US3263603A - Silk screen printing apparatus - Google Patents

Description

Aug. 2, 1966 A. J. FUCHS SILK SCREEN PRINTING APPARATUS 3 Sheets-Sheet 1 Filed Jan. 3, 1964 INVENTOR A74 /m/ a! F0 BY 5 u 7 w H Aug. 2, 1966 FUCHS 3,263,603

SILK SCREEN PRINTING APPARATUS Filed Jan. 5, 1964 5 Sheets-Sheet 2 INVEN TOR.

1966 A. J. FUCHS SILK SCREEN PRINTING APPARATUS 5 Sheets-Sheet :5

Filed Jan. 3, 1964 INVENTOR. #4 //A/ \J. FacH 5 A Trail/E 7'} United States Patent 3,263,603 SILK SCREEN PRINTING APPARATUS Alvin J. Fuchs, Milwaukee, Wis., assignor to M 8; M Research Engineering Co., Butler, Wis., a corporation of Wisconsin Filed Jan. 3, 1964, Ser. No. 335,645 6 Claims. (Cl. 101123) This invention relates to silk screen printing apparatus and more particularly to the drive mechanism for such apparatus. 7

In apparatus of the type to which the present invention relates, the silk screen frame is raised and lowered to permit insertion and removal of the successive sheets on which the printing is done. While the frame is in the lower operative position over the sheet to be printed, the squeegee is pushed over the silk screen to thereby drive the ink through the screen and onto the sheet to effect printing. A flood bar is carried adjacent the squeegee for movement therewith over the silk screen, and this flood bar should also be shifted vertically relative to the squeegee in certain timed relationship; for example, the flood bar is raised from the screen just prior to and While printing occurs and is then lowered into contact with the screen just prior to and while the squeegee is being returned to the starting position.

It is desirable to have the squeegee and flood bar move with harmonic motion when passing in either direction over the screen; that is to say, it is desired to have them accelerate when moving toward the center of the screen and then decelerate as they approach the ends of the screen.

Furthermore, it is desired to have a certain period of dwell of the squeegee and flood bar at both ends of their travel over the printing screen, that is, before the printing cycle starts again, in order to give the frame time to lower without forward printing motion of the squeegee and consequent premature delivery of the paint through the screen, and also at the end of the printing stroke in order to give the screen time to be raised off the work and give the flood bar time to contact the screen before the flood bar and squeegee start their return stroke.

Another requirement in the operation of this type of apparatus is that no backlash in the various linkages or drives occurs which results in an unsmooth operation and misregister of the screen and sheet material being printed.

Prior art devices, having cams for controlling the operation of the squeegee and flood bar, have been used with some degree of success but have usually resulted in too much backlash in the drive mechanism.

Another type of prior art device utilized a drive shaft with actuating arms fixed thereto for direct connection to the parts to be actuated, but this was unsatisfactory because of the excessive length required for the arms, particularly in larger size machines.

The present invention provides silk screen printing apparatus which has improved drive means that results in the above-mentioned desirable characteristics and eliminates the objectionable features of the prior art. More specifically, an improved drive linkage is provided which has no lost motion or backlash, provides positive and precise control over the moving parts at all times, pro- Patented August 2, 1966 vides a simplified and compact linkagedrive arrangement, and cannot bind or malfunction in operation.

These and other objects and advantages of the present invention will become apparent as this disclosure progresses, reference being had to the accompanying drawings, in which:

FIGURE 1 is an elevation view of a press embodying the present invention, certain parts being shown in section, broken away or removed for clarity in the drawing, and showing the press during a printing stroke;

FIGURE 2 is a plan view of the press shown in FIG- URE 1, certain parts being shown as broken away or removed;

FIGURE 3 is a view similar to FIGURE 1 but showing certain of the parts in a different position, namely, when the screen frame has stopped in the upper position and as the squeegee assembly has just started its return stroke;

FIGURE 4 is an enlarged, fragmentary view of certain of the parts as shown in FIGURE 1 during the printing stroke;

FIGURE 5 is a view similar to FIGURE 4 but showing the parts when moving in the opposite direction, namely, at the end of a return stroke;

FIGURE 6 is a fragmentary view of the linkage shown in FIGURE 3 but in a slightly different position just over a dead center relationship;

FIGURE 7 is a fragmentary view similar to FIGURE 6 but showing the linkage moved to a bottom dead center position;

FIGURE 8 is a fragmentary perspective view of the press just before the position shown in FIGURE 3 is reached;

FIGURE 9 is another fragmentary, perspective view of the squeegee assembly of the press as shown in FIG- URES l and 4.

Referring in greater detail to the drawings, the base 1 of the machine supports a table top .2 on which the sheet to be printed (not shown) is placed and is held thereon by suction or other suitable means in a conventional manner. An oscillatable power frame F is pivoted by the bolt means 4 to the base for swinging between a printing position shown in FIGURE 1 and an open, inoperative position shown in FIGURE 3. This power frame includes a generally rectangular, lower section SL including a rear member 5, a front angle iron member 6 and two side members 7 and 8, all of which are welded together into a rigid lower frame section. This section also includes four vertical members 9, 10, 11 and 12 extending upwardly and to the upper ends of which an elongated, rectangular, upper frame section SU is rigidly secured by bolt means 13.

The upper frame section SU includes two parallel side members 14 and 15 which extend over the edge of the table and have a handle '16 secured across their outer ends by bolt means 17. A screen hook 1 8 extends through and downwardly from the handle and its vertical position, relative to the handle, can be adjusted by the wing nuts 19 and lock nuts 20 which are threadably engaged on the upper ends of the hooks. The purpose of hooks 18 are to support a screen frame 2 1 when it is raised off the table, as shown in FIGURE 3.

The parallel side members 14 and are formed of steel tubular stock of square cross section and their inner 3 sides have a slot 22 (FIGURE 1) cut therealong which act as guidevvays for the reciprocable squeegee and flood bar assembly A to be described.

The screen frame 21 is rectangular as viewed in FIG- URE 2 and is formed of four wooden members 24, 25, 26 and 27 which are rigidly fastened together.

The rear member 24 is clamped in a rear screen clamp 28 by threaded handwheels 29 which are threadably engaged in the clamp and bear against the wooden frame 21. The clamp 28 is loosely held on the frame F by two adjustable turnbuckles 30, one being located on each end of the clamp and secured to the clamp and frame by its conventional swivel joint ends. Thus, the rear end of the screen frame 21 can move vertically a small distance relative to the main frame F.

The front side of the screen frame is embraced in a clamp 32 by the handwheel member 33 which threadably extends through the clamp and abuts against the frame.

Bolt means 35 extend from the clamp and through each hook 18. When the screen frame rests on its stops 36 on the table, that is, in the printing position shown in FIG- URE 1, the bolt means 35 do not engage the hook 18. When the frame F raises the screen frame off the table, the bolt means then rest on the hook and are supported thereby.

In this manner the screen is more or less loosely suspended from the main frame and can be set on its stops on the table in an exact printing position in respect thereto.

A silk screen 38 is stretched across the frame 21 in the conventional manner and the printing ink is placed on the top of this screen where it is wiped across, by the assembly A to be described, to effect printing by the ink passing through the screen.

The drive for the press is furnished by the electric motor 40 carried on the frame F, and through a flexible belt 41 which drives a gear reduction unit 42. The frame is raised and lowered by means of a cam 43 which is carried on a shaft 44 of the unit 42 and is rotated thereby. This cam bears against a fixed roller 45 which is mounted on a rigid bracket 46 (FIGURES 2. and 3) mounted on the base of the press.

As shown in FIGURE 3, the frame is in the uppermost position due to the fact that the portion of the cam with the greatest radius is then bearing against the stationary roller. It will be noted that this portion of the cam is more or less fiat and gives a certain amount of dwell to the frame movement when in the fully raised position.

When in the FIGURE 1 position, the small radius portion of the cam does not influence the screen frame and the latter sets freely on its table stops 36.

An adjustable sequence timer 47 (FIGURE 1) is provided for the electric motor to stop the drive when the frame F is in the upper position shown in FIGURE 3, to thereby give the operator time to unload the printed sheet and insert a new sheet to be printed. A micro switch 48, actuated by a small cam 49 carried on shaft 44, starts the timer, and whenever the micro-switch runs over the small radius portion of the cam, as shown in FIGURE 3, and a period of dwell commences for the frame.

The squeegee and flood bar assembly A includes a transverse frame member 51 which has side members 52 and 53 welded to its ends and on which are pairs of rollers 54 and 55, respectively. These rollers extend through the guide slots 22 of the upper frame section SU and ride the members 14 and 15. A squeegee 57 is adjustably mounted in the member 51 by the threaded studs 58 and their handwheels 59. Thus a squeegee carriage is formed for drawing the squeegee across the silk screen 38 in a printing direction as indicated by the arrow in FIGURE 1.

A flood bar 60 is also mounted on this carriage for movement with the squeegee but also for movement in a generally vertical direction relative to the squeegee. In other words, during the printing stroke as shown in FIG- URE 1, the flood bar is raised relative to the squeegee and is held off of the screen; at the beginning of the return stroke as illustrated in FIGURES 3 and 5, the flood bar is down on the screen, and is in a lower position than the squeegee, so that during the return stroke the ink is re-- turned or pushed back across the screen to the starting side of the screen.

The flood bar 66 has a pair of threaded rods 61 which extend upwardly and through the cross shaft 62. Lock nuts 61a on rods 61 hold the flood bar in any adjusted position relative to the cross shaft 62, the adjustment being made by the handwheels 63 at the top of the rods. The actuating means for effecting the shifting of the flood bar is as follows. The shaft 62 has a vertical plate 64 pivoted at each of its ends, and these plates are also pivotally mounted on the same stud shaft 65 used for the rear rollers 54 and 55. The plates 64 have projections 66 and 67 which are abuttable against member 51 so as to act as stops for the flood bar as it is shifted, respectively, in an upward and downward direction, by the pair of arms 68 pivotally attached to plates 64.

A pair of slotted guides 69 (FIGURES 4, 5 and 9) are welded to cross frame member 51 and a pin 69a carried by the flood bar slide in the slots of these guides to thereby maintain the flood bar at a substantially constant attitude to the frame F.

Thus the flood bar is vertically shiftable relative to the squeegee by the actuating means in the form of plates 64, this shifting is within the limits defined by the stops 66 and 67 which abut against member 51 as the arms 68 pivot the plates 64 prior to urging the assembly A in either the printing direction (as shown in FIGURE 1) or the return direction as shown in FIGURE 3. The stops 66 and 67 form a lost motion connection on the actuating means between the latter and the flood bar.

The drive for reciprocating the assembly and actuating the flood bar in timed relationship therewith is comprised of a rotatable member 70, levers 71, and arm 68. More specifically the arrangement is as follows.

The reducer unit 42 has a crank arm 70 that constitutes a power driven rotatable member which is fixed to the other end of its shaft 44. A pair of levers 71 are pivoted at their lower ends to the frame F on a rotatable shaft 72 and their upper free ends are pivoted at 73 to the rear end of the corresponding arm 68. An intermediate link 74 is. pivotally connected between one of the levers 71, as at 75, and the free end of the crank arm 70, as at 76. Thus one of the levers is pivoted to the frame and then also has two other spaced apart pivoted connections with the drive source and the reciprocable assemble. It is also to be noted that lever 71 is longer than arm 70 and link 74 combined.

As shown in FIGURE 3, when the frame F is at its uppermost position, the arm 70 and link 74 are in such a position that the linkage has just begun to swing levers 71 in a clockwise direction and thereby push arms 68 and their associated assembly A to the right, that is in a return stroke. During this return stroke, flood bar stop 67 bears against members 51 and the flood bar is in the down or wiping position. A

As shown in FIGURE 3, the assembly A has just started in its return stroke. When the assembly A is about one-half way through its return stroke, the frame F then begins to be lowered. When the frame reaches the horizontal or printing position, the linkage comprising members 70 and 74 continues through its dead center position as shown in FIGURE 7, and in doing so swings the flood bar assembly upwardly. This swinging or lost motion movement causes a period of dwell of the assembly just prior to commencement of the printing stroke. Stated otherwise, when the assembly A has reached the end of its return stroke (FIGURE 5), the arm 70 and link 74 are in the lower dead center position (FIGURE 7) which give a slight period of dwell to the assembly before it starts back across the screen in its printing stroke.

It will be recalled that cam 43 at this time also affords a dwell in the swinging movement of the frame.

The linkage also provides a period of dwell at the end of the printing stroke in order to give the frame time to be raised off the work just printed, before the flood bar begins pushing the ink back across the screen. Referring to FIGURE 1, as the crank arm 70 moves in a counterclockwise direction and reaches its upper position where the linkage pivot points 75 and 76 are in alignment with shaft 44 (just prior to the FIGURE 6 position), then assembly A has been pulled to the maximum extent of its travel to the left, and the printing stroke is completed. During this time cam 43 has been in a period of dwell. As rotation of shaft 44 then continues, the cam 43 begins to raise the frame F, but the flood bar is not yet lowered nor is the assembly A moved in its return stroke, because of the lost motion or dwell provided when the arm 70 and link 74 go over dead center and also because of the lost motion of the flood bar assembly in swinging from position where stop 66 is effective to the position where stop 67 abuts against the member 51, thereby rendering arms 68 effective to begin pushing the assembly A to the right.

When the linkage 70 and 74 is in the FIGURE 6 position where link 74 and arm 70 are just past a dead center position, it will be noted that these members are never in alignment with the pivot point 72 of lever 71; if they were the linkage would be toggled in and binding thereof would result.

Thus the above arrangement provides a period of dwell for the actuation of the flood bar relative to the frame and squeegee, at either end of the stroke of the assembly across the screen. Furthermore, the action is very smooth and is such that the assembly accelerates evenly in its movement towards the center of the screen and then decelerates evenly as it approaches the end of its travel in either direction.

The present construction provides an accurate and positive control of the various parts and their relative movements at all stages of a complete cycle of operation.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

What is claimed is:

1. In silk screen printing apparatus, a frame pivotally mounted for swinging between a printing position and an inoperative position, a squeegee and flood bar assembly mounted on said frame for reciprocation therealong, said assembly having a squeegee and also having a flood bar, actuating means on said assembly for shifting said flood bar relative to said squeegee, and drive means mounted on said frame for reciprocating said assembly and operating said actuating means; said drive means including a power driven rotatable member located above the point of pivotal connection of said frame, a lever pivotally mounted on said frame, an arm pivotally connected between said lever and said actuating means, and an intermediate link pivotally connected between said lever and said rotatable member, whereby rotation of said member swings said lever to cause said arm to operate said actuating means prior to reciprocating said assembly.

2. In silk screen printing apparatus, a frame pivotally mounted for swinging between a printing position and an inoperative position, a squeegee and flood bar assembly mounted on said frame for reciprocation therealong, said assembly having a squeegee and also having a flood bar, actuating means on said assembly for shifting said flood bar relative to said squeegee, and drive means mounted on said frame for reciprocating said assemly and operating said actuating means; said drive means including a power driven rotatable member located above the point of pivotal connection of said frame, a lever pivotally mounted at one end on said frame and extending upwardly therefrom, an arm pivotally connected be tween the other end of said lever and said actuating means, and an intermediate link pivotally connected between said lever and said rotatable member, the length of said lever being greater than the combined length of said link and said rotatable member, whereby rotation of said member oscillates said lever to cause said arm to operate said actuating means and reciprocate said assembly.

3. The apparatus as defined in claim 2 further characterized in the rotatable member and the link are in aligned dead center relationship with one another for each revolution of said member, and that the arrangement of the pivotal connections between the rotatable member, lever, arm and link are such that when the member and link are in said dead center alignment with one another, they are not aligned with the pivot point between said lever and frame.

4. In silk screen printing apparatus, a frame pivotally mounted about a horizontal axis for vertical swinging between a generally horizontal printing position and a raised inoperative position, a squeegee and flood bar assembly mounted on said frame for reciprocation therealong, said assembly having a squeegee and also having a flood bar, actuating means on said assembly for shifting said flood bar in a generally vertical direction relative to said frame, and drive means mounted on said frame for swinging said table and for reciprocating said assembly and operating said actuating means; said drive means including a rotatable cam means for vertically swinging said frame, and also including a power driven rotatable member, located above the point of pivotal connection of said frame, a lever pivotally mounted on said frame, an arm pivotally connected between said lever and said actuating means, and an intermediate link pivotally connected between said lever and said rotatable member, whereby rotation of said member oscillates said lever to cause said arm to operate said actuating means prior to reciprocating said assembly, the arrangement of said cam relative to said member and lever being such that a period of dwell is provided in the reciprocal movement of said assembly just prior to upward swinging of said frame.

5. In silk screen printing apparatus, a frame pivotally mounted about a horizontal axis for vertical swinging between a generally horizontal printing position and a raised inoperative position, a squeegee and flood bar assembly mounted on said frame for reciprocation therealong, said assembly having a squeegee and also having a flood bar, actuating means on said assembly for shifting said flood bar in a generally vertical direction relative to said frame, and drive means for swinging said table and for reciprocating said assembly and operating said actuating means; said drive means including a rotatable cam means mounted on said frame for vertically swinging said frame, and also including a power driven rotatable member located above the point of pivotal connection of said frame, a lever pivotally mounted at one end on said frame and extending upwardly therefrom, an arm pivotally connected between the other end of said lever and said actuating means, and an intermediate link pivotally connected between said lever and said rotatable member, the length of said lever being greater than the combined length of said link and said rotatable member, whereby rotation of said member oscillates said lever to cause said arm to operate said actuating means prior to reciprocating said assembly, the arrangement of said cam relative to said member and lever being such that a period of dwell is provided in the reciprocal movement of said assembly just prior to upward swinging of said frame.

6. In silk screen printing apparatus, a support base, a frame pivotally mounted about a horizontal axis on said base and for swinging in a vertical direction between a printing position and an inoperative position, an assembly having a squeegee and flood bar and mounted on said frame for reciprocation therealong, actuating means in- 7 cluding a lost motion connection on said assembly for shifting said flood bar relative to said squeegee, and drive means mounted on said frame including a power driven rotatable member located above the point of pivotal connection of said frame, a lever pivotally mounted at one end on said frame and extending upwardly therefrom, an arm pivotally connected between the upper end of said lever and said actuating means, and an intermediate link pivotally connected between said lever and said rotatable member, and means to rotate said member to consequently swing said lever and thereby cause said arm to operate said actuating means through said lost motion connection and then reciprocate said assembly.

References Cited by the Examiner UNITED STATES PATENTS 10 ROBERT E. PULFREY, Primary Examiner.

H. P. EWELL, Assistant Examiner.

Claims (1)

1. IN SILK SCREEN PRINTING APPARATUS, A FRAME PIVOTALLY MOUNTED FOR SWINGING BETWEEN A PRINTING POSITION AND AN INOPERATIVE POSITION, A SQUEEGEE AND FLOOD BAR ASSEMBLY MOUNTED ON SAID FRAME FOR RECIPROCATION THEREALONG, SAID ASSEMBLY HAVING A SQUEEGEE AND ALSO HAVING A FLOOD BAR, ACTUATING MEANS ON SAID ASSEMBLY FOR SHIFTING SAID FLOOD BAR RELATIVE TO SAID SQUEEGEE, AND DRIVE MEANS MOUNTED ON SAID FRAME FOR RECIPROCATING SAID ASSEMBLY AND OPERATING SAID ACTUATING MEANS; SAID DRIVE MEANS INCLUDING A POWER DRIVEN ROTATABLE MEMBER LOCATED ABOVE THE POINT OF PIVOTAL CONNECTION OF SAID FRAME, A LEVER PIVOTALLY MOUNTED ON SAID FRAME, AN ARM PIVOTALLY CONNECTED BETWEEN SAID LEVER AND SAID ACTUATING MEANS, AND AN INTERMEDIATE LINK PIVOTALLY CONNECTED BETWEEN SAID LEVER AND SAID ROTATABLE MEMBER, WHEREBY ROTATION OF SAID MEMBER SWINGS SAID LEVER TO CAUSE SAID ARM TO OPERATE SAID ACTUATING MEANS PRIOR TO RECIPROCATING SAID ASSEMBLY.

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