EP0209408A1 - Apparatus for thermochemical treatments at various temperatures and atmospheres, especially for car manufacturing - Google Patents

Abstract

The apparatus comprises, in succession: - a loading table (10) which ensures that the apparatus is fed with loads to be treated (22); - at least one low-temperature oven module (12); - at least one high-temperature oven module (14) receiving the loads originating from the low-temperature oven module; - a quenching tank module (16); - at least one gas-lock (18) common to the various treatment modules, this gas-lock being designed so as to ensure the transfer of loads between the low- and high- temperature modules and the quenching tank module, under a protective atmosphere; - load transfer mechanisms ensuring a continuous feed of loads to be treated and their removal after treatment; and - means ensuring distribution and control of the various atmospheres in the ovens. <IMAGE>

Description

The present invention relates to an installation designed so as to provide continuous thermochemical treatments, such as, in particular: gas carburizing, gas carbonitriding, nitriding, etc.

At present, these treatments are carried out either in charge ovens, or in one or two chamber ovens, or in continuous lines with pushing plates, and, in certain specific cases, in vertical ovens.

This invention proposes to provide an installation in which the treatment chambers are separated, in order to allow treatments at different temperatures and atmospheres.

• - une table de chargement assurant l'alimentation de l'installation en pièces à traiter, celles-ci étant disposées sur un support, tel qu'un plateau ;
• - au moins un module four basse température ;
• - au moins un module four haute température, recevant les pièces à traiter provenant du module four basse température ;
• - un module bac de trempe ;
• - un sas commun aux différents modules de traitement, ce sas étant conçu de façon à permettre les transferts de charge entre les modules fours basse et haute températures et le module bac de trempe sous atmosphère de protection ;
• - des mécanismes de transfert de charges, constitués : de moyens prévus sur la table de chargement pour assurer la prise des plateaux supportant les charges et leur évacuation vers la porte dudit sas commun ; d'un mécanisme de transfert longitudinal, disposé dans ledit sas commun et assurant, d'une part, le transfert des charges délivrées par la table de chargement jusque sur la sole du four basse température, et, d'autre part, le transfert des charges de la sole du four basse température à la sole du four haute température ; de mécanismes élévateurs, assurant l'alimentation des fours à partir dudit mécanisme de transfert longitudinal ; d'un mécanisme de transfert des charges du four haute température au bac de trempe ; d'un mécanisme de défournement de la charge du bac de trempe vers un sas de sortie de l'installation ; d'une table transporteuse assurant l'évacuation des pièces traitées dans l'installation, et de moyens assurant une distribution et une régulation des différentes atmosphères des fours.

An installation according to the present invention is characterized in that it comprises:

• - a loading table ensuring the supply of the installation with parts to be treated, these being arranged on a support, such as a tray;
• - at least one low temperature oven module;
• - at least one high temperature oven module, receiving the parts to be treated coming from the low temperature oven module;
• - a quenching tank module;
• - an airlock common to the various treatment modules, this airlock being designed so as to allow load transfers between the low and high temperature oven modules and the quenching tank module under a protective atmosphere;
• - load transfer mechanisms, consisting of: means provided on the loading table to take hold of the trays supporting the loads and their evacuation to the door of said common airlock; a longitudinal transfer mechanism, disposed in said common airlock and ensuring, on the one hand, the transfer of the charges delivered by the loading table to the floor of the low temperature oven, and, on the other hand, the transfer of loads from the bottom of the low temperature oven to the bottom of the high temperature oven; lifting mechanisms, supplying the ovens from said longitudinal transfer mechanism; a mechanism for transferring the charges from the high temperature oven to the quench tank; a mechanism for discharging the charge from the quenching tank to an airlock leaving the installation; a conveyor table ensuring the evacuation of the parts treated in the installation, and means ensuring a distribution and a regulation of the different atmospheres of the ovens.

According to a variant of this invention, designed so as to double the production of the treated parts, an additional low temperature oven module and a high temperature oven module are provided, and an additional common airlock connected to the existing airlock, the quench tank module then being common.

According to a characteristic of this invention, the low and high temperature ovens are of the lift type, the hearth of each oven being placed at the end of the rod of a vertical and guided hydraulic cylinder, during its vertical movements, so as to ensure the supply of the charges in said ovens as well as their evacuation.

• - la Figure 1 représente une installation selon l'invention, en coupe selon I-I de la Figure 2 ;
• - la Figure 2 est une vue en plan de l'installation représentée sur la Figure 1, en coupe selon II-II de la Figure 1 ;
• - la Figure 3 est une coupe selon III-III de la Figure 1 ; et,
• - la Figure 4 est une coupe selon IV-IV de la Figure 2.

Other characteristics and advantages of this invention will emerge from the description given below with reference to the appended drawings, which illustrate an embodiment thereof devoid of any limiting character. In the drawings:

• - Figure 1 shows an installation according to the invention, in section along II of Figure 2;
• - Figure 2 is a plan view of the installation shown in Figure 1, in section along II-II of Figure 1;
• - Figure 3 is a section on III-III of Figure 1; and,
• - Figure 4 is a section on IV-IV of Figure 2.

• - une table de chargement 10 ;
• - un module four basse température, désigné dans son ensemble par la référence 12 ;
• - un module four haute température, désigné dans son ensemble par la référence 14 ;
• - un module de trempe 16 (voir la Figure 2) ;
• - un sas commun 18, muni des différents moyens de manipulation des pièces à traiter, qui seront décrits en détail ci-après ;
• - une table d'évacuation 20 ; et,
• - des moyens assurant la distribution et la régulation des différentes atmosphères des fours.

The installation which is the subject of the present invention is of the modular type. In the embodiment illustrated in the drawings, it essentially comprises the following elements:

• - a loading table 10;
• - a low temperature oven module, generally designated by the reference 12;
• - a high temperature oven module, generally designated by the reference 14;
• - a quenching module 16 (see Figure 2);
• - A common airlock 18, provided with various means for handling the parts to be treated, which will be described in detail below;
• - an evacuation table 20; and,
• - means ensuring the distribution and regulation of the different atmospheres of the ovens.

In the embodiment described here, without limitation, the installation object of the invention is used to perform milking thermochemical elements, for example carbonitriding, on parts intended for the automobile industry, for example gearbox gears. These parts are placed on supports, such as refractory plates, introduced four by four into the installation. In the drawings, reference 22 designates such a charge.

The trays supporting the parts to be treated 22 are delivered to the installation using a means of transport such as a conveyor belt 24, from which they are transferred to the loading table 10. This ensures, on the one hand the grip of the plates 22 on the conveyor 24, and, on the other hand, their evacuation to the airlock 18, from which the plates are delivered to the various treatment ovens. This loading table essentially comprises a chassis 26 placed on the ground, comprising, at its upper part, two retractable ratchet bars 28, arranged on either side of the surface of the table, and controlled by means of a endless wheel-chain system, designated by the reference 30. A motor, hydraulic or electric, actuates the system 30, which is driven by an alternative movement of translation making it possible to transfer a plate 22 from the conveyor to the airlock, and a return to empty bars 28 for loading the following trays.

The airlock 18 is designed to transfer the charges 22 between the ovens 12, 14 and the quenching tank 16. In order to minimize the pollution of the protective gas maintained in this airlock, the latter is designed so that the the load is introduced via its lower part. For this purpose, the airlock includes a charging module 18 ', which is provided with a door 32 placed at the top of a lifting table 34, moved by any suitable means, such as a jack 36, for example . In FIG. 1, the lifting table 34 is shown in the high position (solid lines) and in the low position (mixed lines). It is understood that the load 22 is pushed onto the door 32 by the bars 28, then it is brought into the charging lock 18 'using the lifting table 34. In the high position, the door 32 is applied to a gasket that seals the airlock.

We will now describe, respectively, the low and high temperature oven modules 12, 14. These ovens are of the lift type, allowing simultaneous heating of all the faces of the load, and an elimination of all the drawbacks brought by the "hot doors ", such as atmospheric leakage, deformation, etc. These ovens 12 and 14 are therefore provided with movable hearths, respectively 38, 40, placed at the end of vertical hydraulic cylinders 42, 44, respectively, each hearth being guided during its vertical movements, in order to avoid any possible rotational movement. .

The carcass of the ovens is of cylindrical shape, and it comprises, in the upper part, a watertight pad 46, 48, respectively, and, in the lower part, a seal intended to receive the movable hearth 38, 40, respectively.

The heating system of the low-temperature oven 12 consists, for example, of heating frames such as 50, produced in extruded wires and positioned between the jacket 54 of the oven and a recirculation muffle 52. An internal and external metal lining is provided, as well as a filling of fibrous material (tablecloths and panels of mineral wool, for example), allowing any rapid change in temperature and quality of atmosphere. A continuous low nitrogen flow is provided inside the insulation thus produced, in order to avoid its pollution during production stoppages.

Recycling in the enclosure of the oven 12 is obtained using a centrifugal turbine 56, mounted on the roof of the oven and driven by a motor 58. This turbine draws the atmosphere into the useful volume of the enclosure of the furnace and the discharge outside the muffle 52, on the heating frames 50, from which this atmosphere is redistributed under the load. The circulation of the atmosphere has been shown diagrammatically by arrows in Figure 1. The oven has a conventional temperature control system (not shown).

• a) son chauffage est assuré à l'aide d'éléments tubulaires, tels que 60, suspendus à la voûte du four, par exemple à l'aide de tampons fixés de façon étanche à cette voûte. Etant donné que certains cycles de traitement peuvent exiger un refroidissement rapide de l'enceinte du four et de la charge qu'elle contient, les tubes sont raccordés à un ventilateur (non représenté) soufflant de l'air frais, permettant d'utiliser les éléments tubulaires de chauffage comme tubes de circulation d'air. Si on le désire, ce refroidissement peut être accéléré en prévoyant une circulation d'air frais dans un tube noyé dans le calorifugeage du four ;
• b) le brassage de l'atmosphère active sur la charge introduite dans le four est assuré par une turbine 62, entraînée par un moteur 64, soufflant directement au travers d'un moufle 66, à l'intérieur duquel est placé la charge. Pour éviter un craquage trop important du gaz d'atmosphère sur les éléments chauffants, l'arrivée de ce gaz est prévue à proximité de la turbine, côté soufflage.

The high temperature oven 14 is similar in design to the low temperature oven 12 which has just been described, except for the following points:

• a) its heating is ensured by means of tubular elements, such as 60, suspended from the roof of the oven, for example by means of buffers tightly fixed to this roof. Since certain treatment cycles may require rapid cooling of the oven enclosure and the load it contains, the tubes are connected to a fan (not shown) blowing fresh air, allowing the use of tubular heating elements such as air circulation tubes. If desired, this cooling can be accelerated by providing a circulation of fresh air in a tube embedded in the heat insulation of the oven;
• b) the mixing of the active atmosphere on the load introduced into the oven is ensured by a turbine 62, driven by a motor 64, blowing directly through a muffle 66, inside which the load is placed. To avoid excessive cracking of the atmospheric gas on the heating elements, the arrival of this gas is provided near the turbine, on the blowing side.

The quenching tank module 16 is surmounted by an airlock 68, allowing the charge to be transferred under an atmosphere before its immersion in the quenching liquid (oil) contained in the tank. A movable screen 70 protects the atmosphere of the transfer lock 18, during a quenching operation. This module includes an elevator, consisting of a lifting cage 72, in rigid profile, the platform of which receives the load, and which moves between guide columns. The elevator is suspended from a hydraulic cylinder 74, arranged in the upper part. The load, at the end of heating, is transferred from the high temperature oven to the platform of the lifting cage 72, where it is kept in the standby position in the soaking lock 68. It is then brought into the quench tank 16 , thanks to the displacement of the elevator, and, at the end of quenching, the elevator is reassembled, to allow the evacuation of the load after draining.

Heating of the quenching oil is ensured by electric immersion heaters 76, arranged on either side of the turbine 78 which mixes the oil bath. The oil is sucked at the top of the tank and discharged in the lower part via the conduits 80, emerging under the load maintained on the platform of the elevator 72, a set of deflectors ensuring distribution. Oil cooling is obtained by forced circulation of air outside the quench tank. The entire tank is provided with fins and a heat-insulated shell 82, delimiting a sheath 84 in which the cooling air circulates. The air circulation is ensured by a centrifugal fan motor unit 86, placed at the top of the tank, the air penetrating in the sheath 84 by the orifice 90 and being evacuated by the orifice 88, formed in the ferrule 82.

• - de tremper la charge dans un grand volume d'huile Calme, par exemple en effectuant un refroidissement de la charge jusqu'à 600°C environ ; pendant cette période, l'élévation, moyenne de la température de l'huile est de 10°C ; et,
• - de démarrer le brassage de l'huile environ 15 secondes plus tard.

The quenching tank module also includes conventional equipment such as: oil filtration system; automatic level control device; means for regulating the temperature of the quenching oil, and system for activating the stirring turbine 78. This latter system can be equipped with a time delay, allowing:

• - soak the load in a large volume of calm oil, for example by cooling the load to around 600 ° C; during this period, the average rise in oil temperature is 10 ° C; and,
• - start brewing the oil about 15 seconds later.

• - le transfert d'une charge 22 depuis le sas d'enfournement 18' jusque sur la sole 38 du four à basse température 12 ;
• - le transfert d'une charge 22 de la sole 38 du four à basse température à la sole 40 du four à haute température.

We have seen above that the common airlock 18 allows the transfer of the charges 22 between the ovens 12 and 14, and between the high temperature oven 14 and the quenching tank 16. This airlock is provided with a longitudinal transfer mechanism , which performs two functions:

• - The transfer of a load 22 from the airlock 18 'to the bottom 38 of the low temperature oven 12;
• - The transfer of a load 22 from the bottom 38 of the low temperature oven to the bottom 40 of the high temperature oven.

In the embodiment shown in the drawing, this longitudinal transfer mechanism consists of two endless chains 92,92 ', arranged on each side of the airlock, which drive a guided carriage 94 according to an alternative translational movement. Each of the above functions is associated with a push bar, such as 96, 96 ′, which is arranged in the carriages using lateral jacks, each bar being raised, in order to release the carriages, as soon as the movement corresponding to the function performed is performed. This arrangement makes it possible to carry out all the displacements of the loads by traction on the chains 92, 92 ′. The chains are driven using a motor, for example hydraulic.

The installation also comprises means for transferring the charges between the high-temperature oven 14 and the quenching tank. In this exemplary embodiment, in order to limit the overall size of the installation, these means are produced in the form of a hydraulic scissor mechanism 98, operating horizontally and controlled by hydraulic jack, the thrust head of this mechanism sliding on the rails supporting the plate on which the load rests (Fig. 2). It will be noted that, according to the invention, these mechanisms operate in a cold zone of the installation, the protective casings being removable in order to allow maintenance operations to be carried out on the exterior of the installation.

The same system is provided as described above for transferring the charges from the enclosure containing the quenching tank 16 to the airlock lock 100. This system has been designated by the reference 108, and it is preferably of the type with hydraulic scissors, identical to system 98.

The loading lock 100 is similar in design to the loading lock 18 'described above. It is designed so as to minimize the pollution of the protective gas maintained in the common airlock 18, and, for this purpose, the discharge of the charge is carried out by its lower part. This airlock 100 therefore includes a watertight door 102, placed at the top of a lifting table 104, moved by any suitable means, such as a jack 106 for example. In Figure 4, there is shown the lifting table 104 in the high position (solid lines) and in the position low (mixed lines). The load from the quenching module is thus delivered to the discharge table 20. The latter is of identical design to the loading table 10 described above.

From reading the above description, it will be understood that the installation which is the subject of the invention operates in the following manner; .

• a) brought parts to be treated, arranged on their trays, on the loading table 10;
• b) transfer of the loads, preferably four by four, into the airlock 18 ', thanks to the ratchet charging system 28 and to the lifting table 34;
• c) load transfer to the bottom of the low-temperature oven 12, using the system of bars 96 and the carriage 94, then introduction into the oven 12, thanks to the jack 42;
• d) treatment in this oven 12;
• e) transfer to the oven 14, via the bar system 96 - carriage 94 and the movable floor 40 of this oven 14;
• f) treatment in the oven 14;
• g) transfer from the oven 14 to the quench tank 16, via the transfer system 98, the bottom of the oven 14 having been brought to the low position;
• h) quenching of the charge;
• i) evacuation of the quenching tank, and discharge of the airlock by the system 98 and the lifting table 104;
• j) delivery of loads processed on the receiving table 20.

• - une table de chargement 10' ;
• - un sas commun 18', équipé de ses mécanismes de manutention des charges, comme décrit ci-dessus, ce sas supplémentaire étant raccordé au sas 18 de façon étanche, afin de constituer une seule enceinte ;
• - un module four basse température 12' ; et,
• - un module four haute température 14'.

The installation described above can be completed by adding the following additional equipment, which doubles production (see Figure 1):

• - a 10 'loading table;
• - A common airlock 18 ', equipped with its load handling mechanisms, as described above, this additional airlock being connected to the airlock 18 in a sealed manner, in order to constitute a single enclosure;
• - a 12 'low temperature oven module; and,
• - a high temperature oven module 14 '.

• - une très grande souplesse, en ce qui concerne les traitements thermiques sous atmosphère, grâce aux fours à atmosphère séparées ;
• - possibilité d'utiliser plusieurs systèmes de trempe, grâce à la conception modulaire de l'installation ;
• - possibilité d'effectuer des cycles thermiques rapides, étant donné que l'on maîtrise les atmosphères entre les différents fours de traitement.

Among the advantages provided by the invention, there may be mentioned in particular:

• - great flexibility with regard to heat treatments in an atmosphere, thanks to ovens with separate atmospheres;
• - possibility of using several quenching systems, thanks to the modular design of the installation;
• - possibility of carrying out rapid thermal cycles, given that the atmospheres between the different treatment ovens are controlled.

It remains to be understood that this invention is not limited to the embodiments described and shown, but that it encompasses all variants thereof.

Claims (13)

1. Installation of thermo-chemical treatments at different temperatures and atmospheres, characterized in that it successively comprises: - a loading table (10), which supplies the installation with loads to be treated (22); - at least one low temperature oven module (12); - at least one high temperature oven module (14), receiving the charges from the low temperature oven module -a quenching tank module (16); - At least one airlock (18) common to the various treatment modules, this airlock being designed so as to transfer the charges between the low and high temperature modules and the quenching tank module, under a protective atmosphere; _- charge transfer mechanisms, ensuring a continuous supply of loads to be treated and their evacuation after treatment; and, - means ensuring distribution and regulation of the different atmospheres of the ovens. 2. Installation according to claim 1, characterized in that the load transfer mechanisms (22) comprise means (28, 30, 32, 34) provided on the loading table to ensure the taking of loads and their evacuation to the door of said common airlock (18); a longitudinal transfer mechanism (92, 94, 96), disposed in said common airlock and ensuring, on the one hand, the transfer of the charges delivered by the loading table to the floor of the low temperature oven, and, on the other hand firstly, the transfer of the charges from the bottom of the low temperature oven to that of the high temperature oven; mechanisms elevators (42, 44), supplying the ovens from said longitudinal transfer mechanism; a load transfer mechanism (98) from the high temperature oven to the quench tank; a mechanism for discharging (108) the charges from the quenching tank to bring them into an exit airlock (100), and a conveyor table (20), ensuring the evacuation of the treated charges. 3. Installation according to one of the preceding claims, characterized in that the low and high temperature ovens (12, 14) are of the lifting type, the hearth (38, 40) of each oven being placed at the end of the rod a vertical cylinder (42, 44) and guided during its vertical movements, in order to ensure the supply of the charges in the respective ovens, as well as their evacuation after treatment. 4. Installation according to any one of the preceding claims, characterized in that the loading table consists of a chassis _- sis (26) placed on the ground, comprising, at its upper part, two retractable ratchet bars (28) to handle the loads, the ratchet bars being controlled using an endless wheel-chain system (30), driven by an alternating translational movement. 5. Installation according to any one of the preceding claims, characterized in that the low temperature oven module (12) comprises a movable hearth (38), heating means (50), positioned between the lining (54) of the oven and a muffle (52) in which the load to be treated is placed, an atmosphere recycling turbine (56) sucking the atmosphere inside the enclosure of said muffle and discharging it outside of the latter, on the means of heating, from where it is redistributed under the load, and temperature regulation means. 6. Installation according to any one of the preceding claims, characterized in that the high temperature oven (14) comprises a movable hearth (40), heating means produced in the form of tubular elements (60); an air cooling system, using said tubular elements as air circulation tubes by connecting them to a fan; a mixing turbine (62) for the active atmosphere on the load, this turbine blowing directly on the charge placed in an enclosure delimited by a muffle (66) channeling the atmosphere; and temperature regulation means. 7. Installation according to any one of the preceding claims, characterized in that the quenching tank module (16) is surmounted by an airlock (68) allowing the charge to be transferred under atmosphere before immersion, and in that it comprises an elevator (72) whose platform supports the load to be quenched, this elevator, moved by a jack (74), ensuring the transfer of the load from the high temperature oven, at the end of heating, to the quenching tank, and the discharge of the charge when the quenching is complete. 8. Installation according to any one of the preceding claims, characterized in that the airlock (68) of the quenching tank is isolated from the common airlock (18) by a movable door (70), in order to avoid any pollution of said common airlock . 9. Installation according to any one of the preceding claims, characterized in that the introduction of a load into the common airlock (18) is effected by the lower part of the latter, the load (22) being pushed by the ratchet bars of the loading table (10) on the movable door (32) of an airlock (18 '), this door being placed at the top of a lifting table (34) and coming apply, in the high position, to a seal ensuring the tightness of said airlock. 10. Installation according to claim 2, characterized in that said longitudinal transfer mechanism consists of two endless chains (92, 92 ') arranged on each side of the airlock and driving a guided carriage (94) moving the loads, bars retractable thrust (96, 96 ') ensuring the movement of the carriages, the drive of the chain system being effected by an alternative movement of translation. 11. Installation according to any one of the preceding claims, characterized in that the load transfer mechanisms from the oven high temperature to the quench tank, and from the latter to the discharge table, are of the hydraulic scissor type (98, 108). 12. Installation according to any one of the preceding claims, characterized in that the discharge table (20) is of similar design to the loading table (10). 13. Installation according to any one of the preceding claims, characterized in that it further comprises: an additional loading table (10 '); an additional common airlock (18 '), equipped with its load handling mechanisms, this additional common airlock (18') being tightly connected to the common airlock (18), so as to produce a single enclosure; an additional low temperature module (12 '), and an additional high temperature module (14').

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