WO2001038624A1

WO2001038624A1 - Compression packing products using interwarp knit construction techniques

Info

Publication number: WO2001038624A1
Application number: PCT/US2000/032090
Authority: WO
Inventors: Albert L. Harrelson, Iii
Original assignee: Garlock Inc
Priority date: 1999-11-22
Filing date: 2000-11-22
Publication date: 2001-05-31
Also published as: AU1791001A; WO2001038624A9

Abstract

One aspect of the present invention is a compression packing material that is constructed using interwarp knit construction techniques to form a sheath (14) having a plurality of base yarns (1) and a plurality of filler yarns. The filler yarns are positioned at predetermined locations within the sheath structure to give the sheath a predetermined geometric configuration, e.g., a square cross-section. The filler yarns are introduced into the sheath in a partially extended condition and are therefore at least partially compressible and extendible in a longitudinal direction. In this regard, the sheath (14) is at least partially longitudinally compressible along an inner radius when the packing material is bent around a shaft. The resulting effect of the compression along the inner radius is a reduction of 'keystoning' of the packing material. Another aspect of the present invention is a compression packing material that is constructed using an interwarp-knit cord construction with localized distributions of yarns on selected sides thereof. Yet a further aspect of the present invention is a compression packing material that is constructed using an interwarp-knit construction with localized distributions of yarns on selected corners thereof.

Description

COMPRESSION PACKING PRODUCTS USING INTERWARP KNIT CONSTRUCTION TECHNIQUES

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application Serial No. 60/166,843, filed November 22, 1999, which is incorporated herein by reference. BACKGROUND AND SUMMARY OF THE INVENTION An aspect of the instant invention relates to mechanical packing materials for controlling leakage around shafts and other cylindrical or curved surfaces, and more particularly to a packing material which is formed using previously knit interlace or filler yarns which will naturally expand and compress in a longitudinal direction when the packing is wrapped around a shaft, and thus reduce keystoning of the packing material. In general, mechanical packings are usually manufactured in relatively long coils of packing material of square or rectangular cross-section from which many individual lengths can be cut to form packing rings. Conventionally, a packing is formed by cutting several lengths from the coil of material, each length then being formed into a ring with abutting ends and installed around a shaft or around another cylindrical object. One longstanding drawback of existing packing materials is a deformation, i.e. bunching, or "keystoning" of the packing material when it is bent around corners, or around a shaft. Keystoning is generally defined as a bunching of material along the inner radius of a bend when the material is wrapped around a corner or curved surface. The extra material on the inner radius of the corner bunches up and creates wrinkles at the corner which in turn create pressure points, and reduce facing contact with the surrounding structures. Although there have been many attempts to reduce keystoning by changing the initial shape of square or rectangular packings to a trapezoidal formation so that keystoning is reduced when wrapped, the problem still exists and still reduces the effective life of the existing packing materials. The instant invention provides an improved packing material of square, rectangular or other geometric construction, which reduces keystoning of the packing material. In particular, the improved packing material comprises an elongate cord-like construction having an inner core and an outer sheath that is constructed from a plurality of base yams and a plurality of interlace or filler yams. The inner core can include a variety of different types and constructions of varying materials including bundles of straight yams, knit bundles of yams, knit or braided cords, etc. or even such materials as elastomers, plastics, etc. to obtain desired cord properties. The outer sheath is knit or braided around the core in a tubular configuration wherein the base yams comprise yam compositions which are typically used to form packing materials, such as Teflon®, glass, fiberglass Kevlar®, graphite, carbon, Inconel®, copper, stainless steel, etc. The term "yam" should be interpreted broadly herein to include any longitudinally stranded structure sufficiently pliable for use in an interwarp-knitted tube construction. As will be further described herein, it is known in both braiding and knitting techniques to insert "filler" yams within the construction to achieve certain desired characteristics to the cords. In the braiding art, such yams are typically referred to as "filler" yarns, and in the interwarp-knitting art, the yams are typically referred to as "interlace or inlaid" yams. To simplify further discussion of the sheath construction, it is to be understood by the reader that the term "filler" yam will be used interchangeably with respect to both knitting and braiding techniques, and that the term "filler" is intended to cover either an interlace yam in knitting- or a filler yam in braiding.

Filler yams are selectively positioned at predetermined locations within the sheath structure so as to give the sheath a predetermined geometric configuration when formed. In one construction, four filler yams are arranged in a square configuration to give the packing material a generally square configuration. A feature of the present invention is that the filler yams comprise natural yam materials or yam constructions which are naturally extendible and compressible in a longitudinal direction. In this regard, the filler yams include a chain stitched knit yam construction which is naturally extendible and compressible in a longitudinal direction. The previously knit filler yams are introduced into the knit or braided sheath structure in partially extended condition, i.e. under back tension, and will thereafter be at least partially compressible and extendible in a longitudinal direction in the finished packing material. In this regard, the sheath is at least partially longitudinally compressible along an inner radius when the packing material is bent around a curved surface. The resulting effect of the use of the previously knit filler yams is a noticeable reduction of "keystoning" of the packing material along the inner radius. It should be understood that the filler yams are only required on the innermost co ers because keystoning is only a significant problem on the inner radius of a packing ring.

Another aspect of the instant invention relates to a shaped (multi-sided) interwarp-knit cord having selected types of yam localized on selected side surfaces of the shaped cord to provide the selected side surfaces of the cord with particular surface characteristics attendant to the localized yam materials. Shaped cords, such as used for packing materials, have heretofore been known in the art. The term "shaped" as used within this specification is intended to encompass all types of cords, packings, etc. having a non-circular cross-section, and/or having at least one flat surface, such as in a square or triangular cross-section. With regard to known prior art, U.S. Pat. Nos. 1,771,912 and 3,124,032 represent different types of shaped packing materials. In the context of the invention, it is worthwhile to note that each of the packing materials described in these patents is formed by a braiding method and has uniform exterior surface properties on all sides. While these types of braid configurations are adequate for the intended purpose, it has been found that there is a need for a shaped, or multi-sided cord or packing material, wherein a single type of yam material can be localized on one or more given sides of the cord, while other yam materials are localized on the other sides. For example in a packing cord, it would be advantageous to be able to provide a specialized Teflon® yam material on the inner side of the packing which engages the rotating shaft, and to utilize other less expensive materials on the other sides of the packing which do not contact the shaft. Such a configuration would utilize less of the more expensive Teflon® materials and reduce the overall cost of such products. In general, braiding procedures utilize a single type of yam wherein during braiding the yams migrate around the periphery of the braid to provide a uniform distribution of yams throughout the braid. Different types of yams can be utilized in the braid. However, since the yams are uniformly distributed during braiding, the exterior surface properties are uniform across all sides of the braid configuration. Because of the uniform yam distribution in a braided material, the desired localized material configurations are impossible to achieve in a braiding method.

The instant invention provides the desired shaped cord construction having localized distributions of yams on selected sides of the cord. The shaped cord of the present invention is formed using an interwarp-knitting method wherein selected types of yams are grouped together and rotated in such a manner that yarns of the same type of material are repeatedly located in the same knitting position for each knitted course. Shaping of the cord is accomplished by selectively locating interlace yams around the circumference of the cord construction. For example, four equally circumferentially spaced interlace yams will form a square knit configuration having four distinct sides when viewed in cross-section.

In yet another aspect of the instant invention a compression packing material is constructed using an interwarp-knit construction with localized distributions of yams on selected comers thereof.

Other features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings. DESCRIPTION OF THE DRAWINGS In the drawing figures which illustrate the best modes presently contemplated for carrying out the present invention:

FIG. 1 is a perspective view of a length of knit packing material constructed in accordance with the teachings of the present invention;

FIG. 2 is a cross-sectional view of the packing material as taken along line 2-2 in FIG. 1;

FIG. 3 is a perspective view of a length of knit packing material wrapped in a packing ring around a cylindrical shaft;

FIG. 4 is a fragmented cross-sectional view taken along line 4-4 of FIG. 3; FIG. 5 is a cross-sectional view of a triangular packing material including three filler yams;

FIG. 6 is a schematic diagram of a first cord construction fabricated in accordance with the teachings of the present invention and showing a localized yam distribution along a single outer side of the cord;

FIG. 7 is a rotation diagram of the knitting method used to knit the cord of FIG. 6 showing the placement patterns of the base ya s and interlace yams, a single needle rotation (shift) of the base yam guide, and the independent rotation of the interlace yarn guide during knitting thereof; FIG. 8 is a schematic knit diagram thereof showing knitting of the loops of the base yams and the crossover of yams between the wales during the single needle shift rotation;

FIG. 9 is a schematic diagram of another cord construction showing localized yam distribution along a single outer side of the cord; FIG. 10 is a rotation diagram of a second knitting method showing the placement patterns of the base yams and interlace yams, a two needle rotation (shift) of the base yam guide and the independent rotation of the interlace yam guide during knitting thereof;

FIG. 11 is a schematic diagram of yet another cord also showing localized yam distribution along a single outer side of the cord; and

FIG. 12 is a rotation diagram of a third knitting method showing the placement patterns of the base yams and interlace yams, a thirteen needle rotation (shift) of the base yam guide and the independent rotation of the interlace yam guide during knitting thereof. DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, the packing material of an aspect of the instant invention is illustrated and generally indicated at 10 in FIGS. 1-5. As will hereinafter be more fully described, the instant invention provides an improved packing material of square, rectangular, triangular or other geometric construction, which overcomes the keystoning drawbacks of the prior art by providing an outer sheath which can naturally extend and compress in a longitudinal direction when bent around a comer or around a curved surface.

More specifically, the improved packing material 10 comprises an elongate cord- like construction having an inner core generally indicated at 12 and an outer sheath generally indicated at 14. Construction 10 is shown having four distinct side surfaces generally indicated at 12, 14, 16, and 18 respectively (see FIG. 2). The inner core 12 can comprise a variety of different types and constructions of varying material including bundles of straight yams, knit bundles of yams, knit or braided cords, etc. The particular types of yams utilized in the core 12 can vary according to use of the packing. In the present embodiment, the inner core 12 includes a bundle of longitudinally oriented yams. The outer sheath 14 is either knit or braided around the core 12 in a tubular configuration. The tubular construction of the sheath 14 is formed using both base yams and "filler" yams as known in the art. Typically, the sheath 14 is constructed from base yams including yam compositions which are typically used to form packing materials, such as Teflon®, glass, fiberglass Kevlar®, graphite, carbon, Inconel®, copper, stainless steel, etc. As will be further described herein, it is known in both braiding and knitting techniques to insert "filler" yams within the construction to achieve certain desired characteristics to the cords. In the braiding art, such yams are typically referred to as "filler" yams, and in the interwarp-knitting art, the yams are typically referred to as

"interlace or inlaid" yams. To simplify further discussion of the sheath construction, it is to be understood by the reader that the term "filler" yam will be used interchangeably with respect to both knitting and braiding techniques, and that the term "filler" is intended to cover either an interlace yam in knitting or a filler yam in braiding. The sheath 14 is preferably knit using an interwarp-knit method, and in conjunction with the drawings, FIGS. 1 and 2 illustrate an interwarp-knit outer sheath. The term interwarp-knit refers to a tubular interwarp-knit fabric which is formed by supplying a number of individual yams to the needles of a circular knitting machine, and then knitting with all of the needles at the same time to produce a complete course at once. For the sake of clarity and illustration, the interwarp-knit materials illustrated in the drawing figures are shown in a simplified fashion, and specifically with fewer yams than would be utilized in a preferred commercial product. It will be understood that the principles of interwarp knitting can be completely understood with respect to the drawing figures and that more complex drawings with larger numbers of yams would be more confusing rather than more illustrative.

The interwarp-knit sheath 14 is generally knit from a plurality of base yams B-1 through B-4, each comprising a yam composition which would be typically used to form a packing material, such as Teflon®, glass, fiberglass Kevlar®, graphite, carbon, Inconel®, copper, stainless steel, etc. Shading has been added to the yams B-1 through B-4 to help distinguish each from the other in the drawings. The present interwarp-knit tube 12 has four wales, indicated at W-l through W-4 circumferentially spaced around the tube 12. The base yam needle loops form successive courses illustrated C-l through C-7. The separate base yams each form base yam needle loops in corresponding wales W-l through W-4 of course C-l and form circular and diagonally extending laps generally indicated L-l through L-4 extending between and interconnecting the circumferentially spaced wales of the course C-l with opposite needle loops positioned in the opposite wales in the next successive course. Generally speaking, interwarp-knitting and the automatic knitting machines utilized for rapid interwarp-knitting of tubular structures as illustrated herein are well known in the art. In this regard, interwarp-knitting machines and specific knitting procedures which may be utilized for producing a interwarp-knit tube of the type referred to herein are further disclosed in detail in U.S. Patents Nos. 4,838,043, 4,977,759, 5,512,709 and 5,603,514, each of which is entirely incorporated herein by reference. The interwarp-knit sheath 14 is by the nature of its construction substantially free of torque bias that would otherwise inhibit free movement and bending of the structure. Accordingly, the interwarp-knit sheath has a natural ability to conform to curved and other irregular surfaces. The interwarp-knit sheath 14 is further knit with a plurality of interlaced filler yams 1-1 through 1-4 which are respectively interlaced within the wales W-l through W-4 of the structure 10. The interlace yams 1-1 through 1-4 extend generally longitudinally in a zig-zag path along the corresponding wales W-l through W-4 and are generally utilized to control the longitudinal stability of the interwarp-knit tube. The filler yams of the interwarp-knit are selectively positioned at predetermined locations within the knit so as to give the sheath a predetermined geometric configuration when knitted. In a constmction of 4, 8, 12, 16, 20, 24 knitting needles, four filler yams are arranged in a symmetrical square configuration to give the packing material a generally square configuration. However, it is noted that movement of the four fillers to non-symmetrical locations in the knit would provide the sheath with other configurations, such as rectangular or trapezoidal. Similarly, the provision of only three fillers would provide the sheath 14 with triangular configurations (FIG. 5).

A feature of the present invention is that the interlaced filler yams 1-1 through 1-4 comprise yams or yam constructions which are extendible and compressible in a longitudinal direction, i.e. any type of yam or yam constmction which naturally has the ability to extend or compress in a longitudinal direction. Typically natural fiber yams will have some inherent ability to extend and compress compared to synthetic type yams, such as glass, or synthetic polymer yams. However, the filler yams may comprise a chain-stitched knit yam construction which is naturally extendible and compressible in a longitudinal direction. When a chain-stitched knit constmction is formed, the individual yams utilized to form the stitch may comprise non-extendible ya s, such as those commonly used in packings since the natural form of the knit constmction provides the ability for the entire construction to extend and compress longitudinally. The previously knit filler yams 1-1 through 1-4 are laced into the interwarp in partially extended condition, i.e. under back tension, and will thereafter be at least partially compressible and extendible in a longitudinal direction in the finished interwarp-knit packing material. The filler yams 1-1 through 1-4 may alternatively include other types of yam constructions, such as braided, twisted, and plied yam constructions, which also have some natural ability to extend and compress in a longitudinal direction. Still further, it is contemplated that the filler yams might comprise a length of coiled wire or synthetic polymer monofilament, or even further an elastic line, each of which would be introduced into the structure under back tension in a partially extended condition. One distinct advantage of a coiled wire-type filler yam is that the coiled structure provides added interior space within the packing for receiving lubricating materials such as Teflon®, which are often imbedded into the packing material prior to use. In use, a length of the packing 10 is formed into a ring, and wrapped around a shaft 16 (FIG. 3). In the finished product, the interwarp-knit sheath 14 is at least partially longitudinally compressible along an inner radius when the packing material 10 is bent around the curved outer surface of the shaft 16. More specifically, the previously knit filler yam constructions 1-1 and 1-4 on the inner radius of the bend will collapse into themselves to form a smooth inner radius rather than bunching up while the knit filler yam constructions 1-2 and 1-3 on the outer radius of the bend will extend to accommodate the increased length. The resulting effect of the compression along the inner radius and extension on the outer radius is a reduction of "keystoning" of the packing material. Referring to FIG. 4, although it is preferred to utilize the previously knit filler yams on all comers of the packing, it is to be understood that the filler yams are really only required on the inwardly facing comers because keystoning is only a significant problem on the inner radius of a packing ring. Accordingly, in a triangular packing, only two of the three comers would need to comprise the compressible yams.

Although the use of previously knit interlaced filler yams has been specifically described in connection with interwarp-knitting techniques, it is to be understood that the concept of using previously knit yams in packings can also be applied as comer or post fillers to other knitting techniques as well. The resulting sheath structures may have similar extension and compression characteristics as the interwarp-knit structure.

It can therefore be seen that the instant invention provides an improved packing material which significantly reduces keystoning of the packing material when wrapped around comers or curved surfaces. The use of a interwarp-knit sheath which has the natural ability to conform to curved surfaces, along with the use of previously knit interlaced filler yams which can expand and contract to accommodate different radii when bent around co ers significantly reduces the incidence of keystoning of the packing material.

Turning now to another aspect of the present invention, as described in the background herein above, it is advantageous to be able to provide the inner-side surface of the packing ring with a localized distribution of Teflon® or other selected yams so as to provide a low friction surface against the rotating shaft. While this example specifically refers to use of the shaped cord as a packing material, it is to be understood that this is a representative example only, and that there are other potential uses for shaped cords with localized yam distributions. As will hereinafter be more fully described, the instant invention provides a shaped, interwarp-knit composite cord having localized distributions of selected yams on a selected side surfaces of the cord so as to provide the side surfaces with predetermined surface properties. A feature of the present embodiment resides in a unique knitting method which permits the localization of a selected type of yam on a selected side of the shaped cord to provide one surface of the cord with a particular type of yam material and other surfaces with another type of material.

Referring to FIG. 6 there is illustrated a shaped, interwarp-knit cord generally indicated at 24 having a square configuration with sides indicated at 26, 28, 30, 32. The cord 24 has a core 34 and an outer sheath 36, although it is to be understood that the cord 24 could be manufactured without the central core 34. Four interlace yams Ii through I₄ occupy the four comers of the square configuration. In accordance with the teaching of the present invention, base yams of a first type T are localized on a single side surface 26 (single cross-hatched area) of the cord 24 while base yams of a second type X are localized on the three remaining sides 28, 30, 32 (not cross-hatched). Overlapped areas of yams X and T (double cross-hatched) are localized on opposing sides 28 and 32. The overlap results from a needle shift during knitting. In a packing material of the type described above, it is contemplated that the first type of base yams (face yams) T might comprise Teflon®, Kevlar®, graphite coated, etc. yams while the second type of base yams (backing yams) X might comprise a low cost natural or synthetic fiber yam. The localized use of the Teflon® yams would significantly reduce the material cost of producing the packing since the low friction materials are used only where necessary for proper function of the packing material, i.e. on the inner bearing surface 26.

Referring to FIG. 7, the knit pattern utilized to provide this configuration is shown in schematic form. The cord 24 is knit in a knitting machine using two reciprocating yam guides (not shown) and a twelve (12) needle configuration, the needles being identified in the drawings as Ni through N₁₂. For a description of the location and operation of the yam guides in an interwarp-knitting machine, see reference numerals 22 and 51 in U.S. Pat. No. 4,977,759, which is fully incorporated herein by reference. The square shape of the resulting cord 24 is illustrated in broken line within the illustration. The needles N are physically represented by squares in the drawings. The four interlace yams Ii through I₄ are equally circumferentially spaced around a first yam guide to coincide with needles N₂, N , N₈, and Nn to form the comers of the cord 24. For purposes of the illustration, the interlace yarns I are represented by triangles. Only one interlace yam I₃ is illustrated in FIG. 7 for purposes of clarity of the illustration. However, all four interlace yams are illustrated in thick solid black lines in FIG. 8 with respect to their respective needle locations. FIG. 8 is a schematic view of the movement of the yams between the needles during knitting, and shows the various courses and wales as they are formed during knitting. During knitting of the cord, the interlace yam guide will repeatedly jog back and forth in a single needle shift so as to zig-zag the interlace the yams back and forth through the respective needle at the comer position. The degree of rotation of the first yam guide (carrying interlace yams I) is represented by fheta-_. (about 20-30 degrees) with alternating timing positions indicated as ti, t₃ . . . and t₂, t₄ . . . . Following this example, interlace I jogs back and forth between positions I₃ ¹¹' ^{13 "} (open triangle) and I₃ ^β' ^{14 "} (filled triangle). Referring to FIGS. 7 and 8, the knit cord 24 utilizes twelve base yams equally circumferentially spaced around a second yam guide to coincide with needles Ni through Nj₂. To provide a localized distribution of T type yams on a given side of the cord, the knit uses five (5) T type yams (lighter lines in FIG. 8) T₅ through T₉ positioned on the second yam guide to coincide with needles N₅ through N₉, and further uses seven (7) backing yams (darker lines in FIG. 8) Xi through j and Xio through Xj positioned on the second yam guide to coincide with needles Ni through N₄ and N₁₀ through N[ . The yams T and X are generally represented by circles in FIG. 7. The rotation of the second yam guide (carrying base yams T and X) is a single needle shift represented by theta₂ (about 45 degrees) with alternating timing positions indicated as tj_, 1_{3 . . .} and t₂, 1_{4 ...} Following this example, base yam X₃ jogs back and forth between positions X₃ ^l ' ^{l "} (open circle) and X₃ ' ' ^{4 " " '} (filled circle). Referring to FIG. 8, movement of the yams in the single needle shift is clearly illustrated. Each of the yams is shaded in a different thickness to more clearly show the movement from one needle to the next. For example, yam X₃ shifts back and forth between needles N₃ and N₄ forming alternating loops in wales W₃ and W₄. The knit creates a generally square configuration having single side formed from wales W₅ -W which is exclusively formed of yams T. Wales W₄ and W₉ have alternating loops of yams X and T forming a transition adjacent to the comers and the remaining wales W- -W₃ and Wι₀ -W₁ are formed exclusively of yams X.. Referring to FIGS. 9 and 10, there is illustrated another shaped interwarp-knit cord 38 also having a square configuration. The cord 38 has four sides 40, 42, 44, and 46 respectively, and includes a central core 48 and outer sheath 50. As in the previous embodiment, four interlace yams Ii through I₄ occupy the four comers of the square configuration. The resulting one-sided configuration of this cord 38 is similar to the previous configuration 24. However, the yam configuration and knitting method used to achieve the configuration is slightly different. The knit pattern utilized to provide this configuration is shown in schematic rotation diagram in FIG. 10. The cord 38 is knit in a knitting machine using two reciprocating yam guides (not shown) and a twelve (12) needle configuration identified in the drawings as Ni through Nι₂. The square shape of the resulting cord 38 is illustrated in broken lines within the illustration in FIG. 10. The needles N are physically represented by squares in the drawings. The four interlace yams Ii through I₄ are equally circumferentially spaced around a first yam guide to coincide with needles N₂, N₅, N₈, and Nπ to form the comers of the cord. For purposes of the illustration, the interlace yarns I are represented by triangles. During knitting of the cord, the interlace yam guide will repeatedly jog back and forth in a single needle shift so as to zig-zag the interlace the yarns back and forth through the respective needles at the comer positions. The degree of rotation of the first yam guide (carrying interlace yams I) is represented by thetaj (about 20-30 degrees) with alternating timing positions indicated as tι_; t_{3 . . .} and t _; t_{4 . . .} . Still referring to FIG. 10, the knit cord 38 utilizes twelve (12) base yams equally circumferentially spaced around a second yam guide to coincide with needles Ni through N₁₂. To provide a localized distribution of T type yams on side T 40 of the cord 38, the knit uses six (6) backing yams Xi - X and Xι₀ - X₁₂ positioned on the second yam guide to coincide with needles Nj - N₃ and N_JO - N₎₂, respectively, and further uses six (6) T type yams T₄ through T₉ positioned on the second yam guide to coincide with needles N₄ through N₉, respectively. The yams T and X are generally represented by circles in the drawings. The degree of rotation of the second yam guide (carrying base yams T and X) is represented by theta (about 90 degrees) with alternating timing positions indicated as ti_, t_{3 . .}. and t_2ι t₄.._. . Following this example, base yam X₂ jogs back and forth between positions X₂ ^{tL t 3 ' ' '} (open circle) and X?^{12' t 4 ' ' '} (filled circle), the rotation of all other yams being the same, but not shown. The combination of yarn position and rotation of the second yam guide exclusively places base yams T within wales W₅ - W₈ to form side 40. Wales W₃ - W₄ and W₉ - Wι₀ have alternating loops of yams X and T forming a transition at the comers and the remaining wales Wi - W₂ and Wπ - Wj₂ are formed exclusively of yams X..

Referring to FIGS. 11 and 12, there is illustrated yet another shaped interwarp- knit cord 52 also having a square configuration. The cord 52 has four sides 54, 56, 58, and 60, and includes a central core 62 and outer sheath 64. As in the previous two embodiments, four interlace yams Ij through I₄ occupy the four comers of the square configuration. The resulting one-sided configuration of this cord is again the same as the previous configurations. However, the knitting method used to achieve the configuration is also different from the two previous methods. The knit pattern utilized to provide this configuration is shown in schematic rotation diagram in FIG. 12. The cord 52 is knit in a knitting machine using two reciprocating yam guides (not shown) and a twelve (12) needle configuration identified in the drawings as N* through N₁₂. The square shape of the resulting cord 52 is illustrated in broken line within the illustration in FIG. 12. The needles N are physically represented by squares in the drawings. The four interlace yams Ii through I₄ are equally circumferentially spaced around a first yam guide to coincide with needles N₂, N₅, N₈, and Ni i to form the comers of the cord. For purposes of the illustration, the interlace yams I are represented by triangles. During knitting of the cord, the interlace yam guide will repeatedly jog back and forth in a single needle shift so as to zig-zag the interlace the yams back and forth through the respective needles at the corner positions. The degree of rotation of the first yam guide (carrying interlace yams I) is represented by thetai (about 20-30 degrees) with alternating timing positions indicated as tj, t _{. . .} and t _, t _{. . .} . Still referring to FIG. 12, the knit cord 52 utilizes twelve (12) base yams equally circumferentially spaced around a second yam guide to coincide with needles Nj through Nι₂. To provide a localized distribution of T type yams on side T 54 of the cord 52, the knit uses eight (8) backing yams Xi - X₄ and X₉ - Xι positioned on the second yarn guide to coincide with needles N* - N₄ and N₉ - N₁₂, respectively, and further uses four (4) T type yams T₅ through T₉ positioned on the second yam guide to coincide with needles N₅ through N₉, respectively. The yams T and X are generally represented by circles in the drawings. The degree of rotation of the second yam guide (carrying base yams T and X) is represented by theta₂ (about 375 degrees) with alternating timing positions indicated as tj. 1_{3 . . .} and t₂. 1_{4 . . .} . Following this example, base yam X₂ jogs back and forth between positions X₂ ^U' ^l " (open circle) and X₂ - ^{14 * * *} (filled circle), all other yarns being the same, but not shown. The combination of yam position and rotation of the second yam guide exclusively places base yams T within wales W₅ - W₈ to form side 54. Wales Wj - W₄ and W₉ - W₁ are formed exclusively of yams X with no transition wales at the comers. As indicated above, the rotation of the second yam guide generally places the base knitting yams on the same knitting needles for each knitting course, circling the yams back and forth around the core through the respective knitting needles. It should be readily apparent to those of ordinary skill in the art that there are numerous advantages in a packing having one, two, or three sides with yams of different properties.

Another aspect of the present invention utilizing concepts taught herein above includes providing a packing having a square cross-section with a different yam system used on one or more comers. The greatest abrasive wear on packing rings from media is at the leading point of the braid ID that faces the media. A packing that uses an enhanced abrasion resistant yam on one comer will increase the service-sealing life of the product. Abrasion resistant materials are usually also abrasive to shaft surfaces. In this design, only the leading edge of the product would have the enhanced abrasion resistance, leaving the majority of the ID contact surface of the product to be constmcted from a less abrasive yarn. Axial loading forces primarily expand the central portion of the product sides rather than the comers. The abrasion resistant comers would increase the abrasion resistance of the product without being forced into a hard contact against the shaft surface. Using a packing that includes a different yam system on two opposing comers and on four-comers increases the mechanic-friendly nature of the packing by enabling the product to-be correctly installed in several different orientations.

Another aspect of the present invention utilizing concepts taught herein above includes a packing having a square cross-section wherein one-half of the body and the corresponding sides are constmcted of a different yam system than the other half and its corresponding sides. Such a packing is advantageous, for example, if one side is constmcted of a firmer yam material and the firmer side is oriented toward a packing box OD, then the softer side could be used as a flexible and resilient wiper system in reciprocating services. Constmcted of thermally conductive materials, the varying side, oriented toward the media side or the outside of the stuffing box, could be used to more effectively transfer heat from the shaft/packing interface to the outside walls of a stuffing box.

While there are specific illustrations of methodology and yam arrangement herein described, it is to be understood that the same inventive principles can be applied to achieve various geometric shape cord configurations including but not limited to triangular, pentagonal, octagonal, varied yam localization on single or multiple sides of the resulting cord shape, and various combinations of core and outer sheath materials. It is also noted that any of the cords herein described can be formed in a tubular configuration without a central core. It is still further noted that when knitting using 16 or more needles, tapering of the comers may be needed to produce planar side surfaces. Tapering is defined herein as the addition of interlace yams at the comers and at positions adjacent to the comers to fill out the comer areas. For example, in a 20 needle knit, a group of four interlace yams are used at each comer interlace position to bulk up the comer, and single interlace yams are positioned directly to the sides of the comers to fill in the area between the comer and the center of the respective face.

It can therefore be seen that the present invention provides a unique shaped cord constmction having selected yam types localized on selected portions of the cord. The interwarp-knitting methods utilized to construct the cords provide for high-speed knitting and production of these types of cords while also providing the unique ability to shape the cord, and provide desired surface or corner characteristics on selected sides and comers, respectively. The number of needles may vary from a few to many with various needle shifts from one to a full circle on the total number of needles in use to achieve various end products. While there is shown and described herein certain specific structures embodying the different aspects of the instant invention, it will be manifest to those skilled in the art that various modifications and rearrangements of the parts may be made without departing from the spirit and scope of the underlying inventive concept and that the same is not limited to the particular forms herein shown and described except insofar as indicated by the scope of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A packing material comprising: an inner core; and an outer sheath covering said inner core, said outer sheath comprising an interwarp-knitted tube knitted from a plurality of base ya s and a plurality of interlace yams, said interlace yams being positioned at predetermined locations within the knit and configured in their circumferential location so as to give said outer sheath a predetermined geometric configuration when viewed in cross section, said interlace yams each comprising a yam construction that is compressible and extendible in a longitudinal direction, said yam constmction comprising a previously fashioned yam constmction selected from the group consisting of: knit yam constructions, braided yam constructions, twisted yam constructions, plied yam constructions, and combinations thereof, said previously fashioned yam constmction allowing said outer sheath to be at least partially longitudinally compressible along an inner radius when said packing material is bent around a curved surface, said longitudinal compression along the inner radius being effective for reducing keystoning of the packing material in use thereof.

2. The packing material of claim 1 wherein there are four filler yams and said four filler yams are arranged in a quadrilateral configuration thereby giving the packing material a quadrilateral configuration.

3. The packing material of claim 1 wherein there are three filler yams and said three filler yams are arranged in a triangular configuration thereby giving the packing material a triangular configuration.

4. The packaging material of claim 1 wherein said yam constmction comprises a chain stitch knit yam constmction.

5. A shaped interwarp-knit cord construction comprising: a shaped interwarp-knit tube formed from a plurality of base yams and a plurality of interlace yams, said interwarp-knit tube having an exterior side surface, said interlace yams being selectively distributed and positioned within said interwarp-knit tube so as to define a longitudinally extending, flattened, side surface portion of said exterior side surface, said plurality of base yams comprising a plurality of yams of a first type that are localized on said flattened side surface portion, and a plurality of yams of a second type that are distributed throughout remaining side surface portions of the exterior side surface of said interwarp-knit tube, said localized distribution of said base yams of said first type on said flattened side surface portion providing said flattened side surface portion with surface characteristics attendant to said yams of said first type, said plurality of base yarns being selectively positioned at predetermined circumferential knitting positions on a rotating yam guide, said yams of said first type being grouped together in adjacent relation in circumferential knitting positions corresponding to said flattened side surface portion of said interwarp-knit tube, said rotating yarn guide being reciprocated during knitting of the tube so as to repeatedly locate each of said base yams in a predetermined knitting position for each knitted course and to thereby localize each of said yams of said first type on said flattened side surface portion of said tube, and to localize each of said yams of said second type on said other remaining side surface portions of said tube.

6. The shaped interwarp-knit cord constmction of claim 5 further comprising a longitudinal core element positioned within said interwarp-knit tube.

7. The shaped interwarp-knit cord constmction of claim 5 wherein said interwarp- knit tube is knitted in a square configuration using four interlace yams and having four flattened side surface portions.

8. The shaped interwarp-knit cord construction of claim 6 wherein said interwarp- knit tube is knitted in a square configuration using four interlace yams and having four flattened side surface portions. 9. The shaped interwarp-knit cord constmction of claim 5 wherein each of said plurality of ya s of said first type comprises a yam having a predetermined coefficient of friction thereby providing said flattened side surface portion with said predetermined coefficient of friction. 10. The shaped interwarp-knit cord constmction of claim 6 wherein each of said plurality of yams of said first type comprises a yam having a predetermined coefficient of friction thereby providing said flattened side surface portion with said predetermined coefficient of friction. 11. The shaped interwarp-knit cord constmction of claim 7 wherein each of said plurality of yarns of said first type comprises a yam having a predetermined coefficient of friction thereby providing said flattened side surface portion with said predetermined coefficient of friction. 12: The shaped interwarp-knit cord construction of claim 8 wherein each of said plurality of yams of said first type comprises a yam having a low coefficient of friction thereby providing said flattened side surface portion with a low coefficient of friction. 13. A method of forming a shaped, interwarp knit cord constmction utilizing an interwarp-knitting machine having a first reciprocating yam guide for guiding base yams into the needles, and a second reciprocating yam guide for guiding interlace yams into the needles, said method comprising the steps of: positioning a plurality of interlace yams at predetermined circumferential knitting positions around the second yam guide, said interlace yams being selectively spaced and positioned to define a longitudinally extending, flattened side surface portion on said cord constmction;

9 positioning a plurality of base yams at predetermined circumferential locations

10 around the first yam guide, said plurality base yams comprising a plurality of yams of a

11 first type and a plurality of yams of a second type, said plurality of yams of said first type

12 being grouped together in adjacent circumferential knitting positions corresponding to

13 said flattened side surface portion of said cord constmction, said plurality of yams of said

14. second type occupying other selected circumferential knitting positions; and

15 knitting said base yams together in successive courses while interlacing said

16 interlace yams within said base yams to form said cord constmction having said

17 longitudinally extending, flattened side surface portion, said step of knitting including the

18 step of repeatedly reciprocating said first yam guide so as to repeatedly locate each of

19 said base yams in a predetermined knitting position for each knitted course and to thereby 0 localize each of said yams of said first type on said flattened side surface portion of said 1 tube and to localize each of said yams of said second type on other side surface portions 2 of said cord constmction.

1 14. The method of claim 13 further comprising the step of feeding a longitudinal

2 core element within the center of said yam guides wherein said knitted cord construction

3 is knit around said longitudinal core element.

1 15. The method of claim 13 wherein said step of providing said interlace yams

2 comprises providing four equally spaced interlace positions to define a square cord

3 configuration and four flattened side surface portions.

1 16. The method of claim 15 wherein base yams of said first type are positioned as

2 a group on the first yam guide generally between two of said interlace positions on said

3 second yam guide, and further wherein said base yams of said second type are provided

4 in a plurality of other positions, said first yam guide being reciprocated to repeatedly

5 place said base yams in the same circumferential knitting position for each knitted

6 course, said knitting arrangement localizing said plurality of base yams of the first type

7 on said flattened side surface portion of the knitted cord constmction while said plurality of base yams of the second type are located on the remaining three sides of the cord constmction. 17. A packing material, comprising: an interwarp-knitted tube formed from a plurality of base yams and a plurality of interlace yams; said interlace yams positioned at predetermined circumferential locations within said tube so as to give said tube a predetermined geometric configuration when viewed in cross section, each interlace yam having a yam constmction that is compressible and extendible in a longitudinal direction; said base yams forming a plurality of wales circumferentially spaced around said tube and having a plurality of yams of a first type that are positioned adjacent one or more of said interlace yam locations, said base yarns of said first type having characteristics attendant to said yams of said first type, and a plurality of yams of a second type, said base yams of said second type having characteristics attendant to said yams of said second type. 18. The packing material of claim 17 wherein said interlace yams are positioned in a quadrilateral configuration thereby giving the packing material a quadrilateral configuration. 19. The packing material of claim 18 wherein the wales formed by the base yarns of said first type are positioned adjacent each of two adjacent comers of the quadrilaterally configured packing material .

20. The packing material of claim 18 wherein the wales formed by the base yams of said first type are positioned adjacent each of two opposite comers of the quadrilaterally configured packing material.

21. The packing material of claim 17 wherein the base yams of said first type are abrasion resistant.

22. The packing material of claim 17 further including an inner core element extending longitudinally, inside said circumferentially spaced wales of base yarns. 22. A packing material, comprising: an interwarp-knitted tube formed from a plurality of base yams and a plurality of interlace yams; said interlace yams positioned in a quadrilateral configuration thereby giving the packing material a quadrilateral configuration, each interlace yam having a yam constmction that is compressible and extendible in a longitudinal direction; said base yams forming a plurality of wales circumferentially spaced around said interwarp-knitted tube and forming laps interconnecting said circumferentially spaced wales, said base yams including a plurality of yams of a first type that are knitted to form a first half of said interwarp-knitted tube when said interwarp-knitted tube is viewed in cross-section, and said base yams having a plurality of yams of a second type that are knitted to form a second half of said interwarp-knitted tube when viewed in cross-section.

23. The packing material of claim 22 wherein said plurality of yams of said first type that are knitted to form said first half of said interwarp-knitted tube and said plurality of yams of said second type that are knitted to form said second half of said interwarp-knitted tube are blended at each side of said packing material in which they meet over two or more wales.

24. The packing material of claim 22 wherein said interlace yams positioned in said first half of said interwarp-knitted tube include a plurality of yams of said first type and said interlaced yams positioned in said second half of said interwarp-knitted tube include a plurality of yams of said second type.

25. The packing material of claim 22 further including an inner core element extending longitudinally, inside said circumferentially spaced wales of base yarns.

26. The packing material of claim 25 wherein said inner core element is a plurality of yams, said plurality of yams that are positioned in said first half of said interwarp-knitted tube being made up of yams of said first type and said plurality of yams that are positioned in said second half of said interwarp-knitted tube being made up of yams of said second type.