WO2007027149A1

WO2007027149A1 - A spray gun arrangement

Info

Publication number: WO2007027149A1
Application number: PCT/SE2006/050304
Authority: WO
Inventors: Stig Johansson; Teuvo PÖYHÖEN
Original assignee: Ecco Finishing Ab
Priority date: 2005-08-31
Filing date: 2006-08-30
Publication date: 2007-03-08
Also published as: WO2007027147A1; SE0501925L; WO2007027148A1

Abstract

A spray gun arrangement comprising a first part (1) that comprises a spray nozzle (9) and at least one control element (7) for controlling the flow of a fluid in said spray nozzle, said control element (7) being dis- placeably arranged in said first part (1) of the spray gun arrange¬ ment, and a second part (2) that forms a holder onto which the first part (1) is mounted, and means (18, 19) for sensing the displacement position of the control element (7), said sensor means comprising a magnet arranged at the control element (7) and a gauge (19) arranged to sense the magnetic field generated by the magnet (18) in response to the displacement position of the magnet (18). The spray gun arrangement comprises a metal return spring (8) arranged to act against the control element (7) in one of the displacement directions of the latter, and in that the magnet (18) is arranged externally of said spring (8).

Description

A spray gun arrangement

TECHNICAL FIELD

A spray gun arrangement comprising a first part that comprises a spray nozzle and at least one control element for controlling the flow of a fluid in said spray nozzle, said control element being displaceably arranged in said first part of the spray gun arrangement, a second part that forms a holder onto which the first part is mounted, and means for sensing the displacement position of the control element, said sensor means comprising a magnet arranged at the control element and a gauge arranged to sense the magnetic field generated by the magnet in response to the displacement position of the magnet.

Generally, the invention can be implemented in all applications in which a substance, such as paint or lacquer is applied to a surface, and in which a control element arranged in the air gun head is used for controlling the flow of a pressurized fluid, such as paint, lacquer and/ or air, and in which there is a reason to continuously sense the displacement position of the control element, in order to be able to control the process. In particular, the invention is related to so called automatic spray guns that are used within, for example, the automotive industry for surface treatment or painting of vehicle bodies, sealing of seams, etc.

THE BACKGROUND OF THE INVENTION

In the car painting and material deposition field, automatic spray gun arrangements comprising a gun unit, possibly an adapter unit, and a robot arm connected with a robot are often used. The gun unit is connected with the robot arm directly or indirectly through the possibly present adapter unit. The gun unit may be provided with control elements, for example paint needles or other types of valve elements for the control of the flow of fluids into a nozzle of the gun unit. Typically, a control element for controlling a flow of paint, includes a so called paint needle and a piston, controlled by means of pressurized air and connected with said needle, provided with a return spring for the returning of the piston to a start position upon absence of pressurized air. There are provided channels for the flow of fluid in the gun unit, in the adapter unit and in or by the robot arm.

The control element is arranged so as to move between a first posi- tion, in which it opens for a flow of fluid, and a second position, in which it stops the flow of fluid. A gauge or sensor provided to sense one of these positions is arranged in the gun unit and delivers a confirmation signal to a central processing unit, CPU, which, in its turn, controls the spraying process according to which the spray gun arrangement is operating. The gauge may be of a contacting type or a type arranged to sense when the control element is its vicinity without any contacting thereof. When the control element is not in said first position, one assumes that it is in the opposite, second position, which, however, must not be the case. Accordingly, arrangements according to this prior art do not present any information if, for example, the control element would have got stuck in an intermediate position or would not have reached all the way to the second, non- sensed position. Further, they do not give any information about the reaction time of the control element, since they do not present any information about when the second position is attained.

The gauge forms part of an electric circuit that passes the borders or interfaces between the gun unit, the adapter unit and the robot arm. In said interfaces there are flexible lead connectors for the necessary electric and signalling leads. In particular, the interface between the gun unit and the adapter unit is a critical region, in the very spray zone, in which there is a major risk of having a disintegrating erosion on such leads, or to have the leads cut off by mistake in connection with the cleaning or replacement of the gun unit.

THE OBJECT OF THE INVENTION

It is an object of the present invention to provide a spray gun arrangement that permits a well defined determination of the displacement position of a control element displaceably arranged therein for the control of a flow of fluid.

SUMMARY OF THE INVENTION

The object of the invention is achieved by the initially characterized spray gun arrangement, characterized in that that it comprises a metal return spring, arranged to act against the control element in one of the displacement directions of the latter, and in that the magnet is arranged outside said spring. In other words, the magnetic field sensed by the gauge will vary depending on the position of the magnet. Thanks to the use of a magnetic field generated by the magnet, a sensing of a relatively large range of displacement of the position of the control element is permitted at each moment. Thanks to the characterizing feature of the invention, the generated magnetic field is not interfered by the spring to the same degree that would have been the case if the latter had been arranged outside the magnet. For the sake of clarity, it should be mentioned that the magnet is arranged between the gauge and the return spring, in other words that the gauge is arranged radially outside the return spring and the magnet. The disadvantages of prior art in this respect are thus remedied.

Preferably, the control element is displaceable between a first position, in which it stops the flow of fluid, and a second position, in which it opens for a flow of fluid, and the magnet and the gauge are arranged such that the gauge senses both these positions. Thereby, it becomes possible to sense the reaction time of the control elements, and to detect whether the control element reaches or not reaches any of its end positions.

It is preferred that the magnet is a permanent magnet. The alternative would be an electromagnet, which, however, would complicate, or even make the positioning of the magnet on the control element impossible.

According to one embodiment, the control element is at least partly rotationally arranged in relation to said first part, and the magnet is ring-shaped, the rotational axis of the control element coinciding with the central axis of the magnet. Thanks to this feature, any possible rotation of the control element will not affect the strength of the magnetic field sensed by the gauge. Thereby, it is assumed that the magnet, or at least the field generated thereby, is rotationally symmetric. The magnetic field should be radially directed.

Preferably, the gauge is a Hall-effect sensor. In other words, it is preferred that the magnet be so strong that it generates a magnetic field that is strong enough not to be effected by the earth's magnetic field. Accordingly, it would then be possible to use a more robust Hall- effect sensor instead of the more sensitive electro-resistive sensors that otherwise would have been necessary.

Further features and advantages of the invention will be disclosed in the following detailed description and in the enclosed dependent patent claims.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention will here be described by way of example, with reference to the annexed drawings, on which:

Fig. 1 is a view in perspective of a spray gun arrangement according to the invention,

Fig. 2 is a schematic, exploded view in perspective of parts of a spray gun arrangement according to Fig. 1 ,

Fig 3 is a view similar to the one of Fig. 2 of an alternative embodiment of the invention, and

Fig. 4 is a circuit diagram with an interface between two parts of the spray gun arrangement according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Fig. 1 schematically shows a spray gun arrangement according to the invention, comprising a first part 1, a second part 2, and a third part 3. The first part comprises a gun unit or a spray head 1. The second part 2 is an adapter unit which, on one hand, is releasably connected with the first part 1 , and, on the other hand, is releasably connected with the third part 3, said third part being formed by a robot arm 3 connected with a robot 4. The arm 3 may also be regarded as a part of the robot 4.

Fig. 2 shows the first and second parts 1 , 2 as well as a portion of the third part 3, in a perspective view. The first part 1 is shown partly as an exploded view, and comprises a body 5, a fluid channel, not visible on the figure, a control element 7 for controlling the flow of a fluid in said fluid channel, a return spring 8 acting against the control ele- merit 7, and a nozzle 9 through which said fluid is sprayed towards an object onto which it is to be applied.

The control element 7 comprises a needle 10 and a piston 11 that drives the needle. The piston 11 comprises a hole coaxially with its central axis, said needle 10 extending through said hole. An end cap 12 to be screwed into the body 5 acts as a support for the return spring 8 against the end thereof directed away from the piston 11.

The piston 7 is displaceably arranged in the body 5 parallel to its central axis. Further, it is free to rotate around its central axis. In a way known per se, there is provided a channel for the supply of pressurized air towards the end of the piston 11 that is turned away from the return spring 8, for the generation of a force that counteracts the force of the return spring 8. If the force generated by the pressurized air is sufficient for overcoming the force of the return spring, the control element 7 will be displaced such that the needle 10 will open for a flow of fluid to and through the nozzle 9. Other, equivalent solutions as to the control of the control element 7 are, of course, con- ceivable, and obvious to a person skilled in the art.

On the piston 11 there is provided a magnet 18. The magnet 18 is a permanent magnet, with the shape of a ring, the central axis of which coincides with the rotational axis of the piston 11 , and is arranged in a groove in one end of the piston 11 , in this case the end that is turned towards the return spring 8. The return spring 8 abuts the end of the piston 11 radially inside the magnet 18. The magnet 18 is arranged to be displaced together with the piston 11 , and it will generate a rotationally symmetric, radially directed magnetic field. The magnet 18 may, alternatively, have any other position on the piston 11 , depending on the design of the spray head 1 , for example, in a groove anywhere on the outer periphery of the piston. In the embodiment according to Fig. 2 there is provided a gauge 19 for sensing the magnet field generated by the magnet 18, said gauge being provided in a recess 14 in the surface of the second part 2 that is turned towards the first part 1. The gauge 19 is arranged axially displaced in relation to the motion region of the magnet 18, such that the sensed magnetic field will provide an unambiguous indication of the position of the magnet 18, and thereby the position of the control element 7, at each moment. The gauge 19 forms part of a first electric circuit 20, which is shown more in detail in Fig. 4. The circuit 20 is, with except for the gauge 19, arranged on a printed circuit card 15 that, in its turn, is provided in a recess, not shown in Fig. 2, on the second part 2 at a surface thereof that borders to the third part 3, onto which the second part 2 is mounted. The gauge 19, together with the circuit 20, is covered from the surrounding environment. For example, it may be hidden behind a cover sheet that has been attached by soldering or in any other way, such that it encloses the gauge 19 in the second part 2. The printed circuit card 15 is arranged in a similar way in the recess in which it is provided. However, for clarity reasons, no such cover sheet has been shown in the figures.

A second circuit 22 that co-operates with the first circuit 20 is provided in the third part 3 of the spray gun arrangement, in this case in the robot arm 3. In Fig. 2, at least a part of the second circuit 22 is arranged in a printed circuit card 16 that is provided on the surface of the third part 3 that is turned towards the second part 2. Also the second circuit 22 is protected from the surrounding environment, at least in the interface or border line between the second part 2 and the third part 3. The first and second circuits 20, 22 comprise means for a contactless transmission of supply voltage from the second circuit 22 to the first circuit 20, and in this case there are also means for a contactless transmission of signals from the first circuit 20 to the second circuit 22. "Contactless" is referred to as without any mechanical contact between or any interconnection of the two circuits.

With reference to Fig. 4, the first and second circuits will not be described more in detail. The first circuit 20 mainly comprises the gauge 19, a voltage-controlled oscillator circuit 23, a secondary transformer winding 24, and a voltage regulator 25.

The gauge 19 is constituted by a Hall-effect sensor with a sensitivity of, for example, 2,5 mV/Gauss, and requires a supply voltage of 3-5 volts. The oscillator circuit 23 outputs a digital output signal which is a square wave, the frequency of which is determined by the analogue input signal from the gauge 19. The transformer winding 24 picks up a 200 kHz square wave from a corresponding primary transformer winding provided in the second circuit 22. The voltage regulator 25 full-wave-rectifies said square wave and stabilizes the latter to the supply voltage required for feeding, on one hand, the gauge 19, and on the other hand, the oscillator circuit 23. The voltage regulator 25 compensates the variation of the air gap between the ferrite cores that may arise.

The output from the VCO-circuit is connected, through a transistor, to a load of, approximately, 1 mA, in order to increase the power con- sumption by, approximately, 10 kHz-pulses. If the power consumption is measured on the primary side, that is, in the second circuit 22, this measurement will also contain the measurement signal. The signal is band pass filtered and is amplified by means of an operation amplifier. It should be noted that the amplitude of the signal that is transferred between the transformer windings does not contain any information, but that it's only the frequency thereof that is dependent of what the gauge 19 has sensed from the magnetic field. The second circuit 22 mainly comprises a connection 26 with a voltage source of 8-12 volt (not shown), a voltage regulator 27, a control unit CPU 28, a bridge connection 29, a primary coil 30, and an operation amplifier 31.

The voltage regulator 27 delivers a supply voltage of 2-5 volt to the control unit 28, which, in its turn, generates a 200 kHz square wave directed to the bridge 29 that drives the primary coil 30. The supply voltage to the bridge circuit is measured over a shunting resistance to earth. The measurement signal is filtered in a band pass filter and is amplified in the operation amplifier 31. The amplified signal is treated in said control unit, or CPU, 28. The result of the calculations made in the control unit 28 based on the input signal thereto, is compared to calibration values stored in a non-volatile memory in the control unit. Each one of two digital outputs 32, 33 drives 1,65 mA in a NAMUR-connected output. If both signals are low or high, this results in an acceptance-signal that is indicative for the end positions of the control element 7, while the intermediate positions only have one output high, which makes the NAMUR-receiver 34 indicate a transition region. If a more detailed surveillance of the position of the control element 7 is required, more outputs may be arranged for a plurality of intermediate positions. Should the control unit 28 detect any fault in the circuit or the circuits, it will only send one signal high, i.e. corresponding to the transition region.

In the embodiment described above, the signals from the gauge 19 are treated in such a way that they reach the control unit through the first and second circuits 20, 22. Alternatively, it would be possible to let the means for contactless transmission comprise a transmitter provided in the first circuit for the transmission of signals that corresponds to the output signals of the gauge, and to use a receiver which is operatively connected with a control unit. In such a case, the transmitter is, preferably, an RF-transmitter, and the receiver is an RF-receiver.

In the shown embodiment, the control element 7 is arranged for the regulation of a flow of a liquid fluid, preferably a paint or a lacquer. Fig. 2 shows the side of the second part 2 that is intended to be mounted onto a corresponding side of the first part 1. The spray head 1 is provided with a plurality of channels for the flow of fluids, in this case air and lacquer/ paint. Corresponding channels are provided in the adapter unit 2. Muzzles into these channels are seen in Figs. 2 and 3. Channel 35 leads pressurized air to the end of the piston 11 that is directed away from the return spring 8, channel 36 leads paint to the nozzle 9, channel 37 leads air for effecting the pattern of the sprayed paint, the colour picture, channel 38 leads air for the disintegration of the sprayed paint, and channel 39 is a so called leakage hole for the detection of a leakage in the paint channel.

Fig. 3 shows an alternative embodiment of the invention, wherein the gauge 19 and the first circuit 20 connected therewith are arranged in a printed circuit card 40 in the first part 1 , on a surface thereof that is directed towards the second part 2. The second circuit 22, or at least a part thereof, is arranged in a printed circuit card 41 arranged on the surface of the second part 2 that is directed towards the first part 1 and opposite to the first printed circuit card 41 , for the purpose of performing a contactless transmission of supply voltage to the first circuit 20, and to transmit measurement signals to the second circuit 22. Further, a part of the second circuit 22 is provided in a printed circuit card 42 that is arranged on that surface of the second part 2 that is directed towards the third part 3 for the purpose of being supplied with a voltage from a further circuit 43, provided in the third part 3 and connected with a voltage supply source (not shown). It should be realized that, in this case, the second circuit may be extensively modified in relation to the circuit shown in Fig. 4. A central part of this aspect of the invention is, however, that the circuits, in all cases, are arranged for the contactless transmission of the supply voltage to the gauge 19, and for a contactless transmission of measurement signals back to the central control unit CPU 28. Thereby, the latter does not need to be provided in the second circuit 22, but may, as for example by an arrangement similar to the one of Fig. 3, be arranged in the further circuit belonging to the printed cir- cuit card 43.

It should be realized that the invention has only been described by way of example, and that variants of the embodiments disclosed will be obvious for a person skilled in the art without, however, departing from the scope of protection of the invention, such as defined in the enclosed patent claims, support by the description and the annexed drawings.

For example, the presented adapter unit may be excluded, whereby the first part will be formed by the spray head, while the second part then will be formed by the arm, which, in the preferred embodiment, is a robot arm, but which may be any other type of arm, i.e. not necessarily connected with a robot. The arm might even be manually operated.

Claims

PATENT CLAIMS

1. A spray gun arrangement comprising

- a first part (1) that comprises a spray nozzle (9) and at least one control element (7) for controlling the flow of a fluid in said spray noz- zle, said control element (7) being displaceably arranged in said first part (1) of the spray gun arrangement,

- a second part (2) that forms a holder onto which the first part (1) is mounted, and

- means (18, 19) for sensing the displacement position of the control element (7), said sensor means comprising a magnet arranged at the control element (7) and a gauge (19) arranged to sense the magnetic field generated by the magnet (18) in response to the displacement position of the magnet (18), characterized in that it comprises a metal return spring (8) arranged to act against the control element (7) in one of the displacement directions of the latter, and in that the magnet (18) is arranged externally of said spring (8).

2. A spray gun arrangement according to claim 1, characterized in that the control element (7) is displaceable between a first position, in which it stops a fluid flow, and a second position, in which it opens for a flow of fluid, and that the magnet (18) and the gauge (19) are arranged such that the gauge (19) senses both these positions.

3. A spray gun arrangement according to claim 1 or 2, characterized in that the magnet (18) is a permanent magnet.

4. A spray gun arrangement according to anyone of claims 1-3, characterized in that the control element (7) is at least partly rotationally arranged in relation to said first part (1), and in that the magnet (18) is ring-shaped, the rotational axis of the control element (7) coinciding with the central axis of the magnet (18).

5. A spray gun arrangement according to anyone of claims 1-4, characterized in that the gauge (19) is arranged radially outside the return spring (8) and the magnet (18).

6. A spray gun arrangement according to anyone of claims 1-5, characterized in that the gauge (19) is a Hall-effect sensor.

7. A spray gun arrangement according to anyone of claims 1-6, characterized in that the first part comprises a spray gun unit, the sec- ond part (2) comprises an adapter unit connected with the spray gun unit, and in that it comprises a third part formed by a robot arm (3) connected with a robot, said robot arm being connected with the adapter unit (2).