WO2020254608A1

WO2020254608A1 - Roll unit for guiding a strip

Info

Publication number: WO2020254608A1
Application number: PCT/EP2020/067154
Authority: WO
Inventors: Albert MANTINGH; Johannes Henricus KUYLAARS; John De Boer; Richard Victor VERVEST; Davud YILDIZ; Petrus Cornelis Johannes MOLENAAR; Thomas Hendrikus Johannes DE LINCEL; Mark Bright
Original assignee: Tata Steel Ijmuiden B.V.
Priority date: 2019-06-19
Filing date: 2020-06-19
Publication date: 2020-12-24

Abstract

The present invention relates to a roll unit for guiding a strip comprising a safety bracket and a safety bracket.

Description

ROLL UNIT FOR GUIDING A STRIP

Surface coated strip products such as surface coated steel ranks amongst the key materials for a great number of applications, in particular in the automotive, building and household appliance industries. Nowadays the requirements for surface coated strip products become increasingly complex. In addition to sufficient corrosion protection, improved processing such as forming, joining or painting is required. Moreover, decorative finish aspects as colour and structure and defined surface properties e.g. scratch resistance or anti-fingerprint properties are of increasing importance. The appliance of one or more coating layers to the strip product is hence necessary.

Coating of a strip product is often performed in a continuous production line wherein the strip is submerged in a coating bath, for example during hot-dip galvanizing or galvanealing of a steel strip. Typically the steel strip is guided through the coating bath by a coating roll, also known as a sink roll, wherein the strip enters the bath through a snout, makes a u-turn around the sink roll and exits the bath for further process steps. The rotation of the sink roll is typically caused by the line speed of the strip. In addition, one or more guiding rolls can be present which guide the strip in the correct direction upon entry or exit of the bath. Each of these rolls have extended shafts that rotate in support arms. The different rolls are part of roll units which are generally known in the prior art.

Shaft failures of rolls submerged in a coating bath occasionally occur. When the shaft breaks, an unsafe situation develops when trying to pull the broken roll from the coating bath. If the broken shaft is not secured properly, the other shaft can break as well causing the whole roll to fall back into the coating bath. Thus, operators must use cables to retain the roll when lifting. However, in order to install the cable, the operator must hang over the coating bath, which often contains hot and/or unhealthy chemicals such as molten zinc. For the stability of the system as well as the safety of the operator, it would be desired to prevent such human intervention.

Having regard to the state of the art, the technical problem outlined above is solved by providing a roll unit according to claim 1 and a safety bracket according to claim 15.

In a first aspect of this invention there is provided a roll unit for guiding a strip through a coating bath comprising a roll having a roll body with two shafts projecting axially from each end of the body and a pair of support arms, each shaft being supported in a roll bearing connected to a support arm, further characterized in that the roll unit comprises a pair of safety brackets having a receiving portion, wherein each receiving portion is arranged underneath the shaft and between the roll bearing and roll body.

A roll unit comprising a roll body with shafts projecting axially from each end of the body supported in roll bearings connected to a support arm are well known from the prior art. These elements are arranged such that the strip material only engages with the roll body of the roll unit. In the roll unit according to the invention, safety brackets are arranged underneath the shaft and between the roll bearing and roll body in order to retain the roll if shaft failure takes place. In addition, this location ensures that the safety bracket will not engage with the strip during normal operation. The receiving portion will thus only interact with the shaft of the roll upon shaft failure.

In the context of this application, all types of shafts projecting axially from the roll body are meant. The shaft always comprises a shaft end which is supported by the roll bearing. The shaft may comprise a neck portion, which is typically a tapered shaped portion between the shaft end and the roll body. The receiving portion of the safety bracket is arranged between the roll bearing and roll body and can thus either receive the shaft or the neck portion of the shaft upon shaft failure.

The roll unit according to the invention is especially suitable for a coating installation used to coat metal strips such as a steel strip with a corrosion-resistant layer of metal melt, such as zinc, tin, lead, aluminum, MagiZinc®, Galvalloy®, Galvalume® or Galfan®. The coating bath temperature is typically between 400 °C and 700 °C. A typical pulling force of a metal strip is between 0.8 and 6.5 t and will pass by the roll units at band speeds up to 250 m/min. In these conditions a shaft failure can have major impact on the whole installation and securing the roll afterwards puts the operator in a dangerous situation. Although the roll will be lighter in the metal melt initially, major forces will arise once the roll is lifted out of the bath due to difference in density between the atmospheric and bath environments. These forces can result in the breakage of the other shaft and will result in full drop of the roll in the coating bath at that time. A roll unit according to the invention, comprising a pair of safety bracket, will make sure that the roll is still carried at both ends, even if a shaft failure takes place. Therefore, it will not be necessary to secure the roll with additional external securing means. In addition, even if the other shaft will break during lifting out the roll from the bath, the roll cannot drop down in the coating bath as the other end is then also secured by the safety bracket.

The safety brackets are integrated in the roll unit which makes it possible to retrieve the unit as a whole, either during maintenance or after a shaft failure. For example, the safety bracket may be attached to the support arm or to the connecting bar. In a preferred embodiment according to the invention the safety bracket is attached to the support arm, as the support arm is by design sufficiently strong to hold the weight of the roll.

In a preferred embodiment according to the invention the receiving portion of the safety bracket is dimensioned to retain the roll upon shaft failure. The receiving portion should preferably be horizontal or tilted at an angle in a range of 0 ° - 40 °. Preferably, the receiving portion has an inclined portion wherein the shaft can rest easily, which may have a rectangular or rounded shape. The receiving portion is preferably spaced apart from the shaft at a distance H. The minimal distance H between the receiving portion and the shaft is preferably 5 mm, more preferably 10 mm, most preferably 15 mm to ensure that the safety bracket will not obstruct normal operation of the roll. The maximal distance H between the receiving portion and the shaft is preferably 100 mm, more preferably 50 mm, most preferably 25 mm. As the receiving portion is attached to the support arms of the roll unit, the whole unit can be safely taken out of the coating bath, without additional need to stabilize the roll. This results in a reduction of the effort needed to replace a broken roll, a reduction of downtime of the coating installation and will prevent operators from being in an unsafe situation.

In a preferred embodiment according to the invention the receiving portion of the safety bracket is arranged around the shaft of the roll.

A receiving portion which is arranged around the shaft of the roll has the advantage that the roll is stabilized in all directions if a shaft failure occurs. The safety bracket underneath the shaft already secures the roll unit in the vertical direction. However, by having a safety bracket arranged around the roll, the roll unit is secured in all directions. This embodiment has an additional advantage that the impact of a shaft failure on the strip is even further reduced.

In a preferred embodiment the safety bracket comprises a closing means.

If the receiving portion is arranged around the shaft, the receiving portion of the safety bracket can either be made of one piece or of two or more pieces. A two piece safety bracket with a closing means will be beneficial during assembly of the roll unit, which will be especially useful if the roll body is large and heavy, for example a sink roll in a hot-dip galvanizing installation, as the safety bracket can easily be installed around the sink roll and closed with the closing means.

In a further preferred embodiment the closing means is connected to the receiving portion of the safety bracket by fastening means.

The fastening means provide an additional advantage that the safety bracket can be flexibly assembled and disassembled. In a further preferred embodiment the closing means is connected to the receiving portion of the safety bracket by welding.

By welding a permanent connection will be obtained. In addition, welding, especially in a workshop where big rolls are assembled to form a roll unit is the most practical way of assembling such a roll unit with a safety bracket.

In a further preferred embodiment the safety bracket is connected to the support arm by fastening means.

The fastening means provide an additional advantage that the safety bracket can be flexibly connected and disconnected to the support arm.

In a further preferred embodiment the safety bracket is connected to the support arm by welding.

By welding a permanent connection will be obtained. In addition, welding, especially in a workshop where big rolls are produced, will be the easiest way of assembling such a roll unit.

In a further preferred embodiment the safety bracket is made of a corrosion resistant alloy steel.

Preferably, the safety bracket is made of a heat and corrosion resistant stainless steel, consisting by weight of 0.02 to 0.30 percent C, not more than 1 percent Si, not more than 2 percent Mn, 10 to 30 percent Cr, 0.1 to 20 percent Ni, 0.1 to 6 percent Mo and balance iron and incidental impurities. Preferably, the safety bracket is made from 316 L stainless steel. A corrosion resistant alloy steel will ensure that the safety bracket can be used in harsh operating conditions, for example in a hot-dip galvanizing coating bath where temperatures of 420 °C to 500 °C are typical.

In a further preferred embodiment the safety bracket is spaced apart from the roll body at a distance D of at least 1 mm.

As the roll body has to withstand many forces during operation, the roll can undergo slight deformation. In order to ensure a sufficient distance between the roll body and the safety bracket, the safety bracket is spaced apart from the roll body at a distance D of at least 1 mm, preferably at least 2 mm, more preferably at least 5 mm, most preferably at least 20 mm.

In a further preferred embodiment the coating bath contains a metal melt.

The metal melt can, for example, consist of liquid zinc, tin, lead, aluminum, MagZinc®, Galvalloy®, Galvalume®, Galfan® or another metal suitable for metal dip coating. Depending on the metal melt chosen, the metal melt has a typical temperature of 400 degrees centigrade to 700 degrees centigrade and the coating process is generally effected at band speeds of up to 250 m/min.

In a further preferred embodiment the roll is a sink roll.

The sink roll is used in hot-dip galvanizing and is submerged in a metal melt containing liquid zinc and optionally additional elements such as aluminium. The sink roll is typically made of a heat resistant alloy such as 316L stainless steel or alternative with equivalent properties and has a roll body with a diameter of 0.5 to 1 meter and a roll body length in a range of 2 to 3 meters. The total length from shaft to shaft end is in a range of 3 to 5 meter. The strip is typically guided around the sink roll in a U-turn between 135o and 180o.

In an alternative preferred embodiment the roll is a guiding roll.

The guiding roll may also be used in hot-dip galvanizing and is submerged in a coating bath. One or two guiding rolls, also known as control rolls, stabilizer rolls or correction rolls, are used to guide the strip in a vertical direction before the strip enters or exits the coating bath. The guiding roll is typically made of a heat resistant alloy such as 316L stainless steel or alternative with equivalent properties and has a roll body with a diameter of 100 to 380 millimeter and a roll body length in a range of 2 to 3 meters. The total length from shaft to shaft end is in a range of 3 to 5 meter.

In a second aspect of this invention there is provided a safety bracket for a roll unit, wherein the safety bracket comprises a connection portion and a receiving portion, and wherein the connection portion is adapted for attachment to a support structure of the roll unit and wherein the receiving portion is adapted to receive the shaft portion of the roll.

The safety bracket can be fitted on a roll unit as known in the art as a after-market solution. Once mounted to the roll unit the safety bracket will secure the roll unit once a shaft failure occurs as already elucidated above.

In a preferred embodiment there is provided a safety bracket for a roll unit wherein the receiving portion further comprises a closing means and optionally fastening means.

A safety bracket wherein the receiving portion comprises a closing means will make it more convenient to assemble the safety bracket around the roll of a roll unit as known in the art. As roll units are heavy, a sink roll for example weights around 3500 kg, guiding the roll unit through the safety bracket will be complicated. A safety bracket according to this preferred embodiment can easily be fitted around the roll unit and will still secure the roll in all directions. The invention will hereinafter be further elucidated with reference to the drawing of exemplary embodiments of a roll unit according to the invention and according to the prior art.

-FIG 1A shows a roll unit according to the prior art;

-FIG 1 B - D show a roll unit according to the invention;

-FIG 2A - D show a close up of different embodiments according to the invention;

-FIG 3A shows a safety bracket according to the invention.

Whenever in the figures the same reference numerals are applied, these numerals refer to the same parts.

Making first reference to FIG 1A and 1 B. Figure 1A shows a roll unit according to the prior art. The roll unit comprises a roll with a roll body (11) with shafts (20a, 20b) projecting axially from each end of the body. The roll unit also comprises a pair of support arms (30a, 30b) with roll bearings (40a, 40b). The shafts comprise a neck which may be tapered and a shaft end which is supported by the bearings. The roll unit may optionally include a connecting bar (not shown). FIG 1 B shows a roll unit according to the invention. The roll unit comprises a roll (100) with a roll body (1 10) with shafts (120a, 120b) projecting axially from each end of the body. The roll unit also comprises a pair of support arms (130a, 130b) with roll bearings (140a, 140b). The shafts comprise a neck which may be tapered and a shaft end which is supported by the bearings. The roll unit may optionally include a connecting bar (not shown). The roll unit according to the invention further comprises safety brackets (150a, 150b) attached to each support arm wherein the receiving portion (151a, 151 b) of the safety bracket is arranged underneath the shaft and between the roll bearings and roll body. FIG 1 C shows a close up of the roll unit of the invention and shows that the safety bracket is spaced apart from the roll body at a distance D and from the shaft at a distance H. The safety bracket is attached to the roll unit at a distance R with respect to the centre of the shaft. FIG 1 D is a cross sectional view of the safety bracket according to the invention, wherein it is clear that the safety bracket does not interact with the roll (100) during normal operation.

The roll unit as shown in FIG 1A and 1 B is typically used in continuous hot-dip galvanizing lines as a so called correction or passline roll. The roll as such is submerged in a coating bath with a zinc based metal melt with typical temperatures of more than 420 °C. In case of a shaft failure, the roll unit will break in between the roll bearing (40a, 40b) and roll body (110) as indicated with the squiggly arrow. In a roll unit according to the prior art, this will lead to the roll body being suspended in the metal melt. However, when the whole roll unit is replaced, during the lifting of the roll body out of the zinc bath the forces will increase resulting in breakage of the other shaft and a let-down of the whole roll deep in the zinc bath, which is an unsafe situation for everyone involved. As a solution according to the prior art, the broken side can be supported by a chain. However, the addition of this chain while the roll body is partially suspended in the metal melt, requires operators to be in a dangerous situation and will take a large amount of time and hence money due to production stop.

The safety brackets in FIG 1 B are attached to the support arms by welding and have a receiving end which is located between the roll bearing and roll body and underneath the shaft. The safety bracket is made from a heat resistant 316 L stainless steel and can easily support the roll weight which is about 150kg for a stabilizer. It is spaced apart at a distance D from the roll body and is attached at each support arm at a distance R from the centre of the roll bearing. The safety bracket is not disturbing the normal operation from the roll as it has no direct contact with the shaft upon normal operation as its receiving portion is spaced apart at a distance H from the shaft, as shown in FIG 1C and FIG 1 D. When the shaft breaks, the shaft will be supported by the safety bracket and the roll unit as a whole can be easily transported for repair and replacement, thereby simultaneously providing a significantly reduction of the downtime of the production and a safer work environment for everyone involved.

FIG 2A-D provide a close up of different preferred embodiments of the roll unit according to the invention. FIG 2A shows an embodiment wherein the safety bracket(250a) is attached to the support arms by welding and the receiving portion (251a) of the safety bracket is below the shaft. FIG 2B shows an embodiment wherein the receiving portion (351a) of the safety bracket (350a) is arranged around the shaft of the roll. FIG 2C shows an embodiment wherein the safety bracket (450a) is connected to the support arm by fastening means (455a) and wherein the safety bracket comprises a closing means (453a) which is connected by fastening means (454a). The roll unit as such can be easier assembled than the embodiment of FIG 2B, and will still safeguard the roll in all direction upon shaft failure. In addition, this embodiment could be easily disassembled if used for a coating bath containing for example, an organic chemical pre-treatment. However, when the same embodiment will be used in a hot metal melt, the fastening means will be treated by the hot metal melt as well and will be permanently fixed. FIG 2D shows an embodiment according to the invention wherein the safety bracket (550a) comprises a closing means which is connected by welding. For all embodiments described in FIG 2A-D the safety bracket is connected to the support arm at a distance R, measured from the centre of the roll bearing to the attachment point of the safety bracket to the support arm. The distance R is preferably at least 5 cm and at most 100 cm. In the figures the distance R shown is 20 cm, such that the safety bracket is attached to the support arm below the optional connecting bar. The distance D between the receiving portion of the safety bracket and the roll body is preferably at least 1 mm and at most 200 mm. Most preferably the receiving portion is arranged halfway between the roll body and roll bearing as shown in FIG 2A-D, typically corresponding with a distance D of 100 mm. The distance H between the receiving portion of the safety bracket and the shaft is 30 mm.

FIG 3A shows a safety bracket (150) according to the invention which can be used as an aftermarket solution. The connection portion (152) may be welded to a roll unit, for example to the support arm, whereas the receiving portion (151) may be fitted around the shaft.

Claims

1. A roll unit for guiding a strip through a coating bath, comprising a roll (100) having a roll body (110) with two shafts (120a ,120b) projecting axially from each end of the body and a pair of support arms (130a, 130b), each shaft being supported in a roll bearing (140a, 140b) connected to a support arm (130a, 130b), further characterized in that the roll unit comprises a pair of safety brackets (150a, 150b) having a receiving portion(151a, 151 b), wherein each receiving portion is arranged underneath the shaft (120a, 120b) and between the roll bearing (140a, 140b) and roll body (110), and wherein the receiving portion is configured as such that it will only interact with the shaft of the roll upon shaft failure.

2. The roll unit of claim 1 wherein the safety bracket (150a, 150b) is attached to the support arm (130a, 130b).

3. The roll unit of claim 1 or 2 wherein the receiving portion (151a, 151 b) of the safety bracket (150a, 150b) is horizontal or tilted at an angle in a range of 0 ° - 40 °.

4. The roll unit of any of claim 1 - 3 wherein the receiving portion(151 a, 151b) of the safety bracket is arranged around the shaft of the roll.

5. The roll unit of any of the claims above, wherein the safety bracket comprises a closing means(453a).

6. The roll unit of claim 5, wherein the closing means is connected to the receiving portion(151a, 151 b) of the safety bracket by fastening means(454a).

7. The roll unit of claim 5 or 6, wherein the closing means is connected to the receiving portion(151a, 151b) of the safety bracket by welding.

8. The roll unit of any of the claims above, wherein the safety bracket is connected to the support arm by fastening means (455a).

9. The roll unit of any of the claims above, wherein the safety bracket is connected to the support arm by welding.

10. The roll unit of any of the claims above, wherein the safety bracket is spaced apart from the roll body at a distance D of at least 1 mm.

11. The roll unit of any of the claims above, wherein the coating bath contains a metal melt.

12. The roll unit of any of the claims above, wherein the roll is a sink roll.

13. The roll unit of any of the claims above, wherein the roll is a guiding roll.

14. A safety bracket(150) for a roll unit according to any of the claims above, wherein the safety bracket comprises a connection portion (152) and a receiving portion (153), and wherein the connection portion is adapted for attachment to a support structure of the roll unit and wherein the receiving portion is adapted to receive the shaft portion of the roll (100).

15. The safety bracket according to claim 14, wherein the receiving portion further comprises a closing means and optionally fastening means.