EP0960294A1 - A chain sprocket - Google Patents
A chain sprocketInfo
- Publication number
- EP0960294A1 EP0960294A1 EP98903166A EP98903166A EP0960294A1 EP 0960294 A1 EP0960294 A1 EP 0960294A1 EP 98903166 A EP98903166 A EP 98903166A EP 98903166 A EP98903166 A EP 98903166A EP 0960294 A1 EP0960294 A1 EP 0960294A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- sprocket
- tooth
- cam
- chain
- teeth
- 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
Links
Classifications
-
- 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
- F16H—GEARING
- F16H55/00—Elements with teeth or friction surfaces for conveying motion; Worms, pulleys or sheaves for gearing mechanisms
- F16H55/02—Toothed members; Worms
- F16H55/30—Chain-wheels
Definitions
- the present invention relates to a chain sprocket, particularly but not exclusively, a sprocket of the type that is used in combination with an endless roller and bush chain.
- a sprocket for a drive chain comprising a wheel body with at least one chain-engaging tooth that is retractable into the body.
- the tooth is arranged so that as a chain is presented to the periphery of the sprocket it is in the withdrawn position and as the sprocket rotates the tooth gradually moves towards the extended position so as to engage the chain.
- the tooth is preferably reversibly retractable from a chain-engaging extended position in which it protrudes from the body to a retracted position.
- the tooth is preferably radially retractable.
- the tooth is preferably biased into the retracted position and may be moved to the extended position by means of a cam.
- the cam may be fixed relative to the sprocket so that the tooth is moved during rotation of the sprocket.
- the cam is eccentric and engages a radially inward end of the tooth when the latter is moved to the extended position.
- the sprocket comprises a plurality of retractable teeth each being moveable in sequence as it passes over the cam.
- the teeth are supported on a resilient annulus that is engaged by the cam.
- the cam may rotate about a fixed point offset from a centre of rotation of the sprocket.
- Figure 1 is a schematic partially sectioned side view of a sprocket according to a first embodiment of the present invention
- Figure 2 is an enlarged view of part of the sprocket of figure 1 showing teeth in an extended position
- Figure 3 is a schematic side view illustrating a second embodiment of the present invention.
- figures 1 and 2 show a rotary drive sprocket 1 of the present invention that has a centre of rotation 2 and is designed to engage with a roller chain 3 only part of the outline of which is represented schematically by parallel lines. The remainder of the chain 3 is removed for clarity but it will be understood that it approaches the sprocket 1 in direction of arrow A, engages approximately 180° of the periphery of the sprocket 1 and emerges in the direction of arrow B.
- the sprocket 1 has a plurality of equi-angularly spaced teeth 4, each of which is radially moveable within a respective radial slot 5 in the sprocket 1.
- Each tooth 4 is resiliently biased into a withdrawn position by means of, for example, a spring or hydraulic pressure (not shown).
- Radially inner ends of the teeth 4 have semi-cylindrical formations 6 that are designed to come into sliding contact with an eccentric cam 7 that is fixed at the centre of rotation 2 of the sprocket 1.
- the sprocket 1 rotates clockwise to drive the chain 3 in the direction of arrows A and B.
- the teeth 4 ride over the eccentric of the cam 7 they are gradually forced radially outwardly to a fully extended position (as represented by tooth 4a in figure 2) and after passing the cam they gradually return to a retracted position.
- the cam 7 is carefully positioned so that its eccentric portion coincides with the point where the chain 3 fully engages the sprocket 1.
- the nearest sprocket tooth represented by 4b in figure 1
- the nearest sprocket tooth represented by 4b in figure 1
- the tooth 4b When fully extended the tooth (as represented by tooth 4b) is in complete engagement with the chain 3.
- radially inner ends of the teeth 4 engage an elastic annulus 8 which on its inner circumferential surface is engaged at one point by a rotary circular cam 9.
- the annulus 8 rides over the cam 9 and is locally deflected so as to cause the adjacent teeth 4 to move radially outwards and into engagement with the chain 3.
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Gears, Cams (AREA)
Abstract
A sprocket (1) for a drive chain (3) has a plurality of radially retractable teeth (4). As sprocket rotates the teeth pass over a cam (7) that force them in sequence from a retracted position into an extended position where they engage the chain. The teeth are resiliently biased into the retracted position so that after they have engaged the cam they return to the retracted position. The retracting teeth ensure that noise caused by impact of the chain on the sprocket teeth is significantly reduced.
Description
A CHAIN SPROCKET
The present invention relates to a chain sprocket, particularly but not exclusively, a sprocket of the type that is used in combination with an endless roller and bush chain.
It is well known that a significant proportion of noise generated in chain drives occurs when a chain engages with its drive sprocket and in particular when rollers in the links of the chain impact with teeth defined on the sprocket periphery.
It is a object of the present invention to obviate or mitigate the aforesaid disadvantage and provide for a relatively low noise chain drive assembly.
According to the present invention there is provided a sprocket for a drive chain, the sprocket comprising a wheel body with at least one chain-engaging tooth that is retractable into the body.
The tooth is arranged so that as a chain is presented to the periphery of the sprocket it is in the withdrawn position and as the sprocket rotates the tooth gradually moves towards the extended position so as to engage the chain.
The tooth is preferably reversibly retractable from a chain-engaging extended position in which it protrudes from the body to a retracted position. The tooth is preferably radially retractable.
The tooth is preferably biased into the retracted position and may be moved to the extended position by means of a cam. The cam may be fixed relative to the sprocket so that the tooth is moved during rotation of the sprocket.
In a preferred embodiment the cam is eccentric and engages a radially inward end of the tooth when the latter is moved to the extended position.
Preferably the sprocket comprises a plurality of retractable teeth each being moveable in sequence as it passes over the cam.
In one embodiment the teeth are supported on a resilient annulus that is engaged by the cam. In this embodiment the cam may rotate about a fixed point offset from a centre of rotation of the sprocket.
Specific embodiment of the present invention will now be described, by way - of example only, with reference to the accompanying drawings in which:
Figure 1 is a schematic partially sectioned side view of a sprocket according to a first embodiment of the present invention;
Figure 2 is an enlarged view of part of the sprocket of figure 1 showing teeth in an extended position; and
Figure 3 is a schematic side view illustrating a second embodiment of the present invention
Referring now to the drawings, figures 1 and 2 show a rotary drive sprocket 1 of the present invention that has a centre of rotation 2 and is designed to engage with a roller chain 3 only part of the outline of which is represented schematically by parallel lines. The remainder of the chain 3 is removed for clarity but it will be understood that it approaches the sprocket 1 in direction of arrow A, engages approximately 180° of the periphery of the sprocket 1 and emerges in the direction of arrow B.
The sprocket 1 has a plurality of equi-angularly spaced teeth 4, each of which is radially moveable within a respective radial slot 5 in the sprocket 1. Each tooth 4 is resiliently biased into a withdrawn position by means of, for example, a spring or hydraulic pressure (not shown).
Radially inner ends of the teeth 4 have semi-cylindrical formations 6 that are designed to come into sliding contact with an eccentric cam 7 that is fixed at the centre of rotation 2 of the sprocket 1.
In operation the sprocket 1 rotates clockwise to drive the chain 3 in the direction of arrows A and B. As the teeth 4 ride over the eccentric of the cam 7 they are gradually forced radially outwardly to a fully extended position (as represented by tooth 4a in figure 2) and after passing the cam they gradually return to a retracted position.
The cam 7 is carefully positioned so that its eccentric portion coincides with the point where the chain 3 fully engages the sprocket 1. At the point where the chain 3 is first presented to sprocket 1, the nearest sprocket tooth (represented by 4b in figure 1) is virtually fully retracted but as the sprocket 1 rotates the tooth 4 gradually
protrudes furhter from its radial slot. When fully extended the tooth (as represented by tooth 4b) is in complete engagement with the chain 3.
This arrangement significantly reduces noise in a chain drive since the noise caused by the impact of the chain on fully extended teeth is virtually eliminated as the teeth are only extended when required for driving engagement with the chain.
In an alternative embodiment shown in figure 3 radially inner ends of the teeth 4 engage an elastic annulus 8 which on its inner circumferential surface is engaged at one point by a rotary circular cam 9. As the sprocket 1 rotates the annulus 8 rides over the cam 9 and is locally deflected so as to cause the adjacent teeth 4 to move radially outwards and into engagement with the chain 3.
Claims
1. A sprocket for a drive chain, the sprocket comprising a wheel body with at least one chain-engaging tooth that is retractable into the body.
2. A sprocket for a drive chain according to claim 1 , wherein the tooth is preferably reversibly retractable from a chain-engaging extended position in which it protrudes from the body to a retracted position.
3. A sprocket according to claim 2, wherein the tooth is radially retractable.
4. A sprocket according to claim 2 or 3, wherein the tooth is biased into the retracted position and is moved to the extended position by means of a cam.
5. A sprocket according to claim 4, wherein the cam is fixed relative to the sprocket so that the tooth is moved during rotation of the sprocket.
6. A sprocket according to claim 4 or 5, wherein the cam is eccentric and engages a radially inward end of the tooth when the latter is moved to the extended position.
7. A sprocket according to claim 4 or 5, wherein the tooth is supported on a resilient annulus that is engaged by the cam.
8. A sprocket according to claim 7, wherein the cam rotates about a fixed point offset from a centre of rotation of the sprocket.
9.. A sprocket according to any one of claims 4 to 8, wherein the sprocket comprises a plurality of retractable teeth each being moveable in sequence as it passes over the cam.
10. A sprocket substantially as hereinbefore described with reference to figures 1 and 2, and figure 3 of the drawings.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GBGB9702910.2A GB9702910D0 (en) | 1997-02-13 | 1997-02-13 | A chain sprocket |
GB9702910 | 1997-02-13 | ||
PCT/GB1998/000397 WO1998036193A1 (en) | 1997-02-13 | 1998-02-10 | A chain sprocket |
Publications (1)
Publication Number | Publication Date |
---|---|
EP0960294A1 true EP0960294A1 (en) | 1999-12-01 |
Family
ID=10807531
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP98903166A Ceased EP0960294A1 (en) | 1997-02-13 | 1998-02-10 | A chain sprocket |
Country Status (7)
Country | Link |
---|---|
EP (1) | EP0960294A1 (en) |
JP (1) | JP2001511872A (en) |
KR (1) | KR20000070939A (en) |
AU (1) | AU5999098A (en) |
GB (1) | GB9702910D0 (en) |
WO (1) | WO1998036193A1 (en) |
ZA (1) | ZA981166B (en) |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE159407C (en) * | ||||
DE316883C (en) * | ||||
DE425382C (en) * | 1925-02-21 | 1926-02-20 | Buckau Act Ges Zu Magdeburg Ma | Gripper disc |
DE1234456B (en) * | 1962-09-01 | 1967-02-16 | Gewerk Eisenhuette Westfalia | Drive chain star |
DE1425949A1 (en) * | 1963-11-05 | 1969-04-03 | Carlos Gonzalez Rodriguez | Chain sprocket with extendable teeth |
-
1997
- 1997-02-13 GB GBGB9702910.2A patent/GB9702910D0/en active Pending
-
1998
- 1998-02-10 WO PCT/GB1998/000397 patent/WO1998036193A1/en not_active Application Discontinuation
- 1998-02-10 KR KR1019997007204A patent/KR20000070939A/en not_active Application Discontinuation
- 1998-02-10 AU AU59990/98A patent/AU5999098A/en not_active Abandoned
- 1998-02-10 JP JP53545498A patent/JP2001511872A/en active Pending
- 1998-02-10 EP EP98903166A patent/EP0960294A1/en not_active Ceased
- 1998-02-12 ZA ZA9801166A patent/ZA981166B/en unknown
Non-Patent Citations (1)
Title |
---|
See references of WO9836193A1 * |
Also Published As
Publication number | Publication date |
---|---|
AU5999098A (en) | 1998-09-08 |
GB9702910D0 (en) | 1997-04-02 |
WO1998036193A1 (en) | 1998-08-20 |
JP2001511872A (en) | 2001-08-14 |
ZA981166B (en) | 1999-08-12 |
KR20000070939A (en) | 2000-11-25 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
17P | Request for examination filed |
Effective date: 19990812 |
|
AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): AT BE CH DE DK ES FI FR GB GR IE IT LI NL PT SE |
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GRAG | Despatch of communication of intention to grant |
Free format text: ORIGINAL CODE: EPIDOS AGRA |
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17Q | First examination report despatched |
Effective date: 20010531 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION HAS BEEN REFUSED |
|
18R | Application refused |
Effective date: 20011126 |