JPH05200872A - Welding device - Google Patents

Abstract

PURPOSE:To provide a welding device which can perform welding even for a product of synthetic resin such as polyurethane terephthalate of thick wall, on which a stable welded face cannot be formed because of whitening or deterioration, without the generation of whiting to lose its value of commodity. CONSTITUTION:A welding device for whitening and pressurizing synthetic resins for welding 5 and 6 placed on a support 3 consisting of (a) a whitening means for heating the synthetic resin for welding 5 and 6 up to the given temperature almost instantly, (b) a pressurizing means for pressurizing the synthetic resins for welding 5 and 6 already heated to the given temperature only for the given time, (c) a support 3 provided with a component 4 for the shut-off of transmission of heat to the support and (d) a means 2 for quenching the synthetic resin for welding after welding, and said heating means comprises a heating body 1 to which pulse large electric current is applied from an laternating current power source through a voltage regulator and a transformer.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a welding device.

[0002]

2. Description of the Related Art Items relating to welding are described in detail on pages 765 to 781 of "Handbook of Plastic Processing Technology", published by Nikkan Kogyo Shimbun, December 5, 1969, which is widely used as a resin that can be currently welded. In addition to polyvinyl chloride, polyethylene, and polypropylene that are currently being used, polyester, which is a superordinate concept of polyethylene terephthalate (PET), which is currently considered as a substitute for polyvinyl chloride for pollution-free purposes, is impulse seal and ultrasonic seal. It is described that it can be welded by. The rationale for this description is based on the results obtained in the laboratory by the method shown in FIG. Certainly, as described in this description, even a polyethylene terephthalate can be welded to some extent on a thin one having a wall thickness of 0.1 mm or less and having a rapid heat penetration. However, polyethylene terephthalate with a wall thickness of 0.1 mm or more, particularly 0.2 mm or more,
It was impossible for the welded portion to be completely whitened, that is, to deteriorate, and for the welded portion to be carbonized and substantially welded.
Therefore, it has been attempted to use a hot melt adhesive for bonding thick polyethylene terephthalate, but it is inefficient and costly. However, due to pollution problems, polyethylene terephthalate has to be used even though it is much more expensive than polyvinyl chloride as an alternative to polyvinyl chloride, and nowadays it is not possible to provide a machine that can heat seal polyethylene terephthalate. It is an urgent task for the general.

[0003]

[Purpose] The purpose of the present invention is to whiten the conventionally welded portion,
Even a synthetic resin such as thick-walled polyethylene terephthalate that could not form a stable weld surface due to deterioration,
The point is to provide a welding device that enables welding without bleaching and losing commercial value.

[0004]

[Structure] The inventors of the present invention have conducted earnest research on why a thin sheet can be welded to some extent, but cannot be welded when it is thick. As a result, polyethylene terephthalate has an extremely narrow temperature range where it can be welded, and its deterioration progresses rapidly near that temperature, so when it is thin, it rapidly heats, melts, and rapidly cools to its center before deterioration occurs. Even if it is possible, the time required for heating (immersion) is inevitably long in the case of thick wall as compared with the case of thin wall. The heating time of the heating plate by the conventional impulse is up to about 0.5 seconds at most, and it is impossible to continue the heating for a longer time than this, because an overheat disconnection occurs. The only way to heat and melt a thick product in such a short time is to raise the temperature of the heating plate. As a result, it was revealed that the resin had to be heated to a high temperature that caused deterioration (carbonization) of the resin. Therefore, even if the present inventor uses the impulse method, it is possible to stably flow the current for about 2 to 10 seconds instead of the conventional pulse current for about 0.5 seconds. Therefore, it was thought that the thick resin film could be melted to the central portion at a temperature lower than the deterioration temperature of the resin, and that it could be welded without causing whitening. Then, after repeating trial and error variously, the present inventor thought that a method of heating the heating element through a rectifying circuit such as a plating device or a smoothing path after adjusting the voltage from an AC power source is also possible. .. However, with this method, the structure is complicated and a separate device is required, so that it is not possible to satisfy the range of installation specifications and the economical requirement that are the objectives of the present invention. Therefore, as a result of further research, when one or more transformers are inserted after the voltage regulator, the temperature curves of the heating elements for each pulse are strangely almost the same, and moreover, they are constant for 2 to 10 seconds. The inventors of the present invention discovered that they can be kept at a temperature and arrived at the present invention. That is, the first aspect of the present invention is to (a) heat a synthetic resin for welding to a predetermined temperature almost instantaneously in a welding device for heating and pressing the synthetic resin for welding placed on a cradle. Heating means for (b) a means for pressurizing the synthetic resin for welding heated to a predetermined temperature for a predetermined time,
(C) a pedestal having a member for blocking heat transfer to the pedestal, and (d) means for rapidly cooling the synthetic resin for welding after welding, and the heating means has a voltage from an AC power source. The present invention relates to a welding device characterized by a heating element to which a large pulse current is supplied via a regulator and a transformer. A second aspect of the present invention is, in a welding device for heating and pressing a synthetic resin for welding placed on a pedestal, to heat the synthetic resin for welding [1] (a) to a predetermined temperature almost instantly. Means (b) means for pressurizing the welding synthetic resin heated to a predetermined temperature for a predetermined time, (c)
On the pedestal moved by the heating block including the pedestal having a member for blocking heat transfer to the pedestal, [2] pedestal moving means, and [3] (d) pedestal moving means It comprises a quenching block having means for quenching the synthetic resin for welding, and the heating means is a heating element to which a large pulse current is supplied from an AC power source through a voltage regulator and a transformer. The present invention relates to a characteristic welding device. The present invention does not whiten a resin which is easy to decompose and crystallizes easily like polyethylene terephthalate only when a large current is pulsed from the AC power source for a longer time than a conventional one through a voltage regulator and a transformer. Welding can be achieved. Although the effect of interposing a transformer is not clear, it is surprising that the temperature of the impulse heating element can be accurately controlled to a constant temperature of 2 to 4 seconds longer than before by only interposing the transformer. It should be. It is preferable that the transformer used here has a large hysteresis loss, which is generally disliked by ordinary transformers. It is preferable that this transformer has a hysteresis loss of 1.3 times or more, and preferably 1.5 times or more of that of a transformer currently commercially available. Normally, when the circuit is turned on, at the moment when the circuit is turned on, energy larger than the target electric energy flows. This is not preferable for accurately controlling the heating element at a constant temperature. Therefore, it is preferable to absorb such a protrusion phenomenon by the hysteresis loss of the transformer. Further, in order to control the voltage and the current very accurately, it is preferable that the output voltage of the voltage regulator is adjusted around 200V so that the voltage can be controlled around 30V by the transformer. This is suddenly 3 by the voltage regulator
The voltage control becomes much more accurate than the step-down to around 0V, and as a result, the temperature control of the heating element is ± 2 ° C.
It is possible to control correctly in such a variable order. Preferably, all mechanical actuation of the device of the invention is pneumatic. The cradle moving means is preferably a rotary type, but is not limited to this. The quenching means may be a water-cooling type quenching means installed behind the heating element, but an air-cooling method, particularly a jet-type air-cooling method, and particularly air cooled to 10 ° C., preferably 5 ° C. or lower, is jetted. It is preferable to use an air-cooling method that wipes with a method. As a member for blocking heat transfer to the pedestal, one having a thermal conductivity of 0.5 W / mK or less is preferable, and examples thereof include Teflon, silicone resin, polyurethane rubber, phenol resin, and the like. And a paper laminate. It is preferable to perform welding by interposing a release sheet such as a Teflon sheet or a silicone sheet between the heating element and the resin sheet for welding in order to prevent adhesion between the two.

Since the heating means eliminates the variation in the output and enables the stable supply of energy, the temperature of the heating portion can be controlled extremely accurately to a constant temperature in coordination with the sensor and the timer. As a result, overheating does not occur, and the welded part does not whiten or deteriorate. Thus, maintaining the heating element at a constant temperature accurately during the welding period of 2 to 10 seconds can be achieved only by the heating means of the present invention. The voltage regulator, so-called sliderox, is indispensable for setting the heating wire at a predetermined temperature. In the present invention, a temperature sensor that accurately measures the temperature of the required location and a timer that accurately indicates the processing time are used, and the solenoid valve is opened and closed according to the instructions of the sensor and the timer, thereby opening and closing the air compressor. .. As a result, the operating time of the air compressor is almost one-third that of the hydraulic mechanism, and the time difference is extremely small, so the time when the synthetic resin in the welded part is exposed to the risk of decomposition and deterioration can be greatly reduced. It will be possible. It is preferable that the temperature during welding is strictly controlled particularly when the sheet is thick. When the resin to be deposited is polyethylene terephthalate, the melting recrystallization temperature is ± 5 ° C, preferably ± 2.
It is particularly preferable to set in the temperature range of ° C. Excellent welding results can be obtained even with resins other than these by performing welding within the above temperature range. Although the present invention has been described focusing on polyethylene terephthalate, any resin that can be conventionally welded can be applied as the resin to be welded.

[0006]

【Example】

Example 1 The circuit shown in FIG. 1 was used as a means for heating the heating element. MC is a solenoid valve for opening and closing the circuit. 2 and 3 show a welding apparatus used in this embodiment of the present invention, wherein FIG. 2 is a front sectional view and FIG. 3 is a side sectional view. The heating element 1 is connected to the above circuit, and is heated by passing a large current in a pulsed manner using this circuit. In order to apply a current to the circuit, the solenoid valve (indicated by MC in the figure) is set to operate when the sheets 5 and 6 of 0.3 mm thick polyethylene terephthalate are pressurized. Thus, at the same time as the pressurization, a large current flows in a pulsed manner, and the heating element is instantaneously heated to 180 ° C (set at a temperature 5 ° C lower than 185 ° C, which is the melting and recrystallization temperature of this resin).
Heat to. Also, the circuit is turned off at the same time when the pressure is released. At the same time, the resin sheet is cooled as quickly as possible by blowing air cooled to about 5 ° C. from the jet air-cooling type cooler 2 to the welding point. After the welding, the heat-insulating sheet 4 is provided on the pedestal 3 so that the heat at the time of heating is not transmitted to the pedestal as much as possible so that the fused sheet can be cooled promptly.
It is necessary to provide. Although Teflon was used in this embodiment, silicone can be used instead of Teflon. Polyethylene terephthalate (A-PET Mineron trade name) used in Examples, melting point 2
58 ° C., melting recrystallization temperature (DSC method) 185 ° C., thickness 0.4 mm, 3 mm width, length 28 mm
Welded over 0 mm. For the welding, a large current is supplied to the heating element in a pulsed manner by using the above circuit, and the temperature of the heating element is set to 1
Maintaining a constant temperature of 85 ° C., under a pressure of 4 kg / 560 mm ² ,
PET was welded by applying heat and pressure for 2.5 seconds. As a result of insulating the pedestal by laying a Teflon sheet on its surface,
The temperature during heating and pressing was kept at 20 ° C. After 2.5 seconds, the press plate was lifted and at the same time, cooling jet air of 5 ° C. was blown from the cooler 2 for 2.5 seconds to cool the welded portion. The welded part was inspected, but no whitening occurred, and it was transparent like other parts. 20k welding part
It was pulled with a pulling force of g, but there was no change at all. Moreover, no abnormality occurred at all even if a 10 kg impact was applied to the welded portion.

[0007]

[Effect] The present invention has made it possible to substantially weld a thick polyethylene terephthalate film, that is, a sheet, which has been impossible so far.

[Brief description of drawings]

FIG. 1 is a circuit diagram for electrically heating a heating element according to an embodiment of the present invention.

FIG. 2 is a front sectional view of a welding device according to an embodiment.

FIG. 3 is a side sectional view of the welding apparatus of the embodiment.

[Explanation of symbols]

 1 heating element 2 cooler 3 pedestal 4 heat insulating material 5 polyethylene terephthalate sheet 6 polyethylene terephthalate sheet

Claims (6)

[Claims] 1. A welding device for heating and pressing a synthetic resin for welding placed on a pedestal to weld the synthetic resin for welding (a) to a predetermined temperature almost instantly. (B) means for pressurizing the synthetic resin for welding heated to a predetermined temperature for a predetermined time only, (c) a pedestal having a member for blocking heat transfer to the pedestal, and (d)
It consists of means for rapidly cooling the synthetic resin for welding after welding,
The heating means is a heating element supplied with a large pulse current from an AC power source via a voltage regulator and a transformer. 2. A welding apparatus for heating and pressing a synthetic resin for welding placed on a cradle to weld the same, [1]
(A) A means for heating the synthetic resin for welding to a predetermined temperature almost instantly, (b) A means for pressurizing the synthetic resin for welding for a predetermined time only at a predetermined temperature, and (c) Heat is transferred to a pedestal. The heating block including a pedestal having a member for shutting off the heat, [2] the pedestal moving means, and [3] (d) the synthetic resin for welding on the pedestal moved by the pedestal moving means is rapidly cooled. And a heating block to which the heating means is supplied with a large pulse current from an AC power source through a voltage regulator and a transformer. 3. The welding device according to claim 1, wherein all the mechanical operations of these means are pneumatic. 4. The welding device according to claim 2, wherein the cradle moving means is a rotary type. 5. The welding device according to claim 1, wherein the quenching means is a water-cooling type quenching means. 6. The welding device according to claim 1, wherein the rapid cooling means is an air cooling system.