Abstract:
The invention is a retractable magnetic sheet. A cylindrical rod is biased in a first rotational direction to retract the sheet which is mounted at a first edge to the rod. The sheet is magnetically-receptive, which means magnets can attach to it. The sheet is extended by pulling downwardly against the bias until the ratchet locks the cylindrical rod&#39;s position. Upon pulling downwardly again, the ratchet releases and the rod retracts, winding the sheet up.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates generally to structures to which magnets can be mounted by magnetic attraction between the magnet and the structures.  
           [0003]    2. Description of the Related Art  
           [0004]    Magnetically receptive structures are well-known as being desirable, because they permit convenient attachment of objects to a surface. For example, magnets can be attached to a household refrigerator door made of steel for the purpose of displaying the magnets themselves or an object partially interposed between the door and the magnet.  
           [0005]    Educational material suppliers have noticed the value of magnetically receptive structures to hold educational materials, such as names, letters, numbers and pictures. Such structures typically take the form of plain panels that can be mounted to walls and conventional chalkboards made of painted steel. More recently, it was discovered that thin steel can be sandwiched between polymer layers to construct a flexible panel that can be cut with scissors and other conventional office tools. This is shown in U.S. Pat. No. 6,235,378 to Lowder, which is incorporated herein by reference. Such panels can be placed in notebooks, on easels, behind or within wallpaper, and in many other places for ease in use.  
           [0006]    Despite the ease in use of the above discussed devices, there is still a need for a conveniently located, compact surface upon which magnets can be mounted.  
         BRIEF SUMMARY OF THE INVENTION  
         [0007]    The invention is an apparatus for providing a substrate to which a magnet can be attached. The preferred apparatus comprises a cylindrical rod having an axle about which the rod is rotatably mounted. The rod is preferably a circular cylinder. A preferred magnetically receptive sheet has a first edge mounted to the cylindrical rod. A central region of the sheet winds circumferentially around the cylindrical rod and terminates in a second edge opposite the first edge. The second edge is displaceable relative to the cylindrical rod&#39;s axle by, for example, grasping the edge by hand and pulling tangentially from the cylindrical rod.  
           [0008]    In the preferred embodiment, a bias is drivingly linked to the cylindrical rod for rotatably biasing the cylindrical rod in a sheet-retracting direction. Furthermore, a ratchet is preferably mounted to the cylindrical rod near the axle, and the ratchet selectively stops rotation of the cylindrical rod in the sheet-retracting direction.  
           [0009]    The invention operates in the following manner. When it is not in use, the sheet is stored by being wrapped essentially completely around the cylindrical rod. When the sheet is desired to be exposed, the free edge of the sheet is grasped by hand and pulled downwardly away from the cylindrical rod. When a desired amount of sheet is exposed, the user stops pulling the sheet and relaxes the downward movement of the sheet while still grasping the sheet. The ratchet catches and stops continued rotation of the cylindrical rod in the sheet-retracting direction. 0Magnets are then placed on the sheet. After the user is finished using the sheet, the sheet is simply pulled downwardly again, thereby releasing the ratchet. This allows the biased cylindrical rod to retract the sheet around the cylindrical rod for storage. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a view in perspective illustrating the present invention in a retracted state.  
         [0011]    [0011]FIG. 2 is a view in perspective illustrating the present invention in an extended state.  
         [0012]    [0012]FIG. 3 is an end view illustrating the preferred ratchet mechanism.  
         [0013]    [0013]FIG. 4 is a view in perspective illustrating an alternative embodiment of the present invention.  
         [0014]    [0014]FIG. 5 is a view in perspective illustrating another alternative embodiment of the present invention.  
         [0015]    [0015]FIG. 6 is a view in perspective illustrating another alternative embodiment of the present invention. 
     
    
       [0016]    In describing the preferred embodiment of the invention which is illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, it is not intended that the invention be limited to the specific term so selected and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. For example, the word connected or term similar thereto are often used. They are not limited to direct connection, but include connection through other elements where such connection is recognized as being equivalent by those skilled in the art.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0017]    The preferred embodiment of the present invention is shown in FIG. 1. The apparatus  10  includes a cylindrical rod  12 , which is preferably a circular cylinder approximately one inch in diameter, to which a pair of end caps  14  and  16  are rigidly mounted. The end caps  14  and  16  have axles  18  and  20 , respectively, which mount to a fixed structure, for example conventional window shade brackets or similar structures. The rod and end caps of the preferred embodiment are substantially identical to the rod and end caps used with conventional retractable window shades.  
         [0018]    A preferably rectangular sheet  30  has an elongated inner edge  32  (see FIG. 2) mounted longitudinally to a radially outwardly facing surface of the rod  12 . The inner edge  32  is preferably glued to the outer surface of the cylindrical rod  12 , but can be fastened by other conventional fasteners, such as staples, ultrasonic welds, tape, stitching, etc. The opposite, free edge  34  of the sheet  30  is preferably oriented parallel to the inner edge  32 . The region of the sheet  30  between the opposite edges  32  and  34  is wound around the radially outwardly facing surface of the cylindrical rod  12 , with each winding being wound around each previous winding of the sheet  30 . The flexible sheet  30 , which preferably has essentially no “memory” that would cause it to be permanently deformed by being wound around the preferred rod  12  of one inch diameter, thereby conforms generally to the shape of the cylindrical rod  12 . A cylindrical rod of greater diameter would be less likely to deform the sheet, and a sheet with significant memory could be used if a larger diameter rod is used. In its retracted position shown in FIG. 1, the apparatus  10  forms an overall size not appreciably larger0 than the rod itself.  
         [0019]    The preferred sheet  30  is made entirely of a magnetically-receptive material, and preferably is made by combining a ferromagnetic powder and an acrylic latex. Alternatively, one or both sides can be coated with paper or any other material that does not interfere with magnetic attraction to the sheet. The sheet  30  can be constructed, for example, in accordance with the teaching of U.S. Pat. No. 5,843,329 and 5,609,788, both to Deetz, which are incorporated herein by reference. Alternatively, the sheet can be made of thin steel with polymer layers on opposite sides in accordance with U.S. Pat. No. 6,235,378 to Lowder, incorporated by reference above. The resulting sheet has two opposing major surfaces to which magnets can attach.  
         [0020]    The axle  18  is rotatably mounted to the corresponding end cap, and a spring is mounted between the axle and the cylindrical rod to bias the cylindrical rod in one direction relative to the axle. Preferably, the cylindrical rod is biased in the direction that tends to wind the sheet  30  around the cylindrical rod  12 , which is counterclockwise when viewed from the left end of the rod  12  in FIG. 1. The axle  20  is preferably rigidly mounted to the end cap  16 , and is rotatably mounted in a bearing in which the axle  20  rotates. Both axles are mounted in brackets mounted to, for example, a portable frame, a wall, a ceiling, or some other fixed object.  
         [0021]    When the sheet  30  is in the retracted position shown in FIG. 1, it is out of view and compact, thereby saving space. In order to extend the sheet  30  for use, the user grasps the free edge  34  by hand and pulls in a direction away from the cylindrical rod  12  (preferably downwardly along a tangent to the rod) with enough force to overcome the bias that tends to keep the sheet  30  in the retracted position. Thus, the user displaces the free edge  34  away from the cylindrical rod  12 , and, as the user continues to pull, exposes an increasing amount of the region of the sheet  30  between the inner edge  32  and the free edge  34 . By thus extending the sheet  30 , the sheet  30  is exposed to hang vertically by gravitational force, thereby exposing one or both of the major surfaces to which one or more magnets can be attached, as is illustrated by the magnets  36  and  38  in FIG. 2. The sheet can be guided by a track or other structure, if desired, to be positioned other than vertically.  
         [0022]    In the preferred embodiment, the major surfaces of the entire sheet  30  are magnetically receptive. Alternatively, of course, selected sections of the sheet could be made to be magnetically receptive, and other sections of the sheet could be magnetically non-receptive. This could be for the purpose of reducing costs, or for some other reason. Because the sheet  30  is magnetically receptive, meaning magnets (whether permanent or electromagnets) are attracted to the major surfaces thereof, the sheet  30  in its extended position has two convenient major surfaces to which magnets can be attached, such as for teaching or for decoration.  
         [0023]    The preferred sheet  30  remains in the fully extended position shown in FIG. 2, or in a partially open position, by a ratchet mechanism that selectively stops the rotation of the cylindrical rod  12  in the rotational direction in which the cylindrical rod  12  is biased. The preferred ratchet mechanism is substantially identical to the ratchet mechanism used on conventional window shades, and is illustrated in FIG. 3. A circular member  50  has a pair of teeth  51  and  52  on opposite sides of an inner aperture  54  that seats against one of four pawls  56 ,  57 ,  58  and  59  formed on the axle  18  that extends through the aperture  54 . Of course, other ratchet mechanisms can be substituted as will become apparent to one of ordinary skill upon reading the instant description.  
         [0024]    In an alternative embodiment shown in FIG. 4, a prime mover, such as the electric motor  80 , is drivingly linked to a cylindrical rod  82  to rotate the rod  82  for extending and/or retracting the sheet  84 . A still further alternative, shown in FIG. 5, includes a manually rotatable cylindrical rod  92 , which can be rotated in one direction or the opposition direction by a rope  94  or cord that extends around a pulley  96  drivingly linked to the cylindrical rod  92 . By rotating the pulley  96 , the drivingly linked cylindrical rod  92  is thereby driven to retract or extend the sheet  98 . Alternatively, the cylindrical rod  92  could be hand rotated to extend and retract the sheet  98 .  
         [0025]    While the outwardly facing major surface of the sheet  30  is preferably a solid color, such as white, gray, black or any other color, it is also possible to imprint or attach indicia to this surface. Such indicia can include alphanumeric characters, such as letters and numbers, and drawings, such as maps, images of the human skeleton, etc. This permits the user to attach magnets having images of corresponding indicia to the surface to aid instruction. Of course, it is impossible to list all indicia that could be imprinted or attached to the sheet. However, it will become apparent to a person of ordinary skill from the instant description that any indicia that can be imprinted upon other surfaces can be imprinted upon the instant invention&#39;s magnetically receptive sheet.  
         [0026]    In another alternative embodiment of the present invention shown in FIG. 6, the orientation of the apparatus is reversed from that of the preferred embodiment. The cylindrical rod  112  is mounted at its free edge  134  to a fixed structure, such as a portable frame or a wall. The opposite edge of the sheet  130  is attached to the cylindrical rod  112  in a manner essentially identical to the preferred embodiment. However, the sheet  130  is unwound from the cylindrical rod  112  by rolling the cylindrical rod  112  downwardly away from the free edge  134 . The sheet  130  is retracted by rolling the cylindrical rod  112  upwardly toward the free edge  134 . Unwinding and retracting of the sheet  130  can be accomplished manually by hand, or by a motor, bias and ratchet, looped cord, or any other equivalent means for winding and unwinding the cylindrical rod  112 .  
         [0027]    In a still further alternative, one or both of the major surfaces of the sheet is a dry-erase material, thereby permitting marking thereon with special-purpose marking pens that subsequently can be erased. Alternatively, one or both of the major surfaces of the sheet can be a surface upon which chalk can write and from which chalk can be erased. Such a sheet has two uses: attachment of magnetic devices thereto and marking thereon.  
         [0028]    Of course, it is also possible to use the present invention as a combination of a magnetic receptive surface and at least one of the following: movie projector screen, window shade and retractable map.  
         [0029]    Additionally, although the preferred cylindrical rod is a circular cylinder, it is possible to instead have an octagonal cylinder or any other polygonal cylinder substituted for the preferred rod. Such polygonal cylinders will likely leave deformations in the sheet where the sheet contacts the intersections of the sides, and therefore are less desirable.  
         [0030]    While certain preferred embodiments of the present invention have been disclosed in detail, it is to be understood that various modifications may be adopted without departing from the spirit of the invention or scope of the following claims.