Device for adjusting inclination of a front fork of a vehicle having two or three wheels, particularly a cycle or a motorcycle

A device is described, for adjusting the inclination of a front fork of a two- or three-wheeled vehicle having a steering assembly (S) including a frame tube (3) and a steering tube (4) rotatable in the frame tube. The adjusting device comprises an upper connecting unit (10a) and a lower connecting unit (10b), for rigidly connecting the steering tube (4) to two substantially parallel fork rods (5). The connecting units (10a, 10b) are prearranged for enabling to vary in an adjustable manner the inclination of the fork rods (5) relative to the steering tube (4), without the need of relative separation or disassembling among the units, the fork rods and the steering tube.

FIELD OF THE INVENTION

The present invention relates to a device for adjusting the inclination of the steering front fork of a two- or a three-wheeled vehicle.

The typical function of devices of the described type is to enable changing the distance between the front and the rear axle of a motorcycle, in order to modify the vehicle's attitude and thus the driving characteristics thereof depending upon the requirements of use. These devices enable to adjust the distance between the front and the rear axle without necessarily the need of disassembling the motorcycle steering assembly and/or replacing one or more of the parts thereof.

PRIOR ART

Vehicles equipped with known adjustment devices have a steering assembly including a frame tube, within which a steering tube is mounted in a rotatable manner. The adjustment device, or the steering assembly incorporating it, comprises an upper plate support and a lower plate support, which rigidly connect both front rods of the fork bodies to the upper and lower ends of the steering tube, said ends being axially protruding out of the frame tube. In some known solutions the adjustment device is designed in a way enabling to vary in an adjustable manner the inclination of the frame tube relative to the vertical, while in other solutions the adjustment device is designed in a way that enables changing the inclination of the steering tube within the guide tube.

The adjustment devices according to prior art generally have a complex and expensive construction. Furthermore, the known devices require a specific pre-arrangement of the vehicle frame.

SUMMARY OF THE INVENTION

One aim of present invention is to obtain a device for adjusting the inclination of a steering front fork of a two- or three-wheeled vehicle having a simple and cheap structure, and also easy to use for the users. Another aim of present invention is to obtain one such device that can be easily applicable also on vehicles not initially provided with means to adjust the inclination of the front fork.

According to present invention, one or more of these aims are achieved by a device for adjusting the inclination of a steering front fork of a two- or three-wheel vehicle. The aims of present invention are also achieved by a steering assembly incorporating the above said adjustment device and by a two or three-wheeled vehicle incorporating such a device or assembly.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1schematically shows a two-wheeled vehicle, indicated with1as a whole, equipped with an adjustment device according to the invention. Hereinafter it is assumed that the vehicle1is a cross-country motorcycle, but it has to be considered that the invention can be used also on other types of motor-vehicles, and even on bicycles. Furthermore the invention can be used also on three-wheeled vehicles having a front steering fork.

Referring also toFIGS. 2 and 3, vehicle1has a frame2, having a known general structure, including a frame tube3which is part of a steering assembly, indicated with S as a whole. The steering assembly S further comprises a steering tube4, rotatably mounted in the frame tube3. The ends of the steering tube4axially protrude out of the frame tube3and on them nuts indicated with4ainFIG. 2are screwed, to axially constrain the tube4in the tube3, according to known technique. Two substantially parallel fork rods, for example being part of a telescopic front suspension system as normally used on motorcycles, are indicated with5(see particularlyFIG. 3).

The steering assembly S also comprises means for rigidly connecting the two fork rods to the steering tube4. According to a feature of the invention, these means are part of a device for adjusting the inclination of the steering front fork of the vehicle1and comprise an upper connecting unit and a lower connecting unit, respectively indicated with10aand10bas a whole. Each connecting unit10aand10bof the device according to the invention consists of a plurality of components that are mechanically interconnected in an adjustable manner and replaces the traditional upper and lower plates used in the prior art to rigidly connect the fork rods to the steering tube, at different heights.

As explained later, the two units10aand10bare prearranged for allowing an adjustable variation of the inclination of the fork rods5relative to the steering tube4, without the need of separating or disassembling the units, the fork rods and the steering tube. For this purpose, the axis of the steering tube4is indicated with A4inFIG. 1, while the axis of one of the fork rods is indicated with A5, being represented, respectively in solid and dashed line, in two different adjustment conditions of the device according to the invention; Bminand Bmaxindicate the two angles of axis A5relative to the vertical and visually express the different inclination of the front fork, in the above said two adjustment conditions.

Reference6indicates a handlebar of the vehicle1, which is preferably connected to the upper unit10aas described later. Reference7and8inFIG. 1designates the front and the rear wheels of the vehicle1, with the respective hubs7aand8a; also the front wheel7is represented in two different adjustment conditions of the device according to the invention, respectively in solid and dashed line.

As particularly shown inFIGS. 2 and 3, each connecting unit10aand10bcomprises:one pair of side fastening members, hereinafter referred to as side supports, indicated with20, each of them designed to be rigidly connected to a respective fork rod5,an intermediate fastening member, hereinafter referred to as intermediate support, indicated with40, operatively interposed between the side supports20of the respective pair and designed to be rigidly connected to the steering tube4.

Each of the intermediate supports40of the upper unit10aand of the lower unit10bis connected to a respective end region of the steering tube4, preferably in the zone interposed between a nut4aand the frame tube3, as for example shown inFIG. 2. InFIGS. 2 and 3it can be also seen how the side supports20of the upper unit10aare rigidly connected to the fork rods5at a greater height with respect to the side supports20of the lower unit10b.

In the preferred embodiment of the invention the means of the adjustment device which enable to adjust the inclination of the front fork comprise at least one eccentric or cam system associated to each connecting unit10aand10b. This eccentric system is designed to mechanically constrains each side support20to the respective intermediate support40and is operable for varying the position of the side supports relative to the intermediate support, in order to modify as a consequence the inclination of the fork rods5relative to the steering tube4.

The eccentric system of each unit10aand10bcomprises a respective connecting element, hereinafter referred to as cam pin, indicated with60and shown in different views inFIGS. 4-6(scale ofFIG. 5is larger relative toFIGS. 4 and 6).

The cam pin60is preferably made of steel and is shaped to comprise more portion, among which there are at least:two side portions61, substantially shaped as shaft having a circular cross section, which are longitudinally extended according to one same axis A61, andone intermediate portion62, being eccentric relative to the side portions61.

In the exemplified embodiment also the intermediate portion62is shaped as a shaft with circular cross section, longitudinally extending according to a respective axis A62, which is parallel to axis A61of the side portions; in any way, the intermediate portion of the cam pin can be differently shaped with respect to the shown example, but its functions must remain the same as described later.

Again with reference to the presently preferred embodiment, and as clearly shown inFIGS. 4-6, the cam pin60includes two substantially disk-shaped parts63, between the intermediate portion62and the side portions61. The disk-shaped parts63has substantially the function to strengthen the structure of the pin60at the transition zones between portion62and portions61; another function of the disk-shaped parts63is to guide the rotation of the pin60during the adjustment phase, and for this reason they are preferably disk-shaped. Each end of the intermediate portion62of pin60is rigidly connected or integral to a face of a respective disk shaped part63, in an eccentric position; the other face of each disk shaped part63is instead rigidly connected or integral to the end of a respective side portion61in an eccentric position, such that axes A61and A62are reciprocally staggered and parallel to each other.

As explained later, in the shown exemplified embodiment, each side portion61of pin60is rigidly connected to the side support20of respective unit10aor10b, but can be released from it, while the intermediate sector62is connected to the intermediate support40of the same unit.

FIGS. 7-9show in different views one of the side supports20of the upper unit10a, being evident that the shape of the other side support of the same unit has a substantially mirror-shape to the one being represented, an that the configuration of the side supports20of the lower unit10bis substantially similar to that of the side supports of the upper unit10a.

Support20has a body that is preferably made of metal or composite material, for example magnesium or a light metal alloy, such as ERGAL (aluminium alloy). In the body of support20a main through-passage21is provided, having a circular cross section and extending axially, designed for receiving one axial section of a respective fork rod (seeFIGS. 2 and 3). In the body of support20a second axially extended passage is provided, indicated with22, designed to receive one side portion61of the cam pin60(FIGS. 4-6), respectively of the upper or lower unit. As shown inFIG. 7, the axis A21of passage21is preferably—but not necessarily—perpendicular to the axis A22of the passage22. In the given example also passage22is configured as a through-passage.

The body of side support20has a first cut23, substantially parallel to axis A21in the shown example, which cut ends in the passage21: in this way, in the body of support20two first clamp portions are defined, indicated with24, to clamp within passage21the respective section of the fork rod5. For this purpose, the clamp portions have holes or passages25a,25b, transverse to cut23, for receiving suitable loosenable tightening members, only schematically shown inFIG. 8, where they are indicated with26; these tightening members26can be conveniently embodied by screws, for example provided with hexagonal notch, in which case the holes25aare shaped to house at least part of the screw head, whereas passages25bare threaded. Obviously screws and threaded holes can be replaced by bolts and non-threaded holes.

The body of side support20has a second cut27, substantially parallel to axis A22in the example, ending in passage22. In this way, in the body of support20two second clamp portions are defined, indicated with28, for clamping within passage22the respective side portion61of pin60ofFIGS. 4-6. Also the clamp portions28have holes or passages29a,29btransverse to cut27, for receiving loosenable tightening members, that are only schematically shown inFIG. 9, where they are indicated with30. Using passage22and clamp portions28with the respective tightening members30, the side support20can be rigidly connected—in a releasable way—to a respective side portion61of pin60.

The diameter of passages21and22is such to allow, when screws26and30are loosened, an easy insertion of the rods5into passages21and of one side portion61of pin60into passage22. Preferably, the diameter of hole21is, with the screws26and30being loosened, slightly greater then the diameter of the fork rods5, in order to avoid possible damage of the rods' surface during the insertion of the supports20; the diameter of holes22can also be substantially similar to the diameter of the side portions61of pin60, such that it can receive them with a slight interference: by tightening screws26and30a rigid connection is then obtained, of supports20to rods5and pin60, respectively.

It can be seen inFIGS. 7-9that passage22has, at the axial ends thereof, respective widenings o seats indicated with31and32, coaxial to ach other and to passage22. Seat31is formed at the outer flank of support20(that is the flank opposite relative to the one facing the intermediate support40of the corresponding unit10aor10b). This seat31is designed for cooperating with an annular blocking member, preferably a seeger ring, mounted at the corresponding end of pin60: one such ring is schematically shown inFIGS. 4 and 6, where is indicated with64, inserted into a respective circular groove formed at the outer end of each portion61of pin60. The function of rings64is to avoid axial movements of pin60within components20,40of the upper or lower connecting unit, when the unit at issue is assembled and operative. Seat32, formed at the inner flank of support20(that is the flank facing the intermediate support40of the corresponding unit10aor10b), substantially forms a cam seat belonging to the above said eccentric system, and is designed to accommodate a respective disk-shaped part63of the cam pin60(FIGS. 4-6), so as to enable and guide rotation thereof, as described later.

FIGS. 10-14show in different views the intermediate support40of the lower connecting unit10b.

The intermediate support40is formed by two parts, indicated with41and51, and hereinafter referred to as rear component and front component, respectively. Components41and51—preferably made of the same material as supports20(metal, composite, light alloy)—are configured to clamp therebetween the intermediate portion62of cam pin60of unit10b. For this purpose, in each component41and51there is defined an axially extended portion of a receiving transverse seat: inFIGS. 10-12the above said seat portions are indicated with42and52and are shaped as cavity having a substantially semicircular cross section, whereas the seat is indicated as a whole with50only inFIG. 13, with the corresponding axis A50.

Component41, which in the example has overall dimensions bigger than component51, has a substantially cantilevered rear part43, wherein a through-passage44is formed. Axis A44of this passage44(seeFIG. 13) extends transversely, preferably perpendicularly, relative to axis A50of the receiving seat50. Passage44is aimed at receiving a section of the lower region of the steering tube4that is between the lower end of the frame tube3and the lower nut4a(seeFIG. 2for example).

Components41and51of the intermediate support40have respective receiving seats for loosenable tightening members, such as screws or bolts. In the example, to this purpose, component51has through-holes55, while component41is frontally provided with threaded blind holes45; socket head screws are only schematically shown in FIG.13, where they are indicated with46. As can be imagined, fromFIG. 13, in the assembled condition of components41and51, holes45and55are in axial alignment to receive screws46; by tightening these screws, the intermediate portion62of cam pin60results in being rigidly clamped by the transverse seat50; for this purpose, preferably, the diameter of the intermediate portion62of cam pin60is slightly bigger than the diameter of seat50, as defined by seat portion42and52of components41and51.

As is visible inFIG. 14, component41can be advantageously provided with, in the rear part thereof, of oblique passages or seats47, being preferably threaded, for mounting elements, not shown, aimed at delimiting the steering angle.

The intermediate support40of the upper connecting unit10ais shown in different views inFIGS. 15-19and has a general construction similar to the intermediate member10. In the exemplified embodiment, the intermediate support40of the upper unit10ahas fastening means to rigidly connect the central portion of handlebar6. These fastening means comprise in particular an upper and a lower clamping elements, indicated with56and57inFIGS. 2 and 3. As can be seen for example inFIGS. 15-18, the lower clamping elements57have first through-holes57a, for screws57b(FIGS. 17 and 18) used to rigidly connect the same elements to the upper part of component41; for this purpose threaded blind holes—not shown but clearly visible for example in FIGS.17and18—are located on the upper part of component40. The lower clamping elements57have further threaded holes58, for tightening by means of screws—not shown—the upper clamping elements56, such that a respective central portion of handlebar6is clamped between the clamping elements56-57, as shown for example inFIG. 3.

FIG. 19shows that the rear part43of the rear component41has a cut47, ending in passage44: in this way, two clamp portions48are defined in portion43, for clamping within the passage44a section of the upper region of the steering tube4that is located between the upper end of the frame tube3and the upper nut4a(seeFIG. 2). The clamp portions48have at least one respective hole or passage48a,48b, for receiving a suitable loosenable tightening member, such as a screws having a head with hexagonal socket, not shown in figure.

The device according to the invention also comprises manoeuvring means, for allowing a user to carry out manually the adjustment of the inclination of the front fork, using a tool. In the shown example these manoeuvring means are provided for allowing to operate the above mentioned eccentric system, or to impart the cam pin60a rotation movement about axis A61(FIG. 4), of the respective side portions61which, in the assembled condition of the device, are housed within passages22of the side supports20.

As shown inFIGS. 4-6, in the presently preferred embodiment, these manoeuvring means comprise a keyhole or seat65, formed at the end face of at least one of the side portions61of cam pin60and configured for cooperating with a suitable tool. In the shown example, each seat65has hexagonal cross section and the tool used for carrying out a the adjustment is a normal Allen key, not shown. Not that, though preferable, it is not strictly necessary that both end faces of pin60have a seat65, since a single seat65at one end is sufficient to impart the pin the required rotation during the adjustment.

The device according to the invention is also preferably provided with reference means, to give a visible indication of the adjustment position. In the shown example these means are configured for giving a visible indication of the angular position of cam pin60relative to the side supports20, or of the amount of rotation imparted from time to time to the pin during the adjustment, and consist of a reference element, indicated with66, for example a notch or incision, on at least one end face of cam pin60, preferably a face provided with a seat65.

The adjustment device according to the invention is easy to install. Suppose that the adjustment device has to be installed on a normal motorcycle not having means for adjusting the inclination of the front fork thereof. In a first step the front fork of the motorcycle has to be disassembled: the traditional upper and lower plates of the steering assembly are firstly uncoupled from the steering tube3and then extracted from the above the rods5, and the handlebar is disassembled from the upper plate, all the above in a known manner.

Between the two side supports20of each unit10aand10bis pre-assembled the cam pin60; for this purpose, both side portions61of pin60are inserted into the passages22of both supports20, while the screws30are loosened, to ease the insertion; then the seeger rings64are mounted at the two ends of pin60. Then the side supports20of the two units10aand10bare inserted onto the fork rods5, the screws26being loosened to ease the slipping of rods within the passages22of supports20. On the other hand, the rear components41of the intermediate supports40of the two units are loosely secured to the upper and lower end regions of the steering tube4, that protrude out of the frame tube3, using for this purpose the portions43having the passages44and the nuts4a(FIG. 2).

The fork assembly is then approached to the front part of the motorcycle frame2, for example such as to firstly positioning the intermediate portion62of cam pin60of the upper unit10aat the seat portion42of component41of the intermediate support40of the same unit; thereafter component51of the intermediate support40of the same unit is mounted, by means of the screws46. Similar operations are performed concerning the cam pin60and the intermediate support40of the lower connecting unit10b. Then the front components51of the two intermediate supports40are tightened, using the screws46, onto the respective rear components41, so as to rigidly clamp between these components41-51the respective portions62of pins60. Preferably pins60are rigidly clamped to the intermediate supports40in substantially similar angular positions within the respective seats50. Thereafter:the side portions61of pins60are tightened within passages22of the side supports20, by means of the clamp portions28and the screws30,the side supports20are tightened onto the fork rods5, by means of the passages21, the clamp portions24and the screws26, andthe screw of the clamp portions48(FIG. 19) of the intermediate support40of the upper unit10bis tightened, as well as the nuts4aat both ends of the steering tube4.

As a result, the unit consisting of units10a,10bwith the rods5is rigidly connected to the steering tube5. Obviously, in order to carry out this operations, the fitter has to visually check and—if necessary—to manually register the reciprocal positions of the various parts4,5,20,40,60. Thereafter the handlebar6is rigidly connected to the upper unit10a, specifically to the intermediate support40thereof, using the clamping elements56and57.

The assembled device according to the invention thus becomes an integral and substantial part of the steering assembly S of the motorcycle1, which can be used in a customary way. As previously stated, the two units10aand10breplace the upper and lower plates of a steering assembly according to the prior art.

Also the operations required for adjusting the inclination of the front fork of the motorcycle1are very simple. For this purpose the user must firstly loosen the screws30of the side supports20and the screws46of the intermediate supports40, for both units10aand10b, in a way enabling the rotation of the cam pin60in the direction desired for each of them. The two pins60can be rotated substantially simultaneously, for example in opposite directions, using two Allen keys, or the two pins60can be rotated in sequence, or also only one of the two pins60can be rotated, the above depending upon the type and amount of the desired adjustment of inclination for the front fork. As can be imagined, in fact, due to the eccentric systems of the two units10a,10b, the rotation around axis A61of each cam pin60(FIG. 4) causes a restrained displacement of the corresponding side supports20with respect to the intermediate support40of the relevant unit, which is fixed to the steering tube4: thus, at each unit, the rods5are approached to a greater or a lesser extent relative to the steering tube4. Consequently, by acting in this way on one or both pins60, depending upon the adjustment needs, it is possible to change the inclination of the fork rods5—which are rigidly fixed to the side supports20—relative to the steering tube4and to the vertical, as evidenced inFIG. 1. Presence of the reference66enables the user to visually locate the different adjustment positions, and for this purpose a fixed reference element or sign can be conveniently provided for also on the outer flank of at least one of the side supports20; due to the presence of reference66the user can recognize preferred adjustment positions depending on use requirements of the motorcycle (for example, a first adjustment position for use of the motorcycle on highway, another adjustment position for use of the motorcycle in towns or on roads with many curves, another adjustment position for off-road use of the motorcycle, and so on). Note that variation of the inclination of the front fork allowed by the device according to the invention has also the effect of varying the height of the front part of the vehicle, thus also varying the position of the barycentre thereof. Once pin or pins60are have been brought in the desired angular position, the user has only to newly tighten screws30and46of the supports20and40, respectively, so as to rigidly connecting again the different parts20,40,60to each other.

As can be seen, by means of the device according to the invention the adjustment of the inclination of the front fork can be done manually in a simple and quick manner, by a single operator and without the need of disassembling the adjustment device or replacing parts of the steering assembly of the vehicle. The components of the device according to the invention are also simple and cheap to manufacture, and have overall dimensions and weight comparable—or even reduced—with respect to the traditional upper and lower fork plates. Another clear advantage is that the device according to the invention can be easily mounted also on cycles and motorcycles not initially having means for regulating the inclination of the front fork.

Obviously, the constructive details and the embodiments can largely change with respect to those described and shown herein, without departing from the scope of present invention as defined by the claims that follow. Also the materials used to manufacture the components of the units10a,10bcan be changed with respect to those given as examples and the various particulars of the units can be worked by metal machining and/or casting.

The cam seats designed to receive the disk shaped parts63could be each defined in a respective flank of the intermediate support40, and therefore with the two components41,51of the intermediate support that each define a portion of each cam seat. Such case has been schematically shown inFIGS. 10 and 15, wherein the cited portions of one of the cam seats are indicated with41aand51a, respectively for components41and51.