U.S. patent application number 13/485401 was filed with the patent office on 2012-12-06 for methods and apparatus for position sensitive suspension damping.
Invention is credited to Christopher Paul Cox, Everet O. Ericksen, Sante M. Pelot.
Application Number | 20120305350 13/485401 |
Document ID | / |
Family ID | 46210142 |
Filed Date | 2012-12-06 |
United States Patent
Application |
20120305350 |
Kind Code |
A1 |
Ericksen; Everet O. ; et
al. |
December 6, 2012 |
METHODS AND APPARATUS FOR POSITION SENSITIVE SUSPENSION DAMPING
Abstract
An apparatus and system are disclosed that provide position
sensitive suspension damping. A damping unit includes a piston
mounted in a fluid-filled cylinder. A vented path in the piston may
be fluidly coupled to a bore formed in one end of the piston rod,
creating a flow path for fluid to flow from a first side of the
piston to a second side of the piston during a compression stroke.
The flow path may be blocked by a needle configured to engage the
bore as the damping unit is substantially fully compressed, thereby
causing the damping rate of the damping unit to increase. In one
embodiment, the piston includes multiple bypass flow paths operable
during the compression stroke or the rebound stroke of the damping
unit. One or more of the bypass flow paths may be restricted by one
or more shims mounted on the piston.
Inventors: |
Ericksen; Everet O.; (Santa
Cruz, CA) ; Cox; Christopher Paul; (Capitola, CA)
; Pelot; Sante M.; (Santa Cruz, CA) |
Family ID: |
46210142 |
Appl. No.: |
13/485401 |
Filed: |
May 31, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61491858 |
May 31, 2011 |
|
|
|
61645465 |
May 10, 2012 |
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Current U.S.
Class: |
188/269 ;
188/313; 188/317; 267/217 |
Current CPC
Class: |
F16F 9/46 20130101; B62K
25/08 20130101; B62K 25/06 20130101; F16F 9/342 20130101; F16F
9/486 20130101; B62K 2025/048 20130101; F16F 9/3405 20130101 |
Class at
Publication: |
188/269 ;
188/317; 188/313; 267/217 |
International
Class: |
B60G 13/08 20060101
B60G013/08; B60G 13/10 20060101 B60G013/10; B60G 15/06 20060101
B60G015/06; B60G 13/06 20060101 B60G013/06 |
Claims
1. A vehicle suspension damper comprising: a cylinder having a
compression chamber and a rebound chamber and containing at least a
portion of a piston rod having a piston attached thereto, wherein
an outer diameter of the piston engages an inner diameter of the
cylinder and is relatively movable therein, and wherein the piston
borders each of the compression chamber and the rebound chamber; a
damping liquid within the cylinder; and a bypass fluid flow path
connecting the compression chamber and the rebound chamber, wherein
the bypass flow path comprises a fluid path extending between an
inner diameter of the piston and a side surface of the piston
directly bordering one of the compression or rebound chambers.
2. The vehicle suspension damper of claim 1, wherein the bypass
flow path further comprises a valve member restricting fluid flow
through the piston.
3. The vehicle suspension damper of claim 2, wherein the piston
further comprises a damping flow path extending between a first
side surface of the piston and a second side surface of the piston,
the damping flow path comprising the valve member.
4. The vehicle suspension damper of claim 1, wherein the piston
further comprises a damping flow path extending between a first
side surface of the piston and a second side surface of the piston
and including a valve member.
5. The vehicle suspension damper of claim 1, further comprising a
second valve member connected to the cylinder and operable to
restrict the bypass flow path at predetermined positions during a
stroke of the damper and to be unrestrictive of the bypass flow
path at other positions during the stroke.
6. The vehicle suspension damper of claim 5, wherein the second
valve member comprises a needle.
7. The vehicle suspension damper of claim 6, further comprising a
floating piston mounted in fluid communication with an interior of
the cylinder, the floating piston separating the damping liquid
from a volume of gas contained adjacent a second side of the
floating piston.
8. The vehicle suspension damper of claim 7, further comprising a
reservoir, the reservoir comprising: a reservoir cylinder having a
first end and a second end, wherein the first end of the reservoir
cylinder is fluidly coupled to the cylinder; and the floating
piston mounted inside the reservoir cylinder and axially movable
relative thereto, the floating piston forming a reserve volume of
damping liquid between a first side of the floating piston and the
first end of the reservoir cylinder and forming a volume of gas
between a second side of the floating piston and the second end of
the reservoir cylinder.
9. The vehicle suspension damper of claim 7, wherein the floating
piston surrounds and moves relative to a needle.
10. The vehicle suspension damper of claim 7, wherein the needle
restricts an opening of the bypass flow path proximate the inner
diameter of the piston at predetermined positions during a stroke
of the damper.
11. A vehicle suspension damper comprising: a cylinder having a
compression chamber and a rebound chamber and containing at least a
portion of a piston rod having a piston attached thereto, wherein
an outer diameter of the piston engages an inner diameter of the
cylinder and is relatively movable therein, and wherein the piston
borders each of the compression chamber and the rebound chamber;
and a damping liquid within the cylinder, wherein the piston
includes multiple flow paths that enable the damping liquid to flow
from the compression chamber to the rebound chamber, the multiple
flow paths including: a damping flow path that comprises a first
fluid path extending between a first side surface of the piston
directly bordering the compression chamber and a second side
surface of the piston directly bordering the rebound chamber, and a
bypass flow path that comprises a second fluid path extending
between an inner diameter of the piston and one of the first side
surface of the piston or the second side surface of the piston.
12. The vehicle suspension damper of claim 11, wherein the multiple
flow paths further include a rebound flow path that comprises a
fluid path extending between an inner diameter of the piston and
one of the first side surface or the second side surface.
13. The vehicle suspension damper of claim 12, wherein the damping
liquid is forced through the damping flow path and the bypass flow
path during a compression stroke of the vehicle suspension damper,
and wherein the damping liquid is forced through the rebound flow
path during a rebound stroke of the vehicle suspension damper.
14. The vehicle suspension damper of claim 12, wherein the bypass
flow path further comprises a valve member restricting fluid flow
through the piston and a second valve member connected to the
cylinder and operable to restrict the bypass flow path at
predetermined positions during a stroke of the damper and to be
unrestrictive of the bypass flow path at other positions during the
stroke.
15. A vehicle suspension system comprising: a first damper unit
that includes: a cylinder having a compression chamber and a
rebound chamber and containing at least a portion of a piston rod
having a piston attached thereto, wherein an outer diameter of the
piston engages an inner diameter of the cylinder and is relatively
movable therein, and wherein the piston borders each of the
compression chamber and the rebound chamber, a damping liquid
within the cylinder, and a bypass flow path connecting the
compression chamber and the rebound chamber, wherein the bypass
flow path comprises a fluid path extending between an inner
diameter of the piston and a side surface of the piston directly
bordering one of the compression or rebound chambers.
16. The vehicle suspension system of claim 15, wherein the bypass
flow path further comprises a valve member restricting fluid flow
through the piston.
17. The vehicle suspension system of claim 15, wherein the piston
further comprises a damping flow path extending between a first
side surface of the piston directly bordering the compression
chamber and a second side surface of the piston directly bordering
the rebound chamber, and wherein the piston includes a valve
member.
18. The vehicle suspension system of claim 15, further comprising a
spring mounted coaxially with the first damper unit.
19. The vehicle suspension system of claim 15, wherein the first
damper unit is included in a leg of a fork.
20. The vehicle suspension system of claim 15, further comprising:
a second damper unit substantially similar to the first damper
unit; and one or more springs mounted substantially in parallel
with the first and second damper units.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of U.S. Provisional Patent
Application Ser. No. 61/491,858 (Atty. Dkt. No. FOXF/0055USL),
filed May 31, 2011, and U.S. Provisional Patent Application Ser.
No. 61/645,465, filed May 10, 2012, which are herein incorporated
by reference in their entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates generally to vehicle suspensions and,
more specifically, to variable damping rates in vehicle shock
absorbers and forks.
[0004] 2. Description of the Related Art
[0005] Vehicle suspension systems typically include a spring
component or components and a damping component or components.
Often, mechanical springs, like helical springs, are used with some
type of viscous fluid-based damping mechanism, the spring and
damper being 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.
[0006] Conventional damping components provide a constant damping
rate during compression or extension through the entire length of
the stroke. As the suspension component nears full compression or
full extension, the damping piston can "bottom out" against the end
of the damping cylinder. Allowing the damping components to "bottom
out" may cause the components to deform or break inside the damping
cylinder.
[0007] As the foregoing illustrates, what is needed in the art are
improved techniques for varying the damping rate including to
lessen the risk of the suspension "bottoming out."
SUMMARY OF THE INVENTION
[0008] One embodiment of the present disclosure sets forth a
vehicle suspension damper that includes a cylinder having a
compression chamber and a rebound chamber and containing at least a
portion of a piston rod having a piston attached thereto, where an
outer diameter of the piston engages an inner diameter of the
cylinder and is relatively movable therein, and where the piston
borders each of the compression chamber and the rebound chamber.
The vehicle suspension damper further includes a damping liquid
within the cylinder and a bypass fluid flow path connecting the
compression chamber and the rebound chamber, which forms a fluid
path extending between an inner diameter of the piston and a side
surface of the piston directly bordering one of the compression or
rebound chambers.
[0009] Another embodiment of the present disclosure sets forth a
vehicle suspension damper that includes a cylinder and a damping
liquid within the cylinder, the cylinder having a compression
chamber and a rebound chamber and containing at least a portion of
a piston rod having a piston attached thereto, where an outer
diameter of the piston engages an inner diameter of the cylinder
and is relatively movable therein, and where the piston borders
each of the compression chamber and the rebound chamber. The piston
includes multiple flow paths that enable the damping liquid to flow
from the compression chamber to the rebound chamber. The multiple
flow paths include a damping flow path that comprises a first fluid
path extending between a first side surface of the piston directly
bordering the compression chamber and a second side surface of the
piston directly bordering the rebound chamber and a bypass flow
path that comprises a fluid path extending between an inner
diameter of the piston and one of the first side surface of the
piston or the second side surface of the piston.
[0010] Yet another embodiment of the present disclosure sets forth
a vehicle suspension system that includes a first damper unit. The
first damper unit includes a cylinder having a compression chamber
and a rebound chamber and containing at least a portion of a piston
rod having a piston attached thereto, wherein an outer diameter of
the piston engages an inner diameter of the cylinder and is
relatively movable therein, and wherein the piston borders each of
the compression chamber and the rebound chamber. The first damper
unit further includes a damping liquid within the cylinder and a
bypass fluid flow path connecting the compression chamber and the
rebound chamber, which forms a fluid path extending between an
inner diameter of the piston and a side surface of the piston
directly bordering one of the compression or rebound chambers.
[0011] One advantage of some disclosed embodiments is that multiple
bypass flow paths enable the vehicle suspension damper to be setup
such that the damping rate changes (i.e., is increased) as the
damper nears full compression. The increased damping rate, caused
by fluid being forced through fewer flow paths formed by the
multiple bypass flow paths causes the force opposing further
compression of the damper to increase, thereby decreasing the
chance that the damper "bottoms out."
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] So that the manner in which the above recited features can
be understood in detail, a more particular description, briefly
summarized above, may be had by reference to certain example
embodiments, some of which are illustrated in the appended
drawings. It is to be noted, however, that the appended drawings
illustrate only typical embodiments and are therefore not to be
considered limiting the scope of the claims, which may admit to
other equally effective embodiments.
[0013] FIG. 1 shows an asymmetric bicycle fork having a damping leg
and a spring leg, according to one example embodiment;
[0014] FIGS. 2A-2C show sectional side elevation views of a
needle-type monotube damping unit in different stages of
compression, according to one example embodiment;
[0015] FIG. 3 shows a detailed view of the needle and bore at the
intermediate position proximate to the "bottom-out" zone, according
to one example embodiment;
[0016] FIGS. 4A and 4B illustrate the castellated or slotted valve,
according to one example embodiment;
[0017] FIGS. 5A and 5B illustrate a damping unit having a "piggy
back" reservoir, according to one example embodiment;
[0018] FIG. 6 illustrates a half section, orthographic view of a
damping unit, according to another example embodiment;
[0019] FIGS. 7A through 7E illustrate the piston of FIG. 6,
according to one example embodiment; and
[0020] FIGS. 8A and 8B illustrate the shaft of FIG. 6, according to
one example embodiment.
[0021] For clarity, identical reference numbers have been used,
where applicable, to designate identical elements that are common
between figures. It is contemplated that features of one example
embodiment may be incorporated in other example embodiments without
further recitation.
DETAILED DESCRIPTION
[0022] Integrated damper/spring vehicle shock absorbers often
include a damper body surrounded by or used in conjunction with a
mechanical spring or constructed in conjunction with an air spring
or both. The damper often consists of a piston and shaft
telescopically mounted in a fluid filled cylinder. The damping
fluid (i.e., damping liquid) or damping liquid may be, for example,
hydraulic oil. A mechanical spring may be a helically wound spring
that surrounds or is mounted in parallel with the damper body.
Vehicle suspension systems typically include one or more dampers as
well as one or more springs mounted to one or more vehicle axles.
As used herein, the terms "down", "up", "downward", "upward",
"lower", "upper", and other directional references are relative and
are used for reference only.
[0023] FIG. 1 shows an asymmetric bicycle fork 100 having a damping
leg and a spring leg, according to one example embodiment. The
damping leg includes an upper tube 105 mounted in telescopic
engagement with a lower tube 110 and having fluid damping
components therein. The spring leg includes an upper tube 106
mounted in telescopic engagement with a lower tube 111 and having
spring components therein. The upper legs 105, 106 may be held
centralized within the lower legs 110, 111 by an annular bushing
108. The fork 100 may be included as a component of a bicycle such
as a mountain bicycle or an off-road vehicle such as an off-road
motorcycle. In some embodiments, the fork 100 may be an "upside
down" or Motocross-style motorcycle fork.
[0024] In one embodiment, the damping components inside the damping
leg include an internal piston 166 disposed at an upper end of a
damper shaft 136 and fixed relative thereto. The internal piston
166 is mounted in telescopic engagement with a cartridge tube 128
connected to a top cap 180 fixed at one end of the upper tube 105.
The interior volume of the damping leg may be filled with a damping
liquid such as hydraulic oil. The piston 166 may include shim
stacks (i.e., valve members) that allow a damping liquid to flow
through vented paths in the piston 166 when the upper tube 105 is
moved relative to the lower tube 110. A compression chamber is
formed on one side of the piston 166 and a rebound chamber is
formed on the other side of the piston 166. The pressure built up
in either the compression chamber or the rebound chamber during a
compression stroke or a rebound stroke provides a damping force
that opposes the motion of the fork 100.
[0025] The spring components inside the spring leg include a
helically wound spring 115 contained within the upper tube 106 and
axially restrained between top cap 181 and a flange 165. The flange
165 is disposed at an upper end of the riser tube 135 and fixed
thereto. The lower end of the riser tube 135 is connected to the
lower tube 111 in the spring leg and fixed relative thereto. A
valve plate 155 is positioned within the upper leg tube 106 and
axially fixed thereto such that the plate 155 moves with the upper
tube 106. The valve plate 155 is annular in configuration,
surrounds an exterior surface of the riser tube 135, and is axially
moveable in relation thereto. The valve plate 155 is sealed against
an interior surface of the upper tube 106 and an exterior surface
of the riser tube 135. A substantially incompressible lubricant
(e.g., oil) may be contained within a portion of the lower tube 111
filling a portion of the volume within the lower tube 111 below the
valve plate 155. The remainder of the volume in the lower tube 111
may be filled with gas at atmospheric pressure.
[0026] During compression of fork 100, the gas in the interior
volume of the lower tube 111 is compressed between the valve plate
155 and the upper surface of the lubricant as the upper tube 106
telescopically extends into the lower tube 111. The helically wound
spring 115 is compressed between the top cap 181 and the flange
165, fixed relative to the lower tube 111. The volume of the gas in
the lower tube 111 decreases in a nonlinear fashion as the valve
plate 155, fixed relative to the upper tube 106, moves into the
lower tube 111. As the volume of the gas gets small, a rapid
build-up in pressure occurs that opposes further travel of the fork
100. The high pressure gas greatly augments the spring force of
spring 115 proximate to the "bottom-out" position where the fork
100 is fully compressed. The level of the incompressible lubricant
may be set to a point in the lower tube 111 such that the distance
between the valve plate 155 and the level of the oil is
substantially equal to a maximum desired travel of the fork
100.
[0027] FIGS. 2A-2C show sectional side elevation views of a
needle-type monotube damping unit 200 in different stages of
compression, according to one example embodiment. In one
embodiment, the components included in damping unit 200 may be
implemented as one half of fork 100. In another embodiment, damping
unit 200 may be implemented as a portion of a shock absorber that
includes a helically-wound, mechanical spring mounted substantially
coaxially with the damping unit 200. In yet other embodiments,
damping unit 200 may be implemented as a component of a vehicle
suspension system where a spring component is mounted substantially
in parallel with the damping unit 200.
[0028] As shown in FIG. 2A, the damping unit 200 is positioned in a
substantially fully extended position. The damping unit 200
includes a cylinder 202, a shaft 205, and a piston 266 fixed on one
end of the shaft 205 and mounted telescopically within the cylinder
202. The outer diameter of piston 266 engages the inner diameter of
cylinder 202. In one embodiment, the damping liquid (e.g.,
hydraulic oil or other viscous damping fluid) meters from one side
to the other side of the piston 266 by passing through vented paths
formed in the piston 266. Piston 266 may include shims (or shim
stacks) to partially obstruct the vented paths in each direction
(i.e., compression or rebound). By selecting shims having certain
desired stiffness characteristics, the damping effects can be
increased or decreased and damping rates can be different between
the compression and rebound strokes of the piston 266. The damping
unit 200 includes an annular floating piston 275 mounted
substantially co-axially around a needle 201 and axially movable
relative thereto. The needle 201 is fixed on one end of the
cylinder 202 opposite the shaft 205. A volume of gas is formed
between the floating piston 275 and the end of cylinder 202. The
gas is compressed to compensate for motion of shaft 205 into the
cylinder 202, which displaces a volume of damping liquid equal to
the additional volume of the shaft 205 entering the cylinder
202.
[0029] During compression, shaft 205 moves into the cylinder 202,
causing the damping liquid to flow from one side of the piston 266
to the other side of the piston 266 within cylinder 202. FIG. 2B
shows the needle 201 and shaft 205 at an intermediate position as
the damping unit 200 has just reached the "bottom-out" zone. In
order to prevent the damping components from "bottoming out",
potentially damaging said components, the damping force resisting
further compression of the damping unit 200 is substantially
increased within the "bottom-out" zone. The needle 201 (i.e., a
valve member) compresses fluid in a bore 235, described in more
detail below in conjunction with FIG. 3, thereby drastically
increasing the damping force opposing further compression of the
damping unit 200. Fluid passes out of the bore around the needle
through a valve that is restricted significantly more than the
vented paths through piston 266. As shown in FIG. 2C, the damping
rate is increased substantially within the "bottom-out" zone until
the damping unit 200 reaches a position where the damping unit 200
is substantially fully compressed.
[0030] FIG. 3 shows a detailed view of the needle 201 and bore 235
at the intermediate position proximate to the "bottom-out" zone,
according to one example embodiment. As shown in FIG. 3, the needle
201 is surrounded by a check valve 220 contained within a nut 210
fixed on the end of shaft 205. During compression within the
"bottom out" zone, the valve 220 is moved, by fluid pressure within
the bore 235 and flow of fluid out of bore 235, upward against seat
225 of nut 210 and the bulk of escaping fluid must flow through the
annular clearance 240 that dictates a rate at which the needle 201
may further progress into bore 235, thereby substantially
increasing the damping rate of the damping unit 200 proximate to
the "bottom-out" zone. The amount of annular clearance 240 between
the exterior surface of the needle 201 and the interior surface of
the valve 220 determines the additional damping rate within the
"bottom-out" zone caused by the needle 201 entering the bore 235.
In one embodiment, the needle 201 is tapered to allow easier
entrance of the needle 201 into the bore 235 through valve 220.
[0031] During rebound within the "bottom out" zone, fluid pressure
in the bore 235 drops as the needle 201 is retracted and fluid
flows into the bore 235, causing the valve 220 to move toward a
valve retainer clip 215 that secures the valve 220 within the nut
210. In one embodiment, the valve is castellated or slotted on the
face of the valve 220 adjacent to the retainer clip 215 to prevent
sealing the valve against the retainer clip 215, thereby forcing
all fluid to flow back into the bore 235 via the annular clearance
240. Instead, the castellation or slot allows ample fluid flow into
the bore 235 during the rebound stroke to avoid increasing the
damping rate during rebound within the "bottom out" zone. The valve
220 is radially retained within the nut 210, which has a recess
having a radial clearance between the interior surface of the
recess and the exterior surface of the valve 220 that allows for
eccentricity of the needle 201 relative to the shaft 205 without
causing interference that could deform the components of damping
unit 200.
[0032] FIGS. 4A and 4B illustrate the castellated or slotted valve
220, according to one example embodiment. As shown in FIGS. 4A and
4B, the valve 220 is a washer or bushing having an interior
diameter sized to have an annular clearance 240 between the
interior surface of the valve 220 and the exterior surface of the
needle 201 when the needle 201 passes through the valve 220.
Different clearances 240 may be achieved by adjusting the interior
diameter of the valve 220 in comparison to the diameter of the
needle 201, which causes a corresponding change in the damping rate
proximate to the "bottom-out" zone. A spiral face groove is
machined into one side of the valve 220 to create the castellation
or slot 230. It will be appreciated that the geometry of the slot
230 may be different in alternative embodiments and is not limited
to the spiral design illustrated in FIGS. 4A and 4B. For example,
the slot 230 may be straight (i.e., rectangular) instead of spiral,
or the edges of the slot 230 may not be perpendicular to the face
of the valve 220. In other words, the geometry of the slot 230
creates empty space between the surface of the retainer clip 215
and the surface of the valve 220 such that fluid may flow between
the two surfaces.
[0033] When assembled, the valve 200 is oriented such that the side
with the slot 230 is proximate to the upper face of the valve
retainer clip 215, thereby preventing the surface of the valve 220
from creating a seal against the retainer clip 215. The slot 230 is
configured to allow fluid to flow from cylinder 202 to bore 235
around the exterior surface of the valve 220, which has a larger
clearance than the annular clearance 240 between the valve 220 and
the needle 201. In one embodiment, two or more slots 230 may be
machined in the face of the valve 220. In some embodiments, the
valve 220 is constructed from high-strength yellow brass (i.e., a
manganese bronze alloy) that has good characteristics enabling low
friction between the valve 220 and the needle 201. In alternate
embodiments, the valve 220 may be constructed from other materials
having suitable characteristics of strength or coefficients of
friction.
[0034] FIGS. 5A and 5B illustrate a damping unit 300 having a
"piggy back" reservoir 350, according to another example
embodiment. As shown in FIG. 5A, damping unit 300, shown fully
extended, includes a cylinder 302 with a shaft 305 and a piston 366
fixed on one end of the shaft 305 and mounted telescopically within
the cylinder 302. Damping unit 300 also includes a needle 301
configured to enter a bore 335 in shaft 305. However, unlike
damping unit 200, damping unit 300 does not include an annular
floating piston mounted substantially co-axially around the needle
301 and axially movable relative thereto. Instead, the piggy back
reservoir 350 includes a floating piston 375 configured to perform
a similar function to that of floating piston 275. A volume of gas
is formed between the floating piston 375 and one end of the piggy
back reservoir 350. The gas is compressed to compensate for motion
of shaft 305 into the cylinder 302. Excess damping liquid may enter
or exit cylinder 302 from the piggy back reservoir 350 as the
volume of fluid changes due to ingress or egress of shaft 305 from
the cylinder 302. In FIG. 5B, the damping unit 300 is shown
proximate to the "bottom out" zone where needle 301 has entered
bore 335.
[0035] FIG. 6 illustrates a half section, orthographic view of a
damping unit 400, according to another example embodiment. As shown
in FIG. 6, damping unit 400 includes a piston 466 fixed on one end
of a shaft 405 and mounted telescopically within a cylinder 402.
The shaft 405 includes a bore 435 that enables ingress of a needle
(e.g., 201, 301) to change the damping characteristics of the
damping unit 400 proximate to the "bottom out" zone. The piston
assembly includes a top shim stack 481 and a bottom shim stack 482
attached to the top face and bottom face of the piston 466,
respectively, which enable different damping resistances to be set
during the compression stroke and the rebound stroke. During
operation, where a needle has not entered bore 435, the damping
liquid flows from one side of the piston 466 to the other side
through multiple flow paths 451, 452, and 453. In compression, a
first flow path 451 (i.e., a damping flow path) allows the damping
liquid to flow from an upper portion of the cylinder 402 through
vented paths in the piston 466 and into a lower portion of the
cylinder 402, forcing the bottom shim stack 482 away from the
bottom face of the piston 466. A second flow path 452 (i.e., a
bypass flow path) allows the damping liquid to flow from an upper
portion of the cylinder 402 through the bore 435 and shaft ports
440 in shaft 405 and into additional vented paths in the piston 466
through the bottom shim stack 482 and into the lower portion of the
cylinder 402. In rebound, a third flow path 453 (i.e., a rebound
flow path, not shown in FIG. 6) allows the damping liquid to flow
from a lower portion of the cylinder 402, through different vented
paths in the piston 466, through the top shim stack 481, and into
an upper portion of the cylinder 402. In some embodiments, the
first flow path 451 and the second flow path 452 may be associated
with separate and distinct shim stacks. For example, the bottom
shim stack 482 may be replaced by two shim stacks configured in a
clover pattern and arranged such that a first shim stack covers the
vented paths in the piston 466 corresponding to the first flow path
451 and a second shim stack covers the additional vented paths in
the piston 466 corresponding to the second flow path 452.
[0036] When a needle just enters bore 435, the needle impedes the
damping liquid in the upper portion of the cylinder 402 from
flowing through the second flow path 452 due to the "plugging"
effect of the needle blocking the entrance to the bore 435.
However, the damping liquid may continue to pass through the piston
466 through the first flow path 451. In addition, some damping
liquid may continue to flow out of ports 440 from bore 435 as the
needle continues ingress into bore 435 and decreases the fluid
volume inside the bore 435. It will be appreciated that the damping
rate will increase as the needle blocks the second flow path 452,
thereby forcing substantially all damping liquid in the upper
portion of the cylinder 402 to move through piston 466 via the
first flow path 451. At some point during ingress of the needle,
the full diameter of the needle is adjacent to the shaft ports 440,
substantially blocking additional damping liquid from leaving bore
435 through the shaft ports 440. Again, the damping rate will
increase as the needle blocks the shaft ports 440 and fluid
pressure rapidly builds up within bore 435 and acts on the needle
to oppose any further compression of the damping unit 400.
[0037] FIGS. 7A through 7E illustrate the piston 466 of FIG. 6,
according to one example embodiment. As shown in FIGS. 7A and 7B,
the piston 466 includes two vented paths (i.e., 421, 422) that
allow damping liquid to flow from the upper portion of the cylinder
402 to the lower portion of the cylinder 402 via the first flow
path 451 (i.e., bypassing the top shim stack and entering the
piston 466 proximate to the inner surface of cylinder 402). The
piston 466 also includes two additional vented paths (i.e., 423,
424) that allow damping liquid to flow from the upper portion of
the cylinder 402 to the lower portion of the cylinder 402 via the
second flow path 452 (i.e, through the bore 435 and shaft ports
440). The additional vented paths are connected to the bore 435 via
channels 425 that fluidly couple the additional vented paths to the
shaft ports 440 in shaft 405 through a surface on the inner
diameter of the piston 466. The four vented paths described above
(i.e., 421-424) allow damping liquid to flow from an upper portion
of the cylinder 402 to a lower portion of the cylinder 402 during a
compression stroke. In rebound, yet another set of four vented
paths (i.e., 426, 427, 428, 429) allow damping liquid to flow from
the lower portion of the cylinder 402 to the upper portion of the
cylinder 402 via the third flow path 453 (i.e., bypassing the
bottom shim stack 482 and passing into the upper portion of the
cylinder 402 through the top shim stack 481). FIG. 7C shows a side
view of the piston 466 of FIGS. 7A and 7B. FIG. 7D shows a cross
section of the piston 466 showing the inner diameter that is fit
over shaft 405 as well as one channel 425 connected to one of the
additional vented paths in the piston corresponding to the first
second flow path 452. FIG. 7E shows a cross section of the piston
466 showing vented paths 423 and 424.
[0038] FIGS. 8A and 8B illustrate the shaft 405 of FIG. 6,
according to one example embodiment. As shown in FIGS. 8A and 8B,
the shaft 405 includes a bore 435 formed (e.g., drilled, milled,
etc.) into a top portion of the shaft. In one embodiment, the top
portion of the shaft may have a smaller diameter than the body of
the shaft 405, forming a seat a particular distance from one end of
the shaft 405. The piston assembly including the piston 466 and the
shim stacks may be mounted over the top portion of the shaft 405
and secured with a nut threaded onto the end of the shaft 405. In
alternative embodiments, the nut may be press fit onto the shaft
405 or secured in any other technically feasible manner.
[0039] Shaft ports 440 may be formed through an outer face of the
top portion of the shaft 405 proximate a surface on the inner
diameter of the piston 466 when mounted on the shaft 405. The shaft
ports 440 fluidly couple the bore 435 in the shaft 405 with the
additional vented paths (i.e., 423, 424) in the piston 466 such
that fluid may flow through the bore 435 via the second flow path
452. In other words, the second flow path 452 enables additional
fluid to flow through the bottom shim stacks 482 when a needle is
not blocking the bore 435.
[0040] It should be noted that any of the features disclosed herein
may be used alone or in combination. While the foregoing is
directed to embodiments of the present disclosure, other and
further embodiments may be implemented without departing from the
scope of the disclosure, the scope thereof being determined by the
claims that follow.
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