Patent Publication Number: US-3878031-A

Title: Packing for movable machine parts

Description:
United States Patent Dormer Apr. 15, 1975 [54] PACKING FOR MOVABLE MACHINE 2.578.523 12/1951 Llewellyn 277/227 X PARTS 2,691,814 10/1954 Tait 277/227 X 2,767,768 10/1956 Jelinck 277/228 X [76] Inventor: Frederic J. Dormer. 315 Central 3.534.652 10/1970 Zumeta et a1 277/230 x Park West, New York, NY. 10025 3,046,846 3/1972 Houghton et a1. 277/230 X 5 2 9 277 23 Flled: Oct 12,1973 3 7916 8 /l 74 Zumeta 0 [21] Appl. No.: 406,132 Primary ExaminerPhilip Dier Attorney, Agent, or Firm-Browne, Beveridge, 52 us. 01. 428/365; 87/1; 277/22s; Demand Klme 277/230; 428/373; 428/390 511 1m. (:1... B32b 15/04; F16j 15/00; B32b 27/06; [57] ABSTRACT 1332b 5/16; 365d 53/04 A packing to be arranged between movable machine [58] Field of Search 161/42, 189, 89, 162; parts, Comprising a core which n ains a mixture of 277/230 227423; 37/] polytetrafluoroethylene and at least one element selected from the group consisting of silicone oil, graph- [56] References Cited ite and molybdenum, and a coating of fibrous material Slll&#39;I&#39;OUfldlIlg said COI&#39;C.  
 2,217,915 10 1940 Mehnert 161/42 6 Claims, 2 Drawing Figures PACKING FOR MOVABLE MACHINE PARTS The invention relates to a packing to be arranged between movable machine parts. in particular for pumps. compressors or the like.  
  ln general. the material for packings to be arranged in pumps or other machines which have rotating elements is rubber, plastics or metal. These packings of prior art are not sufficient for extreme conditions.  
 Object of the invention is to provide an improved packing which has a long life under extreme conditions too.  
  The packing of the invention comprises a core which contains a mixture of polytetrafluoroethylene and at least one element selected from the group consisting of silicone oil, graphite and molybdenum, and a coating of fibrous material surrounding said core.  
  Advantageously. the packing of the invention has a core which contains 60 to 80 7r by weight of polytetrafluoroethylene, 4.25 to 13.75 71 by weight of silicone oil, to 7: by weight of graphite. and 0.75 to 1.25 7! by weight of molybdenum disulfide.  
  The coating of fibrous material may be a. porous web or a porous tubular knitting.  
  These and other more detailed and specific objects will be disclosed in the course of the following specification. reference being made to the accompanying drawing. in which FIG. 1 is a top plan view of an embodiment ofa packing according to the invention. and  
  FIG. 2 is a vertical cross section along the line 2-2 in FIG. 1.  
  Referring to the drawing, it will be seen that the packing comprises a core 1 and a coating 2. The core 1 consists of a mixture of polytetrafluoroethylene and at least one element selected from the group consisting of silicone oil. graphite and molybdenum disulfide. The porous coating 2 is of fibrous material such as, for instance, plastics, asbestos, vegetable or mineral fibres, in the form of a web or a tubular knitting.  
 EXAMPLES l. The core of the packing contains 60 7: by weight of polytetrafluoroethylene. 13.75 7: by weight of silicone oil, 25 7: by weight of graphite, and L25 7: by weight of molybdenum disulfide.  
  2. The core of the packing contains a mixture of 80 7: by weight of polytetrafluoroethylene, 4.25 by weight of silicone oil, 15 7: by weight of graphite, and 0.75 7c by weight of molybdenum disulfide.  
  3. The core of the packing contains a mixture of 79.5 7c by weight of polytetrafluoroethylene, 4.25 7: by weight of silicone oil. 15 7c by weight of graphite, and 1.25 7: by weight of molybdenum disulfide.  
  4. The core of the packing contains 70 7: by weight of polytetrafluoroethylene, 9 7? by weight of silicone oil, 20 by weight of graphite and l 7: by weight of molybdenum disulfide.  
  The core of the packing is produced by extruding. The core is produced as follows:  
  A powder of polytetrafluoroethylene is mechanically mixed with an aqueous dispersion of polytetrafluoroethylene and subsequently stirred to form a viscous mass. Then graphite and/or asbestos powder or the like are added to that mass and the latter is worked by means of a kneader into a pasty consistency. A plastic in the form of granules of low friction coefficient is then charged into the kneader. whereupon the kneading process is continued until a homogeneous mass is formed. This mass is then charged into an extrusion press. According to the particularly preferred embodiment of the process, the mass discharged from the extrusion press with the desired profile is then heated for a period of advantageously about one hour. ln this, the mass is heated to about 150C for about I hour and then air-dried.  
  A practical feature consists in the fact that a 30 71 dispersion of polytetrafluoroethylene of low friction coefficient is used.  
  The extruded material is rolled up and unrolled later for the application of the coating. The permeability of the coating must be adjusted to the viscosity of the core. as the latter is heated during operation. due to the friction of the respective machine parts. The adjustment can be effected by changing the mesh size of the web or knitted fabric.  
  Polytetrafluoroethylene is a polymerization product of tetrafluoroethylene. Fluor polymers have specific properties as compared to other polymers. not only because their temperatures of use are higher, but also because they are either insoluble or virtually resistant to swelling by nearly all solvents and are not affected by any of the conventional chemicals. it is recognized in this that polytetrafluoroethylene is not a thermoplastic in the usual sense of the term. It is characterized, when cooled off slowly. by high compressive strength and low permeability to gas. At fast cooling. the mass is tough and flexible, which is of particular advantage for the present invention.  
  The coating may be impregnated. as well. Suitable for this purpose is any given dispersion of plastics. for instance polytetrafluoroethylene.  
  The improved packing according to the invention is permanently ductile; it is further chemically stable and application is possible for temperature ranges between 50C and 250C.  
 I claim:  
  1. A packing to be arranged between movable parts. comprising a core which contains an homogenous mixture of polytetrafluoroethylene and at least one element selected from the group consisting of silicone oil. graphite and molybdenum disulfide forming a viscous mass. and a porous coating of fibrous material surrounding said core.  
  2. A packing according to claim 1 wherein the coreconsists essentially of polytetrafluoroethylene and at least one element selected from the group consisting of silicone oil, graphite and molybdenum disulfide forming a viscous mass, and a porous coating of fibrous material surrounding said core.  
  3. A packing according to claim 1 wherein said core contains 60 to 80% by weight of polytetrafluoroethylene, 4.25 to 13.75% by weight of silicone oil, 15 to 25% by weight of graphite and 0.75 to 1.25% by weight of molybdenum disulfide.  
  4. A packing according to claim 1 wherein said core contains by weight of polytetrafluoroethylene, 9% by weight of silicone oil, 20% by weight of graphite and 1% by weight of molybdenum disulfide.  
  5. A packing according to claim 1 wherein said porous coating is a porous web of fibrous material selected from the group consisting of vegetable fibres, mineral fibres, asbestos fibres and such plastic fibres which establish a permanent porous structure of the web.  
 6. A packing according to claim 1 wherein said porous coating is a porous tubular knitting.