US2863383A - Printing machine - Google Patents

Description

Dec. 9, 1958 Filed March 31, 1955 C. R. JOHNSON PRINTING MACHINE 2 Sheets-Sheet 1 aza-dliJoizmo 5 Mam fliioflrzeg;

Dec. 9, 1958 Filed March 31, 1955 C. R. JOHNSON PRINTING MACHINE 2 Sheets-Sheet 2 Inversionazz' R. JOWOW, AM; 0 M

: ent

ul atented Dec. 9, 1958 PRINTING: MACHINE Carl R. Johnson, Keene, N; l-I.,assiguo'r to I A. Putnam Mfg. C0., lnc., Keene; N. -ll-l., a corporation of New Hampshire Application March 31, 1955, Serial No. 498,145

3 Claims. (Cl. 101-426) This invention relates to printing. machines of that type which use a stencil fonmaking the imprint, and especially stencils that aresupported on a screen of some suitable material such as silk, nylon, linen, glass fibre, metal, etc., and which may. for convenience be referred to as screen stencils, although the invention is not limited to stencils of this character but may be used with stencils of other types.

A method now commonly used for making imprints with a screen stencil involves placingthe screen stencil in contact with the work piece on which the imprint is to be made and then forcing the ink through the screen stencil by a squeegee operation. This squeegee method of making a succession of imprints has a disadvantage that it isa rather slow process.

Another known method of making imprints with a stencil is by means of a printing machine of the type having a printing head carrying an inkreservoir containing ink, the bottom of which is constituted by an imprint forming stencil, and which is movable into and out of printing position so at each movement of the printing bead into printing position an imprint willbe made.

This type of printing machine is sometimes provided with means to subject the ink in the reservoir to pressure when the stencil is brought into printing position thereby to force the ink through the stencil to make the imprint.

This operation of bringing the screen stencil against the work piece and subjecting the ink in the reservoir to the desired pressure and then separating the ink reservoir from the work piece occupies a space of time much less than that occupied by the ordinary squeegee operation for forcing the ink through the stencil to make the imprint.

One object of the present invention is to provide novel means for subjecting the ink in the reservoir to the desired pressure at the time that the imprint is being made.

In the drawings which show one embodimentof the mventlon;

Fig. 1 is a side view of a printing machine equipped with the new printing unit;

Fig. 2 shows one form of printing unit in section;

Fig. 3 is a detail of one means for controlling the pressure on the ink in the reservoir.

Fig. 4 is a sectional view showing a different embodiment of the invention;

Fig. 5 is a fragmentary view of means for. controlling the pressure on the ink in the device shown in Fig. 4.

In Fig. lthe invention is shown as embodied in a well known type of printing machine having a frame It carrying a work support 2 and having the printing head mounted in a vertically reciprocating member 3 which is movable toward and from the work support 2. As herein shown, the member 3 is in the form of an arm pivoted to the frame 1 at 4, and it receives an upand down movement through the medium of a toggle member comprising the two toggle arms 5 and 6 which are pivotally connected together at 7, the arm 5 being pivoted. at its upper end to the frame 1 at 8, and the lower end of the arm 6 being pivoted to the member 3 at 9. The up and down movement of the arm 3 is produced by breaking and straightening the toggle member 5, 6. When the toggle member is broken, the member 3 is in its raised position, as shown in full lines Fig. l, and when said toggle member is straightened the member 3 carrying the printing element is in its lowered printing position as shown in dotted lines. This operation of making and breaking the toggle may be provided for by any suitable means, such, for instance, as a crank disk 10 carried by a drive shaft 11 and having a crank pin 12 which is connected by the link 13 to the joint 7 of the toggle lever member. The rotation of the crank disk 10 will give the toggle member its breaking and straightening movement, as will be clearlyunderstood.

Printing machines of this type are in common use and the construction as thus far described forms no part of the present invention.

in embodying the present invention in a printing machine of this type, the printing head is provided with a reservoir 14 containing the ink used for making the imprint, which reservoir may be mounted on the member 3, the lower end of the reservoir being constituted by the stencil 15, which may be a screen stencil or a stencil of any other suitable type.

One feature of thepresent invention relates to means for subjecting the ink 16 in the reservoir 14 to pressure at the time that the stencil i5 is in contact with the work piece, thereby forcing the ink through the stencil onto the work piece 13 which is supported bythe work support 2, thereby to make theimprint.

in the construction shown in Figs. 1 and 2 the ink reservoir it has a plunger l7 located therewithin which rests on the ink is, and means are employed for applying a momentary downward pressure to the plunger at the time when .the 'screen stencil is brought against the work piece, thereby subjecting .the ink in the reservoir to the necessary pressure to force a sufficient quantity thereof through the screen to make a proper imprint.

One means of accomplishing this is to provide an air cylinder 19 which is mounted on top of the reservoir 14 and to provide a piston 24 within the air cylinder having a piston rod 21 which extends through the top of the reservoir 14 and is connected to the plunger 17, and also to provide means for subjecting the piston 20 to a momentary downward pressure at the instant that the screen stencil has been brought against the work piece 18. This may be accomplished in various ways, and for the purpose of illustration there is shown herein a pneumatic means to accomplish this end. The upper end of the air cylinder 19 has an air supply pipe 22 connected thereto above the piston Zti, which. pipe is supplied with air under pressure fromany suitable source. Located in the pipe 22 is a valve 23 of a well known type which is constructed so that normally it closes the communication between the cylinder and the source of compressed air supply and vents the upper end of the cylinder 19 to the atmosphere, but whichwhen actuated closes the vent and opens momentarily the cylinder to the pipe 2.2, thereby admitting compressed air to the cylinder above the piston 2h, whereby said piston is subjected to a downward pressure which is transferred to the plunger 17 through the piston rod 21 and thus to the ink in the reservoir. While the valve 23 may be operated in any desired way, a construction is herein shown by which this valve is operated electrically through the medium of a control switch 24 mounted on the frame 1. This control switch is normally open and, assuming the to make the imprint on the work piece.

valve 23 is a solenoid operated valve, said valve will thus normally be in a condition to vent the upper end of the air cylinder 19 and close the pipe 22. leading to the source of compressed air supply. The crank disk iltt is provided with'a cam portion 25' which is positioned to actuate the switch member 24 at the time that the screen stencil has been brought into contact with the work piece 18. The closing of the switch 24 activates the solenoid valve 23 so that the upper end of the cylinder is placed momentarily in communication with the source of compressed air through the air pipe 22, and an impulse of compressed air will be thus delivered to the cylinder 19 above the piston 26 which will apply downward pressure to the piston 28* and thus subject the ink 16 in the reservoir to a momentary increased pressure which will force sufficient ink through the screen stencil As soon as the cam portion 23 passes out of engagement with Lu switch 24 the valve 23 will resume its normal condition I in which it blocks the air flow from the air pipe 22 into the cylinder and opens a vent for venting the cylinder.

The contact of the screen stencil 15 against the work piece is a momentary contact only and the present invention provides means whereby just at the time the screen I stencil is about to be separated from the work piece after the imprint has been made, the ink within the reservoir will be subject to a momentary negative pressure, thus assisting the breaking of the ink in the stencil from the imprint and producing an exceptionally clear imprint. In the construction herein shown this is accomplished by providing a second air pipe 27 leading from the source of compressed air to the bottom of the cyinder '19 below the piston and employing a second solenoid valve 28 for controlling the flow of compressed air into the cylinder 19 below the piston 20 through the pipe 27 which communicates with a source of compressed air. This valve 28 is controlled by another switch 29 similar to the switch 24, and said switch 29 is controlled by the cam projection carried by the crank disk it).

The cam projection 25 is so positioned on the cam disk 10 that it will actuate the switch 24 just as the printing head has been moved into its printing position with the screen stencil 15 in contact with the work, thereby to actuate the valve 23 so that compressed air will be delivered to the cylinder 19 above the piston 2t), whereby said piston 2d and the ink 16 in the reservoir will be subjected to pressure by the plunger 17 thereby to force ink through the screen stencil onto the work for making the imprint. As soon as cam projection 25 has passed by the switch 24, the latter will resume its normally open condition, andthe valve 23 will also resume its normal condition in which it vents the upper end of the cylinder 19 to the atmosphere and closes the pipe leading to the source of compressed air.

Immediately after the crank disk 10 has moved forwardly to withdraw the cam projection 25 from the switch '24, said projection will engage and operate the switch 29, as shown in dotted lines Fig. 3, so that the valve 28 will be actuated to admit compressed air to the cylinder 19 beneath the piston 20, thereby producing an upward impulse to the plunger 1'7 and producing a negative pressure within the ink reservoir which will result in quick breaking of the ink between the screen stencil and the work piece as the printing head begins its backward movement. When the cam projection 25 passes by the switch 29, said switch will resume its normally open condition and valve 28 will also resume its normal condition in which it vents the lower end of the cylinder 19 to the atmosphere and closes the pipe 27 leading to the source or" compressed air.

In Fig. 4- there is shown another embodiment of the .invention in which the plunger 17 is omitted and the compressed air is delivered into the upper end of the j reservoir and thus applies pressure directly to the ink. In this embodiment the reservoir is indicated at Ma and the ink therein at 16a, the lower end of the reservoir being constituted by the stencil 15a. For producing the increased pressure on the ink the compressed air is delivered directly into the upper end of the reservoir 14a. The delivery of such compressed air into the reservoir at the proper time and the subsequent venting of the reservoir may be controlled by a valve 30, which is shown as a plug valve having a valve case 31 and a valve plug 32 within the case and capable of turning movement. The valve is connected to the top of the reservoir by a pipe connection 33 and also has a compressed air supply pipe 34 leading to the interior of the valve casing. The valve plug has a recess or port 35 which in one position of the plug connects the pipe 33 with a vent 36 and in another position connects the pipe 33 with the supply pipe 34. Any suitable means may be provided for operating the valve plug. As illustrated in Figs -t and 5, the valve plug 32 is provided with an actuating arm 37 by which it can be turned to bring the pipe 33 either into communication with the supply pipe 34 as shown in Fig. 4 or into position to connect the pipe 33 with the vent 36. This arm 37 is shown as acted upon by a pulling spring 39 which normally holds it in the dotted line position, Fig. 5, in which position the port 35 forms a communication between the pipe 33 and the vent 36.

The arm 37 may be turned from the dotted line position Fig. 5 into the full line position (dotted line position Fig. 4) by means of an arm or projection 40 which may be mounted on the crank disk 10 or any other suitable rotating part carried by the shaft 11. The arm 40 will be so positioned that it engages the valve arm 37 at the correct point in the operation of the printing machine to supply the air pressure to the reservoir 14a at the required time.

The reservoir or cylinder 14 may be secured to the vertically moving part 3 of the marking machine in any proper way. As herein illustrated, the lower end of the cylinder 14 projects through an opening in the member 3 and said cylinder is secured to the member 3 by a collar 50 which may be welded or otherwise secured to the cylinder and the member 3.

The screen stencil 15 may be secured to the lower end of the cylinder 14 in any suitable fashion. As illustrated, said cylinder has at its lower end an annular lip 30 which inclines inwardly toward the bottom thereof, and the screen stencil 15 spans the opening defined by the lip 30 and the edge 31 of the stencil is clamped to the outside of the lip 30 by a clamping ring 32 which is secured to the bottom of the cylinder 14 by means of suitable screws 33.

While the ink reservoir with the screen stencil forming one wall thereof is herein illustrated as in the form of a cylinder with the screen stencil forming the bottom of the cylinder, and is also illustrated as being mounted on a vertically moving part of a marking machine, yet it is to be understood that the particular shape of the ink reservoir and the manner of operation of the machine to bring the screen stencil and the work into contact for making the imprint may be varied in many ways without departing from the inventive idea covered by the claims.

The timing of the operation of the valves 23 and 28 and also of the valve 30 may be varied relative to the movement of the printing head toward and from the work support so that the pressure may be applied to the ink either just before the printing head is brought into contact with the work or just at the instant of such contact, or immediately thereafter. Such timing, of course, depends upon the position of the cam 25 on the crank 10, and this position may be varied to obtain the desired result. Similarly, the moment during the operation of 'the machine at which the ink is subjected to negative pressure may be varied by proper adjustment of the switch 29.

Moreover, if it is desired to submit the ink in the res ervoir to more than one pressure impulse, this may be accomplished by proper arrangement of valves and switches for operating them, the basic feature of the invention being means for subjecting at the proper time the ink in the reservoir to pressure to force it through the stencil for making the imprint.

I claim:

1. A printing machine comprising a work support to support a work piece, a printing head havingan ink reservoir adapted to contain ink, the bottom of said reservoir being constituted by an imprint forming stencil, a plunger in the ink reservoir resting on the ink therein, an air cylinder mounted on and located above the reservoir, a piston in said cylinder, a piston rod connecting the piston and plunger and extending through the top of the reservoir, printing head moving means to move the printing head into and out of printing position, means actuated by the printing head moving means as the stencil is making an imprint to admit momentarily compressed air to the cylinder above the piston, thereby to subject the piston and the plunger to downward pressure to force ink through the stencil, and immediately thereafter to admit compressed air into the cylinder below the piston, thereby to subject said piston and plunger to an upward impulsio-n to efiect a quick breaking from the work piece after the imprint has been made.

2. A printing machine comprising a work support to support a work piece, a printing head having an ink reservoir adapted to contain ink, the bottom of said reservoir being constituted by an imprint forming stencil, a plunger in the ink reservoir resting on the ink therein, an air cylinder mounted on and located above the reservoir, a piston in said cylinder, a piston rod connecting the piston and the plunger and extending through the top of the reservoir, printing head moving means to move the printing head into and out of printing position, an upper compressed air supply pipe leading to the cylinder above the piston, a lower compressed air supply pipe leading to the cylinder below the piston, a normally closed valve in each supply pipe, means rendered operative by the printing head moving means as the stencil is brought into printing position to open momentarily the valve in the upper compressed air supply pipe to admit air to the cylinder above the piston, thereby to produce a downward pressure against the piston and plunger to force ink through the stencil, and as the printing head starts its return movement to open the valve in the lower compressed air supply pipe thereby to admit compressed air to the cylinder beneath the piston thereby to give the piston and plunger an upward impulsion to effect a quick breaking of the ink from the work piece after the imprint has been made.

3. A printing machine as defined in claim 2 in which the means for operating the two valves is a crank disk rotating in timed relation with the movement of the printing head and having a single cam projection on its periphery, and in which said two valves: are situated closely together with a portion of each valve in the path of the cam projection as the crank disk rotates and with said portions placed so as to be engaged by the cam projection successively.

References Cited in the file of this patent UNITED STATES PATENTS

Images