Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
  • B29D11/00—Producing optical elements, e.g. lenses or prisms
  • B29D11/00009—Production of simple or compound lenses
  • B29D11/00423—Plants for the production of simple or compound lenses
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
  • B29D11/00—Producing optical elements, e.g. lenses or prisms
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
  • B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
  • B29C35/08—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
  • B29D11/00—Producing optical elements, e.g. lenses or prisms
  • B29D11/00009—Production of simple or compound lenses
  • B29D11/00432—Auxiliary operations, e.g. machines for filling the moulds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
  • B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
  • B29C35/08—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation
  • B29C35/0805—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation
  • B29C2035/0827—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation using UV radiation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
  • B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
  • B29C35/08—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation
  • B29C35/0805—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation
  • B29C2035/0833—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation using actinic light
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C37/00—Component parts, details, accessories or auxiliary operations, not covered by group B29C33/00 or B29C35/00
  • B29C2037/90—Measuring, controlling or regulating
  • B29C2037/903—Measuring, controlling or regulating by means of a computer

Definitions

• the lens making systems control the duration and time of light provided from the curing lamps to produce an ophthalmic lens.
• the light is modulated with mechanical shutters to control the amount of radiation exposure.
• Mechanical shutters do not necessarily permit as fine a control over the modulation of the light as desired.
• the mechanical parts comprising the shutters are susceptible to breaking and thus may present a reliability problem with respect to the lens making system.
• some lens making systems use liquid crystal spatial light modulators (LCSLMs), which tend to heat up during operation of the system due to their inherently limited transmission in the clear state.
• LCDSLMs liquid crystal spatial light modulators
• lens making systems are relatively inefficient in managing thermal energy. As a result, lens casting systems typically require excessive cooling with multiple fans and/or circulating pumps.
• the present invention therefore, provides an improved ophthalmic lens making system designed to minimize the disadvantages associated with the prior art.
• the system includes a
• the present invention provides a lens making system capable of in-office processing that produces a high quality ophthalmic lens with very short cure times, typically
• This system is particularly well suited for making bifocal and multifocal ophthalmic lenses, but can also be used to cure a uniform layer of resin on a single focus lens.
• the system is controlled by a microprocessor, permitting the development of a lens 0 making system having a personal computer- based architecture.
• a personal computer- based system facilitates the implementation of two important features of the present invention.
• An optical scanner or bar code-scanning wand or pen is provided for automatically reading in information on the resin tube and on the single vision lens envelope, permitting the system to 5 keep track of all the prescriptions processed on the system. Scanning in this information also allows the microprocessor to check compatibility between the materials and the resin and to ensure that the appropriate cure cycles are activated.
• the system is provided with a modem to allow remote accessing of the information stored in the system. The presence of a modem in the system greatly facilitates automatic reordering and subsequent stocking of the lens making material.
• the system provides a high degree of consistent thermal and ultraviolet and/or visible 5 radiation that produces very repeatable curing results. These results are improved by maximizing the light source efficiency of the system by separating the lamps from the curing chamber and by providing an air flow design that keeps the lamps cools.
• the cooling fan of the power supply for the system is utilized to provide substantially all the necessary cooling for the system. This eliminates the need to include additional cooling fans or circulating pumps, and has the added benefit of providing a much quieter system.
• the system also provides a mechanism for temporally modulating the light from the curing lamps by controlling the power supplied to a set of electronic ballasts used to control the curing lamps.
• electronic ballasts to modulate the light sources overcomes the problems associated with the modulating means used in the prior art, such as mechanical shutters and LCSLMs.
• the system also provides a unique and highly efficient method of managing thermal energy with very low power requirements.
• a divider plenum is provided in the curing chamber of the apparatus and separates hot air entering from the heating element from return air flowing out of the curing chamber.
• the divider plenum may be positioned within the curing chamber to adjust the temperature balance within the chamber.
• FIG. 1 is a schematic perspective view of a lens making system according to the present invention
• FIG.2 is an electronic block diagram of the electronic system for the lens making system of FIG. 1;
• FIG. 3 is a schematic front view of the thermal and optical systems of the lens making system of FIG. 1;
• FIG. 4 is a side cross-sectional view of a curing chamber of the lens making system of
• FIG. 1; FIG. 5 is a front cross-sectional view of the curing chamber of the lens making system of FIG. 1; 5
• FIG. 6 is a back cross-sectional view of the lens making system of FIG. 1;
• FIG. 7 is a plot of selected thermal characteristics of the lens making system of FIG. 1, including oven temperature, mold temperatures, and lamp temperatures, along with a lamp duty , rs cycle for a representative cure cycle;
• FIG. 8 is a schematic illustration of the automatic inventory and processing parameter features of the lens making system of FIG. 1.
• the system 10 has a computer-based architecture and includes a curing chamber for producing ophthalmic lenses, especially bifocal and multifocal lenses, using a 0 combination of heat and actinic radiation, specifically ultraviolet and/or visible light, to cure a layer of resin on a single focus lens.
• the curing chamber includes an insulated oven 12 and ultraviolet and/or visible light sources 14 (FIG. 3) positioned above and below the oven 12.
• the light sources 14 provide ultraviolet and/or visible light to the interior of the oven, where a mold 5 tray 16 is located.
• electronic ballasts 18 are provided to control the light applied by the lighting sources to the curing chamber.
• a dispenser assembly 20 allows for resin to be automatically dispensed into the molds of the mold tray.
• the dispenser assembly 20 includes a stepper motor 22 (FIG. 2) and a plunger that discharges resin from a disposable syringe within the system.
• the stepper motor 22 is preferably capable of carefully dispensing resin to the 5 nearest 0.01 milliliter.
• Additional dispensing assemblies 24 may be added to increase the dispensing capabilities of the system.
• These components are contained within an outer shell 11 of the system 10, which is preferably constructed from cold rolled steel, but can also be made from other suitable materials, 5 such as aluminum or plastic.
• a back-lit liquid crystal display 26 indicates the system status, and allows the system to prompt a user for information.
• Other system information such as lamp hours, cure status, and ⁇ oven conditions are displayed on light emitting diodes 28 (LED's) along the front of the status indicating panel 30 of the system.
• LED's light emitting diodes 28
• a keypad 29 on the front of the system permits a system operator to select various options and enter data.
• An optical sensor or bar code-scanning wand 31 facilitates the automatic entry of
• a modem 33 within the system facilitates automatic reordering and subsequent stocking of materials used in the ophthalmic lens making process, such as single vision lenses, wafers, and resins.
• the system 10 also includes
• FIG. 2 a preferred embodiment of the electronic control system is illustrated.
• the heart of the electronic system of the present invention is a motherboard 34, preferably equipped with Intel 386, 486, or 586 microprocessors.
• a lens making system permits the lens making system to have a personal computer-based (PC-based) architecture, which has several distinct advantages over other noncomputer-based lens making systems currently available.
• PC-based personal computer-based
• a PC-based architecture provides the ability to develop and
• TM maintain software for the system in a high level language, such as C or C++.
• Another advantage of a PC-based architecture is the availability of additional and supplemental hardware designed for the personal computer. By utilizing modular "plug and play" technology available for the personal computer, new and important features may be added to the lens making system with
• An interface board 36 provides a communication link between the motherboard 34 and the rest of the system through a standard AT bus.
• the primary purpose of the interface board 36 is to provide the necessary logic link between the AT bus and the components of the system.
• the interface board 36 provides the digital logic to a set of switching electronics 38 where all logic levels used for power switching are optically isolated from the rest of the digital electronics.
• optically isolated drives 40, 42 are used to turn power transistors, such as metal oxide semiconductor field-effect transistors (MOSFETs), on and off to connect or remove 12 VDC power to the electronic ballasts 18.
• MOSFETs metal oxide semiconductor field-effect transistors
• a heating element 44 for the oven 12 is powered by 115 VAC or 240 VAC, and is also controlled via optically isolated switching of a TRIAC with built in zero crossing detection.
• the zero crossing detection prevents unwanted noise during AC switching.
• the zero crossing detection also facilitates pulse width modulated control of the heating element 44 to provide consistent and efficient heating of the system.
• a DC motor 46 is used to rotate an oven fan 48 that circulates the heat within the curing chamber.
• the logic levels used to control this motor are also optically isolated and controlled via high power MOSFETs.
• a thermal sensor 50 located within the curing chamber provides temperature information directly to the interface board 36.
• a multi I/O board 52 is used to provide communication between the motherboard 34 and a hard drive 54 of the system's computer.
• the hard drive 54 is used to store the system software and the system operator's material usage history.
• the multi I/O board 52 also provides communication to the floppy disk drive 32, such as a 3.5 inch disk drive, which is used to install and upgrade the system software. Additionally, the multi I/O board 52 provides a communication port to the bar code-scanning wand 31 , which is used to enter information about the lens and resin directly into the system via bar codes on the resin tubes and lens envelopes.
• An optical sensor 56 is used to limit the motion of the stepper motor 22 of the dispensing assembly 20.
• the dispensing assembly 20 is activated by pushing a fill switch 58, which is connected directly to the interface board 36. Additionally, the keypad 29 allows the system operator to input commands directly to the interface board 36, which passes the commands to the motherboard 34.
• the backlit LCD 5 display 26, which provides system status information, is also connected to the interface board, which passes information to the LCD display from the motherboard.
• the power supply 55 for the system is a standard PC power supply that has enough
• the cooling system has a simple, yet elegant design in which the cooling fan 57 of the power supply provides substantially all of the
• FIG. 3 illustrates a presently preferred embodiment of the optical and thermal systems of the present invention.
• the light is used to polymerize a liquid resin on a single focal lens placed in the curing chamber.
• the light sources 14 are separated and thermally insulated from the heat source of the system. As can be seen from FIGS 3-6, the light sources 14 are located above and below the curing oven 12. Placement of the light sources outside the heated oven maximizes the lamps
• the lamps 25 efficacy by allowing the lamps to remain at a much lower temperature than the oven.
• the oven may be as hot as 220 degrees Fahrenheit, the lamps remain somewhere between 80 and 120 degrees Fahrenheit. Maintaining the lamps at lower
• temperatures is important for long lamp life and good lamp efficacy.
• the light sources 14 are preferably either ultraviolet and/or visible fluorescent tube lamps, such as Phillips PLS-9W/08, PLS-9W/10, or PLS-9W/27, with a maximum illumination between 300 and 400 nanometers. Although the lamps will operate at different line
• Electronic ballasts 18 are provided to modulate the ultraviolet and/or visible light from the light sources 14.
• the use of electronic ballasts provides a clean method for modulating the lights.
• the lamps are easily turned on and off to meter the amount of ultraviolet and/or visible light that is applied to the resin. This 5 is preferred over the use of liquid crystal spatial light modulators and mechanical shutters for the reasons already stated.
• MOSFETs are preferably provided to connect or remove 12 VDC power to the electronic ballasts 18.
• the electronic ballasts also provide
• the electronic ballasts are Bodine 12TPL7-9E or equivalent, and produce 20 to 30 kHz of AC power from a 12 VDC source. As mentioned above, the electronic ballasts are preferably powered by the 12 V rail of the PC power supply.
• the oven 12 is constructed from a durable material, such as stainless steel or aluminum, and is thermally insulated with a suitable material, such as fiberglass or high temperature foam rubber. Since the light sources 14 are placed outside of the curing oven, optical ports 60 are constructed in the oven 12 to allow the transmission of light into the curing chamber. In the 0 embodiment illustrated in FIGS. 3-6, two optical ports 60 are provided in each of an upper and lower surface 62, 64, respectively, of the curing oven 12 to permit light to reach the molds in the curing oven.
• the optical ports 60 are preferably constructed from high temperature glass with an optical transparency of at least 90% at 360 to 600 nanometers. To secure the optical ports in 5 position, metal rings constructed from stainless steel or anodized cold rolled steel and high temperature foam rubber gaskets are used.
• the optical ports 60 are preferably surrounded by collimating reflectors 66 to ensure that 0 the light entering the oven 12 is uniform. Uniform light intensity is critical for uniform curing of the resins used to form the additional optic on the single focus lenses.
• FIG. 4 is a side cross-sectional view of the curing oven 12, which is covered with a layer of fiberglass 5 or foam insulation 68.
• Optical ports 60 allow the ultraviolet or visible light to enter the curing oven from above and below.
• the mold tray 16 is positioned within the curing oven 12, and includes a pair of molds 70 held in place by a metal tray 72.
• the molds 70 can be either glass or plastic, and are preferably ground from crown glass or molded from transparent plastics, such as polycarbonate, polypropylene or a polyethylene polypropylene copolymer. 5
• liquid resin and a pair of plastic, single vision lenses are placed in the molds 70.
• the oven is heated by blowing air with the squirrel cage fan
• the fan 48 is driven by the DC motor 46, and is ⁇ p. designed to pull air in towards the motor along its axis of rotation, and to blow air outward in all directions.
• a specially designed dividing plenum 74 located between the heating element and the molds facilitates even circulation of the heated air throughout the oven.
• FIG. 5 a front cross-sectional view of the curing oven 12 is illustrated.
• the divider plenum 74 is shown to be shorter than the width of the oven 12, by about 45%). This allows the hot air being blown across the heating element 44 to enter the oven 12 evenly across the top 75 of the oven and the return air from the bottom of the oven to be drawn out evenly from the lower left 77 and right 79 hand sides of the oven. It should be noted
• the position of the divider plenum 72 can be moved to the left or the right relative to the oven to adjust the temperature balance within the oven.
• the thermal sensor 50 is located in an upper 81 right hand corner of the oven 12 .
• the location of the thermal sensor 50 is important to achieving an accurate and
• FIG. 5 is a back cross- sectional view of the entire system.
• a plurality of louvers 80 are placed on the side walls of the system to allow cool air into the system.
• the louvers 80 are partially covered with a set of duct work 82 that directs air flow over the lamps while preventing unwanted light leakage through
• Cool air is drawn through the ducts and forced across the lower half of the system by the cooling fan 57 on the system power supply 55. By controlling the air movement in this manner, the coolest air is pulled across the lamps 14, removing the heat generated by the lamps and keeping the lamps operating at a very high efficacy. The remaining air flows across the system electronics, which are arranged on a chassis 84 mounted to the inside lower left hand side 5
• the chassis 84 provides easy access to the serial port of the multi I/O board
• the modem 33 is also readily accessible through the back of the chassis 84.
• the cooling system works in conjunction with the optical and thermal systems to provide proper curing of the resins. It should be noted that proper curing of the resins is also affected by the thermal control of the oven. In a presently preferred embodiment, oven temperature is carefully controlled by a Proportional, Integral, Derivative (PID) control algorithm.
• PID Proportional, Integral, Derivative
• the heating power also allows the maximum duty cycle to be adjusted to the different AC voltage levels used throughout the world.
• a heating element that provides 350 watts of power at 120 VAC at a maximum duty cycle of 100% is employed in the system. Because power is proportional to the square of the voltage, the same heater provides 350 watts of power
• the same heating element can be used for 120 VAC or 240 VAC and still provides all the thermal energy required to cure the resin.
• the lens making system provided herein can be used throughout the world.
• the thermal control of the curing oven needs to be within certain limits to achieve consistent and repeatable curing results.
• the system has the following thermal control characteristics: (1) the actual air temperature in the oven is controlled to within +/- 5 degrees Fahrenheit of the set point temperature throughout the
• the variation in left to right mold temperatures is never more than 7.5 degrees Fahrenheit; (3) the temperature ramp rate is preferably controlled to be no more than 15 degrees
• the lamp intensity needs to be within certain limits to achieve consistent and repeatable curing results. In a presently preferred embodiment, the lamp intensity is between
• FIG. 7 is an illustrative example of a representative cure profile for a pair of ophthalmic lenses produced by the present invention.
• the upper dashed line 87 represents the temperature set point that was programmed into the software of the system. This temperature profile is
• the sold upper line 89 is the actual oven temperature, measured from the center of the oven with a J-type thermocouple. Additionally, the middle dashed line 91 represents the left mold 70a temperature and the middle solid line 93 represents the right mold
• the mold temperatures are very consistent from left to right, as a result of the carefully balanced air flow.
• the mold temperatures significantly lag the air o 0 temperature due to the large thermal masses of the glass or plastic molds. This is an important factor to consider in the development of thermal profiles for making lenses.
• FIG. 7 also illustrates the lamp profile of the system during the curing process. During the first five minutes of the curing process, no lights are turned on, and the mold, lenses and resin
• the second five minutes of the cycle allows for a very gradual ramp in oven temperature, with simultaneous flashing or blinking of the actinic radiation sources from the top and bottom of the oven. After the first ten minutes, the lamps are turned on continuously while the oven continues to ramp in temperature until the final dwell temperature is reached. 5
• the lower solid line 95 in FIG. 7 represents the air temperature near the center of the upper lamps in the system. It is important
• this solid line indicates that the temperature near the upper lamps 14a is slowly but steadily falling for the first ten minutes of the cure cycle, despite the fact that the oven is actually heating from approximately 115 degrees Fahrenheit to 130 degrees Fahrenheit during that same period. This suggests that there is very little heat transfer between the oven and the lamps.
• the lower dashed line 97 near the bottom of the graph in FIG. 7, represents the air 0 temperature near the center of the lower lamps 14b in the system. While following a similar trend as the upper lamps, the lower lamp temperature never exceeds 105 degrees Fahrenheit due to slightly better air circulation at this location.
• the longer dashed line 99 near the bottom of FIG. 7 represents the air temperature near 5 the digital electronics inside the system. Here the temperature stays relatively low, less than 110 degrees Fahrenheit throughout the entire cure cycle. As indicated in FIG. 7, very little thermal energy actually leaks from the curing oven 12 into the rest of the system.
• a resin tube 100 may include bar coded information 102 about the resin chemistry, the expiration date, the batch number, as well as a unique identification number.
• bar coded information 104 on a single vision lens envelope 106 may include, for example, information on the material type, lens distance, and astigmatic power, as well as a unique identification number.
• the system operator can provide the system with the necessary information for complete record keeping on the materials used by the system, thereby allowing the tracking of all prescriptions processed on the system. Additionally, this information permits the system ⁇ r, to check compatibility between materials and resin automatically and ensure that appropriate cure cycles are activated.
• the encoded data is sent directly into the system via the serial port on the back of the system.
• a modem line 33 allows the system to be accessed remotely; thus all of the lens casting
• 15 records can be downloaded to a central office location 110. Once the central office 110 reviews the casting log from a system location, the exact materials required for restoring the system operator's inventory can be shipped by ground or air transportation, depending on the system operator's requirements. This provides an important advantage to both the system operator and
• the material supplier can maintain a smaller inventory of materials if he can rely on quick restocking from the manufacturer. Additionally, the material supplier can schedule production runs based on a running average of all system usage throughout its regional market. Moreover, remote access of the casting log will permit the material supplier to keep on-
• PID Proportional, Integral, Derivative
• the Derivative component is not used.
• the PID equation has a Proportional component (Pterm which is directly proportional to the error value between the Setpoint (desired) temperature and the Actual (measured) temperature, and an Integral component (lterm which represents a history of the error value).
• Pterm Proportional component
• Integral component Lterm which represents a history of the error value.
• the Integral term is computed in 2 ways depending on the Heat Regulation mode.
• Pterm PconstWARM * Error lterm * IconstWARM * (Average of last 6 Errors)
• 550ms time period is divided into 50 11ms increments. At the start of a given 550ms time period, 5 the Oven heat is turned ON. Then based on the PID out value, the Oven Heat is turned OFF at the start of a given 550ms time period.
• the Pconst and Iconst values are modifiable in the Utilities Menu. They can be adjusted from 0 to 99.
• the AID Heat Sensor value is read and saved in a 3 element circular buffer and the average of these 3 latest readings is computed. 5
• the new measured temperature is computed based on the current average A/D Heat Sensor reading value. This measured temperature value is computed as follows: Assume that:
• A/D reading - 0 is equivalent to 70 °F
• A/D reading - 255 is equivalent to 230 °F
• TEMPerr TEMPset - TEMPmease
• ERRORbuff ERRORbuff + TEMPerr
• TEMPerr TEMPset - TEMPmeas
• the Duty Cycle is base on the PID output.
• OFFcnts the number of 11 ms increments (out of a possible 50) until the heat will be turned OFF.
• Duty Cycle OFFcnts/50 x 100%
• the value 500 is the maximum PIDout value allowed. This means that a PIDout value greater than or equal to 500 is equivalent to 50 11ms increments or a 100% Duty Cycle.
• Oven Heat is to be turned off is calculated based on a PID output value (possibly attenuated).
• the Oven Heat is then turned ON (if at least 1 11ms period of ON time is calculated). When the calculated number of 11ms periods passes, the Oven Heat is turned OFF and it remains OFF until this cycle is repeated at the beginning of the next 550ms period.

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• Engineering & Computer Science (AREA)
• Health & Medical Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Ophthalmology & Optometry (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Toxicology (AREA)
• Oral & Maxillofacial Surgery (AREA)
• Thermal Sciences (AREA)
• Heating, Cooling, Or Curing Plastics Or The Like In General (AREA)
• Eyeglasses (AREA)
• Materials For Medical Uses (AREA)
• Prostheses (AREA)

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• 1997
  • 1997-12-19 CA CA002275239A patent/CA2275239A1/en not_active Abandoned
  • 1997-12-19 BR BR9714515-7A patent/BR9714515A/pt not_active Application Discontinuation
  • 1997-12-19 IL IL13019797A patent/IL130197A0/xx unknown
  • 1997-12-19 WO PCT/US1997/023667 patent/WO1998028126A2/en not_active Application Discontinuation
  • 1997-12-19 EP EP97953375A patent/EP0949994A2/en not_active Withdrawn
  • 1997-12-19 KR KR1019990705523A patent/KR20000057678A/ko not_active Application Discontinuation
  • 1997-12-19 AU AU57135/98A patent/AU5713598A/en not_active Abandoned
  • 1997-12-19 JP JP51980398A patent/JP2001516292A/ja active Pending
• 1998
  • 1998-06-17 TW TW086119444A patent/TW407106B/zh active

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