CA2330065A1

CA2330065A1 - Continuous method for producing a refrigerator

Info

Publication number: CA2330065A1
Application number: CA002330065A
Authority: CA
Inventors: Karl Werner Dietrich; Hans Gunter Vleurinck
Original assignee: Individual
Current assignee: Bayer AG
Priority date: 1998-04-28
Filing date: 1999-04-16
Publication date: 1999-11-04
Also published as: HUP0101686A2; JP2002513134A; DE19818890A1; CN1298482A; ZA200005543B; TR200003132T2; PL343762A1; ES2181435T3; ATE221979T1; EP1075634A1; WO1999056068A1; AU4030999A; BR9910026A; DE59902274D1; HUP0101686A3; KR20010043078A; EP1075634B1

Abstract

The invention relates to a method for producing a refrigerator, characterized in that a continuously produced foam sandwich element is cut into measured sections or mitre-cut and arranged as shown in Figures 1, 2 and 3 so as to form a box which is open on two sides.

Description

Le A 32 764- foreign countries ' -1-Continuous process for the production of a fr~d~e The invention relates to the production of a fridge from continuously produced sandwich foam elements.
Cooling and freezing units are conventionally back-filled with foam on stationary supporting moulds. These supporting moulds have the task of supporting the prepared outer and inner parts of the housing in spaced manner against the foaming pressure which arises. Any one producer will require a large number of supporting moulds corresponding to the large number of different models varying in design, size and unit wall thickness. An important factor is the position of the housing in the supporting moulds; a door aperture-upwards moulding position is conventionally preferred.
This position of the units is of great significance for uniform distribution of the foam and achievement of the foam properties, since the length of the flow path which the foam has to travel is determined thereby. However, it is impossible to produce units entirely devoid of bubbles and air pockets. Furthermore, relatively large variations in bulk density always occur, which results in an increased material requirement.
The object of the invention was to provide a process for the production of a fridge from foam elements, in which the use of supporting moulds may be dispensed with.
The invention thus provides a process for the production of a fridge, in which sandwich elements are continuously manufactured with corresponding outer layers and cut to size (Fig. 1) or cut in a mitred manner as in Fig. 2. The blank is folded three times, as in Fig. 3, and connected at the joint. This produces a box open on both sides, the sides of which represent the side walls, the base and the top. The rear may either be foamed-in-place in moulds, as hitherto conventional, wherein the moulds are substantially simpler than the conventional supporting moulds, or a sandwich element produced in the same process and cut to the appropriate length may be foamed-in-place or mounted. The remaining opening is closed by a door of appropriate design, which is either produced conventionally or may be a sandwich element produced on a twin belt.

Le A 32 764 _2_ Rigid polyurethane foam is preferably used as the foam in the process according to the invention.
In a variant of the process according to the invention, production of the pre-cut element proceeds according to Fig. 4, said element then being folded together in accordance with Fig. 5 to form base, rear wall and top; the side walls are then either foamed-in-place or attached as continuously produced sandwich elements which have been cut into sections. With this continuous production method, the necessary seals for the front of the fridge, for example, may be continuously foamed-in-place.
In the process according to the invention, the conventional outer layers may be foamed-in-place directly and continuously. The complex production of metal box profile parts and the complex and high-loss thermoforming of the liner may be dispensed with. Moreover, considerable quantities of materials may be saved in the case precisely of the liner owing to the uniform thickness of the thermoplastics. The complex prefabrication of different housing sizes may likewise be dispensed with, as may the high levels of investment for cores and mould carriers for back-filling with foam and thermoforming. Any variation in insulation thickness may be simply established by means of the gap width of the twin conveyor belt.
The labour-intensive incorporation of vacuum insulation panels into the insulating layer in conventional processes is also substantially simplified, these vacuum insulation panels being introduced during said continuous process. They may optionally be attached to an outer layer by the application of a portion of the foam and then the remaining volume may be introduced by the foam in oscillating or stationary manner in a twin belt (see Figs. 6 and 7).
The great advantage of the continuous production according to the invention over the traditional production of cooling units in corresponding supporting moulds lies in the uniform production of the polyurethane foam with ordered and defined cell structure.
The cell structure of the foam may namely be oriented horizontally and Le A 32 764-Foreign _3_ anisotropically in the direction of travel on a twin conveyor belt (see Fig.
9). Such orientation of the cells ensures that the foam has a markedly better coefficient of thermal conduction in the direction of thickness, which is also the service direction in the refrigeration unit, than an isotropic foam structure or even an amsotropic S orientation in the direction of the cross section.
Figures 1 to 11 Le A 32 764 Examples Comparative Example 1: Variations in bulk density Twin conveyor belt: 31 to 32 kg/m3 Housing: 31 to 35 kg/m3 It is clear from Comparative Example 1 that S to 10 % total bulk density may be saved by the process according to the invention in the case of a comparable minimum bulk density.
Bulk density is provided by the quotient of mass and volume. A rigid foam test specimen is cut from the panel, which is measured and weighed.
Comparative Example 2: Coefficient of thermal conduction 1) Isotropic foam: 20.5 mW/Km 2) Anisotropic foam: 19.5 mW/Km (cell orientation horizontal) (measurements performed with an n-pentane-blown polyurethane system) 3) Cooling and freezing unit: 22.5 - 23.5 mW/Km (measurements performed with an n/i-pentane-blown polyurethane system) Comparative Example 2 provides an approximately 10 % lower coefficient of thermal conduction; experience shows that this results in 5 to 7 % lower energy consumption in refrigeration units with the same wall thickness.
The thermal conductivity of foams is measured using the 2-plate method (according to Poensgen) and is defined to DIN 52 612. Measurements are performed at different temperatures (conventionally -18 to +25°C). The average temperature difference between the measured temperatures amounts to 10°C. Measurement of thermal Le A 32 764 conductivity is directly based on the current strength and voltage of the hotplate and this measurement may thus be designated an absolute method.

Claims

1. Process for the production of a fridge, characterised in that a continuously produced foam sandwich element with horizontally, anisotropically oriented cell structure is cut to size or cut in a mitred manner and is arranged to form a box open on 2 sides.

2. Process for the production of a fridge, characterised in that a continuously produced sandwich element with horizontally, anisotropically oriented cell structure is cut in a mitred manner, cut into sections and arranged to form a U- or W-shaped member.

3. Process for the production of a fridge according to claim 1 or claim 2, characterised in that the rear wall or the side walls are foamed-in-place in corresponding supporting moulds.

4. Process for the production of a fridge according to claim 1 or claim 2, characterised in that the rear wall or the side walls are formed of sandwich elements according to the invention cut to appropriate lengths, which elements are secured mechanically or by adhesives or by foaming-in-place.

5. Process for the production of a fridge according to any of claims 1 to 4, characterised in that vacuum insulation panels are introduced during the continuous foaming process, preferably by being foamed-in-place on an outer layer prior to entry into the compression zone.

6. Process for the production of a fridge according to any of claims 1 to 5, characterised in that metallic outer layers or outer layers of organic polymers are used as the outer layers.

7. Process for the production of a fridge according to any of claims 1 to 5, characterised in that paper, preferably a paper/aluminium foil complex, is used as the outer layer on one or both sides.

8. Process for the production of a fridge according to any of claims 1 to 7, characterised in that side profiles are used during sandwich production which may form the front closure of the fridge or may also be used as assembly aids.

9. Process for the production of a fridge according to any of claims 1 to 8, characterised in that components for final assembly, such as for example door hinges, seals, lines, together with components such as evaporators are introduced into the twin belt so as to be rigidly foamed in.