REAR SUSPENSION SYSTEM FOR BICYCLES

Abstract

A rear suspension system for bicycles comprised of a bicycle main frame, upper link, lower link, swingarm, and rotatable idler member. The rear wheel follows a primarily rearwards and upwards axle path which is determined by the specific linkage geometry. The idler member is fixed to the bicycle main frame at one precise location. This idler member is positioned in such a way as to redirect drivetrain forces to create highly stable anti-squat characteristics at the statically loaded sag point in every gear combination.

Claims

1. A driven wheel suspension system for a two wheel vehicle comprising: a chassis; a rotatable idler member fixed to said chassis; a rotatable crank mechanism fixed to said chassis for the transfer of power from a human pedaling; a swingarm; a driven wheel attached to said swingarm; a looped power transmission element configured to transmit power from said crank mechanism to said driven wheel; wherein said looped power transmission element is redirected up and over said idler member and positively engages with said idler member on the upper power transmitting segment of the looped power transmission element; an upper linkage member and a lower linkage member each with a first end pivotally connected to said chassis and a second end pivotally connected to said swingarm to control the movement of said swingarm with respect to said chassis; wherein all upper linkage member and lower linkage member pivotal connections are positioned entirely forwards of a vertical axis which extends from an axis of rotation of said crank mechanism; and wherein said upper linkage member and said lower linkage member rotate in opposite directions as the suspension moves; an instant center defined as the intersection point of the force lines through both pivots of each of said linkage members; wherein said instant center position is in front of said lower linkage member pivotal connection to said chassis at full extension of the suspension and said instant center travels forwards as the suspension system is compressed; a shock absorber with a first end pivotally connected to said chassis and a second end pivotally connected to said lower link; wherein said lower link acts as a lever arm to compress or extend said shock absorber and damp the motion of said swingarm in relation to said chassis during suspension movement.

2. The suspension system of claim 1, wherein said looped power transmission element is a chain.

3. The suspension system of claim 2, wherein said rotatable idler member is a sprocket.

4. The suspension system of claim 1, wherein said looped power transmission element is a belt.

5. The suspension system of claim 4, wherein said rotatable idler member is a pulley.

6. The suspension system of claim 1, wherein the power source is a human powered pedal and crank mechanism.

7. The suspension system of claim 1, wherein the power source is a human powered pedal and crank mechanism combined with an electric motor.

8. The suspension system of claim 1, wherein said rotatable idler member axis is fixed to said chassis within a 40 mm radius of said lower link pivotal connection axis to said chassis.

9. The suspension system of claim 6, wherein said shock absorber first end and second end are positioned entirely forwards of an axis which extends from a seat to an axis of rotation of said crank mechanism.

10. The suspension system of claim 7, wherein said shock absorber first end and second end are positioned entirely forwards of an axis which extends from a seat to an axis of rotation of said crank mechanism.

11. The suspension system of claim 1, wherein said upper linkage member has an axis from said first end pivot through said second end pivot thereof which extends in a forward and downward direction when said rear suspension is at full extension, and said lower linkage member has an axis from said first end pivot through said second end pivot which extends in a rearward and downward direction when said rear suspension is at full extension.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 is a profile view of a preferred embodiment of the present invention illustrating all of the components that define the suspension system;

[0013] FIG. 2 is a profile view showing the method for graphically calculating anti-squat force in this type of suspension system; and

[0014] FIG. 3 is a graph of the anti-squat percentage vs vertical wheel travel percentage for the present invention in all gear combinations.

DETAILED DESCRIPTION OF THE INVENTION

[0015] FIG. 1 depicts a preferred embodiment of a rear wheel suspension system of a bicycle of the present invention. The bicycle main frame 1 generally includes a head tube 2 attached to a down tube 3 and a top tube 4, a seat tube 5 attached to the top tube 4 and down tube 3, a bottom bracket 6 attached to the down tube 3 that houses a pedal/drive apparatus (not shown), a front fork mounted through the axis of the head tube 2 (not shown), and an idler member 7 attached to a down tube 3. In the preferred embodiment of the present invention there is a lower link pivot 8 located on the down tube 3 in front and above of the bottom bracket axis, an upper link pivot 9 located on the top tube 4 in front and above of the bottom bracket axis. Additionally, there is a connection near the top tube 4/seat tube 5 junction for the upper connection of a shock absorber 10 placed above and behind of the bottom bracket axis. These elements are typically welded, molded, or otherwise secured together to define the main frame 1 of the bicycle. Although the main frame 1 typically includes all of the foregoing members, alternative embodiments can have more or less of the foregoing members, and can include them in various forms, sizes, and configurations, and still achieve the intended functionality and beneficial aspects of the invention.

[0016] The rear wheel suspension system generally includes a rear wheel swingarm 11, an upper link 12, a lower link 13, an upper shock mount 10, a lower shock mount 14, and an idler member 7. The rear wheel swingarm 11 of the preferred embodiment includes a pivotal connection to the upper link 12 91.5 mm in front and 302.9 mm above the bottom bracket axis. The pivotal connections of the rear wheel suspension system are typically achieved through the use of bearings. The pivotal connection between the rear wheel swingarm 11 and the lower link 13 is located 69.4 mm in front and 70.8 mm above the bottom bracket axis. The pivotal connection between the upper link 12 and bicycle main frame 1 is located 37 mm in front and 371.7 mm above the bottom bracket axis. The pivotal connection between the lower link 13 and main frame 1 is located 112 mm in front and 123.7 mm above the bottom bracket axis. The main frame 1 includes a pivotal connection 10 near the top tube 4/seat tube 5 junction for the upper end of the shock absorber placed 17.6 mm behind and 320.3 mm above the bottom bracket axis. The lower link 13 includes a pivotal connection 14 for the lower end of the shock absorber placed 30.2 mm in front and 95.3 mm above the bottom bracket axis. The bicycle main frame 1 includes a connection for the rotatable idler member 7 placed 83.6 mm in front and 130.5 mm above the bottom bracket axis. It should be clear to one skilled in the art that a pivotal connection other than a bearing could be utilized for either pivotal connection. The pivotal connections could be contained within either the main frame 1, rear wheel swingarm 11, upper link 12 or lower link 13, and the distance between the pivotal connections in relation to the bottom bracket axis could be adjusted to accommodate various configurations without changing the scope of the present invention.

[0017] The rear wheel swingarm 11 includes a pair of rear wheel dropouts 15 joined to a pair of chain stays 16 at their rearward ends that are joined to a forward swingarm assembly 17 at their forward ends. The forward swingarm assembly 17 includes pivotal connections to the upper link 12 and lower link 13. The rear wheel dropout axis is placed 435 mm behind and 27 mm above the bottom bracket axis. The idler member 7 is 97.3 mm in diameter and has 24 teeth evenly spaced about its circumference with the correct tooth profile to engage positively with a bicycle chain.

[0018] The upper link 12 includes two pivotal connections: a pivotal connection to the bicycle main frame 1, and a pivotal connection to the rear wheel swingarm 11. The lower link includes three pivotal connections: a pivotal connection to the bicycle main frame 1, a pivotal connection to the rear wheel swingarm 11, and a pivotal connection to the lower end of the shock absorber 14. A shock absorber is pivotally engaged between the main frame upper shock mount 10 and lower shock mount 14 on the lower link 13. As the rear wheel is articulated generally upwards along its axle path, the shock absorber is compressed in length between the two mounting points providing resistance to the rear wheel's motion.

[0019] In addition to the above described members of the preferred embodiment, additional conventional elements such as those used to secure cables, brakes, drivetrain components and the like to the frame and keep them away from interfering with the movement and operation of the bicycle may also be attached at various locations. Persons of ordinary skill in the art will appreciate that the exact configuration and relationship between the chain stays 16, seat stays 18, rear wheel dropouts 15, forward swingarm assembly 17, main frame 1, upper link 12, lower link 13, idler member 7, and attachment points between all of these components can vary depending on, among other things, the size of the bicycle frame, and the size of the rear wheel. While a preferred embodiment in accordance with the present invention has been described and shown, it should be clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.

[0020] Referring to FIG. 2, the percent anti-squat can be calculated graphically by: drawing line 19 vertically through the front wheel axle 20, drawing line 21 by connecting the upper link to main frame pivot 9 through the upper link to rear wheel swingarm pivot 22, drawing line 23 by connecting the lower link to main frame pivot 12 through the lower link to rear wheel swingarm pivot 24, the intersection of lines 21 and 23 (represented as point 25) is the instantaneous force center, drawing line 26 by connecting the rear wheel dropout axis 27 with the instantaneous force center 25, drawing line 28 by connecting the top of rear cog 29 tangent to the top of idler member 30, the intersection point of lines 26 and 28 is the anti-squat instant center and is represented by point 31. To draw the anti-squat line, draw a line connecting the rear wheel's contact point with the ground 32 through point 31 and project it forwards to where it intersects line 19 (represented by point 33), this is the calculated anti-squat height measured vertically from the ground. The combined bike and rider center of gravity used in this anti-squat calculation is represented by point 34. Once the vertical height from the ground is known for points 33 and 34, the actual percentage of anti-squat is calculated by using the following equation (Anti-Squat height/Center of Gravity height)×100.

[0021] The center of gravity height is determined by taking the average center of gravity of two main riding positions (both bike and rider in a common seated pedaling position and standing position) for the average height and weight of rider for a given frame size.

[0022] It is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative only of particular embodiments and not limiting. Changes in detail or structure may be made without departing from the basic elements of the invention as defined in the following claims.