Abstract:
Electrical apparatus includes a tray, having a surface on which a tool containing a rechargeable power source can be placed, and a magnetic field generator, which is located below the surface of the tray and is operative to generate a time-varying magnetic field of sufficient power at the surface of the tray so as to inductively charge the power source in the tool.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to cordless electrical tools, and specifically to methods and devices for inductive recharging of electrical tools used in medical procedures. 
       BACKGROUND OF THE INVENTION 
       [0002]    Electrical surgical tools are commonly used in operating rooms. For example, electrocautery devices are used in many procedures, and orthopedists commonly use power saws and drills. Operating rooms are often crowded with personnel and equipment, and electrical cords for powered surgical tools add to the difficulty of maneuvering and performing the operation. Maintaining the sterility of power cords can also be problematic. In response to these difficulties, cordless, battery-powered surgical tools, such as cordless orthopedic drills and saws, are becoming increasingly popular. 
         [0003]    In the course of a surgical procedure, the battery in a surgical tool may run down. In this case, the battery must be recharged or replaced while maintaining sterile conditions. The tool, and possibly the battery and charger (if used), must generally be capable of withstanding sterilization. U.S. Pat. No. 4,288,733, for example, describes a battery charger system suited for use in a sterilized environment, such as an operating room. The system includes a sterilizable battery pack adapted for connection to a non-sterilized charger through a sterilizable tray-interface. The tray-interface includes a connecting structure on an upper side for mechanical and electrical connection to the battery pack and additional connecting structure on a lower side for mechanical and electrical connection to the charger. A sterilizable drape is constrained between the tray-interface and the charger to isolate the charger from the sterilized environment. 
       SUMMARY OF THE INVENTION 
       [0004]    Embodiments of the present invention provide a charging tray for inductive charging of cordless electrical tools that simplifies recharging, while maintaining sterility of the tools. The tray may have the form of tool trays that are commonly used in the operating room. A magnetic field generator is located below the surface of the tray and generates a time-varying magnetic field of sufficient power at the surface of the tray so as to inductively charge tools that are placed on the tray. Inductive charging is advantageous in this context since it does not require that there be any physical contact between the field generator and the tools. The tools are recharged whenever they are placed on the tray, thus reducing the chances that a tool will run out of power in the course of a procedure. 
         [0005]    Some embodiments of the present invention are arranged so that tools may be placed on the tray in arbitrary orientations, without special receptacles for holding the tools in some predetermined position during charging. Typically, for this purpose, the inductive charging circuit in the tools is configured to receive power from the magnetic field produced by the field generator regardless of the orientation of the tool. This feature may be achieved, for example, by incorporating in the charging circuit two or more receiver coils with different orientations. In such embodiments, the tray may also be covered with a sterile drape without affecting its function. 
         [0006]    There is therefore provided, in accordance with an embodiment of the present invention, electrical apparatus, including: 
         [0007]    a tray, having a surface on which a tool containing a rechargeable power source can be placed; and 
         [0008]    a magnetic field generator, which is located below the surface of the tray and is operative to generate a time-varying magnetic field of sufficient power at the surface of the tray so as to inductively charge the power source in the tool. 
         [0009]    The surface of the tray may be flat. Alternatively, the surface of the tray may have one or more recesses for receiving the tool. 
         [0010]    Typically, the magnetic field generator includes a coil, which is encapsulated in the tray. 
         [0011]    In one embodiment, the apparatus includes a cover, which is configured to be placed over the tool on the tray so as to confine the magnetic field to a vicinity of the tray. Additionally or alternatively, the apparatus may include a sterile drape, which is placed over the surface of the tray, wherein the tool is charged by the magnetic field generator while the tool lies on the sterile drape. 
         [0012]    There is also provided, in accordance with an embodiment of the present invention, electrical apparatus, including: 
         [0013]    a cordless electric-powered tool, including a rechargeable power source and a charging circuit for charging the power source; 
         [0014]    a tray, having a surface on which the tool can be placed; and 
         [0015]    a magnetic field generator, which is located below the surface of the tray and is operative to generate a time-varying magnetic field of sufficient power at the surface of the tray so as to inductively charge the power source in the tool via the charging circuit. 
         [0016]    In some embodiments, the magnetic field generator, tray and charging circuit are configured so that the magnetic field generator charges the power source in any orientation in which the tool is placed on the surface. Typically, the charging circuit includes a plurality of coils, which have different, respective axes and are adapted to inductively receive energy from the time-varying magnetic field. Additionally or alternatively, the magnetic field generator and tray are configured so that the magnetic field generator charges the power source in the tool at any location at which the tool is placed on the surface. 
         [0017]    There is additionally provided, in accordance with an embodiment of the present invention, a method for recharging a tool containing a rechargeable power source, the method including: 
         [0018]    placing the tool on a surface of a tray; and 
         [0019]    generating a time-varying magnetic field, using a magnetic field generator located below the surface of the tray of sufficient power at the surface of the tray so as to inductively charge the power source in the tool. 
         [0020]    The present invention will be more fully understood from the following detailed description of the embodiments thereof, taken together with the drawings in which: 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is a schematic, pictorial illustration showing a tool tray with inductive charging capability in use during a surgical procedure, in accordance with an embodiment of the present invention; 
           [0022]      FIG. 2  is a schematic bottom view of a tool tray with inductive charging coils, in accordance with an embodiment of the present invention; 
           [0023]      FIG. 3  is a schematic side view of a tool tray with a rechargeable tool placed thereon, in accordance with an embodiment of the present invention; and 
           [0024]      FIG. 4  is a schematic cutaway view of a rechargeable tool, in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0025]      FIG. 1  is a schematic, pictorial illustration showing a tool tray  20  with inductive charging capability in use during a surgical procedure, in accordance with an embodiment of the present invention. A surgeon  22  uses cordless, electrically-powered tools  24 ,  26  during the procedure. When a given tool is not in use, the surgeon places it on a surface  28  of tool tray  20 . While the tool is on the tray, it is inductively charged by a magnetic field produced by a field generator below the surface of the tray (shown in the figures that follow). 
         [0026]    Tool tray  20  and tools  24 ,  26  may be designed, as described hereinbelow, so that the tools are charged regardless of the orientation in which they are placed on the tray. The charging magnetic field may be concentrated in one area of the tray, or it may be generated over the entire tray surface, so that the tool is charged regardless of location on the tray, as well. Thus, there is no need for receptacles to hold the tools on the tray. Surface  28  may be flat, and the operating room staff may use the tray to hold tools in the same manner as conventional tool trays without charging capability. The tray may be covered with a sterile drape  29  without compromising its function. Alternatively, tray  20  may be constructed so as to permit the tray to be sterilized between uses, in which case drape  29  may not be needed. (Tools  24  and  26  are typically constructed so as to permit them to be sterilized by methods known in the art, such as autoclaving or chemical sterilization.) 
         [0027]    In alternative embodiments of the present invention (not shown in the figures), the tool tray may have one or more recesses in its upper surface in which tools are placed for recharging. In such embodiments, the charging magnetic field may be localized in the area of the recesses, and the tools may be constrained by the shape of the recesses to an orientation that maximizes energy transfer from the magnetic field generator to the tool. Alternatively, the optimal locations and orientations of the tools on the tray may simply be marked graphically on the tray surface or drape, so as to indicate to surgeon  22  how and where to place the tools on the tray. Additionally or alternatively, the tools themselves may be marked and/or shaped to indicate the proper orientation. 
         [0028]      FIG. 2  is a schematic bottom view of tool tray  20 , in accordance with an embodiment of the present invention. One or more magnetic field generators  30  are positioned below surface  28  of the tray. In the pictured embodiment, the field generators have the form of flat coils, which may be encapsulated within the tray. Alternatively, the field generators may be positioned below the tray. Tray  20  is typically made of a plastic or other non-magnetic material, so as not to block the passage of the magnetic fields from the field generators below surface  28  to tools that are placed on the surface. 
         [0029]    Although the field generators shown in  FIG. 2  comprise a certain type of coils, any suitable field generator design may be used in tray  20 , such as coils of other shapes and forms, with or without a magnetic core, or a “bird cage” magnetic field generator, for example. The field generator or generators may be configured to generate the magnetic field over all of surface  28 , or they may alternatively be positioned and configured to generate the field only in a certain area or areas of the surface. The field generators are typically designed so that the field they generate is localized near the surface of the tray, thereby minimizing interference by the magnetic field with sensors and other equipment used in the operating room. Shielding may be added to the tray (including an optional tray cover) to limit the interference with other equipment, as well as for safety reasons. 
         [0030]    A driver circuit  32  drives an alternating current through field generators  30  in order to generate magnetic fields at the desired frequency. Typically, the field frequency can be anywhere in the range of 100 kHz-30 MHz, depending on the application and the resonant frequency of the charging circuit in tools  24 ,  26  (as described further hereinbelow). Alternatively, higher or lower magnetic field frequencies may be used. 
         [0031]      FIG. 3  is a schematic side view of tool tray  20  with tool  26  resting on surface  28 , in accordance with an embodiment of the present invention. Field generator  30  generates a magnetic field with field lines passing vertically through surface  28  and intercepting tool  26 . Optionally, a magnetic shield  34  may be lowered over tool  26  while it is being charged by field generator  30 . This shield typically comprises a metal or other material with high magnetic permeability, in order to confine the radiation of the magnetic field to the area of tray  20 . 
         [0032]      FIG. 4  is a schematic, cutaway view of tool  26 , showing circuitry contained in a handle  40  of the tool, in accordance with an embodiment of the present invention. Coils  44  and  46  are wound on a core  48 , which typically comprises a ferrite or other magnetic material. In this embodiment, coils  44  and  46  have mutually-orthogonal axes. As a result, when tool  26  is laid on tray  20 , at least one of coils  44  and  46  will be suitably oriented to receive energy from the magnetic field perpendicular to surface  28  that is produced by field generators  30 , regardless of the orientation of the tool. (“Orientation” in this sense can mean either the direction in which the tool is pointing or the roll angle of the tool about its longitudinal axis, or both.) For optimal energy transfer, coils  44  and  46  are typically connected in respective resonant circuits, whose resonant frequency matches the driving frequency of field generators  30 . 
         [0033]    Coils  44  and  46  are connected to a rectifier circuit  50 , which provides a DC input to charge a power source  52 . The rectifier circuit may also comprise a regulator and power management controller, as are known in the art, in order to prevent overcharging of the power source. Power source  52  may comprise a super-capacitor or a rechargeable battery, of any suitable type known in the art. The power source in this embodiment supplies energy to a motor  54 , which drives a shaft  42 . Alternatively, the power source may be coupled to drive any other suitable type of mechanism or device, such as a saw, drill, electrocautery scalpel, ablation head, laser or other light source, as well as other electrical circuit components, such as amplifiers, microcontrollers and wireless communication electronics. 
         [0034]    It will be appreciated that the embodiments described above are cited by way of example, and that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art.