US3024623A - Blast tunnels - Google Patents

Description

March 13, 1962 G. L. FORSTER ETAL. 3,024,623

BLAST TUNNELS 2 Sheets-Sheet 1 Filed .April 4, 1960 INVENTORS GERALD L FORSTER MERVIN ILTROWER BY i '91; .,I.'

THEIR ATTORNEYS rates Patented Mar. 13, 1932 3,024,623 ELAST TUNNELS Gerald isothan Forster, Chaifont St, Peter, and Mervin Hubert Trower, @reenter-d, England, assignors to Lever Brothers Qompany, New Yorlr, NSY., a corporation of Maine Filed Apr. 1i, 19th), Ser. No. 19,671 Claims priority, application Great Britain Apr. 6, 1959 7 Claims. (Cl. 62-330) This invention relates to improvements in refrigerating apparatus, and it relates particularly to apparatus by means of which plastic, semi-plastic and other materials can be frozen or hardened by subjecting them to the refrigerating action of streams of low-temperature air or gas as the materials are being conveyed along a predetermined path.

Apparatus embodying the present invention includes a conveyor on which the materials to be refrigerated are carried through a tunnel having gas inlets adjacent its opposite ends through which refrigerated gas, such as air, is introduced into the tunnel for flow towards the middle of the tunnel before it is discharged, and recirculated.

ln an apparatus according to the invention, the streams of gas coming from the gas inlets towards the middle of the tunnel can be discharged through a common gas outlet port or through two separate 4gas outlet ports.

in a preferred apparatus according to the invention, the gas ilows substantially in a ligure 8 pattern, owing into the tunnel at one end, out at about the middle of the tuna nel, back into the tunnel at the other end, out again at about the middle of the tunnel, and then back into the tunnel through said one end again. Preferably, each loop of the figure d path is provided with `a refrigerating coil or the like to chill the air 'before returning it to one end or the other of the tunnel.

The new apparatus is designed and constructed so that pressure conditions can be established at the ends of the tunnel or tunnels such that escape of the refrigerated gas is reduced or substantially prevented, and the tunnel or tunnels are provided with appropriate insulation to prevent absorption of heat from the surrounding atmosphere and thereby render the apparatus highly etiicient in operation.

For a better understanding of the present invention, reference may be had to the accompanying drawings in which:

FIGURE l is a view in side elevation 'and partially broken away of a typical refrigerating apparatus embodying the present invention;

FIGURE 2 is a plan view with parts broken away of the apparatus shown in FIGURE l;

FlGURE 3 is a perspective View of a portion of the apparatus; and

FiGURE 4 is a perspective view on a larger scale of a portion of the apparatus.

A typical apparatus according to the present invention may be used ier hardening ice cream briquettes or for freezing or hardening other liquid, plastic or semi-plastic materials. The apparatus disclosed herein comprises two parallel tunnels 1, Z through which run the upper and lower flights of a stainless steel, endless belt conveyor 4. Pulleys 5, 6 support the `belt 4 so that it moves through a narrow inlet opening 7 in the end of the tunnel 1 extends parallel to and near the bottom of the tunnel l and passes under a platform 8 midway along the tunnel. The belt leaves the tunnel i through 'an exit opening 9 and passes into a chamber 1i) which completely encloses the pulley 6 and then back through an inlet opening 11 into the lower tunnel 2, over a platform i2 midway along the tunnel 2, out through a narrow exit opening 13 and over the pulley 5. Thus, the belt is enclosed from its entrance through the opening 7 until it emerges through the opening 13.

Between the platform t; and the top of the tunnel 1 is a partition 14 (see particularly FIGURE 4) 'arranged obliquely across the tunnel 1. Gas outlet ports 15 and 16 are located in the side walls of the tunnel 1 on each side of the partition 14. Adjacent each end of the tunnel 1 are gas inlet ports 17 and 1S. Part of the tunnel wall has been broken `away in FlGURE 1 to show the inlet port 17, While only the position of the inlet port 18 is indicated. Ducts connect the outlet port 15 to the inlet port 13 and the outlet port 16 to the inlet port 17. The plat form 3, partition 14, outlet port 15 and outlet port 16 constitute the gas outlet means for the tunnel 1.

T he ducts connecting the outlet port 15 to the inlet port 1? comprise a branch duct 19, a compartment 20, a branch duct 21 and the casing of a centrifugal fan 22.

The ducts connecting the outlet port 16 to the inlet port 17 similarly comprise a branch duct 23, a compartment 2d, a branch duct 25 and the casing of a centrifugal fan 26.

A partition 27 is disposed obliquely across the tunnel 2 between the platform 12 and the bottom of the tunnel. The partition 27 is disposed parallel to and vertically below the partition 14 of the tunnel 1. Gas outlet ports lare provided in the walls of the tunnel 2 on opposite sides of the partition 27. The arrangement is similar to that shown in FIGURE 4 for tunnel 1. The outlet port on the near side of the partition 27 in FGURE l is connected by a duct 2S to the compartment 2). The outlet port on the far side of the partition 27 in FIGURE 1 is connected by means of a duct 29 to the compartment 24.

Gas inlet ports 30, 3l are located adjacent each end of the tunnel 2, part of the wall being omitted in FGURE i to show the inlet port Sil while only the position of the inlet port 31 is indicated. The inlet port 36 is connected to the compartment 24 -by the casing of a centrifugal fan 32 and a branch duct 33. inlet port 31 is similarly conected to the compartment 2t) by means of the casing o f a centrifugal fan 34 and a lbranch duct 35. Thus, the outlet ports of the tunnel 2 are connected by means of ducts to the inlet ports Sil, 3l in a manner similar to the connection of the outlet and inlet ports in the tunnel 1.

An ammonia coil refrigerating unit or an equivalent heat-exchange unit is located in each of the compartments Ztl and 2a. An insulating housing (not shown) encloses the two tunnels 1 and 2 and all the ducts.

The four fans Z6, 22, 34 and 32 are of equal capacity and are arranged to operate at equal speeds. The gas flow, when these fans are operating, will now be described.

A gas, such as air, is drawn by the fan 26 from the compartment 24 through the branch 25 and is directed in a stream through the gas inlet port 17 and along the part 1a of the tunnel 1 in a direction away from that end of the tunnel. The air stream passes over part of the platform S and is dellected by the partition 14 through the outlet port 15 into the branch i9 from which it passes into the compartment 2i) where it is refrigerated.

The fan 22 draws air from the "compartment 2t) through the branch 21 and directs a stream of air through the inlet port 18 and along the part 1b of the tunnel 1 in a direction away from that end of the tunnel (this direction being opposite to that of the air stream in part 1a of the tunnel). The stream of air passes over part of the platform 3 and is directed by the partition 14 through the outlet port 16 and through the branch 23 into the compartment 24 where it is again refrigerated. The air thus is circulated virtually in a ligure S pattern.

In a similar Way, the fan 32 draws air from the compartment 24, blows it through the part 2d of she tunnel 2 until it is deilected by the partition 27 through the branch 28 into ,the compartment Ztl.. Similarly, fan 34 3 draws air from compartment 20, blows it through the part 2b of the tunnel 2 from which it is deflected by the partition 27 through the branch 29 into the compartment 24.

Air drawn from the compartments 20, 24 is directed at high velocity by means of the fans substantially straight into the tunnels in the desired direction of flow. While air passes through the compartments 2) and 24, it is cooled by the refrigerating units therein. Thus, the fans 26 and 32 both draw refrigerated air from the compartment 24 and blow it through a half of each tunnel, this air then passing from the tunnels through the compartment 20 where it is again cooled. This re-cooled air is then drawn from the compartment 20 by both the fans 22, 34 and blown in the opposite direction through the other halves of the tunnels. It then passes through the compartment 24 again.

Pivoted air control valves or flaps 37, 38 (see FIGURE l) are arranged to regulate the areas of the inlet ports 17, 30, respectively, so that the venturi effect at the inlet ports 17, 30 maintains substantially atmospheric pressure at the entrance 7 and the exit 13, thereby effectively reducing leakage of refrigerated air out of the entrance and exit.

In a typical apparatus each tunnel is 90 feet long. Air is circulated through each tunnel part at the rate of about 5,000 cubic feet per minute at a velocity of about 2,000 feet per minute and at a temperature of about 5 F.

An apparatus of the kind described can be used for hardening ice cream briquettes or the like. The soft or plastic briquettes are deposited on the upper surface of the conveyor belt 4 at a position between the pulley 5 and the inlet opening 7 and are conveyed through the opening 7, through the part 1a of the tunnel 1, under the platform 8, through the part 1b of the tunnel 1, where the briquettes are hardened and freeze to the surface of the belt. They move around the pulley 6 in the compartment 10 and pass in an inverted position through the tunnel 2, passing over the platform 12, and emerge through the exit opening 13. The hardened briquettes are removed from the belt before it passes around the pulley 5.

From the foregoing description it will be apparent that the present invention provides an apparatus for refrigerating products of various types and makes efcient use of the refrigerating capacity of the refrigerating coils with a minimum of escape of refrigerated air or heating of the air by heat exchange with the surrounding atmosphere. Moreover, continued recirculation of the air establishes in the system a relatively stable humidity condition in the system. The high velocity flow of the air in contact with the products cools them quickly and uniformly and in many instances, permits the use of gas of higher temperatures than is normally required in other apparatus used for the same purposes.

The apparatus is susceptible to considerable modification in the size, arrangement and number of the flights of the conveyor and the tunnels through which the flights pass. Accordingly, the example of the apparatus described above should be considered as illustrative.

We claim:

l. A refrigerating apparatus comprising an elongated tunnel, an endless conveyor having a substantially horizontal flight extending through said tunnel, air inlets at about the ends of said tunnel, air outlets adjacent to the midportion of said tunnel, duct means connecting said outlets to said inlets, means for circulating air through said tunnel and said duct means in substantially an 8-shaped path, and means for refrigerating the air flowing from at least one of said outlets to an inlet.

2. The refrigerating apparatus set forth in claim l Comprising a second tunnel, said conveyor having a second flight extending through said second tunnel, second tunnel air inlets, second tunnel air outlets and duct means connecting said second tunnel outlets to said second tunnel inlets for flow of air in substantially an S-Shaped path through said second tunnel and said second tunnel duct means, said refrigerating means for the air for said rst tunnel also refrigerating the air flowing through said second tunnel.

3. A refrigerating apparatus comprising a tunnel, a conveyor belt inlet opening, a conveyor belt outlet opening, a conveyor belt extending through the tunnel between the conveyor belt openings, a gas inlet port adjacent each conveyor belt opening for directing a stream of gas into said tunnel in a direction substantially parallel to the conveyor belt adjacent to said opening, gas outlet means disposed along the tunnel between the gas inlet ports, refrigerating means connected between the gas outlet means and each gas inlet port, and a fan disposed between each refrigerating means and the gas inlet port to which said refrigerating means is connected, the arrangement being such that when the fans force streams of gas through the gas inlet ports, each stream passes through the tunnel for part of its length, leaves the tunnel through the gas outlet means, and then passes through one of the refrigerating means before re-entering the tunnel.

4. A refrigerating apparatus comprising a tunnel, a conveyor belt inlet opening, a conveyor belt outlet opening, a conveyor belt extending through the tunnel between these conveyor belt openings, a first air inlet port adjacent the conveyor belt inlet opening, a second air inlet port adjacent the conveyor belt outlet opening, first and second air outlet ports disposed along the tunnel between the first and second air inlet ports, means separately connecting the first air outlet port to the second air inlet port and the second air outlet port to the first air inlet port, fans for circulating air through the first air inlet port, along the tunnel for part of its length, out of the tunnel through the first air outlet port, back into the tunnel through the second air inlet port, along the tunnel for another part of its length, out through the second air outlet port and into the tunnel again through the first air inlet port, and refrigerating means in said connecting means for cooling the circulating air.

5. A refrigerating apparatus as claimed in claim 4 including another tunnel similar and parallel to said first mentioned tunnel, said conveyor belt also passing through said another tunnel, a chamber connecting the conveyor belt outlet opening of said first mentioned tunnel to the conveyor belt inlet opening of said another tunnel, and said refrigerating means for cooling the air circulating through said first mentioned tunnel also cooling the air circulating through said another tunnel.

6. A refrigerating apparatus comprising a tunnel, a conveyor belt having a flight extending through the tunnel, a first air inlet port adjacent one end of the tunnel, a second air inlet port adjacent the other end of the tunnel, centrifugal fans adjacent the first and second air inlet ports and being arranged to direct streams of air into the tunnel through said air inlet ports substantially parallel to said flight of the conveyor belt, first and second air outlet ports disposed approximately midway along the tunnel, a partition separating the first and second air outlet ports so that air flowing along the tunnel from the first air inlet port leaves the tunnel through the first air outlet port and air flowing through the tunnel from the second air inlet port leaves through the second air outlet port, first means connecting the first air outlet port to the Second air inlet port, second means connecting the second air outlet port to the first air inlet port, and refrigerating means in each of said rst and second connecting means for cooling the air flowing from said air outlet ports to said air inlet ports.

7. A refrigerating apparatus comprising an endless conveyor belt having two straight flights, rst and second tunnels, one of said straight flights extending through the first tunnel and the other straight flight extending through the second tunnel, an air inlet port adjacent each end of each tunnel, air outlet means approximately midway along each tunnel, means connecting said air outlet means directs it n the opposite direction through another said t0 Sad air inlet PONS, effiefating IneanS dSPOSed in air inlet port so that the only sharp turns in the air Sad Connecting means, and fans adjacent Said ail' inlet streams are adjacent the suction sides of said fans.

ports for directing streams of air into the tunnels through said air inlet ports substantially parallel to said straight 5 References Cited in the me of this patent nights, each said stream of air passing from a said air inlet port along a said tunnel for part of its length, leaving UNITED STATES PATENTS through the air outlet means of this tunnel, passing 1,930,414 Buhl- Oct. 10, 1933 through part 0f said refrigerating means, and then pass- 2,837,855 Glass May 25, 19 59 ing to one of said fans which turns this air stream and 10

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