Roll or roller – With specific roller exterior surface structure – Surface projections – indentations – or slits
Reexamination Certificate
1999-08-09
2001-08-28
Rosenbaum, I Cuda (Department: 3726)
Roll or roller
With specific roller exterior surface structure
Surface projections, indentations, or slits
C492S049000, C492S054000, C241S293000, C029S895320
Reexamination Certificate
active
06280370
ABSTRACT:
TECHNICAL FIELD
This invention relates to mill rollers and abrasion resistant surface coatings for mill rollers, as well as methods of constructing mill rollers and forming abrasion resistant surface coatings on mill rollers.
The invention has particular application to sugar mill rollers and for illustrative purposes, reference will be made to such application. However, it is to be understood that the invention may have use in other applications where improved mill rollers are required.
BACKGROUND ART
In the sugar industry, sugar cane is typically crushed between rollers arranged in pairs or in groups of three. Generally, the rollers have a plurality of machined ridges extending circumferentially about the roller forming a surface of alternate ridges and valleys. The grooves are typically evenly spaced along the roller, however, it will be appreciated that in some applications, it may be desirable to have unevenly spaced grooves. The grooved arrangement provides for gripping of the sugar cane fibre as it passes between the rollers, the groove of an upper roller being operatively aligned with the ridges of its opposing lower roller or rollers.
A sugar mill roller is usually constructed as a cast roller mounted on a shaft and turned by drive means. Wear resistant material has on occasion been provided on the caps of the ridges of grooved rollers, but only at intermittent locations around the circumference of the roller. This approach has been taken partly because it was believed that the intermittent application of the abrasion resistant material produced the best gripping surface for the milling of sugar cane. Typically, conventional hardfacing material is used, including, for example, high speed steels, austenitic manganese steels, austenitic high chromium irons, cobalt or copper based alloys, or nickel-chromium-boron alloys according to the practices set forth in Jones, F D, & Horton, H L,
Machinery's Handbook
, ISBN 0-8311-1155-0. Additionally, abrasion resistant material such as chips of tungsten carbide, for example, may be laid up in the matrix to form a hardfacing composite in the hardfacing materials listed in this reference or in mild or stainless steel weld.
After a period of use, sugar mill rollers require refurbishment due to the hardfacing wearing smooth, causing slippage of the cane and/or bagasse between the rollers. In order to refurbish such a roller according to traditional practice the entire roller is removed from the mill, broken up and recast into a new roller. This approach is costly in terms of replacing the entire roller and requires a significant downtime for the sugar mill in having the roller replaced. There are also costs for heavy transport for removing and delivering the rollers to site.
The present invention aims to alleviate one or more of the above disadvantages and to provide a roller having a wear resistant surface and method of forming same which will be reliable and efficient in use.
DISCLOSURE OF INVENTION
With the foregoing in view, this invention in one aspect resides broadly in a sugar mill roller including:
a roller body of substantially circular cross-section having a plurality of circumferentially running machined ridges formed to be substantially parallel and spaced along a substantial part of said roller body, each said machined ridge including one or more land portions, and a ridge capping on said one or more land portions, each said ridge capping including a plurality of layers of weld supporting therein a wear resistant material.
Preferably, each machined ridge includes two or a multiple of two land portions, separated by a wall portion and one or more of the layers of weld are supported on respective ones of the land portions against the wall portion. It is also preferred that the roller body be formed of grey cast iron, and the ridge capping includes a first layer of stainless steel weld, and further preferred that the first layer includes no wear resistant material.
In another aspect, this invention resides broadly in a method of applying hardfacing to a sugar mill roller, the method including:
providing a roller body of substantially circular cross-section;
machining a plurality of circumferentially running ridges on said roller body, said ridges being substantially parallel and axially spaced along a substantial part of said roller body, each said ridge including one or more land portions, and
on each said ridge, forming a weld matrix on the or each innermost land portion by successively applying weld on the previous layer until a ridge capping of desired profile is formed substantially all the way round said roller body, at least some of said layers of weld having particulate wear resistant material supported therein.
Preferably, a wall portion is machined on each ridge so as to provide one or more land portions on each side of the wall portion, and weld is applied against each side of the wall portion in successive layers until the height of the wall portion is substantially reached. One or more further layers of weld are preferably applied to each respective ridge to substantially encapsulate the wall portion.
The weld may be applied by any suitable welding process, however metal inert gas (mig) welding or tungsten inert gas (tig) welding is used, and the weld pool first applied to the or each said land portion is formed from a stainless steel welding rod without any wear resistant material added thereto and successive layers are formed from a mild steel welding rod used in which respective successive weld pools are impinged with a particulate wear resistant material. The layers are laid up until a ridge capping of desired profile is formed substantially all the way round each ridge.
In another aspect, this invention resides broadly in a sugar mill roller including a roller body formed in accordance with the method as hereinbefore described. However, it will be appreciated that the hardfacing may be applied to substrates other than sugar mill rollers.
In another aspect, this invention resides broadly in a roller assembly including:
a mounting shaft;
a plurality of shell portions, each said shell portion being mountable to said mounting shaft and shaped for abutment together to form a roller cap;
each said shell portion having an outer perimeter and an inner diameter of a dimension permitting tight engagement of said roller cap onto said mounting shaft, and
a wear resistant surface applied to the outer perimeter.
The roller caps may have a substantially smooth outer surface for receiving the hardfacing, but preferably, the roller caps include a plurality of grooves extending circumferentially about the outer perimeter as hereinbefore described. The roller assembly is preferably circular in section, although it will be appreciated that other sections may be utilised, such as elliptical or dog-bone interengageable sections.
The wear resistant surface is preferably in the form of a wear resistant weld applied to the outer perimeter as hereinbefore described. Preferably, at least some of the ridges between the grooves include a cap portion with an abrasion resistant material on each cap portion.
The roller cap may include shell portions connectible to form an annular shell element, or be comprised of a unitary annular shell element, each shell element being abuttable to form the roller assembly such as for example, a sugar mill roller.
In sugar milling applications, the groove profile is selected to be similar in size and shape of cross-section to the groove profile of cast sugar mill rollers, that is generally between 15 mm and 80 mm pitch, but more commonly, either 25 mm, 37.5 mm or 50 mm pitch.
Preferably, the groove profile includes a ridge profile which includes an elongate projection and a land area on each side of the elongate projection such that successive layers of weld may be applied sequentially, allowing sufficient time between the respective layers for cooling of the weld. Suitably, the first layer of weld on each side of the projection is applied to the respective land areas. The elongate projection is o
Abelman ,Frayne & Schwab
Cuda Rosenbaum I
The Track Shop Pty Ltd.
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