Acceleration sensitive shock absorber

Details Acceleration sensitive shock absorber Acceleration sensitive shock absorber

1999-09-21

2001-07-03

Graham, Matthew C. (Department: 3613)

Brakes

Internal-resistance motion retarder

With fluid regulated in response to inertia of valve member

Reexamination Certificate

active

06253889

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to vehicle shock absorbers which are typically mounted between the wheels and chassis or body of an automobile, truck, motorcycle, etc. The invention relates to a shock absorber with damping characteristics that change depending upon the acceleration of parts of the shock absorber, most importantly, during downward acceleration of the vehicle wheel.
Shock absorbers which respond to accelerations of a vehicle wheel have demonstrated a remarkable ability to improve the performance of vehicles equipped with such shock absorbers. One such shock absorber has a movable inertia valve for opening a port during downward acceleration of the vehicle wheel. The acceleration sensitive shock absorber further includes means for biasing the inertia valve towards its open position in response to fluid flow through the shock absorber.
It is desirable to apply an upwardly directed spring load to the inertia valve in the shock absorber to reduce the effects of gravity. Ideally, the inertia valve is a pure inertial element unaffected by gravity. As the inertia valve approaches a weightless condition, the more sensitive it becomes to acceleration inputs and premature opening. A “weightless” inertia valve also becomes sensitive to pressure differentials during non-inertia valve extension events or body motion events. Body motion events create high pressure inside the piston as fluid is metered through the body motion valving.
Some inconsistency in performance was noted in mass produced shock absorbers. It was deduced, that sometimes the inertia valve would open in absence of a downward acceleration of the vehicle wheel. The inertia valve might open due to a body motion rather than a wheel motion. Opening of the inertia valve leads to a reduction in damping force when high forces are necessary to control vehicle body motions. Conversely, it might occur that the inertia valve did not open properly upon downward wheel acceleration.
It is desirable that the inertia valve should consistently open when it should, and should remain closed when it should not be opening. It is desirable to modify the structure only slightly to alleviate such inconsistencies in mass produced shock absorbers.
SUMMARY OF THE INVENTION
There is, therefore, provided in practice of this invention a flow sensitive, acceleration sensitive shock absorber with a tubular housing for connection to one portion of a vehicle and a piston assembly in the housing and a piston assembly in the housing comprising a piston and a piston rod for connection to another portion of the vehicle, one of said portions being a chassis of the vehicle and the other portion being a wheel of the vehicle. Shock absorber fluid passes between portions of the shock absorber through a restricted flow rate path during one of compression or extension of the shock absorber. There is a fluid flow port in a first portion of the shock absorber for bypassing fluid flow past the restricted flow rate path and a movable inertial mass in the shock absorber for opening the port during acceleration of the first portion of the shock absorber for increasing bypass flow of fluid. An improvement in the shock absorber is an increased diameter relief portion inside the inertial mass sufficiently close to the port when the inertial mass is in the port-closed position to avoid unbalanced pressure increase at an end of the inertial mass that would open the port in absence of acceleration a selected portion of the vehicle.


REFERENCES:
patent: 3319741 (1967-05-01), Hauck
patent: 4254849 (1981-03-01), Pohlenz
patent: 4917222 (1990-04-01), Bacardit
patent: 5598903 (1997-02-01), Richardson
patent: 5823305 (1998-10-01), Richardson et al.
patent: 5954167 (1999-09-01), Richardson et al.
patent: 19 85 453 (1968-05-01), None
patent: 21 39 942 (1972-11-01), None
patent: WO96/27091 (1996-09-01), None

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