Conveyors: power-driven – Conveyor having impinging fluid to feed – shift or discharge... – Having cleaning means
Reexamination Certificate
2000-01-14
2001-06-26
Bidwell, James R. (Department: 3651)
Conveyors: power-driven
Conveyor having impinging fluid to feed, shift or discharge...
Having cleaning means
Reexamination Certificate
active
06250456
ABSTRACT:
DESCRIPTION
The present invention relates to conveyor belts containing an areal textile configuration based on predominantly synthetic yarns, the use of a belt in conveyor systems, particularly conveyor belts in the foods industry, mining or the dye industry, a method of conveying goods by means of a traveling belt, and a conveyor device comprising guide elements that propel a belt.
Conveyor belts are employed in mining, in heavy and light industry, in machinery and equipment, in the foods industry, in transportation and communications, by government agencies and banks, in offices, as well as in many other areas, in order to transport the goods to be conveyed economically over considerable distances and/or differences in elevation. Conveyor belts generally take the form of endless belts passing over rotatable rollers mounted on stands.
From “Technische Information, Herstellung von Transport-bändern,”® Trevira Hochfest, by firm of Hoechst AG, conveyor belts are known that contain polyester, cotton, nylon 6.6, steel, rayon, cellulose fiber or steel fabrics as skeleton. These fabrics are coated with PVC, latex, polyurethane, rubber or fluorine polymers. The yarns contained exhibit a high strength and a low maximum tensile [el]ongation of not more than 22%, so that small surface elongations of only 1 to 2% occur in a conveyor belt produced therefrom.
From
Conveyor Belt Technology,
Volume I/86, Trans Tech Publications, Federal Republic of Germany 1987, methods of cleaning conveyor belts are known. Means are described for turning the belt, means of washing, spraying, airblasting and aspiration. Also, devices for beating, brushing, wiping and scraping by means of stripping elements are described.
Elastic fabrics for paper machines are disclosed in EP A 0,379,967, U.S. Pat. No. 5,225,270, EP B1 0,446,355 and EP A 0,549,917. These fabrics contain elastic monofilaments and are produced in the form of endless strips. The fabrics are generally built up of several layers, the supper layer being a needle felt.
The multilayer fabric described in EP 0,549,917 for conveyor belts in paper machines comprises a supporting fabric that may contain thermoplastic elastomer copolyether ester monofils of ®Riteflex by firm of Hoechst Celanese Corp., USA. The supporting fabric, as viewed in cross-section, is so bound that twice the number of wet threads will lie on the top of the fabric than on the bottom. According to the data in this source, the fabrics described may optionally comprise elastic threads in machine direction. As to the arrangement or orientations of the elastic threads in relation to the running direction of the conveyor belt, there is no information.
EP A 0,379,967 describes monofils of a thermoplastic elastomer polyether ester containing at least 5 wt. % polyurethane as elastomer component, and their use in textiles for conveyor and drying belts and for supporting fabrics of needle felts.
U.S. Pat. No. 5,225,270 describes a needle felt for paper machines consisting of elastic monofils with a proportion of, among other things, at least 30 wt. % polyphenylene ether and at least 30 wt. % polyamide.
EP B1 0,446,355 likewise describes supporting fabrics for paper machine needle felts of elastic monofils. The monofils used consist of an elastomer block copolymer with hard segments of polyamides and soft segments of polyethers. To enhance dimensional stability, it is proposed that the elastic monofils be employed only in the direction of the width of the supporting fabric.
Thus the problem still remained of developing a conveyor belt having adequate extensibility in running direction and suitable for transporting goods with a cleaning zone by the method of the invention.
The present invention relates to a conveyor belt (
5
) containing an areal textile configuration based on predominantly synthetic yarns, characterized in that the belt is in the form of an endless strip, the yarns extending in the running direction of the belt being elastic, the elastic yarns having a maximum tensile elongation of at least 60% and consisting at least 70 wt. %, referred to the total weight of the yarn, of a thermoplastic elastomer copolyether ester containing the recurrent structural units of formulas I and II,
—O—OC—Ar
2
—CO—O—R
4
— (I)
—O—OC—Ar
3
—CO—O—R
5
— (II)
where Ar
2
and R
3
, independently of each other, represent bivalent aromatic radicals,
R
4
represents a bivalent aliphatic or cycloaliphatic radical, and
R
5
represents the bivalent radical of a polyalkylene ether.
The conveyor belts may be built up of one or several layers. Thus it is possible for example that besides the areal textile configuration, still other, non-textile layers, such as for example rubber layers or coatings, are present. For certain applications in the foods industry, it may be expedient for the conveyor belt to consist preferably of an upper and a lower layer of an areal textile configuration, an additional layer of rubber or plastic being located between these two layers.
Especially preferred are conveyor belts containing only one layer of an areal textile configuration.
Preferably the conveyor belts are uncoated. These so-called light conveyor belts, except for operations commonly used for the dressing of yarns, such as for example smoothing or avivage, exhibit no additional films or coatings, such as rubber, latex or PVC matrix for example.
The areal textile configurations contained in the conveyor belts according to the invention are preferably woven, knit, fleece, laid or spiral fabrics. Especially preferred are areal textile configurations in the form of woven fabrics.
The term ‘yarn’ in the context of this description is to be understood in its broadest imaginable sense. The term includes for example monofilaments, multifilament yarns, staple fiber yarns, and two-component yarns, or mixtures of these as well.
Preferred are at least those yarns which go in running direction of the conveyor belt, monofilament yarns, so-called monofils that is to say. Especially preferred in the conveyor belts according to the invention are areal textile configurations made entirely of monofilaments.
In the context of this description, a yarn extending in running direction of the conveyor belt is understood to be a yarn which, considered over a fairly great length of yarn, extends practically parallel to the running direction of the conveyor belt. Such a yarn generally does not extend quite exactly along a straight line, but may certainly deviate slightly from the theoretical direction in smaller subregions. Such a deviation may for example occur in weaving or quite generally due to minor inaccuracies in the production of the conveyor belt.
By a ‘thermoplastic, elastomer copolyether ester’ in the context of this description is meant a polymer whose vitreous transition temperature is below 23° C., preferably below 0° C.
Preferably the thermoplastic elastomer copolyether ester contains at least 80 wt. %, in particular at least 95 wt. %, referred to the total weight of the thermoplastic, elastomer copolyether ester, of the recurrent structural units of formulas I and II. Very specially preferred are thermoplastic, elastomer copolyether esters containing at least 98 wt. % of these structural units.
Preferably Ar
2
and Ar
3
independently of each other stand for a phenylene and/or a naphthylene radical.
It is especially preferred for Ar
2
and Ar
3
each to stand for 1,4-phenylene.
R
4
as a bivalent aliphatic radical stands for straight-chain or branched alkalene or alkylidene; these are usually radicals having 2 to 20 carbon atoms, preferably 2 to 8 carbon atoms and in particular 2 to 4 carbon atoms.
It is especially preferred for R
4
to be straight-chain alkylene with 2 to 6 carbon atoms, in particular ethylene.
R
4
as a bivalent cycloaliphatic radical usually stands for a radical containing 5 to 8, preferably 6 ring carbon atoms; with special preference, this carbon ring is part of an aliphatic chain. An example of an especially preferred representative of this type is the radical of cyclohexanedi
Sohn Achim
Striegl Peter
Bidwell James R.
Burns Doane Swecker & Mathis L.L.P.
Johns Manville International Inc.
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