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(11) | EP 1 275 921 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Device with a vacuum drying chamber equipped with mechanisms for an adjustable compression of the product to be dried |
| (57) A device with a chamber for drying materials under vacuum conditions, in which, thanks
to the presence of a adjustment and compensation chamber (4) and of a flexible membrane
(5), it is possible to exercise a finely tuned compression on the material to be dried
(7), which is independent of the degree of vacuum created in the drying chamber (3). |
[0001] The invention regards a device with a vacuum drying chamber equipped with mechanisms for the adjustable compression of the product to be dried.
[0002] The accelerated drying of products, such as timber cut into boards for example, is quite common, where the internal humidity is reduced through industrial procedures. One of these procedures contemplates the use of hermetically sealed drying chambers. The product to be dried is placed inside these chambers, it is heated and, at the same time, inside the said chambers the air pressure is reduced to aid the evaporation of the internal humidity of what is to be dried. The reduction of pressure stimulates the evaporation of the internal humidity of the product to be dried even when it is heated at a relatively low temperature, allowing, in this way, to accelerate the procedure and reduce the cost of the thermal energy used.
[0003] In order to obtain a higher regularity in the geometric shape of the dried product, one of the previously known procedures contemplates the heating and the contemporary compression of the product to be processed.
[0004] In the Italian Patent N. 1.180.094, at least one of the panel walls of the drying chamber is made of flexible material, so that the depression generated inside the drying chamber creates an inflexion, with the consequent compression of the product to be dried placed inside the same chamber. This compression is strong if the internal decompression of the chamber is normally very high so as to aid in the evaporation of the internal liquid of the product to be dried, even when it is subjected to relatively low drying temperatures. If on the one hand all of this is advantageous since it helps to obtain undeformed dried products, on the other it is problematic because the compression is un-controllable, that is it cannot be adjusted independently from the vacuum created inside the chamber. Due to this reason the normal shrinkage due to the evaporation of the internal humidity of the compressed product is impeded, so that, in some cases, great stresses are generated inside it, causing the breakage of the said product, therefore in some cases its destruction.
[0005] The aim of the present invention is the production of a device with vacuum drying chamber equipped with mechanisms to allow the adjustable compression of the product to be dried. In this way it is possible to use a high vacuum pressure inside the chamber that houses the product to be dried, and a compression of the same product that will not cause damage to it.
[0006] The invention that has permitted us to obtain these results is composed of a device with an hermetically sealed drying chamber, equipped with previously known heating mechanisms, with a first chamber that is appropriate for housing the product to be dried, with a second adjustment and compensation chamber and with a panel wall in flexible material which separates the two chambers. The latter is capable of inflecting towards the inside of the first chamber and to generate the compression effect on the product to be dried, due to a greater vacuum inside the first chamber versus the second.
[0007] Said device is also equipped with the mechanisms for generating and regulating said vacuum so as to control the "suction" effect on the said flexible membrane, exercised by the greater vacuum in the first chamber versus the second.
[0008] Such an invention is particularly advantageous since inside the two chambers, the degree of vacuum, produced by previously known mechanisms, can be finely adjusted. The adjustment in the first chamber allows us to obtain a high evaporation speed in the product to be dried and that is placed inside it. The adjustment in the second chamber allows us to obtain a difference in the vacuum levels in the two chambers, that is capable of operating a compression, on the product to be dried, with the desired pressure value and such as to prevent the irregular geometric deformations caused by its drying, without damaging the product.
[0009] The invention in its structure and function is described hereinafter with reference to the preferred embodiment reproduced schematically in the enclosed drawings, in which:
- Fig. 1 is the general layout of the device with the drying chamber equipped with two chambers, the second of which is for adjustment and compensation;
- Fig. 2 is a schematic drawing of the solution in which the second chamber is substituted by a pressure group of fluid dynamic cylinders.
[0010] It is understood that said drawings, reproduced schematically, have the only aim of aiding the comprehension of the invention, without constituting in any way a limitation to it.
[0011] In them we have indicated with 1 the hermetically sealed drying chamber, with 2 the top panel wall capable of sealing it hermetically, with 5 the flexible membrane, capable of separating the inside of the drying chamber 1 into a first chamber 3 and a second chamber 4. With 6 we have indicated the sliding uprights applied to the internal panel walls of the main structure of the drying chamber 1, at the top of which is anchored the rigid compression plate 20. With 14 we have indicated the pipe by means of which the chamber 3 is connected to the suction of the vacuum pump 8. With 9 we have indicated the de-humidifying condensation group which can be installed inside the pipe 14. With 10 we have indicated the adjustment valve which connects the chamber 3 to the outside. Chamber 3 where, along with the previously known heating mechanisms, the pressure indicator indicated as 11 is housed, by means of which the degree of vacuum, and therefore of depression versus the external environment, is measured inside the same chamber 3.
[0012] On the top panel wall 2 we have, instead, the entry valve for air, indicated with 13, the pressure detector, indicated with 12, and finally the extremity of the tube, indicated with 15, which joins the chamber 4 with the adjustment valve, indicated with 18, therefore the vacuum pump input, capable of produce a vacuum inside the chamber 3 and 4.
[0013] With 30 we have indicated the programmable electronic control unit, whose inputs are connected with the vacuum indicators 11 and 12 and whose outputs are connected with the adjustment valves 13 and 18, and through which the control and regulation of the vacuum inside the chambers 3 and 4 are effected.
[0014] The chamber is normally shaped like a parallelepiped, with a rigid top panel wall 2 connected along a closed line with the airtight and flexible membrane 5, this is appropriate for dividing the inside of the drying chamber 1 into a first chamber 3, the one intended to house the product to be dried, and into a second chamber 4. Said membrane 5 is capable of inflecting towards the chamber 3 and, in said inflection, to effect the compression of the product 7 to be dried. The drying chamber is also equipped with, according to one of its first embodiment, an apparatus containing an appropriate vacuum pump 8 with which the gasses are aspirated from the chambers 3 and 4, so as to generate two different states of vacuum in the said chambers. In particular in chamber 3, where the product to be dried is housed, a higher vacuum than in chamber 4 is generated. The drying chamber is therefore equipped with the appropriate mechanisms 11 and 12 to read the pressures inside said chambers 3 and 4, while the combined device with chamber 1 is equipped with valves 13 and 18 with which the regulation of airflows, respectively into and out of the chamber 4 to adjust the state of the vacuum inside it. The device associated with the drying chamber 1 also includes the appropriate mechanisms 30, normally programmed, for the adjustment of the said valves 13 and 18. They allow the regulation of the amount of vacuum in the chamber 3, therefore the regulation of the difference in pressure between the chambers 3 and 4 and therefore the compressing action exercised by the flexible membrane 5 on the product 7 to be dried.
[0015] During operation the chamber 3 is brought to a state of vacuum so that the membrane 5 can effect its compressing action; said chamber is equipped with at least one input valve 10, normally adjustable by hand. It permits the restoration of external atmospheric pressure in chamber 3 when, at the end of the drying process, entry into the same chamber 3 is required and the termination of the pressing action of the membrane 5 is also required to allow the extraction of the dried product.
[0016] In the tube 15, which connects the chamber 4 with the ingress of the vacuum pump 8, we have the adjustment valve 18 through which the vacuum pressure in the chamber 4 is reduced in respect to that generated by the same pump 8 in the chamber 3 housing the product to be dried. In this way we generate, between the two chambers 3 and 4, the difference in vacuum pressure required for the activation of membrane 5. By operating on the adjustment valve 18 it is therefore possible to reduce the difference in pressure between the chambers 3 and 4. By operating on the second valve 13, which allows the input into chamber 4 of air originating outside the chamber, it is possible to increase the difference of pressure between the two chambers. The valves 18 and 13 permit us therefore to adjust the compression effect of the flexible membrane 5 on the stack of the product 7.
[0017] Alternatively, the adjustment can be effected by substituting one of the two valves 13 and 18 with a calibrated airflow orifice and by operating on the remaining valve.
[0018] The apparatus that is associated with the drying chamber 1 foresees the presence of an adjustment servomechanism 30, normally of the programmable type, through which we can control the difference in vacuum pressure, between chambers 3 and 4, which is registered by the sensors 11 and 12. Said servomechanism 30 permits therefore, on the one hand the adjustment of vacuum pressure in chamber 3, on the other hand the adjustment of the compression exercised by the flexible membrane 5 on the product to dried. An alternative system for the modulation of the compression that is exercised by the membrane 5, on the product to be dried, is that represented in the enclosed drawing 2.
[0019] The system is composed of the vacuum drying chamber 3, of the hermetically sealed type, in which one panel wall is connected, along a closed line, with the airtight flexible membrane 5 that is capable of compressing the product to be dried 7 by means of a rigid plate 20. Operating on said plate 20, are the hydraulic pistons 21, or other equivalent counter reacting systems, capable of exercising on the same plate 20 a force that counters that of the membrane 5. By properly modulating the pressure exercised by the pistons 21 on the plate 20 through the appropriate adjusting mechanisms 25, one can obtain the desired compression action on the product to be dried.
1. A device with a vacuum drying chamber equipped with mechanisms for an adjustable compression
of the product to be dried, comprising an hermetically sealed drying chamber (1) capable
of housing the product to be dried (7) placed inside it, equipped with previously
known mechanisms for heating and characterized by a closing panel wall (2) connected, along a closed line, with a airtight flexible
membrane (5), the latter appropriate for separating the drying chamber (1) into a
first chamber (3), intended to house the product to be dried (7), and a second chamber
(4), where said membrane (5) is capable of compressing the product to be dried (7)
following its inflection towards the chamber (3), as well as said device being characterized by an appropriate vacuum pump (8), or equivalent mechanisms, for aspirating the fluids
present in the chambers (3) and (4) so as to generate in said chambers (3) and (4)
two different adjustable vacuum levels, so as to adjust the compression effect exercised
by the membrane (5) on the stack of product (7) to be dried.
2. The device with a vacuum drying chamber, as claimed in claim 1, comprising two chambers
(3) and (4) characterized by the mechanisms (11) and (12) for registering the pressure inside them, by valves
(13) and (18) for the adjustment of the airflows entering and exiting from the chamber
(4) as well as by the mechanisms (30) for the adjustment of said valves and therefore
for the regulation of the difference of the pressures in the same chambers.
3. The device with a vacuum drying chamber, as claimed in claim 1, characterized by the fact that in the tube (15) which connects the intake of the vacuum pump (8) with
the compensation chamber (4) there is an adjustment valve (18) capable of causing
a smaller reduction in pressure within chamber (4) versus that in chamber (3) housing
the product (7) to be dried.
4. The device with a vacuum drying chamber, as claimed in claim 1, characterized by mechanisms capable of adjusting the difference in vacuum pressure between the chambers
(3) and (4) that are separated by the flexible membrane (5).
5. The device with a vacuum drying chamber, as claimed in claim 1, characterized by the fact that the chamber (3) is connected to the outside by the valve (10), capable
of defining the increase of the pressure inside when the drying of the product (7)
is completed.
6. The device with a vacuum drying chamber, as claimed in claim 1, characterized by a programmable adjustment servomechanism (30), capable of controlling the difference
in the vacuum of the chambers (3) and (4) registered by the pressure sensors (11)
and (12).
7. A device with a vacuum drying chamber equipped with mechanisms for the adjustable
compression of the product to be dried, with said drying chamber (3) of the hermetically
sealed type, appropriate for housing the product to be dried (7) and equipped with
previously known heating mechanisms, characterized by a wall panel combined, along a closed line, with the airtight flexible membrane (5),
by a rigid plate (20), placed between the airtight flexible membrane (5) and the product
to be dried, and by hydraulic pistons (21), or equivalent systems, capable of exercising
on said plate (20) a force that is contrary to that exercised by the membrane (5)
and with an intensity that is adjustable by the appropriate adjusting mechanisms (25).