US3411217A

US3411217A - Method and apparatus for drying printed silk screened articles

Info

Publication number: US3411217A
Application number: US604720A
Authority: US
Inventors: Eugene J Daley
Original assignee: CINCINNATI PRINTING AND DRYING SYSTEMS Inc
Current assignee: CINCINNATI PRINTING AND DRYING SYSTEMS Inc
Priority date: 1966-12-27
Filing date: 1966-12-27
Publication date: 1968-11-19
Anticipated expiration: 1985-11-19

Description

E. J. DALEY Nov. 19, 1968 5 Sheets-Sheet 1 Filed Dec. 27. 1966 few/ace SW 3 Sheets-Sheet 2.

E. J. DALEY METHOD AND APPARATUS FOR DRYING PRINTED SILK SCREENED ARTICLES Nov. 19, 1968 Filed Dec.

Nov. 19, 1968 E. J. DALEY METHOD AND APPARATUS FOR DRYING PRINTED SILK SCREENED ARTICLES 3 Sheets-Sheet 5 Filed Dec. 27, 1966 INVENTOR. iz/d i/t f 2745/ BY anvil/16- United States Patent 3,411,217 METHOD AND APPARATUS FOR DRYING PRINTED SILK SCREENED ARTICLES Eugene J. Daley, Union Township, Clermont County,

Ohio, assiguor to Cincinnati Printing and Drying Systems, Inc., Cincinnati, Ohio, a corporation of Ohio Filed Dec. 27, 1966, Ser. No. 604,720 Claims. (Cl. 3413) ABSTRACT OF THE DISCLOSURE A silk screen drier machine having an insulated drying chamber separated by a perforated or orificed plate or base from a plenum chamber having a volumetric gradient constructed therein and in which a minimum temperature gradient for the drying medium is maintained, the medium being distributed at a uniform temperature throughout the drying chamber; means for ascertaining and means for regulating the temperature of the drying medium in the plenum chamber so that temperature in the drying chamber is critically controlled to prevent distortion of plastic articles on which printed indicia has been silk-screened and to properly dry, cure, or bake such indicia thereon at a temperature past which distortion would occur. Cooling means is provided to permanently condition the printed article; tilting features for stablely supporting the drying articles are provided in a conveying means for such articles.

Background of the invention Field of the inventi0n.The field of art to which the invention is most likely to pertain is generally located in the class of drying apparatus, and particularly, in driers utilized in the silk-screen industry. Class 34, Drying and Gas or Vapor Contact With Solids, United States Patent Office Classification, appears to be the applicable general area of art in which the claimed subject matter of the type involved here has been classified in the past.

Description 0 the prior art.-Driers designed for use in connection with the drying of articles is generally known. For example, US. Letters Patent #l,283,242 discloses a drier for articles made of clay. U.S. Letters Patent #1,305,599 discloses a drier utilized to dry vegetables. The drying machine disclosed in US. Letters Patent #2,297,318 dries cops, bobbins and the like utilized in the textile industry.

None of the drying art including other art in addition to the examples set forth in the last paragraph and of which applicant has knowledge and is disclosed in US. Letters Patent Nos. 1,450,235 and 2,295,475, has been helpful in solving problems in drying, baking or curing into a unified substance plastic articles having silk screened printed indicia thereon without distortion of either the article or appearance of the printed indicia thereon. This problem of distortion has not been solved by skill d adaptation of known drying devices thereto. Temperatures of the drying medium in known devices have not been critically controlled whereby such distortion is eliminated and proper drying, cure, or baking is effected, in connection with high production rates required in the industry.

Summary My invention solves the above problems by combining features into a drying apparatus by which temperature of the drying medium is controlled in the drying chamber by regulating the temperature thereof in a plenum chamber separated by a perforated plate from the drying chamber, so that production rate required of silk-screened articles is efficiently achieved. The following disclosed 3,411,217 Patented Nov. 19, 1968 novel combination of structural features also provides for uniform distribution of the drying medium in the drying chamber. Means may be additionally provided to exhaust solvent-ladened air in the event that solvents in inking materials utilized evaporate and are not to be returned to the drying cycle.

An object of this invention is to provide for a novel silk screen drying apparatus.

Another object of this invention is to provide for a uniform distribution of the drying medium into the drying chamber proper of the drying apparatus.

A further object of this invention is to provide for a minimum temperature gradient in a plenum chamber in a drying apparatus whereby control of a critical temperature throughout the entire drying chamber is efficiently and uniformly effected.

Another object of this invention is to provide for regulation of the temperature of a drying medium so that distortion of plastic articles silk-screened with printed indicia is eliminated and drying or curing or baking into one unitary substance is achieved.

These and other objects and advantages of the invention will become more apparent by a full reading of the following description, claims appended thereto, and the drawing comprising two sheets and being part of this disclosure.

Brief description of the drawing FIG. 1 is a longitudinal cross-sectional view of an apparatus embodying my invention;

FIG. 2 is a cross-sectional view taken on line 2-2 of FIG. 5 is a view of link means and mounted pegs thereon supporting an article while passing through the drier.

Description of the preferred embodiment Referring now to the drawing in which reference characters correspond to like numerals in the following description, 10 represents a drying machine embodying the invention.

Drier 10 comprises a housing 12, a drying chamber 14, a perforated or orificed plate or base 16 disposed adjacent to, and preferably below, drying chamber 14, and a plenum chamber 18 separated from chamber 14 by plate 16. A duct 20 is provided to connect a blower 22 to plenum chamber 18 at the latters one end through a specially-restricted neck 24. Heating means 26 for the drying medium is mounted in duct 20, between blower 22 and neck 24, and preferably positioned immediately adjacent to neck 24, heated air or other medium being utilized to dry printed material on articles conveyed through drying chamber 14.

Temperature-regulating means including thermocouples at 27 is suitably mounted on the plane of neck 24 for ascertaining and regulating the temperature or degree of heated air entering and in plenum chamber 18, although its location is not limited to such plane.

A feeding compartment 28 is mounted adjacent drying chamber 14 at the article ingress end 29 of drier 10 and serves the function of translation from an article-mounting station exterior of drier 10 to a drying chamber-entry station for a conveying means on which the articles are mounted. A cooling compartment 30 is disposed physically adjacent drying chamber 14 for accepting treated silk-creened articles to permanently condition them without distortion before egress out of end 32 of drier 10 at opening 34.

A conveying means 36 for conveying articles through drier is suitably mounted therein and extends continuously throughout drying chamber 14 and

compartments

28 and 30. Conveying means 36 comprises an endless link chain 38 (FIG 5) on which a plurality of rods or pegs 40 are securely mounted and extending therefrom in a direction towards the rear of drier 10.

Link chain 38 is supported in known manner by and on a series of spaced sprocket wheels 42 secured on suitable rotating shafts 44. Each of rotating shafts 44 is bearingly supported in ball-bearing elements 46, some of which are fixedly attached to the exterior of a wall 48 (FIG. 3) forming part of drying chamber 14, and extends therethrough into chamber 14, as shown in FIGS. 1 and 3. Additionally sprocket wheels 42 mounted on shafts and bearings similar to 44, 46 respectively, are provided for

compartments

28, 30. These sprocket wheels 42 are suitably mounted on the walls composing such compartments. All sprocket wheels 42 are suitably spaced at intervals on their respective walls to maintain proper translation of movement of conveying means 36 through drier 10. An opening 50 (FIG. 1) at entry station to drying chamber 14 connects feeding compartment 28 to drying chamber 14 at its top, and an opening 52 connects drying chamber 14 at its base to cooling compartment 30, the openings 50. 52 respectively providing for entry and exit of conveying means 36 into and from drying chamber 14.

Power or motive means (not shown) such as a motor, shaft and attachment in conventional manner to link chain 38 is provided for driving conveying means 36. Translation of conveying means 36 throughout drier 10 is clearly illustrated in FIG. 1. Fro-m an opening 56 in ingress end 29 and at a height at which articles are readily mounted on pegs 40 of conveying means 36 (FIG. 5) prior to entrance into opening 56, conveying means 36 translates into and through feeding compartment 28 into drying chamber 14 at opening 50, thence through drying chamber 14 into cooling compartment 30 through opening 52, followed by exit therefrom through opening 34 at egress end 32 of drier 10, again at a suitable height for removal of articles 58 (FIG. 5) from pegs 40. Conveying means 36 thence returns to ingress end 28 via a channel 60 within the framework of drier 10 after articles 58 have been removed from pegs 40. In the conveyor system 36, a conventional take-up sprocket 62 is interposed for adjusting the slack thereof.

The portion of the series of sprocket wheels 42 mounted in drying chamber 14 is divided into two vertical groups, as shown in FIG. 1, so that any one peg 40 in conveying means 36, in the latters translation through drying chamber 14, descends therein by alternatively directed, horizontally disposed paths between height-corresponding sprocket wheels 42 in the two vertical groups thereof. Consequently, as a silk-screened article 58 on a peg 40 is thrust into drying chamber 14 through opening 50, it proceeds across the length thereof and around a sprocket wheel 42 to the next lower horizontal level, then horizontally back towards ingress end 29 and around another sprocket wheel 42 to the next lower horizontal level, and so forth, until it passes parallel to and immediately above orificed plate 16 through which temperaturecontrolled air is coming. Immediately after last passing over place 16, conveying means 36, with an article 58 mounted and supported thereon, translates through opening 52 into cooling compartment 30. Cool air is drawn through a cleaning filter 72 mounted in the rear wall 74 of drier 10 by means of an exhaust means 76 mounted on top of cooling compartment 30 and by which heated printed article 58 is permanently conditioned before egress at opening 34.

A collection duct 80 for spent air is mounted atop drying chamber 14. Means such as a screen 82 is provided at the top of drying chamber 14 to form duct 80. An exhaust means (not shown) may be connected -to collection duct 80 in the event a closed cycling system is not desired, such as in the case of use of printing material having solvents therein.

Duct extends the length of drying chamber 14 and feeding compartment 28 although not in direct communication with compartment 28 (FIGS. 1 and 2). Duct 80 communicates with a pair of

ducts

84 and 86 each disposed to a side of feeding compartment 28.

Ducts

84, 86 communicate with the intakes of blower 22. Operation of

ducts

84, 86 is not required, of course, should an exhaust system be utilized in connection with duct 80.

As shown in FIG. 1, the vertical cross-sectional appearance of plenum chamber 18 illustrates construction of a volumetric gradient, measured along an axis disposed longitudinally of drier 10, thereby providing for a reduced volumetric space at its one end. By such a formation, transmission of heated air within and through out plenum chamber 18 at the same temperature is effected. In other words, the construction of planum chamber 18 includes a reduction of volumetric measurement towards its end opposing the end at which entrance means such as neck 24 is disposed, thereby increasing pressure progressively towards the reduced end and correspondingly maintaining the same temperature of the drying medium at the reduced end as at its larger end. Elimination of passage of cooler air and passage of hotter air at localized Zones along the length of plenum chamber 18 into drying chamber 14 is effected. Thus, the temperature of the drying medium is substantially uniform in drying chamber 14 as it is discharged from perforated plate 16.

Neck 24 is formed between duct 20 and the larger end of plenum chamber 18, said end being opposed to the end of plenum chamber 18 at which its volumetricallyreduced space is disposed. As th heated medium from heating means 26 passes from duct 20 into plenum chamber 18, an effective measurement of temperature of the drying medium is ascertained by a suitable thermocouple in means 27. Knowledge of this temperature provides the basis for regulating the critical temperature required in drying chamber 14 for proper conditioning of silkscreened articles 58. Suitable regulating controls are coupled to the thermocouple at means 27 to obtain such knowledge.

Heating means 26 includes electrical structure by which the variance of temperature values in the cycling system is minimized, for ease of control of the critical temperature required to properly condition silk-screened plastic articles 58. Preferably, heating means 26 comprises a 2- stage blast coil or coils each stage operatively functioning under certain temperature conditions in duct 20 to deliver the heated medium to plenum chamber 18. In initial operation of a cold drier 10, both stages may be set to function to obtain operating temperature in drier 10 in the shortest time possible. After operating temperature is reached, one stage including a high kilowatt-rated coil can be shut off automatically, with the second stage including a low kilowatt-rated coil continuing to function in order to maintain the operating temperature for the cycling system, and in particular, for plenum chamber 18 and drying chamber 14. In the event the operating temperature for the system rises over set maximum value, the low kilowatt-rated coil automatically ceases to function, but will function again should be operating temperature return to within the set maximum value. In the event the operating temperature falls below a set minimum value, the high kilowatt-rated coil automatically functions to return the reduced operating temperautre to its norm within the range of temperature values set into heating means 26.

Thus, a minimum temperature gradient for the heated medium in the cycling system, whether an open or closed system, is eificiently achieved, so that plastic articles 58 can be properly conditioned at a cricial temperature required therefor. An example of a heating means 26, known in the silk-screening industry, is a 2-stage blast coil, the coils being made of thin tubular stock, with amperage dependent upon the values of voltage and power required for a particular drier application (size and production rate).

The walls and sides of drier and its various chambers, compartments, ducts, and channels are constructed in accordance with the skills required in sheet metal construction work. Insulation 90 is provided throughout the thickness of the walls forming drier 10 and drying chamber 14, as clearly shown in FIGS. 1-4.

Preferably, drying chamber 14 and compartments 28,

' 30 are tilted in their front and rearwalls 48, 49 (FIG. 3)

held perpendicular to rotatable shaft 44. This provides not only for ease and facilitation of incorporation of a tilt in conveying means 36, preferably 3 to the vertical, and by which articles 58 do not slip off their respective pegs 40 supporting them as means 36 translates through machine 10, but also provides for substantially a constant measure of volume in drying chamber 14 through which the heated drying medium is evenly distributed at a uniform temperature.

A short description of the cycling system for the drying medium follows. Blower 22, operated by rotation of its shaft 78 (FIG. 2) connected to a suitable source of power such as a motor (not shown), pulls air into duct 20 through opening 56, in the case of an open system, and also from return ducts 84 and 86 (FIG. 2) disposed to each side of and isolated from feeding compartment 28, in the case of a closed system. Such medium is heated and its temperature efficiently controlled by heating means 26 and its temperature measured by the thermocouple at means 27. The heated medium jets through orificed or perforated plate 16 in a uniformly distributed and evenlytemperatured manner. The medium rises in drying chamber 14 and is expelled through screen 82 into collection duct 80, in communication with

return ducts

84 and 86 of a closed system, or through an exhaust system (not shown) for an open system.

A short description of the operation of drier 10 follows, and reference to the description heretofore should be made for a more fuller knowledge thereof if necessary, and it is to be understood that what is expressed hereinafter is part of the disclosure of making and using the subject matter of the invention where it may not be explicitly disclosed heretofore. Articles 58, such as polyethylene tubes having printed indicia silk-screened thereon, are mounted on pegs 40, after which conveying means 36 is driven to translate through drier 10. Articles 58 pass through opening 56 into feeding compartment 28 to elevated opening 50 and into drying chamber 14. As articles 58 descend in drying chamber 14, they are exposed to the drying medium at a uniform temperature. This temperature controls the state of the plastic material and the printing material drying, curing, or baking thereupon. For example, in the case of polyethylene plastic, at 190 F. the material begins to melt, and consequently, would distort the shape or form of article 58 out of which it is made should the temperature continue to increase. However, at 190 F. the printing material silk-screened onto article 58 begins to fuse with the plastic material of article 58. In drier 10, by the time articles 58 reach opening 52, the critical temperature of 190 F. has been imposed upon or reached in the article and print material and at which the two are capable of fusing into one substance. Distortion of the plastic and print material is eliminated at this point by immediately exposing or subjecting the printed articles to cooling chamber 30 and articles 58 are permanently conditioned therein without distortion and temperature thereof is reduced to a lower or room temperature by exposure in cooling compartment 30 before egress of drier 10 at waist-high opening 34. They are then removed from their respective pegs 40 while conveying means 36 runs endlessly back to ingress side 29 of drier 10 via channel 60.

The temperature of the drying medium entering drying chamber 14 from plenum chamber 18 can be ascertained and controlled by regulation of the temperature of the drying medium in plenum chamber 18. Such-regulation is accomplished by the means at 27. Consequently, the critical temperature of F. above which the plasticity of articles 58 would begin to soften and distort the shape of articles 58 can be maintained in drying chamber 14. The immediate cooling of printed articles 58 then effects a cure or drying of the printed indicia therein, and the articles are permanently conditioned for normal use.

Pursuant to the requirements of the patent statutes, the principle of this invention has been explained and exemplified in a manner so that it can be readily practiced by those skilled in the art to which it pertains, or with which it is most nearly connected, such exemplification including what is presently considered the best embodiment of the invention. However, it should be clearly understood that the above description and illustrations are not intended to unduly limit the scope of the appended claims, but that therefrom the invention may be practiced otherwise than as specifically described and exemplified herein, by those skilled in the art, and having the benefit of this disclosure.

Therefore, what I claim as patentably novel is:

1. In an apparatus for drying and permanently conditioning plastic articles on which silk-screened indicia has been printed, said apparatus including a drying chamber through which a heated drying medium is uniformly distributed, means mounted in and out of said apparatus for conveying such articles through said apparatus, the combination therewith of:

a plenum chamber,

a perforated plate connecting said plenum chamber to said drying chamber,

means for cycling a drying medium to said plenum chamber for direct discharge into said drying chamber,

means for heating the drying medium disposed adjacent said plenum chamber,

means for ascertaining and controlling the temperature of the drying medium in the plenum chamber whereby temperature in the drying chmaber is critically controlled with respect to the plastic articles, and

a cooling compartment into which the silk-screened plastic articles are immediately conveyed from said drying chamber at the critical heated temperature above which distortion of the plastic articles occurs and at which the silk-screen material making up the indicia and the plastic of the articles fuse into one substance, said articles being permanently conditioned for use at normal temperatures upon removal from said cooling compartment.

2. The method of drying a silk-screened plastic article comprising the steps of:

mounting the undried silk-screened plastic article on conveying means,

feeding the conveying means and article into a drying chamber, heating a medium for drying such article, cycling the heated medium into a plenum chamber, discharging the heated medium from the plenum chamber into the drying chamber, the heated medium being uniformly distributed in the drying chamber,

critically controlling the temperature of the heated medium in the drying chamber to prevent distortion of the plastic article and to fuse the plastic of the article and silk-screened material thereon into one substance, and

removing the critically heated article from the drying chamber at the critical temperature above which the plastic article distorts.

3. The method of claim 2 including the additional step of cooling the critically heated article upon its removal from the drying chamber to permanently condition the silk-screened article.

4. The combination of claim 1 in which said plenum chamber includes in its construction a volumetricallygraded measurement from one of its longitudinal ends to the other so that a minimum temperature gradient for the drying medium in said plenum chamber is effected and the temperature of the drying medium being discharged from such a plenum chamber into said drying chamber is uniform.

5. In a dried apparatus including a drying chamber, a plenum chamber connected to said drying chamber, means for conveying articles-to-be-dried mounted therein, and a drying medium cycling system including means for driving the medium through the plenum chamber and the drying chamber, the combination therewith of:

a perforated plate between said plenum chamber and said drying chamber and through which the heated medium passes from said plenum chamber into said drying chamber,

said plenum chamber including in its construction a volumetrically-graded measurement from one of its longitudinal ends to the other so that a minimum temperature gradient for the drying medium in said plenum chamber is effected and the temperature of the drying medium being discharged from said plenum chamber into said drying chamber is uniform,

a conduit connecting said driving means to said plenum chamber for cycling said drying medium to said plenum chamber,

heating means mounted in said conduit between said driving means and plenum chamber,

means for regulating the temperature of the drying medium in the plenum chamber,

the temperature of the drying medium in said drying chamber being controlled upon regulation of the temperature of the medium in said plenum chamber, to efficiently effect drying of the articles being conveyed therethrough, and

a cooling compartment associated in physical proximity with said drying chamber and into which the heated articles are conveyed immediately from the drying chamber, for permanently conditioning the articles.

References Cited UNITED STATES PATENTS 2,440,648 4/1948 Walter et al. 34159 3,112,692 12/1963 Cookson 11040 XR 3,182,589 5/1965 Green et a1 34-105 XR 3,273,498 9/1966 Martin 101416 XR 3,318,018 5/1967 Steele et al 3462 KENNETH W. SPRAGUE, Primary Examiner.