Abstract:
A renewable energy flashlight comprises a housing and a barrel located within the housing. A wire coil wraps around the barrel, between the barrel and the housing. A magnet oscillates within the barrel when the flashlight is shaken, generating an alternating current in the coil. Two springs at either end of the barrel cause the magnet to recoil when the magnet strikes the springs. As an alternative, rebound magnets oriented to repel the charging magnet may be installed within the barrel at either end, to cause the magnet to recoil from the ends. An electronics assembly within the housing includes a capacitor for storing charge, a rectifier connected to the capacitor, and means for conducting current flowing in the coil to the rectifier, to charge the capacitor. An LED is connected to the capacitor by means of a switch, and lights up when the switch is switched on.

Description:
This application is a continuation-in-part of application Ser. No. 09/022,103, filed Feb. 11, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a renewable energy flashlight. 
     2. Description of the Prior Art 
     Flashlights are extremely useful as portable lighting devices. However, several features of conventional flashlights limit their usefulness. Flashlights are commonly needed in emergencies, such as when the owner&#39;s car breaks down or the owner&#39;s electricity goes out. But there is no guarantee that when the emergency occurs, the flashlight will work. Currently, most flashlights use batteries, which rely on chemical reactions and therefore have limited useful life, as well as limited storage life. So, even if the flashlight was put in a drawer with fresh batteries, it may not work three years later when it is needed. Batteries can also cause corrosion due to leakage, rendering the flashlight unusable, even with fresh batteries. Further, most flashlights use incandescent lamps, which are prone to filament damage from shock, such as from being dropped. Incandescent lamps also burn out. 
     A second concern with conventional flashlights is how wasteful they are, both in the environmental sense and in a financial sense. Batteries are rapidly becoming a hazard to our environment due to their current methods of disposal. Also, they are expensive, and have to be replaced frequently. 
     A need remains in the art for a renewable energy flashlight that always works, even after being dropped or left in the car for years, without requiring batteries or incandescent lamps. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a renewable energy flashlight that always works, even after being dropped or left in the car for years, without requiring batteries or incandescent lamps. 
     The renewable energy flashlight of the present invention utilizes a magnet, which is oscillated through a coil of wire by shaking the flashlight, to generate electricity for charging a capacitor to power a light emitting diode. 
     The renewable energy flashlight comprises an elongated housing forming an opening at one end, a barrel assembly located within the housing which includes a hollow elongated barrel disposed within the housing, a wire coil wrapped around the barrel and disposed between the barrel and the housing, a magnet disposed within the barrel and sized to freely oscillate within the barrel when the barrel is shaken, two springs attached within the barrel and at either end of the barrel to cause the magnet to recoil when the magnet strikes the springs, wherein the magnet oscillates within the barrel when the barrel is shaken, whereby the magnet passes back and forth through the wire coil and causes current to flow within the coil. As an alternative, rebound magnets oriented to repel the charging magnet may be installed within the barrel at either end, to cause the magnet to recoil from the ends and oscillate efficiently. The flashlight also includes an electronics assembly located within the housing, including a capacitor for storing charge, a rectifier connected to the capacitor, means for conducting current flowing in the wire coil to the rectifier, which rectifies the current and provides rectified current to the capacitor, charging the capacitor, a light emitting diode (LED) located near the housing opening, and switch means for selectively connecting the charged capacitor to the LED, whereby the LED selectively lights up. 
     As a feature, the flashlight includes an LED protecting diode connected between the LED and the capacitor, for protecting the LED from high voltage surges. A resistor and a capacitor protecting diode connected between the LED and the capacitor, protect the capacitor from sustained overvoltage conditions. The LED protecting diode and the capacitor protecting diode are zener diodes. 
     The switch comprises a reed switch located within the housing, and a selectively movable magnet located external to the housing for activating the reed switch. Generally the charging magnet and the switch magnet are neodymium magnets. The wire coil is formed of magnet wire, and the housing and the barrel are formed of plastic. The springs are formed of stainless steel. Alternatively, the rebound magnets are neodymium magnets. 
     The flashlight also includes a lens affixed within the housing opening adjacent to the LED, for focusing light from the LED. The lens and the housing are hermetically sealed. This forms a hermetically sealed compartment containing the electronics assembly and the barrel assembly, making the flashlight explosion proof. 
     In general, the lens is located less than its focal distance away from the LED, whereby the light from the LED forms an expanding beam. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cutaway side view depicting a first preferred embodiment of the flashlight. 
     FIG. 2 is a cross section of the flashlight of FIG. 1, taken along section A—A. 
     FIG. 3 is a cross sectional view of the barrel of the flashlight of FIGS. 1 and 2. 
     FIGS. 4 a ,  4   b  and  4   c  are detailed cutaway views showing the switch of the flashlight of FIG.  1 . 
     FIG. 5 is a schematic diagram showing the electrical circuit of the flashlight of FIG.  1 . 
     FIGS. 6 a ,  6   b  and  6   c  are waveform diagrams showing voltage waveforms at specific points in the circuit of FIG.  5 . 
     FIG. 7 is a cutaway side view depicting a second preferred embodiment of the flashlight. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 is a cutaway side view depicting the preferred embodiment of flashlight  100 . FIG. 2 shows a cross sectional view of flashlight  100 , taken along A—A. Electricity is generated when flashlight  100  is shaken longitudinally, which causes charging magnet  12  to slide back and forth inside barrel  14 , and thus through wire coil  18 , which is wound around barrel  14 . Magnet  12  bounces between springs  16 , which conserve energy while changing the direction of magnet  12 . As magnet  12  passes through wire coil  18 , a sinusoidal voltage wave is created between two wires  19  exiting coil  18 , as shown in FIG. 4 a , thus generating an alternating current. Each sinusoidal wave is converted into a pair of positive going waves by bridge rectifier  20 , as shown in FIG. 4 b . These positive waves charge gold capacitor  22 , which accumulates charge with each pass of magnet  12 , as shown in FIGS. 4 b  and  4   c . Charged gold capacitor  22  supplies energy to high intensity light emitting diode (LED)  23 , coupled via a reed switch  26 . LED protection zener diode  24  protects high intensity LED  23  from excessive voltage surges. Lens  36  collects light from high intensity LED  23  and focuses the light beam. 
     Housing  10  is sized to contain the mechanical, electrical, and optical components of flashlight  100 . Housing  10  is preferably formed of plastic with an inside diameter of 1.270 inches and a wall thickness; of 0.100 inches. It is nonmetallic to prevent eddy currents from forming in housing  10 , which would slow charging magnet  12  during its  10  travel through barrel  14 . A means for sealing lens  36  and capping the end opposite lens  36  is provided to maintain a watertight and explosion proof seal (i.e. flashlight  10  can be used in an explosive environment, as it will not generate sparks which could ignite natural gas, for example). 
     Charging magnet  12  is preferably composed of three neodymium disc magnets stacked to form one magnet having poles on opposite ends of its cylindrical body. Neodymium magnets are preferred due to their high magnetic field strength. The individual magnets are 0.75 inches in diameter and 0.375 inches thick, and are stacked end to end to form one magnet array 1.125 inches long. The size of charging magnet  12  determines the current output and rate of charge. A larger charging magnet diameter can provide higher current. A longer charging magnet will provide longer current pulses. A length-to-diameter ratio of one and a half or more is recommended to maintain proper alignment in barrel  14 . 
     Lens  36  is attached to housing  10  by lens retainer  44 , which threads onto housing  10 . Lens sealing o-rings  38  are formed of a pliable material such as silicone. Two lens sealing rings  38  are used, one on each side of lens  36 . They provide a hermetic seal between housing  10  and lens  36 , and cushion lens  36  from shock and stress. Lens retainer o-ring  42  provides a seal and protects threads between lens retainer  44  and housing  10 . Note that a double hermetic seal is formed between housing  10  and lens retainer  44 , both at the lens and at the join between retainer  44  and housing  10 , by use of the two lens sealing rings  38  and lens retainer o-ring  42 . 
     Lens  36  has a focal length of approximately one inch. The diameter of lens  36  is preferably about an inch and a half. Lens  36  should be sized and positioned so that nearly all of the light emitted light from LED  23  is collected by the lens. When lens  36  is located one focal length away from LED  23 , the light emitted from LED is collimated. Moving the lens closer to LED  23  results in an expanding beam of light, which is the preferred position of the lens. Moving lens  36  farther away from LED  23  results in a converging beam of light. Lens  36  may be glass, but preferably is formed of an unbreakable optical material such as polycarbonate plastic. The curvature of lens  36  helps provide pressure resistance for underwater applications. 
     FIG. 3 shows barrel  14  and electronics assembly  21 . Electronics assembly  21  may be disposed within barrel  14 , as shown, or may be located within housing  10 , beyond barrel  14 . Barrel  14  is made from a hard nonmetallic substance such as plastic. It forms a spool  34  for winding wire coil  18 , serves as a guide for magnet  12 , and houses the electronic components. Spool  34  for winding wire coil  18  is created by reducing the outside diameter of barrel  14  midway along magnet  12 &#39;s travel path. Barrel  14  has a longitudinal bore having a diameter slightly larger than that of magnet  12 , to reduce air compression and reduce friction by minimizing wall contact with magnet  12 . Clearance would preferably be around 0.020 inches. The length of the longitudinal bore in barrel  14  should be approximately five times the length of magnet  12  plus the length of two springs  16 . This allows both polarities of the magnetic field to pass completely through wire coil  18 , thus avoiding an overlapping condition of current waves during consecutive passes. 
     Springs  16  are preferably formed of stainless steel, and have enough resiliency to prevent “bottoming” of magnet  12 . Stainless steel should be used because of its antimagnetic property. Springs  16  are not absolutely required for operation, but they do assist in conservation of energy by rebounding magnet  12 . 
     Wire coil  18  is formed of insulated copper magnet wire. The preferred wire gauge is AWG #30. Wire coil  18  is optimized for the desired application by carefully selecting the wire gauge and coil geometry. Altering the wire gauge changes the voltage generated by the wire coil. As the wire is made smaller, the voltage increases, resulting in a reduction in current. 
     With regard to the geometry of wire coil  18 , the inside portion of wire coil  18  must be as close to magnet  12  as possible, meaning that the thickness of the barrel wall at spool  34  must be very thin, around 0.05 inches, to keep the coil in the highest magnetic density region of the magnetic field. The diameter of barrel  14  is about 0.88 inches. The outside portion of wire coil  18  is limited by the strength of magnet  12  and the bore of barrel  14 , because magnetic field strength drops off rapidly as distance from the magnet increases. The length of coil  18  should be close to length of magnet  12 . If coil  18  is shorter than magnet  12 , there is a loss of efficiency, because the magnetic field is being cut by the coil less of the time. If coil  18  is longer than magnet  12 , both magnetic fields will be cut by the coil at the same time, canceling the current during this time. 
     In the preferred embodiment, the dimensions of coil  18  are 1.125 inches long, 0.87 inches inside diameter, and 1.25 inches outside diameter. Such a coil will require approximately 2000 turns of AWG #30 magnet wire with an approximate length of 200 yards. 
     FIG. 5 shows electronics assembly  21  in greater detail. Wires  19  connect wire coil  18  to bridge rectifier  20 . Wires  19  may simply be the same wire used in coil  18 , extended beyond the coil and terminated at bridge rectifier  20  during assembly. 
     Bridge rectifier  20  is a conventional bridge rectifier with four diodes  29 . The AC inputs are connected to wires  19  from coil  18 , and the DC outputs are connected to capacitor  22  in the standard configuration, rectifier positive to capacitor positive and rectifier negative to capacitor negative. Bridge rectifier  20  may be built using discrete diodes  29 , or a conventional modular bridge rectifier may be used. 
     Gold capacitor  22  is preferably a microcomputer CMOS memory backup gold capacitor. In the preferred embodiment, capacitor  22  is 1.0 Farad with a rated voltage of 5.5 WVDC (working volts D.C.). If a larger capacitor is used, the time of shaking required to charge the capacitor is longer, and so is the amount of energy that can be stored. 
     LED protection zener diode  24  protects LED  23  from excessive forward voltage. The zener voltage is selected to not exceed the maximum forward voltage of LED  23 . Capacitor protection zener diode  27  and current limiting resistor  25  protect capacitor  22  from overvoltage for extended periods of time. The zener voltage is selected to be slightly less than the maximum voltage rating of capacitor  22 . The resistor is selected to bleed excess voltage from capacitor  22  while having minimal effect on charging pulses. 
     Reed switch  26  is single pole single throw with low resistance contacts made for low voltages at low currents. It is placed in series with the load to provide a means of connecting LED  23  to capacitor  22  to generate light. Reed switch  26  disconnects LED  23  from capacitor  22  when light is not required, conserving energy in capacitor  22 . LED  26  should be disconnected from capacitor  22  during shaking in order to store energy in capacitor  22  more efficiently. LED  26  may be left connected to capacitor  22  during shaking, to provide a flashing effect. 
     Reed switch  26  is mounted in barrel  14  in a position very close to the inside wall of housing  10  when barrel  14  is installed. Barrel  14  must be properly oriented, by rotating it, within housing  10  to assure alignment of Reed switch  26  and actuating magnet  30 . After proper alignment is obtained, barrel  14  is glued or otherwise secured into housing  10 . 
     Reed switch  26  must be properly oriented, in order to prevent charging magnet  12  from affecting it. Reed switch  26  must be oriented perpendicular to the axis of charging magnet  12 . It is spaced apart from this axis, but centered with relation to it (put another way, reed switch  26  is parallel to a plane through the center of charging magnet  12 ). 
     FIGS. 4 a  and  4   b  show the operation of reed switch  26  in detail. FIG. 4 a  shows reed switch  26  in the open position, and FIG. 4 b  shows reed switch  26  is the closed position. Switch activating magnet  30  is preferably a small neodymium magnet, 0.25 inches in diameter, ⅛ inch thick, with poles o opposite ends of its cylindrical shaft. Switch activating magnet  30  is captivated by switch slide  28 , which is retained by switch retainer  32 . Switch activating magnet  30 , switch slide  28  and switch retainer  32  are inserted into a pocket in housing  10  adjacent to reed switch  26 . Reed switch  26  will be off when switch activating magnet  30  is directly over it. In this position it is effectively immune to the magnetic field of charging magnet  12 . Reed switch  26  will turn on when switch activating magnet  30  is moved approximately 0.1 inch from the off position. 
     Alternatively, switch activating magnet  30  may also be placed so that in its first position, it is a sufficient distance away from reed switch  26  for reed switch  26  to be off, and in its second position, it is even further from reed switch  26  so that reed switch  26  turns back on. 
     FIG. 6 a  shows a voltage waveform across wire coil  18 . The waveform is sinusoidal, with gaps between the sine waves when the magnet is away from coil  18 . The amplitude and frequency of the sine wave will vary depending upon the speed at which charging magnet  12  passes through coil  18 . 
     FIG. 6 b  shows the voltage across capacitor  22  (due to the rectified current provided by rectifier  20 ). The underlying voltage of capacitor  22  rises with time as flashlight  100  is shaken. 
     FIG. 6 c  shows the voltage across capacitor  22  after flashlight  100  has been shaken sufficiently to charge up capacitor  22 . At this point, capacitor protection zener diode  27  and current limiting resistor  25  bleed voltage from capacitor  22 , preventing overcharging of capacitor  22 . 
     FIG. 7 is a cutaway side view depicting a second preferred embodiment  200  of the flashlight, which utilizes rebound magnets  17  rather than springs  16  in the ends of barrel  14  to assist in oscillating the charging magnet  12 . The embodiment of FIG. 7 is very similar to the embodiment of FIG. 1, and duplicated reference numbers indicate similar features. Rebound magnets  17  are installed in both ends of barrel  14 , and oriented to repel charging magnet  12 . Thus, the south end of one rebound magnet  17  faces the south end of charging magnet  12 , and the north end of the other rebound magnet  17  faces the north end of the charging magnet. Each rebound magnet  17  opposes the travel of charging magnet  12  as it approaches that magnet  17 , and cause it to repel back towards the center of barrel  14 . The operation of flashlight  200  is therefore similar to that of flashlight  100 , except that operation is smoother and quieter since magnets rather than springs provide the recoil from the ends. 
     Rebound magnets  17  are preferably neodymium disk magnets, and are preferably 0.5 inches in diameter, and 0.25 inches thick. Rubber bumbers  15  are attached to the ends of charging magnet  12  (or alternatively to the inner ends of rebound magnets  17 ) to prevent sharp impact between the rebound magnets and the charging magnet, if the flashlight is shaken vigorously or dropped. Rubber bumbers  15  are typically dome shaped or semispherical, and may attached with pressure sensitive adhesive on the flat side of the bumper. 
     While the exemplary preferred embodiments of the present invention are described herein with particularity, those skilled in the art will appreciate various changes, additions, and applications other than those specifically mentioned, which are within the spirit of this invention.