Vacuum cleaner with device for adjusting sensitivity of dust sensor

Abstract: A vacuum cleaner with a dust sensor (7) comprising a light-emitting element (1) and a light-receiving element (3) for receiving light emitted from the light-emitting element (1). The dust sensor (7) is provided in a suction passage (39) between a suction nozzle (38) and a dust collector of the vacuum cleaner (35) for detecting dust in air drawn through the suction nozzle (38) to generate a current corresponding to the detection result. Also included in the vacuum cleaner is an adjusting device (40) which is coupled to the dust sensor (7) for adjusting the sensitivity of the dust sensor (7) for the dust detection. The adjusting device (40) is composed of a variable resistor to change the value of the current generated by the dust sensor (7).

Description: The present invention relates generally to vacuum cleaners, and more particularly to a sensitivity adjusting apparatus of a dust sensor for use in such a vacuum cleaner. Known is a vacuum cleaner with a dust sensor provided in an air passage between a suction opening and a dust collecting device. When dust is included in the drawn air, the dust sensor senses the dust to indicate the presence of the dust by means of an indication lamp, and for example, heighten the rotational speed of an electric blower for a predetermined time period. However, for adequate cleaning, the sensitivity of the dust sensor is different for different kinds of object to be cleaned by the vacuum cleaner. For example, when cleaning a shaggy carpet, the dust detection sensitivity is required to be lowered as compared with the sensitivity for a board floor, because the dust sensor tends to detect as dust pile of the shaggy carpet. US-A-4601082 discloses a vacuum cleaner comprising a suction nozzle, dust sensor means for detecting dust in air drawn through the suction nozzle and for generating an electric current signal depending on the result of the detection, and adjustment means coupled to the dust sensor means for adjusting the sensitivity of the dust sensor means, the adjustment means including resistor means. The dust sensor means comprises a light emitting element and a light-receiving element. By varying the value of the resistor means, the sensitivity of the light receiving element is adjustable. US-A-3579706 discloses a vacuum cleaner having a first electric motor for a motor fan unit, a second electric motor for a floor-contacting motor brush unit and a switch, mounted on the handle of the hose assembly for connection to the motor brush unit, for controlling both of the motors. The switch includes a switch circuit for energising the motor of the motor brush unit in cleaning the floor. According to the present invention there is provided a vacuum cleaner comprising a suction nozzle, dust sensor means for detecting dust in air drawn through the suction nozzle and for generating an electric current signal depending on the result of the detection, and adjustment means coupled to the dust sensor means for adjusting the sensitivity of the dust sensor means, the adjustment means including resistor means, characterised in that the cleaner further comprises a suction nozzle electric motor driveable by a power source in response to operation of a first switch, the resistor means and a second switch being coupled in parallel to each other and arranged so that the second switch shorts the resistor means when closed, the second switch being coupled to the first switch so as to be operated with the first switch. The dust sensor means preferably comprises a light-emitting element and a light-receiving element for producing an electric current corresponding to the intensity of light received from the light-emitting element, the light-emitting element and the light-receiving element being provided in a suction passage provided between the suction nozzle and dust collecting means of the vacuum cleaner. An embodiment of vacuum cleaner in accordance with the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Fig. 1 is a circuit diagram showing a circuit arrangement for use in a vacuum cleaner not in accordance with the present invention; Fig. 2 is a more detailed illustration of the Fig. 1 circuit arrangement; Fig. 3 is a perspective view of a vacuum cleaner having a dust sensor in a suction passage; Fig. 4 is an illustration of an operating section of the Fig. 3 vacuum cleaner; and Fig. 5 is a circuit diagram showing a vacuum cleaner circuit arrangement including a function for automatically adjusting the sensitivity of detection of dust drawn into an embodiment of vacuum cleaner in accordance with the present invention. Referring now to Fig. 1, there is illustrated a circuit arrangement for use in a vacuum cleaner not in accordance with the present invention. In Fig. 1, the circuit arrangement includes a dust sensor 7 comprising an infrared light-emitting diode (LED) 1 which emits infrared light and a phototransistor 3 which produces a current corresponding to the light emerging from the infrared LED 1. The output of the phototransistor 3 is led into a dust sensor circuit 6. Numeral 2 represents a resistor for determining the current to be introduced into the infrared LED 1 and numeral 4 designates a load resistor for the phototransistor 3. In response to rotation of a fan motor 9 coupled to a power source 14, air is drawn into the suction passage, and when dust is included in the drawn air, the infrared light from the infrared LED 1 is interuppted and the dust sensor circuit turns on an indication lamp 5. The dust sensor circuit 6 is coupled to a variable resistor 8 whose resistance is varied by the user so as to adjust the sensitivity of detection of the drawn dust. Numeral 10 depicts an electric motor for an agitator such as a rotatable brush of the vacuum cleaner which is driven by operation of a switch 11. Fig. 2 is an illustration of a more detailed arrangement of the circuit illustrated in Fig. 1. In Fig. 2, the signal (current) determined by the phototransistor 3 is supplied through a capacitor 15, which is provided to extract only the alternating-current component of the current due to the phototransistor 3, and the variable resistor 8 to an operational amplifier 19. The amplification degree of the operational amplifier 19 depends upon the resistance value of the variable resistor 8 and a resistor 20, and therefore, changing the resistance value of the variable resistor 8 causes variation of the amplification degree of the operational amplifier 19. The dust detection sensitivity becomes higher in accordance with increase in the amplification degree of the operation amplifier 19. Thus, the dust detection sensitivity is adjustable by means of the control of the resistance value of the variable resistor 8. The output of the operational amplifier 19 is supplied to an indication circuit 21 for driving the indication lamp 5 and further led to a phase control circuit 26 for driving a bidirectional thyrister 29 to control the speed of the fan motor 9. A variable resistor 27 is also coupled to the phase control circuit 26 so as to perform the phase control. In Fig. 2, numerals 17, 18, 22 and 25 respectively represent resistors. The dust sensor 7, as illustrated in Fig. 3, is provided in a suction passage between a suction nozzle 38 and an operating section 37 of the vacuum cleaner, the operating section 37 being coupled through a hose 36 to a body 35 of the vacuum cleaner having therein the fan motor 9 and others. As illustrated in Fig. 4, on the operating section 37 are provided an adjusting device 40 operatively coupled to the variable resistor 8 for adjusting the resistance value of the variable resistor 8 and another adjusting device 41 operatively coupled to the variable resistor 27 for adjusting the resistance value of the variable resistor 27. Referring now to Fig. 5, there is illustrated a circuit arrangement of an embodiment of vacuum cleaner in accordance with the present invention, where parts corresponding to those in Fig. 1 are marked with the same numerals. In Fig. 5, the circuit arrangement of this embodiment includes a dust sensor 7 which is composed of an infrared light-emitting diode (LED) 1 for emitting infrared light and a phototransistor 3 for producing a current corresponding to the intensity of the light emerging from the infrared LED 1. The output of the phototransistor 3 is led into a dust sensor circuit 6. Numeral 2 represents a resistor for determining the current to be introduced into the infrared LED 1 and numeral 4 designates a load resistor for the phototransistor 3. In accordance with a signal from the dust sensor circuit 6, an indication lamp 5 turns on so as to indicate the presence of dust in the air drawn into the suction passage. Numeral 9 designates a fan motor driven due to a power source 14 and numeral 10 depicts an electric motor for an agitator of the vacuum cleaner which is driven by operation of a switch 11. Also included in the circuit arrangement are a switch 12 and a resistor 13 which are respectively coupled to the dust sensor circuit 6. The switch 12 is a change-over switch for adjusting the sensitivity of the dust sensor circuit 6 for dust detection and the resistor 13 is provided in order to set the detection sensitivity of the dust sensor circuit 6. The change-over switch 12 is connected in parallel to the resisotor 13 and is mechanically connected to the switch 11 for operation of the agitator driving motor 10, so as to be operated in connection with the operation of the switch 11. The switch 11 may be provided on the operating section 37. The rotatable-brush driving motor 10 is operated when cleaning a carpet and stopped when cleaning the other objects such as a bare floor. In response to the closing operation of the switch 11 for the driving of the motor 10 made when cleaning a carpet, the change-over switch 12 automatically enters into the closed state because of the mechanical connection therebetween. The closing of the change-over switch 12 causes the short of the resitor 13, thereby resulting in lowering the detection sensitivity of the dust sensor circuit 6. That is, the detection sensitivity of the dust sensor circuit 6 is automatically lowered due to the operation of the switch 11 made when cleaning a carpet.

Claims: A vacuum cleaner comprising a suction nozzle (38), dust sensor means (7) for detecting dust in air drawn through the suction nozzle (38) and for generating an electric current signal depending on the result of the detection, and adjustment means (12, 13) coupled to the dust sensor means (7) for adjusting the sensitivity of the dust sensor means, the adjustment means including resistor means (13), characterised in that the cleaner further comprises a suction nozzle electric motor (10) driveable by a power source (14) in response to operation of a first switch (11), the resistor means (13) and a second switch (12) being coupled in parallel to each other and arranged so that the second switch (12) shorts the resistor means (13) when closed, the second switch (12) being coupled to the first switch (11) so as to be operated with the first switch (11). A vacuum cleaner as claimed in claim 1, wherein the dust sensor means (7) comprises a light-emitting element (1) and a light-receiving element (3) for producing an electric current corresponding to the intensity of light received from the light-emitting element (1), the light-emitting element (1) and the light-receiving element (3) being provided in a suction passage provided between the suction nozzle (38) and dust collecting means (35) of the vacuum cleaner.

Inventors: TAKASHIMA YOSHINORI, TANAKA TOSHIICHIRO, TAKASHIMA, YOSHINORI, TANAKA, TOSHIICHIRO
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1989
Main classification: A47L9
IPC codes: A47L9