Connection device between a conduit and a container, and a drying and dehumidification plant for granulated plastics materials provided with such a device

Description Technical field

This invention relates to a connecting device for connecting a conduit to a container. It is also intended for a granulated plastics material drying and dehumidification plant provided with such a device. Technological background In particular this device has been conceived to connect together successive containers in a drying and dehumidification plant in which granulated plastics material is treated and stored prior to being subjected to the requisite processing operations. The aforesaid device may also be used to connect containers to other devices, for example pumps or loading/discharge hoppers, through appropriate conduits.

At the present time the plastics materials used for the manufacture of products of the kind are distributed and used in the form of granules, also referred to as pellets, which are processed into finished or semi-finished objects by heating, melting and moulding or extrusion.

Many types of plastics materials, in granules or pellets, used for moulding or extrusion are hygroscopic and as a consequence readily absorb moisture, which is a serious disadvantage because during the thermal moulding or thermal extrusion process the water gives rise to bubbles and cavities in the liquefied plastics material.

It is therefore necessary for granules to be dried and dehumidified before they are subjected to the requisite processing, that is melting, moulding or extrusion, and particular measures have to be adopted in order to keep the moisture content of the material low during the stages of storage and transport.

A first type of drying-dehumidification plant comprising three or more cylindrical containers vertically arranged on a movable structure such that the various cylindrical containers can be subsequently positioned at three consecutive granule loading, drying and discharge stations is known in the art.

In detail, at the first station the granular plastics material is loaded into the containers from a suitable hopper, and hot air is blown in to pre-dry the granules.

At the second station an extraction pump draws out the water vapour- saturated air present in the containers, further dehumidifying the granules. At the third station the granular plastics material is discharged from the containers, typically at a subsequent processing station. Plants of this type however have limited efficiency and functionality, because they require extremely robust supporting structures equipped with movement means which must be of adequate strength. Plants of this kind also require frequent maintenance work. In addition to this, because the containers are open and closed at every station, there is inevitable ingress of moist air and impurities which compromise the efficiency of the plant, and also give rise to energy losses. In addition to this, the operations of completely discharging the containers

and cleaning their interiors cannot be carried out with the necessary care. Drying-dehumidification plants for granular plasties materials comprising a number of containers located in succession connected together by flexible conduits and designed to receive granulated plastics material in succession are also known.

In such containers the granular plastics material is subjected to drying- dehumidification treatments and is subsequently stored in the downstream container before being used for the requisite processing. The containers have a substantially cylindrical body, with corresponding removable tops and bottoms provided with seals to provide a leak-tight seal at each of the two ends of the cylinder.

The seal can also be produced through the thrust of pneumatic actuators. The covers are connected to the container bodies through suitable quick opening/closing devices so that the covers can be quickly and easily removed from the corresponding containers and the containers can be completely discharged and cleaned.

Each cover is also provided with an attachment through which the abovementioned flexible conduits are firmly attached to the containers. The flexible conduits connect the containers together, and/or two other devices, for example to feed the material which has to be treated, or to blow in or suck out air.

The attachments are designed in such a way as to ensure that the containers are sealed in a leak-tight manner. The flexible conduits make it possible to move the container covers without detaching the conduits from the covers for the necessary maintenance and

cleaning operations.

This type of drying-dehumidification plant partly solves the previously mentioned problems and disadvantages of movable structure driers, because there are no mechanically moving parts, it permits effective cleaning of the containers, which can be opened by removing their covers, and makes it _. possible to achieve good dehumidification efficiency and reduce operating and maintenance costs.

However, the presence of conduits of flexible material, although making it possible to solve the abovementioned problems give rise to other disadvantages because these conduits are subject to the effect of changes in temperature, pressure and humidity.

These conduits are not durable over time, in particular they can crack or deform allowing moisture to enter and/or plastics material to leak out, so that the containers cease to be leak-tight, thus compromising the overall efficiency of the plant.

It is therefore necessary to carry out frequent checks on the integrity of the conduits, with corresponding maintenance and/or replacement. This considerably increases the operating costs of the plant. In addition to this, it is difficult to remove the container covers for cleaning operations because of the presence of conduits fixed to the covers, and this can also give rise to breakage of the conduits.

There is therefore a need for a new type of connection device for containers which makes it possible to overcome the disadvantages mentioned with reference to the known art. Description of the invention

The problem underlying this invention is that of providing a connection device between the conduit and the container which is reliable, which makes it possible to keep the container sealed in a leak-tight manner, which is economic and which makes it possible to carry out normal container maintenance and cleaning operations quickly and simply and without causing damage to the conduit and/or container.

In the context of this problem one object of the invention is to provide a connection device between a conduit and a container which is resistant to the operating conditions of a granulated plastics material drying- dehumidification plant.

Consequently another object of the invention is to provide a granulated plastics material drying-dehumidification plant which overcomes the disadvantages of the abovementioned known plants. This problem is resolved and this and other objects are accomplished by this invention through a connection device between a conduit and a container, and a granulated plastics material drying-dehumidification plant constructed according to the appended claims. Brief description of the drawings Other advantages and characteristics of the present invention will become clear from the following detailed description which is given with reference to the appended drawings which are provided purely by way of non-limiting example and in which:

- Figure 1 is a partial diagrammatical view of a container of a granulated plastics material drying-dehumidification plant provided with a connection device between the conduit and a container

constructed according to the invention,

- Figure 2 is a diagrammatical view of a detail of the connection device in Figure 1,

- Figure 2a is a cross-section of the detail in Figure 2 along the plane U-II,

- Figure 3 is a magnified detail in cross-section of the plant in Figure 1 showing the connection device in greater detail.

Preferred embodiment of the invention

With reference to the Figures, a plant 100 for the drying-dehumidification of granules of plastics material is shown in part.

Plant 100 comprises a plurality of containers connected together by corresponding connecting conduits and designed to successively receive granules of plastics material requiring treatment before being delivered to subsequent processing operations. In plant 100 the granules of plastics material are subjected to dehumidification/drying to reduce the moisture which would compromise subsequent processing operations to as low a level as possible. In the version illustrated, plant 100 comprises an upstream container 1, only partly shown in Figure 1, into which the granulated material is loaded and in which it is subjected to a first drying, a central container 2, connected by means of a first feed conduit 20 to upstream container 1, in which further drying under vacuum is performed, together with a downstream container 3, also only shown in part in Figure 1, connected to central container 2 through a second feed conduit 21 in which the granules are stored awaiting use in subsequent processing.

As will be seen from the drawings, containers 1-3 have a feed connection of the bottom to top type.

Containers 1-3 are preferably of vertical cylindrical shape and are provided with corresponding top covers 4, 5, 6 and bottom covers 7, 8, 9 located to seal off the top opening la-3a and bottom opening lb-3b of containers 1-3 respectively.

Each cover 4-9 is provided with seals to seal in a leak-tight manner openings la-3a, lb-3b of corresponding containers 1-3 to prevent the escape of material or the ingress of air. At least one of upper covers 4-6 or bottom covers 7-9 of each container 1-3 can be removed from the corresponding container 1-3 so that containers 1- 3 can be repeatedly opened/closed to provide access to their interior, for example for the operations of cleaning, maintenance, loading/unloading granular material, etc. The removable covers of each container 1-3 are provided with a connection device 10 arranged to connect a particular conduit to a particular container 1-3 and constructed in such a way as to permit repeated movement of the cover with respect to the container, as more particularly described below. In the Figures, the connection device is shown only on top cover 5 of central container 2 and in part on the top cover of downstream container 3, however, it may alternatively be fitted to the bottom cover or even both covers of the same container, and/or to all the containers in a given treatment plant. Preferably, the connection device is provided on the top covers 4-6 of containers 1-3, the top cover being movable and the bottom cover being

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fixed.

In this case the bottom cover acts as a self-centering base for containers 1-

3 of plant 100.

In the version illustrated, cover 5 is fitted with a first connection device 10 for first feed conduit 20 and a second connection device 11 for an extraction conduit 23.

First and second connection devices 10, 11 are structurally similar, so only one will be described in detail.

Connection device 10 comprises a sleeve 12 attached by suitable attachment means 13 to an external surface S of top cover 5 opposite the interior of container 2.

Attachment means 13 render sleeve 12 of one piece with cover 5.

Sleeve 12 is internally shaped so as to define a seat 14 into which an end portion 20a of first feed conduit 20 is movably inserted. End portion 20a extends along a longitudinal axis Z, and is preferably straight.

Sleeve 12 is located on top cover 5 in such a way that seat 14 is open in relation to an opening 15 provided in cover 5 in order to place conduit 20 in communication with the interior of central container 2. Sleeve 12 is also provided internally with grooves 16 to house seals 17 to provide a tight seal for portion 20a within seat 14.

Seals 17 are of annular shape, preferably of the V-ring or O-ring type, according to the functions required in service.

Seat 14 of sleeve 12 is shaped in such a way that end portion 20a can move within seat 14 along a direction of movement which is substantially parallel

T/IT2008/000362

to longitudinal axis Z of end portion 20a, indicated by arrow F in Figure 3. In this way cover 5, to which sleeve 12 is rigidly attached, and conduit 20 can be moved with respect to each other.

In addition to this, seals 17 used are shaped in such a way as to ensure a leak-tight seal and therefore leak-tight closure of central container 2, when end portion 20a is in any position within seat 14.

Feed conduit 20 is normally fixed, while cover 5 can be moved with respect to central container 2 to open/close central container 2 without having to detach end portion 20a of feed conduit 20 from sleeve 12. Preferably, the direction of movement F of portion 20a is effectively perpendicular to the external surface S of cover 5.

End portion 20a is designed so that it is completely external to central container 2, in particular it is provided that its end 20b is at a distance of "d" from upper opening 2a on the side opposite central container 2. In addition to this the dimensions of sleeve 12 along the X axis and in particular the distance between seals 17 of cover 5 attached to the base of sleeve 12 are such that seals 17 remain in contact with end portion 20a even when cover 5 is in the closed position on central container 2, as shown in position X illustrated in Figure 3. In order to remove cover 5 from upper opening 2a of central container 2, cover 5 is lifted producing relative movement between end portion 20a and sleeve 12 causing more of portion 20a to be inserted into seat 14 until its end 20b eventually penetrates cover 5 through opening 15. Once cover 5 has been lifted, container 2 may be removed laterally (through lateral movement perpendicular to direction X) without interfering

with end portion 20a, thanks to the provision of distance "d" between end 20b and top opening 2a in central container 2.

Connection device 10 therefore makes it possible to move the cover with respect to the container without in fact detaching the conduit connected to it.

For the reasons stated above, second connection device 11 is not described in detail and its parts are indicated using the same reference numbers as are used for device 10. In other versions which are not illustrated, the same cover may be provided with a different required number of connection devices, constructed in a similar way to that previously described and each located so as to connect the container cover to a particular conduit, with the arrangement that the corresponding end portions of the conduits extend along corresponding longitudinal axes which are parallel to each other to permit movement of the cover.

The arrangement of connection device 10 also makes it possible to prevent the conduit(s) connected to it from being damaged by repeated opening/closing of the container. Thanks to the arrangement of the connection device it is advantageously possible to use conduits made of non-flexible materials in plant 100.

It is therefore possible to use rigid materials which ensure good resistance to the high temperatures and pressure conditions which obtain in the drying-dehumidification client. In particular materials which resist high temperatures (even of the order of 200 ⁰ C), vacuum (even of the order of 990 mbar) and abrasion.

The conduits may for example be made of stainless steel.

This increases the durability of the conduits over time, greatly reducing plant operating costs.

In addition to this, the desired operations of maintaining the containers and the plant in general may be performed without problems.

Extraction conduit 23, connected to cover 5 via second connection device

11, extends between cover 5 and a three-way valve 25 which is arranged in such a way as to place the interior of central container 2 in communication through suction conduit 23 with a second suction conduit 26 of a vacuum pump 24 so as to generate a desired level of negative pressure within central container 2, or with a third extraction conduit 27 extending between three-way valve 25 and a compressor/extractor, which is not shown in the figure and which is more particularly detailed elsewhere.

Second feed conduit 21 is inserted into bottom cover 7 of central container 2 to permit the transfer of granulated material from central container 2 to downstream container 3.

The individual conduits provided in plant 100 may be fitted with valves 30 to open/close the aforesaid conduits and prevent/allow the passage of the desired material and/or fluid. As mentioned above, plant 100 also comprises at least one extractor/compressor, or similar device, designed to blow or extract air into or from a particular container.

In particular, a heater device may be provided on the extractor/compressor delivery line so that hot air can be blown into a particular container. In addition to this the various containers may be selectively connected through

dedicated valves to the suction line of the extractor/compressor to permit granular material to be transferred between successive containers. When in operation, granules of plastics material are fed to upstream container 1, preferably through top opening Ia, and in this they are subjected to a preliminary drying treatment in order to remove moisture. For this purpose the valve provided in upstream container 1 is opened and the extractor/compressor blows hot air into upstream container 1 through a heating conduit, which is not shown, preferably inserted into bottom cover 7. The hot air flows across the granules, raising them to the desired temperature and absorbing moisture, and leaves upstream container 1 as moist hot air through a suitable vent valve provided in top cover 4. Subsequently the connection valve between extractor/compressor and upstream container 1 is closed, valve 30 on feed conduit 20 is open, the valve for the extractor/compressor connecting central container 2 with the suction line of the extractor/compressor is opened and three-way valve 25 is turned so as to connect extraction conduit 23 with third extraction conduit 27 and the extractor/compressor is operated again keeping the vent valve open. This creates a desired degree of vacuum within central container 2 which causes the granular material to be transferred from first upstream container 1 to central container 2 through feed conduit 20. In other versions, a dedicated extractor may be provided for each container. Once filled with heated granules, central container 2 is isolated and placed under vacuum. In particular three-way valve 25 is turned so as to place the interior of central container 2, that is extraction conduit 23, in

communication with vacuum pump 24, through which a desired degree of vacuum is created within central container 2.

Vacuum pump 24 is preferably dimensioned in such a way as to create vacuum conditions down to 750 mbar or even down to 990 mbar. The extreme vacuum conditions within central container 2 make it possible to remove residual moisture from the granules of plastics material. On completion of treatment in central container 2, a further extractor provided in connection with downstream container 3 is again activated to collect the granules of plastics material in downstream container 3, via second feed conduit 21, where they are stored while awaiting use in subsequent processing operations envisaged in the production process. The same extractor/compressor as is used for transfer between the first and second container may also be used, with suitable connections.