To more effectively exert thrust action on bicycle pedals, especially during sporting activity, it is necessary to securely fix the shoe to the pedal.

The user also needs to be able to quickly and easily release the shoe from the pedal, especially in the case of loss of balance, so as to be able to rest the foot on the ground.

To solve these problems automatic enagement devices have been proposed comprising a plate fixed to the sole of the shoe and provided at its front and rear with flanges engagable in corresponding coupling means provided on the pedal. Said means consists substantially of a fixed front element and an elastically operable movable rear element. Engagement is achieved by inserting the front flange of the plate into the fixed element and pressing the rear flange downwards onto the movable coupling element to achieve snap engagement against the reaction of elastic means.

Said elastic engagement means are shaped such that rotation of the plate about an axis perpendicular to the plane of the pedal causes rear movement of the movable element to enable the plate to be disengaged from the pedal.

An object of the invention is to provide an improved fixing device of reversible type, ie which can be used either on the right or on the left without distinction.

A further object of the invention is to provide a fixing device which if necessary can completely lock the shoe to the pedal.

A further object of the invention is to provide a fixing device which enables the intensity of shoe locking to the pedal to be adjusted.

A further object of the invention is to provide a fixing device which enables the shoe to be rapidly secured to the pedal even if these are not aligned in position.

All these and further objects which will be apparent from the ensuing description are attained according to the invention by a device for fixing a shoe to a bicycle pedal comprising a plate rigid with the sole of the shoe, said plate being provided at its front with a flange engaging in corresponding coupling means arranged on the pedal, said plate being provided at its rear with a self-centering seat for elastic engagement by a pin provided on the pedal.

The present invention is further clarified hereinafter with reference to the accompanying drawings, on which: Figure 1 is a plan view from below of a pedal according to the invention with the shoe fixing plate; Figure 2 is a cross-section therethrough on the line ll-il of Figure 1; Figure 3 is a side view thereof in the direction Ill-Ill of Figure 1; Figure 4 is a section therethrough on the line IV-IV of Figure 1; and Figure 5 is a longitudinal section through the pedal rotation pin.

As can be seen from the figures, the fixing device according to the invention comprises substantially a profiled plate 2 to be rigidly fixed to the shoe sole 4, and a pedal 6. Both the plate and the pedal are of aluminium construction. The plate 2 is provided with a rounded front flange 8, which is step-shaped to define a further curved projecting portion 10, and is also

provided with slotted holes 12 for engagement by screws for its fixing to the shoe.

In correspondence with its rear edge the plate 2 comprises a seat housing a steel insert 14 which in its outwardly facing part comprises a substantially hemisperical central notch 16 interposed between two longitudinal depression 18 the depth of which decreases from the notch outwards.

The pedal 4 internally comprises a substantially cylindrical seat 20 of different diameters, into which there is inserted a hinge pin 24 screwed to the pedal crank (not shown on the drawings).

The pedal is provided with coupling means consisting of a front profiled portion 28 cooperating with the step-shaped portion 8 of the plate, and also comprises a seat housing the front appendix 10 of the plate.

The coupling means provided on the pedal also comprise a pin 30 housed in a seat 32 provided in a block 34 provided in the rear end of the pedal and urged elastically by the action of a coil spring 36. A grub screw 38 enables the spring to be preloaded to the desired extent.

In some cases the block 34 can be constructed of transparent material and comprise reference marks on its outer surface. In this manner the degree of preload of the spring can be checked visually.

The pedal rotation pin 24 comprises a shank 40 provided at one end with a threaded stem 42 for engagement in a corresponding threaded seat provided in the pedal crank, and is housed within a cylindrical casing 44.

Rotation of the shank within the cylindrical casing is enabled by ball bearings

46, whereas its axial movement is prevented by a nut 48 which engages its end portion emerging from the cylindrical casing.

A seal ring 50 prevents moisture from entering the cylindrical casing.

The pedal of the invention is used as follows: after inserting the curved portion 10 of the plate into the seat in the pedal, the user presses downwards to cause the pin 30 to engage in the corresponding hemispherical seat 16.

This operation is facilitated in that even if the shoe is positioned such that the pin 30 does not lie coaxial to the hemispherical notch 16 of the block, self- centering is obtained by the presence of the two lateral depressions 18.

When the shoe is to be disengaged from the pedal, the user merely has to rotate the shoe along an axis perpendicular to the sole 4 so that, by overcoming the elastic reaction of the spring 36, the plate insert 14 is disengaged from the pin 30. Again in this case, disengagement is facilitated by the "inclined plane" formed by the depressions 18.

From the aforegoing it is apparent that the fixing device of the invention has numerous advantages, and in particular: - it enables the shoe to be engaged with and disengaged from the pedal in a simple and comfortable manner; - it is reversible; - it enables the locking intensity of the plate to the pedal to be adjusted; - it enables the plate to be totally locked to the pedal by totally preloading the spring 52, this being particularly advantageous in track competitions.