Textiles: knitting – Fabrics or articles – Warp
Reexamination Certificate
1998-07-13
2001-06-12
Calvert, John J. (Department: 3741)
Textiles: knitting
Fabrics or articles
Warp
C066S190000, C139S38300A
Reexamination Certificate
active
06244077
ABSTRACT:
The invention concerns a multilayer flat or circular knitted structure comprising two plain knitted webs which are interconnected by a third thread system. The invention also concerns a method of producing the same, especially of producing semi-finished structures for fibre composites.
By DE-PS 458 906 there is known a multilayer knitted structure comprising two plain knitted webs, their fabric backs facing each other and being interconnected by a third thread system. In this knitted structure the third thread system consists of a bundle of standing threads by which the coherence of the outer knitted webs is ensured. The knitwear has the function of connecting two different product surfaces. The third thread system is intended to stuff the knitted structure better and to provide strength in the longitudinal direction.
According to DE 29 27 414 A1 a reinforcing knitted structure for resinous laminates is known which consists of a warp-knitted fabric or a knitted structure with reinforcing interlining. The reinforcing knitted structure consists of a large number of parallel warp interlining layers and a large number of parallel weft interlining layers in the knitwear. The warp interlining is limited by the bottom half arcs, and the weft interlining is limited by the plain stitches. A disadvantage is the construction which is connected to a specific sequence. Moreover, a reinforcing textile with reinforcing threads adapted to stress cannot be produced or can be produced only conditionally.
It is also known to produce two separate knitted webs on knitting machines at the same time parallel to each other by means of two needle beds. By interconnecting in places also three-dimensional knitted structures can be made. The knitted webs can be connected by a third knitted web according to DE 40 08 057 A1. According to DE 36 43 357 A1 the connection is made by at least one knitted-in or inwrought, comparatively thin, separate intermediate thread or a knitted structure. With this kind of connection of two halves of knitted structure the coherence is established by the formation of loops. The binding thread itself forms stitches or loops. The knitted structures therefore do not have stretched thread layers and are only conditionally suitable as reinforcing knitted structure.
It is the object of the invention to produce a multilayer knitted structure of the above-mentioned kind which can be designed thin-walled as well as thick-walled, has a high drapability and is capable of absorbing tensile, compressive and bending forces.
In accordance with the invention the problem is solved by the means mentioned in the claims and explained in detail by the embodiments.
Layers of warp threads and weft threads are inserted into the plain knitted structures limiting the outer sides. The coherence of the warp-thread and weft-thread layers is ensured by the back foots which pass the layers and loop all present warp threads. The multilayer knitted structure is held together by warp threads looped by bottom half arcs alone or together with weft threads which are covered with plain stitches, depending on the structure of the warp-thread and weft-thread layers.
Warp and weft threads follow the transfer of forces in the fibre composite in an advantageous way.
The density of the warp threads or/and weft threads need not necessarily be equidistributed over the width and length of the knitted web; it may be locally zero, for instance, for the reception of parts such as screws.
Changing of the warp threads into other planes formed by the weft threads is furthermore possible, and vice versa. In this way, transfer tails are created, which prove to be advantageous in a later shaping-out of the reinforcing textile.
By the stretched layers of warp and weft threads the forces are absorbed in the fibre composite. The coherence of the layers over the two knitting-thread systems guarantees a high drapability of the knitted structure and a good delamination behaviour if the knitting thread consists of high-performance material.
Of course, the multilayer knitted structure is suitable for the production of other fabrics, besides the production of fibre composites, e. g. for the production of surfaces with fabric and insulation properties.
With the process according to the invention a knitting thread is crosswise fed to at least one bundle of warp threads from two sides, e. g. from two needle beds. By means of needles the knitting thread is pulled through in loops and interlooped with the preceding knitting thread of the same knitting-thread system on the other side. Subsequently, on the other side (opposite the side of the first knitting thread) a second knitting thread is crosswise fed and processed in the same way as the first knitting thread.
To increase the thickness of the knitted structure, several bundles of warp threads are fed between the two knitted webs. A limitation is given by the design, e. g. the needle size. Besides the feeding of warp threads or bundles of warp threads, between the knitting of the individual courses there can be laid single weft threads between the warp-thread bundles or at their sides.
Warp and weft threads may be carried almost unlimitedly in any direction and change into other planes. The direction is determined mainly by the transfer of forces in the fibre composite or by spots with special reinforcement.
The advantage of the invention is that a large number of warp and weft threads are interconnected by two knitting threads. Therefore, the knitted structure is very drapable, the interconnection of the layers being ensured. The knitted structure is thus especially suitable for the production of fibre composites.
The invention will now be explained in greater detail with reference to embodiments thereof. In the drawings there are shown by
FIG. 1
a representation for illustrating the method with warp thread and two needles
FIG. 2
a cross-section of a multilayer knitted structure with 2 layers of warp threads and 3 layers of weft threads
FIG. 3
a top view of a multilayer knitted structure with a stretched warp-thread layer
FIG. 4
a top view of a multilayer knitted structure with an empty space made by racking of the warp threads
FIG. 5
a top view according to
FIG. 4
with an additional layer of stretched weft threads and different density of weft threads
FIG. 6
a top view according to
FIG. 4
with weft threads carried around the empty space
FIG. 7
a representation for illustrating the method with 2 warp threads and 3 weft threads
FIG. 8
a representation with variable design of the weft-thread layers
REFERENCES:
patent: 393185 (1888-11-01), Stowe
patent: 628818 (1899-07-01), Koch
patent: 3859824 (1975-01-01), Krylov et al.
patent: 4787219 (1988-11-01), Sato et al.
patent: 5191777 (1993-03-01), Schnegg
Engelmann Uwe
Hoffmann Gerald
Offermann Peter
Calvert John J.
Jordan and Hamburg LLP
Muromoto Jr. Robert H.
Technische Universitaet Dresden
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