EP1070471A2

EP1070471A2 - Door leaf for display refrigerators and the like

Info

Publication number: EP1070471A2
Application number: EP00113197A
Authority: EP
Inventors: Walter Valentini
Original assignee: Vetreria Valentini Srl
Current assignee: Vetreria Valentini Srl
Priority date: 1999-07-20
Filing date: 2000-07-03
Publication date: 2001-01-24
Also published as: IT246866Y1; ITMI990468V0; EP1070471A3; ITMI990468U1

Abstract

A door leaf (1) for display refrigerators and the like, comprising a double-glazing unit (2) supported by a frame (3) and further comprising, on the outer pane of the double-glazing unit, a layer of coating with low electrical resistivity. The coating layer is connected to a secondary winding of a voltage transformer (10) with an output voltage between 12 and 48 volts.

Description

The present invention relates to a door leaf for display refrigerators and the like.
It is known that door leaves for display refrigerators and the like are normally provided by means of a double-glazing unit accommodated within a supporting frame.
Due to the low internal temperatures, which can be estimated at approximately -20/25°C, and due to the relatively high ambient temperature, with a certain degree of humidity, the double-glazing unit inevitably mists over.
In order to solve this problem, double-glazing units for display refrigerators have already been produced, in which the internal surface of the outer pane has a conductive coating having a relatively high electrical resistivity, so that by subjecting two spaced ends of the pane to a voltage of 220 volts, a flow of current occurs which causes the pane to heat to temperatures of 30/35°C, thus preventing formation of mist.
In practical execution, the high electrical resistivity of the coating can vary by 20%, and therefore there can be cases in which resistivity decreases by 20% and hence, for an equal applied voltage, there is an excessive flow of current which inevitably leads to an increase in the temperature of the pane; likewise, excessive resistance leads to an insufficiently heated pane, with the consequent possibility of formation of mist.
It should also be noted that if the pane is heated to an excessive temperature value, the temperature inside the refrigerator increases, forcing the compressor that cools the internal part to work harder and consequently expend energy.
Additionally, another drawback arises from the fact that a voltage of 220 volts is applied at the door, i.e., at a part which is normally in contact with the outside, with severe problems as regards electrical insulation and external safety.
The aim of the present invention is to eliminate the drawbacks noted above, by providing a door leaf for display refrigerators and the like which allows to always have a perfectly controlled temperature level, with consequent reduced consumption and no possibility of formation of mist.
Within the scope of this aim, a particular object of the present invention is to provide a door leaf in which it is possible to achieve a high level of electrical safety without incurring insulation problems and the like.
Another object of the present invention is to provide a door leaf for display refrigerators and the like which, owing to its particular constructive characteristics, is capable of giving the greatest assurances of reliability and safety in use.
Another object of the present invention is to provide a door leaf for display refrigerators and the like which can be easily obtained starting from commonly commercially available elements and materials and is also competitive from a merely economical point of view.
These and other objects which will become better apparent hereinafter are achieved by a door leaf for display refrigerators and the like, according to the invention, comprising a double-glazing unit supported by a frame, characterized in that it comprises, on the outer pane of said double-glazing unit, a layer of coating with low electrical resistivity, said coating layer being connected to a secondary winding of a voltage transformer with an output voltage between 12 and 48 volts.
Further characteristics and advantages of the present invention will become better apparent from the following detailed description of a preferred but not exclusive embodiment of a door leaf for display refrigerators and the like, illustrated only by way of non-limitative example in the accompanying drawing, wherein the only figure is a view of a door leaf according to the invention, illustrating the electrical diagram.
With reference to such figure, the door leaf for display refrigerators and the like, according to the invention, generally designated by the reference numeral 1, comprises a double-glazing unit 2 which is supported by a frame 3.
On the outer pane of the double-glazing unit, and more precisely on the internal face of the pane, there is a layer of coating having a low electrical resistivity which can be estimated at approximately 5x10^-4 ohm.cm. The coating has a thickness of preferably 450 nm ± 50 nm and has less than 1% fogging.
The adoption of a low-resistivity coating layer is particularly important, since it is possible to use a low-voltage current to achieve heating.
In particular, calculating that the power required for heating is 50/80 W/m², it is sufficient to use a voltage transformer, designated by the reference numeral 10, having a secondary winding at a voltage between 12 and 48 volts.
The particularity of the assembly resides in the possibility to provide the pane with the exact amount of current required for its heating, according to its dimensions and resistance, thus avoiding any risk of overheating or underheating.
Moreover, a very important aspect of the door, which normally has a metallic frame, is that a low voltage is being used which is entirely free from electric shock risks, thus meeting the strictest standards for electrical devices.
In order to facilitate optimum distribution in the flow of current, there are contact bars 20 which are applied to the opposite ends of the glass pane, so that a uniform flow of current occurs, accordingly preventing localized heating which might cause undue tensions on the glass pane.
From the above description it is thus evident that the invention achieves the intended aim and objects, and in particular the fact is stressed that a door leaf for display refrigerators and the like is provided which allows to heat the pane by using a voltage transformer having a secondary winding at low voltage, i.e., between 12 and 48 volts, and which can be set in each instance according to the specific requirements of the application so as to always have optimum application conditions.
In practice, the materials used, as well as the contingent shapes and dimensions, may be any according to requirements.
The disclosures in Italian Utility Model Application No. MI99U000468 from which this application claims priority are incorporated herein by reference.
Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

A door leaf (1) for display refrigerators and the like, comprising a double-glazing unit (2) supported by a frame (3), characterized in that it comprises, on the outer pane of said double-glazing unit, a layer of coating with low electrical resistivity, said coating layer being connected to a secondary winding of a voltage transformer (10) with an output voltage between 12 and 48 volts.
The door leaf for display refrigerators and the like according to claim 1, characterized in that said coating layer is provided on the internal face of said outer pane.
The door leaf for display refrigerators and the like, according to the preceding claims, characterized in that said coating layer has a thickness of 450 nm ± 50 nm.
The door leaf for display refrigerators and the like, according to one or more of the preceding claims, characterized in that said coating layer has a resistivity of 5 x 10^-4 ohm.cm.
The door leaf for display refrigerators and the like, according to one or more of the preceding claims, characterized in that it comprises, proximate to two opposite ends of said pane, contact bars (20) which are electrically connected to said secondary winding.
The door leaf for display refrigerators and the like, according to one or more of the preceding claims, characterized in that the output voltage of the secondary winding of said voltage transformer (10) is set in each instance according to the specific characteristics of the glass pane.