Patent Application
20190119832
This application claims the benefit of European Patent Application No. 17197463.7, filed Oct. 20, 2017, the contents of which is incorporated herein by reference as if fully rewritten herein.
The invention relates to a card wire for a roller of a carding machine.
Carding machines, cards or carders are used to open (individualize) and align the fibres of a fibrous material, e.g. of wool, cotton, synthetic fibres or of a fibre blend, to homogenize them (for fleece production) and/or to parallelize them (for yarn production). The carding process may be used to produce a fibre mat from a fibrous material. The fibre mat consists of a loose collection of ordered individual fibres. A nonwoven, for example, may be produced from a fiber mat of this kind. During carding, the fibre mat is formed by removing the fibres, by way of a removal means, from a large carding roller, also known as the cylinder, and combining them.
The carding machine may have various carding rollers, each of which has teeth, serrations or spikes projecting outwards in approximately radial direction. The number and/or size and/or density of the teeth, serrations or spikes, as well as their shape and configuration, may vary.
Carding rollers are generally provided with all-steel card clothing. This consists of a profiled card wire wound under tension onto the carding roller in question. The card wire has a foot segment and a blade segment. The foot segment may have, for example, a rectangular or square cross section. In the operating position, the blade segment projects away from the foot segment approximately at right angles to the curved surface of the carding roller. The blade segment features a sawtooth profile for the formation of teeth or serrations. The card wire is wound, under longitudinal tension, around the curved surface of the carding roller, and the two ends are attached to the carding roller.
Known card wires exist in many different configurations, and special groups of card wires, each with specific geometric features, are proposed for different functions of the particular carding roller in the carding machine.
WO00/26450A1, WO2011/138322A1 and WO2013/037711A1 show card wires which are especially suitable for rollers generally known as workers, doffers or transfer rollers. In comparison with the total height of the card wire, the teeth of these card wires are typically punched relatively deep, with the tooth face leaning relatively far forwards towards the foot segment. The tooth face is the side of the tooth that makes direct contact with the fibres during carding. The cited publications show portions of the tooth face that lean even further towards the foot of the clothing in order to enhance the carding effect of the clothing. A portion of the tooth face which leans more strongly towards the foot of the clothing may be termed an undercut. An undercut of this kind may negatively influence the stability of the teeth, especially if consecutive teeth come closer together. WO2013/037711A1 accordingly proposes a special geometry for the tooth face, in particular in the undercut, as a refinement of WO00/26450A1.
If the card wires in the above-cited publications, but also card wires without an undercut for worker, doffer or transfer rollers, have a small tooth pitch compared with the tooth depth, they have the disadvantage that, near to the tooth base, fibers may jam in the tooth gap and, with time, cause the clothing to clog. Even if not many fibres are normally held in the lower section of the tooth gap (near the tooth base), an undesirable pile-up of fibres may occur rapidly once the first fibres have jammed.
The objective of this invention is to provide a card wire with which fibres jam less easily and clogging of the clothing is reduced.
The card wire of the invention is especially suitable for the clothing of a doffer roller, a worker roller or a transfer roller. In its longitudinal direction, the card wire has consecutive teeth, which are spaced apart in the longitudinal direction by a distance known as the pitch. The pitch may be measured advantageously from tooth tip to tooth tip. The teeth are bounded in the longitudinal direction by a tooth face on a first side and by a tooth back on a second side. As seen looking down in the height direction of the card wire, the tooth face and the tooth back of consecutive teeth merge in a tooth base. As seen looking up in the height direction of the card wire, the tooth face and the tooth back form the tooth tip at their point of intersection. The tooth depth is defined by the greatest distance, in the height direction of the card wire, from the tooth tip to the tooth base. If the mathematical ratio of pitch to tooth depth is less than 1.1, conditions prevail that favour the jamming of fibres in the lower section of the tooth gap. The card wire of the invention is characterised in that an interspace, measured at right angles to a tangent to an inflection point between tooth back and tooth base, between this inflection point and the opposite tooth face is greater than a quarter of the pitch. It is also advantageous if the distance is greater than the quotient of the pitch and 3.5, or greater than the quotient of the pitch and 3. Thanks to the greater distance between consecutive teeth in the lower portion of the tooth gap, fibres jam less often in this lower portion of the tooth gap and the clothing clogs less frequently. The larger distance additionally has the synergistic effect that the surface on the tooth face is smoother in many of the card wires in question. In consequence, the initial jamming of fibres becomes even less frequent because the fibres are able to slide more easily on the surface. As is known, the surface of most of the card wires concerned undergoes a finishing process at a late stage of their production, the purpose of which is also to smooth the surface. Where the distance between the teeth is greater, this process produces enhanced smoothness.
The inflection point at the transition between tooth back and tooth base may be determined non-ambiguously as follows: except for localized shape elements such as elevations or depressions, the tooth back has, essentially at every point, a tangent that encloses an acute angle with the longitudinal direction. In the tooth base there is at least one point at which the tangent to the card wire runs in the longitudinal direction. Starting from this point with a tangent to the tooth back running in the longitudinal direction, the inflection point is at the first position at which, compared with the nearest preceding point, the angle enclosed by the tangent and the longitudinal direction assumes a smaller or equal value.
The card wire according to the invention preferably has a pitch of less than 3.2 mm. A pitch of less than 2.6 mm is particularly advantageous.
At the tooth face, the card wire may enclose an angle between 45° und 65° with the longitudinal direction. At the tooth face, the card wire may enclose an angle between 50° und 60° with the longitudinal direction. It may be particularly advantageous if this angular portion exists on the tooth face below a possibly existent steeper tip section and below a possibly existent undercut. The tooth face may be straight and have a single angular value over this portion. However, it is also possible for the tooth face to be curved and for it to assume different angles over this angular portion.
The card wire may be configured as a circular arc in the tooth base. A rounded tooth base is particularly advantageous because there are then no edges or corners at which fibres jam more easily. The rounded tooth base advantageously transitions tangentially and kink-free into the bordering tooth back and the bordering tooth flank.
The radius in the tooth base of the card wire may exceed one eighth of the pitch. A radius greater than 0.4 mm may be particularly advantageous. A radius that exceeds one seventh or one sixth of the pitch is also advantageous.
The card wire may have a tooth back with two or more straight sections. A straight section that borders on the tooth base may enclose a larger angle with the longitudinal direction of the card wire than another straight section of the tooth back. The straight section bordering on the tooth base preferably transitions tangentially into the tooth base. The straight section, bordering on the tooth base, of the tooth back of the card wire preferably extends upwards towards the tooth tip for a maximum distance of 50% of the tooth depth. For one thing, this ensures that the teeth are the required distance apart at the tooth base. For another, this nevertheless enables the teeth to be configured with the requisite small pitch and still to have a tooth face that encloses a small angle with the longitudinal direction or has an undercut.
The card wire may have an undercut in the tooth face. The undercut leans more strongly towards the longitudinal direction than does the adjoining part of the tooth face below the undercut. In other words, the undercut encloses a smaller angle with the longitudinal direction than does the adjoining portion of the tooth face. The angle enclosed between the undercut and the longitudinal direction is preferably between 0° and 40°. The angle enclosed between the undercut and the longitudinal direction may be between 5° and 35°.
The foot segment of the card wire according to the invention may be freely selected to suit the specific application. The card wire may have, for example, prism- or v-shaped interlocking foot segments or plain rectangular ones.
The card wire according to the invention, shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 17197463.7 | Oct 2017 | EP | regional |
