WO2000040352A1

WO2000040352A1 - Coupling

Info

Publication number: WO2000040352A1
Application number: PCT/GB2000/000036
Authority: WO
Inventors: John Rushe
Original assignee: Vacmetal (Uk) Limited
Priority date: 1999-01-07
Filing date: 2000-01-07
Publication date: 2000-07-13
Also published as: GB2363442A; AU1990400A; GB9900295D0; GB0117061D0

Abstract

A steel making system including a coupling for the supply of stirring gas to a ladle (10). The coupling includes a male member (6) mounted on a ladle car or stand (3) which is controllably actuable to move in a substantially horizontal plane between a first retracted position and a second extended position. The rear of the male member (6) is mounted on a universal joint (4) and its front is hung from springs (5). This mounting allows the male member to move in a vertical plane and makes it tolerant of misalignment between the ladle and the car or stand (3).

Description

COUPLING

In many steel and iron making processes it is necessary to stir the liquid metal. This is normally done by introducing a gas such as argon or nitrogen into the liquid metal through a porous element in the lining of the ladle holding the liquid melt.

Since the ladle is a moveable object and the gas is stored at a fixed position in the steel or iron making works, it is necessary to supply the stirring gas to the ladle from a fixed station once the ladle is in or is approaching the treatment position. The fixed gas supply station may be near to or on the store of stirring gas, or separated therefrom and connected thereto by pipework.

Due to the heat, dust and splashing of liquid metal, manually connecting the gas supply to the ladle is hazardous. In some cases the ladle is, in any case, inaccessible when in its treatment position.

For this reason, automatic gas coupler units have been proposed. The idea of an automatic gas coupler unit is not new, and there are already a number of these units in use.

There are basically, at the moment, two known types of automatic gas coupler design.

In the first type (for ease of reference, coupler type A) the coupler unit is mounted in a fixed position adjacent to the ladle treatment or material/melt processing station.

When the ladle is in its treatment position the coupler unit is driven forwards to make a connection between the male or female half of the coupling attached to the ladle, and the corresponding female or male half of the coupling which forms part of the actuated coupler unit .

Generally speaking, in this type of design the actuated coupler unit incorporates various devices to allow for a certain degree of tolerance in the ladle position. Even so, the total allowable tolerance in ladle position is only about ±75mm.

For practical purposes this degree of accuracy in positioning the ladle is difficult to achieve, particularly if the ladle is transported into its treatment position on a travelling car. In this case the variation in positional accuracy of the car must be added to the variation in positional accuracy of the ladle on the car.

To achieve the required positional accuracy involves sophisticated (and expensive) ladle car drive system controls, positional transmitters and/or limit switches and extensive ladle guides on the ladle car. It also presupposes that the ladles are all the same size and shape, which is not always the case. Although all the ladles in use at a particular processing plant may begin their service as being of the same shape (typically round) some of the ladles will, over the course of time, become misshapen due to thermal and stress distortion. Formerly round ladles typically become oval with expansion taking place along the axis at right angles to the trunnion axis.

For these reasons, the fixed coupler unit (coupler type A) has not proven itself to be a practical and cost- effective proposition.

The other basic type of automatic gas coupler unit (for ease of reference, coupler type B) is mounted on the car or ladle stand which supports the ladle during treatment of the melt held in the ladle. This method eliminates the problems arising from possible variations in positional accuracy of the ladle car itself by carrying out the coupling as the ladle is placed on the ladle car or stand.

Although there are a number of variations of this type of coupler, the basic design is similar in all cases; a stirring gas supply is coupled to the ladle as the ladle is lowered onto the car or stand and the coupling is actuated by the lowering and positioning movement.

One half of the coupling is attached to the ladle and the other half to the ladle car or stand. The two halves of the coupling engage each other as the ladle is lowered onto the ladle car or stand. The two halves of the coupling move together in a vertical plane as the ladle is lowered into position. In other words, both halves of the coupling move along a substantially common vertical axis. A bracket connected to the ladle incorporates a vertical cone shaped receiver (the female part of the coupler) .

A vertical, spring loaded male connector is attached by a bracket to the ladle car or stand. This bracket is connected to a vertical hinge, which allows the male part of the coupling to move (within limits) in a horizontal plane .

As the ladle is lowered onto the car or stand the two halves of the coupling come together, and join when the ladle is fully lowered. Springs incorporated in one half of the coupling hold the two halves of the coupling together.

The springs are stressed by the weight of the ladle as the ladle is lowered into position. The stressed springs then provide a sufficient force to keep the two halves of the coupling together when pressurised gas is supplied to the ladle via the coupling.

This type of coupling (coupler type B) has a number of important disadvantages. Although it is designed to accept a certain amount of tolerance in the horizontal positioning of the ladle, it cannot accept any axial movement, that is, rotation of the ladle about a horizontal axis.

If the ladle is at an angle as it is lowered onto the car or stand, because it is not hanging vertically in the crane hooks (this is a common occurrence, since a full ladle never hangs exactly vertical on the crane hooks) , then a misalignment takes place between the female and male parts of the coupler. There is a sudden rotation of the ladle about a horizontal axis as the ladle begins to contact the car or stand. The known coupler type B designs do not accommodate this rotation, and extended vertical guides are therefore required on the car or stand. When the ladle is placed on a car or a stand therefor, and the weight of the ladle is transferred from the crane hooks to the car or stand, the ladle rotates quite quickly about a horizontal axis if it is not hanging exactly vertically. Since at this stage the two halves of the coupling are already in contact, this type B coupling can be damaged by the sudden rotation of the ladle about a horizontal axis. To prevent this rotation damaging the coupler unit, it is therefore necessary to install extensive vertical guide systems on the ladle car or stand to ensure that the ladle is forced to lower vertically for the last metre or so of its movement . Since there may be many positions where gas stirring is required (ladle cars, stands etc) each must be modified at considerable cost to prevent the coupler being damaged. Another disadvantage of this type of coupler is that it relies on the spring compressed by the lowering of the ladle to maintain the two halves of the coupling together. If the springs fail, the coupling fails.

The maximum force which can be supplied by the springs of the known coupling is determined by the nature and size of the springs and the material from which they are made. Consequently if an extensively high pressure gas supply should be connected to the coupling it will fail. The known spring loaded coupling therefore has a definite failure load which can be exceeded. Furthermore, as the springs deteriorate, failure becomes more likely. In the extreme conditions involved in steel making this is a serious problem due to the effects of wear, heat etc. The present invention provides a stand or car, coupling and method as defined in claims 1, 8 and 16 respectively.

The stand or car of claim 1 allows one to position and secure a ladle on a stand or car before coupling a gas supply thereto. This reduces or eliminates the problem of excessive wear on the coupling as the ladle is being lowered and located. Perhaps more importantly, it eliminates the requirement for vertical guidance of the ladle as in coupler type B.

The present invention also allows one to provide a coupler unit which is significantly smaller and simpler than the known fixed coupler unit (coupler type A) designs. The fixed coupler (coupler type A) designs must be capable not only of extending and retracting to engage with and disengage from a ladle and/or ladle car, but must also be capable of slewing or moving horizontally since it must clear the moving ladle and/or ladle car as the ladle is moved into and out of its treatment position. The preferred embodiments of claims 4 and 12 allow one to connect two separate gas supplies to a ladle.

The preferred embodiments of claims 5 and 13 are easily controlled. The use of gas under pressure rather than mechanical elements such as springs, to hold and/or move the piston also reduces the wear on a coupling. Furthermore, a change in ladle dimensions during the ladles life corresponding to the typical increase in length of the ladle axis at right angles to the trunnion axis would not cause a problem since the only effect would be a slightly reduced length of travel of the piston rod or male member.

The preferred embodiments of claims 6 and 14 ensure that the cylinder force holding a coupling together is in excess of the counter force generated by the pressurised gas at all operating pressures. This removes the risk of failure of a coupling when high pressure gases are passing therethrough. The use of a common source of gas for the stirring gas and coupling mechanism also allows one to significantly simplify the coupler unit.

The known coupler units must incorporate both pneumatically (compressed air) and electrically actuated components whereas the system of claims 6 and 14 may operate with only the stirring gas supply which must, in any case, be connected to the ladle car or stand. The arrangement of claims 6 and 14 is only a preferred one and in some establishments the present invention may incorporate both pneumatically and electrically actuated components .

Further advantages of the invention and its various preferred embodiments will be clear from the following description of a particular embodiment of the invention with reference to the attached figures in which:

Figure 1 shows a view in elevation of a ladle car or stand embodying the present invention and having its piston rod or male member extended; Figure 2 shows a plan view of a ladle car or stand embodying the present invention and having its piston rod or male member retracted;

Figure 3 is a plan view of the coupler unit of Figures 1 and 2; and Figure 4 is a more detailed view in elevation of the coupler unit shown in Figure 1; and

Figures 5a and 5b illustrate an alternative coupling construction .

The coupler unit 1 consists of a high pressure cylinder 2 which is mounted within the body of a ladle car or stand 3. To allow greater flexibility in positioning the end of the cylinder is connected to the body of the ladle car or stand by a universal joint 4.

The front end of the cylinder 2 is suspended from the frame of the car or stand by two springs 5. These springs increase the flexibility in positioning of the cylinder 2. The combination of an universal joint and springs allows the cylinder to move in both horizontal and vertical planes and makes the coupling tolerant of misalignment of the ladle and ladle car or stand. The cylinder 2 includes a piston rod 20 which is movable between retracted and extended positions. A hardened steel male coupling attachment 6 with a rounded end is connected to the piston rod of the cylinder. This rounded end has a hole 7 drilled into the end of the attachment 6 which is attached to a supply of stirring gas by fixed and flexible piping 8. The gas supply on the car may be a chamber or a source of pressurised gas on the car itself, or a flexible line in communication with a source of pressurised gas which is not on the car. In both cases there is a point or station on the car or ladle from which gas may be supplied.

When the cylinder 2 is extended (as shown in Figures 4 and 5) the rounded end of the piston rod attachment 6 comes into contact with a cone shaped hardened steel funnel 9 attached to the ladle 10. A hole 11 is drilled into the centre of this funnel, and the hole 11 is connected by fixed and flexible pipework 12 attached to the ladle to the stirring element 13 defined by a porous element located in the bottom of the ladle. A seal 14 is located round the drilled hole in the funnel.

An important feature of this coupler unit is that the supply of stirring gas is used to actuate the cylinder 2 as well as stir the melt in the ladle. This feature eliminates one of the problems of the known spring loaded coupler arrangement since in the case of the present invention the force 6 with which the rounded end of the piston rod attachment 6 is pressed against the seal in the funnel by the pressurised gas supply is always in excess of the counter force tending to pus apart the coupling resulting from the supply of the pressurised stirring gas to the ladle. The pressurised stirring gas is supplied to the full bore side of the cylinder to maximise the force with which the piston rod is biased against the funnel.

The whole assembly is protected by a cover 15 connected to the stand or ladle car. When not in use, the piston rod 20 of the cylinder 2 is retracted, and the whole cylinder assembly is below the protective cover 15 (see Figures 2 and 3) .

When required for use, the operation is as follows. First the ladle 10 is placed on the stand or car 3. Guides are required to locate the ladle on the stand or car. It is important to note however that in the case of the described embodiment of the present invention there is no contact between the gas coupler unit 1 and the ladle 10 as the ladle is lowered. For this reason, the extensive vertical guiding of the ladle required with the known systems with coupler units on the car or stand, is unnecessary, and the ladle guides required can be relatively short and inexpensive.

Only when the ladle has been placed on the stand or car 3 is the gas coupler unit 1 actuated. This is a major difference with previous gas coupler units.

The operator then initiates the gas stirring process from a remote position. The valve and pipework system is designed so that when a remotely actuated valve in the gas stirring line is opened to allow the stirring gas into the main line, the stirring gas first actuates the cylinder 1 pushing the piston rod 20 forward until the piston rod attachment 6 makes contact with the funnel 9. The flexible mounting of the cylinder ensures that the end 6 of the piston rod 20 centres in the funnel 9 even with wide variations in the ladle location.

A flow of stirring gas to the piston rod head attachment 6 and hence via the funnel 9 connection to the ladle 10 only begins when the cylinder 2 is fully extended and in contact with the funnel.

In the embodiment of Figure 4, this is achieved by only allowing stirring gas to flow to the piston head 6 and hence via the funnel 9 to the ladle when sufficient pressure has built up. This prevents the seal 14 in the funnel being displaced by the stirring gas flow as the two halves 6, 7, 9, 11 of the coupler come together. In the embodiment of Figure 4 this is achieved by overcoming the resistance of a spring loaded non-return valve or alternatively by providing electrically actuated valves under the control of a microprocessor. Both solutions control the flow of gas such that gas is first supplied to the cylinder 2 to extend the piston rod 20 and male coupling attachment 6 before then also being supplied to the stirring element or porous plug 13. The system described above relates to a single stirring line. It is also possible to supply two gas stirring elements in the ladle with a single coupler unit. This is done (see figures 5a and 5b) by modifying the piston head attachment 6 to incorporate a central bore 7 and, around it, an annulus 27. The central bore is connected to a gas supply line connected to a first gas supply, and an essentially annulus shaped hole or series of holes are independently connected to a second gas supply.

The funnel is also modified to incorporate a corresponding central bore 11 and a corresponding annulus 21 such that when the piston rod head attachment 6 is located in the funnel 9, the central bore 7 of the piston head attachment 6 is in communication with the central bore 11 of the funnel 9, and the annulus 27 of the piston head attachment 6 is in communication with the annulus 21 of the funnel 9.

The bore and annulus of the funnel are independently connected to separate stirring elements such that the gas from one gas supply can be supplied and controlled to one stirring element and the gas from the other supplied and controlled separately to the other element.

During the gas stirring process the flow of gas can be increased or decreased to suit the process requirements. This is done by remote control, using an actuated flow control valve in combination with a flow transmitter and suitable displays.

In cases where the coupler unit is designed to accommodate two gas stirring supplies, the flow from each supply can be altered individually.

At the end of the gas stirring process, the remotely actuated gas supply valve is closed. The valve and pipework system attached to the cylinder 2 incorporates a small receiver 19 on the annular side of the cylinder.

Pressure built up in the receiver 19 during the stirring process is sufficient to retract the piston rod, back into ambush under the protective cover.

The ladle can then be removed from the stand or car. If for some reason the cylinder does not retract, the springs 5 allow sufficient movement of the cylinder to allow removal of the ladle without damage to the cylinder 2.

Claims

1. A stand or car 3 for supporting a steel making ladle 10 including a gas supply station and a coupling member 6 connected to the gas supply station for coupling with a ladle 10 placed on the stand or car 3 so that gas may be supplied to the ladle 10, the coupling member 6 being controllably actuable to move between a first retracted position and a second extended position.

2. A stand or car according to claim 1, wherein the coupling member 6 moves in a substantially horizontal plane between its retracted and extended positions.

3. A stand or car according to any preceding claim wherein the distal end of the coupling member 6 is supported by a spring 5 and the proximal end is mounted on the ladle car or stand by a universal joint 4.

4. A stand or car according to any preceding claim, wherein the coupling member 6 has a rounded end for engaging a funnel 9 on the side of a ladle 10 placed on the stand or car 3, the coupling member 6 having a passage therethrough with one end in communication with the gas supply station and the other end terminating in a hole 7,27 in the surface of the rounded end of the coupling member.

5. A stand or car according to claim 4, wherein the coupling member 6 includes two separate non- intercommunicating passages and two corresponding holes 7,27 in the surface of the rounded end of the coupling member .

6. A stand or car according to any preceding claim wherein the coupling member 6 is mounted on a piston rod 20 slidable within a cylinder 2 connected to a supply of gas under pressure, the piston being slidable in a substantially horizontal direction.

7. A stand or car according to claim 6, wherein a common supply of gas under pressure is connected to the cylinder

2 and to the coupling member passage.

8. A stand or car according to any preceding claim, wherein the gas supply station is connected to the coupling member passage via a valve which only allows gas to flow from the supply to the coupling member when its pressure exceeds a predetermined value.

9. A coupling 6,9 for connecting a gas supply station to a steel making ladle 10 including cooperating male 6 and female 9 coupling members, one of the coupling members being mountable or fixable to a steel making ladle 10, the other coupling member being mountable or fixable to a gas supply station on a stand or car 3 for transporting and/or supporting a steelmaking ladle and the male 6 and female 9 coupling members being controllably movable relative to each other independently of movement of the ladle relative to the car or stand when mounted or fixed on a ladle and car or stand respectively.

10. A coupling according to claim 9, wherein the coupling member 6, 9 mountable or fixable on the car or stand 3 is controllably movable relative to the car or stand 3 when fixed thereto.

11. A coupling according to claim 10, wherein the coupling member 6, 9 mountable or fixable on the car or stand 3 is controllably movable in a substantially horizontal plane when fixed thereto.

12. A coupling according to any of claims 9 to 11, wherein the male member 6 has a rounded end and the female member has a funnel, the male member having a passage therethrough with one end in communication with the gas supply and the other end terminating in a hole 7,27 in the surface of the rounded end of the male member, the female member having a hole 11,21 in communication with the inside of the ladle.

13. A coupling according to claim 11 wherein the male member 6 includes two separate non-intercommunicating passages and two corresponding holes 7,27 in the surface of its rounded end, and the female member includes two corresponding holes 11,21 both separately communicating with the inside of the ladle.

14. A coupling according to of claims 9 to 13, wherein the male member 6 is mounted on a piston rod 20 slidable within a cylinder 2 coupled to a supply of gas under pressure .

15. A coupling according to claim 13, wherein a common source of gas under pressure is coupled to the cylinder 2 and to the male member passage.

16. A coupling according to any of claim 12 to 15, wherein the gas supply is coupled to the male member passage via a valve which only allows gas to flow from the supply to the male member when its pressure exceeds a predetermined valve.

17. A method of connecting a supply of stirring gas to a ladle 10 for processing ferrous materials comprising the steps of: a) providing a gas supply station on a car or stand 3 for supporting the ladle 10 during processing of material contained therein, b) placing the ladle 10 on the car or stand 3, c) and then coupling the gas supply station to the ladle.

18. A method according to claim 17, wherein the step of coupling the gas supply station to the ladle includes controllably actuating a coupling member 6 connected to the gas supply station to move from a first retracted position to a second extended position in which it is connected to the ladle to provide a gas conduit from the gas supply station to the ladle.

19. A method according to claim 18, wherein the coupling member 6 is controllably actuable to move in a substantially horizontal plane.