EP1280438B1

EP1280438B1 - Climatic control for a showcase

Info

Publication number: EP1280438B1
Application number: EP01936340A
Authority: EP
Inventors: Alessandro Goppion
Original assignee: Goppion SpA
Current assignee: Goppion SpA
Priority date: 2000-05-09
Filing date: 2001-05-08
Publication date: 2006-08-09
Anticipated expiration: 2021-05-08
Also published as: DE60122133D1; EP1280438A1; AU2001262273A1; ITMI20001012A1; WO2001084986A1; ITMI20001012A0; ATE335428T1; DE60122133T2; ES2269405T3

Abstract

The climatic control in a showcase is based on the combined use of a hygroscopic material and of an active humidication/dehumidification equipment or, preferably, of a conditioning equipment. In this way, relative humidity is stably maintained at the desired value, free of failures and with a small equipment.

Description

The present invention relates to the climatic control of showcases, in particular for museums or private exhibitions of works of art, antiques and the like.
In the present description and attached claims, the term "showcases" is used to indicate wall-hung and floor-standing showcases, shrines, display cases, and the like.
Besides antitheft protection, in many situations showcases have the function of maintaining the content in a controlled environment as regards pollutants, temperature and, of particular interest as far as the present invention is concerned, humidity, that is, of actually maintaining a "microclimate" within the showcase. In fact, climatic preservation conditions are particularly critical in the case of works of art, handworks and ancient organic materials.
Thus, showcases available on the market are structurally designed so as to exhibit a high tightness degree in order to minimise uncontrolled atmospheric exchanges with the outside.
At present, basically two types of systems are used for controlling the microclimate inside a showcase.
A first class is represented by the so-called passive systems, that is, systems that use mineral materials that, thanks to their chemical and physical characteristics, stabilize relative humidity conditions in restricted environments. Hygroscopic materials, in particular silica gel, operate so as to absorb or release such a quantity of water as to substantially maintain them balanced with the surrounding environment -the display chamber of the showcase in the case here of concern- as regards relative humidity, and they are available on the market at different "conditioning" levels. By this term it is meant that before being marketed, the hygroscopic materials are brought to particular conditions of relative humidity around which they will tend to maintain the display chamber inside which they are inserted.
WO 99/09867, on which the preamble of the independent claims is based, discloses a showcase having a display chamber, comprising means for housing a predetermined quantity of a hygroscopic material in atmospheric contact with said chamber, at least one air inlet for ambient air or inert gas and at least one air outlet for extracting the old air from the showcase.
Passive systems for controlling the climate within showcases are widespread thanks to their simplicity of use, to the fact that they are effective in a quite wide relative humidity range, and to the fact that they are immune from the attack of micro-organisms that could become a harmful pollution source for the preserved materials. However, they exhibit some disadvantages: the hygroscopic material must be periodically replaced, or at least when it is close to saturation or, respectively, dryness conditions, with non-neglectable costs especially for large showcases; a given system cannot be easily adapted to relative humidity values different from that for which it is initially designed, that is to say, different from the value at which the hygroscopic material is initially conditioned; they do not allow any control of the internal temperature of the showcase, whose changes affect the relative humidity itself, and which may be an important factor for some displayed materials.
A second class of climatic control systems for showcases is represented by the so-called active systems, that is, systems that use power-supplied equipment to regulate the relative humidity within the display chamber of the case, and optionally, the temperature, so as to keep them constant at settable values. Dehumidification is normally obtained through cooling and condensing of the water vapour present in the air inside the showcase, for example with a normal coolant compression and expansion frigorific cycle, or through endothermic chemical reactions. However, with both methods there is the risk of leaks of coolant fluid or chemical agents that may damage the preserved material.
Thus, cooling methods that make use of the reverse thermoelectric effect, or Peltier effect, are preferred. As known, this consists in the onset of a difference of temperature between the joints of a bimetallic pair as a consequence of the passage of a direct electrical current through the pair. Besides being free from polluting substances, and thus safe, Peltier-effect cooling equipment is also relatively simple.
However, since they need external energy sources, active conditioning systems are subject to the possibility of electrical failures, mechanical failures, and to the possibility of power supply failure. To obviate this, it has been proposed to provide for the automatic connection - in case of emergency- of independent energy sources, such as spare batteries and generating sets, or of duplicate or alternative equipment. However, this solution implies a relatively complex, expensive and bulky climatic control system.
The technical problem at the basis of the present invention is that of providing a climatic control for a showcase which should be versatile and reliable with respect to the conditions maintained inside the case, and which should result in a small equipment.
Thus, in a first aspect thereof, the present invention relates to a method for controlling the climate in a display chamber of a showcase, comprising the step of:

arranging a predetermined amount of a hygroscopic material in atmospheric contact with the chamber,
characterised by the step of:
introducing a predetermined air flow having a predetermined relative humidity value into the chamber in a substantially continuous manner.

In a second aspect thereof, furthermore, the present invention relates to a showcase having a display chamber, comprising means for housing a predetermined amount of a hygroscopic material in atmospheric contact with the chamber, at least one air inlet and at least one air outlet, characterised in that at least the inlet is connected to a humidification/dehumidification equipment for the air introduced in the inlet.
The presence of the hygroscopic material within the air volume whose relative humidity is regulated, by a suitable active humidification/dehumidification equipment, has the effect of stabilizing the relative humidity conditions around the desired value. Moreover, the hygroscopic material allows maintaining the desired relative humidity conditions in case of failure or malfunctioning of the equipment, or of power supply failure. In turn, the active intervention allows maintaining, restoring or resetting the relative humidity conditions of the hygroscopic material itself, thus preventing it from reaching saturation or dryness conditions.
Moreover, the step of re-circulating the air flow essentially in a closed circuit from an outlet of the chamber to an inlet of the chamber is preferably also provided.
In parallel, in the showcase the equipment is connected in closed circuit between the inlet and the outlet.
In this way, the operating costs decrease.
Advantageously, the step of pre-conditioning the predetermined quantity of hygroscopic material substantially at the predetermined relative humidity value may be provided for before the arrangement step.
This provision allows reducing the work needed to bring the load controlled by the active equipment, that is, the air within the chamber and the hygroscopic material itself, to the desired values.
Preferably, moreover, the method comprises the step of detecting the humidity conditions at the chamber and/or at the hygroscopic material arranged in the arrangement step and the predetermined air flow and/or the predetermined relative humidity value are selected according to the detected relative humidity conditions with respect to a presettable desired relative humidity value.
In parallel, the showcase further comprises means for detecting the relative humidity at the chamber and/or at the hygroscopic material housing means, the equipment being responsive to the output signal of the relative humidity detection means.
This feedback control allows automating the active intervention by limiting it to when the need of humidification or dehumidification arises, thus minimising the operating costs. In particular, in this intermittent operation of the equipment, the hygroscopic material has a beneficial effect since it dampens the oscillations around the preset set-point.
Advantageously, the predetermined relative humidity value can be changed according to a presettable progressive program.
This can be advantageous for progressively adapting delicate preserved materials to the desired preservation conditions.
Typically, the predetermined air flow is dehumidified through condensation on a surface cooled through Peltier effect.
Thus, in the showcase the equipment usually comprises a Peltier-effect cooled surface for dehumidification.
This has the advantage of avoiding the use of potentially polluting substances, besides that of requiring a relatively simple equipment.
Preferably, the predetermined air flow is introduced into the chamber at a predetermined temperature value.
In parallel, the equipment in the showcase is further suitable to regulate the temperature of the air introduced in the inlet to a predetermined temperature value.
This is advantageous for some types of displayed materials.
In this case, it is possible to advantageously provide for detecting the temperature within the chamber, and selecting the predetermined temperature value according to the detected temperature with respect to a presettable desired temperature value.
Thus, the showcase can further comprise means for detecting the temperature at the chamber, the equipment being responsive td the output signal of the temperature detection means.
This provision exhibits the typical advantages of a feedback control.
Typically, the arranged hygroscopic material is silica gel.
This material exhibits the advantage of being solid, thus preventing the risk of accidental leaks that may damage the displayed material.
Advantageously, the predetermined amount of silica gel is selected within a range comprised between 500 and 1500 g/m³ of internal volume of the chamber.
Within such ranges, the amount of silica gel is selected according to the internal volume and tightness of the chamber, to the type and quantity of displayed material, and to the difference between relative humidity required in the chamber and relative humidity outside the case. The amount of introduced silica further depends on the initial relative humidity conditions of the displayed material and on those which are desired to be maintained for its optimum preservation.
From the point of view of the showcase, the housing means is typically selected from the group consisting of a drawer for granular or sheet silica gel, a porous tube and a permeable bag.
Features and advantages of the invention will now be illustrated with reference to an embodiment represented by way of a non-limiting example in the attached drawing, wherein the only Figure shows a showcase according to the present invention.
The showcase 1 of the Figure is exemplified as of the floor-standing type, and as for displaying on four sides, and therefore it has a base 2, typically with non-transparent walls, and a chamber 3 with transparent walls, suitable to house one or more items to be displayed (not shown).
The display chamber 3 exhibits at least two air-exchange openings, in Figure there being represented an air inlet 4 and an air outlet 5. As for the rest, chamber 3 is as tight as possible. Moreover, chamber 3 communicates with a housing for a hygroscopic material, represented as a drawer 6 for granular or sheet silica gel. Of course, different housing means can be provided, such as a porous tube, a permeable bag or the like, provided that they are suitable to maintain the hygroscopic material in atmospheric contact with chamber 3.
In principle, different hygroscopic materials can be used, such as for example saline solutions. However, since they are liquid materials, leaks harmful for the displayed items may occur.
As regards silica gel, different qualities are available on the market, which are essentially distinguished based on two parameters. A first parameter is the "humidity level" (EMC), that is to say, the actual amount of water contained in the silica gel when its vapour pressure is balanced with a given relative humidity. The higher the humidity level, the higher the capability of stabilizing relative humidity changes in the controlled environment, chamber 3 in the case here of concern. Moreover, this parameter is itself a function of the relative humidity, so that also its pattern in the relative humidity range of interest, typically from 35% to 65% RH, is important.
A second parameter of interest is the so-called "M-Value", which represents the amount of water in grams that is absorbed or yielded per each kilogram of silica gel when relative humidity undergoes changes within 1%. Also this parameter must be as high as possible, in the relative humidity range of interest, in order that the silica gel has a good capacity of stabilizing relative humidity changes.
Finally, the silica gel must exhibit hysteresis phenomena to the least possible extent. These phenomena are due to the fact that the absorption curve, in the plane EMC against relative humidity, lies lower than the desorption curve in the same plane, which implies an inactivity period during the inversion from the humidification to the dehumidification function and vice versa.
The above properties of hygroscopic materials must preferably be affected as little as possible by temperature changes.
Turning back to the Figure, the air exchange openings 4 and 5 are shown in communication with base 2, which houses a conditioning equipment 7 electrically supplied by a cord 8 provided with a plug 8' for the connection to the supply mains. This arrangement of the conditioning equipment 7 is preferred for aesthetical reasons, but equipment 7 can be on sight if the aesthetic factor is not a requirement, or where no cabin space is available, for example in wall-hung cases.
The conditioning equipment 7, schematically shown, can simply consist of a humidifier/dehumidifier, but preferably it is also suitable to heat or respectively cool the air that it introduces into chamber 3 of case 1. Equipment 7 preferably forms a hermetic air circulation system with chamber 3, since it is connected to the air inlet 4 and outlet 5 of chamber 3 in a closed circuit through respective piping 4' and 5'. An alternative solution can consist in providing an open circuit for the conditioning air. In this case, equipment 7 will suck ambient air from a suitable air intake and will send the treated air, that is, at the desired values of humidity and optionally, temperature, to chamber 3 through the air inlet 4, whereas the air exiting from the air outlet 5 of chamber 3 will be vented in the environment outside case 1. This solution exhibits higher consumptions but may be advantageous for displayed materials requiring a certain change of air. Finally, it will be understood that intermediate solutions are also possible, wherein a portion of the air flow is recirculated and a portion is exchanged with the external environment.
Equipment 7 is preferably of the type where dehumidification occurs through the condensation of excess humidity on a surface (not shown) cooled by Peltier effect. The condensate water is then collected and pumped into a water reservoir (not shown). Vice versa, humidification occurs by pumping water from the reservoir and vaporizing it into the air introduced into chamber 3 through inlet 4.
Equipment 7 has a control panel 7' for setting the desired humidity, and preferably temperature, value of the treated air. Preferably, however, equipment 7 is feedback-controlled and the values settable through control panel 7' are therefore those desired in chamber 3. By way of an example, the Figure shows a relative humidity probe 9 and a thermometer 10 arranged in chamber 3 and a relative humidity probe 11 arranged in the drawer-like support 6 for detecting the relative humidity of the hygroscopic material housed therein.
Through the described showcase 1, the climatic control method according to the present invention can be implemented as follows.
First of all, a predetermined quantity of a hygroscopic material, for example 1000 g of silica gel for each square meter of internal volume of chamber 3, is arranged in the drawer-like housing 6, where it is in atmospheric contact with chamber 3. Preferably, the silica gel has been previously pre-conditioned at a predetermined relative humidity value, for example at 55%, before said arrangement step.
Equipment 7 is then made to operate substantially continuously so that a predetermined air flow is introduced into chamber 3, after having set its relative humidity to the predetermined value, 55% in this example. Equipment 7 preferably re-circulates air from outlet 5 of chamber 3 to its inlet 4.
The predetermined relative humidity value can be set in equipment 7 through the control panel 7' Preferably, however, the desired final relative humidity value in chamber 3 is set in equipment 7 through the control panel 7', and through a suitable controller (not shown) the equipment provides for regulating the flow rate or the humidity value of the air that it introduces into inlet 4 based on said desired final value and on the relative humidity each time existing in chamber 3 itself, as detected by the humidity probes 9 and/or 11.
Even more preferably, the controller changes the predetermined relative humidity value according to a presettable progressive program, for example for bringing the relative humidity within chamber 3 from the existing conditions to the desired final conditions in a sufficiently long period to avoid shocks to the displayed material within chamber 3.
When equipment 7 allows it, the air is introduced into chamber 3 not only at the predetermined relative humidity value, but also at a predetermined temperature value, that is to say, it is cooled or heated according to the need. Also in this case, through the control panel 7', the predetermined air temperature that equipment 7 introduces into chamber 3 through inlet 4 can be set. Preferably, however, the value that is set is the desired final value within chamber 3, and the controller of the equipment provides for regulating the temperature of the air that it introduces into chamber 3 according to said desired final value and to the temperature each time existing in chamber 3, as detected by thermometer 10.
Therefore, it will be understood that the control of humidity, and preferably, of temperature of the display chamber 3 is mainly carried out by equipment 7. The hygroscopic material, on the other hand, performs a dual role. In the first place, it acts as an emergency control of the relative humidity in case of failure of equipment 7 or power supply failure. In the second place, the hygroscopic material has a beneficial effect on the operation of equipment 7 since it dampens the oscillations around the programmed set-point, oscillations which otherwise occur as hysteresis in the active conditioning systems of the prior art, of the intermittent operation, feedback type. On the other hand, the silica gel need not be periodically replaced since, thanks to the active humidification/dehumidification through equipment 7, it never reaches dryness or saturation conditions.
Experimental tests, moreover, have allowed determining that in the case of combined use of the hygroscopic material and of the conditioning equipment 7, the amount of hygroscopic material needed is reduced. In fact, while according to the passive conditioning type prior art, amounts of silica gel from 500 g to 20 kg per cubic metre of internal volume of the chamber of the showcase are used, according to the present invention an amount comprised between 500 and 1500 g/m³ of internal volume of the showcase turns out to suffice. Within these ranges, the quantity of hygroscopic material is selected according to the tightness of the case, to the type and quantity of displayed material, and to the difference between relative humidity required inside the case and relative humidity outside the case.
It is manifest that several changes, variations, replacements and integrations can be made to the previously described embodiments without however departing from the scope of the invention as defined by the following claims.
It is however worth noting that the showcase 1 represented in the Figure and described above must be regarded as merely illustrative, as for the purposes of the principles at the basis of the present invention it is sufficient that such showcase comprises means for housing a predetermined quantity of a hygroscopic material in atmospheric contact with its internal chamber and arrangements to be connected to an active air humidification/dehumidification and optionally heating/cooling equipment. In fact, the conditioning equipment 7 might be turned on only when needed, when the hygroscopic material, after having provided to the humidification or vice versa, dehumidification of chamber 3 as far as allowed by its volume and by its initial conditions, approaches saturation or vice versa, dryness conditions, as detected by the humidity probe 11. In that case, the conditioning equipment 7 would intervene to introduce air into chamber 3 through inlet 4 at the predetermined relative humidity and optionally temperature value, and, provided that the operation period of equipment 7 is sufficiently long, typically of 48 hours, it would recondition the hygroscopic material to said relative humidity value. In this case, the conditioning equipment 7 might be disconnected from chamber 3 during the periods when it is not used, which may be advantageous both from the aesthetical point of view, in particular for wall-hung cases or in any case, not provided with sufficient cabin space for housing the equipment, and in terms of use of a single equipment for different showcases. In this case, the air openings 4, 5 of chamber 3 should of course be provided with check valves or sufficiently tight plugs.

Claims

Method for controlling the climate in a display chamber (3) of a showcase (1) , comprising the step of:
- arranging a predetermined amount of a hygroscopic material in atmospheric contact with said chamber (3),
characterised by the step of:

- introducing a predetermined air flow having a predetermined relative humidity value into said chamber (3) in a substantially continuous manner.
Method according to claim 1, characterised by the step of re-circulating said air flow essentially in a closed circuit from an outlet (5) of said chamber (3) to an inlet (4) of said chamber (3).
Method according to claim 1 or 2, characterised in that it comprises the step of pre-conditioning the predetermined quantity of hygroscopic material substantially at said predetermined relative humidity value before said arrangement step.
Method according to one of the previous claims, characterised in that it further comprises the step of detecting (9, 11) the humidity conditions at said chamber (3) and/or at the hygroscopic material arranged in said arrangement step and in that said predetermined air flow and/or said predetermined relative humidity value are selected according to the detected relative humidity conditions with respect to a presettable desired relative humidity value.
Method according to one of the previous claims, characterised in that said predetermined relative humidity value is changed according to a presettable progressive program.
Method according to one of the previous claims, characterised in that said predetermined air flow is dehumidified through condensation on a surface cooled through Peltier effect.
Method according to one of the previous claims, characterised in that said predetermined air flow is introduced into said chamber (3) at a predetermined temperature value.
Method according to claim 7, characterised in that it further comprises the step of detecting (10) the temperature of said chamber (3) and in that said predetermined temperature value is selected according to the detected temperature with respect to a presettable desired temperature value.
Method according to one of the previous claims, characterised in that said arranged hygroscopic material is silica gel.
Method according to claim 9, characterised in that said predetermined quantity of silica gel is selected within a range comprised between 500 and 1500 g/m³ of internal volume of said chamber (3).
Showcase (1) having a display chamber (3), comprising means (6) for housing a predetermined quantity of a hygroscopic material in atmospheric contact with said chamber (3), at least one air inlet (4) and at least one air outlet (5), characterised in that at least said air inlet (4) is connected to a humidification/dehumidification equipment (7) for the air introduced into said inlet (4).
Showcase (1) according to claim 11, characterised in that said equipment (7) is connected in closed circuit between said inlet (4) and said outlet (5).
Showcase (1) according to claim 11, characterised in that said housing means (6) is selected from the group consisting of a drawer for granular or sheet silica gel, a porous tube and a permeable bag.
Showcase (1) according to one of claims from 11 to 13, characterised in that for dehumidification, said equipment (7) comprises a surface cooled through Peltier effect.
Showcase (1) according to one of claims 11 to 13, characterised in that it further comprises means (9, 11) for detecting the relative humidity at said chamber (3) and/or at said hygroscopic material housing means (6), said equipment (7) being responsive to the output signal of said relative humidity detection means (9, 11).
Showcase (1) according to one of claims 11 to 15, characterised in that said equipment (7) is further suitable to regulate the temperature of the air introduced into said inlet (4) to a predetermined temperature value.
Showcase (1) according to claim 16, characterised in that it further comprises means (10) for detecting the temperature at said chamber (3), said equipment (7) being responsive to the output signal of said temperature detection means (10).