US3492942A

US3492942A - Adjustable printing head assembly for screen printing apparatus

Info

Publication number: US3492942A
Application number: US692780A
Authority: US
Inventors: Charles F Forslund
Original assignee: Individual
Current assignee: Individual
Priority date: 1965-02-15
Filing date: 1967-12-22
Publication date: 1970-02-03
Anticipated expiration: 1987-02-03

Description

Feb-3,1970 .F'. FQRSLUND 3,492,942

ADJUSTABLE PRINTING HEAD ASSEMBLY FOR SCREEN PRINTING APPARATUS Original Filed Feb. 15, 1965 7 Sheets-Sheet 1 Z k N k l\ N N 0 1 & N S E IIVEITOR CHARLES E. PORSLUID ATTORIE S I Feb.- 3, 19.70

c r. FQRSLUND ADJUSTABLE PRINTING HEAD ASSEMBLY FOR SCREEN PRINTING APPARATUS 7 She ets-Sheet 2 Original Filed Feb. 15, 1965 II'EITOR CHARLES E. FORSLUJI I r arcus" 3,492,942 ADJUSTABLE PRINTING HEAD ASSEMBLY FOR SCREEN PRINTING APPARATUS Original Filed Feb. 15, 1965 Feb. 3, 1970 c F, FoRsL JNd 7 Sheets-Sheet 3 INVENTOR CHARLES F. FORSLUII? Feb. 3, 1970 c. F. FORSLUND ADJUSTABLE PRINTING HEAD ASSEMBLY FOR SCREEN PRINTING APPARATUS 7 Sheets-Sheet 5 Original Filed Fb l5, 1965 IIvz i-ol umxnzs r. ronsnuln ATTORIIB s Feb. 3, 1970 c. F. FORSLUND ADJUSTABLE PRINTING HEAD ASSEMBLY FOR SCREEN PRINTING APPARATUS 7 Sheets-Sheet 6 Original Filed Feb. 15, 1965 FIG.7

INVENTOR CHARLES E. FORSLUND c. F. FORSLUND 3,492,942

7 Sheets-Sheet 7 INVBNTOR CHARLES F. FORSLUND BY flan/ 4 M, M

ATTORNEY FIG.9

Feb. 3, 1970 ADJUSTABLE PRINTING HEAD ASSEMBLY FOR SCREEN PRINTING APPARATUS Original Filed Feb. 15, 1965 United States Patent 3,492,942 ADJUSTABLE PRINTING HEAD ASSEMBLY FOR SCREEN PRINTING APPARATUS Charles F. Forslund, 3660 Lorna Vista Ave., Oakland, Calif. 94619 Original application Feb. 15, 1965', Ser. No. 432,528, now Patent No. 3,359,895, dated Dec. 26, 1967. Divided and this application Dec. 22, 1967, Sen-1N0. 692,780 Int. Cl. B41f 15/34 US. Cl. 101-123 2 Claims ABSTRACT OF THE DISCLOSURE A printing head including an attached porous screen pivotally mounted to a stationary horizontal base for raising and lowering the head with screen into arid out of registration with a work piecefarranged on the base. The base and pivotal mounts for thehead are coupled by a pair of spaced apart vertically disposed screw members mounted to the base and journaled for rotation. A pair of cooperatively threaded follower or nut members are arranged on the screws and connected to the pivotal mount. The screws are rotatable for precise vertical adjustment of the head relative to the base during registration of the screen with the work piece. Additionally, the printing head is provided with a pair of arcuate slots, which cooperatively receive cylindrical pins projecting from the pivotal mounts. The slots are positioned to provide stops at the corresponding terminal ends thereof for maintaining the head in raised and lowered positions.

The invention relates to screen printers and particularly to automatic printers capable of printing circuit boards and other objects where high fidelity, accuracy and close printing tolerances are required. The present application is a division of US. patent application Ser. No. 432,528, filed Feb. 15, 1965, for Screen PrintingApparatus and Method. A I v An object of the present invention is to provide a printer which will provide a more precision control of the printing parameters, particularly maintaining registration with each part of a number of simultaneously printed parts within extremely close printing tolerances such as required in the production of electronic printed circuit boards.

Still another object of the present invention is to provide a printer in which the base is constructed from a minimum number of extremely rugged parts and a minimum number of controls which may be manipulated to easily and quickly bring the base into registration with the stencil of the printing screen.

A further object is to provide easy, rapid and rigid frame mounting. I V

A still further object of the present invention is to provide a printer which has accurate and flexible adjustments to accommodate operators utilizing printing techniques and materials essential inthe production of high quality printed circuit work pieces. I h I Another object of the present invention is to provide a basic printer which may be readilymodified to accommodate screens of varying size.

The invention possess other objects and features of advantage, some of which of the foregoing will be set forth in the following description of the preferred form of the invention which is illustrated in the drawings accompanying and forming part of this specification. It is to be understood, however, that variations in the showing made by the said drawings and description may be adopted within the scope of the invention as set forth in the claims.

Referring to the drawings (seven sheets):

Patented Feb. 3, 1970 FIGURE 1 is a perspective view of the printer constructed in accordance with the present invention.

FIGURE 2 is a plan view of the printer shown in FIGURE 1. v

FIGURE 3 is a plan view of the device taken substantially along the plane as indicated by line 3-3 of FIG- URE 1 with parts partially broken away for purposes of clarity.

FIGURE 4 is a partial cross section of the device taken substantially along the line 4-4 of FIGURE 2. I

FIGURE 5 is an end elevation of the device with portions removed for purposes of clarity and shown on an enlarged scale.

FIGURE 6 is a partial cross section of the device taken substantially along the line 6-6 of FIGURE 2 and shown on an enlarged scale.

FIGURE 7 is an end elevation of a portion of the device taken substantially along the line 7-7 of FIGURE 2 and shown on an enlarged scale.

FIGURE 8 is partial plan view of a portion of the device taken substantially along the line 8-8 of FIG- URE 7 with portions broken away for purposes of clarity.

FIGURE 9 is a cross section of a portion of the device taken substantially along the line 9-9 as shown in FIG- URE 2 and shown on an enlarged scale.

FIGURE 10 is a cross section of a portion of the device taken substantially along the line 10-10 of FIGURE 9.

The printing device of the present invention consists briefly of a base 6 adapted for receiving a part 7 to be printed, a printing head 8 adapted for receiving a screen 9 and pivotally and slideably mounted to the base for rotational movement between a lowered operative printing position in registration with the base and an elevated inoperative position and rectilinear movement for raising or lowering the pivotal axis of head 8 relative to base 6. A motor means13, is provided and a drive shaft 14 is connected to a driven shaft 16 mounted for rotation on the head. A cam 17 is mounted on driven shaft 16 for rotation therewith, and a cam follower 18 is and positioned so as to react with the cam for moving the head to an operative position during the squeegee return stroke.

A primary feature of the present invention is the ease and speed with which the part to be printed can be brought into precise registration with the stencil on the screen. Precision of registration is required in numerous types of printing, such as multi-color printing, electrical circuitry printing (printed circuit boards). Moreover, for these applications, off contact printing is a common and desirable procedure which requires exacting and minute separation between the work piece and porous screen during printing. In the present machine, 0.001 inch repeatability is obtainable for this separation and adjustments of the separation may be made to within a tolerance of several thousandths of an inch.

Base 6 having supporting

legs including legs

2, 3, and

' 5 is constructed of heavy, accurately machined castings and includes a sub-base 21 which is preferably made of ground aluminum plate and is mounted on the base for controlled side to side, fore and aft, and rotational move.- ment in a plan for registration with a stencil on the screen when the head is in the operative position. Such displacement of the sub-base is effected by first manual control means 32 and 40 connecting the sub-base and the base for movement of the sub-base along a first axis of the plane, and second manual control means 68 with shaft 69 connecting the sub-base and the base for movement along a second axis at substantial right angles to the first axis as described in application Ser. No. 432,528.

The printing head 8 consists briefly of a pair of spaced and 104 for receiving shaft 106 for pivotal movement ih t ont arms are held. .in. spaced, apart. relation .hy-

attachedto cross member 108..and by means of an adjustable cla rnp 118 having a registrated dove-tail section ,119 ,and a clampingscrew handle 121. The screen frame rests firmly against the printing head' and thus is asrigid as the arms andcross .membersof the printing head. A

second clamp means 122 with an adjustable knob. 123

holds the screen securely in place. 1 I 7 Also as described in application Ser. No. 432,528 a continuous loop means 11 is provided for driving a squeegee means 12. Loop means 11 consists of a link chain mounted on idler sprockets 125 and 126 mounted for rotation on stub shafts 127 and 128 connected to arm 101. A second link chain 131 is driven by sprocket 132 mounted for rotation shaft 133. The other end of the link chain is mounted on a sprocket 134 mounted for rotation on stub shaft 128. An identical continuous loop means ismounted on arm 102; parts of which may be seen in FIGURES 2, 5, and 6 as sprocket 136 mounted on shaft 133, link chain 137 mounted between

sprocket

136 and 138, idler chain 139 mounted on sprocket 140.

A carriage means is provided for guiding squeegee means 11 and here consists of a base 146 having openings for receiving stub shaft 147 and 148 with rollers 149 and 150 mounted thereon for rolling receipt in channel groove 152 formed in arm 101.

Principally the present invention provides a vertically adjustable, pivotally mounted printing head wherein positioning of the head to and above the sub-base is accomplished by a single control. Vertical adjustments of 2 inches or more'may be obtained allowing for various size work pieces and porous screens. The structural elements necessary to accomplish the foregoing include a pair of

ear bases

266 and 267, upon which are mounted a pair of

standards

268 and 269. The right hand standard as shown in FIGURES l, 5 and 6 consist of a side wall 271, front wall 272, a back wall 273 and an inner wall 274 formed with an elonged slot 276 therein, and a top wall 277. A base journal block 278 is attached to the ear base by fasteners 279, 280 and 281. An upstanding threaded head screw member 286 is journaled for rotation with its lower end 287 mounted in bore 288 formed in base278. The upper end 289 of threaded member 286 is journaled for rotation in bore 291 formed in upper wall 277. End 289 is threaded and mounted thereon is a stop nut 292 and a lock nut 293. Follower member 296 is mounted for travel on member 286 and is formed with a pin 297 connected to a journal or carriage means providing a moveable pivotal support for head 8.

The journal means consists of a T-shaped member 298 having a portion formed for sliding fit in slot 276 and having lugs 299 and 300 formed thereon to prevent transverse movement through the slot. Member'298 is formed with a smooth walled bore 302 formed for receiving an end of shaft 106, and a bore 303for receiving pin 297. Member 298 is formed with an upright member 306 which carries an arm 307 upon which a cam follower 308 is mounted forfree rotation. s v

Arms

101 and 102 are brought to a substantially parallel position with the baseby a pair of slot engaging members. mounted to reciprocate in Ca pair of associated arcuate slots formedin

arms

101 and 102. As shown in FIGURE 5, .one. such slot engaging member 311 is mounted at the upper end of upright member 306. The. slot engaging member 31-1 is dimensioned to protrude through'arcuate slot 312 formedin arm 102, the ends of theslot cooperating with member'311 to limit the rotation of arm 102. i

Precise adjustable. alignment of the arms 102- and 101 in parallel relation to the base is obtained by varying the effective length of the'- elongated arcuate slot for arm 102a threaded bore 314 is formed in an end there of opening to slot 312: :At. threaded screw 316 is dimensioned for. i-threadable receipti-in". the: bore "314 and protrudes into the: opening formd'by slot 312 t'o provide an adjustable" sto'p meansengaging-member 311 when the arm is substantially" parall'el to 't'hefbase in an operative brimm n s fi ni- 'Move m eht of the entire pr{inting head -assembly iseffected by rotating handiwheel 321 connected for rotation on shaft 322, formed with a worm gear 323. Gear 324 is formed to mesh with gear 323 and is mounted for rotation on upright threaded member 286fThus turning of hand wheel 321 rotates 'ilpright member 286 which causes nut member 296 to movein a vertical direction which in turn moves the entire printing head assembly in a vertical direction. W Q I v A pivotal support or jonrnal means .is also mounted on the left side of the1machine,,as partially shown in FIG- URE 2 enclosed standard 268 and is similar to the journal means mounted on the right side andjenclosed in standard 269. Some'of the essential parts may be seen by referring to FIGURE], Arin .101 is formed with an arcuate slot 332 formed for, receiving a slot engaging member 333 mounted oh stub shamt 334 protruding from upright member 33 6. A threaded screw, like screw 316 arm 102, is adjustablyfrhounted to protrude into the slot of arm 101 as shown to provide a separate stop means for arm 101. Upright member 336 supports arm 337 upon which cam follower" 18 is mounted for engagement with cam 17. I j

The drive mechanism for reciprocating" printing head 8 consists of a motor 13, a motor shaft 341 driving a pulley 342 which drives a fiexible belt 343 and in turn drives a pulley wheel 344 mount ed for rotation on driven shaft 14. A worm gear346 is'm'ounted on shaft 14. Shaft 14 is mounted in housing 348 carried by the printing head.

Sleeve bearings

351 and 352 are mounted in housing 348 for rotation of shaft 14.10

am

17 and 309, keyed toa shaft 16 are rotated by motor 13 by means of shaft 341, pulley 342, belt 343, wheel 344, shaft 14, worn gear 346 and gear 347. Associated cam followers 18. and 308 are mounted to the Tfsli'aped journal means. For example follower 30 8 is mounted to member 298 at a fined distance from the pivotal axis of shaft 106, Shaft 16 is journaled in housing 348 by bearings388 and 389.. By this arrangement,

cams

17 and 309 engage with followers 18 and 308 forcing shaft 16 and this printing head 8 to pivot about shaft 106. The reciprocation 'of head 8 between operative and inoperative positidnsis thereby achieved about a pivot point having an adjustable elevation relative to base 6. H

Additionally as best disclosed in Ser. No. 432,528, motor 13 drives loopmeans 11 for which a clutch mech anism is carried by end 356 of shaft 14 on which is mounted sleeve bearings362 and .363 carrying a worm gear 357 formed for engagement with gear 358. The components associated with the clutchare worm gear 357, sleeve'extension member 3.59,.fian'ge 361, clutch 366, washer 367, thrust bearing ssgpi 369, solenoid 371,

' 1 solenoid arm 372, jarm 373, pivot pin 374, opening .376,

lever arm 377, pin 378, spring 381, spring.382, shaft 383, opening 384, thrust pin386, lock nut 387, shaft 133, and

sleeve bearings

391 and 392. i i Also described in thea b ove application is an electromechanical control means for causing the printcr to move through one complete cycle which includes atmicroswitch 407 having a leyer1 40 8, control cam, 406, switch 413, lever 414, arm. 183 on'thecontinuous loop, control ca'm 421, "microswitch 422', aria lever 423. g

. lug 117 to cross bar'108i'The In operation, the"tii'st step is'to t ta'c h the mounting A a I, sthe'n positioned on the screen and the screen' frame attached to the printing head by dove-tailing clamps 118 and 122 into the matching sections of the screen frame.

The next step is to attach a holding fixture or registrating device (not shown) to the adjustable base 21 in relation to the position of the stencil on the screen.

The next step is to register the screen to the part which consists of the steps of turning knobs 32, 40 and 68 which move the sub-base 21.

After the screen is in registration with the part to be printed the head is set for oif contact printing by rotating hand wheel 321. Rotation of the wheel rotates shaft 322, which turns worm 323 which in turn moves gear 324 connected for rotation of threaded member 286. Nut 296, threadably connected to member 286 is connected to journal means 298 and moves vertically on threaded shaft 286. Shaft 106 is pivotally connected to the journal means and

arms

101 and 102 are journaled on shaft 106. Thus movement of wheel 321 causes the pivot axis of the entire printing head assembly which rests on

arms

101 and 102 to move in a straight vertical path relative to base 6.

As described in application Ser. No. 432,528, and with reference to FIGURE 4, the next operation is to set the squeegee pressure which consists of adjustments involving squeegee backing plate 166, cross member 162, knobs 167 and 227, knobs 176 and 236, bar 191,

knobs

201 and 259,

levers

192 and 252, pins 193 and 253 and springs 202 and 262.

The squeegee assembly reciprocates back and forth along

arms

101 and 102 in a channel 152 on sets of rollers attached to the sub-base 146 and 206. The squeegee reciprocates on guides 158 and 218 which are held in position by

blocks

153 and 213. The angle of the squeegee to the screen may be varied by adjusting guides 158 and 218, screws 155 and 215, blocks 153 and 213, and pivot pins 154 and a pin connected to block 213 but not shown.

Squeegee means 12 is connected to link chain means 11 by a pivot arm 183 which moves in a counter clockwise direction. As shown in FIGURE 4, the flood bar 191 is in the flooding position and the squeegee is in the raised position when lever arm 181 is in the position shown. Further movement of pin arms 183 in a counter clockwise direction causes lever 181 to pivot about point 182 into a more nearly horizontal position thus causing crank arm 184 to move block 161 to a lower position and carrying cross member 162, back bar 166 and squeegee 171 downwardly with squeegee 171 coming into contact with screen 9.

The electrical operation of the printer is effected by circuitry disclosed in Ser. No. 432,528. Briefly, however, a switch energizes motor 13 causing shaft 14 to rotate which turns shaft 16 through worm gear 346 and gear 347.

Cams

17 and 309, keyed to shaft 16, rotate and move against cam followers 18 and 308, causing

arms

101 and 102 to pivot about shaft 106 and move away from the subbase 21. When the solenoid is energized the clutch means is engaged and worm gear 357 rotates with shaft 14 thus turning gear 358 and rotating shaft 133 which causes link chain 131 to run, shaft 128 with sprocket 126 is rotated and link chain 11 is thereby rotated which moves the squeegee means 12. The squeegee continues to move with chain 11 until the clutch is disengaged by the solenoid. The pivoting of the

arms

101 and 102 and the movement of the squeegee means 12 is timed so that the flood bar will flood the screen 9 while the arms are being lowered to operating position. Once the arms are lowered, lever 181 automatically raises the flood bar and lowers the squeegee. The squeegee continues its printing stroke moving from left to right as shown in FIGURE 4. A micro-switch 413 is located so that when the end of the printing stroke is reached, pin arm 183 will move lever 414 of the micro-switch and break the circuit de-energizing the solenoid 317 and spring 382 will move lever 377 so that the clutch will become disengaged. Movement of the squeegee will stop while the motor continues to raise the

arms

101 and 102 out of position with the sub-base so that a new part can be placed thereon for printing. When the arms are in the highest raised position, a control cam 412 is positioned so that it will strike lever 423 on micro-switch 422 thus breaking the circuit causing the motor to stop operation and the printing is set for the next cycle.

I claim:

1. In a printing apparatus, a base for receiving a work piece, a printing head having a pair of spaced elongated arms and clamp means carried thereby, a pivotal support carried by said base and journaling said arms adjacent one end thereof for rotation about a common axis and for movement between a printing position adjacent and substantially parallel to said base and a non-printing position remote from said base, manually operable means for moving said support to and from said base for manually adjusting the spacing between said axis and base, a printing screen demountably secured by said clamp means and extending between and substantially coextensive with the length of said arms, and separate manually adjustable stop means carried by each of said arms for individually adjusting the angular position of said arms relative to said base in printing position for precise positioning of said screen on the work piece.

2. In a printing apparatus as defined in claim 1, each of said pair of arms being formed with an arcuate slot having a center of curvature on the pivotal axis of said head, said support having a pair of slot engaging members positioned for reciprocation in said slots between terminal ends thereof limiting rotation of said arms between said printing and non-printing positions, adjustable means mounted on each of said arms and positioned to project into said slots and engage said slot engaging mem bers when said arms are in said printing position to provide said adjustable stop means.

References Cited UNITED STATES PATENTS 3,098,431 7/1963 Weaver 101126 1,939,965 12/1933 Flockhart 101--123 2,991,711 7/1961 Ehrhard et a1. 101298 X 3,263,603 8/1966 Fuchs 101-123 FOREIGN PATENTS 777,022 6/ 1957 Great Britain.

ROBERT E. PULFREY, Primary Examiner.

C. D. 'CROWDER, Assistant Examiner U.S. Cl. X.R. 101126