the following discussion of the preferred embodiments of the present invention focuses on athletic shoes , and in particular , the incorporation of the novel lighting system in the midsole 20 of an athletic shoe . while athletic shoes are used for purposes of describing the preferred embodiments of the invention , it should be understood that the present invention is not limited to use with athletic shoes , but is suitable for use in all types of footwear , including , but not limited to , work shoes , children shoes , dress shoes , walking shoes , and specialty footwear . referring to fig1 - 4 , the exemplary preferred embodiment of the present invention is illustrated in the context of footwear that includes an upper ( not shown ), typically made of leather , nylon fabric , or other suitable , flexible material , and a resilient midsole or sole 20 . the sole 20 is preferably formed in an injection - molding or thermoforming process from a foamed , resilient , synthetic material , such as ethylene vinyl acetate ( eva ), or polyurethane ( pu ), either of which is capable of providing support for the wearer of the footwear and resiliency to absorb impacts associated with normal walking and running activities . in an athletic shoe , the sole 20 typically comprises a midsole provided with an outsole ( not shown ) attached at a lower surface thereof . the outsole is typically molded from a solid , wear - resistant material , such as rubber and certain polyurethane materials . the use of the solid material for the outsole provides for greater durability , as the typical midsole material tend to wear relatively poorly when exposed to contact with ground surfaces . an insole 21 can be positioned above the sole 20 for additional wearer comfort . in the exemplary embodiment illustrated , the sole includes a lens structure 22 disposed at a rear portion thereof , and one or more thumb grooves 24 are formed in the sole material 20 to enable the wearer to access the lens structure 22 for its easy insertion and removal . the lens structure 22 may be held in place in the sole 20 through a friction fit , an over - center locking arrangement , or more permanently , may be suitably adhered to the midsole material . in the exemplary embodiment shown in fig1 - 4 , the sole 20 incorporates a so - called &# 34 ; cup - sole &# 34 ; type of construction , in which the sole 20 is formed as an upwardly - facing cup into which the upper portion of the shoe is received during attachment of the two respective portions . the side walls of the sole cup may be extended upwardly to lap and adhere to the upper portion for added lateral support of the foot and to provide enhanced adhesion with the upper . for illustration purposes , the sole 20 of the exemplary embodiment is shown with a cutout portion 26 , which reveals a cavity 28 formed in the sole 20 adapted to receive therein a light module 30 . the light module 30 preferably includes a plurality of light emitting diodes ( leds ) 32 protruding therefrom . while the preferred embodiment of the present invention uses light emitting diodes , any suitable , low - power - consumption light source , including incandescent , neon , etc ., light sources would be suitable for use with the present invention . the light generated by the leds 32 is conveyed exteriorly of the shoe by the lens structure 22 , which is preferably formed of a clear plastic or other suitable light - conducting material . the light module 30 , which is preferably formed of a pliable , resilient rubber or plastic material , is provided with a flexible cover 34 . the lighting module 30 , which may be formed in an injection molding process , may also be formed of other suitable materials , such as plastic , fiberglass , etc ., that are capable of supporting therein a lighting circuit for controlling operation of the leds 32 . the light module 30 has a bottom surface 35 and a cavity 33 that contains the light circuit . the light circuit preferably includes a printed circuit board 36 having disposed thereon a pressure sensitive switch 38 , conductive layers 40 , 42 , for conducting power from a power source , such as battery 48 , to a plurality of led contacts 44 , as well as a control circuit 54 and a plurality of terminal contacts 46 , which provide contact locations for connecting the battery 48 to the printed circuit board 36 . the battery 48 may be connected to the terminal contacts 46 using battery support leads 50 , 52 , which serve both to support the battery 48 and to provide electrical connections between the positive and negative terminals of the battery 48 and the printed circuit board 36 . the leds 32 connect to the led contacts 44 through a plurality of led connector leads 45 . in the preferred embodiment of the present invention , the battery 48 is comprised of a standard , 3 - volt , lithium &# 34 ; button &# 34 ; cell , similar to that found in electronic games , calculators , etc . however , it should be understood that other battery types and form factors , such as &# 34 ; aaa &# 34 ; nickel - cadmium , nickel - metal - hydride , alkaline , etc ., dry cells may be utilized in place of the coin - shaped lithium battery shown , in an appropriate design . the leds are relatively low - power - consumption light sources such that , under normal wear conditions , and in the context of the power - conserving circuit of the present invention , the useful life of the battery can exceed the useful life of the shoe , and hence , should not need replacing . in the preferred embodiment , the light module 30 is permanently installed in the sole 20 in a cavity 28 molded in the sole material , and is affixed therein with a suitable adhesive . alternatively , the lens 22 can be held in place via a friction - fit , or over - center locking mechanism , to allow the wearer access to the light module in an embodiment in which the light module 30 is removable in a plug - in , plug - out fashion for easy maintenance , repair , battery replacement , etc . the thicknesses of the sole materials overlying and underlying the module 30 , as best seen in fig3 coupled with the resilient nature of the module 30 in the preferred embodiment , are such that the module 30 is typically not noticeable by the wearer of a shoe in which the light module 30 is incorporated . further , such shoes typically incorporate a resilient insole to support the wearer &# 39 ; s feet , thus further decreasing the wearer &# 39 ; s ability to feel the module 30 with the foot . the pressure switch 38 is preferably a membrane switch , which is disposed on an upper surface of the circuit board 36 . preferably , the switch 38 is disposed on an upper surface of the circuit board 36 , substantially adjacent the cover 34 of the module 30 when the module is disposed in the sole 20 . without pressure being applied to the module 30 , the cover 34 essentially abuts the switch 38 but does not activate it . in response to pressure from the wearer &# 39 ; s foot , the cover 34 of the module 30 is displaced downwardly , thereby causing pressure to be applied to the membrane switch 38 . the membrane switch 38 responds to the pressure by switching from an &# 34 ; open ,&# 34 ; or non - conducting , condition , to a &# 34 ; closed ,&# 34 ; or conducting , state . the change in the conductivity of the membrane switch , which is virtually undetectable by the wearer , causes the light circuit to switch on and off in the manner described in more detail below without the wearer noticing . it should be noted that the thicknesses of the sole 20 and the insole 21 overlaying the module 30 are selected so as not to interfere with the operation of the switch 38 . the control circuit 54 , which is shown in schematic form in fig5 includes a 25 ohm ( ω ) current limiting resistor 540 connected at one end thereof with the switch 38 and battery 48 , and at the other end thereof to the leds 32 . the resistor 540 serves to limit the current supplied to the leds 32 . the drain of an enhancement mode metal oxide semiconductor field effect transistor ( fet ) 548 is connected to the other end of the leds 32 . the fet , which acts as a driver for the leds , is operated in the &# 34 ; switch mode ,&# 34 ; i . e ., it is normally &# 34 ; off ,&# 34 ; or in a non - conducting state , until an appropriate turn - on voltage is applied to the gate thereof , thereby turning it &# 34 ; on &# 34 ; and causing it to be in a conductive state . a 0 . 22 microfarad (&# 34 ; μf &# 34 ;) capacitor 542 is connected with the gate of the fet 548 and to a first end of each of two , 1 - megohm (&# 34 ; mω &# 34 ;) resistors 544 and 546 . the first resistor 544 is connected at a first end thereof to the capacitor 542 and to one side of the switch 38 . the second resistor 546 is connected at a first end thereof to the capacitor 542 and the gate of the fet 548 . the second ends of both resistors are both tied to the negative terminal of the battery 48 and the source of the fet 548 , all of which are commonly tied to electrical ground . the operation of the lighting control circuit 54 illustrated is as follows . in the quiescent state , with the wearer standing still in the shoe , the switch 38 will be in the closed condition . if the capacitor 542 is fully charged , no current can flow into the gate of the fet 548 , and thus , the fet 548 will not conduct . the fet 548 is therefore &# 34 ; off ,&# 34 ; and the leds 32 are likewise &# 34 ; off .&# 34 ; as soon as the wearer removes pressure from switch 38 , such as by taking a step , or by jumping , the switch 38 opens . this permits the capacitor 542 to discharge through the resistor 544 at a rate defined by the rc time constant defined by the capacitor 542 and the resistor 546 , in this case , 0 . 22 seconds . it will be noted that , while switch 38 is closed , the first end of the resistor 544 is maintained at a potential of 3 volts by the battery 48 , thereby preventing the capacitor 542 from discharging . upon landing , or other re - application of pressure to the switch 38 , the switch 38 closes . this permits current to flow through the capacitor 542 , causing it to charge at a rate defined by the same rc time constant ( i . e ., the capacitance of capacitor 542 , multiplied by the resistance of resistor 546 ) described above . it will be noted that a discharged capacitor is initially a &# 34 ; short circuit &# 34 ; when current is first applied to it . thus , as soon as the switch 38 closes , the voltage at the gate of the fet 548 ( connected to the node defined by capacitor 542 and resistor 546 ) is almost instantaneously at the same voltage as the battery , in this case , 3 volts . the fet 548 thus turns on and the leds 32 light up . as the capacitor 542 charges , the voltage at the gate of the fet 548 begins to drop . a capacitor , when fully charged , does not pass current . thus , when the gate voltage drops below the level needed to maintain the fet 548 in an on state , it will turn off and stop conducting . this will occur in approximately 0 . 22 seconds for the component values discussed above . the circuit is thus again in the quiescent state . accordingly , what is provided by circuit 54 is a timer that uses the switching capabilities of the fet 548 to switch the leds on and then off again in a predetermined manner . one feature of the circuit shown in fig5 is its operation for a predetermined period of time after the switch 38 has been operated , in order to &# 34 ; pulse &# 34 ; the leds 32 &# 34 ; on &# 34 ; for such period . after the predetermined period of time , the fet no longer conducts , due to the charging of the capacitor , and the leds cease illumination . in addition , if the switch 38 is re - opened ( such as when the wearer lifts a foot ) during the charging of the capacitor 542 , the capacitor will quickly drain any acquired charge through resistor 544 , and the fet will no longer conduct , since the voltage at the gate of the fet will be zero . thus , the operation of the leds is controlled both by the rc time constant of the circuit and the switch 38 . this , essentially &# 34 ; digital ,&# 34 ; operation can be seen with reference to fig8 which shows the initiation of illumination of the leds 32 at time t 0 , where the led output goes from &# 34 ; 0 &# 34 ;, or &# 34 ; off &# 34 ;, to &# 34 ; 1 &# 34 ;, or &# 34 ; on &# 34 ;. the leds remain &# 34 ; on &# 34 ;, i . e ., lit , for a predetermined period of time , and then cease illumination at time t n . in the embodiment shown in fig5 t n = 0 . 22 seconds . however , as skilled practitioners will readily recognize , the rc time constant for the circuit 54 , and hence , the value of t n , can easily be modified , one way or the other , by an appropriate adjustment of the respective values of the capacitor 542 and the resistor 546 . as an alternative embodiment to that shown schematically in fig5 it is possible to use the fet 548 to switch a flasher control circuit , or oscillator , such as the device 550 shown in fig6 . the flasher control circuit 550 preferably comprises a vitelic vh215 led flasher circuit , which is a known , monolithic integrated circuit that is fabricated using a metal gate complementary metal - oxide semiconductor ( cmos ) process . while other suitable oscillator circuits may be used with the present invention , the vh215 is a preferred device for use in flashing the leds 32 because of its selectably - different modes of operation , as described more fully below . the vh215 circuit has multiple flash modes , including a &# 34 ; one - shot &# 34 ; mode and an &# 34 ; on / off &# 34 ; mode for flashing a series of connected leds . in the one - shot mode , the vh215 responds to the grounding of a selected input to the circuit by providing for either a sequential or a random flashing of the leds for 12 or 24 flashes . in the on / off mode , the vh215 will perform either a sequential or a random flash of the leds for as long as an on / off &# 34 ; trigger &# 34 ; is tied to ground . in the preferred embodiment , the vh215 is set to the on / off mode and the fet 548 is used as the on / off trigger . the length of time the on / off trigger is tied to ground is controlled by the rc time constant defined by the capacitor 542 and the resistor 546 , as described above in connection with the first embodiment . in this fashion , after the capacitor 542 is discharged upon a first operation of the switch 38 ( e . g ., the wearer jumps ), a sequential flashing of the leds is initiated upon the next operation of switch 38 when the gate of the fet 548 is supplied with voltage , due to the capacitor 542 initially behaving as a short in the manner discussed above . the length of time that the on / off trigger of the vh215 is tied to ground , and thus , &# 34 ; on &# 34 ;, is controlled by the factory - selectable rc time constant and the switch 38 in the same manner as described above . as can be seen in fig8 with the circuit shown in fig6 the leds 32 can be made to flash on and off at a predetermined rate for a predetermined period of time . that is , as shown in fig8 the leds 32 will flash &# 34 ; on &# 34 ; at time t 0 , &# 34 ; off &# 34 ; at time t 1 , &# 34 ; on &# 34 ; at time t 2 , &# 34 ; off &# 34 ; at time t 3 , and so on , for the prescribed length of time determined by the rc time constant discussed above . the rate of flashing will depend on the oscillator rate of the pulse control circuit 550 , which is also factory selectable . while the vitelic vh215 is the preferred flashing control circuit 550 , those skilled in the art will recognize that any suitable oscillator circuit may be substituted for the vh215 circuit to provide for the flashing of the leds 32 for a predetermined period of time . as with the vh215 circuit , the operation of the oscillator will be determined by the factory selectable rc time constant and the switch 38 in the same manner as discussed above . fig7 shows the use of a generic oscillator circuit for causing the leds 32 to flash at a predetermined rate in a manner similar to that discussed above with reference to fig6 . in fig7 an oscillator circuit 560 is disposed between the capacitor 542 and the fet 548 . in this embodiment , with a discharged capacitor 542 , and when the switch 38 is operated , the oscillator circuit 560 is provided with an input voltage equal to the voltage on the battery 48 . upon receipt of this input voltage , the oscillator circuit 560 provides a stream of pulses at a desired frequency to the gate of the fet 548 . the pulse stream , in turn , causes the fet 548 to switch between a conducting and a non - conducting state at a rate equal to the frequency of the oscillator 560 . this , in turn , causes the leds 32 to flash on and off at a frequency equal to that of the oscillator 560 . this is represented in fig8 by the dashed lines . as with the embodiments of the invention shown in fig5 and 6 , the oscillator circuit 560 will remain &# 34 ; on &# 34 ;, and thus produce flashes in the leds , until the input voltage thereto drops below a threshold voltage of the oscillator circuit 560 , due to the charging of the capacitor 542 , or until the switch 38 is again operated , whichever occurs first . while any suitable oscillator circuit 560 may be utilized with the present invention , such circuits being known to those skilled in the art , it is preferred that a low - power - consumption oscillator be utilized to increase the life of the battery 48 . while the above discussed embodiments of the present invention have been described using &# 34 ; enhancement mode &# 34 ; field effect transistors , one skilled in the art will readily recognize that &# 34 ; depletion mode &# 34 ; field effect transistors can also be utilized to good effect . the operation of the circuit can also be altered using the depletion mode transistors such that the lighting circuit is operative to light when the wearer &# 39 ; s foot is lifted from the ground , as opposed to when the wearer &# 39 ; s foot contacts the ground . in addition , the exemplary embodiments of the present invention described above employ an rc time constant of 0 . 22 seconds , as defined by the 0 . 22 μf capacitor 542 and the one mω resistor 546 . those skilled in the art will readily recognize that the rc time constant can be varied by changing the values for the capacitor 542 and / or the resistor 546 to make the period , or pulse , during which the leds 32 flash on and off , shorter or longer , as desired . further , while the preferred embodiments illustrate the placement of the lighting module 30 in the heel area of the shoe generally below the calcaneus , or large heel bone , of the wearer &# 39 ; s foot , one skilled in the art will readily recognize that the lighting module may be disposed at almost any desired location within the shoe . for example , it is possible to locate the switching mechanism in other positions , such as the toe area or arch area of the shoe , without departing from the scope of the present invention . in addition , it should be understood that it is not necessary for the lighting devices such as leds 32 to be located adjacent to the lighting module 30 , as shown in the exemplary preferred embodiment . the lighting devices may be positioned at any desired location about the shoe and connected with the lighting module 30 by means of thin wires , or flat , flexible conductors . thus , lights may be positioned on the front , top , sides , tongue or upper of the shoe , as well as or in addition to , the rear of the shoe , as shown in the drawings . of course , those skilled in the art will readily appreciate that numerous other modifications and / or additions can be made to the above - discussed features of the present invention without departing from its spirit . it is intended that all such modifications and / or alternative embodiments , including those discussed above , fall within the scope of the claims appended below .
a device for use in footwear for producing pulsed light can be disposed in the sole of a shoe . the device includes a circuit having a switch responsive to pressure from the wearer &# 39 ; s foot that activates a lighting circuit for a predetermined period of time or until the switch is operated again . the lighting circuit produces a pulsed light visible exteriorly of the sole of the shoe . the circuit can be controlled to operate either when the wearer &# 39 ; s foot is brought into contact with , or when it is removed from , the ground .