GB2130280A

GB2130280A - Glass door for refrigerated show case

Info

Publication number: GB2130280A
Application number: GB08326682A
Authority: GB
Inventors: Bengt Lindgren
Original assignee: Termofrost Sweden AB
Current assignee: Termofrost Sweden AB
Priority date: 1982-10-05
Filing date: 1983-10-05
Publication date: 1984-05-31
Also published as: GB8326682D0; SE8205677L; NO833587L; SE8205677D0; SE444636B; FR2534007A1; FI833600A; FI833600A0; DE3335842A1

Abstract

A glass door for refrigerating and deep-freeze chambers, where the front pane (2) remote from the refrigerating and deep-freeze chamber is heated, comprises four glass panes (2,3,4,5) in parallel with each other. <IMAGE>

Description

SPECIFICATION Glass door This invention relates to a glass door for refrigerating and deep-freeze chambers in everyday commodities trade primarily for exposing refrigerated and deep-frozen goods in food shops.

Such doors are used to an ever increasing extent for shielding off refrigerating and deepfreeze chambers from the remaining room in a food shop. Through the glass doors refrigerated and deep-frozen goods are exposed, and when a customer intends to select a goods, he or she opens the door, takes the goods and closes the door.

As the doors are opened frequently, they are exposed alternatingly to the climate of the shop and to the climate of the refrigerating and deep-freeze chamber.

The doors normally comprise two or three glass panes, and most usually three glass panes are used. In such cases the pane facing to the shop and the pane facing to the refrigerating or deep-freeze chamber consist of hardened glass so as to be capable to resist normal stresses without bursting. The intermediate pane most often consists of window glass.

As the doors alternatingly are exposed to different climates in respect of relative humidity and temperature, the glass pane facing to the shop normally is heated in order to prevent vapour formation, so that the goods always are clearly exposed.

The front pane facing to the shop normally is heated with a supplied effect of about 80-120 W/m2. In addition about 60 W are used for heating the door frame. This effect maintains the door clear and free of vapour when the temperature in the shop is, for example, + 25 C and the temperature in a deep-freeze chamber is - 30"C.

At these and corresponding conditions, about 60% of the supplied effect is led into the deep-freeze chamber, and about 40% into the shop. This implies that 72 to 96 W/m2 are led into the deep-freeze chamber. This energy amount causes substantial costs per year when a number of doors, for example five of 1 m2 per door, are used. A continuous energy supply of 600-800 W is required, which at an energy price of SEK 0,20 per kWh implies costs of 300-400 SEK per year.

In addition to this cost, of course, the energy amount supplied to the deep-freeze chamber charges the refrigerating machine of the deep-freeze chamber, by which machine the supplied energy amount must be cooled away. The cost for this is higher because the refrigerating machine does not have an efficiency degree of 100.

The present invention has the object to reduce to a substantial degree the aforesaid problem.

The present invention, thus, relates to a glass door to be used for refrigerating and deep-freeze chambers, where the front pane remote from the refrigerating and deep-freeze chamber is heated by means of an electrically conductive layer attached on the inner surface of the pane, and is characterized in that the glass door comprises four glass panes arranged in parallel with each other, which in known manner are sealed against each other by sealings extending about the edges of the panes.

The invention is described in greater detail in the following, with reference to the accompanying drawing, in which Fig. 1 is a schematic cross-section of a door according to the invention.

In Fig. 1 a glass door according to the invention is schematically shown which comprises a front pane 2 of hardened glass remote from the refrigerating and deep-freeze chamber and a rear pane 3 of hardened glass facing to the refrigerating and deep-freeze chamber.

The front pane is designed for being heated. The heating is effected in that the pane is coated with an extremely thin layer of an electrically conductive material, for example stannic oxide. In the upper and, respectively, lower part of the pane 2 the layer is connected to collecting conductors 6, 7, which in their turn are connected to regular mains voltage.

Between said panes 2, 3 according to the invention two intermediate panes, preferably of window glass, are located, which panes are designated by 4, 5.

According to the invention, thus, four panes 2,3,4,5 are arranged in parallel with each other. The panes are sealed against each other by sealings 8,9,10 extending about the edges of the panes.

The use of four panes, of which the front pane 2 is heated, is based on the discovery, that the effect demand can be reduced substantially, at the same time as the main direction of the effect losses can be reversed compared to the conventional glass door with three glass panes.

At an additional number of glass panes the technical effect is insignificant.

At the same prerequisite conditions as mentioned in the introductory portion of the present application, viz. a shop temperature of + 25 C and a temperature in the deep-freeze chamber of - 30"C, with the glass door according to the invention it is only necessary to heat the front pane 2 with a maximum effect below 50 W/m2, preferably about 40W/m2, i.e. a halved effect. In addition, the main direction of the effect losses is reversed. At a conventional glass door about 60% of supplied effect is led into the deep-freeze chamber while about 40% is led into the shop.

At a glass door according to the invention, about 25% of supplied effect is led into the deep-freeze chamber while 75% is led into the shop. This is illustrated by the arrows 11, and respectively, 12 in Fig. 1. The effect losses thus, in the meaning that all energy supplied goes off as losses, are reversed, which implies that the refrigerating machine of the deep-freeze chamber is charged to a smaller degree because the energy amount supplied to the deep-freeze chamber is lower than at a conventional glass door.

From an economic aspect, of course, the glass door according to the invention implies that the energy costs for heating are halved at the same time as the cost of cooling away energy supplied to the deep-freeze chamber is reduced drastically. At a conventional door about 72-96 W/m2 are supplied to the deepfreeze chamber while at a door according to the invention about 28-32 W/m2 are supplied to the deep-freeze chamber.

Considering the simultaneous reduction of the energy demand on the refrigerating machine, according to the invention the total of saved effect per door is 73 W to 130 W.

What is said above in respect of deep-freeze chambers applies analogous to refrigerating chambers.

The invention, of course, can be varied in that the intermediate and/or the outer glass panes are made of a glass type other than window glass and, respectively, hardened glass.

The invention must not be regarded restricted to the embodiment described above, but can be varied within the scope of the attached claims.

Claims

1. A glass door for use for refrigerating and deep-freeze chambers, which comprises four glass panes arranged in parallel with each other and sealed against each other by sealing means extending about the edges of the panes; the front pane having heating means.

2. A glass door according to claim 1 wherein said heating means comprises an electrically conductive layer attached to the inner surface of the front pane.

3. A glass door according to claim 1 or claim 2 wherein said heating means is operable to effect heating at a rate of 50 W/m2 or less.

4. A glass door substantially as described herein with reference to and as illustrated in the accompanying drawing.

5. A refrigerating or deep-freeze chamber or cabinet having a door according to any preceding claim.