US3456834A - Condensation-deterring container - Google Patents

Description

July 22, 1969 H. N. K. PATQN CONDENSATION-DETERRING CONTAINER Filed Oct. 6, 1966 7 She ets-Sheet 1 I N VENTOK HAM/[TON lYf/L KING PATON Arm/m5) July 22, 1969 H. N. K. PATON 3,455,334

CONDENSATION-DETERRING CONTAINER Filed Oct. 6, 1966 I 7 Sheets- Sheet 2 A TTOANE Y July 22, 1969 H. N. K. PATON 5 CONDENSATION-DE'IERRING CONTAINER Filed Oct. 6. 1966 7 Sheets-Sheet 5 I N VENTOR. HAM/l TON NEIL K ING PATON A TTORNE Y y 1969 H. N. K. PATON CONDENSATIQN-DETERRING CONTAINER 7 Sheets-Sheet 4 Filed Oct. 6. 1966 INVENTOR. HAM/170A M71 KING PATDN July 22, 1969 H. N. K. PATON CONDENSATION-DETERRING CONTAINER 7 Sheets-Sheet 5 Filed Oct. 6, 1966 INVENTOR. HAN/L70 NEIL KING PATON ATTORNEY July 22, 1969 H. N. K. PATON CONDENSATION -DETERRING CONTAINER 7 Sheets-Sheet 6 Filed Oct- 6. 1966 IN VENTOR.

4 TTOPNE Y ly 2 1969 H. N. K. PATQN 3,456,834

CONDENSATION-DETERRING CONTAINER Filed Oct. 6. 1966 7 Sheets-Sheet '7 I aJ INVENTOR. HAMILTON IVE/L KING PATOH A T TOPNE Y 3,456,834 CONDENSATION-DETERRING CONTAINER Hamilton Neil King Paton, Bellevue, Wash, assignor to Dynabulk Corporation, Bellevne, Wash, a corporation of Washington Continuation-impart of application Ser. No. 498,467, Oct. 30, 1964, now Patent No. 3,357,235, which is a continuation-in-part of application Ser. No. 367,447, Sept. 9, 1963, now Patent No. 3,396,762. This application Oct. 6, 1966, Ser. No. 584,863

Int. Cl. B656 25/18, 25/14; 367d 5/42 US. Cl. 220-9 5 Claims ABSTRACT OF THE DISCLOSURE A container comprising an impermeable wall having a top portion of a good heat-conducting material, a flexible lining membrane within said container and movable toward and from said top portion and having its edge portion secured in sealed relationship to said wall at least partially below said wall top portion to form a fiuid-tight space between said lining membrane and said wall top portion, a substantially continuous layer of thermal insulating material disposed within said fluid-tight space between said wall top portion and said lining membrane, and means to provide a pressure differential on opposite faces of the liner membrane to move same toward and from a position in lining relationship to said wall top portion.

This application is a continuation-in-part of my United States patent application Serial No. 408,467, filed October 30, 1964, now Pat. No. 3,357,235 for Internal Membrane Material Discharging Device for Containers, and of my United States patent application Serial No. 307,447, filed September 9, 1963, now Pat. No. 3,396,762. for Container With Internal Membrane. This invention relates to a method and apparatus for deterring the formation of c011- densation in containers, which term is intended to include storage bins or rooms in buildings, for holding material composed of particles which may be very small, such as in cement or flour, or comparatively large, such as in grain or pellets. Such moisture-deterring method and appara'tus is particularly important While warm, moist material of such character is being loaded into a cold container in cold weather.

An important object of the present invention is to provide a thin impermeable membrane between a wall of the container and material stored in the container, which will serve as a vapor barrier to deter formation of condensation on the inner surface of a container wall exposed to the material stored in such container, particularly if the wall is of metal, and to protect such material from being moistened by such condensation running down or dropping from the container Wall. Such membrane also decreases convection and heat conduction between the container wall and discrete particle material within the container, and affords at least some insulating effect. The insulation effect is greatly increased if the membrane is held out of direct contiguous engagement with the container wall, such as by providing a layer of material interposed between the container wall and the membrane. This deters freezing of the contained material when the exterior of the container is exposed to low temperatures, and deters spoilage of organic material in the container resulting from such material being sub- States Patent 6 F 3,456,834 Patented July 22, 1969 jected to undesirably high temperatures when the exterior of the container is exposed to high temperature condition s. Various types of construction can provide dead-air insulating space between the liner membrane and the container wall to reduce further heat conduction between material in the container and the wall of the container.

More specifically it is an object to provide a convenicut and practical construction for spacing a lining membrane from the outer wall of a container, and particularly one of metal, so as to deter conduction of heat from the liner membrane to the container wall, and to enable the liner membrane to be heated quickly by relatively warm material being supplied to the container to a temperature considerably higher than the temperature of the outer container wall.

Particularly it is an object to provide a construction wihch will limit movement of a liner membrane in the upper portion of a container so that it cannot come into contact with the outer container wall at all, or which contact will at least be over a comparatively limited area.

It is also an object to provide a membrane which can be held in lining relationship to the wall of a container by differential pressure during loading to permit utilization of the entire internal volume of a container.

A further object of the invention is to provide such a construction for preventing contact with the outer wall of a container by a membrane which can be manipulated effectively to expedite initial discharge from a container of discrete particle material, which can be used advantageously to complete substantially the operation of discharging material from a container and which can generally facilitate the operation of discharging discrete particle material from a container. Such manipulation of the membrane can be accomplished most effectively by producing a differential fluid pressure on opposite sides of the membrane and preferably such fluid is air.

The present invention can be utilized either in stationary or mobile containers and it is an object to utilize for the membrane a material which is impermeable, substantially inelastic and tough, while being highly flexible, wear resistant and economical. At the same time the membrane material should be inert so as not to contaminate material in the container which is edible or which is subject to deterioration or adulteration.

The foregoing objects can be accomplished by membrane installations in containers of various types and shapes having either rigid or flexible walls. Protection of the material in a container from being dampened by condensation can be accomplished by providing a thin, flexible, impermeable membrane which occupies at least a major part of the upper portion of the container and is held out of contiguous engagement with the outer wall of the container by interpos'ing material which is a poor heat conductor between such outer wall and the membrane while the membrane is pressed into wall-lining position by differential pressure acting on it. Such material can be in the form of spacer ribs, or can simply be a sheet of material, and can be secured either to the inner surface of the containers outer wall or to the outer surface of the membrane, or some ribs can be attached to the liner and others to the wall.

More specifically, an elongated storage chamber has two cup-shaped membranes installed respectively in its opposite end portions which, by differential pressure, can be moved simultaneously toward each other to shift material between them into the space between such membranes, and which pressure of the membranes on the material will have the further effect of compacting and/ or breaking up agglomerated stored material. The mem branes are spaced apart sufficiently far so that each membrane can be inverted completely, that is, turned inside out for the purpose of moving material toward a'discharge opening. The insulating material in the form of ribs or a continuous insulating layer is interposed between the membranes and particularly such upper portions of the container wall which the membranes otherwise could contact.

FIGURE 1 is a longitudinal section through a railway tank car having a representative type of membrane arrangement, and FIGURE 2 is a transverse section through such railway car taken on line 22 of FIG- URE 1, showing the container partially loaded.

FIGURE 3 is a longitudinal section through a container of rectangular cross section, such as a box car, and FIGURE 4 is a transverse section taken on line 4-4 of FIGURE 3.

FIGURES 5, 6, 7 and 8 are somewhat diagrammatic side elevations of one end portion of a railway car equipped with a membrane according to the present invention, showing such membrane in various operating positions which it may occupy during a tank-unloading operation.

FIGURE 9 is a side elevation of a tank car including a modified membrane installation showing the central portion in section, and FIGURE 10 is a transverse section on line 1010 of FIGURE 9.

FIGURE 11 is a side elevation of a tank car having a different type of membrane installation in its central portion, such central portion being shown in section, and

FIGURE 12 is a transverse section taken on line 1212 0 of FIGURE 11.

FIGURE 13 is a top perspective of a railway car container in which an upper membrane is installed, parts being broken away, and FIGURES 14, 15 and 16 are transverse sections through the tank of FIGURE 13 showing the liner in different operative positions.

FIGURE 17 is a detail top perspective of a portion of the tank of FIGURE 13 and a corresponding portion of the liner, showing a modified construction, parts being broken away.

FIGURE 18 is a vertical transverse section through a different type of railway car body in which a membrane is installed, and FIGURE 19 is a similar view showing a slightly modified type of membrane.

FIGURES 20, 21 and 22 are top perspectives of a different type of container in which a membrane is installed, parts being broken away.

FIGURES 23, 24 and 25 are top perspectives of a container similar to that shown in FIGURES 20, 21 and 22, but having a different type of membrane installation, portions of the container and membrane within it being broken away. Such figures show the membrane in different conditions.

FIGURES 26 and 27 are horizontal transverse sections through the container, FIGURE 26 being taken on line 2626 of FIGURE 23, and FIGURE 27 being taken on line 27-27 of FIGURE 25. FIGURE 28 is a longitudinal vertical section through the container on line 2828 of FIGURE 27.

FIGURES 29, 30 and 31 are transverse sections through a tank showing somewhat diagrammatically a membrane installation associated with different types of insulation.

An important function of the various membrane installations in the containers illustrated in the drawings is that of constituting a vapor barrier and insulation element in a container. The membrane installation also facilitates unloading of discrete particle material from a container by exerting controlled pressure on the material to move it toward a discharge opening.

The membrane installations are especially concerned with containers for storing or transporting discrete particle material, which term is intended to embrace any material having reasonable flow characteristics including fine powdered material, such as flour or cement; granular material such as sugar, salt or sand; coarse particle material such as whole grain or corn kernels; chunky material such as pellets, pulp chips, briquets and crushed limestone and small objects such as corn cobs, fruit and vegetables, such as oranges and potatoes, and other materials of irregular shape, as long as particles of the mass are or can be made discrete. All of such products are included within the term discrete particle material because all of them have the characteristic of not being liquid, their particles not adhering into a mass and of forming a reasonably steep angle of repose when piled. It should be understood that the specific items mentioned are only intended as examples to illustrate material having the characteristics pertinent to utilization of the present invention.

A principal application for the present invention is in rail cars, which may take the form of either a tank car, shown in FIGURES 1 and 2, or a boxcar, shown in FIGURES 3 and 4 or a hopper car, shown in FIG- URES 18 and 19. The tanks shown in FIGURES 1 to 15 may either be stationary, or may be carried on a rail car, a truck or a trailer, a ship or an aeroplane. In each instance the membrane 311 in FIGURE 1 should be of relatively strong and tough very flexible sheet material, which preferably is dimensionally stable.

Such material may be a fabric rendered air impermeable and waterproof, such as urethane-coated Dacron fabric, or the membrane can be of nonwoven material such as polyester resin sheet, available under the trade name Mylar. Such membrane materials are to be understood as merely representative. When such a membrane is interposed between discrete particle material in the container or tank and the tank shell there will be only a very small air space around the liner when the container is loaded. Such air can carry only a small amount of moisture. The membrane barrier prevents the ascension of moisture from the material received in the container into contact with the upper portion of the container wall.

Normally, tank cars, hopper cars and ships holds are metal and boxcars may be metal. If flour, for example, is loaded into such cars and the exterior of their containers is subjected to low temperature, warm moist air will rise from the material in the car into contact with the cold container wall so that such air will be cooled below the dew point and the moisture will therefore be precipitated from it onto the interior of the container wall. As sufficient moisture collects it will form a paste with the flour dust on the wall and may also drip off the container walls as condensate to dampen the surface of the flour. This moist condition promotes mold on the surface of the flour, which is undesirable. Such moisture condition will also produce an undesirable effect on other types of material which may be transported or stored in a container. Provision of the membrane barrier deters the occurrence of such condition because the membrane itself, even where it is in contact with the interior of the container wall, is a poor enough conductor of heat so that usually it will not chill air coming in contact with it sufliciently to precipitate the moisture from the air.

Further, the membrane 3h provides an insulation effect tending to stabilize the temperature of the material in the container, or at least tending to prevent the dew point of the moisture in it from being reached until the product itself has had time to absorb such moisture or reabsorb it without condensation actually occurring. Dead air space formed between the membrane and the rigid container wall increases the insulation effect. The contents of the container will tend to maintain a higher temperature than the atmosphere to which the container is subjected, if such atmospheric temperature is below freezing, so as to afford at least some protection against freezing of the container contents. Conversely, conduction of heat from the exterior of the container through the dead air space and/ or the membrane is deterred, so as to decrease damage to the contents of the car which might result from its exterior being subjected to undesirably high temperatures.

In FIGURES 1 to 8 the container or tank 100 could be used as a stationary in-plant storage container, or a land transportation container such as a tank car, a tank truck, a semitrailer tank. a trailer tank or a boxcar. In each tank a plurality of flexible membrane partitions are provided which conform to the internal shape of the container so that in one position a membrane section will serve as a liner for a portion of the tank. In each case at least a portion of the liner must be in roof-lining relationship as opposed to only wall-lining relationship. The membrane can be moved to and held up in such lining position, however, only by exerting on the liner a greater fluid pressure on its side away from the container Wall than on the wall side. In FIGURES l, 2 and 5 to 8 the tank is shown as being of cylindrical shape and cup-shaped membrane elements are of substantially circular cross section. They are reversible and must be able to turn completely inside out. In each instance membrane sections are located at opposite sides of the circumferential band of the tank where the filler port and the discharge port are.

In FIGURE 1 the cylindrical cup-shaped membrane section fitting each tank end has a curved end or bottom. The peripheral edges of such membrane sections are suitably secured by fluid-tight joints 14 extending circumferentially of the container. Each membrane element may then shift its position relative to its edge joint 14 from a position in which it constitutes a liner for one portion of the tank into a fully reversed position where the side of the membrane which was convex when the membrane was a liner has become concave, and the side of the membrane which was concave at the time it functioned as a liner has become convex.

As shown in FIGURE 1, connections or openings through the wall of the container 100 are rovided in the wall portions of the container to be engaged by the membrane sections 311 as liners. By connecting a suction source to an opening 108, therefore, the membrane section 3h for the corresponding portion of the container can be pressed by air under higher pressure at the opposite side of the membrane into substantially contiguous engagement with the container wall. In order to supply adequate air under pressure for this purpose it may be necessary to open a loading port 109 or a discharge port 102. When a section of the container is to be filled with discrete particle material both of its openings 108 are connected to a suction source, or such openings are vented and pressure fluid supplied inside the tank section, so that both membrane sections 311 are moved into tank-lining position, as shown in FIGURE 1. Material may be loaded by blowing it into the storage chamber. If such a pressure differential is not provided the limp membrane material will simply hang from its attach point at the roof and material could easily be loaded on top of folds which would prevent full loading of the container.

In the particular tank 100 shown in FIGURES 1 and 2 six loading ports 101 are shown, two of which are located between the membrane attachment lines 14, two more of such ports at the top of that portion of the tank which can be lined by one membrane 311 in one end portion of the tank, and two other ports at the top of the other end portion of the tank which can be occupied by another membrane. The purpose of providing such a number of loading ports is to expedite loading of the car by enabling material to be fed into more than one or all of such loading ports simultaneously and to enable the material to be distributed more uniformly along the length of the car as the tank approaches the filled condition and thus utilize fully the interior of the container.

The material is unloaded from the tank through discharge hoppers 102, of which there are preferably two, located in the central portion of the tank between the membrane attachemnt lines 14. It is necessary to provide a discharge opening of adequate size through which to move the discrete particle material quickly. Use of the two discharge hoppers 102 deters plugging of the outlet by the membranes during an unloading operation. Material can be dislodged from the space between the hoppers by a bridge 104 preferably inclined downward toward the two hoppers. Flow of material from such bridge into each of the hoppers can be expedited by supplying air under pressure through a connection 105 to the cavity 106 beneath the bridge and perforating the bridge so that air can escape through it to loosen particulate material above the bridge, and/ or the bridge can be connected resiliently to the adjacent portions of the tank and provision made for vibrating the bridge to loosen material for flow from it into the hoppers. A vent opening 103 is located in the top of the tank preferably at approximately thecenter.

While each of the membranes 3h being of nonmetallic fabric material affords some insulation between the contents of the tank and the tank wall, which usually is of metal, it may be desirable to increase the amount of insulation between the membrane and the tank wall, particularly around its upper portion. At the central portion of the tank between the membrane attachment lines 14 a layer of insulation 107 can be provided extending over approximately the upper quadrant of the tank. It is not necessary for the insulation to extend farther down around the sides than this, because warm moist air, which produces internal condensation, rises from the material in the tank into the dead air space only above the load and in addition the material is in contact with the bottom and lower portions of the tank wall, thus acting to prevent condensation.

It is not necessary to have a complete layer of insulation above the end portions of the tank capable of being occupied by the membranes 3h if provision is made for spacing such membranes from the metal tank wall to provide air space by pressing the membranes down onto the load during storage. However, during slow loading under very low temperature conditions it may be desirable to provide additional insulation as a blanket or ribs 107' between the membranes proper and the tank wall'proper to prevent condensation occurring inside the membranes, particularly if it should be necessary to interrupt such loading operation for a substantial period of time. Such ribs preferably are parallel but may extend either longitudinally of the tank, as shown in FIGURE 1, and then radially toward its center over the upper portions of the tank end walls, as shown in FIGURES 1 and 2, or such ribs may extend circumferentially of the tank or even in some other direction. Also, such ribs preferably are secured to or integral with the tank wall but, if desired, they could be mounted on the outer side of the membranes 3h.

Such ribs 107 should be made of insulating material such as rigid or semirigid foam plastic, or the ribs may be of the inflatable type. Any suitable means could be provided in the latter case to effect pneumatic inflation, or even hydraulic inflation, of such ribs. In any event, the liner 3h will be held by such ribs in spaced relationship to the tank wall 100, so as to increase the insulating value of the membrane alone and further deter condensation. If such ribs are mounted on the membrane, rather than on the tank wall, it is preferable for them to be of the inflatable type. Inflatable ribs can be deflated when filling of the tank has been almost completed to increase the capacity of the container.

When it is desired to load the tank a suction source is connected to each of the pipes 108, which extends through the shell of the tank 100, to communicate with the space between the shell and a membrane 3h. Only a very small suction is required for this purpose, such as one-half a pound per square inch, or even less. At the same time the vent 103 is open to supply air to the interior of the container. Such air may be under atmospheric or higher pressure and may be heated air or cooled air. Atmospheric air can be supplied directly to the vent 103 and higher pressure air or heated air or cooled air can be supplied through a hose 103' as shown in FIGURE 5. Heated air will increase the internal temperature to deter condensation in cold weather. Cooled air will deter deterioration of food products in hot weather. The connections 108 can simply be vented if the air supplied through hose 103' is under small pressure. The differential pressure on the membranes resulting from the higher internal pressure will press the membranes away from their attachment lines 14 into the tank wall-lining relationship shown in FIGURE 1. The groove between two adjacent ribs 107 would afford a channel for flow of air between the connection 108 and all parts of the space between the membrane and the wall lengthwise of the membrane and container, or equivalent flow channel provision should be made.

While the membranes are being held in the wall-lining positions shown in FIGURE 1, particulate material can be loaded into the space within the membranes through one or more of the loading ports 101. When the loading has been completed the covers 109 are closed and secured, but the interior of the tank may continue to be vented through the vent opening 103. The material is then thus stored or transported until it is ready to be discharged from the tank.

While FIGURES 1 and 2 show the membranes 3h installed in a tank of cylindrical cross section such membranes can be utilized in a tank of a difierent shape, such as the tank 100' shown in FIGURES 3 and 4, which has a cross section of substantially rectangular shape. This tank is shown as serving as the body of a railway boxcar. In this instance the membranes 31' are also of substantially rectangular cross section, corresponding in shape to the interior of the tank 100', so that when suction is applied to the connections 108 and the vent 103 is open the membranes will be drawn into lining relationship to the interior of the tank, as shown in FIGURES 3 and 4.

In the tank 100 of rectangular cross section ribs 107" are provided which extend across the roof of the tank transversely of its length and part way down the side walls. These ribs constitute means for spacing the membrane away from the inner wall of the tank to avoid contiguous contact with it, which would tend to promote condensation, as discussed in connection with the ribs 107 of FIGURES 1 and 2. These ribs also may be of solid material which is preferably of insulating character and at least somewhat resilient, or such ribs can be inflatable. Moreover, these ribs again can be integral with or secured to the inner wall of the container, or can be carried by the membrane. Particularly in the latter instance the ribs should be of the inflatable type.

To expedite loading, a plurality of loading ports 101 are provided in the top of the tank shown in FIGURES 3 and 4, and unloading of such tank can be accomplished through one or more central discharge hoppers 102'. The structure of the loading ports 101, their covers 109 and the discharge hoppers 102' and related mechanism may be essentially the same as the corresponding elements embodied in the tank construction illustrated in FIG- URES 1 and 2. This structure is described in greater detail below.

The functions of the membranes 3!: of FIGURES 1 and 2, and 3i of FIGURES 3 and 4, are generally the same. When the tank is being filled with material the cupshaped membranes must be held in substantially contiguous engagement with the inner wall of those portions of the tank with which such membranes are in registry, as illustrated generally in FIGURE 5. In this position the membranes can accommodate the greatest possible quan tity of material in the tank. When the tank has been filled initially, the filling openings can be closed, and a small amount of differential pressure, such as one pound per square inch, applied to the membranes by a suction source connected to port 103 in FIGURES 1 and 3 while having the connections 108 open to atmosphere or, in the case of FIGURE 1, while supplying pressurized gas to the two connections 108. The differential pressure of the gas will force the two membranes toward the center to compact the loaded material.

After the material in the tank has thus been compacted suction sources may again be connected to the ducts 108 and the central section vented to move the membranes into tank wall-lining condition, and the loading ports 101 can be reopened and more material loaded through them. The loading operation can be stopped several times during the last portion of the operation and in each instance the loading ports can be closed and differential fluid pressure applied to the membranes to press them inward. The material in the tank may thus be subjected periodically to a compaction force which, in the case of lightweight compactable material, such as diatomaceous earth, will increase the specific gravity of the mass considerably and allow much more of such material to be loaded into the tank than would otherwise be possible. When the tank has been filled to as great an extent as desired the loading ports can be closed, and suction can be applied to connection 103 to move the membranes into firm engagement with the loaded material, connections 108 being vented to atmosphere, or, in the case of FIGURE 1, gas under pressure higher than atmospheric pressure can be supplied to the connections 108. The connections 108 and 103 can then be closed by suitable valve means so that differential pressure will remain in the tank applied to the membranes to maintain continuing engagement with the material in the tank until it is desired to unload it.

During the period of time which the stored material remains in the container in transit, or in a plant, it is desirable for a slight positive pressure to be maintained between the membrane and the tank wall so that the membrane will hug the stored material to minimize the amount of air in contact with it, and to enable the air between the membrane and the tank wall to serve as thermal insulation between the exterior of the tank and the stored material.

In the membrane installation shown in FIGURE 3 the attaching means 14 for the open ends of the two membranes 3i are located considerably farther apart than the attaching means 14 for the open ends of the membranes 311, shown in FIGURE 1. The length of the container must exceed twice the axial length of each of the membranes in order to enable both membranes to turn inside out completely. Moreover, the space between the membrane attach lines must be more than half of the axial length of each membrane. Also, it is important that the discharge hoppers 102, 102', be located respectively adjacent to the two attaching means 14 for the open ends of the membranes, so as to prevent the accumulation of discrete material on a shelf between such attaching means and a discharge hopper.

The first step in the unloading operation is to arrange for proper removal of material through the two hoppers. When material can flow out of the discharge ports the material immediately above the hoppers 102, or 102', will move down through them first. Slope sheets 110 in FIG- URES l and 2, and 110 in FIGURES 3 and 4, will facilitate movement of material from the side zones of the longitudinally central compartment of the container down into the hoppers. Aeration of the bridge 104, or vibration of the bridge, will deflect material between the honuers into one or the other of them.

When the discrete particle material in the space between the attachment means 14 has been discharged through the discharge hoppers and the faces of the bodies of material stored wihtin the membranes have assumed a stable angle of repose, or even before such a stable condition is reached, gas under pressure may be supplied to one of the connections 108 to provide higher pressure between the corresponding membrane and the container wall than within such membrane. Gas thus supplied may have a pressure of as much as 50 pounds per square inch, for example, but the differential pressure across the membrane should not exceed 1 /2 pounds per square inch, to force the membrane to move into the central portion of the tank in turning inside out generally as illustrated by the broken lines in FIGURES 5, 6, 7 and 8, which illustrate representative sequential positions of the membrane. It will be seen from FIGURE 6 that, if the lower portion of the membrane is unrestrained except by weight of the stored material within the membrane, the entire closed end portion of the membrane will slide toward the central portion of the container while the portion of the cup-shaped membrane adjacent to its open end assumes a return bend shape, as illustrated in FIGURE 6.

As discharge of material continues the membrane will move farther toward inverted position, generally in the manner shown in FIGURE 7, until the forward bulge of the membrane engages the inclined slope face of the body of material stored within the opposite membrane. Because the membrane-attaching means are closer together in the arrangement shown in FIGURE 1 than in the arrangement shown in FIGURE 3, this engagement of the membrane with the face of material will occur sooner in the tank of FIGURE 1 than in that of FIGURE 3. In any event, when this situation does occur the supply of gas under pressure to the connection 108 behind the manipulated membrane should be cut off and suction should be applied to this connection, or such connection should be vented and gas under pressure supplied within such membrane, so that the membrane will be returned to its initial wall-lining condition.

Next, gas under pressure is supplied to the other connection 108 so as to force the other membrane out of wall-lining position and cause it to move through the inverting sequence illustrated in broken lines in FIGURES 6 and 7. Because most of the stored material has been emptied from the container as the result of the manipulation of the first membrane described, movement of the second membrane to be manipulated can progress from the position shown in FIGURE 7 to that of FIGURE 8, where the membrane will be inverted completely. It will be found that as the membrane approaches the completely inverted position it will dump a residue of the material stored in it which had lodged in the bottom crease of such membrane, as illustrated in FIGURE 7. If the attaching means 14 are spaced apart sufliciently far in relation to the axial length of the membrane being inverted, as shown in FIGURE 3, such residue will be dumped within the central portion of the container between the attaching means 14 so that it will be discharged through a hopper 1132'.

On the other hand, if the axial extent of the membrane is sufficiently greater than the distance between the two membrane attaching means, as shown in FIGURE 1, at least a portion of such residue will probably be dumped beyond the central portion of the container. In that case it will be necessary to discontinue the application of differential pressure to the membrane being manipulated and to apply opposite differential pressure to such membrane for reversing movement of that membrane into walllining position again, and then to supply gas under pressure for the second time to the other connection 108 for again inverting the membrane which was first inverted in order to scavenge all of the stored material from the container.

In the membrane installation illustrated in FIGURES 9 and 10 the cup-shaped membranes installed in opposite ends of the tank 100 may be similar to either of the membrane arrangements discussed above. In this embodiment, however, a further membrane 18 is provided which extends between the two attaching means '14 of the end membranes. The membrane 180 is substantially a sleeve, which would be of generally cylindrical shape if the container were cylindrical. The lower portion of this membrane is secured around the discharge ports 102 and the opposite sides of the intermediate bridge 104 in cases where this is provided. Two filling ports 101 are shown in the container between the attachment means 14 for the end membranes, and the central membrane has apertures 101" in it disposed in registry with the loading ports 101. Also, this membrane has in it an aperture 103' which is in registry with the connection 103 for venting the interior of the container between the end membranes, or supplying to such central portion air under pressure, or connecting to it a suction source.

As has been discussed above, it may be desirable during loading of a container to press a membrane down onto the stored material for the purpose of compacting it and increasing the insulating air space between such material and the container wall. To enable the membrane 180 to be moved downward a substantial distance to engage material stored in the central portion of the container between the two membrane-attaching means 14, the membrane must have fullness lengthwise of the container so that its upper portion can move downward away from the top of the container generally into the position shown in FIGURE 9. The apertures 101" in the membrane can be closed under such circumstances. Alternatively, an accordion tube 178' has its opposite ends connected to the container in a position encircling the loading port 101 and to the membrane 180 encircling the port 101". A further accordion tube 178" may have its opposite ends connected to the container wall in a position encircling the connection 103 and to the membrane 180 in a position encircling the aperture 103, respectively. In the lower end of each such tube is an aperture-closing neck 158' which can be sealed by a separable fastener 161. Also a small pressure-equalizing aperture through each tube should be provided.

As differential pressure is applied to the membrane 180, either by connecting a suction source to the connection 103" and opening the vent 103, or by connecting a source of air under pressure to the connection 103 and venting the connection 103" to atmosphere, the membrane 180 will be held substantially in wall-lining position even though there may be some folds in the membrane material resulting from its fullness lengthwise of the container. When the differential pressure acting on the main membrane is reversed, such as by connecting a suction source to the opening 103 and either venting the connection 103 to atmosphere or applying a source of air under pressure to such connection, the membrane will be pressed down onto material stored in the central portion of the container. As the upper portion of the membrane 180 thus moves downward from the top of the container the membrane apertures 101 and 103' will remain sealed from the space between the membrane and the container wall, so that no material loaded into the container can enter this space.

FIGURES 13 to 16 show a tank car 1 and FIGURES 18 and 19 show a hopper car 2 having a membrane installation of a type different from the membranes 3h discussed above. A membrane 3a in FIGURES 13 to 17 and 3b in FIGURES 18 and 19 extends Within the upper portion of the container, preferably approximately the upper half of the container, as a liner. The lower edge portion of this membrane is secured to the wall of the rigid container around the container periphery substantially in a horizontal plane. The membrane preferably is shaped generally complementally to the interior of the container so that it can fit the inner sides of the container walls reasonably contiguously. Thus in FIGURES 13, 14, 15 and 16 the membrane 3a is of generally semicylindrical shape, and the membrane 3b of FIGURES l8 and 19 is of generally rectangular pan shape. In both instances the membrane is reversible without being detachable so that it can move between a position lining the upper portion of the container and a position substantially inverted and sagging below the edge portion of the membrane secured to the container wall.

The membranes 3a and 3b like the membranes 371 are of strong, tough, very flexible sheet material, which preferably is inelastic.

In the use of these membranes also interposed between discrete particle material in the lower portion of the car and the rigid upper portion of the car shell there will be only a very small air space above the liner, as shown in FIGURES 17, 18 and 19, when the container is loaded. The membrane barrier prevents ascension of moisture in this instance also from the material in the container into contact with the upper portion of the container wall. Moreover, like the membrane 311 discussed above, the membranes 3a and 3b provide some insulation etfect.

While it is essential that the membrane form a subst-antially airtight barrier within the container between opposite sides of the membrane it is convenient to load the container from the top. In order to place the load beneath the membrane, therefore, it is necessary for the material received in the container to pass through openings in the membrane. In FIGURES 13, 14, and 16 filler openings 4 in the upper side of the container are shown as having upwardly projecting flanges encircling them. The membrane 3:: is then provided with elongated necks 5 at locations along its length corresponding to the container filler ports 4. The ends of these necks can be drawn upward through the container ports, as shown in FIGURE 14, and folded reversely over the filler port flanges in which position the necks 5 can be retained by an elastic or clamping band 6.

In order to maintain the membrane necks 5 open during the filling operation the membrane may be pressed into substantially contiguous contact with the inner wall of the container by connecting a suction source to the opening 7 through the upper portion of the container wall in communication with the space between such wall and the membrane. As air is sucked out of this connection the atmospheric pressure within the container will press the membrane outward into engagement with the container wall to form a liner, as shown in FIGURE 14. Since the upper portion of the membrane neck 5 is secured to the filler port 4 flange the neck will droop in return-folded condition within the container, as shown in FIGURE 14.

With the liner 3a held in the position of FIGURES 13 and 14 material is loaded through the filler ports 4 into the car tank until it reaches a level generally like that shown in FIGURE 14. The suction applied to opening 7 can then be discontinued and fluid under pressure, in this particular case preferably being air, can be supplied to the opening 7 to press the membrane away from the tank wall. The membrane will be pressed against the material in the tank generally in the manner shown in FIGURE 15, so as to squeeze air from the spaces between the particles of the material which will escape through the ports 4. The material will thus be compacted and densified and thus reduced in volume. Suction can then again be applied to the connection 7 to draw the membrane back into the position of FIGURE 14 to enable addition material to be fed into the tank through the ports 4. After a substantial additional amount of material has thus been received in the car a supply of air under pressure again can be connected to the opening 7, or suction can be applied to a filler port 4 or to the discharge port 10, to press the membrane lie down against the material to compact it further. This procedure can be repeated until the tank of the car has been virtually completely filled.

\Vhen the filling operation has thus been completed the securing ring 6 can be removed from the liner neck 5 and such neck can be contracted and sealed closed,

bound and pushed down into the filler port. Such port can then be covered by a suitable cap 8, as shown in FIGURE 16. Instead of the liner having necks 5 it may be possible simply to provide a cover 9 for an opening in the membrane 3e, as shown in FIGURE 17. Preferably this cover is attached to the membrane at one point so as to prevent it from sliding into the space between the liner and the tnak wall inadvertently. If such a closure is used a filling spout of suitable type should be provided to extend down through the tank loading port 4 into, or through, the liner opening.

Membrane 3b in the hopper car of FIGURES 18 and 19 is similar to the membrane 32 described above, and serves the same general function. In the case of a hopper car the loading ports 4 usually are staggered along the length of the car to enable the material to be supplied more readily to opposite sides of the container. The liner necks 5 can be like those described above and when the loading has been completed they can be bound and pushed into the upper portion of the car, as shown in FIGURE 18. In FIGURE 19 the liner openings are closed by covers 9, like that shown in FIGURE 17.

Usually such discrete particle material, if it is of powdered or granular character, is removed from a container by suction. FIGURE 16 illustrates the procedure of removing such material from the tank car 1 through the discharge port 10 by suction. During such operation either the opening 7 or the loading port 4 is uncovered to vent the space within the tank above the membrane 3e, which is in contact with the load. As the suction reduces the pressure within the material below atmospher ic, the atmospheric pressure above the membrane 3a presses such membrane against the upper portion of the material, which presses the material toward the outlet.

It will be appreciated that as material continues to be withdrawn from the tank the membrane 3a continues to follow the upper portion of the material downward until the tank has been emptied completely. Consequently, it is necessary for the membrane to be reversible from the upwardly extending position in FIGURE 14 to substantially a corresponding downward position. For that reason the edge of the membrane must be secured circumferentially around the car tank, as shown in FIGURE 13, approximately in the horizontal central plane of the tank. If the membrane is to be of minimum extent the necks 5 should be long enough so that they will not be stretched undesirably when the membrane is pressed against the upper portion of the load of material in the tank to compact it. While such compacting is not necessary it is highly desirable, particularly in transportation tanks, in order to increase the density of the material and consequently increase the load of a given type of material which can be transported by a given tank vehicle. Also, by subjecting the membrane to differential pressure in which the pressure below the membrane is lower, and above the membrane is higher, the membrane will act to force material toward and through the discharge port, even though the material itself, such as chunky material, would not be moved readily by suction.

In FIGURES 20, 21 and 22 a storage tank 11 of a shape different from those of FIGURES l3 and 18 is shown having in it a membrane 3c generally comparable to the membrane 3a of the tank in FIGURE 13, and the membrane 3b in the tank of FIGURE 18. In this instance the tank would be used primarily for plant storage purposes, rather than for transportation, and is shown to be of cylindrical shape in which the axis of the tank extends vertically. The liner 3c is of generally cylindrical shape, having one end closed by a circular end portion, except for a central port which may have a neck 5. The end of the membrane liner opposite the circular end wall is secured circumferentially to the wall of the tank ap proximately midway between the upper and lower ends of the tank. Such tank has a filling port 4 located centrally in its upper end and of a diameter corresponding gen- 13 erally to the diameter of the membrane neck 5. The lower end of the container has in it a discharge port and such container bottom may be of hopper shape to facilitate complete emptying of the tank.

The operation of the membrane installation, shown in FIGURES 20, 21 and 22, is similar to that described in connection with FIGURES 13, 14, and 16. In FIG- URE the membrane 30 is shown as being pressed upward into substantially contiguous engagement with the inner side of the wall of tank 11 by atmosphere pressure within the tank as the opening 7 is connected to a suction source. After the tank has been filled while such suction remains applied, the neck 5 can be removed from the filling port 4 by taking off the retaining band 6 and the neck can be sealed and pushed into the tank through the filling port, as shown in FIGURE 21. When material is being removed from the tank the Opening 7 can be in communication with the atmosphere and the differential pressure on opposite sides of the membrane can cause the membrane to press against the upper portion of the material in the tank and follow it down as it is discharged.

The container liner installation, shown in FIGURES 20, 21 and 22, is not suited to compaction of the material at intervals because of the short length of the neck 5 extending from the liner to the filler opening. A longer neck could, of course, be used if desired, but even then it would be diificult to obtain such compaction of discrete particle material in the container if the container wereless than half full of such material. Also, since the membrane 3c extends only approximately half way down the wall of the container, reliance could not be placed on this liner to assist in discharging the material completely from the container. The membrane arrangement shown in FIGURES 23 to 28, however, has the capability of compacting discrete particle material in the container, however full the container may be, of effecting complete emptying of the container and also serving to provide insulation and a moisture barrier between the discrete particle material in the container and the container wall.

In this form of membrane installation the membrane is composed of four sections including an upper section 3d and three lower sections 3e. The upper membrane section 3d is of generally circular shape having a neck 5 in its central portion, which can be pulled upward through the filler port 4 and folded over the flange of such port and secured in place by a band 6, which may be an elastic ring, as discussed in connection with the membrane and container disclosed in FIGURES 20, 21 and 22. The three lower membrane sections 3e are similar to each other, being of cylindrically arcuate shape approximately 120 in extent complemental to the curvature of the cylindrical container 11. A greater number of sections could be used, if desired. The length of such membrane sections corresponds to that portion of the height of the container 11 below the upper membrane section 3d. The upper edge portions of the membrane sections 3e are secured to the periphery of the upper membrane section 3d, so that, as shown in FIGURE 23, the three lower membrane sections 32 and the upper membrane sections 3d cooperatively will constitute a liner for the entire wall area of the container above its bottom. The bottom of the lower membrane sections 3e may be closed and the container bottom can be lined by a further membrane section 3 overlying the bottom of the container, of generally circular shape, and the peripheral edge portions of which are joined to the lower edge of the lower wall membrane sections 3e.

The upper membrane section 3d is secured to the container only by its neck 5 extended through and secured around the filler port 4. The bottom membrane section 3 has an opening 12 in its central portion corresponding in size and location to the discharge port 10 in the bottom of the container 11. Such membrane section opening 12 is suitably secured by a fluidtight joint around the periphcry of the container discharge port 10. The edges of the three wall membrane sections 3e are secured to the container adjacent to each other at longitudinal locations spaced apart approximately as shown in FIGURES 24 and 27, for example. Such wall sections thus cooperate in forming a substantially cylindrical container liner complemental to the cylindrical container 11 and forming fluidtight partition means.

A suitable connection or connections 7 through the container wall provide for air or inert gas under atmospheric pressure, or at a pressure higher than atmospheric, to be supplied to the space or spaces between the membrane and the container wall. One of such connections is provided in each of the container wall sections across which a membrane section 32 is sealed. Initially, suction may be applied to each fluid connection when the filler port 4 is open and the discharge port 10 is suitably closed, so that the atmospheric pressure within the membrane will press the various membrane sections into substantially contiguous engagement with the inner side of the container walls, top and bottom, as shown in FIGURES 23 and 26. With the liner membrane thus held in expanded condition discrete particle material can be supplied to the filling opening 4- to fill the interior of the membrane assembly.

When the container has been approximately one-half filled the filling procedure can be interrupted and air under pressure can be supplied to the connections 7 instead of suction. As the pressure on opposite sides of the membrane sections 36 becomes equalized the joints between the upper portions of the wall sections 3e and the periphery of the upper membrane section 3d will droop generally along chords of the container between the lines of attachment of the wall sections 3e to the container. Where three lower sections are used and the upper section is attached at three locations to the wall three chord lines will form generally an equilateral triangle, as shown in FIGURE 24. If four equal lower sections are used and the upper section is attached at four locations to the wall four chord lines will form a square. If air under pressure in excess of atmospheric pressure is then supplied to expel air from the interstices through the filler port 4 and the joint portions between the membrane sections 3e and the upper membrane sections 3d will be folded under along the chord lines, as shown in FIG- URE 28. The discrete particle material can thus be densified at intervals during the container filling operation, when desired.

When the container has been filled completely with discrete particle material the neck 5 of the upper membrane section 3d can be released from the filler port, sealed and moved downward through the filler port as shown in FIGURE 21, so that the filler port can be closed by a suitable cap while the material is being stored. While the container is sealed the membrane sections 3d, 3e and 3 will function to a considerable extent as insulation for the contents of the container to deter its deterioration either from freezing or from being heated excessively. Also, as described above, the membrane 3d will deter condensation of moisture on the interior of the container top and will protect the material within the container from being dampened by any condensation which may occur within the upper portion of the container When it is subjected to low external temperatures.

When discrete particle material is to be discharged from a container equipped with a membrane installation such as shown in FIGURES 23 to 28, inclusive, the discharge port 10 will be opened and any suitable provision can be made for transporting the material away from the container. A differential fluid pressure should be established on opposite sides of the membrane installation and such differential can be established by applying a suction to the discharge port 10 and opening the connections 7 to atmosphere, or by connecting to the openings 7 a source of air under pressure higher than atmospheric, or both. In any case the filler port 4 will remain closed so that the membrane installation will be 1 5 virtually fiuidtight and will be substantially completely filled with discrete particle material at the inception of the discharge operation. The membrane will therefore be in substantially contiguous engagement with the body of material in the container.

The differential pressure on opposite sides of the membrane partition will cause the membrane to press against the discrete particle material, the effect of which will be to press such material toward the discharge port 10. As material is discharged from the bottom of the container the material will be moved generally downward by gravity to maintain the lower portion of the container reasonably well filled. Normally, the material would tend to be discharged first from the upper central portion of the co tainer, but the effect of the differential pressure on the wall membrane sections 3e will be to press the material toward the center of the container so that the central portion of the liner in profile, as seen at the left of FIGURE 28, will form a reverse curve shape, the upper portion of which is convex at the material side and the lower portion of which is concave at the material side. The upper portions of the Wall membrane sections will move progressively toward each other as material is discharged from the container until they abut in contiguity, as shown in FIGURE 27. The upper membrane section 3d will be collapsed onto the upper portions of the wall membrane sections 3e.

As material continues to be discharged from the discharge port the inwardly convex upper portions of the membrane sections 3e will increase in extent and the lower inwardly concave portions of the membrane sections will decrease in extent as the membrane urges the discrete particle material from above toward a position overlying the discharge port 10. During this operation it will be evident from a comparison of FIGURES 24 and 25 in conjunction with FIGURE 28 that the membrane sections 3e will be peeled progressively from the container wall from the top down in a rolling type of motion to press the material toward the center of the container. When this peeling action has progressed to the lower edge of the wall membrane sections 3e the pressure on such sections will raise outer edge portions of the bottom membrane section 31 to c ntinue the procedure of moving the material toward the center of the container over the discharge port. Where three wall sections 3e are provided, as shown in FIGURES 27 and 28, the edge portions of the bottom membrane 3 will be raised initially at locations spaced apart 120 and from these locations the bottom membrane will be progressively peeled from engagement with the bottom to fol low the inward movement of the wall membrane sections 3e.

During the operation of emptying the container 11 in the manner described above, it will be evident that the wall membrane sections 3e are reversed or turned inside out as far as their material holding ability is concerned. Thus, when the container is filled with discrete particle material or is ready to be filled, as shown in FIGURES 23 and 26, the membrane sections 3e are inwardly concave; whereas, at the completion of the container emptying operation such wall membrane sections have been inverted to the positions shown in FIGURE 27 in which their inner sides are convex. Throughout the material discharge operation it will be evident that, despite application of suction to the discharge port 10 for the purpose of removing the material, no portion of the container 11 has been subjected to pressure below atmospheric pressure. On the contrary, the pressure between the membrane and the container is always equal to or higher than atmospheric pressure except when suction is applied to the connections 7 to move the membrane into substantial contiguity with the inner wall of the container, as shown in FIGURES 23 and 26. Even then, the membrane is pressed against the container wall by internal atmospheric pressure so that the container is never subjected to a highor external collapsing pressure.

If air under pressure greater than atmospheric is supplied to the connections 7 for the purpose of expediting discharge of discrete particle material from the discharge port 10, whether or not suction is applied to such discharge port, the container may be subjected to some degree of internal bursting pressure. For that reason it is desirable for the container 11 to be of cylindrical cross section so as to be able to resist such bursting tendency satisfactorily. Whatever may be the differential in the air pressure at opposite sides of the membrane such pressure differential can be maintained until the entire contents of the container have been discharged because there is no possibility of the air supplied to the container through the connections 7 providing a sudden blast of air through the discharge line, as would be possible if the container were simply air-pressurized without provision of the partition membrane. Instead, at the end of the discharging operation the membrane sections are simply pressed together at the center of the container in the manner indicated in FIGURE 27, and pressed against the discharge port while containing within the container the air at pressure higher than atmospheric. Consequently, it is entirely practical to utilize the same pressure differential at opposite sides of the membrane until the very last material has been discharged from the container.

When the emptying operation has been completed the supply of air under pressure to the connections 7 is interrupted and suction again may be applied to these connections while air is admitted through the discharge port 10. The ditferential pressure thus applied in reverse to the membrane will distend it again into the position shown in FIGURES 23 and 26. The filler port 4 may then be opened and the neck 5 pulled out through it for securement in the manner shown in FIGURES 23 and 28 preparatory to the container being filled again.

As has been discussed above, the liner membrane 311, 3i, 3a, 3b, 30 or 3d provides some insulation between the particle material within the container and the container wall, which usually is of metal. Such membrane alone may not afford sufiicient insulation to prevent condensation occurring where warm particle material is being loaded into a cold metal tank in cold weather. In order to prevent condensation under such circumstances it may be necessary to provide additional insulation between the liner and the container wall, and in general it is preferred that such additional insulation be of a type which will provide an air space between the liner and the container wall, and particularly the upper portion of the container wall. One type of insulating spacer means for this pur ose has been described above in connection with FIGURES 1, 2, 3 and 4 as including generallly parallel ribs 107 or 107, which can either be carried by the container wall or which can be mounted on the outer side of the liner.

Other types of spacing and insulating structure which has been found to be effective for substantially decreasing the heat transfer between a liner membrane and a metal container wall are-illustrated in FIGURES 29, 30 and 31. In all of these figures the container is shown as being of circular cross section, but the insulation construction could be applied to containers of various types. Also the containers in this instance are shown as having loading ports 101 and discharge hoppers 102, such as disclosed in FIGURE 1, for example, but it will be understood that such loading ports and discharge hoppers are only representative of a typical type of container in which the insulation construction can be utilized.

In each of FIGURES 29, 30 and 31 a lining membrane 200 is shown of an extent and located to be disposed in lining relationship to the upper part of the container 100. Such a membrane thus could be substituted for the central membrane of FIGURES 9 and 10 or'the central membrane 180' of FIGURES 11 and 12. Alternatively, such membrane could be the membrane 3a of FIGURES 13 to 17, or the membrane 3b of FIGURES 18 and 19, or the membrane 30 of FIGURES 20 to 22,

or the membrane 3d of FIGURES 23 to 28. The insulation features of FIGURES 29, 30 and 31 are applicable to a membrane such as indicated at 200, or could be used in conjunction with the membranes 311 of FIGURE 1 in place of the ribs 107', or the membranes 3i of FIG- URES 3 and 4 in place of the ribs 107', or in conjunction with the membrane 180 of FIGURES 9 and 10 in place of the insulation 107, or could be used in conjunction with the membrane 180 of FIGURES 11 and 12, or the membrane 3a of FIGURES 13 to 17, or the membrane 3b of FIGURES l8 and 19, or the membrane 3c of FIGURES 20 to 23, or the membrane 3d of FIGURES 23 to 28.

In conjunction with whatever type of liner the interlayer constructions shown in FIGURES 29, 30 and 31 are used, such constructions are of most value within the upper portion of a container and are far more effective than an exterior cap of insulation such as the cap 107 shown in FIGURES 1 and 9 for deterring condensation within the tank. In FIGURE 29 a layer 201a of coarse open-weave cloth or fabric is shown disposed between the liner 200 and the wall of the container. Such cloth or fabric should be sufiiciently porous to enable air to flow through it so that the air can be scavenged from the space between the membrane and the container wall. Also, it is very desirable that such fabric be made of material which will not deteriorate readily, such as glass cloth or Dacron, although under some circumstances the cloth could be a loose weave of jute, or pile material, or material such as carpeting. The cloth or fabric should be of a sufficiently coarse weave to space the liner 200 an appreciable distance from the container wall.

In FIGURE 30 an alternative to cloth or fabric is shown in the form of a mat 201b, which preferably is polypropylene fiber mat, although it could be glass mat or other durable mineral mat, or could be a durable felted material. Again, such material should be sufliciently porous to enable air to pass through it and should be of material which will not deteriorate readily. Moreover, the mat or felt should be sufiiciently cohesive so that it will not be disintegrated appreciably by pressure of the membrane against it if it is carried by the container wall, or by pressure or flexure if it is carried by the membrane.

FIGURE 31 shows as a further alternative an interlayer 2010 of sponge material, such as sponge rubber or sponge plastic, which is at least somewhat resilient. Again, the plastic should be porous to allow air to pass through it and should be sufficiently durable so as not to deteriorate readily and sufficiently strong and flexible to be able to withstand considerable pressure and perhaps flexure.

It has been found that the thickness of the interposed layer 201a, 201b or 2010 need not be very great so long as it does not conduct heat readily and will serve to form an insulating air space between the membrane and the container wall sufficient to prevent substantial conduction of heat between these elements. Thus the interposed layer can be one-eighth of an inch to one-quarter of an inch in thickness, for example. If the interposed material layer is carried by the rigid container wall, it need only be sufliciently strong to withstand the pressure of the membrane 200 against it when the pressure on the inner side of the membrane is greater than the pressure on the outer side of the membrane during an operation of loading material into the container as described above. Alternatively, the membrane can be carried by the liner 200, such as being bonded to the outer side of the liner if the material of the interposed layer will withstand not only the pressure conditions mentioned above but also is sufli ciently flexible so that it can follow movement of the membrane without too greatly decreasing the membrane flexibility or injuring the interposed layer material.

The effectiveness of such an interposed layer is particularly apparent when warm particle material is being loaded into a container during cold weather, such as warm flour under weather conditions when the exterior temperature is below freezing. Under such circumstances the ability of the cold air to hold moisture is very small so that it is necessary to prevent chilling of the air within the container if condensation inside the container is to be avoided. Any condensation which may occur between the liner and the container is of little consequence because it cannot reach the material in the container through the waterproof liner. It has been found that provision of the interposed layer will serve the dual function of deterring the transfer of heat by conduction from the liner to the container Wall and of enabling the relatively thin liner to be warmed quickly by the incoming flour by deterring radiation of heat from the outer surface of the liner.

Formation of condensation can be prevented by use of the construction described above not only in materialholding containers but also in rooms or buildings which are humid and the outdoor temperature is lower, such as ships holds, warehouses, and hospital operating rooms. In such cases a pressure below atmospheric would be maintained between the liner membrane and the wall.

I claim as my invention:

1. A container comprising an impermeable wall having a top portion of good heat-conducting material, a flexible lining membrane inwardly of said wall and movable downward from said top portion of said Wall but having its edge portion secured in sealed relationship to said wall at least partly below said top portion to form a fluid-tight space between said lining membrane and said wall top portion, a substantially continuous layer of thermal insulating material interposed between said top portion of said wall and an oppositely disposable corresponding portion of said lining membrane, and means for removing gas from said space between said lining membrane and said wall top portion and for subjecting opposite sides of said lining membrane to ditferential fluid pressure to dispose said corresponding portion of said lining membrane in lining relationship to said top portion of said wall but spaced downward therefrom by the thickness of said insulating layer which deters transfer of heat through said top portion of said wall between the exterior of the container and the interior of the container below said lining membrane when said corresponding portion of said lining membrane is in said lining relationship to said top portion of said wall.

2. The container defined in claim 1, in which the thermal insulating layer includes fabric material.

3. The container defined in claim 1, in which the thermal insulating layer includes mat material.

4. The container defined in claim 1, in which the thermal insulating layer includes porous plastic material.

5. A container comprising an impermeable wall having a top portion of good heat-conducting material, a flexible lining membrane inwardly of said wall and movable downward from said top portion of said wall but having its edge portion secured in sealed relationship to said wall at least partly below said top portion to form a fluid-tight space between said lining membrane and said wall top portion, a layer of thermal insulating material covering the inner face of said top portion of said wall, and means for removing gas from said space between said lining membrane and said wall top portion and for subjecting opposite sides of said lining membrane to differential fluid pressure to dispose said corresponding portion of said lining membrane in lining relationship to said top portion of said wall, said insulating layer deterring transfer of heat through said top portion of said wall between the exterior of the container and the interior of the container below said lining membrane when said corresponding portion of said lining membrane is in said lining relationship to said top portion of said wall.

(References on following page) 19 20 References Cited 3,172,556 3/1965 Stiefel.

P T NT 3,272,373 9/1966 Alleaume et :11.

UNITED STATES A E S 3,291,333 12/1966 House 220-15 11/1937 Maryott.

12/1951 Plumber. 5 FOREIGN PATENTS 5/1952 Erlkson 220-63 X 800,824 9/1958 Great Britain. 1/1956 Watts. $322 gender 94 220 63 JOSEPH R. LECLAIR, Primary Examiner 11/1959 P212315 n JAMES R. GARRETT, Assistant Examiner 2/ 1960 Beremand.

8/1963 Mearns et a1. 220 10 11/1964 Cornelius. 1os 24s; 22063, 85; 222-3865

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