# Patent

## Title
Method and apparatus for an adjustable damper

## Abstract

An air bleed system for a suspension fork or shock absorber includes: a fluid passage between an interior of the suspension and an exterior of the suspension; and a manually operable valve having a first position substantially closing the fluid passage and a second position allowing fluid flow between the interior and the exterior.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of and claims priority of U.S. provisional patent application Ser. No. 61/644,859, filed on May 9, 2012, entitled “METHODS AND APPARATUS FOR PRESSURE EQUALIZATION” by William H. Becker, assigned to the assignee of the present application, and is hereby incorporated by reference in its entirety herein.


BACKGROUND
1. Field of the Invention
Embodiments of the invention generally relate to methods and apparatuses for use in suspension components. Particular embodiments of the invention relate to method and apparatus useful for equalizing ambient pressure within vehicle suspension.
2. Description of the Related Art
Vehicle suspension systems typically include a spring component or components and a dampening component or components. Typically, mechanical springs, like helical springs are used with some type of viscous fluid-based dampening mechanism and the two are mounted functionally in parallel. In some instances, a spring may comprise pressurized gas and features of the damper or spring are user-adjustable, such as by adjusting the air pressure in a gas spring. A damper may be constructed by placing a damping piston in a fluid-filled cylinder (e.g., liquid such as oil). As the damping piston is moved in the cylinder, fluid is compressed and passes from one side of the piston to the other side. Often, the piston includes vents there-through which may be covered by shim stacks to provide for different operational characteristics in compression or extension.
Ambient air pressure at the time of building a suspension fork is sealed inside the fork legs. When the fork is assembled at low elevation and then taken to ride at high elevations, the air pressure sealed in the lower leg, because of the decreased high elevation exterior air pressure and corresponding differential pressure, adds pressure and load to the seal, which ultimately creates significantly higher axial friction in the telescoping suspension fork.
As the foregoing illustrates, what is needed in the art are improved techniques for lowering equalizing ambient pressure within a vehicle suspension.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 depicts a front bicycle fork, in accordance with an embodiment.
FIG. 2 depicts a cross-sectional view of the air bleed assembly and the vent hole between the seal and the upper busing, in accordance with an embodiment.
FIG. 3 depicts a perspective view of the air bleed assembly, in accordance with an embodiment.
FIG. 4 depicts a positioning of the air bleed assembly relative to the oil bath lubrication in the lower leg/shock tube, in accordance with an embodiment.



The drawings referred to in this description should be understood as not being drawn to scale except if specifically noted.
BRIEF DESCRIPTION
Reference will now be made in detail to embodiments of the present technology, examples of which are illustrated in the accompanying drawings. While the technology will be described in conjunction with various embodiment(s), it will be understood that they are not intended to limit the present technology to these embodiments. On the contrary, the present technology is applicable to alternative embodiments, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims.
One embodiment hereof comprises a shock absorber for a vehicle. In one embodiment, the vehicle is a bicycle. The shock absorber, for example, a front fork 100 as shown in FIG. 1, is advantageous because it includes a damper 118/114 (lower fork tube and upper fork tube, respectively, of the damper leg) having a manually adjustable damping resistance. In one embodiment, the manually adjustable damping function allows a user to adjust a “platform” threshold which must be exceeded before the shock absorber can experience significant compression travel. It allows the user to establish a level, in one embodiment, for compression damping whereby such damping is increased or decreased selectively.
U.S. Pat. No. 6,135,434, which patent is herein incorporated by reference in its entirety, shows certain variations of positive and negative spring mechanisms. Another selectively variable damping mechanism is shown in U.S. Pat. No. 6,360,857, which patent is herein incorporated by reference in its entirety. Optionally, any of the foregoing mechanisms may be integrated, or used in combination, with any other features disclosed herein.
U.S. Pat. Nos. 6,415,895, 6,296,092, 6,978,872 and 7,308,976, each of which patents is herein incorporated by reference in its entirety, show certain variations of position sensitive damping mechanisms. Another position sensitive damping mechanism is shown in U.S. Pat. No. 7,374,028, which patent is herein incorporated by reference in its entirety. Another position sensitive damping mechanism is shown in U.S. Pat. No. 5,190,126, which patent is herein incorporated by reference in its entirety. Optionally, any of the foregoing mechanisms may be integrated, or used in combination, with any other features disclosed herein.
U.S. Pat. Nos. 6,581,948, 7,273,137, 7,261,194, 7,128,192, and 6,604,751, each of which patents is herein incorporated by reference in its entirety, show certain variations of inertia valve mechanisms for controlling aspects of compression damping. Additionally, U.S. Published patent Application Nos. 2008/0053768 A1, 2008/0053767 A1, 2008/0035439 A1, 2008/0007017 A1, 2007/0296163 A1, 2007/0262555 A1, 2007/0228691 A1, 2007/0228690 A1, 2007/0227845 A1, 2007/0227844 A1, 2007/0158927 A1, 2007/0119670 A1, 2007/0068751 A1, 2007/0012531 A1, 2006/0065496 A1, each of which patent applications is herein incorporated by reference in its entirety, show certain variations of inertia valve mechanisms for controlling aspects of compression damping. Optionally, any of the foregoing inertia valve mechanisms or other features may be integrated, or used in combination, with any other features disclosed herein. A shock absorber or fork may be equipped, for example, with an inertia valve for controlling an aspect of damping and a position sensitive valve for controlling another aspect of damping.
FIG. 1, FIG. 3, and FIG. 4, show suspension fork legs, either or both of which would, in one embodiment, comprise portions of a bicycle fork (or motorcycle fork). During operation, the damper leg of the fork is subject to compression and rebound loads. The compression is induced by disparities in the terrain being traversed by a vehicle equipped with the fork. The rebound is induced by a spring (e.g. gas spring, mechanical spring, coil—not shown but for example in leg 104/108), preferably located in another leg of the fork, which stores energy during compression of the fork and then releases that energy when the disparity is passed. The energy is released in urging the suspension unit to elongate axially following the axial compression during which the energy is stored. The top cap 103 and its connected parts move with the upper fork tube 114 and 108 during compression and rebound and the lower nut assembly 101 and its connected parts move with the lower fork tube 104 or 118.
Movement of the upper fork tube (e.g., 114) relative to the lower fork tube (e.g., 118) causes a piston assembly to move axially within the damper body. During a compression stroke, the piston assembly moves downward in the damper body and thereby reduces the volume of the compression chamber. As fluid is displaced from the compression chamber, some of it flows through passages and deflects a one way shim valve to enter the rebound chamber. Some of the displaced fluid flows through an orifice into a reservoir. The resistance to movement of fluid from the compression chamber, through passages (and shim valve on piston) and the orifice provide compression damping for the suspension unit in which the damper cartridge is included.
Ambient air pressure at the time of building a suspension fork is “sealed” inside the upper leg/lower leg assembly (e.g., upper fork tube 114 telescopically positioned within lower fork tube 118). In one embodiment, it is preferred that the air pressure within the assembly at static (unloaded) extension be substantially equal to ambient exterior air pressure so that there is no net differential pressure acting across the lower leg seal 135 (see FIG. 3). Suspension forks are often ridden at many different elevations, however, and the ambient air pressure reduces (decreases) as a function of increasing elevation (and increases at lower elevations).
Air pressure above sea level can be calculated as:

P=1091325(1−2.2577 10−5h)5.25588 

Where p=pressure absolute and h=altitude above sea level.

The typical ambient air pressure at 8,000 ft. elevation is 3.80 psi lower than the trapped air pressure inside the fork. The typical ambient air pressure at 10,000 ft. elevation is 4.60 psi lower than the trapped air pressure inside the fork. (http://www.engineeringtoolbox.com/air-altitude-pressure-d462.html.)
When a fork is assembled at low elevation and then taken to ride at high elevations, the “sealed lower leg air pressure”, because of the now decreased high elevation exterior air pressure and corresponding differential pressure, adds pressure and load to the lower oil control lip of the seal which creates significantly higher axial friction in a telescoping suspension fork.
The presently disclosed system allows a rider to push a button and let the pressure in the lower leg equalize to ambient pressure at high elevation and therefore restore a lower-friction fork. Generally, it is important to seal a fork to prevent the lower leg oil bath lubrication from leaking out of the fork. In one embodiment, the air bleed assembly 300 (of FIG. 4) is located right below the lower leg seal 135 so that when excessive air pressure in the fork is relieved at high elevation, the oil bath 140 typically leveled in the lower leg (typically 20-50 cc) does not spray/leak out. In other words, a substantial portion (most of the oil bath 140), if not all, of the oil bath 140 remains within the lower leg (and does not spray/leak out of the lower leg) when the air bleed assembly 300 is opened to release excessive air pressure from the fork.
FIG. 3 shows the air bleed assembly 300 including button 150 positioned on a die-cast feature of the lower leg. Pressing the button 150 equalizes the air pressure in the fork/shock assembly with the local ambient air pressure.
FIG. 2 shows a cross-section of the air bleed assembly 300 and the vent hole 154 between the seal (not shown) and the upper bushing 120 (or behind foam ring 125). When the button 150 is pressed, the sealing o-ring 151 moves into the diametrical recess 152 and thereby becomes unsealed, letting the air pressure by-pass into or out of the fork leg via vent hole 154 to equalize the pressure in the fork leg with an exterior pressure. When the button 150 is released, a spring 153, which biases the button/valve 150 toward a closed position, urges the o-ring 151 into a sealing engagement with a seal bore 155.
FIG. 4 shows positioning of the air bleed assembly 300 relative to the “oil bath” lubrication in the lower leg/shock tube.
It should be noted that any of the features disclosed herein may be useful alone or in any suitable combination. While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be implemented without departing from the scope of the invention, and the scope thereof is determined by the claims that follow.

## Claims

1. A shock absorber comprising:
a damper comprising:
an upper leg/lower leg assembly, said upper leg/lower leg assembly comprising:
an upper fork tube;
a lower fork tube, wherein said upper fork tube is telescopically positioned within said lower fork tube and enters said lower fork tube at a first end of said lower fork tube, said first end of said lower fork tube comprising:
a lower leg seal located at an outermost edge of said first end of said lower fork tube, said lower leg seal configured for sealing closed a gap disposed between said upper fork tube and said lower fork tube, thereby preventing an oil bath lubrication occupying an area within said lower fork tube at a second end of said lower fork tube from leaking out of said damper, said second end being opposite said first end; and
an upper bushing attached to and positioned adjacent to said lower leg seal; and

an air bleed system located directly below said lower leg seal and positioned closer to a second end of said lower fork tube than said lower leg seal is positioned on said lower fork tube, said air bleed system configured for equalizing ambient pressure within said damper by opening to release excessive air pressure from said damper, said air bleed system comprising:
a vent hole positioned between said lower leg seal and said upper bushing, said vent hole being connected to a fluid passage positioned between an interior of said lower fork tube and an exterior of said lower fork tube, wherein said vent hole is configured for allowing said air pressure to pass into and out of said lower fork tube; and
a manually operable valve located in said lower fork tube and attached to said fluid passage, said manually operable valve having a first position substantially closing said fluid passage and a second position allowing a fluid to flow between said interior and said exterior.

2. The shock absorber of claim 1, wherein said fluid comprises:
a gas.

3. The shock absorber of claim 1, further comprising:
a valve activator coupled with said manually operable valve, said valve activator comprising:
an activation position configured for, upon activation, positioning said manually operable valve into said first position; and
a deactivation position configured for, upon deactivation, positioning said manually operable valve into said second position, and whereupon said activation, the air pressure in said damper is equalized with a local ambient air pressure.

4. The shock absorber of claim 3, wherein said valve activator comprises:
a button configured for being pressed for said activation and said deactivation.

5. The shock absorber of claim 3, wherein said valve activator is positioned on a die-cast feature of said lower fork tube.

6. The shock absorber of claim 5, further comprising:
a diametrical recess; and
a sealing o-ring comprising:
a sealed position; and
an unsealed position, wherein said sealed position seals between said die-cast feature and said lower fork tube, whereupon said activation, said sealing o-ring moves into said diametrical recess, thereby attaining said unsealed position and letting air pressure by-pass into or out of said lower fork tube via said vent hole.

7. The shock absorber of claim 3, wherein said manually operable valve comprises:
a spring coupled with said valve activator, whereupon said deactivation, said spring biases said valve activator toward said first position.

8. The shock absorber of claim 6, wherein said second position comprises:
a sealing engagement between said sealing o-ring and a seal bore, wherein when in said sealing engagement, said air pressure does not by-pass into or out of said damper.