Patent Publication Number: US-2004051324-A1

Title: Magnetic sweeper with flux optimizing channel structure

Description:
FIELD OF THE INVENTION  
       [0001] The present invention pertains generally to magnets and magnetic devices and, more particularly, to magnetic hand tools with functional features which cooperate with housed or mounted magnets.  
       BACKGROUND OF THE INVENTION  
       [0002] Magnetic tools, such as hand tools, require some type of support structure or housing for magnetized material, and other functional aspects such as a grip, conveyance such as wheels or other mechanism for performance of the tool. The type and purpose of the tool dictates the mounting or housing structure for the magnet, with a primary operational concern being that the magnetic flux is directed in the desired orientation relative to the tool. For example, in a hand-held magnetic tool with some type of grip, it is desirable that the magnetic flux be directed generally away from the grip to maximize the operational efficiency of the tool. In a hand-operated magnetic sweeper, such as described for example in U.S. Pat. No. 6,158,792, designed to pick up ferrous objects off the floor, it is desirable to have the magnetic flux directed downward by the housing which supports and surrounds the magnet or magnets.  
       [0003] Directing magnetic flux in one general direction typically requires that the magnet or magnets be shrouded or otherwise encapsulated on all sides but the desired flux direction. The magnetic sweeper described in U.S. Pat. No. 6,158,792 has three-sided magnet housing, with the top side directing the flux downward through an aluminum channel which protects the front and underside of the magnet. This downwardly directed flux tends to attract ferrous object on the frontal surface of the magnet housing of the tool, rather than to the bottom surface of the magnet housing. The rear facing surface of the magnet is left exposed. U.S. Pat. No. 3,646,492 describes another type of magnetic sweeping device which has a three-sided magnet housing which leaves a bottom surface of the magnet exposed. While this may direct the magnetic flux downward, attraction of sharp objects directly against the exposed magnet may result in chipping, breaking or soiling of the magnet, resulting in diminished performance of the tool. In this design the three-sided channel which serves as the magnet housing is attached to a support structure which is in turn attached to a handle. This adds to the complexity of construction of the device.  
       BRIEF SUMMARY OF THE INVENTION  
       [0004] The present invention provides a magnetic sweeper tool with an integrated construction which optimizes magnetic flux in a desired direction for maximum pick-up efficiency. In accordance with the principles of the invention, a magnetic sweeper has a three-sided channel which houses one or more magnets in a generally planar arrangement, with an open side of the channel being covered by a plate which covers the remaining exposed surface of the magnet(s). The channel serves both as the primary structural member of the magnetic sweeper tool, and to direct the magnetic flux downward away from the channel toward a floor surface over which the tool is conveyed by wheels or other conveyance. The plate covering the open side of the channel and the exposed surface of the magnet(s) is of a different, non-magnetic material than the channel, such as plastic, aluminum or stainless steel, so as to not short the magnetic circuit within the housing formed by the channel and plate. As the primary structural member of the tool, the channel further functions to support axles for mounting of wheels at opposite ends of the channel. This design avoids the need to attach the channel to a separate member or piece for attachment to wheels and a handle or other manipulation part. In one embodiment, a wheel axle is attached to a top side of the channel at each end. In another embodiment, a wheel axle is attached to an underside of the top of the channel at each end. A manipulation handle is attached directly to the channel, preferably at a mid-point along the top of the channel.  
       [0005] These and other aspects of the invention are described herein in detail with reference to the accompany Figures which are denoted with reference numbers associated with the various components, parts and assemblies of the invention. 
     
    
    
     DESCRIPTION OF THE FIGURES  
     [0006]FIG. 1 is a perspective view of a magnetic sweeper tool of the present invention;  
     [0007]FIG. 2 is a perspective sectional view of a channel end and wheel mounting portion of the magnetic sweeper tool of the invention;  
     [0008]FIG. 3 is a perspective view of a portion of the magnetic sweeper tool of the invention;  
     [0009]FIG. 4 is a top view of the magnetic sweeper tool of the invention, with arrows indicating the directions of magnetic flux paths between the north and south poles, and  
     [0010]FIG. 5 is a cross-sectional view of a channel portion of the magnetic sweeper tool of the invention, with arrows indicating the directions of magnetic flux paths between the north and south poles. 
    
    
     DESCRIPTION OF PREFERRED AND ALTERNATE EMBODIMENTS  
     [0011] With reference to FIG. 1, there is illustrated a magnetic sweeper tool  10  which includes the main component parts of a channel  12  which serves as a support structure and housing for a one or more magnets  18 , and as a mounting structure for any type of conveyance, which in this case is in the form of wheels  15  mounted upon axles  13  at opposite distal ends  14  of the channel  12 . The channel  12  can be made of any material of sufficient structural strength, but is preferably made of a ferrous, magnetically conductive material which directs the magnetic flux in the desired direction, as further described.  
     [0012] As shown in FIGS. 2, 3 and  4 , one or more magnets  18  are located within channel  12  in an operative arrangement to attract ferrous objects, for example from underneath the channel as the tool is conveyed over a surface. In this example the magnets  18  are in the form of generally rectangular bar magnets. Although illustrated as two commonly sized magnets arranged side-by-side or end-to-end, a single piece magnet running substantially the length of the channel could also be used. The magnets  18  are held in position within the channel  12  by a plate  20 , shown in cross-section in FIG. 5, which covers the open side of the channel from end-to-end. The plate  20  is secured to the channel by fasteners  23  which pass through the plate and the traverse the depth of the channel adjacent to the magnet(s) which are thereby fully encapsulated in the housing formed by the channel  12  and plate  20 . As further described, this complete enclosure of the magnet(s) is advantageous for complete physical protection of the magnet(s) from mechanical damage and dirt.  
     [0013] As also shown in FIG. 5, the channel  12  is preferably in the form of a three-wall channel, having a top wall  121  and side walls  122  which extend generally perpendicular from the top wall  121 , terminating at edges  123 . Preferably the top wall  121  has a width dimension, measured as the distance from one side wall to the opposite side wall as shown in FIG. 5, which is greater than a width dimension of the side walls  122 , measured as the distance from the top wall  121  to the terminal edges  123  of the side walls  122 . This configuration provides an adequate housing for magnet bar stock which has a generally rectangular cross-section as shown in FIG. 2. Plate  20  preferably fits flush inside the side walls  122  at edges  123 .  
     [0014] To optimize the magnetic flux pattern of the tool, plate  20  is ideally made of a non-ferrous material, such as plastic, aluminum or stainless steel, so as to not short the magnetic circuit within the channel  12 . The enables the flux pattern shown in FIGS. 4 and 5, wherein the channel  12  serves to conduct the pole of the magnet in contact with the channel (N) through the top wall  121  and through the side walls  122 , exiting at the side wall edges  123 . The flux from the opposite pole of the magnet (S) passes through the non-magnetically conductive plate  20  between the edges  123  of the channel  12 . In the double magnet configuration shown in FIGS. 3 and 4, the right and left magnets are preferably of opposite polarity, creating the cross-lateral flux pattern illustrated by the arrows. Plate  20  also functions as a physical shield to the underside of the magnet(s), providing protection from chipping, keeping the magnet(s) free from dirt and debris, and facilitating cleaning of the tool by easy removal of attracted objects from the smooth surface of the plate.  
     [0015] As shown in FIG. 2, axles  13  can be supported by and secured to the ends of the channel  12  by welds  17  formed on the top wall  121  of the channel. This arrangement provides a somewhat lower mounting height for the channel/magnet assembly relative to the contact surface of the wheels  15 . Alternatively, as shown in FIG. 3, the axles  13  may be attached to an underside of channel top wall  121 , on the inside of the channel proximate to magnet(s)  18 . Other means of attachment of the axles  13  to the channel, such as through bearings or other mounting fixtures or by appropriate formation of the channel ends to receive a distal end of an axle are all within the scope of the invention.  
     [0016] Any type of manipulative device may be attached to the channel  12  to facilitate operation of the tool. As illustrated in FIGS. 1, 3 and  4 , a handle  30  is attached to channel  12 , for example at top wall  121  by fasteners or other means, with the handle fitting  31  being in the form of a tube, wire rod, or fitting such as a threaded fitting to engage an extension having a cooperating fitting such as a threaded receiving bolt or ferrule. In this example the handle fitting  31  is attached to channel  12  by fasteners  32 . Other types of manipulative devices may be attached to the channel in similar manners, the common design aspect being that the channel  12  serves the multiple functions of the central support structure which houses and protects the magnet(s), provides points of attachment for conveyance such as the wheels and wheel axles, and provides a point or points of attachment for manipulative means such as a handle or grip; and the further function of the described magnetic flux direction control in cooperation with the plate  20 .