GB2139554A

GB2139554A - Heat shrinkage apparatus

Info

Publication number: GB2139554A
Application number: GB08409531A
Authority: GB
Inventors: Andreas Streng; Sabine Streng; Manfred Rohstock; Erhard Blechschmidt
Original assignee: Nagema VEB
Current assignee: Nagema VEB
Priority date: 1983-05-02
Filing date: 1984-04-12
Publication date: 1984-11-14
Also published as: GB2139554B; DE3407145A1; GB8409531D0; FR2545414A1; DE3407145C2; DD217482A1

Abstract

Shrinkage apparatus for thermoplastics foils, comprising a housing open at two ends, heat radiators disposed in the housing and a conveying device passing through the housing. The internal space of the housing is of spherical or parabolic form and all elements situated in the internal space are constructed with radiation- reflecting surfaces. The objective of the invention is to reduce the specific energy consumption of the apparatus while assuring high shrinkage quality. The task is to keep the shrinkage chamber small and to reduce the emission factor. All elements situated in the internal space of the housing may be constructed as polished metal components, or all surfaces oriented towards the interior of the housing and also the surfaces of the conveying rolls of the conveying device coated with a polished, radiation-reflecting facing. Radiators and conveying device can be switched on as a function of the shrinkage units that arrive. <IMAGE>

Description

SPECIFICATION Shrinkage Apparatus This invention relates to a shrinkage apparatus for thermoplastics foils, comprising a housing open at two ends, heat radiators disposed in the housing and a conveying device passing through the housing.

Shrinkage apparatuses of various functional types are known. The majority are operated with hot air, the air being heated by known suitable means and circulated in the shrinkage chamber.

Shrinkage apparatuses are, however, also known, in which hot gas is used. In a further known solution, heat radiators are used in the shrinkage chamber.

In all known functional principles, the specific energy consumption is very high. Consequently, solutions have already been proposed from time to time, by which the energy consumption can be reduced, by keeping the heat losses as low as possible. Thus, for example, in shrinkage apparatuses operating with hot air, screens or orifice plates and closure plates for the feed opening are provided (DE-OS 24 47 016) or heat locks are provided (DE-OS 1 9 30 097) Both these measures are suitable for reducing heat losses in continuous methods of operation.

Nevertheless, the heat energy to be suppiied by heat throughput and between the shrinkage processes, which should be regarded as loss, still remains very high. In the case of hot air heating, this loss is also very difficult to get rid of.

While heat readiators are used, by contrast, it has already been proposed to switch on the radiators only intermittently, that is when an article wrapped with shrink foil passes the radiators (DE-OS 22 33 182). In this shrinkage apparatus, and in all others which operate in through flow and with radiators, the shrinkage chamber is cubic, which leads to a relatively large surface area, and it possesses a surface structure which absorbs radiant heat. Only the radiators are backed by radiation-reflecting means. Both of these features lead to the result that a relatively large quantity of thermal energy is stored. The same is true also for the conveying means used.

The stored heat, is, however, given up to the surroundings, when the shrinkage tunnel is emptied. This again implies energy losses.

The objective of the invention is to reduce the specific energy consumption in shrinkage apparatuses which operate with heat radiators, while still assuring high shrinkage quality.

In accordance with the energy transport law, as a consequence of radiation between solid, selfenclosed objects, the energy absorption and consequently the later emission is at its lowest when the irradiated surface and the emission coefficient are low. Deduced from this, the task underlying the present invention is to keep the shrinkage chamber small and to reduce the emission factor compared with known shrinkage apparatuses.

According to the invention this task is achieved in that the internal space of the housing is of parabolic or spherical form and all the elements situated in the internal space of the hollow sphere are constructed with radiation-reflecting surfaces.

All the elements situated in the internal space of the housing are constructed as polished metal components or all the surfaces oriented towards the interior of the housing and also the surfaces of the conveying rolls of the conveying apparatus and coated with a polished, radiation-reflecting facing. Radiators and conveying equipment can be switched on as a function of the shrinkage units that arrive. Due to the chosen internal form of the shrinkage chamber as a parabaloid, or especially a hollow sphere, the smallest possible surface area is achieved and due to the radiationreflecting surfaces of all the elements situated in the radiation zone, a low emission factor is achievable. In this way an energy consumption lower by 50% to 85% than that of known shrinkage apparatuses can be achieved.

The invention will be explained in more detail below with reference to an example of embodiment thereof shown in the accompanying drawing.

The associated drawing shows an apparatus highly schematically in longitudinal section. The shrinkage apparatus consists of a housing 1, erected on a frame, the housing possessing at two opposite ends housing openings 2 for the passage of the package P to be shrunk. The housing openings 2 are covered by curtains 3, which consists of individual, overlapping strips.

The curtains are of a heavy material in the upper part and light material in the lower part, so that they easily slide off the package. In the interior of the housing 1, a shrinkage chamber 4 is provided, which consists of a hollow sphere 5 made from steel sheet. At each of two opposite ends, a portion or sector of a sphere is cut away from the hollow sphere 5, so that two openings analogous to the housing openings 2 are produced. On the internal surfaces of the hollow sphere and on the internal surfaces of the curtains, an aluminium coating 6 is sprayed, this coating being polished.

The entire internal surface of the hollow sphere is covered with heat radiators 7 at closely spaced intervals.

In the lower region of the hollow sphere, a conveying means 8 is provided. It consists of two drive chains 9, between which conveying rolls 10 having a polished surface are rotatably mounted at close spacings. The conveying rolls 10 constituting the upper side of the conveyor are carried by support rails 11 disposed on both sides, along which the freely rotatable conveying rolls 10 roll when loaded. At either end of the housing 1, a conveyor belt 12; 1 3 respectively is disposed in front of the housing openings 2, for the purpose of feeding and removing the packages P. All three conveying elements 12, 8 and 13 are drivingly connected by intermediate chains 14. The conveyor belt 12 is driven by a motor 1 5 through the intermediary of a drive chain 1 6.

After a package P, assembled in a collecting packing machine and wrapped in shrink foil, has been completed, a microswitch is actuated, by which the motor 15 is switched on. The conveying means 12, 8 and 13 are thereby brought into action, with the result that the package P to be shrunk is conveyed into shrinkage chamber 4 and the package already situated in the shrinkage chamber is conveyed out of same. The conveying distance is determined by a timing element, which is so adjusted that the package is moved to the centre of the shrinkage chamber 4. At this instant, the motor 1 5 is switched off and the heat radiators 7 are briefly switched on. The switched-on period is controlled by a second timing element. The latter is set as a function of the shrinkage behaviour of the foil.

After the heat radiators 7 have been switched off, the package P remains in the shrinkage chamber 4 until a new package is ready.

Claims

1. Shrinkage apparatus for thermoplastics foils, comprising a housing open at two ends, heat radiators disposed in the housing and a conveying device passing through the housing, characterized in that the internal space of the housing (1) is of parabolic or spherical form and that all the elements situated in the internal space (4) are constructed with radiation-reflecting surfaces.

2. Shrinkage apparatus according to claim 1, characterized in that all the elements situated in the internal space of the housing are constructed as polished metal components.

3. Shrinkage apparatus according to claim 1, characterized in that all the surfaces oriented towards the interior of the housing and the surfaces of the conveying rolls (10) of the conveying device are coated with a polished, radiation-reflecting facing.

4. Shrinkage apparatus according to claim 1 and one other claim, characterized in that the radiators (7) and the conveying device can be switched on as a function of the shrinkage units that are present.

5. Shrinkage apparatus substantially as herein described with reference to the accompanying drawing.