US2583906A - Constant temperature cabinet - Google Patents

Description

Jan. 29, 1952 w. VAN GUILDER CONSTANT TEMPERATURE CABINET 6 Sheets-Sheet 1 Filed Jan. 13, 1948 QM/fer 26/7 Gza/aer 4P4 4 4/ a; J TTO NZ;

Jan. 29, 1952 w. VAN GUILDER CONSTANT TEMPERATURE CABINET 6 Sheets-Sheet 2 Filed Jan. 15, 1948 zo 46 /8 49 5 J5 *1 ia 1 Jan. 29, 1952 w. VAN GUILDER 2,533,906

CONSTANT TEMPERATURE CABINET Filed Jan. 13, 1948 6 Sheets-Sheet 3 mp; %/fer )6)? Gui/dew O mE Jan. 29, 1952 w. VAN GUILDER CONSTANT TEMPERATURE CABINET 6 Sheets-Sheet 4 Filed Jan. 13, 1948 %l Ler- Van 5' Jan. 29, 1952 w, VAN GUlLDER 2,583,906

CONSTANT TEMPERATURE CABINET Filed Jan. 13, 1948 6 Sheets-Sheet 6 Wag Qkfmfek Va Guilder- Q g H-rrchmaY-J Patented Jan. 29, 1952 CONSTANT TEMPERATURE CABINET Walter Van Guilder, River Forest, Ill., assignor to Precision Scientific 00., Chicago, 111., a corporation of Illinois Application January 13, 1948, Serial No. 1,946

12 Claims.

The invention relates to constant temperature cabinets generally, and more particularly to cabiof the type in which the working chamber is maintained at a constant temperature by circulating a tempered gaseous heat exchange medium thereabout.

One object of the invention is to provide a cabinet of the above general character embodying novel features of construction for maintaining the temperature throughout the working chamber very uniform and within closer limits than has been practical heretofore.

Another object is to provide a novel heat exchange system for cabinets adapted to maintain a selected constant and uniform temperature at all times in the working chamber of the cabinet, which may be either above or below the temperature of the room in which the cabinet is located.

Still another object is to provide a constant temperature cabinet constructed and arranged so that a gaseous heat exchange medium may be cir-- culated over substantially the entire outer surface of the working chamber.

A more specific object is to provide a constant temperature cabinet having an inner or working chamber and an outer shell or housing, both provided with doors, in which a gaseous exchange medium is normally circulated over substantially the entire surface of the working chamber, including the door, and embodying novel means for closing off the doors of the chamber and the housing from the circulating system when the outer door is opened, thereby permitting continued circulation of the heat exchange me dium over the remainder of the working chamber.

A further object is to provide air tempering means for constant temperature cabinets including elements for heating, cooling, circulating and controlling the temperature of the heat exchange medium wherein the elements are arranged and mounted in a novel manner which enables the tempering means to be assembled and tested as a unit independently of the cabinet and which can be quickly and easily installed in or removed from the cabinet.

It is also an object of the invention to provide various structural improvements which simplify manufacture, which facilitate assembly of the parts, which materially reduce costs, and which substantially improve the ruggedness and general efficiency of the cabinet.

Other objects and advantages of the inventinn will become apparent from the following detail description of the preferred embodiments illustrated in the accompanying drawings, in which:

Figure l is a perspective view of one form of cabinet embodying the features of the invention.

Fig. 2 is a perspective view of the cabinet shown in Fig. 1, with the top cover removed.

Fig. 3 is a sectional view of the cabinet shown in Fig. 1, taken in a vertical plane extending from the front to the rear of the cabinet.

Fig. 4 is a sectional view taken in a horizontal plane substantially on the line 44 of Fig. 3.

Fig. 5 is a. fragmentary sectional view taken in a vertical plane substantially on the line 55 of Fig. 3.

Fig. 6 is a fragmentary sectional view taken in a horizontal plane on the line 6-6 of Fig. 3.

Fig. '7 is a sectional view of a modified form of the cabinet taken in a vertical plane extending from the front to the rear of the cabinet.

Fig. 8 is a sectional view taken in a horizontal plane substantially on the line 8-8 of Fig. '7.

Fig. 9 is a fragmentary rear view of the cabinet shown in Fig. 7, with a part of the rear wall broken away to show details of construction.

Fig. 10 is an exploded perspective view showing the manner in which the air tempering unit fits into and coacts with the base of the cabinet.

Fig. 11 is a perspective view of the constant level device for regulating the flow of cooling liquid through the cooling coil.

While the invention is susceptible of various modifications and alternative constructions, I have shown in the drawings and will herein describe in detail the preferred embodiments, but it is to be understood that I do not thereby intend to limit the invention to the specific forms disclosed, but intend to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

For purposes of illustration, the invention has been shown as incorporated in two cabinets of the type commonly known as bacteriological incubators. The exemplary cabinets are generally alike, except for the manner in which the air tempering means is incorporated therein. Thus, each cabinet comprises a generally rectangular outer shell or housing In enclosing an inner shell H of sheet metal or other suitable conductive material which defines a working chamber l2 adapted to receive the material to be treated. Doors l3 and M respectively in the front walls of the housing l0 and shell ll provide access to the chamber I2. To maintain a predetermined temperature in the working chamber, a gaseous heat exchange medium, such as air tempered by a thermostatically controlled heating unit l5 or by a cooling coil I5 is circulated around the inner shell II by a fan or blower l6 driven by a motor M.

In carrying out the invention, provision is made for supporting the shell H with its door 14 and its top, bottom, rear and side walls spaced from the door l3 and corresponding walls of the housing Ill.

passage through which the heat exchange medium may be circulated in contact with substantially the entire outer surface of the work chamber. More particularly, the space is partitioned to form an air circulating passage including a section extending downwardly along the back and sides of the chamber and a second section extending upwardly along the front and sides of the chamber. The two sections open respectively into adjacently disposed communicating compartments which, in the particular cabinet shown in Figs. 1-6. are located at the top of the housing for receiving the heating unit 15, the coil I5, the thermostatic controls and the blower l6. Thus even distribution of heat throughout the working chamber is insured. To minim ze temperature changes in the chamber l2 incident to the opening of the cabinet door 13, means is provided for automatically closing off the front or door portions of the chamber and cabinet from the circulating system when the cabinet door is opened so that circulation of the heating medium may be maintained over the major portion of the chamber surface during the open period.

Preferably, the housing 10 is of double walled construction, the space between the walls being filled with suitable insulating material (Fi s. 3-6) to reduce heat losses to a minimum. The housing is supported by suitable legs I! and the too is closed by a removable cover I8. To secure the cover [3 in place, angle brackets l9 are spot welded in four corners of the cabinet and threaded for the reception of screws extending through the cover.

In the exemplary cabinet, the door l3 is generally rectangular and, like the other cabinet elements, is constructed with insulated double walls. The door is supported along one side edge by a suitable hinge 2| (Fig. 4) the edge portion of the door being reinforced by an angle member 22 to provide a rigid base for the hinge. Similar reinforcement is provided at each side of the housing Ill by angle members 23 mounted between the inner and outer Walls of the same.

The inner shell ll forming the working chamber 12 is simply a rectangular sheet metal box having top, bottom, rear and side walls 25, 26, 21 and 28. The front wall of the box is open and is arranged to be closed by the door M as shown in Figs. 3. 4; and 7. A flange 29 (Figs. 3 and 7) bent down from the top wall 25 forms a stop for the upper edge of the door while a stop for the lower edge of the door is provided by an upstanding flange formed on the forward edge of a tray structure 3| removably supported in the chamber l2. The forward edge of the bottom member 26 of the working chamber is preferably cut off flush with the surface of the member to facilitate cleaning of the chamber. Perforations in the top and bottom walls 25 and 26 and in the tray 3! permit circulation of air through the working chamber.

As herein shown, the side walls 28 of the shell H are formed with outturned flanges 32 (Fig. 4)

The space between the walls is partitioned in a novel manner to form a, continuous adapted for attachment to vertical members 33 projecting from the interior of the cabinet Ill. The flanges 32 are disposed in a common plane with the flanges 29 and 30 and with the latter, form a seat for the door 14.

The door 14, as herein shown, is generally rectangular and comprises a channel member frame 35 fitted with a pane 36 of glass or other suitable transparent material. Hinges 31 secured to one edge of the door and to the adjacent wall of the housing I!) support the door so that it may be closed flush against the flanges 32 to effectually seal the working chamber. As will be seen by reference to Fig. 4, the reinforcing member 23 in the cabinet is extended rearwardly to provide rigid support for the hinges 31.

Provision is made for supporting the working chamber shell H with its door I4 and its top, bottom, rear and side walls spaced from the door l3 and corresponding walls of the housing In and for partitioning the intervening space so as to form a continuous passage for the circulation of the gaseous heat exchange medium around the working chamber. The supporting means, in its preferred form, comprises a pair of vertically disposed channel members 40 (Fig. 6) rigidly secured to opposite side walls 28 of the shell II and adapted to interfit with similar y disposed channels 4| attached to the side walls of the ho sing m. In the cabinet shown in Figs. 1-7, the channels 40 are preferably extended below the bottom wall 26 of the working chamber to rest on the bottom of the housing and thus hold the shell II in scaced relation with respect thereto. The channel members 40 and 4|, of course, serve to hold the side walls 28 of the shell II in the desired spaced relation to the side walls of the housing I0 and, as they extend the full height of the working chamber, they serve to definethe front and rear sections of a continuous air circulating passage extending entirely around the chamber. In the particular cabinets shown. the channel members are located substantially cen trally of the cabinet structure, thus providing two passage sections of approximately equal cross sectional area.

In the form of the cabinet shown in Figs. 1-6, the inner shell is supported in the housing III with its too wall 25 spaced substantially below the top of the housing, thus providing space for the accommodation of the h ating unit IS, the coil l5, the blower l6, and the motor M. This space is divided by a transverse par itioning member into front and rear compartments 46 and 41 respectively coextensive with the upper ends of the two air circulating passage sections heretofore referred to. The partitioning member 45 preferably comprises a flat sheet metal panel mounted with its opposite side edges in abutting engagement with the channel members 4| which are extended rela ively close to the top of the housing l0 shown in Figs. 2 and 3. The member is also provided with a flange 48 along its lower edge for attachment to the top wall 25 of the shell H. A flange 49 on the upper edge of the member is adapted to extend over and rest on the upper ends of the channel members 4| while the edge portion of the panel is bent up as at 50 for engagement by the underside of the cover l8. Communication between the compartments 46 and 41 is by way of a restricted opening 5| in the partitioning member 45, herein shown as generally circular and located substantially centrally of the member.

It will be evident from the foregoing that the 55 pattitionlngzsmembcm 45: inucoomration; channel members 40 and" H .the'irmer-rwallszofv the Illa andtthe'; shell; II? forming the In: the: present: instance the coolmg'. coil I8:

' is-rarranged" between: the .heatingIunit-I 5t and .the:

mrkinglchamberz I 2"; define azcommuousmassagel having; two: parallel; sections: extending: respect;- ttvely along: the 1 front and aback of" the: working;

chamber-rand each" including:. subotanti'adlyfiequah' I of. the -1 top; 7 side? and bottom: walls: of the-q chamber-:2 The: passage. sectlonsformed:

commumcate'atitheir-uppersand lower ends; com

mtnieaflon 1 at the upper 'end i being; way; of? compartments .46 and: 41 through. the restricted I In the :eioeznptary: cabineti. the' blower: I 6 is mounted in" the reariicompartment 241 closely ad:- jaeemi theiopening J; 5.1-:- so as: to draw air. from the forwardicompartment flfirtoward theirearxof partitioningmember' 45. preferably closely ads jacent the front: face of. the-member with portions of thercoilextendingtacrossr the opening:

51; Provisiomismadefor circulating a liquid, such cold water, through the. coil. whenithe temperaturetofthe chamberrl2 istosbe;

' maintained. at or:below-'thetemperaturc of the;

tho cabinet. To: prevent? the blower. motor." M:

from. inmiencing. the: temperature" oftheicirculatmg air; the housing I III is :formed to provide j i a motor casing which is completely'insulatedf rm: the --interior of the cabinets. ASiShOW'l'I in 5,: the' casln'g' includes: an insulated; double walled, box likeipartitlonlng: structure 52:- pro iectmgdnwardly from therearrwall of "the housing I!adjacentlthewtop: thereon. Support for tha structure is providedbydepending flanges 58 (F'igs. 3 and -5)-extendin'g along'the side-edges of the-structureand adapted to' rest on the top:

for the worklng chamber is drawn through-the restricted opening 51 into the blower: chamber 41 and" is dlrected rearwardly r and downwardly along the back and-sidesrof theworking-chamber I 2 at the rearsof thechannel members II -and M After-passing along: the bottom of "the chamb'ery the air flows upwardly along the front and side walls of the chamber forwardly: of f the channel I members-to the front-compartment lat thet'op" of'thecabinet from which it'ls again'drawn by the b lower f or recirculation;

Imorder -to -temper the circulating air as requtred for the maintenance of a predetermined i temperature in: the: working. chamber I 2,. provi sion is madefor passingsubstantially the entire mass-:- of: air through the effective area: of the heating.='unit I5"anditheicoolingcoil Ii.- ineach: circuit through. theaair: passage; To this end;v theeheating :unitzand the .coil' are-'located at the suction side -of. the" blower: I 6 in the path of the-- air stream issuing fromthe retin'fnsection of the aha passage. v In: the a embodiment illustrated? in Figs: 1-6'..-0f; thedrawings: .therheatinggmrit' I5.- isr: constructecldn two parts; each" consisting of an: elongated generally: rectangular; frame: 55' (Rigs: 2.- and 3) upon which anrelectrical heating element 56 suchasiazlengthsof resistancewire. lsswound.

As shown in-Fig f the drawings; the-frames: Stare mounted in diverging relation with respect to theopenlng-SI through which the air is drawn by ;-the-blower I6; Morerparticularly, the=framcs arew-arrangedsto extend respectively from" oppos site; ends of? the partltioning member 45: to; a point-closely adjacent thefrontwallbf the he rs-. mg I land substantially with; the -center of the opening 51 in the member. Accordingly} air streams 'fiowingenpwardly'along the sides' and; front of the working chamber aredirected the grids formed onthe'frames 55 by" 555 room intwhich.theacabinetiistlocated. To insure:

uniform flow of water throughxthe coil. I5 the: circulating system; includes. flow control means, suchast a constant level: device D (Fig; 11),. hereinafter? described in detail. A- valve V is alsoincluded' in the systemsothat-the flow of? water may be regulated or: discontinued when: thetemperature of..the.cabinet-is to be main! tained above'room temperature:

To. maintain: a: desired temperature in the:

.umrkinguchamber, the operation of'the heating;

unit: I5' is". controlled by. adjustabletemper; ature' responsivedevice; such as az'thermostat Sljwhichmay be-of any suitable orwellknown type, arranged to open andxclosejthe electrical.

- circuit 1 of the. .heating'eiement .56 in response "to appropriate: changes in the temperature of the: air circulating .in.the'cabinet. By reason of its: position" in-the'. air stream; the thermostat. is subjected-.to the-same air." temperatures as the shell II. forming the workingchamber and. the:

thermostat. is therefore enabled to; perform its L temperaturecontrolling function :when the cool-.- ingzcoil I5, is'in operation as well aswhen the coi'lisidle. ASpShOWIlTin Fig; .3, .the thermostat" 5.! 5 is supported" forwardly of f and adjacent the":

apexof: thez-framesi- 55, in. this instance by. atrearwardly. projecting. bracket 58 mounted the: front wall ofthe housing 7. III.

hereirrshown; adjustment of the thermos statil is* effected by; means ofia rotatable: adejusting rod. 59. projecting" forwardly -through an: aperturein thev'front wall ofjthezhousing III: and provided .1 on; its outer; end. with a: suitable knob: or handle 60 for manual actuation. A convenetionalt switch 62I, conveniently mounted. at the front of" the cabinet; is providedsfor" turning the 1 heafingelementonior; off as required. A pilot lamp-6i connected in cirouittwith the heating; unit imay'a'lso besprovided I to; give: axvisual indiecationxwhen i the heating :unit is in' operation;

Its-explained above; the :air after passing" over the :heating; element I5, and the cooling :coilv I5! is.-:='dra\vn through the restricted opening 5 I and forced rearwardly along. the top of the working 1 chamber, then downwardly along the side and rear walls.of.theworkingchamber and finally upwardly alongthe side walls. and doorof thechamber by way of the front and rear sections of the passage formed by. the channel members IT-and M5. Thefrontsection of "the passagels subdtvlded'into' three parallel branches by the vertical flanges 32 and members 33 heretofore described; One of the branches thus formed extends along the front or' door Ilof the workingchamberwhile the others extend along the opposite sides of' the chamber;

In=the-normal operation of the cabinet, the circulating air passes freely through each of the three branch" passages above referred to: thus serving'to apply heat uniformly to substantially'the entire outer surface of the working chamber with the result that the chamber uniformly heated. To prevent excessive temperature changes in the chamber I2 when theouter door" Ilis opened,'- provision" is made for automatically closing off the branch passage along the front of the chamber from the rest of the circulating system at such times.

In its preferred form, the means for closing ofi the front of the cabinet comprises a pair of dampers or vanes 65, preferably in the form of elongated sheet metal strips respectively SllD'. ported by hinges 66 on the housing walls adjacent the top and bottom of the door opening. The vanes are dimensioned to extend entirely across the housing I as shown in Fig. 4 and, when in closed position, to extend over and engage the top and bottom of the shell II and the upper and lower ends of the flange 32 as shown in broken lines in Fig. 3. The outer marginal edge portion of each vane may be turned back slightly to provide a rounded contact surface effective to insure a tight seal between the vane and the shell. Springs 61 (Fig. 4) yieldably urge the vanes to their closed position while abutments 68 on the inner side of the door I3 coact with rearwardly projecting arms 69 rigid with the vanes to rock the same to open position when the door is closed.

With the above arrangement, the vanes 65 are operative automatically in accordance with the open or closed condition of the door I3 to permit or interrupt the circulation of air along the front of the chamber I2 between the doors I3 and I4. When the door I3 is closed, the heated air is circulated over substantially the entire outer surface of the working chamber I2, thus providing efficient heat exchange and insuring a uniform temperature through the entire chamber. When the door I3 is opened, circulation may be maintained over the major portion of the working chamber without incurring loss of tempered air and without resulting in cooler outer air being drawn into the circulating system. The working chamber is accordingly maintained substantially at the desired temperature since the application of tempered air to the major portion of its outer surface is continued.

The constant level device D is provided for maintaining a uniform head of liquid for the coil I5, thereby insuring a steady even flow of cooling liquid therethrough. As shown in Fig. 11

of the drawings, the constant level device com' prises a pair of cylindrical receptacles I0 and II arranged one within the other, the inner receptacle II being of smaller diameter and substantially shorter than the outer receptacle I0. Cooling liquid is introduced into the inner receptacle through the bottom by way of a conduit I2 adapted to be connected to a suitable liquid source, such as an ordinary water supply system.

Opening from the bottom of the inner receptacle is an outlet conduit I3 adapted to be connected as by a flexible tube I4 with one end of the coil I5, the other end of the coil being connected to a suitable drain. A wire strainer I5 enclosing the outlet from the receptacle II prevents foreign material from entering and clogging the coil I5. In the exemplary apparatus, the control valve V is interposed between the outlet conduit 13 and the connecting tube 14, whereby the rate of flow through the coil may be readily controlled. Water is supplied through the inlet conduit I2 at a rate in excess of the flow through the coil I5 so as to maintain the inner receptacle 'II full at all times. The excess water admitted to the receptacle spills over the edge into the outer receptacle I0 and is conducted to the drain by way of a conduit I6.

In the cabinet shown in Figs. 7-10 of the drawings, the housing I0 and the inner shell II are assembled in the manner above described to provide a continuous air passage around the working chamber I2. As in the previously described construction, the passage includes a section at the rear of the cabinet and a second section at the front of the cabinet both connecting with a compartment 11 housing the air tempering and circulating means. In the present instance, the compartment 11 is formed below the working chamber I2 by supporting the shell II in spaced relation to the bottom of the housing I0. Support for the housing is provided by an angle bar 80 secured at opposite ends to the channel members M which are secured to the inner walls of the housing In and serve to define the sections of the air circulating passage as heretofore described.

While air tempering means of any preferred type may be employed, the exemplary cabinet has been shown as equipped with air tempering means including a heating and controlling system of the type disclosed in the copending application of Frederik Koht Serial No. 4,532, filed January 27, 1948, owned by applicants assignee and now abandoned. This system comprises a two-stage electrically operated heating element controlled by an adjustable thermally responsive device or thermostat 86 through the medium of a pair of relays 8! and 88. The thermostat 86 is adjustable by means of a manually rotatable adjusting rod 89. Pilot lamps 90 and 9| are interconnected with the heater 85 so as to indicate when the latter is operating respectively at the high and low heating rates.

Also included in the air tempering system is a cooling coil 92 similar to the coil I5. Cooling liquid, such as cold water, is supplied to the coil from the constant level device D which, in this instance, is mounted in a recess 93 (Fig. 7) in the top cover I8 of the housing I0. The device D is connected to the coil by the flexible tube 14 and a conduit 94 in which the valve V is interposed to control the rate of flow through the coil. Adjustment of the valve is effected by means of a manually rotatable stem 95. After passing through the coil, the water is discharged to the drain through a conduit 96. Circulation of the air over the heating unit 85 and the cooling coil 92 and around the chamber I2 is eifected by a blower I00 similar to the blower I6 and driven by an electric motor M-I.

To facilitate assembly and testing of the air tempering and circulating means and to permit convenient installation in and removal of the same from the cabinet, the various elements are assembled as a compact, self-contained unit on a supporting structure in the form of a drawer I0l adapted to be inserted in the compartment I1. As shown in Fig. 10, the drawer I M comprises a generally rectangular bed I02 of sheet metal or the like having downwardly turned flanges I03 at opposite side edges. An upright panel I04 secured to the front edge of the bed serves as a closure for the front of the compartment 'II. Preferably, the panel I04 is constructedwith double insulated walls similar to those of the housing I0 to minimize heat losses. As shown in Fig. 'I, the panel I04 abuts at its lower and side edges against a suitable gasket I04 mounted on the housing ID to efiectually seal the cabinet. The panel extends upwardly for engagement with the lower edge of the door I3 and, in the exemplary cabinet, it supports the hinged damper 65 by which the front of the housing is shut off from the air circulating system when the door I3 is opened.

Extending transversely across the bed I02 is a partitioning member I05 adapted to abut against the angle bar 80 andv inward extensions I06 formed on the inner flanges of the channels 4| to divide the compartment TI into front and rear chambers communicatin respectively with the front and rear sections of the air circulating passage. A gasket II of felt or other suitable material is interposed between the parts to insure a tight joint. Communication between the two chambers formed by the partitioning member I is provided b an opening I08, herein shown as generally circular in form.

The heating unit 85 and the cooling unit 92 are mounted in the front chamber generally parallel to the partitioning member I05 and suitably spaced therefrom. Side members E09 extending from the partitioning member I05 to the front panel I04 and a top member IID extending over the rear portion of the chamber partially enclose the heating and cooling units and serve to direct the circulating air therethrough on its way to the opening I08.

As in the previously described cabinet, the

thermostat 86 is supported forwardly of the heating unit 85 and its adjusting rod 89 is extended through the front panel I04 and equipped with an operating knob Ill (Fig. 7). The valve V is preferably mounted in front of the thermostat with its stem 95 projecting through the front panel for manual actuation. As shown in Figs. 7 and 8, the relays 81 and 88 are mounted on the front wall of the panel I04 and the pilot lamps 80 and 9| are mounted in sockets formed in the panel.

The rear chamber of the compartment 11 accommodates the blower I00 and the motor M-I. The blower is located adjacent the opening I08 so as to draw air therethrough from the front chamber. This air is then forced upwardly along the sides and back of the shell II, that is, through. the rear section of the air passage and, after passing over the top of the shell, it descends along the front and sides of the shell to the front chamber of the compartment 11.

To minimize the effect of the heat generated by the motor M-I on temperature regulation, the motor is completel enclosed in an insulated casing II2 mounted on and secured to the bed I02. For ventilating purposes the rear end of the motor is arranged to project into a sheet metal box I I3 mounted on the bed I02 within the casing II2. A gasket I I4 of felt or other suitable material tightly fitted around the motor prevents leakage of air between the box and the interior of the casing I02. The box communicates through openings H5 in the bed I02 with an air passage II6 formed between the bed I02 and the bottom of the housing I0 by longitudinally disposed partitioning strips IIl seated in channels II8 secured to the lower face of the bed. These strips are preferably of soft resilient material and in cooperation with similar strips I support the drawer and assembled apparatus on the bottom of the housing I0.

The passage H6 is adapted to receive outside air through an opening I2: (Figs. '7 and 10) in the bottom of the housing I0. Air drawn through the openings II5 into the box H3 and circulated through the motor M-I is discharged 10 into the casing 2 from the other end of the motor and exhausted to the atmosphere through a series of openings I22 in the back wall of the housin I0. In this way the motor is adequate- 1y ventilated without materially affecting the temperature of the cabinet.

The channel IIG also serves to convey outside air to the tempering means whereby an increment of fresh air is continually added to the circulating air stream. For this purpose the channel is extended forwardly of the partition I05 and communication with the front chamber of the compartment I1 is provided b a series of openings I23 in the bed I02. In the particular embodiment illustrated the openings I22 are located at the rear of and closely adjacent the heating unit 85.

Provision is also made so that the working chamber I2 may be vented to the atmosphere when desired. For this purpose the top wall 25 of the shell I I is formed with an opening I25 communicating with a vent tube I25 which is secured to the top wall and extended through an opening I21 in the top cover I8 of the housing I0. An adjustable cap I28 of conventional construction is fitted on the projecting end of the vent tube so that the tube can be closed or opened variable amounts to regulate the flow of air therethrough. Leakage of air from the circulating system through the opening I2! is prevented by an annular gasket I29 mounted on the vent tube for engagement with the inner surface. of the cover I8.

By reason of its novel unitary construction, the air tempering and circulating means may be completely assembled and tested on the bench before it is installed in the cabinet. Assembly and testing is thus facilitated as all of the parts are readily accessible and are easily handled.

.a Installation of the unit in the cabinet is effected 2-15 made sufficiently large to accommodate the bent quickly and easily by simply sliding it into the compartment IT in the base of the cabinet and making the necessary water and electric connections. In practice, the flexible tube I4 connecting the constant level device D with the cooling tube 92 is made of sufiicient length so that it may be connected with the conduit 94 as by a coupling I30 before the unit is inserted in the cabinet. The conduit 94 may comprise a thinwalled metal tube and is preferably extended rearwardly of the partition I05, as shown in Fig. 8, to make it readily accessible. The drain conduit 96 may also comprise a thin-walled metal tube and is extended rearwardly to project through an opening I3I (Fig. 8) in the rear wall of the housing I0. A plug I32 of rubber or other suitable material is provided on the conduit to seal the opening against leakage of air from the circulating system.

In order to simplify the connection and disconnection of the motor M-l when the unit is installed in or removed from the cabinet, the current supply leads for the motor are enclosed in a rigid, rearwardly projecting conduit I33 (Fig. 8) terminating in a connector plug I34 adapted to seat in an opening I35 in the rear wall in the housing. To permit the motor to be oiled without requiring removal of the unit from the cabinet, a rearwardly extending oil tube I36 is provided and arranged to extend through an opening I31 in the rear wall. of the housing when the unit is installed. The projecting end of the oil tube is bent upwardly so that it may be readily filled with oil. The opening I 31 is 11 up end of the tube so that it does not interfere with installation or removal of the unit. Suitable plugs or gaskets I38 provided on the conduit I33 and the oil tube I36 seal the openings I35 and I3! to prevent leakage of air from the circulating system.

It will be apparent from the foregoing, that the invention provides a constant temperature cabinet of novel and advantageous construction which insures uniform temperature throughout the working chamber and which enables the temperature of the chamber to be maintained within very close limits. Such temperature uniformity results largely from the novel arrangement whereby a gaseous heat exchange medium is normally circulated over substantially the entire outer surface of the working chamber. Maintenance of uniform temperature is facilitated by the provision of air tempering means constructed and arranged to act on substantially the entire mass of circulating air in each cireuit through the apparatus. Abrupt temperature changes in the working chamber are eiTectually avoided by the provision of novel means for automatically closing off the door portion of the cabinet from the circulating system when the outer cabinet door is opened, thus permitting continued circulation of the tempered air around the major portion of the working chamber.

The invention also provides an air tempering and circulating unit of novel and advantageous construction which greatly facilitates assembly and testing and which can be quickly and easily installed in or removed from a constant temperature cabinet. Repairs may be made at the bench when required, or the defective unit may be returned to the factory for repair or adjustment. Moreover, should trouble develop while test specimens are undergoing treatment in the cabinet, the unit may be readily replaced to maintain the cabinet in operation without seriously affecting the tests.

I claim as my invention:

1. In a constant temperature cabinet, in combination, a generally rectangular housing having a door opening in its front wall, a hinged door for said opening, an open front sheet metal shell enclosed in said housing, a hinged panel closing the front of said shell, interengaging flang members on said cabinet and said shell operative to support the shell with its walls in predetermined spaced relation to the corresponding walls of the housing for the circulation of air thereabout, said flanges defining an air passage extending along the front of the housing between said door and said panel and communicating at its upper and lower ends with the space between the shell and housing walls, and vanes supported in said housing adjacent the upper and lower ends of said shell operable to close off said passage from said space.

2. In a constant temperature cabinet, in combination, a housing having a door in its front wall, a shell supported in said housing with its walls spaced from the corresponding walls of the housing, said shell having a door in its front wall substantially aligned with the door of said housing, partitioning means within said housing defining an air passage between said doors opening at opposite ends to the space between said shell and said housing, and vanes operable by the housing door for closing off said passage from said space when the door is opened.

3. In a constant temperature cabinet, in combination, a housing, a shell supported in said housing with each of its walls spaced from the corresponding walls of the housing, said housing and said shell having doors in their front walls, partitioning means dividing the space between said shell and the housing into front and rear air passages, means dividing the front air passage into branch passages one of which includes said doors, and means for closing said one branch passage from the rear passage when the housing door is opened.

4. In a constant temperature cabinet, in combination, a generally rectangular housing, a generally rectangular shell enclosed within said housing to define a working chamber, interfitting channel members secured to adjacent walls of said housing and said shell to support the shell in spaced relation to the housing walls, said members additionally forming a partition dividing the space between the housing and the shell into parallel air passages communicating at the top and bottom of the housing, and means for circulating air through said passages.

5. In a constant temperature cabinet, in combination, a generally rectangular housing, a shell supported in said housing with its walls spaced from the corresponding walls of the housing to define a compartment communicating with air passages extending along three sides of the cabinet, said compartment having an outlet located opposite the intermediate one of said sides, means for effecting a flow of air through said passages into said compartment and out by way of said outlet, an air tempering unit in said compartment including an elongated heating element, said element being positioned so that the air stream entering the compartment through said passages is directed through the element, and a cooling coil positioned in the air stream.

6. In a constant temperature cabinet, in combination, a generally rectangular shell of heat conducting material defining a working chamber, means cooperating with the walls of said shell to form a continuous air passage extending around the shell, a partitioning member extending across said passage and having a restricted opening, blower means disposed at one side of said partitioning member for circulating air through said opening and said passage, a heating unit disposed at the other side of said partitioning member and positioned to heat the circulating air, a cooling coil disposed at said other side of the partitioning member for cooling the circulating air, and a thermostat adapted to control the operation of said heating unit, said thermostat being located so that th air impinges upon it after circulating through said passage but before it reaches said heating unit or said cooling coil.

7. In a constant temperature cabinet, in combination, a housing, a shell of heat conducting material defining a working chamber for the cabinet, means supporting said shell in said housing with its walls in predetermined spaced relation to the corresponding housing walls so as to form a passage extending entirely around the shell and communicating at opposite ends with a compartment, partitioning means dividing said compartment into two chambers opening respectively to the ends of said passage, said partitioning means having an opening providing communication between said chambers, air tempering means disposed in one of said chambers, and air circulating means disposed in the other of said chambers adjacent said opening, said air tempering means, said partitioning means and said air circulating means being assembled for insertion in and removal from said compartment as a unit.

8. In a constant temperature cabinet, in combination, a housing, a shell of heat conducting material defining a working chamber for the cabinet, means supporting said shell in said housing with its walls in predetermined spaced relation to the corresponding housing walls so as to form a passage extending entirely around the shell and communicating at opposite ends with a compartment, partitioning means dividing said compartment into two chambers opening respectively to the ends of said passage, said partitioning means having an opening providing communication between said chambers, air tempering means disposed in one of said chambers, and air circulating means disposed in the other of said chambers adjacent said opening, and a drawer-like structure supporting said air tempering means, said partitioning means and said air circulating means for insertion in and removal from said compartment as a unit.

9. In a constant temperature cabinet, in combination, a sheet metal shell defining a working chamber, a housing enclosing said shell and providing a closed air circulating passage extending around the shell, said system including a compartment located within said housing and opening at one side thereof, air tempering means including a heating element and a cooling coil, air circulating means including a blower and a driving motor therefor, a drawer structure supporting said air tempering and circulating means, said drawer structure being removably insertable in said compartment, and a panel at one end of said drawer structure operative to close the open side of the compartment.

10. In a constant temperature cabinet, in combination, a sheet metal shell defining a working chamber, a housing enclosing said shell and providing a closed air circulating passage extending around the shell, said passage including a compartment located within said housing and opening at one side thereof, air tempering and circulating means for the cabinet including a heating element, a thermostat for controlling the operation of said element, a cooling coil, a valve controlling the operation of said coil, a blower, and a motor for driving said blower, a drawer structure supporting said air tempering and circulating means for insertion in and removal from said compartment as a unit, said drawer having a panel at one end closing the open side of said compartment, and manually operable means accessible at the front of said panel for adjusting said thermostat and for actuating said valve.

11. In a constant temperature cabinet, in combination, a generally rectangular shell of heat conducting material defining a, working chamber, means cooperating with the walls of said shell to form a continuous air passage extending around said shell, a partitioning member extending across said passage and having a restricted opening therein, a blower arranged at one side of said partitioning member to draw air through said opening and circulate it through said passage, air tempering means at the other side of said partitioning member including a heating unit and a cooling coil disposed in the path 01' the circulating air adjacent said partitioning member, and means for supplying a cooling liquid under constant head to said coil.

12. In a constant temperature cabinet, in combination, a generally rectangular shell of heat conducting material defining a working chamber, means cooperating with the walls of said shell to form a continuous air passage extending around said shell, a partitioning member extending across said passage and having a restricted opening therein, a blower arranged to draw air through said opening and circulate it through said passage, air tempering means including a heating unit and a cooling coil disposed in the path of the circulating air adjacent said partitioning member, a liquid supply system for said coil including a constant level device, and a valve for controlling the flow or liquid from said device to said coil.

WALTER VAN GUILDER.

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

UNITED STATES PATENTS Number Name Date 1,848,440 Spitzenberger et a1. Mar. 8, 1932 1,859,613 Bailey May 4, 1932 2,135,181 Jones Nov. 1, 1938 2,150,064 John et al Mar. 7. 1939 2,233,394 Ashbaugh Mar. 4, 1941

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