Not Applicable
Not Applicable
Not Applicable
This application relates to an apparatus which is a seat post assembly used to attach a bicycle seat to a bicycle frame which allows a rider of the bicycle to change his seat height with hands-free operations. The seat post assembly has a first portion which is fixed to the frame, a second portion, to which the seat is secured, which is slidably secured in the first portion, and one or more detents which urge the second portion to remain in one or more positions relative to the first portion, thereby providing one or more seat heights. A rider of the bicycle can adjust his seat height while riding by appropriate application and removal of forces to and from the seat.
A bicycle's seat height is an important consideration in determining a rider's power and stability. In general, a relatively high seat position is desirable so the rider can develop maximum power, but a relatively low position is desirable for stability. Therefore, an ability to adjust a bicycle's seat height is beneficial, especially if the adjustment can be made while riding. Also, since many bikes have two hand-operated derailleurs and two hand-operated brakes, an apparatus which allows seat height adjustment using hands-free operations is desirable.
Bicycle seats can be attached directly to a bicycle frame, but this makes it difficult to change seat height. A seat post is therefore typically used to make the attachment. Fixed length seat posts are most common and they normally comprise a cylindrically shaped post with a seat clamp at its top to which the seat is attached. The seat post is attached to the frame by inserting its post into a tubular member of the frame called a seat tube and securing it therein by a clamping device. A fixed length seat post allows relatively easy adjustment of seat height by changing its post's insertion depth into the seat tube, but this adjustment is difficult to perform while riding. A variation on fixed length seat posts is a class of posts called suspension seat posts which are similar to fixed length seat posts but they have a suspension mechanism to reduce impacts to the rider resulting from riding on uneven terrain.
To enable a rider to change his seat height while riding, “dropper” seat post assemblies, or “droppers” for short, have been developed. A typical dropper has a first portion comprising a sleeve which is adjustably attached to a seat tube of a bike's frame and a second portion having a post, slidably inserted in the sleeve, to which the seat is attached. It also has an energy storage device, typically a metal spring or a piston and cylinder gas spring, which urges the second portion to extend upwardly from the first portion, thus urging seat movement to a higher position. It also has a locking mechanism which can lock the second portion at desired positions relative to the first portion and a hand-operated control mechanism, typically mounted to a bike's handlebar, which allows the rider to engage or disengage the locking mechanism. A dropper therefore allows the rider to extend and retract the second portion relative to the first portion to provide respectively a high or low seat position.
Several patents pertaining to dropper seat post assemblies include U.S. Pat. No. 2,644,504 to Vick, U.S. Pat. No. 6,354,557 to Walsh, U.S. Pat. No. 7,025,522 to Sicz, and U.S. Pat. No. 8,079,772 to Brennan and Throckmorton. In U.S. Pat. No. 2,644,504, for instance, a dropper post is described which comprises a post slidably inserted into a sleeve, an energy storage device which is a spring, a locking mechanism comprising a sliding bolt which engages one of several notches in the post, and a control mechanism which is a hand-operated control knob mounted to a handlebar and connected to the bolt by a cable. If a rider wants to change seat height, he uses a hand to operate the knob to disengage the bolt from its present notch, he changes the length of the dropper by applying a force to the seat which, along with a force supplied by the energy storage device, positions the dropper at a desired length. The rider then again uses a hand to operate the knob, thereby engaging the bolt in another notch to lock the seat at a different height. This hand-operated control knob, or any hand-operated control mechanism, can be problematic because the rider is otherwise using his hands for braking or changing gears. Also, control mechanisms add additional parts and complexity when mounting a dropper seat post assembly to a bicycle.
Another type of dropper seat post assembly is described in U.S. Pat. No. 5,011,174 to Ross-Clunis in which changing seat height is a hands-free operation and does not need a control mechanism. In this adjustable height seat mechanism, a first portion slidably accepts a second portion, and these two portions are prevented from relative rotation by a guide member engaged in a guide slot which has two locking slots perpendicular to it. This mechanism's seat height is locked by positioning the guide member in either locking slot, accomplished by having a rider apply a torque to the mechanism resulting from application of a force which is perpendicular to and spaced apart from an axis of the mechanism. This torque must be applied with the mechanism's first portion in a particular position relative to its second portion wherein the guide member is positioned at one of the locking slots. This operation is inherently difficult to perform, especially when riding over rough terrain wherein forces are frequently applied which try to move the second portion relative to the first portion. When the mechanism is locked, no reasonable amount of axial force, a force which is parallel with the axis of the mechanism, applied to the mechanism will cause the first portion to move relative to the second portion.
It is desirable to have a seat post assembly for a bicycle which has one or more detents to urge the seat post assembly to have one or more preferred lengths and which therefore allows a rider to perform seat height adjustments while riding using hands-free operations.
In accordance with one embodiment of an apparatus which is a seat post assembly for a bicycle, the seat post assembly has an extended position with a detent, an intermediate position with a detent, and a retracted position. The detents urge the seat post assembly to remain in their respective positions. Because the detents do not lock but merely urge the seat post assembly to have either its extended or its intermediate length, they allow a rider of the bicycle to change his seat height while riding by application and removal of forces he applies to the seat, allowing him to easily change his seat position using hands-free operations.
Drawings of the present invention are as follows:
Bicycle seat 19, shown in
The energy storage device of assembly 1, the gas spring discussed above, provides a supporting force which urges post 20 to extend upwardly relative to sleeve 14 if a positive gauge pressure is in its cylinder. This urging is a product of the cylinder's area, an area enclosed by the inner diameter of post 20, times the gauge pressure in the cylinder. The urge to extend can be adjusted by how much gas, typically air, is introduced into the cylinder through valve 37, thereby adjusting the pressure in the cylinder. As post 20 retracts downwardly with respect to sleeve 14, plug 22 moves upwardly in post 20, the cylinder's volume decreases, the gauge pressure in the cylinder increases, and the urge to extend provided by the energy storage device of assembly 1 increases.
An axial force, a force parallel with axis 12, applied to post 20 and urging it to move with respect to sleeve 14, will urge balls 40 to move inwardly along hole 42 in plug 22 and away from holes 43 against the urging of spring 46 and ramp bushing 44 which urge them to remain against holes 43. Assuming no force is supplied by the energy storage device of assembly 1, an axial force just sufficient to move balls 40 entirely within the inner diameter of post 20, thus fully “disengaging” the detent, is called the detent's “breakaway force”.
With assembly 1 in its extended position with its extended position detent engaged, assembly 1 can support a rider with an extended position supporting force which includes a supporting force provided by its energy storage device when assembly 1 is in its extended position and the breakaway force provided by the detent. A rider normally has a portion of his weight supported apart from seat 19. For instance, his arms are at least partially supported by a handlebar and his feet and legs are at least partially supported by a pair of pedals. An extended position supporting force which is less than the rider's total weight is therefore satisfactory for operation of assembly 1. An extended position supporting force which is approximately 50-65% of the rider's weight works well in preventing unwanted disengagement of the detent while allowing the rider to apply reasonable downward force to seat 19 to overcome the extended position supporting force, disengage the detent, and lower seat 19. Adjustment of the extended position supporting force of assembly 1 can be accomplished primarily in a couple of ways. Firstly, the supporting force provided by its energy storage device can be adjusted by changing the pressure in the gas spring's cylinder. Secondly, the detent's breakaway force can be adjusted by turning screw 48 to change the force applied by spring 46 to ramp bushing 44 and hence the outward force applied to balls 40 which presses them against holes 43. If screw 48 is turned so that the compression in spring 46 is increased, this increases the detent's breakaway force, and vice versa.
This selection of a supporting force for assembly 1 which is less than the rider's weight means assembly 1 can provide another important benefit to the rider, the benefit that assembly 1 performs as a suspension seat post. Since assembly 1 is only urged to remain in its extended position by its extended position supporting force rather than being “locked” in this position as in other “droppers”, the amount of force which assembly 1 can transmit upwardly to the rider through seat 19 as a result of the bicycle traveling over rough terrain is reduced from that which would be delivered by a fixed length seat post or a conventional dropper with a locking mechanism.
Bicycle seat 19, shown in
The energy storage device of assembly 51, spring 78, provides a supporting force which urges post 60 to extend upwardly from sleeve 14 if there is a compression in spring 78. Spring 78 is shown as a coiled wire spring, and it has a spring rate. The urging of spring 78 at any position of post 60 relative to sleeve 14 has a magnitude which is the spring rate of spring 78 times its compression at that position. For instance, the extensional urging of spring 78 when assembly 51 is at its extended position is the spring rate of spring 78 times its compression when assembly 51 is at its extended position.
A downward axial force applied to post 60 will urge post 60 with its entrance 81 to move downwardly with respect to sleeve 14, therefore urging o-ring 80 to move downwardly off the large diameter portion 82 of plug 62. Assuming no force is supplied by the energy storage device of assembly 51, an axial force just sufficient to move o-ring 80 off the large diameter portion of plug 82 and onto the small diameter portion 83, thereby allowing o-ring 80 to slide inside post 60 and thus disengaging the extended position detent, is the extended position detent's breakaway force. Therefore, assembly 51, when in its extended position with its extended position detent engaged, can support a rider with an extended position supporting force which includes a supporting force provided by its energy storage device, spring 78, when assembly 51 is in its extended position and the breakaway force of the extended position detent. Other than in the construction of their detents, assemblies 1 and 51 operate similarly when in their extended positions.
As in assembly 1, an extended position supporting force which is about 50-65% of the rider's weight works well for assembly 51. Adjustment of the extended position supporting force can be accomplished primarily in two ways. Firstly, the supporting force supplied by the energy storage device can be adjusted by changing the load in spring 78 when assembly 51 is in its extended position, either by changing the characteristics of spring 78, such as its spring rate and/or free length, or by changing its initial compression. Secondly, the extended position detent's breakaway force can be adjusted by turning screw 88 to change the compression of spring 86 and hence the force it applies to o-ring 80 to hold it on the large diameter portion 82 of plug 62. Turning screw 88 to increase the compression in spring 86 will increase the extended position detent's breakaway force, and vice versa.
The intermediate position detent of assembly 51, when engaged as shown in
When assembly 51 is in its intermediate position with its intermediate position detent engaged, the intermediate position detent of assembly 51, like its extended position detent, can support a portion of a rider's weight. But this intermediate position detent of assembly 51 also provides an additional benefit to the rider of the bicycle. In many cases, a rider wants to be “behind his seat”; he wants seat 19 to be in a low position and out of the way so he can readily get rearward of it and move side to side to improve his handling of the bicycle. As discussed above, when the intermediate position detent of assembly 51 is engaged, it urges assembly 51 to remain in its intermediate position and not retract. But the breakaway force of this detent works in both directions, in extension and in retraction; in other words, the intermediate position detent, when engaged, also urges assembly 51 to not extend. If the intermediate position detent's breakaway force is greater than the urge to extend provided by spring 78 when assembly 51 is in its intermediate position, then the intermediate position detent can hold assembly 51 in its intermediate position against the urging of spring 78 to extend assembly 51, even if the rider removes all his weight from seat 19. Therefore, the intermediate position detent of assembly 51 provides two benefits when engaged. Firstly, it provides a portion of the intermediate position supporting force described above, and secondly, with its breakaway force adjusted so that it is greater than the urge to extend provided by spring 78 when assembly 51 is at its intermediate position, the intermediate position detent can hold assembly 51 in its intermediate position even if the rider removes all his weight from seat 19.
With assembly 51 in its retracted position, the rider can remove some of his weight from the bicycle seat and allow post 60 to move upwardly with respect to sleeve 14. With proper removal of his weight, the rider can cause assembly 51 to move to its intermediate position and be held there by the intermediate position detent, or he can allow assembly 51 to extend to its extended position. If the rider wants assembly 51 to be held at its intermediate position, he can accomplish this by removing only a portion of his weight from the bicycle seat, causing assembly 51 to extend slowly. Therefore items which are moving upwardly with respect to sleeve 14, such as seat 19 and some components of assembly 51, have a momentum which is relatively small due to their slow speed. If this momentum is kept sufficiently small by the rider when assembly 51 is at its intermediate position, the intermediate position detent will engage and hold assembly 51 at that position against the extensional urging of spring 78. If the rider wants assembly 51 to move from its retracted position to its extended position, this can be accomplished if he removes a sufficient portion of his weight from seat 19 to allow spring 78 to extend assembly 51 relatively rapidly. In this case, the intermediate position detent will not be able to engage due to an impulse provided by a momentum resulting from the relatively rapid upward movement of some components of assembly 51 and seat 19 resulting from the extensional urging of spring 78.
In the operation of assembly 51, it is important to note the usefulness of its intermediate position with its detent as well as its retracted position. In almost any riding situation, it is relatively easy for a rider to apply more or less of his weight to seat 19. But in a racing or otherwise technical riding situation, the rider must almost always have both hands on the handlebars and therefore it is nearly impossible for the rider to actually pull up on seat 19 or any other part of assembly 51. In other words, when the intermediate position detent of assembly 51 is engaged and assembly 51 is held at its intermediate position, it cannot be assumed that the rider can apply an upward force to post 60 to release the intermediate position detent. By placing the intermediate position detent at the intermediate position but allowing assembly 51 to further retract from the intermediate position to the retracted position, this allows the rider to apply a downward force to release the intermediate position detent and move assembly 51 to its retracted position. In moving assembly 51 from its intermediate position to its retracted position, additional energy is stored in the energy storage device of assembly 51, namely spring 78. This additional energy can be used to provide an upward momentum to the upwardly moving parts of assembly 51 and seat 19. As discussed above, this momentum can be used to prevent the intermediate position detent from engaging as post 60 is moving upwardly with respect to sleeve 14 and thereby allowing spring 78 to continue moving post 60 past its intermediate position and on to its extended position. Therefore, a benefit of having the retracted and intermediate positions of assembly 51 is to allow the rider, using hands-free operations, to return assembly 51 to its extended position from its intermediate position where it was held by its intermediate position detent.
A prototype of assembly 51 which worked well for a rider having a weight of 68 kgf (150 pounds) was constructed with the following parameters. The prototype had an extended position, and it had an intermediate position and a retracted position in which post 60 was retracted into sleeve 14 a distance of 8.9 cm (3.5 inches) and 9.9 cm (3.9 inches) respectively from its extended position. Spring 78 was a coiled wire spring having a spring rate of 4.0 N/cm (2.3 pounds/inch) and a compression at the prototype's extended position wherein spring 78 supplied a supporting force at the extended position of about 89 N (20 pounds). The prototype had an extended position detent which used an o-ring 80 having a size 207 and a material 90A durometer nitrile. Spring 86 of the extended position detent was adjusted so that the extended position detent's breakaway force was about 285 N (65 pounds). Adding the supporting force of spring 78 at the extended position (89 N (20 pounds)) to the breakaway force of the extended position detent (285 N (65 pounds)) gives an extended position supporting force of the prototype of 374 N (85 pounds) which is about 57% of the rider's weight. Movement of the prototype from its extended position to its intermediate position and its retracted position caused the compression of spring 78 to increase by 8.9 cm (3.5 inches) and 9.9 cm (3.9 inches) respectively, so that spring 78 supplied a supporting force at the intermediate position and the retracted position of 6.3 N (28 pounds) and 6.5 N (29 pounds) respectively. The prototype had an intermediate position detent which had balls 90 which were made of steel with a diameter of 0.79 cm (0.312 inches) and which had holes 93 in post 60 with a diameter of 0.71 cm (0.281 inches). By turning screw 98 to change the compression in spring 96, the intermediate position detent's breakaway force was adjusted to about 7 N (31 pounds), making it slightly greater than the extensional urging of spring 78 when the prototype was at its intermediate position. This prototype supported the rider at the extended position with few “nuisance” retractions, it could be moved by the rider to its intermediate position and held there using the intermediate position detent, and it could be moved by the rider to its retracted position and then to its extended position, all movements being performed using hands-free operations.
Accordingly, the reader will see that the two embodiments presented are bicycle seat post assemblies which can be moved between an extended position to provide a rider with a relatively high seat height and a retracted position to provide him with a relatively low seat height. In these two assemblies, a detent is used to support a portion of the rider's weight when the assemblies are at their extended positions. In the second embodiment, the second assembly also has a detent at a position intermediate to the extended and retracted positions which can hold the second assembly in the intermediate position absent a force applied to the seat by the rider, but the rider, with an appropriate application and removal of forces to his seat, can position the second assembly in its retracted position and then allow it to return to its extended position. All movements of these assemblies can be performed by the rider using hands-free operations.
Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of several embodiments. For instance, in the second embodiment, a third detent could be added at a second intermediate position. Also, in the second embodiment, the extended position detent could be of the same form as the intermediate position detent, namely one which uses balls instead of one which uses an o-ring as described. Also, the diametrical step in the extended position detent of the second embodiment is the entrance to its post, but other diametrical steps such as steps farther inside the post could also be used. Also, a detent which only uses one ball could be used. The scope of the invention should be determined by the appended claims and their legal equivalents rather than by the examples given.