TOOTHED WHEELS

The present invention relates to a gearbox with coaxial front toothed wheels , in particular o f a conical shape .

More speci fically, the invention provides a gearbox with gears with coaxial front toothed wheels to be applied in all those uses which require , or prefer, a coaxial wheel arrangement , for example for integration into the hub of the driving wheel of a bicycle .

Gearboxes with gears are known in the art , in particular for use on a bicycle .

However, these known gearboxes are not satis factory and have the problems of being relatively bulky, heavy, complex and of using mechanisms which are di f ficult to protect from dirt with a consequent decrease in reliability .

Obj ect of the present invention is solving the aforesaid prior art problems by providing a gearbox with gears with coaxial front toothed wheels which is not bulky, simple to manufacture and reliable .

The aforesaid and other obj ects and advantages of the invention, as will appear from the following description, are achieved with a gearbox with gears with coaxial face gears such as the one described in claim 1 . Preferred embodiments and non-trivial variants of the present invention form the subj ect of dependent claims .

It is understood that all attached claims form an integral part of the present description .

It will be immediately obvious that innumerable variations and modi fications may be made to what is described ( for example relating to shape , dimensions , arrangements and parts with equivalent functions ) without departing from the scope of protection of the invention, as appears from the attached claims .

The present invention will be better described by some preferred embodiments thereof , provided by way of non-limiting example , with reference to the attached drawings , in which :

Figure 1 is a perspective view of an embodiment of a gearbox with coaxial face gears according to the present invention;

- Figure 2 is a top view of an embodiment of a gearbox with coaxial front gear wheels according to the present invention; and

Figure 3 is a sectional view of an embodiment of a gearbox with coaxial face gears according to the present invention .

With reference to the Figures , a preferred embodiment of the gearbox 10 with coaxial gear wheels of the present invention is illustrated and described; such gearbox 10 comprises a driving wheel 4 and a driven wheel 3 rotating on an axis 13 , for example a fixed axis , and a cursor 9 arranged transversely to the axis 13 and sliding with respect to it , preferably inside a seat 15 formed in the axis 13 .

The gear wheels 4 , 3 preferably comprise respective crown gears 5A, 5B arranged on di f ferent diameters of the driving wheels 4 and driven wheels 3 , said crown gears 5A, 5B being made with teeth protruding from facing surfaces 21 , 22 of the wheels 4 , 3 .

The cursor 9 also comprises two gears 7A, 7B arranged at its ends , said gears 7A, 7B being preferably integral with each other and fixed to the axis 19 of the cursor 9 , rotating around it and configured to transmit the motion from the driving wheel 4 to the driven wheel 3 , engaging each gear 7A, 7B in respective crown gears 5A, 5B arranged on dif ferent diameters of the driving wheel 4 and driven wheel 3 .

Preferably, the surfaces 21 , 22 of the drive 4 and driven 3 wheels are conical in shape , inclined with respect to their axis 13 by an angle a which is preferably equal to the angle of inclination of the axis 19 of the cursor 9 , and the crown gears 5A, 5B are arranged on said surfaces 21 , 22 ; in a preferred way, the driving wheels 4 and driven wheels 3 are specular .

In a first configuration of the gearbox 10 with gears with coaxial front gear wheels of the invention, the axis 13 is fixed and has the task of supporting the rotation of the driving wheels 4 and driven wheels 3 and of guiding the sliding of the cursor 9 .

Other configurations of the invention are possible , in which the functions of the components can be exchanged or used in any other way, such as for example the movable driving wheel 4 , the fixed wheel 3 , the axis 13 can rotate together with the cursor 9 and the two gears 7A, 7B behave like satellites . The operation of the gearbox with coaxial front gear wheels will be described below in the first configuration of the invention shown in the figures and described above .

In this configuration, the driving wheels 4 and the driven wheels 3 are specular, each comprising four crown gears 5A, 5B arranged on dif ferent diameters and made on the surfaces 21 , 22 inclined by the angle a equal to the inclination angle of the axis 19 of the cursor 9 , so as to allow the cursor 9 to slide and move radially with respect to the wheels 4 , 3 , and to bring the gears 7A, 7B integral with each other, to mesh with the crown gears 5A, 5B arranged on di f ferent diameters of the two wheels 4 , 3 , the first gear 7A meshed with the driving wheel 4 and the second gear 7B meshed with the driven wheel 3 .

The inclination angle a of the axis 19 of the cursor 9 allows the gearbox to operate : in fact the cursor 9 can slide along its axis 19 to ef fect the change of ratio between the driving wheel 4 and the driven wheel 3 , allowing the former gear 7A to mesh only with the crowns 5A of the driving wheel 4 , without interfering with the driven wheel 3 , and allowing the second gear 7B to mesh only with the crowns 5B of the driven wheel 3 , without interfering with the driving wheel 4 , which would prevent the gearbox from functioning, as is evident from the figures .

As a result , the driving wheel 4 transmits the motion to the first gear 7A, through one of the crowns 5A, which in turn transmits it to the second gear 7B which finally transmits it to the driven wheel 3 , through one of the crowns 5B .

The gearbox with gears with coaxial front gear wheels of the invention further comprises means for controlling the axis 19 of the cursor 9 , not shown in the figures , configured to move the cursor 9 , when the ratio is required, upwards or downwards along its axis 19 , moving it by a distance equal to the distance between the crowns 5A, 5B, obtaining a change in the rotation speed of the driven wheel 3 with respect to the driving wheel 4 , increasing or reducing the speed of the driven wheel 3 depending on the cursor movement direction 9 .

In the configuration j ust described, there are four crown gears 5A, 5B and they allow obtaining four ratios , but the number of crown gears varies according to the need for ratios and to the manufacturing skills . The cursor 9 is designed to be moved by a cursor moving mechanism, which, according to a preferred embodiment, is housed in the central axis 13, which is usually fastened to the chassis, and therefore unmoving. This movement, necessary for changing the gear ratio, can be performed manually by means of levers, rack rods, gears, etc. (not shown) , as well as by using a small electric motor, or sliding magnets, in order to make the gear ratio selection automatic.

Another important feature, made possible by the above described embodiment, is that the mechanism can be completely closed and also made waterproof, by installing a tube (not shown) on the external circumference between the conical wheels 3, 4, equipped with suitable gaskets, which anyway allows a free rotation of the mechanism, which closes the room interposed between the wheels 3, 4. Of the conical wheels 3, 4, one (4) is the driving wheel and receives a motion to be transmitted, the other (3) is the driven wheel and, due to the control system through the central axis 13, becomes the carrier hub of a traction wheel of the means on which the gearbox of the invention is used.