Instrument Panel Radio Antenna

Abstract

An instrument panel assembly located beneath the windshield opening of an automobile, including a metal conductor in the form of a metal coating sprayed onto a non-conductive top portion of a rigid insert within the instrument panel assembly for collecting radio waves directly through the windshield opening from outside the vehicle to thereby provide an antenna for a radio receiver.

Description

FIELD OF INVENTION

This invention relates to a radio antenna for an automobile and more particularly to a radio antenna integrally associated with the instrument panel of an automobile.

DESCRIPTION OF PRIOR ART

The provision of an ideal antenna for an automobile has been a problem virtually since radios became a commonplace feature of the automobile. External antennas such as the common mast antenna have the obvious advantage of being totally exposed to the radio waves. They also have obvious disadvantages of being subject to physical damage or loss due to collision with tree branches and the like, chemical deterioration such as corrosion, vandalism and theft. Efforts to deal with these disadvantages have usually been at considerable expense in the form of chrome plated telescopic antenna structures, motorized withdrawal devices and the like.

The design of interior antennas involves a serious problem in that the metal vehicle roof and body functions as an electromagnetic shield which impairs proper operation of an antenna located within the automobile body. A form of interior antenna in successful use today is the windshield antenna wherein one or more thin conductors are supported upon or embedded within the windshield of the vehicle. Although this form of antenna avoids many of the problems associated with the mast antenna, it has been found to have disadvantages in that windshield wipers may have undesirable effects on the windshield antenna operation including the generation of noise and the precipitation of FM station swapping. Further, the location of the conductors in the windshield is relatively costly and, of course, adds to the cost of windshields and windshield replacement.

SUMMARY OF THE INVENTION

It is an object of this invention to provide an efficient and economically constructed radio antenna formed as an integral part of and within the instrument panel pad of an automobile which is located under the windshield so that radio waves passing through the windshield opening from outside the vehicle irradiate the top portion of the radio instrument pad and hence the antenna located within the pad. This antenna construction avoids the disadvantages of the outside antenna and also that of the windshield antenna previously mentioned.

It is a further object of this invention to provide an antenna which is made incident to the normal method for making the instrument panel pad whereby the cost of making the antenna is minimized.

These and other objects are accomplished by a method including the steps of providing a rigid electrically non-conductive insert or structural frame as is conventional in present day methods for making instrument panel assemblies, flame spraying a suitable metal over a suitable pattern on the top side of the insert in a desired configuration to provide a thin adherent metal layer on the insert, providing an electrical connector means for connecting the sprayed metal layer to a radio lead, providing a flexible preformed thermoplastic resin cover layer for the instrument panel pad and thereafter foaming a synthetic resin between the insert and the skin layer so that a cushion is provided over the insert and the metal layer is embedded within the instrument panel pad.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will be apparent from the following detailed description of an embodiment of an invention reference being made to the accompanying drawings in which

FIG. 1 is a perspective view of a rigid electrically non-conductive insert for an instrument panel pad with a sheet metal mask positioned thereover having a pattern cut therethrough to expose predetermined portions of the insert;

FIG. 2 is another perspective view of the instrument panel insert of FIG. 1 having a metallized layer formed on the said predetermined portions of the insert;

FIG. 3 is a cross-sectional view of the insert taken along line 3--3 of FIG. 2 showing the electrical connector;

FIG. 4 is a perspective view of the instrument panel pad of this invention with a portion broken away which includes the insert of FIG. 1 located in an automobile beneath the windshield thereof, and

FIG. 5 is a cross-sectional view taken along line 5--5 of FIG. 4 showing the completed instrument panel pad including the antenna.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A typical instrument panel assembly in use on automobiles today which will be hereinafter described in greater detail, consists of a rigid glass fiber-reinforced synthetic resin insert 10 as shown in FIG. 1 of the drawings which is covered with a suitable decoratively grained synthetic resin skin layer and has a suitable cushion or pad interposed between the insert 10 and the skin layer. The skin layer serves as the top surface of the instrument panel pad which is located directly beneath the windshield opening of the automobile.

In general, the method of making the instrument panel pad includes the steps of molding the insert 10 having a top substantially horizontal portion 12 and a depending portion 14 including an opening 16 for receiving the instrument cluster on the driver's side of the automobile. The insert 10 is usually formed of a glass fiber-reinforced polystyrene or a glass fiber-reinforced styrene-acrylo-nitrile copolymer. A flexible grained thermoplastic synthetic resin skin or surface layer is preformed which serves as the cover layer or skin of the instrument panel assembly. The skin layer is usually made by a vacuum forming method in which a sheet of the synthetic resin is heated to its softening temperature and then drawn by vacuum over a suitable mold. After cooling the preformed skin is placed into a female mold cavity which has the same contours of a preformed skin layer with grained or outer surfaces being in contact with the mold surface. The insert is then located within the mold in a fixed spaced relation to the skin layer. A foamable synthetic resin mixture such as one leading to the formation of polyurethane-foams is injected into the space between the skin layer and the insert. Usually the mold is preheated to accelerate the foaming reaction. After the resin mixture has reacted fully to fill the space between the insert and the skin layer, the resultant instrument panel pad is ready for installation in the vehicle body.

This invention involves flame spraying a layer of molten metal in suitable antenna configuration on the top surface 12 of the insert 10. A suitable electrical connection is provided whereby the sprayed layer may be electrically connected to a radio antenna lead. Thereafter the insert 10 is associated with the skin and foam layers as above described to form the pad in the conventional manner.

Referring to FIG. 1, the insert 10 is formed of a rigid electrically non-conductive material, preferably glass fiber-reinforced polystyrene or a styrene-acrylonitrile copolymer. The antenna is made by first degreasing the surface 12 of the insert 10 to insure that the metal layer sprayed thereon adheres firmly thereto. This is accomplished by washing the surface 12 with a water and soap solution or by subjecting the surface to the flame of a torch whereby oil or like materials are burned off. Thereafter a sheet metal mask 18 is placed over the insert surface 12 with the cut-out portion 20 of a desired antenna configuration. The mask is formed so that it may be placed within approximately 0.05 in. of the insert to assure adequate definition of the antenna.

An important feature of this invention is that it permits considerable flexibility in antenna design to obtain optimum performance. It is desirable to provide an antenna with a maximum length-width configuration to maximize the area which is exposed to radio wave bombardment. On the other hand it is necessary to match the capacitance of the radio with the capacitance of the antenna. This is accomplished by removing the portions of antenna surface as necessary to achieve proper capacitance balance. In the embodiment shown in the drawings, the antenna is in the form of a series of fingers extending from an elongated bar to provide good length-width configuration. The portions between the fingers are such portions as have been removed to achieve capacitance balance. Further, the antenna is located on the passenger side of the instrument panel pad to avoid interference from the instruments. The antenna could be made to extend over the driver's side of the instrument panel pad and hence substantially across the entire length of the instrument pad provided that suitable shielding is provided between the antenna and the instrument cluster situated in the opening 16.

Next a layer 23 of zinc about 0.002 inch thick is sprayed over the cut-out portion 20 of the shield 18. This is accomplished by means of a flame spraying gun such as the Metco System using an oxyacytelene wire gun. It has been found that two hand passes with this gun spraying zinc forms a continuous layer about 2 mils in thickness with excellent adhesion to the synthetic resin substrate. The electrical reistance from end to end of the antenna was 0.2 ohms. Satisfactory ohmic resistance with good adhesion to the plastic substrate may be obtained with a sprayed metal thickness of from about 0.002 to 0.005 inch. In general it is preferred to use the minimum metal thickness which will provide a coextensive sprayed coating on the insert. Metal thickness in excess of 0.005 inch have inferior adhesion. Zinc is preferred as the antenna material because its relatively low melting temperature of 790.degree.F makes relatively rapid spraying practical without damage to the plastic insert, the metal is non-toxic, adheres well to the plastic insert and has a suitably low ohmic resistance.

The shield 18 is then removed to reveal the antenna 23 shown in FIG. 2 in the form of the 2 mil thick layer of zinc. The zinc layer 23 is then electrically connected to a connector device 21 shown in FIG. 3 which consists of a stud 22 and a mushroom shaped head 24 having yieldable peripheral portions 25 which are yieldably urged into contact with the antenna 23 and held in this condition by means of the annular resilient retainer 26 which engages the stud 22 in a well known manner. The end of the stud 22 is adapted for attachment to the radio lead-in wire. The location of the connector device is important in that it determines the capacitance of the antenna in relation to the capacitance of the radio and lead-in wire. An important advantage of the antenna of this invention is that the location of the connector 21 may be varied to meet the electrical design requirements.

The insert 10 is then incorporated into an instrument panel pad assembly 28 as above described and as shown in FIGS. 4 and 5. The instrument pad assembly 28 accordingly consists of the outer skin layer 30, the said insert 10 having the flame sprayed antenna 23 including the electrical connector 22 and the flexible foam resin 32 which encapsulates the antenna in the instrument panel pad. The pad assembly 28 is located beneath the windshield 34 and the windshield opening so that radio waves passing through the windshield opening from outside the vehicle may irradiate the horizontal portion of the pad.

Although zinc (790.degree.F MP) is preferred for use as the antenna metal, other low melting point metals have been found satisfactory. Using the mask 18 of FIG. 1 and a suitably cleaned insert 10, a coextensive tin (450.degree.F MP) layer was flame sprayed on the insert in two passes with good adhesion. The ohmic resistance was found to be 0.4 compared to 0.2 for zinc. A lead free babbit (450.degree.F MP) layer was applied in a similar experiment with good adhesion and an ohmic resistance of 1.0. On the other hand in a similar experiment aluminum (1,200.degree.F MP) applied by five passes of the spray gun produced a discontinuous and cracked coating with poor adhesion. Similarly a copper layer applied with 10 passes produced a cracked and discontinuous layer with poor adhesion. Lead is considered undesirable because of its toxicity.

As shown in FIGS. 4 and 5 the instrument panel pad is adapted for insertion directly under the vehicle windshield where the performance of the antenna has been found to be equal to or superior to the windshield antenna.

It is preferred to spray the antenna over the top side of the insert 10 because this surface is usually relatively smooth. Applying the coating to the underside is not preferred because the underside usually has recesses which are difficult to spray into and because of the danger of grounding the antenna. Further the coating should be located so as to be at least two inches from car body metal.

The term babbit as used in the claims is intended to refer to alloys consisting essentially of 65 to 95 parts by weight tin, 8 to 12 parts antimony and about 1 part copper.

While the invention has been shown and described in terms of certain embodiments various modifications will be apparent to those skilled in the art.

Claims

It is claimed:

1. A method for making a radio antenna in combination with an instrument panel pad for an automobile, said panel pad having a generally horizontal portion adapted to underlie the windshield opening so that radio waves passing through said windshield opening from outside the vehicle may irradiate said horizontal portion comprising the steps of:

providing a rigid electrically non-conductive insert having a generally horizontal portion corresponding to said instrument panel horizontal portion and a preformed decorative electrically non-conductive cover portion for said panel,

masking off a portion of said insert horizontal portion to leave exposed thereon a predetermined elongated portion along the length thereof,

flame spraying and bonding on said elongated exposed portion a continuous layer of an electrical conductor metal,

locating said cover portion in a female mold,

locating said insert within said female mold in spaced relation to said cover portion with said metal layer facing said skin layer,

injecting a foamable synthetic resin composition between said skin layer and said insert and foaming said composition to fill the space between said insert and said cover layer therewith and to encapsulate said metal layer within said instrument panel.

2. A method for making a radio antenna in combination with an instrument panel pad for an automobile, said panel pad having a generally horizontal portion adapted to underlie the windshield opening so that radio waves passing through said windshield opening from outside the vehicle may irradiate said horizontal portion comprising the steps of:

providing a rigid electrically non-conductive insert having a generally horizontal portion corresponding to said instrument panel horizontal portion and a preformed decorative electrically non-conductive cover portion for said panel,

masking off a portion of said insert horizontal portion to leave exposed thereon a predetermined elongated portion along the length thereof,

flame spraying on said exposed elongated portion a metal selected from the class consisting of zinc, tin and babbit to provide thereon a metal layer about 0.002 to 0.005 inch thick bonded to said insert,

locating said cover portion in a female mold,

locating said insert within said female mold in spaced relation to said cover portion with said metal layer facing said skin layer,

injecting a foamable synthetic resin composition between said skin layer and said insert and foaming said composition to fill the space between said insert and said cover layer therewith and to encapsulate said metal layer within said instrument panel.

3. The method of claim 2 wherein said metal is zinc.

4. A radio antenna in combination with an instrument panel for an automobile, said panel having a generally horizontal portion adapted to underlie the windshield opening so that the radio waves passing through said windshield opening from outside the vehicle may irradiate said horizontal portion comprising:

a rigid electrically non-conductive insert having a generally horizontal portion corresponding to said instrument panel horizontal portion and a preformed decorative electrically non-conductive cover portion,

a continuous elongated flame sprayed electrically conductive metal layer of a predetermined elongated configuration coextensively bonded to said horizontal portion,

said insert being disposed in spaced relation to said cover portion with said metal layer facing the cover portion and a layer of foamed synthetic resin interposed between said insert and said cover layer and encapsulating said metal layer within said instrument panel.

5. A radio antenna in combination with an instrument panel for an automobile, said panel having a generally horizontal portion adapted to underlie the windshield opening so that the radio waves passing through said windshield opening from outside the vehicle may irradiate said horizontal portion comprising:

a rigid electrically non-conductive insert having a generally horizontal portion corresponding to said instrument panel horizontal portion and a preformed decorative electrically non-conductive cover portion,

an elongated flame sprayed metal layer about 0.002 to 0.005 inch thick selected from the class consisting of zinc, tin and babbit of a predetermined elongated configuration coextensively bonded to said horizontal portion,

said insert being disposed in spaced relation to said cover portion with said metal layer facing the cover portion and a layer of foamed synthetic resin interposed between said insert and said cover layer and encapsulating said metal layer within said instrument panel.

6. The antenna of claim 5 wherein said metal layer is zinc.