as used throughout the specification , including the claims , the term “ hands - free ” means control of a dispensing mechanism without the need for use of hands . in addition , as used throughout the specification , including the claims , the term “ towel ” refers generally to an absorbent paper or other suitable material used for wiping or drying . as shown in fig1 , in a preferred embodiment of the invention , a hands - free towel dispenser 10 comprises a cabinet 12 comprising a back wall 14 , two side walls 16 , 18 , a top wall 20 , a bottom or base wall 22 , and an openable and closable front cover 24 . the front cover 24 may be pivotally attached to the cabinet , for example , by hinge 26 , for easy opening and closing of the cover 24 when a supply of towels such as main roll 28 is placed in the cabinet 12 . the towel dispenser 10 may be mounted to a wall or other supporting member by any convenient means such as brackets , adhesives , nails , screws or anchors ( not shown ). as shown in more detail in fig2 , 3 and 4 , the hands - free dispenser 10 further comprises a dispensing mechanism for dispensing a length of towel to the outside of the dispenser 10 . such dispensing mechanism may comprise drive roller 32 , pinch roller 34 , transfer bar 36 and roll support cup 38 a and roll support arm 38 b . the dispensing mechanism enables dispensing of a predetermined length of towel to the outside of the towel dispenser 10 through slot 40 , where the towel can be grasped by the user and torn off along a serrated edge 43 of a blade 42 . the dispensing mechanism operates to dispense towels either from a main roll 28 or a stub roll 30 . the means for controlling dispensing of a paper from the main roll 28 once the stub roll 30 has been depleted comprises a transfer bar 36 , which is described in detail in u . s . pat . no . 4 , 165 , 138 , the disclosure of which is incorporated by reference herein . as shown in fig1 , 2 and 3 , main roll 28 is first loaded into the cabinet 12 onto roll support cup 38 a and roll support arm 38 b located opposite each other on side walls 16 , 18 , respectively , and forming main roll station 48 ( fig1 ). a length of towel from main roll 28 is then threaded behind transfer bar 36 including a fork 37 a and a cam 37 b , and over drive roller 32 so that towel sheeting 50 will be pulled between the drive roller 32 and the pinch roller 34 in a generally downward motion when the drive roller 32 is rotated by operation of a motor 88 shown in fig4 . as the towel sheeting 50 is pulled downwardly , it is guided along a wall 52 of the serrated blade 42 and out slot 40 . the length of towel sheeting 50 dispensed from towel dispenser 10 can be set to any desired length . preferably , the dispenser 10 releases about ten to twelve inches of towel sheeting 50 per dispensing cycle . the towel sheeting 50 is then removed by tearing the length of dispensed towel sheeting 50 at the serrated edge 43 of blade 42 . when the main roll 28 has been partially depleted , preferably to about a four - inch diameter as indicated by low paper indictor 56 , the dispenser cover 24 is opened by an attendant , and the main roll 28 is moved down to a stub roll station 54 . the main roll 28 then becomes stub roll 30 and enables a new main roll 28 to be loaded onto roll support cup 38 a and roll support arm 38 b in main roll station 48 . when stub roll 30 is completely depleted the new main roll 28 begins feeding paper 50 between the drive roller 32 and pinch roller 34 out of the dispenser 10 when the motor 88 is activated . when the low paper indicator 56 indicates that the new main roll 28 is low , the attendant opens cover 24 , an empty core ( not shown ) of stub roll 30 is removed from the stub roll station 54 and discarded , and new main roll 28 is dropped into position into the stub roll station 54 where it then becomes stub roll 30 and continues feeding . a main roll 28 is then positioned on the roll support cup 38 a and roll support arm 38 b . the basic transfer mechanism for continuously feeding towels from a stub roll until completely used and then automatic transfer to a main roll is described in detail in u . s . pat . no . 4 , 165 , 138 . hands - free operation of the dispenser 10 is effected when a person places an object such as their hands in front of a photo sensor 82 shown in fig4 . the photo sensor 82 activates the motor 88 to dispense a predetermined length of towel sheeting 50 . the dispenser 10 has electric circuitry which , as will be described below with reference to fig4 – 8 , ensures safe , efficient and reliable operation of the dispenser 10 . referring now to fig4 , a cutaway view of a portion of the dispenser 10 is shown . in fig4 , a circuit board 81 is mounted to a mechanical plate 80 of the dispenser 10 . note that the circuit board is mounted between the mechanical plate 80 and the wall 16 of the cabinet 12 . the photo sensor 82 is seated within a mounting tube 83 and is coupled to the circuit board 81 by leads or wires 84 , 85 . as will be described below with reference to fig5 , the photo sensor 82 reacts to changes in light intensity . light passes from a room , through an opening 86 in the movable front cover 24 of the dispenser 10 , to the photo sensor 82 . a clear plastic lens 87 is fitted into the opening 86 . the lens 87 prevents debris from clogging or blocking the opening 86 which might prevent light from reaching the sensor 82 . the lens 87 also prevents debris from falling into the dispenser 10 which might cause the dispenser 10 to malfunction . also shown in fig4 is the motor 88 which is attached to the drive roller 32 . the motor 88 , including a gearbox ( not shown ), are available from skil corporation in chicago , ill . the motor 88 is placed partially within the drive roller 32 and is powered by a rechargeable battery 90 , also available from skil corporation . the battery 90 is coupled to the motor 88 via the circuit board 81 by wires or leads 92 , 94 which are connected or soldered to the circuit board 81 . a solar panel 96 , is located on the top 20 of the dispenser 10 as shown in fig1 . the solar panel 96 shown , which comprises an array of one or more photovoltaic cells , is made by solarex corporation in frederick , md . the solar panel 96 is coupled to the battery 90 and control circuitry 98 via the circuit board 81 by wires or leads 100 , 102 which are connected or soldered to the circuit board 81 also . the solar panel 96 provides power to control circuitry 98 for controlling the dispensing mechanism of the dispenser 10 . in a preferred embodiment , the solar panel 96 provides power to control circuitry 98 ( fig5 ) which will manage motion sensing , rotation control , safety features , and recharging of the battery 90 . in a second embodiment , the solar panel 96 provides power to the control circuitry 98 which will manage motion sensing , rotation control and safety features , but the battery 90 will be replaced at desired intervals and will not be recharged by the control circuitry 98 . when the solar panel 96 is not exposed to light , the solar panel 96 does not supply power to the control circuitry 98 and the motor 88 cannot be turned on . the solar panel 96 functions as an on - off switch for the dispenser 10 and thereby prevents the battery 90 from becoming unnecessarily discharged when the lights are off . if the control circuitry 98 is not powered by the solar panel 96 , the motor 88 cannot be turned on . referring now to fig5 , a schematic diagram of the control circuitry 98 is shown . the control circuitry 98 controls the “ hands - free ” operation of the dispenser 10 . more specifically , the control circuitry 98 controls and / or performs the following functions : ( 1 ) sensing when an object such as a person &# 39 ; s hand is in front of the photo sensor 82 and turning the motor 88 on ; ( 2 ) sensing when the proper length of towel sheeting 50 has been dispensed and then turning the motor 88 off ; ( 3 ) sensing when towel sheeting 50 has jammed inside of the dispenser 10 and turning the motor 88 off ; ( 4 ) sensing when the front cover 24 of the dispenser 10 is open and preventing operation of the motor 88 ; ( 5 ) creating a short delay , preferably about two seconds , between dispensing cycles ; and ( 6 ) charging of the battery 90 by the array of one or more photovoltaic cells 96 . the values of the components shown in the schematic diagram of fig5 are as listed below : all diodes are part nos . in4148 or in914 from diodes , inc . operational amplifiers ic 1 a and ic 1 b are on circuit board icl7621dcpa from maxim . transistors q 1 and q 2 are part no . 2n3904 from national . reed switches rd 1 and rd 2 are part no . mins1525 - 052500 from cp - claire . the photo sensor 82 shown is a cadmium sulfide (“ cds ”) motion detector manufactured by silonex corporation located in plattsburg , n . y . the photo sensor 82 is a variable resistance resistor . the resistance of the photo sensor 82 changes depending on the amount of light to which the photo sensor 82 is exposed . if the amount of light on the photo sensor 82 is high , the photo sensor &# 39 ; s resistance becomes relatively low . if the amount of light on the photo sensor 82 is low , the photo sensor &# 39 ; s resistance becomes relatively high . in ambient light , the photo sensor 82 has a certain resistance which causes voltage v a to be less than a reference voltage v b . voltage v a and reference voltage v b are the positive and negative inputs , respectively , of operational amplifier ic 1 a . when voltage v a is less than reference voltage v b , the operational amplifier ic 1 a output voltage v m1 , goes to negative , i . e ., v m1 is at zero voltage . when voltage v m1 is at zero voltage , the motor 88 will not operate . note that the reference voltage v b is determined by and adjusts according to the ambient light level in a room . therefore , the reference voltage v b is not preset to any particular light level . a reference voltage circuit 104 sets the reference voltage v b according to the ambient light level of a room . because the reference voltage circuit 104 sets the reference voltage v b according to the ambient light level in a room , no adjustments need to be made to the dispenser 10 based on how high or low the ambient light level is for a particular room . furthermore , the combination of the photo sensor 82 and the reference voltage circuitry 104 permit the photo sensor 82 to trigger the dispenser 10 when a person &# 39 ; s hand comes within approximately 10 – 12 inches from the sensor 82 . the reference voltage circuit 104 includes resistors r 2 and r 3 and capacitor c 1 . resistors r 2 and r 3 are connected to the positive terminal , solar panel +, of the solar panel 96 which provides a voltage b + when the solar panel 96 is exposed to light . in ambient light , voltage v a is approximately 0 . 5 ( b + ). when a person places an obtrusion such as their hand within a predetermined distance of the photo sensor 82 , preferably within 10 – 12 inches , the amount of light reaching the photo sensor 82 is decreased sufficiently to cause the photo sensor &# 39 ; s resistance to increase to a level where voltage v a becomes greater than voltage v b and thereby causes the output v m1 of operational amplifier ic 1 a to be a positive voltage . the operational amplifier ic 1 a output voltage v m1 is passed through diode d 1 and is coupled to the positive input of operational amplifier ic 1 b . reference voltage v c is provided between resistors r 5 and r 6 and is the negative input of operational amplifier ic 1 b . if voltage v m1 is greater than reference voltage v c , then the output of the operational amplifier ic 1 b , v m2 , is at a positive voltage . when the output voltage v m2 is at positive voltage , n - p - n transistor q 1 is closed , thereby causing a current to flow through coil cl 1 which in turn closes coil relay rly 1 . when rly 1 is closed , the motor 88 runs because the motor &# 39 ; s positive terminal , motor +, is connected to the battery &# 39 ; s positive terminal , battery +. in order to stop the motor 88 from turning after a predetermined amount of towel sheeting 50 has been dispensed , a roller sensing circuit 106 is provided . the roller sensing circuit 106 includes a magnet , 108 , an n - p - n transistor q 3 , a capacitor c 6 , resistors r 7 and r 8 and a reed switch rd 1 . the magnet 108 is mounted on drive roller 32 . the magnet 108 activates or closes the reed switch rd 1 when the magnet 108 is aligned with the reed switch rd 1 . when the reed switch rd 1 is closed , a one time voltage drop is made across capacitor c 6 . the voltage drop across capacitor c 6 turns on transistor q 3 which causes voltage v m1 , to drop to less than reference voltage v c and therefore produces a negative output or zero voltage output v m1 from operational amplifier ic 1 b and stops the motor 88 from operating . by changing the radius of the drive roller 32 , the length of paper 50 that is dispensed can be varied . the time it takes for the motor 88 to turn the drive roller 32 one full turn , i . e ., the time it takes for the magnet 108 to become aligned with reed switch rd 1 , is approximately 0 . 47 seconds . when the drive roller 32 has made one full turn , the predetermined amount of towel sheeting 50 has been dispensed and the magnet 108 is aligned again with the reed sensor rd 1 to stop operation of the motor 88 , as described above . preferably , the motor 88 will power an approximately 3 – 4 inch diameter roller for one revolution , sufficient to dispense approximately 10 – 12 inches of paper towel 50 . if the reed sensor rd 1 is not activated within 1 . 0 second , e . g ., if a paper jam occurs , a safety time circuit 110 turns the motor 88 off . the safety timer circuit 110 includes capacitor c 2 and resistor r 4 . if the reed switch rd 1 does not sense the magnet 108 within 1 . 0 second , the safety time circuit 110 causes voltage v m1 to drop below reference voltage v c and thereby causes output voltage v m2 to be at zero volts and turns the motor 88 off . when the front cover 24 is open , e . g ., to add towel sheeting 50 in the dispenser 10 , the motor 88 is prevented from operating by a door safety circuit 120 . the door safety circuit 120 includes resistors r 5 and r 6 , a reed switch rd 2 and a magnet 121 . one lead 122 of the reed switch rd 2 is attached to resistor r 5 and the other lead 124 is attached to ground g 2 . reference voltage v c is created between resistors r 5 and r 6 . when the front cover 24 is open , the reed switch rd 2 is open and causes voltage v c to be higher than voltage v m1 , and therefore causes the output voltage , v m2 , of operational amplifier ic 1 b to be at zero voltage . note that voltage v m2 is never higher than voltage b + . when the front cover 24 is closed , the magnet 121 causes the reed switch rd 2 to close and allows reference voltage v c to be less than voltage v m1 , which in turn causes the output voltage v m2 of operational amplifier ic 1 b to be at positive voltage and turns the motor 88 on . in ambient room light , the solar panel 96 generates enough current to power the control circuitry 98 . in the preferred embodiment ( shown in fig5 ), the solar panel 96 generates enough current to also charge the battery 90 . in this preferred embodiment , a positive lead , solar panel +, of the solar panel 96 , is connected to battery charging circuitry 126 . the battery charging circuitry 126 includes a diode d 5 , resistors r 11 and r 16 , a capacitor c 4 and a p - n - p transistor q 2 . the positive lead , solar panel +, of the solar panel 96 charges capacitor c 4 through resistor r 16 . when capacitor c 4 is charged to a certain voltage level , preferably approximately 1 . 2 volts higher than the battery voltage b + , resistor r 11 biases the capacitor c 4 to discharge through the p - n - p transistor q 2 and into the positive terminal , battery +, of the battery 90 . as long as light reaches the solar panel 96 , the battery charging process will be repeated and the solar panel 96 continually charges the capacitor c 4 and battery 90 . in the second embodiment ( not shown ), the solar panel 96 only provides power to the control circuitry 98 . disposable , d - cell batteries ( not shown ) or other disposable batteries can be used to power the motor 88 , instead of the rechargeable battery 90 . because the control circuitry 98 is powered by the solar panel 96 , the motor 88 will not operate unless there is light in the room , thus preventing the disposable batteries from becoming unnecessarily discharged . after the disposable battery has been fully discharged , the disposable battery can be replaced . the control circuitry 98 also includes delay circuitry 112 to prevent the dispenser 10 from starting a new cycle of dispensing towel sheeting 50 until a predetermined time after the motor 88 has turned off from a prior dispensing cycle . the predetermined time is preferably approximately 2 seconds . the delay circuitry 122 includes a diode d 2 , resistor r 3 , and capacitor c 1 . when voltage v m2 is high , the motor 88 is running and causing towel sheeting 50 to be dispensed from the dispenser 10 . when v m2 is high , capacitor c 1 is charge to a very high level , forcing reference voltage v b very high . it takes approximately 2 seconds for v b to return to its ambient light level setting . during that time , if a person places their hand in front of the photo sensor 82 , voltage v a will not be forced higher than v b . as a result , the motor 88 cannot be turned on again until approximately 2 seconds after it has been turned off . this prevents a continual discharge of towel sheeting 50 from the dispenser which could cause the battery 90 to discharge and the motor 88 to burn out . the manner in which the motor 88 is turned on is described in the flowchart of fig6 . the motor 88 cannot be turned on if there is not enough ambient light in the room to power the control circuitry 98 . the solar panel 96 acts as an “ on - off ” switch for the dispenser 10 and will not permit the dispenser 10 to dispense towel sheeting 50 unless there is sufficient light in the room . if there is sufficient light in the room to power the control circuitry 98 , the various checks , which have been described above with reference to the circuitry in fig5 , are shown in the flowchart of fig6 . these checks are performed before the motor 88 is turned on . the manner in which the motor 88 is turned off , which has been explained above with reference to fig5 , is described in the flowchart in fig8 . similarly , the charging of the battery 90 by the solar panel 96 , which has been explained above with reference to fig5 , is described in the flowchart of fig8 . the embodiments of the inventions disclosed herein have been discussed for the purpose of familiarizing the reader with novel aspects of the invention . although preferred embodiments have been shown and described , many changes , modifications , and substitutions may be made by one having skill in the art without necessarily departing from the spirit and scope of the invention .
a hands - free paper towel dispenser including a housing with a front cover that is pivotable between open and closed positions . a sensing mechanism is disposed entirely within the interior space of the cabinet at a location adjacent to the front cover and is oriented toward the front cover of the cabinet to permit detecting of an object adjacent the front cover without the object contacting the front cover . at least a portion of the sensing mechanism is accessible when the front cover is at the open position . a dispensing mechanism is disposed within the housing for dispensing a length of towel , with the dispensing mechanism including a drive roller and a motor in driving engagement with the drive roller . the dispenser also includes an electric power source for powering operation of the dispenser .