US 3505951 A
Description (OCR text may contain errors)
April 14, 1970 J. T. GARTRELL SCREEN'PRINTING ON SHEET 5 Sheecs-SheerI 1 Filed June 24. 1968 'lla'. l..
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ATTORN EYS API'ii 14 1970y J. T. GARTRELL 3,505,951
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Ji y B U/ l t ATTORNEYS April 14, 1970 Filed June 24. 1968 J. T. GARTRELL.
SCREEN-PRINTING ONQSHEET ATTORNEYS United States Patentv Oice 3,505,951 Patented Apr. 14, 1970 U.S. Cl. 101--123 8 Claims A moving web of steel is screen printed by clamping the web to a table carrying the printing mechanism. The table moves with the web during a portion of the web travel until the printing is completed. The table is then released from the moving web and retracted to a rearward position on the moving web for a repetitive cycle.
DESCRIPTION OF THE INVENTION The present invention relates to mechanism and a process for screen-printing on a moving straight sheet.
A purpose of the invention is to progress a sheet, for example an enamelled sheet of steel, or alumnum, across a table, the table being guided to move forward with the sheet, to intermittently clamp the table to the sheet, to move screen-printing mechanism from a remote position on the table into contact with the sheet on the surface to be printed, and to perform the operation of screen-printing while the table and the screen-printing mechanism are moving forward with the sheet.
A further purpose is to move the squeegee out of contact with the screen and retract the squeegee while thus out of contact.
A further purpose is to retract the table while its clamp has been released.
A further purpose is to pull the sheet into firm contact with the table prior to screen-printing so that the sheet will be level.
A further purpose is to measure the progression of the sheet and to actuate the clamping and screen printing cycles according to the progression,
A further purpose is to pull the sheet into firm Contact with the table automatically in accordance with the measurement of the progression.
Further purposes appear in the specification and in the claims.
In the drawings I have chosen to illustrate a few only of the numerous embodiments in which the invention may appear, selecting the form-s shown from the standpoints of convenience in illustration, satisfactory operation and clear demonstration of the principles involved,
FIGURE 1 is a diagrammatic side elevation of the device of the invention, partly in vertical section.
FIGURE 2 is a central vertical sectional enlarged dagrammatic view of the table and related mechanism of FIGURE 1.
FIGURE 2a is a view similar to FIGURE 2 showing a variation in the construction of the table itself.
FIGURE 3 is a diagrammatic end section of the table of the invention on the line 33 of FIGURE 2.
FIGURE 4 is a diagrammatic fragmentary plan view of the table of the invention, showing the printing-screen.
FIGURE 5 is an end elevation of a switch and cam for measuring the progression of the sheet.
FIGURE 6 is an electrical diagram of the mechanism.
FIGURE 7 is a developed view of contact tracks on a timing drum employed in the circuit of FIGURE 6.
FIGURE 8 is a diagram for the fluid operating circuit employed in the invention.
In the prior art extensive use is being made of sheet materials such as vitreous porcelain enamelled steel sheet for building construction such as outer walls of buildings, partitions, panels, signs and the like. It is desirable to further decorate such sheet by applying designs or patterns While avoiding the work involved in hand decoratlng.
A further problem arises because the sheet is usually processed in indefinite lengths while it is moving forward.
By the present invention it is possible to screen-print on sheets of even very large size during forward progression with a relatively high degree of precision in pattern match.
I am aware that it is old to move a printing screen tangentially with respect to an object to be decorated, as in Campbell U.S. Patent 2,340,643, dated Feb. 1, 1944 for Process and Apparatus for Decorating Articles of Manufacture.
In accordance with the invention, the sheet to be decorated, suitably a sheet of metal such as steel having a vitreous enamel coating on its upper surface, is progressed across the top of a table, the table being mounted and guided so that it can move forward with the sheet when desired. For a portion of a period of one cycle, the sheet is clamped to the table at a point adjacent the rearward end of the table with respect to the direction of progression forward. Screen-printing means mounted on or moving with the table is then lowered into contact with the upper surface of the sheet and the screen-printing operation is performed while the sheet and the table are moving forward together. Then the screen-printing mechanism is raised above the sheet and the table is unclamped with respect to the sheet so that the lsheet can move forward independently of the table. While this is happening the table and screen-printing mechanism are retracted t0 their starting position ready to begin another cycle.
The squeegee may move on the printing stroke in the direction of progression of the sheet, or opposite thereto, or transverse to the direction of progression of the sheet as may be desired. Immediately after the progression has been completed, the screen is retracted away from the sheet.
It is important that the sheet be as flat as possible at the time of screen-printing and with this object in view the sheet is pulled into firm contact with the top of the table, suitably by vacuum or by magnetic means.
The entire operation of the screen-printing mechanism and the determination as to when a cycle is to begin will desirably be made by measuring mechanism which coordinates with the forward progression of the sheet. At a proper point the measuring mechanism determines the time for starting a new cycle, initiates clamping of the table so that it will move forward with the sheet, initiates the downward motion of the screen-printing mechanism to contact the top of the sheet, initiates the pulling of the sheet into firm contact to the table, and initiates the printing stroke of the squcegee. A11 of these desirably take place as the table, the clamp and the printing mechanism move forward with the sheet. Unclamping, termination of screen-printing and retraction of the table are then accomplished either by a timing device or measuring device as desired.
In a desirable form of the device, the entire cycle can be performed in approximately ten seconds or less, during which time the sheet will have moved forward a suitable distance, for example one or more feet. It will be understood, of course, that the length of the pattern repeat area in the screen and its width can be adjusted for a particular screen-printing mechanism by rendering more or less of the area of the screen impervious to the screenprinting composition, as is well known in the art. In a typical installation it is believed that the size of pattern repeat on the screen-printing device may be of the order of five feet -by twelve feet. Much smaller pattern repeats can be used, however, and larger can also be employed if desired.
Elongated stock 20 which is called herein a sheet, but can where appropriate be designated as strip, plate, or otherwise, suitably has on its upper surface 21 a layer of enamel, preferably vitreous enamel or porcelain enamel. In some cases the bottom surface 22 will be bare, or itself may have an enamel coating or may have some other coating such as corrosion protecting coating. The sheet 20, which may also be termed a web, is progressed forward at a uniform speed by driven pinch rolls 23, engaging the top and bottom and applying suitable pressure. The pinch rolls 23 are operated by a suitable drive 24.
The sheet 20 beyond the pinch rolls passes through a suitable screen-printing mechanism 25, to be described, and then over a guide roller 26 mounted on a bearing stand 27, and forward thereof the sheet 20 enters the chamber 28 of a suitable enamelling furnace 30, as well known in the art.
As part of the screen-printing mechanism, a suitably adjustable frame 31 supports at the top in spaced relation parallel longitudinally extending horizontal rails 32 on which ride suitably ilanged wheels 33 mounted on axles on the bottom of a horizontal table 34. Limit on motion of the wheels 33 in the forward and rearward direction is provided by stops 35.
The table has a ilat top 36 which in the preferred embodiment is provided with means to hold the sheet into rm at horizontal engagement with the table top. This is preferably done by making the top of the table beneath the sheet of a foraminous plate 37 which is connected to vacuum in a Vacuum chest 38 connected by a flexible pipe 40 with a suitable vacuum pump. Optionally the sheet if magnetic may be made to lie at against the table top by an electromagnetic clutch 41 provided in the table top as shown in FIGURE 2a.
n either side of the sheet 20 and extending from the table upward, there are brackets 42 which support clamp cylinders 43 having pistons and piston rods 44 which support a horizontally extending clamp bar 45 which in lowered position is adapted to clamp the table with respect to the sheet and cause the table to move forward with the sheet 20. Inside the cylinders 43 and around the piston rods below the pistons are placed helical compression springs 46 which urge the pistons and the clamp bar 45 in the direction of unclamping. Flexible fluid connections 47 are made to the upper ends of the cylinders 43 to apply fluid pressure where required.
Immediately in advance of the brackets 42 for the clamp cylinders and also at the forward end of the table there are at both sides of the table brackets 48 which support four cylinders 50 having downwardly directed piston and rod combinations 51. The pistons are urged upwardly for retraction by helical compression springs 52 surrounding the piston rods in the cylinders. Flexible fluid connections 53 are made to the tops of the cylinders. A screen-printing frame 54 large enough to extend laterally beyond the sheet is supported from the piston rods and has extending across the bottom a screen-printing screen 55 having a pattern area 56 near the center which has suitable openings for downward ow of screen-printing composition 57, suitably an enamel frit in any desired printing ink vehicle. In the printing area 56 there are also, as well known, areas in which the openings in the screen are closed to prevent printing. All around the pattern area 56 there is a non-pattern area 58 (merely indicated, but covering everything but the pattern area) where all of the openings in the screen are closed, and it will be evident that as the pattern repeat is larger the non-printing area will be smaller and vice versa so that adjustment in the pattern cycle can readily be made by replacing the screen.
At suitable points on the opposite sides of the screenprinting frame 54 there are screened upwardly extending brackets 60 mounted on the frame 54 and supporting longitudinally extending squeegee tracks 61 at each side of the screen. The tracks 61 are desirably of channel shape with the flanges directed toward the center of the screen, so that they provide top and bottom track surfaces. Sliding in the tracks at each side are shoes 62 cross connected at the front and back by bars 63 and supporting a transversely extending bracket 64 which reciprocates longitudinally with the shoes 62. At each side of the machine there is a squeegee support plate 65 pivoted at 66 on the shoes 62 so as to permit changing the attitude of the squeegee as later explained. Each of the squeegee support plates 65 is angularly positioned by a fluid operated cylinder 67 having therein a piston and rod combination 67 which is urged toward retraction by a spring 672. Each cylinder is pivotally mounted on the bracket 64 at 673 and each piston rod is pivotally connected to a plate 65 at 674. Fluid connections are provided to the cylinders by flexible connections 675. In retracted position of the piston and rod combination 67', a squeegee blade 68 supported on the plates 65 is positioned in operative relation pressing rmly against the screen-printing screen 55 as shown in full lines in FIGURE 2, while in this position a spreader bar 68 also supported on the plates 65 is raised remote from the screen-printing screen. Thus, when the squeegee is in engagement the spreader bar is remote from the printing medium 57.
At the right in FIGURE 2 there is shown in dot-anddash lines the position at which retraction of the squeegee will take place, except that when this occurs the squeegee is out of Contact with the sheet. Under these conditions cylinders 67 are energized and spreader bar 68 is brought into operative relation with the screen-printing screen (lightly touching it) so as to move in retraction, but at that time the piston and rod combinations 51 are retracted so that 4no printing action can take place. The reciprocation of the squeegee is controlled by iluid cylinder 69 having a piston and rod combination 69 which connects with the sliding shoes 62 by means of connection at one of the cross bars 63. The piston and rod combination 69 is urged toward retraction by a spring 692 and for forward motion is energized by fluid connection to the cylinder at 693 by a exible hose. The cylinder is supported to move with the screen-printing frame by a bracket 694.
The squeegee and the spreader bar respectively may be of a suitable rubber, plastic or synthetic rubber composition as desired.
At a suitable point before the screen-printing, forward progression of the sheet 20 is measured by a roller 71 engaging the sheet, which through suitable adjustable gearing in the gear box 72 drives a cam 73 (FIGURE 5) which makes one revolution per cycle. The cam 73 has has a projection 74 which at one position in the cycle will close a timer starting switch 75 of well known type which is internal in a timer 76, suitably a drum timer which is adjusted to turn the drum one rotation in the cycle. A development of the drum 77 of the timer is shown in FIGURE 7, the drum, suitably of insulating material, having a contact track 78 for control of clamping engaged by a fixed contact 80 in the timer, a vacuum contact track 81 engaged by a fixed contact 82 in the timer, a screen control contact track 83 engaged by a fixed contact 84 in the timer, a squeegee reciprocation contact track 85 engaged by a fixed contact 86 in the timer and a squeegee attitude contact 85' Vengaged by a fixed contact 86 in the timer. There is also a contact 87 on the drum which when it engages a xed contact 88 on the timer starts the retraction of the table to begin the next cycle as later described.
A fluid cylinder 90 mounted on the frame has therein a piston and piston rod 91 which is connected for retraction of the table 34 and which has a uid connection 92 for retraction purposes.
The uid operating system, which can of course be hydraulic or pneumatic, as shown in FIGURE 8, cornprises a pressure pipe line 93 connected to a suitable fluid pressure pump and an exhaust pipe line 94 connected to the sump or to atmosphere in the case of a pneumatic system. A two-way valve 95, which is preferably solenoid operated'and spring returned, when energized connects to a pipe 96 to the uid pressure, admitting uid pressure to the operating upper ends of cylinders 50 which lower the screenfprinting screen into contact with the sheet. When inf its retracted position it connects to lexhaust through pipe 97.
Likewise, a suitably solenoid operated spring return valve 98 when energized connects pressure from a pipe 100 to the uper ends of clamp cylinders 43 in order to clamp. When deenergized it connects the clamp cylinders to exhaust through pipe 101.
A solenoid operated spring return valve 102 when energized connects pressure from a pipe 102to the rearward end of squeegee advance cylinder 69 in order to advance the cylinder. When deenergized it connects the squeegee advance cylinder 69 to exhaust through pipe 103 so that the spring acts to retract the squeegee.
A solenoid operated spring return valve 104 when energized connects pressure from a pipe 104' to squeegee attitude change cylinders 67 to bring the squeegee into raised position and to bring the spreader bar into .operative position as shown in dot-and-dash in FIGURE 2. When valve 104 is denergized it connects the squeegee attitude cylinders to exhaust through pipe 10,5.
Table return cylinder 90 is actuated by a suitable solenoid energized and spring retracted valve 106 which when energized admits fluid pressure from a pipe 107 to the end of retraction cylinder 90 to cause retraction of the table, and when deenergized connects the cylinder 90 to exhaust through pipe 108. v
FIGURE 6 shows an electric circuit diagram in which power leads 110 and 111 from a suitable source of electric power, preferably alternating current at commercial frequency, are connected to the timer 76. In a separate circuit branch, solenoid 95 which controls the solenoid valve for the screen lowering cylinders is in series with switch track 83 on the timer drum. In a separatevcircuit branch, solenoid 98 of the solenoid valve which operates the clamp is in series with switch track 78 in the timer 76.
In a separate circuit branch, squeegee solenoid 102 is in series with switch track 85 in the timer 76. Also in a separate circuit branch, squeegee attitude control solenoid 104 is in series with switch track 85 in the timer 76'. In an independent circuit branch, solenoid 106 of a solenoid valve which controls the return of the table is in series with switch contact 87. In still another circuit branch solenoid 112 in series with timer switch 81 operates the solenoid valve which turns on and oli:` the vacuum in vacuum chest 38.
In operation of the mechanism of the invention,- with the sheet 20 progressing at a uniform speed acrsthe table, when the roller measuring the forward motion brings cam projection 74 into position to close timer start switch 75, the table being retracted, the clamp and the screen being raised and the vacuum in the vacuum box 38 turned off, the timer drum 77 moves in the direction of the arrow shown in FIGURE 7, closing clamp switch track 78 to energize solenoid 98, and applies fluid pressure to the upper portion of the clamp cylinders 43 so that the clamp bar 45 clamps the moving sheet to the table and begins to move the table in the same direction and at the same speed as the sheet. Timer switch 81 closes and energizes solenoid valve 112 to admit vacuum to the vacuum chest 38 in the table and grip the sheet rmly and in smooth at relation against the top of the table. If instead a magnetic clutch 41 is used the magnetic clutch is energized at this time. Timer switch track 483 also closes and energizes solenoid valve 95 which admits uid pressure to the top of the cylinders 50 which cause the screen-printing screen 55 to 'be lowered into engagement with the top of the sheet. As soon as this has been achieved timer switch track closes to energize the squeegee solenoid valve 102 to advance the squeegee against the upper side of the screen 55.
To accomplish screen-printing, the squeegee 68 completes its forward stroke during the time that the screen is clamped against the sheet and then remains at the end of its forward stroke as long as the screen remains in contact with the sheet. Then the time switch track 83 disconnects to cause the screen 55 to be raised by the springs 52. At this point contact track 85' energizes in contact with its xed switch 86 which operates attitude cylinders 67 to bring the spreader bar 68 into operative position during the time that the spring 692 is retracting the squeegee. This tends to redistribute the screendprinting medium during the retraction stroke of the squeegee while the screen is out of contact with the sheet. Switch track 81 times out, causing the vacuum valve 112 to close and by virtue of its two-way construction connects the interior of the vacuum space to atmosphere. This having taken place, clamp switch track 78 times out and releases the clamp so that the table is now free to retract. A moment later switch contact 87 closes to retract the table and then immediately opens in preparation for the next cycle.
It will be evident, of course, that the timing shown in FIGURE 7 is merely diagrammatic and is not intended to be the precise timing which would be used.
In view of my invention and disclosure, variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art to obtain all or part of the benefits of my invention without copying the structure and method shown.
Having thus described my invention what I claim as new and desire to secure by Letters Patent is:
1. In mechanism for screen-printing on a moving web, a table, means for continuously advancing the web across the table, means for intermittently clamping the table to the web, means mounting the table for forward movement with the web, screen-printing means including a printing screen extending above the web and movable with the ta'ble and means for raising and lowering the screen-printing means with respect to the web.
2. Mechanism of claim 1, in which the screen-printing means includes a squeegee and means for moving the squeegee in contact with the upper portion of the screen.
3. Mechanism of claim 1, in combination with means for retracting the table and screen-pnting means while the means for clamping is unclamped.
4. Mechanism of claim 1, in combination with means to pull the web into rm contact with the table.
5. Mechanism of claim 1, in combination with means for measuring the progression of the web, and automatic means responsive to the measuring means for actuating the clamping means and the screen-printing means.
6. Mechanism of claim 5, in combination with means to pull the web into firm contact with the table, and automatic means responsive to the measuring means for actuating the means to pull the web into rm contact with the table.
7. A method for screen-printing on a web, which comprises continuously progressing the straight web forward adjoining the surface of a table, clamping the web to the table and thereby progressing the table forward with the web, bringing a screen-printing screen into contact with the surface of the web remote from the table and moving the screen-printing screen, in this position, with the web, printing a screen-printed design on the web, removing the screen-printing screen from the web, unclamping the table and retracting the table to its initial position.
8. A method of claim 7, which comprises holding the web into rm engagement with the table during the screen- References Cited UNITED STATES PATENTS Porter et a1 101-44 Steinitz 101-126 X Freeman 101-288 X Jaa et al 101-124 X Melton 101-123 10 8 FOREIGN PATENTS 1,240,568 8/1960 France.
U.S. C1. X.R.
lOl-126, 129, 288; 118-406