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GB2322095A - Moulded parts used as power and/or motion transmission components - Google Patents

Moulded parts used as power and/or motion transmission components Download PDF

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Publication number
GB2322095A
GB2322095A GB9803155A GB9803155A GB2322095A GB 2322095 A GB2322095 A GB 2322095A GB 9803155 A GB9803155 A GB 9803155A GB 9803155 A GB9803155 A GB 9803155A GB 2322095 A GB2322095 A GB 2322095A
Authority
GB
United Kingdom
Prior art keywords
component according
nylon
skin
core
skin portion
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.)
Withdrawn
Application number
GB9803155A
Other versions
GB9803155D0 (en
Inventor
Frederick Jeremy Dugard
Brian Robert Duke
Douglas Walton
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.)
CTP DAVALL Ltd
University of Birmingham
Original Assignee
CTP DAVALL Ltd
University of Birmingham
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 CTP DAVALL Ltd, University of Birmingham filed Critical CTP DAVALL Ltd
Publication of GB9803155D0 publication Critical patent/GB9803155D0/en
Publication of GB2322095A publication Critical patent/GB2322095A/en
Withdrawn legal-status Critical Current

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/16Making multilayered or multicoloured articles
    • B29C45/1642Making multilayered or multicoloured articles having a "sandwich" structure
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16HGEARING
    • F16H55/00Elements with teeth or friction surfaces for conveying motion; Worms, pulleys or sheaves for gearing mechanisms
    • F16H55/02Toothed members; Worms
    • F16H55/06Use of materials; Use of treatments of toothed members or worms to affect their intrinsic material properties
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29KINDEXING 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
    • B29K2105/00Condition, form or state of moulded material or of the material to be shaped
    • B29K2105/06Condition, form or state of moulded material or of the material to be shaped containing reinforcements, fillers or inserts
    • B29K2105/16Fillers

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Thermal Sciences (AREA)
  • Compositions Of Macromolecular Compounds (AREA)
  • Gears, Cams (AREA)

Abstract

A two-part moulding for use as a gear, cam or pulley in a transmission system comprises a core made of a reinforced polymer, e.g. nylon or acetal, for strength, and an outer skin of a polymeric plastics material which has good tribological properties but is also a mechancical load-bearing material. The skin may be unalloyed nylon or acetal, or may include PTFE and/or silicone and/or molybdenum disulphide.

Description

This invention relates to moulded parts for use in mechanical power and motion transmissions, and also to the manufacture of such parts.
The fact that moulded polymer parts can run under dry conditions is a major factor in choosing them for mechanical power and motion transmissions. To obtain high performance, plastics components such as gears, cams and pulleys are frequently moulded from polymers containing strengthening materials and compounds. The strengthening materials and compounds, typically glass fibre or carbon fibre, add to both the strength and the stiffness of components. Injection moulded gears, cams, tooth belt and vee belt pulleys and both male and female bearing journals and shafts are often further modified by the addition of internal lubricants. These in turn increase the lubricity of the components, leading to lower friction and less wear. However, the use of polymer composites in this way can lead to a compromise in performance as: internal lubricants can weaken the bulk strength of the polymer internal reinforcements can lead to surfaces which have poor tribological properties because the fibres are often left on or protrude from the surface, interfere with sliding and so result in high wear.
In W093/21450 there is described a sleeve-shaped friction bearing in which a thin lubrication film of a suitable polymer is applied to a mandrel, and the film is covered by a support layer of hard or flexible polymer.
US-A-5219499 describes a helical screw rotor comprising a central shaft, a rotor body, and an outer layer of polymer based material. The aim is to avoid problems of shrinkage in manufacture and to achieve high precision. The outer layer consists solely of PTFE plastics material. Although PTFE has good frictional properties under pure sliding conditions, it has poor mechanical properties and would not be able to withstand the Hertzian contact stresses which occur in gear transmission systems for example.
It is an object of the present invention to provide moulded parts, especially for gear and cam transmission systems, which overcome these deficiencies.
In accordance with the invention there is provided a moulded power and/or motion transmission component comprising: a) a core portion of a polymeric plastics first material, and b) a skin portion of a polymeric plastics second material bonded to the core portion, wherein the skin portion extends over at least the part of the component which in use makes contact with another component, the first material is stronger than the second material, and the second material has a lower coefficient of friction than the first material but is a mechanical load-bearing material.
The first and second materials must be chosen to give sufficient bond strength between the core and the skin portions.
The core of the component is preferably made from a polymer containing strengthening reinforcement whilst the skin is made from a material chosen to give low friction, support Hertzian stresses, and have good wear properties. In the case of components which mesh together, such as gears, cams, tooth belt and vee belt pulleys and both male and female bearing journals, the materials of the respective meshing surfaces need not be of the same or a similar compound in order to give optimum tribological properties at the point of contact.
A two-part moulding in accordance with the invention has a number of advantages. Inner core materials can be chosen for maximum strength or other properties, while surface materials can be chosen for optimum surface properties, e.g. tribological properties.
Certain embodiments of moulded parts in accordance with the invention have the following characteristics, either singly or in combination.
1. The outer layer is of a thickness which will withstand the Hertzian contact stresses which range in depth according to the application but are typically up to 2.0 millimetres deep, and obey the following formula, or its derivatives: Hertzian contact stress zc=(1/n x(((1-vl**2)/E1) + ((1-v2**2)/E2)) where:- the values of Poissons ratio vl and v2 are typically between 0.3 and 0.4 the values of elastic modulus El and E2 are above a level of 0.35 x 10-3 N/mm2.
2. The outer layer has a coefficient of friction, , of below 0.4.
3. The outer layer is able to withstand a combination of Hertzian pressure x slide velocity PV, represented by the formula or its derivative: PV=ZcV where:- Zc may be derived as above.
V may be derived from the slide/roll ratio.
PV is limited by the allowable wear rate at a given stress and temperature, and is a balance of heat-in to heat-out (heat-in being friction/load dependent and heat-out being largely convection and conduction dependent).
4. The inner core is able adequately to support the bending stresses imposed upon it which are usually up to and above SOMPa and which broadly obey the following formula or its derivatives: Bending stress Q=Ft/(b.mn) where:- the value of tangential force Ft varies according to application and size the value of face width b varies according to application and size the value of normal module mn varies according to application between the limits of 0.4 and 10.
If a material is too weak in tensile stress it will fail due to root bending stress overload and Hertzian stress fatigue.
If a material has poor lubricity it will fail due to wear.
Thus this invention brings together a combination of properties which push the power throughput properties of gears, pulleys and cams to higher limits than a monolithic construction can achieve.
Examples of materials which can be used are the following: Cost-reduced supporting core material with enhanced property surface material such as when solid lubricants (PTFE powder and fibres, silicone spheres, aramid fibres, graphite and MoS2) are introduced at the surface to enrich it, along also with silicone oil, special mineral and synthetic oil.
An absorbent core material may be used with a specialised permeable surface layer to enhance lubricity.
Conductive surface coatings may be used particularly for statically sensitive applications.
None of the above preclude the possibility of operating these moulded components in external lubricants such as oil, grease, water or aqueous based substances.
Manufacturing methods by which the moulded parts may be made include: the Battenfeld GmbH 2K process employing a single shot twin barrel injection technique. the Admix Ltd process employing a single shot side chamber injection technique, and by over-moulding a specialised surface layer upon a supporting core.
Other methods such as powder coating could alternatively be employed. The first two of these manufacturing methods employ simultaneous injection moulding of the two materials. Size of moulding is not seen as a limitation to this technique; the normal size limitations of injection moulding apply.
Gear mouldings using these two techniques have been successfully produced. As a result it has been possible to demonstrate that complex shapes such as gears with many teeth and with normally accepted flange and rim geometries can be successfully moulded superior wear (as compared to plain polymer and reinforced polymer composites) resulting from dual moulding a PTFE enriched nylon or acetal surface layer onto a core of glass fibre reinforced nylon under a high torque and speed. the surface bond between the surface and core materials is able to withstand the Hertzian sub surface stresses as well as the bending stresses resulting from normal gear action without degradation.
Various materials have been found acceptable for both the core and the skin. The core is preferably a reinforced polyamide (nylon) material or a reinforced acetal material.
Alternatively, one can use polybutyleneterephthalate (PBT), polyestersulphone (PES), aliphatic polyketone ("Carilon"), liquid crystal polymer (LCP) or polyetherketone (peek), suitably reinforced. The reinforcement for any of the aforesaid materials can be glass fibres, carbon fibres, steel fibres, ceramic fibres or aramid fibres. The reinforcement is preferably in the range of 10 to 70% by weight, more preferably 30 to 45% by weight.
The skin can be unalloyed polyamide (nylon) material, e.g. nylon 66. Alternatively, one can use an acetal material, PBT, PES, "carillon", LCP or PEEK, as above. Each of these materials, if not used in unalloyed form, can be alloyed with one or more of PTFE, silicone oil, molybdenum disulphide, graphite and mineral lubricants. If PTFE is used, it is preferably in an amount up to 30% by weight, more preferably between 15 and 20% by weight.
The following Table 1 shows test results for various materials. Gears comprising a driven gear and a driving gear were moulded and tested for weight loss over 24 hours under load. The results show clearly that the monolithic gears without fibre reinforcement performed poorly. The monolithic polyamide nylon gears with fibre reinforcement performed better, but the two-part moulded gears in accordance with the invention all showed very little weight loss.
TABLE 1
Material Grade Base Weight loss Key Polymer of tested gears over 24hrs on load Monolithic acetal Acetal 4.908 C1 (driven) Monolithic acetal Acetal 3.916 C1 (driver) Monolithic polyamide Nylon 66 1.68 C2 (driven) Monolithic polyamide Nylon 66 1.688 C2 (driver) Monolithic polyamide 30% GF Nylon 66 0.485 C2 (driven) Monolithic polyamide 30% GF Nylon 66 0.517 C2 (driver) Unalloyed Nylon Skin/30% GF Nylon Core Nylon 66 0.173 2P1 (driven) Unalloyed Nylon Skin/30% GF Nylon Core Nylon 66 0.153 2P1 (driver) 20% PTFE Nylon Skin/30% GF Nylon Core Nylon 66 0.088 2P2 (driven) 20% PTFE Nylon Skin/30% GF Nylon Core Nylon 66 0.078 2P2 (driver) Unalloyed Nylon Skin/30% CF Nylon Core Nylon 66 0.187 2P3 (driven) Unalloyed Nylon Skin/30% CF Nylon Core Nylon 66 0.181 2P3 (driver) 20% PTFE Nylon Skin/30% CF Nylon Core Nylon 66 0.082 2P4 (driven) 20% PTFE Nylon Skin/30% CF Nylon Core Nylon 66 0.09 2P4 (driver) Unalloyed Nylon Skin/43% GF Nylon Core Nylon 66 0.09 2P5 (driven) Unalloyed Nylon Skin/43% GF Nylon Core Nylon 66 0.087 2P5 (driver) Note: C1 and C2 are controls. P1 to P5 are of two part construction.
GF - Glass Fibre. CF - Carbon Fibre

Claims (12)

1. A moulded power and/or motion transmission component comprising: a) a core portion of a polymeric plastics first material, and b) a skin portion of a polymeric plastics second material bonded to the core portion, wherein the skin portion extends over at least the part of the component which in use makes contact with another component, the first material is stronger than the second material, and the second material has a lower coefficient of friction than the first material but is a mechanical load-bearing material.
2. A component according to claim 1, in which the core portion is a reinforced polymeric plastics material.
3. A component according to claim 2, in which the core portion comprises reinforced polyamide or reinforced acetal material.
4. A component according to claim 1, in which the core portion is made of polybutyleneterephthalate, polyestersulphone or aliphatic polyketone.
5. A component according to any preceding claim, in which the core portion is reinforced with one or more of glass, carbon, steel, ceramic and aramid fibres.
6. A component according to claim 5, in which the fibre reinforcement is present in an amount of 10 to 70% by weight, preferably 30 to 45% by weight.
7. A component according to any preceding claim, in which the skin portion comprises a polyamide material.
8. A component according to any of claims 1 to 6, in which the skin portion comprises an acetal material.
9. A component according to any of claims 1 to 6, in which the skin portion comprises polybutyleneterephthalate, polyestersulphone or aliphatic polyketone.
10. A component according to any of claims 7 to 9, in which the skin portion includes polytetrafluoroethylene.
11. A component according to claim 10, in which the polytetrafluoroethylene is present in an amount up to 30% by weight, preferably 15 to 20% by weight.
12. A component according to any of claims 7 to 11, in which the skin portion comprises silicone oil and/or molybdenum disulphide.
GB9803155A 1997-02-13 1998-02-13 Moulded parts used as power and/or motion transmission components Withdrawn GB2322095A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GBGB9702918.5A GB9702918D0 (en) 1997-02-13 1997-02-13 Composite material

Publications (2)

Publication Number Publication Date
GB9803155D0 GB9803155D0 (en) 1998-04-08
GB2322095A true GB2322095A (en) 1998-08-19

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Family Applications (2)

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GBGB9702918.5A Pending GB9702918D0 (en) 1997-02-13 1997-02-13 Composite material
GB9803155A Withdrawn GB2322095A (en) 1997-02-13 1998-02-13 Moulded parts used as power and/or motion transmission components

Family Applications Before (1)

Application Number Title Priority Date Filing Date
GBGB9702918.5A Pending GB9702918D0 (en) 1997-02-13 1997-02-13 Composite material

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GB (2) GB9702918D0 (en)
WO (1) WO1998035820A1 (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1126174A3 (en) * 2000-02-14 2002-06-19 Joma-Hydromechanic GmbH Plastic gear for gear pump
WO2014139676A1 (en) * 2013-03-14 2014-09-18 Wilo Se Pump unit comprising a one-piece bearing unit
CN114746254A (en) * 2019-11-12 2022-07-12 赛峰短舱公司 Component with improved wear resistance

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB858124A (en) * 1956-05-09 1961-01-04 Charles Samuel White A method of forming a mechanical assembly having low-friction bearing surfaces between relatively movable parts, and article produced by the method
GB1249586A (en) * 1969-03-26 1971-10-13 Ici Ltd Improved thermoplastic gear wheels
GB1581930A (en) * 1976-03-24 1980-12-31 Curran D G Coverings
GB2253261A (en) * 1991-02-27 1992-09-02 Nippon Oil Co Ltd Composite rolls
US5296183A (en) * 1992-08-21 1994-03-22 Dow-United Technologies Composite Products, Inc. Method for comolding property enhancing coatings to composite articles
US5688054A (en) * 1992-04-09 1997-11-18 Rabe; Thore Process for the production of a sleeve-shaped friction bearing and a friction bearing produced according to this process

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1383645A (en) * 1971-04-19 1974-02-12 Oiles Industry Co Ltd Composite material for use as a low friction element
DE2820180C2 (en) * 1978-05-09 1980-07-31 Elteka Kunststoff-Technik Gmbh, 7950 Biberach Polyamide laminated body
AT362149B (en) * 1979-03-14 1981-04-27 Faigle Heinz Kg PLASTIC / PLASTIC PAIRINGS IN TRIBOLOGICAL SYSTEMS
JPS6021541B2 (en) * 1978-09-25 1985-05-28 オイレス工業株式会社 Sliding member coated with synthetic resin and its manufacturing method
DE2947025A1 (en) * 1979-11-22 1981-06-04 Glyco-Metall-Werke Daelen & Loos Gmbh, 6200 Wiesbaden TWO OR MULTILAYER COMPOSITE
JPS6210165A (en) * 1985-07-09 1987-01-19 Taiho Kogyo Co Ltd Resin bearing materials and their manufacturing method
NL8603138A (en) * 1986-12-10 1988-07-01 Stamicarbon MULTI-LAYER POLYAMIDE SHAPE BODY.
DD292875A5 (en) * 1990-03-19 1991-08-14 Technische Hochschule "Carl Schorlemmer" Leuna-Merseburg,De PROCESS FOR PRODUCING COMPOSITE BODIES FROM THERMOPLASTIC MATERIALS

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB858124A (en) * 1956-05-09 1961-01-04 Charles Samuel White A method of forming a mechanical assembly having low-friction bearing surfaces between relatively movable parts, and article produced by the method
GB1249586A (en) * 1969-03-26 1971-10-13 Ici Ltd Improved thermoplastic gear wheels
GB1581930A (en) * 1976-03-24 1980-12-31 Curran D G Coverings
GB2253261A (en) * 1991-02-27 1992-09-02 Nippon Oil Co Ltd Composite rolls
US5688054A (en) * 1992-04-09 1997-11-18 Rabe; Thore Process for the production of a sleeve-shaped friction bearing and a friction bearing produced according to this process
US5296183A (en) * 1992-08-21 1994-03-22 Dow-United Technologies Composite Products, Inc. Method for comolding property enhancing coatings to composite articles

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1126174A3 (en) * 2000-02-14 2002-06-19 Joma-Hydromechanic GmbH Plastic gear for gear pump
WO2014139676A1 (en) * 2013-03-14 2014-09-18 Wilo Se Pump unit comprising a one-piece bearing unit
CN114746254A (en) * 2019-11-12 2022-07-12 赛峰短舱公司 Component with improved wear resistance
EP4058276A1 (en) * 2019-11-12 2022-09-21 Safran Nacelles Part having improved abrasion resistance
CN114746254B (en) * 2019-11-12 2025-07-01 赛峰短舱公司 Components with improved wear resistance

Also Published As

Publication number Publication date
WO1998035820A1 (en) 1998-08-20
GB9702918D0 (en) 1997-04-02
GB9803155D0 (en) 1998-04-08

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