This invention relates to hooks and clips having a magnet attached for holding objects on metal surfaces.
There have been a wide variety of hooks and jaw-type clips which have magnets attached thereto for holding objects on refrigerator doors and other metal surfaces. For example, the jaw-type clip of my U.S. Design Pat. No. Des. 286,013 has been sold for many years with a magnet attached to the back surface. For that product I have used the magnet arrangement shown in my U.S. Pat. No. 5,340,634 and U.S. Pat. No. Des. 350,943. A rectangular magnet is held in a U-shaped magnet holder. A fastener passes through a hole in the magnet and magnet holder and into the jaw-type clip. I have used metal and plastic rivets as fasteners.
The load carrying capability of a magnetic hook or magnetic jaw-type clip is dependent upon the size and strength of the magnet as well as the type of mounting surface to which the magnet is attached. Conventionally, magnets used for hooks have been rectangular or square in shape ranging from approximately one to two inches in length and width. A clip or hook having a magnet approximately one inch square attached to a metal surface such as a refrigerator door will hold from about one half to one pound before sliding. Larger magnets have been proposed to hold more weight. For example, a flat circular magnet two inches in diameter has been sold for hanging Christmas wreaths on metal doors or other metal surfaces.
Efforts have been made to increase the holding power of a magnet mounted hook. In U.S. Pat. No. 5,411,231, Buck discloses a suction cup in the center of a circular magnet. Sheiner et al. in U.S. Pat. No. 4,825,526 provide a washer formed of a medium durometer elastomer such as rubber or neoprene around the rivet which attaches the magnet to the body of the fastener. They teach that the thickness of the washer should be such that the washer protrudes slightly above the housing containing the magnet. The suggested slight protrusion is one mil. The height of the washer is critical. If the washer is too thick, the magnetic attraction between the magnet and the metal mounting surface will be reduced. If the washer is too thin, the washer will not press against the mounting surface.
There are several variables which affect the amount by which a washer or spacer attached to a magnet will protrude above the magnet holder which holds the magnet. Magnets vary in thickness by as much as xc2xd mil. The height of a plastic or metal channel which serves as a magnet holder can vary by as much as xc2xd mil. A plastic rivet which fits through the magnet and the socket into which the rivet fits can vary in height or depth by up to 1 mil.
Magnet mounted hooks usually are made to be both decorative and functional. Often the manufacturer wishes to offer the product in a variety of colors. I have found that the pigment placed in both the molded vinyl washer and the plastic on which it is mounted affects the thickness of the washer. Two pieces of plastic made in the same mold but of two different colors may differ in thickness from xe2x85x9 to xc2xd mils depending upon the thickness of the part. If one is attempting to obtain precisely the one mil protrusion needed, and recommended by Steiner et al, a different mold may be required for each color washer and for each color of plastic base. Obviously, this is impractical. Furthermore, separate molds for each washer color will not overcome the combinations of variations in heights or thickness of the magnet, magnet holder, rivet and socket.
Other variables are introduced by ambient temperatures and humidity around the molding machine. Differing rates of shrinkage in washer, base, and plastic rivet make it impossible for one size or thickness of washer to guarantee high-quality magnetic attraction and maximum slide-resistance. Other changes in thickness are caused by material changes. If the rivet is made of polycarbonate, it will be a different length than if it is polypropylene, even though it is made in exactly the same cavity. A manufacturer must compensate for these minute changes.
As Sheiner et al. disclose and those skilled in the art recognize, the magnetic attraction between a magnet and a metal surface decreases as the distance between the magnet and the metal surface increases. Furthermore, a magnetic hook placed on a smooth flat surface will hold more weight than the same magnetic hook placed on a curved or irregular surface.
It is quite common for a magnetic hook to attract metal filings and other grit during storage or prior to being placed upon a metal surface. If the magnetic hook is slid across that surface the grit on the magnet may scratch the surface. Very often a person seeking to remove the magnetic hook from a metal surface will slide the hook across the surface during removal, scratching the surface. Consequently, there is a need for a magnetic hook that can be easily removed from a magnetic surface without sliding. More particularly the magnetic hook should be configured to encourage and facilitate removal without sliding the magnet across the surface.
There is a need for magnetic hooks and clips which will have increased holding power and can be made in a variety of colors. Preferably, the size of the magnets in these hooks should not be significantly larger or more expensive than those currently in use. Indeed, the optimal solution would utilize the same magnets, magnet holders and rivets that are commercially available and make them more effective. Then the cost of adopting the improvement would be small and perhaps insignificant. Furthermore, those magnetic hooks should be configured to facilitate removal from a metal surface without sliding the magnet across the metal surface.
I provide a magnetic hook or clip which has a plurality of magnets attached to a plastic housing. The housing is preferably rectangular and has a hook or clip near the bottom edge. A finger tab is provided on the housing for removal of the hook from a surface without the hook sliding across the surface to which it is attached.
The housing has a base and a wall extending from the perimeter of the base a distance greater than the thickness of the magnets attached to the base. The difference in distance should not exceed {fraction (1/32)} of an inch. Each magnet is attached by a metal or plastic fastener having a head and a shaft. The shaft extends through a hole in the magnet and into the housing. The length of the shaft may be somewhat greater than the thickness of the magnet allowing the magnet to pivot and move up and down on the shaft. A flexible wall having a height slightly greater than the height of the housing may be provided between or around magnets. The wall extends slightly beyond the housing. When the magnet is placed against a mounting surface, the flexible wall will bend and press against the mounting surface. The wall provides increased frictional contact between the magnet and the mounting surface thereby increasing the holding power of the hook. This product can be made using the same magnets as are presently being used for comparable hooks and clips presently available in the marketplace.
These and other advantages and features of the present invention will become more fully understood upon reference to the accompanying drawings illustrating certain presently preferred embodiments of the invention.