The subject of the invention is a bicycle with a drive on at least a front wheel. Construction of this bicycle makes possible to considerably and very quickly decrease its overall dimensions and to adjust it easily for two persons.

The bicycles with the drive on the front wheel are known for long time (SHIRE & BONESHAKER 1870, or DEKSTER 1869), and functionality of the overall dimensions reduction is realised in many ways.

In known bicycles the functionality of folding is realised most often by use of additional constructional elements. The bicycle known from Polish application P.344428 is for example fitted with additional joints making possible to "break" the bicycle in places of junction of the frame beams and in the handlebar plane. Introduction of such additional elements is troublesome because it lengthens the time of the bicycle preparation for driving, increases its weight and cost.

Folding bicycle is known as well from Polish application P.354284. In this bicycle rear rocker is joined to the end of the frame through telescopic suspension of rear wheel. Front and rear wheels are joined to front and rear rockers, respectively. Telescopic elastic suspension of front wheel, rail suspension of rear wheel, the handlebar axle and the treadles with cranks are fitted with quick releases. Functionality of folding is realised in this bicycle also with use of additional elements.

Also from Polish application P.292655 a bicycle is known with a rhomboidal frame cut along shorter diagonal, where these cuts are subsequently joined separably with articulated locks. The bicycle is folded by releasing of locks on the frame.

A bicycle with rear drive is known from Polish application P.377279, where the axis of the handlebar fixed to the frame runs through the point of intersection of front wheel with the floor, and the angle made by this axis with the floor equals about 70°. To summarize, all known constructions of the bicycles with functionality of folding require usage of additional elements.

The aim of the invention is to propose a bicycle construction that makes possible easy, fast (less than 1 sec.) and considerable reduction of its overall dimensions. The construction should be light, comfortable, easy to keep it clean, with good driving qualities, and making possible easy adjustment for two persons.

The bicycle according to the invention has the wheels joined by the frame beams, a handlebar, a seat and a drive. In this bicycle the frame consists of the frame of the front wheel fitted with the driving system with an axis of rotation comprised within this wheel, and the rear wheel frame, with a seat and a back-rest fixed. Both frames are coupled by a joint and a crossed line transmission. In this coupling the axis of the joint being common to both frames intersects the floor surface at an angle of 66° ± 5°, at a distance of 20 ± 4 cm behind the point of contact of the front wheel with the floor. According to the invention the rear wheel may also be fitted with the driving system, like the front wheel. The driving system applied is placed on the axis of driven wheel and it is a treadle crank system. One-way clutch and planetary transmission, preferably an automatic variable ratio transmission are placed on an axis of rotation of this wheel. The handlebar is fixed rotationally in a swivel axle of the front wheel frame and is immovably joined through the swivel axle with big wheel of the crossed line transmission. The swivel axle of the front wheel frame has two bearings, where the bearing close to the handlebar has small friction momentum, preferably the ball bearing, while the bearing at big wheel of the crossed line transmission is a transverse slide bearing with big friction momentum.

The ratio of the crossed line transmission equals to 1,4±0,1 : 1. Small wheel of this transmission is immovably fixed to the rear wheel frame in an axis of the joint that couples both frames, and big wheel of the transmission is immovably joined with the handlebar and it rotates in the axis of the swivel axle of the front wheel frame.

The line joining both wheels of the transmission is crossed between the big wheel and the relief rollers placed close to big wheel of the transmission.

The bicycle according to the invention is comfortable, easy in maintenance and is characterized by low failure frequency. It has good driving qualities and is characterized with little impact of changing forces during pedalling on the steering system. It may be easily adjusted for two persons and quickly reduced in overall dimensions.

The invention is explained in preferred embodiments shown on the drawings, where Fig. 1 shows a single-seat bicycle, Fig. 2 shows this bicycle after reduction of overall dimensions, Fig. 3 shows a bicycle for two persons, and Fig. 4 shows the bicycle for two persons in folded state.

The bicycle has the front wheel (15) with a diameter of 28", the rear wheel (16) also with the diameter of 28". The wheels are coupled with combined frame consisting of the frame (1) of the front wheel (15) and the frame (2) of the rear wheel (16). The frames (1) and (2) are coupled by the joint (3) and by the crossed line transmission (10, 11, 12) with a ratio of 1,4 : 1. The frame (1) has the swivel axle (4) with the handlebar (7) fixed rotationally around the axis (6). The swivel axle (4) with the handlebar (7) fixed has two bearings (8) and (9). The bearing (8) is placed close to the handlebar (7) and it is common ball bearing. At the big wheel (10) of the crossed line transmission the bearing (9) is placed, which is a transverse slide bearing with high friction momentum. The handlebar (7) is immovably joined through the swivel axle (4) with the big wheel (10) of the crossed line transmission (10, 11, 12). This transmission has a ratio of 1,4 : 1 and its small wheel (11) is fixed immovably on the axis (5) of the joint (3) joining the frames (1) and (2).

If the handlebar (7) turns against the frame (1), it makes the frame (1) to turn relative to the frame (2).

The bearing (9) of the swivel axle (4) is relieved with use of two relief rollers (13) in case of equal line tension on both sides of the transmission. The rollers (13) are placed close to the wheel (10) of the crossed transmission, and the line (12) of the line transmission is crossed between the big wheel (10) and the rollers (13). The difference of the line (12) tensions on both sides of the transmission made by the frame (1) turn relative to the frame (2) without the handlebar turning relative to the frame (2) generates on both sides of the transmission proportional friction momentum in the bearing (9), which restrains movement of the frame (1) relative to the frame (2).

If by turning the handlebar (7) relative to the frame (1) one generates a difference in the line (12) tension on both sides of the transmission, the momentum of force applied to the handlebar relative to the rotation axis (5) of the joint (3) compensates this difference in tension making possible to turn the handlebar easily. The front wheel of the bicycle is driven by the crank drive system (18) with the treadles (17). The drive system consists of the one-way clutch and the planetary transmission, placed on the axis of rotation of the wheel (15).

In preferred embodiment the axis (5) of the joint (3) which is a part common for both frames (1) and (2) intersects the floor surface in the point (C) at an angle of 69°, and the distance of this point from the point of contact of the first wheel (15) with the floor equals 20 cm.

In the beam of the frame (2) of the rear wheel the seat (19) is mounted, fitted with the back-rest (14). On this beam, behind the back-rest (14) second seat may be mounted, if the bicycle shall be adjusted for two persons (Fig. 3). This embodiment requires also replacing the rear wheel (16), preferably by a wheel 26", with the crank drive similar to that in the front wheel.