SE530124C2 - Arrangement and method of heating metal objects - Google Patents

Description

The inlet of the intermediate chamber communicates with the outlet of the front and rear chambers. In this way, the drive of the spout will generate a rear gas circulation which passes twice through the conveyor and a front gas circulation which also passes twice through the conveyor.

In one embodiment, a temperature sensor is located inside the jacket and is connected to a control device which controls the temperature of the heating element as a function of a nominal value and a value indicated by the temperature sensor. The temperature sensor may be located in the front chamber, between the conveyor and the outlet of the front chamber.

In some embodiments, the arrangement comprises a number of hubs and a number of heating elements which are arranged in rows extending perpendicular to the direction of movement of the conveyor. The heating arrangement can be followed by a cutting device which cuts metal objects which have been heated by the heating arrangement.

The invention also relates to a method for heating metal objects. The method comprises passing on a permeable conveyor the metal objects through an inner space which is enclosed by a jacket and by inner walls divided into a rear jug, at least an intermediate chamber and a front chamber. As the conveyor passes through said at least one intermediate chamber, the lu fi is heated up and the heated air is blown through the conveyor. A first part of a heated air which has passed through the conveyor in said at least one intermediate chamber is diverted to a rear air circulation. The rear liquor circulation is caused to pass through the conveyor in the rear chamber and back to said at least one intermediate chamber. A second portion of a heated air which has passed through said at least one intermediate chamber is diverted to a front air circulation. The upper air circulation passes through the conveyor in the front chamber and back to said at least one intermediate chamber. i In a form of dehumidification, the leaching temperature inside the jacket is measured and the heating of the air is regulated as a function of a nominal value and the measured value. A suitable nominal value for the ternperattir may be 70 ° C. If the temperature is measured, this can be done in the front frame at such a position that the air temperature is measured or that it has passed through the conveyor in the front chamber. In an advantageous embodiment, the air is heated by a heater located inside said at least one intermediate chamber, the temperature of the heater being kept in the range of 200-300 ° C.

The metal objects are elongated metal rods. The heating can advantageously be followed by a subsequent operation such as cutting metal rods. The heating operation itself can then be seen as part of a method for heating and cutting metal rods.

FIGURE DESCRIPTION FIG. 1 is a schematic cross-sectional view of a heating arrangement according to the present invention.

Fig. 2 is a cross-sectional view taken along the line II-II in Fig. 1.

Fig. 3 is a schematic representation of a cutting device.

F ig. 4 Illustrates the operation of the cutting device shown in Fig. 3.

Fig. 5 is a schematic cross-sectional view of a heating arrangement according to an alternative embodiment.

DETAILED DESCRIPTION OF THE INVENTION Referring to Figs. 1, the invention relates to an arrangement 1 for heating metal objects 19, in particular as a preparatory operation which precedes a subsequent cutting operation. In the embodiments illustrated in Fig. 1, metal objects such as elongate rods 19 are placed in a bearing 20. The metal objects 19 can be loaded on a conveyor 17 and transported through the heating arrangement 1. In order to be able to eject objects such as elongate rods 19 from the bearing 20, the bearing 20 be provided with one or more flexible elements 37 on which the metal objects rest in the bearing 20. If the flexible element 37 is shortened, the rods 19 are lifted up and the weight will cause the rods 19 to fall onto the conveyor 17. The flexible element 37 can e.g. . be one or more straps 37 which can be made shorter by winding one end of the strap 37 on a reel (not shown). In the embodiment illustrated in Fig. 1, the conveyor 17 is provided with teeth 18 which make the transmission to the conveyor more reliable and also keeps the rods 19 at a distance from each other on the conveyor 17.

The heating arrangement 1 comprises a jacket 2 which encloses an inner space 3.

The jacket 2 has an entrance opening 4 and an exit opening 5. Inside the jacket 2 divide inner walls 6, 7 of the inner space 3 in a rear chamber 8, at least one intermediate chamber 9 and a front chamber 10. The conveyor 17 is pennable for lu fi and extends from the inlet opening 4 of the jacket 2 to its outlet opening 2, via the rear 10 15 20 25 30 35 530 124 P1897 48, intermediate 9 and the front chamber 10. In this way, objects 19 loaded on the conveyor 17 can be transported through the chambers 8, 9. , 10 from the inlet opening 4 to the outlet opening 5. In the embodiment of Fig. 1, the conveyor extends past the casing 2, on both sides of the casing 2. The conveyor 17 can be followed by a cutting device 31 which is symbolically indicated in Fig. 1. After a metal object such as an elongate rod 19 has been heated in the heating arrangement 1, it becomes somewhat softer and can be more easily cut into smaller pieces by the cutting device 31.

In said at least one intermediate chamber 9, a genuine 21 is arranged to direct an air (or possibly another gas) towards the conveyor 17 and objects 19 which are placed on the conveyor 17. A heating element 22 in the intermediate chamber 9 is arranged to heat air which flows from the 21 shaft 21 before the lug reaches the conveyor 17. In the embodiment illustrated in Fig. 1, the fl shaft 21 is driven by a motor M which may be an electric motor M. The electric motor M is preferably located inside the intermediate chamber 9, together with the kten shaft 21.

The chambers 8, 9, 10 are connected to each other in such a way that at least one outlet 14 of said at least one intermediate chamber 9 communicates with the rear chamber 8, 10. At least one outlet 14 of the intermediate chamber 9 communicates with the front chamber 10 and at least one inlet 13 of the intermediate chamber 9 communicates with outlets 12, 16 of the front and rear chambers 8, 10. In this way, operation of the 21 shaft 21 will generate a rear air circulation which passes twice through the conveyor 17 and an irrational air circulation. which also passes twice through the conveyor 17. As indicated in Fig. 1, a dividing wall 23 may be located at the outlet 14 of the intermediate chamber 9. The dividing wall 23 has the function of dividing the air flow from the intermediate vessel 9 into an upper air circulation and a rear air circulation.

In one embodiment, a temperature sensor 25 is located inside the jacket 2 and is connected to a control device 26 which controls the temperature of the heating element 22 as a function of a nominal value and a value indicated by the temperature sensor 25.

The temperature sensor 25 is preferably located in the inner chamber 10 between the conveyor 17 and the outlet 16 of the front chamber 10, but it may also be located in other places, e.g. in the intermediate chamber. The heating element 22 can e.g. be an electric loop. As indicated in Fig. 2, certain embodiments of the arrangement according to the invention may comprise a plurality of hooks 21 and a plurality of heating elements 22 which are arranged in rows extending perpendicular to the direction of movement of the conveyor 17. In a realistic embodiment of the heating, the arrangement may comprise 12 fans 21 and 12 heating elements 22. In a realistic embodiment, each heating element 22 can be dimensioned for about 3500 W. With 12 heating elements, the entire heating arrangement could then provide 42 kW.

The operation of the inventive arrangement is as follows. Metal objects 19 on the permeable conveyor 17 are caused to pass through the inner space 3 enclosed by the jacket 2 and through the comrade 8, 9, 10 of the inner space. 1, metal objects 19 move through the inner space 3, from left to right, in the direction of the arrow A. Luñ is blown by the fan 21 towards the permeable conveyor 17 and through the conveyor 17, as the conveyor 17 passes through the intermediate chamber 10.

Before the air reaches the conveyor 17, the air is heated by a heating element 22 which may be an electric heating element 22. When the heated air passes through the conveyor 17, the metal objects 19 are heated by the air. The permeable conveyor 17 and the objects 19 loaded on the conveyor act as a throttle which forces an increase in the speed of the air as it passes through the conveyor 17. The increased air velocity improves the heat transfer to the metal objects 19. In a realistic embodiment the air velocity can be about 8 -10 rn / s when the hot air passes through the conveyor 17. Preferably, there is no restriction other than that represented by the conveyor 17. In other parts of the system, the air flow can be relatively slow, which reduces friction losses. Immediately downstream of the shaft 21, the lu speed may be about 4 rn / s in a realistic embodiment of the invention.

When the hot air has passed the conveyor 17 and transferred some of its heat energy to the metal objects 19, a first part of the heated air is diverted to a rear air circulation RA which is led to the rear chamber 8, through the conveyor 17 in the rear chamber 8 and back to said at least one intermediate chamber 9. A second part of the heated air which has passed through the conveyor 17 in the intermediate chamber 9 is diverted to a front air circulation FA which is led to the front chamber 10 and through the conveyor 17, when the conveyor 17 passes through the front chamber 10. The air in the front air circulation FA is then led back to the intermediate chamber 9. 10 15 20 25 30 35 530 124 P1897 6 It is preferred that the motor M motor 21 be located inside the casing 2 of the arrangement. To place the motor M outside the jacket 2 would result in a more complicated design. If the motor M is an electric motor, it must realistically be expected that the motor will malfunction or collapse if the ambient temperature becomes too high. For electric motors that are available today and that the carriers love, the ambient temperature should preferably not exceed 70 ° C. In a preferred embodiment of the invention, the temperature inside the jacket 2 is measured and the heating of the air is regulated as a function of a nominal value and the measured value. In the form of exhaust illustrated in Fig. 1, a temperature sensor 25 is located in the front chamber 10 adjacent the conveyor 17, so that the temperature of the air is measured after it has passed through the conveyor 17 one last time before it reaches the shaft 21 again. 25 may be located elsewhere, this particular position is considered appropriate because the air temperature will not change much from this point before the air reaches the fan 21 again. Other suitable positions for the sensor 25 may be further downstream in the front circulation FA, i.e. . closer to fl marriage 21.

The position of the sensor 25 can thus be anywhere in the front chamber 10, between the conveyor 17 and the outlet 16 of the upper chamber. The sensor 25 can also be located in the intermediate chamber, upstream of the shaft 21 and its motor M.

As indicated in Fig. 1, the temperature sensor 25 may be connected by a cable 28 to a control device 26, such as e.g. a thyristor. In the discharge form shown in Fig. 1, the thyristor 26 can be connected by means of a cable 30 to a further control device 27, such as a computer 27. The thyristor 26 can also be connected by means of a cable 29 to the heating element 22. The computer 27 gives a nominal value for the temperature to the thyristor 27, while the actual temperature value is given by the sensor 25, via kabehi 28. The thyristor can then regulate the working power of the heating element (s) (22) by increasing or decreasing the working power. To protect the motor M of the fl shaft 21, the temperature measured by the temperature sensor 25 should preferably not be allowed to exceed 70 ° C. This means that the nominal value given by the date 27 is 70 ° C. To the extent that the motor M is capable of operating reliably at temperatures above 70 ° C, the temperature measured by the temperature sensor 25 can be allowed to be correspondingly much higher. In the embodiment shown in Fig. 1, the thyristor 26 is connected to the heating element, the temperature sensor 25 and the computer 27 by means of cables or wires 28, 29, 30. However, the thyristor 26 may also have wireless communication with these elements.

If electric loops are used as heating elements, the temperature of the loop or loops 22 can be kept in the range of 200-300 ° C so that the air reaching the conveyor in the intermediate chamber 9 has a temperature which is also in the range of 200-10. 124 P1897 7 300 ° C. The life expectancy of electric loops depends strongly on the temperature at which the loops are heated. For loops that are commercially available today, the expected service life is almost unlimited if the temperature does not exceed 300 ° C.

Of course, the temperature of the air will be much lower after the air has passed twice through the conveyor 17 and some of the heat of the air has been transferred to the metal objects 19. The metal objects to be heated can normally be heated to temperatures well above 300 ° C without harmful effects occur on the metal objects themselves. The temperatures used are instead limited by the desired life of motor M or the desired life of the loops 22.

As mentioned earlier, the heating arrangement 1 can be followed by a cutting device 31.

With reference to Fig. 3, a possible design of a cutting device will now be explained. The cutting device may comprise a fixed tool 32 and a movable tool 33. A channel 34 extends through the fixed tool 32 and the movable tool 33.

A piston 35 is arranged to strike the movable tool 33. A damping element 36 may be included to receive the impact from a cutting stroke and return the movable tool 33 to its original position. When a metal rod 19 is to be cut, the rod is inserted into the channel 34 so that it extends through the fixed tool 32 and into the movable tool 33. The punch 35 strikes the movable tool 33 as indicated in Fig. 4 and the rod 19 is cut off. Of course, a suitable cutting device 31 can take many other forms. If the rods have been heated before the cutting operation, the cutting will be easier and the cut surface can be smoother and smoother.

In a realistic embodiment, the heating arrangement and method can be used to heat stainless steel rods with a length of about 5.5 m and a diameter of 16 ~ 25 mm. With cutting devices available today, such rods can then be cut into 180 pieces over a period of about 50 seconds. This means that new rods must be added quickly and continuously.

The inventors have found that the use of heated air has an advantage over the use of induction heating. When objects such as elongate metal rods 19 are heated, it can be difficult to achieve even heating of the rods when induction heating is used. Then e.g. elongated stainless steel rods are heated by induction, the surface of the rods can be heated to a harmful temperature while internal parts of the rod are still too cold to allow the rod to be cut as easily as desired. The inventors have also found that objects with a shiny surface are more difficult to heat by induction. Objects with a glossy surface 10 15 20 25 30 35 530 124 P1897 8 surface can include objects made of stainless steel. Stainless steel has poor thermal conductivity, which makes it more difficult to heat such objects. The inventors have found that it is more efficient to heat metal objects such as stainless steel rods by convection than to heat the metal objects by induction. A practical way of heating by convection is to cause the rods to pass through a flow of heated air. As indicated earlier, a realistic embodiment of the invention may comprise 12 fans and 12 heating coils where each has a capacity of 3.5 kW, so that the total heating arrangement can provide 42 kW. To achieve a comparable heating power for stainless steel by induction, the required power would be about 100 kW. Furthermore, the induction heating could cause damage to the surface of the stainless steel bars.

A practical problem associated with the heating process is that the metal objects heated by the hot air can have very different enclosure temperatures. Rods to be cut are often stored outdoors and can be taken in from an outdoor warehouse directly for cutting. Depending on the season and climate, the temperature of the rods can very well vary from below -30 ° C to above +3 0 ° C. This means that the requirements for heating operation can vary greatly. Furthermore, the size of the objects, e.g. the diameter of the stainless steel bars, the degree of heating required. To control the temperature of the rods to be cut, it is desirable that the amount of heating can be controlled. The use of the temperature sensor and the control equipment such as the thyristor makes it possible to control the temperature to which the rods are heated. This ensures that the rods, when they reach the cutting device, will always have the same temperature. In addition, the fan motor M can be protected from heat and it is easier to ensure a long life of the loops 22.

The division of the heating device into three separate chambers 8, 9, 10 is for the following reasons a very troublesome design. Immediately downstream of the 21 shaft 21, there is an overpressure on the fan is in operation. However, the throttling formed by the conveyor 17 in combination with the suction power generated by the shaft 21 in the rear chamber 8 and the front chamber 10 will have the effect that a negative pressure is created in the rear and the front chamber. This counteracts leakage to the environment by heated air. Therefore, this has the advantage that less energy is required to run the process.

In order to heat stainless steel rods with a diameter of 16-25 mm, it may be convenient to keep the rods at a distance of approximately 50 mm from each other on the conveyor. The gap is determined by the distance between the teeth 18 of the conveyor 17.

In realistic embodiments of the heating, the distance from the inlet opening 4 to the outlet opening 5 can be about 7 00-1000 mm, which allows at the same time about 14-20 bars inside the heating arrangement 1.

It is also to be understood that the temperature control system described above may also be used for heating arrangements which are not divided into three separate chambers. It should also be understood that the concept of using three separate chambers can be used regardless of whether the temperature is measured and regulated or not.

However, the temperature control is preferably combined with the principle of using three separate chambers.

There may be two or more intermediate chambers, each with its own set of fans 21 and heating elements 22.

An alternative embodiment will now be described with reference to Fig. 5. In Fig. 5, the rear chamber 8 according to the embodiment in Fig. 1 has been completely eliminated and the entrance opening 4 leads directly into the chamber 9 where 22 are located. In this form of exhaust there is no intermediate chamber but only an inlet chamber 9 and an outlet chamber 10.

An alternative way of describing this embodiment would be to say that there is only a first chamber 9 and a second chamber 10, the element (s) 21 and the heating element (s) 22 being located in the first chamber 9.

Apart from the elimination of the rear chamber 8, the embodiment in Fig. 5 functions in substantially the same way as the discharge form in Fig. 1. When the heater (s) 22 and the fls / fls 21 are located in the first chamber 9 adjacent to the outside of the jacket 2, it can be expected that heat losses through the inlet opening 4 will be greater than in the embodiments according to Fig. 1. Therefore, it is assumed by the inventors that the embodiment according to Fig. 5 is less advantageous than the embodiment in Fig. 1.

However, the leakage of hot air to the surrounding atmosphere will still be somewhat reduced because there will still be a negative pressure in the second chamber 10, which counteracts leakage of hot air through the outlet opening 5.

The invention can thus be described in a more general manner, such as an arrangement and a method in which air is heated in a chamber 9 and blown by a real fan or fan 21 through a permeable conveyor 17 and in which at least a part of the air is diverted to at least one further chamber 8, 10 and is passed back in a loop to the chamber in which the lid has first been heated. In principle, this may even include two-chamber embodiments where heating takes place in the second chamber 10, although it is believed by the inventors that such an embodiment is less inferior to the embodiments of Figs. 1 and Fig. 5.

Since the invention has been described above in terms of an arrangement and an mG10d, it is to be understood that these categories reflect various aspects of the invention. Therefore, the method of the invention may include any method step which would constitute a natural consequence of using the inventive arrangement, OaVSßfI Whether such steps have been explicitly mentioned or not.

Claims (1)

1. 0 1597 25 5 35 P1s974 530 124 11 CLAIMS 1) Arrangement (1) for heating metal targets (19), which arrangement comprises: 2) 3) a) b) d) a jacket (2) enclosing an interior space (3), which jacket (2) has an entrance opening (4) and an exit opening (5); inside the jacket (2), inner walls (6, 7) dividing the inner space (3) in a rear chamber (8), at least one intermediate chamber (9) and a front chamber (10); a permeable conveyor (17) extends from the inlet opening (4) of the jacket (2) to the outlet opening (5) of the jacket (2), via the rear (8), intermediate (9) and front chamber (10), so that objects loaded on the conveyor (17) can be transported through the chambers (8, 9, 10); in said at least one intermediate chamber (9), a fl genuine (21) arranged to direct a gas fl fate towards the conveyor (17) and objects (19) placed on the conveyor (17); in said at least one intermediate chamber (9), a heating element (22) arranged to heat a gas flowing fi- from fl the spout (21), before the gas reaches the conveyor (17); and wherein the chambers (8, 9, 10) are connected to each other so that at least one outlet (14) from said at least one intermediate chamber (9) communicates with the rear chamber (8 10), at least one outlet (14) from the intermediate the chamber (9) communicates with the front chamber (10) and at least one inlet (13) of the intermediate chamber (9) communicates with outlets (12, 16) from the inner and the rear chamber (8, 10), so that during operation of the fan (12), a rear gas circulation is generated which passes twice through the conveyor (17) and a front gas circulation which also passes twice through the conveyor (17). Arrangement according to claim 1, wherein a temperature sensor (25) is located inside the jacket (2) and is connected to a control device (26) which controls the temperature of the heating element (22) as a function of a nominal value and a value indicated by the temperature sensor (2). 5). Arrangement according to claim 2, wherein the temperature sensor (25) is located in the front chamber (10), between the conveyor (17) and the outlet (16) of the front chamber (10). Arrangement according to claim 1, wherein the arrangement comprises a plurality of fl pegs (21) and a plurality of heating elements (22) which are arranged in rows extending perpendicular to the direction of movement of the conveyor (17). A method of heating metal objects (19) comprising the steps of: a) on a permeable conveyor (17) causing the metal objects (19) to pass through an inner space (3) enclosed by a jacket (2) and by inner walls (6, 7) divided into a rear chamber (8), at least one intermediate chamber (9) and a front chamber (10). b) heating air and blowing the heated air through the conveyor (17) as the conveyor (17) passes through said at least one intermediate chamber (10), c) diverting a first part of the heated air which has passed through the conveyor (17) in said at least one intermediate chamber (9), to a rear air circulation which is caused to pass through the conveyor (17) in the rear chamber (8) and back to said at least one intermediate chamber (9); and d) diverting a second part of the heated air which has passed said at least one intermediate vessel (9), to a front air circulation which is caused to pass through the conveyor (17) in the fi-upper vessel (10) and back to said at least an intermediate chamber (9). Method according to claim 5, wherein the lu fi temperature is measured inside the jacket (2) and the heating of the air is regulated as a function of a nominal value and the measured value. A method according to claim 6, wherein the temperature is measured in the front chamber (10) at such a position that the air temperature is measured after it has passed through the conveyor (17) in the front chamber (10). A method according to claim 5, wherein the air is heated by a heater (22) located inside said at least one intermediate chamber and the temperature of the heater (22) is kept in the range of 200-300 ° C. The method of claim 6, wherein the nominal value is 70 ° C. A method according to claim 5, wherein the metal objects (19) are elongated metal rods (19). Arrangement (1) allows heating of metal targets (19), which arrangement comprises: a) a jacket (2) enclosing an inner space (3), which jacket (2) has an entrance opening ( 4) and an exit opening (5); b) inside the jacket (2), at least one inner wall (6, 7) as parts of the inner space (3) in separate chambers (8, 9, 10); c) a permeable conveyor (17) extending fi from the entrance opening (4) of the jacket (2) to the exit opening (5) of the jacket (2), via separate core carriers (8, 9, 10), so that objects (19) loaded on the conveyor (17) can be transported through the chambers (8, 9, 10); d) in at least one of the chambers (9), at least one fl genuine (21) which is arranged to direct a gas fl destiny towards the conveyor (17) and objects (19) placed on the conveyor (17); e) at least one heating element (22) arranged to heat a gas flowing from said at least one fl pair (21), before the gas reaches the conveyor (17); i) and wherein the core frames (8, 9, 10) are connected to each other in such a way that lu fi which has been heated in a chamber (9) and blown through the conveyor (17) of said at least one fl pair (21), is diverted to at least an additional chamber (8, 10) and led back in a loop to the chamber (9) in which lu fi one was initially heated, the further chamber (8, 10) being a chamber (8, 10) with an inlet opening (4) or an exit opening (5) for the conveyor (17).