Knitting method

Abstract: A continuously weft-knitted three-dimensional fabric cover having sutures to accommodate its three-dimensional format in which each suture defines a straight line or a series of straight lines joined end-to-end, each straight line lying at an angle of between 0° and 50° to the course-wise direction of the fabric.

Description: Field This invention relates to a method of continuously knitting a fabric cover for a three dimensional object, the whole cover being formed in a single operation requiring no further sewing or processing. Background The invention is useful in machine knitting on a weft knitting machine having independently operable needles disposed in at least two needle beds, for example a flat V-bed machine producing a mainly double jersey structure. In such machines, the width of the knitted fabric is restricted by the maximum number of needles available for forming a course across the machine beds. Three-dimensional fabric structures for covering three dimensional objects are produced from two-dimensional material and have in the past been produced by weaving or knitting shaped parts and panels of said two-dimensional material and sewing them together. More recently it has been found possible to knit one-piece upholstery fabric, which removes the need for sewing portions together, and has the desired shape to serve as covers for the base and back cushions for vehicle seats, see for example GB-A-2,223,034. A problem that has arisen with the continuous knitting of three-dimensional fabric structures is that it has hitherto been impossible to knit satisfactory joint edges where the angle between the edges-to-be-joined in the two-dimensional form exceeds 135° and generally the maximum angle for continuous knitting together of edges should not exceed an angle of 90° depending upon the application. Generally the larger the angle between the edges-to-be-joined the poorer the appearance and strength of the joint. GB-A-2,223,036 discusses in detail the problems associated with continuous knitting of edges-to-be-joined having large angles therebetween. DE-A-3937408 discloses a continuously knitted three dimensional preform for a helmet Object of Invention The invention provides for a continuous knitted three-dimensional cover, and a method of knitting the same. Statements of Invention According to one aspect of the present invention there is provided a method of continuous knitting a three dimensional weft knitted fabric cover according to a knitting pattern, the pattern being a two dimensional development for needles operating to form fabric along vertical needle lines only and having a plurality of pairs of edges-to-be-joined, each having a bias angle to the horizontal course-wise direction of knitting that lies between 0 and 45°, the pattern having at least one point on at least one side selvedge margin with two edges extending away from the said point, one edge extending in a substantially course-wise direction and the other edge extending at a bias of 45° thereto, the two edges being intended to form different sutures in the knitted cover. Preferably, the pattern on at least said one side has at least two adjacent points spaced along the selvedge with the said one edge extending from one of said two points intersecting with an edge extending from the second of said two points. According to a second aspect of the Invention there is provided a method of continuously knitting a three dimensional cover in which said method includes; determining the shape of a knitting pattern by forming a two-dimensional development of the cover; determining the walewise direction for knitting such that needles operate to form wales of knitted fabric along needle lines, the development having at least one pair of opposed convex curved original edges-to-be-joined together which extend away from a point of intersection and in which the tangents to the curved edges increase in angle relative to the course-wise direction for knitting outwardly from said point and where the angle between opposed tangents to points-to-be-joined on the two curved original edges exceeds 90°, and in which each original edge-to-be-joined terminates at a particular needle line extending in the wale-wise direction; performing a geometric rearrangement on the development so that each edge is re-aligned as a first new edge along a tangent at a 45° bias to the course-wise direction, extending between said needle-line and a point on the convex edge, and a new course-wise second edge is formed from the point of intersection of the 45° bias first edge with the needle-line inwardly thereof such that the course-wise second edge extends across said original edge-to-be-joined by a course-wise distance substantially equal to the distance between the edge and the particular needle line, and continuously knitting said cover. Preferably, at least one of the convex curved edges is of a length which requires at least a second new bias first edge to be created which extends from the inner end of the new course-wise second edge to the particular needle line. Description of Drawings The invention will be described by way of example and with reference to the accompanying drawings in which: Figure 1 shows a prior art knitting pattern; Figure 2 shows a conventional knitting pattern; Figure 3 shows a first knitting pattern according to the present invention; Figure 4 and Figure 5 are enlargements of portions of Figure 2 and Figure 3, respectively, showing how the pattern according to the invention is derived from the conventional pattern; Figure 6 is a sketch of a cover formed from the knitting pattern of Figure 3; Detailed Description Figure 1 is a conventional pattern for a seat cover and which would be knitted in a similar manner to a cover described in EP-A-361,855. A fabric piece 1 for covering a seat base of an automobile seat can be continuously weft-knitted in a single operation. The fabric piece 1 is of mainly double jersey structure and is knitted on a flat V-bed knitting machine provided with a conventional presser foot device or other loop hold-down device for holding down the knitted fabric between the opposed needle beds of the machine. The direction of knitting, indicated by arrow A is such that the wales of the fabric piece extend in a desired manner across the seat base. This may be dictated by a pattern on the fabric or by other technical considerations. The knitting of the fabric piece 1 is described in detail in GB-A-2,223,034 and will only be further described herein so as to give background information for understanding the present invention. In Figure 1, the line B-L represents the length of opposed needle beds of the machine on which the piece 1 is knitted. The needles operate to form fabric along vertical lines only (that is in wales). Essentially the knitting begins on a few needles at point D on the needle bed and more needles are brought progressively into action course-by-wale in the direction from D-B and from D-E to begin to define the edges of the material. Similarly knitting will commence at point K with needles being brought progressively into action from K-H, and from K-L. The needles are then made progressively active and/or inactive in order to obtain the required shape of the fabric. During the continuous knitting operation from bottom to top of the fabric, edges of the fabric between which double-ended arrows are located are knitted together. Taking the two edges indicated by double-headed arrows M and N, for example, this requires that needles made inactive between the point C and E, and H and J respectively, are progressively reactivated to "join" the two edges indicated by M and N along vertical lines. Integral open-ended loops may be formed by knitting areas 2 and 3 on one needle bed only, or alternatively the areas 2 and 3 are utilised by folding along the dotted lines for forming open ended loops beneath the seat cover for facilitating incorporation of the cover into a seat. With reference now to Figure 2, there is illustrated a conventional knitting pattern 11 for an automobile seat base cover and which is knitted with its wale-wise direction in the direction of arrow A. The pattern is basically a two- dimensional development of the base cover. The course-wise extent of the pattern is set by the needle lines B and L. It will be readily apparent that during knitting only those points that lie on a vertical line (a needle-line) can be integrally joined. The pairs of edges-to-be-joined 21 to 22, 23 to 24, 25 to 26, and 27 to 28 are again shown by double headed arrows. The two pairs of edges-to-be-joined 25,26, and 27,28 have horizontally equally bisected angles therebetween which are each equal to about 45°. This is a preferred arrangement for joining of edges as is described in our copending British Patent Application 9422674. The other two pairs of edges-to-be-joined 21-22, 23-24 again have horizontally equally bisected angles but the edges are curved with the angle between opposing parts to be joined changing so that it increases outwardly from a crutch 29 of the join being about 10° at the crutch 29 and increasing to about 140° adjacent the outer needle line B. Therefore in the pattern as shown in Figure 2, the suture for the joints between the edges 21-22, 23-24 will be difficult to mask, and since it will be present in the front panel 102 of the seat (see Figure 6), it will be immediately apparent on initial view. According to one aspect of the present invention, the conventional pattern shown in Figure 2 and partially in Figure 4 can be rearranged to the form shown in Figure 3. In the rearranged state most of the original edges-to-be-joined have been reformed so that edges-to-be-joined have a bias angle to the course-wise direction of knitting that lies between 0°-45°. An angle of up to 45° to the course-wise direction gives acceptable join characteristics in that during the knitting process the needles along the suture will hold no more or no less than two loops when compared with the preceding active neighbouring needle depending upon the knitted structure. The left lateral edge of the pattern along needle line B in Figure 3 now has a pair of spaced points 31,32 located along the needle line B on the lateral edge, or immediately adjacent the edge (that is within 1 or 2 needles), with two edges 33,34, 35,36 respectively, extending away from each point, one edge 33 or 35 being substantially in a course-wise direction, and the other edge 34, 36 being biased at 45° to the course-wise direction. The course-wise edges 33,35 each intersect with a second 45° bias edge 37,38 respectively, parallel to the other edge 34,36. The edges 21 and 23 have been reformed on an opposite 45° bias as edges 39 and 40. The right lateral edge margin of the fabric in Figure 3 has also been rearranged so that the edges 25 and 27 in Figure 2 have been altered to edges 45, 47 in Figure 3 with a 45° angle bias, and the edges 26 and 28 in Figure 2 have been altered to course-wise edges 46 and 48 in Figure 3, with necessary adjustments to the lateral edges of the pattern. The rearrangement to the left lateral edge margin of the pattern shown in Figure 3 is determined from the shape of the original development as shown in Figure 4. For the sake of simplicity only a lower part of the development is shown, but the same technique is applied to the upper part of the development as shown in Figure 2. A tangent line T is drawn at a 45° bias to the course-wise direction between the needle line B and a point P on the convex edge 23, the point P being the only point to which a 45° tangent T can be drawn. A course-wise line "L" is drawn from the intersection point P 3 of the tangent T and the needle line B across the development. Since the added area within the lines T and L is substantially equal to the now excluded area below the line "L", the line T becomes the edge 39 of Figure 3 and Figure 5, and the line L becomes the new set up edge 41 of the final pattern (Figure 3). Similarly a second tangent line T 2 is drawn at an opposite bias of 45° to the course-wise direction between the needle-line B and a point P 2 on the convex curved edge 24. A course-wise line L 2 extends inwardly from a point P 4 at the intersection of the tangent T 2 with the needle line B, such that the line L 2 extends inwardly beyond the edge of the pattern by a course-wise distance equal to the distance between the needle-line B and the edge 24, such that D 1 equals D 2 as shown. Since the point P 4 , is in alignment with a point only midway along the length of the curved edge 24 it is necessary to repeat the above procedure. Another 45° bias line L 3 is drawn from the inboard end of the line L 2 to the intersection with the needle line B at point P 5 . Since P 5 substantially coincides with the original end of the edge 24 there is no further need to repeat the procedure. In some cases it is thought that up to three pairs of 45° biased edges and course-wise edges meeting at points on the needle-line B may be generated in reforming an original edge. The tangent T 2 and lines L 2 and L 3 become the edges 34,33 and 37 respectively in Figures 3 and 5. The areas of the original development that have been excluded are substantially balanced by the areas added. Since the wale-wise length of the pattern has been reduced there is a saving in knitting time. Further since all the joins are pairs of edges having bisected angles therebetween of up to 90°, and pairs of edges having angles therebetween of 45° or less, then the sutures created by these joins will be practically invisible. Any slight reduction in lengths in the three-dimensional form after knitting are accommodated by the natural give in the knitted fabric. A fabric weft-knitted seat cover 100 is shown in Figure 6. The seat has an upper surface 101 with a front face 102 and side faces 103 which are substantially normal to each other. The seat cover 100 will be continuously knitted from the pattern shown in Figure 3 as previously described with reference to Figure 1 to form a three-dimensional seat cover from the two-dimensional pattern merely by knitting together the edges of the flat areas during the knitting process. The seat cover will have sutures S 1 S 2 which will have approximately a 45° bias to the course-wise direction of the fabric, and allowing for some distortion on fitting on the seat, should not exceed a bias of 50°. The points P 3 , P 4 and P 5 in Figure 5 will all come together at a single point P 6 on the selvedge of the knitted article, which will have a pair of suture lines S 1 , S 2 extending away from the point P 6 with an angle α of about 45° therebetween. The original sutures have been moved away from the mid-front face 102 of the seat to a less visible location nearer to the sides.

Claims: A method of continuous knitting a three dimensional weft knitted fabric cover (100) according to a knitting pattern (11), the pattern being a two dimensional development for needles operating to form fabric along vertical needle lines only and having a plurality of pairs of edges-to-be-joined (33,37)(34,39)(35,38), characterised in that each edge has a bias angle to the horizontal course-wise direction of knitting that lies between 0 and 45° and the pattern has at least one point (31,32) on at least one side selvedge margin with two edges (33,34)(35,36) extending away from the said point (31 or 32) respectively, one edge extending (33 or 35) in a substantially course-wise direction and the other edge (34 or 36) extending at a bias of 45° thereto, the two edges (33,34)(35,36) being intended to form different sutures (S 1 S 2 ) in the knitted cover (100). A method as claimed in claim 1 characterised in that said point (31,32) is on an outer needle line (B) of the cover to at least one side thereof. A method as claimed in claim 1 or claim 2, characterised in that the pattern on at least said one side has at least two adjacent points (P 4 ,P 5 ) spaced along the selvedge margin of said outer needle line (B) with the said one edge (33)(35) extending from one of said two points (P 4 ) intersecting with an edge (37) extending from the second of said two points (P 5 ). A method of continuously knitting a three dimensional cover in which said method includes determining the shape of a knitting pattern (11) by forming a two-dimensional development of the cover, by determining the walewise direction for knitting such that needles operate to form wales of knitted fabric along needle lines only, said method being characterised by the development having at least one pair (21 22)(23 24) of opposed convex curved original edges-to-be-joined together which extend away from a point of intersection (29) and in which the tangents to the curved edges increase in angle relative to the course-wise direction for knitting outwardly from said point and where the angle between opposed tangents to points-to-be-joined on the two curved original edges exceeds 90°, and in which each original edge-to-be-joined (21,22,23,24) terminates at a particular needle line (B) extending in the wale-wise direction, characterised by performing a geometric rearrangement on the development so that each edge (23,24) is re-aligned as a first new edge (39,34) along a tangent (T, T 2 ) at a 45° bias to the course-wise direction, extending between said needle-line (B) and a point (P,P 2 ) on the convex edge, and a new course-wise second edge is formed from the point of intersection of the 45° bias first edge (39)(34) with the needle-line (B) inwardly thereof such that the course-wise second edge (40,33) extends across said original edge-to-be-joined (23,24) by a course-wise distance (D 2 ) substantially equal to the distance (D 1 ) between the edge (23,24) and the particular needle line (B), and continuously knitting said cover. A method as claimed in claim 4, characterised in that at least one of the convex curved edges (24) is of a length which requires at least a second new 45° bias first edge (37) to be created which extends from the inner end of the new course-wise second edge (33) to the particular needle line (B). A method as claimed in claim 5, for knitting a vehicle seat cover (100) having at least two surfaces (101)(102)(103) which are substantially at right angles to each other.

Inventors: GREGORY GILES T, LEEKE GARY J, PROCTOR MALCOLM F, SMITH STUART T, GREGORY, GILES T., LEEKE, GARY J., PROCTOR, MALCOLM F., SMITH, STUART T.
Applicants: LEAR CORP, LEAR CORPORATION
Application year: 1996
Main classification: D04B1
IPC codes: D04B15, D04B1