US2966045A

US2966045A - Vacuum cooling apparatus

Info

Publication number: US2966045A
Application number: US717908A
Authority: US
Inventors: Chester R Anderson
Original assignee: GAY ENGINEERING CORP
Current assignee: GAY ENGINEERING Corp
Priority date: 1958-02-27
Filing date: 1958-02-27
Publication date: 1960-12-27
Anticipated expiration: 1977-12-27

Description

Dec. 27, 1960 c, ANDERSON 2,966,045

VACUUM COOLING APPARATUS Filed Feb. 27, 1958 2 Sheets-Sheet 1 IN VENT OR. 6 /557,522. ,4/vpieso/v Dec. 27, 1960 c. R. ANDERSON 2,966,045

VACUUM COOLING APPARATUS Filed Feb. 2'7, 1958 2 Sheets-Sheet 2 IN VENTOR. 642-5722 2. 4N050N FIG. 2.

United States VACUUM COOLING APPARATUS Filed Feb. 27, 1958, set. No. 717,908

Claims. (Cl. 62-270) This invention relates to devices employed in cooling systems, and more particularly to means including ice condensers employed for cooling by water vaporization at very low pressures, commonly known as vacuum cooling.

Although the invention is not to be limited to any special application, it has been found unusually useful when employed in conjunction with produce vacuum cooling methods and especially in the process of vacuum cooling lettuce.

As is well known, vacuum cooling is performed with a retort to house produce connected to a condenser, both retort and condenser being evacuated by a vacuum pump in communication with the interior of the condenser chamber. Condensers are extremely helpful in reducing the time required to cool produce. For example, water vapor must be removed continuously from the produce retort in order to continue the boiling process to cool the produce. However, at very low pressures an extremely small amount of water can vaporize and produce a tremendous amount of gas. Thus, in order to reduce the necessary capacity of the vacuum pump, it is necessary to dispose of as much water vapor as possible as soon as possible. This is done by means of a condenser.

Ice condensers utilized in conjunction with vacuum cooling apparatus are by no means unknown in the vacuum cooling art. However, to the present time, a conduit has been provided between the produce retort and the condenser. This means that water vapor must be pumped from the produce retort to the condenser chamber, and this adds substantially to the time required to cool produce.

In accordance with the invention, vacuum cooling time is substantially reduced by using a single housing means providing an airtight enclosure which is divided into a retort and condenser chamber by means of a partition, the retort chamber being adapted to hold produce to be cooled and the condenser chamber being adapted to hold ice. Perforate means are then provided in the lower half of the partition to prevent ice from falling into the retort chamber while permitting water vapor in the retort chamher to pass into the condenser chamber and immediately into contact with ice therein. A vacuum pump is then connected from the condenser chamber above the perforate means to draw the water vapor in the retort chamher through the ice.

The invention reduces vacuum cooling time required in the prior art for at least two reasons. In the first place, since only perforate means separate the retort and condenser chambers, it is not necessary for the vacuum pump to pump vapor from one to the other as it is in the case of prior art apparatus where a conduit is provided between the retort and condenser chambers. Another advantage of the invention which reduces vacuum cooling time resides in the fact that water vapor has an unusual aflinity for a wetted surface. In the first place, ice in the condenser chamber presents a wetted surface to condense water vapor passing from the retort atent C chamber into the condenser chamber very rapidly. Still further, the ice, WhlCh is withheld from falling into the retort chamber only by the perforate means, is in such proximity to water vapor in the retort chamber that the vacuum cooling time is substantially reduced.

According to a feature of the lHVEIltiOIl, a grating is disposed horizontally across the condenser chamber to support the ice above a water drainage compartment. Preferably the grating is disposed immediately below the perforate means and thus holds ice above condensed water but in a position immediately adjacent the retort chamber to speed the vacuum cooling process by providing a cold wetted surface in proximity to water vapor in the retort chamber. In this regard, it is to be noted that it is also an advantage that the perforate means is positioned above the grating because it would again be necessary to move vapor an excessive distance if it were necessary to pump water vapor from the retort chamber outwardly through the perforate means and through the drainage compartment and upwardly through the grating since no ice fills the drainage compartment.

According to another feature of the invention, a defiector is disposed through the partition from a position inside the retort chamber downwardly through the partition immediately below the perforate means and into the water drainage compartment. This means that water condensing on the partition and perforate means in the retort chamber will be deflected into the water drainage compartment. This is, of course, an advantage in that it is desirable to keep the retort chamber as dry as posible in order to remove only water evaporated from produce deposited therein.

In accordance with another feature of the invention, a header, which preferably includes simply a pipe, is disposed in an upper corner of the apparatus housing in the condenser chamber, for example, completely along its length. The pipe is provided with holes through it to withdraw air from the condenser chamber. The pipe is then maintained in communication with the vacuum pump for evacuation of both the retort and condenser chambers. The position of the pipe in the upper corner of the apparatus housing facilitates drawing water vapor upwardly through the ice in the condenser chamber over its longest path, viz. from the perforate means diagonally to the upper corner of the housing apparatus. The position in the upper portion of the condenser chamber of the header also facilitates drawing water vapor in a reverse flow arrangement for most efiicient condensation. That is, gravity flow of condensed water on ice bodies in the condenser chamber will be in a direction opposite the direction of water vapor flow upwardly through the ice.

Preferably the ice condenser chamber is rectangularly shaped and elongated. In accordance with a specific aspect of the invention, preferably means are provided to automatically fill and replenish the condenser chamber with ice. In accordance with the invention, such means are provided including a troughless screw conveyor disposed longitudinally along the top of the condenser chamber. It is thus seen that the position of the screw conveyor at the top of the condenser chamber prevents any packing around it until a portion below it is completely filled. Ice is then moved down along the length of the condenser chamber and the ice packed under the screw conveyor actually forms its own trough and facilitates movement of ice completely from one end to the other. Thus, it is necessary to deposit ice in the screw conveyor only at one end. Conveniently, an inspection port may be disposed in the top of the condenser chamber at the end thereof opnoste the end in which the ice is deposited to determine when the chamber is completely filled.

According to still another feature of the invention, special bearing hangers for the screw conveyor are preferably provided when it is supported at more than two points. The hanger is preferably V-shaped in horizontal section to deflect ice away from it and thereby to prevent the conveyor and it from being damaged and to prevent the hangers from damaging their mountings at the top wall of the condenser chamber.

The above-described and other advantages of the invention will be better understood when considered in connection with the following description.

In the accompanying drawings, which are merely illustrative:

.Fig. 1 is a perspective view of the vacuum cooling apparatus of the invention; and a Fig. 2 is a vertical sectional view 2--2 of the apparatus shown in Fig. 1.

In Fig. 1, the vacuum cooling apparatus of the invention is shown including unitary housing means 10, which is divided into a retort chamber 11 and a condenser chamber 12 by a partition 13 extending along the length of the apparatus. Retort chamber 11 is adapted to hold produce to be vacuum cooled. Produce, which is generally loaded onto pallets, is deposited in retort chamber 11 through a door 14 having balanced weights 15. Similarly, produce is removed from retort chamber 11 through a door 16 having balanced weights 17.

A vacuum break valve 18 is located in an inlet conduit 19 connected to the top of retort chamber 11. A water drainage valve 20 is located in a water drainage outlet conduit 21 connecting a water drainage compartment 22 to the atmosphere.

Condenser chamber 12 is divided into an upper ice compartment 23, shown filled with ice 24, and a lower water drainage compartment 22 by means of a grating 25. Grating 25 extends along substantially the complete length of the condenser chamber 12. Communication between the interior of retort chamber 11 and condenser chamber 12 is made through a screen wire mesh 26 eX- tending along the length of partition 13.

Air is Withdrawn from both retort chamber 11 and condenser chamber 12 by means of a pump 27 operated by a motor 28. Pump 27 is connected via a conduit 29 to a header 30 extending lengthwise of condenser chamber 12 in the upper right-hand corner of housing means 10. Communication is provided from the interior of chamber 12 into the interior of header 30 by means of holes 31 along the length of header 30 through a bottom portion thereof.

A vacuum break valve 61 is also located in conduit 29. Either vacuum break valve 18 or vacuum break valve 61 may be eliminated; however, each of these valves in their particular locations may have unusual utility. Under some circumstances, it may be desirable to permit air to enter both retort and condenser chambers 11 and 12 through holes 31 in header 30 so that air is passed through the ice in condenser chamber 12 before it is permitted to enter retort chamber 11 through screen wire mesh 26 in partition 13. This will make the air entering retort chamber 11 more humid and cooler. This may be des rable when storage is anticipated for a short length of time or where it s desirable to keep produce in a moist atmosphere for some length of time.

On the other hand, much produce is not heated or cooled appreciably at least at any substantial rate by conduction. For this reason, Warm air may not be damaging toproduce in retort chamber 11 when left there a short time. In this case, vacuum break valve 18 may be employed rather than vacuum break valve 61, the latter of the two causing cool, moist air to enter retort chamber 11 and the former permitting warm air to enter retort chamber 11. Still further, if valve 18 is employed to break the vacuum of the chambers 11 and 12, a saving may be made in the amount of ice melted. That is, air entering chambers 11 and 12 via. valve 61 certainly will tend to melt ice in condenser chamber 12 and this is undesirable from an economic standpoint.

Ice 24 is loaded into condenser chamber 12 by means of loading apparatus 32, which forms no part of the pres ent invention. Ice is loaded through a port in the forward end of condenser chamber 12 closed by a cover 33. Cover 33 thus provides an airtight seal; whereby pump 27 may maintain a high vacuum in retort chamber 11 and condenser chamber 12. Similarly, at the end of condenser chamber 12 opposite the end at which input cover 33 is positioned, cover 34 is provided 'to seal an inspection port through the top wall of chamber 12.

Ice 24 is moved from the forward to the rear end of condenser chamber 12 in an unusual manner by means of a troughless screw conveyor 35. Conveyor 35 simply is a worm having forward and

rear sections

36 and 37 driven by a motor 39 for rotating conveyor 35 in a manner to move ice loaded at the forward end of condenser 12 rearwardly in it.

Sections

36 and 37 are supported at their mutually adjacent ends by means of a specially shaped bracket 38. Bracket 38 is angularly shaped in horizontal section, the angular shape of which may also be seen in Fig. 2. Ice then is prevented from jamming between the rearward end of conveyor section 36 of the worm and the bracket. This not only protects the bracket but also protects the rear end of section 36 from damage.

The fact that conveyor 35 is troughless means that ice is deposited through the forward end of chamber 12 by means of loading apparatus 32 until ice fits up snugly against the bottom of the conveyor 35 at the forward end of chamber 12. As more ice is loaded on top of the conveyor 35, it is moved rearwardly in chamber 12 because the ice itself forms a trough. It is to be noted that the use of the conveyor 35 at the top of chamber 12 without a trough provides the unusual advantage of eliminating ice packing while being able to fill and replenish condenser chamber 12.

The operation of the vacuum cooling apparatus of the invention may be better understood in connection with the sectional view shown in Fig. 2. Lettuce is shown in crates 40 in retort chamber 11 in Fig. 2. As stated previously, the crates 40 are loaded into retort chamber 11, for example, through door 14. Door 14 is closed and door 16 is also closed. Ice 24 is deposited in condenser chamber 12 by means of loading apparatus 32. Motor 39 is then operated and ice is continuously loaded into chamber 12 at its forward end until ice appears to fill the complete chamber at its rearward end as viewed through the inspection port closed by cover 34. As a general rule, it will be necessary to replenish the supply of ice in condenser chamber 12 only after two to four loads of produce have been cooled. Chamber 12 will generally be loaded completely full or at least as full as indicated in Fig. 2, on initial loading. Covers 33 and 34 are then placed in the positions shown in Fig. 1 and motor 28 is started to evacuate chambers 11 and 12. Air is withdrawn through holes 32 in header 30 and outwardly of the housing 10 via conduit 29. Water vapor is moved simply from chamber 11 to chamber '12 as indicated at arrows 41. Substantially the only gas drawn through holes 31 in header 30, as indicated at arrows 42, is air. Ice 24 condenses substantially all the water vapor evaporated from the lettuce in the crates 40.

A wet-bulb thermometer is generally incorporated inside retort chamber 11 to determine the temperature of the produce therein. When a sufiiciently low temperature has been reached, motor 28 is shut off to stop the operation of pump 27. Vacuum break valve 18 is then opened to permit air to enter chambers 11 and 12 until atmospheric pressure is reached inside of it.

During the vacuum cooling process when vapor in chamber 11 is condensed in chamber 12, condensation in the form of droplets 43 falls into water drainage compartment 22. After vacuum break valve 18 has been operated, water drainage valve 20 is then opened to permit 23 water to be drained from compartment 22. Although the supply of ice 24- in condenser chamber 12 is not replenished each time a load is vacuum cooled, generally it is desirable to drain water indicated at 4 in cornpartment 22 after each individual produce load has been vacuum cooled.

As best shown in Fig. 2, a deflector 45 is disposed downwardly through partition 13 to deflect moisture condensing at 46 on partition 13 and perhaps on mesh 26 into water drainage compartment 22. Deflector 45 is disposed downwardly from retort chamber 211 into water drainage compartment 22 through partition 13 immediately below mesh 26 and grating 25.

It can thus be seen that by using single housing means providing an airtight enclosure, substantial reduction in vacuum cooling time may be made for several reasons. In the first place, wire mesh or perforate means 26 is the only thing that separates condenser chamber 12 from retort chamber 11. Thus it is not necessary to pump vapor from one chamber to the other as it is in the case of the prior art apparatus where conduit means are provided between the retort and condenser chambers. Still further, water vapor has an unusual afiinity for a wetted surface. Thus the ice 24 in condenser chamber 12 presents a wetted surface to condense water vapor passing from retort chamber 11 into condenser chamber 12. That is, a wetted surface is provided immediately adjacent retort chamber 11 at the wire mesh 26. The condensing medium, wetted surfaces of ice bodies, also improves the vacuum cooling time because of their proximity to retort chamber 11 at Wire mesh 26.

The position of grating 25 relative to the Wire mesh 26 and deflector 45 is also unusually useful in that waterfree ice, i.e., except for the wetted surfaces, is maintained immediately adjacent wire mesh 26 for fast condensation. it is an advantage of perforate means 26 that it i; also disposed above grating 25 rather than below it in order to eliminate any necessity of pumping vapor from retort chamber 11 into the drainage compartment 22 and then upwardly through ice 24 rather than directly through ice 24 as shown in Fig. 2. This again reduces vacuum cooling time.

Deflector 45 also provides a useful function since it is desirable to keep retort chamber 11 as moisture-free as possible in order to condense water evaporated only from the produce in crates 4% Still further, it is to be noted that the position of header 36 is unusually useful in that it draws vapor from retort chamber 11 through the longest path through ice 24 because it is diagonally opposite the position of perforate means 26.

The fact that mesh 2a is located in a bottom portion of partition 13 also facilitates most eflicient condensation of vapor withdrawn from retort chamber 11. That is, reverse flow is relied upon. Vapor from chamber 11 is drawn upwardly through the openings in mesh 26 toward the upper right hand corner of the housing means it} as shovm in Pig. 2. Drawing vapor upwardly from mesh 26 means that it will be flowing in a direction reverse to the gravity flow or." droplets 43 downwardly through the bodies or" ice 24.

Only one specific embodiment of the invention has been shown and described. Changes and modifications of the invention, of course, will suggest themselves to those skilled in the art. The specific embodiment of the invention shown and described is thus merely illustrative and it is to be noted that the true scope of the invention is defined only by the appended claims.

What is claimed is:

1. Vacuum cooling apparatus comprising: housing means providing an airtight enclosure; 21 substantially vertical partition in said housing means dividing said enclosure into retort and condenser chambers, said retort chamber being adapted to hold products to be cooled and said condenser chamber being adapted to hold ice;

perforate means in the lower half of said partition to prevent ice from falling into said retort chamber while permitting water vapor in said retort chamber to pass into the said condenser chamber and immediately into contact with ice therein; and a vacuum pump connected from said condenser chamber above said perforate means.

2. Vacuum cooling apparatus comprising: housing means providing an airtight enclosure; a substantially vertical partition in said housing means dividing said enclosure into retort and condenser chambers, said retort chamber being adapted to hold products to be cooled and said condenser chamber being adapted to hold ice; substantially horizontal water drainage means dividing said condenser chamber into an upper ice compartment and a lower drainage compartment; perforate means in said partition above said water drainage means to prevent ice from falling into said retort chamber while permitting water vapor in said retort chamber to pass into said condenser chamber and immediately into contact with ice therein; and a vacuum pump connected from said condenser chamber above said perforate means.

3. Vacuum cooling apparatus comprising: housing means providing an airtight enclosure; a substantially vertical partition in said housing means dividing said enclosure into retort and condenser chambers, said retort chamber being adapted to hold products to be cooled and said condenser chamber being adapted to hold ice; a substantially horizontal water drainage grating dividing said condenser chamber into an upper ice compartment and a lower drainage compartment; perforate means in said partition immediately above said grating to prevent ice from falling into said retort chamber while permitting water vapor in said retort chamber to pass into said condenser chamber and immediately into contact with ice t rerein; and a vacuum pump connected from said condenser chamber above said perforate means.

4. Vacuum cooling apparatus comprising: housing means providing an airtight enclosure; a substantially vertical partition in said housing means dividing said enclosure into retort and condenser chambers, said retort chamber being adapted to hold products to be cooled and said condenser chamber being adapted to hold ice; a substantially horizontal water drainage grating dividing said condenser chamber into a larger upper ice compartment and a smaller lower drainage compartment; perforate means in the lower half of said condenser chamber immediately above said grating to prevent ice from falling into said retort chamber while permitting water vapor in said retort chamber to pass into said condenser chamber and immediately into contact with ice therein; a deflector extending from a position in said retort chamber downwardly through said partition below said perforate means into said drainage compartment to deflect water condensing on said partition and said perforate means in said retort chamber into said drainage compartment; and a vacuum pump connected from said condenser chamber above said perforate means.

5. Vacuum cooling apparatus comprising: a rectangular housing providing an elongated airtight enclosure; a substantially vertical longitudinal partition in said housing dividing said enclosure into retort and condenser chambers, said retort chamber being adapted to hold products to be cooled and said condenser chamber being adapted to hold ice bodies; a wire mesh in a lower portion of said partition extending substantially along its complete length to prevent ice from falling into said retort chamber While permitting water vapor in said retort chamber to pass into said condenser chamber all along its length and immediately into contact with ice therein; a grating disposed substantially horizontally in said condenser chamber below said wire mesh dividing said condenser chamber into an upper ice compartment and a lower drainage compartment; a deflector extending from said retort chamber downwardly through said partition below said wire mesh into said drainage compartment; an exhaust header including a pipe disposed longitudinally in an upper corner of said housing in said condenser chamber, said pipe having holes for communication between said condenser chamber and the interior of the pipe; and a vacuum pump connected from said pipe.

6. Vacuum cooling apparatus comprising: a rectangular housing providing an elongated airtight enclosure; a substantially vertical longitudinal partition in said housing dividing said enclosure into retort and condenser chambers, said retort chamber being adapted to hold products to be cooled and said condenser chamber being adapted to hold ice bodies; a wire mesh in a lower portion of said partition extending substantially along its complete length to prevent ice from falling into said retort chamber while permitting water vapor in said retort chamber to pass into said condenser chamber all along its length and immediately into contact with ice therein; a grating disposed substantially horizontally in said condenser chamber below said wire mesh, said grating dividing said condenser chamber into'an upper ice compartment and a lower drainage compartment; a deflector extending from said retort chamber downwardly through said partition below said wire mesh into said drainage compartment; an exhaust header including a pipe disposed longitudinally in an upper corner of said housing in said condenser chamber, said pipe having holes for communication between said condenser chamber and the interior of the pipe; a vacuum pump connected from said pipe; an inlet conduit connected from said retort chamber; a vacuum break valve connected in said inlet conduit; an outlet conduit connected from said drainage compartment; and a drain valve connected in said outlet conduit.

7. In an elongated ice condenser having an ice compartment, an arrangement for distributing, replenishing, and filling the compartment with ice bodies deposited in the compartment at one end, said arrangement comprising: a troughless screw conveyor disposed longitudinally along and at the top of the compartment; and means to rotate said screw conveyor in a direction to move the ice bodies deposited therein at said one end towards the end of said compartment opposite said one end.

8. An ice condenser comprising: an elongated ice housing having top, bottom, side and end walls to hold ice bodies, said housing having an input port through one of said walls near the top of said housing at one end thereof; means to provide an airtight seal for said input port; a worm rotatably mounted longitudinally in an upper portion of said housing and extending adjacent said input port, said bottom wall of said housing being the only structure spaced from said worm downwardly thereof, said bottom wall being spaced from said worm a distance several times the diameter thereof; and means to rotate said worm in a direction to move ice bodies deposited in said housing to said input port toward the end of said housing opposite the end provided with said input port.

9. The invention as defined in claim 8, wherein an inspection port is additionally provided through the top wall of said housing at the end thereof opposite said one end, and wherein means are additionally provided to seal said inspection port in an airtight manner.

10. In an elongated ice condenser having a condenser chamber, an arrangement for distributing, replenishing, and filling the chamber with ice bodies deposited in the chamber at one end, said arrangement comprising: a troughless screw conveyor disposed longitudinally along the top of the chamber, said conveyor having a plurality of sections supported by bearing brackets having a V-shaped horizontal section to deflect ice bodies away from it; and means to rotate said conveyor in a direction to move ice bodies deposited in said one end toward the end of said chamber opposite said one end.

11. Vacuum cooling apparatus comprising: housing means providing an airtight enclosure; a substantially vertical partition in said housing means dividing said enclosure into retort and condenser chambers, said retort chamber being adapted to hold products to be cooled and said condenser chamber being adapted to hold ice; perforate means in the lower half of said partition to prevent ice from falling into said retort chamber While permitting water vapor in said retort chamber to pass into the said condenser chamber and immediately into contact with ice therein; a vacuum pump; a conduit connecting said condenser chamber from a point above said perforate means to said vacuum pump; and a vacuum break valve in said conduit to permit warm air from the atmosphere to enter said retort chamber only after passing through ice in said condenser chamber.

12. Vacuum cooling apparatus comprising: housing means providing an airtight enclosure; a substantially vertical partition in said housing means dividing said enclosure into retort and condenser chambers, said retort chamber being adapted to hold products to be cooled and said condenser chamber being adapted to hold ice; perforate means in the lower half of said partition to prevent ice from falling into said retort chamber while permitting water vapor in said retort chamber to pass into the said condenser chamber and immediately into contact with ice therein; a vacuum pump connected from said condenser chamber above said perforate means; and a vacuum break valve connected from said condenser chamber to permit warm air from the atmosphere to enter said retort chamber only after passing through ice in said condenser chamber.

13. In an elongated ice condenser having a condenser chamber, an arrangement for distributing, replenishing and filling the chamber with ice bodies deposited in the chamber at one end, said arrangement comprising: a screw conveyor disposed longitudinally along the top of the chamber, said conveyor having a plurality of sections supported by bearing brackets having a V-shaped horizontal section to deflect the ice bodies away from it; and means to rotate said conveyor in a direction to move ice bodies deposited in said one end toward the end of said chamber opposite said one end.

14. Vacuum cooling apparatus comprising: housing means providing an airtight enclosure; a partition extending upwardly in said housing means dividing said enclosure into retort and condenser chambers, said retort chamber being adapted to hold products to be cooled and said condenser chamber being adapted to hold ice; means extending across said condenser chamber to support ice therein; perforate means providing free and open communication between said chambers through said partition at a vertical position therethrough spaced downwardly from the top of said partition and extending therethrough upwardly from said ice support means, said perforate means also preventing ice from falling into said retort chamber while permitting water vapor in said retort chamber to pass into the said condenser chamber and immediately into contact with ice therein; a vacuum pump connected from said condenser chamber above said perforate means; and a plurality of ice bodies filling said condenser chamber to a height everywhere greater than the height of said perforate means over the complete area of said partition occupied thereby.

l5. Vacuum cooling apparatus comprising: housing means providing an airtight enclosure; a partition extending upwardly in said housing means dividing said enclosure into retort and condenser chambers, said retort chamber being adapted to hold products to be cooled and said condenser chamber being adapted to hold ice; means extending across said condenser chamber to support ice therein; perforate means providing free and open communication between said chambers through said partition at a vertical position therethrough spaced downwardly from the top of said partition and extending therethrough upwardly from said ice support means, said perforate means also preventing ice from falling into said retort chamber while permitting Water vapor in said retort chamber to pass into the said condenser chamber and immediately into contact with ice therein; a vacuum pump connected from said condenser chamber above said perforate means; a plurality of ice bodies filling said condenser chamber to a height everywhere greater than the height of said perforate means over the complete area of said partition occupied thereby; and a vacuum break 10 valve connected from said condenser chamber to permit warm air from the atmosphere to enter said retort cham- References Cited in the file of this patent UNITED STATES PATENTS 222,122 Bate Dec. 2, 1879 2,634,592 Beardsley Apr. 14, 1953 2,770,111 Rear Nov. 13, 1956 FOREIGN PATENTS 280,043 Italy Nov. 28, 1930