US3835773A

US3835773A - Printing apparatus

Info

Publication number: US3835773A
Application number: US00247835A
Authority: US
Inventors: M Vasilantone
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-04-26
Filing date: 1972-04-26
Publication date: 1974-09-17
Anticipated expiration: 1991-09-17

Abstract

A continuous screen printing apparatus of the type having an endless screen mounted on spaced parallel cylinders for printing insignia on a flexible web supported on a movable platen adjacent said screen. Means are provided for laterally and longitudinally adjusting the tautness of the screen and for maintaining the screen taut in the area between the rolls.

Description

[ Sept. 17, 1974 United States Patent [1 1 Vasilantone Xwx EH H02 8 9 H 1.

t m F B3 7 m 7 0H0 m1 mN S U k Tae AVM R dR Aa, Ph Pkw MMA mm mm n m PI MN U 647,059 12/1950 GreatBritain......................156/229 [22] Filed: Apr. 26, 1972 [21] Appl. N0.: 247,835

Primary Examiner-Clyde 1. Coughenour 52 US. 101/122, 74/24214 R, 118/34, g f g Agent F"mEdward Dyson [57] ABSTRACT A continuous screen printing apparatus of the type having an endless screen mounted on spaced parallel cylinders for printing insignia on a flexible web sup- O 9 Hun 7 h mmw ue m 1 MUN O; 1% B "W MR m4 2 m4 5 WS 61 I10 C l m u IFZ 11 1 55 [56] References Cited UNITED STATES PATENTS ported on a movable platen adjacent said screen.

g .m .m m .m ms m m 01 u m m an e He 6W M mm 3 wbm ea hm t 1 1 9 0c mi s a e mll m c wu2 t w n i gr .m t 6 mi t MMM ///9 888 111 ..6

PRINTING APPARATUS This invention relates to a textile printing apparatus for continuously printing textile webs of an indeterminent length. More particularly this invention relates to Y a stencil screen printing apparatus employing an endless screen mounted on spaced cylinders and having a screen in printing engagement with a movable webcarrying platen.

This invention is related to the continuous stencil screen printing apparatus disclosed in my US. Pat. No.

3,468,247, issued Sept. 23, 1969, entitled CONTINU-.

OUS PRINTER WITH MEANS T MAINTAINA MOVING WEB LATERALLY TAUT, and in my US. Pat. No. 3,688,692, issued Sept. 5, 1972, entitled PRINTING APPARATUS.

One of the primary objectives of the invention disclosed in the above-mentioned US. Pat. No. 3,468,247 is to maintain the web of textile material to be printed laterally taut on the moving platen to insure proper registration and optimum printing contact when the web is brought into printing engagement with the stencil screen.

It is also desirable to maintain the printing screen laterally taut at all times for optimum and accurate printing contact. It is generally not difficult to maintain the screen laterally taut and at a uniform width as it passes over the cylinders, in that the cylinders are provided with annular grooves or other means on the outer edges thereof for gripping the edge portion of the endless stencil screen for purposes of maintaining a uniform width. However, there is a tendency for the screen to contract in those areas of the screen that are between the cylinders and are not in contact therewith.

Therefore, it is a principal objective of this invention to provide bridging means extending between the cylinders for engaging the side edge portions and holding taut the endless stencil screen in that area between the cylinders.

It is a further objective of this invention to provide cylinders which are adjustable axially of their lengths such that the lateral tautness of the screen mounted thereon can be easily adjusted.

It is a further objective of this invention to provide means mounting the rolls supporting the stencil screen in a manner such that the cylinders can be moved toward each other to facilitate the placement or removal of the stencil screen.

It is a further objective of this invention to provide a screen printing apparatus whereby the cylinders supporting the screen are adjustable during operation of the printing apparatus such that where, more than one screen printing assembly is used in tandem as in multicolor printing operations, one printing assembly may be readily adjusted relative to the other to obtain the proper relative registration.

More particularly the objectives of this invention are realized by providing an apparatus for continuously printing insignia on a moving flexible material, comprising a framework, a moving platen on said framework for receiving said meterial to be printed, stencil printing means on the framework comprising a pair of spaced apart cylinders roatably mounted on axes extending transversely to the direction of movement of the platen. An endless tubular screen is mounted over the cylinders and has upper and lower runs at least one of which is maintained in printing engagement with the platen. The bridge means extends between the cylinders and engages the side edges of the screen to maintain the screen laterally taut in the areas between the cylinders. The cylinders are mounted for movement toward and away from each other in a direction parallel to the direction of movement of the platen for adjusting the longitudinally tautness of the screen and for facilitating the placement and removal of the screen on the cylinders. The stencil screen has enlarged edge portions on each side thereof, and the bridge means comprises a pair of elongated rigid members extending between the drums and on each side thereof and having an elongated track therein for slidably receiving the enlarged portions-on each side of the stencil screen respectively. Anti-friction means are mounted in the track for engaging with the enlarged portions, the antifriction means preferably including an endless band of a flexible metal material extending around rollers rotatably mounted in the track on axes perpendicular to the planeof the platen.

These and other objects of the invention will become more apparent to those skilled in the art by reference to the following detailed description when viewed in light of the accompanying drawings wherein:

FIG. 1 is a diagrammatic illustration of the type of printing system in which the screen printing unit of this invention is employed;

FIG. 2 is a perspective view of the screen printing unit of this invention;

FIG. 3 is a perspective exploded view of the end assembly of one of the cylinders of the screen printing unit;

FIG. 4 is a view similar to that of FIG. 4 except in elevational cross section;

FIG. 5 is a perspective exploded view of the bridge means of this invention;

FIG. 6 is a perspective view of the bridge means of this invention;

FIG. 7 is a plan view of a detailed segment described as a pop-out device;

FIG. 8 is a side view in elevation of the cylinders with the upper and lower bridge means in position;

FIG. 9 is a perspective view showing the relationship of the bridge means, retainer ring and printing screen;

FIG. 10 is a partial cross sectional view taken in the area of one of the cylinder ends when the cylinder is in the non-expanded position;

FIG. 11 is a view similar to FIG. 10 but is a plan view;

FIG. 12 is a partial cross sectional-view taken in the area of one of the cylinder ends when the cylinder is in the expanded position;

FIG. 13 is similar to FIG. 12 but in a plan view;

FIG. 14 is a perspective view of the cylinder support mechanism;

FIG. 15 is a plan view of the cylinder support mechamsm;

FIG. 16 is a perspective view of the cylinder support mechanism in a collapsed condition;

FIG. 17 is an end view of the screen printing unit of this invention illustrating the cranks used in longitudinally and laterally adjusting the cylinder ends;

FIG. 18 is a view similar to that of FIG. 14 except that the cylinders are in the collapsed condition.

GENERAL ARRANGEMENT This invention is primarily concerned with the construction of the twin cylinder stencil screen printing unit, generally indicated by the numeral in FIG. 2. The twin cylinder screen drive unit is designed to be used in a multiweb printing machine generally indicated by the numeral 12 in FIG. 1. A framework 14 supports a plurality of screen printing units 10 in tandem relationship. Though it is not shown or described herein, an ink supply assembly is disposed between the cylinders of each of the screen printing units to flood the runs of the screens, both top and bottom, in the areas between the cylinders in a manner well known in the screen printing art. A particular ink supply system suitable for use with the screen printing units of this invention is disclosed in my copending application filed May 14, 1970, Ser. No, 37,113, entitled PRINTING APPARATUS. Again with reference to FIG. 1, a bottom endless platen 16 is mounted on idler roll 18 and driven roll 20 and carries a web 22 to be printed. The web is taken from supply roll 24 and passed through the screen printing apparatus and drier 26, and is accumulated on take up roll 28. Since the printing screen units are endless and are constantly rotating at speeds corresponding to the platen and the web supported thereon moving through the printing apparatus, the units can print on the top runs and lower runs simultaneously. Accordingly, an upper endless platen is mounted on idler roll 32 and driven roll 34 and carries a web 36 to be printed from a supply reel 38, through the printing machine and adjacent and in contact with the upper runs of the screen printing unit. The web passes through a drier 40 at the opposite end of the web printing assembly and is accumulated on a take up roll 42. Support rolls 44 and 46 support the non-web supporting runs of the endless platen of the bottom and top endless platens respectively. Upper and lower tables 48 and 50 provide firm support on the sides of the printing runs of each platen opposite the web supporting sides.

The remainder of this specification will be directed to the inventive aspects of the individual screen printing units. More particularly, this invention includes means in each unit for incrementally adjusting the distance between the two cylinders in each unit thereby longitudinally stretching the printing screen. Further, means are provided for rapidly drawing the two cylinders closer to each other to permit easy insertion and removal of the endless printing screens. Additionally, means are provided for axially lengthening the two cylinders uniformly to stretch the screen in a lateral direction. Finally, means are provided for bridging the area between the two cylinders such that the edges of the printing screens are, .supported in these areas to maintain the same degree of lateral tautness achieved when the edges of the screen are actually in engagement with the ends of the respective cylinders.

BRIDGE ARRANGEMENT With reference to FIG. 2, the unit 10 includes a pair of

cylinders

50 and 52 mounted on

shafts

54 and 56 respectively. The cylinders rotate relative to the shafts as will be pointed out more fully hereinafter. An endless tubular stencil printing screen 58 is slipped over the cylinders, in the manner shown, for movement in an endless path as the cylinders are rotated. The screen has an upper run 60 and a lower run 62.

Referring now to FIGS. 3 and. 4, the end plate assembly of cylinder 50 will be described. It is to be understood that the end plate assembly of cylinder 52 is identical, and the end plate assemblies on the opposite ends of the respective cylinders are identical.

The cylinders are provided with internal reinforcing plates 64 one of which is seen in FIGS. 3 and 4. The reinforcing plates are provided with central apertures 66 which receive and center the shaft 54, and the thrust bearing assembly 57 which is fixed to the shaft 54, such that the cylinder rotates while the shaft and hearing assembly remain stationary. An externally threaded sleeve 68 is slidably received over the the shaft 54 and has a thrust bearing assembly 70 afiixed to the inner end thereof for rotatably supporting the inner channel ring 72. The sleeve 68 and the ring 72 move axially relative to the cylinder 52 for lateral tensioning of the screen printing web as will be more fully described hereinafter.

. The inner channel ring 72 includes an annular recess 74 which receives upper and lower pop-out

devices

76 and 78 which are affixed to a bridge retainer ring 80. An outer channel ring 82, having a cylindrical section 84 and a flange 86, is secured to the inner channel ring 72 in a manner to be described below. A web support ring 88 is affixed to the outer surface of the flange 86 of the outer channel ring 82. Fasteners 90 in the form of threaded fasteners or any other suitable fastener secures the web support ring to the outer surface of the flange 86 of the outer channel ring 82, and the channel ring 82 to the inner channel ring 72. The axial edge of the cylindrical portion 84 of the ring 82 abuts the outer surface 92 of the inner channel ring 72 to define an annular groove 94 therebetween as best seen in FIGS. 10 through 13. The groove 94 receives the bridge retainer ring 80.

Wheels 96 are spaced about the inner periphery of the ring 80 and ride on the outer peripheral surface of the cylindrical portion 84 when the cylinder is rotating.

Guide pins 98 permit relative axial movement between the inner channel ring 72 and the cylinder 50 while insuring that the channel ring rotates with the cylinder when the latter is rotated relative to the supporting shaft 54. Since the web support ring 88 and the outer channel ring 82 are affixed to the inner channel ring 72 by means of the aforementioned fasteners 90, the cylinder, inner channel, ring, outer channel ring and web support ring will rotate as a unit relative to the shaft 54. The bridge support retainer ring 80, however, remains stationary as the other elements rotate with the cylinder. v

The ring 80 is provided with upper and lower

bridge locking members

100 and 102 which receive

bridge locking elements

104 and 106 on bridging

members

108 and 110 respectively, as will be described in greater detail below.

The web end support ring 88 when affixed to the outer surface of the flange 86 forms a cylindrical supporting surface for receiving a resilient or elastomeric web-lock ring 112. The lock ring 112 has a channel 114 therein snugly receiving an endless locking band 116. The band 116 is affixed to the side edges of the stencil printing screen 58 such that when band 116 is in the channel 114 the screen is locked to the web-lock ring 112 for movement therewith.

The bridge means will now be described in greater detail. It is to be understood that for each twin cylinder unit there are four bridge members, a pair on each end for each end'of the cylinders for the top and bottom runs of the stencil printing screen. Each bridge member 108 comprises an elongated body of metallic bar stock 118 having a pair of elongated axially extending

slots

120 and 122, one at each end of the body 118. As seen in FIG. 8, the bridge member is of a length somewhat greater in distance between the axes of the two

cylinders

50 and 52. A spacer plate 124 of a height generally corresponding to the height of the body 1 18 is attached to the mid-portion of the body 118 in the area between the inner ends of the

slots

120 and 122. Attached to the outer surface of the spacer member 124 is an antifriction band-supporting body 126. The ends of the body member 126 are arcuately undercut at 128 and 130 respectively generally in conformity to the surface configuration of the cylinders. An endless anti-friction band 132 preferably of stainless steel or the like is journalled on

rollers

134 and 136, which are joumalled on vertical axes extending generally perpendicular to the axes of the

cylinders

50 and 52 and the plane of the platen. The anti-friction band assembly is positioned within a recess 138 in the upper surface of the body 126. The purpose of the anti-friction band is to generally reduce frictional contact between the web support ring 112 and the surfaces of the stationary bridging member. The body 118, spacer 124 and anti-friction band-supporting body 126 are shown as being formed of separate pieces joined together by a fastener means 140. It is to be understood that these parts could be integrally formed within the limitations of manufacturing processes.-

The pop-out devices 76 briefly referred to earlier are mounted on the inner surface of the bridge retainer ring 80 such that the bridge retainer ring is disposed between the bridge member and the pop-out devices in the area of the

slots

120 and 122. The pop-out device 76 includes a supporting block 77 having a pivotal mounting 79 on the side thereof facing the cylinder end for pivotally receiving

roller supporting legs

81 and 83. The pivotal connection 79 includes a pin 85 inserted in aligned openings in the support block 77 and in the

legs

81 and 83. J ournalled to the outer ends of the

legs

81 and 83 are

rollers

87 and 89 respectively. The outer ends of the

legs

81 and 83 and, therefore, the

rollers

87 and 89, are urged toward each other by an interposed tension spring 91 spanning the outer ends of the

legs

81 and 83. The legs tend to assume the position shown in FIG. 7.

Locating pins 93 and 95 extend through the supporting block 77 in a direction toward the bridge retainer ring 80 and as best seen in FIGS. through 13 are received in openings 97 and 99 in the retainer ring. The

locators

93 and 95 are of such length that they extend beyond the outer surface of the retainer ring 80 and are received in one of the

elongated slots

120 and 122 of the bridge member when the bridge member is in position spanning the two

cylinders

50 and 52. Upper and lower pop-out devices are provided for each bridge retainer. The relative positions of the cylinders, retainer rings and bridge members including the pop-out devices are clearly shown in FIG. 8.

Referring now to FIGS. 10 through 13, the operation of the pop-out devices will be described more fully. In FIG. 10, it is to be seen that the inner channel 72 and the members attached thereto; namely, the outer channel ring 82 and the web and support ring 88 are in their innermost position relative to the cylinder 50. The mechanism for moving the entire assembly toward and away from the cylinder will be described more fully hereinafter as part of the web tensioning system mechanism. In the position shown in FIG. 10, the stencil printing screen 58 is loose and can be easily slipped off of the twin cylinders. The edge of the screen 58 is bonded to the lock strip 116 which is press-fitted into recess 114 in the elastomeric ring 112.

The slot 94 defined by the inner channel rings and the outer ring 82 is substantially equal to the total thickness of the bridge retainer support ring .80 and the body and spacer plates I18 and 124 of the bridge member 108. Consequently, when the end ring 82 is moved axially outwardly from thecylinder as indicated in FIG. 12, the bridge member, retainer ring and pop-out device will tend to nest against the outer surface of the end plate 82 by the force from the lateral stretching of the stencil printing screen, and, thereby, the force generated by lock strip 112 acting against the bridging member. In the position shown in FIG. 12, the pop-out device 76 is positioned within the recess 74 against the action of the tension spring 91. In the position shown in FIGS. 12 and 13, the anti-friction band support plate is in the same vertical plane as the flange 86 of the outer channel ring 82. However, when the inner channel ring is shifted inwardly, the tension is released on the stencil printing screen 82 and the pop-out device forces the retainer ring and the bridging member to the right and also forces the lock strip 112 to the right as shown in FIGS. 10 and 11. In this position, the web is loose and can beeasily removed from the twin cylinders when they are shifted toward each other.

In the perspective view of FIG. 9, the cylinders are portrayed in their broken down position or in that position when their axes are close to each other to permit the ready replacement or removal of the web. In this position, the locking elements 104 of the bridge member 108 are received in undercut portions 105 of the locking members 100. Inwardly of the undercut portions 105, however, is an upstanding ridge 107 which defines a trackway with the outer surfaces of the retainer rings 80, for purposes of receiving the locking elements 104. Therefore, when the cylinders are moved apart, the retainer ring will move therewith and the locking elements 100 will move relative to the locking elements 104 such that the locking elements will be received in the aforementioned trackway defined by the upstanding ridge 107. This locking arrangement effectively serves to prevent relative axial movement of between the bridge member and the retainer ring. The elongated slots and 122, and the

pins

93 and 95, effectively prevent relative vertical displacement the bridge member and the retainer ring. However, the

elongated slots

120 and 122 pennit the cylinders to be shifted toward and away from each other with the bridge in position thereon.

The engagement of the lock strip 112 and the antifriction band 132 in the lock-strip trackway can be clearly seen in FIG. 9. Further, it can be readily seen, particularly from FIG. 9 how the bridging member maintains the stencil printing screen laterally taut in the areas between the

cylinders

50 and 52. When the web is in engagement with and travels around the cylinder, the upstanding flange 86 maintains the screen laterally taut. However, prior to this invention, the edges of the endless screen tended to draw together in the areas between the cylinders thereby causing a distortion in the printed image.

To insure that the locking strip 112 will not be displaced vertically and therefore out of engagement with the bridge member, an outer channel 142 is attached to the outer surface of the anti-friction band support and is provided with an overhandling lip 144 which prevents the lock strip and the attached printing screen edge from shifting upwardly and out of contact with the bridge. The channel 142 does not interfere with the removal of the screen when the assembly is in the collapsed state.

LATERAL AND LONGITUDINAL TENSIONING MECHANISM The mechanism by which the cylinders are moved toward or away from each other to longitudinally tension the screen printing web, and the mechanism for shifting the inner channel rings and the bridge members supported thereon axially of the cylinders to laterally tension the screen printing web, will now be described in detail with reference to FIGS. 14 through 18.

Shafts

54 and 56 are supported by front and rear support frames 200 and 202 respectively. Both of the

shafts

54 and 56 are suitably keyed in the front rear support frames to prevent relative rotation. The shaft 54 is mounted for movement toward and away from shaft 56 by means of front and rear trunnion blocks 204 and 210 in the front and rear support frames. The

cylinders

50 and 52 are joumalled on front and rear roller thrust bearings 57 and 59. The bearings are suitable keyed to the shafts to prevent relative rotation therebetween. Therefore, as explained earlier, the cylinders rotate relative to the shaft on the bearings. Threaded sleeves 68 are mounted on the

shafts

54 and 56 respectively and include the roller thrust bearings 57 for purposes of supporting the inner channel rings 72. A complete description of the inner channel ring structure and the entire cylinder end assembly is set forth earlier herein.

Note that the lateral sleeves 68 are readily received in openings 214 in the pivoted block assembly 218. The pivoted block assembly 218 comprises a first section 220 and a second section 222 joined together by

interdigitated fingers

224 and 226 respectively. A threaded lateral adjustment post 228 is threadedly received in internally threaded openings in fingers 226, while the fingers 224 are provided with elongated slots which permit the two

sections

220 and 222 to move toward. and away from each other as the cylinders are adjusted. The lateral adjustment post 228 includes an extension actuator rod 230 having a crank 232 affixed to the outer end thereof. Note that longitudinal fine adjust wheel 266 has an extension post 264 that is rotatably bushed through the first section 250 of the crank and is in turn threaded through the aligner block 251 that is pivotally engaged to the second section 252.

It can be seen then, that by rotating the crank 232 the entire block assembly 218 will be caused to move inwardly or outwardly axially of the cylinders by means of the threaded engagement of the lateral adjustment post with the block assembly 218. The sleeves 68 as mentioned earlier are threadedly engaged in the block assembly 218 for movement therewith. The sleeves are permitted to slide axially on the shaft 54 and shaft 56; therefore, any axial movement of the block 218 by the turning of crank 232 will cause the end assemblies of the cylinders and the bridge members supported thereon to move toward and away from the cylinders. In this manner the stencil printing screen supported on the ring assemblies and the bridge members will be stretched laterally of the web and axially of the cylinders. The end assemblies can be aligned with each other and with the block 218 by threadedly adjusting the sleeves 68.

The longitudinal tensioning mechanism of the web will now be described. Front and rear crank

assemblies

240 and 242 receive the front and rear ends of

shaft

54 and 56. The shafts are keyed against relative rotating within the connector sleeves 246 and in turn with the crank mechanisms. The connector bushings 246 are fixed to section 252 at one end of shaft 56 and to drive gears 278 at the other end of shaft 56. Connector sleeves 245 are fixed to the first section of cranks 250 and are rotatably bushed through trunnions 210 on shafts 54. It is to be understood that the rear and front crank assemblies are identical. Each of the crank assemblies includes a first section and a second section. The first section 250 includes an extension 254 which is slidably received into the pivotal aligner block 251. The aligner block is in turn snugly and pivotally received into the internal portion of the second section 252. Extension 254 is provided with an elongated slot 256 which allows the actuator extension 230 of the lateral adjust post 228 to pass through. The post 228 acts as a pivot for the crank collapse action as it is rotatably bushed through the walls of the section 252.

The aligner block 251 is held in linear check by the threaded post 260-262, adjust extension 264 and wheel 266. The slot 256 of the extension 254 allows for telescopically increasing or decreasing the lengths of the cranks and for adjusting and paralleling the shaft and cylinder respectively.

It can be seen that by turning the cranks 266, the first section 250 of the crank assembly will be caused to move toward or away from the second section 252 to move the shafts and cylinders toward and away from each other thereby longitudinally tensioning the stencil printing screen supported on the cylinders. This adjustment can be made while the assembly is printing. it should be noted that the purpose of the longitudinal adjustment 266 is for infinitely adjusting and locking the spacing and parallel relationship of the shaft and cylinders and for the adjustment of print register. Longitudinal tensioning is accomplished simply by turning the crank 266.

The mechanism for rapidly collapsing the cylinders by moving them toward each other to permit rapid removal or placement of a stencil printing screen on the cylinders will nowbe explained. This is a twofold system and the collapsing may be accomplished by the raising or lowering of only one of the crank handles since the fixed shaft 56 is rigidly connected to both crank mechanisms. A lever 270 is attached to the second section 252 of each crank assembly 240. The front and rear supporting frames each includes shelves 274 supporting reciprocating racks 276. Rack dirving gears 278 are attached to the ends of complementary connector bushings 246. As the levers 270 of either front or rear crank assemblies are pulled upwardly the drive gears are both actuated and are interconnected by the fixed shaft 56. The drive gears in turn actuate and drive both racks 276 which in turn are meshed with and drive pinion gears 284 at the bottom ends. The pinion gears are meshed with trunnion racks and to a large extent support the trunnions, which are in partial, slidable engagement with the lower portion of slots 211. Therefore, as the lever 270 of either crank is pulled upwardly, the second sections 252 of the crank assemblies will be rotated around the axis of shafts 56, and the first and

second sections

250 and 252 will be caused to pivot with respect to each other about a pivot point defined by the lateral adjustment post 228. A clearance opening 199 is provided in the journal support 200 so that the lateral actuator post 230 may seat without interference. FIG. 14 indicates the post 230 in its seated position. FIG. 18 shows the post 230 pivoted in the Up position out of seat.l99.

The lever will cause the variable shaft 54 and cylinder thereon to be pulled and drawn toward the fixed shaft 56 and the cylinder thereon. Additionally, the drive gears will rotate as the two sections 252 of the front and rear crank assemblies are pivoted upwardly and cause the racks to be driven to the left as viewed in FIG. 14. The racks 276 are meshed at their other ends with small pinions 284 which are rotatably mounted on both journal support frames 200-202. The trunnions 210 are caused to move within the slots 211 toward the other cylinder thereby further drawing the cylinders together. Then, assuming that the lateral adjustment post has been rotated to move the ring assemblies and the bridge members toward the cylinders, the stencil printing screen will be easily removable from the cylinders. FIGS. 16, 17 and 18 fully depict the operation of the cranks in collapsing the cylinders toward each other.

It is desirable for uniform tension and to maintain the individual threads of the stencil fabric parallel and vertical to each other and to maintain uniform apertures through the full width and breath of the fabric by achieving lateral and longitudinal tensioning. It is customary to tension the fabric to an extreme as to arrive at a point where the fabric assumes the character of a rigid plate. This condition provides a stable stencil plate with a minimum of flexure, thus overcoming stresses imparted by the applicator and squeegee. This tension condition retains register throughout its full surface, aids in release from the printed matter, and maintains its grip on the supporting cylinders thereby greatly minimizing chances for movement from its frictional contact with its supporting means.

The bridges and their interconnected cylinders are a unitary system designed to achieve from two supporting cylinders a system that is close in function to a single cylinder but yet having all of the advantages of a multi-cylinder system.

In a general manner, while there has been disclosed effective and efficient embodiments of the invention, it should be well understood that the invention is not limited to such embodiments as there might be changes made in the arrangement, disposition, and form of the parts without departing from the principle of the present invention as comprehended within the scope of the accompanying claims.

I claim:

1. An apparatus for continuously printing insignia on a moving flexible material comprising a framework, a moving platen on said framework for receiving said material to be printed, stencil printing means on said framework comprising a pair of spaced apart cylinders rotatably mounted on axes extending transversely to the direction of movement of said platen, an endless screen mounted over said cylinders and having upper and lower runs one of which is maintained in printing engagement with said platen, relatively stationary bridge means extending between and generally supported by said cylinders and engaging the side edges of said screen to maintain said screen laterally taut in the area between said cylinders.

2. The apparatus of claim 1 wherein at least one of said cylinders is mounted for movement toward and away from the other of said cylinders in a direction parallel to the direction of movement of said platen for rendering said screen longitudinally taut.

3. The apparatus of claim 2 wherein toggle cranks extend between and join said cylinders, said cranks having a first or locked position wherein said cylinders are held apart a predetermined distance, and a second or unlocked position whereby said cylinders are drawn closer to each other.

4. The apparatus of claim 3 and including adjustment means for adjusting the spacing of said cylinders when said crank is in the first position.

5. The apparatus of claim 1 wherein at least one of said cylinders is mounted for movement toward and away from the other of said cylinders in a direction parallel to the direction of movement of said platen for rendering said screen longitudinally taut.

6. The apparatus of claim 5 wherein said screen has an enlarged edge portion on each side edge thereof, and said bridge means comprises a pair of elongated rigid members extending between said cylinders and on each side thereof and each having an elongated track therein for slidably receiving said enlarged portions respectively.

7. The apparatus of claim 6 and including antifriction means mounted in said track for engagement with said enlarged portions.

8. The apparatus of claim 7 wherein said anti-friction means is an endless band extending around rollers rotatably mounted in said track on axes perpendicular to the plane of said platen.

9. The apparatus of claim 8 wherein said band is of a flexible metal.

10. The apparatus of claim 5 wherein toggle cranks extend between and join said cylinders, said cranks having a first or locked position wherein said cylinders are held apart a predetermined distance and a second or unlocked position whereby said cylinders are drawn closer to each other.

11. The apparatus of claim 10 and including adjustment means for adjusting the spacing of said cylinders when said crank is in the first position.

12. The apparatus of claim 1 and including lateral adjusting means for axially extending each of said cylinders and for laterally shifting said bridge means to adjust the lateral tension on said screen.

Claims

7. The apparatus of claim 6 and including anti-friction means mounted in said track for engagement with said enlarged portions.

9. The apparatus of claim 8 wherein said band is of a flexible metal.