ARRANGEMENT FOR LEADING HUMID AIR INTO A HEAT TREATMENT OVEN LIKE INTO A ROAST OVEN FOR BAKERY PRODUCTS

The invention relates to an arrangement to conduct humidified air into a heat treatment oven of goods, as for instance into a bakery oven of bakery products, which oven comprises a conveying track, along which the products are conveyed to the oven, arrangements of holes fitted in the oven, through which moving of products into the oven and out from it is carried out by means of said track, and an equipment heating the oven, as a gas burner.

Previously known, from patent publication WO 01/59370, among others, is a water or steam feeding system arranged inside the oven, where the air in the oven is recycled through a channel portion into the oven, and in this channel portion water or steam is added to the air. The humidity of the oven is measured also in the said channel portion.

In this solution the humidity added to the air in the oven does not especially reach the products getting baked in the oven in case the content of humidity in the air is great and the surface temperature of the products close to the dew point. If one wants the humidity to have any effect on the products, there must in the oven be a relative humidity .In order to produce humidity in evaporating water, it will in this solution take a part of the heating energy in the oven. All wall constructions in this solution are quite close to the dew point temperature and certain parts of the wall are perforce just in this temperature. It is possible to conduct humidified air mainly to place, from where water is sucked into the channel portion included in the evaporator. Elsewhere in the oven the air stays still or circulates slowly and humidification does not reach so far. The solution presented above also enlarges the necessary oven volume. If in the solution water is fed to the channel portion in order to get evaporated, it reduces the temperature of return air strongly. If in the channel portion steam is added to the air, a separate steam generator is needed somewhere else, from where the steam is conducted to the channel portion.

By means of the humidification arrangement according to the invention, certain above presented disadvantages appearing in the present solutions are avoided and an essential and a surprising improvement of the control of the humidity of baking ovens is achieved. The humidification arrangement according to the invention is characterized in that the

arrangement includes a humidification unit mountable/after-mountable outside the oven, comprising a heated massive evaporator unit and nozzle units spraying water into it, whereby in the outer unit of said oven steam is produced, and steam is arranged to be conducted together with the conveying track through the same hole into the oven.

The advantage of the invention is that the humidification can be directed to a certain part in the oven, especially to the forepart, and if needed, also to the goods in the oven itself. When into the oven steam is conducted, in other words humidifed air from the inlet hole of the oven, it has at once in the forepart of the oven an effective humidification effect on the relatively cold bakery products in the forepart of the oven and even later on still in the direction of the oven. Humidity does not escape from the oven, because it is fed from the inlet hole. Due to humidity, the surface of goods closes, at least by bakery products, and prevents humidity from vanishing off the inside of goods. Since the humidification arrangement is formed as a movable unit, it can be moved or moved afterwards into connection with an oven that needs it. By means of the solution a built-in in equipment in the oven can be replaced.

In the following the invention is disclosed with reference to the enclosed drawing, where Fig. 1 presents an oven seen from the side. Fig. 2 presents a massive humidification unit seen from the side.

Figure 1 shows a bakery oven 1 of bakery products through which products 3 to be baked move along conveying track 2. In both ends of oven 1 there are arrangements of holes, by way of which products 3 can by means of track 2 move into and out from the oven. The heating of the oven is taken care of, for instance, by burner 11, which uses fluid gas. Figure 1 shows a humidification unit placed with its whole breadth, in front of the oven above track 2, which is a separate mountable unit or as an afterwards mountable unit to replace former humidification equipment in the oven.

To humidification unit 4 water is brought pre-heated or without that through nozzles 6. The nozzles are water spraying nozzles, out of which a jet of dispersed water or of fog discharges to the massive evaporating unit 5. Figure 1 shows the location of jets 6 in humidification unit 4 outside the oven, which is at the same time also a channel portion for return air from the oven along channel, which air is by means of blower 8 returned to the oven through

the inlet hole in the oven. Humidification unit 4 is a of channel extension for said return air. New air is taken under control through branch channel 9. The flow arrangement is so made that the air humidified through the inlet hole of the oven strives into the oven. Most suitably the oven is kept under low pressure. Blower 8 is as to its capability adjustable and the intake quantity of new air from channel 9 is adjusted, for instance, by means of a damper shown in figure 1.

Figure 2 shows a massive evaporator unit 5 with the construction opened, which construction comprises a rear board 12, which has grooves for heating elements 10, further a massive front board 13, towards which the water jets are directed. The construction is in use kept tilted.

The front board 13 comprises certain transverse levels, which are, for instance, only step surfaces, where water drops do not stay for long. In the step surfaces there can situated grooves 14, whereby water drops stay longer on the steps. The grooves are in one embodiment from their one end or both ends dropping water downwards, and under the unit there is a collecting basin, into which not-evaporated drops fall.

The construction of figure 2 is collected to a unit in placing the heating elements in the grooves of the rear board 12 and the front board 13 is connected tightly to the rear board. The front or rear board or both of them are, for instance of steel or stone, so as to get enough mass for them. Also cast iron can come into question as well as ceramic materials.

In the oven a sensor that measures information of humidity can be placed and on basis of it an adjusting device to control the spraying. Since the nozzles of jets 6 work at best only on a certain pressure and flow area, the most suitable way to adjust them is adjustment of the length of the spraying cycle. Heating elements 5, as electric resistances are most suitably controlled by means of a thermostat sunk into the front board.

The equipment is as a separate unit easily mounted in front of the oven. Easy access to the equipment only opening the capsular wall in the front.