Bicycle seat post shock absorber assembly

A bicycle seat supporting device is of the type having a shock absorber mounted within an elongated tubular housing which telescopingly receives a lower end of a shaft opposite to the upper seat mounting portion, a roller bearing being positioned to engage a flat surface portion on the shaft to prevent relative rotation between the shaft and housing, and an adjustable locking member effectively renders the shock absorber unit inoperative by preventing longitudinal movement between the shaft and the housing member.

This invention relates to seat post assemblies for vehicles, such as, 
bicycles or motorcycles; and more particularly relates to a novel and 
improved seat post assembly of the type having a shock absorber which can 
be selectively locked out by the cyclist so as to be rendered inoperative. 
BACKGROUND AND FIELD OF THE INVENTION 
Numerous types of seat post supporting devices have been designed over the 
years to the end of increasing riding comfort for the bicycle rider. One 
of the more popular approaches has been to incorporate a shock absorber 
into a housing which receives the seat post so as to cushion any shocks. 
There are occasions when it is desirable to block out the shock absorber, 
for example, in pedaling uphill, or in mounting or dismounting. Moreover, 
it is desirable to be able to adjust the height between the telescoping 
seat post and housing member, and it is important that the cyclist be able 
to control the height of the seat as well as to selectively lock the shock 
absorber unit in and out without having to dismount. A particular problem 
encountered in the telescoping seat post assemblies now in use is that of 
effectively locking the seat and seat post against rotation with respect 
to the housing and for preventing the seat post from binding when the 
weight or load of the rider is applied. These problems have been 
previously addressed and representative of the approaches which have been 
taken in the past is the seat support assembly set forth and described in 
U.S. Pat. No. 4,182,508 to C. Kallai et al wherein a latch is utilized 
with a protrusion on one telescoping member which will fit into an 
aperture on the other telescoping member to prevent relative rotation 
therebetween. In U.S. Pat. No. 2,467,676 to R. A. Labine a supplemental 
spring suspension is employed although not for the express purpose of 
preventing rotation of the main seat post. In U.S. Pat. No. 4,421,357 To 
K. Shimano, the seat frame itself is designed in such a way as to 
discourage relative rotation between the seat post and saddle. Other 
representative patents are U.S. Pat. Nos. 4,502,727 to S. A. Holcomb et 
al; and 2,639,760 to F. Von Szilagyi. 
There continues to be a need for a telescoping seat post assembly for 
cycles in which the telescoping members can be effectively locked against 
rotation with respect to one another and nevertheless facilitate vertical 
adjustment and not be subject to loosening under constant jarring or 
vibration. In this relation, it is highly desirable that a single locking 
member be provided both for height adjustment of the seat and selectively 
locking out the shock absorber; and further wherein the telescoping 
members are fixed against relative rotation, irrespective of whether the 
shock absorber is in use, while at the same time being freely telescoping 
or movable without binding. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide for a 
novel and improved telescoping seat post assembly for cycles, particularly 
motorcycles and bicycles, which is highly dependable and effective in use. 
It is another object of the present invention to provide for a novel and 
improved telescoping seat post assembly including a shock absorber unit 
associated with the assembly which can be selectively rendered inoperative 
when desired by the rider and wherein the assembly is capable of fixing 
the telescoping members against rotation irrespective of whether the shock 
absorber unit is in use. 
It is a further object of the present invention to provide for a novel and 
improved telescoping seat post assembly for bicycles in which the 
telescoping members are not subject to relative rotation while being 
freely movable lengthwise with respect to one another. 
An additional object of the present invention is to provide in a 
telescoping seat post assembly of the type having an inner telescoping 
shaft extending through an outer housing for a bearing member on the outer 
housing which is engageable with a flat bearing surface on the shaft in 
such a way as to prevent binding and to absorb a major part of the load; 
and the bearing member can be incorporated as a part of a locking unit to 
permit selective height adjustment of the bicycle seat. 
In accordance with the present invention, a telescoping seat-supporting 
device for cycles, such as, motorcycles and bicycles has been devised and 
which comprises in combination an elongated shaft having an upper 
seat-mounting portion and a flat surface portion extending longitudinally 
along an exterior surface portion of the shaft beneath the seat-mounting 
portion, an elongated tubular housing member for telescopingly receiving 
an end of the shaft opposite to the seat-mounting portion, bearing means 
mounted on the housing member engageable with the flat surface portion 
whereby to prevent relative rotation between the shaft and the housing 
member while being free to roll freely in a lengthwise direction along the 
flat surface portion, and adjustable locking means between the shaft and 
the housing member for preventing relative longitudinal movement between 
the shaft and the housing member. In a preferred embodiment of the present 
invention, it is desirable to incorporate shock absorbing means in the 
housing member to yieldingly resist downward movement of the shaft 
relative to the housing member, and the adjustable locking means is 
operative to selectively lock out the shock absorbing means when the shaft 
is locked against relative longitudinal sliding movement with respect to 
the housing member. 
The preferred form of bearing means is a roller bearing mounted in the 
housing member for rotation about an axis transverse to the longitudinal 
axis of the shaft which roller bearing will rollingly engage the flat 
surface portion on the shaft to fix the shaft against relative rotation 
with respect to the housing member and will absorb a substantial part of 
the load applied through the shaft while permitting it to advance freely 
in either longitudinal direction with respect to the housing member. 
The above and other objects, advantages and features of the present 
invention will become more readily appreciated and understood from a 
consideration of the following detailed description when taken together 
with the accompanying drawings in which:

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring in more detail to the drawings, there is shown in FIGS. 1 to 5 a 
preferred form of seat post assembly 10 for a bicycle seat S. The assembly 
10 is broadly comprised of an elongated shaft 12 having an upper 
seat-mounting portion in the form of an enlarged cylindrical end 13, a 
cushioning washer 14 located at the undersurface of the portion 13, and a 
flat milled surface portion 16 extends longitudinally along and is formed 
out of an exterior surface portion of the shaft 12. It should be noted 
that the surface portion 16 extends the greater length of the shaft but 
terminates short of lower cylindrical end 17 of the shaft. A seat post 
housing is in the form of a hollow cylindrical member or tube 18. The tube 
18 includes a cylindrical liner 20 composed of a rugged low coefficient of 
friction material, such as, Nylon for close-fitting but slidable insertion 
of the shaft 16. In this regard, the shaft 16 is of a uniform external 
diameter, except for the flat surface portion 16, and the inner diameter 
of the liner 20 extends along the substantial length of the tube 18 but 
terminates just short of its lower end. 
A shock absorber assembly is generally designated at 22 and comprises a 
guide rod 24 including an upper end portion 25 inserted in a counterbore 
at the lower end of the shaft 12 and affixed by a crosspin 27. The guide 
rod has a lower threaded end 28 for reception of a nut 30, flat metal 
washer 31 and a plurality of rubber cushioning washers as generally 
designated at 32. The washers 31 and 32 are interposed between the upper 
end of the nut 30 and a snap ring 33 inserted in an internal groove in the 
wall of the outer tube 18. A Nylon bushing 34 is interposed between the 
snap ring 33 and lower end of a coiled spring 35 which is disposed in 
surrounding relation to the guide rod and with the upper end of the spring 
35 bearing against the lower end 17 of the shaft 12. In this relation, the 
coil spring is mounted under compression between the bushing 34 and lower 
end 17 so as to yieldingly resist any downward movement of the shaft 12 
and seat S. 
In accordance with conventional practice, a generally bellows-shaped, 
rubber boot 36 is disposed in surrounding relation to the upper end of the 
shaft 12, the upper extremity of the boot being clamped or otherwise 
secured to the washer 14 as indicated at 37 and the lower end being 
clamped as designated at 38 to the upper end of the tube 18. As shown in 
FIG. 1, the tube 18 may be mounted within a tubular frame member F of a 
bicycle and clamped in position in a conventional manner, not shown. 
An important feature of the present invention resides in adjustable locking 
assembly 40 which is preferably disposed in a recess 39 which extends 
through the full thickness of the wall of the tube 18. The assembly 40 
comprises an outer housing 41 in which is journaled a bearing member in 
the form of a roller bearing 42 journaled on a bearing axle 44. The axle 
44 is removably inserted across the housing so as to extend transversely 
with respect to the longitudinal axis of the tube 18 and causes the 
bearing 42 to firmly engage the flat surface portion 16 of the shaft 12. 
In this way, the roller bearing 42 is free to roll in a longitudinal 
direction with respect to the shaft 16 but prevents relative rotation 
between the shaft 12 and the tube 18. The liner 20 has sufficient give 
that it will effectively preload the surface 16 of the shaft 12 against 
the roller bearing 42, although it will be appreciated that the bearing 
itself may be preloaded to assure that it exerts a constant pressure 
against the shaft 12. 
In order to selectively lock the shaft 12 against longitudinal movement 
with respect to the tube 18, a brake pad 50 including an inner frictional 
brake lining 51 is disposed in the housing 41 to bear against the surface 
portion 16 directly beneath the roller bearing 42. The brake pad is 
selectively adjusted for radial movement toward and away from the surface 
portion 16 by a threaded stem 54 having an enlarged end portion 55 
externally of the housing 41. The end 55 includes a hexagonal-shaped 
recess 56 which is engaged by locking lever 60 for threaded adjustment of 
the brake pad 50 toward and away from the surface portion 16. As shown in 
FIGS. 2, 4 and 5, the lever assembly 60 includes a lever arm 61 which 
terminates in an enlarged generally circular head 62 provided with a 
hollow interior which is adapted to be placed over the end portion or pin 
56. A set screw 62 in a sidewall of the head 61 is provided for locking 
the head 61 against the end 56 and to prevent accidental removal. In 
addition, an internal pin 58 within the hollow interior of the head 61 is 
of hexagonal-shaped cross-section to conform to the cross-sectional size 
and configuration of the interior of the end 56 so that rotational 
movement of the lever arm 60 will cause corresponding movement of the 
threaded stem 54 in advancing the brake pad 50 toward and away from the 
surface portion 16. 
The stem 54 is threaded such that clockwise rotation of the lever arm 60 
will impart inward threaded movement of the brake pad against the surface 
portion to effectively lock the shaft 12 against longitudinal movement. 
For example, this is desirable in mounting or dismounting by exerting 
downward pressure on the seat against the upward urging of the spring 35 
thereby lowering the seat and locking it in position either for the 
purpose of mounting or dismounting. In riding the bicycle, it may be 
desirable also to lock the seat against slidable movement, for example, in 
pedaling uphill. When the seat post and seat are locked out in this 
manner, the brake pad 50 will effectively cooperate with the roller 
bearing 42 in preventing any relative rotation between the shaft 12 and 
tubular housing 18. 
Conversely, when the lever arm 61 is rotated in a counterclockwise or 
downward direction, it will be threaded outwardly to release the brake pad 
50 from engagement with the surface portion 16 and permit the upper shaft 
to slide freely in a longitudinal direction with respect to the tube 18. 
The roller bearing 42 will continue to maintain pressure against the flat 
surface portion 16 thereby preventing relative rotation between the shaft 
12 and the tube 18 and in this way effectively fix the seat S against 
rotation whether or not the shaft 12 is locked against longitudinal 
slidable movement. In a conventional manner, the boot 36 will effectively 
seal or encapsulate the shaft 12 with respect to the tube 18 to prevent 
entry of dirt or other foreign matter. 
In the preferred form of invention as described, the housing 41 is of 
generally rectangular configuration and is formed as an integral part of 
the housing 18 by welding the outer walls of the housing to the 
correspondingly shaped surrounding edge of the recess 39 so that the 
innermost edge of the housing projects into the thickness of the tube 18 
and stops outwardly of the inner liner portion 20 and above the enlarged 
lower end 17 of the shaft. For this reason, the bearing 42 is installed in 
the recess 39 after the shaft 12 has been inserted into the tube 18 and 
will limit upward sliding movement of the shaft 12 to the position shown 
in FIG. 2. In the alternative, it will be appreciated that the lever arm 
assembly 40 may be a self-contained unit including a sleeve member which 
would be affixed to the upper end of the tube 18 so that it can be 
retrofit for existing bicycle seat post assemblies. In other words, the 
housing 40 could be inserted over the upper end of the tube and held or 
locked in place by set screws or other suitable attaching means and avoid 
the need for the recess 39 in the tube 18. 
It will be further evident from the description of the preferred form of 
invention that more than one bearing member may be employed to work in 
cooperation with flat surface portions at opposite sides of the shaft 12 
in fixing the shaft 12 against rotation with respect to the tube 18. Still 
further, it will be evident that the bearing member 42 as described may be 
used either with or without a shock absorber assembly in order to prevent 
the rotation of the seat S with respect to the tube 18. As illustrated in 
FIG. 1, the frame F of the bicycle which receives the housing member 18 
typically inclines in an upward rearward direction so that the weight of 
the rider when seated on the bicycle is applied downwardly and somewhat 
vertically against the rearward surface of the housing 18 and frame F. It 
is therefore important that the roller bearing 42 be oriented along the 
rearward inclined surface of the housing so as to absorb a greater part of 
the load as applied downwardly through the rearward flat surface of the 
shaft 12. This will also greatly minimize any tendency of the shaft to 
bind against the inner surface of the tube 18. 
It is therefore to be understood that various modifications and changes may 
be made in the construction and arrangement of elements comprising the 
preferred form of invention as set forth without departing from the scope 
of the invention as defined by the appended claims.