JPS6328188Y2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Field of Industrial Application The present invention relates to an internal heating type sintering furnace for heating and sintering a powder molded product in a tight box placed in a chamber.

(b) Prior art The process of heating and sintering powder molded products using organic agents such as paraffin or wax as a forming medium requires a wax removal process and a sintering process to prevent the harmful effects of vaporized gases such as wax generated during heating. Conventionally, it has been common to carry out the bonding process in separate furnaces, but recently some systems have appeared in which this process is carried out continuously in a single furnace. However, in this type of sintering furnace, there is an inconvenient problem in that carbon-containing vaporized gas generated in the process of removing the wax and the like adheres to and permeates the furnace wall, heat insulating material, etc. and contaminates the inside of the furnace. Once the furnace walls become contaminated, wax gas, etc. re-vaporized from the furnace walls during the high-temperature preliminary to main sintering stages will cause carburization of the sintered product, degrading its properties. .

In order to deal with such problems, the applicant has previously devised a continuous sintering furnace of this type so that the furnace wall surface, insulation material, and other internal materials would not be contaminated during the wax removal process. We offer what we have.
That is, as shown in Japanese Patent Application No. 57-129327, this system adopts an internally heated structure in which a tight box (inner chamber) that can be opened and closed is placed in a chamber (furnace body), and in particular, it uses wax, etc. In the removal process, when the tight box is in the closed state, a difference is made between the inside and outside of the tight box to make the inside of the tight box relatively low pressure through a ventilation system passage provided to communicate the inside of the chamber with the inside of the tight box. The structure is such that the vaporized gas generated from the molded product within the tight box can be directly discharged to the outside together with the atmospheric gas without leaking from the tight box to the chamber.

By the way, in this conventional system, the ventilation system path necessary to generate a differential pressure between the chamber and the tight box is formed by actively utilizing the gap in the door attached to the tight box. There is. However, with such a structure, while there is no need to provide a dedicated ventilation path, the mounting and holding structure of the door to the tight box is complicated and dimensional accuracy is required, and furthermore, the gas flow from the tight box into the chamber is complicated. There is also the disadvantage that it cannot have a function to prevent backflow of water.

(c) Purpose The present invention has been developed with attention to this point, and uses the above-mentioned differential pressure generation method to directly discharge the atmospheric gas inside the tight box to the outside when removing wax, etc. As for the thermal sintering furnace, by devising the means for installing the necessary ventilation system, the structure can be simplified, and at the same time,
The purpose is to more completely prevent gas leakage and at the same time increase the versatility of the sintering furnace.

(d) Configuration In order to achieve the above objectives, the present invention
It is constructed by arranging an openable/closable tight box having a gas exhaust port in a chamber having at least a gas inlet and an exhaust port, and when the tight box is closed, the inside of the chamber and the inside of the tight box are connected. A pressure difference is generated between the inside and outside of the tight box through a ventilation system passage provided so as to communicate with each other, and the atmospheric gas inside the tight box is directly discharged to the outside from the gas exhaust port. In the internal heating type sintering furnace configured, the ventilation system path is provided in a part of the tight box, for example, a door that opens and closes the tight box, and a mechanism is provided to prevent backflow of gas from the inside of the tight box to the inside of the chamber. It is characterized by

(E) Embodiment An embodiment of the present invention will be described below with reference to the drawings.

In the internal heating type sintering furnace shown in FIG. 1, a chamber 1 has lids 1a, 1a provided at both ends thereof so as to be openable and closable, and is opened at an appropriate position on its peripheral wall to serve as a gas inlet 2. It has an exhaust port 3,
Each is connected to a gas supply device or a gas suction device (not shown) via valves 2a and 3a, respectively. Inside this chamber 1, a tight box 4 supported by a support member (not shown) is arranged, and a powder molded product a etc. is charged into the box 4 and subjected to a series of sintering processes. That will happen. A heater 6 is installed on the outer periphery of the tight box 4,
Furthermore, a heat insulating wall 7 is provided to surround these. Further, the tight box 4 has a gas outlet 8 opening at one side of its lower part, and communicates with a wax processing container (not shown) or the like via a valve 8a. Furthermore, both ends of the tight box 4 are closed by doors 5, 5 so as to be openable and closable. The doors 5, 5 are integrally formed by lining the inner surface of a thick heat insulating main body 5a with an inner wall 5b forming the lid of the tight box 4, respectively. That is, the doors 5, 5, which are lined with the inner door wall 5b, each have their outer ring members 10 gimbally supported by the brackets 9 protruding from the upper inner surface of the chamber lid 1a, at both peripheral edges thereof in a direction orthogonal to the vertical direction. It is mounted eccentrically (not shown). Therefore, the doors 5, 5 move in conjunction with the opening operation of the chamber lid body 1a, and are swingable about both the vertical and horizontal axes. The door 5, which is lined with the inner wall 5b, supports and abuts the connecting rod 13 of the actuating cylinder 12, which is inserted from the outside, on the bracket 11, which is connected in an overhanging manner at the lower end of the outer ring member 10. , is opened and closed by the expansion and contraction operation of the operating cylinder 12. The tight box 4 and the heat insulating body 5a are made of fired graphite, and the heat insulating wall 7 and the door inner wall 5b are made of graphite felt.

Next, in the center of the door 5 lined with the inner wall 5b, a ventilation member 14 is provided to form a ventilation path that communicates the inside and outside of the tight box 4. This ventilation member 14 serves as a fixing pin for fixing the door inner wall 5b of the tight box 4 to the inner surface of the heat insulating body 5a, and at the same time has a ventilation path in which a check valve is interposed. That is, as shown in FIG. 2, this ventilation member 14 has flange portions 15a, 15a for fastening at both ends, and is inserted into the ventilation hole 15c of the outer cylinder 15, which has stepped ventilation holes 15b, 15c inside. , stepped ventilation hole 16a, ball 16
b. An inner cylinder 16, which is provided with a biasing spring 16c and a plug member 16d and forms a check valve, is screwed into the inner cylinder 16. Therefore, the ventilation member 14 allows the gas to flow only into the inside of the tight box 4, and prevents the gas from flowing back to the outside of the tight box 4.

In addition, in the figure, 17 is a baffle plate mounted on the door 5, 18 is a stirring fan disposed facing the opening of the baffle plate, and 19 is a stirring fan that is used as a rotational drive source to move the chamber lid. A motor attached to the outside of the body 1a is shown, and 20 indicates an electrode of the heater 6.

The operation of the sintering furnace described above will be explained.
First, open the interlocking chamber lid 1a and tight box door 5, charge the powder molded product a into the tight box 4, and then insert the chamber lid 1a.
At the same time, the operating cylinder 12 is operated to seal the tight box 4. Next, the process moves to a process of removing wax and the like at a relatively low temperature. At this time, the valves 2a and 8a are opened, while the valve 3a is closed. In this state, gas is supplied into the chamber 1 through the gas inlet 2, or the inside of the tight box 4 is sucked through the exhaust port 8 by a pump (not shown), or the tight box 4 is closed under the joint action of both. A differential pressure is generated between the inside and outside of 4. Then, gas flows unilaterally from the relatively high pressure chamber 1 into the relatively low pressure tight box 4 through the ventilation member 14, and as a result, wax gas generated from the molded product 5 The atmospheric gas inside the tight box 4, including the gases, is sequentially discharged to the outside from the exhaust port 8. In other words, the atmospheric gas in the tight box 4 does not pass through the space inside the chamber 1.
It is directly discharged outside. Since the ventilation member 14 is provided with a backflow prevention mechanism using a check valve, gas leaks from the tight box 4 into the chamber 1 regardless of fluctuations in conditions such as the magnitude distribution of the differential pressure. Never.

When the process of removing wax and the like is completed, the temperature inside the furnace is further increased and the process moves from the preliminary to the main sintering process. At this time, the tight box door 5 is opened and the valves 2a and 8a are closed.
On the other hand, the valve 3a is opened and the inside of the furnace is sucked from the gas exhaust port 3 via a pump (not shown). Vacuum sintering is thus performed.

When the sintering process is completed, the stirring fan 18 is rotated with the tight box 4 in an open state to forcibly cool the inside of the sintering furnace, and after cooling, the sintered product is taken out.

In the internal heat type sintering furnace according to the present invention, a series of sintering processes can be carried out continuously in a single furnace, and in the process of removing wax etc. By generating a pressure difference, the atmospheric gas in the tight box 4 is discharged to the outside without leaking into the chamber 1, and the problem of contamination in the furnace due to wax gas or the like can be accurately solved. The present invention is not limited to providing a ventilation system path in the door, but also includes a structure in which the ventilation system path is provided in the outer cylindrical part of the Tightbox in a form that penetrates the heat insulating wall. Compared to a system that uses the gap between the box and its door as a path, the structure for attaching and holding the door 5 can be simplified. Furthermore, since it is of course possible to seal the tight box 4 when the door 5 is closed, it is possible to increase the versatility of the sintering furnace. Since a ventilation system path is provided in the tight box 4, it is easy to provide a mechanism for preventing gas from flowing back into the chamber 1 from inside the tight box 4.

Incidentally, in the case where the door 5 of the tight box 4 is independent and not lined as in the above embodiment, the ventilation member 14 does not need to also serve as a fixing pin. In that case, the ventilation member
As shown in the figure, it may be a pipe-shaped member 21 that simply passes through the door 5, or more simply, the door 5
A ventilation hole may be provided in the opening to form a required ventilation path. Further, in the above embodiment, the necessary gas backflow prevention mechanism is provided on the door 5 together with the ventilation member 14.
However, as shown in FIG. 3, for example, a conduit 22 may be connected to the ventilation member 21 to provide a ventilation system outside the tight box 5. Since the gas backflow prevention mechanism is to prevent gas from leaking from the tight box 4 into the chamber 1, it is of course not limited to the check valve 16 of the above embodiment, but may also be used, for example, such as the flow rate control valve 23 shown in FIG. It may be something. Further, the installation position, number, etc. of the ventilation members or ventilation holes forming the ventilation system path with respect to the door 5 can be arbitrarily changed, increased or decreased as necessary.

(f) Effects Since the present invention has the above-mentioned configuration, it can be used as an internal heating type sintering furnace and can be used continuously during the process of removing wax etc. without contaminating the inside of the furnace due to the generated gas. In addition to being able to carry out sintering work in a timely manner, it is also equipped with a ventilation system path that communicates between the inside and outside of the tight box, which is necessary for the existing differential pressure generation method, in a part of the tight box, and a mechanism to prevent gas backflow. , the mounting and holding structure of the door is simplified, and at the same time, it is possible to more reliably prevent contamination inside the furnace, and furthermore, there are advantages in that the versatility of the sintering furnace is increased.

[Brief explanation of drawings]

The drawings show an embodiment of the internal heat type sintering furnace according to the present invention, and FIG. 1 is a longitudinal sectional view thereof, FIG. 2 is an enlarged sectional view of the main part of FIG. 1, and FIG. It is an explanatory view showing a modification. 1...Chamber, 2...Gas inlet, 3...
Gas exhaust port, 4...Tight box, 5...Door,
8... Gas discharge port, 14... Ventilation member, 16...
Check valve, 15b, 15c, 16a...ventilation hole, 21...ventilation member, 23...flow control valve.

Claims (1)

[Claims for Utility Model Registration] (1) A tight box having a gas inlet and an exhaust port that can be opened and closed is disposed in a chamber having a gas inlet and an exhaust port, and when the tight box is closed, the chamber is closed. A pressure difference is generated between the inside and outside of the tight box to make the inside of the tight box relatively low pressure through a ventilation system passage provided to communicate the inside of the tight box with the inside of the tight box, and the atmosphere inside the tight box is removed from the gas outlet. In an internally heated sintering furnace configured to allow gas to be directly discharged to the outside, the ventilation system path is provided in a part of the tight box, and a mechanism is provided to prevent backflow of gas from the inside of the tight box to the inside of the chamber. An internal heating sintering furnace featuring: (2) The internal heat type sintering furnace according to claim 1, wherein the ventilation system passage is provided in the door for opening and closing the tight box.