Seal for a joint or juncture – Seal between relatively movable parts – Circumferential contact seal for other than piston
Patent
1995-12-01
1998-09-08
DePumpo, Daniel G.
Seal for a joint or juncture
Seal between relatively movable parts
Circumferential contact seal for other than piston
277534, 277538, 277539, F16J 1528
Patent
active
058034641
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a gland packing which is useful as a shaft seal device for a hydraulic machine such as a valve or a pump, and more particularly to a gland packing which is charged into a stuffing box and pressed by a packing gland in an axial direction so as to be brought into tight contact with the outer peripheral face of a shaft or a valve rod, thereby forming a shaft seal part.
DESCRIPTION OF THE PRIOR ART
A conventionally known gland packing having the structure shown in FIG. 25 is a die mold packing 51. The die mold packing 51 is configured by laminating a tape-like material 50 such as an expanded graphite tape in a winding manner into a spiral shape, and then die-molding the lamination into a ring-like shape. Such a die mold packing 51 is used in the following manner. As shown in FIG. 26, in a stuffing box 54, the die mold packings 51, and a plurality of laminate packings 53 which are obtained by laminating ring-like sheet materials 52 having impermeability are alternately disposed on the outer periphery of a shaft or a valve rod 55 (hereinafter, referred to as "valve rod or the like") in an axial direction. Alternatively, as shown in FIG. 27, the die mold packings 51, and braided packings 56, which are well known in the art, are combined. These packings are pressed in the axial direction by a packing gland 57 so that their inner peripheral facing surfaces are brought into tight contact with the outer peripheral face of the valve rod 55 or the like, thereby performing a shaft sealing operation.
Furthermore, a gland packing 58 is also known in which, as shown in FIG. 28, a circumferentially projected part 51a is formed on an end face in the axial direction of the die mold packing 51 and in an outer end portion in the radial direction so that the circumferentially projected part is projected outward in the axial direction, and a ring-like recess 56a which is formed on an end face in the axial direction of the braided packings 56 and in an outer end portion in a radial direction is fitted onto the circumferentially projected part 51a, thereby integrating the packings 51 and 56 into one body. Also the integrated gland packing 58 is used in the following manner. As shown in FIG. 29, the integrated gland packings 58 are combined in the stuffing box 54 and include the die mold packings 51 having the circumferentially projected part 51a. In the same manner as described above, these packings are pressed in an axial direction by the packing gland 57 so that their inner peripheral facing surfaces are brought into tight contact with the outer peripheral face of the valve rod 55 or the like, thereby performing a shaft sealing operation.
In a prior art gland packing mainly consisting of the die mold packings 51, as shown in FIGS. 25 and 28, minute gaps 59 are inevitably formed in parts that are laminated by winding of the tape-like material 50. A pressurized fluid penetrates into the minute gaps 59, and leakage indicated by the arrow a easily occurs. Particularly when a gas fluid of low molecular weight flows through the hydraulic machine, it is very difficult to prevent penetration leakage from occurring.
Furthermore, the die mold packing 51 has originally a lower strength. In a use manner, the die mold packing is disposed substantially parallel to the axis of the valve rod 55 or the like. When the material is pressed in an axial direction, the material is swollen out to enter the gaps so that stress relaxation easily occurs. Furthermore, the process of die molding is conducted at a high face pressure. When the die mold has a rectangular section shape, therefore, the die mold cannot exhibit sufficient sealing performance at a low tightening force.
Moreover, when the die mold packings 51 and the laminate packings 53 are used in combination as shown in FIG. 26, the amount of deformation of the laminate packings 53 in the pressurizing process is small, and hence the laminate packings 53 must be produced with very high dimensional accuracy. Furthermore, the parts of the la
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Fujiwara Masaru
Ueda Takahisa
DePumpo Daniel G.
Nippon Pillar Packing Co. Ltd.
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