GB2120280A

GB2120280A - An apparatus for the control of a medium circulated within a space

Info

Publication number: GB2120280A
Application number: GB08307501A
Authority: GB
Inventors: Dieter Warga
Original assignee: Mahler Dienstleistungs-Gmbh Loeten-Haerten-Anlagenbau; Mahler Dienstleistungs GmbH Loeten Haerten Anlagenbau
Current assignee: Mahler Dienstleistungs-Gmbh Loeten-Haerten-Anlagenbau; Mahler Dienstleistungs GmbH Loeten Haerten Anlagenbau
Priority date: 1982-03-27
Filing date: 1983-03-18
Publication date: 1983-11-30
Also published as: GB2120280B; IT1203700B; FR2524172A1; GB8307501D0; JPS58174521A; CH653366A5; DE3211412A1; IT8320121A0

Abstract

An apparatus for the control, in respect of direction and/or quantity, of a medium flow which is circulated within a space 1, is capable of regulating the flow of protective gas in a continuous heat treatment furnace with adjoining cooling zone. The space 1 in question comprises inlet and outlet orifices 6, 4 and 5 respectively interconnected by a medium- circulation pipe 10 for the circulated medium and at least one exit 3 through which one portion of the medium leaves the space. Valves 7, 8 are arranged at the inlet or outlet orifices and are actuated in relation to the quantity of medium discharged through the exit (3) from the space. By means of such an arrangement it is possible, in particular, to control the outflow of a protective gas at the exit end 3 of a cooling zone 1 in such a manner as to prevent an inrush of air into the cooling zone. <IMAGE>

Description

SPECIFICATION An apparatus for the control of a medium circulated within a space The invention relates to an apparatus for the control in respect of direction and/or quantity of a medium which is circulated within a space the apparatus having inlet and outlet orifices for the medium which is circulated in the space, said orifices being interconnected by a mediumcirculation pipe, and with at least one exit opening from said space through which a portion of the medium is discharged.

Arrangements of this kind are required, for example, in cooling apparatus which is arranged downstream of a continuous furnace having open feed and discharge ends for the heat treatment of workpieces under a protective gas which is combustible in external air, the protective gas forming flame curtains at the work-feed end of the furnace and at the work-discharge opening of the cooling apparatus and in which means are provided for circulating and cooling the protective gas.

In a known cooling apparatus of the aforementioned kind the direction of flow of the protective gas which is circulated through the cooling apparatus is regulated by means of baffle plates arranged at the points of entry of the said gas into the cooling apparatus, in accordance with the temperature of the protective gas which is burnt up on leaving the cooling apparatus under admission of external air.

However, using such baffle plates it is frequently not possible to achieve effective control of the flow of medium, particularly where small baffle adjustment angles are involved. Moreover, such baffle plates are cumbersome and bulky and often constructional considerations prevent the fitting of such baffle plates.

It is the object of the invention to provide a fiow-control system for use in an apparatus of the kind specified which is capable of functioning effectively without the provision of baffle plates.

This aim is achieved, according to the invention, by the provision of valves which are associated with the entrance or exit openings of the space and which are actuated in relation with the quantity of medium which is discharged through the said exit of the space.

Whilst the arrangement according to this invention will preferably be applied to continuous furnaces for the heat treatment of workpieces with adjacent cooling zone it is by no means confined to this application. It is generally suitable for the control of circulating currents or media in spaces of any kind, chambers and containers the said medium being incompressible or compressible, that is to say, notably, a liquid or a gas.

The invention is further explained by the following description of preferred embodiments considered in conjunction with the accompanying drawing which shows a flow control system for a medium flow which is circulated within a defined space.

A cooling apparatus for a continuous furnace which is open at the work-feed and discharge ends thereof for the heat treatment of workpieces under a protective gas which is combustible with external air is already known from German PS 26 01 658. In this known arrangement the protective gas forms flame curtains at the workfeed end of the furnace and at the work-discharge end of the cooling zone and means are provided for circulating and cooling the protective gas in the cooling apparatus.

A cooling apparatus of this type is schematically shown in the drawing. The space 1 which encloses the actual cooling zone has an entrance 2 for the workpieces which are to be cooled and an exit 3 for the cooled workpieces. The workpieces (not shown) are carried through the cooling zone by a conveyor device also not shown.

At the entrance end 2 the cooling zone is immediately adjacent to a continuous furnace for the heat treatment of the workpieces and as a general rule the conveyor means will extend through the furnace as well as through the cooling zone.

The clear passage sections of entrance 2 and exit 3 are of such dimensions that a combustible protective gas, e.g. hydrogen, which protects the treated workpieces from oxidation, can escape to the exterior from the exit 3 and flow into the continuous furnace from the entrance 2. The protective gas which enters into the continuous furnace is burnt up at the work-feed opening of the furnace to form a flame curtain. A flame curtain is also formed at exit 3.

The protective gas is continually circulated within the space 1. For this purpose the space is provided with two discharge or outlet orifices 4, 5 and one feed or inlet orifice 6 and these are interconnected by a protective gas-circulation pipe 10. This pipe 10 includes a pump 9 which effects the circulation of gas and the pipe 10 may further include a cooling apparatus (not shown) for the circulated gas or medium. The gas or protective medium which is lost through the exit and entrance is made up with fresh gas or medium introduced into the pipe 10 conveniently at position A.

The orifices 4, 5 are arranged, preferably symmetrically one on either side of orifice 6.

Immediately downstream of the discharge orifices 4, 5, valves 7, 8 are provided which are actuable by means of servo-motors 18, 1 9 respectively.

The medium in space 1 is sucked through the orifices 4, 5 and flows through valves 7, 8, pump 9 (and cooling means, where provided) through pipe 10 and back through orifice 6 into the space.

The process may also be directionally reversed in which case the inlet orifice 6 becomes a discharge or outlet orifice whilst orifices 4, 5 become inlet orifices.

The medium which enters through orifice 6 splits up in accordance with the pressure distribution to form branch flows or currents of equal quantity as indicated by arrows 11, 12. The medium which is discharged through orifices 4, 5 is made up from branch flows or currents which are indicated by arrows 13, 14, and 15 16 respectively.

If equal quantities of medium are sucked out through orifices 4 and 5 quantity 11 must be equal to quantity 14 and 1 2 must be equal to 15.

This means that quantities 13 and 1 6 equal zero and there is no flow between entrance 2 and exit 3.

When valve 8 is closed the same quantity of medium which enters through orifice 6 must be sucked out through orifice 4. Since however the amount 11 is equal to amount 14 the complementary quantity 13 must be aspired through entrance 2. The quantity 12 which is not aspired through orifice 5 flows out through exit 3.

In this manner a through-flow or medium flow is set up through space 1 from entrance 2 to exit 3.

By an appropriate regulation of the medium quantity which is sucked through orifices 4, 5 by corresponding actuation of the valves 7, 8 (by means of servomotors 18, 19) a facility is obtained of establishing within space 1 a variable flow of medium from entrance 2 to exit 3 or in the reverse direction.

If the quantity of medium which leaves at exit 3 is measured by a pick-up 1 7 the valve members 7 and 8 may be automatically actuated by means of the servo-motors 18, 19 responding to the pick-up 1 7 to maintain a specified ideal value of flow.

The described control system is, as already mentioned, preferably applied to continuous furnaces with adjoining cooling zone for the heat treatment of workpieces.

In order to protect the hot workpieces in the furnace and in the cooling zone against the oxidising influence of air it is necessary to ensure that the furnace entrance not shown and the cooling zone exit 3 are at all times covered by a protective gas flow of a predetermined quantity, the emerging protective gas burning up on admission of external air to form a flame curtain (see the earlier mentioned German PS 26 01 658). The outflowing quantity of protective gas can very easily be increased or decreased by varying conditions or faults occurring outside or inside the furnace. In the last mentioned case, namely if the quantity of discharged protective gas is too small which corresponds to an insufficiently covered cooling zone exit 3, there is a risk of an inrush of air into the cooling zone resulting in the oxidation of the workpieces before these have sufficiently cooled down.

Such inrush of harmful external air can be prevented with the aid of the aforedescribed control system by suitable regulation of the value or magnitude of protective gas outflow at exit 3.

To this end (in a manner per se known and therefore not shown in drawing), a probe or sensor 1 7 is arranged in the exhaust gas passage adjacent exit 3 which senses the prevailing temperature in this region that is to say the temperature of the protective gas which has burnt up in the flame curtain at exit 3. The temperature of the mixture of exhaust gas and air depends on the amount of air which is admitted, on the calorific value of the protective gas and on the quantity of burnt protective gas. However, since the amount of air which is admitted to produce the flame curtain and the calorific value of the protective gas are constants the temperature which is measured in the exhaust passage provides a measure for the amount of protective gas leaving through exit 3. Thus the emerging quantity of protective gas can be regulated by monitoring this temperature by means of the pickup 17 and the servo-motors 18, 19 which are controlled by this pick-up and in their turn actuate the valves 7, 8.

The hereinbefore mentioned flame curtains at exit 3 and at the entrance of the furnace (not shown) are not absolutely indispensable. They may be replaced, for example when using nitrogen as a protective gas, by an outflow of non-burning protective gas which likewise prevents access of outside air. The sensor or pick-up 1 7 does not necessarily have to be a thermo-sensor. The magnitude of protective gas flow at exit 3 may also be monitored and measured by alternative measuring means, for example by flow meters.

Claims

1. An apparatus for the control in respect of direction and/or quantity of a medium flow which is circulated within a space with inlet and outlet orifices for the medium which is circulated in the space, said orifices being interconnected by a medium-circulation pipe, and with at least one exit opening from said space through which a portion of the medium is discharged characterised in that valve members (7, 8) are associated with the inlet or outlet orifices (4, 5) and these valve members are actuated in relation with the magnitude of medium outflow through the exit (3) of the space (1).

2. An apparatus according to Claim 1, characterised in that the space (1) comprises one inlet or feed orifice and two outlet or discharge orifices (6, 4, 5 respectively) for the circulating medium.

3. An apparatus according to Claim 1 or 2, characterised in that the outlet orifice(s) (4, 5) is/are arranged symmetrically relative to the inlet orifice(s) (6).

4. An apparatus according to Claim 1, 2 or 3, characterised in that the space (1) is designed as a cooling zone for heat-treated workpieces and the circulated medium is a protective gas.

5. An apparatus according to Claim 4, characterised in that the cooling zone is preceded by a heat treatment furnace which is also traversed by a flow of protective gas and that the protective gas (being combustible in air) forms flame curtains at the entrance end of the furnace and at the exit of the cooling zone 6.

6. An apparatus according to any of Claims 1 to 5, characterised in that the valve members (7, 8) are actuated by servo-motors (18, 19) which in their turn are controlled by a thermoprobe (17) arranged at the exit (3) of the space (1).

7. An apparatus according to Claim 6, characterised in that the thermoprobe (17) is arranged in an exhaust channel or flue adjoining the exit end (3) of the cooling zone and picks up the temperature of the protective gas which has burnt up in the flame curtain.

8. An apparatus for the control in respect of direction and/or quantity of a medium flow within a space comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawing.