The subject of the invention is a downhill bicycle structure with enhanced suspension. The structure includes a tube structure with down tube, top tube, and seat post, a gear, a stay frame with seat stay and chain stay, a rear shock, and at least one upper swing-bar and at least one lower swing-bar.

Mountain bikes - one of the most commonly used bicycle types - are already known. Downhill bicycles represent an extreme type of mountain bikes. During downhill biking, sportsmen usually take an elevator to ascend a mountain and compete in reaching the valley within the shortest possible time. For this reason, the technical requirements concerning such bicycles are extremely high. The wheel suspension mechanism is of extraordinary importance. Bicycle tubes used to weigh around 18 to 22 kg, but now they weigh around 4 to 5 kg. Out of this weight, the spring component weighs approximately 0.5 to 1 kg. Races on difficult tracks are frequently decided by hundredths of seconds.

The most important requirements are the followings: active suspension while breaking, turning stability with the lowest possible centre of gravity, back suspension with high resistance against twists, reliable tube structure, and easy access to the spring component of the back suspension. The latter is of importance, as the spring suspension needs to be set on the field track by stopping occasionally on the track during the practice sessions before the race. Downhill bicycles and their suspensions are covered by numerous known inventions. Publication document No. EP 2527239 Al describes a tube layout facilitating the functioning of bicycles. As protection against shocks, the tube of the bicycle includes a shock absorber. The shock absorber is mounted onto the tube with a joint using a swing- bar. European publication document No. EP 2527239 Al describes the suspension of the rear wheel of a bicycle. The suspension is located in the triangle formed by the tubes of the bicycle and is connected to the rear wheel-fork through a swing-bar. International publication document No. WO 2011142882 Al describes a bicycle tube structure. The tube structure includes a main frame structure and a shock absorber. The shock absorber is connected to the centre of the rear wheel and to the rear wheel-fork as the extension thereof and is located below the seat post. This supplementary frame regulates the flexible connection between the rear wheel and the main tube structure. International publication document No. WO 2012025705 Al describes a device with adjustable geometrical structure and a vehicle including the device. International publication document No. WO 2013028138 Al describes a bicycle that can be used to ride up and down on slopes and may be easily adjusted to the terrain. The seat post may be adjusted along the tube of the bicycle.

International publication document No. WO 2013029928 Al describes a bicycle tube structure. A frame with the rear wheel is connected to the main tube structure of the bicycle through a shock absorber. The frame can move in a flexible manner due to the connecting joints, thereby absorbing shocks to the bicycle. A disadvantage of this structure is that the centre of gravity is at a high level and that both ends of the shock absorber, as well as the wing-bar, is mounted onto the seat post. Thus, intensive use may break the seat post. While moving inward, the upper swing-bar pulls the seat post upward and backward. The bar, pressing against the lower suspension point, forces the suspension point upward and forward, hence the seat post is subjected to two forces pointing in opposite directions.

Hungarian patent document No. HU 210386 describes the shock absorbing suspension of the rear wheel of a bicycle. The axle of the rear wheel of the bicycle is mounted to a wheel holding component through a front bar and a rear bar connected to the ends of the tube structure with joints. The bars include a shock absorber. Due to the appropriate location of the joints of the bars, no yanking effect arises in the gear and on the pedals during the bouncing movement of the rear wheel. A disadvantage of this solution is the excessive load on the seat post through the two swing-bars mounted on it. Other disadvantages include that the centre of gravity is at a high level and that only the rear wheel may bounce due to the closeness of the swing-bars. Resistance against twisting forces is also low, as the rear wheel is connected to a swing- fork and the swing-bars are too close to each other. USA publication document No. US 2012/280470 Al describes a tube structure for bicycles. A shock absorbing device for the rear wheel is mounted onto the tube structure. The shock absorber is connected to the tube through a joint and to the fork of the rear wheel through a swing-bar. The shock absorber is placed above the gear axle and is connected to the seat post through a joint. The disadvantages of this solution include that the centre of gravity is at a high level and that the length of the chain changes significantly, up to 39 mm in the entire range of the spring. USA publication document No. US 5685553 A describes a bicycle with suspension. The suspension has one pivot point, melded into one with a stay frame including the gear box. The unified and triangle-shaped tube structure ensures that the length of the gear chain remains unchanged. The shock absorber is connected to the tube structure through a joint at the intersection of the Y shaped tube structure. A disadvantage of this solution is that it has only one pivot point. Systems with only one pivot point have low resistance against twisting forces. The upper ends of the seat stay are connected to the shock absorber directly, so the shock absorber is forced to bear high traverse load. The bore length and the pin located at the ends of the shock absorber are short and cannot force the wheels to stay on track. Other disadvantages include that the bounces become harder during breaking and that the gear-box is integrated into the stay frame, as the changing distance between the seat and the gear-box significantly reduces the comfort feeling when sitting on the seat, while the bicycle becomes stiff when standing and fails to absorb the shocks produced by pits and stones. Theoretically, the bicycle suspension described in publication document No. ES 2316316 Al is fit for being set for the given terrain at races in advance. However, its disadvantage is that access to the shock absorber is not easy, so setting becomes difficult at the very location where it should be performed - i.e. on the race track. Other disadvantages include that the centre of gravity is at a high level and that the length of the chain changes - up to 39 mm in the entire range. Furthermore, the seat stay of the stay frame is too long and its right and left sides are not connected before the wheel. This fact significantly reduces the resistance against twisting forces. The bicycle reacts to handlebar movements with a delay in turns, thereby reducing stability to a significant extent. Another disadvantage is that the down tube is bended, and thereby weakens the tube structure at one of the key points of the suspension. Publication document No. ES 2285952 Al describes a shock absorption mechanism set for bicycle tube structures, which is fit for constructing bicycle tube structures. The set allows wheels with different rear axles to be mounted onto the tube structure, in line with the terrain. A disadvantage of this solution is that the shock absorber goes through a break in the seat post, so the setting parts of the shock absorber are hard to access. The high level of the centre of gravity is another disadvantage that may be characterized with the location of the middle centre of rotation of the upper swing-bar. This centre of rotation is located at the top third of the section between the axis of the down tube and the upper seat tube. The high centre of gravity reduces turning the stability and, consequently, the turning speed. Other disadvantage is the changing length of the chain, which is 20 mm in the entire shock absorbing range, but is only 12 mm in the first 70 mm range. The bicycle may be driven by pedals in this latter range, as the terrain does not allow pedalling, if the movement of the rear wheel exceeds this range. The distance between the axle of the gear and the axle of the rear wheel increases when the rear wheel is bouncing in, so the stretched chain moves the pedals backward. The opposite situation occurs upon bouncing out: the gear rotates forward without driving the wheel. This negative phenomenon is further increased by the location of the lower swing-bar, the upper centre of rotation of which is above the axle of the gear, while the lower centre of rotation is behind, and somewhat below, of the axle of the gear. The stay frame and the tube structure are connected to each other through a swing-bar at the bottom. When the weight of the cyclist is loaded onto the suspension system, the lower swing-bar moves from its backward traversing position toward a horizontal position. When the cyclist starts to pedal, the chain pulls the stay frame forward and moves the swing-bar toward its default position, thereby forcing the system to bounce out. This absorbs some of the energy used for pedalling, which loss translates into the loss of time in races.

The purpose of the invention is to eliminate the defects of already known solutions and to develop a downhill bicycle, where the centre of gravity is lower than that of already known solutions, access to the setting controls of the rear shock is not prevented by any part of the bicycle, which does not absorb energy while pedalling, where changes to the chain length are minimal, which absorbs the impacts of the uneven terrain also while standing on the pedals, and where the down tube is sufficiently strong.

The invention is based on the recognition that a more advantageous solution may be realised by implementing the device according to claim 1. We have recognised that the movement of the stay frame may be allowed while breaking, if a mechanism with four centres of rotation is applied. Such a structure increases the distance between the centres of rotation, thereby increasing resistance against twisting forces. If the gear is mounted onto the tube structure, the distance between the seat and the gear remains constant and the suspension absorbs shocks even while standing on the pedals. The parts of the tube structure are subjected to excessive load, if the swing-bars involved in shock absorption are connected to various parts of the tube structure. The point defining the centre of gravity - i.e. the middle centre of rotation of the upper swing-bar - is located below and the lower swing-bar is set to a horizontal position. The most critical lower parts of the tube structure are fitted with bracing.

According to the set objective, the most general embodiment of the invention is described in claim 1 , while each embodiment is presented among the sub-claims.

The invention is presented in more detail below, using embodiments and drawings. On the attached drawings,

Figure 1 shows the side-view of the bicycle,

Figure 2 shows the drawing of the gear-box,

Figure 3 shows the drawing of the tube structure and the stay frame,

Figure 4 shows the side-view of the tube structure,

Figure 5 shows the top-view of the tube structure,

Figure 6 shows the A-A section indicated on Figure 4,

Figure 7 shows the B-B section indicated on Figure 5,

Figure 8 shows the exploded view of the combination of the gear-box and the swing-bar,

Figure 9 shows the side-view of the upper swing-bar, Figure 10 shows the drawing of the two upper swing bars,

Figure 11 shows the drawing of the lower swing-bar.

Figure 1 shows the side-view of the complete bicycle. It presents the tube structure 1, as well as the down tube 3, top tube 4, and seat post 5 the tube structure 1 consists of. The stay frame 2 connected to the back axle 8 consists of the seat stay 6 and the chain stay 7. The figure also shows the stanchion tube 30 and the gear 31 with combined axle 10 located in the gear-box 17. The compression-absorption of the pneumatically and hydraulically operated rear shock 27 can be adjusted with the button located on top of the oil tank pin located on the right. Thus, it is important that the bicycle structure is designed in a way that allows easy access to this turning button. The longitudinal axis 36 of the rear shock 27 is also visible. The rear shock 27 is mounted between the upper swing-bar 23 and the lower swing-bar 9 so that its longitudinal axis 36 is approximately parallel with the longitudinal axis 37 of the down tube 3. The front part of the lower swing-bar 9 is inserted into the gear-box 17 so that the inserted part and the centres of rotation of the gear 31 make up the combined axle 10, The middle centre of motion 25 of the upper swing-bar 23, which is connected to the tube structure 1, is located - at 1/3 on this implementation example - at the bottom 2/10 - 4/10 section - calculated from the longitudinal axis 37 - dividing the distance 32 between the longitudinal axis 37 of the down tube 3 and the straight line 35 drawn at the connection of the top tube 4 and the seat post 5 in parallel with the longitudinal axis 37. It is possible to place the centre of gravity of the device to a position below that of already known solutions. The same purpose is served by the fact that the centres of rotation of the bores on the upper swing- bar 23 align on the straight line 33. Also, the lower swing-bar 9 is set to a horizontal position. These measures allow the rear shock 27 - the weight of which may be up to 20 to 25% of the weight of the device - to be located at a lower position. The lower swing- bar 9 can be lowered by inserting its front part into the gear-box 17, so the axis of its first bore is the combined axle 10. The main parts of the bicycle include the independently known wheels, breaks, handlebars, seat, pedals, and chain.

Figure 2 shows the gear-box 17 and its environment - in a larger scale than Figure 1 - with a break. The figure also shows the monolithic, two-armed lower swing-bar 9, integrated into the gear-box 17, the rear shock 27 connected to the middle bore thereof, the chain stay combining mould 28 connected to the rear bore thereof, and the down tube 3. The barred mount 26 is fitted into the lower two-third section of the down tube 3. The barred mount 26 is connected to the gear-box 17 with pins. Figure 2 also shows the swing-bar bearing 12, the screw-in stay-nut 16, the gear bearing 18, the combining screw 19, and the combining nut 19a.

Figure 3 shows the tube structure 1 and the stay frame 2 in more detail. One can observe the down tube 3, the top tube 4, and the seat post 5. The stay frame 2 consists of the seat stay 6 and the chain stay 7. The seat stay 6 is connected by the seat stay combining mould 29 at the top. The chain stay 7 is connected by the seat stay combining mould 29 in the front. The front part of the chain stay combining mould 28 is connected to the lower swing-bar 9 - made of a single part - in a turnable manner, so the lower swing-bar 9 connects the stay frame 2 to the gear-box 17. The rear shock 27 is connected to the middle bore of the lower swing-bar 9, which is connected to the left-side bore of the upper swing-bars 23 at the top.

Figure 4 shows the side-view of the tube structure 1. The upper swing-bar 23 and the rear shock 27 are also visible. One can observe that the lower swing-bar 9 connecting the gear-box 17 and the horizontal chain stay 7 of the stay frame 2 is in a horizontal position. Figure 5 shows the top- view of the tube structure 1 and the stay frame 2.

Figure 6 shows the enlarged drawing of the A-A section indicated on Figure 4, as the lower swing-bar 9 connects the gear-box 17 to the chain stay combining mould 28. The essence of the connection is that the bore in the first part of the lower swing-bar 9 is integrated into the gear-box 17, so they can rotate around the same combined axle 10. In order to achieve this outcome, the gear needed to be enabled to pass through the lower swing-bar 9 as well. To this end, the gear-box 17 had to be mounted onto the lower swing-bar 9 with the combining screws 19, which - together with the swing-bar bearings 12, the screw-in stay-nuts 16, and the gear bearings 18 - allow the performance of this task. The combining screws 19 are fixed with the combining nuts 19a. The gear is placed into the through bore created this way. The back of the lower swing-bar 9 is placed into a position so that it has the same axle - that is the combined axle 11 - with the through bore of the chain stay combining mould 28 of the stay frame. It is fixed by the combining screw 15 on two sides. Rotation is supported by the bearings 14 and the stay- nuts 13. Parts of the down tube 3 and the barred mount 26 are also visible on the left side.

Figure 7 shows the enlarged drawing of the B-B section indicated on Figure 5. The longitudinal section shows the down tube 3, top tube 4, and seat post 5 of the tube structure 1, the seat stay 6 and chain stay 7 of the stay frame 2, and the chain stay combining mould 28, the seat stay combining mould 29, and the back axle 8. In the down tube 3, one can see the barred mount 26 - reaching up approximately to two thirds of the tube - which is fixed to the gear-box 17. The monolithic lower swing-bar 9 is located between the gear-box 17 and the stay frame 2, the combined axles 10 and 11 of which are also visible. The rear shock 27 is connected to the lower swing-bar 9 and the two upper swing-bars 23 in a tumable manner; the suspension point 21 and the shock mount 22 of the rear shock 27 are also indicated. The middle centre of motion 25 of the upper swing- bar 23 is connected to the tube structure 1 with a turnable pin, while its upper combined axle 24 is connected to the seat stay combining mould 29 of the stay frame 2. Figure 8 shows the exploded view of the parts already shown as a section on Figure 6, so that a key feature of the solution according to the invention - i.e. connection between the gear-box 17 and the lower swing-bar 9 made of a single unit - can be observed in more detail. The gear-box - also made of a single unit - allows the intake of the lower swing- bar 9 so that their combined axle 10 will be the same as the centre of rotation of the gear. This becomes possible after the assembly of the parts. Two-two swing-bar bearings 12, screw-in stay-nuts 16, and gear bearings 18 are necessary for assembly. The parts are held together by the combining screw 19 inserted from the inside, which is held in place by the disk shaped combining nuts 19a. One can also see the connection between the single-unit chain stay combining mould 28 of the ribbed stay frame 2 and the lower swing-bar 9. This is implemented with two-two stay-nuts 13, bearings 14, and combining screws 15. Their common centre of rotation is the combined axle 11. The seat stay combining mould 29 and the chain stay 7 are also indicated. It is noted that the barred mount 26 is fixed into the down tube 3 with pins and by welding.

Figure 9 shows the side-view of the upper swing-bar indicating the three axle centres 23a, 23b, and 23c. A feature of these is that they identical to the straight line 33. Figure 10 shows the two upper swing bars 23 in space, indicating the axle centre 23a. Figure 11 shows a spatial drawing of the single-unit lower swing-bar 9.

The bicycle structure according to the invention has numerous advantages. Due to its active floating suspension, movement is fast even when passing through extremely uneven terrain. Turns can be taken in a fast and stable manner both on narrow and wide curves. This feature is due to the centre of gravity being placed in a lower position than that of other solutions forming parts of the state of the art. Resistance against twisting forces serves the same purpose. Acceleration is excellent. This is due to the horizontal position of the lower swing-bar and to the minimal changes to the chain length. Due to the extraordinary stiffness of the structure, stable landing after jumps is also possible. There are no tension collection points or other weak points from bending the tube frame. The rear shock can be accessed and set easily. The weight of the device is in the lowest weight range of downhill bicycles. The downhill bicycle structure according to the invention may be recommended even for sports events held under extreme circumstances.