Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24C—DOMESTIC STOVES OR RANGES ; DETAILS OF DOMESTIC STOVES OR RANGES, OF GENERAL APPLICATION
  • F24C15/00—Details
  • F24C15/20—Removing cooking fumes
  • F24C15/2021—Arrangement or mounting of control or safety systems

Definitions

• the invention relates to a cooker hood controlled by at least one sensor element reacting to fumes and vapours given off from the food to be cooked within the catchment range of said cooker hood.
• Most cooker hoods are disposed generally above the food giving off fumes and vapours but the present invention is not limited to such a configuration.
• Cooker hoods which are controlled by e.g. a humidity sensor or a temperature sensor, commencing extraction of fumes or increasing the rate when the humidity or temperature reaches a pre-determined level. It is also known to use a number of sensors, each sensitive to particular compounds in gas form, to control a cooker hood. It appears that the known constructions which depend on sensors for chemicals all only react to a very specific range of chemical susbstances, and they are inherently very sensitive to contamination which means that their performance and service life in a kitchen environment is less than desired.
• each sensor has a sensitivity to a separate broad range of chemicals, the instantaneous rate of extraction being determined by a specific combination of sensor signals.
• three sensors are used, the first sensor being sensitive to water vapour but not sensistive to grease and fat vapours, the second sensor being sensitive to both water vapour and to fat vapour, with opposing reactions, and the third having a high sensitivity to fat vapours, and a low sensitivity to water vapour.
• the output from each sensor is compared to corresponding data stored in a permanent memory.
• the data stored in permanent memory is obtained during a calibration run with foods of predetermined compositions being heated with a predetermined amount of heat at a predetermined rate.
• Fig. 1 shows a disposition of a cooker hood in relation to a pan on a cooker
• Fig. 2 shows a block diagram of the control for a cooker hood employing the invention.
• the cooking of food in conjunction with a cooker hood proceeds as follows: the heating provided by the cooker heats the food, and a series of chemical processes are activated, each creating vapours, the mixture and concentrations of which may be detected as specific to the particular process by means of dedicated sensors. At low temperatures water vapour is given off, and at higher temperatures certain oxidation of some of the components in the food takes place, and at still higher temperatures fatty components are also given off as vapours, and from parts of the food covered with the most heat tolerant components of the fat, various forms of decomposition may also occur. All of these processes provide quite specific volatile compounds. Known sensors for cooker hood control are directed to the detection of such compounds and to activate the fan or blower.
• three semiconductor gas sensors are mounted generally above the cooking area, and above the grease filter and below the impeller of the fan
• they are semiconductor sensors which change their electrical resistance when influenced by the vapours they respond to Sensor 1 is sensitive to water vapour but not sensitive to grease and fat
• Sensor 2 is sensitive to both water vapour and to fat vapour but influence the resistance in opposite directions
• Sensor 3 has a high sensitivity to fat vapour but lower sensitivity to water vapour
• the sensors When power is first applied to the control, the sensors are monitored for a period of time (typically 5 minutes), this in order to make sure that the sensors are thermally and electrically stable and to gain a knowledge (to be stored) of the sensor output pattern that represents a clean kitchen atmosphere After this time the monitoring programme starts All the resistance values (signal levels) of all three sensors are continously monotored The signals are read into RAM memory every 30 seconds (optional), and this value is compared to a rolling average over 5 minutes (optional) Both of times indicated are pre-programmed and adjusted to obtain a reliable and speedy response, with a minimum of false starts, nuisance speed changes and false shut downs
• Sensor 1 and 3 have a high signal stability over time under clean air conditions and are therefore mainly used to detect and confirm the existence of and return to clean air conditions
• Sensor 2 does not have a stable signal over time in clean air, bur responds quickly to levels of fat vapour and is therefore mainly used to select fan speed changes, rather than to switch the fan on or off
• the fan switches from off to speed level 1 - the ratio (sensor 1 at 30 sec signal)/( sensor 1 at 5 min average) is ⁇ 0 9 and the ratio (sensor3 at 30 sec signal)/(sensor3 at 5 min average) is ⁇ 0 85
• the fan switches from level 1 to level 2 - the ratio (sensor 1 at 30 sec signal)/( sensor 1 at 5 min average) is ⁇ 0 75 and the ratio (sensor3 at 30 sec signal)/(sensor3 at 5 min average) is ⁇ 0 5, or sensor 2 drops below the value lOOkohm
• the fan switches from level 2 to level 3 - the ratio (sensor3 at 30 sec signal)/(sensor3 at 5 min average) is ⁇ 0 3, or sensor 3 drops below 50kohm
• the fan can switch directly from level 0 to level 2 or level 3, and it can also switch back from level 3 to level 1 or level 2 before switching off, in dependence of the precise inputs provided by the sensors

Landscapes

• Engineering & Computer Science (AREA)
• Ventilation (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Fire-Extinguishing Compositions (AREA)
• Fireproofing Substances (AREA)
• Combinations Of Kitchen Furniture (AREA)
• Glass Compositions (AREA)
• Meat, Egg Or Seafood Products (AREA)

Priority Applications (5)

Applications Claiming Priority (2)

Publications (1)

Family

ID=8095371

Family Applications (1)

Country Status (7)

Cited By (4)

Citations (4)

• 2000
  • 2000-05-01 AT AT00920427T patent/ATE260445T1/de not_active IP Right Cessation
  • 2000-05-01 WO PCT/DK2000/000218 patent/WO2000066950A1/en active IP Right Grant
  • 2000-05-01 ES ES00920427T patent/ES2215636T3/es not_active Expired - Lifetime
  • 2000-05-01 PT PT00920427T patent/PT1159566E/pt unknown
  • 2000-05-01 AU AU41012/00A patent/AU4101200A/en not_active Abandoned
  • 2000-05-01 DE DE60008506T patent/DE60008506T2/de not_active Expired - Fee Related
  • 2000-05-01 EP EP00920427A patent/EP1159566B1/de not_active Expired - Lifetime

Patent Citations (4)

Also Published As

Similar Documents

Legal Events