Title:
PRESSURE RESPONSIVE SWITCH
United States Patent 3718791
Abstract:
A normally open pressure responsive switch includes spaced first and second substantially planar members having opposed paddle-like configurations and composed of a dielectric generally flexible material such as plastic. First and second planar contacts of fork-like configurations are respectively laminated to the opposed faces of the planar members. The members and contacts are stamped to form depressions of frustoconical configuration. First and second terminals for connecting the switch to an electric circuit are respectively connected laterally spaced to handle portions of the contacts. The lateral spacing prevents engagement of the terminals and resultant closing of the switch. A resilient foam pad positioned between and adhesively bonded to the blade portions of the planar members includes a plurality of apertures of variable configuration whose opposite ends open to the tine portions of the respective contacts. The foam pad normally maintains a spaced relationship between the frustoconical apexes of the depressions respective the opposite ends of each aperture and deflects to allow engagement of these apexes and closing of the switch when the planar members are subjected to a normal pressure above a predetermined value.
US Patent References:
Mat switch and method of making the same
Larson - September 1962 - 3056005
Mat type floor switch
Wikkerink - September 1960 - 2954446
Surface mounted treadle
Hohmann - November 1960 - 2959647
Treadle and treadle frame
Cooper et al. - September 1956 - 2761928
PRESSURE-OPERATED LAYERED ELECTRICAL SWITCH AND SWITCH ARRAY
Brave - November 1971 - 3617666
Mat switch and method of making the same
Larson - September 1962 - 3056005
Mat type floor switch
Wikkerink - September 1960 - 2954446
Surface mounted treadle
Hohmann - November 1960 - 2959647
Treadle and treadle frame
Cooper et al. - September 1956 - 2761928
PRESSURE-OPERATED LAYERED ELECTRICAL SWITCH AND SWITCH ARRAY
Brave - November 1971 - 3617666
Application Number:
05/181013
Publication Date:
02/27/1973
Filing Date:
09/16/1971
View Patent Images:
Export Citation:
Assignee:
General Motors Corporation (Detroit, MI)
Primary Class:
Other Classes:
200/86R
International Classes:
H01H3/14; H01H3/02; H01H3/02
Field of Search:
200/85,86R,86A,86.5,159B
US Patent References:
| 3487451 | BRAKE CONTROL MEANS FOR VEHICLES | December 1969 | Fontaine |
Primary Examiner:
Scott J. R.
Claims:
What is claimed is
1. A normally open pressure responsive switch comprising, spaced first and second substantially planar members of a dielectric generally flexible material, electrically conductive generally planar first and second contacts respectively laminated to the opposed faces of the planar members, resilient spacing means between the planar members and defining a plurality of voids extending through the spacing means and opening to the contacts, and a plurality of stamped depressions formed in the planar members and their respective contacts and received within the voids of the spacing means with portions of the contacts forming apexes of the depressions supported by the depressed portions of the planar members, the spacing means normally maintaining a spaced relationship between the apexes of the depressions respective the opposite ends of each void and deflecting to allow engagement of these apexes and closing of the switch when the planar members are subjected to a normal pressure above a predetermined value.
2. A normally open pressure responsive switch comprising, spaced first and second substantially planar members of a dielectric generally flexible material, electrically conductive generally planar first and second contacts respectively laminated to the opposed faces of the planar members, resilient spacing means between the planar members and adhesively laminated by a bonding agent thereto with a plurality of apertures extending through the spacing means and opening to the contacts, and a plurality of stamped depressions formed in the planar members and their respective contacts and received within the apertures of the spacing means with portions of the contacts forming apexes of the depressions supported by the depressed portions of the planar members, the spacing means normally maintaining a spaced relationship between the apexes of the depressions respective the opposite ends of each aperture and deflecting to allow engagement of these apexes and closing of the switch when the planar members are subjected to a normal pressure above a predetermined value.
3. A normally open pressure responsive switch comprising, spaced first and second substantially planar members of a dielectric generally flexible material, resilient spacing means between the planar members and adhesively laminated by a bonding agent thereto with a plurality of apertures extending through the spacing means and opening to the planar members, a plurality of frustoconical stamped depressions formed in the planar members and respectively received within the apertures of the spacing means, a plurality of generally planar contacts laminated between the spacing means and the planar members and including stamped depressions covering and supported by the depressions of the planar members, the spacing means normally maintaining a spaced relationship between the apexes of the contact depressions respective the opposite ends of each aperture while deflecting to allow engagement of these apexes and closing of the switch when the planar members are subjected to a normal pressure above a predetermined value, and the contacts defining spaces in their respective planes between the depressions thereof to reduce the rigidity imparted to the switch by the contacts.
4. A normally open pressure responsive switch comprising, spaced first and second substantially planar members of a dielectric generally flexible material and having paddle-like configurations in opposed relationship, electrically conductive generally planar first and second contacts having fork-like configurations respectively laminated to the opposed faces of the planar members with the tine portions of the contacts on the blade portions of the planar members and with the handle portions of the contacts on the handle portions of the planar members, terminal means for connecting the handle portions of each contact to an electric circuit, resilient spacing means between the planar members and adhesively laminated by a bonding agent thereto with a plurality of apertures extending through the spacing means and opening to the tine portions of the contacts, and a plurality of frustoconical stamped depressions formed in the planar members and the respective tine portions of the contacts and received within the apertures of the spacing means with portions of the contacts forming apexes of the depressions supported by the depressed portions of the planar members, the spacing means normally maintaining a spaced relationship between the apexes of the depressions respective the opposite ends of each aperture and deflecting to allow engagement of these apexes and closing of the switch when the planar members are subjected to a normal pressure above a predetermined value.
5. A normally open pressure responsive switch for use within a seat to detect occupancy of the seat, the switch comprising, spaced first and second substantially planar members of a dielectric generally flexible material and having paddle-like configurations in opposed relationship, the planar members being positionable generally parallel to a seating surface of the seat with the blade portion of the upper planar member larger than the blade portion of the lower planar member to shield the switch from liquid accidentally spilled on the seat, electrically conductive generally planar first and second contacts having fork-like configurations respectively laminated to the opposed faces of the planar members with the tine portions of the contacts on the blade portions of the planar members and with the handle portions of the contacts on the handle portions of the planar members, terminal means for connecting the handle portions of each contact to an electrical circuit, resilient spacing means between the planar members and adhesively laminated by a bonding agent thereto with a plurality of apertures extending through the spacing means and opening to the tine portions of the contacts, and a plurality of frustoconical stamped depressions formed in the planar members and the respective tine portions of the contacts and received within the apertures of the spacing means with portions of the contacts forming apexes of the depressions supported by the depressed portions of the planar members, the spacing means normally maintaining a spaced relationship between the apexes of the depressions respective the opposite ends of each aperture and deflecting to allow engagement of these apexes and closing of the switch when the planar members are subjected to a normal pressure above a predetermined value by a seated occupant.
6. A normally open pressure responsive switch according to claim 5 wherein the stamped depressions along the tine portions are connected by strip portions having widths less than the diameter of the depressions to further reduce the rigidity of the switch.
7. A normally open pressure responsive switch according to claim 5 wherein the handle portions of the contacts are laterally offset to prevent engagement of the terminal means connected thereto and resultant closing of the switch.
8. A normally open pressure responsive switch according to claim 5 wherein the terminal means for each contact includes a connector member having a portion for connecting a lead and a flattened portion engageable with the contact handle portion and having an aperture aligned with aligned apertures in the handle portions of both the planar member and contact, and an insert having a portion received within the aligned apertures and terminating in lips respectively engageable with the outer side of the planar member handle portion and the inner side of the connector member flattened portion to maintain engagement between the connector member and the handle portion of the contact.
9. A normally open pressure responsive switch according to claim 8 wherein the insert is composed of metal and the lip engageable with the outer side of the planar member handle portion is covered with a dielectric member to prevent electrical connection of the terminal with any conductive member of the seat the switch is for use within.
10. A normally open pressure responsive switch according to claim 5 wherein the apertures of the spacing means are elongated and extend for the length of the tine portions of the contacts.
11. A normally open pressure responsive switch according to claim 5 wherein a plurality of the apertures within the spacing means open to each opposed set of tine portions of the contacts.
1. A normally open pressure responsive switch comprising, spaced first and second substantially planar members of a dielectric generally flexible material, electrically conductive generally planar first and second contacts respectively laminated to the opposed faces of the planar members, resilient spacing means between the planar members and defining a plurality of voids extending through the spacing means and opening to the contacts, and a plurality of stamped depressions formed in the planar members and their respective contacts and received within the voids of the spacing means with portions of the contacts forming apexes of the depressions supported by the depressed portions of the planar members, the spacing means normally maintaining a spaced relationship between the apexes of the depressions respective the opposite ends of each void and deflecting to allow engagement of these apexes and closing of the switch when the planar members are subjected to a normal pressure above a predetermined value.
2. A normally open pressure responsive switch comprising, spaced first and second substantially planar members of a dielectric generally flexible material, electrically conductive generally planar first and second contacts respectively laminated to the opposed faces of the planar members, resilient spacing means between the planar members and adhesively laminated by a bonding agent thereto with a plurality of apertures extending through the spacing means and opening to the contacts, and a plurality of stamped depressions formed in the planar members and their respective contacts and received within the apertures of the spacing means with portions of the contacts forming apexes of the depressions supported by the depressed portions of the planar members, the spacing means normally maintaining a spaced relationship between the apexes of the depressions respective the opposite ends of each aperture and deflecting to allow engagement of these apexes and closing of the switch when the planar members are subjected to a normal pressure above a predetermined value.
3. A normally open pressure responsive switch comprising, spaced first and second substantially planar members of a dielectric generally flexible material, resilient spacing means between the planar members and adhesively laminated by a bonding agent thereto with a plurality of apertures extending through the spacing means and opening to the planar members, a plurality of frustoconical stamped depressions formed in the planar members and respectively received within the apertures of the spacing means, a plurality of generally planar contacts laminated between the spacing means and the planar members and including stamped depressions covering and supported by the depressions of the planar members, the spacing means normally maintaining a spaced relationship between the apexes of the contact depressions respective the opposite ends of each aperture while deflecting to allow engagement of these apexes and closing of the switch when the planar members are subjected to a normal pressure above a predetermined value, and the contacts defining spaces in their respective planes between the depressions thereof to reduce the rigidity imparted to the switch by the contacts.
4. A normally open pressure responsive switch comprising, spaced first and second substantially planar members of a dielectric generally flexible material and having paddle-like configurations in opposed relationship, electrically conductive generally planar first and second contacts having fork-like configurations respectively laminated to the opposed faces of the planar members with the tine portions of the contacts on the blade portions of the planar members and with the handle portions of the contacts on the handle portions of the planar members, terminal means for connecting the handle portions of each contact to an electric circuit, resilient spacing means between the planar members and adhesively laminated by a bonding agent thereto with a plurality of apertures extending through the spacing means and opening to the tine portions of the contacts, and a plurality of frustoconical stamped depressions formed in the planar members and the respective tine portions of the contacts and received within the apertures of the spacing means with portions of the contacts forming apexes of the depressions supported by the depressed portions of the planar members, the spacing means normally maintaining a spaced relationship between the apexes of the depressions respective the opposite ends of each aperture and deflecting to allow engagement of these apexes and closing of the switch when the planar members are subjected to a normal pressure above a predetermined value.
5. A normally open pressure responsive switch for use within a seat to detect occupancy of the seat, the switch comprising, spaced first and second substantially planar members of a dielectric generally flexible material and having paddle-like configurations in opposed relationship, the planar members being positionable generally parallel to a seating surface of the seat with the blade portion of the upper planar member larger than the blade portion of the lower planar member to shield the switch from liquid accidentally spilled on the seat, electrically conductive generally planar first and second contacts having fork-like configurations respectively laminated to the opposed faces of the planar members with the tine portions of the contacts on the blade portions of the planar members and with the handle portions of the contacts on the handle portions of the planar members, terminal means for connecting the handle portions of each contact to an electrical circuit, resilient spacing means between the planar members and adhesively laminated by a bonding agent thereto with a plurality of apertures extending through the spacing means and opening to the tine portions of the contacts, and a plurality of frustoconical stamped depressions formed in the planar members and the respective tine portions of the contacts and received within the apertures of the spacing means with portions of the contacts forming apexes of the depressions supported by the depressed portions of the planar members, the spacing means normally maintaining a spaced relationship between the apexes of the depressions respective the opposite ends of each aperture and deflecting to allow engagement of these apexes and closing of the switch when the planar members are subjected to a normal pressure above a predetermined value by a seated occupant.
6. A normally open pressure responsive switch according to claim 5 wherein the stamped depressions along the tine portions are connected by strip portions having widths less than the diameter of the depressions to further reduce the rigidity of the switch.
7. A normally open pressure responsive switch according to claim 5 wherein the handle portions of the contacts are laterally offset to prevent engagement of the terminal means connected thereto and resultant closing of the switch.
8. A normally open pressure responsive switch according to claim 5 wherein the terminal means for each contact includes a connector member having a portion for connecting a lead and a flattened portion engageable with the contact handle portion and having an aperture aligned with aligned apertures in the handle portions of both the planar member and contact, and an insert having a portion received within the aligned apertures and terminating in lips respectively engageable with the outer side of the planar member handle portion and the inner side of the connector member flattened portion to maintain engagement between the connector member and the handle portion of the contact.
9. A normally open pressure responsive switch according to claim 8 wherein the insert is composed of metal and the lip engageable with the outer side of the planar member handle portion is covered with a dielectric member to prevent electrical connection of the terminal with any conductive member of the seat the switch is for use within.
10. A normally open pressure responsive switch according to claim 5 wherein the apertures of the spacing means are elongated and extend for the length of the tine portions of the contacts.
11. A normally open pressure responsive switch according to claim 5 wherein a plurality of the apertures within the spacing means open to each opposed set of tine portions of the contacts.
Description:
BACKGROUND OF THE INVENTION
This invention relates generally to normally open pressure responsive switches that are closed when subjected to a pressure above a predetermined value.
It is known to provide normally open pressure responsive switches which close when subjected to a pressure above a predetermined value. One manner in which this type of switch is utilized is positioned within the seat cushion of a vehicle seat adjacent the seating surface and connected to a suitable electric circuit, with the switch closing when an occupant assumes a seated position and the circuit providing an indication that the seat is in an occupied condition. Generally, these switches include spaced first and second substantially planar members of a dielectric generally flexible material and have electrically conductive generally planar first and second contacts respectively laminated to their opposed faces. The planar members may be composed of a suitable plastic such as a polyester while the contacts are generally composed of copper. A plurality of resilient laterally spaced foam strips or a resilient apertured foam pad is situated between the planar members to normally maintain the contacts in a spaced relationship. When the planar members are subjected to a normal pressure above a predetermined value, the foam deflects to allow engagement of the contacts and closing of the switches. To prevent deflection of the foam without engagement of the contacts, it is known to provide the contacts with projecting portions received within the voids or apertures defined by the foam. Since these projecting portions are not supported by the planar members, they may plastically deform under the pressures the switches are subjected to when used with vehicle seats.
SUMMARY OF THE INVENTION
This invention provides a normally open pressure responsive switch of the type described in which spaced planar members and their opposed respective laminated planar contacts include a plurality of stamped depressions, with the depressed portions of the contacts supported by the depressed portions of the planar members, and with the apexes of the depressed contact portions received within the opposite ends of voids defined by a resilient material normally maintaining these apexes in spaced relationship.
In the preferred embodiment of the invention, the planar members are composed of a polyester and have generally paddle-like configurations positioned in an opposed relationship, while the contacts have generally fork-like configurations with their tine portions laminated to the blade portions of the planar members in opposed relationship and with their handle portions laminated to the handle portions of the planar members in laterally spaced relationship. First and second terminals for connecting the switch to an electric circuit are respectively connected to the contact handle portions whose lateral spacing prevents engagement of the terminals and resultant closing of the switch. A resilient foam pad is located between the blade portions of the planar members and adhesively bonds the switch in a generally sandwich construction. The foam pad includes a plurality of apertures whose opposite ends open to opposed sets of respective tine portions of the contacts. The apertures may be elongated and extend for the length of the tine portions or may be shortened to provide a plurality of apertures along each set of opposed tine portions. A plurality of frustoconical stamped depressions are formed in the blade portions of the planar members and the respective tine portions of the contacts such that the depressed portions of the planar members support the depressed portions of the contacts. The depressions are received within the apertures of the foam pad which normally maintains the opposed apexes of the respective contacts in a spaced relationship such that the switch is open. The foam pad deflects when the planar members are subjected to a normal pressure above a predetermined value to allow engagement of the apexes and closing of the switch. The lateral spaces between the tine portions of each contact reduce the rigidity imparted to the switch by the contacts and prevent the possibility the switch will cause discomfort to a seated occupant when it is used to detect occupancy of a seat. Between the depressions, the tine portions include strip portions having widths less than the diameter of the depressions to further reduce the rigidity of the switch.
Accordingly, one feature of this invention is that it provides an improved normally open pressure responsive switch that includes spaced first and second substantially planar members of a dielectric generally flexible material, with electrically conductive generally planar first and second contacts respectively laminated to the opposed faces of the planar members, and with a plurality of stamped depressions formed in the planar members and their respective contacts and received within voids defined by a resilient material that normally maintains the apexes of the contact depressed portions in a spaced relationship. Another feature of the invention is that the resilient material may take the form of an apertured foam pad whose opposite sides adhesively bond the planar members in the spaced relationship and whose apertures receive the stamped depressions of the planar members and the contacts. Another feature of the invention is that the stamped depressions of the planar members and contacts have a generally frustoconical configuration and the contacts define spaces in their respective planes between the depressions such that the rigidity of the switch is not appreciably increased by the contacts. Another feature of the invention is that the planar members have paddle-like configurations positioned in opposed relationship and the contacts have fork-like configurations, with the tine portions of the contacts laminated to blade portions of the planar members and stamped to form the depressions while the spaces between the tine portions of each contact provide the reduction in the rigidity of the switch, and with the handle portions of the contacts laminated to the handle portions of the planar members. Another feature of the invention is that the blade portion of one of the planar members is larger than the blade portion of the other planar member such that the larger blade portion may be located on the upper side of the switch when used with a vehicle seat for detecting seat occupancy and shields the switch from liquid accidentally spilled on the seat. Another feature of the invention is that the handle portions of the contacts have respective terminals connected to them and are laterally spaced to prevent engagement of the terminals and resultant closing of the switch. Another feature of the invention is that the stamped depressions along the tine portions of the contacts are electrically connected by strip portions of a width less than the diameter of the depressions to further reduce the rigidity imparted to the switch by the contacts.
BRIEF DESCRIPTION OF THE DRAWINGS
The above detailed features and other features of this invention are apparent from the following description of the preferred embodiment and from the drawings in which:
FIG. 1 is a partially broken away perspective view of a vehicle seat whose seat cushion supports a normally open pressure responsive switch, according to this invention, that is closed when a seat occupant assumes a seated position;
FIG. 2 is an enlarged top plan view of the switch shown in FIG. 1;
FIG. 3 is an enlarged sectional view taken along line 3--3 of FIG. 2 and showing the sandwich construction of the switch which includes spaced upper and lower planar members to whose opposed faces are laminated respective planar contacts, a foam pad whose aperture opens to the contacts, and stamped frustoconical depressions in the planar members and their respective contacts which are received within the opposite ends of the aperture and maintained in a spaced relationship by the pad;
FIG. 4 is an enlarged sectional view taken generally along line 4--4 of FIG. 2 and showing a terminal of the switch;
FIG. 5 is an enlarged disassembled perspective view of the switch showing the foam pad, the fork-like configurations of the contacts, and the relative positioning of the contacts on the paddle-like configurations of the planar members; and
FIG. 6 is a perspective view of a foam pad whose apertures are of a smaller size than the foam pad of FIG. 5.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the drawings and more particularly to FIG. 1, a vehicle floor 10 supports a vehicle seat generally indicated by 12 in a conventional manner by a support arrangement that is not shown. The seat cushion 14 of seat 12 supports a normally open pressure responsive switch 16, according to this invention, generally adjacent the seating surface. As will be more fully hereinafter described, switch 16 closes when an occupant assumes a seated position such that the switch may be connected to a suitable electric circuit that indicates the occupied seat condition or controls a desired function concomitant with such condition.
Referring additionally now to FIGS. 2, 3, and 5, the switch 16 includes upper and lower generally planar members 18 and 20 manufactured from suitable planar stock of a generally flexible material, such as a polyester of a thickness approximately equal to 0.004 inches. The upper planar member 18 includes a blade portion 22 that is of a slightly larger size than the blade portion 24 of the lower planar member 20 such that the switch is protected from liquid accidentally spilled on the seat cushion 14 of seat 12. Respective handle portions 26 and 28 of the planar members 18 and 20 extend from the blade portions 22 and 24 and are generally of the same width. As best seen in FIG. 5, fork-like contacts generally indicated by 30 and 32 are respectively laminated to the planar members 18 and 20 and are manufactured from copper foil having a thickness approximately equal to .0015 inches. The contacts 30 and 32 each include a plurality of respective tine portions 34 and 36 that extend along the length of the respective blade portions 22 and 24. The contacts 30 and 32 also include respective handle portions 38 and 40 that extend along the handle portions 26 and 28 of the planar members. A die stamping operation may be used to laminate the contacts to the planar members. To perform this operation, copper foil slightly larger than the contact is superimposed on the planar member. A heated die with a cutting edge that defines the outline of the contact is then placed above the copper foil. Downward movement of the die severs the contact portion of the foil from the adjacent excess material and the heat bonds both the contact and the excess material to the planar member. The excess material is then peeled from the planar member and the planar member and contact are subsequently heated, as will be later described, to provide a bond between the planar member and contact within the contact outline.
A generally rectangular pad as generally indicated by 42 in FIG. 5 is situated between the blade portions 22 and 24 and is composed of a suitable resilient material such as an open cell polyurethane foam. An adhesive bonding agent is applied to the opposite sides of pad 42 and protected from undesired adhesion prior to assembly by a suitable protective layer, not shown. Upon assembly of the switch, the protective layer is removed from pad 42 to expose the adhesive bonding agent which secures the blade portions 22 and 24 and the pad 42 in a generally sandwich construction. In the assembled switch, a plurality of elongated apertures 44 in pad 42 extend longitudinally of and open to respectively opposed sets of tine portions 34 and 36 of the contacts 30 and 32. It is also possible to use a similar foam pad as generally indicated by 46 in FIG. 6 with a plurality of apertures 48 opening to the opposed sets of tine portions 34 and 36 of the contacts.
The planar members 18 and 20 with the outlines of the contacts 30 and 32 die stamped onto them are heated to a temperature between 300° and 350° Fahrenheit prior to assembly of the switch. This heating bonds the contacts and planar members within the contact outlines. With the planar members and contacts maintained at this temperature, a suitable die is used to stamp the blade portions 22 and 24 and the respective tine portions 34 and 36 of the contacts to form frustoconical depressions 50 and 52, best seen in FIGS. 3 and 5. The die remains in engagement with the planar members during cooling to ambient temperature to prevent the depressions from snapping back to planar configurations. When the switch is assembled, the apertures 44 of pad 42 receive the depressions 50 and 52 as best shown in FIG. 3 and the pad 42 normally maintains the apexes of the depressions in spaced relationship. When the blade portions 22 and 24 of the planar members are subjected to a normal pressure above a predetermined value, as when an occupant assumes a seated position on seat 12, the pad 42 deflects to allow engagement of the apexes of depressions 50 and 52 and closing of the switch. During this engagement, the depressed portions of the planar members support the depressed portions of the contacts to aid in preventing plastic deformation of the contacts.
The engaged contacts provide a conductive path through their respective handle portions 38 and 40 between a pair of terminals 54 and 56, FIGS. 2 and 5. These terminals allow attachment of a pair of leads 58 and 60 and attachment of the switch within the electric circuit. FIG. 4 shows an enlarged sectional view of terminal 54 which includes a connector member 62 that supports lead 58 by a portion 64 and electrically connects to the lead by a portion 66. The connector member includes a flattened portion 68 having an aperture 70 aligned with apertures 72 and 74 in handle portions 26 and 38 of planar member 18 and contact 30, respectively. A metal insert 76 extends through the aligned apertures and includes an upper support lip 78 suitably bonded to the upper side of handle portion 26 and covered by a polyester patch 80, see also FIG. 2, to prevent electrical contact of insert 76 with any conductive seat member. The lower side of insert 76 includes a lip 82 that maintains the portion 68 of connector member 62 in engagement with the handle portion 38 of contact 30. Terminal 56 is similar to terminal 54 and as such will not be further described except to say that the handle portions 38 and 40 of contacts 30 and 32 are laterally offset from each other such that the terminals do not engage each other even if there is no foam spacer pad or the like between the handle portions of the planar members.
Within the respective planes of the contacts, the spaces between the tine portions 34 and 36 reduce the rigidity imparted to the switch by the contacts and the possibility it will cause discomfort to a seated occupant of seat 12. Between the depressions 50 and 52, the tine portions 34 and 36 include respective strip portions 84 and 86 of a width less than the diameter of the depressions, the purpose being to further reduce the rigidity imparted to the switch by the contacts and the possibility of discomfort to a seated occupant.
As seen in FIG. 2, the lower side of blade portion 20 is covered by an adhesive bonding agent protected by a covering 88. When this covering is removed, the adhesive bonding agent positions switch 16 on a pad seat cushion 14 prior to covering of the switch with the material providing the seating surface. After the switch is covered, the covering material and the pad cooperate to further position the switch.
The invention thus provides an improved normally open pressure responsive switch.
This invention relates generally to normally open pressure responsive switches that are closed when subjected to a pressure above a predetermined value.
It is known to provide normally open pressure responsive switches which close when subjected to a pressure above a predetermined value. One manner in which this type of switch is utilized is positioned within the seat cushion of a vehicle seat adjacent the seating surface and connected to a suitable electric circuit, with the switch closing when an occupant assumes a seated position and the circuit providing an indication that the seat is in an occupied condition. Generally, these switches include spaced first and second substantially planar members of a dielectric generally flexible material and have electrically conductive generally planar first and second contacts respectively laminated to their opposed faces. The planar members may be composed of a suitable plastic such as a polyester while the contacts are generally composed of copper. A plurality of resilient laterally spaced foam strips or a resilient apertured foam pad is situated between the planar members to normally maintain the contacts in a spaced relationship. When the planar members are subjected to a normal pressure above a predetermined value, the foam deflects to allow engagement of the contacts and closing of the switches. To prevent deflection of the foam without engagement of the contacts, it is known to provide the contacts with projecting portions received within the voids or apertures defined by the foam. Since these projecting portions are not supported by the planar members, they may plastically deform under the pressures the switches are subjected to when used with vehicle seats.
SUMMARY OF THE INVENTION
This invention provides a normally open pressure responsive switch of the type described in which spaced planar members and their opposed respective laminated planar contacts include a plurality of stamped depressions, with the depressed portions of the contacts supported by the depressed portions of the planar members, and with the apexes of the depressed contact portions received within the opposite ends of voids defined by a resilient material normally maintaining these apexes in spaced relationship.
In the preferred embodiment of the invention, the planar members are composed of a polyester and have generally paddle-like configurations positioned in an opposed relationship, while the contacts have generally fork-like configurations with their tine portions laminated to the blade portions of the planar members in opposed relationship and with their handle portions laminated to the handle portions of the planar members in laterally spaced relationship. First and second terminals for connecting the switch to an electric circuit are respectively connected to the contact handle portions whose lateral spacing prevents engagement of the terminals and resultant closing of the switch. A resilient foam pad is located between the blade portions of the planar members and adhesively bonds the switch in a generally sandwich construction. The foam pad includes a plurality of apertures whose opposite ends open to opposed sets of respective tine portions of the contacts. The apertures may be elongated and extend for the length of the tine portions or may be shortened to provide a plurality of apertures along each set of opposed tine portions. A plurality of frustoconical stamped depressions are formed in the blade portions of the planar members and the respective tine portions of the contacts such that the depressed portions of the planar members support the depressed portions of the contacts. The depressions are received within the apertures of the foam pad which normally maintains the opposed apexes of the respective contacts in a spaced relationship such that the switch is open. The foam pad deflects when the planar members are subjected to a normal pressure above a predetermined value to allow engagement of the apexes and closing of the switch. The lateral spaces between the tine portions of each contact reduce the rigidity imparted to the switch by the contacts and prevent the possibility the switch will cause discomfort to a seated occupant when it is used to detect occupancy of a seat. Between the depressions, the tine portions include strip portions having widths less than the diameter of the depressions to further reduce the rigidity of the switch.
Accordingly, one feature of this invention is that it provides an improved normally open pressure responsive switch that includes spaced first and second substantially planar members of a dielectric generally flexible material, with electrically conductive generally planar first and second contacts respectively laminated to the opposed faces of the planar members, and with a plurality of stamped depressions formed in the planar members and their respective contacts and received within voids defined by a resilient material that normally maintains the apexes of the contact depressed portions in a spaced relationship. Another feature of the invention is that the resilient material may take the form of an apertured foam pad whose opposite sides adhesively bond the planar members in the spaced relationship and whose apertures receive the stamped depressions of the planar members and the contacts. Another feature of the invention is that the stamped depressions of the planar members and contacts have a generally frustoconical configuration and the contacts define spaces in their respective planes between the depressions such that the rigidity of the switch is not appreciably increased by the contacts. Another feature of the invention is that the planar members have paddle-like configurations positioned in opposed relationship and the contacts have fork-like configurations, with the tine portions of the contacts laminated to blade portions of the planar members and stamped to form the depressions while the spaces between the tine portions of each contact provide the reduction in the rigidity of the switch, and with the handle portions of the contacts laminated to the handle portions of the planar members. Another feature of the invention is that the blade portion of one of the planar members is larger than the blade portion of the other planar member such that the larger blade portion may be located on the upper side of the switch when used with a vehicle seat for detecting seat occupancy and shields the switch from liquid accidentally spilled on the seat. Another feature of the invention is that the handle portions of the contacts have respective terminals connected to them and are laterally spaced to prevent engagement of the terminals and resultant closing of the switch. Another feature of the invention is that the stamped depressions along the tine portions of the contacts are electrically connected by strip portions of a width less than the diameter of the depressions to further reduce the rigidity imparted to the switch by the contacts.
BRIEF DESCRIPTION OF THE DRAWINGS
The above detailed features and other features of this invention are apparent from the following description of the preferred embodiment and from the drawings in which:
FIG. 1 is a partially broken away perspective view of a vehicle seat whose seat cushion supports a normally open pressure responsive switch, according to this invention, that is closed when a seat occupant assumes a seated position;
FIG. 2 is an enlarged top plan view of the switch shown in FIG. 1;
FIG. 3 is an enlarged sectional view taken along line 3--3 of FIG. 2 and showing the sandwich construction of the switch which includes spaced upper and lower planar members to whose opposed faces are laminated respective planar contacts, a foam pad whose aperture opens to the contacts, and stamped frustoconical depressions in the planar members and their respective contacts which are received within the opposite ends of the aperture and maintained in a spaced relationship by the pad;
FIG. 4 is an enlarged sectional view taken generally along line 4--4 of FIG. 2 and showing a terminal of the switch;
FIG. 5 is an enlarged disassembled perspective view of the switch showing the foam pad, the fork-like configurations of the contacts, and the relative positioning of the contacts on the paddle-like configurations of the planar members; and
FIG. 6 is a perspective view of a foam pad whose apertures are of a smaller size than the foam pad of FIG. 5.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the drawings and more particularly to FIG. 1, a vehicle floor 10 supports a vehicle seat generally indicated by 12 in a conventional manner by a support arrangement that is not shown. The seat cushion 14 of seat 12 supports a normally open pressure responsive switch 16, according to this invention, generally adjacent the seating surface. As will be more fully hereinafter described, switch 16 closes when an occupant assumes a seated position such that the switch may be connected to a suitable electric circuit that indicates the occupied seat condition or controls a desired function concomitant with such condition.
Referring additionally now to FIGS. 2, 3, and 5, the switch 16 includes upper and lower generally planar members 18 and 20 manufactured from suitable planar stock of a generally flexible material, such as a polyester of a thickness approximately equal to 0.004 inches. The upper planar member 18 includes a blade portion 22 that is of a slightly larger size than the blade portion 24 of the lower planar member 20 such that the switch is protected from liquid accidentally spilled on the seat cushion 14 of seat 12. Respective handle portions 26 and 28 of the planar members 18 and 20 extend from the blade portions 22 and 24 and are generally of the same width. As best seen in FIG. 5, fork-like contacts generally indicated by 30 and 32 are respectively laminated to the planar members 18 and 20 and are manufactured from copper foil having a thickness approximately equal to .0015 inches. The contacts 30 and 32 each include a plurality of respective tine portions 34 and 36 that extend along the length of the respective blade portions 22 and 24. The contacts 30 and 32 also include respective handle portions 38 and 40 that extend along the handle portions 26 and 28 of the planar members. A die stamping operation may be used to laminate the contacts to the planar members. To perform this operation, copper foil slightly larger than the contact is superimposed on the planar member. A heated die with a cutting edge that defines the outline of the contact is then placed above the copper foil. Downward movement of the die severs the contact portion of the foil from the adjacent excess material and the heat bonds both the contact and the excess material to the planar member. The excess material is then peeled from the planar member and the planar member and contact are subsequently heated, as will be later described, to provide a bond between the planar member and contact within the contact outline.
A generally rectangular pad as generally indicated by 42 in FIG. 5 is situated between the blade portions 22 and 24 and is composed of a suitable resilient material such as an open cell polyurethane foam. An adhesive bonding agent is applied to the opposite sides of pad 42 and protected from undesired adhesion prior to assembly by a suitable protective layer, not shown. Upon assembly of the switch, the protective layer is removed from pad 42 to expose the adhesive bonding agent which secures the blade portions 22 and 24 and the pad 42 in a generally sandwich construction. In the assembled switch, a plurality of elongated apertures 44 in pad 42 extend longitudinally of and open to respectively opposed sets of tine portions 34 and 36 of the contacts 30 and 32. It is also possible to use a similar foam pad as generally indicated by 46 in FIG. 6 with a plurality of apertures 48 opening to the opposed sets of tine portions 34 and 36 of the contacts.
The planar members 18 and 20 with the outlines of the contacts 30 and 32 die stamped onto them are heated to a temperature between 300° and 350° Fahrenheit prior to assembly of the switch. This heating bonds the contacts and planar members within the contact outlines. With the planar members and contacts maintained at this temperature, a suitable die is used to stamp the blade portions 22 and 24 and the respective tine portions 34 and 36 of the contacts to form frustoconical depressions 50 and 52, best seen in FIGS. 3 and 5. The die remains in engagement with the planar members during cooling to ambient temperature to prevent the depressions from snapping back to planar configurations. When the switch is assembled, the apertures 44 of pad 42 receive the depressions 50 and 52 as best shown in FIG. 3 and the pad 42 normally maintains the apexes of the depressions in spaced relationship. When the blade portions 22 and 24 of the planar members are subjected to a normal pressure above a predetermined value, as when an occupant assumes a seated position on seat 12, the pad 42 deflects to allow engagement of the apexes of depressions 50 and 52 and closing of the switch. During this engagement, the depressed portions of the planar members support the depressed portions of the contacts to aid in preventing plastic deformation of the contacts.
The engaged contacts provide a conductive path through their respective handle portions 38 and 40 between a pair of terminals 54 and 56, FIGS. 2 and 5. These terminals allow attachment of a pair of leads 58 and 60 and attachment of the switch within the electric circuit. FIG. 4 shows an enlarged sectional view of terminal 54 which includes a connector member 62 that supports lead 58 by a portion 64 and electrically connects to the lead by a portion 66. The connector member includes a flattened portion 68 having an aperture 70 aligned with apertures 72 and 74 in handle portions 26 and 38 of planar member 18 and contact 30, respectively. A metal insert 76 extends through the aligned apertures and includes an upper support lip 78 suitably bonded to the upper side of handle portion 26 and covered by a polyester patch 80, see also FIG. 2, to prevent electrical contact of insert 76 with any conductive seat member. The lower side of insert 76 includes a lip 82 that maintains the portion 68 of connector member 62 in engagement with the handle portion 38 of contact 30. Terminal 56 is similar to terminal 54 and as such will not be further described except to say that the handle portions 38 and 40 of contacts 30 and 32 are laterally offset from each other such that the terminals do not engage each other even if there is no foam spacer pad or the like between the handle portions of the planar members.
Within the respective planes of the contacts, the spaces between the tine portions 34 and 36 reduce the rigidity imparted to the switch by the contacts and the possibility it will cause discomfort to a seated occupant of seat 12. Between the depressions 50 and 52, the tine portions 34 and 36 include respective strip portions 84 and 86 of a width less than the diameter of the depressions, the purpose being to further reduce the rigidity imparted to the switch by the contacts and the possibility of discomfort to a seated occupant.
As seen in FIG. 2, the lower side of blade portion 20 is covered by an adhesive bonding agent protected by a covering 88. When this covering is removed, the adhesive bonding agent positions switch 16 on a pad seat cushion 14 prior to covering of the switch with the material providing the seating surface. After the switch is covered, the covering material and the pad cooperate to further position the switch.
The invention thus provides an improved normally open pressure responsive switch.