and vapor rent flowing at constant potential greatly.

-tion toa relatively small amount,

pressure is suiiicient to cause them to. escape around the edges of the electrodes, so that the e'ective resistance of the liquid conductor between the electrodes, at first decreases to a marked de ee and then increases suddenly as new liquid Hows into the space between the electrodes after the bubbles have escaped. In some instances, the violence of the escape of the bubbles may momentarily remove all of the conducting. liquid from the space between theelectrodes andthereby completely stop the flow of current, after which the current rises to an undue extent as new liquid, free of bubbles, Hows in and re-establishes the circuit. This irregularity in the current How is not only objectionable in its immediate ef-V fects, but it tends further to render indefiniteV and uncertain the duration of operation of` the device inperforming a particular task or cooking operation.

It is the principal object of' the present invention to provide a liquid'conductor heating device adapted to operate with a predetermined quantity of'li uid in such a mannertliat the current owing in the liquid is free of substantial fluctuations and is maintained at a relatively high value throughout the major portion of the period of operation and is shut olf abruptly'to zero at the end of adefinite predetermined period. It has been discovered that this desirable result may be obtained by employing an electrode having means for permitting a ready dissipation of the vapor between-the electrodes and for increasing the current density per unit (of active area of the electrodes. If one of the electrodesbe-constructed as a perforated grid or plate. it is 'found that the holes inthe platesl permit a rapid dissipation of energy and a 'read-y escape of the bubbles so that the liquid- .between the plates is maintained in a condition adapted to produce a substantiall uniform current fiow throughout the period of operation. This construction brings about a greater current intensity on each unit of the active area 'of the electrodes and brings intoaction a't greater proportion of the total area l of the electrodes, their would be the case if and a given. cooking or eating operation may be performed in a lesser period of time.

Moreover, it is 'found that after the quantity of liquidv in the device is reducedBy'vapor-izamentire 1w' to decrease from the normal value which is tical section through a mo maintained during the major portion of the operation to a zero value ina very short space of time at the end of the period of operation. Other objects of the lnvention re-v late to various features of construction' and arrangement which will appear more fully hereinafter.

The nature of the invention will be understood from the following specification taken with the accompanying drawings in which Figure 1 shows a top plan view of the device; Fig. 2 shows a front elevation thereof; Fig. 3 shows a vertical section taken on the line 3 3 of Fig. 1; Fig. 4 shows a section taken on the line 4-4 of Fig. 3; Fig. 5 shows a perspective view of the measuring vessel;

`ig. 6 shows a top plan view of the tray for holding the eggs to be cooked in the device; Fig. 7 shows a top plan view of the base 8 shows a top planview of the upper electrode; Fig. 9 shows Ia top plan view ofthe lower electrode; Fig. 10 is a side elevation of the lower electrode' Fig. 11 is a chart showing diagrammatically by means of curves a comparison of the operation of the device wit-h and without the perforated electrode of the present invention; Fi 12 shows a verified form of construction; Fi 13 shows a vertical section through anot er modification and Fig. 14 shows a section on the line 14-14 of Fig. 13. As illustrated in the drawings, the device comprises a sheet-metal base adapted to rest on a table-or the like, having formed integrally therewith an upwardly extending back plate 21 on which may be mounted a name plate 22 containing rinted directions for the operation of the evice. The base 20 supports a receptacle 25 of insulatpprtion of the device illustrated in Fig. 4;

' ing material, preferably porcelain, having a lower annular'flan e 26 adapted to rest on the base 2O to whichl 1t is secured by means of the fixed clips 27 extending upwardly from the base at one side of the receptacle and a removable clip 28- which engages the other side of the base Iiange 26, being secured in osition by a screw 29. Thereceptacle 1s hollowed' out on its u per side to form a v chamber 30 and the le ge 31 at the upper ytained the chamber 30.- The lateral edge of the chamber 30`is adapted to support a tray 32, having the form shown articularly in Fig. 6, w ich is provided wit a p'lurality of circular apertures 33 adapted'to receive and -support the eggs 35 which are to be cooked by the vaporiz'ation of liquid cm- 1sl l placement of the tray 32 is prevented by lugs 36 which are for-med integrally on the upper surface of the ledge 31. The receptacle 25 is provided around the ledge 31 with an annular upwardly extending iange 37 which is adapted to receive within it the domeshaped cover 38, formed preferably of sheetmetal', and having an aperture 39 therein through which the vapor is adapted to escape.

The lower part of the chamberg30 is cylindrical in form as shown at 40 and is adapted to contain the

electrodes

41 and 42 which are ofthe. grid type, being circular plates of slightly less diameter than the diameter of the, cylindrical portion 40 of the chamber. The lower electrode 41 has formed thereon or secured thereto a pair of bolts 43 which extend downwardly through apertures 44 in the bottom wall of the receptacle 25, being enga-ged at their lower ends by washers 45 and nuts 46. One of these bolts, is adapted to serve as a binding post, having connected to it the extremityof an electrical conductor 47 which is held in place by 'a nut 48. The lower electrode 41 is providedwith a plurality of apertures 49 whichare 'adapted to receive lugs 50 formed integrally with the lower wall of the receptacle 25 and extending upwardly therefrom, as shown in Fig. 4, to

engage the upper electrode'42 and space it from the .lower electrode.l The lower electrode 41 is also provided with a central aperture 51 through which extends the insulating boss 52 formed on the lower wall ofthe receptacle around the has a reduced part 54extending through an aperture 55 in the lower wall of the' receptacle to be engaged on its threaded extremity by nuts 56 which secure between them the end. of an electrical conductor 57 which, with the conductor 47, completes the circuit to the devicefrom a suitable source of electrical ower. The terminal post 53-is threaded at its upper end as shown at 53 to be threadedly engaged by a central aperture 60 which is formed in the upper electrode 42. This construction permits the upperelectrode to be removed readily from the receptacle to permit the cleaning of the upper surface of the lower electrode and the projecting portion of the terminal post by which the connection is madejto the upper electrode. 4When the upper electrode is 1n its` normal o'sition, as shown'in Fifr. '3, it isv in proximity to the lower electrode but is spaced a fixed distance therefrom by the porcelain lugs 50. Aquantity of liquid such as water is adapted to be contained in the chamber 30 of the receptacle 25, 'as shown at 62. PAssuming that the

conductors

47 and 57 are connected to a source of electricall potential, the introduction of the water or other liquid into the receptacle 25 completes the circuit between the electrodes 41 and 42so that the liquid is heated by the passage of thecurrentLtherethrough rminal post 53 which` by cooking the e of, preferably as shown in Fig.

and is vaporized vapor passes upwardly into the chamber -30 and into the space within the cover 38," theregs 35. lIn order to o tain the desirable results heretofore described, the upper electrode 42 is provided with a plurality of perforations .63 which are distributed over the area there- 8. As bubbles are formed between the electrodes by the boiling of the liquid, these bubbles are permitted to escape upwardly through the apertures 63 as well as around the peripheral edge of the electrode 42, so that the bubble structure between the electrodes is maintained in a condition adapted to produce substantially uniform current flow throughout the Yperiod of operation. The vaporization of .the liquid proceeds at a substantially uniform rate with the flow of a substantially uniform current throughout substantially the entire period of operation of the device until the quantity of liquid between the electrodes is relatively small, when the distribution of this remaining quantity of liquid over a relatively large area of the erforated electrodes causes'itto be vaporize racreased sudden zero as the end reached. The u per electrode 42 ma 0 provide adjacent its outer e ge with a nonconducting coating`64 for preventing a short circuit in case vit accidentally engages the lower electrode 41 in the operation of inserting or removing it from the receptacle 25. The coating 64 may extend `over any desired portion of the upper electrode or 1t may be on any portion of the lower'electrode or the containing vessel, as may be deslred.

ln order to prevent the passage of an excessive current through the liquid at the bey from its normal value 'to of the period of operation 1s ginning of the operation of the device, the

water or the like, is fed to the a feeding vessel 65, of which is mounted onthe 38. The vessel 65 the cover by means 66 which is in the form of a bolt having a lower threaded eX- tremity engaged by a nut 67 within the cover, as shown particularly in Fig. 3. The upper surface of the member 66 lies flush with the upper surface of the lower wall of the vessel liquid, such as receptacleA 25 from porcelain or the like, upper wall of the cover is secured in position on of a clamping member 65 and the measured quantity of water which is placed in the vessel is adapted to pass downwardly through a small opening 68 havinga relatively tacle 25 when the device is started in' operation, thereby insuring a prompt vaporiza tion of the initial quantity of water lwhich comes into contact with `the electrodes and preventing the rise of the current to an undue extent when the circuit is first completed.

with the .result that the` idly so that the current is dey A fine outlet so that the water y l or other liquid passes slowly into the recepi The predetermined. quantity of water which is introduced into the feeding vessel 65 may. preferably be measured in a measurjing cup orvessel 70, having the form shown is provided with a hanin Fig. 5. This cup dle 71 having A'a downwardly-turned Vextremity 72 so that it may be conveniently supported on the edge of a water glass 73, containing a supply of water and supported in a ring 74 carried by the bracket 75. The bracket 75 rests on a lug 76 which -is pressed out of the back wall 21 .of the base and the end of the bracket lis provided with an upturned hook 77 which engages the upper edge of an aperture 78 formed in the plate 21, thus supporting the bracket 75 detachably on the plate 21 of the base so that it can be removed therefrom when desired.

In the operation of the apparatus, the opwater with the cup70, transferring the water from the supply vessel 73 to the feeding vessel 65, this being been placed on the tray 32 and after the'cover 38 has been placed in position on the receptacle 25. to the condition of soft-boiled eggs, for example,l the operator places in the vessel 65 one cup full of water as measured by the vessel v 70, 'and if it be desired to have medium boiled preferably be eggs, for example, two cup fulls of water may be transferred from the vessel 73 tothe receptacle 65, the extent of the cooking and the period of operation of the device being determined by the measured quantity of waterl which is placed in the feeding vessel 65,.-

As soon as the water is placed in the feeding vessel it passes downwardly .through the opening 68 and through an aligning opening 79 in the tray 32 into the space at the bottom of the chamber 30 where it forms a connection between the upper and the lower `electrodes and thereby completes the circuit. Aa soon as the circuit is completed, a bubble structure forms in the small quantity of water which is present and as more water is added the bubble structure increases in extent and simultaneously increases the area of the electrodes which are in active operation. As the bubbles are formed, they escape upwardly through the openings 63 in the upper elec'- trode 42 and around the outer edge 'of the upper electrode neath the cover 38, serves to cook the eggs 35. -The perforated stri'icture of the upper electrode produces such uniformity in thev If it be desired to cook the eggs and this vapor, collecting ben done-after the eggs have llll) For the purposel of illustrating the effect of the present invention in effecting an abrupt `termination of the' operation -o the apparatus, therevis illustrated in Fig. 11 anumber' of .curves which represent vdiagrammatierator measures a predetermined quantity of 55 l cally the operation of the apparatus, described above as compared with the operation of a similar apparatus having solid electrodes. In the chart shown in Fig. 1l, the abscissae 80 represent minutes of time and the ordinates 8l represent amperes of curr-ent flowing in the circuit. The curve 82 represents the conditions prevailing in the circuit of the apparatus described above, embodying a perforated upper electrode, when the entire measured quantity of water is placed inthe chamber before the current is turned on. Under these circumstances, lthe 'upper vand lower electrodes are connected by a solid body of water when the circuit is established so that the current at first rises to a relativ-ely high value as shown at 82a. As the bubbles are formed in the liquid to decrease its conductivity the value of the current drops rapidly during the first few seconds of operation, as shown at 82h. After the bubble formation has increased sufficiently to establish a stable condition, the curve assumes a gradual incline as shown at 82. The gradual decrease of the current continues until a point is reached Where only a drop or so of liquid is left between the electrodes. As this remaining quantity of liquid is quickly evaporated, the current drops off rapidly as shown at 82d and the current finally shuts off sharply to zero as shownat 82e. This curve represents the condition when the feeding recep` tacle is not employed for effecting a gradual application of the liquid to the electrodes.

.- If the liquid were gradually fed to the electrodes, the initial value of the current would of course be much lower than that represented at 82a. It will be observed that the apparatus has a relatively brief period of operation during which the currentis maintained at a relatively high value and at the end of which the current is shut off sharply to zero. The curve 83 represents the conditions which prevail in the circuit using the same appa-v ratus as that which was employed in taking the data for curve 82 exceptl .that the upper grid electrode was free of perforations although of the same diameter and thickness as the corresponding electrode used in taking the data for curve 82.r As before, the current was turned on after the entire measured quantity of liquid had been poured into the chamber 30 and upon closing the circuit,`the current rose to a relatively high value asl shown at 83a. The bubble formation in the liquid then caused the current to drop rapidly as shown at 83b until it finally assumed a sub# stantially constant and relatively low value as shown at 83. The value indicated at 83 continues with a gradual decrease as shown' at 83, the current finally reaching zero as shown at 83". This. curve shows that with ai solid electrode, the current hasa much higher value atvstarting, a much lower value during the major portion of the operation'of ythe apparatus, and a more gradual falling off to zero, so that the period of operation of the apparatus was more than twice the period of operation represented by the curve 82. The curve 84 represents the conditions prevailing in the circuit when a solid electrode was employed having the same area as the net area of the perforated electrode employed in taking the datafor curve 82-after making allowance for the area of they perforations. Vith the solid electrode of reduced area, the current at first rose to a value Sila'when the circuit was established through the body 0f liquid previously introduced into the chamber 30. This initialu value f the current is substantially midway between the initial values indicated by the curves 82 and 83. After the circuit was established, the current fell off rapidly and then assumed a more nearly constant value as represented bythe portion 84 of the curve, then the value of the current fell off gradually as shown at 84d and finally reached Zero at 84e. This curve indicates that the reduction of the area of the electrode had some effect in reducing the initial value of the starting current and that it effected a slight decrease in the total period of operation, but the value of the current during the major portion of the period of operation was substantially the same as that representedby the curve 83 and the period of operation was substantially twice that represented .by the curve 82. The perforated electrode not only maintains the current at a higher value during the period of operation but materially reduces the period of operation and when a point is reached where the quantity of water or other liquid remainin in the chamber 30 Ais relatively small, the istribution of this water over a relatively large active area ofthe perforated upper electrode causes this remaining quantity to be evaporated rapidly so that there is an abrupt shut-off ofthe current, indicated by the curve 82, as contrasted with the continuance for a protracted eriod Yofa relatively small current when soli electrodes are employed. .With the present invention, therefore, the liquid is vapor-ized more rapidly and the same Cookin operation is performed in a lesser period o time than is possible with the device constructed as represented by thecurves 83 and 84. It will be understood that the showing of Fig. 11 is for illustrative purposes and that other desirable operating conditions may be obtained vith apparatus embodying the present invenion.

In Fig. 12 there is illustrated a modified form of construction in which a vessel 85 is provided with a chamber 86 adapted to cntain a quantity 'of 'vaporizable' liquid 87. The vessel 85 is supported on an annular base portion 88 and is constructed of conducting material so that the annular tapered wall 89 thereof constitutes one of the electrodes lin conjunction `lith the bottom wall 90. An electric connection is made tothe vessel electrode through a conductor 91 havin a connection with the base at 92 and anot er conductor 93 leading to a terminal 94 which is mounted in an insulating bushin '95 located -lower wall of the electrode 96 but these are not considered necessary to the successful operation of this form of device because of the arrangement of the upwardly inclined surfaces 89 and 96a of the electrodes which are adapted to effect an increase in the active area of the electrodes when a bubble formation is formed while at the same time permitting a ready escape of the bubbles u wardly to the vapor space 100 in which any esired cooking operation may be performed. The vessel 85 is provided with a cover'101 having mounted thereon a feeding receptacle 102, similar to that previously described, and provided with `a restricted opening 103 through which, a

measured quantity of-liquid may befgradually fed to the electrodes in order to limitv the value of the starting current.

In Figs. 13 and 14, there is illustrated a third form of construction comprising alvessel 105 of insulating material supported on one or more legs 106 and provided with a cover 107 carrying a feedingreceptacle 108 having a restricted opening Y109 throughv which a measured d. quantity of'vaporizable liquid may be fed gradually to theinterior of the vessel 105. This vessel is provided in the lower part thereofwith a pocket 110 adapted to contain a quantity of liquid 111 fed thereto from the receptacle 108. The pocket 110 contains a lower trough shaped electrode 112 and an u per electrode 113 in tric with the electrode .112. The lower elec-- trode 112 is mounted firmly in position in the bottom of the pocket 110 bycmeans of a bolt 114 which is secured to or formed integrally with the electrode and which extends through the lowerwall of the pocket being engaged on its threaded extremity bynuts 115. The holt 114 also serves as a. binding post for an electric conductor 116 which is clamped between the nuts. The upper electrode 113 is removably mounted in the guide slots 117,

formed in the end walls of the pocket, and j rests upon terminal osts 118 which pass through the lower wa of the pocket110 and are engaged on their threaded extremities by e or cylinder concenf nuts 11 9. 'Ihe conductors 120 leading to the other side of the circuit are connected to both of the-terminals 118 to insure greater security of contact with the removable electrode 113. This construction spaces the

electrodes

112 and 113 from each other and when the current is established in the circuit the current flows between the electrodes throu h theli uid which is contained in the poc et 110. current 1s distributed over the entire length of the electrodes and the curved surfaces of the electrodes, permits a ready escape of the bubblesas they are formed by the passage of the current so that the current is maintained at a relatively high value free of ob- Jectionable fluctuations and an abrupt termination of the operation of the apparatusis l vbrought about.

A further advantage of the persent invention is that it enables the electric heatin pr cooking device to be used with liquids, suc las water, which vary widely in chemical composition. The device may therefore be used in various localities without the necessity of any preliminary treatment of the water or the electrodes in .order to secure the desired vaporization. l

i his application is in part a continuation of our co-pending application, Serial No. 665,761, tiled October 1, 1923, inwhich the use o f an electrode held in place entirely by gravity, and other features, are claimed. f In the 'present specication, and in the accompanying claims, where referenceis made to evaporation to substantial dryness of the vmeasured quantity of liquid contained in the receptacle, it will be understood that this evaporation includes not only the evaporation of t e liquid originally put into the receptacle but also ofthe water or other li uid condensate which collects and flows bac to the bottom of the receptacle. The amount of this condensate may vary depending upon the condition and surface areaof the objects, such as eggs, which are treated in the heating chamber of the receptacle.

. Although one form of' the invention has been'shown and described by way of illustration, it will be understood that it may be constructed'in various other embodiments with# out departing from the scope of the appended claims.

We claim; y.

l1. A liquid conductor heater in which a measured quantity @of liquid Vis evaporated substantially to dry-ness, comprising a receptacle provided with a heat treating chamber, and spaced electrodes in said receptacle adapted to make circuit closing contact lwith saidliquid and formed to eect aread'y 'es-l Sli lle

cape from the s ace between said electrodes measured quantity of liquid is evaporated y va',

substantially to dryness, comprising a receptacle provided with a heat treating chamber, and spaced horizontal electrodes located one above the other in said receptacle make circuit closingv contact with said liquid and formed to eii'ect a ready escape from the space between said electrodes of bubbles produced in said liquid by the passage of current therethrough, the evaporation to substantial dryness opening thecircuit between said electrodes.

3. A liquid conductor heater in which a measured quantity of liquid isevaporated substantially to dryness, comprising a receptacle provided with a heat treatingchainber, and spaced horizontal electrodes in s aid receptacle adapted vto make circuit closing contact with said measured quantity of liquid, one of said electrodes being perforated to effect a relatively rapid escape from the space between said electrodes of bubbles produced by the passage of-a current through said liquid y 4. A liquid conductor heater in which a measured quantity of liquid is evaporated substantially to dryness, comprising a recep tacle for retaining said measured quantity lof liquid until it substantially disappears by evaporation, and spaced electrodes located one above the other in said receptacle and comprising parts formed to effect a ready escape of bubbles from th'e space beween said electrodes, and means4 for supporting an object to be heated ina place having communication with the space occupied by said electrodes. A y

5. A liquid conductor heater in which a measured quantity of water is evaporated substantially to dryness, comprising a receptacle provided with a heat treating chamber, means for measuring said quantity of liquid', and spaced horizontal electrodes in said receptacle adapted to make circuit closing contact with said measured quantity of liquid, one of said electrodes being lperiorated to effect a ready escape from the space between said electrodes of bubbles produced by the passage of current through said liquid.

v6. A liquid conductor heater inv which a measured quantity of/liquid is evaporated substantiallyvto dryness, comprising a receptacle for retaining said measured quantity ofv liquid until it substantiallyv disappears by evaporation, and a pluralit of grid electrodes for making circuit c osing contact with said li uid in said receptacle, one of said electrodesl eing perforated to permit the ready escape of bubbles from the space between said electrodes. v

7. A liquid conductor heater in which a measured 'quantity of liquid is evaporated substantially to dryness, comprising a receptacle for a measured quantity of vaporizable liquid,- me'ans for eii'ec'ting a gradual introduction of .said liquidV into said receptacle,

and spaced electrodes located horizontally y escape of bubbles from the space between said electrodes.

8. A liquid conductor heater in which a measured quantity of liquid is evaporated substantially to dryness, comprising a receptacle for a measured quantity of vaporizable liquid, means for eecting a gradual-.introduction of said `liquid into said receptacle, and spaced electrodes located one above the other in said receptacle to make circuit closing contact with said liquid, the upper one ofsaid electrodes being perforated to permit the ready escape of bubbles from the space between said electrodes.

9. A liquid conductor heater for vaporizing a measured quantity of liquid to substantial dryness, comprising a receptacle for a measured quantity of vaporizable conducting liquid, means for introducing into said receptacle a measured. quantity of said liquid, and a pairv of spaced electrodes in the form of fiat plates located one above the other in said receptacle for making circuit-closing contact with saidli uid, the evaporation of the liquid opening t e circuit between said electrodes, the upper one of said electrodes having a plurality of distributed perfo'ra tions therethrou h to permit the escape of bubbles formed letween said electrodes. l0. A liquid conductor heater for va orizing a measured quantity of liquid to su stanvtial dryness, comprising a receptacle for a'.

lml

measured quantity of vaporizable conducting 'i liquid, means for intro ucing into said receptacle a measured quantity of said li uid, and a pair of spaced electrodes in the orm of iiat plates located one above the other in said receptacle for making circuit-closing contact with said liquid, the upper one of said electrodes having a plurality of distributed perforations therethrough to permit the ready escape of bubbles formed between said levaporation ofthe li uid to substantiall dryness opens the circuit etween said electrodes,

means for forming electric connections with said' electrodes, and insulatin means for spacing said electrodes apart, said upper electrode being perforated to permit the escape of bubbles created by the passage of current through then liquid between said electrodes.

12. A liquid conductor heater in which a measured quantity of liquid is evaporated substantially to dryness, comprising a receptacle for retaining said measured quantity of liquid until it substantially disappears by evaporation, spaced electrodes located one above the other in said receptacle for making circuit closing contact with said liquid, andv msulatmg means covering a portlon of said upper electrode. C

13. An electric apparatus of the class described, comprising a receptacle for a body of vaporizable liquid, upper and lower grid l electrodes mounted in said receptacle, said and lower grid electrodes mounted in sal -electrodes apart.

lower electrode having apertures therethrough, and insulating members formed on the bottom of said receptacle and extending upwardly through said apertures to engage said upper electrode and thereby space said 14. An electric apparatus of the class described, comprising a receptacle for a measured quantity of vaporizable liquid, upper and lower grid electrodes mounted in sai receptacle, means for forming an electric connection with said lower electrode, land a ter`- minal post extending upwardly through and linsulated from said lower electrode, said upper electrode lhaving a threaded connection with said terminal post; i

15. An electric apparatus of the class described, comprising a receptacle for a measured quantity of vaporizable liquid,v upper receptacle, means for forming an electric connection with said lower electrode, a central terminal post extending upwardly through and insulate-d from said lower electrode, said upper electrode having a threaded connection with said terminal post, and' insulating lmeans spacing said upper electrode from said lower electrode'.

16. An electric apparatus ofthe class de- Y scribed, comprising a receptacle for a meas- .ured quantity of vaporizable liquid, upper and lower grid electrodes mounted i'n said re'- ceptacle, an electric circuit connected to said lower electrode, a terminal post connected to said circuitand extending' upwardly through said lower electrode, means for insulating said terminal post from said lower electrode,

said lower electro-de having an aperture therethrough, and an insulating member extending through said aperture and engaging said upper electrode to space said electrodes apart,

said upper electrode being connected to said terminal post.

17. An electric apparatus of the class described, comprising a receptacle 'lor a measured quantity of vaporizable liquid, upper and lower grid electrodes mounted in said receptacle, an electric circuit connected to said lower electrode, a terminal post connected to lsaid circuit and extending upwardly through said lower electrode, means for insulating 'said terminal post from said lower electrode,

said-lower electrode having an aperture therethrough, an insulating member extending through said aperture and engaging said upper electrode to space said electrodes apart,

said terminal post being threaded, said upper electrode having a threaded connection with said terminal post.

18. The method of operating a liquid conductor heater in which electrodes are-adapted d to be connected by .a liquid conductor, which consists in impressing an electrical potential on said electrodes, applying a measured quantity of liquid to said electrodes, retaining said liquid in contact with saidelectrodes until said liquid has been evaporated substantially to dryness, and effecting an-,abrupt shut-oil of the passage of current'between said electrodes as the condition ofdryness is reached.

*19. -The method of operating a liquid cond ductor heater in which electrodes are adapted to be connected by a liquid conductor in a ves-