Abstract:
A thin layer of a magnetizable coating is extruded or coextruded onto a external surface portion of a tubular sponge bulb seal for an automotive door or hatch. The coating is of a thickness, location on the seal and formulation to be selectively magnetized to provide a desired magnetic force level to optimize the balance between effective sealing and ease of door opening.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to seals for doors or hatches of automotive vehicles. More particularly, the present invention relates to a sponge bulb tubular seal for a door or hatch of an automotive vehicle wherein the tubular seal has a magnetic coating for enhanced sealing contact with an associated metal frame surface. 
     The conventional primary door or hatch seal for an automotive vehicle consists of a co-extruded dense carrier which carries a sponge bulb tubular seal. 
     The carrier functions to secure the sponge seal to a door or hatch flange and the sponge bulb tubular seal is positioned in compression between adjacent surfaces of the door or hatch and the associated automotive frame when the door or hatch is closed. This type of seal has been in use for many years and usually functions in a satisfactory manner. However, under some conditions a conventional seal may not provide an adequate sealing function. For example, at high speeds air pressure may exceed the maximum sealing force provided by the sponge bulb and cause a failure of the sealing function. Therefore, there remains room for improvement in such seals. 
     Magnetic elements have been employed in the past in conjunction with seals especially in conjunction with refrigerator seals. Magnetic elements are commonly used in seals for refrigerators such as is disclosed in U.S. Pat. No. 4,469,383 Sep. 4, 1984 to Losert for “Refrigerator Cabinet and Method of Construction”, U.S. Pat. No. 4,644,698 Feb. 24, 1987 to Gerdes et al. for “Refrigerator and Method of Gasket Assembly Construction and U.S. Pat. No. 4,653,819 Mar. 31, 1987 to Swerbinsky for “Refrigerator Cabinet and Gasket Construction”. In the automotive field, U.S. Pat. No. 4,999,951 Mar. 19, 1991 to Keys et al. discloses a magnetic window assembly for frameless and full flush window systems of automotive vehicles which comprises a flexible sealing strip having a compressible body portion with a first magnetic element embedded therein. Also, U.S. Pat. No. 5,367,831 Nov. 29, 1994 to Gunkel discloses a magnetic header seal assembly for an automotive vehicle which includes an integrally attached magnetic element. U.S. Pat. No. 5,575,485 Nov. 19, 1996 to Meria and U.S. Pat. No. 5,257,791 Nov. 2, 1993 to (Cittadimi) relate to a magnetic gaskets for automobiles which gaskets are said to be suitable for forming a seal in regions of curviliniear extension and which include a magnetized bar or insert. There are also known patents for gaskets or seals for doors for building structures. For example, U.S. Pat. No. 4,753,042 Jun. 28, 1988 to Adkins; U.S. Pat. No. 5,077,948 Jan. 7, 1992 to Olson et al.; U.S. Pat. No. 5,606,828 Mar. 4, 1997 to Hall et al.; and No.  5 , 161 , 346  Nov. 10,1992 to Olson et al. Each of the above patents is specifically incorporated by reference herein. 
     Although several patents are known to use magnetic force in combination with a seal or gasket, the present invention provides a novel improvement wherein a thin, elastomeric magnetic coating is provided on an automotive seal. Further understanding of the present invention will be had from the following disclosure and claims taken in conjunction with the accompanying drawing. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention a thin layer of a magnetizable coating is extruded or coextruded onto a external surface portion of a tubular sponge bulb seal for an automotive door or hatch. The coating is of a thickness, location on the seal and formulation to be selectively magnetized to provide a desired magnetic force level to optimize the balance between effective sealing and ease of door opening. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 a  side elevation of an automotive vehicle having a door sealed by a preferred embodiment of the present invention; 
     FIG. 2 is a cross-sectional view taken along line  2 — 2  in FIG. 1, in perspective and broken away, showing a preferred embodiment of a seal with magnetic coating of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Now referring to the Figures, a preferred embodiment of a door seal of the present invention is shown and indicated generally by the numeral  10 . Door seal  10  is shown in sealing relationship about door  12  of an automotive vehicle which is indicated generally by numeral  14 . Door seal  10  is preferably used to seal around the periphery of a door or hatch opening of an automotive vehicle as is illustrated herein. However, door seal  10  can be adapted for and is suitable for other similar uses as are common for tubular seals of its type. To impart a clear understanding of the present invention, the description of door seal  10  will be set forth herein in the context of its use in an automotive vehicle environment which is its preferred use. 
     Door seal  10  broadly comprises a U-shaped (in cross-section) carrier  16  and a tubular sealing element  18 . Carrier  16  has a metal core  20  with elastomeric cover  22  extruded thereover as is conventional in the art. Suitable materials for cover  22  include EPDM rubber. The U-shape of carrier  16  provides an open-mouth channel opening indicated at  24  into which an associated flange extends when carrier  16  is secured thereon. Ribs  26  and  28  extend from legs  30  and  32  of carrier  16  to securely retain carrier  16  onto an associated flange. Carrier  16  can also carry additional sealing elements as is illustrated in the figure as sealing lip  34 . Carrier  16  serves the function of attaching or securing door seal  10  to a perimeter flange about a door or hatch opening of a vehicle and is thus means for attaching door seal  10  to an associated automotive vehicle. Carrier  16  can be of any suitable construction so long as it serves its purpose of attaching door seal  10 . 
     Tubular sealing element  18  is preferably extruded from sponge rubber such as sponge EPDM rubber and can be coextruded with carrier  16  in a conventional manner so that sealing element  18  heat bonds to carrier  16 . 
     As thus far described, carrier  16  and tubular sealing element  18  are entirely conventional and would function as a satisfactory automotive seal under all but the more challenging sealing situations. It is to the more challenging situations, however, that the present invention is directed. In accordance with the present invention, a substantial improvement in sealing is obtained by provision of a thin magnetic coating  36  onto a portion of the exterior surface  38  of sealing element  18 . Magnetic coating  36  covers a selectively limited surface area of sealing element  18  and is selectively thin so that magnetic coating  36  will provide an attraction to an associated metallic surface to be sealed thereby but such attraction will be limited so that the force of attraction can be easily overcome to open the door  12 . The magnetic force is from 0.5 gf/cm 2  to 43.85 gf/cm 2 , preferably from 1.1 gf/cm 2  to 4.5 gf/cm 2  and most preferably about 2.08 gf/cm 2 . 
     Magnetic coating  36  is formulated by incorporating a magnetizable ferromagnetic powder such as barium or strontium type ferromagnetic powder into an elastomeric material such as EPDM in a mixer or blending apparatus to form an extrudable rubber compound. EPDM or similar rubber compound can comprise a broad range of ferromagnetic powder, for example, from about 15% to about 90% powder by weight. The rubber compound can then be applied to the selected exterior surface of sealing element  18  by alternative methods. For example, where sealing element  18  has already been made, the magnetizable compound can be extruded directly onto the surface of element  18  to which it will heat bond and thereafter the seal  10  can be passed through an in-line magnetizer to magnetize the rubber compound. Alternatively, cover  22  of carrier  16 , sealing element  18  and the magnetizable compound can be triple-extruded together and then passed through the magnetizer. The magnetic force of coating to automotive body should be optimized to provide balance between effective sealing and ease of door opening. Such a balance can be achieved by selectively optimizing the coating formulation. 
     While a preferred embodiment of the present invention has been described in conjunction with its preferred use in the automotive environment, it will be appreciated that the invention has other uses and variations and modifications within the broad scope thereof and therefore it is intended that the present invention is to be limited only by the following claims.