Patent Application
20130026197
The invention relates to an application head for dispensing a free-flowing medium and application device having at least one such application head. In particular, it relates to dispensing adhesives and the use of hot glue. The invention can also be used for the controlled dispensing of cold glue or glue which comprises aggressive (e.g., corrosive) components.
The priority of application EP 10151806.6, which was filed on 27 Jan. 2010 with the European Patent Office, is claimed.
In numerous industrial manufacturing processes, adhesives, sealants, and similar free-flowing media are used, which are applied or sprayed in liquid form onto a workpiece or substrate.
The corresponding application heads must be robust and allow precise, high-precision dispensing of the medium. The application heads are simultaneously to be rapidly switchable, in order to be able to portion out adhesive quantities or apply them precisely in points or strips. In addition, the application heads are not to be excessively large, since frequently only limited space is available in the corresponding application devices.
Furthermore, application heads are to be flexibly usable and are to be able to be refitted as needed or preferably are to be able to be switched over or monitored at the controller.
Further problems arise if hot glue is to be processed. Thus, for example, the great heat in the interior of an application head can damage the drive unit. There are also types of glue which contain additives, which can be aggressive. The pH value of a glue can thus be in the acid range, for example. Glue can also contain corrosively or abrasively acting components. In order to protect an application head therefrom, suitable measures must be taken.
The problem presents itself of providing a precisely operating and reliable application head which avoids or entirely remedies a part of the disadvantages of previously known solutions.
The problem is solved by an application head according to claim 1 and by an application device having corresponding control module according to claim 6.
A first application head according to the invention is especially designed for dispensing a free-flowing medium. It comprises a (nozzle) chamber in the interior of the application head and a nozzle needle, a needle valve, or a slide (designated here in summary as a “movable element”), which is mounted so it is movable in the interior of the nozzle chamber. The movable element executes a movement and releases an outlet opening for a short time in each case. The application head can also act in reverse, in that the movable element closes an outlet opening for a short time in each case. A supply channel is provided, which is connected to the (nozzle) chamber and is connectable with respect to flow to a supply line. The free-flowing medium can be introduced into the (nozzle) chamber through the supply line and the supply channel. A drive generates the opening movement or closing movement of the movable element. A lever arm is provided, whose first extremal end is fastened so it is movable on a rear end of the movable element and whose second extremal end is connected/coupled to the drive. Furthermore, the application head comprises a membrane suspension having a membrane. The lever arm extends essentially perpendicularly through a surface spanned by the membrane of the membrane suspension. The membrane is used for the purpose of connecting the lever arm to the application head so it is movable. Furthermore, the membrane suspension is used as a seal to prevent an escape of the free-flowing medium from the (nozzle) chamber. In addition, the membrane is preferably implemented so that it is resistant in relation to the free-flowing medium. In all embodiments, the membrane is preferably temperature-resistant and/or corrosion-resistant and/or abrasion-resistant and/or resistant in relation to chemical additives in the medium.
Depending on the embodiment, the membrane can comprise at least one sealing ring, which is used as a seal and for elastically clamping the membrane in the application head. This embodiment can be used in all embodiments of the invention and offers an improved seal in relation to escaping adhesive, for example.
An embodiment is particularly preferred in which there is a metallic membrane, which can execute back and forth movements particularly rapidly and therefore allows rapid opening or closing of the outlet opening. Such a metallic membrane is particularly suitable for alternating load at high frequency, i.e., for embodiments in which very rapid opening or closing is required. A metallic membrane is particularly advantageous and can be used in all embodiments of the invention.
The invention is very particularly suitable for thermoplastic (hot melt) adhesives. However, it is also suitable for aggressive types of glue and, e.g., for cold glue.
Further advantageous embodiments of the invention are set forth in the dependent claims.
Further details and advantages of the invention are described in greater detail hereafter on the basis of exemplary embodiments and partially with reference to the drawings. All figures are schematic and are not to scale and corresponding structural elements are provided with identical reference numerals in the various figures, even if they are differently formed in detail. It shows:
The principle of the invention will be described hereafter on the basis of a first embodiment.
Each of the outlet openings 12 is implemented on or in a respective application head 15. Each application head 15 is especially designed for dispensing a free-flowing medium M, preferably adhesive, and comprises a (nozzle) chamber 10 in the interior of the application head 15. In the example shown, a nozzle needle 11 is mounted so it is movable up and down in the interior of the (nozzle) chamber 10, the nozzle needle releasing the outlet opening 12 through an opening movement P of the nozzle needle 11. An arrow P is shown in
In the interior, a supply channel 13 is provided (see, e.g.,
Furthermore, a drive 20 is provided for generating the opening movement P of the nozzle needle 11. In
Embodiments in which the drive 20 is arranged spaced apart from the application head 15, as can be seen in
Further details will be explained on the basis of another embodiment, which is shown in a section in
The following further details distinguish this embodiment. However, these details are also applicable to all other embodiments. The (nozzle) chamber 10 is implemented so that in its lower region, close to the outlet opening 12, a stop point 17 or a stop surface (also referred to as a needle seat), respectively, is provided for the tip 18 of the nozzle needle 11. In
The nozzle needle 11 is connected so it is movable (like a toggle joint) to the lever arm 30 in the region of the rear end 14. The nozzle needle 11 more or less “dangles” in the nozzle chamber 10. Because the nozzle chamber 10 and the nozzle needle 11 are implemented as conically rotationally-symmetric in the lower area (close to the stop point 17), the nozzle needle 11 is guided centered during a downward movement in the −Z direction. In addition, the medium M, which flows from the supply channel 13 through the (nozzle) chamber 11 in the direction of outlet opening 12, contributes to stabilization or self-centering, respectively, of the nozzle needle 11. This type of “dangling” mount or suspension can be applied in all embodiments.
The lever arm 30 is implemented here so that it comprises a flat, rectangular, or strip-shaped rod, which is optionally provided with holes 39 here. These holes 39 are used to make the rod lighter, to reduce the mass to be accelerated. In addition, the holes 39 allow a displacement of the attachment point A of the drive 20. Therefore, if the effective lever arm is to be lengthened, the drive 20 (or the attachment point A, respectively) can be shifted further in the direction of the second extremal end 32 and vice versa. In the example shown, the drive 20 is seated almost on the extremal end 32, i.e., the effective lever arm is relatively long. The closer the drive 20 (or the attachment point A, respectively) is displaced in the direction of the membrane suspension 33, the shorter the effective lever arm. A step-down transmission occurs in the case of a long lever arm, i.e., a large movement P1 causes a small movement P in the opposite direction. The step-down factor in
A step-down transmission having a step-down factor between 2:1 and 10:1 is preferably used in all embodiments.
However, the lever arm 30 can also have any other rod or lever shape. The lever arm 30 is preferably manufactured from torsion-resistant material. In addition, the lever arm 30 is to be as light as possible, in order to have a small moved or accelerated mass. The membrane 34 is used in all embodiments as a kinematic support, which carries/mounts a part of the mass of the lever arm 30. In addition, the membrane 34 defines the precise pivot or tilting point (referred to as the virtual pivot axis) of the lever arm 30 in all embodiments. The lever arm 30 can also be referred to as a “free-floating” lever because of the special membrane mount 34.
In order to be able to mount or hold the lever arm 30 in the membrane suspension 33, a cylindrical rod 40 is provided on the lever arm 30 in the embodiment shown. This cylindrical rod 40 pinches or clamps the membrane 34 and therefore provides a suspension of the lever arm 30 on the membrane 34. Details of an exemplary preferred arrangement can be inferred from
Furthermore,
A metallic membrane 34 is preferably used in the various embodiments, which is particularly suitable for alternating load at high frequencies. A membrane 34 in which either the entire membrane surface consists of metal, or in which a planar membrane substrate (e.g., made of plastic) is provided with a metal layer/metal vapor deposit, is designated as a metallic membrane 34.
Furthermore,
Through the special arrangement of the slots 36, which nearly define a complete circle, two small webs 42 result at the positions three o'clock and nine o'clock. These two small webs 42 allow bending of the inner part 41 (i.e., the circular region 41 of the membrane 34 which is delimited on the outside in the radial direction by the slots 36) of the membrane 34. The two small webs 42, with the inner part 41 of the membrane 34, quasi-define a virtual pivot axis VA. This virtual pivot axis VA is shown in
In the various described embodiments, an
electromagnetic or
pneumatic or
piezoelectric drive
is suitable as the drive 20, which generates a corresponding linear movement P1 (up and down movement) at the desired frequency, which is relayed by the effective active lever arm 30 through a step-down or step-up transmission to the nozzle needle 11 and induces the linear movement P therein. In the case of a piezoelectric drive 20, however, one preferably operates with a step-up transmission, in order to convert the very small movements of the piezoelectric drive 20 into sufficiently large opening and closing movements P.
An electromagnetic drive 20 which is constructed according to the principle of a voice coil motor or a Lorentz coil has particularly proven itself. In this case, a 1:1 lever transmission ratio or a step-down transmission is particularly suitable in this case as the effective transmission ratio. A voice coil motor or a Lorentz coil can be used in all embodiments.
A voice coil drive 20 has the advantage that it is deenergized in the idle state, i.e., the power consumption is less than in previous application heads.
The stroke in the region of the nozzle tip 18 or the outlet opening 12 in the direction of the Z axis is preferably between 0.1 mm and 1 mm. In the case of a 1:1 lever transmission ratio, the drive 20 must thus make a corresponding movement P1 in the opposite direction having a stroke of 0.1 mm to 1 mm.
With a suitable control of the drive 20, e.g., via a driver module 21 and/or a control module 50, which can be arranged in the proximity of the drive 20, as indicated as an example in
The greater the lever step-down transmission ratio is selected to be, the more precisely may the nozzle needle 11 be moved, because a large movement P1 of the drive 20 is stepped down into a small movement P of the nozzle needle 11. A disadvantage of such a large step-down transmission ratio, however, is the lengthened route which must be covered on the drive side. The achievable frequency or the maximum cycle, respectively, of the opening and closing movement of the nozzle needle 11 is thus possibly reduced.
Complete parameterization of the curve P(t, Z) can be given by the following value pair matrix (if the curve P(t, Z) is a traverse made of linear segments):
(t=0, Z=0)
(t=4T/10, Z=1)
(t=6T/10, Z=3)
(t=9T/10, Z=7)
(t=T, Z=0).
A complete parameterization of the curve P1(t, −Z) can be given by the following value pair matrix (if the curve P1(t, −Z) is a traverse made of linear segments):
(t=0, −Z=0)
(t=4T/10, −Z=5)
(t=6T/10, −Z=15)
(t=9T/10, −Z=35)
(t=T, −Z=0).
The parameters PA and PB of all embodiments are preferably distance-correlated parameters.
During the parameterization, in all embodiments, in addition to specifying/predefining the parameters (or the value pairs, respectively), the maximum points, and slope changes, further parameters can also be predefined. These further parameters can describe, for example, the extension of the curve between two value pairs. The further parameters can also establish, for example, the cycle duration T and/or the timing (e.g., T/10).
In a preferred embodiment, on the drive side, an intelligent controller (e.g., in the form of the driver module 21 and/or control module 50) of the drive 20 is designed so that the current which is fed into the drive 20 is observed. When the current increases, this is an indication that the nozzle needle 11 or the movable element is at the stop point 17. Through an intelligent control module 50, a gradual adaptation of the movement profile stored in the driver module 21, which can be defined in all embodiments by the cited parameterization, can be performed, which compensates for wear of the needle tip 18 in that the movement P1 on the drive side is successively increased when the current signal indicates that the current increase only occurs later in relation to earlier. This is because the later occurrence of a current increase means that the needle tip 18 is at the stop point 17 later than heretofore. This is an indication of wear. The use of such an intelligent controller (e.g., in the form of the driver module 21 and/or control module 50) lengthens the service life of the application head 15, since the nozzle needle 11 or the movable element must only be replaced later.
In a preferred embodiment, on the drive side, an intelligent controller (e.g., in the form of the driver module 21 and/or control module 50) of the drive 20 is designed so that the movement of the nozzle needle 11 or the movable element is regulated according to a predefined movement profile (e.g., P1(t, −Z)). The switching times and the stroke of the nozzle needle 11 can be monitored and the application picture of the application head 15 can be automatically corrected by the control module 50.
The driver module 21 and/or the control module 50 is preferably located directly on each drive 20, so that the drive 20 can be activated directly using a 24 VDC signal (also directly by a PLC) (PLC stands for programmable logic controller). This has the advantage that each application head 15 can be activated individually. A corresponding driver module 21 and/or control module 50 can be used in all embodiments.
In a preferred embodiment, on the drive side, an intelligent controller of the drive 20 is designed so that error, warning, service, or maintenance indicators are output. The control module 50 is appropriately equipped and/or programmed for this purpose. This approach can be used in all embodiments.
It is an advantage of the invention that a spatial thermal separation (see, e.g.,
The thermal separation between drive 20 and application head 15 is preferably achieved without a screw connection, as can be seen in
In all preferred embodiments, the lever arm 30 causes a reversal of the movement direction (P1 points in the opposite direction as P; see
The invention allows a precise custom adhesive application. It can be used in electromagnetic, electropneumatic, piezoelectric, or electromechanical application heads 15, whether hot or cold glue processes, whether based on distance or time, and whether constant or variable substrate speed.
The control module 50 (also referred to as the application controller) can be integrated directly in the device (e.g., in a melting device), or it can be provided as an independent unit. It is also possible according to the invention to control and monitor multiple application heads 15 from a common (multichannel) control module 50, as indicated in
Embodiments are particularly preferred in which the control module 50 is designed so that it can be controlled/monitored by a PLC.
In all embodiments, the control module 50 has a connection to guidance systems via a typical interface (e.g., a CAN interface).
The control module 50 preferably has a capability for parameterization, as described, in all embodiments. The parameterization can either be performed directly at the controller 50, or the parameterization can be performed indirectly via an interface of the control module 50.
A software module for parameterization is preferably used in all embodiments.
The term “parameterization” is used here to describe that the activation of the application head or heads 15 is performed based on parameters (preferably in the form of value pairs). The parameters are converted by the controller 50 into commands, regulating variables, or values which induce a result on or in the application head 15 (e.g., through implementation in the driver module 21). The parameters can be used, for example, to drive the drive 20 so that at the output side, i.e., at the movable element 11, a monitored opening movement P(t, Z) is induced. This can be achieved, for example, in all embodiments via a programmable output voltage profile or output current profile at the drive 20 or at the driver module 21. The parameters, which are predefined by the parameterization define, e.g., the output voltage profile or output current profile. The output voltage profile or output current profile is then correlated with the movement profile P1(t, −Z) and, via the lever arm 30, with the movement profile P(t, Z).
If the control module 50 is implemented as self-learning, the corrected parameters, which correspond to the closed position, can be stored in a parameter memory 54. The new parameters are then used during the next opening and closing.
In all embodiments, the parameters PA, PB, etc. are preferably taken from a parameter memory 54 and transferred by the control module 50 to an optional driver module 21. The driver module 21 converts these parameters PA, PB, etc. into control variables. However, it is also possible that the control module 50 processes parameters PA, PB, etc. in order to then transfer processed parameters PA*, PB*, etc. to the driver module 21. The processing of the parameters PA, PB, etc. is dependent on the specific configuration and can take into consideration the step-up or step-down transmission factor, for example.
The control module 50 can be designed, for example, having a module for self-recognition of a clogged nozzle. This self-recognition can recognize an impending nozzle clog on the basis of direct and/or indirect measured information (e.g., from a sensor 53). It can also comprise a module which allows recognition of an impending problem (early recognition). In this case, a preventative warning is preferably performed by the control module 50, for example, via an optional LED maintenance recognition 60 (see
All embodiments are preferably designed to be self-initializing. For this purpose, the control module 50 makes an initialization run, in order to be able to compare the parameters PA, PB, etc. to the actual values. Initial correction values can be derived therefrom, which are then applied during the productive use.
Through the special mounting of the lever arm 30 using a membrane 34 and through the described control module 50 having parameterizing ability, a precise lead time can be guaranteed in all embodiments. This is important for many applications. If the guaranteed lead time in a first application head 15 is 10 ms, for example, and this application head must be replaced with another application head 15 because of maintenance work, it must be ensured that this second application head 15 also maintains the guaranteed lead time of 10 ms. Additionally or alternatively, the invention guarantees a fixed reaction time (response time) of, e.g., 1 ms, which is important for the activation, e.g., via a PLC.
All application heads 15 behave identically with respect to the fixed reaction time (response time) and/or the lead time.
The invention offers the single electrically driven application head 15 which is activatable using PLC without booster and using a proprietary controller.
The application head 15 is preferably designed in all embodiments so that it is also closed in the non-activated mode or when the device is shut down.
The application head 50 is preferably equipped in all embodiments with a sensor, which monitors the sealing function or leak tightness of the membrane 34. This sensor is designed and arranged so that the medium M escaping in case of fault is detected. The case of fault is transmitted to the controller 50. The controller 50 stops the glue delivery (e.g., by shutting down a pump) using a corresponding control signal. This feature has the advantage that in the event of a fracture of the membrane 34, the escaping medium M can be prevented from being conveyed into the machine.
Inductive, capacitive, or optical sensors, which are preferably arranged in the rear area (i.e., in the medium-free space) of the application head 15, i.e., on the side opposite to the chamber 10, are particularly suitable for monitoring the sealing function or leak tightness of the membrane 34.
The application head 15 is preferably equipped in all embodiments with a monitor of the glue pressure. The controller 50 analyzes (pressure) signals in this case, from which the glue pressure curve may be derived. The analysis of the glue pressure curve allows the controller 50 to perform a diagnosis in the matter of glue conveyance. In this way, for example, an impending nozzle clog and/or the occurrence of a leak on the membrane 34 can be recognized and reacted to. This form of the monitoring of the glue pressure by means of the controller 50 allows simple and reliable monitoring of the glue application.
The application head 15 is preferably equipped in all embodiments with a so-called stroke regulation. This stroke regulation can be used for flow regulation, i.e., for dosing the medium M to be dispensed. For the purposes of the stroke regulation, a distance or position encoder is preferably arranged in the application head 15 in the region of the movable element 11 and/or in the region of the lever arm 30. The current position (actual position) of the movable element 11 and/or the lever arm 30 is thus communicated to the controller 50 and can be used therein for regulating purposes.
Instead of the application head 15, the application device 100 as a whole can also comprise a stroke regulator and/or a sensor monitor and/or a monitor of the glue pressure curve, as described above.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10151806.6 | Jan 2010 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2011/050991 | 1/25/2011 | WO | 00 | 10/16/2012 |
