DE102020117624B4 - Device and method for applying cold glue - Google Patents

Abstract

Device (100) for applying cold glue, comprising an application nozzle (116) which can be connected to a glue reservoir (104) and acts in a transfer area (120), by means of which cold glue can be applied to a target material (122) fed to the transfer area (120), wherein the application nozzle (116) is arranged in a housing (126) that takes out the transfer area (120) and wherein a moist air charging device (130) is also included, by means of which the interior of the housing (126) can be removed from the housing ( 126) can be charged with escaping moist air, characterized in that the housing (126) surrounds the application nozzle (116) coaxially and with the formation of an annular gap (128).

Description

field of invention

The invention relates to a device for applying cold glue, comprising an application nozzle that can be connected to a glue reservoir and acts in a transfer area, by means of which cold glue can be applied to a target material fed to the transfer area, the application nozzle being arranged in a housing that takes out the transfer area and wherein a moist air charging device is also included, by means of which the interior of the housing can be charged with moist air escaping from the housing in the transfer area.

The invention further relates to a method for operating such a device.

State of the art

Generic devices for applying cold glue are known from EP 2 878 382 A1 .

The application of cold glue, i.e. water-based dispersion adhesives, to different target materials is a task that is frequently asked in industry. The production of folding boxes, the processing of corrugated cardboard, the production of envelopes and mailing bags, etc. are mentioned as purely exemplary areas of application. The use of paper, cardboard or cardboard as the target material is widespread, but by no means restrictive. In order to achieve high production quantities, automated systems are common.

With regard to the special application technique, ie the structural design of the application means with which the cold glue is transferred from, for example, a vat-like glue reservoir to the target material, two basic concepts have prevailed in a special way. In a first approach, which is not the subject of the invention and is referred to as the contact method, an application wheel is at least partially wetted on its circumference with cold glue and rolls on the target material in order to transfer the cold glue from the edge of the wheel to the target material. The application wheel can be wetted directly or indirectly. In the case of direct wetting, the application wheel also acts as a scoop wheel, which rotates partially immersed in a glue pan and protrudes into the transfer area with a non-immersed wheel segment, where it contacts the target material. With indirect wetting, the scoop and application wheels are separate components that roll off one another directly or with the interposition of one or more transfer wheels, thus transferring the cold glue from the glue pan to the application wheel. A special form of the latter technique is the cliché application. In this case, the applicator wheel is designed as a roller with elastic elevations, with only the radially outermost areas of said elevations being wetted with glue and a corresponding glue pattern being transferred to the target material. These elastic elevations can be designed as polymer cushions, for example. However, it is also known to provide tappets with corresponding functionality that are spring-loaded radially outward. Such contact methods are, for example, in the DE 878 595 B the DE 10 2019 208 131 A1 , the DE 197 01 224 A1 and the DE 603 14 992 T2 described.

In a second approach, which is the subject of the invention and is referred to as a contactless method, the cold glue is transferred between the application means and the target material without direct contact. The application means are often designed as one or more dosing valves, by means of which the cold glue is thrown onto the target material positioned in the transfer area at predetermined times and in well-dosed portions. Such metering valves usually work electromagnetically. Other drive concepts, for example pneumatic, piezoelectric or hydraulic concepts, are also known and can be used in principle. The usual dosing valve is an intermediate vessel which is connected to a glue reservoir via lines and is under pressure and is provided with an application nozzle which acts into the transfer area and in particular hurls glue into the transfer area. The glue reservoir can, for example, be a pressure tank or a suction tank of an intermediate pump. The application nozzle typically has a conical shape on the outside and has a coaxial glue channel. This can be opened and closed in the metering valve by means of an axially movable valve body. In the open state, the pressure in the dosing valve ejects glue through the glue channel into the transfer area and in particular onto the target material. This is not possible when closed. The dosing is carried out by precisely adjusting the pressure, opening size and opening time, taking into account the properties, in particular the viscosity of the glue.

A hybrid of the two approaches mentioned above is the so-called slot method, in which a wide nozzle with a slot extending across its width is placed on the target material and drawn perpendicularly to the slot extension over the target material, while glue is applied from the slot in strips and at the same time warped.

A central problem of automated cold glue application devices is soiling of order funds and/or environment. Glue splashes, so-called satellites, which can occur in a variety of ways, e.g. due to centrifugal forces, rebound, droplet formation in dead spaces, etc., dry quickly and form adhesion points for other satellites, so that "beards", "threads" and similar dirt structures quickly form, which hinder the correct application of glue. For example, targeted imports of glue from an application nozzle can be deflected by such soiling structures; it is also possible that such structures lead to smearing of the applied glue on the target material or to the clogging of fine structures in cliché rollers.

the DE 10 2016 000 064 A1 tries to avoid the contamination problem by structuring the surface of the application nozzle. In particular, the outside of the application nozzle should be provided with a so-called "lotus effect" in order to allow satellites to run off before they dry. However, it seems unlikely that a general, universally applicable "lotus -Structure" can be found.

From the EP 2 386 363 A2 it is known to build up an electric field around the nozzle outlet and to deflect the resulting satellites electrostatically onto special collecting structures. These collecting structures, which in principle have to be arranged in the vicinity of the transfer area, become correspondingly more soiled, which therefore only leads to a delay in the problem described above.

From the EP 1 802 191 A2 it is known to provide the applicator nozzle with exchangeable casings, so that when it becomes dirty it is only necessary to exchange the casing and not to clean the nozzle itself. However, replacing the protective cover also requires a production stop and is technically complicated in complex systems with a large number of closely spaced, filigree nozzles.

From the EP 0 568 365 B1 it is known to position a cleaning nozzle immediately next to each application nozzle, which sprays dirty application nozzles with cleaning liquid during downtimes of the system and thus cleans them. This approach is technically very complex, disadvantageously space-intensive and also limited to idle times of the system.

From the aforementioned, generic EP 2 878 382 A1 it is known to feed a space in front of the nozzle opening with warm humid air which condenses on the cooled nozzle tip. The condensation water that forms at the tip of the nozzle is intended to loosen dried glue or make it impossible to dry from the outset. This is disadvantageous insofar as the glue itself, which runs through the upstream moist air space during application, can also absorb moisture and thus water it down. Another disadvantage is that the formation of condensate at the tip of the nozzle can lead to water droplets falling onto the target material or even being entrained there by the glue. Nevertheless, the basic idea of exposing the application nozzle to a moist air atmosphere in order to prevent the glue from drying must be viewed as a promising approach.

task

It is the object of the present invention to specify an improved moist air-based approach for avoiding contamination of cold glue application devices.

Presentation of the invention

This object is generally achieved in connection with the features of the preamble of claim 1 in that the housing surrounds the application nozzle coaxially and with the formation of an annular gap.

A preferred method for operating a device according to the invention is characterized in connection with the features of the preamble of claim 4 in that the moist air charging device is operated continuously to protect the housing both during work phases in which cold glue is applied to the target material fed to the transfer area and to be charged with moist air during idle periods between the work phases, which then escapes from the housing in the transfer area in the form of a particularly laminar stream of moist air.

Preferred embodiments of the invention are subject of the dependent claims.

The invention initially adopts the known basic idea of enclosing the application nozzle and the transfer area, which is particularly sensitive to contamination, in a moisture-saturated atmosphere which prevents splashes from drying on. As a result, no larger pollution structures leading to problems can build up. This is in particular a result of the housing according to the invention. The housing delimits a space surrounding the applicator nozzle, so that moist air that is directed into this space initially envelops the applicator nozzle, is moisture-saturated and therefore does not contain water, without interacting with the environment haze-permitting atmosphere. The humid air used to generate this atmosphere is preferably produced outside the housing and is introduced into the housing via a humid air line. The specific details of the humid air production are immaterial to the effectiveness of the invention. The optimal composition of the humid air depends on the physical environmental conditions, such as the temperature in particular. The humid air is preferably composed in such a way that, depending on the temperature inside the housing, a moisture-saturated atmosphere forms, ie an atmosphere that is just slightly below the dew point. In such a moisture-saturated atmosphere, evaporation of water from the cold glue is impossible. This also applies in particular to cold glue spatter which adheres to areas of the application nozzle surrounded by the moisture-saturated atmosphere. If they don't drip off immediately, at least they don't dry up, so that when several splashes come together, larger, drainable drops form. The flow path of such drops can be specified by appropriate surface design. For example, the outside of the application nozzle can be designed in such a way that the drop is guided to the nozzle outlet and applied with the next shot.

Of course, the transfer area must be outside the enclosure. However, the application nozzle must work into the transfer area. Consequently, the housing cannot be completely closed, but must exclude the transfer area, i.e. have a recess through which the application nozzle can work. This recess also serves as an outlet for the moist air from the housing. On the one hand, this ensures that constant air exchange prevails in the housing. On the other hand, the transfer area itself is also flushed through and/or around by the moist air leaving the housing. Here, too, drying of spatter and thus the build-up of soiling structures is avoided. On the other hand, the desired drying of the cold glue on the target material is not impaired, since this is immediately removed from the transfer area and therefore from the area of influence of the moist air after the glue has been applied.

According to the invention, the housing surrounds the application nozzle coaxially and with the formation of an annular gap.

As a result, the outflow of moist air from the housing into the transfer area leads to an additional advantage that goes beyond the pure avoidance of contamination. As already explained at the outset, in devices of this type, well-metered portions of glue are thrown onto the target material by means of the application nozzle. Both when the portions are produced and when they hit the target material, atomization and the formation of satellites can occur, which attach themselves to the outside of the application nozzle in an uncontrolled manner. As explained, the invention counteracts the drying on of these splashes of dirt. At the same time, however, the airflow also leads to a reduction in satellite attachment itself. The application nozzle acts from the housing through its recess into the transfer area. This also corresponds to the flow direction of the moist air flowing out of the enclosure. This takes the satellites that are formed at the nozzle outlet with it in the direction of flow, so that the number of satellites that are moved “backwards” and stick to the outer wall of the application nozzle is significantly reduced. The same applies to satellites that are formed from the target material when the cold leach importation hits it. Those of them who threaten to fly "backwards" in the direction of the application nozzle are counteracted by the moist air flow, so that the formation of dirt on the application nozzle is also significantly reduced here.

The applicator nozzle preferably has an outer contour in the shape of a truncated cone with an outlet opening at its narrow end. Such a design leads to a particularly effective acceleration of any satellites that may be produced in the direction of the transfer area, i.e. away from the application nozzle, which is thus protected from contamination. In particular, a sharp, hollow-cylindrical curtain of moist air can be generated from the tip of the nozzle to the target material, inside which the importation of lead can fly largely undisturbed, whereas laterally outgoing satellites are caught by a sharp stream of air and accelerated in the direction of the target material. A distraction of the well-dosed import of glue by the stream of moist air escaping from the housing should be avoided as far as possible.

In general, the person skilled in the art sets up the moist air charging device, in particular with regard to its volume flow and with regard to the outlet opening of the housing, in such a way that the housing is charged with moist air in such a way that it escapes from the housing in the form of a laminar flow of moist air in the transfer area. Turbulence should be avoided as far as possible, as it is difficult to calculate on the one hand and suitable on the other; to divert the well-dosed cold leach import from its intended trajectory.

From the foregoing, it should be apparent to those skilled in the art that the invention is suitable for continuous operation, which in particular also includes both the working and the idle phases of the device according to the invention. Because, as explained, the avoidance of contamination according to the invention does not interfere with the glue application operation; On the other hand, the moist air feed can easily remain in operation even when the system is idle, for example overnight and/or when the operating personnel change shifts, in order to avoid thickening of the cold glue and/or subsequent drying of splashes.

Further details and advantages of the invention result from the following specific description and the drawings.

character list

• 1 eine schematisierte Schnittdarstellung einer erfindungsgemäßen Kaltleim-Auftragsvorrichtung.

It shows:

• 1 a schematic sectional view of a cold glue applicator according to the invention.

Description of Preferred Embodiments

1 shows a glue application device 100 working according to the non-contact method. This comprises a metering valve 102 with a glue channel 106 connected to a glue reservoir 104 via a glue pump 103. Inside the glue channel 106 is a valve body 112 that can be moved axially by means of an electromagnet 108 against the biasing force of a compression spring 110. On the outlet side, the valve body 112 bears against a valve seat 114 of the glue channel 106 in order to close or open it according to the actuation of the electromagnet 108 . The specific actuation technique of the valve body 112 does not play a role in the context of the present invention. Instead of an electromagnet 108, for example, a motor, pneumatic, piezoelectric, hydraulic or other type of technology can also be used.

On the outlet side, the metering valve 102 transitions into an application nozzle 116 which, in the embodiment shown, has a truncated cone shape on the outside with a central nozzle channel (end piece of the glue channel 106). During operation, the glue channel 106 is pressurized, so that a well-timed opening of the dosing valve 102 leads to the ejection of a well-dosed glue import 118 into a transfer area 120 in which a target material 122 was previously positioned. Typically, the target material 122, for example cardboard, paper, cardboard, etc., is conveyed through the transfer area 120 in accordance with the feed arrow 124 and, by repeatedly opening and closing the metering valve 102, is provided with a glue seam that is built up point by point.

The application nozzle 116 is surrounded by a housing 126 which, in particular, creates an annular gap 128 coaxially surrounding the application nozzle 116 . The housing is connected to a moist air charging device 130 . Consequently, a moisture-saturated atmosphere forms around the application nozzle 116 , which prevents glue splashes from drying on the surface of the application nozzle 116 . At the same time, a preferably laminar stream of moist air is generated from the annular gap 128 into the transfer area 120 . The trajectory of the glue importation 118 from the application nozzle 116 to the target material 122 is not influenced by the essentially hollow-cylindrical air flow curtain that forms. However, satellites spurting off to the side are intercepted by the airflow and accelerated in the direction of target material 122 . This prevents them from spraying back onto the application nozzle 116 in particular.

Of course, the embodiments discussed in the specific description and shown in FIG. 1 only represent illustrative exemplary embodiments of the present invention.

Reference List

100

glue applicator

102

dosing valve

104

glue reservoir

106

glue channel

107

glue pump

108

electromagnet

110

compression spring

112

valve body

114

valve seat

116

application nozzle

118

Lean import

120

transfer area

122

target material

124

feed arrow

126

enclosure

128

annular gap

130

moist air charging device

Claims (5)

Device (100) for applying cold glue, comprising a with a glue reservoir (104) ver Bindable application nozzle (116), acting in a transfer area (120), by means of which cold glue can be applied to a target material (122) fed to the transfer area (120), the application nozzle (116) being in a housing (126) excluding the transfer area (120) and wherein a moist air charging device (130) is also included, by means of which the interior of the housing (126) can be charged with moist air escaping from the housing (126) again in the transfer area (120), characterized in that the housing (126) Application nozzle (116) coaxially and encompasses with the formation of an annular gap (128). Device (100) according to claim 1 , characterized in that the application nozzle (116) has an outer contour in the shape of a truncated cone with an outlet opening at its narrow end. Device (100) according to one of the preceding claims, characterized in that the moist air feeding device (130) is set up to feed the housing (126) with moist air in such a way that it emerges from the housing (126 ) escapes. Method (100) for operating a device (100) for applying cold glue according to one of the preceding claims, characterized in that the moist air charging device (130) is operated continuously to feed the housing (126) both during work phases in which cold glue is applied to the dem Target material (122) supplied to the transfer area (120) is applied, as well as during rest phases between the working phases with moist air, which then escapes in the transfer area (120) in the form of a stream of moist air from the housing (126). procedure after claim 4 , characterized in that the humid air escapes from the housing (126) in the form of a laminar flow of humid air.

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