BACKGROUND OF THE INVENTION Adjustable bicycle seats are known in the art and are primarily designed to increase comfort and body power when riding on non-level terrains. For example, United States Patent 5,297,846 to Rafter describes a pivoting bicycle seat assembly. The assembly includes a primary seat and a secondary seat, and the entire seat assembly pivots about a single point. For normal riding, a rider sits on the primary seat. For uphill climbing, the rider can swing the seat assembly forward such that the secondary seat is position for supporting the rider in a standing position.

United States Patent 5,344,170 to Ochoa describes a bicycle seat assembly that permits a bicycle seat to rotate or to be laterally displaced short distances in order to absorb movement of a rider's body.

United States Patent 5,346,235 to Holman describes a pivoting bicycle seat that includes a set of pivoted parallel bars which maintain the bicycle seat in a constant orientation throughout adjustment of the seat along an arced rack. The arced rack has a series of detents for positioning contact with a spring loaded locking member. The seat can be selectively positioned along the arced rack by selectively spring-locking the locking member with one of the detents. The set of pivoted parallel bars maintains the bicycle seat in a constant orientation with respect to the bicycle frame, but does not maintain a horizontal orientation of the seat at all times.

United States Patent 5,352,016 to Hobson describes a bicycle seat with an adjustable base that can be made narrower or broader during riding.

United States Patent 5,395,155 to Yach describes an adjustable bicycle seat assembly having an in situ operator controlled seat position changing apparatus.

United States Patent 5,513,895 to Olson et al describes an adjustable bicycle seat assembly wherein a seat is affixed to a sliding block which is received in an elongate slot formed in a body member secured to the bicycle so that the seat can be moved to different positions along the body member under the control of a rider.

SUMMARY OF THE INVENTION The present invention seeks to provide an improved adjustable bicycle seat

system. The system maintains a horizontal orientation of the seat at all times, thereby increasing seating comfort and convenience. In other words, the seat is always parallel to a horizontal reference plane, no matter how the frame of the bicycle is oriented.

The present invention helps achieve proper balance of pressure between the front and rear wheels of the bicycle, which is very important for safe and efficient riding. When riding uphill, proper pressure on the front wheel helps maintain steering control. Pressure on the rear wheel is important in order not to lose drive power. When riding downhill, too much pressure on the front wheel is liable to cause the rider to topple forwards; too much pressure on the rear wheel is liable to cause the rider to topple backwards. In the present invention, by constantly maintaining a horizontal orientation of the seat, a proper balance of pressure between the front and rear wheels of the bicycle is also maintained. The rider's center of gravity is maintained approximately above a midpoint between contact points of the front and rear wheels with the ground.

There is thus provided in accordance with a preferred embodiment of the present invention, a bicycle including a frame defining a pedal crank axis, a back wheel axis and a front sprocket axis, a front wheel and handlebar assembly mounted onto the frame for pivotable movement relative to the front sprocket axis, a curved seat mounting track attached to the frame and defining a curved path, a seat selectably mountable at any position along the curved seat mounting track, and a user controllable seat positioning assembly for selectably and changeably determining the position of the seat along the curved seat mounting track.

There is also provided in accordance with a preferred embodiment of the present invention, a bicycle including a frame defining a pedal crank axis, a back wheel axis and a front sprocket axis, a front wheel and handlebar assembly mounted onto the frame for pivotable movement relative to the front sprocket axis, a seat mounting assembly attached to the frame and defining a path that extends along a portion of a periphery of a conical section, a seat selectably mountable at any position along the path, wherein the conical section has a focus disposed closer to the pedal crank axis than to the seat, and a user controllable seat positioning assembly for selectably and changeably determining the position of the seat along the path.

In accordance with a preferred embodiment of the present invention the curved seat mounting track extends along a portion of a periphery of a conical section. Preferably the conical section has a focus disposed closer to the pedal crank axis than to the seat, and the focus is preferably located generally between the pedal crank axis and the seat.

Additionally in accordance with a preferred embodiment of the present invention, the path extends forwardly and upwardly with respect to the frame, such that as the seat is moved upwardly, it moves away from the pedal crank axis.

Further in accordance with a preferred embodiment of the present invention, the path extends forwardly and upwardly with respect to the frame, such that as the seat is moved upwardly or downwardly along the path, a rider sitting on the seat maintains his center of gravity generally vertically above a midpoint midway between contact points of front and rear wheels of the bicycle with the ground.

Still further in accordance with a preferred embodiment of the present invention, the user controllable seat positioning assembly includes a biasing mechanism which urges the seat forwardly and upwardly generally along the path and a stopper which applies a force against the biasing mechanism so as to arrest movement of and fixedly hold the seat along the path.

In accordance with a preferred embodiment of the present invention, a cable assembly is attached to the handlebar assembly which actuates the user controllable seat positioning assembly.

Additionally in accordance with a preferred embodiment of the present invention, a control system is provided which automatically controls an operation of the user controllable seat positioning assembly so as to automatically adjust a position of the seat along the path in accordance with a riding condition.

There is also provided in accordance with a preferred embodiment of the present invention, a method for adjusting a position of a rider riding a bicycle, including maintaining a seat of the bicycle generally horizontal, and maintaining a generally constant orientation of a gravity vector from the seat towards a midpoint midway between contact points of front and rear wheels of the bicycle with a ground surface In accordance with a preferred embodiment of the present invention, the method also includes moving the seat of the bicycle along a path that extends along a portion of a periphery of a conical section, the conical section having a focus disposed closer to the pedal crank axis of the bicycle than to the seat.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which: Fig. 1 is a simplified pictorial illustration of a bicycle and adjustable bicycle seat

system, constructed and operative in accordance with a preferred embodiment of the present invention; Fig. 2 is a simplified pictorial illustration of a rider riding the bicycle of Fig. 1 on a riding surface of an uphill terrain with a slope a; Fig. 3 is a simplified pictorial illustration of a rider riding the bicycle of Fig. 1 on a riding surface of a downhill terrain with a slope ; Fig. 4 is a simplified exploded illustration of the adjustable bicycle seat system ofFig. 1; Fig. 5 is a simplified pictorial illustration of the adjustable bicycle seat system of Fig. 1, in an orientation for fixing a bicycle seat with respect to a curved path; Fig. 6 is a simplified sectional illustration of a portion of the adjustable bicycle seat system of Fig. 5, taken along lines VI - VI in Fig. 5 Fig. 7 is a simplified sectional illustration of another portion of the adjustable bicycle seat system of Fig. 5, taken along lines VII - VII in Fig. 5; Fig. 8 is a simplified sectional illustration of a portion of the adjustable bicycle seat system of Fig. 5, in an orientation for permitting movement of the bicycle seat along the curved path, taken along lines VIII - VIII in Fig. 5; and Fig. 9 is a simplified sectional illustration of another portion of the adjustable bicycle seat system of Fig. 5, taken along lines IX - IX in Fig. 5.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Reference is now made to Fig. 1 which illustrates a bicycle 10 and adjustable bicycle seat system 12, constructed and operative in accordance with a preferred embodiment of the present invention.

Bicycle 10 preferably includes a frame 14 defining a pedal crank axis 16, a back wheel axis 18 and a front sprocket axis 20. A front wheel and handlebar assembly 22, including handlebars 23, is preferably mounted onto frame 14 for pivotable movement relative to front sprocket axis 20. A front wheel 24 rotates about front sprocket axis 20 and a rear wheel 26 rotates about back wheel axis 18.

In accordance with a preferred embodiment of the present invention, a curved seat mounting track 30 is attached to frame 14 and defines a curved path 32. A user controllable seat positioning assembly 34 is provided for selectably and changeably determining the position of a seat 36 along curved seat mounting track 30, as will be described more in detail hereinbelow. Curved seat mounting track 30, user controllable seat positioning assembly

34 and seat 36 form an adjustable bicycle seat system 40. Preferably a cable assembly 42, including an actuating lever 44, is attached to handlebar assembly 22 for actuating seat positioning assembly 34, as will be described hereinbelow.

It may be appreciated from Fig. 1 that curved seat mounting track 30 and path 32 preferably extend along a portion of a periphery of a conical section, such as an ellipse, parabola, hyperbola or circle. In a most preferred embodiment, the conical section is a circle.

Alternatively, path 32 may comprise any other non-straight path, such as sinusoidal. The conical section preferably has a focus 46 located generally between pedal crank axis 16 and seat 36. Focus 46 is most preferably disposed closer to pedal crank axis 16 than to seat 36.

Preferably path 32 extends forwardly and upwardly with respect to frame 14, such that as seat 36 is moved upwardly, it moves away from pedal crank axis 16. Conversely, as seat 36 is moved downwardly, it moves towards pedal crank axis 16.

Fig. 1 illustrates a rider 50 riding bicycle 10 on a riding surface of a generally horizontal terrain. Reference is now made to Fig. 2 which illustrates rider 50 riding bicycle 10 on a riding surface of an uphill terrain with a slope a. Rider 50 may use seat positioning assembly 34 to move seat 36 forward an angle a to correspond to the uphill slope, thereby maintaining seat 36 generally horizontal and approximately maintaining his/her center of gravity 52 generally vertically above a midpoint A midway between contact points B and C of front and rear wheels 24 and 26 with the ground, respectively. Most bicycles are manufactured such that midpoint A is approximately directly below pedal crank axis 16.

In riding uphill, many riders strive to be over the pedals, thereby forcing the rider to an almost standing position. The seat of the present invention permits the rider to achieve an almost standing position while riding uphill, yet remain comfortably seated on seat 36.

Reference is now made to Fig. 3 which illustrates rider 50 riding bicycle 10 on a riding surface of a downhill terrain with a slope . Rider 50 may use seat positioning assembly 34 to move seat 36 backward an angle to correspond to the downhill slope, thereby maintaining seat 36 generally horizontal and approximately maintaining his/her center of gravity 52 generally vertically above midpoint A.

In sharp descents, it may be important for a rider to be able to reach the ground with his/her feet in case of an emergency and get off the bicycle. This is possible with the present invention by sufficiently lowering seat 36 during a descent.

Rider 50 may manually adjust the position of seat 36 while riding. As optionally

shown in Fig. 1, a control system 54 may be provided which automatically controls an operation of user controllable seat positioning assembly 34 so as to automatically adjust a position of seat 36 along path 32, while riding, in accordance with a riding condition. Control system 54 preferably includes a slope sensor 56, such as a clinometer, which senses the slope of the riding surface. Slope sensor 56 sends a signal to an actuator 58 which actuates user controllable seat positioning assembly 34 to adjust the position of seat 36 along path 32 in accordance with the sensed slope so as to maintain seat 36 generally horizontal, and to maintain a generally constant orientation of a gravity vector from seat 36 towards pedal crank axis 16. Actuator 58 may be an electrically powered solenoid, for example, which pulls a cable of cable assembly 42 to actuate user controllable seat positioning assembly 34.

Slope sensor 56 may signal actuator 58 in a variety of manners known in the art. For example, slope sensor 56 may comprise an electronic clinometer which sends electrical signals to actuator 58 in accordance with a sensed angle. Alternatively, slope sensor 56 may comprise a metallic ball or mercury which slides in a tube and makes electrical contact with contacts positioned along the tube so as to send electrical signals to actuator 58 in accordance with a sensed angle.

Reference is now made to Figs. 4 - 7 which further illustrate adjustable bicycle seat system 40 of Fig. 1. Curved seat mounting track 30 is preferably formed with a seat mounting portion 48 to which attaches seat 36 (Figs. 1 - 3), and with a longitudinal aperture 50 for receiving therein a correspondingly curved tube 52. User controllable seat positioning assembly 34 of system 40 preferably includes a track holding element 54 fixedly attached to a seat post 56 of bicycle frame 14. Track holding element 54 has a groove 58 formed therein for slidingly receiving therein track 30.

Seat positioning assembly 34 preferably includes a yoke 60 through which pass track holding element 54, curved seat mounting track 30 and a spring holding element 59.

Yoke 60 is preferably formed with a hole 62 (Fig. 4) through which passes a pin 64 to which is connected a cable 66 of cable assembly 42. A screw or rivet 68 may be used to fixedly attach cable 66 to pin 64. Cable 66 is preferably guided by a pair of rollers 70 and 72 which may be rotatably attached to seat post 56 by means of pins 74 and 76.

Yoke 60 is also preferably formed with a hole 78 (Fig. 4) through which passes a pin 80. A biasing mechanism, such as a longitudinal spring 82, is preferably disposed inside tube 52. One end of longitudinal spring 82 is preferably fastened to an end of tube 52 by a fastening pin 84 and an opposite end of longitudinal spring 82 is fastened to spring holding

element 59 by another fastening pin 86. Longitudinal spring 82 is preferably compressed in the orientation of Figs. 4 - 7, thereby urging seat 36 (Figs. 1 - 3) forwardly and upwardly generally along path 32. It is appreciated that other biasing mechanisms may be used.

Fastening pin 86 effectively fixes spring holding element 59 together with track 30. As seen in Fig. 6, yoke 60 is preferably configured such that pins 64 and 80 normally abut against track holding element 54 and spring holding element 59, thereby forcing spring holding element 59 and track 30 towards track holding element 54 and thus sandwiching and fixedly holding track 30.

Optionally, a plug element 90 may be rotatably fastened to a base 92 of track holding element 54 by means of a pin 94. As seen in Fig. 7, pin 94 abuts against both spring holding element 59 and track holding element 54. Plug element 90 preferably includes a dowel 96 on which is disposed a spring 98. Spring 98 biases against plug element 90 at one end thereof and against a surface 99 of spring holding element 59 at an opposite end thereof.

As mentioned above, and as seen in Fig. 6, yoke 60 normally forces track holding element 54 against track 30 and spring holding element 59, thereby fixedly holding track 30 in place against the forward and upward force exerted upon track 30 by longitudinal spring 82. Yoke 60 thus acts as a stopper that applies a force against the biasing mechanism (longitudinal spring 82) so as to arrest movement of and fixedly hold seat 36 (Figs. 1 - 3) along path 32.

Release of the biasing mechanism and operation of seat positioning assembly 34 will now be described with additional reference to Figs. 8 and 9. By suitable movement of actuating lever 44, cable 66 may be pulled generally in the direction of an arrow 100. This movement causes yoke 60 to rotate slightly about pin 80, which in the sense of Figs. 6 and 8 causes pin 64 and the right side of yoke 60 to move out of the page towards the reader of this disclosure. This movement releases the force yoke 60 applies between spring holding element 59 and track holding element 54, and permits longitudinal spring 82 to apply a generally upward and forward force against track 30 and spring holding element 59, thereby to move seat 36 (Figs. 1 and 3) generally upward and forward.

It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the present invention is defined only by the claims which follow: