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(11) | EP 0 211 372 B1 |
| (12) | EUROPEAN PATENT SPECIFICATION |
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| (54) |
Automatic spray gun Automatische Spritzpistole Pistolet de pulvérisation automatique |
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| Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). |
[0001] The present invention relates to an apparatus for spaying an object with a coating fluid such as a paint. More particularly, the present invention pertains to a spray gun which is so designed that the need for a manually-operated gun trigger is eliminated in a spraying operation.
[0002] Paint spray guns are well known as means for spraying various objects with liquid substances. A typical spray gun of this type is arranged such that an operator holds it in his hand and actuates a trigger or any other similar means such as a push-button provided on the spray gun to start and stop spraying of a liquid substance, thereby effecting the required spraying operation. In this type of operation, however, the operator must repeatedly move his hand and finger to control and trigger the spray gun, and this leads to injury or physical handi- : cap. Therefore, efforts have been made to devise a measure for coping with this situation.
[0003] Further, the distance between the spray gun and the object is a important factor in a spraying operation, and it is necessary to hold the spray gun at an : appropriate distance when spraying a coating on the object. In painting, this distance has a particularly significant effect on the grade or quality of finish, and it is necessary for the operator to conduct painting while constantly maintaining an appropriate spraying distance. However, with the conventional spray guns, the operator must estimate the distance from an object with the naked eye and actuate the trigger of the spray gun accurately and effectively on the basis of his own experience and skill, which means that technical skill is needed to effectively handle the conventional spray guns. In any type of conventional spray gun, it is necessary to actuate a trigger or a similar control member in order to control the amount of paint sprayed and the pressure of compressed air.
[0004] FR-A 2 517 567 relates to an apparatus for controlling the distance between a pulverisation apparatus and an object, for instance a wall. This apparatus can also be used to apply paint to metallic objects, for instance cars. Further, a problem having to do with the distance between the paint apparatus and the object is discussed, but not in the context of a hand held spray gun which is put in action by an operator due to the actuation of a trigger for effect- i ing the required spraying operation. In addition to the trigger operation the operator of a hand held spray gun has to estimate the distance with respect to an object to be painted, a situation which requires special skills on the part of the operator during a ; paint process.
[0005] In view of the above-described circumstances, it is a primary object of the present invention to provide a spray gun which eliminates the need to take account of the distance between the spray gun and an object being sprayed, thereby allowing an operator to effect an optimal spraying operation without it being necessary for him to have particular technical skills in order to constantly maintain an appropriate spraying distance, and which also eliminates the need to conduct a manual operation when starting and stopping the spraying of an object with a coating:
[0006] To this end, the present invention provides an automatic spray gun which is provided with means for judging or measuring the distance between the spray gun and an object, and a solenoid valve which is activated in response to a control signal delivered from the distance measuring means, thereby allowing spraying to be automatically effected when the object is within a predetermined range.
[0007] In a practical embodiment of the present invention, the spray gun has a liquid atomizing means provided at the front end thereof, a needle valve adapted to control the amount of liquid sprayed, and an air piston received in a cylinder at the rear end of the needle valve, the piston being controlled such as to be selectively advanced and withdrawn by means of compressed air. The spray gun further has a sensor incorporated therein, the sensor being adapted to transmit a signal toward an object and receive the signal reflected therefrom so as to measure the distance from the object. In addition, the spray gun is provided with a solenoid valve which allows compressed air to be blown off when the measured distance is within a predetermined range. The piston is adapted to control the needle valve so as to selectively start and stop a spraying operation. The piston is activated by compressed air, and in a pneumatic atomization type spray gun, the atomizing compressed air is employed to activate the piston.
[0008] Accordingly, the opening and closing operation of the solenoid valve replaces the trigger operation of the spray gun. The control of the solenoid valve is automatically effected on the basis of a value measured by the distance measuring means. Therefore, spraying is performed only when the distance between an object and the spray gun is within a predetermined appropriate range while the latter is pointed toward the object. Thus, spraying is automatically effected only when necessary without the need to actuate a manually-operated trigger or the like.
[0009] The above and other objects, features and advantages of the present invention will become more apparent from the following description of a preferred embodiment thereof, taken in conjuction with the accompanying drawing.
[0010] The accompanying drawing is a sectional view of a spray gun in accordance with one embodiment of the present invention.
[0011] Referrring to Fig. 1, which is a sectional view of a paint spray gun in accordance with one embodiment of the present invention, the atomizing means of this spray gun is of the pneumatic atomization type and therefore adopts a conventional arrangement which is composed of an air cap 1, a paint nozzle 2 and a needle valve 3. An air piston 4 is operatively secured at the rear end of the needle valve 3, so that the needle valve 3 is selectively opened and closed by the action of the air piston 4. The air piston 4 is received in a cylinder 5, and a packing 6 for keeping the cylinder 5 airtight is provided on the sliding part of the air piston 4. A knob 7 is provided at the rear end portion of the piston 4. The knob 7 is fitted through a threaded portion 9 thereof into the central portion of a cap 8 which closes the rear end of the cylinder 5 in such a manner that the knob 7 is movable longitudinally for adjustment, thereby limiting the amount of movement (withdrawal) of the piston 4, and thus adjusting the degree of opening of the needle valve 3. The forward portion of the piston 4 is communicated with an air passage 12 which is connected to a compressed air supply source AS. The air passage 12 is selectively opened and closed by the action of a solenoid valve 11 which is provided at the lower end of a handle 10 of the spray gun. The arrangement is such that, when the solenoid valve 11 is opened, compressed air is introduced into the cylinder 5, thus causing the piston 4 to be withdrawn. In addition, a spring 13 is provided for the purpose of returning the needle valve 3 to its previous position when the compressed air is expelled from the cylinder 5. Air passages 14 and 15 for sending the compressed air from the solenoid valve 11 to the atomizing means extend towrad the front end of the spray gun. A part of the air supplied through these passages 14 and 15 is jetted out from an atomizing nozzle 1 a so as to cause a paint to be atomized, and the remaining air is blown off from a spray pattern adjusting orifice lb so as to adjust the pattern of the atomized paint. In this spray gun, the flow rate of both the atomizing air and the spray pattern adjusting air is varied by the operation of a spray pattern adjusting valve 16. A distance measuring means 17 is provided in such a manner as to face the same direction as that of the atomizing means. The distance measuring means 17 is composed of an ultrasonic transmitting transducer and an ultrasonic receiving transducer and is adapted to measure the distance from an object which is located in the forward direction from the spray gun. This type of means is adapted to measure the distance from an object on the basis of the period of time which it takes for an ultrasonic wave to travel from the point where it is transmitted to the object and then to return to a point where it is received on being reflected back from the object. Since this structure is known and its detailed structure per se does not constitute any part of the present invention, description thereof is omitted. Although not shown, the distance measuring means 17 includes a power supply and an arithmetic unit so that a control signal is delivered to the solenoid valve 11 from the means 17.
[0012] In this embodiment, the distance measuring means 17 employs an ultrasonic sensor for detection of the spray distance because this type of sensor works substantially irrespectively of the kind of material of which the object is formed and it is not readily affected by coatings such as paint which are sprayed and become undesirably attached to the sensor. However, the ultrasonic sensor is not necessarily limitative, and other types of known measuring means, e.g., optical and electrical means, may also be employed, provided that the measuring means employed meets particular conditions. It should be noted that a paint is supplied from a paint supply source PS in a manner similar to that in the conventional spray guns, and description of the paint supply method is therefore omitted.
[0013] In operation, the power supply for the distance measuring means 17 is first turned ON to make the spray gun operative. In consequence, the spray gun is immediately brought into a state wherein its spray coating operation is kept under control. More specifically, when the spray gun is directed toward an object, the distance measuring means 17 starts measurement of the distance from the object by means of constant pulses, and when the spray gun comes within a spraying distance of a predetermined range, the solenoid valve 11 is immediately opened and the compressed air is thereby sent to the air cap 1 which constitutes a part of the atomizing means of the spray gun.
[0014] At the same time, the compressed air is also supplied to the air cylinder 5, and the piston 4 is withdrawn by virtue of the pressure of the compressed air, thus causing the needle valve 3 connected directly to the piston 4 to also be withdrawn. In consequence, the paint 2 is jetted out from the paint nozzle 2 and atomized by the compressed air from the air cap 1 before being sprayed on the object. Accordingly, it is possible to effect spray coating simply by moving the spray gun along the object without the need to actuate a manually-operated trigger as in the case of conventional spray guns. In addition, painting is conducted only when the object is in front of the spray gun and is located at an appropriate distance from the spray gun. In the present invention, the amount of paint jetted out from the spray gun and the pattern of the sprayed paint are adjusted by actuating the manually-operated knob. It is therefore only necessary for the distance measuring means to be able to generate an ON-OFF signal to control the spraying operation on the basis of the predetermined spraying distance range. In addition, the spray gun is only required to have a simple structure such as that exemplified in the embodiment which enables the needle valve to be activated by the action of the air piston.
[0015] As has been described above, the spray gun according to the present invention enables painting to be automatically conducted only when an object is located within an appropriate range from the spray gun by confirming the distance from the object with the distance measuring means provided on the spray gun. It is therefore possible for the operator to effect an optimal painting operation simply by pointing the spray gun toward an object and moving the spray gun along the surface of the object, or fixing the spray gun and moving an object relative to it. In particular, a surface of an object which needs to be painted is automatically judged on the basis of the configuration of the object, and the spraying operation is automatically started and stopped. Accordingly, even an unskilled person can effect excellent painting without experiencing hand fatigue and without any fear of a painting failure due to misjudged spraying distance.
a gun body to be carried by an operator;
liquid atomizing means provided at the front end of said gun body;
a needle valve in said atomizing means for controlling the amount of liquid jetted from said atomizing means, said needle valve having a valve member extending toward the rear of said gun body;
a compressed air supply source;
an air piston secured to the rear end of said valve member and a cylinder in which said air piston is received for being activated by compressed air supplied from said air source for moving said air piston in a direction to open said needle valve;
spring means biasing said valve member in the direction for closing said needle valve;
distance measuring means on said gun body directed in the direction in which the liquid is sprayed for measuring the distance between said spray gun and an object to be sprayed;
an air passage means extending from said air source to said cylinder for supplying the compressed air; and
a solenoid valve mounted on said gun body and disposed in said air passage means and connected to said distance measuring means so that it is activated in response to an ON-OFF signal from said distance measuring means for opening the air passage means when the distance between said spray gun and the object to be sprayed is within a predetermined range.
Einen Pistolenkörper, der von einem Benutzer getragen wird;
am vorderen Ende des Pistolenkörpers vorgesehene Flüssigkeitsatomisiermittel;
ein Nadelventil in den Atomisiermitteln zur Steuerung der aus den Atomisiermitteln herausgespritzten Flüssigkeitsmenge, wobei das Nadelventil ein sich zur Rückseite des Pistolenkörpers erstreckendes Ventilglied aufweist;
eine Druckluftversorgungsquelle;
ein Luftkolben, befestigt am hinteren Ende des Ventilglieds und ein Zylinder, in dem der Luftkolben aufgenommen ist, um durch Druckluft aktiviert zu werden, die von einer Luftquelle geliefert wird, um so den Luftkolben in einer Richtung zum Zwecke des Öffnens des Nadelventils zu bewegen;
Federmittel zum Vorspannen des Ventilglieds in die Schließrichtung des Nadelventils;
Abstandsmeßmittel am Pistolenkörper gerichtet in der Richtung in der die Flüssigkeit gespritzt wird um den Abstand zwischen der Spritzpistole und einem zu bespritzenden Objekt zu messen;
Luftdurchlaßmittel, die sich von der Luftquelle zu dem Zylinder erstrecken, um Druckluft zu liefern; und
ein am Pistolenkörper angeordnetes Elektromagnetventil und zwar angeordnet in den Luftdurchlaßmittein und verbunden mit den Abstandsmeßmitteln derart, daß es aktiviert wird und zwar in Folge eines EIN-AUS-Signals von den Abstandsmeßmitteln zum Öffnen der Luftdurchlaßmittel wenn der Abstand zwischen der Spritzpistole und dem zu bespritzenden Objekt innerhalb eines vorbestimmten Bereichs liegt.
Un corps du pistolet pouvant être porté par un opérateur;
Un moyen d'atomisation du liquidé disposé à l'extrémité avant dudit corps du pistolet;
Une soupape à aiguille disposée dans ledit moyen d'atomisation et permettant de contrôler la quantité de liquide pulvérisée par ledit moyen d'atomisation, ladite soupape à aiguille comportant un organe de soupape s'étendant à l'encontre de la partie arrière dudit corps de pistolet;
Une source d'alimentation en air pressurisé;
Un piston pneumatique fixé à l'extrémité arrière de l'organe de soupape et un cylindre dans lequel ledit piston pneumatique est disposé de manière à être actionné par l'air pressurisé qui est fourni par la source d'air précitée afin de déplacer ledit piston pneumatique dans une direction d'ouverture de ladite soupape à aiguille;
Un ressort sollicitant ledit organe de soupape dans la direction de la fermeture de ladite soupape à aiguille;
Un moyen de mesure de distance disposé sur ledit corps du pistolet et dirigé dans la direction vers laquelle le liquide est pulvérisé, ce moyen permettant de mesurer la distance comprise entre ledit pistolet de pulvérisation et l'objet que l'on souhaite pulvériser;
Un passage d'air qui s'étend depuis ladite source d'air jusqu'audit cylindre de manière à conduire l'air pressurisé; et
Une soupape solénoïde montée sur ledit corps du pistolet et disposée dans ledit passage d'air, ladite soupape solénoïde étant connectée au moyen de mesure de la distance de telle façon que celle-ci soit actionnée en réponse à un signal en MARCHE-AR-RET délivré par ledit moyen de mesure des distances afin d'ouvrir le passage d'air lorsque la distance comprise entre le pistolet de pulvérisation et l'objet que l'on souhaite pulvériser est inférieure à une gamme prédéterminée.