The invention relates to a heating oven developed for spindle type tempering process used in production lines of tableware glass products (plates, bowls, glasses, etc).

Background of the Invention

Tempering is a process in which thermal treatment is applied to the glass in order to increase the thermal and mechanical strength thereof. First, the glass is homogeneously heated to a temperature close to the softening point (65Q-700°C), and immediately thereafter it is rapidly cooled down under jet stream (air jets). In this manner, while the outer glass surface becomes solid by being cooled down rapidly, the inner portion at the plastic forming temperature is stressed under pressure. As a consequence, compression stress occurs on the outer glass surface while tensile stress is formed in the inner portion.

The thus produced tempered glass product has higher thermal shock endurance and mechanical breaking strength and when broken, it breaks into small pieces.

In tempering process, heating the glass homogeneously throughout the entire wall thickness to the tempering temperature is critical in terms of the tempering process. In this process, the glass products are carried by means of the so-called metal baskets (i.e. tournette) in tunnel-type ovens and heated along the oven.

In the spindle type tempering furnaces of prior art, the heating tunnel construction is made of a refractory structure absorbing the heat. The burners, the heat sources, are locally located on the tunnel side surface and they heat the tunnel refractory structure with a flame having a temperature between 1300°C and 1700°C. The technical problems regarding such ovens used in the known state of the art are explained below:

• The need for heating the entire refractory structure constituting the oven to a suitable temperature: In order to ensure a homogeneous temperature distribution, the refractory structure, which is heated and cooled slowly, is required to be heated entirely, A refractory structure of a high density (2-2.5 kg/nr) is needed for heat absorption and radiation. A time period of at least 10-12 hour is needed in order for the system to be ready for the tempering process. Hence, the heating process requires high power consumption.

• Low insulation due to the flame burning inside the system: Since the system in the state of the art is an open-flame system, the flame root temperature as well as the temperature of the regions being subject to flame increases excessively, and so it becomes compulsory to use high temperature-resistant materials in these regions. Therefore, not only the insulation of the oven becomes difficult but also heat losses over the wall increase.

• High power consumption: Due to the need for heating the oven as a whole and location of the flame at long intervals inside the oven, the oven must be supplied with energy more than required for heating the glass product. This, in turn, increases power consumption.

One of the applications used in the state of the art with a view to overcome these technical problems and which differs from the typical open-flame ovens described above is the Patent Application No. US5594999. This invention discloses an oven with radiant emitting walls in which the temperature distribution is provided by radiation energy. The radiant emitting walls generate primarily infrared radiation and have a non-uniform temperature distribution so that the temperature of the lower portion of the oven can be selectively adjusted to be significantly higher than the temperature of the upper portion. The burners that are linearly disposed allow for a homogeneous temperature distribution.

Summary and Objects of the Invention

In the heating oven according to the invention, a radiant type burner which performs flameless radiation and emits heat via convection is used as a heat source. The energy is supplied all along the oven and with the used burner system and burner location, an efficient convective heating and radiation is provided for heating the glass product and the medium.

Thanks to the fact that the open flame used in the ovens within the state of the art is not utilized in the oven according to the invention, it becomes possible to use a refractor (0,2 - 0.5 kg/m ³ ) with a lower density, With the elimination of the indirect transfer of the energy to the product, the power consumption values are reduced; and also with the elimination of the need for heating the refractory structure, unlike the state of the art, it is made possible that the oven reaches the temperatures to start the tempering process at a much shorter time (2 - 4 hours).

It is aimed by developing the heating oven according to the invention to:

• Achieve a homogeneous temperature distribution, and thus heat the glassware product homogeneously as a result of supplying the energy to the system ail along the oven,

• Heat the glass product and the environment more efficiently and homogeneously with the efficient and joint use of the convection and fiame!ess burning effect formed on the porous surface,

• Perform a better insulation thanks to the advantages provided by the radiant heating and homogeneous burning,

• Obtain a power consumption 30 - 50% less than that of the ovens in the state of the art,

• Start the production process more rapidly thanks to the shorter time required for the tempering furnace to reach the tempering temperatures (tempering conditions) than that in the state of the art, and

• Increase the process efficiency by 5 - 10%.

Description of the Drawings

The drawings for a better understanding of the heating oven developed with the present invention and the explanations related thereto are given below. Fsg, li Cross-sectional view of the tunnel oven with radiant heating. Fig, 2; Front view of the radiant burner inside the tunnel.

Description ©f the Parts/ Sections/ Aspects forming the Invention The parts and components which are shown in the drawings illustrating the heating oven developed with the present invention for a better understanding of the invention are enumerated individually and the reference numbers corresponding thereto are presented below.

1, Glass product 2, basket

3, Shaft for the basket

4, Tunnel oven with radiant heating

5, Low-density tunnel insulation construction

6, Insulation concrete 7, Insulation brick (low density)

8. Radiant burner

Detailed Description of the Invention

In the heating oven (4) developed with the present invention, there exist more than one heating zones and a radiant burner (8) is used for each zone, said radiant burner extending along the related zone. The radiant burner (8) is positioned at the same height as the glass product (1) in the outer portion of the oven tunnel such that the porous reactor configuration in the front surface thereof will face the interior of the oven (4). The burning occurs in the burner in the radiant burner (8) and the porous configuration (reactor) disposed in the front surface of the burner (8) radiates towards the oven (4) interior.

The burner surface temperature of the radiant burner (8) used in the oven (4) according to the invention may reach up to the temperature value of 1200°C.

The top and side wail of the oven (4), on which the radiant burner (8) is positioned, are covered with low-density (0.2 - 0.5 kg/m ³ ) insulation construction (5), wherein said construction (5) has a geometry starting from the reactor portion in the front surface of the radiant burner (8) and expanding towards the inner portion of the oven (4) and thus, the heat formed in the (8) burner is distributed into the oven (4) and by way of radiation and convective.

The employed low-density insulation construction (5) also prevents the radiant burner

(8) from being affected by the high temperature (600°C - 700°C) inside the oven (4). Thus, there is no longer any need for an additional insulation for protecting the burner reactor configuration against burning.

Furthermore, the wall of the oven (4) facing the radiant burner (8) consists of two layers: the low-density insulation brick (7) above and the low-density insulation construction (5) below; on the other hand, the bottom of the oven (4) on which the spindle (2) located on the shaft (3) carries the glass product (1) along the oven (4) is covered with insulation concrete (6), having a space in order for the spindle (2) to move along the oven (4) tunnel.

The heating oven (4) according to the invention may be used for in-line and off-line tempering of tableware glass made of opal, soda-lime or borosiiicate glass in spindle type tempering system.