Metering apparatus

Abstract

The invention relates to an apparatus for metering a medium comprising a base element provided for fastening to a robot, a metering valve movably supported at the base element, and at least one piezo actuator by which the metering valve is movable relative to the base element.

Claims

1. A metering apparatus adapted to place drops of a medium to be metered onto a substrate, the metering apparatus comprising: a base element adapted to fasten the metering apparatus to a robot; a metering valve movably supported at the base element, wherein the metering valve is held at an intermediate element that is connected to, and movable relative to, the base element with at least one first flexible element; a first piezo actuator by which the metering valve is movable in a first direction relative to the base element, and a second piezo actuator by which the metering valve is movable in a second direction relative to the base element, wherein the first and second directions are at approximately right angles to one another.

2. The metering apparatus in accordance with claim 1, wherein the intermediate element is connected to the base element by means of at least one first leaf spring.

3. The metering apparatus in accordance with claim 1, wherein two first flexible elements are provided that form a parallelogram spring arrangement.

4. The metering apparatus in accordance with claim 1, wherein one of the first and second piezo actuator is connected between the base element and the intermediate element.

5. The metering apparatus in accordance with claim 1, wherein the metering valve is a slider valve.

6. The metering apparatus in accordance with claim 1, wherein a slider of the metering valve is actuable by means of a third piezo actuator.

7. The metering apparatus in accordance with claim 6, wherein a direction of action of the third piezo actuator coincides with a direction of action of a piezo actuator for moving the metering valve.

8. The metering apparatus in accordance with claim 1, wherein at least one sensor is provided for detecting a deflection of the at least one piezo actuator.

9. The metering apparatus in accordance with claim 1, wherein each of the first piezo actuator and the second piezo actuator comprises a piezo element deforming on application of an electrical voltage and a cantilever arm attached to the piezo element.

10. The metering apparatus in accordance with claim 9, wherein the piezo element of each of the first piezo actuator and the second piezo actuator warps on application of the electrical voltage.

Description

(1) The invention will be described in the following purely by way of example with reference to an advantageous embodiment and to the enclosed drawing. There are shown:

(2) FIG. 1 a perspective view of a metering apparatus in accordance with the invention;

(3) FIG. 2 a simplified perspective view of the metering apparatus of FIG. 1;

(4) FIG. 3 a simplified side view of the metering apparatus of FIG. 1;

(5) FIG. 4 a sectional view of the metering apparatus of FIG. 1;

(6) FIG. 5 a detailed view of a metering valve of the metering apparatus of FIG. 1; and

(7) FIG. 6 a perspective view of a metering system in accordance with the invention with a metering apparatus of FIG. 1.

(8) A metering apparatus 10 for placing drops of a medium to be metered, here a solder paste, onto a substrate 110 (FIG. 6) is shown in the Figures.

(9) The metering apparatus 10 comprises a base element 12 that serves to fasten the metering apparatus 10 to a robot 100 (FIG. 6) by means of which the metering apparatus 10 can be moved over a substrate 110 in a horizontal direction. The base element 12 is configured in the form of a rectangular plate and has a bore 14 15 in which a cartridge 16 is received. The cartridge 16 has an at least approximately vertically aligned cylindrical design and contains the medium to be metered, i.e. the solder paste

(10) Elastic connection elements 18, here in the form of leaf springs that extend vertically downwardly from the base element 12 and that serve for connecting an intermediate element 20 to the base element 12 are attached to oppositely disposed sides of the base element 12. The connection elements 18 form a parallelogram spring arrangement that makes it possible that the intermediate element 20 can move to and fro in a predefined horizontal direction relative to the base element 12. In this context, the direction of movement of the intermediate element 20 relative to the base element 12 is defined as the X direction, whereas the vertical direction is also called the Z direction.

(11) The movement of the intermediate element 20 relative to the base element 12 is controlled by a pair of first piezo actuators 22 of which only one arranged at the front side can be recognized in the Figures. A correspondingly formed first piezo actuator 22 is arranged at the rear side of the metering apparatus 10.

(12) Each first piezo actuator 22 comprises a piezo element 24 that is fastened to a lower side of the base element 12 and that deforms, warps in the present embodiment, on the application of an electrical voltage. A cantilever arm 26 is attached to the side of the piezo element 24 remote from the base element 12 and serves to increase the effective deflection of the piezo element 24 and thus the stroke of the piezo actuator 22. The piezo element 24 and the cantilever arm 26 are aligned substantially in the Z direction so that a free end of the cantilever arm 26 faces vertically downwardly and an activation of the piezo element 24 effects a deflection of the free end of the cantilever arm 26 in the horizontal direction, more precisely in the X direction. The cantilever arm 26 is rigidly coupled to the intermediate element 20 by means of a first connecting rod 28 in the region of its free end so that the deflection of the cantilever arm 26 is directly transmitted to the intermediate element 20. The intermediate element 20 can therefore be moved in the X direction relative to the base element 12, for example over a range of several 100 m, by activating the first piezo actuators 22.

(13) A valve carrier 30 is attached to a lower section of the intermediate element 20, and indeed by means of a horizontally aligned second leaf spring 32 that forms a joint that enables a rotation of the valve carrier 30 relative to the intermediate element 20. The valve carrier 30 carries a metering valve 34 that can accordingly in turn be moved relative to the intermediate element 20.

(14) A pair of second piezo actuators 36, of which only one arranged at the front can be recognized in the Figures, is provided to control the movement of the valve carrier 30 and thus of the metering valve 34 relative to the intermediate element 20. A correspondingly formed second piezo actuator 36 is arranged at the rear side of the metering apparatus 10. Each second piezo actuator 36 comprises a piezo element 38 that is fastened to the base element 20 and that deforms, warps in the present embodiment, on the application of an electrical voltage. A cantilever arm 40 is attached to the side of the piezo element 38 remote from the intermediate element 20 and serves to increase the effective deflection of the piezo element 38 and thus the stroke of the piezo actuator 36. The piezo element 38 and the cantilever arm 40 are aligned substantially horizontally so that a free end of the cantilever arm 40 faces in the X direction and an activation of the piezo element 38 effects a deflection of the free end of the cantilever arm 40 in the vertical direction, i.e. in the Z direction. The cantilever arm 40 is rigidly coupled to the valve carrier 30 by means of a second connecting rod 41 in the region of its free end so that the deflection of the cantilever arm 40 is directly transmitted to the valve carrier 30. The valve carrier 30 and thus the metering valve 34 can therefore be moved in the Z direction relative to the intermediate element 20, for example over a range of several 100 m, by activating the second piezo actuators 36.

(15) A metering needle 42 for dispensing the medium to be metered is formed at a lower side of the metering valve 34 and can be moved relative to the base element 12 by a corresponding activation of the first piezo actuators 22 and of the second piezo actuators 36 in the Z direction, that is vertically, or in the X direction, that is horizontally. As mentioned, the first and second piezo actuators 22, 36 are formed such that the metering needle 42 can carry out a respective stroke of several 100 m, for example up to 500 m, relative to the base element 10 both in the X direction and in the Z direction.

(16) If the metering apparatus 10 is moved over the substrate 110 at an at least approximately constant speed in the X direction by the robot 100 and if the first and second piezo actuators 22, 36 are simultaneously suitable controlled, the robot movement can have the piezo movements superposed such that the metering needle 42 describes a cycloid over the substrate 110. Drops of the medium to be metered having a diameter of, for example, 100 m to 200 m, can hereby be placed onto the substrate 110 in an ideal manner. It is understood that the metering needle 42 has a correspondingly adapted diameter that can, for example, be in the range of 100 mm to 150 mm for the present application.

(17) The design of the metering valve 34 is shown more exactly in FIG. 4. The supply of the medium to be metered to the metering needle 42 takes place through a line 44 that connects the cartridge 16 to the metering needle 42. The line 44 is for the larger part implemented by bores in solid material. Since, however, the cartridge 16 is fixedly seated in the base element 12 while the metering valve 34 should move relative to the base element 12, a part section of the line 44 is formed by a flexible tube piece 45 that extends vertically through a cut-out of the intermediate element 20 and connects the cartridge 16 to a bracket 46 that is fixedly inserted into the metering valve 34.

(18) The inlet of the medium to be metered supplied through the line 44 into the metering needle 42 is controlled by a slider 48 (FIGS. 4 and 5) that can be pushed downwardly in the Z direction against the return force of a plate spring 49 to block an inlet opening. The metering valve 34 is in other words a slider valve. The actuation of the slider 48 takes place by means of a third piezo actuator 50 that comprises a piezo element 52 that is fastened to a wall of the metering valve 34 facing the intermediate element 20 and that deforms, warps in the present embodiment, on application of an electrical voltage. A cantilever arm 54 is attached to the side of the piezo element 52 remote from the intermediate element 20 and serves to increase the effective deflection of the piezo element 52 and thus the stroke of the third piezo actuator 50. The piezo element 52 and the cantilever arm 54 are aligned substantially horizontally so that a free end of the cantilever arm 54 faces in the X direction and an activation of the piezo element 52 effects a deflection of the free end of the side arm 54 in the vertical direction, i.e. in the Z direction. The cantilever arm 54 is rigidly coupled to the slider 48 by means of a third connecting rod 56 in the region of its free end so that the deflection of the cantilever arm 54 is directly transmitted to the slider 48. The slider 48 can therefore be moved in the Z direction relative to the intermediate element 20 by activating the third piezo actuator 50 and can correspondingly control the dispensing of the medium to be metered through the metering needle 42.

(19) In the region of the free end of each cantilever arm 26, 40, 54, a sensor 58 is arranged for detecting the actual deflection of the respective cantilever arm 26, 40, 54 (FIG. 1). The detection of the actual deflection of each cantilever arm 26, 40, 54 enables a regulation of the piezo actuators 22, 36, 50 and contributes to a permanently exact operation of the metering apparatus 10.

(20) It is understood that the metering apparatus 10 is equipped with suitable logic modules 58 for processing the signals output by the sensors 58 and for controlling or regulating the piezo actuators 22, 36, 50 (FIGS. 1 and 4).

(21) FIG. 6 shows a metering system comprising a robot 100 and a metering apparatus 10 fastened thereto for the placement of drops of solder paste onto the substrate 110.

REFERENCE NUMERAL LIST

(22) 10 metering apparatus 12 base element 14 bore 16 cartridge 18 connection element 20 intermediate element 22 piezo actuator 24 piezo element 26 cantilever arm 28 connecting rod 30 valve carrier 32 leaf spring 34 metering valve 36 piezo actuator 38 piezo element 40 cantilever arm 41 connecting rod 42 metering needle 44 line 45 tube piece 46 bracket 48 slider 49 plate spring 50 piezo actuator 52 piezo element 54 cantilever arm 56 connecting rod 58 sensor 60 logic module 100 robot 110 substrate