Method and device for applying a paste

Abstract

In the method described, a compound substantially in the form of a paste is fed by means of a pump from a storage container (1) to a metering device (3) which determines the amount of paste to be applied to a workpiece (B). From the metering device, the paste is fed to a spray head (S) where it is mixed with swirled by compressed air from a cylinder (4) or other suitable supply and sprayed on to the workpiece (B). The amount of compressed air supplied to the paste for spraying purposes is controlled by means of a control unit (6) in such a way that a strip of substantially constant width is applied to the workpiece (B).

Description

This is mixed with swirled by the compressed air arriving through the valve V and is sprayed onto the sheet metal B. The spray head S and the workpiece B are at the same time moved relative to one another in a direction of the strip to be applied. In order to obtain a constant strip width on the workpiece B, the same compressed-air stream must be continuously supplied at a constant viscosity of the glue or sealer. The desired value for the amount of air to be admixed with supplied to the glue is forwarded to the control device 6 from the desired-value adjuster 5, through which control device 6 in turn adjusts the cross section of the throughlet of the valve V.

If during the operation, variations in the temperature and the composition, and thus in the viscosity of the glue occur, then the feed pressure must follow accordingly at a pregiven flow of the mass. Because of the simultaneously occurring change in viscosity, the compressed-air supply needs also to be changed in order to arrive at the same strip width. This is done with the help of a calibration-curve generator contained in the control device 6, the variable parameters of which are empirically determined and adjusted. The magnitudes of the regulating or controlling variables, such as the weight rate of flow, pressure, or temperature, are detected with the help of the sensors 7 at the outlet side of the metering device 3 or at the inlet side of the spray head S and are preferably forwarded in the form of electrical signals to the control device 6 for the purpose of controlling the valve V. With this it can be achieved that the amount of compressed air, which is mixed swirled with the stream of glue or sealer, is controlled such that the same spray width is obtained at all times. Thus the problems of an excessive or reduced application of glue or sealer are avoided and a safe gluing of the workpieces is guaranteed.

The sensors 7 are advantageously designed as a temperature sensor, pressure sensor or as an amount-measuring cell. It is also possible to thereby provide several sensors, for example, one at the outlet of the metering device 3 and one at the glue inlet into the spray head S.

Epoxy-resin glues, glues having a polyurethane base or acrylate glues are, for example, suitable for use as glue and sealer; however, also other types of glues are suitable. The paste does not necessarily have to be a glue or sealer. The described device or rather the method carried out with this device is principally suited also for other essentially paste-like materials, the viscosity of which can vary in wide limits and which, in spite of this characteristic, are supposed to be evenly applied onto a workpiece B.

The above described device or the method carried out with this device are particularly suited for use in industrial manufacturing, in particular in connection with an industrial robot.

In summary the following is to be stated: An essentially paste-like compound is fed from a storage container 1 by means of a feed pump 2 to a metering device 3, which determines the amount of paste to be applied onto a workpiece B. The paste is guided to a spray head S, where it is mixed with swirled by compressed air from a further storage container 4 or through a suitable connection and is sprayed onto the workpiece B. The amount of compressed air, which is fed to the paste for spraying, is thereby controlled by means of a control device 6 in such a manner that a strip of an essentially constant width is sprayed onto the workpiece B.

Claims

1. A method for applying a paste material to a workpiece which is moveable relative to a spray device, the method comprising the steps of:

feeding the paste material to the spray device by the action of a feed pressure;

separating and/or mixing the paste material with a compressed gas within the spray device;

spraying the paste material onto the workpiece with the workpiece and the spray device being moved relative to one another;

spraying the paste material in the form of a strand onto the workpiece with the workpiece and the spray device being moved relative to one another;

swirling the strand of paste material with a compressed gas;

measuring a temperature of the paste material prior to its entry into the spray device; and

controlling the amount of compressed gas supplied per unit of time to the paste material in functional dependency on the measured temperature, so that a strip of paste material of essentially constant width is sprayed on along the workpiece.

2. The method of claim 1, further comprising the step of setting the functional dependency using a stored digital or analog, empirically determined calibration curve.

3. The method of claim 1, further comprising the step of controlling the relative velocity of the spray device and the workpiece so that an amount of paste material sprayed onto the workpiece per unit area is maintained constant.

4. A method for applying a paste material to a workpiece which is moveable relative to a spray device, the method comprising the steps of:

feeding the paste material to the spray device by the action of a feed pressure;

separating and/or mixing the paste material with a compressed gas within the spray device; spraying the paste material onto the workpiece with the workpiece and the spray device being moved relative to one another;

spraying the paste material in the form of a strand onto the workpiece with the workpiece and the spray device being moved relative to one another;

swirling the strand of paste material with a compressed gas;

determining the feed pressure of the paste material as a measure of its viscosity prior to its entry into the spray device;

adjusting a volume or mass stream of the paste material to a set value by varying the feed pressure at a constant flow cross section of the spray device; and

controlling the amount of compressed gas supplied per unit of time to the paste material in functional dependency on the measured feed pressure so that a strip of paste material of essentially constant width is sprayed on along the workpiece.

5. The method of claim 4, wherein the step of adjusting the volume or mass stream to the set value includes varying a driving pressure or the electrical driving power of an electrically driven metering device to vary the feed pressure.

6. The method of claim 5, wherein the feed pressure is dependent upon a driving pressure, a driving power or a driving voltage level of the metering device, the step of controlling the amount of compressed gas supplied per unit of time being in functional dependency on the driving pressure or driving power of the metering device or the driving voltage level derived therefrom.

7. The method of claim 4, further comprising the step of directly measuring the volume or mass stream of the paste material with a flow meter or indirectly measuring the volume or mass stream of the paste material by measuring a piston speed of a metering cylinder forming a metering device.

8. The method of claim 4, further comprising the step of setting the functional dependency using a stored digital or analog, empirically determined calibration curve.

9. The method of claim 4, further comprising the step of controlling the relative velocity of the spray device and the workpiece so that an amount of paste material sprayed onto the workpiece per unit area is maintained constant.

10. A device for applying a strip of a paste material to a workpiece, comprising:

a spray head moveable relative to the workpiece;

means for supplying said paste material into said spray head, said spray head forming a strand of the paste material;

means for supplying a compressed gas to the spray head, said compressed gas being mixed with the paste swirled with the strand of paste material before being applied to the workpiece;

temperature sensing means positioned upstream of the spray head for measuring the temperature of the paste materials material;

temperature sensitive regulator means for controlling the supply of compressed gas to the spray head, dependent on a set width of the mass strip to be applied along the workpiece.

11. The device of claim 10, further comprising:

a storage container for the paste material;

feed pump means for feeding the paste material to a metering device;

a second storage container or a connection for compressed gas;

valve means for controlling the compressed gas supply to the spray head;

control device means for controlling said valve for the compressed gas supply so that the amount of compressed gas mixed swirled with the paste material per unit of time is metered such that the spray head sprays a strip of paste material of an essentially constant width along the workpiece.

12. The device of claim 10, wherein the regulator means of the compressed gas supply comprises an analog or digital calibration curve generator.

13. The device of claim 10, further comprising regulator means for controlling the relative speed of the spray head and the workpiece such that an essentially constant amount of paste material per unit area is sprayed onto the workpiece.

14. A device for applying a strip of paste material to a workpiece, comprising:

a spray head moveable relative to the workpiece;

means for supplying said paste material by the action of a feed pressure to said spray head, said spray head forming a strand of the paste material;

means for supplying compressed gas to the spray head, said compressed gas being mixed with swirled with the strand of the paste material before being applied to the workpiece;

pressure sensing means positioned upstream of the spray head for measuring the feed pressure of the paste material as a measure of the viscosity of said paste material;

paste material regulator means positioned upstream of the spray head for adjusting the volume or mass stream of the paste material to a set value by varying the feed pressure at a constant flow cross section in the spray head; and

feed pressure sensitive regulator means for controlling the supply of compressed gas to the spray head, determined by a set width of the mass strip of paste material to be applied along the workpiece.

15. The device of claim 14, further comprising:

metering pump means for the paste material which is controlled by the paste material regulator means, the feed pressure of the paste material being dependent upon a driving pressure, a driving power or a voltage level of the metering pump means; and

a device in communication with said feed pressure sensitive regulator means for controlling the compressed gas supply to the spray head, said device reacting to the driving pressure or the driving power or voltage level of the metering pump means.

16. The device of claim 14, wherein the regulator means of the compressed gas supply comprises an analog or digital calibration curve generator.

17. The device of claim 14, further comprising regulator means for controlling the relative speed of the spray head and the workpiece such that an essentially constant amount of paste material per unit area is sprayed onto the workpiece.

18. The device of claim 14, further comprising flow meter means positioned upstream of the spray head in a feed pipe for determining the volume or mass stream of the paste material.

19. The device of claim 14 15, further comprising a device for measuring the piston speed of a metering cylinder forming the metering device pump as a measure of the volume stream.