FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
THE PATENTS RULES, 2003
As amended by the Patents (Amendment) Rules, 2005
PROVISIONAL SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
A handlebar assembly

INVENTORS
Name :
Nationality :
Address :

Joseph Abraham and Umarji Shrinivas Yalaguresh both Indian Nationals
Bajaj Auto Limited, Akurdi, Pune 411035, Maharashtra, India

APPLICANTS
Name : Bajaj Auto Limited
Nationality : Indian Company
Address : Akurdi, Pune 411035, Maharashtra, India
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention

This invention relates to a handlebar assembly.
Many different handlebar constructions are available. A particularly convenient form of handlebar construction is of the so-called clip-on type. The clip-on handle bar style is a type of motorcycle handlebar in which two separate handles are attached directly to the front forks as opposed to a standard one-piece handlebar attached to the triple tree. The term is often shortened to clip-ons. The individual tubes are attached or clamped to front fork tubes of a motorcycle. Such a construction is popular, particularly for sport type motorcycles, as it allows more control for the rider and a greater flexibility of adjustment of the handlebars.
However, all handlebars are subject to vibration which may make riding a motorcycle uncomfortable. The clip-on type of handlebar is particularly subject to vibration induced by the engine and transmitted through the vehicle chassis or frame that is connected to the fork tubes. More specifically, the outer portion of the handlebar vibrates due to the transmission of vibrational forces from the handlebar holder in which the handlebar tube is mounted. A rider may prefer to avoid such a construction of handlebar and other forms of handlebar assembly, in which the outer handlebar portion and its holder are subjected to engine induced vibrations.
It is an object of the present invention to provide a handlebar construction less prone to vibration.
With this object in view, the present invention provides a clip-on handlebar assembly comprising:
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(a) a handlebar element which is gripped at the outer end by the rider, having an inner end portion and an outer end which is adapted to be gripped by the rider;
(b) a handlebar holder; and
(c) connection means for connecting an inner end portion of the handlebar element to the handlebar holder;
wherein connection of holder and handlebar element at an inner end portion thereof by the connection means is made while isolating an at least predominant portion of the handlebar element from the handlebar holder. Indeed, connection at the inner end of the handlebar element itself may allow isolation of the handlebar element from the holder particularly if connection is made through a vibration damper forming part of the connection means. That is, in design condition, the handlebar element and holder may not make contact, either directly or indirectly thus minimising transfer of vibrational forces from handlebar element to handlebar holder. If connection is made at one end of the handlebar element and other contact between handlebar holder and handlebar element through a vibration damper, amplified vibrational forces, which
may tend to become amplified at the grip end of the handlebar are reduced and therefore less vibration is transferred to the handlebar element and better rider comfort is achieved.
Preferably the mounting of the handlebar element to the handlebar holder via the vibration damper is done in such a way that good driver feel is maintained of the vehicle steering. This can conveniently be achieved by using a suitable selected vibration damping material and dimensions.
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The handlebar holder may include a mounting aperture; and the handlebar element, which may be a tube, may have an inner portion located within the mounting aperture and an outer portion adapted for rider grip. Alternatively, the handlebar element may be mounted over the handlebar holder which forms a spigot for the handlebar element. In either event, the inner portion of the handlebar element is connected to the handlebar holder by connection means having vibration damping capacity.
Preferably, the handlebar holder has a mounting aperture and the inner portion of the handlebar element is located within the mounting aperture to isolate the handlebar element from the handlebar holder so as to minimise transfer of amplified vibration
forces along the outwardly extending length of the handlebar holder to the handlebar element. Where the handlebar element and handlebar holder are tubular, or have
tubular portions, the handlebar element may be isolated from the handlebar holder such that vibrational forces are not transmitted in a radial direction from handlebar holder to handlebar tube. There may be left, in the case of a cylindrical mounting aperture and cylindrical handlebar element or tube, an annular volume or annular gap, which is dimensionally smaller than the thickness of the damping material which is left vacant. Damping material is preferably not to be inserted in the annular gap as this could assist transfer of vibrational forces from handlebar holder to handlebar element.
In addition, it is preferable that the mounting of the handlebar element, via the vibration damper to the holder is in a "fail safe" mode in the event that the vibration damper fails or its limits are exceeded. Conveniently this can be achieved by ensuring that the handlebar element and the holder are in close proximity to each
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other and will come into contact with each other in the event that the vibration damper was to suffer a mechanical failure, or otherwise exceeds its safe operating limits. In this way, excessive relative motion between the handlebar element and the holder can be avoided both to ensure a fail safe operation and to ensure that good and accurate driver feel of the steering is maintained.
The damped connection means is desirably located at as far inward as possible a portion of the mounting aperture such that connection between holder and handlebar element is made at this point. In such manner, the handlebar element is isolated from the holder providing an optimal reduction of vibration. Damping capacity may be achieved by including a damping material, such as rubber, within the connection means. A damping element, including such material, may form part of the connection means and may be configured to isolate handlebar element from handlebar holder to reduce vibration.
The connection means advantageously allows press-fitting of the handlebar element into the connection means and the holder itself. To this end, the connection means may include a damping element such as a sleeve or silent bush which may be press fitted within the mounting aperture. The handlebar element may then be press-fitted within the silent bush with the bush providing a clearance between the handlebar element and the surface of the mounting aperture. This clearance acts to minimise vibration and its design dimension may be selected with that object in view.
Alternatively, the damping sleeve or silent bush may be arranged such that a handlebar element fits over it, preferably by press fitting a handlebar element over the
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silent bush. There is provided a clearance between handlebar element and the surface of the mounting aperture. In this way, the connection between holder and handlebar element is made through a vibration damped connection made through the silent bush. Again, the design dimension of the clearance may be selected to minimise probability of contact between handlebar element and mounting aperture surface and consequential transfer of vibration between the two components.
The connection between holder and handlebar element or tube may be made secure through suitable configuration of the connection means, damping element and mounting aperture. For example, an inner end of a handlebar element may taper inwardly co-operating with a complementary inward taper of an inner diameter of the damping element where the handlebar element is to be press fitted within the inner diameter of the damping element. If the damping element is a silent bush, the inner diameter of the silent bush tapers inward. This tapered configuration allows a better engagement.
The damping element may have an inner end shaped or fitted with engaging elements to allow better fixity within the mounting aperture. In particular, the engaging elements may prevent rotation of handlebar tube -clamp assembly where the connection means is a clamp and a handlebar element is a tube. For example, the silent bush may have an inner end and an outer end. The inner end contacting a base wall of the mounting aperture may be provided with serrations, or other frictional engaging means which allows better fixity of the bush/handlebar tube assembly (connection means) within the mounting aperture.
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A handlebar element or tube may be engaged with a pin secured within the holder, for example by a bolting arrangement. Other arrangements may be envisaged.
Conveniently, handlebar elements are of tubular construction as typically used in motorcycles and motor scooters. Although the handlebar construction of the invention is well adapted to use in 2 wheel vehicles, it could also be used in other vehicles using handlebars.
The handlebar construction of the present invention allows the benefit of a clip on fit while minimising vibration and increasing rider comfort. Vibration is damped significantly because the connection between holder and handlebar element is made as close to the inward end of the handlebar element as possible such that vibration is damped and magnification of vibrations along the length of the handlebar avoided. Other than at the point of connection, the handlebar element is designed to be isolated from its holder.
The handlebar construction of the present invention may be more fully understood from the following description of preferred embodiments thereof made with reference to the accompanying drawings in which:
Fig. la is a top cross-sectional view of a prior art handlebar assembly;
Fig. lb is a top cross-sectional exploded view of the handlebar assembly of Fig. la;
Fig. 2a is a top cross-sectional view of a handlebar assembly in accordance with a first
embodiment of the present invention;
Fig. 2b is a top cross-sectional exploded view of the handlebar assembly of Fig. 2a;
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Fig. 2c is a side view of a damping element used in the handlebar assembly of Figs.
2a and 2b;
Fig 3a is a top cross-sectional view of a handlebar assembly in accordance with a
second embodiment of the present invention; and
Fig. 3b is a top cross-sectional exploded view of the handlebar assembly of Fig. 3a.
Referring now to Fig. la and lb, there is shown a handlebar assembly 90 formed in a prior art clip-on type as is particularly convenient for manufacture. However, this handlebar assembly is also prone to vibration. Such vibration is caused by the connection between the handlebar holder 95 and the handlebar 92 which enables transmission of engine induced vibrations from the front forks (not shown) to the handlebar holder and handlebar 92.
Handlebar element or handlebar 92 is of tubular construction having an inward portion 92a with outer cylindrical surface 92b. At an inner end 92a of the handlebar 92 is fitted a bush 93. The bush 93 is formed with a threading 93a to accommodate a bolt of a clamping arrangement to be described below.
Handlebar holder 95 includes a mounting aperture 97 of cylindrical shape and having a bore 96 at a base end 97a. The mounting aperture 97 has a surface 97b which engages with the handlebar 92 on its connection to the handlebar holder 95.
To connect handlebar 92 to holder 95, the handlebar tube 92 is press fitted into mounting aperture 97 and connected into position by a connection means. The chosen method of connection is clamping. Handlebar 92 is clamped into position using a
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clamping arrangement of bolt type having threading 94b, mounting bolt 94a and washer 94. Bolt 94a is fitted through the washer 94 and the bore 96 of the mounting aperture 97 and into the threading 93a of the bush 93. Contact between outer cylindrical surface 92b and surface 97b of the aperture may be noted along the inner portion of the handlebar 92. This contact or engagement is valuable in achieving interference fitting but also allows vibrational forces, particularly those induced by the engine, to act on the handlebar 92. This causes rider discomfort.
In Figs. 2a and 2b are shown an alternative handlebar construction 192, according to the first embodiment of the invention. Again, the handlebar is of clip-on type.
Handlebar element or handlebar 192 is also of tubular construction having an inward portion 192a with outer cylindrical surface 192b and an inner end 192c. A bore 192d of the handlebar 192 receives a portion of a silent bush 193. Inward portion 192a tapers outwardly towards inner end 192c.
The inclusion of the silent bush 193 forms another aspect of the invention. Silent bush 193 is formed in two parts. A first part 193d of cylindrical shape is formed with a bore 193a to accommodate a bolt of a clamping arrangement to be described below. This first part 193d may also be a polymeric material having some vibration damping capacity. A second part 193e incorporates a primary damping element. Therefore, unlike bush 93, the silent bush 193 is not a simple cylinder of damping material. The silent bush part 193d has one inner end 193b formed as a flange. The silent bush part 193e is generally cylindrical and encloses a cylindrical insert 193f formed of a damping material such as rubber. This enclosure is formed by a metal skin 193g
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forming an outer surface of the silent bush. The metal skin 193g may also be formed as a cylinder enclosing the damping element though it may be open at an outer end 193c of the silent bush 193. Inner end 193b of silent bush 193 is formed with serrations 200 as shown in Fig. 2c which are frictional gripping or engagement means.
Handlebar holder 195 includes a mounting aperture 197 of cylindrical shape and having a bore 196 at a base end 197a. Bore 196 is of lesser diameter than an outer diameter of handlebar 192. The mounting aperture 197 has a surface 197b and a base wall 197c.
Handlebar 192 is connected to handlebar holder 195 by clamping. The silent bush 193 is first press fitted into the bore 192d of the handlebar 192. It is the silent bush which will engage with a clamping arrangement to allow connection of handlebar 192 to handlebar holder 195.
The clamping arrangement is again of bolt type having washer 194 and mounting bolt 194a with threading 194c. A cap 194b may be provided for the bolt arrangement enclosing aperture 199 of handlebar holder 195 when connection is finished. Cap 194b may also be formed of a damping material, portion of which may surround the bolt isolating it from the handlebar holder 195. Such enclosure prevents transfer of vibration between bolt 194a and handlebar holder 195 as well as ingress of water and dirt to the clamping arrangement which may make servicing more difficult. Bolt 194a is fitted through the washer 194 and the bore 196 of the mounting aperture 197 and into the threaded bore 193a of the silent bush 193. The bolt is tightened to clamp the handlebar 192 into position within the mounting aperture 197. As clamping proceeds,
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serrations 200 come into frictional engagement with the base wall 197c of mounting aperture 197 and connection of handlebar 192 to handlebar 195 is completed.
The connection varies in significant manner from that described in Figs, la and lb to achieve lesser vibration. First, the handlebar 192 is not press fitted within the mounting aperture 197. The outer surface 192b of the handlebar 192 has a clearance C (illustrated in Figure 2a) from surface 197b of the mounting aperture 197 which means that engagement between surfaces 192b and 197b cannot be achieved under design conditions. Second, the inner end 192c of handlebar 192 is isolated from the base wall 197c of the mounting aperture 197 by inner end or flange 193a of the silent bush 193 and a further clearance D of the inner end 192c of handlebar 192 from the silent bush flange 193b. Consequently, vibration forces acting on surface 192c are avoided because handlebar 192 and handlebar holder 195 are vibrationally isolated from each other. Rider comfort is increased. On the other hand, the benefit of a clip-on type construction is maintained.
In an alternative arrangement depicted in Figure 3a and 3b, the handlebar holder 295 has a mounting aperture 297 of cylindrical construction. Portion 297a has lesser diameter than portion 297b and is arranged on a handlebar side of the handlebar holder 295. Mounting aperture portion 297b has a surface 297c.
The silent bush 293 is also of different construction though having two parts 293a and 293b, each part being of generally cylindrical shape. Part 293b, located outwardly of damping part 293, forms a sleeve for part 293a which is again a silent bush formed of
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a vibrationally damping material such as rubber. Silent bush 293a has an inner diameter of tapered cross-section.
Handlebar 292 may also have an inner end 292a of the handlebar 292 fitted with a bush 303. Bush 303 is formed with a threading 303a into which a bolt 294 of a clamping arrangement of nut and bolt type is fitted. The inward taper of handlebar 292 may also be noted. The tapered portion 292a of the handlebar 292 co-operates with the correspondingly tapered inner diameter of silent bush 293.
To connect handlebar 292 to handlebar holder 295, the inner portion 292a of the handlebar 292 is inserted through the mounting aperture and the silent bush 293 is fitted over its inner end. The bolt 294, with a threaded portion 294b is inserted through the washer 294a and then tightened. As the bolt 294 is tightened, the silent bush 293 expands to form an interference fit within mounting aperture portion 297b thus completing connection of handlebar 292 to handlebar holder 295. The handlebar 292 has a clearance from the mounting aperture surface 297c formed by the silent bush 293. The clearance C left between the handlebar 292 and the surface 297d of mounting aperture portion 297a may also be noted. This clearance C is designed to avoid contact, let alone engagement, between the handlebar and mounting aperture 297. In this manner, the handlebar 292 is vibrationally isolated from the handlebar holder 295 and rider comfort is improved while the benefit of a clip-on handlebar assembly is maintained.
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Modifications and variations to the handlebar assembly of the present invention may be apparent to the skilled reader of this disclosure. Such modifications and variations are within the scope of the invention.
Dated this 27th day of November 2006
(Prita Madan)
ofKhaitan&Co
Agent for the Applicants
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