US3625135A

US3625135A - Automatically controlled cooking area ventilating system

Info

Publication number: US3625135A
Application number: US30738A
Authority: US
Inventors: Elmer A Carlson
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1970-04-22
Filing date: 1970-04-22
Publication date: 1971-12-07
Anticipated expiration: 1988-12-07

Abstract

A cooking area ventilating system which operates automatically through the expedient of an aerosol particle sensor. The system operates automatically in response to aerosol particles or smoke, and has a varying speed for the ventilator fan depending on the concentration of the particles that are to be removed by the ventilating system.

Description

United States Patent Inventor Elmer A. Carlson Richfield, Minn. App]. No. 30,738 Filed Apr. 22, 1970 Patented Dec. 7, 1971 Assignee Honeywell Inc.

Minneapolis, Minn.

AUTOMATICALLY CONTROLLED COOKING AREA VENTILATING SYSTEM 6 Claims, 3 Drawing Figs.

US. Cl

' [56] References Cited UNITED STATES PATENTS 2,726,594 12/1955 Cooper et al. 98/49 3,489,345 l/l970 Moreland 236/9 A 2,339,987 [/1944 Evans 98/49 3,207,058 9/l965 Gaylord 98/115 K Primary Examiner Edward J. Michael Attorneys-Lamont B. Koontz and Alfred N. Feldman ABSTRACT: A cooking area ventilating system which operates automatically through the expedient of an aerosol particle sensor. The system operates automatically in response to aerosol particles or smoke, and has a varying speed for the ventilator fan depending on the concentration of the particles that are to be removed by the ventilating system.

PATENTED BEE 7 ISYI FIG. 3

ELECTRIC HEATER 24- METAL OX'DE 6| PARTICLE DETECTOR v 4 8| CONTROL KlTCHEN OR RANGE VENT HOOD FAN MOTOR INVliN'I ()IL ELMER A. CARLSON WWW ATTORNEY.

AUTOMATICALLY CONTROLLED COOKING AREA VENTILATING SYSTEM BACKGROUND OF THE INVENTION The use of ventilating systems for kitchens or cooking areas, either in a vent hood or for the general room area, are quite well known. In the past, the ventilating system has been put into operation manually depending on the need for ventilation as sensed by the person working in the cooking area.

SUMMARY OF THE INVENTION The present invention is directed to a system for automatically turning on the ventilating fan in a kitchen or range hood in response to aerosol particles in the air. The term aerosol particles generally encompasses all types of particles generated during the cooking process including smoke unburnt hydrocarbons, etc. The presently disclosed system not only operates the ventilating fan in response to aerosol particles, but varies the speed of the fan based on the concentration of these particles.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a representation of a typical installation encompassing the present invention;

FIG. 2 is a schematic circuit diagram of a complete system; and

FIG. 3 is a representation of part of a solid-state aerosol particle sensor means.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. I a conventional kitchen range vent hood I is disclosed. It is understood that the vent hood could in fact be the kitchen itself where no specific hood is provided but where a ventilating fan is used. The fan and its driving motor are shown at 11 connected by conductors l2 and 13 to the automatic control 14 which in turn is energized by conductors l5 and I6 from a conventional source of potential. The automatic control I4 is disclosed in detail in FIG. 2.

In FIG. 2 the conductors I5 and I6 are shown connected to the automatic control 14 which includes a primary winding ofa stepdown transformer 21 that has a further winding 22 to provide a low voltage to an aerosol type of sensor 23. The sensor 23 is a solid-state aerosol particle sensor means of a wellknown type. This sensor will be disclosed in more detail in connection with FIG. 3, but at the present it is sufficient to understand that the solid-state aerosol particle sensor means 23 includes a heater 24 that is connected across the secondary transformer winding 22 so that the sensor means 23 is heated to an elevated temperature as compared to room ambient during the normal operation of the sensor means 23. The sensor means 23 has a further terminal 25 that has developed between it and the heater 24 a varying resistance value as a function of the number of aerosol particle particles which are present in the atmosphere around the sensor means 23. The aerosol particles, as used in the present description, are particles such as unburnt hydrocarbons, smoke, etc. and these particles vary or reduce the resistive connection between the heater 24 and the terminal 25 as an increase in concentrations exists. This variation in the resistance value is used for the operation of the balance of the system, as will be described below.

The transformer secondary 22 and sensor means 23 are connected by conductor 26 to conductor I5 so that the line voltage is applied across the sensor means 23 to the terminal 25. Terminal 25 is connected by conductor 30 to a switch 31 which in turn is connected through impedance 32 and further impedance 33, in the form of a capacitor, to a current limiting inductance 34 which in'turn is connected to conductor 16. The switch 31 has two positions, 35 and 36. Position 35 is for automatic operation wherein the sensor means 23 is connected to impedance means 32, 33, and 34. The position 36 is for manual operation and bypasses the sensor means 23 by the insertion of a resistor 37 which is connected by conductor 38 to the supply line 15. It is obvious that when switch 31 is in the position shown, that is connected to terminal 35, the sensor means 23 is connected in the system. When the switch 31 is connected to the resistor 37 and conductor 38, the system is in a manual or continuously operating mode.

Connected across the sensor means 23 and switch 31 are a group of fixed and variable resistances 40, 41, an and 42 which are used for adjusting the operating parameters of the system in a conventional fashion. Connected to line 15 is the fan motor 43 which is part of the fan and motor structure I I of FIG. 1. The fan motor 43 is connected by conductor 44 to a solid-state switch means 45 disclosed as a triac. The triac 45 is connected by conductor 46 back to the inductance 34 to complete a main current conducting path for the fan motor 43. The gate 50 of the solid-state switch means 45 is connected by conductor 51 to a voltage breakdown means 52 disclosed as silicon bilateral switch or a diac. The voltage breakdown means 52 is connected at junction 53 between the impedance 32 and the capacitor 33. The diac 52 and triac 45 are used in a conventional motor speed control circuit which in itself is well known in the art. A pair of

capacitors

54 and 55 along with a resistor 56 are provided across the triac 45 as a filter, which is also well known in the use of the triac 45 for motor speed control purposes.

OPERATION OF FIGURE 2 As soon as the line voltage is applied on conductors l5 and 16 the transformer 21 provides a low voltage to heater 24 of the sensor means 23. This heater raises the sensor means 23 in temperature, well above the ordinary ambient, thereby providing a proper mode of operation of an oxide type of aerosol sensor as is disclosed in the present application. After the sensor 23 has stabilized in temperature, the system is ready for operation and in a normal installation the sensor would be activated at all times. With line voltage applied between conductors l6 and 26, a current would flow through the sensor means 23, the switch 31, the impedance 32, the capacitor 33. and the inductor 34. The level of current flow is a function of the resistance between the terminal 25 and the heater 24. This resistance varies as a function of the aerosol particles present at the sensor with the resistance decreasing with the particle concentration increasing. The particle concentration is a function of the smoke and unburnt hydrocarbons being generated at the kitchen or range vent hood 10 of FIG. I. The sensormeans 23 is placed within the kitchen or range vent hood 10. When the particle concentration raises to a selected level the sensor means resistance drops sufficiently low so that the energy supplied to the capacitor 33 is sufficient to cause the diac 52 to breakdown and conduct through the gate 50 of the triac 45. This conduction causes the traic. 45 to conduct thereby supplying electric energy to the fan motor 43. The point in which the breakdown of the diac 52 occurs with respect to the applied alternating current voltage is a function of the impedance of the system that charges the capacitor 33. The lower the impedance of the circuit, the earlier within the applied half wave of the alternating current the breakdown of the diac 52 occurs thereby supplying more energy to the fan motor 43. It can thus be seen that as the concentration of aerosol particles at the sensor means 23 increases, the speed of the fan motor 43 increases. This arrangement automatically compensates for increase in smoke and aerosol particle concentrationto increase the fan motor speed to clear the undesired combustion products present at kitchen or range vent hood 10. Negative feedback of the control system occurs due to locating the sensor 23 within the intake duct hood 10. Increased fan speed draws more excess air to the range thereby diluting the particle concentration. The diluted signal thereby provides a form of negative feedback to stabilize the fan speed. The minimum fan speed also provides a continuous sample of room and range air to the sensor for greater response to the room conditions.

In the event that it is desired to operate the fan motor 43 for removal of odors or materials that the sensor might not respond to, a manual position 36 is provided for switch 31. In the manual position 36. the impedance 37 placed in the charging circuit for the capacitor 33 is sufficiently low to cause the fan motor 43 to operate at a predetermined and fixed speed. A minimum speed is set into the installation by the position selected for the potentiometer 41 and potentiometer 42.

In FIG. 3 a partial section of a typical solid-state aerosol sensor means is disclosed. The sensor means 23 includes a glass sensor member 60 which is coated by a metal oxide coating 61. A typical metal oxide would be tin oxide and this metal oxide coating completely encircles or encapsulates the glass 60. Embedded in the metal oxide 61 is an electric heater 24 which raises the temperature of the sensor means 23 when the ends of the electric heater 24, disclosed at 62 and 63, are connected to the transformer secondary 22 of FIG. 2. in FIG. 2 a terminal 25 for the metal oxide of the sensor means 23 was disclosed. This can be any type of a terminal embedded in the metal oxide 61 of FIG. 1, so that the complete circuit can be completed from the terminal 25 to the electric heater 24 of the sensor means 23.

The simple system disclosed in the present application provides for complete and automatic control of a kitchen or range vent hood for the removal of undesired smoke and odors which accompany many types of meal preparation. The automatic operation provides for the removal of undesired airborne components without the need of the housewife being present and allows for the automatic removal of odors that occur due to inadvertent spills or the boiling over of foods during preparation. in many cases, this type of odor generation occurs when the housewife is not present to turn on the vent fan in time to prevent the odors from being distributed throughout the cooking area. The simple automatic control provided allows for continuous automatic monitoring of the cooking operation and the varying speed necessary to clear the generated aerosol particles at a rate commensurate with their production. The simple system disclosed is but one way of carrying out the present invention and the applicant wishes to be limited in the scope of his invention solely by the scope of the appended claims.

I claim: The embodiments of the invention in which an exclusive property or right is claimed are defined as follows:

1. An automatically controlled cooking area ventilating system including: solid-state aerosol particle sensor means mounted in a cooking area and having a varying impedance in the presence of varying concentrations of aerosol particles; circuit means including said sensor means and impedance means adapted to be connected to a source of voltage so that a varying voltage is developed across said impedance means with variations of concentration of aerosol particles at said sensor means; and motor control system means adapted to be connected to ventilating fan motor with said motor control system means responsive to said varying voltage to automatically ventilate said cooking area when a predetermined concentration of aerosol particles are present in said cooking area.

2. An automatically controlled cooking area ventilating system as described in claim 1 wherein a ventilating hood is mounted above said cooking area and said sensor means is mounted within said ventilator hood so that when said ventilating fan motor is operating an air flow through said ventilator hood passes over said sensor means.

3. An automatically controlled cooking area ventilating system as described in claim 1 wherein said solid-state aerosol particle sensor means is a metal oxide type of sensor including heater means with said heater means operating said sensor at an elevated temperature.

4. An automatically controlled cooking area ventilating system as described in claim I wherein said motor control system means includes solid-state switch means in series circuit with said fan motor; and voltage breakdown means connecting said solid-state switch means to said impedance means to control the current flow in said solid-state switch means to vary the speed of said fan motor with the amount of aerosol particles present at said sensor means.

5. An automatically controlled cooking area ventilating system as described in claim 4 wherein said solid-state switch means is a triac and where said voltage breakdown means is a silicon bilateral switch.

6. An automatically controlled cooking area ventilating system as described in claim 4 wherein said solid-state aerosol particle sensor means is a metal oxide type of sensor including heater means operated at an elevated temperature by said heater means.

Claims

4. An automatically controlled cooking area ventilating system as described in claim 1 wherein said motor control system means includes solid-state switch means in series circuit with said fan motor; and voltage breakdown means connecting said solid-state switch means to said impedance means to control the current flow in said solid-state switch means to vary the speed of said fan motor with the amount of aerosol particles present at said sensor means.