It is well-known that one of the major problems encountered in the design of folding bicycles, such that they may transported, for example, in the boot of a car, consists in the permanently projecting parts of the bicycle, said parts including mainly the handlebars and the pedals.

As regards the handlebars, various solutions are possible, such as rotating the two arms about the axis of the support column so that these arms lie in a plane parallel to the plane of the bicycle frame, even though this solution also results in the need for mechanical adjustments before and after transportation.

In the case of the pedals, however, such a solution is not possible.

The main object of the present invention is that of providing a pedal crank mechanism in which the pedals may be oriented so as to project outside of or inside the plane passing through the pedal crank depending on whether the bicycle is in the operating condition or it is required to stow away substantially the parts which otherwise project from the volume of the frame.

Another object of the present invention is that of providing a mechanism of the aforementioned type in which switching over between the two aforementioned positions can be achieved easily, rapidly and without the use of special equipment or tools.

These and other objects are achieved with a pedal crank mechanism of the type comprising a hub which is rigidly joined to a toothed wheel actuating the main chain for transmission of motive power to the rear wheel, a pair of pedal cranks fixed to the two ends of said hub and a pair of pedals fixed rotatably to an eyelet situated at the ends of said pedal cranks, characterized in that each pedal crank comprises a body, the end of which opposite to that provided with said eyelet is in the shape of a"U", the two arms of which are pivotably mounted on the head of said hub about a pivoting axis perpendicular to the axis of said hub, said body having an axial hole which is blind on the side where said eyelet is situated and open towards the U-shaped end of the pedal crank, a piston which is housed in said axial hole and able to project from said open end of said axial hole, a spring housed in said hole so as to bias said piston towards the position projecting from said hole, a pair of recesses formed in said head of said hub and aligned axially with each other and with said axial hole in said body of the pedal crank, so that the end of said piston in the projecting condition engages with the recess situated directly in front of the mouth of said axial hole, and means which can be operated on the outside of the pedal crank so as to retract said piston, disengaging it from said recess against the action of said spring.

As will appear from the detailed description which follows of a preferred embodiment, by operating the means mentioned last in the above description, it is possible to rotate the pedal crank about the pivoting axis of the two arms of the "U"which are fixed to the hub of the pedal crank mechanism, positioning the axial hole and the piston projecting from it so that they are aligned with the diametrically opposite recess. In this way, the pedal which in the initial position projected outside the plane passing through the pedal crank, following said rotation, now projects towards the inside. The reverse action obviously brings each pedal crank and each pedal back into the original operating position.

In the accompanying drawings: Figs. 1 and 2 are views of the pedal crank mechanism in the two conditions, i. e. operating condition and condition where the pedal is folded towards the inside; Figs. 3 and 4 show cross-sectional views, along the plane indicated by III- III in Fig. 1 and IV-IV in Fig. 3, respectively, of the mechanism for switching the pedal cranks between the two positions shown in Figures-1 and 2 ; Figs. 5,6 and 7 show a variant of the mechanism for switching the pedal cranks, where Figures 6 and 7 are cross-sectional views along the planes indicated by VI-VI in Fig. 7 and VII-VII in Fig. 6, respectively..

With reference first of all to Figures 1 and 2, the pedal mechanism comprises two pedal cranks, i. e. right-hand pedal crank 10D and left-hand pedal crank lOS, at the ends of which provided with the eyelet 14 the pedals 12D and 12S are mounted (D and S referring to right-hand and left-hand respectively, even though both the pedal cranks and the pedals are identical to each other). The pedals are mounted on the ends of the hub 16 which is of the conventional type and which has, rigidly fixed thereto, the toothed actuating wheel 20 of the bicycle, while the reference number 18 denotes generally the frame of the bicycle.

The end of each pedal crank 10 fixed to the hub 16 is the shape of a"U", the two arms 22 of which are fixed to the hub by means of two bolts 24. The head 26 of the hub has two recesses 28 with a substantially radial progression and arranged in a plane at right angles to that passing through the axis of the two bolts 24. The recesses 28 in both the conditions shown in Figures 1 and 2 are aligned with the longitudinal axis of the pedal crank.

The body 30 of the pedal crank has an axial hole 32 which is blind towards the outer end of the pedal crank (i. e. the end with the eyelet 14) and open towards the other end (i. e. the end which is U-shaped) and inside which a piston 34 is seated, the outer end or tip 36 of which is shaped so as to match the recesses 28.

A spring 38 is housed between the piston 34 and the blind end of the hole 32 against which it bears and biases the piston 34 so as to project from the axial hole 32.

A transverse pin 40 is integral with the body of the piston 34 and has two ends which project outside the body 30 of the pedal crank through two longitudinally opposite slots 42 which limit the stroke of the piston 34 and also the amount by which its tip 36 projects from the axial hole.

On the outside of the body 30 of the pedal crank each end of the pin 40 is preferably integral with a sliding block or plug which helps facilitate operation of the pin.

If the pedal crank mechanism is in the condition shown in Fig. 1, it is sufficient to operate the two sliding blocks or plugs of each pedal crank, by pulling them parallel to the axis of the pedal crank towards its opposite or outer end, against the opposing action of the spring 38 until the tip 36 of the piston 34 disengages from the recess 28 which is situated directly in front.

In this condition, by rotating the body of the pedal crank about the axis of the bolts 24 (with the movement shown in Fig. 4), the two pedal cranks are brought from the condition shown in Fig. 1 into the condition shown in Fig. 2, following which, upon release of the sliding blocks or plugs, the piston returns into the condition where its tip 36 projects from the axial hole 32 and engages with the recess 28 situated in front, said recess being that which before was situated in the diametrically opposite position.

The pedal crank mechanism is then locked in the new condition which is that shown in Fig. 2, with the pedals 12 projecting towards the inside relative to the plane passing through each pedal crank.

The same sequence is followed if the pedals are to be brought back into the condition shown in Fig. 1.

As already mentioned, Figures 5-7 show a constructional variant in which operation of the piston 34 has been modified.

Essentially the axial hole 32 has a step 44 against which the bottom end of the spring 38 bears, while the rear end of the piston 34 is pivotably mounted, about the pin 46, on the end of a hinged connecting plate 48, the other end of which is pivotably mounted, about the pin 50, on an operating lever 52 which is pivotably mounted on the body 30 about a pin 54 and which has its outer end 56 shaped so as to facilitate gripping and operation of the lever itself.

Aligned with the lever 52 and the plate 48, the body 30 of the pedal crank has two longitudinal facing slits 58 through which the lever 52 and plate 48 may project relative to the body 30.

From a comparison of Figures 5 and 7 it can be readily appreciated how, by operating the lever so that it passes from the condition shown in Fig. 7 to that shown in Fig. 5, against the opposing action of the spring 38, it is possible to disengage the end of the piston 34 from the recess 26 situated opposite, rotate the pedal crank through 180° about the axis of the bolts 24 so as to bring the axial hole 32 of the pedal crank into alignment with the other recess 26, following which the lever 52 is brought back into the condition shown in Fig. 7, locking the pedal crank and the pedal in the new position.

From the above description it can be clearly seen how the present invention solves the technical problem in a simple and effective manner, it being understood that modifications and variants which are conceptually and mechanically equivalent are possible and may be envisaged without departing from the scope of the invention.

For example, instead of the coupling system consisting of piston 34 and recesses 28, other types of mechanisms or devices are possible for releasably locking the end of the pedal crank coupled with the head of the hub in either one of the two positions arranged at 180° with respect to each other and axially aligned with the axis of the pedal crank.