WO1987000868A1

WO1987000868A1 - Container for surface treating, such as hot-dip galvanizing goods

Info

Publication number: WO1987000868A1
Application number: PCT/SE1986/000350
Authority: WO
Inventors: A^oke FLINK
Original assignee: DEFAB INTERNATIONAL AB
Current assignee: DEFAB INTERNATIONAL AB
Priority date: 1985-07-31
Filing date: 1986-07-31
Publication date: 1987-02-12
Anticipated expiration: 1988-01-31
Also published as: EP0244423A1; SE8503651L; AU6198986A; SE8503651D0

Abstract

When performing galvanization a container is used which is open at the top and the outer wall (1) of which is perforated to permit the passage of molten zinc. A central rod (6) extends from the container bottom (13), a sliding body (5) being displaceable about this rod and joined to the outer wall (1). The rod (6) is also provided with a connection (12) to lifting gear. A locking device (9) is arranged to effect locking between the rod (6) and sliding body (5) when the bottom (13) and the outer wall (1) are in contact with each other. According to the invention the outer wall (1) is in the shape of a truncated cone, diverging towards the bottom (13) and the container is preferably provided with an inner wall (15, 17) permanently joined to the bottom (13).

Description

Container for surface treating, such as hot-dip galvanizing goods

The present invention relates to a container for hot-dip galvanizing, comprising a bottom and a wall with a number of holes permitting through- flow of zinc. Such a container is normally provided with a handle enabling it to be moved from place to place. The container is filled with goods and immersed in a zinc bath with the aid of lifting gear, where the zinc can influence the goods. After immersion in the zinc bath the container is lifted and generally subjected to rotation to remove any zinc which has not adhered to the goods, through the perforated wall. The container is then inverted to remove the contents.

Having to invert the container to remove its content is a drawback in hot- dip gal nizing since the zinc coating may be damaged when the goods fall.

The coating is also damaged as described above even if the container has a convex bottom with a central rod extending therefrom. A sliding body is provided along the rod, said body being joined to the wall of the con- tainer. When the container is to be emptied, rotation of the container is stopped and the bottom then lowered. The container is provided with a lifting device.

SE 8101170-2 describes a container of the latter type but differs there¬ from in that the container with bottom can be placed on the ground and the surrounding wall can be raised when the bottom is stationary so that goods can be transferred to ground level without falling. The sliding body is provided with a locking device so designed that when wall and bottom are in contact with each other the locking means can come into operation. The locking means cooperates with the central rod. During emptying of the container, the locking device is out of function and the lower wall edge and bottom part company.

The present invention constitutes a modification of the container for hot-dip galvanizing described in the above-mentioned Swedish patent specification SE 8101170-2. This modification makes better use of the centrifugal forces upon rotation of the container. This is particularly

<§ important when the goods to be galvanized are of a type in which the capillary force must be overcome once the zinc has fully Influenced the goods. Examples of such articles are objects with external screw threads. The present invention also counteracts the tendency of the goods to mount the wall during rotation, as well as reducing splashing as a result of spitting. Spitting is caused by the formation of gas bubbles when damp goods, for instance, are immersed in the zinc bath, and causes the hot zinc to splash out of the container. It is therefore desirable from the safety point of view to reduce this tendency.

The above advantages are achieved in practice by the present invention in which the container wall, in the following termed the outer wall, is in the form of a truncated cone diverging towards the bottom.

To make better use of the centrifugal forces, the container according to the invention is provided with an inner wall arranged around the central rod and permanently joined to the bottom, the space defined between these parts communicating with the surrounding atmosphere during the hot-dip galvanizing treatment via apertures in the upper, part of the inner wall, in the central rod and/or In the bottom. The inner wall causes the centre of gravity for the goods to be hot-dip galvanized to be moved further out towards the periphery.

When in use the container, together with rod and sliding body, constitutes a centrifugal pendulum. This performs three movements simultaneously:

A Rotation around its own centre line which develops a gyroscope force. This tends to keep the axis of rotation vertical and the higher the speed of rotation, the greater will be this tendency. The gyroscope force has a "calming" effect on the pendulum.

B The flat pendulum movement, which becomes slower the longer the pendulum. A pendulum one metre in length has a sweep time of

1 second whereas one which is two metres in length has a sweep time of 1.41 sec. The plane of oscillation is arbitrary and variable. The amplitude is independent of the length of the pendulum but dependent on the forces affecting the centre of gravity.

C The conical pendulum movement. Even with excentric load, the rotary movement of the centrifuge tends towards the axis between the centre of gravity and the point of suspension. The central axis of the basket thus acquires a conical movement, the base being a circle where the radius is the distance between the centre of gravity and the central axis. The longer the pendulum distance, the slower will be the rotation, but the base radius will remain the same. The peri- pheral speed will thus be lower the longer the pendulum is. A pen¬ dulum distance of one metre gives a speed of rotation of 1.99 second and a pendulum distance of two metre will give a speed of rotation of 2.83 second.

From B and C it appears that both movements will be slower the longer the pendulum distance.

Movement B will be superimposed on movement C since the plane of movement in B is arbitrary and variable. If, for instance, the pendulum plane B is tangential to the conical movement C and the pendulum moves in the same direction in both partial movements, there will be an increase in movement which will give the centre of gravity a strongly excentric path, i.e. the amplitude of the flat pendulum movement will increase, i.e. the flat pendulum movement will increase since the sweep time Is constant.

The distance between centre of gravity and suspension point in a loaded container must be at least twice the diameter of the load in order to ensure stability and thus safe operation of the means.

Additional features peculiar to the invention are revealed in the fol¬ lowing claims.

The present invention will be described in more detail with reference to the accompanying drawings in which Figure 1 shows a container according to the invention, In which the bottom and outer wall are in contact with each other,

Figure 2 shows a container according to Figure 1 in which the bottom and outer wall are spaced from each other,

Figure 3 shows an alternative embodiment of the bottom, and

Figure 4 shows a container according to the invention provided with an inner wall.

In the drawings 1 is an outer wall having a number of perforations. The outer wall Is conical. Two legs 2 and 3 extend from the upper edge of the outer wall 1 and are connected by a yoke 4. A sleeve-like part 5 is provided centrally in the yoke, this being provided at the upper end with a lifting eye 12. The sleeve-like part 5 is fitted over a central tube or rod 6 having rectangular cross section. Other polygon cross sections are also feasible. The walls of the rod 6 have perforations 7. The rod 6 is also provided with a collar 8 to prevent material from unintentionally entering the opening of the sleeve-like part 5. The yoke 4 is provided with a locking device 9 to lock the sleeve 5 to the rod 6. Locking is effected with the aid of an arm influencing a transversely movable dowel to enter one of the apertures in the central rod 6. The free lower edge of the wall 1 abuts a domed bottom 13. As shown in Figure 3, the periphery of the bottom 13 may terminate in an annular section 14. The orifice of the central rod 6 is on the lower side of the bottom 13 thus offering free passage between the lower side of the bottom and the cavity of the rod 6.

The lower periphery of the outer wall 1 of the container according to Figure 1 abuts the bottom 13. The locking device is also shown in locking position so that the bottom 13 and wall 1 are stationary in relation to each other. The container can now be filled with the desired quantity of goods and then immersed in a medium which is allowed to influence the goods in the container. The medium may be a zinc bath and the goods may constitute metal articles which are to be galvanized. The medium passes through the perforations in the outer wall 1 , thus reaching the goods in the container. There may be undesired material or fluxing agent on the surface of the zinc bath, and this will pass through the rod 6 and out through the apertures 7 Into the container. It will then rise to the surface of the bath, above or in the container, where it can be removed. When the goods have been suitably treated the container is lifted and subjected to rotation In order to remove medium which has not adhered to the goods or unused zinc. The medium or zinc is removed through the perforations in the outer wall 1.

Figure 4 shows a container provided with an inner wall 15. This inner wall 15 is located Inside the outer wall 1 and is concentric therewith. It should be evident that the inner wall may be cylindrical or optionally conical. The lower periphery of the inner wall 15 is permanently joined to the bottom 13 and its upper edge is in this case joined to the central rod 6. The upper part 17 of the inner wall 15 has different conicity from the lower part. To vent the space defined between the inner wall 15,17, the bottom 13 and the rod 6, the rod 6 Is provided with an opening 16. The rod 6 then communicates with the surrounding atmosphere at the bottom 13 and possibly also at the top of the rod. Alternatively, communication with the surrounding atmosphere may be obtained through openings in the bottom 13 and/or openings in the upper part 17 of the inner wall. The goods to be galvanized are placed in the space between the two walls. With this construction the goods will be subjected to higher centrifugal force than in the alternative without the inner wall.

When unused medium or zinc has been removed by rotation of the container, this is lowered onto a firm surface by suitable lifting gear and the locking device 9 is then released. With the aid of lifting gear connected to the lifting eye 12, the outer wall can now be detached from the bottom 13, as shown in Figure 2. While the outer wall 1 is being lifted, the sleeve 5 will slide along the hollow rod 6. Since the bottom 13 is concave, the goods will leave the container without being damaged. A con¬ siderably more convenient procedure for emptying the container has thus been achieved. It is considerably easier to lift the wall of the con¬ tainer than to invert the container when filled with heavy goods. A container of the type described is particularly suitable for use in hot- dip galvanizing plants. However, it should be evident that it is suitable for other types of goods which are to be treated by a medium. It is most usual for the medium to be liquid, but it might also consist of powdered material.

Claims

1. A container open at the top for hot-dip galvanizing goods, com¬ prising a concave bottom (13) and a perforated wall (1) permitting through-flow of zinc, a rod (6) with arbitrary cross section extending centrally from the bottom (13) and preferably beyond the upper edge of the outer wall (1), as well as an axially displaceable sliding body (5) arranged around the rod (6), said body (5) being permanently joined to the outer wall (1) and provided with lifting means such as a lifting eye (12), the sliding body (5) being provided with a locking device (9) to lock the body (5) against the rod (6) when the outer wall (1) is resting on the bottom (13), c h a r a c t e r i s e d in that the outer wall (1) is in the form of a truncated cone diverging towards the bottom (13), the distance between the centre of gravity of the container plus its contents and the suspension point is at least twice the diameter of the bottom (13).

2. A container open at the top according to claim 1, c h a r a c - t e r i s e d in that an inner wall (15,17) is arranged around the rod

(6), the lower peripheral edge of which is permanently joined to the bottom (13), the space defined between the inner wall (15,17), said bottom (13) and the rod (6) preferably communicating with the surrounding atmos¬ phere during the treatment via one or more apertures (16) located pre- ferably at or close to the upper part of the Inner wall (15,17), in the rod (6) or in the bottom (13), but at all times separated from the treatment medium.

3. A container open at the top according to claim 2, c h a r a c ¬ t e r i s e d in that the upper part (17) of the inner wall is joined to the rod (6).

4. A container open at the top according to one or more of the preceding claims, c h a r a c t e r i s e d in that the bottom (13) is provided around Its periphery with a substantially horizontal, flat, annular part (14) against which the outer wall (1) is designed to abut.

5. A container open at the top according to one or more of claims 2-4, c h a r a c t e r i s e d in that the outer wall (1) and the lower part (15) of the inner wall are concentric.