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WO1993014925A1 - Manufacture of plain bearings - Google Patents

Manufacture of plain bearings Download PDF

Info

Publication number
WO1993014925A1
WO1993014925A1 PCT/GB1993/000152 GB9300152W WO9314925A1 WO 1993014925 A1 WO1993014925 A1 WO 1993014925A1 GB 9300152 W GB9300152 W GB 9300152W WO 9314925 A1 WO9314925 A1 WO 9314925A1
Authority
WO
WIPO (PCT)
Prior art keywords
polytetrafluoroethylene
particles
fibrillation
layer
pressure
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/GB1993/000152
Other languages
French (fr)
Inventor
Glyndwr John Davies
Philip Moisey
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Federal Mogul Shoreham Ltd
Original Assignee
Glacier Vandervell Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Glacier Vandervell Ltd filed Critical Glacier Vandervell Ltd
Publication of WO1993014925A1 publication Critical patent/WO1993014925A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
    • B29C43/006—Pressing and sintering powders, granules or fibres
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
    • B29C43/02—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of definite length, i.e. discrete articles
    • B29C43/18—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of definite length, i.e. discrete articles incorporating preformed parts or layers, e.g. compression moulding around inserts or for coating articles
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
    • F16C33/02—Parts of sliding-contact bearings
    • F16C33/04—Brasses; Bushes; Linings
    • F16C33/20—Sliding surface consisting mainly of plastics
    • F16C33/201—Composition of the plastic
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2027/00—Use of polyvinylhalogenides or derivatives thereof as moulding material
    • B29K2027/12—Use of polyvinylhalogenides or derivatives thereof as moulding material containing fluorine
    • B29K2027/18—PTFE, i.e. polytetrafluorethene, e.g. ePTFE, i.e. expanded polytetrafluorethene
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
    • B29K2105/0088—Blends of polymers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
    • B29K2105/25—Solid
    • B29K2105/251—Particles, powder or granules
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2031/00—Other particular articles
    • B29L2031/04—Bearings
    • B29L2031/045—Bushes therefor

Definitions

  • This invention is concerned with a method for manufacturing a plain bearing.
  • bearings comprise a layer of sintered metallic material, e.g. bronze, formed on a backing material such as steel.
  • the layer of sintered metallic material has an overlay of polytetrafluoroethylene which is forced into the intersticies of at least a surface portion of the layer of sintered metallic material and forms a low friction surface of the bearing.
  • Such bearings may be formed by applying particles of polytetrafluoroethylene to the surface of the layer of sintered metallic material and applying heat and pressure to the particles so that the polytetrafluoroethylene is forced into the intersticies as described above.
  • a dispersion of polytetrafluorethylene is coagulated in the presence of a filler, e.g. lead powder, and a high proportion of toluene.
  • a filler e.g. lead powder
  • toluene a filler
  • This mush is applied to the surface of the sintered metallic layer, the toluene acting as a lubricant to assist the flow of the polytetrafluoroethylene/lead into the intersticies of the sintered material.
  • the mush is extremely shear-sensitive, in that there is a tendency for the particles of polytetrafluoroethylene to fibrillate when they are subjected to relative movement.
  • Even mild working of the mush causes thin fibrilles of polytetrafluoroethylene to be drawn out across the shearing surfaces resulting in the mush quickly becoming very stiff and unusable since it does not possess the good flow characteristics required to enable it to impregnate the intersticies of the sinter.
  • the mush is applied very carefully by hand to the sintered layer and attempts to avoid the necessity for such a hand operation by introducing automatic handling of the mush have so far, so far as is known, been unsuccessful.
  • the invention provides a method of manufacturing a plain bearing comprising applying particles of polytetrafluoroethylene to the surface of a layer of sintered metallic material and applying heat and pressure to the particles so that the polytetrafluoroethylene is forced into the intersticies of at least a surface portion of the layer of sintered metallic material and forms a low friction surface thereon, characterised in that the particles of polytetrafluoroethylene applied are encapsulated in a coating of a material which prevents fibrillation of the polytetrafluoroethylene during application of the particles but which breaks down during said application of heat and pressure to allow such fibrillation.
  • the polytetrafluoroethylene particles are prevented from fibrillating until after they have been applied to the sintered metallic material so that handling of the particles by automatic application means does not cause such fibrillation. Furthermore, as the particles are protected from fibrillation, the particles can be applied as a dry powder which is not possible in the conventional process since the mush of the conventional process when dried is unworkable.
  • toluene as a lubricant to be dispensed with since toluene has been selected as a material which can form a stable emulsion with the polytetrafluoroethylene and as having coagulation characteristics which allow it to coagulate with the polytetraflurorethylene mush leaving toluene within the mush.
  • the lubricant can be added after the dry powder has been applied, for example, in the form of kerosine.
  • the polytetrafluoroethylene can be stored in powder form and used when required with the addition of liquid lubricant.
  • the coating is formed from an acrylic co- polymer, for example an acidic cross-linked acrylic emulsion co-polymer.
  • the polytetrafluoroethylene particles may also contain a filler, for example, lead, molybdenum disulphide, graphite, bronze, or zinc.
  • a filler for example, lead, molybdenum disulphide, graphite, bronze, or zinc.
  • the polytetrafluoroethylene particles may contain an anti-discolouring agent particularly where a filler of lead is used.
  • the anti-discolouring agent may be designed to prevent the formation of lead oxide.
  • a dispersion of 75% polytetrafluoroethylene solids in water was poured in to a Hobart mixer fitted with a K-paddle. The mixer was operated at its slowest speed. To this dispersion in the mixer, a 28% solid aqueous solution of acidic cross-linked acrylic emulsion co-polymer was added. Mixing continued for 4 minutes. Then, sufficient lead powder to produce a 20% by volume lead metal content in the final lead and polytetrafluoroethylene mixture was dispersed in a minimum quantity of water with the minimum quantity of a non-ionic surfactant to give a free flowing liquid. The liquid was added to the mixture in the mixer as rapidly as possible to prevent the heavy lead from separating out.
  • a discolouring agent was added to the mixture to prevent the lead metal from forming oxides during drying.
  • the discolouring agent in question was sodium nitrite stirred into an ammonia solution.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Sliding-Contact Bearings (AREA)
  • Lubricants (AREA)

Abstract

Plain bearings are manufactured by applying particles of polytetrafluoroethylene to a sintered metallic material, and applying heat and pressure to force the polytetrafluoroethylene into interstices of the material surface. The particles are encapsulated in a coating of the material which prevents fibrillation of the polytetrafluoroethylene during application of the particles. The coating material is selected so that it breaks down during the application of heat and pressure to allow fibrillation.

Description

MANUFACTURE OF PLAIN BEARINGS
This invention is concerned with a method for manufacturing a plain bearing.
For many years, plain bearings of the general type described in US Patent Specification NO. 2,689,380 have been in common use. Such bearings comprise a layer of sintered metallic material, e.g. bronze, formed on a backing material such as steel. The layer of sintered metallic material has an overlay of polytetrafluoroethylene which is forced into the intersticies of at least a surface portion of the layer of sintered metallic material and forms a low friction surface of the bearing. Such bearings may be formed by applying particles of polytetrafluoroethylene to the surface of the layer of sintered metallic material and applying heat and pressure to the particles so that the polytetrafluoroethylene is forced into the intersticies as described above.
In the conventional method of manufacturing a plain bearing as described above, a dispersion of polytetrafluorethylene is coagulated in the presence of a filler, e.g. lead powder, and a high proportion of toluene. This produces a wet "mush" containing toluene. This mush is applied to the surface of the sintered metallic layer, the toluene acting as a lubricant to assist the flow of the polytetrafluoroethylene/lead into the intersticies of the sintered material. This method, however, suffers from the disadvantage that the mush is extremely shear-sensitive, in that there is a tendency for the particles of polytetrafluoroethylene to fibrillate when they are subjected to relative movement. Thus, even mild working of the mush causes thin fibrilles of polytetrafluoroethylene to be drawn out across the shearing surfaces resulting in the mush quickly becoming very stiff and unusable since it does not possess the good flow characteristics required to enable it to impregnate the intersticies of the sinter. In order to avoid fibrillation of the mush, the mush is applied very carefully by hand to the sintered layer and attempts to avoid the necessity for such a hand operation by introducing automatic handling of the mush have so far, so far as is known, been unsuccessful.
It is an object of the present invention to provide a method of manufacturing a plain bearing of the type described above in which the above-mentioned hand operation can be eliminated.
The invention provides a method of manufacturing a plain bearing comprising applying particles of polytetrafluoroethylene to the surface of a layer of sintered metallic material and applying heat and pressure to the particles so that the polytetrafluoroethylene is forced into the intersticies of at least a surface portion of the layer of sintered metallic material and forms a low friction surface thereon, characterised in that the particles of polytetrafluoroethylene applied are encapsulated in a coating of a material which prevents fibrillation of the polytetrafluoroethylene during application of the particles but which breaks down during said application of heat and pressure to allow such fibrillation. In a method according to the invention, the polytetrafluoroethylene particles are prevented from fibrillating until after they have been applied to the sintered metallic material so that handling of the particles by automatic application means does not cause such fibrillation. Furthermore, as the particles are protected from fibrillation, the particles can be applied as a dry powder which is not possible in the conventional process since the mush of the conventional process when dried is unworkable. This enables the use of toluene as a lubricant to be dispensed with since toluene has been selected as a material which can form a stable emulsion with the polytetrafluoroethylene and as having coagulation characteristics which allow it to coagulate with the polytetraflurorethylene mush leaving toluene within the mush. The lubricant can be added after the dry powder has been applied, for example, in the form of kerosine. Thus, the polytetrafluoroethylene can be stored in powder form and used when required with the addition of liquid lubricant.
Preferably, the coating is formed from an acrylic co- polymer, for example an acidic cross-linked acrylic emulsion co-polymer.
The polytetrafluoroethylene particles may also contain a filler, for example, lead, molybdenum disulphide, graphite, bronze, or zinc.
The polytetrafluoroethylene particles may contain an anti-discolouring agent particularly where a filler of lead is used. The anti-discolouring agent may be designed to prevent the formation of lead oxide. There now follows a detailed example of a method manufacturing a plain bearing according to the invention which has been selected by way of example and not by way of limitation of the invention.
In the illustrative example, a dispersion of 75% polytetrafluoroethylene solids in water was poured in to a Hobart mixer fitted with a K-paddle. The mixer was operated at its slowest speed. To this dispersion in the mixer, a 28% solid aqueous solution of acidic cross-linked acrylic emulsion co-polymer was added. Mixing continued for 4 minutes. Then, sufficient lead powder to produce a 20% by volume lead metal content in the final lead and polytetrafluoroethylene mixture was dispersed in a minimum quantity of water with the minimum quantity of a non-ionic surfactant to give a free flowing liquid. The liquid was added to the mixture in the mixer as rapidly as possible to prevent the heavy lead from separating out.
Next, a discolouring agent was added to the mixture to prevent the lead metal from forming oxides during drying. The discolouring agent in question was sodium nitrite stirred into an ammonia solution.
Mixing was continued for about 2 minutes producing a dark-coloured, thick, cream-like material. This material was allowed to stand for 24 hours and then the supernatant liquid was decanted. The resulting thick gellatinous mass was then dried in an oven resulting in a dry powder containing 20% by volume of lead and polytetrafluoroethylene particles which were each completely encapsulated in a thin skin of the acrylic resin. This powder was found to be capable of being poured, stirred or mechanically handled with no fibrillation or flow difficulties. The dry powder was mixed with kerosine which acted as a hydro-carbon lubricant and the material was applied to the surface of a sintered metallic material in the conventional manner. Heat and pressure were applied so that the coating of acrylic resin was broken down and burnt off and the polytetrafluoroethylene and lead mixture was able to penetrate the intersticies of the metallic layer and fibrillation was able to occur to give the necessary strength to the polytetrafluoroethylene layer.

Claims

A method of manufacturing a plain bearing comprising applying particles of polytetrafluoroethylene to the surface of a layer of sintered metallic material, and applying heat and pressure to the particles so that the polytetrafluoroethylene is forced into the intersticies of at least a surface portion of the layer of the sintered metallic material and forms a low friction surface thereon, characterised in that the particles of polytetrafluoroethylene applied are encapsulated in a coating of a material which prevents fibrillation of the polytetrafluoroethylene during application of the particles but which breaks down during said application of heat and pressure to allow such fibrillation.
A method according to Claim 1, characterised in that said coating is formed from an acrylic co-polymer.
A method according to either one of Claims 1 and 2, characterised in that the polytetrafluorethylene particles contain a filler.
A method according to either of Claims 1 to 3, characterised in that the polytetrafluoroethylene particles contain an anti-discolouring agent.
A method according to either of Claims 1 to 3, characterised in that the polytetrafluoroethylene particles are mixed with a hydro-carbon-based lubricant.
PCT/GB1993/000152 1992-02-04 1993-01-25 Manufacture of plain bearings Ceased WO1993014925A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9202304.3 1992-02-04
GB9202304A GB2264150B (en) 1992-02-04 1992-02-04 Manufacture of plain bearings

Publications (1)

Publication Number Publication Date
WO1993014925A1 true WO1993014925A1 (en) 1993-08-05

Family

ID=10709771

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1993/000152 Ceased WO1993014925A1 (en) 1992-02-04 1993-01-25 Manufacture of plain bearings

Country Status (2)

Country Link
GB (1) GB2264150B (en)
WO (1) WO1993014925A1 (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996021522A1 (en) * 1995-01-12 1996-07-18 Sintermetallwerk Krebsöge Gmbh Component produced by powder metallurgical means
US6180574B1 (en) 1998-12-16 2001-01-30 Rexnord Corporation Self-lubricating bearing and coating
US6471149B1 (en) 1996-06-29 2002-10-29 Buhler Ag Gap mill

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3996143A (en) * 1972-04-04 1976-12-07 Kamatics Corporation Cured acrylate bearing member
PL131464B1 (en) * 1981-09-23 1984-11-30 Wojskowy Inst Tech Pancerne Method of obtaining antifriction material

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63111312A (en) * 1986-10-29 1988-05-16 N D C Kk Double layer bearing and manufacture thereof

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3996143A (en) * 1972-04-04 1976-12-07 Kamatics Corporation Cured acrylate bearing member
PL131464B1 (en) * 1981-09-23 1984-11-30 Wojskowy Inst Tech Pancerne Method of obtaining antifriction material

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
STN International, File CA, Chemical Abstracts, volume 109, no. 16, 17 October 1988, (Columbus, Ohio, US), Janecki Janusz et al: "Manufacture of antifriction material for slide bearings", abstract 130220b, & PL 131464 B1 20 Mar 1987 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996021522A1 (en) * 1995-01-12 1996-07-18 Sintermetallwerk Krebsöge Gmbh Component produced by powder metallurgical means
US6471149B1 (en) 1996-06-29 2002-10-29 Buhler Ag Gap mill
US6180574B1 (en) 1998-12-16 2001-01-30 Rexnord Corporation Self-lubricating bearing and coating

Also Published As

Publication number Publication date
GB2264150B (en) 1995-05-17
GB2264150A (en) 1993-08-18
GB9202304D0 (en) 1992-03-18

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