Ingesting Catchers For Noncontacting Printing Apparatus

Abstract

A noncontacting printing apparatus in which drops of ink are projected towards a moving web through an electrostatic field and in which certain drops may be given an electrostatic charge before passing through the field so that these drops are deflected from the web into an ink catcher. The ink catcher is formed of a tube having an elongated slot and a blade inserted in the slot with a screen member interposed between the blade and the edges of the slot so that ink droplets deflected onto the blade will pass into the interior of the tube and be withdrawn by a negative pressure imposed on the tube interior.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to copending applications entitled IMAGE CONSTRUCTION SYSTEM USING MULTIPLE ARRAYS OF DROP GENERATORS, Ser. No. 768,790; HIGH SPEED PRECISION PLACEMENT OF LIQUID DROPS, Ser. No. 768,767; and COORDINATE PLACEMENT OF INK DROPS, Ser. No. 768,766, all filed on Oct. 18, 1968, and assigned to the assignee of the present invention.

BACKGROUND OF THE INVENTION

In the above applications a system is disclosed for projecting a series of fine drops of ink or other printing material on a moving web. As the drops are ejected towards the web, they pass through a charge ring which is selectively operable to apply an electrostatic charge to the drops. As the drops continue to move towards the web, they pass between electrodes which provide a continuous deflecting field and operate to deflect drops which have been charged by the charge ring. In this way, a patterned printing can be obtained on the web by either charging or not charging the drops as they are ejected towards the web and catching either the charged or the uncharged drops in a collecting system.

It is important that the collection system be compact because of the small spaces involved, that it be fairly economical to fabricate because of the large number of such catchers required, and that it act efficiently to capture, ingest and remove from the printing area all ink drops which are not intended to be deposited on the web.

SUMMARY OF THE INVENTION

The present invention provides an ink-catching system which is formed from a tubular member having a slot in one wall and a razor-sharp blade extending outwardly of the tube through the slot. The blade acts to catch drops as they pass the deflecting field and a sheet of fine mesh screening is interposed between the edges of the slot and the surfaces of the blade to allow the ink or other printing material to pass into the interior of the tube. In a modification of the invention a sheet of hydrophilic material may be placed on the underside of the blade to capture and absorb ink which might otherwise build up on the undersurface of the blade. A vacuum is applied to the tube to remove all ink drops captured by the catcher and in the modification noted supra ink captured by the hydrophilic material is pumped away via capillary action.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is an exploded, perspective view showing somewhat schematically the parts of a typical printing bar used in one form of the noncontacting printing apparatus;

FIG. 2 is a cross-sectional view through a typical print bar; FIG. 3 is a front view of a catching system;

FIG. 4 is a cross-sectional view taken on line 4--4 of FIG. 3;

FIG. 5 is a side view, with parts in section, showing a second preferred embodiment of the invention;

FIG. 6 is a view taken on line 6--6 of FIG. 5; and

FIG. 7 is a cross-sectional view showing a third preferred embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 2, it will be seen that each print unit 10 comprises a print bar 11 having a reservoir 12 formed in the central portion thereof, an orifice plate 13 mounted beneath the print bar 11 and having a series of regularly spaced apertures or orifices 14 formed therethrough, a charge plate 15 having a series of charge rings 16 mounted therein directly beneath each of the orifices in the plate 13, an insulating plate 17 and a deflection plate 18. Mounted atop the print bar 11 is a transducer 20 which imparts a stimulating vibration of a predetermined frequency to the unit to insure that the droplets emitted through the orifices 14 are emitted at regularly spaced intervals. Ink is supplied to the reservoir 12 by means of a pipeline 22 also mounted atop the print bar 11. A control system 23 receiving signals from an input, not shown, through the line 24 is connected individually to the charge rings 16 by means of conductors in cables 25 and 26 and plugs 27 and 28, to control the charges applied to the drops 21.

The ink catcher 30 is positioned beneath the deflection plate and serves to catch drops which are deflected by the continuous deflecting field; the drops being conveyed away from the catcher 30 by means of the vacuum pump 31. For a detailed description of the above apparatus and the operation thereof, reference is made to the above-noted applications on the same subject. Suffice for present purposes to note that ink is ejected from the reservoir 12 as seen in FIG. 2 through the orifices 14 formed in the plate 13 and by the action of the transducer 20 the resulting liquid filaments are separated into regularly spaced drops 21. The charge rings 16 surround the drops as they part from the ends of the filaments and pass toward the moving web of paper 32, and either impart or do not impart a charge to each drop in response to signals received from the control unit 23. If a drop is not charged it follows the path or trajectory of the drops indicated at 21 in FIG. 2. On the other hand, if a charge is imparted to a drop by means of the charge ring 16, the drop follows the path of the drops indicated by the reference numeral 21' and is deflected into the catching system 30.

Referring now to FIGS. 3 and 4 of the drawings, one preferred embodiment of the catcher 30 is shown as comprising a tubular chamber 40 having portions defining a slot 41 in one wall thereof. A blade member 42 is sandwiched between two laps of a foraminous material 43 which may comprise a fine mesh screen of noncorrosive material. The entire assembly of the blade member 42 and screen 43 is received in the slot 41 and held in place therein by means of tackwelds. A pump, such as the pump 31, applies a negative pressure to the interior of the chamber 40 thereby evacuating any ink caught by the blade member 42 in the direction of the arrow 45 at the right-hand end of the ink catcher 40 as viewed in FIG. 3.

It will be noted, that because the blade member 42 is sandwiched between the foraminous member 43 any ink which is caught on the knife edge 46 of the blade member, and divided thereby to run down both surfaces of the blade, may readily pass into the interior of the chamber 40 along the upper and lower surfaces of the blade.

Turning now to FIGS. 5 and 6 of the drawings, a second preferred embodiment of the invention is disclosed. As seen in FIG. 5, the ink catcher comprises a chamber 50 of tubular cross section having a pair of lip portions 51 and 52 extending in spaced parallel relationship to each other from the chamber 50 and defining an opening 53 into the interior of the chamber. A blade member 54 is provided having a first planar portion 55 received between the outwardly extending lips 51 and 52 and a second planar portion 56 angularly disposed with respect to the portion 55.

As in the case of the previous embodiment described, a portion of the blade member 54 may be sandwiched between two laps of a foraminous material 57, which may again comprise a fine mesh screen of noncorrosive material. It will thus be seen that the screen member 57 provides passageways into the chamber 50 on both sides of the blade 54. Thus, if a droplet is not deflected far enough towards the catcher to fall on the upper surface of the blade, but instead strikes the knife edge 58 thereof, and is divided so that a portion rolls down each surface of the blade, it may be conveyed into the interior of the chamber on the under side as well as the upper side of the blade member 54.

It has been found that malfunctions of the catcher may occur from a buildup of ink on the bottom thereof. This buildup may result from drops of ink spanning the gap between the blade and the body of the tube while managing to avoid contacting the low-pressure areas adjacent the intersection of the lower surface of the blade and the body of the tube.

One method of obviating this type of malfunction is shown in FIG. 7, wherein a sheet 60 of a hydrophilic medium, such as cotton fabric, is wrapped about the underside of the catcher 61. One end 62 of the medium is sandwiched between the wire mesh 63 and the lower surface 64 of the blade 65 and the medium is then attached to an exterior bottom portion of the catcher with its opposite end 66 bonded to the tube body by any suitable bonding compound as at 67. The hydrophilic medium easily captures, absorbs and distributes within itself any errant ink drops which are thereafter easily and quickly pumped away by a capillary action.

It will be noted that both embodiments described above may be readily fabricated. In the case of the catcher illustrated in FIGS. 3 and 4, it is merely necessary to mill a slot in one wall of the tube, crimp one end of the tube closed, lap a piece of foraminous material, such as screening, about the blade, insert the laminate in the slot, and tack or plug weld the assembly in place. Alternatively, the tube may be left open at both ends, provided that in actual use, vacuum is to be applied at both ends. In the case of the embodiment of FIGS. 5 and 6, it is again only necessary to lap a piece of foraminous material about the blade member 54, insert it in the end of the tube which forms the chamber 50 and then crimp the tube down on the laminate of the screening and blade member. With the embodiment shown in FIG. 7, it will be apparent that the sheet of hydrophilic material can be utilized with a tube body of the type shown in either FIGS. 3 and 4 or FIGS. 5 and 6. Additionally, it will readily be seen that the catching systems are extremely compact and economical to manufacture.

While the forms of apparatus herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise forms of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

Claims

What is claimed is:

1. In noncontacting printing apparatus including a plurality of means for projecting a series of spaced, fluid drops toward a moving web, means for selectively electrostatically charging some of said drops, means for providing a deflecting field downstream of said charging means whereby charged and uncharged drops will follow different trajectories, and means for catching drops following one of the trajectories before they contact said web, the improvement comprising said catching means including:

a. a tubular chamber having portions defining an elongated, slotted opening in one wall thereof extending past said plurality of drop-projecting means,

b. a blade member positioned within said opening and projecting outwardly of said chamber, and

c. means defining a fluid passage into said chamber between said blade and said opening defining portions of said chamber.

2. The apparatus of claim 1 wherein:

a. said blade member has a pair of opposed, substantially planar drop-catching surfaces, and

b. both of said drop-catching surfaces are spaced from adjacent, opening-defining portions of said chamber.

3. In noncontacting printing apparatus including means for projecting a series of spaced, fluid drops toward a moving web, means for selectively electrostatically charging some of said drops, means for providing a deflecting field downstream of said charging means whereby charged and uncharged drops will follow different trajectories, and means for catching drops following one of the trajectories before they contact said web, the improvement comprising said catching means including:

a. a chamber having portions defining an elongated opening in one wall thereof,

b. a blade member positioned in said opening and projecting outwardly of said chamber,

c. means defining a fluid passage into said chamber between said blade and said opening defining portions of said chamber, and

d. a foraminous member interposed between said blade and said opening defining portions of said chamber.

4. The apparatus of claim 3 wherein said foraminous member comprises:

a. fine mesh screening.

5. The apparatus of claim 4 further comprising:

a. means for applying a negative pressure to the interior of said chamber.

6. The apparatus of claim 5 wherein said chamber comprises:

a. an elongated tubular member, and

b. said blade member is substantially planar.

7. The apparatus of claim 5 wherein:

a. said chamber has a tubular body portion,

b. said opening-defining portions include a pair of lip portions extending in spaced parallel relationship to each other from said body portion, and

c. at least a portion of said blade member is positioned between said lip portions.

8. The apparatus of claim 7 wherein:

a. said portion of said blade member positioned between said lip portions comprises a first portion thereof, and

b. a second planar portion of said blade member extends from said first planar portion externally of said lip portions and angularly disposed with respect to said first planar portion.

9. The apparatus of claim 3 further comprising:

a. a layer of hydrophilic material interposed between said foraminous member and the lower surface of said blade,

b. said layer of material extending outwardly through said opening and underlying an exterior bottom portion of said chamber.

10. The apparatus of claim 9 wherein:

a. said layer of hydrophilic material comprises cotton fabric.