Measuring valve

Abstract

The present invention relates to a metering valve (10, 10') for viscous materials, comprising a housing (12), a material flow path extending within the housing (12) and opening to a plurality of material discharge openings (26), and a plurality of valve needles (24) movably mounted within the housing (12), wherein the number of valve needles (24) corresponds to the number of material discharge openings (26), each valve needle (24) is associated with a valve seat (22), and each valve needle (24) is movable between a closed position in which it sits on the corresponding valve seat (22) and closes one of the material discharge openings (26), and an open position in which the material discharge opening (26) is exposed. The present invention also comprises a plurality of actuators (64) acting on the valve needles (24). According to the present invention, the number of actuators (64) is less than the number of valve needles (24), and at least one actuator (64) acts on at least two valve needles (24) simultaneously.

Description

Technical Field

[0001] The present invention relates to a metering valve for a viscous material as described in the preamble of claim 1.

Background Art

[0002] Such a metering valve is known, for example, from Patent Document 1. The metering valve described therein has a plurality of valve needles, and each valve needle is associated with a valve seat. Each of the valve needles is movable between a closed position in which it seats on the associated valve seat to close one of the material discharge openings and an open position in which the valve needle is lifted from the valve seat to open the corresponding material discharge opening. Further, each valve needle is associated with an actuator that acts on the valve needle to move it.

[0003] Such metering valves have already proven to be excellent. In particular, they can be miniaturized, and the valve seats, and thus the material discharge openings, are arranged at a close distance from each other. However, one drawback is that the actuator acting on the valve needle is wider than the nozzle spacing in some applications, and therefore has to be arranged so as to spread out fanwise from the nozzle openings. This problem becomes more serious as the number of valve needles of the metering valve increases.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Therefore, the problem to be solved by the present invention is to develop a metering valve of the aforementioned type such that the number of valve needles and valve seats can be increased even when the distance between the valve seats is small.

Means for Solving the Problems

[0006] This problem is solved by a metering valve having the features of claim 1, according to the present invention. Advantageous developments of the present invention are the subject of the dependent claims.

[0007] The present invention is based on the concept of using fewer wide actuators than narrow valve needles. To this end, at least one actuator acts on at least two valve needles simultaneously, and the material discharge openings associated with these valve needles can only be opened and closed in conjunction. The actuators are preferably piezoelectric actuators that can be actuated quickly and apply large forces.

[0008] Advantageously, at least one actuator can be associated with and act on only one valve needle, thereby individually opening and closing the material discharge opening associated with that valve needle. The valve seats are preferably arranged in a row extending laterally with respect to the longitudinal direction of the valve needles, and the valve needles are preferably arranged to extend parallel to each other, where the row of valve seats extends perpendicularly with respect to the longitudinal direction of the valve needles. The two valve needles associated with the first and last valve seats in the row are preferably each associated with one of the actuators acting on the corresponding valve needles. This embodiment is based on the concept that, in order to coat a material with sharp edges and conform to the contour, it is necessary to coat the material as precisely as possible in the edge region of the material coating. For this reason, the central valve needles are preferably combined so that two, three, or more act together as a single unit, or as a group of multiple units, by a single actuator.

[0009] Advantageously, valve needles acting jointly by a single actuator are preferably rigidly connected to one another by a coupling element, the actuator engaging with the coupling element at the point of application of force. This means that one actuator can easily ensure that two or more valve needles act at once. The point of application of force is preferably located at the center or center point of the coupling element, and the valve needles connected by the coupling element are preferably arranged symmetrically with respect to the point of application of force. In this way, it is ensured that no torque acts on the valve needles, or, if the actuator is designed as a piezoelectric actuator, that it does not twist.

[0010] Advantageously, each valve needle is formed from a cemented carbide alloy. The valve needle is guided so as to be displaceable in the longitudinal direction through a through-opening in a guide block positioned at a distance from the valve seat, and it is preferable that the guide block has at least the inner surface of the through-opening facing the valve needle formed from a cemented carbide alloy.

[0011] This embodiment is based on the concept of forming the valve needle and its guide from cemented carbide to achieve sufficiently stable, accurate, and highly sealing guidance of the valve needle, thereby keeping these valve needles small and positioning them at small distances from one another. Positioning the valve needles at small distances from one another also allows for positioning the material discharge openings at small distances from each other, potentially resulting in a smaller cross-section for the material discharge openings. In particular, when the inner surface of the through-opening is in close contact with the valve needle, there is no need to provide additional sealing elements, and the valve needles can be positioned at small intervals from one another. For this purpose, the guide block is fitted to the valve needle, or multiple valve needles, with very high precision, and it (they) are housed within the guide block with virtually no play. This measure also results in very precise guidance of the valve needle, or multiple valve needles.

[0012] It is even more preferable that the valve seat is formed from cemented carbide, and in particular, that the valve needle is also formed from cemented carbide. This advantageous development is based on the concept that parts formed from cemented carbide are more resistant to wear. Therefore, it is advantageous to form the valve needle or multiple valve needles from cemented carbide. This is because cemented carbide is chemically resistant, in particular to the materials to which the metering valve is applied. When the valve needle is formed from cemented carbide, the associated valve seat cannot be formed from a softer material because it would be deformed by the valve needle. In particular, all valve needles and all valve seats can be formed from the same cemented carbide, which simplifies manufacturing. The valve seat is also preferably advantageously positioned on a valve seat block integrally molded from cemented carbide. Furthermore, the guide block can also be integrally molded from cemented carbide.

[0013] Cemented carbides are understood as metal matrix composites in which hard material, existing in particle form, is bonded together by a metal matrix. The hard phases used are particularly metal carbides or metal nitrides, such as tungsten carbide, titanium carbide, titanium nitride, niobium carbide, tantalum carbide, or vanadium carbide.

[0014] Connecting valve needles made of cemented carbide to actuating elements made of other materials and actuated by actuators is no trivial matter. Advantageously, each valve needle is configured to be housed and connected within a sleeve made of metal, preferably stainless steel, with its end facing away from the associated valve seat. The connection is advantageously achieved by soldering. Sleeves connected to adjacent valve needles are advantageously positioned at different distances from their respective valve seats. The sleeves naturally have a larger diameter than the valve needles, but the fact that they do not collide during operation is taken into consideration. Each sleeve can be actuated by an associated actuator, in which case it is advantageous to place a flexure bearing between each sleeve and the corresponding actuator. This bearing can be connected to the sleeve, in particular, by laser welding. Advantageously, each valve needle is associated with an actuator for acting on the valve needle.

[0015] Furthermore, each valve needle can be subjected to a force acting away from its respective valve seat by at least one restoring element attached to the housing, and a corresponding actuator can apply a closing force against that force. In this case as well, the force is preferably applied via a flexible bearing, however this flexible bearing does not need to be rigidly connected to the corresponding valve needle, but rather can be loosely positioned on the valve needle to press it against the valve seat. At least one elastic restoring element preferably engages with the shoulder of the valve needle in each case, and the shoulders of mutually adjacent valve needles can be positioned at equal distances from their respective valve seats. However, advantageously, they can be positioned at different distances from their respective valve seats. The shoulders result in the thickness of the valve needle, which would prevent the valve needles from being positioned at small distances from each other if all the valve needles were positioned at the same distance from their respective valve seats.

[0016] The present invention will be described in more detail below with reference to exemplary embodiments schematically shown in the drawings. [Brief explanation of the drawing]

[0017] [Figure 1] This is a cross-sectional view of a metering valve according to the first embodiment. [Figure 2a] Figure 1 is a schematic diagram of the operating modes of the metering valve. [Figure 2b] This is a schematic diagram of the operating modes of the metering valve according to the second embodiment. [Modes for carrying out the invention]

[0018] The metering valve 10 according to the first embodiment shown in Figure 1 comprises a housing 12 having a plurality of parts detachably connected to one another. A feed section 14 integrally molded from stainless steel has a material channel (not shown in detail) extending from a material inlet opening, through which viscous materials such as adhesives, sealants, insulating materials, or thermal conductive pastes can be introduced into the material channel. A valve seat block 20 integrally molded from cemented carbide is attached to the feed section 14. In this case, as an example, the valve seat block 20 has seven valve seats 22 arranged in a row, each valve seat 22 associated with a valve needle 24. The valve needle 24 is positioned within the housing 12 so as to be linearly movable along its longitudinal axis. In front of the valve seats 22, the material channel branches into seven subchannels, each subchannel terminating at a material discharge opening 26 in the material discharge surface 62 of the valve seat block 20. However, branching of the material channel into subchannels is not necessarily required. For example, the material flow path can also communicate with a material chamber, and when the valve needle 24 is lifted from the valve seat 22, material can be discharged from there through the material discharge opening 26. To open and close the material discharge opening 26, the valve needle 24 can be lifted from or placed on its respective associated valve seat 22. To dispense the material, the metering valve 10 is typically moved relative to the workpiece perpendicular to the longitudinal direction of the row of material discharge openings 26.

[0019] The valve needle 24 is housed in the supply unit 14 and guided within a guide block 28 to which it is detachably connected, and through a through-opening 30 extending through the guide block 28. The dimensions of the through-opening 30 are precisely matched to the dimensions of the valve needle 24, and the valve needle 24 is guided with high precision within the guide block 28. Furthermore, a sealing effect is achieved between the guide block 28 and the valve needle 24, preventing the viscous material from escaping away from the material discharge opening 26. The guide block 28, like the valve needle 24, is made of the same cemented carbide as the valve seat block 20.

[0020] Within the housing 12, a rinsing chamber 34 is located adjacent to the rear surface 32 of a guide block 28 facing away from the material discharge opening 26. This chamber is situated in a closure 36 made of stainless steel and detachably connected to the supply unit 14. A supply line 38 opening into the rinsing chamber 34 and a discharge line 40 also communicating with the rinsing chamber 34 extend from this closure 36. While the metering valve 10 is operating, the rinsing chamber 34 is continuously rinsed with a fluid, for example, Mesamol or Mesamol II. This fluid is introduced into the rinsing chamber 34 via the supply line 38 and discharged from the rinsing chamber 34 via the discharge line 40. In this way, viscous material penetrating from the through-opening 30 is removed from the rinsing chamber 34 despite the sealing effect between the guide block 28 and the valve needle 24. A seal to prevent fluid leakage from the rinsing chamber 34 is provided by a seal ring 42, which is located between the supply section 14 and the guide block 28, between the supply section 14 and the closure section 36, and between the closure section 36 and a guide element 44 located within the closure section 36 (to which the valve needle 24 extends).

[0021] The end portions 46 of the valve pins 24 facing away from the valve seat 22 are each accommodated in a stainless steel sleeve 48 and are soldered to the sleeve 48. The sleeves 48 connected to the valve pins 24 adjacent to each other are arranged at different heights, and the valve pins 24 can be arranged at a small distance from each other. From each sleeve 48, a protrusion 50 integrally connected thereto extends in a direction away from the valve seat 22, and this protrusion 50 acts on each of them via a flexure bearing by a piezoelectric actuator not shown in FIG. 1 to move each valve pin 24 to open and close the corresponding material discharge opening 26. Each valve pin 24 can move independently of the other valve pins 24 and individually.

[0022] Figures 2a and 2b show the operating modes of the meter valve 10 according to the first embodiment and the meter valve 10' according to the second embodiment, respectively. The meter valve 10 according to the first embodiment has seven valve needles 24, and the meter valve 10' according to the second embodiment has six valve needles 24, and these valve needles 24 are each arranged in a row. Multiple piezoelectric actuators 64 are provided to act on these valve needles 24, and the number of piezoelectric actuators 64 is less than the number of valve needles 24. In the meter valve 10 according to the first embodiment (Figure 2a), the three middle valve needles 24 in the row are connected to each other by a connecting element 66. The central of the five piezoelectric actuators 64 engages at an application point 68 located in the center of the connecting element 66, so that these three valve needles 24 can move only simultaneously. The remaining four valve needles 24 are each associated with one piezoelectric actuator 64, which acts on these valve needles 24, allowing them to be moved individually. In the metering valve 10' according to the second embodiment (Figure 2b), the two central valve needles 24 are connected by a connecting element 66, and a piezoelectric actuator 64 engages with an application point 68 located in the center of the connecting element 66. Thus, the two central valve needles 24 are movable only together, while the four additional valve needles 24 are each acted upon by an additional piezoelectric actuator 64, and these are movable individually. In both embodiments, the piezoelectric actuators 64 acting on the central valve needles 24 are positioned symmetrically with respect to the valve needles 24 they act upon by engagement at their respective application points located in the center of each connecting element 66. As a result, when the connecting element 66 acts, no torque is applied to the valve needles 24, and the corresponding piezoelectric actuators 64 are not twisted.

[0023] In summary, the following points should be noted. The present invention relates to metering valves 10, 10' for viscous materials, comprising a housing 12, a material flow path extending within the housing 12 and communicating with a plurality of material discharge openings 26, and a plurality of valve needles 24 movably mounted within the housing 12 corresponding to the number of material discharge openings 26. Each valve needle 24 is associated with a valve seat 22, and each valve needle 24 is movable between a closed position in which it seats on the associated valve seat 22 to close one of the material discharge openings 26 and an open position in which the corresponding material discharge opening 26 is opened, and further comprises a plurality of actuators 64 acting on the valve needles 24. According to the present invention, the number of actuators 64 is less than the number of valve needles 24, and at least one actuator 64 acts on at least two valve needles 24 at a time.

Explanation of Signs

[0024] 10, 10' Metering valve 12 Housing 14 Supply part 20 Valve seat block 22 Valve seat 24 Valve needle 26 Material discharge opening 28 Guide block 30 Through opening 32 Rear surface 34 Flushing chamber 36 Closing part 38 Supply line 40 Discharge line 42 Seal ring 44 Guide element 46 End 48 Sleeve 50 Projection 62 Material discharge surface 64 Piezoelectric actuator 66 Connecting element 68 Loading point

Claims

1. A metering valve for viscous materials comprises a housing (12), a material flow path extending within the housing (12) and communicating with a plurality of material discharge openings (26), and a plurality of valve needles (24) movably mounted within the housing (12), corresponding to the number of material discharge openings (26), each valve needle (24) being associated with a valve seat (22), each valve needle (24) being movable between a closed position where it is seated on the valve seat (22) associated with it and closes one of the material discharge openings (26), and an open position where it opens the corresponding material discharge opening (26), and further comprising a plurality of actuators (64) acting on the valve needles (24). A metering valve characterized in that the number of actuators (64) is less than the number of valve needles (24), and at least one actuator (64) acts on at least two valve needles (24) simultaneously.

2. The metering valve according to claim 1, characterized in that the actuator (64) is a piezoelectric actuator.

3. The metering valve according to claim 1 or 2, characterized in that at least one of the actuators (64) is associated with only one of the valve needles (24) and acts on the valve needle (24).

4. The metering valve according to any one of claims 1 to 3, characterized in that the valve seat (22) is arranged in a row extending laterally with respect to the longitudinal direction of the valve needle (24).

5. The metering valve according to claim 4, characterized in that the valve needles (24) are arranged to extend parallel to each other, and the row extends perpendicular to the longitudinal direction of the valve needles (24).

6. The metering valve according to claim 4 or 5, characterized in that the two valve needles (24) to which the first and last valve seats (22) in the row are associated are each associated with only one actuator (64) that acts on the corresponding valve needle (24).

7. The metering valve according to any one of claims 1 to 6, characterized in that the valve needles (24) which are jointly actuated by one of the actuators (64) are preferably tightly connected to each other by a connecting element (66), and the actuator (64) is engaged with the connecting element (66) at the point of application (68).

8. The metering valve according to claim 7, characterized in that the point of application of force (68) is located in the center of the connecting element (66).

9. The metering valve according to claim 7 or 8, characterized in that the valve needles (24) connected to each other by the connecting element (66) are arranged symmetrically with respect to the point of force application (68).

10. The metering valve according to any one of claims 1 to 9, characterized in that the valve seat (22) is each formed from a cemented carbide alloy.

11. The metering valve according to claim 10, characterized in that the valve seat (22) is preferably arranged in a valve seat block (20) integrally formed from a cemented carbide alloy.

12. The metering valve according to any one of claims 1 to 11, characterized in that the valve needle (24) is each formed from a cemented carbide.

13. The metering valve according to claim 12, wherein the valve needle (24) is guided to be displaceable in the longitudinal direction through a through opening (30) in a guide block (28) which is spaced apart from the valve seat (22), and the guide block (28) is characterized in that at least the inner surface of the through opening (30) facing the valve needle (24) is formed of cemented carbide.

14. The metering valve according to claim 13, characterized in that the inner surface of the through-opening (30) is in sealed contact with the valve needle (24).

15. The metering valve according to claim 13 or 14, characterized in that the guide block (28) is integrally formed from cemented carbide.

Images