WO2003091599A1

WO2003091599A1 - An articulated chain

Info

Publication number: WO2003091599A1
Application number: PCT/IT2003/000204
Authority: WO
Inventors: Ermanno Righi; Sandro Montanari
Original assignee: Pro 2 S.R.L.
Priority date: 2002-04-24
Filing date: 2003-04-03
Publication date: 2003-11-06
Also published as: AU2003224435A1; ITMO20020104A1; ITMO20020104A0

Abstract

The chain comprises a first plurality of external links (2) each having a first external plate (4), a second external plate (5) parallel to the first external plate (4), and a plurality of rotation pivots (6) interpositioned between the first plate (4) and the second plate (5). The chain comprises a second plurality of internal links (3), each having a first internal plate (7) and a second internal plate (8), parallel to the first internal plate (7), and a plurality of bushings (9) interpositioned between the first (7) plate and the second plate (8) of each internal link (3). Each of the rotation pivots (6) is inserted coaxially in a respective bushing (9), to define an alternated succession of first external links (2) and second internal links (3), and defines, together with a bushing of the plurality of bushings (9), a spherical coupling surface.

Description

An Articulated Chain

Technical Field

The invention relates to an articulated transmission chain, preferably for bicycles. Background Art

As is known, the chains commonly used in bicycle transmissions are articulated- link chains. The links in this kind of chain comprise bushings, parallel to one another and rotatably mounted on cylindrical pivots. Each bushing is solidly connected at each end thereof to a plate, and each pivot is solidly connected at each end thereof to another plate. The pivot is longer than the bushing, and accordingly the two plates connected to the bushing are in an internal position with respect to the two plates connected to the pivot, so that the first end of the plates connected to the bushing are supeφosed internally of the second end of the plates connected to the pivot. A further bushing is solidly constrained to the second end of the internal plates, and a further pivot is located internally of the further bushing, which further pivot is solidly connected to the first end of a further two external plates, so that a complete internal chain link is obtained. Similarly an external link is defined by two pivots connected by the ends thereof to the first and the second end of two external plates, so that the chain is closed by alternating closing numerous internal chain links to numerous external chain links. Also known are articulated chains in which the bushings are coupled rotatably to the internal plates, thus assuming the function of rollers, with the aim of preventing relative dragging between the chain and the cogwheels the chain is coupled to.

Thanks to the rotatable coupling between pivots and bushings, each chain link is free to rotate with respect to the contiguous links on a perpendicular plane to the longitudinal axes of the pivots, enabling the chain to transmit motion between pairs of crown wheels of various dimensions. Since the two wheels between which transmission is sent might not be perfectly coplanar, possibly because the chain is mounted on a bicycle equipped with known systems for gear-changing between the driven wheel, or sprocket, and the drive wheel, or crown wheel, in which the chain is made to translate transversally on a number of wheels which are concentrically located, side-by-side, and it is necessary to guarantee a certain degree of transversal deformability in the chain. In traditional chains this result is obtained with a predetermined amount of play in each coupling between each pivot and the bushing it is housed in. Thanks to this play, the pivot can incline with respect to the bushing. Thus each internal link, apart from being free to rotate longitudinally with respect to the two external contiguous links, can rotate transversally, within ceratin limits, also on a plane containing the longitudinal axis of the pivot belonging to a contiguous external chain link. In a rotated configuration, the contact between the pivot and bushing is no longer distributed along a straight line, but is more or less concentrated at points, giving rise to very high pressures that can lead to considerably problems of wear.

Further, as the chain links are aligned where the chain is meshed with the crown wheel, with the links arranged at a more or less nominal step due to the coupling between each bushing and the step between two cogs, the disalignment between the external links occurs suddenly when the links leave the cogs of the crown wheel, and at the same time there is a rapid take-up of the play between the pivots and the bushings; only to be followed by a rapid re-alignment of the links as they enter the other cogs of the other wheel. The shaφ configuration changes are accompanied by corresponding impacts which lead to a certain noisiness in the transmission and accentuate wear in the parts involved in the motion transmission.

It is also true that this wear leads to an increase in play between pivots and bushings, which in turn allows the pivots to assume increasingly inclined positions with respect to the respective bushings. The result is that the inclinations cause the internal links to exert a levering action on the external links to which they are connected, pressuring the links outwards. In extreme situations these external links might be released from the pivots to which they are connected, with an ensuing breakage of the chain.

The main aim of the present invention is to provide a chain which obviates the above-cited drawbacks; in particular the main aim of the invention is to provide a chain in which the contact between bushing and pivot always occurs along a surface, including when the chain is functioning out-of-axis, to guarantee silent operation and long working life.

A further aim of the invention is to provide a chain where the play between pivot and bushing is more or less nill, so that there are no impacts during step changes. A further aim of the present invention is to provide a chain which allows transversal inclinations between two contiguous links, which inclinations are of greater entity than those at present obtainable with traditional chains.

The specific technical aims are achieved with an articulated chain having the characteristics set out in one or more of the accompanying claims. Disclosure of Invention The invention will now be described in a preferred but non-exclusive embodiment thereof, illustrated in the accompanying figures of the drawings, in which: figure 1 is a perspective view of an articulated chain according to the present invention; figure 2 is an exploded view of the main components of the articulated chain of figure 1 ; figure 3 is a plan view, partly sectioned, of a portion of the articulated chain of figure 1 in a first configuration; figure 4 is a plan view, partially sectioned, of the portion of chain of figure 3 in a second configuration.

With reference to the figures of the drawings, 1 denotes an articulated chain according to the present invention. The articulated chain 1 comprises a first plurality of links 2 which will hereinafter be termed external links because of their position, and a second plurality of links

3, or internal links, which are rotatably and consecutively connected about respective main axes of rotation X, i.e. an axis of rotation of a link with'respect to a succeeding link when the two links lie in a same plane. More precisely, as clearly illustrated in figure 1, the chain 1 is formed by an alternating succession of external links 2 and internal links 3.

In particular, each of the external links 2 exhibits a first external plate 4 provided with a respective first 4a and second 4b ends and a second external plate 5 parallel to the first plate 4 and provided with a respective first 5a and a second 5b ends. The two external plates 4, 5 of each first link 2 are solidly connected by two rotation pivots 6 inteφositioned at the first 4a, 5a and the second 4b, 5b ends.

In particular, the two external plates 4, 5 exhibit a same double-lobed shape and are provided with an end hole in each of the two lobes, into which ends 6a and

6b of the pivot 6 are inserted. Similarly, each internal link 3 exhibits a first internal plate 7 having a first 7a end and a second end 7b and a second internal plate 8 parallel to the first internal plate 7 and having a first 8a end and a second

8b end. The plates 7, 8 of the internal link 3 exhibit a double-lobe conformation. The first 7 and the second 8 internal plates of each internal link 3 are reciprocally coupled by two bushings 9 inteφositioned between the first ends 7a, 8a and the second ends 7b, 8b. More precisely, with reference to figure 2, the bushing 9 has two collars 10 which are insertable in special holes 11 made in the first ends 7a, 8a and the second ends 7b, 8b.

The collars 10, once inserted, are deformed to define special washers which hold the bushing 9 in the hole 1 1 while at the same time allowing the bushing 9 to rotate in the hole 11.

Each of the pivots 6 belonging to the external links 2 is inserted coaxially in a respective bushing 9 and so makes the alternated succession of external links 2 and internal links 3 (figure 1) which are rotatably and consecutively connected about the respective main axes of rotation X. Each pivot 6 projects from the respective bushing 9 by ends thereof 6a, 6b, and the bushing 9 is comprised between plates 7 and 8 of the external link 2. Advantageously, each pivot of rotation 6 exhibits a barrel shape, with a spherical profile, and the bushing 9 exhibits a seat 9a having a barrel seating shape, to match the barrel shape of the pivot 6. Each of the pivots 6 defines, with relative bushing 9, a spherical coupling surface, to allow rotation about the main axis of rotation X and also to allow rotation between two adjacent links about axes which are peφendicular to the main axes of rotation X. Each of the bushings 9 is free to rotate between two extreme positions on any plane containing the longitudinal axis of the pivot 6 on which it is mounted. In particular, as can be seen in figure 4, the spherical coupling surface enables a disaligning between the longitudinal axis Y of the pivot 6 and the longitudinal axis Z of the respective bushing 9 which, in reciprocal alignment position, constitute the main axis of rotation X.

The longitudinal axis Y of the pivot 6 and the longitudinal axis Z of the bushing

9 are free to rotate reciprocally about the centre of the spherical surface. The freedom of movement described above enables torsion and inclination with respect to the direction of alignment, of one link with respect to another, according to an angle of at least four degrees.

The limitation of the rotation depends most of all on the presence of the cylindrically-shaped ends 6a, 6b of each pivot 6 which, during rotation, once they have reached the spherical internal surface of the bushing 9, strike against the ends of the seat of the bushing 9 itself; the limitation of the rotation also depends on the dimensional relations between the various elements, in particular the relation between the length of the pivot 6 and the longitudinal extension of the seat of the bushing 9. Changing the relations of the dimensions enables different angles to those mentioned above to be obtained.

Assembly of the chain 1 is carried out by first press-inserting each pivot 6 in a respective bushing 9.

Subsequently, two internal plates 7, 8 are mounted and rotatably constrained on two bushings 9.

The external plates 4, 5 are forced on the pivots 6 and the ends of the pivots 6 are tapped down to constrain them solidly to the external plates 4, 5.

The invention offers important advantages.

Firstly, the contact between the pivot and the bushing is distributed along one surface, which leads to a considerable reduction in the specific pressures and thus reduces wear between the parts in movement. As there are no localised contacts, the system offers high resistance to deformation. a further important advantage is the elimination of play between the pivots and the bushings, with a consequent reduction in impacts and consequently a reduction in the noise the chain makes during operation, especially during a gear change operation.

Another fact of no less importance is the advantage of obtaining angles of inclination and torsion which are much higher than the angles allowed by traditional chains, with a consequent possibility of using the chain for industrial applications, where there is frequently movement between non-coplanar and non- parallel cogwheels.

Claims

Claims.

1). An articulated chain, preferably for bicycles, comprising: a first plurality of external links (2), each of which exhibits at least a first external plate (4) provided with a first end (4a) and a second end (4b) and a second external plate (5) parallel to the first external plate (4) and provided with a first end (5a) and a second end (5b); a plurality of pivots (6) inteφositioned between the first external plate (4) and the second external plate (5) of each external link (2) at the first end (4a, 5a) and the second end (4b, 5b) of the first external plate

(4) and the second external plate

(5); a second plurality of internal links (3), each of which exhibits at least a first internal plate (7) provided with a first end (7a) and a second end (7b) and a second internal plate (8) parallel to the first internal plate (8) and provided with a first end (8a) and a second end (8b); a plurality of bushings (9) inteφositioned between the first internal plate (7) and the second internal plate (8) of each internal link (3) at the first end (7a, 8a) and the second end (7b, 8b) thereof; each of the pivots (9) being coaxially inserted in a bushing (9) to define an alternated succession of first external links (2) and second internal links (3) rotatably and consecutively connected about respective axes of rotation (X); wherein each of the pivots (6), together with a relative bushing (9), defines a spherical coupling surface, to enable a rotation between an adjacent internal and external link (2, 3) about axes which are peφendicular to a respective main axis of rotation (X). 2). The articulated chain of claim 1, wherein each of the pivots (6) exhibits a barrel shape with a spherical profile and each of the bushings (9) exhibits a seating having a barrel shape matching the barrel shape of the pivot (6).