US2485894A

US2485894A - Humidity control system

Info

Publication number: US2485894A
Application number: US768995A
Authority: US
Inventors: Clarence W Kuhn
Original assignee: Cutler Hammer Inc
Current assignee: Cutler Hammer Inc
Priority date: 1947-08-16
Filing date: 1947-08-16
Publication date: 1949-10-25
Anticipated expiration: 1966-10-25

Description

Oct. 25, 1949. c. w. KUHN 2,485,894

HUMIDITY CONTROL SYSTEM v Filed Aug. 16, 1947 2 Shee'tS-Shet 1 ocr., 25,1949. 6W. zum l' 2,485,894

HUMIDITY CONTROL SYSTEM Filed Aug. 1s, 1947 2 sheets-shed 2 *g* '6o 6/ me 44 76 7 45' 70 3 d |||||||||66 60a 69 7343,21@ I|||||| s 469 56 42 67a 6/ 6'7 56a 70 74 7/ 70 5%- 5 @c a 7/ z 46e 56 f6* 57. .57 46 42* 46L 46 46 66C 6366 56a 69 so 69 4.25 6'/ 4a 46566346" 5K3. 4, 70

Patented Oct. 25, 1949 2.485.894 nUMmrrY coN'rnoL sYs'rEM Clarence W. Kuhn, Wauwaton, Wis.. assigner to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation oi' Delaware Application August 16, 1947,- Serial No. 768,995 11 Claims. (Cl. 236-44) 'This invention relates to improvements in humidity control systems. The invention relates more particularly to a novel and simple form of humidostat which is operable automatically to maintain at a substantially constant predetermined value the degree of humidity within a given space; for example, within the main food storage space of a household refrigerator.

A primary object of the invention is to provide a humidostat which may be readily and inexpensively constructed from parts or elements which are commercially available.

Another object is to provide a humidity control system which is adapted to utilize any desired or required portion of the moisture normally present within the area or chamber whose humidity is to be controlled.

Another object is to provide such a humidostat which is operable on the wetand dry-bulb principle.

Another object is to provide novel means for supplying moisture (water) to the wet bulb of the humidostat.

Another object is to provide means of the character just mentioned which is manually adjustable in a manner to insure attainment of the results desired.

Another and more specific object is to provide means associated with the cold evaporator of a refrigerator or the like to enable condensation and collection of moisture fromthe refrigerator compartment and automatic discharge .thereof onto a Wick associated with the wet-bulb of the humidostat.

Another object is to provide for automatic removal of at least a portion of the condensed humidity or frost from the cooling element of said refrigerator compartment as an incident to the aforementioned humidiication of said compartment.

Other objects and advantages of the invention wil1 hereinafter appear.

The accompanying drawings illustrate an embodiment of the invention which will now be described; it being understood that the embodiment illustrated is susceptible of modification in respect of certain structural details thereof without departing from the scope of the appended claims.

In the drawings,

Figure 1 is a schematic and diagrammatic illustration of one form of refrigerator having my improved humidity control means applied thereto.

Fig. 2 is a view, partly in section and partly in elevation, of the elements of a wetand dry-bulb humidostat as constructed in accordance with my invention.

Fig. 3 is a sectional view, on the line 3-3 of Fig. 2, with certain elements of the device omitted, for clarity oi illustration.

Fig. 4 is a bottom plan view of the assembled device, with the cover member removed.

Referring first to Fig. 1, the numeral II! designates in general a known type of domestic or household refrigerator, the various parts of which are shown more' or less schematically and diagrammatically. Thus the same is shown as provided at its upper end with a freezing compartment II, within which foods or liquids are to be frozen and/or maintained in a frozen condition. Fragments of the evaporating coil located within compartment II are shown diagrammatically at I2. I2. A thermostat Tl is located within compartment II; said thermostat being shown diagrammatically, and the same being adjustable manually to preselect any desired relatively low temperature (as for example, 0 F.) to be maintained within compartment II, through the medium of a suitable switch, as shown, controlled thereby.

The refrigerant is supplied to the cooling coil I2 through an expansion valve V, by a conduit I3, the lower end of which leads from a receiver I4 into which the liquid refrigerant is dischargedfrom a condenser I5. The refrigerant is supplied to condenser I5 from a compressor I6, which is preferably driven by an electric motor I1, under the control of the aforementioned thermostat T1. The vaporized or partially vaporized refrigerant is drawn into compressor I6 through conduits 20 and I8 from the left-hand end of the refrigerating coil I2, I2. Thus upon closure of the switch cont'acts controlled by thermostat T1 a circuit is completed for motor I1; which circuit extends from supply line Ll by conductor 2l through the switch contacts of thermostat T1, by conductor 22 to one terminal 23 of motor I1, and from the other terminal 24 of said motor by conductor 25 to line L2. The aforedescribed circuit of motor Il will be maintained by thermostat T1 pending restoration of the predetermined' desired low temperature within compartment Il.

The main food compartment 26 of refrigerator I 0 is provided with a thermostat'Tz, which is preferably manually adjustable to preselect the desired range of temperature to be maintained therein. For example, thermostat T2 may be so adjusted as to provide for closure of the switch contacts, as shown, controlled thereby, when the temperature within compartment 25 rises to 42 degrees F. or above, and to provide for return of the switch contacts to their open position when the temperature within compartment 26 is re duced to about 36 degrees F. Upon closure of the contacts controlled by thermostat T2 a circuit is completed for effecting operation of motor I1 (if said motor is not already in operation by closure o the aforementioned contacts controlled by thermostat T1) and an energizing circuit is simultaneously completed for the operating winding 21 of a solenoid 28.

Said motor circuit may be traced from line L1, by conductor 29 through the movable contact of thermostat 'I2 to the lower stationary contact of the latter, by conductoi's 3| and 22 to motor terminal 23, and from motor terminal 24 by conductor 25 to line L2. The energizing circuit for said winding 21 may be traced from line L1, by conductor 29 through the movable contact of thermostat 'Ie to the upper stationary contact of the latter, by conductor 30 through winding 21, and by conductor 32 to line L2. nThe winding 21 when energized is adapted to eiect movement of a valve, shown diagrammatically at I9, to open position; valve I9 being normally biased to closed position in any suitable manner, as by means of the coiled tension spring 33. Valve I9 when thus opened aiords communication, through

conduits

35 and 36, from the right-hand end of coil I2, I2 to the inlet end of the coil or zigzag path afforded for circulation of the refrigerant through the so-called cold-Wall" 31 of the compartment 26. Although I have shown the cold-wall cooling or refrigerating element 31 at the rear wall of compartment 26, it is to4 be understood that the same may be located in another'or additional walls of said compartment. After circulation through the coil provided in the cold wall 31 the refrigerant discharges through conduit 38 to conduit I8 and is drawn into the compressor I6 in complete the circuit of flow of the refrigerant.

Valve I9 will be maintained in open position pending a drop in the temperature in compartment 26 to the desired value, say, 36 degrees F.

When said temperature has been reached thermostat 'I'2 will act automatically to interrupt the manner aforedescribed to the energizing circuit of winding 21 of solenoid 28 to permit valve I9 to be returned under the bias of spring 33 to its normally closed position. The contacts of thermostat T2 when opened will also interrupt the last mentioned energizing circuit of motor I1; and the latter may or may not continue in operation, depending upon whether or not the contacts of thermostat T1 are then in closed position.

The compartment I I is shown as having a door 39 which may be opened by operation of an unlatching handle 40; whereas compartment 26 is provided with a correspondingly larger door 4I which may likewise be opened by voperation of a second unlatching handle 4l).

As is well understood, there will normally be a quantity of moisture within the food compartment 26 which is more than enough to afford the desired degree of humidity therewithin, if such moisture were diffused in the compartment atmosphere. However, by reason of the cooling eifect produced by the cold-wall element 31 the moisture will be gradually condensed upon element 31 and thus withdrawn from the compartment atmosphere. For example, if the thermostat 'I'2 is so adjusted as to provide for maintenance within compartment 26 of a temperature ranging from 36 degrees F. to 42 degrees F., it will likewise be desirable to maintain a relatively high and substantially constant degree of humidity of the compartment atmosphere; as, for instance, a humidity of ninety per cent, to prevent any substantial degree of dehydration of the articles of food, and to minimize other types of deterioration or spoilage thereof.

I have accordingly provided means which is operable automatically to maintain the degree of humidity of the atmosphere of compartment 26 vat a substantially constant desired Value; said means including manually adjustable means to associated. Therefore the diaphragm of the loW- 4 enable definite preselection or variation of the degree of humidity to be maintained.

As aforestated, my humidity control means is adapted to utilize the well known differential value of the pressures aiorded by thermally responsive elements subjected to the temperature of an ambient medium common thereto, when one of said elements is provided with a so-called dry-bulb and the other element is provided with a wet-bulb. A suitable switch (such as a snap switch of the Micro type) is subject to control in accordance with predetermined variations in said differential value' to provide for maintenance of a substantially constant preselected degree of humidity within the food compartment 26.

As shown somewhat schematically in Fig. 1, and in greater detail in Figs. 2, 3 and 4, the means for control of the degree of humidity within compartment 26 comprises essentially a support member 42, which is attached in any suitable manner (not shown) to a wall of the -compartment 26. Attached to support 42 ina predetermined spaced relationship to each other are a pair of like, or substantially similar, power elements each comprising a housing creasing 43, a flexible member or diaphragm being positioned therewithin and sealed thereto in a well known manner, as indicated in dotted lines at 44 in Fig. 1; and each diaphragm having rigidly attached thereto a pin, the oppositely projecting pointed ends 45 oi which pins are biased toward each other to simultaneously engage opposite surfaces of a lever 46 which is pivotally attached to and supported by an inverted LI-shaped bracket 48 rigidly attached to support 42. The

housings

43, 43 have

nipples

49, 49 sealed thereto, and suitable lengths of tubing 50 and 5| are in turn sealed to said nipples.

As shown, all portions of the tubes 50 and 5I are located within compartment 26, and the same are preferably provided with bulbs or equivalent portions of Well known character. By way of example, I have shown the tubes 50 .and 5I as provided at the outer ends thereof with spirally wound or coiled portions 50a and 5Ia. The bulb 5I is adapted to act as the dry-bulb of my humidity control system. The bulb 5I)a has associated therewith a wick, which as shown at 53 may be in the form of a suitable length of woven fibrous material enveloping said bulb. As will be apparent, the bulb 50B covered or substantially covered by wick 53 is adapted to act as the wet-bulb of the system.

In accordance with my invention means are provided for keeping the wick 53 saturated with moisture (water) Said means is shown as comprising a metal rod 54, at least a portion of the upper end of which is subjected to the relatively low temperature prevailing in the compartment II. Such relatively lowltemperature is, at least in part, transmitted to the lower end portion of rod 54 located within compartment 26; said rod preferably having an enlarged or head portion 55 at its lower end. Due to the relatively lower temperature of head 55, as compared with the temperature normally maintained within compartment 26, a portion of the moisture or humidity of the atmosphere Within compartment 26 is condensed upon head 55 and dripsin a drop-bydrop manner upon wick 53 to effect saturation of the latter.

The dry-bulb portion 5I will inherently be subjected to a relatively higher temperature than the wet-bulb portion 5I)a with which wick 53 is er thermally responsive device in Fig. 1 will cause a preponderance of pressure to be applied to the lower surface of lever 46, to bias the latter upwardly, or in a clockwise direction. Lever 46 has attached thereto the upper end of a coiled tension spring 56; the lower end of said spring being attached to a' threaded bolt 51, with which a nut 56 is associated: nut 56 being manually rotatable with respect to bolt 51 and with respect to bracket 46 (the lower connecting portion of which abuts against the upper end of nut 58), as by means of the knob 56* to adjust the degree of tension of spring 56. By this means the effect of the differential value of the downward, and upward pressures of the respective upper and

lower diaphragms

44, 44 upon lever 46 may be varied at will, to correspondingly vary the percentage value of humidity within compartment 26 at which the lower diaphragm will act, against the bias of upper diaphragm 44 and spring 56, to eifect such a degree of upward movement of lever 46 as will eifect circuit completing operation of a switch 59; which is attached to a bracket 60, in turn attached to support 42.

It is to be understood that switch 56 is preferably of the normally closed Micro type. That is to say, switch 59 in inherently biased toward its circuit completing position. Thus upon a predetermined relatively small degree of upward movement of lever 46 (to permit a corresponding degree of upward movement of plunger 6I) the movable contact of switch 56 will snap into circuit completing engagement with its associated stationary contact. Any other suitable form of normally closed snap switch which requires only a relatively small amount of power for operation thereof may be employed. Also it is to be understood that so long as the percentage of humidity in the air in compartment 26 is within the range preselected therefor, the lever 46 will remain in the position thereof illustrated to restrain switch 56 against movement to its normally closed position.

As shown, I prefer that the metal rod 54 shall be adjustable manually so that more or less oi' the upper end portion thereof shall be subjected tu the temperature prevailing in compartment I I, to correspondingly vary the temperature of the head 55 when the temperature within compartments II and 26 are of given values relatively to each other. For this purpose the rod 54 may be threaded externally for cooperation with a threaded member or recess 62 located within compartment I I. For example, the threaded recess may be formed in the evaporator casing or housing (not shown) located within compartment II. Thus with a given percentage of humidity (say ninety per cent) of the air within compartment 26 at a given temperature therewithin (say 36 degrees F.) the head 55 of rod 54 will be rendered colder as the threaded shank thereof is screwed further up into the compartment II. Such lowering of the temperature of head 55 will result in an acceleration of the rate of condensation of moisture thereon from the air within compartment 26.

As aforeindicated, the percentage of humidity in the air within compartment 26 will be gradually decreased by reason of the condensation of moisture upon the aforementioned cold-wall 31. By reason of the increase in the rate of evaporation of moisture from the latter (because of the lower percentage of humidity in the air in compartment 26, as aforementioned), the temperature of the thermally expansible Iiuid in the wetbulb device will be substantially reduced, with a corresponding reduction in the value of the fluid pressure directed downwardly against the upper diaphragm 44; so that the upward force applied to lever 46 by the lower diaphragm 44 (dry-bulb device) will eventually predominate over the downward forces applied jointly by the wet-bulb device and spring 56 to lever 46; whereupon the lever 46 moves upwardly to an extent sumcient to permit movement of switch 56 to circuit completing position under its own inherent bias.

Upon closure of switch 59a circuit is completed for effecting operation of an electric motor 63 which drives the fan blades 64. Said circuit may be traced from line L1 by conductor 65 through the contacts of switch 59 (when closed), by conductor 66 through the winding of motor 63, and by conductor 61 to line L. Motor 63 may be mounted at a suitable angle, as shown, so that the flow of air from the fan blades 64 is directed upwardly against and along the surface of the coldwall 31 to effect evaporation and removal of at least a portionof the moisture condensed thereon,

and to effect diilusion of such moisture throughout the body of air within compartment 26. Such evaporation of the moisture condensed upon the cold-wall 31 will be effected whether such moisture is in the form of water droplets or in the form of frost.

The resulting increase in the percentage of humidity in the air in compartment 26 will be reflected by a corresponding decrease in the rate of evaporation of moisture from the wick 53, and as a consequence of said decrease in rate of evaporation the downward pressure of the upper diaphragm 44 (of the wet-bulb device) upon lever 46 will be increased without a corresponding decrease of the upward pressure of the lower diaphragm 44 (of the dry-bulb device) upon-said lever; so that the bias afforded jointly by the upper (wet-bulb) diaphragm 44 and spring 56 will eventually predominate over the bias of the lower (dry-bulb) diaphragm 44 to increase the degree of pressure applied by lever 46 to plunger 6 I, until a given point is reached at which switch 59 will be snapped to its circuit-interrupting position, against the normal or inherent bias thereof, thus discontinuing the operation of motor 63.

As will be apparent to those skilled in the art, the humidity control means for the compartment 26 is adapted to function in the manner desired and preselected by the adjustment of nut 56 regardless of the particular settings of the thermostate T1 and T2; although, of course, it is to be understood that thermostat T1 will always be set to aiord a lower temperature within compartment I I than it is desired to maintain within compartment 26 by the setting of thermostat T2.

Although I have herein illustrated my humidity. control device as combined with a known form of refrigeration control system including a freezing compartment and an ordinary refrigerating compartment, itis to be understood that the main features of my humidity control system are like- Wise applicable to other forms of refrigeration control, including various types of air conditioning equipment now on the market.

In Figs. 2, 3 and 4 I have illustrated certain structural details of certain elements of a humidity control system constructed in accordance with my invention. More particularly, the support is preferably formed of a single punched sheet of metal bent to provide a flat top wall portion 42. Said top wall y42 of the support has a pair of parallel side wall portions 42 and 42b formed integrally therewith; the upper edges of portions 42a and 42b being preferably located in a common plane, as best illustrated in Fig. 3. Attached to the top wall portion 42 (Fig. 2) is a relatively smaller U-shaped sheet metal member 60, the downwardly extending parallel arms of which are designated by numerals 8l)a vand 60". The top wall portion 42 is provided with clearance openings and the top portion of member 68 is provided with tapped openings (Fig. 2) to accommodate the shanks of a pair of screws 68, 68 whereby member 60 lis rigidly attached to portion 42. The arms 60B and (illb of member 60 are provided with alined vpairs of openings to accommodate a pair of

bolts

69, 69, the shanks of which penetrate suitable openings or passages extending transversely through the insulating housing or base portion of the aforementioned switch 59. As will be understood, said insulating housing of switch 59 is usually of two-part construction; but the specific construction thereof forms no part of the present invention. Nuts 69 are associated with bolts 69 (as shown in Fig. 4) to rigidly attach and position switch 59 with respect to member 60 and the top wall 42 of the support. The operating plunger 6l of switch 59 is shown depressed in Fig. 2, to provide for disengagement of its contacts.

The aforementioned sheet metal member 48 of channel-shape has its upwardly extending parallel arms 482l and 4Bh bent to form horizontal flange portions 48 and 48d; said flange portions having tapped openings formed therein to accommodate the shanks of a second pair of screws 18, which may be of the same form and size as screws 68, 68 aforementioned. Arms 48 and 48b are provided with a pair of

alined openings

48 and 48; the former being adapted to accommodate the full diameter (Fig. 3) of a pivot pin 1l and the latter being ofsmaller size to accommodate the reduced end portion 1la of said pin; said reduced end portion 1I being upset over the outer surface of arm 48b to rigidly and permanently secure pin 1I in position, as indicated at 1|b in Figs. 3 and 4.

Also as shown the pivot pin 1| extends through bearing openings provided in the upwardly projecting arm portions 12B and 'l2b of a sheet metal member 12, whereby the latter is pivotally supported by pin 1I relatively to member 48 and the top wall portion 542 of the support member. A pin 14 (Figs. 2 and 3) is attached to and extends between the aforementioned arm portions 12a and l2b at a point to the right of, and preferably below, the plane of support of pivot pin 1l (Fig. 2). Pin 14 is adapted to be engaged by the hooked upper end of a coiled tension spring 56, the hooked lowerA end of which engages an eye or opening 51a formed in the upper end of a threaded stud or bolt 51, has clearance through an opening 48g (Fig. 2) formed in the lower or connecting portion of member 48. A specially formed nut 58 is internally threaded for cooperationwith the thread on stud 51; said nut 58 being adapted to seat against the lower surface of the connecting portion of member 48,l so that upon rotation of the nut in one direction or the other the stud 51 will be lowered or raised to increase or decrease the degree of tension of spring 56. Nut 58 is provided with a knob or enlargement 58a to facilitate manual adjustment thereof. Said connecting portion of member 48 is provided on diametrically opposite sides of opening 483 with at least one pair of extruded or downwardly bent portions 48h and 48i of triangular or knife-edge form in transverse cross section, and the upper end of the lower end of which.

nut 58 is provided with four notches or slots spaced ninety degrees from each other; one of said notches being shown at 58h in Fig. 2 and another notch being shown at 58c in Fig. 3.

As will be understood, each diametrically opposed pair of notches is adapted for'movement into alinement and engagement Iwith the extruded portions 48h and 48l to prevent accidental rotation of nut 58. More particularly, the arrangement is such that nut 58 may be moved in either direction and retained in any one of four rotary positions for each complete turn of nut 58 during adjustment of the tension of spring 55.

Member 12 is provided in the lower wall of its channel with an opening 12c (Fig. 2) to provide clearance for spring 56.

The channel-shaped portion of member 12 is preferably made shallower for a part of its length, as indicated by one of the two side walls shown at 12':1 in Fig. 2. The straight left-hand end portion of member 12 is preferably oiset upwardly from the lower end wall of its channelshaped portion, as indicated at 12e in Fig. 2, so that said right-hand end portion is normally located in a substantially horizontal plane, when plunger 6I is depressed to effect circuit interr-uption by switch 59, as illustrated. Also, as shown in Fig. 2,the lower end wall of the channelshaped portion of member 12 is circularly cupped or offset upwardly, as indicated at 12f; the flat upper end wall of said offset having an opening 128 formed therein to accommodate the reduced lower end portion of a hardened steel plug member 13; said reduced portion being peripherally .upset or ring-staked, as indicated at 13B, to rigidly and permanently attach member 13 t0 member 12. Member 13 is provided in its upper and lower ends with recesses 13h and 13 (preferably of conical form) which serve as abutments for the conical ends of

pins

45, 45 respectively attached to the upper and lower diairagms of the thermally responsive members With the parts assembled as shown in'Fig. 2, and with the bulbs 5|)a and 5la subjected to like temperature conditions (but with wick 53 completely saturated with moisture, to provide the wet-bulb effect of the upper power element 43), the nut 58 may` be manually adjusted so that the left-hand end portion of member 12 just touches the outer end of plunger 6I, as illustrated. With the degree of tension of spring 56 adjusted in the manner just described the same is adapted to apply a predetermined degree `of force tending to move lever 12 downwardly, to counteract the corresponding upward force applied to lever 12 by the pin 45 of the lower power element 43 (as an incident to the pressure of the liquid within the latter at a given temperature). For reasons aforedescribed,when the percentage of humidity in the air in the aforementioned compartment 26 decreases the downward presure applied by the pin 45 of the upper power element 43 will correspondingly decrease, and the pressure of the dry-bulb diaphragm will act to gradually effect upward movement of lever 12 to a degree sulcient to permit circuitcompleting operation of switch 59, for the purpose aforedescribed.

As will be apparent to those skilled in the art,

`it may be found desirable in a given installation to either increase or decrease the degree of tension of spring 56, to correspondingly vary the humidity percentage point at which the circuitclosing operation of switch 59 is effected. Al-

though I have disclosed the use of an adjustable tension spring B8 to provide the desired initial downward bias of lever 12, it is to be understood that an adjustable coiled compression spring may be substituted therefor;- such a compression spring, when employed, being interposed between the upper surface of lever 12 and an underlying portion of the aforementioned top wall portion 42 of the support member.

Although as herein illustrated I prefer to employ a pair of thermally-

responsive power elements

43, 43 of substantially equal value, it may be found desirable in certain installations to employ elements of unequal power, but arranged in the manner herein illustrated.

Other changes in the structural form and arrangement of the elements of my humidity con-I trol system will at once suggest themselves to those skilled in the art.-

I claim:

1. In combination, a humidostat comprising a pair of like power members each comprising a bulb, a diaphragm and a filling of thermally expansible fluid, means for flxedly supporting said members with the diaphragms thereof in opposed relationship to each other, one of said members being oi' the dry-bulb type and the other member being of the wet-bulb type, a pivoted lever interposed between said diaphragms, manually adjustable spring means associated with said lever to aiford a preselected degree of force in opposition to the force applied to said lever by the diaphragm of said dry-bulb member, a plunger type snap switch mechanism inherently biased to its closed position and normally held by said lever in open position, said lever being so arranged in operative relationship to the normally projecting operating plunger of said switch as to eiIect release of said plunger to complete an electric circuit when the percentage of humidity in the air to which said humidostat is subjected falls below a value preselected by the adjustment of 'said spring means, a source of moisture, an electric fan the motor of which is adapted to be operated upon completion of said circuit, and said fan when operated being adapted to produce a flow of air coacting with said source of moisture to eil'ect an increase in the percentage of humidity in said air pending attainment of a value thereof so preselected by the adjustment oi' said spring means.

2. In combination, a humidostat comprising a pair of like power members each comprising a bulb, a diaphragm and a filling of thermally expansible fluid, means for fixedly supporting said members with the diaphragms thereof in opposed relationship to each other, one of said members being of the dry-bulb type and the other member being ol.' the wet-bulb type, vif pivoted lever interposed between said diaphragms, manually adjustable spring means associated with said lever to aord a preselected degree of force in opposition to the force applied to said lever by the diaphragm of said drybulb member, a plunger type snap switch mechanism inherently biased to its closed position and normally held by said lever in open position, said lever being so arranged in operative relationship to the normally projecting operating plunger ofvsaid switch as to eilect release of said plunger to complete an electric circuit when the percentage of humidity in the air to which said humidostat is subjected falls below a value preselected by the adjustment of said ated upon completion of said circuit, said fan when operated being adapted `to produce a ow of air coacting with said source of moisture to eil'ect an increase in the percentage of humidity in said air pending attainment of a value thereof so preselected by the adjustment of said spring means, said wet-bulb having a wick associated therewith, and associated means operable automatically to substantially continuously supply moisture to said wick ata rate directly proportional to the instantaneous percentage of humidity in said air.

3. In combination, a humidostat comprising a pair of like power members each comprising a bulb, a diaphragm and a illling of thermally expansible iluid, means for lxedly supporting said members with the diaphragms thereof in opposed relationship to each other, one of said members being of the dry-bulb type and the other member being of the wet-bulb type, a pivoted lever interposed between said diaphragms, manually adjustable spring means associated with said lever to aii'ord a preselected degree of force in opposition to the force applied to said lever by the diaphragm of said dry-bulb member, a plunger type snap switch mechanism inherently biased to its closed position and normally held by said lever in open position, said lever being so arranged in operative relationship to the normally projecting operating plunger of said switch as to effect release of said plunger to complete an electric circuit when the percentage of humidity in the air to which said humidostat is subjected falls below a value preselected by the adjustment of said spring means, a source of moisture, an electric fan the motor of which is adapted to be operated upon completion of said circuit, said fan when operated being adapted to produce a ilow of air coacting with said source of moisture to eilect an increase in the percentage of humidity in said air pending attainment of a value thereof so preselected by the adjustmnt of said spring means, said wet-bulb having a wick associated therewith, associated means operable automatically to substantially continuously supply moisture to said wick at a rate directly proportional to the instantaneous percentage of humidity in said air, said last mentioned means comprising a metal member overlying said wick, and means for maintaining said metal member at a temperature at all times substantially lower than the temperature of said air, to thereby condense a portion of the moisture in the latter and discharge the same upon said wick.

4. In combination, a humidostat comprising a pair of like power members each comprising a bulb, a, diaphragm and a filling of thermally expansible fluid, means for iixedly supporting said members with the diaphragms thereof in opposed relationship to each other, one of said members being of the dry-bulb type and the other member being of the wet-bulb type, a pivoted lever interposed between said diaphragms, manually adjustable spring means associated with said lever to afford a preselected degree of force in opposition to the force applied to said lever by the diaphragm of said dry-bulb member, a plunger type snap switch mechanism inherently biased to its closed position and normally held by said lever in open position, said lever being so arranged in operative relationship to the normally projecting operating plunger of said switch as to eil'ect release of said plunger to complete an elec- 11 tric circuit when the percentage of humidity in the air to which said humidostat is subjected falls below a value preselected by the adjustment of said spring means, a source of moisture, an electric fan the motor of which is adapted to be operated upon completion of said circuit, said fan when operated being adapted to produce a flow of air coacting with said source of moisture to eiect an increase in the percentage of humidity in said air pending attainment of a value thereof so preselected by the adjustment of said spring means, said wet-bulb having a wick associated therewith, associated means operable automatically to substantially continuously supply moisture to said wick at a rate directly proportional to the instantaneous percentage of humidity in said air, said last mentioned means comprising a metal member having a threaded end portion adjustably insertable into an associated freezing compartment whereby said metal member may attain a. temperature substantially lower than the temperature of said air, to thereby effect condensation of a portion of the moisture in the latter and discharge thereof onto said wic 5. In a combined temperature and humidity control system, in combination, a compartment, means operable automatically to maintain at a substantially constant preselected value the temperature within said compartment, such temperature normally tending to effect condensation of the moisture in the air in said compartment whereby the percentage of humidity in said air is gradually reduced, means responsive to a decrease in the percentage of humidity in said air below a predetermined value to automatically effect an increase in the percentage of humidity to said predetermined value, said4 last mentioned means comprising a pairl of thermally responsive power units positioned in differential relationship to each other, one of said units being of the dry-bulb type and the other being of the wetbulb type, an electric motor, a fan to be driven thereby, said fan when operating acting upon said conden-sed moisture to effect an increase in the percentage of humidity in said air to the aforementioned predetermined value, a switch adapted when closed to effect operation of said motor, operating means for said switch subject to control in accordance with the differential action of said power units, and means associated with said wet-bulb unit to modify the temperature effect upon the latter to a degree proportional to the degree of such humidity.

6. In a combined temperature and humidity control system, in combination. a compartment, means operable automatically to maintain at a substantially constant preselected value the temperature within said compartment. such temperature normally tending to effect condensation of the moisture in the air in said compartment whereby the percentage of humidity in said air is gradually reduced. means responsive to a decrease in the percentage of humidity in said air below a predetermined value to automatically effect an increase in the percentage of humidity to said predetermined value. said last mentioned means comprising a pair of thermally responsive power units positioned in differential relationship to each other. one of said units being of the dry-bulb type and the other being of the wetbulb type. an electric motor, a fan to be driven thereby, said fan when operating acting upon said condensed moisture to effect an increase in the percentage of humidity in said air to the aforementioned predetermined value, a switch adapted when closed to effect operation ofsaid motor, operating means for said switch subject to control in accordance with the differential action of said power units, means associated with said wet-bulb unit to modify the temperature effect upon the latter to a degree proportional to the degree of such humidity, and manually adjustable spring means associated with said switch operating means to provide for preselection of any desired percentage of humidity within a given range to be maintained within said compartment. 7. In a combined temperature and humidity control system, in combination, a compartment, means operable automatically to vmaintain at a substantially constant preselected value the temperature within said compartment, such temperature normally tending to effect condensation of the moisture in the air insaid compartment whereby the percentage of humidity in said air is gradually reduced, means responsive'to a decrease in the percentage of humidity in said air below a predetermined value to automatically effect an increase in the percentage of humidity to said predetermined value, said last mentioned means comprising a pair of thermally responsive power units positioned in differential relationship to each other, one of said units being of the dry-bulb type and the other being of the wet-bulb type, an electric motor, a fan to be driven thereby, said fan when operating acting upon said condensed moisture to eiect an increase in the percentage of humidity in said air to the aforementioned predetermined value, a switch adapted when closed to effect operation of said motor, operating means for said switch subject to control in accordance with the diierential action of said power units, means associated with said wet-bulb unit to modifyl the temperature eiect upon the latter to a degree proportional to the degree of such humidity, and manually adjustable spring means associated with said switch operating means to provide for preselection of any desired percentage of humidity within a given range to be maintained within said compartment, said means associated with said wet-bulb unit comprising an element located within said compartment and having a temperature continuously lower than the temperature within the latter, whereby moisture is condensed from the air in said compartment and deposited upon the wet-bulb at a rate directly p'loportional to the percentage of humidity in the a 8. In a combined temperature and humidity control system, ln combination, a compartment, means operable automatically to maintain at a substantially constant preselected value the temperature within said compartment, such'temperature normally tending to eiect condensation of the moisture in the air in said compartment whereby the percentage of humidity in said air is gradually reduced, means responsive to a decrease in the percentage of humidity in said air below a predetermined value to automatically effect an increase in the percentage of humidity to said predetermined value, said last mentioned means comprising a pair of thermally responsive power units positioned in differential relationship to each other, one of said units being of the dry-bulb type and the other being of the wet-bulb type, an electric motor, a fan to be driven thereby, said fan when operating acting upon said condensed moisture to effect an increase in the percentage of humidity in said air to the aforementioned predetermined value, a switch adapted when closed to eect operation of said motor, 'operating means v for said switch subject to control in accordance with the diierential action of said power units, means associated with said wet-bulb unit to modify the temperature eiect upon the latter to a degree proportional to the degree of such humidity, manually adjustable spring means associated with said switch operating means to provide for preselection of any desired percentage of humidity within a given range to be maintained within said compartment, said means associated with said wet-bulb unit comprising an element located within said compartment and having a temperature continuously lower than the temperature within the latter, whereby moisture is condensed from the air in said compartment and deposited upon the wet-bulb at a rate directly proportional to the percentage of humidity in the air, and means providing for adjustment of the position of said element within said compartment to correspondingly vary the temperature of said element.

9. In combination, a refrigerating compartment, means operable automatically to maintain at a substantially constant preselected value the refrigerating temperature within said compartment, such temperature normally tending to effect condensation of the moisture in the air in said compartment whereby the percentage of humidity in said air is gradually reduced, means responsive to a decrease in the percentage of humidity in said air below a predetermined value to automatically effect a predetermined increase in said percentage of humidity, said last mentioned means comprising a pairof opposed thermally responsive power elements one of which is of the dry-bulb type and the other of which is of the wet-bulb type, a pivoted lever interposed between said power elements and normally operable in accordance with the differential value of the forces applied by the latter, spring means associated with said lever to counteract the major portion of said differential value, a normally closed switch mechanism normally held open by said lever and releasable by the latter for movement to closed position upon a predetermined decrease in said differential value as an incident to a corresponding decrease in said percentage of humidity, an electric fan having a motor the cir'- cuit of which is completed upon closure of said switch, and said fan when operated acting upon said condensed moisture to effect an increase in the percentage of humidity in said air to the aforementioned predetermined value in accordance with the counteracting force applied by said spring means.

10. In combination, a refrigerating compartment, means operable automatically to maintain at a substantially constant preselected value the refrigerating temperature within said compartment, such temperature normally tending to effect condensation of the moisture in the air in said compartment whereby the percentage of humidity in said air is gradually reduced, means responsive to a decrease in the percentage of humidity in said air below a predetermined value to automatically effect a predetermined increase in said percentage of humidity. said last mentioned means comprising a pair of opposed thermally responsive power elements one of which is of the dry-bulb type and the other of which is of the wet-bulb type. a pivoted lever interposed between said power elements and normally operable in .accordance with the differential value of the forces applied by the latter, adjustable spring 14 means associated with said lever to counteract the major portion of said dinerential value, a normally .closed switch mechanism normally held open by said lever and releasable by the latter for movement to closed position upon a predetermined decrease in said differential value as an incident to a corresponding decrease in said percentage of humidity, an electric fan having a motor the circuit 'of which is completed upon closure of said switch, said fan when operated acting upon said condensed moisture to effect an increase in the percentage of humidity in said air to the aforementioned predetermined value in accordance with the adjustment of said spring means, and means associated with said wet-bulb to substantially continuously supply to the latter an amount of moisture which is directly proportional to the instantaneous percentage of humidity in said air.

l1. In combination, a refrigerating compartment, means operable automatically to maintain at a substantially constant preselected value the refrigerating temperature within said compartment, such temperature normally tending to effect condensation of the moisture in the air in said compartment whereby the percentage of humidity in said air is gradually reduced, means responsive to a decrease in the percentage of humidity in said air below a predetermined value to automatically effect a predetermined increase in said percentage of humidity. said last mentioned means comprising a pair of opposed thermally responsive power elements one of which is of the dry-bulb type and the other of which is of the wet-bulb type, a pivoted lever interposed between said power elements and normally operable in accordance with the differential value of the forces applied by the latter. adjustable spring means associated with said lever to counteract the major portion of said diierential value. a normally closed switch mechanism normally held open by said lever and releasable by the latter for movement to closed position upon a predetermined decrease in said differential value as an incident to a corresponding decrease in said percentage of humidity. an electric fan having a motor the circuit of which is completed upon closure of said switch, said fan when operated acting upon said condensed moisture to effect an increase in the percentage of humidity in said air to the aforementioned predetermined value in accordance with the adjustment of said spring means. means associated with said wet bulb to substantially continuously supply to the latter an amount of moisture which is directly proportional to the instantaneous percentage of humidity in said air. said last mentioned means comprising a wick surrounding said wet-bulb, a rod upon which the humidity in said air is condensed, and means for. continuously maintaining said rod at a temperature substantially lower than the temperature of said compartment f CLARENCE W. KUHN.

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