More particularly, the invention relates to a master cylinder for motor-vehicle brakes or clutches.

In fact, as is known, in motor vehicles such as, for example motor cycles, the brake generally associated with the front wheel is operated by means of a master cylinder mounted on the handlebars in the vicinity of one of the hand grips, conventionally the right-hand hand grip of the motor cycle.

Similarly, the clutch can also be operated by means of a master cylinder mounted on the handlebars on the opposite side to the brake-operating cylinder, that is,

on the left-hand side of the motor cycle.

A master cylinder of the type described above is generally constituted by a cylinder body in which a chamber is formed for housing a piston. When the piston is operated by the driver, it acts on a working fluid contained in the respective brake or clutch system.

The chamber is arranged in communication with a reservoir which holds the working fluid and may be formed integrally with the cylinder body or may be separate and connected thereto by an external pipe.

A master cylinder of the above-mentioned type also has a control lever which is mounted for pivoting on the cylinder body and is intended to act on the piston.

When the cylinder is mounted on the handlebar of the vehicle, the control lever faces a hand grip of the handlebar and is operated by the driver by being pivoted about its fulcrum.

In known master cylinders, the axis along which the chamber housing the piston extends, which is also defined as the axis of the cylinder, generally lies in the plane defined by the pivoting of the control lever, or in a plane parallel thereto. Moreover, the axis of the cylinder is arranged perpendicular to the axis of the portion of the handlebar to which the cylinder is fixed and is therefore perpendicular to the axis of the

seat in the cylinder body which is clamped onto the handlebar.

In the field of motor vehicles and, above all, in the field of racing motor cycles, there is a particular requirement to achieve the best compromise between braking action and sensitivity of operation, by adjusting various factors such as, for example, the lever ratio, the position of the fulcrum, and the proportioning of the cylinder as a whole.

This requirement is accompanied by the further requirement to limit dimensions, in particular, to prevent the cylinder touching instruments which are normally fixed to the frame in the region of the central portion of the handlebar, during its steering travel.

In the field of mass-produced motor cycles, the cylinder cannot be mounted immediately adjacent the hand-grip since other devices are fitted between the hand-grip and the point where the cylinder is fixed to the handlebar, these devices being constituted, for example, by the electrical controls fitted between the hand-grip and the brake cylinder. In the field of mass- produced motor cycles, these requirements are therefore even more marked.

In fact, with regard to mass-produced motor cycles in particular, the position in which the cylinder is

mounted on the handlebar is quite far from the hand grip and hence from the region gripped by the driver.

In the first place, this positioning leads to a disadvantage of a functional nature, since the fact that the cylinder body is mounted a certain distance from the hand grip affects the lever ratios of the control lever.

In fact, in comparison with racing motor cycles, the distance between the fulcrum of the lever and the region in which it acts on the piston remains substantially unchanged, whereas the portion of the control lever which extends in order to be gripped by the driver must have a length such that it faces the respective grip.

Whereas in racing motor cycles, the lever ratios used are generally designed to achieve an optimal compromise between braking action and sensitivity of operation by the driver, in mass-produced motor cycles, the excessive length of the portion of the lever which faces the hand grip adversely affects sensitivity of operation by the driver.

In the second place, the need to place the control lever in a position remote from the hand grip introduces a problem of bulkiness, which is particularly noticeable with cylinders having axes perpendicular to the axis of the seat for housing the handlebar. In fact, as already stated, there is a risk of the cylinder interfering with

the instruments during steering, because of the position in which the cylinder is mounted on the handlebar.

The problem underlying the present invention is therefore to propose a master cylinder for vehicles controllable by means of handlebars which has structural and functional characteristics such as to satisfy the above-mentioned requirements and at the same time to prevent the problems mentioned with reference to the prior art.

This problem is solved by a master cylinder for vehicles controllable by means of handlebars according to Claim 1.

Further characteristics and the advantages of the master cylinder according to the invention will become clear from the following description of a preferred embodiment thereof, given by way of non-limiting example with reference to the appended drawings, in which: Figure 1 is a side view of a cylinder according to the present invention, and Figure 2 shows the cylinder of Figure 1, mounted on a portion of a handlebar and partially sectioned in a plane II-II of Figure 1.

With reference to the drawings, a master cylinder, generally indicated 1, comprises a cylinder body 2.

In the embodiment shown in Figures 1 and 2, the

cylinder body 2 is formed as a unitary element extended by a yoke 3 and a handlebar seat 4.

In addition to the above-mentioned components, there is a reservoir 5 which, in the embodiment illustrated, is formed as an element separate from the cylinder body 2, whereas in other embodiments, not shown, it may be formed integrally with the cylinder body 2.

A possible reference system relative to the master cylinder 1 can be obtained by means of a vertical axis V and a horizontal plane P, shown in Figure 1 and defined as stated below.

The reservoir in fact contains a working fluid, this definition being intended to define any type of fluid suitable for use in braking or clutch systems, for example, for use in vehicles controllable by means of handlebars. This fluid is disposed in the reservoir, defining a free surface which, since it is subject to the effect of gravity, is arranged in a horizontal plane. Figure 1 shows a horizontal plane P parallel to the horizontal plane corresponding to the free surface of the fluid in the reservoir.

To prevent leakage of fluid from the reservoir and to make maximum use of its capacity, the reservoir is mounted on a motor-vehicle handlebar in a manner such

that its walls are substantially perpendicular to the horizontal plane defined by the free surface of the fluid. When the fluid is in the reservoir, in operating conditions, a vertical axis V perpendicular to the horizontal plane P is therefore defined.

A first, upwardly-directed vector V'can be defined along this vertical axis V, this definition meaning a vector directed away from the free surface of the fluid, generally towards the opening of the reservoir.

Similarly, a second, downward vector V''is defined along the vertical axis V, this definition meaning a vector which is directed from the free surface of the fluid, into the fluid, generally towards the bottom of the reservoir.

Relative to a horizontal reference plane, for example, the horizontal plane P of Figure 1, parallel to the free surface of the working fluid in the reservoir, the first vector V'consequently defines an upper half- space and the second vector V''defines a lower half- space.

A control lever 6 is mounted for pivoting at a point A of the yoke 3 and faces an end portion of a handlebar 7 of the motor vehicle, in particular, a hand grip 8 to be gripped by the driver.

The control lever 6 is advantageously formed in two

portions 6a, 6b. The first portion 6a corresponds to the head of the control lever 6 which is mounted for pivoting in the yoke 3, and the second portion 6b corresponds to a slender portion to be gripped by the driver whilst he is gripping the corresponding hand grip 8. The slender portion has a curved shape designed to favour ergonomic gripping.

The control lever 6 can pivot about its fulcrum A towards the corresponding hand grip 8 as a result of the force exerted by the driver. The pivoting of the control lever 6 defines a plane X of pivoting, a line of which is shown in Figure 1. When the driver subsequently releases the control lever 6, it can pivot away from the respective hand grip 8, in the plane X, and return to the initial rest position.

As stated above, the cylinder body 2 extends as a unitary element defining the seat 4, which is shaped so as to extend around a portion of the handlebar 7. In greater detail, the walls which delimit the seat 4 are defined by an end of the cylinder body and by a U-shaped element 9. Both the end of the cylinder body and the U- shaped element comprise holes for receiving threaded elements 10 which clamp the structure of the cylinder body 2 to the handlebar.

In the embodiment in question, the seat 4 is

cylindrical in order to extend around the tubular structure of the handlebar 7 and extends along a longitudinal axis which, in the mounted condition, coincides with the longitudinal axis of the portion of the handlebar on which the cylinder 1 is mounted. For simplicity of explanation, the axis of the seat 4 and the axis of the handlebar portion on which the cylinder 1 is mounted are indicated by the same reference numeral 11.

Moreover, the end portion of the handlebar 7, corresponding to the region in which it is gripped by the driver, extends along an axis which preferably lies in the plane X of the pivoting of the control lever 6 about its fulcrum A. In the embodiment shown in the drawings, the axis of the end portion of the handlebar 7 coincides with the axis 11 of the portion of the handlebar on which the cylinder 1 is mounted and, in the mounted condition, therefore coincides with the axis 11 of the seat 4 of the cylinder body 2.

As shown in Figure 1, to facilitate gripping of the control lever 6 by the driver, and to allow the driver to adopt the correct position on the motor vehicle, the plane X of pivoting of the control lever 6 may be inclined downwards at about 15° to the horizontal plane P, in the direction of travel of the vehicle. That is,

with reference to the horizontal plane P of Figure 1 in which the axis 11 of the seat 4 lies, the fulcrum of the control lever 6 is disposed in the lower half-space relative to that plane, in accordance with the downward direction indicated by the second vector V''of the axis V, as defined above.

The reservoir 5 contains the working fluid and is closed at the top by a cover 12 with which a flexible membrane is generally associated. The working fluid contained in the reservoir 5 adheres to the membrane and never comes into direct contact with the outside atmosphere when the vehicle is in use.

A chamber 13 defined inside the cylinder body 2 is connected to the reservoir by means of a duct 14 through which the working fluid can pass from the reservoir to the chamber. Moreover, the chamber 13 has conventional delivery and bleed openings, not shown.

As shown in Figure 2, the chamber 13 has a cylindrical shape which extends along an axis 15, generally referred to as the cylinder axis.

In the embodiment shown, the axis 15 lies in the plane X of pivoting of the control lever 6 and intersects both the axis 11 of the seat 4 and of the handlebar 7, and the control lever 6. More specifically, the axis 15 defines the theoretical line

of demarcation between the two portions 6a and 6b of the control lever 6.

The chamber 13 houses a floating piston 16 which can move along the axis 15 forming a seal against the walls of the chamber by means of suitable seals. More particularly, the piston 16 can move between a travel- limit, rest position shown in Figure 2 and an advanced, operative position, not shown. In the travel-limit, rest position, the piston 16 is urged by a return spring 17 to a position corresponding to the maximum distance from the handlebar whereas, to reach the advanced, operative position, the piston 16 overcomes the force of the return spring 17 and the pressure of the fluid contained in the chamber 13 and in the system, and advances towards the handlebar.

This movement is brought about by the pivoting of the control lever 6, by means of an operative connection which comprises a rod 18 the longitudinal axis of which may coincide substantially with the axis 15 or in any case may lie in the plane X of pivoting. The rod 18 has a first portion 18a substantially inside the chamber 13 and interacting with the piston 16 and a second portion 18b which extends out of the chamber 13 and, in particular, towards the control lever 6. The two portions are delimited substantially by a dust-

protection boot 19 which closes the chamber 13 from the outside atmosphere.

The interaction between the first portion 18a and the piston 16 takes place by means of a connection 20 formed by a seat formed at the end of the piston and coupled with a rounded end of the first portion 18a of the rod.

The second portion 18b terminates in a cylindrical swivel joint 21 connecting the rod 18 and the control lever 6. In particular, the cylindrical swivel joint 21 is formed by one end of the second portion 18b which is coupled with a seat of complementary shape formed in the body of the control lever 6.

If the cylinder 1 is mounted, for example, on a mass-produced motor cycle, as shown in Figure 2, electrical controls, indicated 22, are fitted on the handlebar 7, between the hand grip 8 and the cylinder 1.

As shown in Figure 2, in the plane X of pivoting of the control lever 6, the axis 15 of the chamber 13 is advantageously inclined to the axis of the seat 4 and hence to the axis 11 of the handlebar portion 7 on which the cylinder body 2 is clamped.

For a better understanding, the term"inclined" means that the axis 15 intersects the axis 11 at a point and does not coincide with an axis 23 perpendicular to

the axis 11, lying in the plane X of pivoting of the control lever 6 and extending through the point of intersection between the axis 15 and the axis 11.

As a result, with reference to the axis 11 of the seat 4 and the above-mentioned axis 23, the axis 15 intersects both the axis 11 and the axis 23, naturally with reference to the most widely used arrangement in which the axis 11, the axis 15 and hence the axis 23, all lie in the same plane, that is, in the plane X of pivoting of the control lever 6.

With reference to the cylinder which operates the brake, that is, the cylinder which will be operated by the driver's right hand, the axis 11 and the axis 15 are inclined to one another at an acute angle a, where a means the angle shown in Figure 2 which, if the cylinder 1 is viewed from above in the direction of the vector V'', is measured anticlockwise, starting from the axis 11, without the axis 11 covering itself during the rotation.

For greater clarity, the acute angle a may also be defined as the angle between the axis 11 and the axis 15, corresponding to the sector which faces the second portion 6b of the control lever 6. In fact, relative to a plane perpendicular to the axis 11 of the seat 4 and extending through a portion of the seat connected to the

cylinder body, the operative connection between the control lever and the piston is disposed on the side of this plane facing towards the hand grip.

In the cylinder for operating the clutch, that is, the cylinder which will be operated by the left hand, the axis 15 of the chamber 13 is also advantageously inclined to the axis 11 of the seat 4.

In this case also, the term"inclined"means that the axis 15 intersects the axis 11 at a point and does not coincide with an axis 23 perpendicular to the axis 11, lying in the plane X of pivoting of the control lever 6, and extending through the point of intersection between the axis 15 and the axis 11.

Moreover, the axis 11 and the axis 15 are inclined to one another at an acute angle, meaning, in this case, the angle which, if the cylinder is viewed from above in the direction of the vector VI is measured clockwise, from the axis 11, without the axis 11 covering itself during the rotation.

In this case also, for greater clarity, this angle may also be defined as the angle between the axis 11 and the axis 15 corresponding to the sector which faces the second portion 6b of the control lever 6.

The angle a, in the case of the brake cylinder, or its equivalent in the case of the clutch cylinder,

advantageously has a value of between 60° and 80°, preferably between 70° and 75°.

With reference to the cylinder 1 mounted on the handlebar 7, the axis 15 of the chamber 13 and the axis 11 of the seat 4 and of the end portion of the handlebar 7 are inclined to one another in a direction such as to bring the cylindrical swivel joint 21 closer to the hand grip 8 than the position the swivel joint 21 would adopt if the axis 15 were perpendicular to the axis 11.

Similarly, the fulcrum A of the control lever 6 is closer to the hand grip 8 than the position the fulcrum A would adopt if the axis 15 were perpendicular to the axis 11.

The cylindrical swivel joint 21 and the fulcrum A are appreciably closer to the hand grip 8 both for the brake cylinder and for the clutch cylinder.

As shown in Figure 2, the cylinder body 2 extends substantially along the axis 15, following the inclined course thereof relative to the axis 11. As a result, in the plane X of pivoting, the fulcrum A of the control lever 6 is substantially aligned with the seat 4 along an axis perpendicular to the axis 11.

The method of use of the master cylinder according to the present invention is described below with particular reference to a master cylinder for operating

the braking system, although the following description is equally applicable to the clutch-operating cylinder.

When it is necessary to brake, the driver of the vehicle grips the hand grip 8 and the control lever 6 and pivots the latter about its fulcrum A, moving it towards the hand grip. The control lever 6 pivots in the plane X, interacting with the rod 18 and consequently with the piston 16.

In particular, the control lever 6 acts on the rod 18 in the region of the cylindrical swivel joint 21, causing the rod 18 to slide in the plane X of pivoting of the control lever 6. The movement of the rod 18 urges the piston 16 from the travel-limit, rest position to the advanced, operative position, overcoming the force of the return spring 17 and the pressure of the working fluid.

When the driver releases the control lever 6, the cylindrical swivel joint 21 returns to the position shown in Figure 2 and the piston 16 is correspondingly urged back to the travel-limit, rest position by the return spring 17.

As can be appreciated from the foregoing description, the master cylinder according to the present invention solves the problems described with reference to the prior art and satisfies the above-

mentioned requirements, that is, to achieve the best compromise between braking action and sensitivity of operation and to limit dimensions, at the same time preventing the cylinder from interfering with the bodywork and the instruments during steering.

In fact, the largest dimension in the direction perpendicular to the handlebar is reached at a point which is disposed farther out, relative to the longitudinal axis of the motor vehicle, than with cylinders having axes perpendicular to the handlebar.

Moreover, the cylinder according to the present invention enables substantially the same optimal lever ratio as in racing motor cycles to be maintained in mass-produced motor cycles, even though the cylinder is disposed farther from the hand grip.

In particular, the fact that the axis 15 of the cylinder is inclined to the axis 11 of the seat 4 in accordance with the conditions and the definitions described above, enables the length of the second portion 6b of the control lever 6 to be limited, whilst maintaining an optimal lever ratio, as already stated above. By limiting the length of the lever, the parallel advantage of a reduction in the weight of the cylinder is also achieved.

Moreover, the advantageous configuration described

above provides a very compact overall structure which does not extend too far from the handlebar and does not therefore affect the external configuration of the motor cycle either from the aesthetic point of view or from the functional point of view.

Excessive bulkiness, particularly in the vicinity of the handlebar, is thus avoided, facilitating the incorporation of the cylinder in a motor vehicle.

A further advantage of the master cylinder according to the present invention lies in the simplicity of its structure, which enables the problems mentioned with reference to the prior art to be solved without, however, altering the shape and functionality either of the vehicle as a whole or of its braking/clutch systems, in particular.

Clearly, variants and/or additions may be provided for the embodiment described and illustrated above.

Naturally, the definition according to which the axis 15 intersects both the axis 11 and the axis 23 perpendicular to the axis 11 relates to the situation in which the three above-mentioned axes lie in the same plane, corresponding to the plane X of pivoting of the control lever 6.

If the three above-mentioned axes do not lie in the same plane, this definition may be reproduced by analogy

with reference to the plane X of pivoting of the control lever 6 and the straight lines parallel to the above- mentioned axes lying in that plane, or the projections of the above-mentioned axes onto the plane of pivoting of the control lever.

In fact, a possible variant may provide for the axis 11 to lie in the plane X of pivoting and for the axis 15 of the cylinder to be disposed in a plane parallel to the plane X of pivoting. In this case, it will suffice to consider a projection of the axis 15 onto the plane X of pivoting and, in particular, a perpendicular projection thereof. In greater detail, this expression is intended to define the straight line obtained by the intersection of the plane X of pivoting with a plane including the axis 15 of the cylinder and perpendicular to the plane of pivoting.

The characteristics of the axis 15 lying in the plane X as described above and illustrated in the appended drawings apply to this straight line.

A further variant may provide for the axis 11 to lie in the plane X of pivoting and for the axis 15 of the cylinder to intersect the plane X of pivoting. In this condition also, it will suffice to consider a projection of the axis 15 onto the plane X of pivoting of the control lever 6 and, in particular, a

perpendicular projection thereof. In this case also, the expression: perpendicular projection of the axis 15 onto the plane X of pivoting, is intended to define the straight line obtained by the intersection of the plane X of pivoting with a plane comprising the axis 15 of the cylinder and perpendicular to the plane of pivoting thereof.

The characteristics of the axis 15 lying in the plane X as described above and illustrated in the appended drawings apply to this straight line.

With reference to the two possible variants described above, the expression: projection of the axis 15 onto a plane containing the axis 11, for example, the plane X of pivoting, is intended to define either a projection, preferably a perpendicular projection, according to the conditions indicated above, or the axis 15 itself, when the axis 15 and the axis 11 lie in the same plane.

Other possible variants may relate to the handlebar portion on which the cylinder 1 is mounted. In the embodiment shown in Figures 1 and 2, the axis of the handlebar portion on which the seat 4 is mounted coincides with the axis of the end portion of the handlebar corresponding to the hand grip 8.

If the two axes do not coincide, for ergonomic

reasons the plane X of pivoting of the control lever 6 includes the axis of the end portion of the handlebar corresponding to the hand grip. Moreover, when the cylinder is mounted on the handlebar, the axis of the handlebar portion on which the seat 4 is mounted coincides with the axis of the seat.

In this condition, considering the plane including the axis of the seat 4 and the axis of the cylinder, it is true that the latter is inclined to the axis of the seat 4 in the manner described above.

Finally, as already stated above, the reservoir 5 may be formed separately from the cylinder body 2, as shown in Figure 1, or may be formed integrally with the cylinder body 2, according to an embodiment not shown.

In order to satisfy contingent and specific requirements, a person skilled in the art may apply to the above-described preferred embodiment of the master cylinder many modifications, adaptations and replacements of elements with other functionally equivalent elements without, however, thereby departing from the scope of the appended claims.