US2751842A - Screen stencil-printing machines - Google Patents

Description

June 1956 J. N. MCLAURIN SCREEN STENCIL-PRINTING MACHINES 5 Sheets-Sheet 1 Filed June 8, 1955 T (0 03(0 QWQGWWTCYWB B I IIIIIIT F/GZ AI HHIIHU y .,N% m M M 0U, .Im A u 5 My E W 8 2 a 3 8 J. N. MCLAURIN 2,751,842

June 26, 1956 SCREEN STENCIL-PRINTING MACHINES 3 Sheets-Sheet 2 Filed June 8, 1953 Inventor, JAMES N. MQLAURW Attorney June 26, 1956 Filed June 8, 1955 J N. M LAURIN SCREEN STENCIL-PRINTING MACHINES 3 Sheets-Sheet 3 in! 2/ 9 H "Mill. r 111m f HH HH, 2O 3 lm Inventor". JAMES N. McLAUmN Bym fi zw Attorney SCREEN STENCIL-PRBNTING MACHHJES James Napier McLaurin, Edinburgh, Scotland, assignor of one-half to E. T. Marler Limited, London, England Application June 8, 1953, Serial No. 359,987

Claims priority, application Great Britain December 13, 1952 2 Claims. (Cl. 101-123) This invention relates to silk and like screen stencilprinting machines of the kind in which a flexible squeegee is reciprocated over the screen and resiliently pressed into contact therewith during the printing stroke while being maintained at an angle to the screen so as to'press color through the screen, the squeegee being lifted clear of the screen at the end of the printing stroke and during the return non-printing stroke.

The object of the present invention is to utilize the squeegee itself as a carrier for color during the return stroke, the squeegee picking up color at the end of the printing stroke, holding the color during the non-printing stroke, and depositing the color on to the screen preparatory to the printing stroke.

According to the present invention, mechanism is provided for moving the squeegee clear of the screen at the end of the printing stroke of the machine and for rocking the squeegee to cause it to sweep color in front of it, preferably into a receptacle, the squeegee moving into a position in which its front face retains some of the color thereon during the non-printing stroke of the machine, at or near the end of which the squeegee is rocked in the reverse direction to deposit the color on to the screen and the squeegee is moved into contact with the screen preparatory to effecting the printing operation.

Where the squeegee is trailed over the screen during the printing stroke, i. e. with its front face at an acute angle to the screen, the squeegee may be lifted and rocked forwards at the end of the printing stroke to cause color in front of the squeegee to be swept by it into a pan or receptacle, the squeegee moving into a position such that some of the color is held on the front face of the squeegee and retained thereon during the non-printing stroke, whereupon the squeegee is rocked backwards to deposit the color on to the screen and the squeegee is lowered and pressed into contact with the screen preparatory to the printing stroke.

The forward rocking motion of the squeegee may be effected by spring means effective to rock the squeegee when the latter is moved sufliciently away from the screen to allow the squeegee to be moved over the screen from the printing position to the color pick-up position in which it is held during the non-printing stroke, at the end of which the squeegee is rocked backwards by return rocking means prior to being moved into position ready for resilient pressure upon the screen during the printing stroke.

The squeegee may be supported in known manner from a transverse rock shaft supported at its ends in slide blocks movable in guides at each side of the screen frame, the slide blocks being reciprocated by connection to endless travelling chain or like conveyors.

The invention is illustrated in the accompanying drawings as applied to a machine in which the squeegee is trailed over the screen during the printing stroke.

Fig. 1 is a sectional view through the screen frame showing the squeegee assembly in the printing position.

United States Patent 2,751,842 C6 Patented June 26, 1956 Fig. 2 is a similar view of the squeegee at the end of the printing stroke.

Fig. 3 is a similar view showing the squeegee picking up color.

Fig. 4 shows the squeegee in position to commence the non-printing stroke.

Fig. 5 shows the squeegee approaching the finish of the non-printing stroke.

Fig. 6 shows the squeegee coming into contact with the screen preparatory to commencing the printing stroke.

The illustrated embodiment of the invention shows a squeegee reciprocable over a screen which remains stationary during the printing stroke. The screen frame which carries the screen may be pivoted at one end to tilt into an inclined position above a printing bed for enabling the sheet which is to be printed to be laid on the printing bed and to be withdrawn after printing as described in the specification of my prior U. S. A. patent application Serial No. 332,591, filed January 22, 1953.

A screen frame 7 supports a screen 8 in known manner and fitted to each side of the screen frame are front and rear end sprockets 9 and 18 respectively over which passes an endless conveyor chain 11 driven by effecting rotation of the rear end sprockets 10 as described in my aforesaid prior application. Adjacent each chain is a longitudinal guide rail 12 fixed to the side of the screen frame and on each guide rail a slide block 13 is movable. Pivotally mounted on each slide block 13 on a pivot 14 is a lever 15, the two levers supporting between them a rock shaft 16. Extending from a sleeve 17 on the rock shaft 16 are arms 18 to which a squeegee holder 19 is attached carrying a squeegee 29. The holder 19 is adjustably fiXed on the arms 18 and is radially adjustable with respect to the shaft 16 by means of thumb screws 21. A helical spring 22 is coiled on the spindle or rock shaft 16 at each end thereof, one end of the spring being fixed to the rock shaft 16 and the other end acting upon the sleeve 17 or arms 18 to urge the sleeve 17 and squeegee in an anti-clockwise direction when viewed as in Figs. 16. The ends of the levers 15 are pivotally connected at 23 to the chains 11 and the levers 15 are connected together by a transverse bar 24 through which are threaded pressure screws 25 adapted, in the positions shown in Figs. 1-3, to bear against pressure arms 26 projecting from the sleeve 17. A fixed rail 27 at each side of the screen frame, holds the lower run of the chain 11 in a straight line; position for ensuring true rectilinear motion of the; squeegee assembly during the printing operation. At the. front end of the screen frame is a curved plate 28 whichv acts as a color receptacle or dam as will be hereinafter explained, and projecting forwards from the rear end off the screen frame are buffer members 29 adapted to make,- contact with striker arms 39 projecting from the sleeve 17 The operation is as follows: Printing color is first supplied to the screen 8 and spread thereon. A sheet to be printed is then laid on the printing bed (not shown) and the screen frame is held down upon the printing bed to cause the screen to rest on the sheet to be printed. The endless chains 11 are then set in motion to cause the squeegee to travel in the direction of the arrow in Fig. 1, thus effecting printing by pressing color through the screen with the squeegee in the position shown in Fig. 1 in which position the pressure screws 25 press against the pressure arms 26 and hold the squeegee 20 in firm flexible contact with the screen. During this printing stroke the levers 15 are connected to the lower run of the chains 11. At the finish of the printing stroke and as seen in Fig. 2, the pivotal connections 23 of the levers 15 to the chains 11 have reached the front sprockets 9 and the squeegee 20 has reached or nearly reached the lower end of the curved plate or dam 2.8. As the pivotal connections 23 pass around the sprockets 9, the levers 15 are raised,

ing stroke.

thus releasing the pressure of the screws 25 on the arms 26 and at the same time lifting the squeegee holder 19, so that the pressure of the squeegee on the screen is relaxed. The coil springs 22 are thereby enabled to turn the squeegee in the direction of the arrow inJFig. 3 andthe squeegee sweeps a supply of printing color 31 on to the dam 28, continuing this motion until the levers are at the top of the sprockets 9, as in Fig. 4, during which period of motion the coil springs have turned the sleeve 17 and squeegee into a position in which they are held by the abutment of the striker arms 3 against the bar 24 or other suitable stopl As the chains continue their motion, the squeegee assembly is carried rearwards by the levers 15 engaging the upper run of the chains, while the squeegee continues to be maintained in an inclined position in which it holds and carries back with it a supply of printing color 31. During this return or non-printing stroke of the squeegee assembly, the printed sheet is removed from the printing bed and a fresh sheet is placed in position in readiness for the next printing stroke. 7

When the squeegee assembly nears the end of the nonprinting stroke, the striker arms 30 strike the buffer members 29, as seen in Fig. 5, and continued rearward movement of the squeegee assembly causes the sleeve 17 and squeegee to be turned in a clockwise direction against the action of the coil springs 22. At the same time, the pivotal connections 23 of the levers 15'pass downwards around the rear sprockets 10, thus moving the squeegee into light contact with the screen and depositing the supply of printing color 31 upon the screen as seen in Fig. 6.

Finally the levers 15 further descend until the pressure screws are pressed against the pressure arms 26 and the printing stroke commences as in Fig. 1, the cycle of operations being then repeated as already described.

Although the invention has been described as applied to machines in which the screen remains stationary during printing and the squeegee is reciprocated, the invention can also be applied to machines in which the screen (which may be either a fiat or arcuate screen) reciprocates and the squeegee remains stationary, in which case suitable means will be provided for rocking the squeegee, and the pan or like receptacle will be reciprocated with the screen, while the movement of the squeegee clear of the screen, where this is necessary, may be effected either by moving the squeegee towards and away from the screen or by moving the screen towards and away from the squeegee.

Where the squeegee is held incontact with the screen during the printing stroke with its front face at an-obtuse angle to the screen, the action of rocking the squeegee forwards at theend'of the printing stroke will cause some of the color accumulating in front of the screen to be lifted on to the front face of the-squeegee where it will be held during the non-printing stroke until the squeegee is rocked in the reverse direction to return the squeegee into contact with the screen preparatory to the next print- In such case, it is not necessary that the squeegee holder should 'be moved towards and away from the screen at the beginning and end of the printing stroke, as the rocking motion will move the edge of the squeegee into and out of contact with the screen. The squeegee holder may therefore perform a straighttrectilinear reciprocatory motion. Any excess color -at'the end of the printing stroke may be propelled by the squeegee into the corner'space at the forward end of the screen frame. This corner space may, if desired,-be partly filled with a fillet strip to ensure that part of the color will be taken up by the squeegee when it is rocked for-wards at the end of the printing stroke.

I claim:

1. In a screen stencil-printing machine having a screen mounted in a screen frame and a squeegee reciprocable over the screen, a squeegee assembly comprising a transverse suspension supporting the squeegee for rocking motion thereon, levers supporting said transverse suspension, slide blocks movable in guides at each side of the screen frame, means for'pivotaily attaching the forward ends of said levers to said slide blocks, endless conveyor chains travelling over front and rear sprockets at each side of said screen frame, a pivotal connection between the rear end of each of said levers and its adjacent conveyor chain, spring means normally urging the squeegee to rotate about the axis of the transverse suspension in a direction to cause the squeegee to rock forwards when lifted clear of the screen by the travel of said pivotal connections around the front sprockets, adjustable pressure means carried by said levers and operative to hold the squeegee in resilient pressure contact with the screen when said slide blocks are carried forwards by the conveyor chains to effect the printing stroke, and abutment means at the rear end of the screen and operative to rock the squeegee backwards about its axis of transverse suspension when said pivotal connections pass around the rear sprockets.

2. In ascreenstencil-printing machine having a screen mounted in .ascreen frame and a squeegee reciprocable over the screen, a rectilinear guide mounted at each side of the screen frame, members guided by said rectilinear guides for slding movement from one end of the screen frame to the other, a conveyor chain mounted at each side of said screen frame and passing 'over front and rear end sprockets for imparting unidirectional motion to said chains, an arm pivotally connected at its forward end to each of saidmembers and atits rear end to the conveyor chain at the adjacent side of the screen frame to effect sliding movement of said members and to oscillate said arms as said chains pass around the sprockets, a squeegee pivotally suspended between said arms, means for holding said squeegee in resilient pressure contact with and at an angle to .the screen .to press color therethrough during the forward travel and printing stroke of said squeegee under the motion of said chains, means for tilting the squeegee forwards about its pivotal suspension when the rearward ends of said arms are carried by the chains around the forward sprockets and for retaining the squeegee in tilted position while said arms are carried backwards by said chains, an arcuate color dam positioned at the forward end of the screen frame and over which the squeegee sweeps during said tilting movement to retain color on the forward face of the squeegee, andmeans for tilting the squeegee backwards into pressure contact with'the screen when the rearward ends ofsaid arms approach and are carried around the rear end sprockets by said chains, said backward tilting movement of the squeegee depositing the color carried on the front face of thesqueegee to the screen in readiness for the printing stroke. 0

References Cited in the file'of this patent UNITED STATES PATENTS 1,687,080 Beck "00b9, 192

1,901,473 Respess Mar. 14, 1933 1,966,416 'Parmeleet a1. 1J, July 10, 1934 2,421,210 .Louft "May. 27, 1947

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