FR2668722A1 - Mechanism for driving and for positionally controlling a long thin element, such as the rod for positionally actuating the needle of the nozzle of a spray gun - Google Patents

Abstract

The mechanism according to the invention comprises an electric motor (12) driven under voltage, to the output shaft of which is fastened a first plate (13) provided with guides (15) on which is slidably mounted a second plate (14) solidly attached to the rod (1) for actuating the needle (2) of the nozzle (3). Between the plates (13) and (14) are arranged a compression spring (16) and two weighty deformable systems (17), of equal masses, which deformable systems are deformed by moving apart when the plates are rotated. Resulting from this deformation is a traction force exerted on the plate (14), which moves the needle (2) into the nozzle (3). The position of the needle depends on the speed of rotation of the motor and this position is controlled by a Hall-effect cell (22) associated with a magnet (23).

Description

 The present invention relates to a command and control mechanism in position of a slender element such as the actuating rod in position of the needle tip of the nozzle of a spray gun.

 I1 is sometimes necessary that the fluid material sprayed by the gun is affixed to the face of the object intended to receive it, according to a thickness of great regularity or else according to a variable thickness but perfectly controlled.

 In addition, the fluid material can be affixed over the entire face of the object or else cover only certain zones of the latter, which may be of small width and develop along an open or closed contour, which may have rectilinear parts. and curves.

 The moldings that a panel that can be used for making furniture can have can develop along such a contour.

In order to give the piece of furniture an old appearance, the current technique consists in affixing on the faces of the molding a layer of brown material imitating the appearance of the patina.

Currently, this operation is carried out by hand and due to the lack of regularity of the layer of material affixed to the molding, it must be followed by an additional operation in which the excess material is removed by abrasion to using a pad formed by thin metal fibers.

This method is therefore incompatible with high work rates.

On the other hand, if the thickness of the material layer is perfectly controlled, this additional operation can be eliminated.

 In order for the thickness of fluid material affixed to the object to be coated to be perfectly controlled, it is necessary that the relative speed of movement of the gun relative to the object to be coated be controlled at all times. on the other hand, the flow rate of the sprayed material, which depends on the degree of penetration of the needle into the spray nozzle.

 To control the relative speed of movement of the pistol relative to the object, it is known to fix this pistol to the orientable head of a manipulating arm movable in space and whose movements are controlled by a digital control assembly which acts by means of appropriate interfaces on the various motor organs of the arm and the head according to the data of a pre-established program which delivers information representative of the trajectory which the arm and the head must follow as well as of the speed of these.

 Before each change of direction of the trajectory which the pistol must follow or before each reversal of movement, the arm must be decelerated.

Consequently, the apposition on the object of a layer of uniform thickness supposes that, in conjunction with this deceleration, the flow rate of the pulverized fluid material is automatically modified, the control of this modification having to be effected by the assembly. digital control which acts for this purpose on the flow control mechanism fitted to the gun.

 It is necessary for the response times of this mechanism to be as short as possible so that any variation in the speed of the arm during the affixing of fluid material to the object to be coated is accompanied almost instantaneously by a variation of debt.

 In addition, the value of the flow rate must be perfectly controlled, which requires precise control of the position of the needle in the spray nozzle.

 Mechanisms for controlling and controlling the position of the needle in the spray nozzle are known in the prior art.

Some of these mechanisms consist of a single-acting hydraulic cylinder, the piston rod of which is connected to the needle.

One of the chambers of this jack receives a pressurized liquid, which acts on the piston against the action exerted by a compression spring housed in the other chamber.

Because of the relatively long response time, such a mechanism cannot be suitable for the above-mentioned application.

 In addition, its use presupposes the use of an additional energy source such as hydraulic energy. In addition, it is necessary to fix on the handling arm, the hydraulic supply line for the pistol jack I1 is to be noted that this pipe must have suitable connections so that it can follow the movements of the arm and the head. without risk of breaking and wrapping around the arm.

 There are also known control mechanisms equipped with an electromagnet whose advantage lies in the elimination of the auxiliary energy source, but such mechanisms cannot ensure precise positioning of the needle in the spray nozzle.

 The present invention aims to overcome the drawbacks mentioned above by implementing a command and control mechanism in position which has low response time and which ensures precise positioning of the needle in the nozzle.

 For this purpose, the command and control mechanism in position of a slender element such as the actuating rod of the needle point of the nozzle of a spray gun is essentially characterized in that it comprises along the same longitudinal axis. A - an electric motor provided with a rotary output shaft whose rotation speed depends on the value of the electric voltage applied to its electrical input terminals, - a first plate wedged on the output shaft of said motor and rotated by said output shaft, - a second plate, axially movable, integral with the actuating rod, axially spaced from the first and mounted to slide axially on two rigid rectilinear guides parallel to the axis A and diametrically opposed by relative to this axis, which are fixed by one of their ends to the first plate and communicate to the second plate the rotational movement of the first, - an elastic member mounted in compression sion between the first plate and the second, exerting an axial action on the latter, the intensity of which depends on its degree of compression and therefore on the value of the spacing between these two plates, - and two deformable, heavy, mass systems equal, diametrically opposite with respect to the axis A and articulated each to the first plate and to the second, so that during the rotation of the two plates, these two systems deform simultaneously, radially, in separation from one another under the effect of the centrifugal force to which they are subjected and exert in particular on the second plate symmetrically with respect to the axis A, two tensile forces of equal intensities under the effect of the axial component of which and of the action exerted by the elastic member, the second plate is caused to move axially relative to the first and the needle to move in the nozzle, until the result of the axial traction forces exerted on the second plate is not balanced by the action exerted by the elastic member on said second plate.

 It is therefore understood that the position of the needle in the spray nozzle, which determines the flow rate of fluid material sprayed, depends on the value of the speed of rotation and that any variation of this speed will be translated almost instantaneously by a variation the flow of sprayed material.

 According to an additional characteristic of the invention, the electric motor is controlled in voltage by a programmable unit which also controls the handling arm and the head in their trajectory and speed of movement relative to the object to be coated, which allows the 'affixing a layer of perfectly controlled thickness at predetermined locations.

 It is necessary to constantly check the value of the flow rate of sprayed material.

This control can be carried out by controlling the speed of rotation but it is advisable, in order to improve the precision of this control, to permanently measure the axial positional deviation of the needle with respect to an original position which may be that which corresponds to a complete closure of the nozzle nozzle.

 To this end, according to an additional characteristic of the invention, the control mechanism is equipped with a measurement unit which delivers to the programmable unit via an interface an electrical signal whose value is representative of the axial positional deviation of the chest relative to the above-defined original position, whereby said programmable unit can compare this value with a set value attached to the position occupied by the gun on the trajectory it performs, and if a deviation between these two values is detected, can modify the voltage applied to the electrical terminals of the motor.

 According to yet another characteristic, the measurement unit comprises a position sensor mounted in attachment to the structure of the gun and opposite an element integral with the needle actuating rod which delivers a signal to an amplification stage electric, the value of which is representative of the deviation of said element from its original position, said position possibly being that of said element when the needle occupies its original position.

 Other advantages and characteristics of the invention will appear on reading the description of a preferred embodiment given by way of nonlimiting example with reference to the accompanying drawings in which - Figure 1 is a view in longitudinal section of a mechanism according to the invention, - Figure 2 is a top view of the mechanism according to the invention, - Figure 3 shows a handling arm equipped with a gun with mechanism according to the invention, - Figure 4 is a block diagram illustrating the connection of a gun to a programmable unit.

 As shown, the mechanism according to the invention, of command and control in position of a slender element such as the rod 1 for actuating the needle 2 of the nozzle 3 of a spray gun 4 is intended for example to be mounted on the orientable head 5 constituting the end part of a manipulation arm 6 whose trajectory and speed of movement as well as those of the head 5 relative to the object 7 to be coated with a layer of material are controlled by a programmable digital control unit 8 which acts for this on the various motor members equipping said arm and said head 5.

 The mechanism according to the invention comprises along an axis A, which may be the axis along which the needle moves in the nozzle, an electric motor 12 provided with a rotary output shaft whose rotation speed depends for example on the value of the electric voltage applied to its electrical input terminals, - a first plate 13 wedged on the motor output shaft and driven in rotation by said output shaft, - a second plate 14 movable axially integral with the rod actuation, axially spaced from the first and mounted in axial sliding on two rigid rectilinear guides 15 parallel to the axis A and diametrically opposite with respect to this axis, which are fixed by one of their ends to the first plate and communicate with the second plate the rotational movement of the first, - an elastic member 16 mounted in compression between the first plate and the second, exerting on the latter an axial action whose intensity depends on its degree of compression and therefore of the value of the spacing between these two plates, - and two deformable systems 17, heavy, of equal masses diametrically opposite with respect to the axis A and each articulated to the first plate and to the second so that during the rotation of the two plates 13 and 14, these two systems deform simultaneously, radially apart from one another under the effect of the centrifugal force to which they are subjected and exert in particular on the second plate, symmetrically with respect to the axis A, two tensile forces of equal intensity under the effect of the axial component of which and the action exerted by the elastic member, the second plate is caused to move axially relative to at the first and the needle to move in the nozzle until the result of the axial tensile forces exerted on the second plate is not balanced by the action exerted by the elastic member on the said tray.

 According to the preferred embodiment, the mechanism according to the invention comprises a structure by which it is fixed to the body of the gun.

This structure comprises a plate 9 of rectangular shape and a bearing body 10, these two elements being coaxial with the geometric axis A.

The plate 9 and the bearing body 10 are rigidly kept apart from one another by two tie rods 11 parallel to the axis A and arranged symmetrically relative to the latter, each of these tie rods 11 receiving between the body of bearing 10 and plate 9 a tubular spacer.

 The structure thus described is fixed by the plate 9 to the body of the gun 4.

 The two plates 13 and 14 and the systems 17 are mounted in the structure in the interval between the bearing body 10 and the plate 9.

The electric motor 12 is fixed to the bearing body 10 externally at the interval between the latter and the plate 9.

 The bearing body, along the axis A, is traversed right through by a bore in which are mounted two ball bearings guiding in rotation a pin provided with a blind hole in which the motor output shaft is fixed electric.

This pin outside the bearing body receives the plate 13 in fixing.

To this end, in the interval between the bearing body 10 and the plate 9, the journal is equipped with a cylindrical bearing surface of smaller diameter to which the first plate 14 is fixed.

 This plate 14 is provided along the axis A with a cylindrical orifice passing right through, in which the bearing engages, and is pressed against the shoulder of the bearing on the trunnion, by a washer and by a screw 18 engaged in a blind tapping made in the range from the free end of the latter and along the axis A.

 Preferably, each plate 13 and 14 is in the form of a cross, the branches of which develop in pairs according to a diameter.

The branches of one pair are shorter than the branches of the other and each pair has branches of equal length.

 The guides 15 cooperate with the longer branches of each of the two plates.

Each of the longer branches of the plate 13 has a transverse orifice in which the corresponding guide 15 is blocked, which engages with the possibility of sliding in an orifice made in one of the longer branches of the other plate.

 To the second plate externally at the interval which it delimits with the other plate is fixed by all known means a cylindrical cage 19 provided along the axis A with a bore in which is housed a ball stop 20 whose outer ring is fixed to said cage by any known means and the inner ring of which receives one of the ends of the actuating rod 1 in fixing.

Thanks to this characteristic, it is possible to avoid rotation of the rod 1 when the motor 12 is started.

The rod 1 extends along the axis A externally at the interval between the plates 13 and 14 and enters a guide orifice passing right through, along the axis A, the plate 9.

 At the other end of the rod 1 is secured the rear end of the needle 2.

 According to a first embodiment, the needle also develops along the axis A and the actuating rod 1 axially extends said needle.

According to this configuration, the actuating rod has, at the end, along the axis A, a blind tapping into which the threaded end of the needle is screwed.

 According to a second embodiment, the axis A is perpendicular to the axis of the needle and the actuating rod and the needle both cooperate with the same movement return mechanism known per se.

 The second plate internally at the interval which it delimits with the first is fixed a cylindrical finger 21 extending along the axis A in the direction of the first plate.

The head of the screw 18 and the finger 21 are respectively intended to receive in wedging the two ends of the elastic member 16, which is advantageously constituted by a non-contiguous coil spring.

 It can therefore be seen that this spring is mounted in the interval between the two plates 13 and 14 and is held along the axis A by the head of the screw 18 and the finger 21.

 The coil spring 16, mounted in compression between the plates 13 and 14, always exerts an axial action on the latter whether all of said plates and deformable systems 17 are rotated along the axis A or not.

Thus, when the engine is stopped, the axial thrust exerted by the spring 16 on the second plate will have the effect of holding the needle 2 against the nozzle of the nozzle 3 and of closing the latter.

 It is also understood that the nozzle 3 will be closed by the needle as long as the angular speed of the plates and of the systems 17 is not sufficient to create an opposite action greater than the action exerted by the elastic member.

 Thus, the nozzle will be closed when the plates and the assemblies 17 are driven at a low angular speed.

 Each deformable system 17 is articulated at its ends to one of the small branches of the plate 13 and of the plate 14 along two axes of articulation each perpendicular to the longitudinal axis of the corresponding small branch and contained in the plane of the plate.

 Advantageously, each deformable system consists of several links articulated to each other by a Galle type chain, which greatly simplifies their production.

 The electric motor of the mechanism according to the invention is voltage controlled by the programmable unit 8, which also controls the trajectories and speeds of the arm 6 and of the orientable head 6 relative to the object to be coated.

 It is therefore understandable that from the information given by the program, some of which indicate the thickness of the layer of sprayed material to be affixed to the object, the said unit will control the movements of the arm and the head and determine for each point of the path that the gun must carry out the degree of opening of the spray nozzle, this degree of opening depending on the speed of rotation of the motor output shaft and the value of the electric voltage applied to its input terminals .

 To permanently control the value of the flow rate of sprayed material is continuously measured the axial positional deviation of the needle with respect to an original position which may correspond to a complete closure of the nozzle nozzle by said needle.

To this end, the control mechanism is equipped with a measurement unit 26 which delivers to the programmable unit via an interface 27 an electrical signal whose value is representative of the axial positional deviation of the needle with respect to the position d 'above-defined origin, whereby said programmable unit can compare this value with a set value attached to the position occupied by the gun on the trajectory it performs and if a difference between these two values is detected, can modify via an interface 28, adapted the voltage applied to the electrical terminals of the motor.

Thus, the central unit can compare this value to a setpoint value attached to the position occupied by the gun on the trajectory it performs and, if a deviation is detected, modifies the voltage applied to the electrical terminals of the motor so as to decrease or increase the speed of rotation of the plates and deformable systems.

 As known, the interface 27 will be constituted by a digital analog converter.

The interface 28 will be constituted by a digital analog converter under the control of which will be disposed a voltage variator 30 electrically connected to the electrical input terminals of the electric motor.

 According to the preferred embodiment, the measurement unit 26 comprises a position sensor 23 arranged in attachment to the structure of the gun and this opposite an element 22 secured to the actuating rod of the needle.

The measurement unit is also equipped with an amplification stage 33 which receives the electrical signal delivered by the sensor 23 and delivers an amplified signal to the interface 27.

It should be noted that the amplification stage is provided with means to compensate for the offset due to the temperature variation.

As known, one of these means will be constituted by a thermistor 31.

 According to the preferred embodiment, the element 22 is fixedly mounted on a circular plate 24 fixed to the actuating rod 1.

 Still according to the preferred embodiment, this circular plate comprises two diametrically opposite peripheral notches 25 in each of which penetrates the spacer of one of the tie rods 11.

The purpose of this arrangement is to oppose the rotation of the actuating rod while giving it the possibility of moving in translation along the axis A.

 Preferably, the sensor 23 is a "Hall" effect cell and the element 22 is a magnet.

 The cell 23 and the amplification stage with its offset compensation means are mounted on a printed circuit board 32.

The printed circuit board is fixed to the tie rods 11.

 Advantageously, the electric wires reaching the printed circuit board run in at least one protective tube fixed to the mechanism structure parallel to the axis A.

 Finally, the mechanism according to the invention receives a protective casing.

This mechanism as described has a short response time and allows precise positioning of the needle in the spray nozzle.

 It goes without saying that the present invention can receive all arrangements and all variants without departing from the scope of this patent.

Claims (12)

 1. Command and control mechanism in position of a slender element such as the actuating rod (1) of the needle (2) of the nozzle (3) of a spray gun (4) mounted in fixing on the orientable head (5) of a manipulation arm (6) moving relative to the object (7) to be coated, characterized in that it comprises along an axis A - an electric motor (12) provided with a shaft rotary output whose rotation speed depends on the electrical voltage applied to its electrical input terminals, - a first plate (13) wedged on the motor output shaft and driven in rotation by said output shaft, - a second movable plate (14) axially integral with the actuating rod (1), axially spaced apart and mounted in axial sliding on two rigid rectilinear guides (15) parallel to the axis A and diametrically opposite with respect to this axis, which are fixed by one of their ends to the first plate (13) and communicate with u second plate (14) the rotational movement of the first, - an elastic member (16) mounted in compression between the first plate (13) and the second, exerting on the latter an axial action whose intensity depends on its degree of compression and therefore the value of the spacing between these two plates, - and two deformable systems (17), weighing, of equal masses, diametrically opposite with respect to the axis A and each articulated to the first plate and to the second so that during the rotation of the two plates (13) and (14), these two systems (17) deform simultaneously, radially apart from one another under the effect of centrifugal force, to which they are subjected and exert in particular on the second plate (14) symmetrically with respect to the axis A two tensile forces of equal intensities under the effect of the axial component of which and the action exerted by the elastic member, the second crew is required to move axia relative to the first and the needle to move in the nozzle until the result of the axial tensile forces exerted on the second plate is not balanced by the action exerted by the elastic member on said second tray.  2. Mechanism according to claim 1 characterized in that the electric motor (12) is voltage controlled by a programmable unit (8) which controls and controls the trajectories and the speeds of movement of the arm (6) and the head (5 ) in relation to the object to be coated.  3. Mechanism according to claims 1 and 2 characterized by a measurement unit (26) which delivers to the programmable unit (8) via an interface (27) an electrical signal whose value is representative of the axial positional deviation of the needle with respect to its original position, whereby said programmable unit (8) can compare this value with a reference value attached to the position occupied by the pistol on the trajectory which it carries out and if a difference between these two values is detected, can modify via an interface (28) the voltage applied to the electrical terminals of the motor.  4. Mechanism according to claim 3 characterized in that the measurement unit (26) comprises - a position sensor (23) disposed in attachment to the structure of the gun and facing an element (22) integral with the rod actuation of the needle, - and an amplification stage (33) which receives the electrical signal delivered by the sensor (23) and delivers an amplified signal to the interface.  5. Mechanism according to claim 1 characterized in that it comprises a structure by which it is fixed to the body of the gun, said structure being constituted by a plate (9) for fixing to the body of the gun, by a bearing body ( 10) rigidly kept apart from the plate (9) by tie rods (11) with spacers, the two plates (13) and (14) as well as the systems (17) being mounted in the structure in the interval between the bearing body (10) and the plate (9) while the drive member (12) is mounted externally at said interval and is fixed to the bearing body (10).  6. Mechanism according to claims 1 and 5 characterized in that the motor output shaft engages in fixing in the blind hole of a journal mounted for rotation in two ball bearings disposed in a bore of the bearing body (10), said pin receiving in fixing externally to the bearing body (10) the first plate (13).  7. Mechanism according to claim 1 characterized in that in the second plate (14) outside the interval which it delimits with the first is fixed a cylindrical cage (19) provided along the axis A of a bore in which is housed a ball stop (20) whose outer ring is fixed to said cage and whose inner ring receives one of the ends of the actuating rod (1).  8. Mechanism according to claim 4 characterized in that the element (22) is mounted for fixing on a circular plate (24) fixed to the actuating rod.  9. Mechanism according to claims 5, 7 and 8 characterized in that the circular plate (24) comprises two notches (25) peripheral, diametrically opposite in each of which penetrates the spacer of one of the tie rods (11) in order to s' oppose the rotation of the rod (1) while leaving it the possibility of moving in translation along the axis A.  10. Mechanism according to claim 1 characterized in that each system (17) consists of several links hinged to each other of a chain of the type "Galle11.  11. Mechanism according to claim 1 characterized in that the rod (1) for actuation extends the needle axially (2).  12. Mechanism according to claim 1 characterized in that the axis A along which develops in particular the rod (1) is perpendicular to the axis along which the needle develops and that said rod and said needle cooperate with the same movement return mechanism.