GB2028171A

GB2028171A - Powder applicator

Info

Publication number: GB2028171A
Application number: GB7928051A
Authority: GB
Original assignee: Continental Group Inc
Current assignee: Continental Group Inc
Priority date: 1978-08-23
Filing date: 1979-08-13
Publication date: 1980-03-05
Also published as: DE2933641A1; NL7906220A; GB2028171B; AR224630A1; BR7905416A; NO792719L; GR73507B; ES483561A1; FR2461529A1; FI792598A; SE7906817L

Abstract

A powder applicator for applying powder to form side stripes on the interior of can bodies B along side seams thereof includes a device for providing a layering effect on the gas-entrained powder so that although the powder is normally carried by the gaseous stream it is directed into an orifice 24 of a nozzle 21 as a dense stream with the carrier gas forming a separate layer. This separation takes place centrifugally in a loop 22 in the supply conduit 17. In addition, the applicator forms a seal with the interior of the can body to define a limited sealed area within which the powder may pass. This sealed area contains corona charging pins 41 which are arranged in a longitudinal line so that a maximum charging of the powder may be effected. Also, a diffused gas is directed into the sealed area to prevent the powder from clinging to the side walls of the sealed area and the charging pins. <IMAGE>

Description

SPECIFICATION Powder applicator This invention relates to a powder applicator, preferably the electrostatic application of a powder stripe to the interior of tubular bodies, along side seams of can bodies.

Can bodies, which have welded or soldered side seams, are normally formed from blanks which are coated on the interior surfaces thereof, but wherein the coating is omitted from the edges which are joined together to form the customary side seam. After the body blanks have been formed into tubular bodies and the side seams completed, it is necessary to coat the interior of the resultant bodies along the side seam to cover the uncoated metal.

Prior devices have been provided for internally side striping can bodies including U.S.

Patent No. 3,526,027 and No. 3,678,336.

In the past, during powder application of the side stripe, overspraying occurs which results in the powder being deposited away from the narrow area to positions where it is not wanted and where it is not cured. This uncured powder is loose powder particles being mixed with the product. Further, when the can bodies are utilized for non-food cans of the aerosol type, the loose powder particles may block the discharge nozzle of such containers.

In accordance with this invention, stray powder particles are minimized during application.

In particular the invention provides a powder applicator, comprising a discharge nozzle having an orifice for directing powder in a stream, a supply line for directing gas entrained powder towards said nozzle, a device in advance of said nozzle for de-entraining the powder and effecting the supplying of the gas and the powder in separate layers to said nozzle with the powder being concentrated in a preselected sector of said nozzle for effecting the discharging of the powder in a dense stream.

In the preferred embodiment, the gas entrained powder, immediately before the entrance into the discharge nozzle, is subjected to a centrifuging action so that it is separated from the gas carried and is directed into the orifice of the discharge nozzle in a dense stream occupying only that segment of the orifice which is adjacent the surface to which the powder is to be applied. By eliminating the spray action due to the carrying of the powder particles by the gas carrier, there is a concentration of the powder in a segment of the nozzle orifice so that the powder is di rected onto the side seam area in a dense stream.

Another feature of the invention is the seal ing off of a limited portion of the interior of the body being striped so as to confine the area where powder may acidentally flow.

The seaied-off area has a diffused gas directed therethrough through side walls thereof so that any bouncing particles are moved about by the pneumatic effect within the sealed area and are subjected to charging so as to be directed to the desired side seam area.

Excess powder which has not been sufficiently charged to adhere to the can body is moved by the diffused gas and thereafter remained under vacuum applied between adjacent bodies.

The nozzle is pivotally mounted so that the angle at which the powder stream strikes the body may be adjusted so as to minimize powder particle bounce.

In a further preferred embodiment the direction of powder flow is such that it opposes the direction of movement of the can bodies. By directing the powder stream in general opposition to the direction of movement of the can bodies, the film or powder weight variation along the side seam is less. There is a slight decrease in powder thickness at the "lead" edge of the can body, but the decrease in powder thickness is less than the "tail off" decrease using a conventional spray applicator.

In the accompanying drawings: Figure 1 is schematic side elevational view of a can line incorporating the powder applicator; Figure 2 is a fragmentary side elevational view of the powder applicator portion of the can line, with parts broken away and shown in section; Figure 3 is an enlarged transverse sectional view taken generally along the line 3-3 of Fig. 2.

Figure 4 is an enlarged fragmentary horizontal sectional view of the powder applicator in the vicinity of the nozzle.

Figure 5 is an enlarged fragmentary horizontal sectional view taken generally along the line 5-5 of Fig. 4; Figure 6 is an enlarged transverse sectional view taken along the line 6-6 of Fig. 2.

Figure 7 is a schematic side elevational view of a can line having incorporated therein a second embodiment of the powder appiica- tor; Figure 8 is an enlarged fragmentary longitudinal vertical sectional view taken through the powder applicator of Fig. 7; and Figure 9 is a transverse vertical sectional view taken generally along the line 9-9 Fig.

8.

Referring now to the drawings in detail, in Fig. 1 there is illustrated a can line, generally identified by the numeral 10. In the can line 10 flat body blanks are rolled into cylindrical form and the adjacent edges are secured together to define a longitudinal side seam.

The securing together of the body blank edges may be accomplished by welding or by soldering. In the illustrated embodiment of the invention, the bodies have welded side seams.

However, the invention is not so limited.

After the bodies, which are generally identified by the letter B, have been formed, they pass along a powder applicator which is the subject of this invention, the powder applicator being generally identified by the numeral 11. The powder applicator 11 is supported from and forms a continuation of the customary horn 12 of the can line 10.

Referring now to Fig. 2 in particular, the powder applicator 11 includes an elongated support, generally identified by the numeral 13, which carries the various components of the powder applicator and may, at the same time, function as a support for the can bodies which are to be internally side striped. The support 1 3 includes basically a lower support member 1 4 and an upper support member 1 5 which are separately formed and suitably joined together by fasteners (not shown). The exterior diameter of the support 13 is slightly less than the internal diameter of the can body B, there being a diametrical clearance of about 0.762mm. to 2.286mm.

The rear or left portion of the support 13, as viewed in Fig. 2, has an opening 1 6 extending longitudinally therethrough which is in communication with a like opening in the horn 12. Lines 1 7 and 1 8 extend through the opening 1 6. The line 1 7 is a powder supply line, while the line 1 8 is a combined gas supply line and electrical conduit receiver.

A relatively large opening 20 is formed in the support 1 3 with this opening extending .downwardly out of the lower support member 14, as is best shown in Figs. 2 and 4. In the opening 20 there is mounted both a nozzle, identified by the numeral 21, and a device 22 for effecting the separation of the powder from its gas carrier so that there is supplied to the nozzle 21 in a layer of powder and a layer of carrier gas.

A gas entrained powder supply is directed into the supply line 1 7 from a source 23 which is of a conventional construction. The carrier gas has entrained therein the powder particles with there being a thorough mixing of the two until the device 22 is reached.

Thereafter, the layer effect exists and the powder is directed into an orifice 24 of the nozzle 21 as a dense stream, the powder being in the lower part of the orifice 24 and the gas being in the upper part.

The device 22 functions as a centrifuge and basically is a 360' turn 25 in the supply tube 1 7. The shaped portion of the tube 1 7 is mounted within a support block 26 so as to maintain the configuration of the 360 turn 25. The support block 26, as is best shown in Fig. 5, tightly fits within the opening 20 and serves to stabilize the supply tube 17. The support block 26 is formed in two halves secured together by a fastener 27.

The nozzle 21 includes a block 22 having a bore 28 which receives the terminal end portion of the supply tube 1 7. The bore 27 opens into the orifice 24 which is of a slightly flaring construction.

The nozzle 21 is mounted within the opening 20 by means of a generally U-shaped cross sectional support block 30 which is mounted within the opening 20 in an inverted position, as is best shown in Fig. 3. The nozzle 21 is pivotally mounted relative to the support block 20 by means of a transverse pivot pin 31. The angle of the axis of the orifice 24 is adjusted by pivoting the nozzle 21 about the pin 31. The nozzle is retained in an adjusted position by means of a pair of set screws 32, 33 carried by the central portion of the support block 30 and bearing against the upper surface of the block 22.

Referring to Fig. 4, the nozzle 21 is positioned closely adjacent the interior surface of a can body B which is to be coated along the side seam thereof. A stream of powder flowing out of the orifice 24 along the lower segment thereof will flow as a dense stream directly onto the inner surface of the can body in the general pattern shown in Fig. 6.

Since the powder is directed onto the can body as a dense stream, there is little tendency for the powder particles to bounce as would occur in the past. Since the powder particles are not carried by the carrier gas, there is no tendency for the particles to flow, and adjacent particles prevent bounce.

By concentrating the powder in the area to be coated, the effect of machine vibration on the powder is minimized. Without this feature, the powder, which channels onto the wall of the delivery tube, would be caused to shift from side to side on the delivery tube by machine vibration and cause an uneven distribution of the powder on the can side seam.

With the powder so supplied, the can body could be heated to cause fusion of the powder to the can body. However, it is desired to provide effective control over all powder dispensed into a can body. Accordingly, the powder applicator 11 includes downstream of the nozzle 21 powder control apparatus.

Most specifically, the powder control apparatus includes a pair of longitudinally extending brushes 34 (Fig. 6) carried by the lower support half 14 and positioned to engage the interior of the can body on opposite sides of the area to which the powder stripe is applied.

The brushes 34 specifically define that portion on the interior of the can body subject to the application of powder. The width of the portion of the can body between the brushes 34 will not exceed the width of the can body which is heated sufficiently to effect powder bonding.

Between that portion of the lower support 14 carrying the brushes 34 there is a longitudinally extending opening 35 which opens out through the lower part of the support half 14, as is best shown in Fig. 6. Mounted within the opening 35 in downwardly diverging relation is a pair of porous blocks 36 which define side walls of a sealed chamber which is in part defined by the brushes 34 and in part by the lower part of the can body being side striped. These blocks 36 in conjunction with the support half 14 define in the outer parts of the opening 35 and chambers 37. The chambers 37 receive a suitable gas (air) under pressure with the gas being diffused through the blocks 36 into the sealed chamber. The purpose of this diffused gas supply within the sealed chamber will be described in more detail hereinafter.

The upper part of the support half 14 has a longitudinally extending opening 38 formed therein which is closed by the upper support half 15, as is best shown in Fig. 6. The tube 28 extends through an end wall portion 40 into the opening 38, as is best shown in Fig.

4, and supplies gas under pressure into the opening 38. Passages 41 extend down through the lower support half 14 from the opening 38 into the chamber 37 for supplying the gas thereto under pressure.

The lower support half 14 also carries a plurality of centrally located, longitudinally spaced corona charging pins 42 which project down into the sealed area as is also best shown in Fig. 6. The corona charging pins 42 are connected to a common feed wire 43 which, in turn, is connected to a wire 44 delivering a source of high voltage d.c. current. The feed wire 44 has insulating covering 45 and extends through the gas supply tube 18, as is clearly shown in Fig. 4.

A suitable resistor 46 is coupled in the circuitry to each corona charging pin 42 from the common feed wire 43 to the pin 42. The current distributing resistors minimize the tendency of any one corona chaarging pin to monopolize the charging current at the expense of any other pin's charging efficiency.

The corona charging pins function in the usual manner electrostatically to charge the powder by the ions generated at the pins. By having the pins within a confined sealed area, the corona charging pins are effective not only to charge the incoming powder, but also to add an additional charge to any powder particles which bounce without sticking.

The fluidizing action of the side walls of the sealed chamber through the blocks 36 also tend to keep the particles in suspension, preventing build-up on the walls of the sealed chamber and charging pins as well as allowing more time for the charging of powder particles.

Due to the very long length of the opening 37 and the longitudinal arrangement of the charging pins 42, there is allowed a relatively ling time for the charging of powder from the ions. generated at the corona charging pins.

The brushes 34 are formed of a dielectric material as are all parts of the powder applicator 11 with the exception of the charging pins, resistors and high voltage conductors.

The mechanical components can be formed of a suitable plastics material.

The can bodies B are moved along the powder applicator 11 in closely spaced relation, as is shown in Fig. 2. Preferably, movement of the can bodies is effected by a conveyor chain 47 which is part of the body maker 10 and have conveying dogs or fingers 48 thereon, as is best shown in Fig. 3.

The powder is delivered by the nozzle 21 in a continuous stream, and accordingly there is dispensing of the powder when no can body is in position. The small amount of powder which is not deposited is exhausted by the can bodies by a scavenging hood 50 which is mounted closely adjacent to the side seams of the can bodies, as is best shown in Fig. 1.

The scavenging hood has a profound affect on the distribution of the powder with the hood 50 tapering downwardly to provide for a uniform velocity along the length of the hood.

A suction is drawn by the hood 50 so as to draw loose powder out of the can bodies.

Although the powder applicator 11 has been illustrated as applying the powder stripe at the 6 o'clock position, the principles of the powder applicator can also be applied to cans having their side seams formed at the 1 2 o'clock position.

Referring once again to Fig. 2, there is schematically illustrated a heater for heating the can body in the side stripe area so as to effect the bonding of the applied powder to the can body. The heater 51 is conventional and is not a part per se of this invention.

By restricting powder overspraying and limiting powder to a confined area of the can body, not only can there be effected a more efficient side striping of the can body, but also the errant powder particles will all be bonded to the can body thereby eliminating powder particles which can become loose at a later time and form adulterants in foods or, in the case of aerosol cans, causing clogged valves.

While the powder applicator of Figs. 1-6 generally achieves these improvements in a powder applicator, a second embodiment of the powder applicator is shown in Figs. 7-9 which avoids a possible friction loss that may occur in the loop 22 providing the centrifuge action in the first embodiment. It has been found that the necessary centrifuge action required for many applications of the invention can be achieved utilizing only a reverse bend or turn in the supply line. Further, the reverse bend effectively reverses the direction of powder flow so that it opposes the direction of movement of the can bodies.

By directing the powder stream in general opposition to the direction of movement of the can bodies, the film or powder weight variation along the side seam is less. There is a slight decrease in powder thickness at the "lead" edge of the can body, but the decrease in powder thickness is less than the "tail off" decrease using a conventional spray applicator.

Referring now to Fig. 7, there is illustrated a can line 110 similar to can line 10 of Fig.

1. The can line 110 includes a powder applicator, generally identified by the numeral 111. The powder applicator 111 is generally similar to the powder applicator 11 of Fig. I and includes a suitable support, generally identified by tbe numeral 112, which forms a continuation of the horn and which may function as a support for can bodies, although the can bodies could equally as well be carried by external supports.

The support 11 2 has extending into the lead end thereof a powder supply line 11 3 which is suitably connected, as shown in Fig.

7, to a powder dispenser 11 4 wherein powder is entrained in a suitable carrier gas which may he air. The carrier gas entrained powder is directed through the spray tube 11 3 into the interior of the support through the can line 110 until it reaches a position adjacent the desired location of powder application, as is best shown in Fig. 8. The supply tube 1 13 is provided with a centrifuge section 11 5 in the form of a reverse bend which extends through an arc of about 180 .

The radius of curvature of the reverse bend which forms the centrifuge section 11 5 is such that when related to the velocity of the carrier gas entrained powder, the powder will be thrown outwardly against the radial outer wall of the tube, and thus there will be effected a layering or stratifying action with the powder becoming a dense stream separate and apart from the carrier gas.

The supply tube 113 terminates in a nozzle generally identified by the numeral 11 6. basically, the nozzle 11 6 is in the form of a block having a bore 118 opening through one face thereof and receiving the terminal end of the supply tube 113. The bore 118 opens into an orifice 1 20 which has a longitudinal axis selectively disposed at a slight angle to the path of movement of can body side seams or substantially parallel thereto. It is to be under stoop that the powder stream is concentrated in the lower part of the orifice 1 20 which is preferably of an expanded configuration as shown in Fig. 8.

The block 11 7 is mounted on an inverted U-shaped support 1 21 by means of a transverse pivot pin 122. The support 121 has adjustably mounted on the central portion thereof adjusting screws 1 23 through which the tilting of the orifice 1 20 is controlled, and the orifice 20 is maintained- in a selected angular relation with respect to the path of movement of can bodies.

As can bodies B, which are moved in spaced sequence along the predetermined path by a conveyor chain 1 24 having lugs 125, move past the nozzle 116, a dense stream of powder is directed onto the side seam area of each can body B as is diagrammatically shown. Since the powder is applied in a dense stream, and is for the most part not conveyed by the carrier gas, it flows onto the can bodies in the same general manner as a liquid with a minimum of overspray and powder particles bounce.

The powder particles are to be electrostatically charged so that they will remain in position on the interior surface of the can bodies as the can bodies pass further down the can line and are subjected to heating to a temperature which will effect fusing of the powder particles. To this end, downstream of the nozzle 116, the support 11 2 is provided with an elongated opening or channel 1 26 of a cross section best shown in Fig. 9. The channel 1 26 carries a pair of elongated plates 1 27 which define side walls of a sealed chamber defined between a pair of brushes 1 28 carried by the support 112 and internally engaging the can bodies on opposite sides of the side seam area.

The sealed area has projecting therethrough a longitudinal line of corona charging pins 1 30 which effectively charge the powder particles which have passed into the sealed area.

The corona charging pins 1 30 are connected to a common source of high voltage d.c.

current by a conductor 1 31 with there being a resistor 1 32 between each charging pin 130 and the conductor 131 so as to provide for uniform current distribution among the line of charging pins.

The channel 1 26 will be of sufficient length so as to permit an adequate charging of the powder particles disposed within the sealed area so that all of the particles will adhere to the interior surface of the can body B, preferably along the side seam area. The side seam area will later be heated in a conventional manner to effect fusing of the powder particles to the can body, thereby preventing the existence of any powder particle which is adhered to the interior of the can body whereby it may later become disengaged and become either a contaminant for food products or foreign matter which could plug the spray dispensing mechanism should the can body be part of an aerosol container.

The porous plates 1 27 define, together with the support 11 2, exteriorly of the sealed area chambers 1 33. The chambers 1 33 are disposed within a channel 1 34 in the upper part of the support 11 2 and carrying the conductor 131 and the resistors 132. The channel 1 34 opens into the chambers 133 through passages 135, as is shown in Fig. 9.

A suitable gas (air) is directed into the channel 1 34 through a spray tube 1 36 which extends through the body maker horn in the same manner as the spray tube 11 3. The tube 1 36 also carries a lead conductor 1 37 for supplying the electrical energy to the conductor 131.

The gas (air) entering into the channel 1 34 passes into the chambers 1 33 and through the plates 1 27 so that diffused air is directed into the sealed space. The diffused gas serves to keep clean the sides of the sealed chamber as well as the corona charging pins 1 30.

If desired, there may also be provided a hopper 1 37 for receiving excess powder. The hopper 1 37 will extend below the path of travel of the can body as shown in Fig. 1, and be positioned for receiving particles which exit from the nozzle 11 6 between can bodies. A vacuum may be drawing in the hopper 1 37 so as to aid in drawing out any loose powder particles which may exist.

The reverse bend in the supply tube 11 3 and the mounting of the nozzle 1 6 so as to direct a powder stream in opposition to the direction of movement of the articles being coated may be utilized in other environments.

Claims

1. A powder applicator including discharge nozzle having an orifice for directing powder in a stream, a supply line for directing gas entrained powder towards said nozzle, and a device in advance of said nozzle for deentraining the powder and effecting the supplying of the gas and the powder in separate layers to said nozzle with the powder being concentrated in a preselected sector of said nozzle for effecting the discharging of the powder in a dense stream.

2. The powder applicator of claim 1, wherein said device includes centrifuge means.

3. The powder applicator of claim 2, wherein said centrifuge means is in the form of at least a substantially 360 loop in said supply line.

4. The powder applicator of claim 2, wherein said centrifuge means is in the form of a reverse turn in said supply line which preferably extends through an arc of about 180 .

5. The powder applicator of claim 3 or 4, wherein said nozzle and said supply line including said loop or said reverse turn are disposed within said predetermined path.

6. The powder applicator of any of claims 1 to 5, including support means for determining a path of movement for article portions to be coated, said nozzle orifice having an axis disposed generally coextensive wirh but at an angle to said path, and said orifice sector being disposed adjacent said path.

7. The powder applicator of claim 6, wherein said support means is particularly adapted to support tubular bodies having a longitudinal side seam, and the longitudinal side seam is the article portion to be coated with the powder and the nozzle is mounted for applying powder as a stripe to said side seam.

8. The powder applicator of claim 6 or 7, wherein said orifice opens in the direction of article movement.

9. The powder applicator of claim 6 or 7, wherein the opening of said orifice faces generally in a direction opposing the movement of said tubular bodies along said predetermined path.

10. The powder applicator of claim 7, 8 or 9, wherein said support means carries sealing means downstream of said nozzle for engaging the interior of a tubular body on opposite sides of the portion of the body to be coated and forming a confined area within which discharged powder may flow.

11. The powder applicator of claim 10, including supply means providing diffused gas in said confined area for maintaining floating powder particles in suspension.

12. The powder applicator of claim 10 or 11, wherein said support means includes side walls formed of porous material partly defining said confined area, and said gas supply means is arranged to direct gas to said side walls.

1 3. The powder applicator of claim 10, 11 or 12, including corona charging pins projecting into said confined area in longitudinally spaced relation.

14. The powder applicator of any of claims 7 to 1 3 including powder recovery means adjacent the path of tubular bodies for recovering loose powder particles from between adjacent bodies prior to the fusing of said powder particles to said bodies.

1 5. A powder applicator for applying a stripe of powder to a tubular body side seam, said powder applicator including means for supporting tubular bodies for movement along a predetermined path, a nozzle mounted for applying powder as a stripe to the interior side seam of tubular bodies, said support means carrying sealing means downstream of said nozzle for engaging the interior of each tubular body on opposite sides of the portion to be coated and forming with each tubular body a confined area within which discharged powder may flow.

1 6. The powder applicator of claim 15, wherein said nozzle has an orifice for directing powder in a stream, said applicator including a supply line for directing gas entrained powder towards said nozzle, and centrifuge means in advance of said nozzle for de-entraining the powder and effecting the supplying of the gas and the powder in separate layers to said nozzle with the powder being concentrated in a preselected sector of said nozzle for effecting the discharging of the powder in a dense stream.

17. The powder applicator of claim 16, wherein said centrifuge means is in the form of at least a substantially 360 loop in said supply line.

18. The powder applicator of claim 17, wherein said nozzle orifice opens in the direction of movement of said tubular bodies along said predetermined path.

19. The powder applicator according to claim 16, wherein said centrifuge means is in the form of a reverse turn in said supply line which preferably extends through an arc of about 180'.

20. The powder applicator of claim 19, wherein the opening of said nozzle orifice faces generally in a direction opposing the movement of said tubular bodies along said predetermined path.

21. The powder applicator of any of claims 1 5 to 20, including corona charging pins projecting into said confined area in longitudinally spaced relation.

22. The powder applicator of any claims 15 to 21 including powder recovery means adjacent the path of tubular bodies for recovering loose powder particules from between adjacent bodies prior to the fusing of said powder particles to said bodies.

23. The powder applicator of any of the preceding claims, characterized by means pivotally mounting said nozzle for adjusting the angle of said orifice to an article being coated.

24. A powder applicator constructed substantially as herein described with reference to the embodiments shown in the accompanying drawings.