JPS641188B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in coating the inner surface of side wall joints of container bodies, and more particularly to a novel powder coater.

In recently developed powder applicators, centrifugal means are provided in the powder feed tube, by means of which the powder is separated from the carrier gas and concentrated in a portion of the cross section of the feed tube; The powder is then fed into the designated area of the orifice of the nozzle, from where it is
It is given as a flow. Although the above development is advantageous, it still has two drawbacks. That is, firstly, since a 360° bend is used as the centrifugation means, the orifice must be oriented in the direction of movement of the can, and secondly, while the desired centrifugal action is being performed, the orifice must be oriented in the direction of movement of the can. Frictional losses in the supply pipe are increased.

In addition, the can body coated with powder needs to be heated to fuse the powder, but when this heat source is a gas flame, the powder can be heated in the direction of movement of the can body. may cause ignition.

A centrifugal separation method is also used in the present invention, but the direction of the powder flow is reversed and is opposite to the direction of motion of the can body. That is, it has been discovered that an approximately 180° reverse bend in the feed tube provides the necessary centrifugal separation, reduces frictional losses at the bend, and provides better powder flow. It was.

Furthermore, it has been discovered that by directing the powder flow in a direction opposite to the direction of motion of the can body, variations in the weight of the powder bed along the sidewall joints are reduced.
At the leading end of the can there is a slight reduction in powder layer thickness, but this reduction is less than at the tail end which occurs when using a conventional applicator.

A conventional coating device other than the one described above for coating the inner surface of the side wall joint of a can body is disclosed in U.S. Pat. No. 3,526,027 (1970).
September 1, 1972) and No. 3678336 (July 18, 1972)
As shown in et al.

Description will be given below with reference to the accompanying drawings.

The can making machine 10 shown in Figure 1 may be of the conventional type, but in this case it is for making short tubular or cylindrical shaped can bodies with welded sidewall joints. be. A powder coater 11 is attached to the horn (mandrel) of the can manufacturing machine in the usual manner, and the powder coater 11 is mounted on a suitable holder 12.
, the holder 12 forming an extension of the horn;
Although it acts as a holder for a cylindrical can body, other external holders can also hold the can body.

A powder supply pipe 13 enters the holder 12 from its leading end, and the powder supply pipe 13 is suitably connected to a powder discharger 14 as shown in FIG. is entrained in a suitable carrier gas (which may be air). The powder accompanied by the carrier gas is conveyed through the holder 12 by the powder supply pipe 13 to the desired powder application location, as shown in FIG. The tip of the powder supply tube 13 is bent into an arc so that the direction of the tip of the tip is 180 degrees opposite to the main body of the powder supply tube 13, forming a reverse bend section 15 for centrifugation. There is.

The radius of curvature of the reversing bend 15 for centrifugation is determined based on the velocity of the powder entrained in the carrier gas so that the powder is forced outwardly towards the radially outer wall of the powder supply tube. It is being Therefore, the centrifugal force causes a layering effect of the powder, and the powder flows on the outer circumference side of the tube, and the carrier gas flows on the inner circumference side. In this way, the powder is separated from the carrier gas and becomes a dense stream.

The powder supply tube 13 ends in a nozzle 16 which has a body 17 with a hole 18 and a hole 18.
receives the tip of the powder supply tube 13 and opens into an orifice 20, the longitudinal axis of which is placed at a slight angle to the movement path of the can body;
Or placed parallel to this. The flow of powder is concentrated at a predetermined portion of the orifice 20, that is, at the lower part of the can body, and the orifice 20 is desirably flared toward the end, as shown in FIG.

The nozzle body 17 is attached to an inverted U-shaped holder 21 by a lateral pivot pin 22, and the holder 2
An adjusting screw 23 is attached to the center of the can body, and the adjusting screw 23 controls the tilting of the orifice 20, so that the orifice 20 is maintained at a desired angle with respect to the movement path of the can body. .

The can body B has a conveyor chain 2 having claws 25.
4 at intervals along the predetermined path and as it passes the nozzle 16, on the area of the inner side wall joint of each can body B, as shown diagrammatically.
A dense stream of powder is directed. The powder separated from the carrier gas and flowing along the outer periphery of the reverse bend 15 flows through a predetermined portion of the orifice 20, that is, the can body side, and is directly applied to the inner surface of the can body as a dense flow. Since the powder applied to the can body is not carried in large part by the carrier gas, it flows over the inside surface of the can body as if it were a liquid, thus causing little scattering and "spring warping".

Note that the carrier gas separated from the powder passes through the orifice 20 on the opposite side of the can, ie above the dense flow of powder. Therefore, the flow of powder is not disturbed. In addition, the carrier gas discharged outside the orifice 20 flows further backward in the transport direction of the can body than the powder applied to the can body, so that the applied powder can be prevented from scattering. In this way, the powder can be applied to the can body while being separated from the carrier gas, thereby preventing scattering of the powder and allowing the powder to be applied accurately to a defined position. Further, such an effect can be achieved by simply forming the reverse bending portion in the powder supply pipe as described above, so that the structure can be simplified and the cost can be reduced.

This purpose requires that the powder be electrostatically charged to keep the powder particles in place on the inside surface of the can until they are heated for fusing downstream of the can production line. Therefore, the holder 1 is placed downstream of the nozzle 16.
2 has an elongated groove 26 with a cross-sectional shape as shown in FIG.
is provided in the groove 26, and a set of elongated perforated plates 2 are provided in the groove 26.
7, 27 are placed, and the perforated plates 27, 27 are attached to the holder 12 and form a closure formed between a pair of brushes 28, 28 that contact the inner surface of the can body on both sides of the side wall joint. Forms both side walls of the chamber.

A large number of corona charging pins 30 placed in a row in the longitudinal direction protrude into the closed chamber, and the charging pins 3
0... serves to charge the powder particles placed in the closed chamber. The charging pins 30 are connected to a common DC high-voltage power supply via conducting wires 31, and a resistor 32 is placed between each pin 30 and the conducting wire 31 to equalize the current distribution to each charging pin.

The grooves 26 are of sufficient length, thus making it possible to sufficiently charge the powder particles introduced into the closed chamber, so that all the particles are attached to the inner surface of the can body B at the side wall joint. held along the area. The area of the sidewall joint is then heated in a conventional manner to fuse the powder particles to the can body, thus eliminating the presence of any powder particles that are not adhered to the interior surface of the can body;
There is therefore no residual powder particles that can later fall off and become contaminants in the food product or, in the case of aerosol containers, become foreign objects that block the dispensing mechanism.

The perforated plate 27 forms chambers 33, 33 on the outside of the closed chamber together with the holder 12, and the chambers 33, 33
communicates with a groove 34 made in the upper part of the holder 12, in which the conductor 31 and resistor 32 are placed, and the groove 34 is connected to a passage 35, as shown in FIG.
It communicates with chambers 33, 33 through.

A suitable gas (air) is introduced into the chambers 33, 33 via a sparge pipe 36, which also carries a conductor 37 for supplying electrical energy to the conductor 31.

The gas (air) that entered the groove 34 then enters the chamber 3.
3 and is diffused into the closed chamber via the plates 27, 27, the diffused gas serving to keep the side walls of the closed chamber and the charging pin 30 clean.

If desired, as shown in FIG. 1, a hopper 37 can be provided for receiving excess powder, the hopper 37 extending below the can body passage;
It is placed in a position where it can receive the powder discharged from the nozzle 16 through the can body. Inhaling air through the hopper 37 can help draw out suspended powder particles.

As mentioned above, the provision of reverse bends in the powder feed tube 13 and the directing of the powder flow in a direction opposite to the direction of movement of the product to be coated can also be used in other cases.

[Brief explanation of drawings]

Fig. 1 is an explanatory side view of a can manufacturing machine having a powder coating device of the present invention, Fig. 2 is an enlarged partial sectional view of the above-mentioned coating device, and Fig. 3 is a cross section taken along line 3-3 in Fig. 2. It is a diagram. 10...Can body making machine, 11...Powder coating machine, 12...
Holding body, 13... Powder supply pipe, 15... Reverse bending part for centrifugation, 16... Nozzle, 30... Orifice,
27... Porous plate, 28... Brush, 30... Charged pin,
B...Can body.

Claims (1)

[Scope of Claims] 1. A discharge nozzle having an orifice for discharging the powder as a flow, and a supply pipe for supplying the powder accompanied by the gas to the nozzle, and the supply pipe near the nozzle. The distal end of the distal end is bent into an arc so that the direction in which the distal end faces is opposite to the main body of the supply pipe to form a reverse bending part, and the powder is separated from the gas. A powder applicator having a reverse bend, the gas and the powder being supplied to the nozzle in separate layers, thus concentrating the powder in a predetermined portion of the nozzle and discharging it as a dense stream. 2. The powder coater according to claim 1, wherein the reverse bending portion extends over an arc of approximately 180°. 3. It is for applying a linear powder coating to the inner surface of a tubular body, and has a holding means for holding the tubular body so that it can move along the scheduled passage, and the supply pipe is connected to the scheduled passage. 2. A powder applicator as claimed in claim 1, having said reversing bend located within. 4 It is for applying a linear powder coating to the inner surface of a tubular body, and has a holding means for holding the tubular body so that it can move along the planned passage, and the orifice is arranged so that it can move along the passage. The powder coating device according to claim 1, wherein the powder coating device opens in a direction substantially opposite to the direction in which the tubular body moves. 5 It is for applying a strip-shaped powder coating to the inner surface of a tubular body, and has a holding means for holding the tubular body so that it can move along a planned path, and the holding means is located downstream of the nozzle. and sealing means contacting the inner surface of the tubular body on both sides of the part of the tubular body to be coated, said sealing means forming a confined area through which the discharged powder can flow. The powder coating device according to item 1. 6. The powder coating device according to claim 3, wherein the holding means is sized to receive a tubular body having a diameter of about 64 to 76 mm. 7. having means for supplying a diffusion gas into said confined area to keep the suspended powder particles in suspension;
A powder coater according to claim 5.