FR2714852A1 - Coating product projection device comprising a spray bowl. - Google Patents

Abstract

Device for spraying coating product comprising a spray bowl (1) driven in rotation by the rotor (4) of an air turbine, characterized in that means (12, 112, 212) are provided so that the resultant centripetal (F) of the aerodynamic forces induced by the jets of driving air rotating on said rotor (4) is non-zero.

Description

i "Device for spraying coating product comprising a bowl of

  spraying "The invention relates to a device for spraying coating product, liquid or in powder form, comprising a spray bowl. It relates more particularly to the system for driving the spray bowl in rotation by the rotor of a turbine. In the devices of the prior art, one of the essential concerns of those skilled in the art is

  to balance the rotating system as best as possible,

  ie the rotor and the spray bowl. In addition, an effort is made to balance the forces applied to this system, in particular at the level of the aerodynamic forces induced.

on the rotor.

  However, no system being perfect, the spray bowl and / or the rotor necessarily have an unbalance, however light it may be, which implies a moment of inertia not

  zero with respect to the axis of rotation of the turbine.

  This moment of inertia tends to create parasitic oscillation movements perpendicular to the axis of rotation of the turbine. As we tried to minimize the result of the forces applied to the rotor, these oscillations are very weakly damped, and parasitic vibrations

remain almost permanently.

  In addition, the coating product projection devices are often mounted on a robot, of the reciprocating type, lateral machine, roof machine or multi-axis robot. The movements generated by these robots cause accelerations of the turbine perpendicular to its axis of rotation, which creates parasitic oscillations which

are not amortized and continue.

  These oscillations or vibrations can be strong enough to disturb the distribution of coating product at the outlet of the spray bowl. They significantly reduce the efficiency of the turbine. In the case of an air turbine, they can also unbalance the rotor enough for it to compress the air bearing and strike the stator, which can

destroy the turbine.

  The invention solves all of these problems.

  It relates to a device for projecting a coating product comprising a spray bowl entrained in rotation by the rotor of an air turbine, characterized in that means are provided so that the resulting centripetal aerodynamic forces induced by the air jets of rotational entrainment on the rotor is not zero. The means making it possible to carry out the invention are, for example, air injectors for rotating the rotor internally, distributed irregularly at the periphery of the stator of the turbine. One can also provide injectors having angles of incidence on the rotor different from each other. He can too

  be injectors with different flow rates.

  The radial result of the aerodynamic forces induced by the rotating drive air jets on

  said rotor drives the rotating rotor.

  In all cases, this artificial imbalance creates a non-zero force in a plane perpendicular to the axis of rotation of the turbine. Given its orientation, this force does not hinder the operation of the turbine bearing, whether air or ball. On the other hand, the bearing creates a reaction force of modulus equal to that of the centripetal resultant, which guarantees the stability of

the entire turbine.

  The combination of the centripetal resultant and the reaction force is a sufficient damping factor to prevent parasitic oscillations from occurring

  long enough to be disruptive.

  Thanks to the invention, a stable mechanical system has been created which, even if disturbed, recovers by itself

equilibrium position.

  The invention will be better understood and other advantages thereof will appear more clearly in the light of the

  description which follows of three embodiments of

  coating product projection devices in accordance with its principle and of two mechanical models of projection devices, given solely by way of example and made with reference to the appended drawings in which: - Figure 1 is a partial schematic sectional view of 'A device according to the invention; - Figure 2 is a partial schematic sectional view in the direction AA of Figure 1; - Figure 3 is a partial schematic sectional view, similar to Figure 2 of a second embodiment of the invention; - Figure 4 is a partial schematic sectional view, similar to Figure 2 of a third embodiment of the invention; - Figure 5 is a mechanical modeling of a device according to the prior art; and - Figure 6 is a mechanical modeling of a

device according to the invention.

  The device of FIG. 1 comprises a spray bowl 1 supplied with coating product by an injector 2 and with solvent by a second injector 3. It is rotated by a rotor 4 which rests on an air bearing 5 created between the rotor and a stator 6. The air bearing 5 is supplied by a duct 7 connected to an air source, not shown. Several magnets 8, 8 'and 9,

  9 'ensure the centering of the rotor relative to the stator.

  The rotor is driven in rotation by the aerodynamic forces induced on its blades 11 by air exiting from several injectors 12 supplied by an annular distribution chamber 13. A duct 14 connects the distribution chamber 13 to a non-air source shown, through regulation means not shown. As it is apparent in FIG. 2, the air injectors 12a, 12b, 12c and 12d are not evenly distributed in the stator 6 around the rotor 4. Therefore, the centripetal result of the aerodynamic forces is not zero. The injectors 12 could also be fixed in a part of the body of the turbine different from the stator, such as a

external boltier.

  The angles between the injectors 12b and 12c on the one hand and between the injectors 12c and 12d on the other hand are smaller than those between the injectors 12a and 12b on the one hand and 12a and 12d on the other hand. The injectors have the same flow rate because they are supplied from a common distribution chamber 13 and because they have the same angle of incidence 9 relative to the rotor. The angle of incidence of an injector can be defined as being the angle between the jet of air leaving the injector and the straight line passing through the center of rotation O of the rotor and by the injector. From this, it appears that the aerodynamic force F induced is located on the right connecting the centers of the injectors 12a and 12c, that is to say perpendicular to the axis XX 'of rotation of the turbine. In this case, it applies to

  center O and is oriented from 12c to 12a.

  This orientation is particularly advantageous in the case of a spraying device keeping a substantially constant orientation, such as for example a rotary spraying device mounted on a reciprocator or a lateral machine. Indeed, the resulting centripetal F then partially compensates for the weight

of the rotating system.

  The resulting centripetal F tends to move the rotor 4 on the side of the injector 12a, that is to say to offset it relative to the axis XX 'in a position where it is stable. An equal modulus reaction force opposes the resultant F because of the centering effect performed by the magnets 8, 8 ', 9 and 9'. The system is mechanically stable. In other words, thanks to the existence of F, any

oscillation will be damped.

  An important aspect of the invention is that it allows an increase in the efficiency of the turbine. This increase in efficiency makes it possible to rotate the rotor at speeds of several tens of thousands of revolutions per minute, or even more than 100,000 rpm, while keeping

  industrially acceptable air consumption.

  The device of Figure 3 solves the same problem in another way. Elements similar to those of Figures 1 and 2 have the same reference numerals. The three injectors 112a, 112b and 112d have the same angle of incidence 8 relative to the rotor 4. The injector 112c is normal to the external surface of the rotor 4. The force induced by the jet of air leaving 112c is directed towards the center of rotation O of the rotor. The centripetal resultant F of the aerodynamic forces is also directed in the same direction. The device of FIG. 4 differs from the previous two in that each injector 212a, 212k, 212c and 212d is supplied independently with air by conduits 214a, 214b, 214c and 214d. Items similar to those

  Figures 1 and 2 have the same reference numerals.

  The air flows delivered by the conduits 214 are adjustable independently of each other by regulation systems not shown. If they are kept different, the centripetal result F of the aerodynamic forces is not zero. This device has the advantage of being adjustable. By modifying the air flow rates supplied by the ducts 214, it is possible to modify

  the orientation of the centripetal resultant F in its plane.

  For example, if the flow rates are higher for injectors 212b and 212c than those for injectors 212a and 212d, the resultant is oriented in the northwest quarter of the

rotor 4.

  The adjustable character of the orientation of the centripetal resultant F is particularly advantageous in the case of a device mounted on a multi-axis robot or on a roof machine. It allows permanent compensation of the weight of the rotating system according to what has been

  described for the device of figure 2.

  The invention can result from the combination of the systems presented in Figures 2 & 4. It has been shown in Figures 2 to 4 with four injectors but it is applicable with any number of injectors. FIG. 5 is a mechanical modeling of a device according to the prior art. The shaft of the rotating system is represented by a mass M which is supported

  by four identical springs 311, 312, 313 and 314.

  Any excitation force in the plane of the springs generates an undamped movement. On the contrary, in the model of FIG. 6, the mass M is quickly stabilized because the restoring forces of the identical springs 411, 412, 413 and 414 combine to move M towards the

spring attachment point 413.

  Another modeling of the invention could consist of a figure identical to FIG. 5 in which the springs do not all have the same constant

stiffness.

  The invention applies equally to devices for spraying liquid coating product or in powder form. It concerns both

  air bearing or ball bearing turbine devices.

Claims (8)

  1- Device for spraying a coating product comprising a spray bowl (1) driven in rotation by the rotor (4) of an air turbine fitted with air injectors for driving said rotor, characterized in that means (12, 112, 212) are provided so that the centripetal resultant (F) of the aerodynamic forces induced by the jets of drive air in rotation on said rotor (4) is not zero.   2- Device according to claim 1, characterized in that the injectors (12) of rotational air for driving the rotor (4) of said turbine are distributed in a non- regular around said rotor.   3- Device according to claim 1 or 2, characterized in that at least one injector (112c) of air for driving the rotor (4) in rotation of said turbine has an angle (0) of incidence on the rotor different from that others.   4- Device according to one of claims   previous, characterized in that the air flows of the rotational drive air injectors (212)   of said turbine are not all equal.   - Device according to one of claims   above, characterized in that the orientation of the centripetal resultant (F) of the aerodynamic forces induced by the air jets (12, 112, 212) driving in rotation on said rotor in the plane perpendicular to   the axis (XX ') of rotation of the turbine is adjustable.   6- Device according to claim 5, characterized in that the injectors (212) are supplied by specific air supply ducts, the air flows in   these conduits being independently adjustable.   7- Device according to claim 1, characterized in   that said resultant (F) is directed upwards.   8- Device according to one of claims   previous, characterized in that the turbine is bearing air (5).   9- Device according to claim 8, characterized in   what the turbine is magnetic centering.