Apparatus for the intermittent application of a liquid to pasty medium onto an application surface

Abstract

An apparatus for the intermittent application of a liquid to pasty medium onto an application surface, comprising an application valve which can be switched between an open and a closed state and is intended for dispensing the medium onto the application surface, a volumetric delivery pump for metering a volume of the medium to be passed on to the application valve, and a drive for operating the volumetric delivery pump is, inter alia, described and illustrated. The characteristic feature consists in that the apparatus has an electronic controller which, in each case cyclically, activates the drive and the application valve in dependence on each other.

Claims

1. An apparatus for the intermittent application of a liquid to pasty medium onto an application surface, comprising: a driving block, an adapter block mounted on the driving block, an application valve mounted on the adapter block, the application valve switchable between an open and a closed state for selectively dispensing the medium onto the application surface, a volumetric delivery pump connected to the driving block, the volumetric delivery pump configured for metering a volume of the medium to be passed on to the application valve, wherein the volumetric delivery pump is a gear pump, a conducting channel formed in the driving block and the adapter block and extending between the volumetric delivery pump and the application valve configured for passage of the medium from the volumetric delivery pump to the application valve, and a drive for operating the volumetric delivery pump, wherein the apparatus has an electronic controller which, in each case cyclically, switches the drive between an off state and a driven state and switches the application valve between the open and closed state in dependence on each other such that for dispensing the medium, the electronic controller switches the drive to the driven state and the application valve to the open state, and for stopping dispensing of the medium, the electronic controller switches the drive to the off state and the application valve to the closed state, wherein the electronic controller switches the drive to the driven state before switching the application valve to the open state, and wherein the electronic controller switches the drive to the off state before switching the application valve to the closed state.

2. The apparatus as claimed in claim 1, wherein the medium is a molten adhesive or molten adhesive agent and the apparatus further comprises heating means for heating the molten adhesive or adhesive agent conducted in the apparatus, the apparatus being assigned a hotmelt unit for melting the adhesive or adhesive agent.

3. The apparatus as claimed in claim 1, wherein the drive has a motor, the motor being designed as a servomotor or stepping motor, or an eddy current coupling or solenoid coupling being provided between the motor and the volumetric delivery pump.

4. The apparatus as claimed in claim 1, wherein the gear pump which comprises three gearwheels, of which one is designed as a driving gearwheel which interacts with a separate shaft gearwheel assigned to a motor-side drive shaft.

5. The apparatus as claimed in claim 1, wherein the application surface is provided by a two-dimensional substrate, the substrate being a moving, web-shaped substrate, and the apparatus comprises a delivery device for guiding the substrate relative to an outlet nozzle assigned to the application valve.

6. The apparatus as claimed in claim 1, wherein the conducting channel is of a rigid, and sealed, design.

7. The apparatus as claimed in claim 1, wherein the apparatus is designed as a modular system, with a multiplicity of linearly arranged, application modules, each application module having precisely one application valve and being connected to one volumetric delivery pump unit each, and the linearly arranged, volumetric delivery pump units being drivable by a common drive shaft.

8. The apparatus as claimed in claim 1, wherein the medium is a molten adhesive or molten adhesive agent and the apparatus further comprises heating means for heating the molten adhesive or adhesive agent conducted in the apparatus.

9. The apparatus as claimed in claim 1, wherein the apparatus is designed as a modular system, with a multiplicity of linearly arranged, application modules, each application module having precisely one application valve and being connected to one volumetric delivery pump unit.

Description

(1) Further advantages of the invention emerge with reference to non-cited dependent claims and from the description below of the exemplary embodiments which are illustrated in the drawings, in which:

(2) FIG. 1 shows a highly schematic exploded illustration of an apparatus according to the invention for the application of a liquid to pasty medium onto an application surface (not illustrated),

(3) FIG. 2 shows an enlarged schematic view of a volumetric delivery pump or a volumetric delivery pump unit of an apparatus according to FIG. 1, which is in the form of a gear pump and which has a driving gearwheel which protrudes out of the housing and can interact with a shaft gearwheel of a drive shaft (not illustrated in FIG. 2),

(4) FIG. 3a shows, in a highly schematic view, a sectional illustration through the assembled apparatus from FIG. 1, approximately according to the viewing arrows III in FIG. 1, when the application module is in an open state and the application valve is open, with the gear pump being driven,

(5) FIG. 3b shows the apparatus in a view according to FIG. 3a with the application valve in the closed state and the gear pump at a standstill,

(6) FIG. 4 shows a highly schematic illustration in the manner of a diagram of the temporal development of three characteristic variables of an apparatus of the prior art, and

(7) FIG. 5 shows, in a view according to FIG. 4, the temporal development of three characteristic variables of an apparatus according to the invention.

(8) The apparatus according to the invention is denoted in the entirety thereof by 10 in the figures. For the sake of clarity, identical or comparable parts or elements, even if different exemplary embodiments are concerned, are denoted by the same reference numbers, sometimes with the addition of small letters or apostrophes.

(9) The apparatus 10 illustrated in FIG. 1 is an apparatus for the intermittent application of a molten hotmelt adhesive to a two-dimensional substrate, in particular a non-woven capable of being in web form. In this connection, FIG. 1 shows an exploded illustration, in which the individual components of the apparatus 10 are illustrated partially disassembled.

(10) According to FIG. 1, the apparatus 10 first of all has a fluid connection 11 for introducing a molten hotmelt adhesive or another medium into the apparatus 10 according to the invention. The fluid connection 11 here can be connected, for example via a delivery hose, to a reservoir (not illustrated) of a medium, wherein the reservoir can make the molten hotmelt adhesive available.

(11) The reservoir may be, in particular, a hotmelt unit which first of all melts solid adhesive material and then passes said material on via a heated hose. For this purpose, the reservoir may also have a main delivery pump which ensures that the apparatus 10 according to the invention is always supplied with sufficiently molten adhesive.

(12) In this connection, the fluid connection 11 is arranged on a filter block 12 of the apparatus 10, into which interchangeable filter elements 13a and 13b can be inserted. Said filter elements 13 can filter the fluid entering the rest of the apparatus 10, i.e. the liquid adhesive, in respect of impurities such that, as the fluid continues to pass through, deposits and clogging do not occur in the apparatus 10. The apparatus 10 fundamentally consists of an elongate driving block 14 and of an adapter block 15 which is mounted on the driving block 14. The filter block 12 here is fixed on an end side of the driving block 14 and adapter block 15.

(13) As can be seen in FIG. 1, the central driving block 14 has, in the longitudinal direction I thereof, a central passage channel 16 through which the fluid or material which has entered the apparatus 10 through the fluid connection 11 can flow.

(14) Furthermore, the passage channel 16 serves to receive a drive shaft 17 which has yet to be described in more detail further on.

(15) In addition, on a rear side which cannot be seen in FIG. 1, the driving block 14 has connecting options for volumetric delivery pump units 18, wherein, in FIG. 1, eight such delivery pump units or volumetric delivery pumps 18 are already arranged on the driving block 14, and one volumetric delivery pump 18 is illustrated still in the unfitted state. The volumetric delivery pumps 18 are also described in more detail below.

(16) On a front side which is concealed in FIG. 1, the adapter block 15 which has already been mentioned is mounted, substantially congruently, on the driving block 14. Said adapter block 15 serves for the mounting of application modules or application valves 19 and also compressed air modules 20 on the modular apparatus 10.

(17) In the view according to FIG. 1, in each case eight application valves 19 and eight compressed air modules 20 are already fitted on the adapter block 15 and on the apparatus 10, respectively, while one application valve 19 and one compressed air module 20 are illustrated in a non-assembled state. In this case, the application valves 19 may be mounted on a side wall 52 of the adapter block 15 and the compressed air modules 20 may be mounted on an upper side 21 of the adapter block 15.

(18) It should already be mentioned at this juncture, that one compressed air module 20 is assigned to each application valve 19 in such a manner that the corresponding application valve 19 can be switched pneumatically between an open and a closed state via the corresponding compressed air module 20. Similarly, each application valve 19 is assigned precisely one volumetric delivery pump 18 in the manner of a gear pump. For this purpose, sections (not visible in FIG. 1) of a connecting channel for conducting a measured-out fluid volume are provided in each case in the corresponding delivery pump 18, the driving block 14 and in the adapter block 15 and the corresponding application valve 19.

(19) According to FIG. 1, the apparatus 10 furthermore comprises an air heater module 22 which can be fitted under the driving block 14 and the adapter block 15 and serves to heat spraying air conducted through the air heater module 22. The spraying air can be dispensed to the nozzle heads 23 of the application valves 19 by the air heater module 22 in order to serve as carriers for the fluid to be discharged. So that the adhesive which is to be dispensed is not already cooled during the discharging and spraying, the carrier air is pre-heated in the air heater 22.

(20) The drive shaft 17 which is already mentioned and which can be introduced into the passage channel 16 of the driving block 14 is assigned a number of shaft gearwheels 24 (in particular corresponding to the number of delivery pumps 18 provided). Only one of said shaft gearwheels 24 can be seen in FIG. 1. However, it should be noted that the drive shaft 17 has one shaft gearwheel 24 per delivery pump 18.

(21) In addition, in order to assemble the apparatus 10, a closing plate 25 is provided, the closing plate being able to be plugged on over the end section of the shaft 17 and having a central opening 26, through which the drive shaft 17 can interact with a driving motor 27. In the exemplary embodiment illustrated in the figures, said driving motor 27 is designed as a servomotor and can drive the drive shaft 17, for example, via a coupling 28 (not specified in more detail). The motor 27 and coupling 28 accordingly form parts of a drive 51.

(22) The servomotor 27 is connected via a line 29 (merely indicated schematically) to a controller (likewise merely illustrated highly schematically) which is designed as a computer unit 30. The computer unit 30 is furthermore connected via a second line 31 to the application valves 19, namely indirectly via the compressed air modules 20. For example, a connection for the line 21 can be provided on the compressed air modules 20. The line 31 can pass on a control signal, which is output by the computer unit 30, to the compressed air modules 20 and the latter can thereby transmit controlling signals for switching the application valves 19. In FIG. 1, the line 31 and the corresponding connection thereof to the compressed air modules 20 is illustrated merely in principle and highly schematically. In practice, the line 31 may comprise a plurality of signal lines, one each for each compressed air module, and therefore, contrary to the illustration in FIG. 1, each compressed air module 20 can have a dedicated connection for connecting to the controller.

(23) Starting from the exploded illustration of FIG. 1, the apparatus 10 can be assembled and fitted in such a manner that each volumetric delivery pump 18 is assigned precisely one shaft gearwheel 24 of the drive shaft 17.

(24) In the fitted state of the apparatus 10, said shaft gearwheel 24 can engage in a driving gearwheel 32 of the delivery pump unit 18, which is illustrated in enlarged form in FIG. 2, in order to drive the volumetric delivery pump 18.

(25) In this connection, FIG. 2 first of all shows two bolt-like installation aids 34a and 34b, for example screws, which are fixed to the housing 33 of the volumetric delivery pump 18.

(26) A medium passing through the passage channel 16 (not illustrated in FIG. 2) of the driving block 14 can enter the housing 33 of the otherwise encapsulated delivery pump unit 18 at entry points 35a and 35b above and below the driving gearwheel 32. For this purpose, the housing 33 has an entry slot 36, through which the driving gearwheel 32 is partially inserted.

(27) Finally, FIG. 2 also shows a fluid outlet 37 which is arranged in the housing 33 and through which the fluid volume, which is then metered, can leave the delivery pump 18 again in order to enter a corresponding channel extension of the driving block 14 and subsequently of the adapter block 15.

(28) In addition to the driving gearwheel 32, the volumetric delivery pump 18 also has two further gearwheels which cannot be seen in FIG. 2 but which will be described below with reference to FIGS. 3a and 3b, together with the operative principle of the apparatus 10 according to the invention.

(29) It can first of all be seen from FIG. 3a that two further gearwheels, namely the metering gearwheels 38a and 38b, are also arranged within the housing 33 of the volumetric delivery pump 18, said gearwheels being connected to the driving gearwheel 32 in a series connection. The gearwheels 32, 38a and 38b are respectively arranged here in a plane on rotating spindles 39a, 39b and 39c not penetrating the housing 33. The gearwheels which are illustrated in FIG. 3a intermesh in such a manner that driving of the drive shaft 17 by the driving motor 27 (not illustrated in FIG. 3a) leads to rotation of the shaft gearwheel 24 counterclockwise with respect to FIG. 3a. The toothing of the shaft gearwheel 24 engages here in the toothing of the driving gearwheel 32 in such a manner that said driving gearwheel rotates in the clockwise direction with respect to FIG. 3a. Owing to the toothing of the driving gearwheel 32 and metering gearwheel 38a, said metering gearwheel 38a then rotates counterclockwise with respect to FIG. 3a and, owing to the toothing thereof, ensures rotation of the second metering gearwheel 38b in the clockwise direction with respect to FIG. 3.

(30) These rotations of the gearwheels 24, 32, 38a and 38b lead to the viscous medium 40 which flows around the gearwheels and which is illustrated by hatching in FIGS. 3a and 3b being carried along (and, in addition, also lead to metering thereof).

(31) In respect of the conducting path of the medium 40, reference should be made at this juncture to FIG. 1, with regard to which it has already been explained that the medium 40 can enter the apparatus 10 at a fluid connection 11 and is then conducted into a passage channel 16 of the driving block 14. In the driving block 14, said medium flows, according to FIG. 3a, around the drive shaft 17 together with the shaft gearwheel 24 arranged thereon.

(32) The medium or fluid 40 is carried along within the volumetric delivery pump 18 by the gearwheels 32, 38a and 38b and conducted towards an inlet 41 of a conducting channel 42. During the conduction from the driving gearwheel 32 toward the inlet 41, the medium 40 is metered in respect of the volume thereof in such a manner that a certain number of revolutions of the metering gearwheels 38a and 38b lead to a desired metering volume of the medium 40.

(33) The metered volume 40 can then be introduced into the conducting channel 42 through the inlet 41 (not illustrated more precisely in FIG. 3a). The inlet 41 to the conducting channel 42 leads out of the plane of the figure with respect to FIG. 3a. Accordingly, a first subsection 43 of the conducting channel 42 is merely indicated by dashed lines in FIG. 3a, since said subsection does not lie in the sectional plane of FIG. 3a (but rather below the sectional plane of FIG. 3a).

(34) By means of the offset arrangement of the subsection 43 of the conducting channel 42, the metered and delivered medium 40 can leave the housing 33 of the delivery pump 18 via the fluid outlet 37 and enter a continuation of the conducting channel 42 in the driving block 14. The first subsection 43 then has a beveled region in the driving block 14 such that the conducting channel 42 together with medium delivered therein enters the sectional plane of FIG. 3a again.

(35) Finally, at an outlet 44, the delivered medium 40 can leave the driving block 14 and be introduced into the adapter block 15, from which said medium enters the application valve 19. The conducting channel 42 is composed here of a plurality of subsections assigned to the different modules 18, 19 and blocks 14, 15. Within the application valve 19, the medium 40 can then pass into a nozzle chamber 45 and from there (since the valve 19 according to FIG. 3a is in the open state thereof) on into the region of an outlet opening 46.

(36) With regard to the application valve 19 illustrated in FIG. 3a, it should also be noted that said application valve forms what is referred to as a recirculating valve. In this connection, the valve head 47 is illustrated in an open, lowered position, in which it allows the medium 40 to pass. In particular, the lower region of the valve head 47 can have slots or channels (not illustrated) which, in the illustrated position of the valve head 47, allows the medium 40 to pass out of the nozzle chamber 45.

(37) As soon as the medium 40 reaches the outlet opening 46, heated carrier air is fed to the medium 40 via a line 48. This can ensure a spraying effect (which is indicated in FIG. 3a by a snake-like outlet shape of the medium 40).

(38) The carrier air is supplied here via an air heater module 22 having a heating element 49. The heating of the carrier air ensures that the medium 40 does not cool and solidify upon contact with the carrier air 48 but rather, on the contrary, can pass in fluid form onto a substrate which is not illustrated in FIG. 3a (and which would be arranged with respect to FIG. 3a below the illustrated apparatus 10).

(39) With regard to FIG. 3a, it should finally be noted that, in the exemplary embodiment illustrated, the application valve 19 is activated pneumatically and can thereby be switched between the closed and open state thereof. For this purpose, the adapter block 15 provides two compressed air entrances 50a and 50b, the compressed air channel 50b (indicated by the arrow) being able to be charged in order to transfer the application valve 19 into the open state. For this purpose, a compressed air module 20 (not illustrated in FIGS. 3a and 3b) can be arranged above the adapter block 15 and can be activated in particular by the computer unit 30, which is illustrated in FIG. 1.

(40) Since the present apparatus 10 is an apparatus for the intermittent application of a medium 40, after a metered portion of adhesive 40 has been discharged the application valve 19 is transferred from the open state thereof, which is illustrated in FIG. 3a, into the closed state thereof, which is illustrated in FIG. 3b. For this purpose, the compressed air module 20 (not illustrated in FIGS. 3a and 3b) can be activated by the computer unit 30 (likewise only illustrated in FIG. 1) in such a manner that the compressed air channel 50a (illustrated in FIG. 3b) in the adapter block 15 (and no longer the compressed air channel 50b) is charged with compressed air. According to FIG. 3b, this leads to a pneumatically triggered raising of the valve head 47 onto a valve seat 53 in such a manner that the medium 40 arranged in the conducting channel 42 is now prevented from passing into the nozzle chamber 45 (and therefore also into the outlet opening 46). In this case, the spraying air supplied via the line 48 can either also be switched off via the computer unit 30 or can continue to emerge, with the application pattern on the surface being commissioned not being changed.

(41) Since the walls of the conducting channel 42 illustrated in FIG. 3b are of rigid and inflexible design, and since, according to FIG. 3b, the conducting channel 42 is also not assigned any return mechanism, closing of the application valve 19 with the delivery pump 18 continuing to operate would lead to an excessive build up of pressure within the conducting channel 42. Said build up of pressure could lead to activation of a pressure control valve (not illustrated). At any rate, during subsequent opening of the application valve, the application surface being commissioned would be commissioned inhomogeneously with medium.

(42) However, a solution to the problem can be gathered from FIG. 3b to the effect that none of the gearwheels 24, 32, 38a or 38b illustrated is provided with an arrow arranged on the gearwheel. Within the context of the present exemplary embodiment, this is intended to signify that the gearwheels, and in particular the shaft gearwheel 24 and the drive shaft 17, do not rotate at all when the application valve 19 is closed. The result therefrom is that the gearwheels 32, 38a and 38b do not deliver any further medium 40, and therefore no further medium enters the inlet 41 and the conducting chamber 42 either.

(43) The pressure of the medium or of the fluid 40 therefore does not increase (or merely insubstantially increases) in the conducting channel 42. As soon as, subsequently, an opening operation of the application valve 19 takes place, the medium 40, without being under particularly great pressure, can be discharged in the customary manner and delivered on, with a homogeneous application pattern and a homogenous layer thickness.

(44) The fact that, in a state according to FIG. 3b, the drive shaft 17 is not driven is ensured by the servomotor 27 which is illustrated in FIG. 1 and receives the signal from the computer unit 30 to pause the drive shaft 17. Said command is issued by the computer unit 30 synchronously to the command to the compressed air module 20 to close the application valve 19 (or to charge the compressed air channel 50a according to FIG. 3b).

(45) The mutually coordinated activation of the drive 51 (comprising the motor 27 and the coupling 28) and the application valve 19 will now be clarified with reference to FIGS. 4 and 5:

(46) FIGS. 4 and 5 illustrate three characteristic curves, in each case one above another, of an apparatus of the prior art (FIG. 4) and of an apparatus according to the invention (FIG. 5). Said characteristic curves are time-dependent characteristic curves, i.e. the development of characteristic values over the time t. The three characteristic curves a, b, c and a, b, c are arranged here one above another in the same system of coordinates merely for the sake of clarity, but this, however, is not intended to make any statement about the absolute values thereof but rather merely to permit a relative comparison of the temporal developments.

(47) The characteristic curve a or a relates here to the switching of the application valve 19 or of the nozzle valve between the switched-on state (at a relative value of 1) and a switched-off state (at an absolute value of 0). The characteristics curves a according to FIG. 5 and a according to FIG. 4 correspond identically to each other. A switching cycle of the valve, i.e. the time interval in which the application valve is switched to and fro once completely between the open state thereof and the closed state thereof corresponds in the present case to a period of time of 2t. t here can correspond, for example, to a value of 20 to 50 ms, wherein a cycle duration is therefore between 40 to 100 milliseconds.

(48) If the characteristic curves a and a in FIGS. 4 and 5 reach the value thereof which is denoted by 1, the application valve is completely open and, at 0, is completely closed.

(49) The fact that, in the illustrated exemplary embodiment according to FIG. 5, the cycle time has a value of approximately 2 t means that the application valve 19, at any rate in the present exemplary embodiment, is in the closed state thereof for approximately half of the time (or of the cycle duration) and in the open state thereof for the other half of the time. The ratio of the application valve 19 in terms of opening and closing times is therefore approximately 0.5. The present invention is particularly advantageously used with such a ratio, since the described problem arises particularly emphatically in such cases.

(50) By contrast, at a greater value, at which the opening time of the valve dominates, the closing time is so short that no problematic pressure can build up at all. On the other hand, in the case in which the closing time dominates the ratio, the opening time is customarily of such a short duration that the pressure remains consistently high during the opening time.

(51) Accordingly, the present invention is particularly advantageously used in particular at a ratio of opening to closing time of between 0.2 and 0.8 (in particular at a value of between 0.4 and 0.6).

(52) The characteristic curves, which are identified by b and b, in FIGS. 4 and 5 relate to the built-up fluid pressure in the channel 42 directly upstream of the application valve 19. A corresponding measurement can take place, for example, directly at the inlet of the application valve 19. FIG. 4 shows here, with reference to the characteristic curve b, the problem of the prior art, according to which the fluid pressure always dissipates when the valve 19 is opened and continuously builds up again when the application valve 19 is closed. In this case, a maximum value P.sub.1 of the measured pressure can be, for example, approximately between 40 and 50 bar, and the value p.sub.0 can be approximately 20 bar or very much less. FIG. 5 shows, by contrast, that the pressure within the fluid-conducting channel 42 (in the region of the application valve 19) is at a virtually constant level.

(53) The characteristic curves b in FIG. 5 therefore indicates that the problem on which the invention is based of inhomogeneous application can be solved by a uniform fluid pressure of the apparatus 10 according to the invention.

(54) Finally, the characteristic curves c and c in FIGS. 4 and 5 indicate the switching of the drive 51 of the volumetric metering pump 18 and therefore, in particular, the switching of the servomotor 27 used in the exemplary embodiment of FIGS. 1 to 3. According to FIG. 4, in the case of the apparatus of the prior art, the motor runs at a constant power or a constant number of revolutions per minute, for example 10 revolutions per minute.

(55) In the case of the apparatus 10 according to the invention according to FIG. 5, it can be gathered from the characteristic curve c that the servomotor 27 is switched between an off state (0 revolutions per minute) and a driven state synchronously to the switching of the application valve 19 according to the characteristic curve a. In order to achieve the same delivery rate as in the apparatus of the prior art, the servomotor 27 can preferably be adjusted, when the application valve 19 is open, to a value of 2 W, i.e., for example, 20 revolutions per minute. In other words, at a ratio of the opening and closing time of approximately 0.5, the servomotor 27 can preferably drive the metering pump 18 at twice the speed achieved in the case of an apparatus of the prior art (although the latter is driven continuously).

(56) Finally, it is noticeable in FIG. 5 that the motor 27 is activated cyclically in each case slightly before the application valve 19, which can be identified by the fact that the time t.sub.1, at which a signal is output to the motor 27, lies temporally before the time t.sub.2, at which a signal is output to the application valve 19. Such an activation levels out the relatively great inertia of the drive 51 in comparison to the relatively small inertia of the application valve switching, which is itself produced by the mechanical components of the delivery pump 18 and the mechanical components of the drive 51.

(57) According to the characteristic curve a, the switching state of the application valve has in case idealized, perpendicular flanks during the initiation of an opening and closing operation, namely, for example, at the time t.sub.2. During calibration of the controller, the time t.sub.2 is preferably selected in such a manner that said time lies temporally precisely between the time t.sub.1 and the time t.sub.3, wherein the time t.sub.3 characterizes the time at which the servomotor 27 reaches the desired maximum power thereof, in particular 2 W. Although said example is explicitly related to an opening operation of the valve 19, it is analogously also transferable to a closing operation.