Adhesive bonding and miscellaneous chemical manufacture – Surface bonding means and/or assembly means therefor – With braiding or weaving means
Reexamination Certificate
2001-06-28
2004-12-07
Yao, Sam Chuan (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Surface bonding means and/or assembly means therefor
With braiding or weaving means
C156S439000, C156S440000, C156S177000, C156S181000, C264SDIG008
Reexamination Certificate
active
06827118
ABSTRACT:
The invention concerns a process and a device for the placement and fixing of sheets of filaments, in the course of the production of scrims, which are implemented in a connecting station into a flat structure having, among other elements, the filament sheets.
The connecting station can, for example, be a warp knitting machine or a calender in which the previously placed and fixed filaments can be knitted and/or connected with one another in such a way that a flat scrim thereby arises. The filaments serve, on one hand, as so-called weft yarns in the production of scrims and, on the other hand, are increasingly used for purposeful reinforcement of the scrim to be produced, depending on their material. Placing these types of weft yarns continuously and in a meander shape by means of a weft carriage between two rows of needles moving forward via conveyor bands is known, with the yarns being hung on the rows of conveyor needles of a conveyor device. Lateral fixing of the weft yarns placed in this way is only required until the individual yarns are knitted or otherwise connected with one another in the connecting station. Subsequently, laterally projecting weft yarns can be cut off. These cut-off parts of the yarns are to be disposed of as filament waste of the production process.
Increasingly, these types of scrims for reinforcement are produced with high-value yarns and/or filaments, such as glass or carbon fibers. In this regard, the known methods for fixing and placement of the yarns have the disadvantage that on one hand, cost-intensive waste arises due to the cut-off remainders of high-value and thereby expensive yarns projecting at the edge of the scrim and, on the other hand, problems hereby arise because distortions and irregularities in the yarn guiding occur due to the twisting of the yarns or yarn sheets at the reversal points and/or around the conveyor needles, which leads to the placed and fixed yarns not forming a smooth plane. In the subsequent knitting process in a connecting station, this regularly leads to knitted materials of poor quality. The latter problem particularly arises when yarns are collected into so-called yarn sheets, because these cannot, and/or not without further means, be placed smoothly as flat bands around the rows of conveyor needles fixed laterally on the conveyor chains. The problem particularly occurs when so-called “heavy tows,” i.e., filament sheets with a high number of filaments of a magnitude of approximately 10
4
, made of, for example, materials such as carbon or glass, are to be used for the production of scrims. Placement of these types of materials is, any case, only possible in very restricted cases (cf. Kettenwirkpraxis [Practical Warp Knitting] 2/96 p. 7).
The object of the present invention is to provide a process and a device for the placement and fixing of filament and/or yarn sheets, for the production of flat scrims, having an essentially uniform filament density, and to allow the use of filament sheets with various materials and to improve their secure fixing until connecting in a connecting station, particularly in a knitting station.
This object is achieved by a process with the features according to claim
1
and/or by a device with the features according to claim
11
. Advantageous embodiments and further developments of the invention are objects of the respective sub-claims.
According to the process for placement and fixing of a filament sheet according to the invention, the filament sheet is placed as a filament sheet section between two conveyor units supplying a connecting station, with the filament sheet sections each being fixed onto the conveyor unit at each of their end regions with a fixing element and the interval of the fixing elements of one single filament sheet section relative to the conveyor unit being selected in such a way that, in their fixed condition, the filament sheet sections are positioned essentially flat between the conveyor units, at least immediately before entering the connecting station. Because the filament sheet is placed and fixed on the conveyor unit as separate filament sheet sections, each with fixing elements at their ends, the filament sheet is prevented from twisting, as in the meander-shaped placement, and thereby being placed out of its plane and thus irregularly. Rather, it is ensured with high reliability that the filament sheet, i.e., each individual filament of this filament sheet, is placed and fixed in a preset plane. In this way, not only is the quality of the scrim to be produced greatly improved, it is now also possible according to the invention to use relatively wide or stiff filament sheets or yarn sheets for processing into flat high-performance scrims. Furthermore, the resulting residues arising laterally on the scrim, which must be cut off and disposed of as waste, are reduced. Rather, the filament sheet sections can be exactly dimensioned in such a way that the fixing elements have exactly enough hold on the ends of the filament sheet sections to hold the filament sheet sections securely even under light pretension. The productivity of the production of scrims is thereby significantly increased, with the production able to be performed in less time and at lower cost. Because a weft carriage no longer places individual yarns, but rather wide filament sheet sections with an entire sheet of filaments, the placement speed can be increased. In addition, the variability in the placement of filament sheets can be increased with the process according to the invention, for example by also making multiaxial and multilayer placement of yarn sheets possible.
Although the filament sheets are placed without being twisted, good fixing by the lateral fixing elements is ensured at all times. The use of band-shaped filament sheet sections also has the advantage that, because they are a significantly less expensive starting material than individual yarns, the overall cost of the scrim to be produced can also be reduced.
According to an advantageous embodiment of the invention, the fixing elements are attached at a slant to the filament sheet section, i.e., to the lengthwise direction of the filament sheet section, at a selectable angle for diagonal placement of the filament sheet sections. This has the advantage that the strength of the scrim to be produced can be increased further, for example through superposition of straight and diagonally running filament sheet sections. The tensile strength of this type of material can thus be purposely adjusted according to the application in every direction. Because each filament sheet section is provided with two end fixing elements, they can be provided at any angle, i.e., of course also at any distance to one another, depending on the diagonal angle selected, and correspondingly be placed on the conveyor unit, with a reliable, and nonetheless very exact, placement, located in one single plane, of the filament sheets being ensured. The yarn sheets and/or yarn bands can thus not only be simply placed on top of one another, but can also be positioned and fixed unidirectionally, biaxially, or multiaxially in the placement range.
According to a further advantageous embodiment of the invention, the fixing elements of a filament sheet section are hung on holding needles of a conveyor unit. In this way, the individual filament sheet sections are securely fixed between the holding needles in a very simple way. Nonetheless, they can be easily hung as desired, even on top one another, and thereby fixed. For filament sheet sections which are laid on top one another, it is advantageous for the holding needles to have a radius of curvature, so that the individual filament sheet sections have a uniform tension over the working width due to the greater thickness of the fixing elements at the end regions. Continuous, uniform placement and fixing is possible in this way, independent of the individual filament sheet section. The hanging or also removal of filament sheet sections can be performed rapidly and with simple means.
According to a fur
Unglaub Michael
Wienands Christian
LIBA Maschinenfabrik GmbH
Smith , Gambrell & Russell, LLP
Yao Sam Chuan
LandOfFree
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