Antenna Windshield

Abstract

An improved antenna for a laminated windshield comprising a single continuous antenna wire mounted in a plastic interlayer and having its central portion forming a loop in spaced relation to the windshield edge to receive a single solder connection to a metal tab electrically connected to a radio receiver.

Description

This invention concerns an antenna windshield. Prior to the present invention, the automobile industry developed laminated windshields comprising a pair of matched glass sheets laminated to opposite sides of a plastic interlayer in which a plurality of electroconductive wires are embedded in the plastic interlayer to serve as an antenna for a radio installed in the vehicle. The embedded wires were each connected to a common conductor plate that is in turn connected to the radio receiver.

Using the laminated windshield to support the antenna has improved the styling of automobiles by eliminating the whip antenna that extended from the vehicle body. Its use has also avoided a source of vandalism--the snapping of the antenna from the automobile.

Since automobile windshields require a lot of handling before they are installed in an automobile, it is very likely that as many as 10 percent of antenna windshields have electrical connections that become damaged from the time the windshields are assembled in a fabrication plant to the time the windshields are installed in an automobile. It is necessary to have the wires embedded within the windshield to extend substantially the full height and substantially the full length of the windshield to provide an antenna substantially equal in performance to the performance of the conventional whip antenna in its fully extended position. Therefore, any failure of an electrical connection of one or more of the antenna wires to the common plate or tab attached to the lead-in wire for the radio receiver causes the antenna to function in an inefficient manner.

An invention described and claimed in U. S. Pat. No. 3,543,272 of Rodger V. Zawodniak, provides an arrangement of antenna wire such that antenna failure is virtually eliminated even though an electrical connection between the antenna wire and the common plate electrically connected to the radio receiver is broken.

The above objective of the Zawodniak invention is accomplished by utilizing a single continuous electroconductive wire mounted in the plastic interlayer of a laminated windshield with the central portion of the wire extending outside of the interlayer. A pair of spaced electrical connections connect linearly spaced portions of the central portion of the single, continuous antenna wire outside said interlayer to a metal tab electrically connected to the radio receiver in such a manner that loose lengths of said wire are disposed between said pair of electrical connections and also between each of said pair of electrical connections and the portion of said continuous wire that enters the interlayer. While the Zawodniak invention reduced the number of production failures to a considerable extent, this objective required considerable time to make two electrical connections for each antenna windshield.

The present invention provides a simple technique for obtaining a strong electrical connection without requiring the time and expense for two connections and will be understood more clearly in the light of a description of a particular embodiment which follows.

In the drawings forming part of the description of the illustrative embodiment, and wherein like reference numbers refer to like structural elements;

FIG. 1 is a fragmentary, perspective view of an antenna windshield conforming to the present invention looking at the windshield from within a vehicle;

FIGS. 2 to 5 are enlarged views of a critical portion of the windshield depicted in FIG. 1, showing successive steps employed according to the teaching of the present invention; and

FIGS. 6 and 7 are overhead, oblique views of apparatus used to embed a single continuous wire in a plastic interlayer, showing the relation of the apparatus elements to one another during and after a wire embedding operation, respectively.

Referring to the drawings, reference number 11 refers to a laminated windshield comprising an outer glass sheet 12, an inner glass sheet 14 of matching curvature and an interlayer 16 of thermoplastic material, preferably plasticized polyvinyl butyral, which is commonly found in present day commercial windshields. However, other interlayer materials such as polyurethane and other well known interlayer materials may be used. In the usual automotive windshield, the outer and inner glass sheets 12 and 14 respectively are curved and have an outline conforming to the windshield frame in which the laminated windshield is installed. An elongated wire 18 is embedded within the interlayer 16 except for a central portion 19 which extends beyond the outline of the interlayer sheet for folding into a notched portion 20 having an arcuate edge 21 extending along a longitudinal lower side edge of the outer glass sheet 12.

The wire 18 is preferably a 36 gauge copper wire encased in an enamel sheath and has a maximum diameter of 0.005 inch so as to be virtually invisible to an occupant. However, it is arranged in the laminated windshield in symmetrical arrangement relative to an axis extending transversely across the mid-point of the windshield.

A metal tab 22, preferably a thin shim of copper about 10 mils thick connected at 23 to a lead-in wire 24 which terminates in a plug 26, is inserted within the notched portion of the outer glass sheet 12. The lead-in wire 24 is insulated except for its extremity portion that is connected to the metal tab 22 to which it is securely welded or soldered or otherwise securely fastened sufficiently strongly to withstand a pull of more than 25 pounds without failure. The tab 22 has an arcuate inner edge 27 that matches the curvature of arcuate edge 21. The tab has a straight outer edge 28 and is sufficiently narrower than the notched portion 20 so that its outer edge 28 is spaced inward from the edge of the windshield when the arcuate inner edge 27 abuts the arcuate edge 21 of the notched portion.

A spot of solder 29 is provided on the upper surface of the metal tab 22 intermediate its inner edge 27 and its outer edge 28 and to one side of the longitudinal center of the tab. The solder can be any low melting point solder that adheres to copper. A solder composed of 60 percent by weight of lead and 40 percent of tin has been used with success.

The interlayer sheet 16 has the wire 18 embedded therein by using the apparatus depicted in FIGS. 6 and 7. The apparatus is supported on top of a table 30, which preferably supports an illuminated transparent glass sheet 31. A pattern 32 conforming to the outline of the plastic interlayer after the latter is trimmed to conform to the outline of glass sheets 12 and 14 is marked along the under surface of the glass sheet 31 to guide an operator in placing an untrimmed plastic sheet 16 in proper position on the table. A pivotal frame 34 having a handle 35 is mounted for rotation relative to the table about a pivotal axis defined by a pair of hinges 36. The table 30 supports a pivoted hook 37 that engages the frame when the latter is in an upwardly retracted position. The frame 34 contains a template 38 along the inner edge of its margin, which template serves as a guide for a path for moving a heated needle 39 through which thin wire is fed from a spool 40.

The template 38 extends from a first indicator mark 41 denoting its origin to a second indicator mark 42 that denotes its terminal. The template 38 extends from the first indicator mark 41 along a first path 43 extending generally lengthwise of the frame and then curves at a concave corner 44 into a transverse path 45 that extends beyond the outline guide 32 that defines the position of an elongated edge of a properly aligned interlayer sheet 16 to a turn around guide 46. The template continues along a transverse path 47 to another concave corner 48 and another linear path 49 that extends longitudinally of the frame 34 to the second indicator mark 42. The latter indicates where the wire should be cut.

An untrimmed sheet 16 of plasticized polyvinyl butyral or other suitable interlayer material is mounted on the table 30 over the glass sheet 31 in proper registration with its margin disposed beyond the pattern or outline guide 32. The frame is released from hook 37 and pivoted over the table and the needle 39 moved along the template 38 to embed the wire 18 into the sheet 16. The heat of the needle causes the wire fed through the needle 39 as the latter traverses the template 38 to penetrate into the sheet of interlayer material along a line extending from mark 41 to mark 42 along a path conforming to the shape of the template so that substantially the entire length of the wire except for its central portion 19 is embedded within the trimmed interlayer and the portion 19 forms a loop exterior to the interlayer. In order to accomplish this end, an operator lifts the needle 39 from the sheet 16 as it approaches the turnaround guide 46 and reimbeds the needle 39 into the sheet after the latter has completed its turn around the turnaround guide 46 and started to move along transverse path 47. A cam (now shown) may be provided around the turnaround guide 46 to control the movement of the needle out of and into the plastic sheet 16.

In forming the laminated antenna windshield, a pair of glass sheets of matching outline is mounted on a bending mold of outline configuration and concave elevation and the glass is heated sufficiently to sag onto the shaping surface. A suitable parting material, such as a suspension of finely divided diatomaceous earth in water, is applied to the interfacial surface between the two sheets to prevent the sheets from fusing together during the bending operation. After the sheets are bent, they are cooled at a controlled rate while still supported on the bending mold and then removed from the mold when cool enough to handle.

The sheets of plastic containing the embedded wire are stored in a room of controlled temperature and humidity until they are ready for lamination between a pair of bent glass sheets of matching curvature. The bent pair of matching glass sheets are then separated from one another. The unnotched glass sheet 14 is mounted with its concave surface downward over a support of convex elevation. The plastic sheet is then inserted over the glass sheet 14 that is not notched and the notched glass sheet 12 aligned over the plastic sheet 16. The plastic sheet is trimmed with the central portion 19 of exposed wire 18 carefully held to prevent its being cut during the plastic trimming operation. The glass-plastic assembly so formed is prepressed and laminated following conventional commercial practice. A preferred prepressing apparatus used is described and claimed in U.S. Pat. No. 3,351,001 to Anthony A. Achkio, assigned to PPG Industries, Inc.

The prepressed assemblies are then laminated in autoclaves at a temperature of about 275.degree. F. and a pressure of about 225 pounds per square inch for about 45 minutes. The notched portion 20 of the prepressed assembly thus appears as depicted in FIG. 2.

After prepressing and before final lamination, the central portion 19 of the antenna wire is twisted at 50 to form an elongated closed loop 51 shown in FIG. 3. Then, the shim or tab 22 of a highly conductive metal, such as copper, having a curved inner edge 27 and a straight outer edge 28, as described above, is pressed against the portion of the interlayer sheet 16 that faces the notched portion 20 of notched sheet 12 and over a part of the central portion 19 of the wire 18 as shown in FIG. 4 The metal tab 22 is sufficiently smaller than the notched portion to provide a spacing between the outer edge of the tab and the edge of the windshield 11. The portion of the elongated closed loop 51 is folded at 57 over the straight outer edge 28 of the metal tab 22. This enables the entire central portion 19 of the wire 18 to fit within the notched portion 20 of the sheet 12 that lies over the interlayer sheet 16. The wire 18 is then electrically connected to the metal tab 22 at the solder or welding connection 29 which has been previously fabricated on the upper surface of the metal tab 22. The loop 51 that is folded over the upper surface of the tab 22 is located over the solder spot 29 in surrounding relation thereto. A soldering iron heats the solder, which fuses to the upper surface of the metal tab 22 and the wire loop 51 when melted, then cools to form a solid connection therebetween.

The electric circuit so formed is then tested. The plug 26 is inserted in a testing circuit for this test. This indicates whether a signal from the embedded wire will reach a radio circuit in sufficient strength to provide adequate reception.

The assembly is mounted on a rack with the notched portion 20 facing upward and masking tape applied to the unnotched sheet 14 in its portion aligned with and slightly beyond each end of the notched portion 20.

An adhesive tape such as polyurethane tape is then applied to the edge surfaces of the glass sheets to form a wall for the chamber formed by the notched portion in the sheet 12. A suitable fast setting electrical insulating material, such as fast setting polysulfide resin sold under the trade name "Thiokol" by the Thiokol Chemical Company of Bristol, Pennsylvania or a room temperature vulcanizable silicone such as 615 RTV silicone supplied by the General Electric Company, Schenectady, New York or Scotchcast 225 electrical resin sold by the Minnesota Mining and Manufacturing Company, St. Paul, Minnesota, is injected molded into the recess 20.

The masking tape is removed, leaving only the polyurethane tape wall enclosing the injection molded material in the notched portion 20. The assembly is then stored with other assemblies for sufficient time for the injection molded material to harden. Then the assembly is ready for the aforesaid lamination.

Folding the antenna wire 18 in its central portion 19 over the outer edge 28 of the metal tab 22 and limiting the solder connection to within the folded loop portion 51 reduces the likelihood that the antenna wire would be grounded due to electrical connections to the body of the automobile in which the antenna windshield is installed. In addition, rough handling during final lamination, storage, shipment to an automobile assembly plant and/or handling in its final assembly into an automobile frame has not resulted in a significant number of losses due to the breaking of the electrical connection between the embedded wire 18 and the tab 22. In the past, the breaking of any electrical connection caused the loss of the particular wire attached to the broken connection and hence reduced the efficiency of the multiple wire antenna typical of the prior art.

Prior to the Zawodniak invention that suggested two solder connections, approximately 10 percent of the antenna windshields which passed the final test for continuous circuit after assembly were found to be deficient after they were installed in an automobile frame. These antenna windshields subject to such failure frequency comprised two separate antenna wires each separately soldered to the metal tab 22. Changing the structure of the antenna windshield to the embodiment comprising a single continuous antenna wire soldered to the metal tab at two spaced locations with sufficient flexibility of the antenna wire between the electrical connections and also between each of the electrical connections and the point of embedding into the interlayer has resulted in a virtual elimination of these losses. Reducing the number of solder connections between the antenna wire and the metal tab from two to one by using a folded loop to enclose the solder in the single solder connection presently required has speeded up the rate of antenna windshield production without reintroducing the problem of high frequency of failures that the Zawodniak invention solved.

In an illustrative embodiment of this invention, the notched portion 20 of the notched glass sheet is about 21/4 inch long along its straight outer edge 28 and gradually increases in width to about 3/8 inch at its widest portion. The metal tab 22 is about 11/8 inch long and one-eighth inch wide. This permits the metal tab to be spaced about one-quarter inward from the edge of the windshield 11.

Usually, the wire 18 is supplied with a coating of electrical insulation. In such a case, a razor blade is used to strip the insulation from the exposed 2 inches of the central portion 19 only. This step is preferably done after the prepressing and immediately before twisting the trimmed portion. The trimmed and twisted central portion 19 thus makes good electrical connection directly to the major surfaces of the metal tab 22 after the fold 57 is made. Melting the solder spot 29 insures a stronger connection between the central portion 19 and the metal tab 22 than the loosely looped central portion of the prior art antennas. The exposed two inches of length of the central portion 19 of the antenna wire 18 in direct electrical contact with the metal tab reduce energy losses in the antenna system compared to those experienced with loosely looped wires of the prior art.

The form of the invention shown and described in this disclosure represents an illustrative embodiment thereof. It is understood that various changes, such as changes in materials of the interlayer, wire, tab and glass sheet compositions, for example, may be made without departing from the spirit of the invention as defined in the claimed subject matter that follows.

Claims

What is claimed is:

1. A laminated antenna windshield comprising a pair of matched glass sheets, one of which has a notched portion along one of its longitudinal side edges, a metal tab smaller than said notched portion adapted to be electrically connected to a radio receiver, a plastic interlayer bonded between said sheets and a continuous length of electroconductive wire mounted in substantially symmetrical arrangement in said plastic interlayer for use as a radio antenna for said radio receiver, said metal tab being bonded to said interlayer in said notched portion, and wherein the central portion of said electroconductive wire is looped and said resulting loop located in said notched portion in spaced relation to the edge of said windshield, a solder connection enclosed within said loop as the sole means to secure said antenna wire directly to said metal tab in spaced relation to said windshield edge, wherein said metal tab has an inner end abutted against the inner end of said notched portion and a spot of solder on its upper surface, said twisted portion of said loop being in contact with the bottom surface of said metal tab and said loop being folded over said metal tab and enclosing said spot of solder on said upper surface in spaced relation to the edge of the windshield.

2. A windshield as in claim 1, wherein said notched portion is filled with electrical insulating material.

3. A windshield as in claim 1, wherein said electroconductive wire has a coating of insulating material thereon, except for said central portion that is in contact with said metal tab.