US2894450A

US2894450A - Screenprinting machines

Info

Publication number: US2894450A
Application number: US636303A
Authority: US
Inventors: Steinitz Kurt
Original assignee: Individual
Current assignee: Individual
Priority date: 1957-01-25
Filing date: 1957-01-25
Publication date: 1959-07-14
Anticipated expiration: 1976-07-14

Description

July 14, 1959 K. STEINITZ SCREENPRINTING MACHINES Filed Jan. 25, 1957 s Shets-Sheet 1 INVENTOR: K t

K. STEINITZ SCREENPRINTING MACHINES July 14, 1959 Filed Jan. 25, 1957 3 Sheets-Sheet 2 INVENTOR: KM/ut JCdmiibz,

July 14, 1959 K. STEINITZ v 2,894,450

scaaEummwmc MACHINES Filed Jan; 25, 1957 I s Sheets-Sheet 3 v Fi mvamox: Sc

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United States Patent SCREENPRINTIN G MACHINES Kurt Steinitz, Danbury, Conn.

Application January 25, 1957, Serial No. 636,303

' 7 Claims. 01. 101-124 My invention relates to machines for lettering or decorating surfaces of work pieces by the screen-printing process. l

Objects of my invention are to move the screen reciprocatingly, to utilize each single stroke of the screen in either direction for printing one work piece, and thereby to expedite the process.

I have found that one squeegee can not print in both directions because the printing paint or ink is shifted by the squeegee on the screen to one side during one stroke so that the paint moves away from the squeegee during the following reverse stroke of the screen. Hence, further objects are to provide two squeegees, to use one squeegee for printing during strokes in one direction and the other squeegee for printing during strokes in the opposite direction, to arrange these squeegees so that they can be positioned for operation alternately and that they approach the paint on the screen from opposite sides.

Other objects of my invention are to print a series of rollable work pieces in quick succession, to bring one work piece at a time into contact with the screen, to move the screen between the work piece and a stationary squeegee, and thereby to rotate the work piece while it is simultaneously printed.

Still other objects are to provide a track on which the work pieces can roll from one side of the machine to the opposite side, to incline this track so that the work pieces will roll by their own weight and will be discharged automatically, to arrest each work piece and to lift it from the track into contact with the screen along a line juxtaposed to the contact line of the operative squeegee, and thereby to provide simple and reliable means for guiding the work pieces through the machine.

Still further objects are to support each work piece in the lifted position by idle rollers whereby the work piece can be rotated freely by its frictional contact with the moving screen, to use the same rollers for arresting and dismissing the work pieces, and, for this purpose, to provide two rollers or two pairs of rollers which are movable up and down individually so that one roller or one pair may be lowered while the other is raised or vice versa, or all rollers can be lifted simultaneously.

Still other objects are to operate the machine quickly and with a minimum of labor, to provide individual motoric means for the several moving elements of the machine, and to secure proper sequence of the several movements automatically.

Still further objects are to attain these results with simple and inexpensive means and with a structure that can be easily made, assembled, maintained and adjusted for quick and correct performance.

Still other objects and advantages will appear from the following description of an exemplifying embodiment of my invention, from the appended claims and from the accompanying drawing in which:

Fig. 1 shows a side view of an illustrative embodiment of my inventon, the left lower corner being broken ofi.

2,894,450- Patented July 14, 1959 ice Fig. 2 shows a top view of the same embodiment, the left end being broken 01f, some upper parts being cut away along the line 2-2 in Fig. '3.

Fig. 3 shows a partly sectional view seen from the left side in Fig. 1, the sectionally represented parts being out along the line 33 in Fig. 1.

Fig. 4 shows a partly sectional view of a portion of the same embodiment, seen from the right side in Fig. 1, the sectionally represented parts being out along the line 44 in Fig. 5.

Fig. 5 shows a cross-section taken along the line 5-5 in Fig. 4.

Figs. 4 and 5 are represented on a larger scale than Figs. 1, 2 and 3.

Fig. 6 shows a diagrammatic representation of a system for the distribution of compressed air, to be used in the embodiment shown in Figs. 1 to 5, but omitted in these figures.

Fig. 7 shows a diagrammatic representation of elec tric circuits, to be used in the same embodiment, but omitted in Figs. 1 to 5.

The machine shown in the drawings has a supporting frame which may comprise two longitudinal bottom beams '6, two end bottom beams 7 connecting the beams 6, four vertical beams 8 rising from the ends of the beams 6, two further vertical beams 9 rising from the centers of the beams 6, two bottom beams 10 connecting the beams 6, two horizontal beams 11 connecting the beams 9, two longitudinal top beams 12 connecting the upper ends of beams 8 and 9 and two longitudinal beams 13 connecting beams 8 and 9 at a level between the

beams

6 and 12.

At each long side of the machine, a cylindical rod 14 is positioned horizontally, passes through a beam 9 and has ends amxed to two beams 8. Each rod 14 carries two bearings 15 slidably. The four bearings 15 are afilxed to a frame 16. An exchangeable plate 17 is aflixed on the frame 16 and is cut out to fit a screen 18 which is inserted in the plate 17 and exchangeably secured to the same in any suitable manner.

The screen 18 comprises a rectangular rim of Z-shaped cross-section and a thin layer 19 of silk or other suitable permeable material spanned over the bottom of this rim. Portions of the layer 19 are made impermeable whereby a stencil is formed in the manner well known in the art of screen-printing. The screen 18, together with the carrying

parts

17, 16 and 15 is guided horizontally by the rods 14 and can reciprocate in this direction within the limits determined by contacts of the bearings 15 with the beams 8 and 9 or by the limited movability of the later described driving means.

Though it would be possible to move the screen by hand, I prefer to provide motoric means for this purpose. In the shown embodiment, these means are a cylinder 20 containing a piston driven in well known manner by compressed air in one direction or in the opposite direction, and a rod 21 driven by this piston. The cylinder 20 has an extension 22 hinged to a bearing 23. This bearing is affixed to a support 24 which, in turn, is afiixed to a beam 7 of the machine frame.

The movement of the rod 21 is transmitted to the screen by suitable elements which may comprise a head 25 affixed to the rod 21, a rod 26 passing through a crossbore of the head 25, two symmetrically arranged levers 27 rotatably and coaxially hinged to the beams 13 and each having an arm hinged to the rod 26, two connecting bars 28, each having one end hinged to the other arm of one of the levers 27, two plates 29, each hinged to the other end of one of the bars 28 and two long plates 31, each afiixed to one plate 29 and to two bearings 15.

The ratio between the strokes of the rod 21 and of the screen 18 is preferably adjustable in order to facilitate M9 different lengths of prints. For example, the levers 27 have several holes 32, each adapted toreceive an-endof the rod 26 whereby the ratio between the active arms of the lever can be varied.

Duringthe movement of the screen the'plates 31slide outside-of the beams 9, and the silk 19 slides along a squeegee which is formed'by a'rubber strip 33 firmly embedded in a ship 34 of harder material. (Best seen in Fig. '5.) During-astroke'of the screen, this squeegee is held stationary as will be described in the following.

Another identical squeegee is preferably provided for use during reverse strokes of the screen. The two squeegees are preferahly inserted in a comon holder 35 with which their parts 34 are firmly, but adjustably counected by set screws 36. Theholder 35 has two arms 37 afiixed to a shaft 38 which is rotatable in hearings or bores of arms-39 and 4t) ordinarily held in fixed positions as will be described later. A disk 41 is also affixed to the shaft 38. The shaft can rotate about its axis together with the disk 41 and the holder 35, but this rotation is prevented during the movement of the screen by means which will be described later.

The two squeegee-parts 34 extend toward the screen along planes passing through the axis of the shaft 38 and including an angle which, in the shown embodiment, has thirty degrees. When the strip 33 of one squeegee contac'ts the layer19, the other squeegee is spaced from the screen and vice versa. The strips 33 are so inserted in the parts 34'thatthe-contacting squeegee extends vertically oralmost vertically to the layer 19. By turning the shaft '38about thirty degrees, the first squeegee is spaced from the screen while the other squeegee is brought into active contact with the layer 19. Thisturning movement is carried out at the end of eachsingle screen stroke or between subsequent-strokes either by hand orpreferably automatically, for example, by the following means:

The disk 41 has two radial bores positioned at an angular distance of thirty degrees from each other. In each of these bores a pin 42 is slidable. Each pin 42 is urged 'radiallyoutward by a little spring 43 and is affixed to a pin 44 which extends parallel to the shaft 38 through a lateral slot 45 of the disk 41 and through a slot 46 of another disk. 47 which is rotatable on the shaft 38. The slot 45 guides the pin in radial direction. The slot 46 limits this'radial movement and has a length allowing limited rotation of the disks relatively to each other. The ends of the slot 46 are positioned at a larger radius than its middle.

Motoric means are provided for turning the disk 47. These means may comprise a solenoid 48 of well known structure including a core 49 which is pushed downward by a spring when the solenoid current is interrupted. When the solenoid is supplied with current, the tension of the spring is overcomeby magnetism and the core is withdrawn into the position shown'in Figs. 4 and 5. A rod 51 has one end hinged to the core 49 and has another end hinged to the disk 47. The solenoid 48 is affixed to the arm 40 which is secured, in a manner that will be described later, to a shaft 52 passing through the

arms

39 and 40. The shaft 52 is stationarily aflixed to the beams 9.

The described device for therotation of the squeegees operates as follows:

In the shown position, the disk 41 can not turn because it is coupled with the shaft 52 by one of the. pins 42 which extends into a cavity of the shaft 52. When the core 49 moves down, the rod 51 turns the disk 47 whereby the slot 46- slides along the pin 44 which is affixed to the coupling pin 42. Thereby, these pins are forced to move toward the shaft 38, the couplingpin 42 is withdrawn from the shaft 52, and the disk 41 is uncoupled when the middle of the slot 46 has reached the mentioned pin 44.

At this time, the left end of the slot' 46 (Fig. contacts the other pin 44. When now the core 49 moves farther in the same direction, the farther turning disk '47 takes this otherpin 44 withitself, thus making the disk tact line of the squeegee.

' the remaining i portion slopes -more.

41 turn together with the disk 47 until the other pin 42 snaps into'the mentioned'cavity of the shaft 52. In this moment, the movement of the core stops, the disk is coupled again with the shaft 52, and the squeegees have been turned.

When the core 49 is withdrawn into the solenoid, this operation is repeated in reverse direction: First the coupling pin is withdrawn fromthe shaft 52, then the disk 41 turns together with the disk 47 until the disk 41 is coupled again in the position shown in the drawings. The squeegees are thenagain in their originalzposition.

In order to facilitate the exchange of screens, both squeegeescan be lifted simultaneously. For this purpose, the arm 40 is not permanently aflixed to the stationary shaft 52, but is secured to the same by a releasable coupling, for example, in the following manner:

The arm 40 has a channel in. which a pin 53 is slidable. This pin is urged by a spring 54 toward the shaft52 and into a cavity of this shaft. A handle 55 is affixed to the pin 53 and extends through a slot 56 of the arm 40. During the printing operation, these parts are in the shown position in which the arm is immovably secured to'the shaft 52. "By moving thehandleSSupward, the arm 40 is uncoupled. Then, the arm 40 can be turned about the shaft 52 until the pin 53 snaps into another cavity 57 of the shaft '52. The entire aggregate comprising the solenoid '48, the

disks

41 and 47, the shaft 38, the arms 39, the holder 35 and the squeegees turns with the arm 40, for example, about ninety degrees whereby both squeegees are spaced from'the screen.

During each printing stroke of the screen, the active squeegee contacts the'layer'19from the upper side along a line crossing the moving direction of the screen while the work piece being printed contacts the layer from the lower side along a line parallel'to and vertically under the con- The work piece, for example a cylindrical drum or barrel 58, is rotated by the frictional engagement with the screen layer 19 so that successively all parts of itsround surface which should be printed come into contact with the screen.

The work piece 58 is supported in this position by rollers 59 which are preferably arranged in pairs, one 'pairat the left and one at the right side ofthe vertical 'center line -of the workpiece as seen in Fig. l. The rollers '59 can rotate idly on axles 61 which. are held stationary during the printing strokes, but which can be lowered, preferably in the following manner:

shown in the drawings and a lower position, preferably by motoric means. In the shown embodiment, these means are pressure cylinders 67 similar to the cylinder 20, except that their stroke is shorter. The rods '66 are-connected to the pistons of the cylinders 67. Thelatter arehinged to bearings 68 affixed to the beams 10.

These means allow to lower orraise each of the two pairs of rollers 59 individually'or without moving the otherlpairsimultaneously. In their lowest position, the rollers are below the level of a track 69 adapted for supporting'the work piece53 when one or both pairs of rollers 59 are lowered. The track extends from the right side of the machine'in Fig. l to the'left side and declines in this direction. The first portion of the track 'as farastolshortbeforethemiddle of themachine may be horizontal or only slightly inclined while The-track 69 may be form'ediby two rails' affixed to the inner sides of the beams 8 and 9. Preferably, these rails have shoulders 70 which prevent a work piece rolling on the track from excessive lateral dislocation. The distance of the track from the screen or from its way is at all points larger than the height or diameter of the work piece whereby this distance is SllfiiCiQl'lt to allow movement of the work piece on the track out of contact with the screen.

Preferably, the rollers 59 exert an upward pressure on the work piece 58 which is slightly larger than the weight of the work piece whereby proper frictional engagement between screen and work piece is secured. In the shown embodiment, this upward pressure results from the following arrangement:

The block 63 is not firmly affixed to the frame of the machine, but is afiixed to a vertical stem 71 which passes slidably through the two beams 11. A ring 72 is affixed to the stem 71 in an adjustable position. A spring 73 is positioned about the stem, over the ring 72 and under a beam 11 whereby this spring urges the stem and the block down and, hence, the rollers up with a pressure which can be adjusted by changing the position of the ring 72. The adjustment of this ring can be used also for adaptation of the roller positions for work pieces of different diameters.

The

cylinders

20 and 67 may be supplied with compressed air in the manner illustrated by Fig. 6. Each of these cylinders is controlled by an individual valve, the cylinder 20 by valve 74, the right side cylinder 67 by valve 75 and the left cylinder 6'7 by valve '76. These three valves may be of identical structure so designed in well known manner that each valve can be set for movement of the controlled cylinder piston in the one or in the other direction. For example, the valve may in one position connect one end of the cylinder with the pressure supply line and the other end with an exhaust pipe, and may in another position exchange these connections.

The compressed air may be supplied in the direction of the arrow '77 through a master valve '78 which is closed when the machine is not used. From the valve 78, the supply pipe '19 extends to three branches, each leading to one of the valves 74 to 76. From each of these valves, a branch of an exhaust pipe 80 leads to an exhaust in the direction of the arrow 81.

The valves '74 to 76 may be set by any suitable means. For example, these valves are of a well known solenoidoperated type in which the position of the valve depends on whether or not the solenoid is activated by current. In the shown embodiment, each of these valves, when its solenoid is active, supplies air pressure to that side of its cylinder which pushes the piston rod farther out of the cylinder, and when the solenoid current is interrupted, supplies air pressure to the other cylinder side whereby the rod is retracted into the cylinder.

The valves 74 to 76 may be set by hand or automatical ly. Preferably all settings operate automatically except the initial setting of the valve 75 as will be described later. If solenoid valves are used, they may be set by a system of circuits which includes also a circuit operating the solenoid 48 for the squeegee movement. A preferred circuit system for these operations is shown in Fig. 7.

This system comprises two

conductors

82 and 83 which are connected by four electrically parallel branches which, together with parts of the

conductors

82 and 83 form complete circuits 84 to 87. These branches include six switches 88 to 93 and four

solenoids

94, 95, 96 and 48. The

conductors

32 and 83 terminate in a plug 97 adapted for connection with a current source, for example with the local power network. This plug is symbolized in Fig. 7 by two pole points.

The circuit 84 includes the solenoid 94 of the valve 74 and the switch 88. The circuit 35 includes the solenoid 95 of the valve 75 and the two

switches

39 and 90 which are connected by two

parallel branches

98 and 6 99. The circuit 86 includes the solenoid 96 of the valve 76 and the two switches 91 and 92 which are connected by two

parallel branches

101 and 102. The circuit 87 includes the solenoid 48 for the squeegee movement and the switch 93. Each of the switches 88 to 93 are of the Well known type which connects one switch pole alternately with one or two other switch poles and which alternates the connection at each single operation of the switch. The switches may be of the push-button type and are preferably operated in the following manner:

A suitably bent bar 103 is afiixed to the rod 21 (see Fig. 1) and, at each end of any stroke of the rod 21, operates the switch 93 which is afiixed to the cylinder 20 and has a double button for operation either from the right or from the left side.

Other bars

104 and 105 are afiixed to the rods 66. The bar 104 operates, at the ends of its strokes the switches 88 and 91 which are affixed to the right side cylinder 67, and the bar 105 on erates similarly the switches and 92 afiixed to the lef\ cylinder 67. The switch 89 may be affixed at any suitable place to the machine frame and is preferably operated by hand.

The described machine operates as follows:

At the start, the

valves

74 and 76 are positioned as shown in Fig. 6, and the switches are in the positions shown in Fig. 7 in full lines. The master valve 78 is opened and the plug 97 is connected with the electric power network.

The circuit 84, being closed, activates solenoid 94 and thereby sets valve 74 sothat compressed air is supplied to the right end of cylinder 20 and pushes rod 21 into its most outward position if this rod is not yet in this position. The circuit 85 is interrupted. Hence solenoid 95 is inactive and valve 75 is set for retraction of rod 66 of the cylinder controlled by this valve to the lowermost position of this rod whereby the rollers 59 at the right side in Fig. 1 are lowered under the level of the track 69. The circuit 86 is closed whereby the other rod 66 is urged to its highest position and the left pair of rollers 59 are in their highest position over the level of the track. The circuit 87 is open. Hence the solenoid 48 is without current and the spring of this solenoid turns the squeegee which is left in Fig. l and right in Fig. 5 into active contact with the screen.

The operator inserts a work piece 58 into the machine from the right side in Fig. 1 and lets it roll on the track 69 until the left rollers 59 stop the work piece. Then, the operator operates the switch 89, thereby starting the automatic performance of the machine which operates as follows: The operation of the switch 89 has moved the same into the position shown in dotted line whereby circuit 85 is closed over branch 99. Thereby, the solenoid 95 is activated and sets valve 75 for connection of the pressure pipe 79 with the lower end of the cylinder 67 controlled by this valve. Hence, bar 104 with its rod 66 moves upward, the latter raises the right pair of rollers :59 and thereby lifts the work piece 58 from the track 69 into the shown position. At the end of this stroke, the bar 104 operates switch 88, moving the same into the position shown in dotted line in Fig. 7.

This interrupts circuit 84 whereby valve 74 is turned, the pressure in cyinder 20 is reversed and rod 21 is withdrawn into this cylinder. This stroke of rod 21 moves the screen from its extreme right position to its extreme left position. During this stroke of the screen, the work piece is rotated by frictional contact with the. screen and is printed. At the end of this stroke, bar 103, moving with rod 21, operates switch 93.

This opens circuit 86 whereby valve 76 is turned, the pressure in the left cylinder 67 is reversed and its rod 66 is withdrawn to its lowermost position. This lowers the left rollers 59 below the track 69 whereby the work piece is lowered to the track and rolls on the same to the 7 left until it drops out of the machine. At the end of this rod stroke, bar 105 operates switch 92.

This closes circuit 86 again whereby valve 76 is turned again, and the left rod 66 returns to its highest position. At the end of this stroke, bar 105 operates switch 90.

Thereby circuit 85 is interrupted whereby valve 75 is turned again, the pressure in its cylinder 67 is reversed again, and the right rollers 59 are lowered to their starting position. At the end of this stroke, bar 104 operates switch 91.

This closes circuit 87 whereby solenoid 48 is activated and turns the squeegees so that the formerly active squeegee is spaced from the screen and the other squeegee is brought into active contact with the screen. This concludes one cycle of operation, including printing of one workpiece.

The machine now stands with the rollers 59 in the same positions as at the start and with the screen in the end position opposite to its starting position. All switches, each having been operated once, are now in the positions shown in dotted lines in Fig. 7. The machine is now ready for insertion of another work piece.

In order to start another cycle of strokes, switch 8? is operated again. During the second cycle, the other switches are automatically operated in the same succession as during the first cycle. The screen moves back to the right side in Fig. 1, rotating and printing the second work piece which then emerges from the machine at the left side. At the end of the second cycle, the machine is in the same condition as before the start of the first cycle.

The operation of the machine may then continue in the manner described until all pieces of a series of work pieces have been printed. It does not matter whether the operation starts with the first described cycle or with the second one. In either case, the work pieces are printed alternately in one or in the opposite direction.

The described arrangement of motoric means, controls and control-setting means is one way to fulfill the following conditions: The squeegee movement is dependent on the completion of a screen stroke and vice versa. The screen movement is dependent on the completion of an upward stroke of one pair of rollers. The down and up movement of the other pair of rollers and the down movement of the first pair of rollers are dependent on the completion of a screen stroke. These conditions may be fulfilled in equivalent manner by other motoric means than the described pressure cylinders, other controls than the described valves, and other control-setting means than the bars and circuits described.

I desire it understood that my invention is not confined to the particular embodiment shown and described; the same being merely illustrative, and that my invention may be carried out in other ways within the scope of the appended claims without departing from the spirit of my invention as it is obvious that the particular embodiment shown and described is only one of the many that may be employed to attain the objects of my invention.

For example, the described machine can be easily modified for the printing of rollable work pieces which are not circular cylinders with exactly straight side lines parallel to the axis, but which have circular ribs or oval cross-sections perpendicular to the axis or slightly curved side lines or conical round surfaces.

Having described the nature of my invention, what I claim and desire to protect by Letters Patent is:

1. In a machine for screen-printing round surfaces of rollable work pieces, a horizontally movable screen, a squeegee positioned stationarily over said screen and operatively contacting the same along a line crossing the moving direction of said screen,.a track for the support of a rollable work piece, said track extending under the way 'of said screen at a distance therefrom sufiicient for support of said Work piece out of contact with said screen, and recoprocatable'means for lifting said work 8' I piece fromsaid track into rolling contact withsaid screen, the line .of said latter contact being parallel "to and directly under said first mentioned line, saidilatter means comprising tWo rollers positioned under said screen .at opposite sides of the vertical plane defined by 'saidlinesof contact, said rollers being supported rotatablyand being movable between a position in which said rollers are adapted to support said workpiece in said rolling contact with said screen and a position in which said rollers are lower "than the level of said track, each of said rollers being movable individually whereby lowering .of the. roller at one side will allow a work piece to move on said'tra'ck from one track end over the lowered roller as far astothe other roller, and lowering of the other roller will allow said work piece to move onsaid track to the other'track end.

2. In a machine for screen-printing round surfaces of rollable work pieces, a horizontally movable screen, a squeegee positioned stationarily over said screen-and operatively contacting the same along a line crossing the moving direction of said screen, a track for the support of a rollable work piece, said track extending under the way of said screen at a distance therefrom sufiicient for support of said work piece out of contact with said screen, and reciprocatable means for lifting said work piece from said track into rolling contact with said screen, the line of said latter contact being parallel to and directly under said first mentioned line, said latter means comprising two rollers positioned under said screen at opposite sides of the vertical plane defined by said lines of contact, two axles, each supporting one of said rollers rotatably, a vertically movable block, two arms, each hingedly connecting one of said axles with said block, motoric means connected with said arms at points positioned between said axles and said block and adjustable means urging said block downward.

3. In a machine for screen-printing round surfacesof rollable work pieces, a horizontally movable screen, a squeegee positioned stationarily over said screen and operatively contacting the same along a line crossing the moving direction of said screen, a track for the support of a rollable work piece, said track extending under the Way of said screen at a distance therefrom suflicient for support of said work piece out of contact with said screen, and reciprocatable means for lifting said work piece from said track into rolling contact with said screen, the line of said latter contact being parallel to and directly under said first mentioned line, said latter means comprising two rollers positioned under said screen at opposite sides of the vertical plane defined by said lines of contact, said rollers being supported rotatably and being movable between 21 position in which said rollers are adapted to support said work piece in said rolling contact with said screen and a position in which said rollers are lower than the level of said track, each of said rollers being movable individually whereby lowering of the roller at one side will allow a work piece to move on said track from one track end over the lowered roller as far as to the other roller, and lowering of the other roller will allow said work piece to move on said track to the other track end, said track declining in the direction to said other track end.

4. In a machine for screen-printing round surfaces of rollable work pieces, a horizontally movable screen, a squeegee positioned stationarily over said screen and operatively contacting the same along a line crossing the moving direction of said screen, a stationary track adapted to support a rollable work piece rolling along said track, said track extending along and under the way of said screen at a distance therefrom sufficient for supportof said work piece out of contact with said screen, reciprocatable means for lifting said work piece from said track into rolling contact with said screen, the line .of said latter contact being parallel to and directly under said first mentioned line, individual reversible motoric means for moving said screen and said lifting means, individual means for the reversal of said motoric means, the operation of the means for the reversal of said screen-moving means being automatically dependent on the completion of down and upward strokes of said lifting means, the operation of the means for the reversal of said lifting means being automatically dependent on the completion of a stroke of said screen whereby said lifting means reciprocate between every two subsequent oppositely directed strokes of said screen.

5. In a machine for screen-printing round surfaces of rollable work pieces, a horizontally movable screen, a squeegee positioned over said screen, a stationary track adapted to support a rollable work piece rolling along said track, said track extending along and under said screen at a distance therefrom sufficient for support of said work piece out of contact with said screen, two rollers positioned under said screen, and means for moving said rollers individually toward and away from said screen between a position lower and a position higher than said track, whereby lowering of one of said rollers and raising the other roller will allow a work piece to roll over said lowered roller until being stopped by said raised roller, and lowering of said raised roller will allow the work piece to continue rolling along said track, said means being adapted to raise said rollers with said work piece from said track until said screen engages said work piece.

6. In a machine for screen-printing round surfaces of rollable work pieces, a horizontally movable screen, a squeegee positioned over said screen, a stationary track adapted to support a rollable work piece rolling along said track, said track being inclined whereby a work piece rolls on said track automatically in a definite direction, said track extending along and under said screen at a distance therefrom sufiicient for support of said work piece out of contact with said screen, two rollers positioned under said screen, and means for moving said rollers individually toward and away from said screen between a position lower and a position higher than said track, whereby lowering of one of said rollers and raising the other roller will allow a work piece to roll over said lowered roller until being stopped by said raised roller, and lowering of said raised roller will allow the work piece to continue rolling along said track, said means being adapted to raise said rollers with said work piece from said track until said screen engages said work piece.

7. In a machine for screen-printing round surfaces of rollable work piece, a horizontally movable screen, a squeegee positioned over said screen, a stationary track adapted to support a rollable work piece rolling along said track, said track extending along and under said screen at a distance therefrom suflicient for support of said work piece out of contact with said screen, two rollers positioned under said screen, means for moving said rollers individually toward and away from said screen between a position lower and a position higher than said track, whereby lowering of one of said rollers and raising the other roller will allow a work piece to roll over said lowered roller until being stopped by said raised roller, and lowering of said raised roller will allow the work piece to continue rolling along said track, said means being adapted to raise said rollers with said work piece from said track until said screen engages said work piece, and automatic means making the lowering of said other roller dependent on the completion of a stroke of said screen.

References Cited in the file of this patent UNITED STATES PATENTS 2,129,163 Schneider Sept. 6, 1938 2,246,525 Matter June 24, 1941 2,301,119 Holybrook Nov. 3, 1942 2,361,325 Shurley Oct. 24, 1944 2,783,709 Thomas Mar. 5, 1957 2,793,586 Arelt May 28, 1957 2,799,223 Dubuit July 16, 1957 FOREIGN PATENTS 756,133 Great Britain Aug. 29, 1956