Method for dispensing an adhesive and associated device

Abstract

Method for dispensing an adhesive and associated device The method for dispensing an adhesive comprises the following steps:. taking a first volume of a first base (2) having a first reaction time with a hardener (6), taking a second volume of a second base (4) having a second reaction time with the hardener (6), different from the first reaction time, mixing the first volume of the first base (2) and the second volume of the second base (4) to form a volume of a base of the adhesive to be dispensed, mixing said volume of said base with a volume of hardener (6) to form a liquid adhesive whose drying time is adjusted according to the ratio between the first volume and the second volume, dispensing the liquid adhesive through a dispensing nozzle (34). Figure for abstract: 1

Description

Title of the invention: Method for dispensing a glue and associated device

[0001] The present invention relates to a method of dispensing an adhesive.

[0002] The invention also relates to an installation for dispensing a glue allowing the implementation of such a method.

[0003] Such a method makes it possible to dispense an adhesive in liquid form as this adhesive is applied to bond together large elements, such as vehicle wall panels or the like.

[0004] To ensure effective bonding in such applications, it is necessary to control the drying time of the glue precisely. For this purpose, it is known to use two-component glues formed from a base and a hardener, the mixing of which is done just before the application of the glue, this mixing triggering the reaction which causes the glue to dry. The drying time depends on the nature of the base so that by choosing the composition of the base, it is possible to control the drying time of the glue once it is applied.

[0005] Thus, it is known to form the base of the glue by mixing a first base and a second base having different properties. The first base has a reaction time with the hardener resulting in rapid drying of the glue, of the order of a few minutes to make the glued elements handleable without them separating, and the second base has a reaction time with the hardener resulting in slow drying of the glue, of the order of several tens of minutes to make the glued elements handleable. By varying the quantity of first base and second base in the mixture forming the base of the glue to be applied, it is thus possible to vary the drying time of the glue to adapt it to the elements which must be glued.

[0006] The mixing of the two bases is done before mixing the base with the hardener by feeding a mixer with a continuous flow of the first and second bases, these bases being pumped by a booster pump from sources of the first base and the second base.

[0007] However, for the mixing of the two bases to be effective, it is necessary to control the flow rate of the bases in the mixer, this flow rate depending on the viscosity and the pressure of the two bases, these two parameters being very sensitive to variations in ambient temperatures. Thus, upstream of the mixer, two flow regulators are provided to adapt the flow rate of the first base to that of the second base according to the viscosity and the pressure of the two bases, which are measured upstream of the flow regulators. flow rate since a variation of a few degrees in temperature is likely to cause these parameters to vary and require an adaptation of the two flow rates upstream of the mixer.

[0008] The base thus obtained is then mixed with the hardener in a dosing machine making it possible to adjust the quantity of base and hardener mixed to form the glue which is then distributed in liquid form.

[0009] Thus, the installation for producing such glue is particularly complex and bulky. In addition, when the proportion between the first base and the second base must be modified, it is necessary to purge the installation from the base mixer to the glue distribution nozzle, which results in significant losses of materials.

[0010] One of the aims of the invention is to overcome these drawbacks by proposing a method for dispensing glue whose drying time is controlled simply and precisely.

[0011] To this end, the invention relates to a method for dispensing an adhesive comprising the following steps: - take a first volume of a first base presenting a first reaction time with a hardener, - taking a second volume of a second base having a second reaction time with the hardener, different from the first reaction time, - mixing the first volume of the first base and the second volume of the second base to form a volume of a base of the glue to be dispensed, - mixing said volume of said base with a volume of hardener to form a liquid glue whose drying time is adjusted according to the ratio between the first volume and the second volume, - distribute the liquid glue through a dispensing nozzle.

[0012] By taking and mixing volumes of first base and second base to form the base of the glue, it is possible to do without flow regulators upstream of the mixer by not having to worry about the differences in viscosity and pressure between the first base and the second base to ensure good mixing of the two bases. In addition, since the volume of base is then mixed with a volume of hardener, it is also possible to do without the dosing machine between the base and the hardener to control the quantity of base and hardener in the glue. Thus, the glue distribution installation is greatly simplified. In addition, the bases can be mixed together as close as possible to the glue distribution nozzle, which reduces material losses when purging is necessary to vary the proportions of first and second bases.

[0013] The dispensing method may further comprise one or more of the features following characteristics, considered alone or in any technically feasible combination: - the first volume is taken from a source of the first base by means of a first dosing pump, the second volume being taken from a source of the second base by means of a second dosing pump; - the hardener is taken from a hardener source by means of a feed pump, said hardener passing through a metering pump to supply the volume of hardener; - the first base is a polyol whose reaction time with the hardener to form a handleable glue is approximately between 5 minutes and 20 minutes; - the second base is a polyol whose reaction time with the hardener to form a handleable glue is approximately between 40 minutes and 100 minutes; - the ratio between the first volume and the second volume changes during the distribution of the liquid glue, the proportion of the first volume increasing and the proportion of the second volume decreasing in the ratio so that the liquid glue has a drying time which decreases as the glue is distributed.

[0014] According to another aspect, the invention relates to an installation for dispensing a glue, for implementing the method of a method as described above, comprising: - a source of a first base and a first dosing pump for supplying a first volume of the first base, - a source of a second base and a second dosing pump for supplying a second volume of the second base, - a mixer of the first volume and the second volume for supplying a volume of a base at the outlet of the mixer to a mixing zone, - a source of hardener and a device for supplying a volume of hardener making it possible to supply a volume of hardener at the outlet of the supply device to the mixing zone, - a nozzle for dispensing a liquid glue formed by mixing in the mixing zone between the base volume obtained at the outlet of the mixer and the volume of hardener obtained at the outlet of the supply device.

[0015] The distribution installation according to the invention may further comprise one or more of the following characteristics, considered alone or in any technically conceivable combination: - the device for supplying a volume of hardener successfully includes- sively a feed pump and a dosing pump; - a controller of the first and second dosing pumps for adjusting the first volume and the second volume in order to modify the ratio between the first volume and the second volume in the base of the glue to be dispensed; - the controller also controls the dosing pump of the hardener supply device in order to adjust the volume of hardener in the mixing zone; - the first base is conveyed from the first dosing pump to the mixer by a first pipe and the second base is conveyed from the second dosing pump to the mixer by a second pipe, the installation further comprising a first pressure compensation device and a second pressure compensation device arranged to compensate for pressure losses respectively in the first pipe and in the second pipe.

[0016] Other aspects and advantages of the invention will appear more clearly on reading the following description, given solely by way of non-limiting example, and made with reference to the appended drawings in which:

[0017] [Fig-1] - [Fig.l] is a schematic representation of a dis installation distribution of an adhesive making it possible to implement a method of distributing an adhesive according to the invention.

[0018] In the description, the terms “upstream” and “downstream” are defined according to the direction of circulation of the bases and the hardener in the glue distribution installation 1 shown in [Fig.l].

[0019] The installation 1 comprises a source of a first base 2, or first resin, a source of a second base 4, or second resin, and a source of a hardener 6. As shown in [Fig.l], these sources are for example tanks containing respectively the first base 2, the second base 4 and the hardener 6.

[0020] The first base 2 has a first reaction time with the hardener 6, determining the time that a two-component adhesive formed from a mixture between the first base 2 and the hardener 6 would take to dry in the open air and at room temperature. The first reaction time is chosen so that this drying time is short, i.e. of the order of a few minutes to obtain a handleable adhesive. Thus, the first base is for example a polyol having a reaction time with the hardener to form a handleable adhesive substantially between 5 minutes and 20 minutes, for example substantially equal to 7 minutes. By handleable adhesive, we mean an adhesive allowing the elements glued using this adhesive to be handled without them becoming detached. In other words, a handleable adhesive means a glue that is sufficiently dried to hold the elements together without being completely dry. The mechanical strength of the bond between elements held together by such a manipulable glue is, for example, approximately equal to 1 N / mm2 or 1 MPa.

[0021] Downstream of the source of first base 2, the installation 1 comprises a first metering pump 8 arranged to take a first volume of the first base 2 from its source and to convey this first volume to a mixer 10. In other words, the first pump 8 operates by volumetric metering. The first pump 8 is for example a metering pump controlled by means of a controller (not shown) making it possible to adjust the first volume as glue is dispensed, as will be described in more detail later. The first pump 8 is for example an electric pump comprising a brushless motor. The first pump 8 is for example a piston pump whose piston movement speed is adjustable to vary the first volume.

[0022] The first base 2 is conveyed from the first metering pump 8 to the mixer 10 in a first pipe 12. A first pressure compensation device 14 is arranged to compensate for pressure losses in the first pipe 12. Indeed, when the piston of the first pump 8 changes direction, the flow rate of the first base at the outlet of the first pump 8 temporarily becomes zero, which results in a pressure loss in the first pipe 12. The first pressure compensation device 14 makes it possible to compensate for this pressure loss and thus to ensure continuous operation of the conveyance of the first base 2 to the mixer 10. The pressure applied in the first pipe 12 by the first pressure compensation device 14 is adjustable so that it can be adapted to the operating range of the installation.Thus, the first pressure compensation device 14 is for example controlled by the operating range of the first metering pump 8. Such a first pressure compensation device 14 is for example formed by an anti-pulsation device, for example a membrane anti-pulsation device.

[0023] The second base 4 has a second reaction time with the hardener 6, determining the time that a two-component adhesive formed from a mixture between the second base 4 and the hardener 6 would take to dry in the open air and at room temperature. The second reaction time is different from the first reaction time. More particularly, the second reaction time is greater than the first reaction time. The second reaction time is thus chosen so that this drying time is long, that is to say of the order of several tens of minutes to obtain a handleable adhesive. Thus, the second base is for example a polyol having a reaction time with the hardener to form a handleable adhesive substantially comprised between 60 minutes and 100 minutes, for example approximately equal to 80 minutes.

[0024] Downstream of the source of second base 4, the installation 1 comprises a second metering pump 16 arranged to take a second volume of the second base 4 from its source and to convey this second volume to the mixer 10. The second pump 16 is for example a metering pump controlled by means of the controller to adjust the second volume as glue is dispensed, as will be described in more detail later. The second pump 16 is for example an electric pump comprising a brushless motor. The second pump 16 is for example a piston pump whose piston displacement speed is adjustable to vary the second volume.

[0025] The second base 4 is conveyed from the second metering pump 16 to the mixer 10 in a second pipe 18. A second pressure compensation device 20 is arranged to compensate for the pressure losses in the second pipe 12. The second pressure compensation device 20 is for example of the same nature as the first pressure compensation device 14 and makes it possible to ensure continuous operation of the conveyance of the second base 4 to the mixer 10. The second pressure compensation device 20 is for example controlled by the operating range of the second metering pump 16.

[0026] The mixer 10 is arranged to mix the first volume of first base 2 and the second volume of second base 4 in order to form a base of the glue to be dispensed. Thus, by adjusting the first volume and the second volume, the composition of the base of the glue to be dispensed is modified so that the drying time of the glue obtained after mixing with the hardener 6 can be adjusted. In other words, the drying time of the glue to be dispensed is adjusted according to the ratio between the first volume and the second volume. Thus, the greater the proportion of the first volume in the ratio, the shorter the drying time of the glue and conversely, the greater the proportion of the second volume in the ratio, the longer the drying time of the glue.The first and second pumps 8, 16 being digitally controlled by the controller, it is very simple to modify the first volume and the second volume to adjust the ratio of these volumes in the base of the glue to be dispensed and thus adjust the drying time of the glue to be dispensed according to needs.

[0027] The mixing of the first base 2 and the second base 4 in the mixer 10 is done without difficulty and without needing to take into account the viscosity or the pressure of the bases when they are introduced into the mixer 10. Indeed, the control by volume, rather than by flow rate, of the bases introduced into the mixer 10 makes it possible to erase the differences in viscosity and pressure between the first base 2 and the second base 4 during mixing. Thus, it is no longer necessary to calculate the pressure losses between the two products and to control the flow rate of the two products when they are introduced into the mixer 10. The mixer 10 is for example a mixer of the helical static mixer type.

[0028] Thus, at the outlet of the mixer 10, a basic volume of the glue to be dispensed is obtained, this volume corresponding to the addition of the first volume and the second volume. In this basic volume, the proportion of the first volume and that of the second volume are adjusted according to the desired drying time for the glue to be dispensed formed from the mixture of the basic volume and a volume of hardener.

[0029] The hardener 6 is for example a product based on polyisocyanates, for example a diisocyanate, to form with the base a two-component polyurethane adhesive. Alternatively, the hardener 6 is a product based on urethane prepolymers.

[0030] Downstream of the source of hardener 6, the installation 1 comprises a device for supplying a volume of hardener 6 arranged to take a volume of hardener 6 from its source and to convey it to a mixing zone 22 between the base and the hardener 6. The supply device comprises for example successively a booster pump 24 and a metering pump 26 at the outlet of which the volume of hardener 6 is conveyed to the mixing zone 22.

[0031] The feed pump 24 is arranged to continuously draw the hardener 6 from its source and to supply this hardener 6 to the metering pump 26.

[0032] The feed pump 24 is for example a pneumatic or hydraulic feed pump.

[0033] The metering pump 26 is arranged to supply the volume of hardener 6 to the mixing zone 22 from the hardener 6 coming from the feed pump 24. The metering pump 26 is for example a gear metering pump and is also controlled digitally by the controller so that the volume of hardener can be adjusted for example if it is desired to modify the “recipe” of the glue to be dispensed, that is to say to modify the proportion of hardener 6 relative to that of the base in the glue to be dispensed.

[0034] A volume of base being obtained at the outlet of the mixer 10 and a volume of hardener 6 being obtained at the outlet of the hardener supply device, the mixing zone 22 can be formed by a dispensing gun between the pipes conveying the base and the hardener 6. Thus, it is not necessary to provide a bulky dosing machine downstream of the mixer 10 and the supply device. The dispensing gun is for example arranged so that the hardener 6 is coated by the base in the mixing zone 22 in order to improve the quality of this mixture. Thus, the dispensing gun is for example arranged so that the base is injected around the hardener 6 in the mixing zone 22.

[0035] Downstream of the mixing zone 22, the installation 1 comprises a distribution nozzle 34 of the liquid glue obtained at the outlet of the mixing zone 22. This nozzle 34 is for example manipulated by an operator or by a robotic arm to apply the glue in liquid form to an element to be glued.

[0036] It may be advantageous, particularly when the elements to be bonded are large, to modify the drying time of the liquid glue as it is applied so that the glue can be handled at substantially the same time over the entire glued surface. In other words, it may be desirable for the drying time of the glue to decrease as the glue is applied. The method and installation for dispensing the glue according to the invention make it possible to perform this function in a particularly simple manner by controlling the first metering pump 8 and the second metering pump 16 to modify the first volume of the first base 2 taken from its source and the second volume of the second base 4 taken from its source as the glue is applied in order to modify the ratio between the first volume and the second volume in the volume of the base which must be mixed with the hardener.So, for a constant base volume, we increase the first volume and decrease the second volume to modify the ratio and obtain a glue that dries more quickly once this base volume is mixed with the hardener volume.

[0037] As previously indicated, the installation also makes it possible to modify the “recipe” of the glue by modifying the volume of hardener and that of the base to be mixed in the mixing zone 22, simply by controlling the first dosing pump 8, the second dosing pump 16 and the dosing pump 26 of the supply device accordingly.

[0038] When the glue has to be changed again, for example to restore a longer drying time, the amount of material that has to be purged from the installation is limited because the mixer 10 can be placed as close as possible to the dispensing nozzle 34 due to the absence of a dosing machine in the mixing zone 22. In other words, the first base 2 and the second base 4 are only mixed "at the last moment" before the glue is dispensed.

[0039] The method described above makes it possible to dispense a liquid glue whose drying time is easily adjustable in an installation 1 of simplified layout and reduced bulk. In addition, this method also makes it possible to limit the waste of materials when the drying time of the glue must be increased.

Claims

Claims

1. A method of dispensing an adhesive comprising the following steps: - taking a first volume of a first base (2) having a first reaction time with a hardener (6), - taking a second volume of a second base (4) having a second reaction time with the hardener (6), different from the first reaction time, - mixing the first volume of the first base (2) and the second volume of the second base (4) to form a volume of a base of the adhesive to be dispensed, - mixing said volume of said base with a volume of hardener (6) to form a liquid adhesive whose drying time is adjusted according to the ratio between the first volume and the second volume, - dispensing the liquid adhesive through a dispensing nozzle (34).

2. A method of dispensing an adhesive according to claim 1, wherein the first volume is taken from a source of the first base (2) by means of a first metering pump (8), the second volume being taken from a source of the second base (4) by means of a second metering pump (16).

3. A dispensing method according to claim 1 or 2, wherein the hardener (6) is taken from a hardener source (6) by means of a booster pump (24), said hardener (6) passing through a metering pump (26) to provide the volume of hardener.

4. A dispensing method according to any one of claims 1 to 3, wherein the first base (2) is a polyol whose reaction time with the hardener (6) to form a handleable adhesive is between 5 minutes and 20 minutes.

5. A dispensing method according to any one of claims 1 to 4, wherein the second base (4) is a polyol whose reaction time with the hardener (6) to form a handleable adhesive is between 40 minutes and 100 minutes.

6. A dispensing method according to any one of claims 1 to 5, wherein the ratio between the first volume and the second volume changes during the dispensing of the liquid glue, the proportion of the first volume increasing and the proportion of the second volume decreasing in the ratio so that the liquid glue has a drying time decreasing as the glue is dispensed.

7. Installation for dispensing an adhesive for implementing the method according to any one of claims 1 to 6, comprising: - a source of a first base (2) and a first metering pump (8) for supplying a first volume of the first base (2), - a source of a second base (4) and a second metering pump (16) for supplying a second volume of the second base (4), - a mixer (10) of the first volume and the second volume for supplying a volume of a base at the outlet of the mixer (10) to a mixing zone (22), - a source of hardener (6) and a device for supplying a volume of hardener (6) for supplying a volume of hardener at the outlet of the supply device to the mixing zone (22),- a dispensing nozzle (34) for a liquid glue formed by mixing in the mixing zone (22) between the base volume obtained at the outlet of the mixer (10) and the volume of hardener (6) obtained at the outlet of the supply device.,

8. Installation according to claim 7, in which the device for supplying a volume of hardener (6) successively comprises a feed pump (24) and a metering pump (26).

9. Installation according to claim 7 or 8, comprising a controller of the first and second metering pumps (8, 16) making it possible to adjust the first volume and the second volume in order to modify the ratio between the first volume and the second volume in the base of the glue to be dispensed.

10. An installation according to claim 9, wherein the controller also controls the metering pump (26) of the hardener supply device in order to adjust the volume of hardener (6) in the mixing zone (22).

11. Installation according to any one of claims 7 to 10, in wherein the first base (2) is conveyed from the first metering pump (8) to the mixer (10) via a first line (12) and the second base (4) is conveyed from the second metering pump (16) to the mixer (10) via a second line (18), the installation further comprising a first pressure compensation device (14) and a second pressure compensation device (20) arranged to compensate for pressure losses respectively in the first line (12) and in the second line (14).

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