US 3685442 A
An offset silk screening method and apparatus, wherein a continuous screen is the periphery of a rotary head, and wherein ink is forced through image areas of said periphery onto a soft elastomeric roller positioned for tangential contact with said peripherally mounted screen. The image picked up by the soft elastomeric roller is transferred to a work piece delivered to said soft roller, said work piece possibly including irregular surfaces which still take such image. The improved rotary head includes means to reposition the squeegee assembly to change the pressure against the screen, and further including means to change the radial angle of the squeegee assembly relative to the axis of the head.
Description (OCR text may contain errors)
United States Patent [451 Aug. 22, 1972 Harwell, Jr.
 ROTARY OFFSET SILK SCREENING APPARATUS WITH SQUEEGEE ADJUSTMENTS  lnyentor: Roy M. Harwell, Jr., 747 St.
Michaels Lane, Gastonia, NC. 28052 22 Filed: 0a.20, 1 969  Appl. No.: 867,737
 US. Cl ..l0l/ll9, 101/35  Int. Cl. .1 ..B4ll 13/04  Field of Search....lOl/35, 37, 36, 120, 154, 119,
3,155,034 11/1964 Reinke ..l01/l20 3,272,118 9/1966 Ackley 101/37 3,276,358 10/1966 Lusher ..101/35 X 3,425,343 2/ 1969 Jaeger ..101/36 FOREIGN PATENTS OR APPLICATIONS 546,309 7/ 1942 England ..101/426 482,642 4/ 1938 Great Britain ..101/35 Primary Examiner-Robert E. Pulfrey Assistant Examiner-R. E. Suter Attorney-Dominik, Knechtel & Godula  ABSTRACT An offset silk screening method and apparatus, wherein a continuous screen is the periphery of a rotary head, and wherein ink is forced through image areas of said periphery onto a soft elastomeric roller positioned for tangential contact with said peripherally mounted screen. The image picked up by the soft elastomeric roller is transferred to a work piece delivered to said soft roller, said work piece possibly including irregular surfaces which still take such image. The improved rotary head includes means to reposition the squeegee assembly to change the pressure against the screen, and further including means to change the radial angle of the squeegee assembly relative to the axis of the head.
4 Claims, 7 Drawing Figures PATENTEDAUEZZ m2 SHEET 1 BF 3 FIG. 1
INVENTOR Roy M Harwell, Jr. BY
PATENTEDwszz 1912 saw 2 or 3 (I) Q INVENTOR M Harwell, J
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PATENTEU I97? 3,685,442
SHEET 3 BF 3 INVENTOF? Roy M. Harwe/l, Jr
ROTARY OFFSET SILK SCREENING APPARATUS WITH SQUEEGEE ADJUSTMEN'IS This invention relates to an offset silk screening apparatus and method, as well as an improved rotary head which may be advantageously utilized with such offset and other silk screen printing.
The technique of silk screen printing is widely recognized, and such technique includes applying printing ink to a thin silk screen which has pervious image areas, the ink being forced through said screen, generally by a squeegee assembly. The ink which passes through this screen is applied to a work piece which may be a textile material, or various image receiving surfaces. The work pieces which have received such images find widespread use in industry. Various types of silk screens have been used including flat screens and cylindrical screens mounted on a drum. in the drum embodiment, a squeegee assembly is interiorly mounted and accessible means are provided for introducing ink into the drum so that the squeegee may force the ink through the image areas of the screen. Screens for such drums are commonly electroformed as continuous webs which are then variously mounted to drum parts, as by bonding, staking, press fitting, encircling the screen with a flat rubber gasket, and the like.
Such rotary screens can be used to advantage in transferring printed images to cylindrical surfaces, for example. A shortcoming of such rotary screen, as well as flat screens, is that work pieces having irregular conformations are not adaptable to such printing, or are poorly adaptable thereto. Work pieces with irregular transverse cross sections, such as dishes, are not easily printed. In some instances, it is impossible to print such work pieces by the silk screening process.
It is understandable that it would be desirable to utilize the rotary form of the silk screen head to better advantage in printing, particularly in printing work pieces of irregular conformations. Rotary silk screening heads of this type have the squeegee assembly interiorly mounted, and it is desirable to adjust the pressure of such squeegee head against the periphery of the drum, that is, against the continuous silk screen mounted along the peripheral surface of the drum. It is understandable that it would be desirable to provide new constructions of such drum heads wherein the peripherally mounted screen may be efficiently contacted by the squeegee assembly mounted therein. It will further be understood that it is desirable to provide new and efficient means for adjusting the pressure of the squeegee assembly within such head, particularly, in a linear radial path between the axis of the drum and the periphery thereof. It is further desirable to provide means for efficiently and surely adjusting the angular position of the squeegee assembly within the drum. Such angular position is an alternative radial position of the squeegee assembly, that is, another radial position between the axis and the periphery of the drum.
Versatility of printing apparatus leads to readily appreciated advantages in that economic advantages are realized from quickly adapting a particular printing apparatus to various, distinct printing operations. In this respect, it has been discovered that a rotary silk screening member may be combined with a tangentially placed soft, elastomeric roller so that ofiset printing may be accomplished. Such an offset silk screening apparatus and method can be made a further attraction if it can be quickly and effectively converted to conventional gravure printing. The silk screen ofiset printing approach is most advantageously used with longitudinal work pieces in that the elastomeric roller may contact the surface of the longitudinal work piece along portions of its circumferential surface, or multiples thereof.
In view of the foregoing it is one principal object of the invention to provide a method and apparatus to realize important advantages from combining rotary screen printing with offset printing, particularly, by utilizing a soft, elastomeric cylindrical transfer roller to pick up an image from the rotary silk screen and to transfer such image to a work piece. As an example, the silk screen offset printing process permits desired printing patterns such as simulated wood representations to be printed onto metallic strips of indefinite length. In a similar manner, metallic or even cloth ribbon can be printed or decorated. Additionally, panels such as those employed in the interior portions of refrigerators, control panels or continuous webs on appliances, and a wide variety of other metallic strips can be uniformly printed or decorated with an apparatus and by the method to be disclosed. Likewise, recognized fixtures may be employed to print tubes, bottles, and similar cylindrical surfaces.
Another important object of the present invention is to permit the printing of indefinite lengths of material with an economical type of screen pattern member, as distinguished from the more expensive gravure metallic plates. It is a related object of the invention, however, to allow alternative use of gravure type printing members with the apparatus disclosed herein. The versatility which allows a choice of alternative printing methods leads to a readily appreciated economy and reduced inventory of equipment which would otherwise be required by a manufacturer in order to print a wide variety of decorated strips.
A more particular and important object of the present invention is to provide a screen carrying drum for transferring an image to a soft elastomeric roller, and effecting such transfer by an interiorly mounted squeegee assembly in which the pressure can be varied against the screen in the course of operation or for particular operations. Such pressure adjustment being effected quickly and surely to adjust said pressure for a particular job undergoing printing.
It is yet another important particular object of the invention to provide a quick and reliable detachment means by which a printing machine can have its screened drums changed from one pattern to another in a relatively short time.
A still another particular important object of the present invention is to provide and improved rotary silk screening printing head in which an interiorly mounted squeegee assembly may be selectively adjusted to either change its angular contact with the peripheral screen or its pressure against said screen.
Further objects and advantages of the present method and apparatus will become apparent as the following description of an illustrative embodiment procedes, taken together with the accompanied drawings, in which:
v mounted screen on the head, shown on an enlarged scale, and with parts removed;
FIG; 3 is a side elevational view, on an enlarged scale, of the rotary head mounted on the offset silk screening apparatus shown in FIG. 1;
FIG. 4 is a sectional view along line 44 of FIG. 3; FIG. 5 is a side ,elevational view of a squeegee aspressure of. the squeegee against the peripherally mounted screen on the rotary head; FIG. 6 is a perspective view of the cam member which is operatively disposed in the view of FIG. 5; and
FIG. 7 is a perspective view of the squeegee assembly mounting ring shown operatively disposed in the view of FIG.'5. e
Referring now to the drawings, the silk screen'offset printing apparatus 2 includes a machine housing to which is afiixed a work piece support 4 having work piece guides 6,6 on the top surface thereof. A conveyor roller 8 is shown mounted within the support for moving a work piece to a printing area of the apparatus. The silk screen offset apparatus is shown as including a vertically adjustable jack l0 forselectively lowering or raising the support 4.
The apparatus is shown as being provided with an inking assembly 12 which may be optionally used with a gravure roller in the conventional manner. Such an assembly includes an ink tray 14 and a gravure inking roller 16. A bladeassembly l 8'is shown for removing ink from a conventional gravure roller, which is not shown in the. present embodiment. An accessory mounting support is shown on the machine housing, the mounting support 20 being provided for mounting additional rollers or other accessories as may be required by the operator.
The apparatus includes a soft elastomeric roller 22 which is rotatably mounted on a shaft assembly 24. A blade 26 is shown positioned to engage the roller 22 for removing excess ink or the picked-up image on the rollerfollowing a printing operation. A catch tray 28 is shown positioned below the blade. v
The apparatus has a rotary screen head shown generally as 30 which is characterized by particular advantages for the present offset silk screening process, as well as for conventional rotary drum screening. The head is mounted on a driving shaft 32 conventionally rotated by motor means, which are not shown. A stationary cover plate 34 is mounted on the shaft, and such plate has a slotted extension 36 which is positioned overelastomeric roller shaft 24. The shaft 32 of the rotary head has a bearing ring 38 which is held in place by a bearing ring fastener 40. The cover plate 34 is generally circular, but does have a plate cut out 42 to provide access for printing inks inside the drum.
The view of FIG. 2 shows the drum of the rotary head removed from the shaft. A continuous silk screen 44is mounted along the periphery of the drum, and such screen has pervious image areas 46 through which the ink is forced in the printing'operation. The opposite edges of the screen are secured to parts of the drum, as
sembly mounted to a cam member for adjusting the The parts to which the screen 44 is mounted are a circular driving plate 48 positioned inwardly on the shaft 32, said plate being provided with a boss 50 hav-' ing a set screw 52 for engaging said plate to the rotating shaft 32. The other edge of the screen is secured to a screen mounting collar 54 which is further provided with a continuous flange 56. The cover plate is shown provided with rollers 58 which supportingly engage said flange, and roller bolt assemblies 60 attach the rollers to the cover plate. The rollers may be omitted in some embodiments having shorter screens in smaller diameter heads.
The bearing ring 38 is shown positioning plate bearings 62 around shaft 32. The cover plate is flanked on the shaft by an axially positionable locking ring 64 which is fixed to the shaft by said screw 66; and by another axially positionable locking ring 68 placed interiorly of cover plate 34 and also affixed to shaft 32 by a set screw 70.
An eccentric cam assembly shown generally as 72 is mounted on the shaft 32 within the head 30. The eccentric cam assembly includes a rotatable cam member 74 having a cam surface 76 characterized by a high surface 76a and a low surface 76b. The cam member 74 has a shaft passageway or inner cam surface 77 which may be provided with bearings 78 to contactfshaft 32.
The cam member 74 is shown with an extending arm 80 which is mounted to one end of the cam member 74. The arm extends in a plane which is normal to the axis of the cam member, and such arm has a handle 84 at its terminating end which extends normal to the plane of the arm 80..The handle is movably secured to the end of the arm 80 by a threaded connecting stub 86 and this handle stub is secured in an aperture of the arm by a set screw 88, said arm 80 and said connecting stub 86 defining an elongated connecting member. The handle stub extends through an arcuate handle slot 89 in the cover plate 34.
A squeegee assembly mounting ring'90 has a cam member passageway 92 to engage the cam surface 76 when cam member 74 is mounted within said ring. A squeegee assembly shown generally as 94, is secured to the squeegee mounting ring by a mounting bolt 96.
The squeegee assembly is shown to include an upper angle part 98 joined to a lower angle part 100 by a connector, shown as screw 102. A squeegee wiper 104 is held by paired angle brackets 106, 106 which are fastened to lower angle part 100 by screws 108, 108. The wiper 104 has a wiper base 110 from which wiper blade 112 extends. The brackets 106 hold the base portion 110 by a tapered clamping engagement indicated at 114.
The upper angle part 98 is shown as having an angle control rod 116 frictionally mounted in a bore. The control rod lies in a plane which is parallel to the plane of the axis of the rotary head. The angle control rod has an end portion which extends outside of said plate through an oversized plate aperture 1 18. The angle control rod 116 is moved and fixed by means including an anchored block 120 secured to the cover plate by fasteners 122,122. The anchored block has a threaded bore 124 which engages a screw adjustment member 126. The screw adjustment member 126 is fixed to a floating block 128 freely spaced from the surface of the cover plate 34. The screw adjustment engages a threaded bore 130 in the floating block, and such floating block is additionally provided with an elongated slot 132 through which the end of angle control rod 116 extends. A compression spring 129 urges the floating block away from the anchor block during adjustment.
In operation, printing ink is deposited through the entry in the head defined by cut out 42 of the cover plate 30. The shaft 32 is rotated, and driving plate 48 rotates therewith. The screen 44 rotates with driving plate and with mounting collar 54 secured to the screen. The squeegee assembly forces ink through the image areas 46 of the screen onto the peripheral surface of the elastomeric roller 22, which transfers such image to a work piece delivered to the bottom of such roller. It will be understood that the work piece may have an irregular configuration because the softness of the elastomeric roller will readily deform following such irregular conformations. The drum may be quickly replaced with another drum having a different image by releasing locking rings 64, 68 and set screw 52 of driving plate 48; and then, replacing with another drum and again mounting the locking rings and cover plate. Optionally, the drum of the rotary head may be replaced with a conventional gravure roller, and the inking assembly 12 may be used in conjunction with such a gravure to transfer images to the elastomeric roller 22, and then to the work piece.
The pressure of the squeegee 104 is controlled by the eccentric cam assembly 72 by merely turning handle 84 on threaded stub 86 to release such handle from frictional engagement with cover plate 30. The handle is moved in the arcuate slot to selectively move the cam member and thereby change its high and lowsurfaces. This action raises and lowers the cam assembly 72 in a radial lineal path between the axis and the periphery of the drum. It will be seen from the cam assembly that the axis of shaft passageway 77 is eccentric to the axis of ring 90 so that the cam assembly is fully lowered when high cam surface 76a is at the shortest radial distance to the drum periphery; and the squeegee assembly is raised to its highest point when the low cam surface 76b is at the shortest radial distance to the drum periphery.
Thesqueegee assembly may be moved to different angular positions, that is, along differently positioned radial paths relative to the axis of the head by moving angular control rod 116 along a path limited generally by the diameter of the oversized aperture 118 in the cover plate. The rod is moved by a caging member of floating block 128 which is moved back and forth relative to anchoring block 120, under the urgings of screw adjustment 126 and spring 129. This adjustment means will change the angular position of the wiper 104 relative to the elastomeric roller 22 which is in tangential contact with the screen 44 of the drum. Only relatively small angular displacements are generally required in such adjustments.
What is claimed is:
1. An offset silk screening apparatus comprising,
a frame rotatably mounted on a driveable shaft,
a driving plate keyed to said shaft,
a screen mounting collar, l
a continuous screen secured along opposite edges to a non-rotatable cover plate mounted on said shaft adjacent said mounting collar, roller means mounted on said cover plate in supporting contact with said mounting collar,
means within said frame for receiving printing ink,
a squeegee assembly mounted internally of said frame to force the printing ink through said image producing areas of said screen, ,1
means for varying the pressure of said squeegee assembly against said screen along a linear radial path between the axis of rotation and the periphery of said drum,
said means including a cam member having a shaft passageway therethrough and mounted for rotational movement about said shaft,
the axis of said cam member being eccentrically positioned relative to the axis of said shaft passageway,
a squeegee mounting ring mounted circumferentially about said cam member,
means for turning said cam member whereby said squeegee assembly is movably reponsive to the movement of said cam member along a linear path the extent whereof is defined by the eccentricity of said cam member,
and a soft elastomeric roller rotatably mounted and positioned so that said roller periphery is in touching contact with the periphery of said screen,
and a workpiece support adjacent said elastomeric roller for supporting a workpiece which may be positioned adjacent said elastomeric roller to receive the printed ink image applied to said elastomeric roller bysaid screen.
2. The offset silk-screening apparatus as set forth in claim' 1 above, wherein said cover plate further includes an arcuate slot, an elongated connecting member extending from said cam member and through said arcuate slot, and a handle joined to said connecting member exteriorly of said cover plate, and means on said handle for releasably locking the connecting member and the cam member at a selected position along said arcuate slot.
3. The offset silk-screening apparatus as set forth in claim 1 above, wherein said squeegee assembly further includes a mounting bracket having a control rod parallel to the axis of rotation of said screen, said control rod extending exteriorly of said screen, and means on the outside of said screen to limit the movement of said control rod.
4. The offset silk-screening apparatus as set forth in claim 3 above, which further includes an oversized aperture disposed in said cover plate, said control rod extending through said aperture in said cover plate, the end of said control rod being arrested within a member spaced from said cover plate, and means for repositioning said arresting member to thereby move said control rod and squeegee assembly.