Land vehicles – Wheeled – Attachment
Reexamination Certificate
2001-05-30
2003-05-27
English, Peter C. (Department: 3616)
Land vehicles
Wheeled
Attachment
C403S193000, C403S199000, C403S282000, C029S520000
Reexamination Certificate
active
06568703
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention relates to systems and methods for attaching two or more members together. More specifically, the present invention relates to a novel system and method for securely and easily mounting a rounded member, for example, an airbag inflator, to an interior surface of a vehicle.
2. The Relevant Technology
Many methods are currently available for fastening two or more parts together as part of an assembly. Flat parts, such as steel beams, struts, and the like can typically be comparatively easily fastened together through the use of fasteners, adhesives, welding, or a similar method. Adjoining flat surfaces provide an even, simple interface for the attachment.
However, rounded members, such as bars, pipes, pressure vessels, and the like present greater attachment problems. Round, convex surfaces often require the use of a corresponding concave surface to provide an attachment interface. Thus, many implements, such as conventional clamps and the like, that are useful for attaching two flat parts together, cannot be used for rounded parts.
The attachment problem is further multiplied when the rounded member is subject to high stress. In the case of pressure vessels, for example, a comparatively thin wall is subject to high stress from a pressurized internal fluid. The walls of such vessels are typically manufactured to have a uniform thickness and a comparatively uniform curvature so that stresses are evenly distributed throughout the wall. Thus, significant deformation or piercing of the wall is to be avoided. Holes, in particular, are problematic even if they do not extend fully through the wall of the pressure vessel, because stresses tend to concentrate at holes. As a result, cracks often begin forming at holes, and propagate outward from the hole. Although thinner wall sections are not as critical as holes, they are also often failure points because of stress concentration.
As a result, the number of methods that can be used to attach a rounded member under considerable stress to another member is very limited. Fasteners that require holes, such as screws, bolts, rivets, and the like, are clearly undesirable. Welding also has a tendency to weaken the underlying material, and requires that the joint to be welded be accessible to the welding equipment.
Conventional press fitting, or “interference” fitting, is an attachment process by which a member is attached to another member or a fixture by friction. “Frictional engagement” refers to two surfaces that are pressed together such that friction keeps them from sliding relative to each other. “Interference” refers to a geometric state in which one part blocks motion of another part; in an interference fit, one or both parts are deflected to make the relative motion possible.
In order to provide an interference fit, a protrusion in one member is typically inserted into a cavity in another, and the cavity is dimensioned slightly smaller than the protrusion. The cavity must then be stretched, and the protrusion compressed, in order to fit together. A considerable amount of radial pressure between the protrusion and the cavity results, so that the protrusion is held within the cavity by frictional force. Often, the protrusion, the cavity, or both may be tapered so that the protrusion can be gradually forced into the cavity.
The force required to force the protrusion into the cavity is generally proportional to the force required to withdraw it. In order to create an attachment that will withstand a desired axial (along the axis of symmetry of the rounded member) tension, a commensurate degree of compression may need to be applied to insert the protrusion into the cavity. However, in circumstances in which torsion, or rotational force, is to be coupled with the tension, a lower amount of tension may be required to withdraw the protrusion.
One such application in which it is desirable to rigidly mount a rounded member is for automotive safety restraint devices. The inclusion of inflatable safety restraint devices, or airbags, is now a legal requirement for many new vehicles. Airbags are typically installed in the steering wheel and in the dashboard on the passenger side of a car. In the event of an accident, an accelerometer within the vehicle measures the abnormal deceleration and triggers the ignition of an explosive charge. Expanding gases from the charge fill the airbags, which immediately inflate in front of the driver and passenger to protect them from impact against the windshield. Side impact airbags have also been developed in response to the need for similar protection from impacts in a lateral direction, or against the side of the vehicle.
The explosive charge is typically located in an inflator, which often takes the form of a cylindrical metal pressure vessel designed to contain the explosion and channel the resulting gases into the airbag. Since the inflator contains explosive materials, it is very important that it be firmly fastened to an interior surface of the vehicle. The inflator typically has a cylindrical central portion with roughly hemispherical end caps. Thus, the problems described above in connection with attachment of rounded members generally, apply to inflators. Additionally, Department of Transportation regulations restrict the use of any welded joints in motor vehicles. Generally, attachments in motor vehicles, particularly attachments related to safety systems, must be strong enough to withstand the operating vibrations of the vehicle as well as potential impacts.
Furthermore, known attachments are typically not adaptable to inflators of different sizes. Airbag sizes may vary from one vehicle to the next; consequently, an airbag manufacturer may need to be able to make and install several different inflator sizes. With most known attachment systems, each inflator size would require its own specially-sized attachment. The need to pair each size with an associated attachment assembly has increased the time and expense required for inflator installation.
Consequently, it would be an advancement in the art to provide a method and apparatus for attaching a rounded member to another member without welding. More specifically, it would be an advancement in the art to enable the attachment of a rounded member such as an inflator to a comparatively flat surface such as a vehicle surface.
The method and apparatus should preferably be easily carried out with a minimum of equipment. Thus, the method and apparatus should preferably provide a comparatively large holding force with a comparatively small attachment force. Preferably, the method and apparatus should be capable of maintaining attachment even under combined axial and torsional loads. The method and apparatus should also be usable to attach rounded members with a wide range of sizes, without the need to design and use different attachment hardware with each size. Furthermore, the method and apparatus should be simple and inexpensive to implement.
BRIEF SUMMARY OF THE INVENTION
The apparatus of the present invention has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available systems and methods for attaching rounded members. Consequently, the present invention provides a novel system and method for attaching a rounded member, particularly to a flat surface. Although the following disclosure provides the example of an airbag inflator, the method and system disclosed herein may be used with any rounded member.
An inflator attachment may comprise an inflator, a flange, and a spacer. The inflator typically takes the form of a cylindrical pressure vessel with roughly hemispherical ends. The inflator is located within a suitable compartment of a vehicle, such as a passenger side dashboard compartment. The inflator provides pressurized gas to an airbag, either through a conduit, or through direct passage of air into an opening of the airbag from an opening, or d
Abdella Michael
Hesse William O.
Klein Raymond John
Woodward Mark
Autoliv ASP Inc.
Brown Sally J.
English Peter C.
Erickson James D.
LandOfFree
Interference fit attachment for a rounded member does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Interference fit attachment for a rounded member, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Interference fit attachment for a rounded member will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3074881