Electricity: circuit makers and breakers – Solid contact – Membrane type
Reexamination Certificate
1999-12-28
2001-11-20
Bradley, Paula (Department: 2832)
Electricity: circuit makers and breakers
Solid contact
Membrane type
C200S517000
Reexamination Certificate
active
06320147
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a membrane horn switch assembly and, more particularly, to a dual contact membrane horn switch assembly which will not activate the vehicle horn when the cover expands or contracts due to extremes in temperature.
BACKGROUND OF THE INVENTION
This invention relates to a membrane horn switch assembly for a driver side supplemental inflatable restraint (SIR) system. Driver side SIR systems typically include an air bag stored in a housing module. SIR systems are designed to actuate upon sudden deceleration so as to rapidly deploy an air bag in order to restrain the movement of the driver. A driver side SIR system is normally positioned under a steering wheel cover within a hub of a steering wheel. Traditionally, this is where a membrane horn switch is also located. Driver side SIR systems have therefore been adapted to include the membrane horn switch.
Driver side SIR systems are conventionally mounted on the steering wheel along with the membrane horn switch. As is known, the membrane horn switch generally comprises a dielectric substrate, a flexible membrane extending parallel to the substrate and a separator that is inserted between opposing surfaces of the membrane and the substrate. Circuit conductors are provided on the opposing surfaces of the membrane and the substrate. Pressure on the membrane horn switch pushes the conductors together to close a horn circuit that the membrane horn switch is connected to in order to actuate a remote horn. When the flexible membrane that carries the movable contact is deformed, it moves towards a fixed contact on the substrate and upon physically touching the fixed contact, the electrical switch connection is made and the horn is actuated. Upon release of the pressure, the circuit is broken and the horn is silenced.
Membrane horn switches require some form of a rigid base to be compressed against. Having the SIR system and the membrane horn switch located within the steering wheel hub calls for the components that make up the SIR system and the membrane horn switch to be tightly packed. When the membrane horn switch is tightly packed between a folded air bag cushion and the steering wheel cover, it is susceptible to inadvertent actuation. This inadvertent actuation could occur with a minor accidental bumping of the steering wheel cover or with a temperature related compression on the steering wheel cover caused by the expansion or contraction of the integrated parts due to extremes in temperature. For example when the temperature is very cold, the steering wheel cover could contract without any pressure exerted on it by the vehicle driver. The temperature related contraction of the steering wheel cover would therefore cause the switch to react in the way it responds when the driver exerts pressure on the steering wheel cover. In other words, the horn will sound because the conductive surfaces on the substrate and the flexible membrane are forced together to complete the horn circuit. However, unlike actuation of the horn by hand pressure, the contraction that takes place due to the extreme cold temperature causes the horn switch to remain in the contracted position in which the conductive surfaces are in contact until the temperature rises causing the cover to expand to its original position in which the conductive surfaces are separate from one another. This results in the constant sound of the horn in cold temperatures.
Another consideration in designing membrane horn switches is the amount of pressure needed to actuate the membrane horn switch. It is therefore desirous to have a membrane horn switch that can be activated with a consistent minimal pressure. However, orienting the conductive surfaces close together as is needed for minimal contact actuation also has the added risk of the unintentional closing of the circuit or sounding of the horn. Accordingly, in order to ensure that the conductive surfaces are not so close as to accidentally activate the switch, the conductive surfaces of the conventional membrane horn switches are spaced further apart so that a greater amount of pressure on the steering wheel cover is needed to force the conductive surfaces together closing the circuit and thereby actuating the vehicle horn.
It is therefore desirable to provide a dual contact membrane horn switch assembly that when exposed to extremes in temperature will not trigger actuation of the switch and thereby sound the vehicle's horn. In addition, it is desirous to provide a dual contact membrane horn switch assembly which requires consistent minimal pressure to close the circuit and thereby actuate the vehicle's horn.
SUMMARY OF THE INVENTION
Advantageously, the present invention is directed to a membrane horn switch assembly designed so that a steering wheel cover can expand or contract due to extremes in temperature without the unintentional closing of a circuit used to activate a remote horn. Also, the assembly includes a membrane horn gap which is designed so that the space between the cover or reaction plate concentrators and the switch is minimized thereby requiring less pressure exerted on the steering wheel cover to actuate the switch. Additionally, the steering wheel cover is designed so that a greater deflection in the cover results when using the same amount of pressure as was previously exerted on the cover.
In one embodiment, the membrane horn switch assembly of the present invention comprises a membrane horn switch having an upper flexible substrate sheet having a bottom surface coated with a conductive material, a lower flexible substrate sheet with a conductive positive and a negative grid disposed on a top surface thereof and a dielectric spacer interposed between the upper and lower flexible substrate sheets. The dielectric spacer partially defines a predetermined number of switch contact points where an electrical connection may be provided between the upper and lower sheets when assembled. Also included in the assembly is a steering wheel cover which may have any number of suitable steering wheel cover designs such as a one-shot design, two-shot design, etc. In one embodiment, the steering wheel cover is of a two-shot steering wheel cover design having a flexible outer portion and a rigid inner portion, where the membrane horn switch is disposed between the outer portion and the inner portion. The inner portion has a plurality of first and second concentrators integrally formed thereon. In this embodiment, the first and second concentrators comprise elongated members extending away from the inner portion of the steering wheel cover, wherein the first concentrators have a length that is greater than a length of the second concentrators.
With any downward movement (towards a driver side air bag) of the flexible outer portion of the steering wheel cover, the first concentrators formed on a top surface of the rigid inner surface of the steering wheel cover make contact with the membrane horn switch before the second concentrators because of the differing lengths thereof. The first concentrators are oriented and aligned so that they contact either the conductive positive or the negative grid which are preferably interleaved with one another. Likewise, the second concentrators are oriented so that they contact the conductive grid not contacted by the first concentrators when the steering wheel cover is further depressed. In this manner, whenever the steering wheel cover is minimally driven downward, either by contraction due to extremely cold temperature or by an accidental bumping with minimal force, only the first concentrators would contact the switch thereby forcing only selective areas of the conductive material with one of the positive and negative conductive grids. For purpose of illustration only, the first concentrators are described and shown as being orientated to contact the conductive positive grid. Without the subsequent electrical connection between the conductive material and the conductive negative grid, the electrical circuit used to activate the horn i
Bradley Paula
Delphi Technologies Inc.
Marra Kathryn A.
Nguyen Nhung
LandOfFree
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