CA1102635A - Method of coating the interior surfaces of a hollow article - Google Patents
Method of coating the interior surfaces of a hollow articleInfo
- Publication number
- CA1102635A CA1102635A CA277,686A CA277686A CA1102635A CA 1102635 A CA1102635 A CA 1102635A CA 277686 A CA277686 A CA 277686A CA 1102635 A CA1102635 A CA 1102635A
- Authority
- CA
- Canada
- Prior art keywords
- deposit
- produce
- coating
- spraying
- sidewall
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
- B05D7/22—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to internal surfaces, e.g. of tubes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
- B05B13/00—Machines or plants for applying liquids or other fluent materials to surfaces of objects or other work by spraying, not covered by groups B05B1/00 - B05B11/00
- B05B13/06—Machines or plants for applying liquids or other fluent materials to surfaces of objects or other work by spraying, not covered by groups B05B1/00 - B05B11/00 specially designed for treating the inside of hollow bodies
- B05B13/0627—Arrangements of nozzles or spray heads specially adapted for treating the inside of hollow bodies
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Wood Science & Technology (AREA)
- Application Of Or Painting With Fluid Materials (AREA)
Abstract
ABSTRACT
Two spray coatings are successively applied, without an intervening curing step, to coat the inside surface of a shell for a two-piece can. This "wet-on-wet"
coating technique utilizes zone spraying, wherein only the sidewall is covered during the first application, with the second coat being applied to all inside surfaces.
Two spray coatings are successively applied, without an intervening curing step, to coat the inside surface of a shell for a two-piece can. This "wet-on-wet"
coating technique utilizes zone spraying, wherein only the sidewall is covered during the first application, with the second coat being applied to all inside surfaces.
Description
BACK(iROUND ` (~F' " 'r~lF~ :rNVl~`N'l':lON
Various techniques haye ln the past been employed to coat the i`nteriors of hollow articles and, more particularly, the shell or body of two--piece metal cans. Typically, such coatings are applied from a spray nozzle, which is positioned adjacent the open end of the can shell for delivery of the coating material thereinto. I~owever, the spray patterns of co.lventional spray nozzles are such that the resul-tant coatings tend to be nonuniform, thus requiring the over-spraying of certain areas of the can so as to provide a necessary minimum coating on ~ :
other areas. The problem is particularly acu-te in tlle case of can bodies made by drawing and ironing either tinp].ated or tin-frce steel and in-tended for ùse with carbonated beverages, since they require especially heavy, uniform, void-free coatings to prevent corrosion and product contamination.
While attampts have been made to improve upon the ~:
aforementioned spray pattern deficiencies (see for example, the spray nozzle described in United States pa-tent No. 3, 737,108), so far as is known no presently available nozzle provides a 2U spray pattern wnich is capa~le of uniformly covering, in a single :.
operation, the interior surfaces of a can body having one open and one closed end. Consequently, it has been found necessary to apply the spray coating i.n -two applications, with the initial coating being cured prior to the second spray applica-tion;
without such curing, the combined weigllts of the two coatings, as here-tofore applied, would cause them to run and sag, and to accumulate in the corners of the can.
Whil.e entirely satisfactory from the standpoiIlt of produciIlg good quality coatings within the can shell, sucll a "double coat" -techIlicfue i.s rather inefficient, ;n requiri.llg either two passes of tlle can shell through -the spraying and curiIlg apparatus, or a single _ass througll two spraying ~d curing ;~
~r q r~
stations. ~rhus, Lhe tcchnique is disadvantacJcous in Ihat it cntails hic31~ capita] expcllditures for ecluipmc?n-t, cxcessive pian-t spaee, energy, manpower and materials; moreover, the can she]ls are subjectc?d to possible abuse as a result of -the amount of handlillg wllich the double-coat process may invo]ve.
Accordingly, it is an object of this invention to provide a novel method for producing a relatively heavy, uniform and eontinuous eoating on the interior surfaces of ho]low ar-ticles.
It is also an object of the invention to provide such a me-thod wherein the effieieney of the eoating opera-tion is maximized.
~ nother object of the invention is to provide such a method wherein eapital expenditures, and rccllliremen-ts of spaee, energy, manpower and materials are minimized, withou-t saerifiee to the quali-ty of the eoating produecd.
A more speeifie object of the invention is to provide a novel method having the foregoing features and advantages, whieh method is partieularly benefieial for -the coating of ean shells fabrieated by drawing and ironing steel blanks.
SUMMARY OF THE INVENTION
It has IIOW been found that the foregoing and related objeets of the invention are readily attained in a method of eoating the interior surfaees of a hollow article, comprised OL
a siclewall having one end open and an end wall closing the opposite end thereof, which method includes two spraying s-tcps.
In aceordanee therewith, a lic~uid coating material is sprayed into the ar-tiele through the open end thcreof to produce one deposit -therewitllin, which is confined substan-tially to the cn-tire inside surface of the sidewall. ~nother deposi-t is produced within the article by spraying a lic~uid coating material therein-to throuc3h tlle open end thereof, so as to cover substan-tially the entire inside surface of both tlle sidewall and also the end wal].
Finally, the initi~1 solidificat~on of both of t-he deposits is simultaneously effected.
Preferably, the "onet' deposit is applied prior -to the "anotller" deposit, and the spraying steps are effected while the article is rotated about its lonyitudinal axis, most desirably at a rate of rotation of about 1000 to 3000 revolutions per minute.
It is hiyhly advan-tageous that the sprayin~ steps be of a duration of about 1 to 4 revolutions of the article, and that the temp~
eratures of tne coating rnaterial, as applied, be betwecn about 20 and 85 Celsius. Generally each of tile sprays will have a sector-shaped confiyuration, wherein the rates of material delivery will preferably vary from minimum values at the margins of the sector to a maximum value -therebetween, with the maximum value o~ material delivery occurring along a radius which lies at a point which is about 65 to 95 percent of the total arc distance .. ~, between the margins.
In the particularly preferred embodiments, the article ~ employed is the body or shell for a two-piece drawn and ironed ; ~ metal can, fabricated from steel and having a cylindrical side-wall. In such a method, the total weigh-ts of the coating material applied to produce the "one" deposit and the "another"
deposit are desirably within the ranges of about 120 to 200 milligrams and 80 to ]50 milligrams, respectively, with no more than about 10 percent of the total weight of the ma-terial applied to produce the "one" deposit being applied to the end wall of the body. Most advantageously, the combination of the "one"
~eposit and the "another"~deposit will produce a substantially uniEorm and void-free coating having an average distribution of from about 5 to 8 mil]igrams of coating material per square inch. Finally, the coating materials applied should have a viscosity of about 10 to 250 centipoises, and preferably about 15 to 50 centipoises, at the temperature of application.
,, , , ~ .:
~ '~
~2~35 BRIEE D~SCRIP'l'IO~ OF_TI~E D AWING
Figure 1 is a diagrammatical representation of the first spraying step of the method of thepresent invention, showing a spray nozzle and a can shell, -the shell being in cross section and disposed to receive coating material from the nozzle; and Fiyure 2 is a view similar to that of Figure 1, showing the second spraying step of the method.
: DETAILED DESCRIPTION_OF THE ILLUST~ATED EMBODIMENT
Turning now in detail to the appended drawing, therein shown are the two spraying steps of the novel method embodying the present invention. Referring to Figure 1, which illus-trates the spraying step which is preferably effected first, a hori-zontally disposed, open-ended can body or shell, generally ~ -~esignated by the number 10, comprised of a generally cylindrical sidewall 12 and an integral end wall 14, is rotated about its longitudinal axis (by means not shown). Ilhile the shell 10 :-is~rotated at least once, and preferably between one and four revolutions, a spray nozzle 18, positioned adjacent the open end of the shell 10, directs a spray of a liquid coating material into the open end of the can shell 10 to form a deposit which is confined substantially to the entire interior surface of the sidewall 12 of the shell 10.
Following the application of the first deposit, and ; while the shell 10 lS still rotating, a second spray (of similar duration to that of the first application) is applied over the still wet or uncured first deposit. As illustrated in Figure 2 the spray is directed into the open end of the can shell 10 from a second spray nozzle 18l to produce a second deposit which encompasses the entire interior surface of the shell 10 including both the sidewall 12 and also the end wall 14 thereof.
Finally, following the two spraying operations, the co-mingled "wet" coatings are cured, such as by subjecting the ~
sllell to elevated temperatures in all oven. It slloul.d be pointed out that, while there may be some casual drying of the coatings following each of the spray applications, there is no appreciable curing thereof prlor to their exposure to the oven. Accordinyly, their initial solidification may be regarded to be simultaneously effected, as a practical matter~ :~
For each of the spraying operations depicted in the figures the fan- or sector-shaped spray patterns of two preferred conventional spray nozzle orifices are illus-trated, that of the controlled-distribution nozzle, i.n full line AC, A'C', and of the drumhead nozzle, in phantom line AB, A'BI. The drumhead nozzle ;
orifice is designed to provide a fan-shaped spray pattern which has a maximum flow rate of coating material at (ideally) or closely adjacent one margin of the fan which decreases generally ~;
linearly to a point of minimum output at the other end or margin ::
of the fani the point of maximum flow is generally along a radius of the fan which is located at a point approximately 95 percent of the fan width or arc distance from one of the margins thereof : and 5 percent from the other maryin thereof. In contrast, the :20 controlled-distribution nozæle provides a fan-shaped pattern having a maximum rate of flow at a point approximately 75 percent of the distance from one end of the fan and 25 percent from its other end; again, the flow rate decreases generally linearly from the point of maximum flow to the poin-ts of minimum flow, at each margin of the spray fan. The orifice designs and distribution patterns ;^--~:~ of -these nozzles are more fully described and illustrated in United States patent No. 3,737,108.
Regardless of whether the drumhead or controlled-distribution nozzle is emplyed in the first spraying step (Figure 1), each nozzle is oriented, relative to the can shell 10, such that the radius of their spray fan defining the point of ma~imum flow output is directed at the corner 13 of the can .,1 ~.
shell; this generally compensates, al-though not perfectly, for the increased distance the spray must travel to reach -the corner 13. As a result of these nozzle orientations (mostly notably that of the controlled-dis-tribution nozzle), parts of their spray fan will be directed at the annular flat surface 15 o~ the end wall 14. Mowever, in nèi-ther case is there any appreciable coating accumulation on the end wall 14; generally, no more -than about lO percen-t of -the total weight of the coating material applied in the first step.
0 : FOI the second spraying step (Figure 2), if a drur;1llead ; ~ nozzle is employed, it is disposed relative to the she]:l lO, so as to produce a spray defined by margins A'B', which spray ex- ~
~ .
tends from the rim ll of the shell lO along the entire length of the sidewall 12 and onto the end wall 14 to a point sligh-tly beyond the center of the central dome or dimple 16 -thereof (to ensure its full coverage). Alterna-tively, if a con-trolled distribution nozzle is used, it is preferred that it be disposed ; ~ ralative to the can shell lO such that its spray A'C' extends beyond that of the drumhead pattern A~s~, encompassing the entire end wall 1~ as well as a portion of the opposite side of the ;~ ~ sidewall 12 adjacent the corner 13. As can be appreciated, this provides added coverage to the bottom portion of the sidewall, an area of the can shell 10~ which, regardless of whether the spray is directed at only the sidewall (i.e., AB or AC), or at the entire can interior (i.e., A'B' or A'C'), typically receives ; at least amount of spray coverage. Accordingly, a more uniform ~: ~ coating distribution is achieved.
Usually, each of the spraying steps will be completed in a single pass through a spraying machine. This may appropriately ~e accomplislled by feeding a multiplicity of uncoated can shells to successiv~ can~receiving pockets of a rotatable turret, which intermittently inde~es the shells to a first and - 6 ~
:
6~
th~n to a second spray sta-tion, whereat -they are rotated (such as by belts) while they receive the sprays from separ~te]y mounted nozæles. Thereafter, the coated shells are removed from the turret at a discharge station, Eor transfer -to an oven in whicll curing of the coa-t;.ngs is effected.
In such a machine, the cans are preferably coated at the rate of 150 to 325 per rninute, and are rotated at relatively high speeds, typically on the order of about 1000 to 3000 revolutions per minute, wi-th the duration of each of the spraying steps being in the range of about 50 to 120 milliseconds and ~ :
the duration between each of the spraying steps being in -the :
range of about 75 to 250 milliseconds. Generally,.the spray nozzles used will have a flow rate oE about 0.09 to 0.16 gallons of water per minute at a pressure of 500 pounds per square inch, and the coating materials will normally be applied ullder a hy-draulic pressure in the range of about 500 to 1200 pounds per square inch. Preferably, the first gun will apply a total weight ~ ;~
of 120 to 200 milligrams of coating material, with the second gun app~ying a total weight of about 80 to 150 milligrams, so as to achieve an average distribution of between about five and eigllt milligrams per square inch~over the entire interior surface of the shell.
Suitable coating materials for drawn and ironed container can shell fabricated from steel and intended for cax-bonated beverage use include~ among other types of resins, epoxies, acrylics, and polyesters. 'rhese materials are prefera~ly applied at a temperature within the range of about 20 to 85 Celsius, and they will normally have a viscosity in the range ::
of about 10 to 250 centipoises at the temperature of applicat;on;
preferably, they will exhibit viscosities of about 15 to 50 centipoises under the condition.
As a specific example~ a shell for a two~piece drawn ~ 7 _ i35 and ironed can, fabricated from -ti.np]atean~.having an outsi.de diameter of about two and eleven~sixteentlls;nches and a helc3ht of about four and thirteen-sixteenths inches, was coated in accordance with the instant method using two controlled- -distribution nozzles employed in apparatus of the sort previously described. The first gun, used to apply the "sidewa]l" coat, :
was oriented downwardly at an angle of about thir-ty-five degrees relative to the horizontally disposed can shell, and was positioned at a dlstance of about one and one-~uarter inches from the opening of the can shell with its orifice about one-half inch radially inward from the uppermost point of the can sidewall; its spray pa-ttern was about seven inches wide, i.e., from margin to margin, ;
measured at a poin-t ten inches frorn the nozzle. The second gun, used to apply the "ful]." coat, was oriented downwardly at an angle of about twenty~five degrees from t.he horizontal and :~ positioned at a distance of about one inch from the opening of : the can shell with its orifice about three-quarters of an inch radially inward from the uppermost point of the can sidewall;
its~:spray pattern was about ten inches wide, measured as described above. Each of the nozzles' flow rate was rated at 0.12 gallons .
per minute of water at 500 pounds per square inch and operated at a pressure o~ 800 pounds per square inch.
An epoxy-urea formaldehyde resin having a viscosity of:about 20 centipoises was applied by each spray gun at a tem- :
perature of about 52C. As the cans were rotated at about 180Q .
~ ~ revolutions per minute, each coating was applied for about 100 : ~ milliseconds, or for about two and one-half revolutions of the can sllell and the time between sprays was about 100 m.illiseconds.
The first gun applied a total of about 180 milligrams, which 3D provided an average distributi.on of about 5 milligrams per square ; inch on the in-teri.or surface of the side ~all and about 0.5 milligrams per square inch on the annular flat interior surface 15 ~2~i35 of the end wall 14. The second gun applied a total weiyht of ahout 120 milligrams, which provided an average dis-tribution of about
Various techniques haye ln the past been employed to coat the i`nteriors of hollow articles and, more particularly, the shell or body of two--piece metal cans. Typically, such coatings are applied from a spray nozzle, which is positioned adjacent the open end of the can shell for delivery of the coating material thereinto. I~owever, the spray patterns of co.lventional spray nozzles are such that the resul-tant coatings tend to be nonuniform, thus requiring the over-spraying of certain areas of the can so as to provide a necessary minimum coating on ~ :
other areas. The problem is particularly acu-te in tlle case of can bodies made by drawing and ironing either tinp].ated or tin-frce steel and in-tended for ùse with carbonated beverages, since they require especially heavy, uniform, void-free coatings to prevent corrosion and product contamination.
While attampts have been made to improve upon the ~:
aforementioned spray pattern deficiencies (see for example, the spray nozzle described in United States pa-tent No. 3, 737,108), so far as is known no presently available nozzle provides a 2U spray pattern wnich is capa~le of uniformly covering, in a single :.
operation, the interior surfaces of a can body having one open and one closed end. Consequently, it has been found necessary to apply the spray coating i.n -two applications, with the initial coating being cured prior to the second spray applica-tion;
without such curing, the combined weigllts of the two coatings, as here-tofore applied, would cause them to run and sag, and to accumulate in the corners of the can.
Whil.e entirely satisfactory from the standpoiIlt of produciIlg good quality coatings within the can shell, sucll a "double coat" -techIlicfue i.s rather inefficient, ;n requiri.llg either two passes of tlle can shell through -the spraying and curiIlg apparatus, or a single _ass througll two spraying ~d curing ;~
~r q r~
stations. ~rhus, Lhe tcchnique is disadvantacJcous in Ihat it cntails hic31~ capita] expcllditures for ecluipmc?n-t, cxcessive pian-t spaee, energy, manpower and materials; moreover, the can she]ls are subjectc?d to possible abuse as a result of -the amount of handlillg wllich the double-coat process may invo]ve.
Accordingly, it is an object of this invention to provide a novel method for producing a relatively heavy, uniform and eontinuous eoating on the interior surfaces of ho]low ar-ticles.
It is also an object of the invention to provide such a me-thod wherein the effieieney of the eoating opera-tion is maximized.
~ nother object of the invention is to provide such a method wherein eapital expenditures, and rccllliremen-ts of spaee, energy, manpower and materials are minimized, withou-t saerifiee to the quali-ty of the eoating produecd.
A more speeifie object of the invention is to provide a novel method having the foregoing features and advantages, whieh method is partieularly benefieial for -the coating of ean shells fabrieated by drawing and ironing steel blanks.
SUMMARY OF THE INVENTION
It has IIOW been found that the foregoing and related objeets of the invention are readily attained in a method of eoating the interior surfaees of a hollow article, comprised OL
a siclewall having one end open and an end wall closing the opposite end thereof, which method includes two spraying s-tcps.
In aceordanee therewith, a lic~uid coating material is sprayed into the ar-tiele through the open end thcreof to produce one deposit -therewitllin, which is confined substan-tially to the cn-tire inside surface of the sidewall. ~nother deposi-t is produced within the article by spraying a lic~uid coating material therein-to throuc3h tlle open end thereof, so as to cover substan-tially the entire inside surface of both tlle sidewall and also the end wal].
Finally, the initi~1 solidificat~on of both of t-he deposits is simultaneously effected.
Preferably, the "onet' deposit is applied prior -to the "anotller" deposit, and the spraying steps are effected while the article is rotated about its lonyitudinal axis, most desirably at a rate of rotation of about 1000 to 3000 revolutions per minute.
It is hiyhly advan-tageous that the sprayin~ steps be of a duration of about 1 to 4 revolutions of the article, and that the temp~
eratures of tne coating rnaterial, as applied, be betwecn about 20 and 85 Celsius. Generally each of tile sprays will have a sector-shaped confiyuration, wherein the rates of material delivery will preferably vary from minimum values at the margins of the sector to a maximum value -therebetween, with the maximum value o~ material delivery occurring along a radius which lies at a point which is about 65 to 95 percent of the total arc distance .. ~, between the margins.
In the particularly preferred embodiments, the article ~ employed is the body or shell for a two-piece drawn and ironed ; ~ metal can, fabricated from steel and having a cylindrical side-wall. In such a method, the total weigh-ts of the coating material applied to produce the "one" deposit and the "another"
deposit are desirably within the ranges of about 120 to 200 milligrams and 80 to ]50 milligrams, respectively, with no more than about 10 percent of the total weight of the ma-terial applied to produce the "one" deposit being applied to the end wall of the body. Most advantageously, the combination of the "one"
~eposit and the "another"~deposit will produce a substantially uniEorm and void-free coating having an average distribution of from about 5 to 8 mil]igrams of coating material per square inch. Finally, the coating materials applied should have a viscosity of about 10 to 250 centipoises, and preferably about 15 to 50 centipoises, at the temperature of application.
,, , , ~ .:
~ '~
~2~35 BRIEE D~SCRIP'l'IO~ OF_TI~E D AWING
Figure 1 is a diagrammatical representation of the first spraying step of the method of thepresent invention, showing a spray nozzle and a can shell, -the shell being in cross section and disposed to receive coating material from the nozzle; and Fiyure 2 is a view similar to that of Figure 1, showing the second spraying step of the method.
: DETAILED DESCRIPTION_OF THE ILLUST~ATED EMBODIMENT
Turning now in detail to the appended drawing, therein shown are the two spraying steps of the novel method embodying the present invention. Referring to Figure 1, which illus-trates the spraying step which is preferably effected first, a hori-zontally disposed, open-ended can body or shell, generally ~ -~esignated by the number 10, comprised of a generally cylindrical sidewall 12 and an integral end wall 14, is rotated about its longitudinal axis (by means not shown). Ilhile the shell 10 :-is~rotated at least once, and preferably between one and four revolutions, a spray nozzle 18, positioned adjacent the open end of the shell 10, directs a spray of a liquid coating material into the open end of the can shell 10 to form a deposit which is confined substantially to the entire interior surface of the sidewall 12 of the shell 10.
Following the application of the first deposit, and ; while the shell 10 lS still rotating, a second spray (of similar duration to that of the first application) is applied over the still wet or uncured first deposit. As illustrated in Figure 2 the spray is directed into the open end of the can shell 10 from a second spray nozzle 18l to produce a second deposit which encompasses the entire interior surface of the shell 10 including both the sidewall 12 and also the end wall 14 thereof.
Finally, following the two spraying operations, the co-mingled "wet" coatings are cured, such as by subjecting the ~
sllell to elevated temperatures in all oven. It slloul.d be pointed out that, while there may be some casual drying of the coatings following each of the spray applications, there is no appreciable curing thereof prlor to their exposure to the oven. Accordinyly, their initial solidification may be regarded to be simultaneously effected, as a practical matter~ :~
For each of the spraying operations depicted in the figures the fan- or sector-shaped spray patterns of two preferred conventional spray nozzle orifices are illus-trated, that of the controlled-distribution nozzle, i.n full line AC, A'C', and of the drumhead nozzle, in phantom line AB, A'BI. The drumhead nozzle ;
orifice is designed to provide a fan-shaped spray pattern which has a maximum flow rate of coating material at (ideally) or closely adjacent one margin of the fan which decreases generally ~;
linearly to a point of minimum output at the other end or margin ::
of the fani the point of maximum flow is generally along a radius of the fan which is located at a point approximately 95 percent of the fan width or arc distance from one of the margins thereof : and 5 percent from the other maryin thereof. In contrast, the :20 controlled-distribution nozæle provides a fan-shaped pattern having a maximum rate of flow at a point approximately 75 percent of the distance from one end of the fan and 25 percent from its other end; again, the flow rate decreases generally linearly from the point of maximum flow to the poin-ts of minimum flow, at each margin of the spray fan. The orifice designs and distribution patterns ;^--~:~ of -these nozzles are more fully described and illustrated in United States patent No. 3,737,108.
Regardless of whether the drumhead or controlled-distribution nozzle is emplyed in the first spraying step (Figure 1), each nozzle is oriented, relative to the can shell 10, such that the radius of their spray fan defining the point of ma~imum flow output is directed at the corner 13 of the can .,1 ~.
shell; this generally compensates, al-though not perfectly, for the increased distance the spray must travel to reach -the corner 13. As a result of these nozzle orientations (mostly notably that of the controlled-dis-tribution nozzle), parts of their spray fan will be directed at the annular flat surface 15 o~ the end wall 14. Mowever, in nèi-ther case is there any appreciable coating accumulation on the end wall 14; generally, no more -than about lO percen-t of -the total weight of the coating material applied in the first step.
0 : FOI the second spraying step (Figure 2), if a drur;1llead ; ~ nozzle is employed, it is disposed relative to the she]:l lO, so as to produce a spray defined by margins A'B', which spray ex- ~
~ .
tends from the rim ll of the shell lO along the entire length of the sidewall 12 and onto the end wall 14 to a point sligh-tly beyond the center of the central dome or dimple 16 -thereof (to ensure its full coverage). Alterna-tively, if a con-trolled distribution nozzle is used, it is preferred that it be disposed ; ~ ralative to the can shell lO such that its spray A'C' extends beyond that of the drumhead pattern A~s~, encompassing the entire end wall 1~ as well as a portion of the opposite side of the ;~ ~ sidewall 12 adjacent the corner 13. As can be appreciated, this provides added coverage to the bottom portion of the sidewall, an area of the can shell 10~ which, regardless of whether the spray is directed at only the sidewall (i.e., AB or AC), or at the entire can interior (i.e., A'B' or A'C'), typically receives ; at least amount of spray coverage. Accordingly, a more uniform ~: ~ coating distribution is achieved.
Usually, each of the spraying steps will be completed in a single pass through a spraying machine. This may appropriately ~e accomplislled by feeding a multiplicity of uncoated can shells to successiv~ can~receiving pockets of a rotatable turret, which intermittently inde~es the shells to a first and - 6 ~
:
6~
th~n to a second spray sta-tion, whereat -they are rotated (such as by belts) while they receive the sprays from separ~te]y mounted nozæles. Thereafter, the coated shells are removed from the turret at a discharge station, Eor transfer -to an oven in whicll curing of the coa-t;.ngs is effected.
In such a machine, the cans are preferably coated at the rate of 150 to 325 per rninute, and are rotated at relatively high speeds, typically on the order of about 1000 to 3000 revolutions per minute, wi-th the duration of each of the spraying steps being in the range of about 50 to 120 milliseconds and ~ :
the duration between each of the spraying steps being in -the :
range of about 75 to 250 milliseconds. Generally,.the spray nozzles used will have a flow rate oE about 0.09 to 0.16 gallons of water per minute at a pressure of 500 pounds per square inch, and the coating materials will normally be applied ullder a hy-draulic pressure in the range of about 500 to 1200 pounds per square inch. Preferably, the first gun will apply a total weight ~ ;~
of 120 to 200 milligrams of coating material, with the second gun app~ying a total weight of about 80 to 150 milligrams, so as to achieve an average distribution of between about five and eigllt milligrams per square inch~over the entire interior surface of the shell.
Suitable coating materials for drawn and ironed container can shell fabricated from steel and intended for cax-bonated beverage use include~ among other types of resins, epoxies, acrylics, and polyesters. 'rhese materials are prefera~ly applied at a temperature within the range of about 20 to 85 Celsius, and they will normally have a viscosity in the range ::
of about 10 to 250 centipoises at the temperature of applicat;on;
preferably, they will exhibit viscosities of about 15 to 50 centipoises under the condition.
As a specific example~ a shell for a two~piece drawn ~ 7 _ i35 and ironed can, fabricated from -ti.np]atean~.having an outsi.de diameter of about two and eleven~sixteentlls;nches and a helc3ht of about four and thirteen-sixteenths inches, was coated in accordance with the instant method using two controlled- -distribution nozzles employed in apparatus of the sort previously described. The first gun, used to apply the "sidewa]l" coat, :
was oriented downwardly at an angle of about thir-ty-five degrees relative to the horizontally disposed can shell, and was positioned at a dlstance of about one and one-~uarter inches from the opening of the can shell with its orifice about one-half inch radially inward from the uppermost point of the can sidewall; its spray pa-ttern was about seven inches wide, i.e., from margin to margin, ;
measured at a poin-t ten inches frorn the nozzle. The second gun, used to apply the "ful]." coat, was oriented downwardly at an angle of about twenty~five degrees from t.he horizontal and :~ positioned at a distance of about one inch from the opening of : the can shell with its orifice about three-quarters of an inch radially inward from the uppermost point of the can sidewall;
its~:spray pattern was about ten inches wide, measured as described above. Each of the nozzles' flow rate was rated at 0.12 gallons .
per minute of water at 500 pounds per square inch and operated at a pressure o~ 800 pounds per square inch.
An epoxy-urea formaldehyde resin having a viscosity of:about 20 centipoises was applied by each spray gun at a tem- :
perature of about 52C. As the cans were rotated at about 180Q .
~ ~ revolutions per minute, each coating was applied for about 100 : ~ milliseconds, or for about two and one-half revolutions of the can sllell and the time between sprays was about 100 m.illiseconds.
The first gun applied a total of about 180 milligrams, which 3D provided an average distributi.on of about 5 milligrams per square ; inch on the in-teri.or surface of the side ~all and about 0.5 milligrams per square inch on the annular flat interior surface 15 ~2~i35 of the end wall 14. The second gun applied a total weiyht of ahout 120 milligrams, which provided an average dis-tribution of about
2.5 milligrams per square inch on the sidewall, and about 7 milligrams per square inch and 7.5 milligrams per s~uare inch respectively, on the annular flat surEace 15 and the cenkral dome 16 of the end wall 1~; this resulted in a combined total weight for the two spray coatings of about 7.5 milligrarns per ~:
square inch for the entire interior surface of both the sidewall 12 and the end wall 14. The can shell was then baked at about :; :
216C for about two minutes.
.
While the instant.method has been described in relation .~
~`:
to the illustrated and preferred embodiment, it should be under- .
stood that modification may be made, as will be apparent to -those `
skilled in the art. For example~ while mcst advantageously the ~
. . .
"sidewall" coat is applied prior to the "full" coat, their order may be~reversed. It should also be mentioned that, although the .
fan-shaped spray patterns of nozzles having either a 75:25 or 95:5 flow distribution, are.preferred, the rnaximum rate of material delivery may occur along a radius which lies at a point which is about 65 to 95 percent of the total arc distance between the fan margins.
It should be pointed out that, although i.t is preferred that the time between sprays be relatively brief, i.e. 75 to :~ 250 milliseconds, considerably longer periods of time may be tolerated and, in fact, may be advantageous for certain applica~
tions. In addition, the coating materials applied in each spray need not necessarily be the same. Finally, it should be noted that, although the instant method is especially valuable for :~ coating the inside surface of one-piece cylind~ical shells or bodies Lor two-piece cans~ and particularly for such shells fa~ricated from either tinplated or tin~free steel and intended to bè filled with carbonated beverages, it may advantageously be _ g :, ~ .
. ' ' ~ . ' . ' ' ; ' ` ' ' ~ ` . '. ' ' ' ' ' ` .
square inch for the entire interior surface of both the sidewall 12 and the end wall 14. The can shell was then baked at about :; :
216C for about two minutes.
.
While the instant.method has been described in relation .~
~`:
to the illustrated and preferred embodiment, it should be under- .
stood that modification may be made, as will be apparent to -those `
skilled in the art. For example~ while mcst advantageously the ~
. . .
"sidewall" coat is applied prior to the "full" coat, their order may be~reversed. It should also be mentioned that, although the .
fan-shaped spray patterns of nozzles having either a 75:25 or 95:5 flow distribution, are.preferred, the rnaximum rate of material delivery may occur along a radius which lies at a point which is about 65 to 95 percent of the total arc distance between the fan margins.
It should be pointed out that, although i.t is preferred that the time between sprays be relatively brief, i.e. 75 to :~ 250 milliseconds, considerably longer periods of time may be tolerated and, in fact, may be advantageous for certain applica~
tions. In addition, the coating materials applied in each spray need not necessarily be the same. Finally, it should be noted that, although the instant method is especially valuable for :~ coating the inside surface of one-piece cylind~ical shells or bodies Lor two-piece cans~ and particularly for such shells fa~ricated from either tinplated or tin~free steel and intended to bè filled with carbonated beverages, it may advantageously be _ g :, ~ .
. ' ' ~ . ' . ' ' ; ' ` ' ' ~ ` . '. ' ' ' ' ' ` .
3~
cmployed for coating virtually ally hollow article having a closed end.
Thus it can be seen that the present invention provides a novel method for producing a uniform and continuous coating on the interior surfaces of hollow articles. In the rnethod, the efficiency of the coating operation is maxirnized, and capital expenditures and requirements of space, energy, manpower and materials are minimized, without sacrifice to the quality of the coating produced. In particular~ a novel method is provided having the foregoing features and advantages, which method is particularly beneficial for the coating of can shells fabricated : by drawing and lroning steel blanksA
~., ~ 30 ~.
- 10 - ;
cmployed for coating virtually ally hollow article having a closed end.
Thus it can be seen that the present invention provides a novel method for producing a uniform and continuous coating on the interior surfaces of hollow articles. In the rnethod, the efficiency of the coating operation is maxirnized, and capital expenditures and requirements of space, energy, manpower and materials are minimized, without sacrifice to the quality of the coating produced. In particular~ a novel method is provided having the foregoing features and advantages, which method is particularly beneficial for the coating of can shells fabricated : by drawing and lroning steel blanksA
~., ~ 30 ~.
- 10 - ;
Claims (25)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of coating the interior surfaces of a hollow article comprised of a sidewall having one end open and an end wall closing the opposite end thereof, comprising the steps of: spraying a liquid coating material into said article through said open end thereof to produce one deposit therewithin, said one deposit being confined substantially to the entire inside surface of said sidewall; spraying a liquid coating mater-ial into said article through said open end thereof to produce another deposit, said another deposit covering substantially the entire inside surface of both said sidewall and also said end wall; and simultaneously effecting the initial solidification of both of said deposits, said spraying steps effected while said article is rotated about its longitudinal axis, and the tempera-ture of the coating material as applied being between about 20°
and 85° Celsius.
and 85° Celsius.
2. The method of claim 1 wherein said one deposit is applied prior to said another deposit.
3. The method of claim 1 wherein the rate of rotation of said article is about 1000 to 3000 revolutions per minute.
4. The method of claim 3 wherein the duration of each of said spraying steps is about 1 to 4 revolutions of said article.
5. The method of claim 1 wherein the configuration of the spray employed in each of said spraying steps is sector-shaped.
6. The method of claim 5 wherein the rates of material delivery within each of said sector-shaped sprays vary from minimum values at the margins to a maximum value therebetween, said maximum value of material delivery occurring along a radius which lies at a point which is about 65 to 95 percent of the total arc distance between said margins.
7 The method of claim 1 wherein said sidewall of said article is generally cylindrical.
8. The method of claim 7 wherein said article is the body for a two-piece drawn-and-ironed metal can.
9. The method of claim 8 wherein said metal body is fabricated from steel.
10. A method of coating the interior surfaces of a one-piece body comprised of a generally cylindrical sidewall having one end open, and an end wall closing the opposite end thereof, said sidewall and end wall being integrally formed from a steel blank, comprising the steps of: spraying a liquid coating mater-ial into said article through said open end thereof to produce one deposit therewithin, said one deposit being confined substan-tially to the entire inside surface of said sidewall; spraying a liquid coating material into said article through said open end thereof to produce another deposit, said another deposit covering substantially the entire inside surface of both said sidewall and also said end wall, each of said spraying steps being effected for a period of about 1 to 4 revolutions of said can body, with said can body being rotated about its longitudinal axis at a rate of about 1000 to 3000 revolutions per minute, and with said coat-ing material at a temperature of about 20 to 85° Celsius; and simultaneously effecting the initial solidification of both said deposits.
11. The method of claim 10 wherein said one deposit is applied prior to said another deposit.
12. The method of claim 10 wherein the configuration of the spray employed in each of said spraying steps is sector-shaped.
13. The method of claim 12 wherein the rates of mater-ial delivery within each of said sector-shaped sprays vary from minimum values at the margins to a maximum value therebetween, said maximum value of material delivery occurring along a radius which lies at a point which is about 65 to 95 percent of the total arc distance between said margins.
14. The method of claim 10 wherein said coating mater-ials have a viscosity in the range of about 10 to 250 centipoises at the temperature of application.
15. The method of claim 10 wherein said coating mater-ials have a viscosity in the range of about 15 to 50 centipoises at the temperature of application.
16. The method of claim 10 wherein the total weight of the coating material applied to produce said one deposit and said another deposit is about 120 to 200 milligrams and 80 to 150 milligrams, respectively, and wherein no more than about 10 percent of the total weight of the material applied to produce said one deposit is deposited on said end wall of said body.
17. The method of claim 10 wherein said one deposit and said another deposit cooperatively produce a substantially uniform and void-free coating having an average weight distribu-tion of about five to eight milligrams per square inch.
18. A method of coating the interior surfaces of a hollow one-piece container comprised of a generally cylindrical sidewall having one end open, and an end wall closing the oppo-site end thereof, said sidewall and end wall being integrally formed from a thin steel blank, comprising the steps of spraying liquid coating material into said article through said open end thereof to produce one deposit therewithin, said one deposit being con-fined substantially to the entire inside surface of said side-wall and subsequently to produce another deposit, said another deposit covering primarily the entire inside surface of said end wall and the inside surface of said sidewall to produce a final deposit of substantially uniform thickness extending completely over said sidewall and said end wall, said spraying to produce each said deposit being effected for a period of about 1 to 4 revolutions of said container with said container being rotated about its longitudinal axis and with said coating material at a temperature of about 20° to 85° Celsius; and subsequently effect-ing the initial and concurrent solidification of both deposits to produce a substantially uniform void-free coating.
19. The method of claim 18 wherein said one deposit is applied just prior to said another deposit and both deposits are applied before effecting solidification of either.
20. The method of claim 18 wherein the configuration of the spraying pattern employed to produce each said deposit is sector-shaped.
21. The method of claim 19 wherein the rates of mater-ial delivery within said sector-shaped spraying patterns vary from minimum values at the margins to maximum values therebetween the maximum value of material delivery occurring along a radius which lies at a point which is about 65 to 95 percent of the total arc distance between said margins.
22. The method of claim 18 wherein said coating mater-ial has a viscosity in the range of about 10 to 250 centipoises at the temperature of application.
23. The method of claim 18 wherein said coating mater-ial has a viscosity in the range of about 15 to 50 centipoises at the temperature of application.
24. The method of claim 18 wherein the total weight of the coating material applied to produce said one deposit and said another deposit is about 120 to 200 milligrams and 80 to 150 milligrams respectively and wherein no more than about 10 percent of the total weight of the material applied to produce said one deposit is deposited on said end wall of said body.
25. The method of claim 18 wherein said one deposit and said another deposit cooperatively produce a substantially uniform and void-free coating having an average weight distribu-tion of about five to eight milligrams per square inch.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US71158076A | 1976-08-04 | 1976-08-04 | |
| US711,580 | 1976-08-04 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1102635A true CA1102635A (en) | 1981-06-09 |
Family
ID=24858648
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA277,686A Expired CA1102635A (en) | 1976-08-04 | 1977-05-04 | Method of coating the interior surfaces of a hollow article |
Country Status (3)
| Country | Link |
|---|---|
| CA (1) | CA1102635A (en) |
| GB (1) | GB1549487A (en) |
| IT (1) | IT1080088B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111822309A (en) * | 2019-04-23 | 2020-10-27 | 奥瑞金科技股份有限公司 | Two-piece can and processing method thereof |
-
1977
- 1977-05-04 CA CA277,686A patent/CA1102635A/en not_active Expired
- 1977-06-01 GB GB2315177A patent/GB1549487A/en not_active Expired
- 1977-08-04 IT IT5056777A patent/IT1080088B/en active
Also Published As
| Publication number | Publication date |
|---|---|
| GB1549487A (en) | 1979-08-08 |
| IT1080088B (en) | 1985-05-16 |
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