Land vehicles – Wheeled – Attachment
Reexamination Certificate
1999-12-08
2001-05-29
Johnson, Brian L. (Department: 3618)
Land vehicles
Wheeled
Attachment
C242S381000
Reexamination Certificate
active
06237959
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to a hydraulic velocity damper and, more particularly, to a hydraulic velocity damper for use with a seat belt retractor system to control and limit the maximum velocity of seat belt webbing payout during loading.
Conventional load limiting devices are load dependant. These devices allow a seat belt webbing to payout at different velocity rates when various loads are applied to the device. Optimum performance of these conventional systems is targeted to a specifically sized occupant, i.e., an average sized occupant. However, when a smaller occupant, i.e., a small child, or a larger occupant, i.e., a large adult, is positioned within the conventional seat belt retractor system, less than optimum control of webbing payout results. Webbing payout is reduced for smaller occupants due to the relatively smaller force applied by the smaller occupant to the system during rapid deceleration. Conversely, the webbing payout is increased for larger occupants due to the relatively larger force applied by the larger occupant to the system. Thus, conventional load limiting devices fail to provide adequate control of seat belt payout for different sized occupants.
SUMMARY OF THE INVENTION
A general object of the invention is to provide an improved velocity damper such as for use in a seat belt retractor system.
A more specific objective of the invention is to overcome one or more of the problems described above.
The general object of the invention can be attained, at least in part, through a hydraulic velocity damper having a rotatable spindle body having at least one open end and at least in part defining an irregularly shaped housing. The housing, at least in part, defines a chamber that is adapted to hold a fluid. The chamber has a fluid passage to allow fluid to be displaced from within the chamber. A drive screw is positioned within the housing and two rotatable, irregularly shaped pistons are threadedly connected with the drive screw. An end cap, connected to a head portion of the drive screw, is mounted to the spindle body and covers an open end of the spindle body.
The prior art generally fails to provide a seat belt retractor apparatus which limits the velocity of seat belt webbing payout during loading as effectively as desired.
The invention further comprehends a spindle body at least in part defining an elliptical housing. The housing at least in part defines a chamber adapted to contain a fluid. A drive screw having a body section with a first end portion and an opposite second end portion is positionable within the housing. One of the first and second end portions of the drive screw has clockwise threads and the other end portion has counterclockwise threads. An elliptical first piston is threadedly connected with the first end portion and an elliptical second piston is threadedly connected with the second end portion. The housing has at least one fluid passage to allow fluid to be displaced from within the chamber.
The invention still further comprehends a spindle body at least in part defining an elliptical housing which at least in part defines a chamber. A first drive screw is positioned within a first end portion of the housing and a second drive screw is positioned within an opposite second end portion of the housing. The two drive screws are oppositely threaded. A first piston is threadedly connected with the first drive screw and is moveable along a length of the first drive screw. Similarly, a second piston is threadedly connected with the second drive screw and is moveable along a length of the second drive screw. The two pistons and an inner wall of the housing define a chamber which holds or contains hydraulic fluid. The hydraulic fluid is displaced from within the chamber into an inner cavity of each piston through at least one metering hole in each piston.
As used herein, references to “fluid” are to be understood to refer to any material or substance that changes shape or direction uniformly in response to an external force imposed upon it. The term applies not only to liquids, but also to gases and finely divided solids, for example. Fluids are broadly classified as Newtonian and non-Newtonian depending on their obedience to the laws of classical mechanics.
As used herein, references to “Newtonian fluid” are to be understood to refer to a fluid's ability to flow, a property depending largely on its viscosity and sometimes also on the rate of shear. A Newtonian fluid is a fluid that flows immediately on application of force and for which the rate of flow is directly proportional to the force applied. Water, gasoline, and motor oils at high temperatures are examples of traditional Newtonian fluids.
Further, references herein to “Non-Newtonian fluid” are to be understood to refer to fluids which have an abnormal flow response when force is applied, that is, the fluid's viscosity is dependent on the rate of shear. Such fluids are said to exhibit Non-Newtonian flow properties. For example, some Non-Newtonian fluids will not flow until a force greater than a definite value called the yield point is applied to the fluid.
As used herein, references to “fluid-tight” are to be understood to refer to the chamber having minimal fluid leakage between the piston seal and the inner wall of the housing when in a non-pressurized state or condition and, for pressurized operation, at selected corresponding or associated pressures, dependent on the specific application design. For example, in particular embodiments, such “fluid-tight” arrangements desirably avoid fluid leakage at operating pressures up to at least about 20,000 psi or more and, more preferably, desirably avoid fluid leakage at operating pressures up to about 30,000 psi or more.
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Autoliv ASP Inc.
Brown Sally J.
Fischmann Bryan
Johnson Brian L.
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