Aeration apparatus for tanks containing powdered materials or the like

An aeration apparatus to ease the emptying of a mass of powdered material from any kind of container. The apparatus comprises a vibrating membrane coupled to a device for pulling and fastening it to the container wall, so that said membrane adheres to the inner surface of the container wall. The apparatus is characterized in that the inner surface of membrane has a number of grooves shaped as radial recesses formed only on the lower half of the inner surface of the membrane itself. Each radial section of any radial recess is advantageously venturi-shaped.

RELATED APPLICATIONS

This application is a National Stage filing of International Application No. PCT/IB2014/065154, filed Oct. 8, 2014, which claims priority of Italian Application No. BO2013A000552, filed Oct. 8, 2013, which are incorporated herein by reference in their entireties.

TECHNICAL FIELD

The present invention relates to an aeration apparatus for tanks containing powdered materials or the like.

More precisely, the present invention relates to an aeration to ease the emptying of any powdered or granular material from any kind of tank.

In particular, the present invention is advantageously but non-exclusively applied in the tanks for trucks and silos, to which the following description will explicitly refer without losing in generality.

BACKGROUND ART

As is known, pneumatic conveying systems are used, for example, for discharging powdered or granular material from the tank of a truck.

These conveying systems include at least one tube, through which pressurized conveying air flows, which extends between the discharge port of the tank and the end user of the powdered or granular product.

It is also known that in order to ease the emptying of the tank, aeration apparatuses are used preferably placed at the bottom of the tank itself.

The truck tank usually ends at the bottom with a discharge hopper which is often shaped as an upturned truncated cone. At the end of the truncated cone there is said discharge port of the powdered material with possibly a discharge valve.

Aeration apparatuses are usually used to ease the discharge of the material, arranged in the discharge hopper upstream of the discharge valve.

As will be better seen hereafter, each aeration apparatus is provided with a membrane made to vibrate by the output of compressed air in the annular gap between the inner surface of the tank wall and the membrane itself.

As is known, the vibration of membranes with the air flow coming out of the aeration apparatuses are used to break up the mass of particles present at the bottom of the tank and considerably accelerate the output of powdered material from the discharge port.

The above vibro-fluidization technology can normally be used successfully with food or chemical powders (starch, plastic, sugar, coffee, feed, sand, cement, aggregates, fine grit, etc.), all materials which tend to become compacted once stored inside containers.

However, in the solutions adopted so far by all the manufacturers, the outlet of micro-jets into the hopper takes place in all directions.

In other words, the compressed air micro-jets are directed downwards, sideways but also upwards, without having a preferential outlet direction. It was experimentally found that especially the micro-jets facing upwards, rather than easing and favoring the discharge of powdered material from the port of the hopper, somehow slow down the discharge as they are substantially faced in a direction opposite to the natural one of descent by gravity.

Quite recently, in order to make the action of the micro-jets more effective, aeration apparatuses of the above type have been proposed with vibrating membranes provided with substantially helical grooves arranged both on the outer surfaces of the membranes themselves, and on the inner ones. The aim of the inventors of this solution clearly was to create vortices within the granular (or powdered) mass so as to ease the discharge of the material through the discharge port.

However, in the manufacturing practice, it was noted that the inconsistent turbulence which is created in the mass of material partly obstruct the fall by gravity of the material to the discharge port. Moreover, it was experimentally verified that the output turbulent flows from the above annular gap cause an acceleration of the membrane deterioration due to the increased friction of the material (often highly abrasive, such as fine sand) on the inner and outer surfaces of the membrane itself. Moreover, other problems of different nature have been found in aeration apparatuses used in truck tanks.

In fact, in the solutions adopted so far, the aeration systems are fixed to the hopper wall by means of screw systems which provide the use of a threaded rod which causes a pulling action on the membrane as it is tightened by an operator. However, the force modulus with which the membrane is pressed on the inner surface of the hopper wall plays an important part in the whole process. In fact, if the tie rod subjects the membrane to an insufficient pull, there will be too much clearance between the membrane and the wall and therefore the membrane will not be efficiently made to vibrate by the entrance of the compressed air into the tank.

In use on trucks, it was found that the vibrations to which the aeration apparatuses are subjected during the movements of the truck itself cause a loosening of the pull on the membranes which eventually leads to a malfunctioning of the whole system.

Disclosure of Invention

Therefore, the main object of the present invention is to provide an aeration apparatus which is free from the above drawbacks while being easy and cost-effective to be implemented.

Therefore, according to the present invention, an aeration apparatus is provided to reduce the discharge time for the emptying of a mass of powdered material from any kind of container. The aeration apparatus has a vibrating membrane coupled to a device for pulling and fastening it to a hopper wall of a container, so that the membrane adheres to an inner surface of the container. The membrane comprises at least an area of least resistance for an outlet air flow, so that the air comes out from the area of least resistance, and defines a plurality of grooves shaped as radial recesses in a portion of the inner surface of the membrane. The radial recesses are each oriented downwards toward a discharge port, thereby producing a strong preferential downward directionality of air micro jets exiting an annular gap between an inner surface of the hopper wall and an edge of the membrane.

The present invention relates to an aeration apparatus to ease the emptying of powdered material from any kind of container; apparatus comprising a vibrating membrane coupled to a system for fastening it to the container wall, so that said membrane adheres to the inner surface of the container wall; the apparatus is characterized in that said membrane has at least one area of least resistance for the outlet air flow, so that the air preferably comes out from said at least one area.

BEST MODE FOR CARRYING OUT THE INVENTION

InFIG. 1, number reference100generally indicates, as a whole, a storage plant for a powdered or granular material.

Plant100comprises a tank101, for example for trucks, wherein the mass (M) of powdered (or granular) material is stored and a distribution network102of compressed air.

Tank101comprises an upper cap-shaped portion101A which overhangs a lower portion101B shaped as a truncated-cone hopper. The lower portion101B ends with a discharge port101C of the product.

The distribution network102of compressed air, in turn, comprises a supply line102A of compressed air (produced by a compressor, not shown), a main branch102B for the pneumatic conveying of the material discharged from tank101, a secondary branch102C of supply of compressed air to the top of the cap, and a secondary branch102D of supply of compressed air to the aeration apparatus10A,10B installed on the lower portion101B of tank101.

The main branch102B connects tank101with an end user, for example with a concrete production plant (not shown) if the material transported by the truck is cement or sand.

Incidentally, it is noted that since inFIG. 1tank101is shown in cross section, only two aeration apparatuses10A,10B are visible although there would actually be, for example, a third aeration apparatus10C, equally-spaced from the other two and visible inFIG. 2. The number of aeration apparatuses will obviously vary according to the size of hopper101B. In general, the larger hopper101B, the higher the number of aeration apparatuses10mounted thereon.

As shown again inFIG. 1, between the exhaust port101C and the main branch102B a duct103is placed which is provided with a respective discharge valve (S1).

In actual use, when starting the operations for discharging tank101, a control system (CC) (FIG. 1) managed by an operator controls the opening of the discharge valve (S1) and the operation of the distribution network102.

A discharge valve (S2) related to the secondary branch102C, a discharge valve (S3) coupled to the main branch102B, and a discharge valve (S4) related to the secondary branch102D will also open in sequence.

The mass (M) of granular (or powdered) material will fall by gravity from tank101to the main branch102B flowing through duct103and through the corresponding open discharge valve (S1). The material, once arrived in the main branch102B, is then conveyed by the pressurized air to the end user (not shown).

As affirmed above, to ease the discharge of tank101, compressed air is then sent on the upper cap-shaped portion101A of the tank101to put it under pressure, and to hopper101B to feed the aeration apparatuses10A,10B,10C (FIGS. 1, 2).

Since the three aeration apparatuses10A,10B,10C are identical, describing a generic aeration apparatus10will suffice to describe all apparatuses.

In order to describe the first embodiment of the aeration apparatus10, object of the present invention, reference will now be made, in particular, toFIGS. 3, 4, 5A and 5B.

The aeration apparatus10comprises a hollow main body20for supplying compressed air, a membrane30and a device for pulling and fastening said membrane30to a container wall, in this case to the hopper101B wall of tank101.

As will be seen, the pulling and fastening device40is given by the set of three elements41,42,43in the manner shown in particular inFIG. 4(see below).

The hollow main body20comprises a cup-shaped element to which is coupled a supply fitting22of the compressed air coming from the distribution network102is coupled. The cup-shaped element21is provided with a substantial longitudinal symmetry axis (X); while the supply fitting22is provided with a longitudinal symmetry axis (Y), inclined by an angle (α) relative to the axis (X). Angle (α)) has a value advantageously between 20° and 40° chosen with the aim to reduce, as much as possible, the load losses which occur in the compressed air flow during its outflow into the hollow main body20.

The cup-shaped element21is attached to two ducts23,24which serve for the possible conveying of compressed air from one aeration apparatus10A,10B,10C to the other (FIGS. 1, 2).

In other words, any aeration apparatus10A,10B,10C can be supplied either directly by the distribution network102through the supply fitting22, or it can be supplied indirectly by compressed air coming from an adjacent aeration apparatus10A,10B,10C by means of one of the two ducts23,24. The cup-shaped element21can be made in different configurations according to the plant requirements.

The two ducts23,24are aligned along an axis (Z) substantially perpendicular to a plane containing axes (X) and (Y).

In the cup-shaped element21(FIG. 5B) we may see a cup20A with a circular open edge20B and a bottom20C opposite to said open edge20B. A through hole20D aligned with said axis (X) is located on bottom20C.

On bottom20C there is also a guide seat20E in turn comprising a substantially curved lower portion surmounted by two flat lateral portions and an upper portion which is also flat (see below).

The pulling and fastening device40of membrane30comprises:a pulling shaft41; anda tie rod42, at least partially threaded on a cylindrical front portion42A, operated by a pulling element43(in this case a cam handle) resting on a bushing44sliding freely on a cylindrical back portion42B of tie rod42along axis (X).

In particular, the pulling element43comprises a handle43A ending with a cam43B which, in use, rests on the sliding bushing44.

Moreover, as shown inFIGS. 3, 4, handle43A is crossed by the cylindrical back portion42B of tie rod42. The pulling element43is further provided with a through hole43C, while a through hole42C (FIG. 3) is provided on the cylindrical back portion42B of tie rod42.

As will be better described hereinafter, when handle43A is rotated clockwise according to an arrow (F1) about a fixed pin43D which crosses both handle43A and the cylindrical back portion42B of tie rod42, so that the pulling element43pulls membrane30resting on the inner surface of the hopper110B wall (FIGS. 1, 2) (see below), the two through holes43C,42C are aligned (FIG. 3) and it is therefore possible to insert a split pin (not shown) into these through holes43C,42C to keep the pulling element43always in the same fixed position in spite of any vibration to which it may be subjected.

In other words, the split pin (not shown) inserted simultaneously in the two aligned through holes43C,42C is a sort of “safety lock” against possible vibrations and/or jumps (for example of the truck on which tank101is mounted), which could cause the accidental and hazardous counterclockwise rotation of handle43A about pin43D according to an arrow (F2) opposite to said arrow (F1). Such a hypothetical rotation of handle43A according to the arrow (F2) about pin43D would cause the involuntary, and not desirable, loosening of the pulling action on membrane with a consequent increase of the annular gap formed between the outer perimeter of membrane30and the inner surface of the hopper101B wall.

Locking by means of a split pin is just one of the countless ways to lock the cam. Alternative systems may also be used such as, for example, a snap lock of the handle, or an external block which constrains the handle in the closed condition.

On the pulling shaft41we may see an annular groove41A on which, in actual use, a central through opening30A made on membrane30is fitted (FIGS. 4, 5), two stroke end flaps41B,41C which protrude on opposite sides from a substantially cylindrical stem41D.

The surface of the annular groove41A is shaped so as to have a curved upper portion followed by a flat lower portion.

Likewise, the central through opening30A is provided with a curved upper portion and a flat lower portion (FIGS. 4, 10A, 10B). This is to perform a correct assembly of the pieces (see below).

The upper surfaces of the two stroke end flaps41B,41C are curved so as to follow the profile of the inner surface of the inner membrane30. Two lateral flattened areas41E,41F located on opposite sides are made on the surface of stem41D, of which only one lateral flattened area (i.e. the lateral flattened area41E) is visible inFIG. 4.

The reasons for which it is preferable to have these two lateral flattened areas41E,41F will be explained hereafter. Stem41D ends with a pin41G in turn having a curved lower portion, two lateral flattened portions and an upper portion which is also flattened. In other words, the lateral surface of pin41G is designed so as to be coupled in a satisfactory manner with the surface of the guide seat20E.

Pin41G and at least one portion of stem41D have a blind hole41H aligned with axis (X).

The blind hole41H, at least partially, is provided with a threading which can be screwed to the cylindrical front portion42A of tie rod42(see below).

Incidentally, it is useful to note that the through hole (not shown) made on the hopper101B wall has a larger diameter than the maximum diameter of stem41D for letting the compressed air pass in the gap which is formed between the through hole and the stem41D itself (see below).

The radial recesses30B are arranged only on a portion of the inner surface of membrane30.

Recesses30B are mainly arranged in a lower portion of membrane30.

Preferably, but not necessarily, the radial recesses30B are located on the entire lower half of membrane30.

Preferably, but not necessarily, each radial recess30B is shaped as a “drop” which conveys the air accelerating it, by venturi effect, towards the outside of membrane30so as to increase the effectiveness of vibration even at low pressure.

The surface of the outer profile of membrane30is smooth with no ribs for facilitating the sliding of the powders.

As shown inFIG. 10B, the outer profile30C of membrane30is shaped as a “wave” in order to have a constant thickness in the section in the vicinity of the radial recess30B, and a reduction in thickness in the vicinity of edge30D to increase the effect of vibration of the membrane30itself.

In other words, with reference toFIG. 11B, each radial section30E takes the shape of a venturi, and therefore the pressurized air, distributed radially by means of centrifugal motions, will travel a plurality of venturi-like paths. Therefore, there will be an acceleration of the compressed air in the vicinity of edge30D, a factor which will increase the frequency of the vibrations of the edge30D itself with a consequent better distribution of the compressed air in the mass (M) of granular (or powdered) material present in hopper101B.

The increased kinetic energy of the output compressed air from membrane30in its lower part will further promote the penetration of the air itself in the mass (M) of material.

Moreover, since each radial recess30B has a smaller thickness (TH1) (FIG. 10B) than the minimum thickness (TH2) of the part of membrane30without radial recesses30B, membrane30will tend to deform, preferably in its lower portion which results in a lower moment of inertia. For this reason, the compressed air will tend to exit chamber50preferably on the side of membrane30provided with radial recesses30B.

In actual use, therefore, by orienting the radial recesses30B downwards, a strong preferential downward directionality of the air micro-jets exiting the annular gap between the inner surface of the hopper101B wall and edge30D of membrane30is obtained.

As said above, these micro-jets of compressed air directed preferably downwards will generate a consistent thrust directed on the mass (M) of (granular or powdered) material which is located at a given time in hopper101B, thus preventing the formation of bridges, voids, etc., all factors which would delay, even considerably, the discharge of the product from the discharge port101C.

The assembly of the aeration apparatus10on the hopper101B wall is carried out as follows:

(a) the central through opening30A of membrane30is manually fitted on the annular groove41A on the pulling shaft41, so as to obtain the coupling of membrane30to the pulling shaft41itself (FIG. 5); the particular shape (curved at the top and flat at the bottom) of the surface of the two elements30A,41A to be coupled ensures a correct coupling of the two pieces (see below);

(b) then, the pulling shaft41is inserted into the through hole made on the hopper101B wall, obviously so that membrane30remains inside the hopper101B itself; the stroke end flaps41B,41C are also now inside hopper101B on the side of membrane30;

(c) tie rod42is inserted into the through hole20D provided on bottom20C of cup20A;

(d) the threaded cylindrical front portion42A of tie rod42is screwed in the blind hole41H (of axis (X)) made on the pulling shaft41; the assembly of tie rod42with the pulling shaft41is thus obtained;

(e) while performing the screwing referred to in the previous item (d), the operator gradually approaches all the hollow main body20to the outer surface of the hopper101B wall;

(f) the screwing operation ends when:

(f1) the shaped pin41G enters the guide seat20E;

(f2) bushing44is resting on the outer surface of bottom20E; and

(f3) the circular open edge20B is resting on the outer surface of the hopper101B wall.

Now the operator can rotate handle43A according to (F1) (FIG. 5B) so that the pulling action performed by all the pulling and fastening device40on membrane30takes place according to an arrow (F3) (FIG. 5B). Since bushing44, as said, is sliding on the cylindrical back portion42B of tie rod42, the action carried out on such a bushing44by cam43B results in a thrust (according to an arrow (F4), opposite to the direction indicated by arrow (F3)—FIG. 5B) on the hollow main body20which will thus adhere more to the outer surface of hopper101B. In other words, while membrane30is pressed with an increasing force on the inner surface of hopper101B (arrow (F3);FIG. 6B), the open edge20B of cup20A will be increasingly pushed on the outer wall of the hopper101B itself (arrow (F4);FIG. 5B).

The hopper101B wall will then be “closed as a clamp” between membrane30, on one side (i.e. on the side of the inner wall of hopper101B), and the open edge20B of cup20A, on the other (i.e. on the side of the outer wall of hopper101B).

It will then be possible to send compressed air to the aeration apparatus10by means of the distribution network102(FIG. 1).

In more detail, we can say that the compressed air, after entering the hollow main body20through the supply fitting22will flow in the gap specially left free between the through hole made on the hopper101B wall and the outer surface of the pulling shaft41.

The two lateral flattened areas41E,41F (each of which is provided with a respective hollow-shaped discharge) on the pulling shaft41make easier the flow of the compressed air to a distribution chamber50delimited by the inner surface of membrane30and by the inner surface of the hopper101B wall (see enlargement inFIG. 1).

From this distribution chamber50, the compressed air is then distributed inside hopper101B with the fluid dynamic mechanisms described above.

It should also be noted that the shaped couplings between the two pairs of elements30A,41A and41G,20E are the main cause of a correct downward orientation of the radial recesses30B. In fact, if due to such shaped couplings membrane30is properly positioned with respect to the pulling shaft41and, respectively, the pulling shaft41is properly positioned with respect to the hollow main body20, with the supply fitting22facing downwards, the operator will always be sure that the radial recesses30B are also facing downwards and are, therefore, properly oriented with respect to the task they are to perform.

In other words, considering the asymmetry of membrane30, it is necessary to have forced shape couplings between the pieces in order to allow a correct assembly of the membrane30itself, that is, as said, with the radial recesses30B facing downwards, i.e. towards the discharge port101C of tank101and the discharge valve (S1) (FIG. 1).

FIGS. 6, 7, 8A, 8B, 9show a second embodiment of the present invention advantageously applicable to a hopper101B* (FIG. 9) of a silo (not shown entirely).

In the particular embodiment shown inFIG. 9, three aeration apparatuses are mounted on hopper101B*. However, only two aeration apparatuses10B* and10C* are visible inFIG. 9since hopper101B* is shown in section.

Since also in this case the three aeration apparatuses are identical, describing a generic aeration apparatus10* will suffice to describe them all.

As shown in greater detail inFIGS. 6, 7, 8A, 8B, the aeration equipment10* includes a membrane30* having an edge30D*, identical to membrane30described above with reference to the first embodiment, and a pulling and fastening device40* comprising a pulling shaft41*.

Such a pulling shaft41* is provided with an annular groove41A* (virtually identical to the annular groove41A seen for the first embodiment) adapted to receive a central through opening30A* (virtually identical to the central through opening30A seen above) formed on membrane30*.

The pulling shaft41* is longitudinally crossed by a blind hole41H* aligned with an axis (X*) of substantial longitudinal symmetry of the pulling shaft41* itself.

Below the annular groove41A* a collar41C* is placed which is provided with a plurality of radial through holes41M* which put the blind hole41H* in communication with the outside and in particular, in use, with a chamber50* (FIG. 9) delimited, as usual, by the inner surface of membrane30* and by the inner surface of the hopper101B* wall.

In this second embodiment, the outer surface of a pin41G*, which is located below collar41C*, is partially threaded.

Between collar41C* and pin41G* there is a shoulder41N* whose function will be explained hereafter.

The aeration apparatus10* is provided with a washer41P*, a threaded nut41R* and a hollow main body (not shown) similar to that described in relation to the first embodiment.

The assembly of the aeration apparatus10* on the hopper101B wall is carried out as follows:

(a) the central through opening30A* of membrane30* is manually fitted on the annular groove41A* on the pulling shaft41*, so as to obtain the coupling of membrane30* to the pulling shaft41* itself; the particular shape (curved at the top and flat at the bottom) of the surface of the two elements30A*,41A* to be coupled ensures a correct coupling of the two pieces;

(b) then, the pulling shaft41* is inserted in the through hole located on the hopper101B* wall, thus obviously making membrane30* remain in hopper101B*; collar41C* is also located inside hopper101B* on the side of membrane30*; in this case, the hole on the hopper wall has virtually the same diameter as pin41G* and is provided with a sealing gasket (not shown); shoulder41N* rests on the inner surface of the hopper101B wall;

(c) on the side of pin41G* which protrudes outwards of the hopper101B* wall, washer41P* and the threaded nut41R* are inserted;

(d) the threaded nut41R* is screwed on the threaded part of pin41G* so that the hopper101B* wall is clamped on one side by shoulder41N*, and on the other by the upper surface of washer41P* pushed by the threaded nut41R*.

Pin41G* is then fastened to the hollow main body supplying the compressed air.

Moreover, it should also be noted that the free end of pin41G* is provided with two lateral flattened areas41Z*,41W* located on opposite sides. Such lateral flattened areas41Z*,41W* are coupled with a shaped seat (not shown) which is located inside the hollow main body to allow the desired correct orientation downwards of the radial recesses30B* which are located on the inner surface of membrane30*.

The aerodynamic operation of membrane30* is the same as that of membrane30of the first embodiment and therefore will not be described again.

The main advantages of the aeration apparatus made according to the teachings of the present invention are as follows:easy assembly;reduction in the consumption of compressed air and therefore in the overall energy consumption; andreduction of the container discharge time while ensuring a certain interchangeability with the systems currently on the market.