CA1186772A - Multi-voltage disinfector timing circuit - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A contact lens disinfector unit having multi-voltage capabilities includes a timing circuit for controlling the duration of operation of a contact lens disinfector heater. The circuit is particularly suitable for use with a heater consisting of a positive temperature coefficient thermistor. In the preferred form, the contact lens disinfector units are suitable for use regardless of the voltage value at an electrical outlet receptacle providing power to such a disinfector unit.
Depending upon the country in which the device is used, voltages can vary generally anywhere from 95 AC volts to 256 volts AC. Positive temperature coefficient (PTC) thermistors are capable of operation irrespective of such variable voltage range and unique control circuit disclosed is capable of timing control and operation where the input voltage has such a wide value range.

Description

MULTI-VOLTAGE DISINFECTOR TIMING CIRCUIT

ABSTRACT OF THE DISCLOSURE
. . ~ . _ _ A contact lens disinfector unit having mul-ti-voltage capabilities includes a timing circuit for controlling the duration of operation of a contact lens disinfector heater. The circuit is particularly suitable for use with a heater consisting of a positive tempera-ture coefficient thermistor. In the preferred forml -the con-tact lens disinfector units are suitable for use regardless of the voltage value at an electrical outlet receptacle providing power to such a disinfector uni-t.
Depending upon the country in which the device is used, voltages can vary generally anywhere from 95 AC volts to 256 vol-ts AC. Positive temperature coefficient (PTC) thermistors are capable of operation irrespective of such variable voltage range and the unique control circuit disclosed is capable of timing control and operation where the inpu-t voltage has such a wide value range.

BACKGROUND OF THE INVENTION

1. Field of the Invention ~ _ . _ . . .
This invention relates to a contact lens disinfecting unit timing control circuit and more particularly to a timing control circuit for a contact lens disinfector capable of operation under a variable voltage range.

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2. Brief Description of the Prior Art:
Heretofore, disinfecting devices for contact lenses have been rather bulky and have required the operators of such devices to perform multiple ~perations 5 in the process of disinfecting their contac-t lenses.
Typically, the units have been designed for use only with a voltage source of a given value. Those units which have adaptability to multiple voltages require that the operator perform additional manual operations and have necessitated the incorporation of separate circuitry, including separate heating elements to accommodate the different voltage values. These considerations add additional cost and bulk to the individual units.
Further, the opera-tor must be especially mindful and knowledgeable of the value of the voltage source being utilized.
U.S. Patent 4,165,359 for inventor M.D. Thomas et al, for example, discloses a circuit at FIGURE 7 for use with voltages of two given values. The circuit illustrates a manually operable switch~ separate from the start switch, which must be positioned by the operator and is dependent upon the value of the ~oltage source. The circuit also illustrates that two separate heating elements are necessary in order to accommodate each of the two voltage values. Additional resistive elements must be incorporated, as illustrated thereat, to balance the needs of the actuator switch and indicator lamp. The -timer or star-ter unit is schematically shown as a switch Z

and is simultaneously energized when the actuator switch is operated, although no preferred embodiment of the starter unit and no explanation of its simultaneous actuation is provided.

SUMMARY OF THE INVENTION

This invention provides a timing circuit for a contact lens disinfector capable of operation under a wide range of voltages available for powering such units regardless of the country of use particularly where such a disinfecting unithas a positive temperature coefficient thermistor heater equally capable of satisfactory operation under a wide range of voltage inputs. The circuit requires only that the operator perform a single step to start the operation of the unit. This is true regardless of the value of the voltage souxce. Afterwards, the unit completes a full disinfecting cycle without need for further operator assistanceO

The circuit operates to generate a single capable of closing and keeping closed an electronic gate for a period of time sufficient to disinfect contac-t lenses heated by the heating device. A multistage binary counter provides the timing capability within an integrated circuit (IC3 of a programmable timer. The timer is programmed to time for a cycle having a duration which is a function of the period of time necessary to disinfect contact lenses. An oscillating circuit associated with the IC is pr~vided for clocking.
The t:iming circuit is capable of manual initialization 77~

either by the disinfector heating unit being plugged into the voltage source or by providing a mechanical interruption of the powercircuit by a swi-tch to be manually and momentarily depressed to initialize the counter.
The multi-voltage aspect can be applied to circuitry where variable, but selectable, timing is provided for operation of loads, including contact lens disinfector heaters, but not limited to such loads.
Units of manufacture according to the principles of this invention can be made less costly. Additionally, they can be of minimum size and enjoy the luxury of outward ornamental design which is appealing to the eye and thus highly marketable. Further, the circuit features provided are such that the operation of the unit is practically self explanatory. Minimal instruction is necessary and the operator, for all practicalpurposes, need not be concerned about the value of the voltage at the receptacle outlet. Thus, the unit is universal for use on the North American continent and as well in Europe and in all countries where receptacle voltage value is substantially between 95 and 256 volts.

:BRIEF DE5CRIPTION OF THE DRAWINGS
_ _ .. . .
FIGURE 1 is a schematic block diagram of a circuit for a contact lens disinfecting unit according to the principles of the present invention.

7'~2 FIGURE 2 is a detailed schematical ilLustration oE
a contact lens disinfecting unit circuit in -accordance with FIGURE 1.
FIGU~E 3 is an alternate embodiment o~ the voltage control circuitry according to FIGURE 1.
EIGURE 4 is an alternate embodiment oE the circuit control system in accordance with FIG[JRE 1.
FIG~RE 5 is a further alternate embodiment oE the circuit control system in accordance with FIGURE 1.
FIGURE 6 is yet another alternate embodiment of the circuit control system in accordance with FIGURE 1 FIGURE 7 is a schematic circuit of an alternative embodiment for the circuit and timer control of FIGURE 1 according to the principles of the present invention.
FIGURE 8 is a schematic block diagram of a circuit having multiple voltage capabilities with select timing features.
FIGURE 9 is a schematic diagram of an exemplary circuit for use in the selectable timers of FIGURE 80 FIGURE 10 is a schematic circuit diagram of -the time switching mechanism of FIGURE 9.
FIGURE 11 is a schematic diagram oE an exemplary switching circuit for use when the present invention is connected to a DC electrical power source.

DETAILED DESCRIPTION OF THE PREFERRED E'MBODIMENTS
rrhe circuits illustrated in FIGS. 1-6 are suitable for use with various types of loads including the preferred embodiments of disinfectors having heating element~s made from positive temperature coefficient resistance material. A heating device of this material will hereinafter be referred to as a PTC heater. PTC

6~72 heaters have been used, for example, as self-regulating heaters. An example of one is illustrated in ~.S.
Patent 3,489,976. This type of heater ls self limiting and thus has little need fo:r control devices :Eor regulating the amount of cu:rrent received by the PTC
heater.
Although in heating devices PTC hea-ters are generally preferred, the descri~ed circui-t is equally as suitable for use with heaters well known in the art including the full array of resistive type heating devices. In FIG. 1 a circuit 10 having a unit for disinfecting contact lenses is illustrated. ~lthough for practical purposes, the circuit is shown as including a voltage source 12, it is anticipated that in most instances the circuit will terminate at an electrical supply cord suitable ~or accommodation to an electrical receptacle.
This circuit 10 is ideally suited for use with multiple voltages and specifically for voltages which are nominally identified as 100, 110, 220 and 2~0 volts.
The voltage values are typically those found in general use in Japan, the United States, and in European states and countries, respectively, The illustrated unit, according to ~he principles of the invention, is operationally independent of the ~requency of the voltage source.
Circuit 10 has a heating device 14 which, as hereinbefore stated, is preferably a PTC heater serially connected to a switching circuit 16. The heater 14 is operative to heat contact lenses, in a suitable carrying case, placed in close proximity thereto when the switching ~8~

circuit 16 is operated and a closed path is -therefore provided for current to flow. A heating device, of PTC material, can readily accommodate mu].tiple voltages such as 110 volt or 220 volt. However, in addition it can operate effectively when the voltage source provides an alternating current (A.C.) voltage value anywhere appro~imately from 90 to 260 volts. So, in effect, the circuit system 10 is operative in a disinfecting unit for variable voltage sources coverin~ a wide range, as distinctive from selec.ted individual multi voltage sources. Further, the invention is broad enough in concept to only be limited by the load. Any voltage level AC or DC suitable to be used directly or indirectly to operate a selected loadcan be used to function the timer.
The operation and duration of operation of the switching circuit 16 and accordingly heater device 14 is principally controlled by a timer control unit 18.
Control of the operation of the total circuit is accomplished by means of a circuit control system 20 which initializes the timer control circuit 18 and provides a current path for the continued operation of the timer control circuit 18. A voltage control circuit 22 is incorporated to provide a suitable volta~e level 2~ for operation of the circuit control 20 and -the timer control 18 regardless of the value at the voltage source ].2. The timer control circuit 18, once initialized, operates independently o~ any control by the control circuit 20 ~or a period of time which is a function of ;7~

its own circuit. In the environment preferably intended for use by the present circuit the time period selected is -that which is necessary :Eor disinfecting contact lenses. This period of opexation is more fully described in "The May 1980 (,uidelines for Contact Lenses (May, 1980 Revision)" issuecl June 9, 1980 by H.E.W.
As long as switching ci.rcuit 16 is in a closed mode and influenced by an existing signal ~rom the timer control 18, current not only will pass through the heater 14 but al50 through a lamp circuit 24 to provide a visual indication that the dlsinfecting cycle of the contact lenses is in progress.
In FIG. 2 a specific embodiment of the disinfecting heating circuit 10 of FIG. 1 is illustrated. As before, voltage source 12 is illustrated and is bridged by a resistor voltage divider network comprising resistors 30 and 32 having connected to their common terminal a diode 34 for providing a direct current (D.C.) level voltage to the circuit control 20 and timer control 18 of the control circuit 10. A selected capacitor 36 is applied across the output of the diode 34 to ground to act as a filter to remove ripple due to any instability of the voltage at source 12 which may occur in the ~oltage signal appearing at that point.
In the preferred form, a switch 38 is illustrated as being connected directly to initialization pin 6 of an IC unit 40 incorporating the time control circuit 18.
The switch 38 is of the variety known as momentary switches which r~turn to a normal circuit condition of being open 36~7~2 when the actuating force applied by the operator is removed. The IC 40 is a programmable timer as more fully described hereinafter. The input sicle of the switch 38 is connected to a programmable unijunction transistor (PUT) 42. The equivalent circuitry of the PIJT comprises a NPN/PNP transistor ne-twork where the base of the ~PN transistor is connected to the collector of the PNP transistor. Momentary depression of the switch provides a negative pulse which turns on the IC
40 at pin 6 and resets it to commence its oscillator timing operation as soon as the switch 38 is open. A
current is thereby caused to flow from the base of the NPN to the col]ector of the PNP of the PVT 42 to provide circuit operation between the anode and the cathode of the PUT. Once the regenerative condition starts, the equivalent circuitry of the PUT remains in operation until the load drops off, i.e., when ~he IC 40 timing cycle is completed. In order to preven-t the anode to gate voltage of the PUT from floating, a bleed resistor 44 is connected across those points with a capacitor 46 applied to filter out any noise.
The frequency of the oscillator circuit of IC 40 is determined by an ~C network comprising two resistors 48 and 50 and a capacitor 51 connected at pins, 1, 2 and 3 of the IC and valued according to the manufacturer's recommendations. Likewise, to get the proper timing period, pins 12 and 13 of the IC 40 are high. Selecting the proper logic of the IC 40 to provi~e a signal or high value output at pin 8 requires pin 9 also being kept high. Accordingly, pin 9 is common to pins 1~, 13, and 14. Pin 14 is the power connection to the IC
unit 40. Auto reset pin 5 of IC 40 is connected to the power pin 14 and functions as does a signal at pin 6 to reset the logic.
Resistive element 53 is effective :in decreasing the sensitivity of pin 6 so that it is not affected by spuxious signal glitches. A resistor 54 sets -the current at a level to turn on a silicon controlled rectifier (SCR) 56 to provide for current flow through the heater 14.
The timing operation of the IC 40, as no-ted, is a function of the oscillator frequency cixcuit at pins 1, 2 and 3 and the bit capacity preference is dictated by the values at pins 12 and 13. For the duration of the timing or disinfecting cycle, pin 8 is kept high and current to the SCR 56 continues to cause the SCR to provide a path for current flow from the voltage source 12 through the PTC 58 until the disinfecting cycle is timed out.
As an indicator of the operation of the unit during the disinfecting cycle, a lamp 60 is connected in parallel across the PTC 58. The resistor 62 has its value selected dependent upon the indicator lamp and the illumirlation brilliance desired during its operation.
In FIG. 3 there is illustrated an alternate voltage control CirCuI t 22. A zener diode 64 comprises one of the legs of the voltage divider network and sets a constant level of ~oltage at the input side to the PUT.
The other leg of the voltage divider network includes a i77~

resistor 66 and diode 68. Similarly, a capacitor 70 is provided to control ripple. This alternate embodiment is more costly but can provide a ~ery stable influence to the operation of the PUT 42.
FIGS. 4, 5 and 6 illustrate alternate embodiments for the circuit control 20 a In FIG. 4 a momentary switch 72 is illustrated as being connected across pins 5 and 6 of the IC 40. If the circuit of FIG. 4 is incorporated into the circuit of FIG.2, the IC 40 starts its timing cycle when power is applied initially, such as when the unit is connected to its power source.
When the disinfecting cycle is completed, and if the unit remains directly connected to -the power source, the cycle can be initiated again by momentary depression of the switch 72. As hereinbefore explained, a capacitor 36 is connected for practical purposesO When the capacitor 36 is incorporated, recycling of the unit may be delayed due to a residual charge on the capacitor which prevents the IC 40 from being reset immediately following disconnection of the power cord. In this case the residual charge must be allowed to dissipate.
A resistor 73, not unlike resistor 53, provides for desensitizing signals at pin 6 of the IC 40.
The circuit of FIG. 5 differs slightly from that of FIG. 4 in that there is no momentary switching incorporated. With this particular embodiment, starting of the timer in each case is accomplished by plugging in the unit. As before, the charge on the capacitor 36 must be dissipated before operation can be effected.

In FIG. 6 a single pole single throw switch 74 is incorporated. When the switch 74 is manually closed, the timer of the IC 40 is initiali~ed. Act~ation of the switch 7~ takes the place of inserting and removing and reinserting the cord as ~or the circuit of FIG. 5.
~ccordingly, switch 74, a~ter the timer of [C ~0 has timed out and before it can be reset, must be opened and then closed and then the timer of IC ~0 wil:L start up again.
In the preferred embodiment oE FIG~ 2 actual reductions to practice have included the incorporation of a MCR 72-6 SC~ at SCR 56 and a MC 145~1 BCP
programmable timer at IC 40 both manufactured by Motorola.

Further, a 2N6027 PUT unijunction transistor ~2 manufactured by General Electric was included. These devices and their equivalent are acceptable. The remaining elements and their values can be arrived at without undue difficulty and are a function of the particular elements selected for use elsewhere in the circuit~

As hereinbefore stated, the inven-tion is suitable for use with a DC power source. When modified to operate with a DC electrical source the switching circuit can be, for example as seen in Fig. 11, an NPN silicon powered transistor 57 directly replacing the SCR 56 where the gate, anode and cathode of the SCR is equivalent to the base, collector and emitter of the transistor 57.
An alternate circuit is illustrted in E`IG~ 7.
The circuit oE FIG, 7 provides a circuit oE equivalence 77~

for the functional operation described for con-trol circuit 20 and timer contro:l 18 of FIG. 1. An oscillator comprising a PUT transistor 76, a capacitor 78 and resistors 80, 82 and 8~ provides the timing for a counter 86. Switch 92 acts similarl~ to those hereinbefore described to initiate the actuation of the timing circuit. The counter 86 counts the negative pulses of the oscillator. The logic le~el for the counter is out of pin 11 and pin 10 of the counter 86 is -the output. NOR gates 88 and 90 act as a latch to control the output to the switching circuit 16. The latch of the NOR gates 88 and 90 is essentially the circuit control 20 of FIG. 1 and ~hen the latch goes high the SCR is turned on and when the latch goes low the SCR is turned offO A diode 104 is incorporated to stabilize the DC signal level into the latch. Resistor 94 sets the output current level from the latch.
Resistor 102 further controls the current level of the signal passed into the switching circui-t 16 so as, for example, not to overdrive the SCR 56. Resistors 96, 98 and 100 are provided to stabilize signals in the circuit respec~ive to their locations. The counter 86 of FIG.
7 can comprise a CMOS MSI 14 bit counter and, for example, can be a MC14020B element available from Mo-torola Corporation.

i7tf 2 In the embodiment for the invention illustrated in FIG. 8 there is disclosed a circuit fox use with load 106, which load can be variable and selected by the user. Such a selected load can be disposed in the circuit path in any manner commercially suitable. This can be accomplished, :Eor example, by a receptacle being disposed to receive a mating plug connected directly or indirectly with the load selected. It will be appreciated that other methods are available to switch loads into and out of the circuit.
Like elements of this circuit to previously discussed elements of other figures are identified by like re~erence characters which have been heretofore disclosed. The circuit control 108 is modi~ied from the circuit controls previously described with respect to FIGS. 2, 4, 5, 6 and 7 by providing a manually operable switch 110 outside the balance of the previously described circuit control circuits. Switch 110 is i]lustrated in this manner for the convenience of identifying that the alternate circuit of EIG. 8 becomes operational by the actuation of a switch. The operator will select by means of a schematically illustrated time select switching circuit 112 a specific time period desired for operation of the load 106. Each of the illustrated time blocks 114, 116~ , 120 and 122 identi~iecl by letter designations Tl, T2~ T3, T4 and T5, respectively, when connected through the time select switch 112 provided a fixed period of time fox operation 7~

of the circuit of FIG. 9. Each time period can differ in length. During the timing operation master timer control 124 provides for a signal to be passed to the switching circuit 16. It will be appreciated that timer control 124 incorF)orates the baslc elements of the timer control 18 as shown in FIG. 1 as explained in more detail with respect particularly ko FIGS. 2 and 7. This is more fully explained hereinafter with respect to FIG. 10.
Depending upon the type of load 106, the circuit of switching circuit 16 can be operator or desiyn selected to incorporatel for example, a SCR like SCR 56 for a half wave or purely resistive load or a triac device for a load requiring full wave or an NPN transistor where the voltage source is of a DC type as hereinbefore explained.
FIG. 9 illustrates an exemplary circuit for the timers 114, 116, 118, 120 and 122 where, as appreciated, values for resistors 126 and 128, as well as the value for capacitor 130, are selected to provide the desired ti.me period.
FIG. 10 schematically illustrates in part the time select switch 112 and includes switches 132, 134 and 136 and the IC 138 of the master timer control 124. It will be noted that the time select switch 112 is a 3 pole variable throw type switch, as is best appreciated from FIG. 10 ancl mi~ht, for example, be a rotary type switch.
The variable throw is dependent upon the number of time rjJ2 blocks and for the illustraled circui.t of FIG. 8 the throw is 5~ The IC of FIG. lO, for example~ can be the Motorola Corporation element MCl4541B.
While there have been described and preEerred embodiments of this invention at the present time, it should be obvious to those skilled in the art that chan~es and modificat.ions can be made thereto without departing from the spirit and scope of -the invention.

Claims (10)

CLAIMS:

1. A disinfecting unit for contact lenses, comprising:
a positive temperature coefficient resistor operational to elevate the temperature of the contact lenses to a temperature above ambient for disinfecting the contact lenses;
an electrical circuit for controlling the operation of said resistor including input means electrically connected to a source of electrical power having a frequency of from zero to approximately sixty Hertz and a voltage amplitude within a widely varying range of amplitudes, said input means including a voltage control circuit for rectifying electrical power having a frequency greater than zero Hertz and providing a rectified electrical power signal, control means for generating a control signal for a period of time sufficient for said resistor to operate to disinfect the contact lenses, said control means including an automatic timing circuit and an initializing circuit, said automatic timing circuit having a counter for generating said control signal and a timing control circuit in electrical communication with said counter for operating said counter for said period of time sufficient for said resistor to operate to disinfect the contact lenses, said initializing circuit in electrical communica-tion with and for resetting said automatic timing circuit, said automatic timing circuit and said initializing circuit receiving and operable over the range of voltage amplitudes of said rectified electrical power signal; and, switching means in electrical communication with said resis-tor and said source of electrical power and receiving said control signal, for automatically electrically connecting said source of electrical power with said resistor in response to said control signal, whereby said resistor operates to elevate the temperature of and disinfect the contact lenses.

2. A disinfecting unit for contact lenses, as defined in Claim 1, wherein said initialization circuit includes a manually operable switch for providing electrical communication between said automatic timing circuit and said input means to initialize operation of said automatic timing circuit.

3. A disinfecting unit for contact lenses, as defined in Claim 2, wherein said initialization circuit further includes a programmable unijunction transistor selectively operable by said manually operable switch for selectively electrically connecting said rectified electrical power signal with said automatic timing circuit.

4. A disinfecting unit for contact lenses, as defined in Claim 2, wherein said automatic timing circuit includes a plurality of said counters each operational to provide a control signal for a period of time different from that of each other said counters.

5. A disinfecting unit for contact lenses, as defined in Claim 4, wherein said counter is a programmable timer.

6. A disinfecting unit for contact lenses, as defined in Claim 5, wherein said voltage control circuit includes two resis-tors connected across said source of electrical power to insure the voltage amplitude of said rectified electrical power signal is compatible with said control means, and a diode at the common node of said resistors for rectifying electrical power having a frequency greater than zero Hertz.

7. A disinfecting unit for contact lenses, as defined in Claim 6, wherein said switching means includes a switching cir-cuit for operation with a source of direct current electrical power.

8. A disinfecting unit for contact lenses, as defined in Claim 7, wherein said voltage control circuit is directly electrically connectable to said source of direct current electrical power.

9. A disinfecting unit for contact lenses, as defined in Claim 8, wherein said switching circuit is a silicon powered transistor.

10. A disinfecting unit for contact lenses, as defined in Claim 9, wherein said initialization circuit and said automatic timing circuit are directly electrically connected to said source of electrical power.