EP1063018B1 - Automatic spray gun with a membrane - Google Patents

Abstract

A spray gun has a needle fixed to a membrane oscillated by a pulsing device. The needle causes a product to be supplied intermittently to a spray duct. The needle may extend into a central supply channel of a spraying head.

Description

The invention relates to an automatic membrane gun used for spraying products, in particular spraying abrasive or enamel paints, water-soluble or dissolved in a solvent.

There are spray guns in which the spray of the product is obtained exclusively hydrostatically, that is to say by applying a pressure on the product and out through a nozzle at the front end of the gun. Spraying can also be achieved pneumatically, but generally a combination of the two is used, which means that the hydrostatic spray is combined with jets of compressed air which, in addition to a jet of central air spraying, serve to adjust the shape and / or dimensions of the jet of sprayed product.

To regulate the supply of the product to the nozzle and especially to cut this supply when the gun is no longer actuated, conventional automatic no-diaphragm guns use a needle that closes the outlet of the product through the nozzle. The removal of the needle to clear this outlet is controlled by pneumatic control means acting on the piston of a cylinder moving the needle rearwardly. When the control means are no longer actuated, a return spring acts on the cylinder in the opposite direction to move the needle forward to close the outlet.

The invention relates more particularly to automatic membrane guns in which the membrane is controlled by pulsed air so that the product, which is fed into the gun under constant pressure, comes out of the nozzle by intermittent spraying.

In a known automatic diaphragm gun, the diaphragm is driven in an oscillation movement by pneumatic means for controlling the pulsed filling of the feed of the product comprising a pulsed air supply which communicates with an annular chamber formed in the gun body around the rod of a control piston which, when actuated by the pulsating air, is moved backwards against the action of an elastic return means. The piston thus moves back and forth at the frequency of the pulsed air.

The forward end of the piston rod rests against the diaphragm in a central area thereof to impart an oscillating motion thereto. The product to be sprayed is fed under pressure into a product receiving chamber which is immediately in front of the membrane and which towards the rear is delimited by it. This receiving chamber communicates through a central opening with a central product supply channel arranged in the spray head and which opens directly into the nozzle.

When the means for controlling the pulsed air are not actuated, and also between two successive pulsations, the central opening is closed by intermittent sealing means constituted by the membrane itself which is then pressed by the end piston rod against the peripheral area around the opening which thus forms a seat. For this purpose, the diameter of the end of the piston rod is substantially larger than the internal diameter of the opening.

However, this seat is thus at one end of the central channel whose opposite end opens into the nozzle, so that when the control means of the pulsed air are no longer actuated, that is to say ie when the spray is stopped, the entire volume of the central channel is a residue of the product whose flow through the nozzle can not be prevented, causing soiling.

Another disadvantage of this gun lies in the fact that the obstruction and the release of the opening to the central channel during the oscillation of the membrane are inaccurate and do not allow the proper functioning of these intermittent sealing means the supply of the product under constant pressure at frequencies which in this technical context are considered high and which are of the order of 4 Hz.

This diaphragm spray gun further comprises pulsed supply means for spraying air opening near the spray nozzle to improve the spray and to form the jet of the product. The atomizing air is supplied independently of the pulsed output of the product by means of a programmable controller which supplies the spray air into an annular chamber formed in the spray head and which communicates with a first set of orifices. or air nozzles opening close to the exit of the nozzle and with a second set of orifices located in a crown placed at the front end of the gun body. This arrangement allows the orifices of this second set of orifices to direct the spray air jets at a much greater angle to the jet of the product exiting the nozzle.

However, this independent supply of air spray requires a set of ancillary circuits and in addition, the controller that manages the air supply spray requires complicated and expensive settings, which is still a major drawback.

A general problem which affects membrane spray guns as well as the others which operate with a needle valve lies in the fact that some parts are very exposed to wear, especially when the product is an abrasive product such as a paint with enamel. This is primarily the nozzle, but also the membrane in the case of membrane spray guns and the needle in the case of needle spray guns. All these wear parts thus require a regular replacement that must be done more or less often depending on the abrasive nature of the product. It is therefore desirable to extend the life of these wear parts and / or to facilitate their replacement.

The object of the invention is to remedy all the drawbacks mentioned above by proposing an automatic membrane spray gun which avoids contamination by the flow of a residue of the product when the gun is stopped, which operates without problem at a high frequency with an immediate and impeccable response to the pulsation of the diaphragm, which is provided with a simple supply of spray air and at least some of the wear parts of which are designed to allow increased service life and / or replacement ease.

The object of the invention is an automatic membrane gun for spraying a product such as a paint fed with constant pressure into the gun, comprising means for pulsed spraying of the product comprising an oscillation membrane associated with means for intermittently closing the supply of the product to a nozzle, and pneumatic control means of said pulsed product spraying means, characterized in that said sealing means comprise a punch integral with the oscillation membrane and passing therethrough so as to be connected to a pulsation control member comprising a piston rod connected to a piston controlled by pulsed air.

• le pointeau est fixé à la membrane par des moyens de serrage disposés de part et d'autre de la membrane;
• les moyens de serrage sont constitués par des brides solidaires du pointeau et disposées de part et d'autre de la membrane afin de la serrer entre elles;
• l'extrémité avant du pointeau s'étend dans un canal central aménagé dans une tête de pulvérisation, et le pointeau peut venir en appui contre un siège aménagé dans le canal central immédiatement derrière la buse;
• dans un pistolet du genre comportant des moyens d'alimentation pulsée en air de pulvérisation débouchant à proximité de la buse de pulvérisation, et des moyens de commande desdits moyens d'alimentation pulsée en air de pulvérisation, lesdits moyens de commande desdits moyens de pulvérisation pulsée du produit comprennent également lesdits moyens de commande desdits moyens en alimentation pulsée de l'air de pulvérisation;
• l'extrémité du pointeau est constituée d'un embout interchangeable;
• l'embout du pointeau est en résine de synthèse;
• du côté en contact avec le produit, la membrane est revêtue d'une couche en polytétrafluoréthylène.

According to other features of the invention:

• the needle is fixed to the membrane by clamping means arranged on either side of the membrane;
• the clamping means consist of flanges integral with the needle and arranged on either side of the membrane to clamp them together;
• the front end of the needle extends in a central channel arranged in a spray head, and the needle can abut against a seat arranged in the central channel immediately behind the nozzle;
• in a pistol of the kind comprising pulsed supply means for spraying air opening near the spray nozzle, and control means for said pulsed air supply means, said means for controlling said pulsed spraying means the product also comprises said means for controlling said means for pulsed supply of the spray air;
• the end of the needle is made of an interchangeable tip;
• the tip of the needle is in synthetic resin;
• on the side in contact with the product, the membrane is coated with a polytetrafluoroethylene layer.

• La figure 1 est une vue schématique en coupe longitudinale d'un pistolet de pulvérisation à membrane selon l'invention, vu dans sa position d'arrêt correspondant à sa position entre deux pulsations successives des moyens de commande de la pulvérisation pulsée du produit,
• La figure 2 est une vue schématique en coupe longitudinale du pistolet de la figure 1, lorsqu'il se trouve dans sa position de pulvérisation dans laquelle aussi bien la pulvérisation pulsée du produit que l'alimentation pulsée de l'air de pulvérisation sont actionnées.

The invention will now be described in more detail with the help of a non-limiting example of an embodiment of the gun according to the invention with reference to the appended drawings in which:

• The figure 1 is a diagrammatic view in longitudinal section of a membrane spray gun according to the invention, seen in its stop position corresponding to its position between two successive pulsations of the control means of the pulsed spraying of the product,
• The figure 2 is a schematic view in longitudinal section of the gun of the figure 1 , when in its spray position in which as well the pulsed spraying of the product as the pulsating supply of the atomizing air are actuated.

The automatic pistol shown in the drawings is a membrane gun of the type in which the product spray is obtained by pulsed spraying of the product fed into the constant pressure gun, in combination with a pulsed supply of atomizing air which in addition to spraying allows to adjust the shape and / or dimensions of the jet of sprayed product. The process of spraying and adjusting the jet of product sprayed by the compressed air jets is well known and, not forming part of the invention, it will not be described in detail.

The gun comprises a body 1 which, preferably, is made of light metal. This body is at its front and rear ends extended by a cylindrical protuberance before 2 and respectively a rear protrusion 3, which are threaded externally. The front protuberance carries a spray head 4 and the rear protrusion carries a cap 5 inside which are housed intermittent output control means of the product to be sprayed.

The product is supplied under constant pressure by a pipe 6 in a product feed chamber 7 arranged in the front part of the gun and having a generally frustoconical shape with the smaller diameter end opening directly into a central channel 8 of the head 4. The means for obtaining the pulsed spraying of the product comprise a membrane 10 disposed at the end of the larger diameter of the chamber of spray. brought frustoconical 7.

The periphery of the membrane 10 is clamped between a front portion 1 'and a rear portion 1 "of the body 1. These two parts 1' and 1" are assembled by screwing and must be separated for the change of the membrane. to wear caused by the product on the front side of the membrane. The membrane is made of a material such as nitrile. The face exposed to this wear is according to the invention coated with a layer of polytetrafluoroethylene (PTFE), which substantially increases the life of the membrane.

For the pulsed spraying of the product at the nozzle, the membrane 10 is according to the invention mounted oscillating with a needle 11 extending in a central through bore 12 of the second portion 1 "of the body 1 and which is connected to control means reciprocating at this needle The needle 11 passes through the membrane 10 through a central hole (not shown) of the latter and is secured to the latter by clamping means consisting of flanges 13, 14 integral with the needle and disposed on either side of the membrane 10 in order to clamp them together.

The front end of the needle can, as shown in figure 1 , abut against a seat 15 immediately behind the nozzle to form together intermittent sealing means of the supply of the pressurized product into the nozzle. The product passes from the product inlet chamber 7 to the nozzle 9 by an annular spacing defined between the inner wall of the central channel 8 and the outer face of the needle. The space behind the membrane 10 in the product inlet chamber is vented through a conduit 16.

The needle 11 is guided in a guide sleeve 17 placed inside the central bore 12 and provided with seals 18.

The nozzle 9 thus constitutes, with the needle 11 and the membrane 10, pulsed atomization means for the product controlled by pneumatic control means comprising a forced air supply pipe 19 connected to a conduit 20 which opens into an annular chamber 21 formed around a piston rod 22 extending in the central bore 12 to be connected to its piston 23 which is guided in the cap 5.

The pulsed air coming through the pipe 19 is fed into the annular chamber 21 so as to push the piston 23 against the effect of a return spring 24 bearing on one side against the piston and the on the other side against an inner wall of the cap 5. Reciprocating movement of the piston 23 and thus also the needle 11 which drives the diaphragm 10 in a swinging motion.

The figure 1 shows the advanced position of the needle between two pulses of the control air admitted into the annular chamber 21 by the air duct 20, this position also corresponding to the position of the needle when the gun is stopped. In the latter case, there is no product leakage through the nozzle 9, since the end of the needle is in abutment against the seat 15 immediately behind the nozzle.

When the piston 23 is pushed back by a control air pulsation, by compressing the spring 24, to the retracted position shown in FIG. figure 2 , the end of the needle 11 leaves its seat 15 to release access to the spray nozzle 9 for the pressurized product which passes from the product inlet chamber 7 to the nozzle by the annular spacing defined between the wall internal of the central canal and the outer face of the needle. At the same time, the central zone of the membrane 10 is pulled backwards to fill the product inlet chamber to the maximum.

Between two pulses of control air, the device returns to the position shown in FIG. figure 1 by a displacement of the piston 23 towards the front, under the effect of the action of the return spring 24, to thereby move the needle 11 forward by driving the membrane through the central zone thereof and that up to the needle presses against its seat 15 in order to close the access of the product to the nozzle.

In order to improve the spraying and to better form the jet of sprayed product coming out of the spray nozzle 9, the spray gun is also provided with pulsed air supply means for spraying air opening near the spray nozzle 9. spray air supply means comprise a compressed air pipe 25 connected to an air duct 26 opening into a generally circular air inlet chamber 27 arranged around the needle 11 in the rear part 1 "of the body 1 of the gun This air inlet chamber 27 is, via another air duct whose opening is indicated in the figures and which extends in the rear and front parts of the body 1, connected to an outer circular chamber 29 arranged in the spray head 4. This outer chamber 29 is in communication with an inner circular chamber 30 and the two chambers are in a manner known per se connected to the atmosphere p ar orifices opening to the front face of the spray head 4.

The orifices 31 of the outer chamber 29 are arranged in a ring 32 disposed at the front face of the spray head 4, coaxially with the outlet of the nozzle 9. These orifices 31 form inside the ring 32 air directed slightly outward and converging towards the jet of product.

The orifices 33 of the internal chamber 30 form near the outlet of the product of the spray nozzle 9 outwardly directed and diverging air jets to delineate laterally the jet of product.

The control means of these means for supplying the atomizing air are for the pulsed supply of the air included in the control means of the pulsed atomization means of the product. According to the invention, the needle 11 also forms a valve allowing the pulsed supply of the spray air. For this purpose, the needle comprises a valve body 34 constituted by a cylindrical portion of larger diameter which at its rear end is connected to the piston rod 22 and which at its front end has a first beveled shoulder 35 intended to cooperate with a second beveled shoulder 36 complementary to the first and formed inside the central channel 8 immediately in front of the inlet chamber 27 of the compressed air. This second shoulder constitutes a seat for the valve body 34.

In the position shown in figure 1 , which corresponds to a position of the device between successive pulsations of the pulsating control air and to a stationary position, the valve composed of the first and second shoulders 35, 36 acts as a closure means preventing the supplying the spray air to the spray head 4.

Under the effect of a pulsation printed on the piston 23 which moves the needle 11 rearwards, the valve body 34 leaves the seat 36 to allow free passage to the spray air to the spray head. This cycle of opening and closing of the valve is repeated for each pulse.

In order to obtain a slight delay in the opening of the needle 11 with respect to the opening of the valve 34 so that the supply of the atomizing air starts just before the intermittent exit of the product, a second return spring 37 is disposed inside the cap 5 to control the movement of the needle. This second return spring 37 is supported on one side on the rear end of the needle and on the other side on the cap 5 to bias the front end of the needle against the seat 15 thereof. There is a slight axial clearance between the piston 23 and the rear end of the needle 11, which has the consequence that at the beginning of a pulsation of the control air, the needle opens with a slight delay relative to at the valve 34 and when the pulsation ends, the needle 11 closes slightly before the valve 34.

Thanks to the invention, thus obtaining a membrane spray gun in which there is no longer a separate controller to manage the supply of the spray air and can easily apply a high operating frequency with a frank and immediate answer.

In order to improve the wear resistance of the most exposed parts, the invention proposes several solutions.

Thus, the membrane which is usually made of nitrile can advantageously be coated with a polytetrafluoroethylene layer, which considerably increases the service life of this part.

In order to avoid having to disassemble the entire gun to effect the change of the entire needle, the end thereof is according to the invention consists of an interchangeable tip which is simply fixed by screwing. To change this tip, simply remove the spray head to access. Moreover, to improve the wear resistance of this tip, it can advantageously be manufactured in a synthetic resin adapted to the product to be sprayed.

Due to the fact that the nozzle is closed by a needle whose closing end is immediately behind the nozzle, there is no risk of product running through the opening of the nozzle when the gun is stopped.

Other variants are of course possible without departing from the scope of the invention.

Claims (8)

1. Automatic gun with a membrane for spraying a product such as a paint which is supplied to the gun at a constant pressure, comprising pulsed means (10, 11) for spraying the product, comprising an oscillation membrane (10) which is associated with means (11) for intermittent closing of the intake of the product to a nozzle (9), and means (19, 22, 23) for controlling pneumatically the said means for pulsed spraying of the product, characterised in that the said closing means comprise a needle (11) which is integral with the said oscillation membrane (10), and passes through the latter such as to be connected to a pulse control unit comprising a piston rod (22) connected to a piston (23) which is controlled by the pulsed air.
2. Gun according to claim 1, characterised in that the needle (11) is secured to the membrane (10) by clamping means (13, 14) which are disposed on both sides of the membrane.
3. Gun according to claim 2, characterised in that the clamping means consist of flanges (13, 14) which are integral with the needle (11), and are disposed on both sides of the membrane (10) in order to clamp the latter between them.
4. Gun according to any one of the preceding claims, characterised in that the front end of the needle (11) extends in a central channel (8) which is provided in a spray head (4), and in that the needle can be supported against a seat (15) which is provided in the central channel (8) immediately behind the spray nozzle (9).
5. Gun according to any one of the preceding claims, of the type comprising means (25 to 33) of supply pulsed with sprayed air, which open in the vicinity of the spray nozzle (9), and means (11, 23, 34, 35, 36) for controlling the said means of supply pulsed with sprayed air, characterised in that the said means (11, 23, 34, 35, 36) for controlling the said pulsed spray means for the product also comprise the said means (11, 23) for controlling the said means of supply pulsed with sprayed air.
6. Gun according to any one of the preceding claims, characterised in that the end of the needle (11) consists of an interchangeable joining piece (38).
7. Gun according to claim 6, characterised in that the joining piece (38) for the needle (11) is made of synthetic resin.
8. Gun according to any one of the preceding claims, characterised in that on the side which is in contact with the product, the membrane (10) is coated with a layer of polytetrafluorethylene.

Images