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US4953671A Expired / Lapsed US ⏱️ 0.0 years remaining

Damping force adjustable hydraulic shock absorber

Assignee: Hitachi Ltd
•
Filing: 1989-08-10
•
Granted: 1990-09-04
•
Expires: 2009-08-10
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Abstract

Abstract A hydraulic shock absorber is used, for example, in a vehicle, wherein the level of damping force is adjustable in accordance with the road surface conditions or the like during operation of the vehicle. The hydraulic shock absorber includes a piston attached to one end of a piston rod and slidably fitted in a cylinder, the piston dividing the interior of the cylinder into two cylinder chambers. A passage is provided in the piston, the passage communicating with each of the two cylinder chambers. A damping force generating valve is provided at the downstream side of the passage to generate damping force. A back-pressure chamber is formed at the side of the damping force generating valve which is remote from the piston to apply pressure to the valve. A bypass passage is formed in the piston rod to provide communication between the back-pressure chamber and the upstream cylinder chamber that is provided at the upstream side of the passage. A shutter is externally operable to control the condition of communication between the upstream cylinder chamber and the back-pressure chamber, thereby adjusting the level of pressure inside the back-pressure chamber. Thus, it is possible to obtain a plurality of damping force characteristics with a single damping force generating valve provided for each of the extension and contraction strokes.

Inventors

  • 👤 Tomio Imaizumi

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-11-02 12:12
CPC Classifications
B; B60; B60G; B60G13/00; F; F16; F16F; F16F9/00; F16F9/32; F16F9/44; F16F9/46; F16F9/464; F16F9/50; F16F9/512; B60G2500/00; B60G2500/30

Claims Analysis

Total Claims: 7
Claim 1
Independent Claim 153 words
A damping force adjustable hydraulic shock absorber comprising: a piston attached to one end of a piston rod and slidably fitted in a cylinder, said piston dividing the interior of said cylinder into two cylinder chambers; a passage provided in said piston, said passage communicating with each of said two cylinder chambers; a damping force generating valve provided at the downstream side of said passage to generate a damping force; a back-pressure chamber formed at the side of said damping force generating valve which is remote from said piston to apply pressure to said valve; a bypass passage formed in said piston rod to provide communication between said back-pressure chamber and the upstream cylinder chamber that is provided at the upstream side of said passage; and externally operated to control the condition of communication between said upstream cylinder chamber and said back-pressure chamber, thereby adjusting the level of pressure inside said back-pressure chamber.
Claim 2
Dependent Claim 153 words
A damping force adjustable hydraulic shock absorber comprising: a piston attached to one end of a piston rod and slidably fitted in a cylinder, said piston dividing the interior of said cylinder into two cylinder chambers; a passage provided in said piston, said passage communicating with each of said two cylinder chambers; a damping force generating valve provided at the downstream side of said passage to generate a damping force; a back-pressure chamber formed at the side of said damping force generating valve which is remote from said piston to apply pressure to said valve; a bypass passage formed in said piston rod to provide communication between said back-pressure chamber and the upstream cylinder chamber that is provided at the upstream side of said passage; and externally operated to control the condition of communication between said upstream cylinder chamber and said back-pressure chamber, thereby adjusting the level of pressure inside said back-pressure chamber.
Claim 3
Dependent Claim 61 words
A damping force adjustable hydraulic shock absorber according to claim 1, further comprising: a second passage providing communication between said back-pressure chamber and the cylinder chamber in which said back-pressure chamber is disposed; and valve means for closing said second passage in a normal state and opening said second passage when the pressure inside said back-pressure chamber reaches a predetermined value.
Claim 4
Dependent Claim 40 words
A damping force adjustable hydraulic shock absorber according to claim 2, wherein said shutter provides communication between said upstream cylinder chamber and said back-pressure chamber through said bypass passage at one position and cuts off such communication at another position.
Claim 5
Dependent Claim 40 words
A damping force adjustable hydraulic shock absorber according to claim 3, further comprising a second bypass passage which provides communication between said two cylinder chambers through an orifice bore when said shutter cuts off the communication through said bypass passage.
Claim 6
Dependent Claim 40 words
A damping force adjustable hydraulic shock absorber according to claim 1, wherein said shutter provides communication between said upstream cylinder chamber and said back-pressure chamber through said bypass passage at one position and cuts off such communication at another position.
Claim 7
Dependent Claim 39 words
A damping force adjustable hydraulic shock absorber according to claim 5, further comprising a second bypass passage providing communication between said two cylinder chambers through an orifice bore when said shutter cuts off the communication through said bypass passage.

References Cited (Backward Citations)

GB1004233A Cited
GB1128249A Cited
GB1476353A Cited
JPS5911932A Cited
JPS611729A Cited
US4646883A Cited
GB2170572A Cited
US4653617A Cited
US4660689A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1993-09-03 1994-03-05 1994-09-04 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1997-09-03 1998-03-05 1998-09-04 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 2001-09-03 2002-03-05 2002-09-04 $7700.00 Window Closed / Lapsed

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