JPH043273B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field] The present invention relates to a hot melt adhesive applicator equipped with a feeding device.

[Prior Art] Conventional hot melt adhesive applicators are composed of a heated melting tank and a liquid pressure pump, or are composed of a grid heater with a hopper, a reservoir (storage tank), and a liquid pressure pump. It consisted of a pump. The advantage of this device was that the only moving part was a small liquid pressure pump (generally a gear pump), and the reservoir was also attached directly to the bottom of the grid heater, making it extremely compact. However, there were also the following drawbacks.

(1) It takes more than 30 minutes from charging the solid hot melt adhesive to melting and discharging it (this is because all the solid hot melt adhesive charged in the heated melting tank is completely and uniformly melted). Since the liquid pressure pump starts from then on, it takes a lot of time as mentioned above).

(2) When heated for a long time as described above, hot melt adhesives always gel or carbonize.

(3) In general, hot melt adhesive applicators are not suitable for melting hot melt adhesives with too high a viscosity (viscosity is limited to 300,000 cps).

A possible solution to the above problems is to use a feeding device (referred to in the industry as an extruder) having a screw conveyor. The inventor conducted an experiment using a conventional small-sized feeding device 41 as shown in FIG. 2, and the expected results were obtained. In other words, the time was shortened to a few minutes, carbonization was prevented, and hot melt adhesives with a high viscosity of 1,000,000 cps could be melted and discharged in a short time.

To briefly explain the feeding device used in the experiment (see Fig. 2), a small feeding device 41 is used, and a pressure detector 50 is installed in the space 43 between the screw tip 42T and the die plate 47. A nozzle 49 was attached to the die plate via a manifold 48. The pressure detector is connected to the controller 56 and the second controller 59 by
It controls the screw drive motor 45. This made it possible to discharge a fixed amount of molten hot melt adhesive under constant pressure.

However, the following drawbacks were also discovered.

(a) Poor "cutting" in intermittent discharge.

(b) Since the nozzle 49 is fixed, flexible application work is not possible.

[Problems to be Solved] The problems of both the hot melt adhesive applicator described above and the conventional hot melt adhesive applicator equipped with a small feeding device are summarized as follows.

That is, (1) Relatively long melting and heating residence times.

(2) Hot melt adhesives tend to carbonize or deteriorate.

(3) High viscosity hot melt adhesives are difficult to melt.

(4) Poor “cutting” in intermittent discharge.

(5) Flexible application work is not possible.

It is an object of the present invention to overcome the above-mentioned problems in both conventional hot melt adhesive applicators and hot melt adhesive applicators with compact feeders.

[Means for Solving the Problems] The gist of the present invention is that a flexible hose 19 is provided at the tip of a conventional feeding device 1, and a hot melt adhesive discharging gun 20 is provided at the end of the flexible hose 19, and a hot melt adhesive discharging gun 20 is provided in the gun. It is a hot melt adhesive applicator having a feed device incorporating a pressure sensor 30 which is also electrically connected to the screw drive motor 15 via a controller 36.

Next, the structure of the present invention will be explained. Please refer to FIG. Feeding devices generally need to be small (screw diameter 1 inch or less) and have standard length/diameter (16 to
18) is fine. However, screw drive motor 1
5 is preferably an electric variable speed motor. A heat-resistant and pressure-resistant flexible hose 19 is attached to the die plate 17 or manifold attached to the flange 6 at the tip of the feeding device 1.
Generally, the heat resistance is 260℃ and the pressure resistance is around 100Kg/ ^cm2 . A hot melt adhesive dispensing gun 20 is attached to the other end of the flexible hose, and a pressure detector 30 is provided in the liquid passage 22 inside the gun. Although a solenoid type gun is shown in the figure, an air cylinder type gun may also be used, and either type is connected to a timer 35. Further, the pressure detector 30 is electrically connected to a controller 36, which is further electrically connected to the screw drive motor 15 via a second controller 38. Further, as the screw drive motor 15, all electric types other than mechanical types, such as a DC motor and a servo motor, can be used. In addition, an appropriate arithmetic control circuit such as a PID type is incorporated inside the controller.

It goes without saying that when a manifold is attached to the die plate, it is necessary to attach a plurality of gun nozzles.

[Operation] Please also refer to FIG. 1. The hot melt adhesive in the form of pellets, flakes, or granules supplied from the hopper 9 is transferred by the screw conveyor 2 inside the cylinder 3, and is melted by the electric heater 4 provided outside the cylinder. It is kneaded and pressurized and reaches the tip of the cylinder. Until then, the operation is similar to that of a conventional hot melt adhesive applicator with a feeding device. However, as mentioned above, even higher viscosity adhesives can be melted in a shorter time than with conventional hot melt adhesive applicators. For example, screw diameter 18 mm, length/diameter = 17, screw rotation speed
At 100 rpm, it takes about 5 minutes for polyamide-based pellet hot melt adhesive to be discharged from the nozzle. The reason why it takes such a short time is that in the case of a hot melt adhesive applicator with a feeding device, only a small amount supplied to the screw needs to be heated and melted. This is because it is not necessary to melt and homogenize all of the adhesive supplied within.

The hot melt adhesive thus melted and pressurized passes through the heat and pressure resistant flexible hose 19 attached to the die plate 17 and reaches the hot melt adhesive discharging gun 20. When the on-off valve 23 in the gun is opened, the hot melt adhesive is discharged from the nozzle 27 to the outside. It goes without saying that the discharge amount depends on the discharge pressure immediately before discharge, but in the case of the present invention, the detection of the discharge pressure is performed by the opening/closing valve in the gun 20.
3 on the fluid passageway 22 immediately before the controller 36 and the second controller 38.
The screw rotation speed is controlled through. Therefore, the time lag is small, the response is quick, and the discharge pressure can be kept precisely constant. On the other hand, in the conventional case, as shown in Figure 2,
Liquid detection was performed near the tip of the screw 43, and the passage from there to the nozzle 49 was long, resulting in slow response and difficulty in maintaining a constant pressure precisely. Another feature of the present invention is that the feeding device 1 and the gun 20 are connected by a flexible hose 19, so that the gun can be moved freely. On the other hand, in the conventional case, as shown in FIG. 2, the nozzle 49 is mounted and fixed on the feeding device 41, so that the coating operation cannot be performed while freely moving.

An example of experimental data is as follows.

a Hot melt adhesive applicator screw system with feeding device; 18 mm, length/diameter = 17, controller with DC motor PID b Target hot melt adhesive polyamide system (pellet form) Melting point: 230°C Viscosity: 7000 cps c Supply-discharge time 2 Minutes (screw rotation speed: 100 rpm) d Continuous discharge ON - 0.5 seconds, OFF - 4.5 seconds (pitch 5 seconds) Discharge amount - 0.15 g ± 0.02 g (1 pitch) e Discharge quality Good (no carbonization) Also, experimental results This resulted in unexpected, consequential benefits. This means that cleaning after work has been greatly simplified. In conventional hot melt adhesive applicators, a large amount of gel or carbide adheres to the inside of the heating melting tank or grid heater, and cleaning and maintenance thereof is essential and requires a lot of effort. However, in the hot melt adhesive applicator with a feeding device of the present invention, no gelling or charred matter as described above is deposited on the surface of the screw conveyor 2, and cleaning is almost unnecessary. This is because hard chrome plating is applied on the surface of this screw conveyor, and the molten hot melt adhesive moves between the cylinder 3 and the screw conveyor 2 while sliding under strong pressure. As mentioned above, simplifying cleaning and maintenance after work greatly contributes to improving work efficiency.

[Effects] According to the hot melt adhesive applicator with a feeding device according to the present invention, as described above, even high viscosity hot melt adhesive can be discharged in a short time, and the discharge pressure can be kept precisely constant to perform intermittent discharge. Precise dispensing is possible even in small spaces, the residence time is shortened to prevent carbonization, and the flexible hose allows the gun to be moved freely during coating operations, making it possible to save space in the coating work area. It can be set freely, and it is possible to improve work efficiency by making precision and intermittent coating work more efficient and simplifying cleaning after work.

[Brief explanation of drawings]

Fig. 1 is a structural side sectional view of a hot melt adhesive applicator with a feeding device according to the present invention, and Fig. 2 is a side sectional view of a conventional hot melt adhesive applicator with a feeding device. , 2...Screw conveyor, 3...Cylinder, 4...Electric heater, 6...Flange, 15...Screw drive motor, 17...Die plate, 19...Heat and pressure resistant flexible hose, 20... Hot melt adhesive dispensing gun, 22...liquid passage in the gun,
30...Pressure detector, 35...Timer, 36...
Controller, 38...second controller.

Claims (1)

[Claims] 1. In a hot melt adhesive applicator having a feeding device 1, (a) the feeding device 1 has a screw conveyor 2 disposed within a cylinder 3 having a heater 4; b) The screw conveyor 2 is connected to a screw drive motor 15; (c) A heat-resistant and pressure-resistant flexible hose 19 is attached to the die plate 17 or manifold attached to the flange 6 at the tip of the cylinder 3. (d) At the other end of the heat-resistant and pressure-resistant flexible hose 19, an on-off valve 23 is connected by the output of the timer 35.
Hot melt adhesive dispensing gun 20 driven by
(e) A pressure detector 30 is provided in the liquid passage 22 inside the hot melt adhesive dispensing gun 20; (f) The pressure detector 30 is connected to a controller 36 and A hot melt adhesive applicator characterized in that it is electrically connected to the screw drive motor 15 via a second controller 38 and is controlled so that the pressure takes a predetermined value.