Abstract:
A packing is disclosed for hermetically sealing a member. The packing in accordance with the present invention comprises braiding yarns each of which includes a plurality of longitudinally arranged reinforcing fiber yarns and expanded graphite integrally bonded to at least one side of the reinforcing fiber yarns with adhesive, so that the braiding yarns are provided with excellent sealing properties and strong tensile strength and toughness. A plurality of such braiding yarns may be put together to form a core member. The core member may be covered, at the outer periphery thereof, with a braided body of the braiding yarns. A plurality of such braiding yarns as put together may be braided (square-knitted). Alternatively, a plurality of such braiding yarns as put together may be twisted. Thus, packing having a free length may be obtained. The packing thus obtained may be used as cut, at a site, to a predetermined length according to the size of the object member to be sealed. This eliminates production, based on estimations in advance, of a variety of annular packings according to the size of object members to be sealed, as done in molded packing.

Description:
This application is a Divisional of 08/581,050 filed on Dec. 27, 1995 now abandoned; which is a Continuation of Ser. No. 08/332,385 filed on Oct. 31, 1994, now abandoned; which is a Divisional of 08/164,782 filed on Dec. 10, 1993, now U.S. Pat. No. 5,370,405; which is a Continuation of Ser. No. 07/761,362 filed on Aug. 30, 1991, now abandoned; which is the National Stage Proceeding of PCT/JP90/00157 filed Feb. 8, 1990. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to packing suitably used as gland packing to be used at a shaft sealing portion in a fluid apparatus. 
     BACKGROUND OF THE INVENTION 
     As the material of a gland packing used at, for example, a shaft sealing portion in a fluid apparatus or the like, there is known a material using, as its base material, expanded graphite excellent in compression-restoring force and sealing properties. 
     The gland packing of such material is made by a compression molding method of the laminate type, the die molding type, the tip molding type, the ribbon pack type, or the like. Such gland packing should be previously made in the form of a ring having an inner diameter corresponding to the outer diameter of a shaft to be sealed. Accordingly, the gland packing cannot be used for a shaft of which the outer diameter is not fit for the inner diameter of the ring-like packing. Thus, such packing lacks versatility. Further, the expanded graphite itself is poor in tensile strength and therefore fragile. This makes it difficult to take out, for replacement, such gland packing which has been mounted on a stuffing box or the like. Thus, the gland packing presents a problem in view of practical utility. 
     In addition, the respective types of the compression molding present the following problems. 
     In the laminate-type, the yield is low, leading to increase in production cost. In the die molding type and the tip molding type, gland packing is molded with the use of molds, causing the production cost to be increased. Further, such gland packing lacks versatility. The ribbon pack type presents poor workability. 
     The problems mentioned above may be solved by making the expanded graphite in the form of a string or braided packing, so that the string-like expanded graphite may be used as cut into a predetermined length according to the diameter of a shaft to be sealed. However, the expanded graphite itself comprises vermiform particles, each of which is expanded in the direction of the C-axis of the crystal of a graphite particle. These vermiform particles as agglomerated may be compression-molded into a sheet. However, the expanded graphite even made in such a sheet, is poor in tensile strength and therefore fragile. Accordingly, such a sheet cannot be cut into yarn suitable to make a braided body. It is therefore not possible to apply such expanded graphite to a packing which may be used as cut to a predetermined length according to the diameter of a shaft to be sealed and wound around the outer periphery thereof. The same comments apply to a braided packing. 
     SUMMARY OF THE INVENTION 
     In view of the background art mentioned above, an object of the present invention is to provide packing in the form of a string improved in practical utility and versatility. After diligent study of the arrangement of a braiding yarn using expanded graphite, a way has been found to make a braiding yarn of expanded graphite by bonding expanded graphite to a reinforcing fiber yarn with adhesives, so that the synergistic action of the reinforcing fiber yarn and the expanded graphite gives, to the resultant braiding yarn, a great compression-restoring force, excellent sealing properties, and strong tensile strength and toughness. A plurality of such braiding yarns may be put together to form a core member and the core member may be then covered, at the outer periphery thereof, with a braided body of the braiding yarns, thereby to make the assembly in the form of a string. A plurality of such braiding yarns as put together may be braided in the form of a string. A plurality of such braiding yarns as put together may also be twisted in the form of a string. 
     According to the packing of the present invention, the strong tensile strength and toughness of the reinforcing fiber yarns are given to the braiding yarns. Thus, the braiding yarns may be braided or twisted without the yarns cut. It is therefore possible to form a string-like packing in which the core member made of the braiding yarns is covered, at the outer periphery thereof, with a braided body of the braiding yarns. Further, the great compression-restoring force and excellent sealing properties of the expanded graphite are given to the core member and the braided body, thus assuring such sealing properties as inevitably required for packing. 
     Further, a plurality of such braiding yarns provided with strong tensile strength and toughness may be put together and braided. It is therefore possible to form a braided body (as square-knitted) having strong tensile strength and toughness. The great compression-restoring force and excellent sealing properties of the expanded graphite are given to the braided body, thus assuring such sealing properties as inevitably required for packing. 
     Further, a plurality of such braiding yarns having strong tensile strength and toughness may be put together and twisted. It is therefore possible to form a twisted string-like member having such strong tensile strength and toughness. In addition, the great compression-restoring force and excellent sealing properties of the expanded graphite are given to this string-like member, thus assuring such sealing properties as inevitably required for packing. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view, with portions broken away, of an embodiment of a packing in accordance with a first variant of the invention; 
         FIG. 2  is a perspective view, with portions broken away, of an example of a braiding yarn; 
         FIG. 3  is a perspective view of an embodiment of packing in accordance with a second variant of the invention; 
         FIG. 4  is a perspective view of an embodiment of packing in accordance with a third variant of the invention; 
         FIG. 5  is a perspective view of another example of the braiding yarn; 
         FIGS. 6 to 10  are views of various examples of a reinforcing fiber yarn; and 
         FIGS. 11A ,  11 B and  FIGS. 12A ,  12 B are views illustrating variations of the distances between braiding yarns fed from bobbins and a knitting point in circular knitting and square knitting, respectively. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  is a perspective view, with portions broken away, of an embodiment of a packing in accordance with a first aspect of the invention. 
     In  FIG. 1 , packing  1  comprises a core member  2  and a braided body  3  covering the outer periphery of the core member  2 , the braided body  3  being made by, for example, circular-knitting. The core member  2  is formed by longitudinally arranging a plurality of internally reinforced braiding, yarns  4  as put together. The braided body  3  is formed by circular-knitting the braiding yarns  4 . 
     As shown in  FIG. 2 , each braiding yarn  4  comprises a plurality of longitudinally arranged reinforcing fiber yarns  40  made of, for example, cotton, and expanded graphite  41  has a vermiform shape integrally bonded to the outer surface of the yarns  40  with adhesives (for example, acrylic ester) (not shown). 
     The cotton yarns used as the reinforcing fiber yarns  40  have, on the outer surface thereof, an infinite number of extremely short and fine fibers, i.e., so-called fuzz. This improves the adhesion of the adhesives. Accordingly, the reinforcing fiber yarns  40  and the expanded graphite  41  are securely bonded to each other to prevent the expanded graphite  41  from partially falling from the reinforcing fiber yarns  40 . 
     Thus, the braiding yarns  4  are formed by integrally bonding, with adhesives, the expanded graphite  41  to both the outer surfaces of a plurality of longitudinally arranged reinforcing fiber yarns  40  made of, for example, cotton. The strong tensile strength and toughness of the reinforcing fiber yarns  40  are given to the braiding yarns  4 . Accordingly, the braiding yarns  4  may be braided without the yarns  4  being cut. It is therefore possible to form a string-like member  5  in which the outer periphery of the core member  2  made of the braiding yarns  4  is covered with the braided body  3  as obtained by circular-knitting the braiding yarns  4 . This string-like member  5  has characteristics excellent in tensile strength and toughness. Thus, this string-like member  5  may be used, as the packing  1 , as cut to a predetermined length according to, for example, the diameter of a shaft to be sealed. This improves the packing  1  in versatility and practical utility. Further, the great compression-restoring force and excellent sealing properties of the expanded graphite  41  are given to the core member  2  and the braided body  3  forming the packing  1 . It is therefore assured that the packing  1  is provided with such excellent sealing properties as inevitably required for packing. 
       FIG. 3  is a perspective view of an embodiment of a packing in accordance with a second variant of the invention. In  FIG. 3 , like parts are designated by like numerals used in  FIG. 1  and the detailed description of such like parts is here omitted. 
     In  FIG. 3 , the packing  1  is made in the form of a string-like member  5  made of a braided body  3 A as obtained by square-braiding eight internally reinforced braiding yarns  4 . 
     The strong tensile strength and toughness of the fiber yarns  40  are given to the braiding yarns  4 . Accordingly, the braiding yarns  4  may be braided (as square-knitted) without the yarns  4  cut. Thus, the string-like member  5  may be made of the braided body  3 A having characteristics excellent in tensile strength and toughness. It is therefore possible to use, as the packing  1 , this string-like member  5  as cut to a predetermined length according to, for example, the diameter of a shaft. This improves the packing  1  in versatility and practical utility. Further, the strong compression-restoring force and excellent sealing properties of the expanded graphite  41  are given to the braided body  3 A forming the packing  1 . Accordingly, the packing  1  may be provided with such sealing properties as indispensably required for packing. 
       FIG. 4  is a perspective view of an embodiment of a packing in accordance with a third variant of the invention. In  FIG. 4 , like parts are designated by like numerals used in  FIG. 1  and the detailed description of such like parts is here omitted. 
     In  FIG. 4 , the packing  1  is made in the form of a string-like member  5  by roll-molding six braiding yarns  4  formed as described above while these braiding yarns  4  are being twisted 20 times/m. 
     The strong tensile strength and toughness of the reinforcing fiber yarns  40  are given to the braiding yarns  4 . Accordingly, the braiding yarns  4  may be twisted without the yarns  4  cut. It is therefore possible to form the string-like member  5  having strong tensile strength and toughness. Accordingly, this string-like member  5  may be used, as the packing  1 , as cut to a predetermined length according to, for example, the diameter of a shaft to be sealed. This improves the packing  1  in versatility and practical utility. Further, the strong compression-restoring force and excellent sealing properties of the expanded graphite  41  are given to the twisted string-like member  5  forming the packing 1. Accordingly, the packing  1  may be provided with such sealing properties as indispensably required for packing. 
     In the foregoing, the description has been made of expanded graphite  41  in veriform shaped particles. Alternately, there may be used expanded graphite sheets each of which is so cut as to have a small width of, for example, 5 mm or less. 
     Alternately, each braiding yarn  4  may be formed by bonding the expanded graphite  41  only on side surface of a plurality of reinforcing fiber yarns  40  with adhesives. 
     Further, the braiding yarns  4  may be used after twisted as shown in  FIG. 5 . 
     The reinforcing fiber yarns  40  forming the braiding yarns  4  may be made of, instead of cotton mentioned earlier, a single material which is selected from organic fibers such as rayon fibers, phenol fibers, aramid fibers, PBI (polybenzimidazole) fibers, PTFE (polytetra fluoroethylene) fibers, PPS (polyphenylene sulfide) fibers, PEEK (polyether ether ketone) fibers and the like, which is selected from inorganic fibers such as glass fibers, carbon fibers, ceramic fibers and the like, or which is selected from metallic line members such as line members of stain less steel, Inconel, monel metal and the like. 
     The inorganic fibers and the metallic line members present no fuzz on the surfaces thereof, and are therefore slightly inferior in adhesion to the adhesives to the organic fibers. However, the proper selection of the adhesives enables the reinforcing fiber yarns  40  and the expanded graphite  41  to be bonded to each other in a relatively secure manner. This prevents the expanded graphite  41  from partially falling from the reinforcing fiber yarns  40 . In the braiding yarns  4  made of such inorganic fibers or metallic line members, the tensile strength is considerably improved as compared with the braiding yarns  4  made of the organic fibers. 
       FIGS. 6  to  FIG. 10  respectively show modifications of the reinforcing fiber yarn  40 . 
     In  FIG. 6 , the reinforcing fiber yarn  40  is made by twisting a yarn  40 A made of a single material selected from the organic fibers mentioned earlier (cotton or aramid), and a yarn  40 B made of a single material selected from the inorganic fibers and metallic line members mentioned earlier (glass fibers, carbon fibers or stainless steel line members). This reinforcing fiber yarn  40  may be improved in toughness and adhesion of adhesives by the organic fibers, and also improved in tensile strength and toughness by the inorganic fibers or metallic line members. 
     In  FIG. 7 , the reinforcing fiber yarn  40  comprises (i) a yarn  40 B made of at least one material selected from the inorganic fibers and metallic line members mentioned earlier (glass fibers, carbon fibers or stainless steel line members), and (ii) short fibers  6  made of a single material selected from the organic fibers mentioned earlier (cotton or aramid), the short fibers  6  covering the surface of the yarn  40 B. This reinforcing fiber yarn  40  may be improved in toughness and adhesion of adhesives by the covering layer of the short fibers  6 , and also improved in tensile strength and toughness by the yarn  40 B made of at least one material selected from the inorganic fibers and the metallic line members. The short fibers  6  forming the covering layer may be made of a composite short fiber yarn containing, in combination, fibers made of two or more types selected from the organic fibers. 
     In  FIG. 8 , the reinforcing fiber yarn  40  comprises a yarn  40 B made of at least one material selected from the inorganic fibers and metallic line members mentioned earlier (glass fibers, carbon fibers or stainless steel line members), this yarn  40 B being covered with, for example, pulp sheet-form  7 . This reinforcing fiber yarn  40  may be improved in toughness and adhesion of adhesives by the covering layer of the pulp sheet-form  7 , and also improved in tensile strength and toughness by the yarn  40 B made of at least one material selected from the inorganic fibers and the metallic line members. 
     In  FIG. 9 , the reinforcing fiber yarn  40  is made by knitting either a yarn  40 A made of a single material selected from the organic fibers mentioned earlier (cotton or aramid) or a yarn  40 B made of a single material selected from the inorganic fibers and metallic line members mentioned earlier (glass fibers, carbon fibers or stainless line members). This reinforcing fiber yarn  40  may be improved in adhesion of adhesives by the concavo-convex knitted portions in the knit structure thereof. Further, the stretching properties of the knit structure itself may absorb a tensile force. This results in increase in tolerance for stretching, thus improving toughness. 
     In  FIG. 10 , the reinforcing fiber yarn  40  comprises (i) a plurality of longitudinally arranged fibers  40 B in parallel to one another, made of a single material selected from the inorganic fibers and metallic line members mentioned earlier (glass fibers, carbon fibers or stainless steel line members), and (ii) fibers  40 A made of a single material selected from the organic fibers mentioned earlier (cotton or aramid), the fibers  40 A being entangled with the fibers  40 B so that the fibers  40 B are maintained in parallel with one another. This reinforcing fiber yarn  40  may be improved in toughness and adhesion of adhesives by the organic fibers, and also improved in tensile strength and toughness by the inorganic fibers or the metallic line members. 
     The strong tensile strength and toughness of the reinforcing fiber yarns  40  are given to the braiding yarn  4 . Thus, the braiding yarns  4  may be readily braided or twisted without the yarns  4  cut. More specifically, when carrying out circular-knitting while drawing out the braiding yarns  4  from a plurality of bobbins  9  adapted to be moved along loci shown by broken lines as shown in  FIGS. 11A and 11B , there is produced a small difference between the distance  1   a  between a knitting point P and each of the bobbin  9  as located in the outermost parts of one locus, and the distance  1   b  between the knitting point P and each of the bobbins  9  as located in the innermost parts of the other locus. In this case, a relatively small tensile force is applied to the knitting yarns  4 , so that the yarns  4  may be readily braided. On the other hand, when carrying out square-knitting while drawing out the knitting yarns  4  from a plurality of bobbins  9  adapted to be moved along diagonal loci shown by broken lines as shown in  FIGS. 12A and 12B , there is produced a great difference between the distance  1   a  between a knitting point P and each of the bobbins  9  as located in the outermost parts of one locus, and the distance  1   b  between the knitting point P and each of the bobbins  9  as located in the center parts of the other locus. In this case, a relatively great tensile force is applied to the braiding yarns  4 . Even in this case, the yarns  4  may be braided. 
     INDUSTRIAL APPLICABILITY 
     In packing using expanded graphite as a base material, the present invention eliminates a need for provision of a variety of annular packings according to the diameters of shafts to be sealed, as conventionally required for molded packing made of expanded graphite. The packing of the present invention has not only such sealing properties as inevitably required for packing, but also strong tensile strength and toughness. Thus, the packing of the present invention may be suitably used as gland packing or a sealing member for static members.