RU48686U1 - HEATING DEVICE FOR RESISTANCE ELECTRIC FURNACES - Google Patents

Abstract

The utility model relates to electrothermics, in particular to electric resistance furnaces designed for heat treatment of electronic products or other purposes with an increased requirement for uniformity of the temperature field. The proposed heating device for electric resistance furnaces is made as a separate unit on the frame of flat rings 1 mounted on top of each other on metal racks 2. The heating elements 4 of molybdenum wire bent in the form of loops U-shaped are passed through ceramic insulators 3 into the holes of the rings, which are in a suspended state, forming a working chamber. The lower ends of the heating elements are connected by jumpers 5, forming a sequential electrical circuit, divided into sectors electrically isolated from each other according to the number of phases. Current leads are fixed on the lower ring 6. The input ends of each sector are connected to current leads 6 through a flexible isolation 7.

Description

The utility model relates to electrothermics, in particular to electric resistance furnaces designed for heat treatment of electronic products or other purposes with an increased requirement for uniformity of the temperature field.

In electric vacuum production, electric resistance furnaces are most widely used, when heat is released in special heating elements and transferred to the heated body as a result of heat transfer. Heating elements in such furnaces are made in the form of rods, cylinders or wire. The heating elements are mounted on the base or lid of the furnace. [1]..

The closest technical solution, which is selected as a prototype, is a heating element installed in a hydrogen furnace for soldering parts of vacuum equipment [2].

The heating element in the form of a lattice is assembled from a U-shaped molybdenum wire, the ends of which are inserted into the holes in the base and fixed with screws. In the upper part, the heating wire is attached to bonds made also of molybdenum. The lattice is divided into three sectors electrically isolated from each other according to the number of phases.

The disadvantages of such a heating element are:

- the upper part of the heating wire does not have a rigid support and the wire and the connection is quickly destroyed,

- the lower part of the wire is in direct contact with water-cooled conductive rings, which leads to a spread in the temperature of the working chamber,

- the fixing screws burn and stop turning under the influence of high temperatures, and scale forms in the water channels of the current-supply rings, which leads to a decrease in the water flow, reducing the cooling effect.

The technical result of the proposed utility model is as follows:

- increase in utilization rate and service life of furnaces

- ease of maintenance and repair of the device;

- reduction of material costs for the maintenance of the furnace.

The proposed heating device for electric resistance furnaces is made as a separate unit on the frame of flat rings mounted on top of each other on metal racks. Heating elements made of molybdenum wire, which are bent in the form of loops of a U-shape, which are suspended, forming a working chamber, are passed through holes in the rings through ceramic insulators. The lower ends of the heating elements are connected by jumpers, forming a sequential electrical circuit, divided into sectors electrically isolated from each other according to the number of phases. Current leads are fixed on the lower ring. The input ends of each sector are connected to current leads through a flexible isolation. Flexible isolation performs the function of a conductive element.

Flexible decoupling allows a free change in the length of the heating elements under the influence of temperature, excluding their bending and subsequent destruction. The input ends of each sector are attached to the current leads without contacting the cooled surface, which ensures uniform temperature in the working chamber. All this increases the utilization of furnaces and increases their service life.

The implementation of the heating device on the frame as a separate unit makes it easy to repair or replace the device.

Frequent replacement of expensive heating elements made of molybdenum wire is excluded.

Figure 1 presents the proposed heating device.

Three flat metal rings 1 with holes are fixed on 7 metal posts 2. 27 heating elements 3 are made of molybdenum wire and bent in the form of U-shaped loops. The heating elements 3 are passed into the holes of the rings 1 through ceramic insulators 4 and the lower ends are connected by jumpers 5 into a serial electrical circuit, which is divided into 3 sectors isolated from each other. On the bottom ring 1 there are 6 toa inputs 6, two for each sector. The input end of each sector is connected to its current input 6 through a flexible isolation 7 made of copper wire. The device is inserted through current leads 6 into the slots of the cooled plate mounted on the base of the furnace.

The device operates as follows. A voltage phase is supplied to each sector via current lead 6. The heating elements 3 are heated, a flexible decoupling 7 made of copper wire allows them to freely change the length, excluding their deflection and subsequent destruction.

The proposed device has been operating in a hydrogen electric resistance furnace for two years, which exceeds the service life of industrial heating devices by tens of times.

Sources of information

1. L.T. Aleksandrova, S.I. Brodsky, I.I. Sazhin and G.N.Shchirenko “Technological equipment for electrovacuum” State Power Publishing House, 1982, Moscow. p. 163.

2. L.T. Aleksandrova, S.I. Brodsky, I.I. Sazhin and G.N.Schirenko “Technological equipment for electrovacuum” State Power Publishing House, 1982, Moscow, p. 183.

Claims (1)

A heating device for electric resistance furnaces containing heating elements made of molybdenum wire, bent in the form of U-shaped loops, forming an electric circuit divided into sectors electrically isolated from each other by the number of phases, characterized in that it is made in the form of a frame of flat rings mounted one above the other on the racks, and current leads are fixed on the lower ring, with holes made in each ring into which heating elements are inserted through ceramic insulators you form a working chamber, the lower ends of the elements are connected by bridges to form sectors, the current leads and the input ends of each sector are connected by a flexible decoupling.