US2935263A - Silos for the storage of bulk goods such as sugar, grain, artificial fertilizers and the like - Google Patents

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y 1960 N. R. M. WEIBULL 2,935,263

slLos FOR THE STORAGE OF BULK GOODS SUCH AS SUGAR, GRAIN, ARTIFICIAL FERTILIZERS AND THE LIKE Filed Feb. 13, 1956 3 Sheets-Sheet 1 ans -11 8 Fig.1

y 1960 N. R. M. WEIBULL. 2,935,263

SILOS FOR THE STORAGE OF BULK GOODS SUCH As SUGAR, GRAIN, ARTIFICIAL FERTILIZERS AND THE LIKE Filed Feb. 13, 1956 3 Sheets-Sheet 2 I. l. 13 i y 1960 N. R. M. WEIBULL 2, 35,263

SILOS FOR THE STORAGE. OF BULK GOODS SUCH AS SUGAR, GRAIN, ARTIFICIAL FERTILIZERS AND THE LIKE Filed Feb. 13, 1956 s Sheets$heet 3 2b N I Fi .1.

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SILOS FOR THE STORAGE F BULK GOODS SUCH AS SUGAR, GRAIN, ARTIFICIAL FERTILIZERS AND THE LIKE Nils Rudolf Martin Weibull, Limhamn, Sweden, assignor to lngeniors-Firman Nils Weibull AB, Malmo, Sweden, a corporation of Sweden Application February 13, 1956, Serial No. 565,215

Claims priority, application Sweden February 16, 1955 2 Claims. (Cl. 237-2) This invention relates to silos for the storage of bulk goods.

Storage of bulk goods such as sugar, grain, artificial fertilizers etc. is used more and more widely, by reason of the economies involved. A prerequisite of such a storage is, however, that the goods stored are not exposed to the risk of being damaged or deteriorated during storage. Of the risks involved when goods are stored in silos, there may be mentioned that the goods may take up water from the surrounding air, moisture may travel within the mass and thus be concentrated to certain parts of the mass whereby the moisture content of the goods may become too high, or finally the dust in the dust-laden air which is in motion within the silo may ignite with explosive force.

The object of the invention is to eliminate these risks by providing a silo comprising top, bottom and side walls defining a storage space for said goods, means forming a closed air passage system through said top, bottom and side walls, said air passage system being heat-insulated against its surroundings and being non-insulated and airsealed against said storage space, propulsion means in said aid passage system for circulating air in a closed path through such system, and heater means in said path for heating said circulated air to a temperature exceeding the temperature in the goods stored in said storage space.

The invention will be described more in detail in the following, reference being had to the accompanying drawings, illustrating some embodiments of the invention. In the drawings:

Fig. 1 is a simplified vertical section of a silo according to one embodiment.

Fig. 2 is a similar View of a modified embodiment.

Fig. 3 is a semi-diagrammatic view of a system for controlling the heating in the embodiment in Fig. 2.

Fig. 4 is a fragmentary semi-diagrammatic view of a modification of the system in Fig. 3.

The relative moisture content of the air contained in the silo above the goods stored therein can be adjusted by air conditioning so as to be in a condition of balance in which the goods neither take up water from, nor give off water to, the surrounding air. Air can be forced by fans driven by electric motors 2 through passages 3 formed by an inner flooring 4 and a sub-flooring 5 into air passages 6 formed by an inner wall 7 and an outer wall 8 and from there through the space between a ceiling 9 and a roof 10 to a pipe 11 disposed centrally in the silo and having two or more branches at its lower end, each of said branches containing one fan 1. Close to the fans 1 there are disposed heat batteries 12 adapted to heat the air approximately to the temperature of the goods. If the inner flooring 4, the inner wall 7 and ceiling 9 of the silo can be kept, in the manner described, at the same temperature as that of the goods by means of a circulating air flow, no moisture travel will take place within the goods. The outer walls 8 and roof 10 of the silo are made of insulating material to avoid unnecessary heat nited States Patent 0 losses. on the other hand, the inner walls 7 and the ceil- The circulation of air as described above can be pro duced by means of the fans 1, which are driven by the electric motors 2. This air can be heated to a temperature somewhat exceeding that of the goods when the air passes through the heat batteries 12. As the circulating air is exposed to a continuous cooling during its flow from the heat batteries and back, all inner surfaces of the air passages will have a temperature deviating gradually from the original temperature of the stored goods and the silo air above the goods. By reason of heat transmission through the passage walls between their inner and outer surfaces the goods layers in contact with the outer surfaces will either be heated or cooled off during this circulation.

In order to reduce this change of temperature of the, stored goods the fans can be made reversible so that the direction of flow of the circulating air can be reversed. Starting from the heat batteries 12, the heated air during a certain period of time flows away from the heat batteries in a certain direction in the air passages, and thereby becomes sucessively cooler. During the next period of time the air fiows in the opposite direction. The temperature of the passage walls at their inner surfaces will oscillate about a value which is the arithmetic mean value of the incoming and outgoing air temperature on either side of the heat batteries. By reason of the heat capacity of the passage walls, the amplitude of the temperature oscillation will decrease at their outer surfaces, and at sufiiciently short time intervals between the reversals of the direction of flow of the air the temperature will be constant at the outer surfaces, i.e. at the surfaces in contact with the stored goods, and equal to the said mean value. In practice, a certain variation of the temperature of the outer surfaces may be permitted. It is not therefore necessary to reverse the direction of flow of the circulating air as often as would be necessary, owing to the heat capacity of the passage walls, to obtain an absolutely constant temperature at those outer surfaces of the passage walls which are in contact with the goods in the silo.

Provided that a certain temperature variation is permitted in the outer layer of the goods stored, the air contained in the silo in the space above the goods can serve as a temperature equalizing means for the circulating air, since by heat transmission through the surrounding passage walls said air can collect theexcess heat energy of the circulating air when it flows in a certain direction and give ofi said excess when it flows in the opposite direction and when an equally large deficit exists. The reversal of the direction of the air flow can take place in response to a thermostat as shown in the embodiment in Fig. 2.

In this modified embodiment a single fan It: driven by a reversible electric motor 201 is arranged in the central pipe 11 of the silo to circulate the air. In the lower righthand corner of the silo there is mounted a thermostat 13 which may be of the generally known bimetallic type and is responsive to the temperature of the goods in the silo near the right-hand heat battery 12. As shown in Fig. 3, the thermostat 13 controls a switch '14 connected with a power source in series with a fan motor reversing relay 15 adapted to reverse the direction of rotation of the motor 2a of the fan 1a when the circuit to said relay is closed and opened by the thermostat 13.

Below a certain temperature value, the thermostat 13 and the switch 14 can be adapted to hold the relay 15 in 4 goods inthe vicinity of the thermostat being supplied with heat in a degree lower than when the air flows in the firstmentioned direction, because on its now longer way to the thermostat it has had time to give off a greater part of its heat to the goods so that the temperature of the goods in the vicinity of the thermostat gradually sinks below said value and the direction of the air flow is again reversed. The connection between the relay and the motor 2a is indicated merely by a line since it can be of any known type whatever.

a Fig. 2 also illustrates the manner in which a thermostat can control the heating of the circulating air by controlling the supply of a heating medium to the heat batteries 12 to keep the temperature of the circulating air at a substantially constant value. Thus, a thermostat'l is disposed in the air passage system at a place therein where it is responsive substantially to the mean temperature of the circulating air. This thermostat 16 can also be of the bimetallic type and controls a switch 17 connected with a power source in series with a solenoid 18 which is operatively connected with a throttle valve 19. Said throttle valve is disposed in a conduit 20 for the supply of a heat ing medium, for instance hot water, to the heat batteries 12 from which the heating medium, having given off heat to the circulating air, is discharged through a return conduit 21. The solenoid 18 is adapted, when activated as a result of the thermostat 16 closing the circuit therethrough at a certainrtemperature, to adjust the throttle valve 19 from entirely open position occupied when the solenoid 18 is non-activated to wholly or partly throttled position so that the supply of heating medium to the heat battery 12 is caused to cease or is reduced.

In Fig. 4 two motors 2b instead of one reversible motor are adapted each to drive one of two fans 1b which convey air in opposite directions. In this case the thermostat 13 controls through a switch 22 a fan motor reversing relay 23 which in a non-activated state holds only one fan motor energized and, when said relay is activated as a result of the thermostat 13 closing the circuit through the relay at a certain temperature, deenergizes said fan motor and energizes the other fan motor instead, with the result thatthe direction of the air flow is reversed.

The system of Fig. 4 can be arranged as shown in Fig 3 from, dust is generally formed owing to the nature of the goods, and mixing with air, the dust may produce an explosive mixture. Ignition can be caused either by a spark of some kind or by a discharge of static electricity formed by friction of the dust particles. In the silo according to the present invention the air circulating around the goods flows in a closed system of passages and pipes which isair-sealed from the possibly dust-laden air of the silo in order to avoid the danger of a dust ignition. When the goods are filled into the silo or withdrawn therefrom, the air contained in the silo above the goods is relatively stationary and as a result it cannot reach a dust concentration or electrostatic load involving risks of explosion.

What I claim and desire to secure by Letters Patent is:

1. A silo for bulk storage of goods, such as sugar, which is subject to damage from changes in moisture content, comprising means for maintaining goods stored in bulk therein at substantially uniform temperature throughout in order to inhibit changes in moisture coutent of said goods, said silo comprising a roof, a vertical central hollow shaft, hollow top, bottom and side walls disposed around said shaft connected thereto, and deli ning therewith an enclosed storage space for said goods, said central shaft extending through said top and bottom walls, said roof comprising said top wall, said top, bottom and side Walls each comprising an outer insulated side and a parallel inner heat-conductive side spaced therefrom, the heat-conductive sides of said bottom and side walls being in direct contact with the goods stored in said slio, means forming'a central conduit system connecting said hollow top and bottom walls, said means comprising a vertical conduit in said central shaft and lateral ducts on opposite sides at the top and bottom of said conduit connecting it with said hollow top and bottom walls, said hollow top, bottom and side walls and said central conduit system being connected and sealed from said storage space to provide a closed circuit air passage system for circulating air around said storage space, reversible propulsion means in said central conduit system for moving said circulating air around said closed circuit air passage system in either direction, means for heating said circulating air, and reversing means for repeatedly reversing the direction of flow of said circulating air in said closed circuit air passage system.

2. A silo in accordance with claim 1 wherein said propulsion means is a fan driven by a reversible electric motor and said reversing means comprises a reversing switch and means for repeatedly reversing said switch automatically.

'References Cited in the file of this patent UNITED STATES PATENTS 1,168,424 Rohm Ian. 18, 1916 1,923,145 Harsch Aug. 22, 1933 2,271,120 Grant Jan. 27, 1942 2,364,220 Johnson Dec. 5, 1944 2,465,184 Alderman Mar. 22, 1949 2,739,087 Olcott Mar. 20, 1956 2,790,604 Felcus Apr. 30, 1957

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