Patent Publication Number: US-6713905-B2

Title: Electric-motor rotary power tool having a light source with a self-generating power supply

Description:
The present invention generally relates to rotary power tools, and more particularly to an electric-motor power tool having a light source with a self-generating power supply. 
     Hand-held multipurpose rotary tools are commonly known. These tools generally include an elongated spindle and an electric motor for rotating the spindle at high speeds. A holder is secured to an end of the spindle and is adapted to receive various accessories for striping, sanding, grinding, drilling, cutting and sharpening, for example. 
     Very often the rotary tools are used in places where adequate lighting is not always available. Consequently, the tool operator must work under poor lighting conditions, which may hinder him or her from satisfactorily completing the job, especially when the job requires precision and attention to detail. Brightening the work area with an additional light source such as a lamp or a flashlight can be an inconvenience and/or interfere with the job. 
     It may be possible to incorporate a light source directly into the rotary tools and have it connected to the same power source from which the motor of the tool is supplied. This would require substantially reconfiguring the tool to accommodate the added circuitry of the light source, which would increase the cost of tool manufacture. For rotary tools which are equipped with long and flexible extension attachments, having a light source built into the tool may not be helpful, since the light from the tool would not necessarily illuminate the area in which the work is being performed. 
     Accordingly, it is a primary objective of the present invention to provide an improved rotary power tool having a built-in light source. 
     Another object of the present invention is to provide an improved rotary power tool having a light source with a separate power supply from the power supply of the tool. 
     Still another object of the present invention is to provide such an improved rotary power tool having a light source with a power supply which induces current from a magnet when the magnet is rotated by the power tool. 
     The further object of the present invention is to provide such an improved rotary power tool having a light source which is incorporated into the end of an extension attachment. 
     Yet another object of the present invention is to provide such an improved rotary power tool having a light source that receives its power supply from a current generated from a magnet attached to the extension attachment of the power tool. 
    
    
     Other objects and advantages will become apparent upon reading the following detailed description, in conjunction with the attached drawings, in which: 
     FIG. 1 is a perspective view of a rotary power tool embodying the present invention; 
     FIG. 2 is a sectional view of the area indicated by lines  2 — 2  of the rotary power tool shown in FIG. 1; 
     FIG. 3 is circuit diagram of a light source in accordance with the present invention; 
     FIG. 4 is a perspective view of a rotary power tool with an extension attachment embodying the present invention; 
     FIG. 5 is a sectional view of the area indicated by lines  5 — 5  of a light source attachment shown in FIG. 4; 
     FIG. 6 is a side view of an alternate embodiment of the light source attachment in accordance with the invention; 
     FIG. 7 is a front view of the light source attachment of FIG. 6; 
     FIG. 8 is a side view of the light source attachment of FIG. 6, with parts removed for clarity; 
     FIG. 9 is a plan view of an alternate embodiment of a magnet for generating magnetic flux; 
     FIG. 10 is a side view of the magnet shown in FIG.  9 . 
     FIG. 11 is a circuit diagram representation of the light source attachment shown in FIG. 6; and, 
     FIG. 12 is a waveform of current produced in the light source attachment of FIG.  6 . 
    
    
     DETAILED DESCRIPTION 
     The present invention is directed to a multi-purpose rotary power tool which is adapted to receive and hold a number of different tool accessories for various tasks such as striping, sanding, grinding, cutting, drilling and sharpening, for example. The rotary tool includes a built-in light source located near the front of the tool. The power supply for the light source is independent from that of the rotary tool itself, and is generated by a coil of wire which is inductively coupled to a magnet provided in the tool. The magnet spins in conjunction with the spindle in the rotary tool, in close proximity to the stationary wire coil (also known as a choke or inductor in the art). As the magnet spins, the magnet&#39;s flux lines pass through the wire coil, inducing a current in the coil. As long as the light source is connected to the coil, current flows to the light source, which could be, for example, a light emitting diode (LED). 
     Broadly stated, the present invention is directed to a rotary power tool having a light source, and includes a housing, an electric motor provided in the housing and an elongated spindle engaged with and adapted to be rotatably driven by the motor. A rotatable holding assembly is attached to an end of the spindle and extends from a front end of the housing for holding a tool accessory. At least one magnet is adapted to be rotated by the spindle for producing a magnetic field, and a generally tubular sleeve is attached to the front end of the housing. At least one light emitting diode projects from a front end of the sleeve, generally between the inner and the outer surfaces of the sleeve. An inductive coil is also imbedded at least partially in the sleeve generally between the inner and the outer surfaces, proximate the magnet for generating an electric current from the magnetic field. Electrical conductors are also embedded and routed through the sleeve for supplying the electric current from the inductive coil to the light emitting diode. 
     The invention is also directed to a light source apparatus for an electric-motor rotary power tool having a rotatable tool holder assembly and equipped to receive an accessory attachment. The light source apparuatus includes a magnet constructed and adapted to be removably secured to the rotatable tool holder assembly, and a generally tubular sleeve which is configured and adapted to be removably attached to a portion of the power tool configured for receiving the accessory attachment. A current generating device is at least partially imbedded in the sleeve generally between the inner and the outer surfaces of the sleeve, and positioned proximate the magnet when the sleeve is attached to the power tool, for generating an electric current from a magnetic field created by the magnet when the power tool is operated. Lighting devices project from a front end of the sleeve and is adapted to illuminate when supplied with the electric current from the current generating device. Electrical conductors routed through the sleeve between the inner and the outer surfaces supply the electric current from the current generating device to the lighting device. 
     Turning now to FIG. 1, the rotary power tool of the present invention is indicated generally at  10  and includes a housing  12 , a light source attachment  14 , a tool accessory holder assembly  16  and a tool accessory  18 . A pair of light emitting diodes (LEDs)  20  are included in the light source attachment  14  for illuminating the area surrounding the tool accessory  18 . The rotary tool  10  is AC powered as indicated by a power cord  22 . However, it may also be battery operated. The tool accessory  18  shown in FIG. 1 is only one example, and any number of known tool accessories can be used in its place. 
     Turning to FIG. 2, the rotary tool  10  further includes an electric motor  24  (AC or battery powered) for rotating a shaft or spindle  26  about its longitudinal axis. The tool accessory holder assembly  16  includes a hollow, generally cylindrical base portion  28  which slips over the end of the spindle  26  opposite the motor  24  to securely mount the accessory holder assembly onto the spindle. A threaded head portion  30  extends from the base portion  28 . A collet  32  is inserted into the hollow of the head portion  30 , and a collet nut  36  is threaded onto the head portion  30  to enable the collet  32  to securely grab the tool accessory  18  inserted into the collet in a conventionally known manner. 
     A front end  34  of the housing  12  is threaded to receive various attachments that are constructed and adapted to be used with the rotary power tool  10 , for example, a router attachment, a cutting attachment, a sharpening attachment, an extension attachment, etc. In accordance with one embodiment of the present invention, the light source attachment  14  is likewise constructed and adapted to be threaded onto attachment threads  38  at the front end  34  of the housing  12 . 
     The light source attachment  14  includes a substantially tubular sleeve  39  having an inner circumferential surface  40  and an outer circumstantial surface  41 . The inner circumferential surface  40  is threaded to cooperatively receive the threaded front end  34  of the housing  12 . Each of the two LEDs  20  are imbedded in the sleeve  39  generally between the inner and the outer circumferential surfaces  40 ,  41 , and projects from the front end of the sleeve  39  towards the tool accessory  18  (shown in FIG.  1 ), so as to illuminate the intended work area. The LEDs  20  are connected to a pair of wire conductors  42 , which are also connected to a coil of wire or inductive coil  43  to complete an electrical circuit. The wire conductors  42  and the inductive coils  43  are provided within the thickness of the sleeve  39  and generally from the front to the back. In other words, the LEDs  20 , the inductive coils  43  and the wire conductors are embedded in the sleeve  39  generally between the inner and the outer surfaces  40 ,  41 , to form a single integrated piece, which simplifies implementation with the power tool  10 . 
     A magnet ring  44  with at least two poles is secured to the base portion  28  of the tool accessory holder assembly  16  proximate the inductive coils  43 , and rotates synchronously with the base portion  28  and the spindle  26  when the rotary tool  10  is operated. Those skilled in the art will recognize that instead of a ring, the magnet  44  can also be one or more individual magnets attached along the diameter of the base portion  28 . 
     In the preferred embodiment, the sleeve  39  is formed from an easily moldable, nonelectrically conductive plastic or like material, and the LEDs  20  are Infineon Technologies Hyper-Bright LEDs. However, other light sources are contemplated, such as super bright white LEDs and incandescent light bulbs. Moreover, the light source attachment  14  may include only one LED  20 , or more than two. The preferred inductive coil  42  is a Siemens B82144-A2107-J. However, many other similar inductive coils are contemplated. 
     FIG. 3 depicts an electrical circuit representation of the light source attachment  14  of the present invention. In operation, as the magnet ring  44  is rotated about the longitudinal axis of the spindle  26 , either in a clockwise or a counterclockwise direction, electric current is induced in the coil  43  and supplied to the LED  20 . The current causes the LED  20  to illuminate each half cycle when the LED is forward biased, as shown by an arrow  46 . In FIG. 3, the magnet ring  44  is shown to have four poles. It should be understood however that magnetic ring  44  may have two or more poles, depending on the required characteristics in the final configuration of each different application. 
     Turning now to FIG. 4, the power tool  10  is shown with an extension attachment  48  connected to the front end  34  of the housing  12 . The extension attachment  48  allows the user to reach into places not easily accessible by the tool  10  itself. Included in the extension attachment  48  are a connection portion  50 , an extension portion  52 , and a handpiece portion  54 . A flexible shaft  56  (shown in FIG. 5) is routed coaxially and along the length of the extension attachment  48 . The extension attachment  48  connects to the tool  10  at the connection portion  50 , which is constructed and adapted to be threaded onto the attachment threads  38  in the housing  12  (best shown in FIG.  2 ). When the extension attachment  48  is connected to the tool  10 , the flexible shaft  56  transfers the rotation of the spindle  26  in the power tool  10  (shown in FIG. 2) to an accessory holder assembly  60  at a front end  58  of the handpiece portion  54 . 
     Referring to FIG. 5, the handpiece portion  54  is shown, and includes the accessory holder assembly  60  and a light source attachment  62  which are constructed similarly to the accessory holder assembly  16  and the light source attachment  14  shown in FIG.  2 . The accessory holder assembly  60  is configured and adapted to be attached to the flexible shaft  56 , and the light source attachment  62  is configured and adapted to be screwed onto a threaded portion  64  formed at the front end  66  of the handpiece portion  54 . The light source attachment  62  includes (similar to the light source attachment  14  described above) a generally tubular sleeve  67  which is threaded on an inner surface  68  to cooperatively screw onto the threaded portion  64  of the hand piece portion  54 . A pair of LEDs  69  project from the sleeve  67  near the accessory holder assembly  60 , and are at least partially imbedded in the sleeve  67  between the inner surface  68  and an outer surface  70 . Each LED  69  is electrically connected to an inductive coil  71  formed in the the sleeve  67  between the inner and the outer surfaces. When the light source attachment  62  is attached to the threaded portion  64 , the inductive coils  71  become positioned proximate a magnet  72 , which is fixed to a base  74  of the accessory holder assembly  60 . 
     Similar to the description given above with respect to the LEDs  20 , the LEDs  69  are illuminated when the rotary tool  10  is operated and the rotation of the spindle  26  in the rotary tool is transferred to the flexible shaft  56 , thereby rotating the magnet ring  72 . The rotating magnet ring  72  induces a current in the coils  71 , which is supplied to the LEDs  69 . This arrangement allows the light from the LEDs  69  to be focused in the area front of the accessory holder assembly  60 , where the light is most desirable. 
     Turning now to FIGS. 6-8 and in accordance with another embodiment of the present invention, a light source attachment  76  for the extension attachment  48  includes a generally tubular sleeve  78  that is constructed and adapted to be screwed onto the threaded portion  64  formed at the front end  66  of the handpiece portion  54  (best shown in FIG.  7 ). A pair of LEDs  80  project from the sleeve  78  near the accessory holder assembly  60  and are connected in parallel with an inductive coil  82 , which is also partially imbedded in the sleeve  78  near the accessory holder assembly. The wires connecting the LEDs  80  with the inductive coil  82  are also imbedded within the sleeve  78 . As in the light source attachments  14  and  16  described above, the LEDs  80 , the inductive coil  82  and the wires that connect them are at least partially imbedded in an easily moldable plastic type material for ease of manufacture and implementation with the power tool  10  or the extension attachment  48 . 
     For generating current in the inductive coil  82 , a magnet ring  84  is slipped onto the base portion  86  of the accessory holder assembly  60  that is outside the front end  58  of the hand piece portion  54 , and secured by a jam nut  88 , which screws onto a threaded head portion  90  of the accessory holder assembly (best shown in FIG.  8 ). The magnetic ring  84  may also be secured by a collet nut  92  (best shown in FIG. 6) instead of the jam nut  88 . This arrangement allows the light source attachment  76  to be easily incorporated into the existing extension attachment  48  by the tool operator, without the needs to retrofit the extension attachment at the factory or by a technician. 
     As an alternative to the magnet ring  84 /jam nut  88  arrangement described above, and referring to FIGS. 9 and 10, an inside opening  94  of a generally annular magnet  96  is constructed and configured to matingly attach to an outer hexagonal surface  98  of a nut  100 . The inner opening  102  of the nut  100  is constructed and adapted to be threaded onto the head portion  90  of the accessory holder assembly  60  and tightened against the base portion  86 . The nut  100  extends slightly beyond an inner surface  102  of the magnet  96  so as to prevent the magnet, which is relatively brittle, from coming in contact with the base portion  86 . The nut  100  is also configured to extend sufficiently beyond an outer surface  104  of the magnet  96  to enable a tool to tighten or loosen the nut against or from the base portion  86  of the accessory holder assembly  60 . Those of ordinary skill in the art will recognize that the outer surface  98  of the nut  100  can have shapes other than hexagonal that allow the nut to be tightened and loosened by a suitable tool. 
     The light source attachment  76  is also adapted to be operatively connected directly to the rotary tool  10 . In this case, the sleeve  78  would be screwed onto the threads  38  in the housing  12 , and the magnet ring  84  would be slipped onto the part of the base portion  28  that extends outside the front end  34  of the housing  12  (best shown in FIG.  2 ). The magnet ring  84  can either be secured by the jam nut  88  or the collet nut  36 . The magnet  96 /nut  100  arrangement is also adapted to be secured directly to the rotary tool  10 . The magnet  96  would be secured onto to the base portion  28  by the threaded inner is opening  102  of the nut  100 . When the sleeve  78  and the magnet ring  84  (or the magnet  96 ) is secured onto either the handpiece portion  54  or the rotary tool  10  itself, the inductive coil  82  and the magnet ring  84  are positioned proximate each other as shown in FIGS. 6 and 7. 
     As shown in FIG. 11, the magnet ring  84  (or the magnet  96 ) preferably has 4 poles, and accordingly, flux lines  106  extending from the North to South poles. When the magnet ring  84  (or the magnet  96 ) spins in close proximity to the inductive coil  82 , current is induced in the inductive coil as the flux lines  106  pass alternately through it. As the poles pass by the inductive coil  82 , they generate a positive or negative current in the inductive coil, depending on the pole which is in proximity. The current waveform shown in FIG. 12 is the result of this process. The two LEDs  80  are connected so that their polarities are opposite, and since each LED  80  allows current to flow in only one direction, they switch on and off alternately. As long as the frequency of the switching is greater than that which the human eye can detect, each LED  80  will appear to be on constantly when the tool  10  is being operated. This frequency is controlled by the number of magnetic pole pairs and the frequency at which they pass by the inductive coil  82 . Accordingly, the rotational speed of the tool  10 , and thus, the magnetic ring  84  (or the magnet  96 ) controls the frequency. 
     From the foregoing description, it should be understood that an improved electric-motor rotary power tool has been shown and described which has many desirable attributes and advantages. It is provided with a light source which illuminates the area where the tool is intended to be used. The light source is supplied with a current which is generated from the rotation of the spindle of the tool, and therefore, does not require tapping into the power source of the tool itself. This simplifies the circuitry within the tool and does not drain the power source of the battery operated power tools. 
     While various embodiments of the present invention have been shown and described, it should be understood that other modifications, substitutions and alternatives are apparent to one of ordinary skill in the art. Such modifications, substitutions and alternatives can be made without departing from the spirit and scope of the invention, which should be determined from the appended claims. 
     Various features of the invention are set forth in the appended claims.