GB2077629A

GB2077629A - Multi-component adhesive feed for glue spreaders

Info

Publication number: GB2077629A
Application number: GB8115120A
Authority: GB
Original assignee: WOODTECHNIQUE AB
Current assignee: WOODTECHNIQUE AB
Priority date: 1980-05-22
Filing date: 1981-05-18
Publication date: 1981-12-23
Also published as: SE8003833L; DK224481A; NO811637L; GB2077629B; DE3119772A1; FI811463L

Abstract

Apparatus for continuously mixing multi-component adhesives for different types of glue spreaders comprises at least two containers 1, 2 for the adhesive components, a pump unit providing a pump casing head for each glue component, which pump unit is driven by single drive motor 4, a connecting section 5 for a mixing head, at least one static mixer 6 for mixing the components during passage through the same, at least one level sensor device at the surface of the glue as well as control device 9 for conversion of a level signal from sensor/ transmitter 8 to an output signal for speed regulation of the motor 4. Arranged in the wall of the mixer there may be a cooling jacket and a cooling aggregate 7 to maintain a fixed temperature for a cooling medium supplied to the mixer 6. <IMAGE>

Description

SPECIFICATION Method of and apparatus for continuously mixing multi-component adhesives The present invention concerns a method of and apparatus for continuously mixing multicomponent adhesive for feed to a glue spreader e.g. of the single or double type, or of the type having vertical heads.

According to a first feature, the invention provides a method of continuously mixing and feeding multi-component adhesive, whereby adhesive components are pumped by means of a driving motor from respective containers to a mixer and therefrom as a ready mixed adhesive stream to a glue spreader, e.g. of a single or double type or of a type having vertical heads, wherein the components are fed by a single pump having an individuallyadjustable pump head for each component for achieving constant component proportions independent of motor speed or of the total pump quantity, and wherein the motor speed is regulated proportionally by at least one lever sensor/transmitter for sensing the level of the surface of the glue in a glue trough or the like connected to the mixer, a level signal from said sensor/transmitter being converted, in a control device, to an output signal for speed regulation of the motor.

The invention also provides apparatus for carrying this method into effect, whereby the components of the adhesive are intended to be pumped by means of a driving motor from respective containers to a mixer and therefrom, as a ready mixed adhesive stream, to a glue spreader, e.g. of a single or double type or of a type having vertical heads, characterized in that it comprises a single pump having an individually-adjustable pump head for each component for achieving constant component proportions independent of the motor speed or of the total pump quantity, which are adapted to be regulated proportionally by at least one level sensor/transmitter for the glue level in a glue trough or the like connected to the preferably static mixer whereby a level signal from said transmitter is adapted to be converted, in a control device, to an output signal for speed regulation of said driving motor.

In the apparatus according to the invention the different components of the adhesive, e.g.

resin and hardener, or resin, hardener and water, are fed in a closed system from containers, such as tanks, drums or the like, direct to the applicator, without the need for manual intervention in the gluing operation.

As examples of types of adhesive that can be used in the apparatus according to the invention can be named: PVAC-glue with hardeneradditive, carbamid-resin glue with hardener as well as conventional water additive, resorcinolglue with hardener, and phenol glue with hardener. In all of these examples, the components are in fluid form. In the method of the invention, the mixing of the adhesive occurs continuously in the quantity which is consumed in the applicator, i.e. the quantity is controlled automatically in relation to the amount to be consumed in each time period.

The mixing occurs in an easily removable static mixing head, which can be provided with a cooling jacket for circulating a cooling medium, such as cold water, connected to a separate cooling aggregate or connected to the water main. Not only can the apparatus be used in conjunction with practically all types of glue applicators, at present on the market, of conventional type, but it can even be used in combination with new types of applicator. The mixing apparatus is even usable in equipment where larger adhesive distribution systems are installed, in which case the apparatus will be located at each applicator, for individually controlled mixing at each applicator.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic view illustrating an embodiment of the apparatus according to the invention applied to a single glue spreader of conventional type; Figure 2 is a detail view of a corresponding glue applicator; Figure 3 is a schematic view illustrating an embodiment of the apparatus according to the invention applied to a double glue spreader; Figure 4 is a detail view of a corresponding glue applicator unit; Figure 5 is a schematic view illustrating an embodiment of the apparatus according to the invention applied to a glue spreader with vertical heads; Figure 6 is a detail view of a corresponding glue applicator; and Figure 7 illustrates a modification of the embodiment shown in Fig. 3.

With reference to Fig. 1, the illustrated apparatus according to the invention conveys glue from container 1 and hardener from container 2. The glue and hardener are pumped in proportionally-adjusted quantitites via a pump unit 3 having two pump casing heads i.e. two separately-pumped outlets. This pump unit 3 can be equipped with more than two pump casing heads. For instance, with glue required to be diluted with water, the pump can be equipped with a total of three pump casing heads. Each pump casing head is individually adjustable in displacement, i.e the quantity of liquid delivered by each pump casing head can be individually regulated so that a correct concentration is obtained in the eventual mixed adhesive.

The driving of all of the pump casing heads occurs by means of a common motor, e.g. a motor 4 which is run on direct current. This motor 4 can be speed-regulated within a very large range and the pump casing heads then maintain the same relation between glue and hardener, regardless of the total amount pumped. The reason for this is that the rotational speed is regulated for all of the pump casing heads, since these are connected to the same drive unit, i.e. the motor 4.

It should here be pointed out that the connection of the containers 1 and 2 should occur substantially at the same height as the pump unit, in order to avoid under pressure in the suction pipes extending to the pumps.

Glue and hardener are pumped in the pipe connections up to a connection head 5 where the glue and hardener are together conveyed to an outgoing connection for the mixing head itself. Mixing occurs in a static mixer 6 during passage through the same. The mixer 6 can be equipped with a cooling jacket for cooling by means of a cooling medium, e.g. cold water, or via a closed cooling system, where the water temperature is kept at even level with a thermostat-regulated cooling aggregate 7. This cooling aggregate 7 can be of a conventional type having a cooling compressor and a smaller water container which is to be maintained at an even temperature, as well as a circulation pump for water, for pumping cooling water through the jacket of the glue mixer.

The level of mixed glue in the glue applicator (compare Fig. 2) is controlled by a level sensor/transmitter 8. This transmitter 8 may comprise a float arranged to rest directly in the glue mixture, which float is connected to a potentio-meter whereby the height level can be read directly. The potentio-meter can moreover be equipped with maximum and minimum switches for automatic control of the quantity of glue to be applied. The level sensor/transmitter 8 may, if desired, be of the capacitive sensor type or of a type which works with ultra high frequency sound sensing. Both of these types are contact-free sensors.

The signal from the level sensor/transmitter 8, regardless of which type is used, is converted in a control device 9 to a thyristor control signal for direct speed regulation of the direct current motor 4. This results in a so-called inversely-proportional relationship between a highest and a lowest limit. When the glue level in the applicator exceeds a median value, the speed of the pump motor 4 is decreased to a lower value. If on the other hand the glue level falls below a median value in the applicator, the speed of the pump motor is increased to a higher value. In this way, automatic adaptation to the glue consumption in the applicator is achieved. In other words the level sensor/transmitter 8 proportionally senses the deviation from a median value and this is converted, in the control device 9, to a signal for adaptation of the speed of the motor 4.This then compensates, by increasing or decreasing rotational speed, eventual changes of glue consumption in the applicator. During extreme conditions, when no glue is consumed from the applicator, the level rises naturally up to the maximum switch in the level sensor/transmitter 8 which emits a signal. At this point, the pump motor is stopped until the value of the level sensor has left the maximum switch and the pump runs at low speed. This speed will increase if the level falls in the glue spreader.

If the value of the level sensor reaches the minimum switch, despite the pump motor 4 running at its highest speed setting, an output signal is given to an alarm (sound or light signal) so that an operator can investigate asS to whether the low level in the applicator arises from the fact that containers 1 and 2 are empty or from the fact that some other malfunction has occurred.

Concerning shutting off of the apparatus, it can be isolated entirely from the control device 9, e.g. by means of a circuit breaker switch, so that the quantity of glue remaining in the applicator will be such as to be consumed whereupon cleaning can take place.

Referring now to Fig. 3, which shows another preferred embodiment of the apparatus according to the invention, applied to a double glue spreader, the mixing of the adhesive occurs in principle in the same manner as according to the above described embodiment, but with the difference that separate glue mixing heads 6a and 6b convey the glue via a separate cooling jacket to both of the feed troughs on the applicator unit (compare Fig. 4). The level is sensed separately by means of sensor/transmitters 8a and 8b in which each transmitter is of a type as described above, i.e. either of mechanical type with float and potentiometer, or of contactless type with proportional sensing of the glue level in each glue trough on the applicator unit by means of capacitive sensor or ultrasound sensor. The level transmitters 8a and 8b control the static mixer 5. In this way, the glue level can be kept even in both of the glue troughs in the glue applicator. Moreover the level sensor/transmitters 8a and 8b located respectively at the upper and lower glue troughs are equipped with maximum and minimum switches in order partly to control stoppage of the pump motor 4 when the risk for overfilling is imminent if no glue is consumed from the glue applicator unit, and partly to activate the minimum switch output signal for connection to an alarm in the form of a sound or light signal, if the glue level falls under the minimum level in any of the applicator troughs, for example because of the contain ers 1 and 2 having been emptied or some other malfunction having occurred in the unit, which effects the supply of glue or glue mixture.The principal function even according to this embodiment is that the quantity of mixed glue is controlled proportionally by the level sensor/transmitters 8a and 8b, via the control device 9 in order to be adapted to the consumption of glue in the applicator. Moreover the cooling jackets around the pipeshaped mixing heads 6a and 6b can be utilized for cooling the adhesive during the mixing process itself before the mixed adhesive runs out into the feed trough on the applicator. This increases the open period for the adhesive while it is present in the trough of the applicator.

Another preferred embodiment of the apparatus according to the invention is shown in Fig. 5 applied to a glue spreader having vertical heads. In this embodiment, the glue is conveyed to a container 10 from which it continuously runs out to applicator rollers which have tightly fitted heads. The glue mixing apparatus may be utilized with or without cooling means and the quantity to be mixed is proportionally regulated or controlled by the level sensor/transmitter 8 via the control device 9 to correct the speed setting for the drive motor 4. Moreover the container 10 can, in this embodiment, be pressurised by means of compressed air to obtain a more even distribution of the adhesive from the container to the glue heads.Of course in this embodiment, also, cooling of the glue can be effected via a cooling jacket arranged around the static glue mixer 6 ahead of the inlet to the glue container 10 for the ready-mixed glue.

Fig. 7 shows a somewhat simpler embodiment than that of Fig. 3, comprising only one mixer to which is connected a branching conduit, e.g. a T-piece with two soft deformable hoses, which can be blocked and opened by means, e.g. of a pinching valve 10 operated by an air cylinder so that the soft hoses are simply pinched or allowed to open automatically due to their own elasticity, in accordance with the feeding pressure depending on the valve position. Pinching of the one hose can bring about a proportionate opening of the other, or both hoses can be opened or pinched independently from each other.The pinching valve 10 is governed from the control 9 by conversion of signals from 8a and/or Sb into a control signal for both the motor 4 and thus the pump speed and also for the pinching valve 11 for the one and/or the other glue trough or the like of the corresponding applicator.

In accordance with the invention therefore, an apparatus has been achieved wherein the quantity of glue components being mixed is proportionally controlled, depending on consumption in the glue applicator. This is achieved in that the level is sensed with proportional sensor/transmitters and via a control device which controls the speed of the motor which drives the pump unit, in which connection the quantity of glue is regulated without any change in the relationship between hardener and glue. In carrying out the invention, the glue can further be cooled during the mixing process itself by means of a cooling jacket to decrease the heat content in the glue mixture, since a certain development of heat occurs after the mixing of glue and hardener has occurred.If the adhesive mixture is cooled before it is conveyed to the glue trough in the applicator, the open time for the adhesive is essentially increased, before hardening occurs in the applicator.

The mixed quantity can even be proportionally controlled to several applicator locations in the same applicator, i.e. the upper and lower roller in a glue applicator can be supplied with adhesive with separate level controls for proportional supply of glue through two individual mixing heads, for each of the feed troughs in the applicator.

Among the advantages which are achieved by the invention, the following are to be mentioned: 1. Continuous mixing of glue during the entire operational period gives constant glue viscosity during the entire period of consumption.

2. Possibility of cooling the glue during the mixing operation itself, which considerably lengthens the open time of the glue in the applicator, before hardening occurs in the unit.

3. The system is closed, which results in the fact that manual contact and handling of the corrosive glue and hardener is not required.

4. Simple cleaning of the glue mixing section afforded by the removable glue mixer, which can be washed with water.

5. Less glue waste, since no portional mixing occurs and the level in the applicator can be regulated to a minimum before the apparatus is switched off.

The invention has been described above with reference to preferred embodiments, but it is obvious that modifications are possible with the scope of the invention as defined in the accompanying claims.

The glue level can, of course, also be governed by a photocell.

Claims

1. A method of continuously mixing and feeding multi-component adhesive, whereby adhesive components are pumped by means of a driving motor from respective containers to a mixer and therefrom as a ready mixed adhesive stream to a glue spreader, e.g. of a single or double type or of a type having vertical heads, wherein the components are fed by a single pump having an individuallyadjustable pump head for each component for achieving constant component proportions independent of motor speed or of the total pump quantity, and wherein the motor speed is regulated proportionally by at least one level sensor/ transmitter for sensing the level of the surface of the glue in a glue trough or the like connected to the mixer, a level signal from said sensor/transmitter being converted, in a control device, to an output signal for speed regulation of the motor.

2. A method as claimed in claim 1 wherein a signal from the level sensor/ transmitter is converted, in the control device into a thyristor control signal for direct speed regulation of the pump motor in inverse proportional relation between a highest and a lowest limit, e.g. when said glue level exceeds median value, the speed of the pump motor is regulated proportionately down to lower values, whereas with diminishing glue level below said median value, the pump motor speed is regulated proportionately up to a higher value.

3. A method as claimed in claim 1 or 2, wherein the mixer is cooled by a cooling agent, preferably water, the cooling agent temperature being kept constant by means of a thermostatically-controlled cooling aggregate.

4. A method as claimed in any preceding claim wherein said glue trough or the like is pressurized by pressurized air for achieving a uniform distribution of the glue from the trough to said glue spreader.

5. Apparatus for continuously mixing and feeding a multi-component adhesive according to the method of claim 1, whereby said glue components are adapted to be pumped by means of a driving motor from respective containers to a mixer and therefrom as a ready mixed adhesive stream, to a glue spreader, e.g. of a single or double type or of a type having vertical heads, characterized in that it comprises a single pump having an individually-adjustable pump head for each component for achieving constant component proportions independent of the motor speed or of the total pump quantity, which are adapted to be regulated proportionally by at least one level sensor/transmitter for the glue level in a glue trough or the like connected to the preferably static mixer whereby a level signal from said transmitter is adapted to be converted, in a control device, to an output signal for speed regulation of said driving motor.

6. Apparatus as claimed in claim 5 wherein the mixer is surrounded by a cooling jacket which is connected to a thermostatically controlled cooling aggregate for keeping the temperature of a cooling agent, preferably water, constant.

7. Apparatus as claimed in claim 5, or 6, wherein the glue trough is connected to a pressurized air source for achieving a more uniform distribution of glue from the trough to the glue spreader.

8. Apparatus as claimed in claim 5, 6, or 7 wherein the level sensor/transmitter comprises a float within said trough, which float is connected to a potentiometer adapted to indicate glue level, and wherein the potentiometer is provided with a maximum and a minimum switch for security control of the glue quantity.

9. Apparatus as claimed in any preceding claim wherein the level sensor/transmitter is of a contact free type, preferably of capacitive sensor or ultra-sound or photocell type.

10. Apparatus as claimed in any of claims 5 to 9, characterized in that it comprises several said glue troughs or the like each with a level sensor/transmitter which, via the control device is connected to the driving motor, to the mixer or to its connection head, for separate conponent control and keeping constant the level of adhesive in each glue trough or the like.

11. Apparatus as claimed in any of claims 5 to 10 wherein the outlet of one mixer is connected to several of the glue troughs or the like by branching conduits, preferably in the form of flexible hoses, which are adapted to be pinched by means of a valve or the like, preferably a pinching valve capable of opening one hose and closing the other simultaneously or independently, which valve is governed by the control device by signals from one, several, or all of the level sensor/ transmitters.

1 2. A method of continuously mixing multi-component adhesives substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

1 3. Apparatus for continuously mixing multi-component adhesives substantially as hereinbefore described with reference to and as illustrated in Figs. 1 and 2, in Figs. 3 and 4, in Figs. 5 and 6 or in Fig. 7 of the accompanying drawings.