US3090134A - Gas locks - Google Patents

Description

May 21, 1963 w. L. MORRISON GAS Locxs INVENTOR Mam/.90N

5 Sheets-Sheet 1 Armen/frs lll BY PAPA/ff fdl/,eraf

IMI/4f@ Filed June 1, 1960 May 21, 1963 w. L. MORRISON GAS LOCKS 5 Sheets-Sheet 2 Filed June 1, 1960 www...

#fram/ff@ My invention relates to improvements in gas locks and has for one object to provide a gas lock for cooling chambers and the like through which solid objects may pass while inhibiting ow of gas therethrough. Such a lock is especially applicable to a cold chamber wherein foodstuts and the like are cooled by contact with cold gas and cold liquid such as gaseous and liquid nitrogen at substantially atmospheric pressure and temperatures in the order of -320 degrees lF. Tlhe importance of the gas lock is that it makes it possible to prevent or at least t inhibit escape of the gaseous nitrogen and contamination of the gaseous nitrogen by atmospheric air. This is especially important when as in the preferred form of such operation the liquid is used as a bath in which the material to be frozen is immersed with resultant boiling of the gas and the gas boiled off is at substantially bath temperature and substantially atmospheric pressure withdrawn, reliquelied and returned for reuse. Under these circumstances, loss of gas or pollution by air is highly undesirable.

I propose to use a brush or brushes, the bristles `of which close entry and exit ports but may be pressed aside while maintaining contact with food bodies to permit entry and exit of food bodies into and out of the cooling chamber. The brushes may be at rest or may rotate. A single brush may be used or a plurality of brushes in opposition to one another may be used. The brushes may be made of bristles, synthetic or natural, fur fibers or even ilaps of woven material. Because the brush is flexible whatever kind of bristles are used, it furnishes a barrier or curtain inhibiting gas ilow without eiectively impeding movement of solids which merely pass the brush, bending the bristles aside while the bristles stil-l maintain gas flow inhibiting contact with the solids.

If the brushes rotate they may under some circumstances be more effective as a gas llow barrier and also may otter somewhat less resistance to passage of solids through the bristle area but stationary or movable or alone or in opposition to other brushes, the bristles form a barrier which if it does not completely prevent gas ow, inhibits it to minimize mixture of ambient air with the coolmg gas.

I propose under some circumstances to use a gas lock chamber open at one end to ambient atmosphere and at the other end to the cooling chamber. The gas pressure in the cooling chamber will be little if any above atmospheric, thus inhibiting tendency of entrance of ambient air to dilute the cooling gas. Each open end of the chamber will be closed by a brush or brushes. If the brushes rotate they will be rotated in opposite directions and will be masked by shrouds with a clearance between the shroud and the oor along which [the solids travel, being just enough to permit the solid to pass along the oor through the brush. The shrouding will, as the brushes rotate, limit the area through which solids may move to an area but little greater than the area required for passage of the objects. It the brushes operate in opposite directions, under these circumstances they tend to force air or gas outwardly from the lock chamber toward atmosphere on one end and toward the cooling gas at the other, and under these circumstances tend to draw a vacuum in the area between the brushes.

I have illustrated my invention as applied to a food freezing apparatus but the gas lock is equally applicable to many other purposes.

ad States Patent O "ice My invention is illustrated more or less diagrammatically in the accompanying drawings, wherein FIGURE l is a vertical section through the apparatus;

FIGURE 2 is a section along the line 2 2 of FIG- URE l;

FIGURE 3 is a detail section on an enlarged scale similar to a part of FIGURE l;

FIGURE 4 is a section along the line 4 4 of FIG- URE 3 in the absence of the food package;

FIGURE 5 is a section similar to FIGURE 4 showing a food package passing through;

FIGURE 6 is a side elevation similar to FIGURE 3 showing a food package about to enter;

FIGURE 7 is a similar view showing lthe food package about to leave in contact with the brush;

FIGURE 8 is a detailed section similar to FIGURE l showing a modied form;

FIGURE 9 is a section of a modified form along the line 9-9 of FIGURE 10;

FIGURE l0 is a section along the line 10--10 of FIGURE 9;

FIGURE 11 is a view into a modied form of the brush arrangement;

FIGURE 12 is a section along .the line 12-12 of FIGURE 1l.

Like parts are indicated by like numerals throughout the specification and drawings.

The housing 1 is adapted to contain a liquid nitrogen bath 2 and immediately above the bath in direct open communication therewith a gas chamber 3. Liquid nitrogen may be supplied to the bath through the duct 4. Gas evaporated from the bath may be discharged through the [duct 5 and there may be interposed between .the ducts 4 and 5 a nitrogen reliquefaotion plant or as the case may be, liquid nitrogen may be supplied from any suitable source through the duct 4 and the gas wasted through duct 5 though in the interest of economy the gas will normally be reliqueiied as it is evaporated by fthe foodstuff, being immersed in the bath.

Extending laterally from each side of the housing 1 are tunnels 6 and 7. Each tunnel denes a gas lock, the purpose of which as will hereinafter appear is to prevent escape of gaseous nitrogen from the gas chamber and to prevent entrance of ambient air thereto. AS a general proposition, there will normally be maintained a pressure in the gas chamber of `a fraction of an inch of water, enough to inhibit air entrance. The tunnels 5 and 6 dene entrance and exit air locks. The operation of each air lock is the same and a description of one air lock will suffice for both.

The air lock has .a llexible insulating iloor 8 above which are outer and inner barrier brushes 9 and 10, the brushes being driven by any suitable means, for eX- arnple, motors 11 which may be variable speed. Normally the brushes will be driven in unison in opposite directions so that the brush 9 between the gas lock and the outer atmosphere tends to urge gas outwardly from the lock to atmosphere and brush 10 between the gas lock and the cooling chamber tends to urge gas outwardly from the gas lock to the cooling chamber. Each of the brushes comprise central brush bodies 12, 13 with closely spaced, fairly soft bristles 14, 15 which may be of fiber or hair or fur or other material which will not become stiff and brittle in the presence of cold. These brushes are so disposed that they contact at all times the iloor of the gas lock and the two brushes `define between them the lock chamber 16. The oor 8 may be upwardly adjusted by hand wheels 17 and 18 in opposition respectively to the bristles 14, 15 to insure close contact with the bristles as they rotate because it is these bristles that are relied upon to furnish the closure of the barrier between the lock chamber 416 and the ambient air on the one hand and the cooling chamber on the other. The bristles being rotated at high speed are held against the floor 8 as by centrifugal force and their stiffness. Shrouds i9, 2t? are associated with the brushes 9 and 10 and mask a substantial part of the periphery of each brush. The shrouds terminate enough short of the hoor to just permit passage of the maximum size of food solid along the floor through the brush. The shrouds 19 and 20 limit gas iiow and gas contact with the bristles to the narrow area between fthe floor and the brush along which the foodstuff travels, so that the brushes tend to so to speak brush the air or gas along the licor in response to the direction of rotary movement of the brush.

Food packages 22 may be pushed along the oor 8 mechanically or han-d manipulated as the case may be. They pass beneath the brush 9 into the chamber 16 and then beneath the brushltl .into the cooling gas chamber 3, where they pass over .the pulley 23 and engage the belt 24 which moves in the direction of the arrows. The belt 24 passes over the pulleys Z9, 30, 23 and the larger diameter portion of the pulleys 27, 28. The belt 25 passes over the pulley 27a and the smaller diameters of the pulleys Z7 and 28 and carry the food package gripped between them downwardly below the level of the liquid, thus insuring a complete immersion of each food package in the nitrogen bath.

The pulleys 27 and 28 as indicated in FIGURES 1 and 2 are of different diameters. The belt 24 is narrower than the belt 25. The belt 25 engages the `smaller diameter of the pulleys. The belt 24 engages the larger diameters of the pulleys so the belts travel at slightly different speed as a result of the different diameters of the pulleys but the pressure of the belts on the food packages is so slight that they are propelled through the bath without diiiiculty.

As the food packages pass between the pulleys 29 and 27a they are discharged upon the licor 8 to enter the exit or discharge chamber where exactly the same situation prevailed as prevailed in connection with the enltrance chamber.

Referring to FIGURES 3, 6 and 7, it will be noted in FIGURE 6, the food package 22 is just contacting the rapidly rotating brush. Since the package is thinner than the-length of the bristles, it interferes with contact between -the brush and the lioor 8 only in a portion of the brush as indicated in FIGURE 5. Normally when there is no package present, the contact is clear across the brush as in FIGURE 4. As the brush contacts the package 22 `in FIGURE 6, the bristles are displaced as shown but 'no opening is left for the air, the brushes, as a result of their stillness and centrifugal force maintaining contact with the package and inhibiting gas escape. This continues as the package leaves the brush in FIGURE 7, the bristles tending to spring down behind the package to Contact the licor.

In `the modified form shown in FIGURE 8, two opposed pairs of brushes 32, 33 and 34, 35 are substituted for the single brushes. Otherwise, the operation is substantially the same except that under these circumstances it may be necessary .to have brushes 36, 37 on either iside of the lock to contact the sides of the food package.

The previous Vdisclosure applies to a situation where the package is closed but if an open package or rather an open pan is to be used, the brushes from above must .be omitted because they would brush the contents out of the pan. Under these circumstances, the modified form disclosed in FIGURES 1l and 12 is used. In this case, the pan travels along the oor 38 over a brush 39 onto the floor 49 over a brush 4i onto a floor 42. The upper portion of the pan is held by the brushes upwardly against the ceiling or roof 43. The clearance between the floor and the roof in this case is approximately the depth of the pan, there being sufficient clearance so that the pan will not bind but the clearance must be so slight that as the pan is lifted from the floor and squeezed against the roof by the brushes, no spilling will occur.

Under these circumstances, the brush accomplishes exactly the same purpose as it does in the cases where the brush is above or on the side because the sole purpose of the brush is to furnish a barrier which will inhibit gas flow into or out of the lock chamber.

Under ordinary conditions, the rotational speed of any of the brushes will be relied on in part to maintain a snug contact with the -floor or ceiling as the case may be and with the package as it passes through. The stiffness of the brush also contributes to maintaining this contact and under some circumstances, the brush might actually be at rest and still furnish an adequate barrier.

Under some circumstances also `the brush bristles might be metallic subject to magnetization and the oor or surface along which the pan travels would be magnetized s0 that the brush bristles would be held against it by magnetic force. This would be especially appropriate in connection with a brush at rest or being used as the barrier.

l have shown, to illustrate my invention, a complete assembly of cold gas chamber, freezing bath and conveying mechanism. IIf solid food particles are to be frozen, they may be safely contacted by the bristle brushes as the pressures `are so small as not to be harmful. However, if it is desired to cool soft cooked food in pans, such food cannot be contacted by the bristles and therefore I have disclosed an important modification where the pans are above rather than below the bristles and the pan with its open top slides along the floor, being pressed upwardly against `the roof of the chamber.

I have used the term bristle broadly as covering any flexible element, be it woven flaps, synthetic bristles, bers, threads, cords or the like. If flap-s are used, they might extend clear across the brush or might be cut in strips or might be slit in conformity to the width of the package.

I have used the term floor broadly. It might be the bottom, the top or side wall but so long as it is something along which the food package travels, it is the iioor which is in opposition to the brush or brushes. The floor may be continuous or discontinuous. A conveyor may pass along the iioor, the brush sealing the conveyor as well as the food package or the food packages may be propelled from an outside source. The essential element is that the food package no matter how constituted, whether it goes through separately or in train is continuously sealed by the flexible sealing means so that the flexible sealing means, preferably a brush, inhibits gas flow along the bath followed by the food body.

Because the gas lock is continuously operative and is opened and closed merely by the passage of the food body therethrough, no complicated timing mechanism is needed. When a food body is presented to the gas lock, it opens the lock, passes through without substantial gas ow and closes after the food body without substantial gas movement. As a result material may go through the system making its own time.

The arrangement shown in FIGURES l, 8 and 12 showing rotating brushes at opposite ends of the gas lock chamber discloses an arrangement where the rotation of the brush in opposite directions tends to draw a vacuum in the chamber by urging gas flow from the chamber toward atmosphere and toward the cold chamber, thus inhibiting loss of cold gas contamination of the cold gas by air. The rotation of the brushes thus sirnultaneously permitting contact of the bristles with the opposite wall of the chamber and with the object passed through and at the same time to some extent displacing gas.

lf the brushes do not rotate no such vacuum occurs and under these circumstances only the stiffness of the bristle without the centrifugal effect or the stiffness of the bristles with the magnetic effect is relied upon to hold the bristles across the opening to Vmake a gas inhibiting curtain. If

the brush is not rotated the dimensions of the brush can Well be increased and the area occupied by the bristles may be Varied depending upon circumstances. Only a slight thickness `of bristles might be suicient. On the other hand, the bristles mght extend quite a long distance along the path of the object and in some circumstances only a single brush of greater or less width will be sufcient to inhibit gas ow.

I claim:

1. A gas lock including a chamber open at both ends having a smooth oor along which solid objects may travel into, through and be discharged from the chamber, a rotating brush closing each end of the chamber, the bristles thereof being in contact at their free ends with said door and being free to yield to permit passage of solid objects along the oor while maintaining sealing Contact therewith.

2. A gas lock including a chamber open at both ends having a smooth door along which solid objects may travel into, through and be discharged from the chamber, a rotating `brush closing each end of the chamber, the bristles thereof being in contact at their free ends with said floor and being free to yield to permit passage of solid `objects along the door while maintaining sealing contact therewith, the brushes rotating in opposite directions.

3. A gas lock including a chamber open at both ends having a smooth floor `along which solid objects may travel into, through and be discharged from the chamber, a rotating brush closing each end of the chamber, the bristles thereof being in contact at their free ends with said door and Ibeing free to yield to permit passage of solid objects along the oor while maintaining sealing contact therewith a shroud for each brush.

4. A gas lock including a chamber open at both ends having a smooth floor along which solid objects may travel into, through and tbe discharged rom the chamber, a rotating brush closing each end of the chamber, the bristles thereof being in contact at their free ends with said floor and being free to yield to permit passage of solid objects along the iloor While maintaining sealing contact therewith, a shroud tor each brush, the shroud terminating above the lloor a distance sucient to permit uninipeded passage of solid objects.

5. A gas lock including a chamber open at both ends only, a door along which solid objects may travel into, through and be discharged from the chamber, the brush bristles being in contact with the lloor and being free to yield to permit passage of solid objects along the flootl While maintaining sealing contact therewith, means for rotating the brushes in opposite directions whereby the bristles as they contact a solid object traveling along the floor move against such direction of travel at the intake end and with the direction of travel at the discharge end ot the chamber, shrouds Within the chamber masking the brushes, there being clearance between the ends of the shrouds and the iioor sufficient to permit passage of the solid objects.

References Cited in the le of this patent UNITED STATES PATENTS 84,904 Reed et al. Dec. 15, 1'868 890,252 Thompson June 9, 1908 1,298,790 Rich Apr. l, 1919 1,933,257 Goosman Oct. 31, 1933 1,944,857 Atwell Jan. 23, 1934 2,247,865 Zarotschenzeft et al. July 1, 1941 2,286,514 Stebbins June 16, 1942 2,313,666 Webb et al. Mar. 9, 1943 2,951,353 Morrison Sept. 6, 1960 2,977,106 Duft Mar. 28, 1961

Claims (1)

1. A GAS LOCK INCLUDING A CHAMBER OPEN AT BOTH ENDS HAVING A SMOOTH FLOOR ALONG WHICH SOLID OBJECTS MAY TRAVEL INTO, THROUGH AND BE DISCHARGED FROM THE CHAMBER, A ROTATING BRUSH CLOSING EACH END OF THE CHAMBER, THE BRISTLE THEREOF BEING IN CONTACT AT THEIR FREE ENDS WITH SAID FLOOR AND BEING FREE TO YIELD TO PERMIT PASSAGE OF SOLID OBJECTS ALONG THE FLOOR WHILE MAINTAINING SEALING CONTACT THEREWITH.

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