Dispensing – Cutoff operated by selectively preset volume or rate of...
Patent
1992-02-28
1994-01-11
Kashnikow, Andres
Dispensing
Cutoff operated by selectively preset volume or rate of...
222 55, 222 61, 222639, B67D 530
Patent
active
052773337
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a liquid dispensing apparatus adapted for accurately metering and discharging a predetermined quantity of viscous liquid such as resin material, conductive adhesive, cream solder, UV resin, silver paste and the other paste like material used in coating, dotting, fixing and injecting processes.
A liquid dispensing apparatus discussed for example in Japanese patent application laid open 63-97259. This paste dispensing apparatus comprises a syringe containing a paste or the like, an air supply for supplying air under a positive pressure to the syringe, a dispensing solenoid valve arranged between the syringe and the air supply. The solenoid valve is connected to the syringe by means of a first pipe line and to the air supply by means of a second pipe line for communicating the syringe with the air supply when the paste is dispensed from the syringe. A first pressure sensor measure a pressure in the first pipe line and a second pressure sensor measures a pressure in the second pipe line. A controller having inputs for signals of measured pressure is connected to the first and second pressure sensor. The controller also has a voltage signal output for actuating the dispensing solenoid valve to connect the first and second pipe lines to each other at the start of dispensation. The controller controls a duration of the output voltage signal until the pressure measured by the first pressure sensor reaches a preset pressure after the first and second pipe lines are communicated to each other.
The aforementioned paste dispensing apparatus further comprises an air suction device connected to the dispensing solenoid valve by a third pipe line to connect the first and third pipe lines while the first and second pipe lines are not connected to each other. The air suction device supplies air under a negative pressure to the first pipe line to prevent the paste from dripping from the syringe after completion of dispensing.
The controller outputs a voltage signal that actuates the dispensing solenoid valve to supply a positive air pressure from the air supply to the syringe thereby dispensing the paste from the syringe. A variation in the pressure measured by the first pressure sensor in relation to the amount of paste remaining in the syringe is estimated by the controller so that the amount of the paste dispensed by the syringe is constant in spite of a variation in the amount of the paste remaining in the syringe.
The aforementioned paste dispensing apparatus can be controlled to dispense a predetermined amount of paste from the syringe when the air pressure in the syringe reaches a preset pressure P as shown by a curve q in FIG. 5. The aforementioned dispensing apparatus however cannot be controlled to accurately dispense the paste from the syringe when the air pressure in the syringe does not reach the preset pressure P as shown by a curve in FIG. 5 because of change or variation of syringe inner volume, pipe line inner diameter, or compressed pressure.
The present invention solves the foregoing problems and provides an improved liquid dispensing apparatus capable of dispensing a constant amount of liquid in spite of variations in the curve of air pressure in the syringe. The present invention also quickly and effectively prevents liquid from dripping out of the syringe between repeated dispensations of the liquid.
A liquid dispensing apparatus according to the present invention comprises a syringe containing liquid, an air supply for supplying air under a positive pressure to the syringe, a dispensing solenoid valve arranged between the syringe and the air supply, a first pipe line connecting the syringe to the dispensing solenoid valve, a second pipe line connecting the dispensing solenoid valve to the air supply, a first pressure sensor for measuring the internal pressure in the first pipe line, a second pressure sensor for measuring the internal pressure in the second pipe line, an accumulator connected to the second pipe line, and a controller having a
REFERENCES:
patent: 2710115 (1955-06-01), Chandler
patent: 3708088 (1973-01-01), Lesher
patent: 4274552 (1981-06-01), Proni
patent: 4376172 (1983-03-01), Belangee et al.
patent: 4810659 (1989-03-01), Higo et al.
patent: 4874444 (1989-10-01), Satou et al.
patent: 4989756 (1991-02-01), Kagamihara et al.
patent: 5031805 (1991-07-01), Rohmann
patent: 5188258 (1993-02-01), Iwashita
Japanese Patent Laid-open No. 63-97259-Japanese Patent Appln. No. 61-242992.
Bomberg Kenneth
Kashnikow Andres
Musashi Engineering Inc.
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