US 3440748 A
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Description (OCR text may contain errors)
April 29, 1969 J. c. HACKLEY MAGNETIC ROOF TOP SIGN FOR CARS Filed Nov. 14, 1966 INVENTOR f /vfs C AQ QKAEY M ATTORNEYS United States Patent US. Cl. 40-129 9 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a detachable magnetic rooftop sign for automotive vehicles and the like and in particular to an improved construction which is highly stable and resistant to displacement by wind during use. In the preferred construction the sign is constructed in the shape of a frustum of a pyramid, and the undersurface of the base carries peripheral strips of magnetic tape which detachably secure the sign to the metal top of a vehicle. The base is flexible and is separable from the sides at the apices of the structure so as to be capable of following the rounded contours of a vehicle top.
Detachable signs for use on automotive vehicle tops are employed for a variety of purposes, including commercial advertising and temporary identification of the vehicle. The use of distinct permanent magnets for attaching the sign to a metal vehicle top has been suggested in the past, but such magnetic signs have not been completely satisfactory because they have been subject to fluttering and displacement by wind forces as the speed of the vehicle increases.
These disadvantages are substantially eliminated in the present sign by constructing the sign of a relatively flexible base plate and relatively stiff, upwardly extending side members which are connected to the base at spaced apart locations. The undersurface of the base plate c-arries strips of flexible magnetic tape which cause the plate to flex when the sign is placed on a metal vehicle top with the result that the plate follows the contours of the vehicle top. The upper part of the sign, defined by the relatively rigid interconnected side walls, is not affected by the contours of the vehicle top.
In the preferred construction the sides of the sign are inclined upwardly and inwardly, although vertical sides may be employed. Typically, the overall shape of the sign is that of the frustum of a pyramid or cone. In practice the frustum of a triangular pyramid is preferred, and the base plate is connected to each side panel only at the middle of the lower edge of the latter.
The magnetic tape employed by the present invention is a commercially available. product which is variously constructed by embedding or laminating permanently magnetized oriented, particles in or with a tough flexible plastic material of rubber-like consistency. Any of several available products may be used, it being necessary only that the matrix material be a non-slippery material which will develop a high coefficient of static friction when in contact with a typical metal vehicle top and which has suflicient strength to permit a good bond between it and the base plate. Preferably the tape is relatively thin, for example inch, and relatively wide, for example 1 inch.
It has been found that the above-described features of flexible base plate and magnetic tape render the sign highly resistant to flutter and dislodgment by wind forces even at speeds up to 100 miles per hour. This advantage will be described more fully in the following detailed description when considered with the drawing in which:
FIGURE 1 is a perspective view of a sign embodying the principles of the present invention;
3,440,748 Patented Apr. 29, 1969 ice FIGURE 2 is a bottom view of the sign of FIGURE 1; and
FIGURE 3 is a plan view of a sheet metal blank suitable for constructing the sign of FIGURE 1.
In FIGURE 1 there is shown a typical vehicle top 8 having mounted thereon a sign 10 which is constructed of sheet metal in the form of an open-top, box-like structure having three flat, relatively rigid sides 12 and a flat, relatively flexible base plate 14. The base plate 14 is connected to the center portion of the lower edge of each side 12 as by an integral strip 13 or other suitable connecting means. The box-like structure has the overall shape of a frustum of an equilateral triangular pyramid with the result that the base plate 14- is triangular, the sides 12 are trapezoidal and the three edges 16 formed by the junction of adjacent sides 12 are inclined upwardly and inwardly. The sign 10 is detachably connected to the vehicle top 8 by means of strips of flexible magnetic tape 17 permanently secured to the peripheral undersurface of the base plate 14. The tape 17 may be secured by means of a suitable water-proof adhesive or by means of mechanical fasteners such as screws or rivets.
The upper portion of the sign, that-is, the three sides 12, is rendered relatively stiff by securely joining the sides 12 end-to-end along the edges 16, as by welding or brazing or by means of suitable brackets (not shown). Additional stiffness may be imparted to each side 12 by an inwardly turned-over upper edge 18. The manner in which relative stiffness is imparted is of no particular significance, the illustrated construction in this regard being merely exemplary of a convenient way to make the sign 10 of sheet metal.
In this connection FIGURE 3 shows that the sign 10 may be readily constructed from a single piece of sheet metal formed into a suitable blank 20. As shown, the blank 20 is formed by cutting a piece of sheet metal to the shape of a hexagon and then making six straight-line cuts which will define the edges of the base plate .14 and the integral connecting strips 13 between the base plate 14 and the sides 12. The outer edges 18 of the sides 12 are then folded over, and the sides 12 are folded upwardly and joined end-to-end as previously described. In practice the base plate 14 may extend about 24 inches along each edge, and the height of the sides 12 may be about one-half this dimension. It has been found that 26 gauge sheet metal is well-suited to the one-piece type of construction, because it is sufficiently flexible to allow the base plate 14 to follow the contours of the vehicle top 8 and at the same time it can be formed easily into an upper sign portion which has enough rigidity to prevent wind flutter.
It will be appreciated that structural materials other than sheet metal may be employed in assembling the sign 10 and that the base plate 14 and the sides 12 may be separate pieces suitably joined together, if desired. For example, the sides 12 can be constructed of wood or plastic material. The base plate 14 can also be wood or plastic provided that the necessary flexibility is present. In addition, it is contemplated that the magnetized periphery of the base plate 14 can be formed integrally with the base plate 14 rather than being attached later in the form of separate strips. For example, if the base plate 14 is molded of plastic material, the magnetized particles can be embedded in the plastic material during the molding operation. In practice, however, an all-metal construction is preferred from the standpoint of ease and economy of fabrication. In addition, plastic magnetic strip is more effective as an attaching means when it is sandwiched between steel surfaces.
Referring now to the functional aspects of the sign 10 during use it will be seen in FIGURE 1 that when the sign 10 is placed on the vehicle top 8, the relatively flexible base plate 14 is drawn down by the magnetic attraction between the tape 17 and top 8 into flush engagement with the top 8. This is made possible by the absence of any connection between the apices of the base plate 14 and the relatively rigid upper portion defined by the sides. Thus, the sign 10 is capable of flush attachment to a variety of different rounded contours so long as the base plate is sufficiently flexible to conform to the contours. The flush attachment along the periphery of the base plate 14 is highly important because, among other reasons, it prevents wind from creating a direct upward force on the undersurface of the base plate.
The central connection 13 between each side 12 and the base plate 14 is necessary to allow the latter to flex into engagement with the vehicle top 8, but it also contributes heavily to the stability of the sign. It has been found that with this arrangement wind pressure is directed to the central connections 13 in the form of horizontal drag rather than lift. This phenomenon is highly important, because for several reasons it allows the sign 10 to resist displacement by wind forces. First, the entire magnetized area of the tape 17 continues to exert magnetic attraction even in the event that a small amount of relative horizontal movemen occurs between the sign 10 and the vehicle top 8; whereas the total magnetic attraction would decrease suddenly if a portion of the tape 17 were pulled upwardly away from the vehicle top 8. Second, the localization of the forces at the centers of the three strips 17 has less tendency to lift the strips 17 than would be the case if the forces acted at the ends of the strips 17. Thus, even if a lifting force does occur, the arrangement highly resists separation of the sign 10 from the vehicle top 8. Third, the friction between the relatively large surface area of the strips 17 and the vehicle top strongly resists horizontal movement of the sign 10. As previously indicated, the matrix portion of strips 17 is preferably of rubber-like material exhibiting a high coefiicient of friction. The ability of this material to resist sliding movement when pressed in contact with the vehicle top 8 by the magnetic attraction is extremely high.
The upward and inward inclination of the sides 12 also tends to avoid the creation of lifting forces on the sign 10 by the wind during use. In addition, the pyramidal configuration presents a relatively sharp edge to the wind, thereby reducing total wind force. Accordingly, the pyramidal shape is preferred. The equilateral triangular pyramid presents the sharpest edge while providing the largest flat side surfaces, thereby giving maximum visual exposure in all directions for advertising purposes.
In use of the sign 10 the sides 12 will carry indicia including commercial advertising or identification of the car or truck for a special purpose. The indicia may be applied as paint or printed matter directly to the sides 12. Alternatively, separate overlay panels of the same size and shape as the sides 12 may be made up with strips of magnetic tape along their edges and detachably held to the sides 12.
While preferred embodiments of the present invention have been described, further modifications may be made without departing from the scope of the invention. Therefore, it is to be understood that the details set forth or shown in the drawings are to be interpreted in an illustrative, and not in a limiting sense, except as they appear in the appended claims.
What is claimed is:
1. A sign for detachable magnetic connection to the metal top of a vehicle comprising: a frusto-pyramidal structure having a relatively flexible sheet metal base plate and a relatively rigid upper portion defined by upwardly and inwardly inclined side walls extending from the edges of said base plate, each of said side walls being free of said base plate at the apices of the latter and being connected intermediate its ends to said base plate whereby said base plate can flex away from said side walls so as to conform to the contours of a vehicle top; and means for attaching said base plate in flush engagement with a vehicle top, said means including a strip of flexible magnetic tape secured to the substantially entire peripheral undersurface of said base plate, said strip having a lower surface of a non-skid material.
2. A mounting device adapted for detachable magnetic connection to a metal surface of a vehicle comprising: relatively rigid frame means for receiving the structure to be mounted by said mounting device; a flexible base plate of substantial area having one face thereof connected to said frame means, said base plate being deflectable away from said frame means to conform to the contours of the metal surface of the vehicle; and permanent magnet means associated with said flexible 'base plate for deflecting the latter into engagement with the metal surface of the vehicle over the entire periphery of the other face of said base plate whereby lateral forces on said frame means during use of said device are resisted by frictional drag between said base plate and the metal surface of the vehicle.
3. A mounting device as in claim 2 wherein said frame means is connected to the periphery of said one face of said base plate only at spaced-apart locations which permit said deflectability of said base plate.
4. A mounting device as in claim 2 wherein said frame means is a box-like structure having side walls extending upwardly and inwardly from said base plate, the lower edge of said side walls being connected to said one face of said base plate only at spaced-apart locations which permit said deflectability of said base plate.
5. A mounting device as in claim 2 wherein said permanent magnet means includes a tough, flexible non-skid material defining at least the periphery of said other face of said flexible base plate and permanently magnetized particles embedded within said material.
6. A mounting device as in claim 2 wherein said flexible base plate is polygonal, wherein said frame means includes side walls extending from the edges of said base plate upwardly and inwardly, and wherein each of said side walls is free of said base plate at the apices of the latter and is connected intermediate its ends to said base plate.
7. A mounting device as in claim 6 wherein said permanent magnet means includes a tough, flexible non-skid material defining at least the periphery of said other face of said base plate and permanently magnetized particles embedded Within said material.
8. A mounting device as in claim 7 wherein said base plate is triangular.
9. A mounting device as in claim 7 wherein said permanent magnet means is in the form of a tape of said nonskid material with said magnetized particles embedded therein, said tape being secured to said other face of said base plate, said base plate being constructed of metal.
References Cited UNITED STATES PATENTS 3,115,434 12/1963 Hahn 40-142 X 3,230,653 1/1966 Rice 40129 3,254,434 6/1966 Gintoft 40l29 3,290,813 12/1966 Rose 40-429 EUGENE R. CAPOZIO, Primary Examiner.
WENCESLAO I. CONTRERAS, Assistant Examiner.
US. Cl. X.R.