Glass furnace

Abstract

The invention relates to a furnace comprising a metal box provided with a bottom and a crown, an inlet and an outlet, the furnace further comprising means for conveying a substrate between the inlet and the outlet of the furnace, characterized in that the furnace further comprises a fairing made of at least one metal sheet arranged around the furnace.

Description

TECHNICAL FIELD

[0001] The present invention relates to a furnace for treating a glass substrate. BACKGROUND

[0002] The present invention relates to a furnace for treating a substrate, in particular glass. Substrates, in particular glass, sometimes need to be heat treated to improve their properties or to shape them. This heat treatment enables the substrate to be hardened or annealed.

[0003] The furnaces used for this heat treatment are based on a metal box, which can be two parts (a bottom and a crown), and for example the crown is retractable to access the conveyor and the rollers. The entire unit is internally insulated to limit the working temperature to around 700°C, or even lower (around 500°C) for furnaces used for laminated glass.

[0004] While this principle ensures perfect insulation of the heating zone, it does not prevent the dissipation of residual heat on the sheet metal surface. This small amount of dissipation is enough to cause an imbalance in the heating of the furnace interior. This defect is clearly visible on the industrial equipment and its positioning in the workshop. The presence of walls, open areas or doors outside the workshop has an impact on the natural or forced air flow in the workshop. This has a direct impact on the heating imbalance. Since the heat exchange has a preferential side, it is not uncommon to compensate for the heating of the furnace on one side in order to achieve balanced heating of the glass. SUMMARY

[0005] The aim of the present invention is to provide a furnace which solves the problems of the prior art by providing improved insulation and thermal uniformity.

[0006] To this end, the present invention relates to a furnace comprising a metal box provided with a bottom and a crown, an inlet opening and an outlet opening, the furnace further comprising conveyor means for conveying a substrate between the inlet and the outlet of the furnace, characterized in that it further comprises a fairing consisting of at least one sheet metal and arranged around the metal box, the fairing being arranged to comprise an inlet opening aligned with the inlet opening of the box and an outlet opening aligned with the outlet opening of the box.

[0007] According to one example, the fairing is arranged to provide a gap between the box and the fairing.

[0008] According to one example, the fairing comprises a layer of insulating material associated with the sheet metal.

[0009] According to one example, the fairing comprises at least one opening.

[0010] According to one example, the at least one opening is controllable.

[0011] According to one example, said at least one opening is arranged on an upper portion of the fairing and / or on a lower portion of the fairing.

[0012] In one example, said fairing comprises a plurality of openings uniformly spaced.

[0013] According to one example, said fairing comprises a system for recovering air from the openings.

[0014] According to one example, said air recovery system comprises a manifold for collecting hot air from said at least one opening and at least one duct connecting said manifold to the furnace.

[0015] In one example, the furnace comprises additional heating means connected to said duct of the air recovery system.

[0016] According to one example, the fairing is arranged at a distance of between 1 and 20 cm from said furnace.

[0017] According to one example, the crown is mounted so as to be movable with respect to the base, said fairing comprising a fairing portion for the crown, a fairing portion for the bottom, the two portions being connected by a connecting portion.

[0018] According to one example, the connecting portion comprises extension means enabling the connecting portion to allow continuity between the first and second housings. BRIEF DESCRIPTION OF DRAWINGS

[0019] Other particular features and advantages will become clear on reading the following description, given by way of indication and in no way limiting, with reference to the annexed drawings, wherein: - Figure 1 a profile view of a furnace is shown; - Figure 2 and 3 a profile view and an elevation view of a furnace according to the present application are shown; - Figure 4 a variant of a fairing with a thermal insulation layer is shown; - Figure 5 a variant of a fairing with openings is shown; - Figure 6 a variant of a fairing with a heat recovery system is shown; - Figures 7 to 9 different views of a variant of a furnace according to the present application with telescopic portions are shown. DETAILED DESCRIPTION

[0020] Figure 1The invention shown in figure 1 is a furnace 10 according to the application. The furnace according to the application is used for the heat treatment of substrates of the plate or sheet type, preferably glass plates or glass sheets. This furnace is based on a metal box, which can be in two parts: a bottom 11 and a crown 12. The bottom is associated with conveying means 13, such as a roller bed, to allow the substrates S to be able to move through the furnace.

[0021] The whole unit is insulated internally to limit the working temperature to around 700°C, or even lower (around 500°C) for a laminated glass furnace.

[0022] The furnace comprises an inlet and an outlet to enable the substrates to pass through the furnace.

[0023] According to the application, the furnace also comprises an external fairing 20 as seen in Figure 2 and Figure 3 The external fairing 20 is then superimposed on the metal box to form the furnace. This external fairing 20 serves to provide insulation for the furnace. This fairing 20 is monolithic in that it surrounds the entire furnace, i.e. the bottom and the crown, with the exception of the inlet and outlet openings. It will be understood that the metal box comprises the inlet and outlet openings and that the fairing also comprises the inlet and outlet openings. The fairing openings are aligned with the openings of the box. The fairing is made of metal. The fairing is composed of a single sheet of metal sheet 21 cut and deformed to form the fairing for the furnace, or of several sheets of metal sheet or in the form of metal sheets 21 attached to each other. This attachment is achieved by welding, bolting or riveting. The fairing is attached to the box to form the furnace. Since the fairing is not a structural part of the furnace, the furnace can function without the fairing.

[0024] The fairing is spaced apart from the box to define a gap between the box and the fairing.

[0025] The purpose of this external fairing is to improve the insulation performance of the furnace by suppressing thermal radiation. Indeed, the gap between the box and the fairing is closed, acting as a thermal compensator and a direct barrier to external elements.

[0026] The fairing 20 also comprises a layer of thermal insulation 23 on the surface of the fairing facing the box, as shown in Figure 4 The layer of thermal insulation 23 can take the form of a thermal insulation fabric or a thermal insulation sheet. It is of metal material and can be aluminized. The layer of thermal insulation 23 can also be of the asbestos type.

[0027] This layer of thermal insulation 23 serves to improve the insulation function of the furnace.

[0028] If the cowling 20 is to limit the thermal radiation, it must be arranged in an effective manner. To this end, the cowling is designed to be positioned at a distance from the oven. This means that there is a gap e between the cowling and the oven. This gap allows air to circulate between the oven and the cowling. This air circulation allows hot air to circulate, thus ensuring a uniform temperature around the oven.

[0029] To achieve effective air circulation, the distance between the oven and the cowling must be between 1 and 20 centimetres. Below this spacing, the gap is not large enough for air circulation, which can lead to temperature differences. Above this spacing, the distance between the oven and the cowling becomes too large, resulting in temperature gradients.

[0030] In one variant, the cowling 20 comprises regulation means 30. Indeed, whether or not combined with a thermal insulation layer, the cowling makes it possible to ensure that the oven is heated as uniformly as possible. However, the presence of a thermal insulation layer can lead to the accumulation of thermal energy and heat. This heat accumulation can lead to an increase in the temperature of the oven itself, its structure and mechanical parts. If this temperature increase is too great, it can lead to damage to the oven. The regulation means 30 are intended to evacuate the excess heat.

[0031] As shown in Figure 5 , these regulation means 30 comprise at least one opening 31, preferably at least two openings on the cowling. This / these opening(s) 31 generates air flow to regulate the temperature.

[0032] This opening or these openings 31 are arranged on the upper part of the cowling or on the lower part of the cowling 20. This means that the upper part is the top of the oven and the lower part is the bottom of the oven.

[0033] These openings 31 are controllable, i.e. they can be opened and closed. This type of opening comprises, for example, louvres that can be moved to open or close the opening. The opening can also be equipped with rotating louvres. These louvres rotate to open the opening to a greater or lesser extent. Of course, the openings 31 are arranged in a uniform distribution. This uniform distribution of openings prevents temperature gradients. Preferably, the openings 31 are controlled so that the temperature inside the closed space formed by the cowling is at most 90°C, preferably 80°C.

[0034] In another variant, the cowling 20 comprises at least one opening 31, preferably arranged on its upper part. This opening is associated with an air recovery system 40, as shown in Figure 6 . This system comprises a hood or manifold 42. This manifold 42 is arranged above the opening to recover hot air. This hot air is recovered and reinjected into the oven. More specifically, this hot air can be used to feed an auxiliary heating system or additional heating means 48, such as hot air jets. These hot air jets serve various purposes.

[0035] The first is to use these hot air jets to locally heat the substrate. These jets can be controlled to apply heat to specific parts of the substrate for specific treatments.

[0036] The second is to use these jets to pre-heat the substrate. To do this, the jets are located at the entrance to the oven.

[0037] To deliver this hot air to the jets, the recovery system also comprises ducts 44 connecting said manifold to the jets.

[0038] The air recovery system 40 optionally comprises a turbine 46 for increasing the flow, as shown in Figure 6 The turbine 46 can be used to suck in the hot air into the fairing and to eject it into the jets.

[0039] The air recovery system also comprises an optional supplementary heating system to heat the sucked-in warm air to the desired temperature.

[0040] In one variant, the crown 12 is for example a retractable crown providing access to the transport means and to the rollers. Thus, the crown is movable relative to the base, as can be seen in Figure 7 In this case, the fairing is adapted to allow this crown mobility. To do this, the fairing comprises two independent shells linked by a connecting portion, as shown in Figure 8 The first independent shell is dedicated to the fairing of the crown and the second shell is dedicated to the fairing of the base, and the connecting portion links the first shell to the second shell. Thus, the connecting portion comprises extension means enabling it to allow continuity between the first shell and the second shell.

[0041] The connecting portion can take several forms. A first form consists in having a connecting portion comprising several plates that slide relative to one another with stops to limit the sliding, as can be seen in Figure 9 Thus, when the crown is raised or lowered, these plates slide relative to one another to ensure continuity.

[0042] In a second form, the connecting portion comprises several rows of links. Each row pivots relative to the adjacent row (or rows). When the crown is raised or lowered, these rows of links.

[0043] Of course, the application is not limited to the examples shown, but various variants and modifications can be made, as will be apparent to those skilled in the art.

Claims

1. A furnace (10) comprising a metal box provided with a bottom (11) and a crown (12), an inlet opening and an outlet opening, the furnace further comprising conveying means (13) for conveying a substrate between the inlet and the outlet of the furnace, characterized in that, The furnace further comprises a fairing (20) consisting of at least one sheet metal (21) and arranged around the metal box, the fairing being arranged to comprise an inlet opening aligned with the inlet opening of the box and an outlet opening aligned with the outlet opening of the box.

2. The furnace according to the preceding claim, wherein, The fairing is arranged to provide a gap between the box and the fairing.

3. The furnace according to the preceding claim, wherein, The fairing comprises a layer of thermal insulation material (23) associated with the sheet metal (21).

4. The furnace of any of the preceding claims, wherein, The fairing comprises at least one opening (31).

5. The furnace of claim 4, wherein, The at least one opening (31) is controllable.

6. The furnace of claim 4, wherein, The at least one opening is arranged on an upper portion of the fairing and / or on a lower portion of the fairing.

7. The furnace of any of the preceding claims, wherein, The fairing comprises a plurality of evenly spaced openings.

8. The furnace of any one of claims 4 to 6, wherein, The fairing comprises a system (40) for recovering air from the openings.

9. The furnace according to the preceding claim, wherein The air recovery system comprises a manifold (42) for collecting hot air from the at least one opening and at least one duct (44) connecting the manifold to the furnace.

10. The furnace according to the preceding claim, wherein The furnace comprises an additional heating device (48) connected to the duct of the air recovery system.

11. The furnace of any of the preceding claims, wherein, The fairing is arranged at a distance of between 1 and 20 centimetres from the furnace.

12. The furnace of any of the preceding claims, wherein, The crown is mounted so as to be movable relative to the base, the fairing comprising a fairing portion for the crown, a fairing portion for the bottom, the two portions being connected by a connecting portion.

13. The furnace of any of the preceding claims, wherein, The connecting portion comprises extension means enabling the connecting portion to allow continuity between the first and second housings.

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