Magnetically biased velocity change sensor

• US 5,068,502 A
• Filed: 11/13/1989
• Issued: 11/26/1991
• Est. Priority Date: 11/13/1989
• Status: Expired due to Fees

• Current Assignee: Siemens AG, Siemens-Bendix Automotive Electronics Limited Ontario Canada
• Original Assignee: Siemens Bendix Automotive Electronics Ltd (Continental AG)
• Inventors: Davenport, Thomas A.
• Primary Examiner(s): Scott, J. R.
• Application Number:
  US07/435,102
• Time in Patent Office: 743 Days
• Field of Search: 200/61.45 R, 200/61.45 M-61.53
• US Class Current: 200/61.45M
• CPC Class Codes: H01H 35/142 Damping means to avoid unwanted response

Abstract

A magnetically biased velocity change sensor that is designed for mass-production fabrication and ensuing usage in supplemental inflatable restraint systems of automotive vehicles. The sensor is of the type having a metal sphere that is magnetically biased to one axial end of a tube. When the sensor is subjected to a velocity change of suitable magnitude and duration, the sphere travels to the opposite end of the tube to actuate a switch. Damping of the sphere travel is accomplished by sizing the tube to be of just slightly larger inside diameter than the diameter of the sphere. The invention enhances the manufacturability of the sensor by making dimensioning requirements for the tube and sphere less strict and by enabling different models of sensors to be fabricated from commonly dimensioned tubes and spheres. The invention involves manufacturing the sphere as a sintered iron mass and using a mixture of gases within the tube.

Claims

1. In a velocity change sensor of the type comprising a tube having a circular cylindrical inside diameter containing a magnetically permeable sphere whose diameter is just slightly less than the tube'"'"'s inside diameter so that travel of said sphere within said tube is damped by gaseous fluid present within said tube, a magnet for biasing said sphere axially within said tube against a stop proximate one axial end of said tube, a switch disposed proximate the opposite axial end of said tube for actuation by said sphere in response to said sensor experiencing a velocity change of sufficient magnitude and duration to cause said sphere to overcome the bias of said magnet and travel within said tube from the position against said stop to a position causing said switch to give a signal indicative of the occurrence of such velocity change, the improvement comprising said sphere consisting of iron having a density of essentially 5.7 grams per cubic centimeter.

2. The improvement set forth in claim 1 comprising said gaseous fluid consisting of a carbon dioxide-neon mixture that is essentially free of other gases.

3. In a velocity change sensor of the type comprising a tube having a circular cylindrical inside diameter containing a magnetically permeable sphere whose diameter is just slightly less than the tube'"'"'s inside diameter so that travel of said sphere within said tube is damped by gaseous fluid present within said tube, a magnet for biasing said sphere axially within said tube against a stop proximate one axial end of said tube, a switch disposed proximate the opposite axial end of said tube for actuation by said sphere in response to said sensor experiencing a velocity change of sufficient magnitude and duration to cause said sphere to overcome the bias of said magnet and travel within said tube from the position against said stop to a position causing said switch to give a signal indicative of the occurrence of such velocity change, the improvement comprising said gaseous fluid consisting of a carbon dioxide-neon mixture that is essentially free of other gases and can range from essentially all carbon dioxide to essentially all neon.

4. In the method of making different models of velocity change sensors of the type comprising a tube having a circular cylindrical inside diameter containing a magnetically permeable sphere whose diameter is just slightly less than the tube'"'"'s inside diameter so that travel of said sphere within said tube is damped by gaseous fluid present within said tube, a magnet for biasing said sphere axially within said tube against a stop proximate one axial end of said tube, a switch disposed proximate the opposite axial end of said tube for actuation by said sphere in response to said sensor experiencing a velocity change of sufficient magnitude and duration to cause said sphere to overcome the bias of said magnet and travel within said tube from the position against said stop to a position causing said switch to give a signal indicative of the occurrence of such velocity change, wherein the different models are characterized by different velocity response characteristics, the improvement which comprises making all such models from spheres of identical mass and diameter and from tubes of identical inside diameter and length, and filling each model with a gaseous fluid of a viscosity that is unique to the particular model, wherein the gaseous fluid filling each model comprises a mixture consisting essentially of two gases of different viscosity whose relative proportions are varied for different models, said mixture is a carbon dioxide-neon mixture that is essentially free of other gases and can range from essentially all carbon dioxide to essentially all neon.