(51) Int.Cl.4

Patent Claims

1. Device, which is intended for powder recovery from a mixture of powder and air, in particular for electrostatic powder coating installations, and which comprises at least one cyclone, at least one secondary filter, and at least one powder collecting container as well as a sieve device, characterized in that a plurality of cyclones (3) and the secondary filters (4), which are assigned to said cyclones, and at least one powder collecting container (11) form with a sieve device a closed recovery unit (2), which is operated by means of circulated air and which can be connected in a detachable manner to the powder coating installation (1).

2. Device, as claimed in claim 1, characterized in that the recovery unit (2) can be transported together with the cyclones (3) and the secondary filters (4).

3. Device, as claimed in claim 1 or 2, characterized by a stabilizing device (7), which is disposed between the cyclone underflow (6) and the powder collecting container (11) and which is provided with an injector (8) on its end, pointing towards the powder collecting container (11).

4. Device, as claimed in any one of the claims 1 to 3, characterized in that the secondary filter (4) is flanged to the overflow area (5) of the cyclone (3).

5. Device, as claimed in any one of the preceding claims, characterized in that the powder collecting container (11) is open in the direction of the powder coating installation (1).

6. Device, as claimed in any one of the preceding claims, characterized in that the powder collecting container (11) is designed as a powder car, to the top side of which is attached the sieve device (10).

7. Device, as claimed in claim 6, characterized in that the powder car (11) and the sieve device (10) form a subunit, which is separately manipulable.

8. Device, as claimed in any one of the preceding claims, characterized in that a plurality - preferably three - cyclones (3) with the corresponding secondary filters (4) are assigned a common powder collecting container (11) with a common sieve device (10).

9. Device, as claimed in any one of the preceding claims, characterized in that the inlet side (14) of the cyclone(s) (3) of the recovery unit (2) is connected to the interior of the powder coating installation (1) by means of a channel (15).

10. Device, as claimed in claim 9, characterized in that the channel (15) is securely connected to the powder coating installation (1) and is connected in a detachable manner to the recovery unit (2) at the inlet side(s) (14) of the cyclone(s) (3).

Description

The invention relates to a device, which is configured for powder recovery from a mixture of powder and air, and which is intended especially for electrostatic powder coating installations. Such powder recovery devices usually exhibit at least one cyclone for removing the solid particles from the gases, at least one secondary filter, and at least one powder collecting container as well as a sieve device.

There is the increasing desire on the part of the operators of such electrostatic powder coating installations to offer as many colors as possible for the respectively desired coating. To date, however, the color change has caused problems in such electrostatic powder coating installations, because it is time consuming and expensive and because the amount of powder that is lost in this procedure is relatively large.

In order to overcome the above described problems, the object of the invention is to provide a device of the type described in the introductory part for the recovery of powder. According to the invention, this powder recovery device is suitable for a multi-color operation in electrostatic powder coating installations and enables a quick color change with a minimum loss of powder.

According to the invention, a device, which is intended for the recovery of powder from a mixture of powder and air, in particular for electrostatic powder coating installations, and which comprises at least one cyclone, at least one secondary filter and at least one powder collecting container as well as a sieve device, is characterized in that a plurality of cyclones and the secondary filters, which are assigned to said cyclones, and at least one powder collecting container form with the sieve device a closed recovery unit, which is operated by means of circulated air and which can be connected in a detachable manner to the powder coating installation.

In this inventive device for powder recovery, the devices that are required for said recovery, are combined to form one unit. Then in the event of a color change, this unit can be exchanged for a different recovery unit, so that a quick color change is possible without having to accept long downtimes of the electrostatic powder coating installation. In this case, too, there is also no longer any risk of mixing the powder during recovery, because the recovery unit can be completely exchanged and then can be completely cleaned as early as during the operation of the powder coating installation in order to use it then again in the next working step for other color powders. This recovery unit is built in a compact way and forms a closed system, which can be operated with circulated air. Therefore, in contrast to the conventional recovery devices, which are operated with outgoing air, the recovery unit does not require any special blowers or the like, so that the recovery unit, provided by the invention, can also be manufactured and implemented cost effectively. Furthermore, owing to the unit being operated with circulated air the problems associated with the powder coating process in the electrostatic powder coating installation are avoided, because the powder recovery does not use any outgoing air that could adversely affect the air flow conditions in the electrostatic powder coating installation.

Preferably this recovery unit can be transported together with the cyclones and the secondary filters as well as optionally other devices, like the powder collecting container and the sieve device, as a whole. To this end, for example, this recovery unit can be mounted on a chassis with rollers. This configuration makes it easier to exchange one recovery unit for another recovery unit even in the case of larger installations.

In order to generate as high a negative pressure as possible in the closed recirculated air system in the area of the cyclone underflow, but at the same time suppress the tendency of the powder, which was removed from the mixture of powder and air by means of the cyclone, to form a vortex, a practical further development of the invention provides a stabilizing device between the cyclone underflow and the powder collecting container. An injector is provided on that end of the stabilizing device that points towards the powder collecting container. With the aid of the injector, which can be operated preferably by means of a piston, the negative pressure can be increased in the area of the outlet side of the stabilizing device, in order to guide the removed powder directly into the downstream device, comprising a powder collecting container and a sieve device.

Preferably the secondary filter(s) of the cyclone(s) is/are flanged directly to the overflow area of the cyclone(s), so that the secondary filter and the cyclone form one module in order to achieve a design of such a recovery unit that is as compact as possible.

Preferably the powder collecting container is open in the direction of the powder coating installation, so that a closed operation with recirculated air is possible. As a result, the provided injector prevents the recirculated air flow from carrying the powder in the direction of the powder coating installation. Furthermore, such a design also makes possible the dispensing with lock devices, which are very complicated to design at the connecting point between the recovery unit and the powder coating installation.

According to a practical further development of the invention, the powder collecting container is designed as a powder car, to the top side of which is attached the sieve device. Furthermore, the other devices of the recovery unit, like the cyclone, the secondary filter, and the like, are securely connected in an expedient way to this powder car, so that the powder car serves at the same time as the traversing device for the entire recovery unit.

According to an alternative embodiment, the powder car and the sieve device can form a separately manipulable subunit, which can be separated, if necessary, from the cyclone and from the secondary filter during the subsequent cleaning operation of the entire recovery unit, in order to make the use of the inventive recovery unit as versatile as possible.

A preferred embodiment of the invention provides a recovery unit, in which a plurality - preferably three - cyclones with the secondary filters, which are assigned to these cyclones, are combined together with a common powder collecting container and a common sieve device so as to form an independently manipulable unit. In this way it is achieved that cyclones with secondary filters of a smaller design can be used for the recovery unit, since in this case a plurality of such working units are connected in succession, but one common powder collecting container with one common sieve device is assigned to these working units on the powder removal side.

In order to connect to the interior of the powder coating installation, the inlet side of the cyclone(s) of the recovery unit is connected to one common channel. This channel is connected preferably in a stationary manner to the powder coating installation and is connected in a detachable manner to the recovery unit at the inlet side(s) of the cyclone(s). At the same time the channel can remain securely connected to the powder coating installation even when the recovery unit is exchanged, so that the recovery unit is simply moved away from this channel.

In order to form the closed recirculating air system, the outlet side(s) of the secondary filter(s) is/are reconnected to the interior of the powder coating installation by means of a common connecting line. This return connecting line is securely attached to the recovery unit in a practical way and runs approximately horizontally into the interior of the powder coating installation so that the recovery unit can be moved away from the powder coating installation without any problems.

The invention is explained in detail below by means of one example with reference to the attached drawings.

Figure 1 is a schematic rendering of a side view of an electrostatic powder coating installation with one preferred embodiment of a recovery unit, according to the invention; and

Figure 2 is a front view of the recovery unit.

In Figure 1 the reference numeral 1 denotes the electrostatic powder coating installation in its entirety. The electrostatic powder coating installation is designed in the shape of a so-called spray booth. The spray guns or similar devices for electrostatic application of the powder coating are not shown in detail, since the spray booth is assumed to be well-known.

A recovery unit, all of which is labelled 2, is assigned to the powder coating installation 1. As evident from Figures 1 and 2, the recovery unit 2 comprises three cyclones, which are situated side by side and to each of which a respective secondary filter 4 is securely connected by means of a flange connection. In this case the respective secondary filter 4 is flanged to the overflow area 5 of the respective cyclone 3. Adjacent to the underflow area 6 of each cyclone 3 there is a respective stabilizing device 7, which has the task of decelerating the flow of the removed powder that is received at the underflow area 6 of the cyclone 3 and, in particular, to decrease the centrifugal forces of this flow. The outlet end of each stabilizing device 7 exhibits an injector 8, which can be operated preferably with a piston, in order to generate an enhanced negative pressure at this end region of the stabilizing device 7, so that the powder falls in a directed way on a sieve device 10 that is located below. From the sieve device the powder then falls into a powder collecting container 11, which is designed as a powder car in the illustrated example. As shown in Figure 2, the three cyclones 3 with the corresponding stabilizing devices 7 are assigned a common powder car 11 and a common sieve device 10. The powder car 11 has traversing rollers 12, and it forms the undercarriage of the recovery unit 2, so that this recovery unit can be moved altogether from the electrostatic powder coating installation 1 and can be replaced with a new recovery unit during a color change.

As depicted, the sieve device 10 is carried by the powder car 11 and is fastened to the top side of said powder car. In order to facilitate the cleaning of the recovery unit 2 at a later time, the powder car 11 with the sieve device 10 can form a subunit, which can be detached from the rest of the devices of the recovery unit 2.

As the drawing shows, the powder collecting container or rather the powder car 11 is open in the direction of the electrostatic powder coating installation 1, so that it and the recovery unit 2 can be removed quickly and easily during a color change. A connecting line 13 is connected to the powder collecting container 11. This connecting line can run to a coating device (not illustrated), like a powder coating gun, by means of which the powder is applied to the objects that are to be coated.

As one can also infer from the Figures in the drawing, the recovery unit 2 forms a closed recirculating air system. To this end, the inlet sides 14 of the cyclones 3 are connected by way of a common channel 15 to the interior of the electrostatic powder coating installation 1. As one can see especially from Figure 2, the outlet sides 16 of the secondary filters 4 are connected in turn to the interior of the electrostatic powder coating installation 1 by way of an additional common connecting line. In the illustrated preferred embodiment, the channel 15 is securely connected to the electrostatic powder coating installation 1 in the shape of a spray booth, whereas the connecting line 17, which represents a return line for the closed recirculating air system, is securely connected to the recovery unit 2. Therefore, the connecting line 17 runs approximately horizontally in the vicinity of the floor of the electrostatic powder coating installation 1, so that the recovery unit 2 can be moved away from the electrostatic powder coating installation 1 towards the side.

The inventive device for the recovery of powder from a mixture of powder and air works as described below. A mixture of powder and air is carried through the channel 15 away from the interior of the electrostatic powder coating installation 1 and is fed through the inlet sides 14 of the cyclones 3 to the recovery unit 2. Owing to the effect of the centrifugal forces the powder in the cyclones 3 is removed from the mixture of powder and air; and the powder moves downwards in the direction of the underflow area 6 due to gravity. In the adjacent stabilizing device 7, the powder flow is slowed down; and the vortex formation, induced by the centrifugal forces, is deconstructed. Then at the outlet area of the stabilizing device 7 an enhanced negative pressure is generated with the aid of the injector 8, so that at the end of the stabilizing device 7 the stabilized flow of powder falls in a free fall onto the sieve device 10 on account of the negative pressure, generated with the aid of the injector 8. After passing through the sieve device 10, the powder arrives in the powder collecting container or rather the powder car 11, from where said powder can then be fed in turn to a gun for powder coating. The secondary filters 4 are flanged to the overflow area 5 of the cyclones 3; and the rest of the precleaned flow of the powder/air mixture, which rises in said overflow area with the aid of the cyclone 3, is then fed through the respective secondary filters 4, in order to filter out the bulk of the residual powder particles in the secondary filter 4. The outlet sides 16 of the secondary filters 4 are connected to the interior of the electrostatic powder coating installation 1 by means of the connecting line 17, so that the largely pure air flow, which emerges on the outlet sides 16 of the secondary filters 4, is returned again into the interior, so that the result is a closed recirculating air system for the recovery of powder.

Of course, the invention is not restricted to the above described preferred embodiment, but rather numerous modifications are still possible, so that, for example, more or less than three cyclones 3 and the corresponding devices can be combined to form a recovery unit 2. The number of these devices of the recovery unit 2 depends on the desired variety of colors and/or on the size of the electrostatic powder coating installation 1. Therefore, these details can be adapted to the respective requirements.

List of Reference Numerals

1 electrostatic powder coating installation

2 recovery unit

3 cyclone

4 secondary filter

5 overflow area

6 underflow area

7 stabilizing device

8 injector

9 piston

10 sieve device

11 powder collecting container or rather powder car

12 traversing rollers

13 connecting line to the powder coating installation 1

14 inlet side of the cyclone 3

15 channel

16 outlet side of the secondary filter 4

17 connecting line

Number: 37 15 470

Int. Cl.⁴: B 01 D 50/00

Application date: May 8, 1987

Disclosure date: November 17, 1988