Background of the invention A current device for the application of a fluid is in practice implemented as a rotatable spray gun which has a number of spray nozzles and is designed to be mounted on a robotic control device.

Spray guns are used when fluids, such as gases, liquids or plastic materials, are to be sprayed or extruded onto a surface. One example of a field of application of such a spray gun is in the automobile industry, when bodies are to be surface treated or joints are to be sealed. Other fields of application are, of course, also possible.

State of the art A device for the application of fluid is known from W097/02901. The principle is shown in figure 1. The old gun had a swivel 2'consisting of three different material channels between the product valves 4'and the nozzles. The three valves were fed by one common inlet channel. The valves 4'were opened by actuators 20'put on a pneumatic valve block on the robotic arm. All this resulted in slow reaction times between the actuators 20'and valves 4'and in long distances e. g. 20-30 centimetres between valves 4'and nozzles. Circulation was only possible up to the common product inlet. The fact that the material was swivelled after the different valves 4'resulted in pulsation between the seals of the feed ring inside the swivel 2' when changing nozzle. This pulsation resulted many times in that drops of material did leave the other nozzles when a valve was opened.

The present invention seeks to solve the above mentioned problems. A main feature is that the product valve means are arranged in the rotatable nozzle head, close to the nozzles. The distance between valves and nozzles may be reduced to 10-50 millimetres. This means that channels in the swivel may be used for inlet and return channels enabling circulation up to the product valves located close to the nozzles. The feature also allows the channels in the swivel to be used for separate fluids enabling application of different fluids or mixing at the nozzle head for two- component application of fluids. Accordingly, in one embodiment of the invention the gun has a swivel consisting of one material inlet channel and one return channel which leads to the product valves situated at the very end of the nozzle lance. The valves are opened by solenoid controlled actuators, also put on the rotating part of

the gun. This results in very fast reaction times between solenoids, actuators and valves as they are mounted close together. The distance is put to a minimum between product valves and nozzles. This solution makes it possible to circulate the material almost all the way up to the nozzles, resulting in a minimum need to purge.

The actuators are powered by compressed air fed through the swivel in one channel and the electrical signals pass through a slip-ring device. By keeping the valves close to the nozzles, snuff-back effects become more effective and dripping due to pulsation in the material channels is avoided.

Summary of the invention The present invention provides a device for the application of fluid and intended to be mounted as a tool on a holder which is adjustable between different positions and directions. The device comprises at least one nozzle, preferably at least two, for discharge of said fluid, one product valve means associated with each nozzle for control of the supply of fluid to each nozzle, and a swivel means connecting the holder to a rotatable nozzle head carrying said nozzles. At least one channel, preferably at least two, channels are arranged through said swivel means for establishing fluid communication between the holder and the rotatable nozzle head.

Said channels have the capability to rotate freely relative to the holder.

According to the invention the product valve means are arranged in the rotatable nozzle head.

In one embodiment one channel in the swivel is an inlet channel for supplying fluid to the nozzle head, and another channel in the swivel is a return channel for returning fluid from the nozzle head.

In another embodiment a first channel in the swivel is an inlet channel for a first fluid to the nozzle head, and a second channel in the swivel is an inlet channel for a second fluid to the nozzle head.

Preferably, a pneumatic channel is arranged through said swivel means for establishing pneumatic communication between the holder and the rotatable nozzle head, and the product valve means are actuated by means of pneumatic control.

Also, electrical lines may be arranged through said swivel means for establishing electrical communication between the holder and the rotatable nozzle head, and electrical valve actuators, suitably solenoids, are arranged in the nozzle head for controlling the pneumatic actuation of the product valve means.

The invention is defined in claim 1 while preferred embodiments are set forth in the dependent claims.

Brief description of the drawings The invention will be described in greater detail in the following detailed

description, in which reference is made to the accompanying drawings, in which Fig 1 is a schematic view illustrating the principles of a robotic gun according to the prior art; Fig 2 is a schematic view illustrating the principles of a robotic gun according to one embodiment of the present invention ; Fig 3 is a schematic view illustrating the principles of a robotic gun according to another embodiment of the present invention ; Fig 4 is a perspective view of one embodiment of the present invention mounted on a holder; Fig 5 is a cross-section view of the base module one embodiment of the present invention; Fig 6 is an exploded view of the valve actuators; Fig 7A is a perspective view of a first nozzle configuration; Fig 7B is a perspective view of a second nozzle configuration; Fig 7C is a perspective view of a third nozzle configuration; Figs. 8A and 8B are cross-section views of the snuff action valve in a closed and open position, respectively; and Figs 9A and 9B are perspective views of the high-precision configuration needle and high-flow configuration needle, respectively.

Detailed description of preferred embodiments The principles of the device according to the invention are shown in figure 2. The device comprises a non-rotating part or adapter 1 to be connected to a holder on a robotic arm and a rotating part carrying nozzles for application of a fluid. A swivel means 2 provides rotary connections for air, fluid and electric signals. Product valves 4 are located close to the nozzles 12 in the rotating nozzle head. The product valves 4 are pneumatic valves powered by, air and controlled by valve actuators 20 in turn controlled by electric signals by means of electric actuators, e. g. solenoids 19. The fluid to be applied from the nozzles is circulated through the swivel 2 and up to the product valves 4.

As is evident from the non-schematic drawings, see e. g. Fig 4, the device for application of a fluid is designed as a gun-shaped tool which comprises five main components, namely an adapter 1 which serves to connect the gun with a robotic arm, a swivel means 2, which is capable of transmitting a rotary movement, a connection 3 to a feeder means for a fluid, such as a gas, a liquid or a plastic material, a positioning lance 5 and a head 6 having a number of spray or extrusion nozzles 12. The construction and respective function of these different primary components will be described below.

The adapter 1 is designed to be mounted on a robotic arm of any known type,

either directly or by means of an intermediate adapter. A robotic arm can usually perform movements in six degrees of freedom, i. e. motion in three directions, rotation about first and second axes, which are perpendicular to each other and which are at a right angle to the longitudinal direction of the robotic arm, and rotation about a third axis which extends in the longitudinal direction of the robotic arm. The adapter 1 transmits the rotary motion about this longitudinal axis either because the adapter is rigidly rotated or because a shaft located in the adapter is rotated with respect to the adapter. The shaft located in the adapter is connected to a shaft 8 (Fig. 5) rotatably held in the swivel means 2. This shaft can be an integral continuation of the adapter shaft.

With reference to figure 5, the swivel means 2 is outwardly limited by a housing 10, which has an outer mantle surface 11 and an inner cylindrical wall and two end surfaces. The mantle surface of the housing is substantially cylindrical, but other shapes of the mantle surface of the housing are of course also possible. The gun can be mounted on basically any kind of robot. It is just a question of adapting the mechanical adapter and the swivel-locking device.

The spray gun has in the simplest form one, and in the example shown in the drawing three, spray or extrusion nozzles 12 (see also Figs 7A, 7B and 7C). To ensure the functioning of the gun, each of the nozzles has a channel between the product valve and the nozzle. This results in that each nozzle can be opened and closed independently of the others. For this reason, it is possible to open one or more nozzles at the same time.

Figures 7A and 7B show nozzle configurations with three nozzles 12 pointing in different directions. In figure 7A one nozzle is pointing straight forward, a second nozzle is pointing to one side at a right angle, and a third nozzle is pointing at an angle of 45° to the forward direction at a right angle to the plane formed by the first two nozzles. In figure 7B all nozzles are pointing at an angle of 45° to the forward direction and symmetrically spaced by 120° around the circumference. The nozzle configurations are selected on the basis of their intended application. The nozzles are preferably used one at a time with the same or (two) different materials.

Figure 7C shows a nozzle configuration with three nozzles 12 pointing in the same direction. The nozzles may be used simultaneously with the same material in order to form a broader bead or sheet of material. Since the product valves may be controlled individually, it is possible to activate one through three of the nozzles as a way of selecting the width of the bead.

Figure 5 is a cross-section view through the base module. The gun has swivelling functions for electrical signals, compressed air and product. The media enter (or exit, depending on the application) the gun through holes 13 and 14 in the housing and are transferred to the rotating shaft 8. In the shaft are made channels for

air, material and the electrical cables to the solenoid valves. The shaft with the channels may be rotated freely relative to the adapter 1 and holder with unhindered communication through the channels for electrical signals, compressed air and product.

The swivel is also furnished with an electrical slipring device 15. The slipring device has been located next to the coupling in the rear part of the module.

The cables to the solenoid valves runs in a hole drilled through the shaft. The cables, equipped with a contact for the solenoid valves, may be soldered to the shaft part of the slipring device.

The hole 7 in Fig 5 is the inlet for compressed air to the valves. The pneumatic supply hose is connected with a standard threaded quick-connection. The same air supply is preferably used to power all the pneumatic valve actuators. The holes 13 and 14 are inlets/outlets for the fluid material to be applied. The design allows inlet and return of one material for circulation or inlet of two different materials into the non-rotating part. This makes it possible to adapt the gun for application of two different materials and 2-component materials. As will be appreciated, it is possible to design the device with more inlets/outlets for fluid material.

A device according to the invention may be provided with two different types of product valves, one high-flow type and one type based on the so-called snuff-back valve. In this application, the snuff-back type is referred to as the high- precision configuration.

The product valves 4 are actuated by valve actuators 20. The arrangement of the valve actuators is shown in Fig 6. To open the product valves in the gun each valve is manoeuvred by a rod 21 connected to an air-controlled piston 22. Letting in compressed air in to its cylinder 23 moves this piston 22 in its turn. This air inlet is activated and depressurised by a solenoid valve, one for each valve. The same parts are mainly used for both high-precision and high-flow configuration. One difference is that the rods are moved backwards to open the valves in the high-flow gun and forward to do the same in the high-precision version. Modifying an adapter plate for the solenoid valves creates this difference.

As solenoid valves standard valves may be used, which should preferably be fast and very small. These valves are controlled by DC signals passing through the electrical slipring device. The air connection from the solenoid valves to the gun may be made by a plastic air block 18 (Fig 4), manufactured by a laser sinter. This will reduce the dimensions of the mid-section of the gun. By forming different channels in this air block the actuators are configured for the high-flow or high- precision configuration. The sinter manufacturing method gives a large freedom in designing the air channels through the block 18.

As is shown in Fig 6, a design with three pneumatic cylinders located longitudinally after each other, angularly spaced 120 degrees from each other was made to obtain a small diameter of the gun within a minimum of space and weight.

The actuators are supplied with compressed air for the forward and backward motion by the solenoid valves. On the high-flow configuration a spring will be mounted in the actuator cylinder (not shown) in order to close the product valve in case of lost supply of compressed air or malfunction in the solenoid.

As mentioned earlier the high-precision configuration is focused on sharp starts and stops and constant bead widths. The high-precision configuration does not allow as high material flow as the high-flow gun. The design of the high-precision nozzle head is made to allow snuff-back and to give as distinctive starts and stops of the beads as possible. Suitable applications are sealing and other bead application where the cosmetic appearance is of high importance. The high-precision configuration is normally used together with slit nozzles.

The function of the high-precision valve is illustrated in Figs. 8A and 8B, Fig 8A showing the closed position and Fig 8B showing the open position. When the needle is in its rear position there is a distance between the needle 24A and the ball 25, the ball 25 closing the valve seat 26A (see fig. 8A). The valves in the high- precision nozzle head are opened by pulling the piston rod forward, which hits the ball 25 pushing the ball 25 forwards from the seat 26A. The philosophy is that the needle 24A should gain speed before reaching the ball 25 and then hit the ball, with an almost instantaneous opening from closed to fully open valve obtaining a full flow as a result. This distance however increases the reaction time from sent signal until the valve is open.

When the needle is pulled back to the position, shown in figure 8A, it creates a snuff-back force to the material in the nozzle channel. This function has been used in the prior art product valves and has been useful when the valve was located in front of the swivel with different lengths of lances before the nozzle. The ball 25 is pushed towards the valve seat by a return spring 27 to close the flow.

The high-flow type of valve is shown in Fig. 5. The design of the high-flow configuration valve is made to allow maximum material flow. A needle 24B opens the valve when it is pulled backwards by the actuator from the seat 26B. The design does not contain any ball to close the valve, but the needle 24B closes directly against the valve seat 26B. The design provides for high flow rates but no snuff- back is obtained as the piston moves forward to close the valve. In Fig. 5 the valve is shown in closed position.

The lance 5 (e. g. Fig. 5) is used to get different lengths of the gun. This is a parameter, which can be desired to be changed depending on workspace and robot positioning. The design has been done with a stainless steel tube manufactured in

different lengths, with aluminium flanges in both ends. Inside the lance the fluid material pipes and piston rods for the valves are located.

By putting a high-flow configuration nozzle head on the gun it is possible to apply materials with very high material flows. The flow rates are depending on material and nozzle type but flows over 100 ml/s are no problems to achieve.

Suitable applications are vibration dampening, under body coating and other coating applications, normally applied by flat-stream, extrusion or spray extrusion nozzles.

The details for the piston rods 21 are common between high-precision and high-flow configuration except for the needles. The high-precision configuration uses a similar design to the ones used in the product valve for prior art device. As is shown in Figs. 9A and 9B, the needle 24A for the high-precision configuration has a flat front end suitable for hitting the ball 25, while the needle 24B for the high- flow configuration has a rounded front end which closes the valve by abutting against the valve seat 26B.

The high-precision and high-flow configurations only differ in a few parts of the nozzle head and it is easy to modify a gun from one configuration to another.

The high-flow configuration primary was intended for high-flow applications, but tests have shown that this configuration gives excellent results also for sealing applications.

The device according to the invention may be adapted for 2-component material application. Fig. 3 shows the principle. Most of the components of the gun are the same as for a conventional 1-component gun. The gun has however to be adapted to be able to mount a mixer 9, e. g. a static mixer, in the front. The base module (non-rotating part) of the gun is prepared to be able to feed two different materials. The two materials will be able to circulate separated in the base module as it is possible to mount two inlet and two outlet pipes to the gun. There is no circulation in the rotating part. In the rotating part two of the valve actuators 20A and 20B will open each of the two material channels to the mixer 9 having one common outlet for the mixed components. If necessary, a separate valve 4C can be provided at the common outlet and the third valve actuator 20C could be used to open the flow of mixed material to the nozzle 12C.

In another embodiment, the product valves 4A and 4B each open directly to a separate nozzle enabling application of two different fluid materials.

In the gun according to the invention the material can be circulated almost all the way to the nozzles. This provides for good control of material temperature and viscosity and the need for purge operations will be very limited. If two different materials are used for different nozzles of the gun, or if a 2-component material is used, it still will be possible to circulate both materials in the gun. In those cases the circulation is limited to the base module of the gun.

The circulation is controlled by an external circulation valve 28 (Fig 2), which opens the return hose. As an alternative, the circulation valve may be integrated with the gun, e. g. located together with the product valves. If available, even one of the product valves could be used. Between the hose and the gun is installed a non-return valve 29 to eliminate the negative effect of the accumulated pressure in the return hose.

The gun can be equipped with two different temperature sensors: one to measure the product temperature and the other to measure the temperature of the heated body of the gun. Heating elements and temperature sensors may be integrated in the body of the device. Material sensors may be integrated in the connection plate where the material tubes are connected to the body.

Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.