U.S. patent application number 15/347096 was filed with the patent office on 2017-08-24 for regressive hydraulic damper.
The applicant listed for this patent is Bill J. Gartner. Invention is credited to Bill J. Gartner.
Application Number | 20170241505 15/347096 |
Document ID | / |
Family ID | 57234982 |
Filed Date | 2017-08-24 |
United States Patent
Application |
20170241505 |
Kind Code |
A1 |
Gartner; Bill J. |
August 24, 2017 |
REGRESSIVE HYDRAULIC DAMPER
Abstract
A damper of shock and vibration. In one embodiment there is a
hydraulic damper with a regressive damping characteristic in both
compression and extension, such that damping forces decrease with
increased stroking velocity within a predetermined range of
stroking velocity. Outside of this range, damping forces are
progressive, such that the damping force increases with increased
stroking velocity. In another embodiment, there is a hydraulic
damper with a second, slidable piston within one of the internal
chambers defined by the main piston. This secondary piston is
spring loaded and hydraulically latchable at either a first
position or a second position based on the pressure differential
across the main piston.
Inventors: |
Gartner; Bill J.;
(Wyomissing, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Gartner; Bill J. |
Wyomissing |
PA |
US |
|
|
Family ID: |
57234982 |
Appl. No.: |
15/347096 |
Filed: |
November 9, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12144530 |
Jun 23, 2008 |
9494209 |
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15347096 |
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60945365 |
Jun 21, 2007 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F16F 9/3405 20130101;
F16F 9/3214 20130101; F16F 2238/026 20130101; F16F 9/516 20130101;
F16F 9/48 20130101; F16F 9/5126 20130101; F16F 9/3228 20130101;
F16F 2222/123 20130101; F16F 2228/14 20130101 |
International
Class: |
F16F 9/516 20060101
F16F009/516; F16F 9/32 20060101 F16F009/32; F16F 9/512 20060101
F16F009/512; F16F 9/34 20060101 F16F009/34 |
Claims
1. A hydraulic damper, comprising: a first housing defining a
cavity for hydraulic fluid; a first piston slidable within the
cavity and dividing the cavity into a first volume and a second
volume; a rod extending from the cavity, said first piston being
attached to said rod, said rod including an internal passageway for
flow of hydraulic fluid between said first volume and said second
volume; a second housing in fluid communication with the first
volume and attached to said rod, said second housing including an
internal chamber and a second piston slidable within the chamber
between a first position and a second position; wherein in the
first position there is a first flow path for the flow of hydraulic
fluid from the first volume through the internal passageway and
into the second volume, in the second position there is a second
flow path for the flow of hydraulic fluid from the first volume
through the internal passageway and into the second volume, and the
first flow path is more restrictive than the second flow path.
2. the damper of claim 1 wherein said second piston includes a
first aperture in the first flow path and the second flow path,
said second piston includes a second aperture in the second flow
path, and in the first position hydraulic fluid flows through the
first aperture and the second aperture is substantially blocked
off, and in the second position hydraulic fluid flows through the
first aperture and the second aperture.
3. The damper of claim 1 which further comprises a spring biasing
said second piston to the first position.
4. The damper of claim 1 wherein said second piston is in the
second position when pressure in the first volume is higher by a
predetermined amount than pressure in the second volume.
5. The damper of claim 1 wherein said second piston is in the first
position when pressure in the second volume is higher than pressure
in the first volume.
6. The damper of claim 1 wherein said first piston includes a third
flow path for the flow of hydraulic fluid from the first volume to
the second volume.
7. The damper of claim 1 wherein said damper provides a damping
force that opposes compression and rebound, and said second piston
moves to the second position during rebound.
8. The damper of claim 1 wherein said damper provides a damping
force that opposes compression and rebound, and said second piston
moves to the second position during compression.
9. The damper of claim 1 wherein said damper provides a damping
force that opposes compression and rebound, and the second flow
path is not operable during rebound, and the first flowpath is
operable during compression and rebound.
10. The damper of claim 1 wherein said damper provides a damping
force that opposes compression and rebound, and the second flow
path is not operable during compression, and the first flowpath is
operable during compression and rebound.
11. A hydraulic damper, comprising: a first housing defining a
cavity for hydraulic fluid; a first piston slidable within the
cavity and dividing the cavity into a first volume and a second
volume; a rod extending from the cavity, said first piston being
attached to said rod, said rod including an internal passageway for
flow of hydraulic fluid between said first volume and said second
volume; a second housing in fluid communication with the first
volume and attached to said rod, said second housing including an
internal chamber and a second piston slidable within the chamber
between a first position and a second position, said second piston
providing a flow path for the flow of hydraulic fluid from the
first volume through the internal passageway and into the second
volume in the second position, said second piston having a surface
area; and a spring biasing said second piston toward the first
position; wherein in the first position a portion of the surface
area is exposed to pressure in the first volume and the remainder
of the surface area is not exposed to pressure in the first volume,
the portion coacting with pressure above a predetermined value in
the first volume to move said second piston toward the second
position.
12. The damper of claim 11 wherein in the second position pressure
above the predetermined value in the first volume coacts with the
surface area to maintain said second piston in the second
position.
13. The damper of claim 11 wherein said second housing includes
internal walls and the surface area and the internal walls define a
third volume, said second housing includes an orifice providing
fluid communication between the third volume and the first volume,
and said second piston is adapted and configured to discourage flow
from the first volume to the third volume when said second piston
is in the first position.
14. The damper of claim 11 wherein said second housing includes
internal walls and the surface area and the internal walls define a
third volume, said second housing includes an orifice providing
fluid communication between the third volume and the first volume,
and the portion of the surface area is substantially the same as
the area of the orifice.
15. The damper of claim 11 wherein the flow path is a first flow
path, said first piston includes a second flow path for the flow of
hydraulic fluid from the first volume to the second volume, and the
first flow path and the second flow path operate in parallel when
hydraulic pressure in the first volume exceeds a predetermined
value.
16. The damper of claim 11 wherein the flow path is a first flow
path, said first piston includes a second flow path for the flow of
hydraulic fluid from the first volume to the second volume, and the
first flow path and the second flow path operate in parallel when
said second piston is in the second position.
17. The damper of claim 11 wherein the flow path is a first flow
path, said second piston providing a second flow path for the flow
of hydraulic fluid from the first volume through the internal
passageway and into the second volume in the first position, and
the second flow path is more restrictive than the first flow
path.
18. The damper of claim 11 wherein the remainder of the surface
area is greater than the portion of the surface area.
19. The damper of claim 11 wherein the flow path is a first flow
path, and said first piston includes a second flow path for the
flow of hydraulic fluid from the first volume to the second
volume.
20. An apparatus for a hydraulic damper having a rod with an
internal flowpath for hydraulic fluid and a threaded end,
comprising: a housing including a first part coupled to a second
part and defining an internal chamber therebetween, said housing
being adapted and configured for threadably coupling to the rod; a
piston slidable within the internal chamber, said piston including
an aperture adapted and configured to be in flow communication with
the internal flowpath; and a spring biasing said piston toward one
end of the chamber.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/144,530, filed Jun. 23, 2008, now issued as
U.S. Pat. No. 9,494,209, on Nov. 15, 2016, which claims the benefit
of priority of U.S. Provisional Patent Application Ser. No.
60/945,365, filed Jun. 21, 2007, all of which are incorporated
herein by reference.
FIELD OF THE INVENTION
[0002] The present invention pertains to shock and vibration
dampers, and in particular to a hydraulic shock absorber having
regressive characteristics.
BACKGROUND OF THE INVENTION
[0003] Vehicles that traverse a roadway must deal with
irregularities in the roadway such as bumps and depressions. Many
wheeled vehicles incorporate damped suspensions. The damping force
levels are usually a compromise between low speed damping support
of the vehicle body movements and high speed damping of bumps and
depressions. Too much low speed damping for improved body control
can result in a harsh ride at higher speeds with hydraulic dampers,
because the hydraulic damping force is a function of the velocity
of the piston and this force typically increases as the velocity
increases.
[0004] What is needed is a damper that provides adequate low speed
damping for improved body control, without increasing the harshness
of the vehicle ride at higher speeds. The present invention does
this in novel and unobvious ways.
SUMMARY OF THE INVENTION
[0005] The present invention pertains to improvements in gas and
fluid dampers that provide a regressive damping characteristic in
both compression and extension. One aspect of some embodiments of
the apparatus is to produce a damping characteristic during damper
movement in one direction in which the resistance created at low
shaft velocities is greater than the damping resistance created at
higher shaft velocities. In some embodiments, this regressive
characteristic (in which the damping force at a high velocity is
lower than the damping force at a low velocity) occurs in
compression of the shock absorber, whereas in other embodiments
this characteristic occurs in extension or rebound. Some
embodiments of the present invention pertain to hydraulic dampers
that include a hydraulic switching device that increases the flow
area of a restriction in an internal flowpath during moderate
velocity operation. The flow area is not increased during low
velocity operation, and the increased flow area is maintained
during high velocity operation.
[0006] Yet another embodiment of the present invention pertains to
a damper having multiple flowpaths in parallel across the main
piston of the damper. The first flowpath includes multiple fixed
restrictions. The second flowpath includes one or more one-way
valves. A first, higher pressure drop fixed restriction provides
fluid communication during all compression operation of the damper.
A second, lower pressure drop restriction is operative above a
predetermined pressure differential across the main piston.
[0007] Yet another embodiment of the present invention pertains to
a hydraulic damper including a first piston slidable within a first
housing, and a second piston slidable within a second housing, the
second housing being located within one of the chambers defined by
the first piston. The second piston is operable to create multiple
flowpaths between the volume defined by the first piston, with one
flowpath being more restrictive than another flowpath.
[0008] Yet another embodiment of the present invention pertains to
a hydraulic damper including a first piston slidable within a first
housing, and a second piston slidable within a second housing, the
second housing being located within one of the chambers defined by
the first piston. The second piston is biased to a position by a
spring, and slides between two positions based on the pressure drop
across the second piston.
[0009] Yet another embodiment of the present invention pertains to
a retrofit kit for a hydraulic damper. The kit includes a housing
that can be coupled to either the piston or rod of the damper. The
housing includes a piston slidable within an interior chamber. A
spring biases the piston toward one end of the chain.
[0010] Yet another embodiment of the present invention pertains to
an assembly for modifying the damping characteristics of a shock
absorber. In one embodiment, the apparatus is located within a
housing that is not within the cylindrical body of the shock
absorber. This housing includes an inner valve assembly, the valve
assembly containing a spring loaded poppet or piston. The piston or
poppet is slidable relative to the inner housing in which it is
located. One end of the housing has a fluid port that is in fluid
communication with the inlet of the valve housing. Preferably, the
housing further includes a second fluid port that is in fluid
communication with the outlet of the valve housing. The piston and
valve housing coact to form at least two flowpaths from the inlet
to the outlet. Preferably, the first, at-rest position of the valve
housing relative to the piston provides a first, more restrictive
flowpath from inlet to outlet. In yet other embodiments, the second
position of the piston relative to the valve housing opens a
second, additional flowpath from inlet to outlet. The inlet and
outlet are in fluid communication with different ones of the
rebound volume or compression volume within the cylinder, and can
therefore provide, in one orientation of the assembly, a regressive
force characteristic during rebound, and in the opposite
orientation provide a regressive force characteristic in
compression.
[0011] Yet another embodiment of the present invention pertains to
a head valve for a shock absorber, the head valve including a valve
assembly that provides regressive forcing characteristics.
Preferably, the head valve including the valve assembly are mounted
on one end of the fluid and nitrogen reservoir that compensate for
hydraulic fluid expansion, hydraulic volume displaced by the
central rod, or other characteristics.
[0012] In yet another embodiment of the present invention, there is
an externally adjustable valve that provides the user one or more
adjustments by which a regressive forcing characteristic can be
modified without taking the shock absorber apart. In one
embodiment, there is a first adjustment that changes the preload on
a spring that biases a piston toward a first position. In some
embodiments, there is a second adjustment that modifies the higher
velocity portion of the regressive forcing characteristic. In some
embodiments, there is a third adjustment that modifies the lower
velocity portion of the regressive forcing characteristic.
[0013] These and other features and aspects of different
embodiments of the present invention will be apparent from the
claims, specification, and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1a is a cutaway view of a prior art shock absorber.
[0015] FIG. 1b is a cutaway view of another prior art shock
absorber.
[0016] FIG. 1c is a cutaway view of a portion of another prior art
shock absorber.
[0017] FIG. 2 is a cross-sectional perspective view of a portion of
a shock absorber according to one embodiment of the present
invention.
[0018] FIG. 3 is a view of the shock absorber of FIG. 2 operating
in a regressive mode.
[0019] FIG. 4a is a cross-sectional perspective view of a portion
of a shock absorber according to another embodiment of the present
invention.
[0020] FIG. 4b is a schematic representation of the shock absorber
of FIG. 4a.
[0021] FIG. 4c is a schematic representation of an apparatus
according to another embodiment of the present invention providing
regressive operation during rebound.
[0022] FIG. 5 is a graphical depiction of the characteristics of a
shock absorber having regressive characteristics in compression
according to another embodiment of the present invention.
[0023] FIG. 6 is a perspective cross sectional view of the
apparatus of FIG. 8 installed within a damper.
[0024] FIG. 7 is a perspective cross sectional view of the
apparatus of FIG. 8 installed within a damper during a different
mode of operation.
[0025] FIG. 8 is a cross sectional view of a portion of a shock
absorber according to one embodiment of the present invention.
[0026] FIG. 9 is a graphical depiction of the characteristics of a
shock absorber according to another embodiment of the present
invention.
[0027] FIG. 10a is a cross-sectional view of a portion of a shock
absorber head valve according to another embodiment of the present
invention.
[0028] FIG. 10b is a close up of a portion of the apparatus of FIG.
10a.
[0029] FIG. 11 is a graphical depiction of the characteristics of a
shock absorber having regressive characteristics in rebound
according to another embodiment of the present invention.
[0030] FIG. 12 is a graphical depiction of the characteristics of a
shock absorber having adjustable regressive characteristics in
rebound according to another embodiment of the present
invention.
[0031] FIG. 13 is a graphical depiction of the characteristics of a
shock absorber having adjustable regressive characteristics in
rebound according to another embodiment of the present
invention.
[0032] FIG. 14 is a schematic representation of a shock absorber
utilizing the apparatus of FIG. 8 according to another embodiment
of the present invention.
[0033] FIG. 15 is a graphical depiction of the characteristics of a
shock absorber having adjustable regressive characteristics in
rebound according to another embodiment of the present
invention.
[0034] FIG. 16 is a cutaway, perspective view of an apparatus
according to another embodiment of the present invention.
[0035] FIG. 17 is a cross sectional orthogonal view of the
apparatus of FIG. 16.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0036] For the purposes of promoting an understanding of the
principles of the invention, reference will now be made to the
embodiments illustrated in the drawings and specific language will
be used to describe the same. It will nevertheless be understood
that no limitation of the scope of the invention is thereby
intended, such alterations and further modifications in the
illustrated device, and such further applications of the principles
of the invention as illustrated therein being contemplated as would
normally occur to one skilled in the art to which the invention
relates.
[0037] The use of an N-series prefix for an element number (NXX)
refers to an element that is the same as the non-prefixed element
(XX), except as shown and described thereafter. Although various
specific quantities (spatial dimensions, temperatures, pressures,
times, force, resistance, current, voltage, concentrations, etc.)
may be stated herein, such specific quantities are presented as
examples only, and are not to be construed as limiting.
[0038] One embodiment of the present invention pertains to a damper
having regressive characteristics in both rebound and compression.
As one example, during compression of the damper at low velocity,
the force required to compress the damper progressively increases
as the compressive velocity of the damper increases. During
operation at moderate compressive velocities, the force required to
compress the damper regressively decreases as the velocity
increases. At still higher compressive velocities, the damping
force progressively increases with increased compressive
velocity.
[0039] One embodiment of the present invention pertains to a damper
having regressive characteristics. During extension of the damper
at low velocity, the force required to extend the damper
progressively increases as the extensive velocity of the damper
increases. During operation at moderate extensive velocities, the
force required to extend the damper regressively decreases as the
velocity increases. At still higher extensive velocities, the
damping force progressively increases with increased extensive
velocity.
[0040] FIG. 1a shows a cross-sectional view of a prior art shock
absorber 20. A main piston 22 is coupled to a moveable rod 24,
piston 22 being slidably received within the inner diameter 26.1 of
a main cylinder 26. Piston 22 is retained on the end of rod 24 by a
coupling nut 24.2. Main piston 22 generally subdivides the internal
volume of cylinder 26 into a compression volume 26.4 located
between piston 22 and the compression end 28 of shock 20, and a
second rebound volume 26.5 located between piston 22 and the
rebound end 30 of shock 20. The movement of piston 22 and rod 24
toward rebound end 32 results in a reduction in the size of
compression volume 26.1, and the subsequent flow of hydraulic fluid
20.1 through a compression flowpath 32 in piston 22 and into the
simultaneously enlarging rebound volume 26.5. Likewise, movement of
piston 22 toward rebound end 30 of shock 20 results in the flow of
hydraulic fluid 20.1 through a rebound flowpath 34 in piston 22 and
into the simultaneously enlarging compression volume 26.4.
[0041] In order to compensate for changes in the density of
hydraulic fluid 20.1 and shaft-displaced fluid, shock absorber 20
includes a nitrogen chamber separated by a reservoir piston 38 from
the fluid-wetted volume of cylinder 26.
[0042] Shock absorber 20 is typically used with the suspension of a
vehicle. Rod 24 includes a first suspension attachment 26.3, and
end cap 26.2 of cylinder 26 includes a second suspension attachment
26.3. These suspension attachments 26.3 permit the pivotal
connection of shock absorber 20 to a portion of the vehicle
suspension on one end, and on the other end to a portion of the
vehicle frame. It is well known to use shock absorbers on many
types of vehicles, including motorcycles, buses, trucks,
automobiles, and airplanes. Further, although shock absorber 20 has
been referred to for being used on a vehicle, shock absorbers are
also known to be used in other applications where it is beneficial
to dampen the movement of one object relative to another object,
such as dampers for doors.
[0043] Compression flowpath 32 includes a fluid passageway
interconnecting volumes 26.4 and 26.5 with a one-way valve in the
flowpath 32. This one-way valve can be one or more annular shims
which are prevented from flexing in one direction (and thus
substantially restricting flow), but able to flex in a different
direction (and thus allow flow in this opposite direction).
Likewise, rebound flowpath 34 provides fluid communication between
volumes 26.4 and 26.5 through a one-way valve. Often, the one-way
valve of the compression flowpath 32 has different characteristics
than the one-way valve of rebound flowpath 34.
[0044] FIG. 1b shows a cross-sectional view of a second prior art
shock absorber 20'. Shock absorber 20' includes a second, separate
cylinder 37' which includes gas reservoir 40'. A piston 38'
slidably received within cylinder 37' separates gas volume 40' from
compression volume 26.4'. An external fluid connection 39'
interconnects the hydraulic fluid end of piston 37' with the
compression end of shock absorber 20'. Cylinder 37' includes a gas
port in one end of cylinder 37' for entry or removal of
nitrogen.
[0045] Shock absorber 20' includes means for varying the fluid
resistance of a flowpath interconnecting compression volume 26.4'
and rebound volume 26.5'. Rod 24' includes an internal passage
24.1' that extends out one end of shaft 24', and extends in the
opposite direction towards attachment 26.3'. The open end of
internal passage 24.1' is in fluid communication with one or more
orifices 24.4' that extend from internal passage 24.1' to rebound
volume 26.5'. The flow of fluid through this internal passageway
between the compression and rebound volumes is restricted by a
metering needle 24.3' received within internal passage 24.1'. The
position of metering needle 24.3' can be altered by a pushrod 24.6'
also extending within internal passage 24.1'. Push rod 24.6'
includes an end 24.7' that is adapted and configured to mate with
an internal adjustment screw 24.5'. The inward adjustment of screw
24.5' acts on the angled interface to push rod 24.6' and adjustment
needle 24.3' toward a position of increased resistance in the
internal flowpath.
[0046] FIG. 1c is a cross sectional view of a portion of another
prior art shock absorber. The apparatus in FIG. 1c shows a piston
22'' coupled to a shaft 24'' by a coupling nut 24.2''. Shaft 24''
includes an internal flowpath from orifice 22.3'' through internal
passage 24.1'' and into shaft orifice 24.4''. This internal
flowpath bypasses piston 22''.
[0047] Piston 22'' includes a pair of shim sets 36'', each shim set
shown including 4 individual washers. During operation in
compression (i.e., movement in FIG. 1c toward the left) fluid is
able to freely enter compression flowpath 28.1''. However, fluid is
unable to exit through flowpath 28.1'' and into the rebound side of
the shock absorber unless fluid pressure is sufficiently great to
bend the periphery shim stack 36C'' away from the shim edge support
29.4'' of piston 22''. During operation in rebound, (i.e., movement
in FIG. 1c toward the right) fluid is able to freely enter
compression flowpath 30.1''. However, fluid is unable to exit
through flowpath 30.1'' and into the compression side of the shock
absorber unless fluid pressure is sufficiently great to bend the
periphery shim stack 36R'' away from the shim edge support 29.4''
of piston 22''. A resilient seal 22.1'' substantially seals the
compressive side of piston 22'' from the rebound side of piston
22''. An energizing backup seal 22.2'' urges seal 22.1'' outwardly
into contact with the inner wall of the cylinder.
[0048] Although what has been shown described is a shock absorber
20 that is linear in operation, the prior art of shock absorbers
further includes rotary dampers, such as the toroidal damper
disclosed in U.S. Pat. No. 7,048,098, incorporated herein by
reference. In addition, although FIGS. 1a, 1b, and 1c depict
particular types of prior art shock absorbers, the various
embodiments of the present invention are not so constrained. For
example, the regressive valve assemblies and methods described and
shown herein are further applicable with shock absorbers as
disclosed in U.S. patent application Ser. No. 11/261,777, filed
Oct. 31, 2005 for inventors Nygren and Loow.
[0049] As used herein, the word compression refers to the action
and direction of the shock absorber during compression of the wheel
suspension, this term being synonymous with the term jounce.
Therefore, the end of the shock absorber referred to as a
compression end is the end which has a reduction in internal volume
(due to movement of the piston relative to the cylinder) during
compression of the vehicle suspension. The rebound end of the shock
absorber is the end that is opposite of the compression end.
[0050] FIGS. 2 and 3 are prospective, cutaway views of a portion of
a shock absorber 120 according to one embodiment of the present
invention. For the sake of clarity, only certain portions of shock
absorber 120 are shown. Shock absorber 120 includes a housing
assembly 150 according to one embodiment of the present invention.
In one embodiment, valve housing assembly 150 comprises a first
part 152 and second part 154 that are threadably coupled by threads
152.1 and 154.1 to form housing 150. Valve housing assembly 150
includes a piston 160 which is slidable within an internal chamber
formed by the coupling of first part 152 to second part 154.
[0051] A spring 170 biases piston 160 toward one end of the
internal chamber. Spring 170 is received within a spring pocket
defined at one end by a pocket 152.2 in the first part 152 of
housing 150, and defined at the other end by a spring receiving
pocket or spring-receiving surface 160.8 of piston 160. When first
part 152 and second part 154 of housing 150 are threadably coupled
together, spring 170 is adapted and configured to place a
predetermined force on the underside surface 160.8, such that
piston 160 is preloaded toward one end of its range of travel.
[0052] Preferably, housing assembly 150 is threadably coupled to
the end of rod 124 in place of, or proximate to, a coupling nut
(not shown). In one embodiment, housing 150 is threadably coupled
to rod 124 proximate to main piston 122. However, the present
invention also contemplates those embodiments in which housing 150
is further integrated with piston 122, including those embodiments
in which secondary piston 160 and spring 170 are incorporated
within the main piston.
[0053] Referring to FIG. 2, piston 160 is slidable within an
internal chamber formed by the coupling of housing first part 152
to housing second part 154. In FIG. 2 piston 160 is shown in the
first position, as would be experienced during rebound operation of
shock absorber 120, and also during lower velocity compression
operation. A projection 160.9 of piston 160 projects from a
substantially planar face and further extends within an aperture
154.3 of second housing part 154.
[0054] In some embodiments of the present invention, piston 160
includes a central orifice 160.2 that provides fluid communication
between compression volume 126.4 and rebound volume 126.5 by way of
internal passage 124.1 of rod 124 during all operation of the
damper. However, the present invention also contemplates those
embodiments in which a similar flowpath is established through main
piston 122, and also those embodiments in which there is no fixed
restriction between the compression volume and rebound volume that
is operable during all operation of the damper.
[0055] Housing assembly 150 is generally exposed to hydraulic
pressure within the compression volume 126.4 of shock 120.
Therefore, this hydraulic pressure is communicated to a portion
160.6 of piston 160 that is in fluid communication with aperture
154.3. Hydraulic pressure within compression volume 126.4 coacts
with the portion 160.6 of the surface area of piston 160 to apply a
force to piston 160 that tends to push piston 160 away from second
housing part 154.
[0056] The pressure force on piston 160 described above is opposed
by a spring force. Spring 170 is adapted and configured to be
preloaded when installed within housing 150. Spring 170, located
within a pocket 152.2 of first housing part 152, applies a biasing
force to push piston 160 toward the first position. There is
hydraulic pressure applied to the underside 160.10 of piston 160.
This underside pressure is communicated from orifices 124.4 in rod
124 into internal passage 124.1. The hydraulic pressure within
internal passage 124.1 is also influenced by hydraulic fluid that
flows between compression volume 126.4 and rebound volume 126.5 by
way of main orifice 160.2. This pressure is communicated to the
volume of the internal chamber generally bounded by spring pocket
152.2 and the underside 160.10 of piston 160.
[0057] This pressure within passage 124.1 is further communicated
through a plurality of peripheral orifices 160.3 in the body of
piston 160. These orifices communicate this underside hydraulic
pressure to the front side of piston 160 (i.e., the volume between
the opposing planar surfaces of piston 160 and housing part 154).
Because of communication through orifices 160.3, the pressure force
on piston 160 in the first position results from the coaction of
the difference in pressures between compression volume 126.4 and
the pressure within internal passage 124.1, acting on the portion
of surface area of piston 160 that projects from aperture
154.3.
[0058] Piston 160 is slidably received within the inner cylindrical
circumferential wall 154.2 of housing part 154. In some
embodiments, the outer diameter 160.1 of piston 160 discourages
leakage flow within the internal chamber by way of a close fit
between the outer diameter 160.1 of piston 160 and the walls 154.2
of housing 154. However, in some embodiments piston 160.6 includes
a seal to discourage leakage flow, such as a Teflon.RTM. seal
backed up by a spring.
[0059] Leakage flow of hydraulic fluid from compression volume
126.4 into the third internal volume of internal chamber 156 is
discouraged by a close fit between a portion of the outer diameter
of projection 160.9 and the side walls of aperture 154.3. In one
embodiment, projection 160.9 includes a generally cylindrical
portion for sealing purposes, and also a scalloped portion which
maintains guidance of the projection within the aperture, the
scalloped portions also permitting flow of hydraulic fluid after
the sealing portion of projection 160.9 moves out of aperture
154.3. This flow past the scalloped portion occurs when piston 160
moves toward its second position.
[0060] FIG. 3 shows piston 160 in its second position during
regressive operation of shock absorber 120. Piston 160 moves toward
this position when the pressure differential between the pressure
in compression volume 126.4 and the pressure within passage 124.1
coact with the surface area of projection 160.9 sufficiently to
overcome the biasing force of spring 170. As piston moves away from
the first position, the sealing portion of projection 160.9 no
longer discourages flow into the chamber of housing 150. Further,
the scalloped sections of the projection permit flow from
compression volume 126.4 into chamber 156. As hydraulic fluid
enters internal chamber 156, it flows into internal passage 124.1
of rod 124 by way of one or more secondary flow orifices 160.3
located within piston 160. Flow orifices 160.3 are laterally
displaced from central orifice 160.2.
[0061] The operation of a valve assembly 150 having a slidable,
sealed piston preloaded by a spring 170 within threadably coupled
members 154 and 152 can be adapted to provide regressive forcing
characteristics for both compression and extension (or rebound) of
a shock absorber. Further, the general operation of a regressive
valve assembly as previously described can be adapted in various
other configurations of apparatus as will now be shown and
described.
[0062] FIG. 4a is a perspective, cutaway view of a portion of a
shock absorber 220 according to one embodiment of the present
invention. For the sake of clarity, only certain portions of shock
absorber 220 are shown. Shock absorber 220 includes a valve housing
assembly 250 according to one embodiment of the present invention.
In one embodiment, valve housing assembly 250 (which may pertain to
a second housing, in some embodiments in which the main cylinder
can be considered the first housing) comprises a first part 252 and
second part 254 that are threadably coupled by threads 252.1 and
254.1 to form housing 250. Housing assembly 250 includes a piston
260 (which in some embodiments may be considered a second piston,
in reference to a first main piston slidable within the main
cylinder) which is slidable within an internal chamber formed by
the coupling of first part 252 to second part 254.
[0063] A spring 270 biases piston 260 toward one end of the
internal chamber. Spring 270 is received within a spring pocket
defined at one end by a pocket 252.2 in the first part 252 of
housing 250, and defined at the other end by a spring receiving
pocket or surface 260.8 of piston 260. When first part 252 and
second part 254 of housing 250 are threadably coupled, spring 270
is adapted and configured to place a predetermined force on the
underside surface 260.8, such that piston 260 is preloaded toward
one end of its range of travel.
[0064] Preferably, housing assembly 250 is threadably coupled to
the end of rod 224 in place of, or proximate to, a coupling nut
(not shown). In one embodiment, housing 250 is threadably coupled
to rod 224 proximate to main piston 222. However, the present
invention also contemplates those embodiments in which housing 250
is further integrated with piston 222, including those embodiments
in which secondary piston 260 and spring 270 are incorporated
within the main piston.
[0065] Piston 260 is slidable within an internal chamber formed by
the coupling of housing first part 252 to housing second part 254.
Piston 260 is shown in the first position, as would be experienced
during rebound operation of shock absorber 220 and also during low
velocity compression operation. A projection 260.9 of piston 260
projects as a plateau from a substantially planar face of piston
260, and further extends into contact with the face and edge of an
aperture 254.3 of second housing part 254.
[0066] In some embodiments of the present invention, piston 260
includes a central orifice 260.2 that provides fluid communication
(and in some embodiments a first flowpath) between compression
volume 226.4 and rebound volume 226.5 by way of internal passage
224.1 of rod 224 during all operation of the damper. However, the
present invention also contemplates those embodiments in which a
similar flowpath is established through main piston 222, and also
those embodiments in which there is no fixed restriction between
the compression volume and rebound volume that is operable during
all operation of the damper.
[0067] Housing assembly 250 is generally exposed to hydraulic
pressure within the compression volume 226.4 of shock 220.
Therefore, this hydraulic pressure is communicated to a portion
260.6 within plateau 260.9 of piston 260 that is in fluid
communication with aperture 254.3. Hydraulic pressure within
compression volume 226.4 coacts with the surface of portion 260.6
to apply a force to piston 260 that tends to push piston 260 away
from second housing part 254.
[0068] The force on piston 260 described above is opposed by a
pressure and spring force. Spring 270, located within a pocket
252.2 of first housing part 252, applies a biasing force to push
piston 260 toward the first position. There is hydraulic pressure
is applied to the underside 260.10 of piston 260. This underside
pressure is communicated from orifices 224.4 in rod 224 into
internal passage 224.1. The hydraulic pressure within internal
passage 224.1 is also influenced by hydraulic fluid that flows
between compression volume 226.4 and rebound volume 226.5 by way of
a main orifice 260.2. This pressure is communicated to the volume
of the internal chamber generally bounded by spring pocket 252.2
and the underside 260.10 of piston 260.
[0069] This pressure within passage 124.1 is further communicated
through a plurality of peripheral orifices 260.3 in the body of
piston 260. These orifices communicate this underside hydraulic
pressure to the front side of piston 260 (i.e., the volume between
the opposing planer surface of piston 260 and housing part 254.
Because of communication through orifices 260.3, the pressure force
on piston 260 in the first position results from the coaction of
the difference in pressures between compression volume 226.4 and
the pressure within internal passage 224.1, acting on the surface
area of piston 160 that projects from aperture 254.3.
[0070] Piston 260 is slidably received within the cylindrical
circumferential wall 254.2 of housing part 254. In some
embodiments, the outer diameter 260.1 of piston 260 discourages
leakage flow within the internal chamber by way of a close fit
between the outer diameter 260.1 of piston 260 and the walls 254.2
of housing 254. However, in some embodiments piston 260.6 includes
a slidable seal to discourage leakage flow, such as a Teflon.RTM.
seal backed up by a spring.
[0071] Leakage flow of hydraulic fluid from compression volume
226.4 into the third internal volume of internal chamber 256 is
discouraged by a face seal between a portion of the outer diameter
of projection 260.9 and the edge of aperture 254.3. In one
embodiment, projection 260.9 includes a generally cylindrical
plateau for sealing purposes. The abutting faces of plateau 260.9
and the edge of aperture 254.3 are smooth and coplanar to form the
face seal. In yet other embodiments, one or both of these abutting
surfaces can include a resilient face seal, such as a elastomeric
seal molded or placed within a groove on plateau 260.9.
[0072] During regressive operation of shock absorber 220, Piston
260 moves toward the second position. When the pressure
differential between the pressure in compression volume 226.4 and
the pressure within passage 224.1 coact with the surface area of
projection 260.9, is sufficient to overcome the biasing force of
spring 270, piston 260 moves away from the first position, and the
face seal between projection 260.9 and the edge of aperture 254.3
no longer discourages flow into the internal chamber of housing
250. Movement of piston 260 toward the second position creates a
gap between the formerly abutting surfaces into which hydraulic
fluid flows from compression volume 226.4. Such movement of piston
260 is similar to the movement of piston 160 shown in FIG. 3.
Referring again to FIG. 4, as hydraulic fluid enters internal
chamber 256, it flows into internal passage 224.1 of rod 224 by way
of one or more secondary flow orifices 260.3 located within piston
260 (and in some embodiments flow through the secondary flow
orifices along with flow through central orifice 260.2 comprise a
second flowpath, this second flowpath being less restrictive than
the first flowpath because of the addition and uncovering of the
flow orifices 260.3). Flow orifices 260.3 are preferably laterally
displaced from central orifice 260.2.
[0073] FIG. 4b is a schematic representation of the shock absorber
of FIG. 4a. During regressive operation of shock absorber 220,
piston 260 moves toward the second position. Movement of piston 260
toward the second position creates a gap between the formerly
abutting surfaces into which hydraulic fluid flows from compression
volume 226.4. During lower velocity compression of shock absorber
220, hydraulic fluid flows from compression volume 226.4 into
rebound volume 226.5 through central orifice 260.2 of piston 260,
and also through a one-way valve 236 of main piston 222.
[0074] FIG. 4c is a schematic representation of an apparatus
according to another embodiment of the present invention providing
regressive operation during rebound. During regressive operation of
shock absorber 820, piston 860 moves toward the second position.
Movement of piston 860 toward the second position creates a gap
between the formerly abutting surfaces into which hydraulic fluid
flows from rebound volume 826.5. During lower velocity rebound of
shock absorber 820, hydraulic fluid flows from rebound volume 826.5
into compression volume 826.4 through central orifice 860.2 of
piston 860, and also through a one-way valve 836 of main piston
822.
[0075] FIG. 5 graphically depicts the damping force characteristics
110 of a shock absorber according to one embodiment of the present
invention. Damping curves 110 include graphical depictions 111,
112, and 113 of compressive operation, and graphical depiction 114
of rebound operation. In addition, FIG. 5 includes graphical
depictions 115 and 116 of the compressive and rebound
characteristics, respectively, of a known shock absorber.
Explanation of damping curves 110 will now be made in reference to
shock absorber 220, and it is understood that this explanation is
generally applicable to shock absorber 120 as well.
[0076] During lower velocity compression of shock absorber 220,
hydraulic fluid flows from compression volume 226.4 into rebound
volume 226.5 through central orifice 260.2 of piston 260, and also
through a one way valve 236 of main piston 222. Referring to FIG.
5, the relationship between the damping force and shock absorber
relative velocity is indicated by a first progressive portion 111
of composite damping curves 110.
[0077] At moderate compressive velocities, the pressure force
acting on piston 260 causes it to move from a first, sealing
position toward a second, open position. This movement of piston
260 results in the ability of hydraulic fluid from compression
volume 226.4 to flow through secondary orifices 260.3 of piston
260, as well as through central orifice 260.2. This additional flow
area results in a reduction in pressure within compression volume
226.4, such that the pressure drop across main piston 222 is
reduced and the damping force is reduced. Operation in this regime
is depicted by the regressive portion 112 of damping curves
110.
[0078] However, this reduction in pressure does not result in
piston 260 moving back to the first position, since the pressure of
compression volume 226.4 is communicated to a larger surface area
in the second position. Therefore, the coaction of a reduced
pressure differential with an increased surface area results in a
pressure force capable of maintaining piston 260 in the second
position.
[0079] At still higher relative higher compressive velocities (as
depicted by the second progression portion 113 of damping curve
110), the regressive contribution of housing assembly 250 remains
relatively constant, and the overall damping characteristics of the
shock absorber are dictated primarily by the one way valves 236 of
piston 222, as well as any metering needles 224.3, or other flow
components of piston 220. The resultant combined characteristic in
compressive flow is thus that of a higher pressure drop fixed
restriction in parallel with a one way valve at low velocities, and
a lower pressure drop fixed restriction in parallel with a one way
valve the same one way valve at higher velocities. There is an
initial progressive characteristic, followed by a regressive
characteristic, which is followed by a second progressive
characteristic that is substantially parallel to an extension of
the first progressive characteristic. This second progressive
characteristic provides a damping characteristic at higher rod
velocities.
[0080] In one illustrative embodiment, the initial progressive
characteristic extends up to about 4 inches/second. The regressive
characteristic extends from about 5 to 6 inches/second. The second
progressive characteristic extends from about 7 inches/second. In
one illustrative embodiment, the second progressive characteristic
is about 75 lbf lower than a substantially parallel extension of
the first progressive characteristic. FIGS. 6, 7, and 8 represent a
shock absorber 320 according to another embodiment of the present
invention. Shock absorber 320 includes a regressive valve assembly
350 that provides a regressive forcing characteristic during
extension of the shock absorber. These regressive extension
characteristics are shown graphically in FIG. 11.
[0081] Valve housing assembly 350 is similar to valve housing 150
and 250 as previously described, except for the changes discussed
and shown herein.
[0082] Valve housing 350 includes a piston or poppet 360 that is
slidably movable relative to first members 352 and 354. Piston 360
includes an internally threaded bore that is threadably received on
the end of rod 324. Piston 360 thus moves with rod 324. A spring
370 is captured between a spring pocket 352.2 of member 352 and
spring pocket 360.8 of piston 360. Spring 370 biases piston 360
relative to threadably couple the members 352 and 354 such that
surface 360.4 of piston 360 is in sealing contact with face sealing
surface 354.4 of member 354.
[0083] During extension of damper 320 at lower stroking velocities,
rod 324 moves downward and to the left as viewed in FIG. 6.
Hydraulic fluid within rebound volume 326.5 is displaced and moves
toward piston 322. If the pressure in the rebound volume 326.5 is
sufficiently great, then this pressure acts on the stack of shims
336 that act as a one way valve, deflect the shims, and hydraulic
fluid flows through a passageway within piston 322 and into
compression volume 326.4.
[0084] In addition to this flowpath, the fluid within rebound
volume 326.5 being displaced by movement of rod 324 is also able to
flow through a plurality of feed apertures 324.4 into a central
internal passage 324.1. This fluid can flow through the restriction
provided by orifice 354.3 that is provided within member 354. As
shown in FIG. 6, hydraulic fluid in this flow-path flows with
little or no restriction through a central orifice 360.2 within
piston 360. Thus, in comparing valve assemblies 350 and 150, it can
be seen that the location of the most restrictive portion of this
flow-path is preferably located in first member 354 in valve
assembly 350, and in piston 260 of valve assembly 250. However, the
present invention also contemplates those embodiments in which this
most restrictive portion of the flow-path can be placed in either
of the members X54 (154, 254, 354, etc.) or piston X60.
[0085] FIG. 7 depicts valve assembly 350 of shock absorber 320 at
higher stroking velocities. Hydraulic fluid from within compression
volume 326.4 is free to flow within the spring pocket of housing
350 by way of a plurality of apertures 352.4 within member 352.
These apertures permit pressure of the compression volume 326.4 to
be communicated to the underside of piston 360, up to and including
a peripheral resilient seal 360.7. Fluid from compression volume
326.4 is also free to flow to the topside of piston 360 by way of a
plurality of apertures 354.3. Thus, as shown in FIG. 6, pressures
on both sides of piston 360 are the same, although there is a
larger surface area on the side of piston 360 that faces
compression end 328. Therefore, there is a net pressure force that
pushes piston 360 (as viewed in FIG. 6) toward the left. However,
this pressure force is counter-balanced by a preload from spring
370 located within its spring pocket.
[0086] Referring to FIG. 7, as pressure in the compression volume
326.4 increases (as a result of a higher extension velocity) the
difference in area on either side of the piston, co-acting with the
higher fluid pressure is sufficient to overcome the preload of the
spring and move housing 350 toward the right (as viewed in FIG. 7.)
This relative movement between housing 350 and piston 360 opens a
second flow-path from central passage 324.1 of rod 324 to the
plurality of orifices 354.3 of member 354. This second, high
extension velocity flow-path 382 has a higher flow number, and
therefore permits a higher flow of fluid for a given pressure
differential, in comparison to low speed flow-path 380.
[0087] FIG. 9 depicts a portion of a shock absorber 420 having
regressive characteristics in extension. Shock absorber 420
includes a rod 420 having a threaded end that is threadably coupled
to a member 454 of a valve assembly 450. Valve assembly 450 is
similar to valve 150 as shown in FIGS. 2 and 3 except as shown and
described hereafter.
[0088] In comparing FIGS. 2 and 9, it can be seen that rod 124 is
threadably received by housing member 152 of valve assembly 150,
whereas valve assembly 450 is threadably received on the other end
of the assembly by threads 454.5 of member 454. Note that the
relative direction of flow within valves 150 and 450 is the same:
fluid flows in the direction from the first member X54 through
piston X60 and finally through the second member X52. However,
since the valve 450 is oriented as shown in FIG. 9, valve 450
provides regressive flow characteristics in the direction of
extension.
[0089] FIGS. 10a and 10b show cross sectional views of an apparatus
620 according to another embodiment of the present invention. FIG.
10a shows a shock absorber 620 having on one end a head valve and
reservoir assembly 690 that is in fluid communication by passageway
639 with the compression volume of a shock absorber. Assembly 690
includes an adjustable regressive valve that provides a regressive
flowpath into a fluid volume 626.4. That fluid volume is separated
by a floating piston 638 from a gas reservoir 640 which preferably
contains nitrogen gas under pressure.
[0090] FIG. 10b is an enlargement of a portion of the drawing of
FIG. 10a. Fluid flowing in through passageway 639 is received
within a plurality of circumferential orifices in a first valve
member 694a. This flow continues to flow toward the central axis of
the regressive valve assembly through a second series of
circumferential holes within an inner adjustment member 692. In
some embodiments, both adjustment members 694a and 692 can be
externally adjusted, as shown in FIG. 10b. Member 692 has on one
end (to the rightmost of FIG. 10b) a knob that can be turned by the
user. Valve assembly member 694a is coupled to member 691, and
provides a gripping means such as a knurled surface for the user to
grab and thereby turn valve 694a.
[0091] After fluid has flowed through the circumferential apertures
of member 694a and adjustment member 692, it is received within an
inner flow area where it acts on the center of a slidable piston
660. Piston 660 is slidable within and sealed to the inner diameter
of a chamber defined by valve member 694a. A spring 670 is received
within a pocket formed on the underside of piston 660. Spring 670
is further biased against a second member 694b that is threadably
received by member 694a. Spring 670 is thereby captured within a
housing defined by attached members 694a and 694b, and biases
piston 660 away from member 694b.
[0092] The other, downstream end of member 694b is threadably
received within a static member 695. Static member 695 is
threadably coupled to the holding structure of head valve assembly
690, and further locates by threads a static flow member 696. One
end of flow member 696 includes a conically shaped portion 696.1
that extends into a downstream portion of valve member 694b. As
flow from flowpaths 680 and 682 exit member 694, they pass through
an annular restriction formed by the conical nose of member 696 and
the end of the inner passage of member 694b.
[0093] The restriction between the conical portion of member 696
and the exit of member 694b coact to form an adjustable high
velocity restriction for the high velocity flowpath 682. As
external adjustment member 691 is rotated, valve assembly
694a/694b, which is threadably received within static member 695,
moves axially either closer or further from the conical seat of
static member 696. With this action, an annular restriction is
formed which provides a pressure drop for flowpaths 680 and 682.
However, since the magnitude of the high speed flow 682 is
generally greater than the flow along path 680, adjustment of the
restriction formed by the conical member tends to be more
restrictive under high stroking velocity operation.
[0094] Head valve 690 further includes means for adjusting the
preload on the spring, and in this way provides an adjustment that
modifies the force at which the low speed portion of the regressive
curve ends and the intermediate velocity portion (the portion
transitioning to the high velocity regime) begins. Referring to
FIG. 10b, adjustment member 692a is threadably received within
housing 694a (details of which can be seen in FIG. 17, which is a
more detailed view of the apparatus of 10b with regards to this
aspect). Rotation of adjustment member 692 thereby moves member 692
axially left and right, as viewed on FIG. 10b. Adjustment member
692 on its interiormost end 692.1 abuts against a face sealing
surface 660.4 of piston 660. By moving member 692 left, the preload
on spring 670 is increased. By moving member 692 to the right, the
preload member on spring 670 is decreased.
[0095] Piston 660 includes a central orifice 660.2 that provides
most of the low velocity restriction of head valve 690. The low
speed flowpath 680 (through central orifice 660.2) and the high
velocity flowpath 682 (around the face seal formed by surfaces
660.4 and 692.1 during high velocity operation) are both provided
fluid from pathway 639. However, fluid from passage 639 is further
in communication with an annular passage within static valve 695
(and further evident in FIG. 16). Fluid within this annular
passage, once it reaches sufficiently high pressure, can blow off
past the shim 636, and therefore forms a flowpath parallel with
flowpaths 682 and 680 into volume 626.4.
[0096] FIGS. 12, 13, and 15 are graphical representations of the
adjustments that can be made to a shock absorber having regressive
characteristics according to various embodiments of the present
invention. Although FIGS. 12, 13, and 15, show regressive
characteristics in compression, it is understood that the various
adjustments and their subsequent modifications to the regressive
characteristic can also be adapted to a shock absorber having
regressive characteristics in the extension direction.
[0097] FIG. 12 shows the effect of altering the preload of the
spring X70 (i.e., 170, 270, 370, 470, 570, and 670). Plot C shows a
regressive characteristic with a relatively high spring preload.
Graph D shows a regressive characteristic with a relatively low
spring preload. The effect of changing the spring preload has
little or no effect at low stroking velocities (such as below
0.06). Further, there is relatively little effect at higher
stroking velocities, such as from 0.7 to 1.0. The most notable
effect on spring load of varying spring preload is in the poppet
force that establishes the end of the low speed regime.
[0098] For both characteristics C and D, the poppet force occurs at
a velocity of approximately 0.1. From this low poppet velocity to
the high speed characteristic at about 0.7, the piston X60 is
moving from its first, spring-preloaded position to its second
position. In this intermediate speed regime the low speed flowpath
x80 is open, but the second, high speed flowpath x82 is at a
position between fully closed and fully open.
[0099] FIG. 13 graphically shows the effect of altering the high
velocity flow characteristics of the valve assembly. Both graphs A
and B have the same spring preload, and each lifts of at a velocity
of about 0.2. Referring to graph B, the second, high speed flowpath
X82 moves from its first, fully closed position to a fully open
position in an intermediate velocity range from about 0.2 to about
0.50. From a velocity of about 0.55 to 1, the second, high speed
flowpath is fully open. Likewise for graph A, the high speed
flowpath is fully open from a velocity of about 0.50 to about 1.
However, in the case of a valve assembly adjusted to the schedule
of graph A, the high speed forcing characteristic at a velocity of
1 is more than doubled relative to graph B. Indeed, the high speed
adjustment of graph A results in a high speed flowpath that is so
restrictive that the low and intermediate velocity regimes are
dominated by the low speed flowpath X80.
[0100] FIG. 15 shows the effect of adjusting the characteristics of
the low speed region. In each of graphs E, F, and G, there is the
same high speed flow characteristic (beginning at a velocity of
about 13) as well as the same spring preload. It can be seen that
adjusting the flow characteristics of the most restrictive orifice
of the low speed flowpath (whether the orifice is located in the
inner piston or a housing member) moves the velocity at which the
poppet moves off of its preloaded face sealing contact from a
velocity of about 5 (for graph E) to about 10 (for graph G).
However, the force at blow off remains at about 37 in each of these
three examples. It can also be seen that each of the three graphs
show substantially similar high speed characteristics.
[0101] FIG. 14 is a schematic and cross sectional representation of
an apparatus according to another embodiment of the present
invention. FIG. 14 shows a shock absorber 520 including an external
valve assembly that provides a regressive forcing function. Shock
absorber 520 includes an external valve assembly 551 that has a
first fluid inlet port 551.1 in fluid communication through
passageway 556 with the compression volume 526.4 of a cylinder 526.
The other end of housing 551 has a fluid port 551.2 in fluid
connection via passage 557 with the rebound volume 526.5 of
cylinder 526. A piston 522 divides the compression and rebound
volumes.
[0102] Located within external housing 551 is a valve assembly 550
that is substantially the same as valve assembly 350 of FIG. 8,
except as shown and described hereafter. Valve assembly 550 is
threadably coupled at one end to outlet port 551.2, thus fixing the
position of valve assembly 550 within the interior volume 551.3 of
housing 551. Fluid received within port 551.1 is presented to one
side of piston 560 by a plurality of apertures 554.6, as is also
the case in valve 350. Further, fluid from port 551.1 is further in
communication with the central orifice 554.3, and is able to flow
through that orifice into the outlet 551.2.
[0103] As is the case with valve assembly 350, when pressure on
piston 550 is sufficiently high to overcome the preload force
exerted by spring 570, fluid is free to flow through flowpath 582
around the face seal between piston 560 and member 554. This second
flowpath 582 is in parallel with the first flowpath 580, which is
also the case in valve assembly 350.
[0104] As can be understood from the drawings and description given
herein, shock absorber 520 can have either regressive
characteristics in compression or extension based on the
orientation of head valve 551. In the orientation as shown in FIG.
14, shock absorber 520 has a regressive forcing characteristic in a
compression direction. However, by reorienting external valve
assembly 551 such that port 551.1 is in fluid communication with
pathway 557 and port 551.2 is in fluid communication with pathway
556, shock absorber 520 has a regressive characteristic in
extension. Further, the current invention contemplates those
embodiments having first and second external valve assemblies 551,
each with an orientation opposite the other such that the resulting
shock absorber characteristics are regressive in both extension and
compression.
[0105] FIGS. 16 and 17 depict an apparatus 790 according to another
embodiment of the present invention. Head valve assembly 790 is
similar to head valve 690, except as shown and discussed hereafter.
Head valve 790 includes a third means for adjusting the regressive
flow characteristics of valve assembly 790. Head valve 790 includes
a third means 793 for adjusting the low velocity regressive
characteristics of a shock absorber. A shaft 793 includes an
external feature (at the top of page 17) by which a user can grip
and turn shaft 793. Shaft 790 is threadably received within the
inner diameter of adjustment collar 792. Further, shaft 793
includes a sealing groove and seal (not shown) for discouraging
leakage flow between shaft 793 and collar 792.
[0106] At the innermost end of shaft 793 there is a bull nose
projection that is received within a central aperture of piston
760. An annular restriction is formed between the bull nose
projection and the central aperture. Fluid from passageway 739
flows through this annular restriction as the low velocity flowpath
780. By rotating shaft 793 relative to collar 792, the bull nose
projection is moved axially within the central aperture of piston
760. Since the outer surface of the bull nose projection is
contoured, moving the projection upward (referring to FIG. 17)
increases the area of the annular flowpath and thereby decreases
the restrictiveness of flowpath 780.
[0107] In one embodiment, the high velocity regressive adjustment
of member 794b relative to conical projection 796.1 includes
positive means for establishing the relative rotational positions
of member 794b and the static structure of head valve 790, such as
a detent mechanism. As shown in FIG. 17, outer adjustment member
791 is integral with member 794a.
[0108] Preferably, there is a detent mechanism or other method of
positively establishing the relative rotational positions of
adjustment collar 792 and member 794a, such as a detent mechanism.
Further, in some embodiments, there is a detent mechanism
establishing positively the relative rotational positions of shaft
793 and collar 792.
[0109] Although what has been shown and described in FIGS. 16 and
17 are three adjustments features 791, 792, and 793 that act on a
head valve 790, the invention is not so limited. Other embodiments
of the present invention contemplate adjustments of the regressive
characteristics that can be made for valve assemblies X50 located
on either rod X24 or piston X22. As one example, and referring to
FIGS. 2 and 3, the present invention contemplates those embodiments
in which one, two or three adjustments are located within the rod
and extend through the main piston to the regressive valve
assembly.
[0110] Further, although some embodiments such as valve assembly
150 are shown attached to the end of rod 124, the present invention
also contemplates those embodiments in which the valve assembly X50
is attached to piston X22.
[0111] While the inventions have been illustrated and described in
detail in the drawings and foregoing description, the same is to be
considered as illustrative and not restrictive in character, it
being understood that only the preferred embodiment has been shown
and described and that all changes and modifications that come
within the spirit of the invention are desired to be protected.
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