US2739530A

US2739530A - Screen stencil-printing machines

Info

Publication number: US2739530A
Application number: US332591A
Authority: US
Inventors: James N Mclaurin
Original assignee: ET Marler Ltd
Current assignee: ET Marler Ltd
Priority date: 1953-01-22
Filing date: 1953-01-22
Publication date: 1956-03-27
Anticipated expiration: 1973-03-27

Description

March 27, 1956 J. N. M LAURIN 2,739,530

SCREEN STENCIL-PRINTING MACHINES Filed Jan. 22, 1955 2 Sheets-Sheet 1 U'Amss N- Me. Lnu m M 26 A 7'7'OR/VEY March 27, 1956 J. N. M LAURIN 2,739,530

SCREEN STENCIL-PRINTING MACHINES Filed Jan. 22, 1955 2 Sheets-Sheet 2 FIG 7. V'Amzs 1v. McLAuRIN BY. 5W

ATTORNEY United SCREEN STENCIL-PRENTING MAQHINES James N. McLaurin, Edinburgh, Scotland, assignor of one-half to E. T. Marler Limited, London, England Application January 22, 1953, Serial No. 332,591

2 Claims. (Cl. 101-123) This invention relates to silk or like screen stencilprinting machines of the kind in which a resilient squeegee or wiper is reciprocated across the screen and is given a rocking movement at the end of the printing stroke to lift the wiper from the screen.

The machine of the present invention comprises a screen frame pivotally mounted near its rear end on the fixed bed frame of a horizontal printing bed and counterbalanced or otherwise controlled so that the screen frame normally tilts upwards about its pivot into an open position, a resilient squeegee or wiper mounted on a carriage reciprocable across the screen by reciprocating mechanism, means for mounting the squeegee or wiper for rocking movement about a horizontal axis on the carriage, an electric motor arranged to drive the carriage reciprocating mechanism, a switch controlled by tilting opening movement of the screen frame to stop the motor when the screen frame is tilted, releasable locking mechanism for locking the screen frame to the bed frame during printing and released by means operated at the end of the printing stroke of the carriage to release the screen frame and to allow the latter to tilt upwards for the withdrawal of the printed sheet from the printing bed, and mechanism for rocking the wiper to engage the wiper with the screen during the printing stroke and for lifting the wiper clear of the screen at or near the end of the printing stroke and during the return stroke of the reciprocating carriage towards the front end of the machine, in readiness for wiping over the screen during the working stroke of the wiper and simultaneous printing operation.

The momentum of the moving carriage and its driving mechanism is such that, after the motor has been stopped by the tilting of the screen, the carriage continues its travel and completes part of its return stroke, the remainder of the return stroke being completed when the screen frame is closed down upon the bed frame by manual operation after the next sheet to be printed has been laid on the printing bed. This partial return movement of the reciprocating mechanism reduces the interval of time required for the actual printing operation.

A machine according to the invention is illustrated in the accompanying explanatory drawings, whereon:

Fig. l is a diagrammatic side View of the machine.

Pig. 2 is a fragmentary perspective view showing the carriage with the wiper commencing the printing stroke.

Fig. 3 is a view looking at the rear of the color scoop at the commencement of the forward or return stroke.

Fig. 4 is a fragmentary perspective view showing the scoop bein lifted by a lifting rail.

Figs. 5, 6 and 7 are end views of the carriage showing various positions of the wiper and scoop.

An electric motor 1 is mounted on an extension 2a of a screen frame 2 rearward of a pivot 3 for the screen frame, and a counterbalance weight 4 is provided for ensuring upward tilting of the screen frame, which is normally locked to a bed frame 5 by spring catches 6.

"' 7 of the bed frame 5 and the counterweight 4 is suspended The screen frame pivot 3 is supported in upright members from a cable 8 passing over a pulley 9 on the upright members 7 to an anchorage at the front of the screen frame 2 which is provided at the front with a handle 10 for closing or lowering the screen frame. A screen (not shown) is stretched across the screen frame in known manner and reciprocating over the screen is a carriage denoted by the general reference A in Fig. l. The carriage comprises a rotatable cross shaft 11 carried at its ends in slide blocks 12 mounted on rollers or guides running on rails 13 housed in side casings 14 on the screen frame. At or near the end of the printing stroke the said slide blocks 12 are adapted to engage resilient abutments 15 operatively connected by rods or cables 16 to the .locking catches 6 of the screen frame to release the catches. Reciprocation of the carriage is effected by securing on each end of the cross shaft 11 a driving arm 17 pivotally connected at its outer end to an endless chain 18 housed in the side casing on the screen frame, said chain passing around end sprockets 19 and 20 driven from the motor shaft. The arrangement is such that the cross shaft 11 is rocked by the driving arm 17 as the pivotal connection between the driving arm and the chain passes around the end sprockets. A wiper 21 is carried by arms 22 freely mounted for limited angular movement on the cross shaft between a stop (not shown) and adjustable stops 23a on arms 23 fixed on the cross shaft so that the resilient pressure of the wiper on the screen can be adjustably controlled by adjusting the stops 23a to vary the pressure of the arms 23 on the Wiper 21. Fixed arms 24 on the cross shaft and preferably unitary with the arms 23, carry a scoop 25 in a position such that the scoop is lowered and the wiper is raised as shown in Fig. 5 and vice-versa when the cross shaft is rocked. The scoop is pivotally mounted at 26 on carrying arms 27 and is controlled by a spring or springs 28 for limited rocking movement on the carrying arms 27 in order to hold the scoop in resilient contact with the screen during the time the scoop is in contact therewith, as shown in Fig. 5, and pins or projections 29 on the ends of the scoop are arranged to run on tracks or lifting rails 30 in the side casings on the screen frame. The tracks or rails 36 are of such a length that the scoop is raised as in Fig. 6 over the greater part of its travel and is released as shown in Fig. 7 to rest on the screen near the end of the forward stroke of the carriage. As the carriage approaches the rear or pivoted end of the screen frame, the cross shaft 11 is rocked by the chains 18 to lift the wiper as in Pig. 5. As the scoop moves forwards it descends in rear of the color left by the wiper and collects the color as shown in Fig. 5. The scoop rises during the initial forward stroke of the carriage, holding the color as shown in Fig. 6 during the stoppage of the machine, and carrying it forwards again when the screen frame is closed down on to the bed frame and the motor is thereby automatically re-started. At the forward end of the forward stroke, the pins or projections 29 on the scoop drop off the rails 30 and the scoop deposits the color on the screen as shown in Fig. '7 in a position in which it is immediately thereafter engaged by the movement of the wiper into operative position by rocking of the cross shaft as its connections to the chains pass around the front sprockets 19.

Color is fed to the screen by a reservoir 31 mounted across the screen frame and having a discharge outlet or slot controlled by a slide valve which is normally closed by spring means and is temporarily opened during the return of the carriage, a projection on the carriage tripping a trip device operatively connected to the slide valve to open it momentarily, this color charge being picked up by the scoop on the next return stroke of the carriage.

The operation of the machine is as follows:

Starting with the wiper in the position of rest, the motor having been stopped by lifting the screen frame, the carriage of the wiper and scoop will have moved forwards, thus covering part of the forward or non-printing stroke before coming to rest. The operator places a fresh sheet in register position on the base board or bed 32 and closes the screen frame down upon the bed frame. In doing so, an electric switch 3 3 is released and the motor comes into operation, driving the chains 18 in a direction to move the carriage towards the front of the machine, the carriage being drawn by the arms 17 engaging the upper run of the chains. As the connection of the arms to the chains passes over the front sprockets, the wiper or squeegee comes into action, as shown in Fig. 2 and the printing operation takes place during the movement of the carriage and wiper rearwards. When the carriage strikes the abutments 15, the catches 6 are released and the screen frame tilts upwards about the pivot 3 under the action of the counterbalance weight. The wiper is thus lifted clear of the screen and of the color thereon. The action of tilting the screen frame actuates the switch to stop the motor, but the momentum of the moving parts is sufiicient to carry the arms 17 over the end sprockets 2i) and to drive them forward, thus bringing the scoop into operation, lifting the color left by the Wiper and carrying the color part of the way up the screen frame in readiness for depositing it in readiness for the next printing stroke. When the screen frame is again closed down, the scoop rides on the rail 30 as in Fig. 6, and finally deposits the color on the screen as shown in Fig. 7 shortly before the wiper comes into operation as in Fig. 2 to distribute the color over the screen.

During the initial forward run of the carriage by momentum, a projection on the carriage trips a valve beneath the color reservoir 31 to feed a regulated amount of color on to the rear part of the screen in readiness to be picked up by the scoop on its next forward run.

I claim:

1. A screen stencil-printing machine comprising a fixed bed frame, a horizontal printing bed in said frame, a screen frame pivotally mounted near its rear end on said bed frame, means urging said screen frame into a normally upwardly tilted position, releasable locking means for locking the screen frame to the bed frame, a screen mounted in said screen frame, a carriage reciprocable across the screen in said screen frame, reciprocating mechanism for reciprocating said carriage, a rock shaft mounted on said carriage for rocking movement about a horizontal axis, arms having limited angular movement about said shaft, a resilient wiper carried by said arms, fixed arms on said shaft adapted to engage said wiper during the printing stroke to exert resilient pressure on the wiper during printing, secondary fixed arms on said shaft carrying a color scoop in such a position that the scoop is lowered into contact with the screen when the wiper is raised clear of the screen and vice-versa, an electric motor operative to drive said reciprocating mechanism, a switch controlled by tilting movementof said screen frame to stop the motor when the screen frame is in an upwardly tilted position and to start the motor when the screen frame is closed down upon the printing bed, operation of the motor causing reciprocation of the carriage, rock shaft and wiper, means actuated by the carriage near the end of its printing stroke to release said locking means and permit said screen frame to tilt upwards, and mechanism for rocking the wiper shaft to engage the wiper with the screen during the printing stroke and to lift the wiper clear of the screen at or near the end of the printing stroke.

2. A printing machine as specified in claim 1, having the scoop pivotally mounted on said secondary arms and resiliently controlled for limited rocking movement thereon to hold the scoop in resilient contact with the screen during the time the scoop is in contact therewith, and means on the screen frame adapted to coact with a projection on the scoop to raise the scoop clear of the screen and to hold color on the scoop during the greater part of its forward travel and to permit the scoop to rest on the screen near the end of the forward stroke of the carriage and before commencement of the printing stroke.

References Cited in the file of this patent UNITED STATES PATENTS 1,815,021 Bland a- July 14, 1931 1,922,710 Owens Aug. 15, 1933 1,966,416 Parmele et al. July 10, 1934 2,207,818 Perry et al. July 16, 1940 2,267,596 Montague et al. Dec. 23, 1941 2,421,210 Louft May 27, 1947 2,571,685 DAutremont Oct. 16, 1951 2,637,269 Thomas May 5, 1953 2,651,988 Thomas et al Sept. 15, 1953