US4867475A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method and apparatus for controlling shock absorbers
Assignee: Tenneco Automotive Operating Co Inc
•
Filing: 1988-02-16
•
Granted: 1989-09-19
•
Expires: 2008-02-16
Abstract
Abstract The method and apparatus for controlling shock absorbers is disclosed. The shock absorber comprises a pressure balanced shutter sleeve disposed within the piston rod of the shock absorber. The shutter sleeve has a plurality of flow passages in fluid communication with the lower portion of the working chamber. The shock absorber further comprises an orifice sleeve disposed within the piston rod and being displaceable with respect to the shutter sleeve. The orifice sleeve has a plurality of flow passages in fluid communication with the upper portion of the working chamber. The shock absorber further comprises an actuator for applying torque to the shutter sleeve as well as control means for controlling the application of torque by the actuator.
Inventors
- 👤 Gary W. Groves
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 10:43
CPC Classifications
B; B60; B60G; B60G17/00; B60G17/015; B60G17/018; B60G2400/00; B60G2400/30; B60G2400/33; B60G2500/00; B60G2500/10; B60G2500/102; B60G2600/00; B60G2600/02; B60G2600/04; B60G2600/20
Claims Analysis
Total Claims: 78
Claim 1
Independent Claim
168 words
An apparatus for controlling shock absorbers comprising: a pressure cylinder forming a working chamber having first and second portions operable to store damping fluid; first valve means for establishing a first plurality of flow passages, said first valve means being disposed within said pressure cylinder; second valve means for establishing a second plurality of flow passages, said second valve means being disposed within said pressure cylinder and being displaceable with respect to said first valve means, the displacement of said second valve means with respect to said first valve means operable to vary the flow of damping fluid between said first and second portions of said working chamber, the displacement of said second valve means with respect to said first valve means being substantially independent of the damping fluid flowing in said pressure cylinder; actuator means for displacing said second valve means with respect to said first valve means; and control means for controlling the displacement of said second valve member with respect to said first valve means.
Claim 2
Independent Claim
168 words
An apparatus for controlling shock absorbers comprising: a pressure cylinder forming a working chamber having first and second portions operable to store damping fluid; first valve means for establishing a first plurality of flow passages, said first valve means being disposed within said pressure cylinder; second valve means for establishing a second plurality of flow passages, said second valve means being disposed within said pressure cylinder and being displaceable with respect to said first valve means, the displacement of said second valve means with respect to said first valve means operable to vary the flow of damping fluid between said first and second portions of said working chamber, the displacement of said second valve means with respect to said first valve means being substantially independent of the damping fluid flowing in said pressure cylinder; actuator means for displacing said second valve means with respect to said first valve means; and control means for controlling the displacement of said second valve member with respect to said first valve means.
Claim 3
Dependent Claim
60 words
The apparatus of claim 1, wherein said first valve means has at least four flow passages and said second valve means has at least two flow passages, the flow passages in said first valve means operable to selectively fluidly communicate with the flow passages in said second valve means upon displacement of said second valve means by said actuator means.
Claim 4
Dependent Claim
30 words
The apparatus of claim 2, wherein said second valve means is operable to balance the forces acting on said second valve means by the damping fluid in said pressure cylinder.
Claim 5
Dependent Claim
35 words
The apparatus of claim 3, wherein said flow passages of said second valve means are disposed on said second valve member symmetrically about a plane passing axially through the center of said second valve means.
Claim 6
Dependent Claim
75 words
The apparatus of claim 4, wherein the flow passages of said second valve means have first and second diameters, the flow passages having said first diameter being disposed on said second valve member symmetrically about a plane passing axially through the center of said second valve means, said flow passages having a second diameter being disposed on said second valve member symmetrically about a plane passing axially through the center of said second valve means.
Claim 7
Dependent Claim
48 words
The apparatus of claim 1, wherein said second valve means comprises an annular shutter sleeve having a central bore with a closed upper end portion, said closed upper end portion having an annular recess and means for permitting fluid communication between said annular recess and said central bore.
Claim 8
Dependent Claim
56 words
The apparatus of claim 6, wherein said means for permitting fluid communication between said annular recess and said central bore is operable to permit the force exerted on said shutter sleeve by the damping fluid in said annular recess to oppose the force exerted on said shutter sleeve by the damping fluid in said central bore.
Claim 9
Dependent Claim
35 words
The apparatus of claim 1, further comprising check valve means for providing a relatively soft compression stroke and a relatively firm rebound stroke, said check valve means being displaceably independent of said second valve means.
Claim 10
Dependent Claim
38 words
The apparatus of claim 8, wherein said second valve means comprises an annular shutter sleeve having a central bore, said check valve means being disposed within said central bore and being rotationally independent of said second valve means.
Claim 11
Dependent Claim
48 words
The apparatus of claim 9, wherein said annular shutter sleeve comprises a plurality of flow passages and said check valve means comprises a plurality of flow passages, the flow passages in said annular shutter sleeve operable to fluidly communicate with the flow passages in said check valve sleeve.
Claim 12
Dependent Claim
29 words
The apparatus of claim 10, wherein said check valve means comprises an annular member and a closure member, said closure member biased toward said annular member by a spring.
Claim 13
Dependent Claim
27 words
The apparatus of claim 1, wherein said actuator means comprises means for encoding the displacement of said second valve means with respect to said first valve means.
Claim 14
Dependent Claim
41 words
The apparatus of claim 12, wherein said means for encoding is operable to permit said control means to determine whether said second valve means has been displaced with respect to said first valve means to one of at least eight positions.
Claim 15
Dependent Claim
69 words
The apparatus of claim 13, wherein said means for encoding comprises a substrate with three encoder conductors disposed thereon, each of said conductors, having a circular portion and radially extending portion, said circular portion of at least one of said encoder conductors having a first and second plurality of regions, said first plurality of regions being disposed closer to the center of said circular region than said second region.
Claim 16
Dependent Claim
26 words
The apparatus of claim 14, wherein said actuator means further comprises means for causing selective electrical communication between said encoder conductors of said means for encoding.
Claim 17
Dependent Claim
49 words
The apparatus of claim 15, wherein said means for causing selective electrical communication between said conductors comprises a brush disk, said brush disk comprising a circular substrate with conductor disposed thereon, said conductor of said brush disk having a brush portion which is disposed adjacent to said encoder conductors.
Claim 18
Dependent Claim
65 words
The apparatus of claim 16, wherein the width of said brush portion is sufficiently large to cause electrical communication between a first of said encoder conductors and said first plurality of regions of a second of said encoder conductors while being sufficiently narrow to avoid electrical communication between said first of said encoder conductors and said second regions of said second of said encoder conductors.
Claim 19
Independent Claim
189 words
An apparatus for controlling shock absorbers comprising: a pressure cylinder forming a working chamber having first and second portions operable to store damping fluid; an axially extending piston rod disposed in said pressure cylinder; a piston post secured to said piston rod, said piston post having a flow passage in fluid communication with said second portion of said working chamber; a piston secured to said piston post; a pressure balanced shutter sleeve disposed within said piston rod, said shutter sleeve having a plurality of flow passages in fluid communication with the flow passage in said piston post; an orifice sleeve disposed within said piston rod, said orifice sleeve being displaceable with respect to said shutter sleeve and having a plurality of flow passages in fluid communication with the first portion of said working chamber; an actuator disposed within said piston rod operable to apply torque to said shutter sleeve shaft, said actuator including an encoder disk and a brush disk operable to indicate the displacement of said annular shutter sleeve with respect to said orifice sleeve; and control means for controlling the application of torque to said actuator means.
Claim 20
Independent Claim
189 words
An apparatus for controlling shock absorbers comprising: a pressure cylinder forming a working chamber having first and second portions operable to store damping fluid; an axially extending piston rod disposed in said pressure cylinder; a piston post secured to said piston rod, said piston post having a flow passage in fluid communication with said second portion of said working chamber; a piston secured to said piston post; a pressure balanced shutter sleeve disposed within said piston rod, said shutter sleeve having a plurality of flow passages in fluid communication with the flow passage in said piston post; an orifice sleeve disposed within said piston rod, said orifice sleeve being displaceable with respect to said shutter sleeve and having a plurality of flow passages in fluid communication with the first portion of said working chamber; an actuator disposed within said piston rod operable to apply torque to said shutter sleeve shaft, said actuator including an encoder disk and a brush disk operable to indicate the displacement of said annular shutter sleeve with respect to said orifice sleeve; and control means for controlling the application of torque to said actuator means.
Claim 21
Dependent Claim
55 words
The apparatus of claim 18, wherein said orifice sleeve has at least four flow passages and said shutter sleeve has at least two flow passages, the flow passages in said orifice sleeve operable to selectively fluidly communicate with the flow passages in said shutter sleeve upon displacement of said shutter sleeve by said actuator means.
Claim 22
Dependent Claim
28 words
The apparatus of claim 19, wherein said shutter sleeve is operable to balance the forces acting on said shutter sleeve by the damping fluid in said pressure cylinder.
Claim 23
Dependent Claim
32 words
The apparatus of claim 20, wherein said flow passages of said shutter sleeve are disposed on said shutter sleeve symmetrically about a plane passing axially through the center of said shutter sleeve.
Claim 24
Dependent Claim
70 words
The apparatus of claim 21, wherein the flow passages of said shutter sleeve have first and second diameters, the flow passages having said first diameter being disposed on said shutter sleeve symmetrically about a plane passing axially through the center of said shutter sleeve, said flow passages having a second diameter being disposed on said shutter sleeve symmetrically about a plane passing axially through the center of said shutter sleeve.
Claim 25
Dependent Claim
42 words
The apparatus of claim 18, wherein said shutter sleeve comprises a central bore with a closed upper end portion, said closed upper end portion having an annular recess and means for permitting fluid communication between said annular recess and said central bore.
Claim 26
Dependent Claim
56 words
The apparatus of claim 23, wherein said means for permitting fluid communication between said annular recess and said central bore is operable to permit the force exerted on said shutter sleeve by the damping fluid in said annular recess to oppose the force exerted on said shutter sleeve by the damping fluid in said central bore.
Claim 27
Dependent Claim
34 words
The apparatus of claim 18, further comprising check valve means for providing a relatively soft compression stroke and a relatively firm rebound stroke, said check valve means being displaceably independent of said shutter sleeve.
Claim 28
Dependent Claim
31 words
The apparatus of claim 25, wherein said shutter sleeve comprises a central bore, said check valve means being disposed within said central bore and being rotationally independent of said shutter sleeve.
Claim 29
Dependent Claim
46 words
The apparatus of claim 26, wherein said shutter sleeve comprises a plurality of flow passages and said check valve means comprises a plurality of flow passages, the flow passages in said shutter sleeve operable to fluidly communicate with the flow passages in said check valve sleeve.
Claim 30
Dependent Claim
29 words
The apparatus of claim 27, wherein said check valve means comprises an annular member and a closure member, said closure member biased toward said annular member by a spring.
Claim 31
Dependent Claim
26 words
The apparatus of claim 1, wherein said actuator comprises means for encoding the displacement of said second valve means with respect to said first valve means.
Claim 32
Dependent Claim
41 words
The apparatus of claim 29, wherein said means for encoding is operable to permit said control means to determine whether said second valve means has been displaced with respect to said first valve means to one of at least eight positions.
Claim 33
Dependent Claim
70 words
The apparatus of claim 30, wherein said means for encoding comprises a substrate with three encoder conductors disposed thereon, each of said encoder conductors having a circular portion and radially extending portion, said circular portion of at least one of said encoder conductors having a first and second plurality of regions, said first plurality of regions being disposed closer to the center of said circular region than said second region.
Claim 34
Dependent Claim
25 words
The apparatus of claim 31, wherein said actuator further comprises means for causing selective electrical communication between said encoder conductors of said means for encoding.
Claim 35
Dependent Claim
48 words
The apparatus of claim 32, wherein said means for causing selective electrical communication between said conductors comprises a brush disk, said brush disk comprising a circular substrate with conductor disposed thereon, said conductor of said brush disk having a portion which is disposed adjacent to said encoder conductors.
Claim 36
Dependent Claim
65 words
The apparatus of claim 33, wherein the width of said brush portion is sufficiently large to cause electrical communication between a first of said encoder conductors and said first plurality of regions of a second of said encoder conductors while being sufficiently narrow to avoid electrical communication between said first of said encoder conductors and said second regions of said second of said encoder conductors.
Claim 37
Independent Claim
121 words
A method for controlling the flow of damping fluid between the first and second portions of the working chamber of a shock absorber comprising: permitting damping fluid in the first portion of said working chamber to fluidly communicate with first valve means for controlling the flow of damping fluid; permitting damping fluid in said second portion of said working chamber to fluidly communicate with second valve means for controlling the flow of damping fluid; balancing the forces acting on said second valve means by damping fluid in said working chamber; and displacing said second valve means with respect to said first valve means to thereby control the flow of damping fluid between said first and second portions of said working chamber.
Claim 38
Independent Claim
121 words
A method for controlling the flow of damping fluid between the first and second portions of the working chamber of a shock absorber comprising: permitting damping fluid in the first portion of said working chamber to fluidly communicate with first valve means for controlling the flow of damping fluid; permitting damping fluid in said second portion of said working chamber to fluidly communicate with second valve means for controlling the flow of damping fluid; balancing the forces acting on said second valve means by damping fluid in said working chamber; and displacing said second valve means with respect to said first valve means to thereby control the flow of damping fluid between said first and second portions of said working chamber.
Claim 39
Dependent Claim
60 words
The method of claim 35, wherein said first valve means has at least four flow passages and said second valve means has at least two flow passages, the flow passages in said first valve means operable to selectively fluidly communicate with the flow passages in said second valve means upon displacement of said second valve means by said actuator means.
Claim 40
Dependent Claim
30 words
The method of claim 36, wherein said second valve means is operable to balance the forces acting on said second valve means by the damping fluid in said pressure cylinder.
Claim 41
Dependent Claim
35 words
The method of claim 37, wherein said flow passages of said second valve means are disposed on said second valve member symmetrically about a plane passing axially through the center of said second valve means.
Claim 42
Dependent Claim
75 words
The method of claim 38, wherein the flow passages of said second valve means have first and second diameters, the flow passages having said first diameter being disposed on said second valve member symmetrically about a plane passing axially through the center of said second valve means, said flow passages having a second diameter being disposed on said second valve member symmetrically about a plane passing axially through the center of said second valve means.
Claim 43
Dependent Claim
48 words
The method of claim 35, wherein said second valve means comprises an annular shutter sleeve having a central bore with a closed upper end portion, said closed upper end portion having an annular recess and means for permitting fluid communication between said annular recess and said central bore.
Claim 44
Dependent Claim
56 words
The method of claim 40, wherein said means for permitting fluid communication between said annular recess and said central bore is operable to permit the force exerted on said shutter sleeve by the damping fluid in said annular recess to oppose the force exerted on said shutter sleeve by the damping fluid in said central bore.
Claim 45
Dependent Claim
35 words
The method of claim 35, further comprising check valve means for providing a relatively soft compression stroke and a relatively firm rebound stroke, said check valve means being displaceably independent of said second valve means.
Claim 46
Dependent Claim
38 words
The method of claim 42, wherein said second valve means comprises an annular shutter sleeve having a central bore, said check valve means being disposed within said central bore and being rotationally independent of said second valve means.
Claim 47
Dependent Claim
48 words
The method of claim 43, wherein said annular shutter sleeve comprises a plurality of flow passages and said check valve means comprises a plurality of flow passages, the flow passages in said annular shutter sleeve operable to fluidly communicate with the flow passages in said check valve sleeve.
Claim 48
Dependent Claim
29 words
The method of claim 44, wherein said check valve means comprises an annular member and a closure member, said closure member biased toward said annular member by a spring.
Claim 49
Dependent Claim
55 words
The method of claim 35, wherein said step of displacing said second valve means comprises the step of energizing actuator means for displacing said second valve means with respect to said first valve means, said actuator means comprising means for encoding the displacement of said second valve means with respect to said first valve means.
Claim 50
Dependent Claim
41 words
The method of claim 46, wherein said means for encoding is operable to permit said control means to determine whether said second valve means has been displaced with respect to said first valve means to one of at least eight positions.
Claim 51
Dependent Claim
69 words
The method of claim 47, wherein said means for encoding comprises a substrate with three encoder conductors disposed thereon, each of said conductors having a circular portion and radially extending portion, said circular portion of at least one of said encoder conductors having a first and second plurality of regions, said first plurality of regions being disposed closer to the center of said circular region than said second region.
Claim 52
Dependent Claim
26 words
The method of claim 48, wherein said actuator means further comprises means for causing selective electrical communication between said encoder conductors of said means for encoding.
Claim 53
Dependent Claim
49 words
The method of claim 49, wherein said means for causing selective electrical communication between said conductors comprises a brush disk, said brush disk comprising a circular substrate with conductor disposed thereon, said conductor of said brush disk having a brush portion which is disposed adjacent to said encoder conductors.
Claim 54
Dependent Claim
65 words
The method of claim 50, wherein the width of said brush portion is sufficiently large to cause electrical communication between a first of said encoder conductors and said first plurality of regions of a second of said encoder conductors while being sufficiently narrow to avoid electrical communication between said first of said encoder conductors and said second regions of said second of said encoder conductors.
Claim 55
Dependent Claim
58 words
The method of claim 35, wherein said first valve means has a plurality of flow passages and said second valve means has a second plurality of flow passages, rotation of said second valve means being operable to cause fluid communication between said flow passages in said first valve means and said flow passages in said second valve means.
Claim 56
Dependent Claim
75 words
The method of claim 52, wherein the flow passages in said second valve means have first and second diameters, said first diameter being larger than said second diameter, said step of displacing said second valve means comprises the step of causing fluid communication between said flow passages in said first valve means and said flow passages in said second valve means having said first diameter to thereby produce a soft firm compression and rebound stroke.
Claim 57
Dependent Claim
50 words
The method of claim 53, wherein said step of displacing said second valve means comprises the step of causing fluid communication between said flow passages in said first valve means and said flow passages in said second valve means having said second diameter to thereby produce a medium compression stroke.
Claim 58
Dependent Claim
61 words
The method of claim 54, wherein said step of displacing said second valve means further comprises the step of rotating said second valve means with respect to said first valve means to prevent fluid communication between said flow passages in said first valve means with said flow passages in said second valve means to produce a firm compression and rebound stroke.
Claim 59
Independent Claim
162 words
A method for controlling the flow of damping fluid between the first and second portions of the working chamber of a shock absorber comprising: permitting damping fluid in the first and second portions of said working chamber to fluidly communicate with a rotary valve, said rotary valve comprising: (a) an annular orifice sleeve having a plurality of flow passages in fluid communication with first portion of said working chamber; (b) an annular shutter sleeve having a plurality of flow passages in fluid communication with the second portion of said working chamber, said flow passages of said shutter sleeve being disposed on said shutter sleeve symmetrically about a plane passing axially through the center of said shutter sleeve. balancing the forces acting on said shutter sleeve by the damping fluid in said working chamber; and displacing said shutter sleeve with respect to said orifice sleeve to thereby control the flow of damping fluid between said first and second portions of said working chamber.
Claim 60
Independent Claim
162 words
A method for controlling the flow of damping fluid between the first and second portions of the working chamber of a shock absorber comprising: permitting damping fluid in the first and second portions of said working chamber to fluidly communicate with a rotary valve, said rotary valve comprising: (a) an annular orifice sleeve having a plurality of flow passages in fluid communication with first portion of said working chamber; (b) an annular shutter sleeve having a plurality of flow passages in fluid communication with the second portion of said working chamber, said flow passages of said shutter sleeve being disposed on said shutter sleeve symmetrically about a plane passing axially through the center of said shutter sleeve. balancing the forces acting on said shutter sleeve by the damping fluid in said working chamber; and displacing said shutter sleeve with respect to said orifice sleeve to thereby control the flow of damping fluid between said first and second portions of said working chamber.
Claim 61
Dependent Claim
55 words
The method of claim 56, wherein said orifice sleeve has at least four flow passages and said shutter sleeve has at least two flow passages, the flow passages in said orifice sleeve operable to selectively fluidly communicate with the flow passages in said shutter sleeve upon displacement of said shutter sleeve by said actuator means.
Claim 62
Dependent Claim
72 words
The method of claim 57, wherein the flow passages of said shutter sleeve have first and second diameters, the flow passages having said first diameter being disposed on said second valve member symmetrically about a plane passing axially through the center of said shutter sleeve, said flow passages having a second diameter being disposed on said second valve member symmetrically about a plane passing axially through the center of said shutter sleeve.
Claim 63
Dependent Claim
42 words
The method of claim 56, wherein said shutter sleeve comprises a central bore with a closed upper end portion, said closed upper end portion having an annular recess and means for permitting fluid communication between said annular recess and said central bore.
Claim 64
Dependent Claim
56 words
The method of claim 59, wherein said means for permitting fluid communication between said annular recess and said central bore is operable to permit the force exerted on said shutter sleeve by the damping fluid in said annular recess to oppose the force exerted on said shutter sleeve by the damping fluid in said central bore.
Claim 65
Dependent Claim
34 words
The method of claim 56, further comprising check valve means for providing a relatively soft compression stroke and a relatively firm rebound stroke, said check valve means being displaceably independent of said shutter sleeve.
Claim 66
Dependent Claim
36 words
The method of claim 61, wherein said shutter sleeve comprises an annular shutter sleeve having a central bore, said check valve means being disposed within said central bore and being rotationally independent of said shutter sleeve.
Claim 67
Dependent Claim
48 words
The method of claim 62, wherein said annular shutter sleeve comprises a plurality of flow passages and said check valve means comprises a plurality of flow passages, the flow passages in said annular shutter sleeve operable to fluidly communicate with the flow passages in said check valve sleeve.
Claim 68
Dependent Claim
29 words
The method of claim 63, wherein said check valve means comprises an annular member and a closure member, said closure member biased toward said annular member by a spring.
Claim 69
Dependent Claim
50 words
The method of claim 56, wherein said step of displacing said shutter sleeve comprises the step of energizing actuator means for displacing said shutter sleeve with respect to said orifice sleeve, said actuator means comprising means for encoding the displacement of said shutter sleeve with respect to said orifice sleeve.
Claim 70
Dependent Claim
39 words
The method of claim 65, wherein said means for encoding is operable to permit said control means to determine whether said shutter sleeve has been displaced with respect to said orifice sleeve to one of at least eight positions.
Claim 71
Dependent Claim
69 words
The method of claim 66, wherein said means for encoding comprises a substrate with three encoder conductors disposed thereon, each of said conductors having a circular portion and radially extending portion, said circular portion of at least one of said encoder conductors having a first and second plurality of regions, said first plurality of regions being disposed closer to the center of said circular region than said second region.
Claim 72
Dependent Claim
26 words
The method of claim 67, wherein said actuator means further comprises means for causing selective electrical communication between said encoder conductors of said means for encoding.
Claim 73
Dependent Claim
49 words
The method of claim 68, wherein said means for causing selective electrical communication between said conductors comprises a brush disk, said brush disk comprising a circular substrate with conductor disposed thereon, said conductor of said brush disk having a brush portion which is disposed adjacent to said encoder conductors.
Claim 74
Dependent Claim
65 words
The method of claim 69, wherein the width of said brush portion is sufficiently large to cause electrical communication between a first of said encoder conductors and said first plurality of regions of a second of said encoder conductors while being sufficiently narrow to avoid electrical communication between said first of said encoder conductors and said second regions of said second of said encoder conductors.
Claim 75
Dependent Claim
53 words
The method of claim 56, wherein said orifice sleeve has a plurality of flow passages and said shutter sleeve has a second plurality of flow passages, rotation of said shutter sleeve being operable to cause fluid communication between said flow passages in said orifice sleeve and said flow passages in said shutter sleeve.
Claim 76
Dependent Claim
80 words
The method of claim 71, wherein the flow passages in said shutter sleeve have first and second diameters, said first diameter being larger than said second diameter, said step of displacing said shutter sleeve comprises the step of rotating said shutter sleeve comprises the step of causing fluid communication between said flow passages in said orifice sleeve and said flow passages in said shutter sleeve, said means housing first diameter to thereby produce a soft firm compression and rebound stroke.
Claim 77
Dependent Claim
47 words
The method of claim 72, wherein said step of displacing said shutter sleeve comprises the step of causing fluid communication between said flow passages in said orifice sleeve and said flow passages in said shutter sleeve having said second diameter to thereby produce a medium compression stroke.
Claim 78
Dependent Claim
56 words
The method of claim 73, wherein said step of displacing said shutter sleeve further comprises the step of rotating said shutter sleeve with respect to said orifice sleeve to prevent fluid communication between said flow passages in said orifice sleeve with said flow passages in said shutter sleeve to produce a firm compression and rebound stroke.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-09-18 | 1993-03-20 | 1993-09-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-09-18 | 1997-03-20 | 1997-09-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-09-18 | 2001-03-20 | 2001-09-19 | $7700.00 | Window Closed / Lapsed |