JPS583013B2 - Continuous heating device for metal caps - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a continuous heating device for metal caps, and more particularly to a continuous high-frequency heating device that is particularly suitable for heating caps made of non-magnetic metals such as aluminum.

Here, the metal cap refers to a cup or cap, or a crown, etc., manufactured by shallow drawing or deep drawing of a metal plate, and which is further processed with screws as necessary, and includes a pilfer-proof cap. (pilfe
This also includes products such as r proof caps.

The metal cap before heating may be unpainted, printed or painted, coated with adhesive on the inner surface of the bottom, or lined with thermoplastic resin.

The cap material preferably used in the present invention is an aluminum or aluminum alloy thin plate, or a non-magnetic metal plate such as copper or brass, but a magnetic metal plate such as a low carbon steel plate may also be used depending on the conditions as described below. I can do it.

Among metal caps, those used especially for sealing the openings of containers such as bolts and wide-mouthed bottles have cork or a thermoplastic resin sheet (such as vinyl chloride, polyethylene, or polypropylene) on the inner bottom surface of the cap as a backing material. liner) is lined.

In particular, the use of the latter has been increasing recently, but in this case, in order to fix the liner to the inner bottom of the cap, the liner material is generally inserted into the cap whose inner bottom has been coated with an adhesive primer. Means for heating the bottom surface of the cap to approximately 100 to 200° C. in the process or post-process is employed.

Conventionally, as a continuous heating device for the crown of a metal cap (generally made of ferromagnetic material such as tin plate or stainless steel), a heating device using heated air as disclosed in Japanese Patent Publication No. 41-5588 has been used. It has been known.

In this case, the crown is heated to approximately 160°C while being transferred with the crown flared portion seated on the countersink-shaped inner protrusion formed at the top of a number of notches provided separately on the periphery of the turntable. be done.

This type of heating method requires a long time for heating, so in order to perform high-speed heating of about 1,000 pieces per minute, for example, a long heating section is required, which has the disadvantage that the equipment cannot be made compact.

There is also the problem that even the trunk wall portion, which does not necessarily require heating, is heated.

As a means to eliminate the above-mentioned drawbacks,
There is a high frequency heating device as proposed in No. 41398.

This is a device that rapidly heats the crown placed on a conveyor and sent by a hairpin-shaped high-frequency heating coil installed at the bottom of the conveyor.According to experiments conducted by the inventors, such a device In some cases, it has been found that although it is possible to effectively heat a crown made of a ferromagnetic material capable of concentrating magnetic flux, heating is not possible at all in the case of a non-magnetic metal cap such as an aluminum cap.

That is, since a conveyor having a certain thickness is interposed between the heating coil and the cap, the mutual induction coefficient between the two is very small, and the temperature of the cap hardly rises.

In addition, when the conveyor was made to be impractically thin to increase the mutual induction coefficient and the two were brought close to each other, the cap floated and jumped on the conveyor, making heating completely impossible.

The cause of the jump is the repulsion effect formed by the induced current induced at and near the bottom of the aluminum cap and the high-frequency coil magnetic field.

In the case of a ferromagnetic metal cap such as a crown, the cap itself is generally magnetically fielded by the magnetic field generated by the high-frequency current, creating an attractive force acting in the direction of the high-frequency current conductor, which in turn creates a repulsion based on the induced current. Since the force is greater than the force, a jump like the one described above usually does not occur.

In order to solve the above-mentioned problems of the prior art, the inventors of the present invention have carried out various studies, and have provided a guide plate that is movable in the vertical direction so that it faces the high-frequency heating coil and the metal cap is placed between them. The metal cap that is about to float is transferred while being pressed by the guide plate using spring pressure, and in this way, the distance between the bottom of the metal cap and the high-frequency coil can be maintained regardless of slight fluctuations in the height of the metal cap. It has been found that heating efficiency can be increased and relatively uniform heating of the bottom can be achieved by keeping the temperature as small and constant as possible.

The main object of the present invention is to provide a heating device particularly suitable for high-speed, continuous, large-volume heating of the bottom of a non-magnetic metal cap.

Another object of the present invention is to provide a continuous heating device particularly suitable for high-frequency heating of non-magnetic metal caps.

Another object of the present invention is to provide a high frequency continuous heating device capable of heating the bottom of a metal cap as uniformly as possible, regardless of slight variations in the height of the metal cap.

A particular object of the present invention is to provide a high-speed, continuous heating device for aluminum caps to impart adhesion to thermoplastic liners.

According to the present invention, at least one pair of high frequency current conductors having a distance smaller than the diameter of the bottom of the metal cap and having current directions opposite to each other are provided opposite to the high frequency current conductors, and It is characterized by comprising a guide plate that presses the open end of the metal cap, which has a levitation force due to the action of a high-frequency current, on the opposing surface via spring pressure, and a transfer device that slides the metal cap on the opposing surface. A continuous heating device for a metal cap is provided.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to drawings showing examples.

Figure 1 shows an aluminum cap (hereinafter referred to as the cap)
1 is a plan view schematically showing a continuous heating device 1 and ancillary equipment before and after the same.

A large number of semicircular notches 3 are provided at intervals on the periphery of the rotary table 2, which is a cap transfer device.
The cap 5 is loaded from the chute 4 into the notch 3 with the bottom facing downward.

The loaded cap 5 is transferred in the rotational direction of the rotary table 2 (in the direction of the arrow in the figure) and loaded into the heating device 1.

Note that the cap slides on a guide (not shown) before entering the heating device 1 and after leaving the heating device 1.

The heating device 1 includes a high-frequency current conductor 7 to which current is supplied from a high-frequency power source 6, a plurality of guide plates 8, and a guide plate support device 9.
and a guide 10.

FIG. 2 is a front view of a set of guide plates and their support device as seen from the rotary table side, and FIG. 3 is a vertical sectional view taken along line A--A in FIG. 2.

In FIGS. 1 and 3, there are two high-frequency current conductors 7 (hereinafter referred to as conductors) (a pair), but it is important that the current direction of each conductor is opposite to each other.

This is because when the current directions are opposite to each other as shown in Fig. 4, the induced current induced in the non-magnetic aluminum bottom and the lower part of the body wall forms a closed circuit 13 and flows in large quantities. Temperature rise due to Joule heat is also carried out efficiently, but when the current direction is the same, a closed circuit as shown in Figure 4 is not formed and the efficiency of induced current induction is low, so almost no temperature rise is observed. be.

For the same reason, almost no temperature rise is observed when there is only one conductor.

Although only one pair of conductors is shown in the figure, if the cap diameter is large, it is preferable to use one or more pairs of conductors from the viewpoint of temperature rise rate and uniformity of temperature distribution at the bottom of the cap.

It is also important that the spacing between the conductors (meaning the spacing between the center lines of the conductors) is smaller than the diameter of the bottom of the metal cap (if it is not circular, the length of the shortest part).

This is because if one of the conductors becomes an ineffective side, the heating efficiency will drop significantly, making it impossible to heat the cap.

Further, the spacing between the conductors is approximately equal to or slightly thicker than the radius of the bottom of the cap, and the center of the bottom of the cap passes approximately through the center line between the conductors, which increases heating efficiency and makes temperature distribution uniform. preferred above.

The inside of the conductor 7 is water-cooled.

The diameter of the conductor increases with the diameter of the cap to be heated, e.g. when the cap diameter is 15-25 mm, 26-25 mm.
Preferred conductor diameters for 40 mm and 41-60 mm are about 4 mm, about 6 mg, and about 8 mm, respectively.

This is because the larger the cap diameter, the larger the current that needs to flow through the conductor, and the smaller the conductor diameter, the greater the Joule loss in the conductor, while the larger the conductor diameter, the greater the electromagnetic coupling between the conductor and the cap. This is because the heating efficiency decreases as the size becomes smaller.

A slight difference in the distance between the conductor and the bottom of the cap will sensitively affect the mutual induction coefficient between them, causing a change in the amount of induced current at the bottom of the cap, and therefore the heating temperature, as well as short circuits between the bottom of the cap and the conductor. To prevent this, the conductor is a fixed body made of synthetic resin such as Bakelite (when using a vacuum tube oscillator) or an insulating high permeability material such as ferrite (when using a transistor set oscillator), as shown in Figure 3. It is preferable to fix the conductor to 11 with an adhesive 12 such as epoxy resin to prevent the conductor from moving unstably during the heat treatment.

Any type of high-frequency power source 6 can be used, but a vacuum tube type is preferably used for high frequencies of about 100kHz to 10MHz, and a single transistor type is preferably used for frequencies of about 10kHz to 80kHz. be done.

In the case of a transistor set oscillator, by using an insulating high permeability material for the fixed body 11, the degree of electromagnetic coupling between the conductor (coil) and the bottom of the cap is increased, increasing heating efficiency and uniformity of bottom heating. can be raised.

However, in the case of a vacuum tube oscillator, since the operating frequency is high, the impedance of the part corresponding to the gap between the caps of the conductor is increased by using an insulating high permeability material, and current flow is obstructed. Even if an insulating high permeability material is used for the body 11, there is little effect.

In addition, since the operating voltage of a transistor one-way oscillator is low, the generated high-frequency power can be directly supplied to the conductor (heating coil), so there is no need for an output current transformer to adjust the output impedance, and therefore the efficiency is high and the device It has the advantage that it can be made smaller.

The guide 10 is annular so as to surround the peripheral edge of the rotary table, and the distance between its lower inner diameter 10a and the portion 3a of the semicircular notch 3 closest to the center of the rotary table 2 is smaller than the outer diameter of the cap. It is set so that it becomes larger.

As mentioned above, when the cap, which is a non-magnetic material, comes on top of a high-frequency current conductor, the cap floats upward due to the repulsive force.
Forced to jump.

The guide plate 8 has the function of preventing the heating of the cap from becoming impossible due to this jumping phenomenon, and that the open end 5a of the cap 5 slides on the lower surface 8a of the guide plate 8 by being driven by the transfer device.

At the same time, the guide plate 8 has the function of adjusting the distance between the cap bottom surface 5b and the conductor 7 to ensure effective heating of the bottom of the cap and to keep the temperature distribution of the bottom as uniform as possible.

The guide plate 8 is a rectangular plate whose width (short side) is slightly larger than the outer diameter of the cap, and the lower end of the short side is tapered to prevent the open end of the cap from getting caught during transfer. and is provided facing the conductor 7.

In FIG. 3, the width of the guide plate 8 is slightly larger than the outer diameter of the cap, but it may be approximately equal to or slightly smaller than the outer diameter.

The long side of the guide plate has a curvature in the length direction or is a straight line, and even if there are multiple guide plates, they are arranged so that they almost lie on the same arc centered on the center of the rotary table. There is no particular limit to the length of the three guide plates 8, but it is preferable that the length be long enough to allow several metal caps to pass through at the same time, from the viewpoint of ease of height adjustment during work. .

In addition, by doing this, when caps from lots with different heights arrive in the middle, the occurrence of defective products can be minimized.

Therefore, as shown in the example below, the total length of the heating device 1 is 80 cm.
If the guide plate is relatively long, it is preferable that the guide plate consists of a plurality of pieces.

In this case, if the distance between adjacent guide plates is too large, only the part of the metal cap that is not under the guide plate will float up, causing the cap to tilt and get caught at the entrance of the next guide plate, causing work to be interrupted, or In extreme cases, the cap may fly out of the heating device.

It is therefore necessary that the guide discs be close enough to each other to ensure smooth transition of the cap.

The guide plate 8 should not be deformed or damaged by the impact force of the jumped cap, should not have any unevenness on its lower surface that would prevent the opening end of the cap from sliding, and should not be subject to wear or damage due to the above-mentioned sliding. Although there are no particular limitations as long as conditions such as not being present are satisfied, it is preferable to use a ceramic plate, particularly a tempered glass plate with a thickness of about 5 to 10 mm, in order to satisfy these conditions.

Among these, a transparent tempered glass plate is preferred because it allows easy monitoring of work.

FIG. 1 shows the case where transparent glass is used. The guide plate 8 is supported by a guide plate support device 9 having a pressing spring.

The guide plate support device 9 is constructed as follows.

A substantially O-shaped bracket 9 whose bottom part is fixed to the guide 10
The center part of the fixed horizontal rod 9b is fixed onto the upper horizontal part of the horizontal part a.

A vertical bolt 9c is vertically movably inserted through a vertical hole bored near both ends of the horizontal rod 9b.

The horizontal center part of a U-shaped support frame 9d whose center side is horizontal is fixed to the lower end of the vertical bolt 9c, and is screwed into the upper threaded part of the vertical bolt 9c and located at the upper part of the fixed horizontal rod 9b. By rotating the adjusting double nut 9e, the support frame 9
A pressing spring 9f is provided between the upper surface of the 3-support frame 9d and the lower surface of the fixed horizontal rod 9b, which are configured to enable vertical movement adjustment of the vertical movement of d, and a vertical bolt 9c is inserted through the pressing spring 9f. , when the support frame 9d is pushed up, resistance is applied due to spring pressure.

The guide plate 8 is horizontally fixed in the vicinity of both ends in the longitudinal direction inside the support frame 9d by sharp end setscrews 9g.

It is preferable that the members constituting the guide plate support device 9 are made of non-magnetic material such as brass, except for the pressing spring.

After the metal cap is drawn, the edges are usually trimmed so that the body wall has a constant height, and then bead processing, knurling processing, etc. are performed.

In the case of actual work, the same type of cap is used,
Even if the height of the cap body wall after trimming is constant, the height of the cap after beading and knurling varies by about ±0.2 mm depending on the work lot.

Therefore, if the height of the guide plate 8 is fixed, the bottom surface of the cap 5
The distance, ie, the gap, between the upper end portion 7a and the upper end portion 7a of the conductor is approximately 0.
A difference of 4 mm will occur between lots.

As is clear from FIG. 5, the above-mentioned difference of 0.4 mm causes a change in the temperature rise at the bottom of the cap by several tens of degrees.

However, as described below, by using the guide plate support device of the present invention, the difference in the gap between lots can be substantially eliminated, and therefore the temperature at the bottom of the cap can be adjusted throughout each lot. The predetermined temperature can be kept substantially constant.

First, before starting work, adjust the distance between the lower surface of each guide plate and the upper surface of the fixed body using the adjusting double nut 9e so that it is equal to the minimum height of the cap.

During work, the cap moves with a levitation force generated by electromagnetic coupling with the conductor, but if the sum of the weight of the guide plate and the pressing force of the pressing spring is greater than the levitation force, the cap will move. Regardless of the height of the body wall, the open end of the cap slides on the lower surface of the guide plate and the bottom surface of the cap slides on the fixed body, so the gap remains constant and the temperature rise at the bottom of the cap remains constant. It is maintained.

In this case, if a cap of a lot higher than the minimum height is received, the guide plate 8 and hence the vertical bolt 9c are raised by the difference from the minimum height.

FIG. 2 shows this state.

On the other hand, if the floating force is greater than the sum of the weight of the guide plate and the initially set pressing force of the pressing spring, the cap will float.

However, the levitation force is unrelated to the height of the cap body wall.
Moreover, if the pressing spring is sufficiently long, the pressing force from the spring will not substantially change even if the vertical position of the guide plate changes by about ±0.2 mm, so the floating amount will change depending on the height of the cap body wall. do not.

Therefore, the gap is kept constant and the temperature rise at the bottom of the cap does not vary from lot to lot.

In this case, the open end of the cap slides along the lower surface of the guide plate, but the bottom surface of the cap does not contact the solid upper surface.

In order to increase the mutual induction coefficient between the conductor and the bottom of the cap so that the bottom of the cap reaches a predetermined temperature,
As shown in the curve, when a high permeability material is not used, the distance between the conductor upper end 7a and the cap bottom surface 5b is 1 m.
m or less, preferably 0.5 mm or less.

It should be noted that it is undesirable to get closer than about 0.1 mm because there is a risk of short circuit.

Further, when an insulating high permeability material is used for the fixed body 10, the distance between the fixed body top surface 10a and the cap bottom surface 5b is 2 mm or less, preferably 1 mm, as shown in the curve b in FIG.
It is necessary to make it less than mm.

In this case, since ferrite, which is generally used as an insulating high permeability material, is fragile, the upper surface 10a of the fixed body is approximately 0.4 m
Since it is necessary to protect the cap with an insulating sheet such as Bakelite having a thickness of m, it is difficult to reduce the distance between the top surface of the fixed body and the bottom of the cap to about 0.4 mm or less.

Next, a specific example in which the heating device of the present invention is used to bond a polyethylene liner to the inner bottom surface of an aluminum cap will be described.

Adhesive primer (e.g. polyethylene oxide or maleic anhydride modified polyethylene dispersed in epoxy phenol paint) on the inner bottom surface with an outer diameter of 28 mm and a height of 16 mm.
Aluminum cap (thickness 0.2mm) coated and baked with
) 5 is supplied from the chute 4 to the notch 3 of the rotary table 2.

The cap is sent to a heating device 1 with a length of 80 cm, and the bottom portion is mainly heated by high frequency induction.

Transistor oscillator frequency 25kHz, output 10k
W, the distance between the bottom of the cap and the top of the fixed body is 0.7 mm, the number of caps loaded into the heating device at the same time is 20, the time to pass through the heating device is 1 second, and the bottom of the cap is at the lowest temperature of 140°C.
, heated to a maximum temperature of 160° C. (temperature was measured by thermopaint) and exits from the heating device.

This temperature is sufficient for complete adhesion of the adhesive primer and polyethylene at the press station described below.

The heated cap passes through the guide,
It enters a molten polyethylene grain feeder 14 where it is fed with molten polyethylene grains approximately in the center of its bottom surface.

The cap is then sent to a press station (not shown) where a cooled punch compresses the molten polyethylene particles into a sheet and solidifies to form a liner that adheres to the inner bottom surface of the cap.

In this case, since the barrel wall is hardly heated, there is no risk of solidification being delayed by residual heat.

The above has mainly been about caps made of non-magnetic metals such as aluminum caps, but caps made of ferromagnetic materials such as tin caps also have cap weight,
size, shape, etc., as well as the strength and frequency of the current flowing through the conductor,
Depending on conditions determined by the distance between the bottom of the cap and the conductor, the cap may float up.

It goes without saying that the present invention can be applied to such cases as well.

According to the present invention, it is possible to heat the bottom of a metal cap, particularly a non-magnetic metal cap, at high speed and in large quantities at a rate of 1000 caps or more per minute using a compact device.

Furthermore, even if the height of the metal cap changes slightly, its floating height is adjusted to a constant level by the action of the pressing spring, so that the heating temperature at the bottom of the cap can be maintained at a desired constant value.

In addition, since the barrel wall portion that does not require heating is hardly heated, it is possible to prevent product quality from deteriorating, and furthermore, there is an effect that there is less power loss.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view showing one embodiment of the present invention, FIG. 2 is an enlarged front view of a part of the heating device, and FIG.
4 is a perspective view showing the induced current circuit at the bottom of the metal cap and its vicinity. FIG. A diagram showing the relationship is shown. 1... Heating device, 2... Rotating table (transfer device)
, 5... Metal cap, 7... High frequency current conductor, 8
... Guide board, 9... Guide board support device, 9f... Pressing spring.

Claims (1)

[Scope of Claims] 1. at least one pair of high-frequency current conductors whose spacing is smaller than the diameter of the bottom of the metal camp and whose current directions are opposite to each other, and which are provided opposite to the high-frequency current conductors; and a guide plate that presses the opening end of the metal cap, which has a levitation force due to the action of a high-frequency current, on the opposing surface via spring pressure, and a transfer device that slides the metal cap on the opposing surface. A continuous heating device with a metal cap featuring: 2. The continuous heating device for a metal cap according to claim 1, which includes a plurality of guide plates and is adjacent to each other.