DE102012105279B4 - Bicycle frame with a short rear triangle - Google Patents

Abstract

The invention generally relates to bicycles and the design of bicycle frames, in particular for mountain bikes, trekking bikes or racing bikes. More particularly, the present invention relates to seat tubes with a flattening to provide space for a front derailleur linkage mechanism of a derailleur and thus on bicycles, particularly bicycles with large wheels such as 28" or 29" wheels or 28" or 29" wheels, to enable a very short or compact rear end of the bicycle. In this way, the distance between the rear wheel and the seat tube can be kept to a minimum. This allows the rear wheel to be pushed very close to the seat tube. The rear end of the bicycle can therefore be made very short.

Description

The invention relates generally to bicycles and the design of bicycle frames for mountain bikes. More particularly, the present invention relates to seat tubes with a flattening to provide space for a front derailleur linkage mechanism of a derailleur and thus on bicycles, particularly bicycles with large wheels such as 28" or 29" Wheels or 28" or 29" wheels to enable a very short or compact rear end of the bicycle.

Bicycle frames of conventional design typically include a bicycle frame which is designed to accommodate additional components such as front and rear wheels, a bottom bracket assembly and a seat. A bicycle frame often includes a top tube and a bottom tube, which are connected to one another in the area of the mount for a bicycle fork. This connection can also be formed by means of a further control tube. On the side facing the rear wheel, a seat tube typically connects the top and bottom tubes.

In the area of the connection between the seat tube and the top tube, there is usually a seat arrangement. This can be designed, for example, as a saddle with a seat post, the seat post being inserted into the seat tube. The bottom bracket assembly is usually located in the lower area of the seat tube, ie in the area of the connection between the down tube and the seat tube. In addition, the chain stay or rear axle swing arm, which serves to hold the rear wheel, is often arranged in this area of the bicycle frame. Such a construction of a bicycle frame is often also referred to as a diamond frame.

The size of the front and rear wheels can be selected according to the intended use of the bicycle, which means that the geometric arrangement of the upper, lower and seat tube can also be selected accordingly. In this case, the geometric arrangement is to be understood as meaning the length of the respective tubes or the angular range resulting therefrom, which is formed in each case between the central axes of two tubes connected to one another.

As a rule, the selection of the wheel size influences or limits the geometric arrangement possibilities of the bicycle frame.

There is a trend towards larger diameter wheels for certain uses. For example, in the area of so-called hardtail bikes, i.e. bikes that have no rear damping, larger wheels up to so-called 29" bikes are increasingly being used. Bikes of this type can be used in cross-training, MTB, trail and trekking, for example be used.

Significant advantages of such large wheels are, for example, greater traction of the large tires due to the longer contact area. This has an advantageous effect when cornering. The rollover behavior over obstacles and thus the safety when driving off-road is thus significantly improved. Due to the better directional stability compared to smaller wheels, such wheels behave more forgiving and more comfortable.

Due to the size of the wheels, however, there are geometric peculiarities in the arrangement of the tubes, especially in the area of the rear wheel mount.

The rear wheel of such a bicycle is typically connected to the seat tube via the rear axle swing arm or chain stay. There is an angle between the seat tube and the rear axle rocker which is often in the range of about 63° to 75°. Since the rear wheel has to be at a certain distance from the seat tube in order to be able to rotate freely, the size of the rear wheel thus influences this angular range. If, for example, a 29" wheel is installed instead of a 26" wheel or a 28" wheel, this angular range must typically be increased in order to ensure the same distance between the wheel and the seat tube.

This increases the distance between the rear wheel and the bicycle frame. As a result, the bicycle becomes larger in its longitudinal extent. This is unfavorable for certain areas of use of bicycles, for example bicycles that are intended for off-road driving, since the maneuverability of the bicycle is reduced. Also for reasons of optimal weight distribution when driving, a rather small angle is often desired, which is not greater than about 75°.

To make matters worse, such bicycles often have derailleur gears. A derailleur typically includes a front and a rear shifting device, each having one or more gears or chainrings. The front shifting device has the said chainrings and a derailleur that controls the running of the chain when there are several chainrings. In mountain bikes or trekking bikes in particular, this derailleur can be arranged above the chainrings. It is often attached to the saddle tube.

Due to the size of the front derailleur and the limited space between the rear wheel and the seat tube, there is not enough space between the rear wheel and the seat tube, especially with large bikes, to achieve a smaller angular range between the seat tube and the rear axle swingarm.

Bicycle frames with a recess in the seat tube are known from the following documents: U.S.A. 4,513,986 , U.S. 2007/0 210 553 A1 , Stevens catalog 2011 “SLR AERO CARBON”, published by Stevens Vertriebs GmbH.

The object of the present invention is therefore to provide a short or compact bicycle frame for accommodating 26" wheels or 28" wheels or 29" wheels, in particular a bicycle frame for mountain bikes or trekking bikes which has a short rear structure .

This object is already completely solved by the features of claim 1. The dependent claims describe further preferred embodiments.

The invention relates to a bicycle frame with derailleur gears for mountain bikes, comprising a top tube, a saddle tube and a down tube, with the seat tube and down tube being connected to one another in the area of the bottom bracket mount, and a derailleur, with the front derailleur preferably being arranged in the area or above the bottom bracket mount is. The saddle tube is flattened to create enough space to accommodate a linkage mechanism for the front derailleur.

This creates additional space between the seat tube and the rear wheel. In particular, the area or free space between the saddle or seat tube and the rear wheel in the area of the narrowest distance from one another is not additionally reduced by swiveling in the linkage mechanism of the derailleur. In this way, the distance between the rear wheel and the seat tube can be kept to a minimum. This allows the rear wheel to be pushed very close to the seat tube. The rear end of the bicycle can therefore be made very short.

The derailleur of a bicycle typically includes several gears on the hub of the rear wheel, one or more gears, which are arranged next to each other on the pedal crank, a drive chain and a switching device for each of the front and rear gears. The switching device has the task of controlling the running of the drive chain via the different gears. The front shifter is also known as the derailleur; the gears arranged on the bottom bracket crank as chainrings.

The derailleur typically has a shifter linkage that is connected to the bicycle via a linkage mechanism. The shift rocker includes so-called chain wheels or rollers, which guide the drive chain. These components are also often referred to as chain guides. The linkage mechanism has the task of shifting the shifting rocker sideways so that the drive chain is guided to the desired chainring. The lateral displacement is thus approximately perpendicular to the longitudinal axis of the bicycle or approximately parallel to the axis of the bottom bracket. Using a gear cable guide and a spring, the linkage mechanism moves the shifting rocker between the chainring that is closest to the bicycle frame and the chainring that is furthest away.

In the case of mountain bikes, which are suitable for off-road riding, the front derailleur is preferably arranged in the area or above the bottom bracket mount. The articulation mechanism and the shift rocker or the chain guide are therefore particularly preferably designed above the bottom bracket mount. This has the advantage that the ground clearance between the front and rear wheels is not reduced by the rocker arm or the linkage mechanism. The front derailleur can be connected, for example, to the seat tube at its bottom bracket end or directly to the bottom bracket mount.

With a derailleur arranged in this way, the linkage mechanism moves the shifting linkage along a path or line which runs approximately in the direction of the axis of the bottom bracket. In order to guide the rocker arm to the chain ring closest to the bicycle frame, the linkage mechanism is often moved or pivoted into the space between the rear wheel and the seat tube.

In the conventional construction of a bicycle with, for example, a diamond frame arrangement, this leads to a reduction in space between the rear wheel and seat tube and thus to the need to lengthen the rear axle swing arm accordingly and/or to increase the angular range between the center axis of the seat tube and the center axis of the rear axle swing arm. The rear axle swing arm is also often referred to as a chainstay. Together with the seat stay, it can form the rear triangle of a bicycle.

According to the invention, therefore, the saddle tube has a flattening in order to create this space. The articulation mechanism can thus in this through The space created by the flattening of the seat tube can be moved without reducing the space between the seat tube and the rear wheel so much that the freewheeling of the rear wheel is impaired. This configuration is particularly advantageous when large rear wheels are used. Bicycle frames that are equipped with 26" wheels or 28" wheels or particularly preferably with 29" wheels therefore preferably have saddle tubes with a flattening according to the invention between the central axis of the seat tube and the central axis of the rear axle swing arm can either be completely avoided or at least significantly reduced in scope.

Advantageously, the flattening is formed on the side of the saddle tube facing the rear wheel, since the rocker arm is arranged on the side of the bottom bracket assembly facing the rear axle hub.

The flat is open towards the rear wheel to create enough space for the linkage mechanism.

The front derailleur can be connected to the saddle tube above the bottom bracket assembly, for example via a clamp assembly. The front derailleur can also be connected directly to the bottom bracket assembly via a so-called direct mount attachment. It is therefore advantageous to form the flattening of the seat tube in the area of the bottom bracket end.

The seat tube has a length that is measured along a line between the bottom bracket mount and the connection to the top tube and thus runs along the central axis of the seat tube. Seen in the longitudinal direction of the bicycle, the seat tube has a width and seen in the direction of the axis of the bottom bracket has a depth. In the case of a rotationally symmetrical seat tube, the width and depth are identical and are determined by the radius.

The seat tube can be designed as a hollow tube with different cross-sectional shapes, for example with a circular, transversely oval, rectangular or elliptical cross-sectional area. The cross-sectional shape can also be designed differently over the length of the seat tube.

Due to the flattening of the seat tube, the shape of the cross-sectional area is changed in said area.

The flattening can be designed differently. For example, the width of the saddle tube can be reduced, while the size of the cross-sectional area can be retained or also reduced. If, for example, the width of the tube is reduced in said area by a forming process, the depth of the tube can be widened and thus increased at the same time. As a result, the cross-sectional area of the saddle tube can be kept constant over the length. This can be advantageous in order, for example, to ensure sufficiently high flexural and torsional rigidity in the flattened area as well. However, the flattening can also be effected, for example, by a borehole perpendicular to the central axis of the saddle tube, as a result of which the cross-sectional area of the saddle tube is reduced at the point of the flattening.

Advantageously, the flattening is dimensioned to be correspondingly large, in order to give space to at least part of the articulation mechanism that pivots in. At the very least, the flattening should be large enough to ensure that the rear wheel cannot collide with the seat tube and/or the linkage mechanism of the front derailleur. On the other hand, this should not reduce the width of the saddle tube too much in the flattened area, in order to be able to ensure sufficient stability in this area, in which very high torsional and bending forces can act.

The size of the flattening of the seat tube is thus determined by the space required for accommodating the linkage mechanism on the one hand and by the load values of the bicycle for the intended uses and the corresponding material values of the seat tube on the other.

With regard to the extent of the flattening in the longitudinal direction of the seat tube, this is advantageously selected to be rather small. It has also been shown to be advantageous if the reduction in the width of the seat tube is in a range from 1 to 40%, preferably from 5 to 30% and particularly preferably from 10 to 25%. The percentage values refer to the relation to the non-flattened areas of the saddle tube.

In a preferred embodiment, the rear axle swing arm is connected to the bicycle frame in the area of the bottom bracket mount to accommodate the rear wheel. An angle α is formed between the central axis of the rear axle swing arm and the central axis of the seat tube. The minimum size of the angle α depends on the size of the rear wheel, since there is sufficient space between the rear wheel and the seat tube for the rear wheel to run without colliding must be provided. The larger the rear wheel, the larger the angle is typically chosen. In the case of frames designed for 26" or 28" wheels, this angle is in a range from approximately α=65° to α=75°, preferably α=72°.

It is all the more surprising that the flattening according to the invention makes it possible to provide a bicycle frame which is suitable for receiving a 29" wheel as the rear wheel and in which this angle is in a range of α<72°, preferably α=70° ° or less, allowing the frame to be kept very short.

In a particular embodiment, the bottom bracket assembly is offset very far down. The axis of the bottom bracket is therefore significantly lower than that of the rear axle hub. A straight line that runs through the center of the axle of the bottom bracket and through the center of the rear axle hub and a horizontal line through this very center of the rear axle hub define a further angle β. It has been found to be particularly advantageous if the angle β is between β=0° and β=15°, preferably between β=5° and β=10° and particularly preferably between β=5° and β=8° or at β= 6°.

By shifting the bottom bracket assembly downwards, it is possible to reduce the angle α even further. In this way, a bicycle frame can be made available in which the angle α is less than 69°. A frame can thus be made available in which the angle α is preferably <=68° and particularly preferably α<=66°.

This displacement of the bottom bracket arrangement is particularly advantageous if the inclination of the seat tube or the seat tube angle, ie the angle of the central axis of the seat tube with respect to the horizontal, is to be kept largely constant. For ergonomic reasons, maintaining the slant of the seat tube is often preferred.

In addition, in this way the basic arrangement of the frame with regard to the lengths and/or the angles between the seat tube, top tube and down tube can be retained largely unchanged. This is also very advantageous from the point of view of costs, since in this way the number of variants to be manufactured and components or frame assemblies to be kept available can be minimized.

Front derailleurs, in particular front derailleurs fastened to the bottom bracket assembly by means of a direct mount fastening, often have an angular range α within which they can be optimally operated. For example, there are typical front derailleurs that are designed for an angular range from α >= 66° to α <= 69°. If the angle α between the seat tube and the rear-axle swingarm decreases due to the bottom bracket assembly being offset downwards, such derailleurs can often no longer be used optimally or would have to be operated in a non-optimal angle range.

According to the invention, therefore, the derailleur, particularly the derailleur mounted to the bottom bracket assembly by means of a direct mount fastener, is mounted rotated clockwise through an angle Y about the center of the bottom bracket. The derailleur is preferably rotated in such a way that the angular range suitable for optimal operation of the derailleur is again reached. In this way, the reduction in the angular range α can be compensated for again by the displacement of the bottom bracket assembly. In this way, those derailleurs can also be used to particular advantage which would otherwise no longer be suitable due to their operating angle range due to the vertical displacement of the derailleur.

For example, if the angle α is α = 64.5° after the bottom bracket has been moved, then by rotating the derailleur around the center of the bottom bracket by the angle Y = 3° clockwise, an angle for the operation of the derailleur of α = 67, 5° = 64.5° + 3° can be realized.

As a result, commercially available derailleurs can also be used particularly advantageously for a bicycle frame with a lowered bottom bracket. Therefore, the flattening of the saddle tube particularly preferably has sufficient space in order to offer sufficient space for the linkage mechanism even with a correspondingly rotated front derailleur. The front derailleur is rotated clockwise by 0.5° to 5°.

The flattening of the saddle tube according to the invention thus offers space for the pivoting mechanism of a clockwise rotated front derailleur and in this way makes it possible to place the bottom bracket assembly vertically lower.

It is thus possible to produce a bicycle frame with improved rolling resistance, better rolling behavior over obstacles and greater comfort through the use of large wheels, in particular 29" wheels, which is characterized by a particularly compact design.

With the bicycle frame according to the invention, a bicycle with 26" wheels or 28" wheels or 29" wheels can be made available which has a distance between the front and the rear Wheel hub in a range from 90 to 120 cm, preferably in a range from 95 to 117 cm, particularly preferably 100 cm.

Further details of the invention result from the description of the illustrated exemplary embodiments and the appended claims.

The drawings show:

• 1 an overview drawing of a bicycle with a diamond shape frame assembly,
• 2 a schematic representation of a bottom bracket assembly with a flattened seat tube,
• 3 a schematic representation of a section of a saddle tube with a flat area and a representation of cross-sectional shapes of the saddle tube,
• 4 a schematic representation of a rear wheel assembly for a 26" wheel and
• 5 a schematic representation of a rear wheel assembly for a 29" wheel.

Detailed description of preferred embodiments

In the following detailed description of preferred embodiments, like reference characters designate substantially like parts in or on these embodiments for the sake of clarity.

1 shows a diamond-shaped bicycle frame for a mountain bike. 11 shows the seat tube, 12 the top tube, 13 the down tube and 14 the bottom bracket. The rear axle swing arm or chain stay 15 is connected to the frame in the bottom bracket area and carries the rear wheel. In addition to the chain stay 15, the rear wheel structure includes the seat stay 19 and the rear wheel 20. 17 also shows the head tube and 16 the handlebars of the bicycle. 10 shows the saddle. The front wheel 18 is shown in the stem of the bicycle.

The angle α shows the angular range between the central axis of the seat tube 11 and the central axis of the rear axle rocker 15. In the bicycle frame shown, the angle α is 72°.

In 2 a section of a bicycle frame in the area of the bottom bracket mount 14 is shown schematically. A section of the down tube 13 and the rear axle swing arm 15 as well as a section of a rear wheel 20 are shown.

The saddle tube 11 has a flattening 21 in the area on the bottom bracket side. This flattening reduces the width of the seat tube in this area. The width of the seat tube in the non-flattened area A is greater than in the said area with the flattened area B.

Due to the flattening according to the invention, a space is created between a rear wheel 20 and the saddle tube 11 into which the linkage mechanism of the derailleur can pivot. Section 23 shows a section of a linkage mechanism. The front derailleur and the rocker arm are not shown. Due to the flattening of the saddle tube, the linkage mechanism can swing freely into the space between the rear wheel and the saddle tube without touching the saddle tube or the rear wheel. In the example shown, the angle is α = 66°.

3 shows two variants of a flattening of the saddle tube according to the invention in cross section. The seat tube here comprises a rotationally symmetrical tube with an end on the bottom bracket side. The flattening changes the shape of the cross section. A′ shows the cross-sectional area of the seat tube in the upper area without a flattening, B′ shows an embodiment for a cross-sectional area in the flattened area, and B″ shows another embodiment. A flattening as shown in B'' is particularly advantageous for aluminum seat tubes. The flattening is dented and can be easily produced by pressing. The embodiments of the flattening shown have sufficient flexural and torsional rigidity and can thus ensure high stability of the bicycle frame.

The saddle tube can also have other round hollow tube-like profiles, such as elliptical or oval cross-sectional shapes.

In 4 shows a section of a rear assembly of a 26" bike, with the seat tube 11 not having a flattening in this example. The angle α designates the angular range between the center axis of the rear wheel swing arm 15 and the center axis of the seat tube 11. For a 26" bike it is in the example shown 67.5°. The angle β describes the angle that is formed between a straight line through the center of the rear wheel axle 20 and the center of the bottom bracket mount 14 and the horizontal through the center point of the rear wheel axle 20 . Typically, this angle is around β=0 to 15°.

With such an arrangement of the rear wheel assembly, the vertical distance is D1 from the center of the axis of the bottom bracket mount to the horizon talen through the center of the axle of the rear wheel about D1 = 30 mm.

5 shows a rear wheel arrangement according to the invention for a 29" bike. In this arrangement, the bottom bracket 14 is set lower. This displacement of the bottom bracket increases the vertical distance D2 between the center of the axis of the bottom bracket to the horizontal through the center of the axis of the rear wheel to about D2 = 40 to 95 mm, preferably D2=50 to 70 mm and particularly preferably D2=65 mm.

This also increases the angle β. It has been found to be particularly advantageous if the angle β is between β=0° and β=15°, preferably between β=5° and β=10° and particularly preferably between β=5° and β=8° or at β= 6°.

If the inclination of the saddle tube is largely the same, i.e. a constant raw seat angle compared to a typical 26" bike, the angle α is reduced at the same time. The offset of the bottom bracket bracket shown results in a reduced angle α. This can be α' = 64, be 5°.

Therefore, the front derailleur is rotated clockwise through an angle Y in order to be able to set an angle range that is optimal for operation. 55 shows a derailleur rotated clockwise by Y = 3° around the center of the bottom bracket. As a result, the front derailleur can be formed at an angle of α″=67.5°.

The rotation of the front derailleur and/or the displacement of the bottom bracket assembly downwards therefore makes it possible to provide a bicycle frame for large bikes, preferably 26", 28" or 29" bikes, which has a very compact and has a short rear end and is therefore ideally suited for use as a trekking or mountain bike.

Reference List

10

saddle

11

seat tube

12

top tube

13

down tube

14

bottom bracket mount

15

Rear axle swing arm or chainstay

16

handlebars

17

control tube

18

front wheel

19

seatstay

20

rear wheel

21

flattening

23

linkage mechanism

55

pivot mechanism rotated

Claims (15)

Bicycle frame for mountain bikes with derailleur gears, comprising a saddle tube (11) and a down tube (13), which are connected to one another in the area of the bottom bracket mount (14), a front derailleur arranged in the area or above the bottom bracket mount (14), characterized in that the Seat tube (11) has a flattening (21) for receiving the articulation mechanism (23,55) of the derailleur, so that the articulation mechanism (23,55) is free in this space created by the flattening (21) of the seat tube (11) between the seat tube (11) and a rear wheel (20), the angle α between the central axis of the seat tube (11) and the central axis of the rear axle rocker (15) being less than α=75°, preferably less than α=73° and particularly preferred is less than α = 72° and the derailleur is mounted on the seat tube (11) rotated clockwise in a range of 0.5° to 5° around the center of the bottom bracket. bike frame protection claim 1 , characterized in that the flattening (21) of the seat tube (11) is formed on the side facing the rear wheel (20). Bicycle frame according to the preceding claims, characterized in that the flattened area (21) is open in the direction of the rear wheel (20). Bicycle frame according to the preceding claims, characterized in that the flattening (21) is formed on the bottom bracket end of the seat tube (11). Bicycle frame according to the preceding claims, characterized in that the depth of the flattening (21), measured parallel to the longitudinal axis of the bicycle, is the width of the seat tube (11) at the point with the in a range of 1 to 40%, preferably 5 to 30% and more preferably reduced from 10 to 25%. A bicycle frame as claimed in any preceding claim, characterized in that the derailleur is attached to the bottom bracket assembly by means of a direct mount attachment. Bicycle frame according to the preceding claims, characterized in that the derailleur includes the articulation mechanism (23, 55) and a rocker arm and/or a chain guide. Bicycle frame according to the preceding claims, characterized in that the articulation mechanism (23, 55) of the derailleur is arranged above the axis of the bottom bracket. Bicycle frame according to the preceding claims, characterized in that the rocker arm or chain guide is arranged above the axis of the bottom bracket. Bicycle frame according to the preceding claims, characterized in that the rear axle swing arm (15) is connected to the bottom bracket housing. Bicycle frame according to the preceding claims, characterized in that the axle of the bottom bracket is arranged lower than the wheel hub of the rear wheel (20). Bicycle frame according to the preceding claims, characterized in that the angle between a horizontal line through the center of the rear axle hub and a straight line between the center of the rear axle hub and the center of the bottom bracket axis is between β = 0° and β = 15°, preferably between β = 5° and β=10° and particularly preferably between β=5° and β=8° or at β=6°. Bicycle frame according to the preceding claims, characterized in that the bicycle frame is designed to accommodate 26" wheels or 28" wheels or 29" wheels and the distance between the front and rear wheel hubs is preferably in a range from 90 to 120 cm in a range from 95 to 117 cm, particularly preferably 100 cm. Bicycle frame according to the preceding claims, characterized in that the direct mount attachment for attachment of the front derailleur is rotated through an angle Y about the center of the bottom bracket in relation to the seat tube angle. Bicycle frame according to the preceding claims, characterized in that the distance between the axis of the rear wheel hub and the axis of the bottom bracket is between x=400 mm and x=440 mm, preferably between x=410 mm and x=430 mm.

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