US3545377A

US3545377A - Screen printing apparatus

Info

Publication number: US3545377A
Application number: US690656A
Authority: US
Inventors: Roy M Harwell Jr; David W Yoder
Original assignee: Harwell Enterprises Inc
Current assignee: Harwell Enterprises Inc
Priority date: 1967-12-14
Filing date: 1967-12-14
Publication date: 1970-12-08
Anticipated expiration: 1987-12-08
Also published as: GB1176111A

Description

United States Patent [72] Inventors Roy M. Harwell, Jr.; 2,624,276 1/ 1953 Klopfenstein 101/ 123 David W. Yoder, Gastonia, North Carolina 2,704,510 3/1955 Walsh 101/123 [21] Appl. No. 690,656 2,747,502 5/1956 Gattuso 101/126 [22] Filed Dec. 14,1967 2,866,404 12/1958 Laupman 101/123 Patented Dec. 8, 1970 2,881,700 4/1959 Podgor... 101/126 [73] Assignee Harwell Enterprises, Incorporated 2,963,964 12/1960 K1ump.... 101/ 123 Gastonia, North Carolina 3,160,092 12/ 1964 Eisen 101/ 124 a curporauon of North Carolina Primary Examiner-William B. Penn Attorney-Dominik, Knechtel & Godula [$4] SCREEN PRINTING APPARATUS 6 Claims, 18 Drawing Figs.

[52] U.S.Cl. 101/123 TRACT; A screen-squeegee printing apparatus in which j g B41] 27/00 relative reciprocatory movement between the screen and Field of Search 101/123, squeegee is ff t d by a k h ft through a rack and pinion 124, 126,114, 129 connection. The apparatus is specifically characterized by: mechanism for adjusting the relative contact pressure between [56] References (med the screen and squeegee; mechanism for effecting right angu- UNITED STATES PATENTS lar engaging motion between the screen and squeegee at the 1,468,384 9/1923 Hahn 101/123 beginning of the printing stroke and right angular separation 1,840,073 1/ 1932 Williams.. 101/ 123 motion at the end of the stroke; mechanism for adjusting the 2,039,909 5/1936 Kem et al 101/ 123 stroke length; and rotatable mechanism movable coaxially of 2,571,685 10/ 1951 DAutremont 101/ 123 the crankshaft for actuating and locking said stroke adjusting 2,581,775 1/1952 Wade 101/123 mechanism in each adjusted position.

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PATENTED DEC 8 I970 sum 5 or 5 Row Dawn W. Yo

SCREEN PRINTING APPARATUS This invention relates to a screen squeegee printing press and more particularly to a machine for applying indicia or printed matter to various types of articles of commerce.

It is an object .of this in invention to provide a machine of graph, in which the adjustment of the stroke and relative screen squeegee speed may be effected by rotating the coaxial mechanism, and wherein each adjustment may be releasably locked or fixed by moving the mechanism axially thereof.

It is yet anotherobject of the invention to provide a screen squeegee printing mechanism which is capable of effecting right angular engaging motion between the screen and squeegee at the beginningof the printing stroke and right angular separation motion atthe end of the stroke.

It is a further object of the invention to provide a mechanism for yieldingly exerting pressure between the screen and squeegee during the contact or printing stroke, in combination with means for adjustingthis pressure.

Some of the objects of the invention having been stated, other objects will appear as the description proceeds when taken in connection with the accompanying drawings, in t which:

FIG. 1 is a side elevational view of a printing apparatus, embodying the invention; j

FIG. 2 is a sectional planview taken along line 2-2 in FIG. 1;

FIG. 3 is a sectional planview taken along line 3-3 in FIG.

FIG. 4 is a sectional plan view taken along line 4-4 in FIG. 1;

FIG. 5 is a top plan view of FIG. 1, showing the squeegee assembly positioned at the midpoint of the screen during the printing stroke;

FIG. 6 is an elevation of the left. hand end of FIG. 1; FIG.6A is an elevation of the upper right end of FIG. 1; FIG. 7 is a sectional detail view .taken along line 7-7 in FIG.

\ FIGS. 4 and 5, showing the screen in contact with the squeegee;

FIG. 8 is a sectional detail view taken along line 8-8 in FIG. 5, showing mechanism for adjusting yielding pressure between the screen and squeegee;

FIG. 9 is a sectional planview taken along line 9-9 in FIG. 1, showing details of the screen squeegee stroke adjusting mechanism and the means for locking the latter mechanism in each adjusted position;

FIG. 10 is an isometric detail view of certain elements shown in FIG. 9;

Fig. 11 is a plan view of a modification of the device shown in FIGS. 1 and 5;

FIG. 12 is a schematic electrical wiring diagram of the invention;

FIGS. 13 through 17 are five diagrammatic views of the limit switch cams which, in combination with the circuitry shown in FIG. 12, automatically control the printing apparatus; FIG. 13 is a view of limit switch cam LSSB which controls the vertical movement of the screen and squeegee;

FIG. 14 is a view of limit switch cam LS4B which controls lateral screen-squeegee printing stroke;

FIG. 15 is a view of limits witch cam LSlB whichcontrols, in combination with cams [.828 and LSSB, the vertical screen-squeegee movement at the end of the printing stroke;

FIG. 16 is a view of limit switch cam LS2B; and

FIG. 17 is a view of limit switch cam LS3B which controls the operation of the foot pedal switch.

Referring more particularly to the drawings, the numeral 10 denotes the framework of the apparatus generally, said framework supporting a screen assembly 11, a squeegee assembly 12, a cable assembly 14, a rack and pinion assembly 15 for driving the cable assembly, a lockable stroke adjusting assembly 16, a motor or prime mover 17 for driving the assemblies, and the circuitry for automatically controlling the operation of the above elements.

SCREEN ASSEMBLY The screen assembly 11 is composed of a screen 20 supported in cantilevered position from upper and lower

longitudinal shafts

21 and 22 by means of brackets 23, 23 (FIGS. 4- -7). The

shafts

21 and 22, in turn, are supported upon the free end portions of

transverse levers

24, 24 and 25, 25 respectively; and the pivoted ends of the

levers

24, 24 and 25,

25 are respectively secured upon an upper longitudinally disposed shaft 26 and two longitudinally aligned

hubs

27, 27.

Shaft 26 has levers 24, 24 fixed thereto and is also mounted framework.

It will be observed from FIGS. 4-7 that the longitudinal axes of

shafts

21, 22 and 26 and the axis of aligned hubs 27, when viewedfrom the ends, are the corners of a quadrangle having parallel opposite sides. Thus, when the screen assembly is in lowered bold line position the quadrangle has the shape of a rectangle and when the assembly is in the raised dotted line position the quadrangle has the shape of a parallelogram. By means of this arrangement, the supported screen 20, as well as the squeegee assembly later described, will have parallel vertical motion at the. beginning and at the end of the printing stroke.

SQUEEGEE ASSEMBLY FIGS. 5-7illustrate the screen and

squeegee assemblies

11 and 12 in contacting relationship at the midpoint of the print ing stroke. In this position the lower surface of the screen 20 is in face to face contact with the upper surface of an article or object 28 to be printed, said object being removably supported upon a base 29. I t

The assemblies 11 and 12 rise and fall simultaneously but at different rates of travel. For example, as the assemblies move upwardly from contacting position at the end of the printing stroke, the squeegee or wiper 30 travels faster than screen 20 and therefore becomes separated; and at the same time, the screen separates from the object. 28. Similarly, at the beginning of the. machine cycle, both assemblies move verti cally downwardly at said different rates of travel until the screen is in contact with the screen thereabove, after which the squeegee is moved laterally to effect the object 28 and the squeegee is in .contact with the screen thereabove, after which the squeegee is moved laterally toeffect the printing stroke.

Squeegee assembly comprises the wiper 30, a wiper holder 31, a horizontal wiper supporting rod 32, and a mounting bracket 33 for therod (FIGS. 4-8). Holder 31 is adjustably mounted upon rod 32 by means of set screws 31a, which rod is pivotally secured as at 35 to bracket 33, said bracket being pivotally supported as at 36 and 37 upon the free ends of upper and lowerlevers 38 and 39 respectively. Upper lever 38 is slidably mounted upon said longitudinal shafts 21 and 26 (FIGS. 5 and 7) and the lower relatively short lever 39 is slidably mounted. upon said longitudinal shaft 22 FIGS. 4, 5, 7

1 and 8). Since the

swingable pivots

36 and 37 are equidistantly spaced from the respective centers of

rotation

26 and 27, the bracket 33, rod 32 and wiper 30 will remain parallel to their respective starting positions during vertical movement.

SCREEN-SQUEEGEE PRESSURE ADJUSTMENT MEANS The pressure between screen 20 and squeegee or wiper blade 30 may be adjusted by manipulating

screws

40 and 41, said screws being threadably secured in mounting bracket 33 53, 55, 57, 56 and 17a.

(FIGS. 68) and disposed respectively below and above a swingable portion of rod 32. The upper end of screw 40 adjustably limits rotation of rod 32 and the blade 30 toward the screen, whereas the lower end of screw 41 adjustably exerts downward pressure against a compression spring 41a which, in turn, yieldably applies the pressure upon rod 32 to press the wiper against the screen.

SCREEN-SQUEEGEE RISE AND FALL ACTUATING MECHANISM The screen and

squeegee assemblies

11 and 12 are raised and lowered by the oscillationof longitudinal shaft 26 (FIGS. 5, 6, 6A and 7). One end of shaft 26 has a lever 42 fixedly secured thereon, the free end of which has a tension spring 43 connected thereto and normally tending to rotate the assemblies toward the dotted line positions shown in FIGS. 6 and 7. The opposite end of shaft 26 has actuating lever 44 fixedly secured thereon, said lever having its free end pivotally connected as at 45 to the upper end of link 46. The lower end of link 46 is pivotally connected to disc 48 as at 47, the disc being secured on shaft 49 extending through gear box 50. The gear box is drivably connected to motor 17 by means of gear box shaft 53, pulley S3 fixedly secured on the latter, pulley 56 on motor shaft 17a, and belt 57 on

pulleys

53 and 56. Thus the motor 17 oscillates shaft 26 and

assemblies

11 and 12 by means of a

connection comprising elements

44, 46, 48,49, 50,

CABLE ASSEMBLY The cable assembly 14, described below, is employed to reciprocate the squeegee assembly 12 longitudinally of

shafts

21, 22 and 26 (FIGS. 1 and 3--7). Lever 38 of assembly 12 has a downwardly extending Y shaped bracket 60 pivotally secured thereto as at 61, the lower end of said bracket being secured to an intermediate tensioned portion of a flexible cable 62 by means of clamp plate 63 and bolts 64. Cable 62 extends horizontally in opposite directions from bracket 62, through the aligned

hubs

27, 27, then over and downwardly from

guide wheels

66, 66, then partially around and horizontally from

guide wheels

67, 67 to a helically grooved drum 68. The end portions of the cable extend at least partially around the drum and in opposite directions, the ends of said portions being secured to the drum as at 69 and 70. By winding the cable end portions around the drum in opposite directions, the oscillation of the drum willunwindone portion while winding the other and vice versa thereby causing

brackets

38 and 60 and the squeegee assembly 12 to reciprocate. Drum 68 is fixedly secured on transverse shaft 71 rotatably mounted in framework 10.

Instead of attaching the cable end portions to the drum 68 at

points

69 and 70, it is evident that one or more helical turns of the cable around the drum would cause the cable to frictionally adhere securely to the drum and prevent slippage.

RACK AND PINION ASSEMBLY The rack and pinion assembly 15 is employed to a oscillate drum 68 of cable assembly 14. A pinion 74 on shaft 70 meshes with the teeth of a longitudinally extending rack 75 (FIGS. 1, 3 and 9), the opposite endof said rack being pivotally connected as at 76 to an adjustment slide 87 of the throw adjustment and lock assembly 16 to be described in the next section.

The teeth of rack 75 are held in mesh with the teeth of pinion 74 by means of a bracket'swingably mounted upon shaft 70 and consisting of confining rollers 78 and spaced

plates

79, 79.

During operation, the point of attachment of the rack 75 to the assembly 16 is disposed eccentrically of a main drive shaft 77 upon which the latter assembly is mounted (FIG. 1). The slide plate 87, eccentric pivot 76, and the main drive shaft 77, therefore, combine to serve as a crankshaft for the rack and pinion assembly 15.

LOCKABLE STROKE ADJUSTMENT ASSEMBLY The stroke or throw adjustment assembly 16 simultaneously controls the speed and back and forth motion of rack 75, drum 68, and squeegee blade 30. This stroke may be adjusted by varying the eccentricity of rack pivot 76 relative to the center of drive shaft 77 (FIGS. 1, 3, 9 and 10) as described below.

Drive shaft 77 is rotatably mounted transversely on framework 10 and has a bracket 82 secured on one end thereof. A sprocket 83 is also mounted upon the end of shaft, said sprocket being secured to bracket 82 by means such as stud bolts 84. Bracket 82 is provided with

parallel guideways

85, 85 which slidably confine the above mentioned adjustment slide 87 for movement diametrically of shaft 77. Since rack 75 is pivoted to slide 87 as at 76, the diametrical adjustment of the position of the slide will vary the eccentricity of pivot 76 and hence the stroke.

The diametrical movement of slide 87 and pivot 76 is effected by means of a rack 90 integral with the slide, a pinion 91 intermeshing with the rack, a rod 92 upon which the pinion is fixedly secured, and a knob 93 on the end of the end of the rod opposite the pinion end, said rod, pinion and knob being rotatable and coaxially movablerelative to drive shaft 77. A spring 94 is confined upon rod 92 between knob 93 and framework 10, which spring normally urges the rod, knob and pinion axially to an adjusted locked position (FIGS. 3, 9 and 10), at which time, the pinion not only meshes with rack 90 but also with a second rack 95 integral with slide 87.

It will be observed that the teeth of rack 90 are longer than those of rack 95 and, therefore, when the knob 93 is pressed to move rod 92 and pinion 91 axially of the drive shaft 77, the pinion will remain engaged with rack 90 but become disengaged from rack 95. With the pinion engaging only the rack 90, rotation may be imparted thereto to adjust the slide 87 and rack pivot 76 diametrically of the drive shaft; and when the desired adjustment has been made, the release of pressure upon knob 93 will permit spring 94 to return the pinion and rod axially to locked position as shown in the drawings.

DRIVE SHAFT ACTUATING MECHANISM Drive shaft 77 and the sprocket 83 thereon are driven by motor 17 through a connection comprising motor pulley 97. belt 98, pulleys 99 and 100 of variable speed drive unit 101, pulley 103 on transverse shaft 104, gear 105 on shaft 104, gear belt 106, gear 106 on transverse shaft 108, sprocket 109 on shaft 108, and sprocket chain 110, all of said elements being serially connected in the order named.

Variable speed unit 101 may be adjusted to a desired speed transmission from a manual control knob and through a serially connected chain of elements (FIGS. l3) such as sprocket 114 on shaft 114a, sprocket chain 115, sprocket 116 and worm gear 117 on shaft 118, and worm 119 on shaft 121. The above speed variation determines the speed of drive shaft 77 and the elements driven thereby.

ELECTRICAL CONTROLS The connection between motor 17 and the screen-squeegee rise and fall mechanism, namely,

elements

17a, 56, 57, S5, 53, 49, 48, 46, and 48, is controlled by electric clutch and

brake units

124 and 125 respectively, said units being mounted concentrically shaft 53 and actuated by a relay CR2 (FIGS. 3, 6 and 12). The relay CR2 has a normally open switch 127 and an alternately operable normally closed switch 128, which switches disengage clutch 124 while applying brake 125 and vice versa. The operation of relay CR2, in turn, is controlled by foot pedal switch 137 and by limit switch assemblies LS4 andLSS on gear box shaft 49.

Similarly, the series of elements between motor 17 and drive shaft 77 is controlled by clutch unit 130 and brake unit 131, said units being concentrically mounted about shaft 108 and actuated by relay Cr1 (FIG. 12). Relay CR1 has normally open and normally closed switches 132 and 133 respectively which are alternately operable to disengage clutch 127 while applying brake 128 and vice versa. The operation of relay CR1, in turn, is controlled by limit switch assemblies LS1, LS2 and LS3 on main drive shaft 77 (FIGS. 3 and 12).

FIG. 17 further illustrates the construction of limit switch LS3 which is typical of the outer limit switches mentioned above. Switch LS3 comprises relay LS3A, a swingable arm 139 pivoted to the relay, and a roller 140 on the free end of the arm and engageable with the periphery of switch cam LS3B.

FIG. 12 is an electrical wiring diagram showing how relays CR1, CR2, limit switches LS1 through LS5,

clutches

124, 127,

brakes

125, 128, and foot pedal switch 127 are connected to motor 17 and to one another to automatically: (a) vertically lower the screen and squeegee at the beginning of an operating cycle, that is, from dotted line position to bold line position as shown in FIGS. 6 and 7;-(b) move the squeegee laterally of its vertical path of travel to effect a printing stroke; (c) verti cally raise squeegee and screen at the end of the stroke; (d) move the raised squeegee in the reverse direction to that of the printing stroke to starting position and to complete the operating cycle.

Current is supplied to motor 17 through lead wires 143 and i 144, the latter wire having therein an off-on power switch 145 and an off-on motor switch 146. At the beginning of the operating cycle, the roller 140 of limit switch LS5 rests in notch 148 of cam LSSB (FIG. 13). Also at this time, the roller 140 of limit switch LS4 is resting upon its cam element 150 (FIG. 14). Then upon closing the foot pedal switch 137, current is supplied to

switches

127 and 128 of relay CR2, which relay releases brake 125 and causes clutch 124 torengage to thereby permit motor 17 to rotate limit switch cams LS4B and LS5B for one half revolution. At the completion of this partial revolution, roller 140 of limit switch LS5 engages notch 149 in the associated carn-LSSB (FIG. 13) to apply brake 125 and disengage clutch 124. During the above partial revolution as above described, the squeegee and

screen assemblies

11 and 12 are lowered tocause the squeegee and screen to contact one another and to cause the screen and object 128 to also make contact as shown in FIGS. 6 and 7.

Immediately before completion of the abovepartial revolu tion, but subsequent to contact between the screen and squeegee, the element 151 of cam LS4B engages the associated limit switch roller 140 to thereby supply current to switch switchs switches I32 and 133 of relay CR1, which switches cause clutch 127 tobecorne engaged and brake 128 to become released and thereby permit one-half revolution of drive shaft 77. This partial revolution of the drive shaft will impart lateral movement to the squeegee 30 to effect the printing stroke; and atthe end of this stroke, the roller 140 of limit switch LS1 will engage notch 153 in cam LSIB (FIG. to operate clutch 127 and brake 128 and stop drive shaft 77.

At the end of the partial revolution of cam LSlB, the limit switch LS2 is energized momentarily to operate relay CR2 I which, in turn, operates clutch 124 and brake 125 to cause motor 17 to rotate switch cams LS4B and LS5b one-half revolution, thereby raising the squeegee and

screen assemblies

11 and 12 to the dotted line noncontacting position such as shown in FIGS. 6 and 7 and at the end of the printing stroke.

Finally, and at the completion of the last named partial i revolution of cams LS4B and LSSB, the cam element (FIG. 4) causes the relay LS4A 4A to be energized which, in turn, will actuate CR1, clutch 127 and brake 128 to rotate drive shaft 77 and cam LSlB one-half revolution to the starting position and at the end of the operating cycle.

Briefly stated, when roller 140 of switch LS1 is in notch of cam LSlB as shown in FIG. 15, the relay CR1 is deenergized and the roller occupies the dotted line position relative to the notch, the relay is closed, the brake 128 is off and clutch 127 on. At the end of the printing stroke, the roller140 of switch LS2 is in notch 156 of cam LSZB (FIG. 16), at which time, relay CR2 is closed, brake 125 off and the rise and fall clutch 124 on to raise the screen and squeegee to noncontacting positions. At the end of the operating cycle, the roller 140 of switch LS3 is in notch 157 of cam LS3B (FIG. 17), at which time, the foot pedal switch 137 will operate only in this position to start a new cycle. When roller 1400f switch LS5 is in notch 148 of cam LSSB (FIG. 13), the relay CR2 is at rest, clutch 124 disengaged, and brake 125 on; and when this roller 140 is in the dotted line position relative to notch 140, the clutch is engaged and the brake off. When the roller 140 of switch LS4 is resting on either of cam elements 150 or 151 as shown in FIG. 14, an impulse is imparted to relay CR1 to start rotation of drive shaft 77.

FIG. 12 shows the circuitry which electrically connects the above described elements CR1, CR2, LS1 through LS5, 124, 127, 125, 128, 137 and 17 in a manner to accomplish automatic operation of the invention. These elements comprise comprise conduit and related elements 160 through 179.

MODIFIED FORM FIG. 11 illustrates a construction in which the squeegee assembly 12a remains laterally stationary while the screen assembly 11a reciprocates. The squeegee assembly is fixedly secured to shaft 26 by collars 122 while the screen assembly is slidably mounted upon shaft 21. Reciprocatory motion is imparted to assembly 11a by cable 62 through a connection comprising the aforementioned Y-yshaped bracket 60 and a second Y-shaped bracket 12 3.

OPERATION The machine is put into operation by turning on power switch 145 and then turning on motor switch 146 (FIGS. 12- -17).

To start an operation cycle, the foot. pedal switch 137 is depressed, closing a circuit through LS3A which is closed at start position by lever 139 resting in LS3B (FIG. 17), thereby closing relay CR2. The closed relay CR2 releases brake 125 and closes clutch 124 to lower the rise and fall mechanism from dotted line to bold line position (FIGS. 6 and 7) to printing position at the left hand edge of screen 20 (FIG. 5). I

- Atthis time, gear box 50 has been rotated to position cam LSSB from starting position. This cam LS5B maintains contact through LSSA to hold relay CR2 energized, which relay holds clutch 124 closed to rotate gear box 50 through this 180. Just before completing this 180 travel of cam LSSB, the cam 150 on LS4B closes LS4A momentarily to close CR1 which, in turn, opens brake 128 and closes clutch 127 to start the printing stroke from left to right in FIG. 5. When LSSB completes its first 180 travel, it releases LS4A and CR1 is thereby maintained in closed position by LSlA and its controlling cam LSlB during the printing stroke.

The printing stroke is completed when drive shaft 77 has travelled 180 and LSlA has been opened by cam LSlB (FIG. 15) which, in turn, opens CR1 to close brake 128 and open clutch 127. At the end of the printing stroke, the cam LS2B has turned to the position shown in FIG. 16. Atthis point, the

limit switch LS2A is closed which, in turn, closes CR2 to close clutch 124 and open brake 125 thereby rotating gear box 50; the latter rotation raises the screen 20 and squeegee 30 from contact with workpiece 28 as shownin dotted lines in FIGS. 6 and 7.

. At this time, cam LSSB is rotating and will turn 180. Near the end of this rotation, cam LS4B momentarily closes limit switch LS4A by contact with lobe 1.51 (FIGS. 14 and 15) and closes CR1, thereby starting main drive shaft 77 concurrently with the closing of clutch 127 and the opening of brake 128. The drive shaft 77 turns 180 which brings it to the end of the operating cycle, or to the starting point for a succeeding operating cycle.

In the drawings and specification preferred forms of the invention have been disclosed; and although specific terms are employed, these are used in a descriptive sense and not for purposes of limitation, the scope of invention being defined in the following claims:

We claim:

1. A printing apparatus having a screen member, a squeegee member and means for imparting relative reciprocatory movement between said screen and squeegee members between starting and final printing stroke positions, said means includ ing a cable to which one of said screen and squeegee members is mounted, crankshaft means having a driven rotary member, an elongated connecting element repositionable means eccentrically and adjustably connecting one end of said elongated connecting element to said driven rotary member whereby said elongated connecting element is reciprocated by said driven rotary member, translation means coupled to the opposite end of said elongated connecting element and to sald cable translating the reciprocation of said elongated connecting element to said cable to reciprocate said cable, said adjustable to change the eccentric mounting of said elongated connecting element to said driven rotary member along an axis substantially normal-to the axis of said driven rotary member to change the strokeof said elongated connecting element and hence the relative reciprocatory movement between said screen and squeegee members.

2. A printing apparatus-as defined in claim 1 wherein said repositionable means includes a-rack means slidably mounted on said driven rotary member, said elongated connecting element being pivotably mounted to said rack means, a pinion positioned along the axis of said driven rotary member and engaged with said rack means, said pinion being effectively disengageable from said rack means to allow said rack means to be moved and positioned to engage said rack means and fix the position of the rack means relative to said rotary member.

3. A printing apparatus as defined in claim 2 wherein said rack means includes two racks spaced from one another a distance to accommodate the pinion when effectively engaged therebetween.

4. 4 A printing apparatus as defined in claim 1 wherein said translation means comprises an oscillatable drum, said cable being under tension and one of said squeegee and screen members being secured to an intermediate portion of said cable thereof, said cable extending in opposite directions from said one of said squeegee and screen member secured thereto and being wound around at least a part of the drum periphery so as to be reciprocated by said drum as the latter is oscillated, said elongated connecting element being coupled to and oscillating said drum during reciprocation of said elongated connecting element, to thereby translate the reciprocation of said elongated connecting element to said cable.

5. An apparatus as defined in claim 4 wherein said oscillatable drum is mounted on a shaft, a gear is fixed on said shah, and said elongated connecting element having a rack portion engaging said shaft gear so that reciprocation of said elongated connecting element oscillates said shaft and said drum mounted thereon.

6. A printing apparatus as defined in claim 1 wherein said squeegee and screen members are mounted to a parallelogram linkage which permits said members to move in a substantially normal path relative to the surface of the screen, one member of said parallelogram linkage comprising an intermediate portion of said cable, said cable including portions turnable around spaced rollers respectively located generally at the starting and final printing stroke positions of said apparatus, and said cable having another portion joined to said crankshaft means.