US2844888A

US2844888A - Cooling system for industrial ovens

Info

Publication number: US2844888A
Application number: US435445A
Authority: US
Inventors: Charles H Barnett
Original assignee: Foundry Equipment Co
Current assignee: Foundry Equipment Co
Priority date: 1954-06-09
Filing date: 1954-06-09
Publication date: 1958-07-29
Anticipated expiration: 1975-07-29

Description

y 1958 c. H, BARNETT $844,888-

COOLING SYSTEM FOR INDUSTRIAL OVENS Filed June 9, 1954 4 Sheets-Sheet l INVENTOR. CHARLES l-LflAR/VE 7'7 9 FT-.GR NEYS.

July 29, 1958 C. H. BARNETT 2,

COOLING SYSTEM FOR INDUSTRIAL OVENS 4 Filed June 9, 1954 4 Sheets-Sheet 2- IN V EN TOR; C HA RLES H. BARNETT ow/v4 A T ramvms.

July 29, 1958 c. H. BARNETT COOLING SYSTEM FOR INDUSTRIAL OVENS 4 Sheets-Sheet 3 Filed June 9, 1954 Q A r TOR/V575.

July 29, 19 58 I c. H. BARNETT 2, 8

COOLING SYSTEM FOR INDUSTRIAL OVENS Filed June 9; 1954 4 Sheets-Sheet 4 /45 46 45 K 1 67 7b 4 G /5Z Q Q l j I INVENTOR. W CHARLES H. BARNETT greatly increased: costs.

successively.

United, States Patent COOLING SYSTEM FOR- INDUSTRIAL OVENS Charles H. Barnett, Shaker Heights, Ohio, assignor to The Foundry Equipment Company, Cleveland, Ohio, a corporation of Ohio Application June 9, 1954, Serial No. 435,445

8 Claims. c1. s4 20s industry to bake sand cores after the latter have been formed in core blowing machines. The baking process is-fairly slow and requires that the cores be-heated for a considerable period of time at a fairly high temperature. This is usually accomplished in core ovensthrough which conveyors travel, supporting the cores. When the cores leave the oven, if no cooling means is provided, they are much too hot to be handled by workmen and, moreover, smoke very objectionably due to oxidation of the binder material used with the core sand. For this reason, core'ovens employedin large installations include a cooling zone immediately prior to emergence of the conveyor from the oven, and it is conventional .toblow relatively cool air into this portionof the oven and across the moving cores. I The most practical form of oven has been found to be the vertical or tower oven as contrasted to the horizontal oven, but the present invention is adapted to each form.

Core ovens are very large and expensive structures and to extend such an oven even a few feet results in There is, accordingly, attemptation to keep the cooling zone toa minimum, but unless adequate cooling facilitiesare provided, theoven cannot be operated at maximum capacity. Sineethe cores-move continuously through the oven, the-efficiency of the cooling means employed :determines in large measure the permissible rate of production.

It :is among the objects of myinvention to provide an oven cooling system of increased capacity comprising a plurality of cooling stages effective to bring work heated in the oven rapidly to a safe handling temperature without .the danger of thermal shock thereto. Incontinuous core-ovens and the like, the plural stages of such system are-arranged to besuccessively encountered by the moving cores following baking of the same and-prior to their .passage from the oven. 1

Another object ofthe invention is to provide such a cooling system which produces a plurality of distinct air currents of increasingly lower temperatures in adjoining regionsofthe oventhrough whichithe heated work'moves It is also one of my objects to employ refrigerated air as the cooling medium in the 'final, stage of-this system with the work temperature'firstEbeinglowcred in a preceding stage or stages sufl'lciently to elimi mate the thermal shock which would *normally result if theheated work was initially contacted byilthe chille'd air.

- A further-object is to 'providepreecooling means for ovens having defined-heating and cooling zones,; distinct the workvtherebetween tto a value. intermediate :the .re-

'-spective temperatures of-theadjacent endsofzsuch zones.

"ice

- Generally speaking, an oven cooling system is, for practical reasons, designed to handle average work or to meet the requirements of the work processed in greatest quantity and cannot normally be operated at its design efficiency whena ,particular work lot presenting more exacting requirements-is to be processed. For example, most commercial cores and formed of sand, and core ovens are adapted primarily to process articles of this general composition with, of course, adequate flexibility to take care of the usual variations in size, shape and the like encountered in normal operatiom However, for some uses, the cores are formed of plaster of Paris and these are extremely susceptible to destruction by thermal shock, more so than the sand cores. As a result, the normal temperature differential between the oven heating-and cooling zones, while not developing dangerous thermal shock in the case of sand cores may, nonetheless, be suflicient to damage and destroy plaster of Paris cores. Ordinarily, this could be avoided only by raising the average cooling temperature which, in turn, would require the work progress to be slowed. The pre-cooling means of my invention, however, makes it possible to :maintain optimum operating conditions despite such a change in the character of the work by reducing the abruptness of the drop in work temperature on leavingthe heating zone and passing to the cooling zone.

Additional objects of the invention are: to provide automatic.temperaturecontrol of the pre-cooling means set forth; to provide a multi-stage cooling system of extreme flexibility, whereby the operation thereof may readily be adapted as best suited for prevailing ambient conditions; and to provide efiicient and readily controllable use of the air in such system to the extent of reusing .air exhausted from the oven when this affords best results. These and other objects and advantages 'of the, invention will be apparent from the following description.

To the accomplishment of the foregoing and related ends, the invention,-.then, comprises the features hereinafter fully .described and particularly pointed out in :the claims,-.the following description and the annexed drawings setting forth in detail. certain illustrative embodiments of the invention, these being indicative, however, of but a few .of the various ways in which the principle of the invention may be employed.

In said .annexed drawings:

Fig. .1 -is ,an end elevational view of a continuous vertical-core oven .ortowerequipped with the improved cooling system of my invention;

Fig. 2 is a-side elevational view of this oven looking from the right-in Fig. 1 or toward the'unloading side of the oven;

able height andhaving a continuous'conveyor, designated generally ,by reference numeral 1, movable therein to .transportthegreensand cores and the like to be cured by baking. The tower-frame, made up of suitable strucaturalwmembers, jlS preferably supported on the bottom of apit Z'beneath" the level of the. floor 3 of the building within whichitheoven-is situated, in order to conserve {9 height and afford workmen convenient access to the conveyor at floor level.

The pit is enlarged somewhat laterally relative to the tower frame and suitable flooring 4, for example a grating. is provided to bridge the pit opening around the base of the tower at the level of the floor. Beginning at floor level and extending vertically a sufficient distance to allow safe head room, the tower frame is open and divided to form the loading station A and unloading station B respectively at the ascending and descending sides of the conveyor, as indicated by the arrows showing the direction of conveyor movement. The center passageway between the two stations permits workmen to enter therein and load the work from both sides of the loading station.

Secured to the remaining vertical extent of the tower frame above the loading and unloading stations are suitable insulating panels forming end walls and 6,

side walls

7 and 8, and top wall 9. The frame is also closed transversely at the approximate upper limit of the loading and unloading stations, partially by the furnace 10 and its bottom supporting structure, with the result that this upper major extent of the tower forms a substantially completely closed chamber within which the Work may be treated.

The conveyor mechanism employed is conventional, and therefore, has been shown, and will be described, only generally. It comprises two continuous chains, one of which is shown at 11 in Fig. 1, arranged to extend vertically in the respective end regions of the oven and a plurality of cross rods extending horizontally between the two chains at regular intervals therealong. Work carriers 12 in the form of plural tray units are freely suspended on the cross rods at their approximate longitudinal center lines so that, when properly loaded, the carriers will normally be balanced about their connections with the rods. The two chains pass over drive sprockets, one being shown at 13, mounted on a head shaft 14 in the top region of the oven and over a floating structural take-up 15 in the pit 2, the latter serving to guide and tension the chains at the lower turns thereof. At one end of the headshaft 14 there is attached a large drive gear 16 adapted to be driven by a suitable electric motor, not shown. headshaft is driven to rotate the drive sprockets in a clockwise direction as viewed in Figs. 1 and 3, thus providing the aforementioned ascending and descending movement of the work in the loading and unloading zones.

As shown in Fig. 3, a heat supply plenum 17 is arranged centrally of the oven and extends vertically from immediately above the furnace 10 substantially to the headshaft 14. The side wall of the plenum facing the ascending portion of the conveyor above the loading zone and the plenum top is provided with a plurality of horizontal ports 18 with the remaining walls thereof being closed so that air supplied the plenum will flow out such ports and over the work as it ascends with the conveyor. Hot air at a temperature sufficient to cure or bake the green cores is fed to the plenum through the opening 19 in one end wall thereof in communication with the discharge side of a heat supply fan or blower 20. The intake air for this blower is drawn through duct 21 passing through the furnace and is heated in this manner to the desired temperature. It will be understood that any suitable form of furnace, such as those now commonly used in core ovens, may be employed. A series of exhaust conduits 22 is provided in the upper region of the oven to permit a portion of the hot air circulated over the work to be exhausted to the oven exhaust stack 23 and through the latter to the outside atmosphere. Dampers 24 are desirably provided in these conduits to regulate the amount of hot air thus exhausted from the oven. At the descending side of the conveyor a vertical wall 25 is provided rising from the top of the furnace to a height slightly less than that of the plenum in laterally In the construction illustrated, the' spaced relation with the rear wall 26 of the latter. These two walls form the recirculating duct now commonly provided in core ovens of this type for returning a portion of the hot air in the top of the oven to the furnace. 1n the operation of the oven as thus far described, the green cores are placed on the Work carriers moving upwardly through the loading zone A by the workmen, from either or both sides of this station, and each loaded carrier then moves substantially immediately into the heating zone of the upper enclosed oven chamber. In this zone, the hot air supplied by the blower 20 from the furnace to the plenum flows out the several ports 18 over the cores, and convectively in a generally upward direction therewith. As noted, a portion of this air may be exhausted through the stack 23 and a further portion drawn into the recirculating duct for reheating and further use. The cores must be thoroughly and uniformly baked at a fairly high temperature related to the conveyor speed or, in other words, to the length of time the moving cores are subjected to the hot air flow, and before the cores reach the unloading station they must be cooled sufliciently to permit safe handling by the workmen engaged in unloading the conveyor. Since the work is particularly sensitive to thermal shock, an abrupt drop in work temperature must be avoided, while at the same time, adequately cooling the same in a zone of limited extent. It would be obviously uneconomical to increase the already substantial height of the tower for the purpose of lengthening the usual cooling zone, and hence the time the work is in such zone, and my invention provides a rapid but safe cooling within the dimensional limits of conventional vertical core ovens.

Coming now to this cooling system, the physical structure thereof will first be set forth and the operation then discussed in connection with the simplified flow diagrams of Figs. 4 and 5. Extending laterally from the unloading side of the tower are four platforms at different elevations with the lowermost platform at the level of the bottom of the enclosed oven chamber and the uppermost in the region of initial conveyor descent. Supported on the uppermost platform 27 is a first fan or blower 28 having a conduit 29 connecting the outlet thereof to a supply boot 30 arranged against the tower side wall 8. The boot is generally rectangular, as shown, and that portion of the side wall covered thereby is provided with a series of vertically spaced ports 31 which lead to the upper end of the cooling zone. Connected to the inlet of fan 28 is a duct 32 extending downwardly to a T- connection supported on the next lower platform 33. One horizontal branch 34 extends only a short distance from this connection and is open at its end 35 so that ambient air may be drawn therethrough. A second horizontal conduit 36 extends from the connection about one end of the oven and then inwardly to communicate with the recirculating duct. Thus the blower 28 also draws air from such duct, and this portion of the make-up air will be at an elevated temperature. A proportioning damper assembly 37 located in the T-connection includes

dampers

38 and 39 respectively operative to open and close the

branch lines

34 and 36 in varying amounts. The two damper parts are interconnected for joint actuation.

A second fan or blower 40 is supported on platform 41 at the next lower level and has connected to its discharge side a distributor 42 which conveys the air impelled by the blower to a second supply boot 43. The first supply boot 30 is, of course, of predetermined vertical extent, and the second boot 43 likewise extends a predetermined vertical distance from a point closely adjacent the bottom of the boot 30. That portion of the tower side wall 8 covered by the second boot 43 also has a series of vertically spaced openings or ports, shown at 44, to discharge air over a section of the cooling zone in operative succession relative to that supplied with air from the first 75.

boot. A common exhaust means is provided to withdraw actress '5 the air supplied the oven by both thefirs't 'and"v second boots through acool air z'exhaust s't ack 45 vented to the outside atmosphere. This means. comprises a cooling air exhaust fan 46 having its 'outl'et connected to such stack and its inlet side 'to 'a common header 47 extending horizontally along the sidewall of the tower. At each end of the header, a recovery duc't 48 curves downwardly therefrom and extends vertically to the approximate level of the bottom of the second boot 43. A plurality of vertically spaced openings 49 is provided in each end wall of the tower and a series of short ducts 50 extend outwardly between these openings and the respectively associated recovery ducts. It will be apparent then that air impelled into the oven by the'b'low'ers 28 and 40 will be caused to flow over the work in a generally upward direction and to be exhausted by the blower 46. The two currents of air thus produced in successive sections of the cooling zone, therefore, flow generally in a direction opposite to that of the moving conveyor. The lowermost platformSl at the terminal end ofthe cooling zone supports a third and final cooling blower 52 equipped with a distributor 53 to supply air to a third supply boot 54. As with the other boot-s, supply boot 54 overlies a predetermined area of the tower'wall and vertically spaced ports 55 are provided in such area to communicate with the cooling zone. The air caused to flow in the end region of the cooling zone may be exhausted therefrom through openings '56 in each end wall, ducts 57 leading therefrom, and recovery ducts SSarran'ged similarly as the exhaust means described in connection with-the first two supply boots. ii l Here, however, the recovery ducts communicate with a horizontal duct 59 which has a short connection 60 extending outwardly at right angles to a four-way junction indicated generally at 61. The upper vertical branch 62 of this junction leads to the inlet of blower 40 while the opposite vertical branch 63 connects with the intake of the blower 52. The remaining duct =64'at this junction leads therefrom to an inlet stack 65 which extends vertically through the building roof, indicated '-by the dashed line 66, to permit outside air to be drawn in through its outer open end 67, and a damper 69 is positioned 'to be adjustably movable between'position's selectively opening and closing the opening 68 and that-portion'of the stack above such opening. Thus, the stack can supply air from both within and without the building in which the oven is located in adjustable relative amounts depending on positioning of the damper69.

Since the four-way junction 61 connects 'with'th'e intakes of the blowers '40 and 52, air may be drawn from both the inlet stack 65 and the *exhaust header 59. A supply damper 70 is positioned in this junction to regulate adjustably the distribution or division of the'a-ir from these two sources between the

blowers

40 and 52.

A further, and important, feature of the construction I is the inclusion of means for refrigerating theair-circulated by the blower 52 in "the final cooling stage just before the work passes from the oven enclosure to the unloading station. To this end, the branch 63 extending between the junction 61 and the blower 52 is wrapped with coils 71 through which a suitable refrigerant is circulated from a conventional' motor compressorunitshown at 72. Regardlessof the source of'the intake air for this final blower, such air will, therefore, be chil'led before the same flows over thework.

With reference to Fig. 4, the operation of -*the precooling means of the invention will 'inowbe described, it being first :noted that this meansis operative in the region of initial conveyor descent or between the heating zone and the cooling zone proper. -='Since the air drawn in by theblower 28 is taken both from-the ambient atmosphere and the recirculating du'c't,=it will'ibe apparent that the temperature of the combined air will be'in excess of the ambient air temperature. This temperature :should lie between the temperature at theend of theheat- 6 ing zone and that at the beginning of the cooling zone proper to reduce the 'abruptness of the temperature drop which would normally obtain therebetween. Control of the supply air temperature may be had by adjustment of the blending damper 37 which determines the relative amounts of ambient air and air drawn from the recirculating duct making up the intake flow. This control is preferably made automatic by means of a thermocouple,

73, or other comparable temperature sensing element, and a small reversible motor '74 operative to rotate the damper shaft. An indicating instrument 75 is provided between the thermocouple and motor so that the temperature is indicated visually, and the thermocouple is'prefera'b'ly located in the lower or advance end of the precoolingzone. As indicated by the arrows, a portion of the air circulated in this zone will flow to the top of the oven, but the major portion will be exhausted through the blower 46 and the stack 45.

Inthe first or pre-cooling stageof my cooling system, the work temperature is, therefore, reduced only a relativelyslight amount to permit the processing of certain work which may be more susceptible than usual to damage by thermal shock. Plaster of Paris cores have already been mentioned as an example of such work which, without the pre-cooling means I provide, cannot be handled safely at the same rate as the sand cores more commonly processed. Immediately following precooling'of the work in this manner, the work as moved by the'conveyor passes successively through two further cooling stages afforded by that part of my system shown in Fig. 5.

The-second cooling stage is effective over an area indicated by the box 76 in the cooling zone, while the third and final stage is represented by the box 77. The air circulation is generally shown by the arrows in Fig. 5 with the dampers 69 and 70 respectively in their full line positions. With this condition of the dampers, 'air taken in from outside the building through the stack opening 67 andfrom beneath the ceiling through the opening 68 flows to both the

blowers

40 and 52. Both blowers also draw exhaust air through duct 60 from the lower cooling region 77. The air taken in by the blower 52 is, of course, chilled by the refrigerating coils 71 and some of this air is recirculated after passing over the work in a direction generally opposite to the movement thereof, and some flows'to the blower 4t).

I-twill be seen that the air flowing in the second stage will be at higher temperature than that caused to flow in the refrigerated stage. By adjustment of the dampers 69 :and 70, the circulation of air in these two stages may be considerably modified without upsetting the desired temperature relation thereof which affords a progressive cooling. The flexibility of the system permits it to be readily adapted to varying climatic conditions and of the many obviously possible combinations of damper thereof,all this hot air may be fed to the blower 40 and clrcula'ted thereby over the work in an upward direction before being exhausted by blower 46. In the region 76,

therefore, the work is subjected to a cooling flow of fairly warm ambient air. In its position 79, the damper 70 also causes all the exhaust air flowing through the conduit'60 to be returned to the blower 52, and thus all this air is again refrigerated and recirculated. This .redu'ces the load on the refrigeration unit, since it is required to refrigerate only the relatively cool exhaust air.

For'winter operation, the damper 69 may be movedto the dotted line position 80 and damper 70 to its dotted line position 3'1. fWith these adjustments, cold outside air 'Wlll bc drawn in and supplied completely to the blower 52, while all the cool exhaust air from the conduit 60 will How to the inlet of the blower 40. Again this atrangement provides a minimum load on the refrigeration unit, since the outside air will usually be at a lower temperature than the cool exhaust air. It will be noted that in both the summer and winter operation, the work is first subjected to a counter flow of cooling air at a temperature higher than the temperature of the chilled air it encounters in the final cooling stage. Since the refrigerating coils are operative in the branch line between the four-way connection 61 and the blower 52, the minimum cooling temperature will always obtain in the final stage.

The use of refrigerated air permits the work to be cooled rapidly while the preceding stages may be controlled to lower the work temperature sufiiciently to avoid any thermal shock. Within this general operation, the system is extremely flexible and readily controlled. For example, it for some reason the conveyor is driven at slow speed with only a small core production, the second cooling fan may be driven without, however, refrigerating the air supplied thereby. In order to realize maximum productivity, however, the refrigeration unit will be energized with preliminary cooling of the work in one or both of the two preceding stages. understood that the Cooling system is not limited either to core ovens or to continuous vertical core ovens, and may be used to equal advantage in other industrial ovens where it is desirable or necessary to provide cooling in a plurality of stages.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims, or the equivalent of such, be employed.

I therefore particularly point out and distinctly claim as my invention:

1. A cooling system for an industrial oven in which work being processed is moved in a predetermined path, comprising a series of three blowers equipped with distributing means for flowing air over the work as it moves in the oven and arranged to be operative successively with respect to the moving work, air intake means for the first such blower operative to supply ambient air thereto after first subjecting such air to heat from the oven to warm the same, inlet mean for supplying the second blower with ambient air selectviely from within and without the building structure in which the oven is located, refrigeration means for chilling the air supplied the oven by the third blower, and means for recirculating at least a portion of the air flow produced in the oven by the third blower after passing over the work and again being chilled by said refrigeration means.

2. A cooling system for a continuous core oven in which the cores are moved therethrough by conveyor means, comprising a first blower operative to flow air over the cores in a pre-cooling zone following immediately the oven heating zone, air intake means for said first blower including a passage in communication with the heating region of the oven and an inlet for ambient air, inlet damper means for adjustably regulating the relative amounts of heated and ambient air thus supplied the first blower, a second blower operative to flow air over the cores after the same have passed through such pro-cooling zone, a third blower having refrigeration means operatively associated therewith for flowing chilled air over the cores in a final cooling stage, supply duct means connecting the inlet sides of said second and third blowers, an inlet stack extending from said duct means outside of the building structure within which the oven is located, an opening in said stack within such building structure, means for adjustably regulating the air taken in through said stack from within and without the build- .ing structure, an exhaust conduit also connected to said supply duct means for returning thereto the air discharged It will he in the oven by said third blower after the same has flowed over the cores, and supply damper means for ad ustably controlling distribution of the air delivered to the supply duct means by said inlet stack and exhaust conduit between the second and third blowers.

3. In a conveyortype industrial oven, a cooling system comprising first'and second blowers each producing a distinct flow of cooling air over the work as the same connected to said supply duct and extending therefrom through theroof of the building structure within which the oven is located forsupplying outside air, an aperture in said stack just beneath the building roof, inlet damper means for adjustably opening and closing said aperture and the stack portion thereabove, whereby the inlet air may be drawn selectively from under and outside the roof, an exhaust duct also connected to said supply duct for withdrawing the air discharged to the oven by said second blower, supply damper means operative adjustably to direct the inlet air and air from said exhaust duct between the two blowers, the supply damper meansin one condition causing all inlet air to flow to the secondblowerand all such exhaust air to the first blower, and, in another condition, causing the exhaust air to be completely recirculated to the second blower and all inlet air to flow to the first blower, and means for refrigerating the air discharged to the oven by said second blower, the cooling system thus providing adjustable, but gradual, cooling so that the work may be brought rapidly to handling temperature without the danger of thermal shock thereto.

4. In a conveyor type industrial oven, a cooling system comprisingfirst and second blowers each producing a distinct flow of cooling air over the work as the same is moved in the oven by the conveyor, said blowers being arranged in operative succession relative to the heated moving work so that the latter is subjected to the air flow produced by the first blower and thereafter to that produced by the second blower, an inlet stack connected to the inlet side of said first blower and extending therefrom to the outside of the building structure within which the oven is located, an opening in the portion of said stack within the building, inlet damper means adjustably operative to regulate the flow of air through said stack from both inside and outside the building, exhaust duct means for Withdrawing the .air supplied the oven by said second blower and returning at least a portion of the same thereto for recirculation, and means for refrigerating the air discharged by said second blower to the oven, whereby the work after first being subjected to a cooling flow of ambient air is further cooled by chilled air.

5. In a conveyor type industrial oven adapted to process cores and the like which are particularly sensitive to thermal shock, a cooling system operative to cool the cores in two stages after the same have been moved by the conveyor through the heating zone of the oven, said cooling system comprising a first fan, an inlet conduit adapted to supply ambient air to said fan from a region proximately beneath the ceiling of the building structure within which the oven is located, a supply boot con nected to the outlet of said fan so constructed and arranged as to deliver the ambient air impelled by the fan to the oven over a predetermined extent of the conveyor travel, a second fan, duct means for circulating air through said fan and toe section of the conveyor travel in operative advance of that in which the ambient air delivered by said first fan flows, refrigeration means for cooling the air circulating in said duct means, whereby ,the heated cores after first being cooled by ambient air are furthercooled bychilled air, and exhaust means for withdrawing the chilled air discharged in the oven and returning the same to said duct means for recirculation.

6. In a conveyor type industrial oven adapted to process cores and the like which are particularly sensitive to thermal shock, a cooling system operative to cool the cores in two stages after the same have been moved by the conveyor through the heating zone of the oven, said cooling system comprising a first fan, a supply boot connected to the outlet of said fan so constructed and arranged as to deliver air impelled by the fan to the oven over a predetermined extent of the conveyor travel, a second fan, an inlet conduit adapted to supply said second fan with air from outside of the building structure within which the oven is located, duct means for discharging air from said second fan to a section of the conveyor travel in operative advance of that in which the air from said supply boot flows, refrigerating means for chilling the air thus circulated by said second fan, and means for exhausting the chilled air from the oven after flowing over the heated cores in such section of the conveyor travel and delivering the same to the inlet of said first fan, the chilled air having been warmed by its extraction of heat from the cores before passing to the first fan, whereby the cores are subjected to a flow of relatively warm air for a predetermined extent of their movement before encountering air at the minimum refrigerated temperature.

7. In an industrial oven including a housing, conveyor means for moving the work to be processed through such housing, and means for heating the work in a portion thereof; a cooling system comprising first and second blowers having their outlets in spaced relation in the housing at a succeeding portion of the same, refrigeration means in the outlet of said second blower for chilling the air discharged in the housing thereby, supply duct means connected commonly to the intakes of the first and second blowers, recovery duct means in the housing for returning at least a portion of the chilled air supplied by the second blower to said supply duct means after passing over the work, branch duct means connected to the supply duct means and being open externally of the oven for entry of ambient air, and damper means in the supply duct means for adjustably regulating the division of the ambient air and air recovered from the housing by the recovery duct means between said first 10 and second blowers to maintain a predetermined temperature differential in the respective discharges thereof. 8. In an industrial oven including a housing, conveyor means for moving the work to be processed through said housing, and means for heating the work in a portion of the housing; a cooling system operative in a succeeding portion of the housing to cool the work to a safe handling temperature prior to exit from the oven, said cooling system comprising a series of three blowers each equipped with air distributing means, the latter being arranged in the housing along the path of work movement therein to provide three distinct and successive discharges of air in such path, air intake means connected to the first blower producing the discharge initially encountered by the work in the cooling system to supply thereto a mixture of heated air from within the oven and ambient air external to the oven, damper means in said intake means for regulating the proportion of the oven-heated and ambient air thus supplied to said first blower, inlet means open outside the oven and connected directly to the second blower producing the discharge next encountered by the work in its movement through the oven, inlet duct means connected to the third blower and having an opening for entry of air external to the oven, and refrigeration means connected to the outlet of the third blower for chilling the air discharged thereby and caused to flow over the work in the last of the three cooling stages provided, the chilled air flow permitting the heated work to be brought rapidly to safe handling temperature and the preliminary cooling by the relatively warm and ambient air discharges reducing the work temperature gradually to eliminate destructive thermal shock by such chilled air.

References Cited in the file of this patent UNITED STATES PATENTS 1,431,145 Bolling Oct. 10, 1922 1,505,768 Dressler Aug. 19, 1924 2,110,352 Baker Mar. 8, 1938 2,217,452 Peck Oct. 8, 1940 2,406,821 Fox Sept. 3, 1946 2,460,150 Schupp Jan. 25, 1949 2,525,661 Fox Oct. 10, 1950 2,603,882 Mayer July 22, 1952 2,671,969 Mayer Mar. 16, 1954