Catching apparatus for a jet drop recorder

[57] ABSTRACT

There is disclosed a catcher for an array-type fluid jet recorder. The catcher has a catching face upon which intercepted droplets impinge and a series of facial channels for carrying away the intercepted liquid in discrete rivulets. The channels communicate with an internal liquid collection cavity to which the intercepted liquid is delivered. There are disclosed two embodiments of the catcher. In one embodiment the rivulet guiding channels are cut into the drop catching face. In the other embodiment a wire is wound in closely spaced turns around the body of the catcher. In this latter embodiment the spaces between the windings serve as liquid conveying channels. In both embodiments of the invention the channels are mutually parallel and have a spacing equal to the spacing of the jets to be caught. The catcher is mounted in the recording head with the rivulet-guiding channels in alignment with the fluid jets so that each jet has its own channel for collection.

Claims, 11 Drawing Figures

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CATCHING APPARATUS FOR A JET DROP RECORDER

BACKGROUND OF THE INVENTION

This invention relates to fluid droplet recorders of the general type shown in Sweet et al. U.S. Pat. No. 3,373,437, Taylor et al. U.S. Pat. No. 3,560,641, and Mathis U.S. Pat. No. 3,701,998. Such fluid droplet recorders generate drops from a plurality of jets arranged in one or more rows, and accomplish recording by selective catching of the drops so generated. The jets are created by forcing a supply of recording fluid from a manifold through a series of orifices in an orifice plate attached thereto. The jets are stimulated to break up into streams of drops, and the drops are selectively charged in accordance with a set of charging signals. For charging there are provided a series of charging electrodes placed near the point where the jets break up into drops. The charging electrodes are connected to a set of input lines which carry appropriately timed pulses for charging only predetermined ones of the drops.

After charging, the drops pass through an electrical deflection field. At this point the charged drops are deflected for separation from the uncharged drops. The charged drops then are caught by a catcher, but the uncharged drops continue on and strike a recording medium which may be a moving web of paper.

One of the more difficult aspects of the design of such a recorder is the provision of a suitable catcher. For high quality recording it is necessary that the jets be small in diameter, closely spaced, and very short in length. Typically the jets may be about 2 mils in diameter with a jet to jet spacing of about 16 mils, and the distance from the orifice plate to the recording medium may be in the order of about 1/4 inch. Thus the deflection distance for the charged drops is exceedingly small, and the catcher must catch these drops without interfering with the uncharged drops.

A number of different catcher configurations have been proposed for this task. For instance, in Sweet et al. there is disclosed a porous wall catcher. Another type of catcher comprises a slotted cylinder with a blade fitted therein as shown for instance in Rourke U.S. Pat. No. 3,611,422. Other configurations include a capillary catcher as shown in Duffield Ser. No. 277,999 filed Aug. 4, 1972 and a catcher with a convex drop catching face as shown in Duffield Ser. No. 310,073, filed Dec. 20, 1972, now U.S. Pat. No. 3,777,302.

Each of these prior art catchers has its own peculiar operating difficulties. For instance, if the face of the catcher has a rough porous catching surface as shown in Sweet et al., then there is a tendency for drops to splatter on impact thereagainst thereby creating a mist or spray which builds up on electrical components of the head causing a shorting out thereof. On the other hand, if the droplets are caught by a blade as disclosed in Rourke, then there is a tendency for partially charged drops to strike the tip of the blade thereby splattering and causing ink build up on the lower surface of the blade. The capillary catcher slot as shown in Duffield Ser. No. 277,999 can only carry away ink only at a relatively slow rate. Finally, the catcher of Duffield Ser. No. 317,073 can handle relatively large ink flow rates, but it requires application of a relatively

3,675 ' 2 high vacuum at the catcher evacuation port. This vacuum causes relatively large air currents in the region around the face of the catcher. Such currents are objectionable in some cases because they tend to disturb 5 the paths of the uncharged drops. Thus there has existed a need for a catcher which can handle relatively large ink flow rates without attendant drop disturbing air currents and without splattering of intercepted droplets.

SUMMARY OF THE INVENTION

In accordance with the practice of this invention it has been found that a catcher will operate with very little splash and will carry away relatively large volumes 15 of recording liquid under modest vacuum conditions if there is provided a relatively smooth drop catching face and means for carrying the recording liquid away from the face in discrete rivulets. Moreover it has been found that such a liquid flow may be achieved by carry20 ing away the collected liquid in a series of channels which are aligned with the flight paths of the liquid jets. Channels which are suitable for this purpose may be cut into the drop catching face, or alternatively may be formed by winding a wire around the main body of the 25 catcher. In the latter case the spaces between the turns of the wire function as the rivulet-guiding channels. In either case the channels communicate with an internal liquid collecting cavity extending along the length of the catcher.

³⁰ Accordingly it is a principal object of this invention to provide an improved catcher for a fluid jet recorder. Other and further objects and advantages of the invention will be apparent from the following description, ₃₅ the accompanying drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a recording head assembly;

FIG. 2 is a cross section view through the assembly of FIG. 1;

FIG. 3 is an enlarged perspective view of a catcher in operation;

FIG. 4 is a cross sectional view of the catcher of FIG. ³ 3; FIG. 5 is a view taken along lines 5—5 of FIG. 4;

FIG. 6 is an enlarged perspective view of an alternative embodiment of a catcher;

FIG. 7 is a cross sectional view of the catcher of FIG.

FIG. 8 is a view taken along line 8—8 of FIG. 7;

FIG. 9 is a view taken along lines 9—9 of FIG. 7; FIG. 10 is a view taken along lines 10—10 of FIG. 8; and ₅₅ FIG. 11 is a perspective view of the main body portion of the catcher of FIGS. 6 through 10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS ₆₀ With reference to FIG. 1 of the drawings it will be seen that the various elements of a head assembly 10 are assembled for support by a support bar 11. Assembly thereto is accomplished by attaching the elements by means of machine screws (not shown) to a clamp ₆₅ bar 12 which is in turn connected to the support bar 11 by means of clamp rods 13.

The recording head assembly, which is described in detail in Mathis U.S. Pat. No. 3,701,988, generally

3,813 3 comprises a filer plate 14, a fluid manifold 15, an orifice plate 16, a charging ring plate 17, a deflection ribbon 18, and a pair of catchers 19. Deflection ribbon 18 is stretched tightly between a pair of catcher holders 20, and catchers 19 are received within channels 21 of catcher holders 20. A pair of elastic bands 47 maintain catchers 19 within channels 21, and means are provided for adjustment of catchers 19 within their respective channels 21, all as described in detail in the above mentioned Mathis patent.

Orifice plate 16 is provided with a series of orifices 22 through which a recording fluid 23 flows for formation of a series of liquid streams. There is provided a stimulator 25 which bears against orifice plate 16 setting up a series of travelling waves therein to break the liquid streams up into uniformly sized and regularly spaced drops 24 as illustrated in detail in FIG. 2. Charge ring plate 17 is spaced from orifice plate 16 such that charge rings 26 surround the fluid jets at the point of drop formation. Each charge ring 26 is coated with a conductive material, and charge rings 26 are connected via printed circuit leads 27 and connectors 28 to a series of charge control input lines 29. Thus the droplets 24 are selectively charged in accordance with input control signals on lines 29.

Those of droplets 24 which are not charged pass down to a moving web 30 to record an image thereon. Those of drops 24 which are charged are deflected by electrical fields set up between deflection ribbon 18 and the catching faces 31 of catchers 19. Electrical fields for this purpose may be generated by connecting lead wire 32 of deflection ribbon 18 to a source of electrical potential, and connecting lead wires 33 of catchers 19 to a source of different electrical potential. It will be observed in this regard that deflection ribbon 18 and catchers 19 are made of an electrically conductive material. A preferred construction material for such a purpose is stainless steel.

Catchers 19 are provided with an internal liquid collection cavity 34 and a series of facial channels 35 lead- 40 ing thereto (FIG. 4). Catchers 19 also have bottom plates 36 to cover cavities 34 and that portion of channels 35 traversing the lower surface areas of main bodies 38. Liquid which is collected within cavities 34 is withdrawn from catchers 19 by means of a vacuum 45 source (not shown) connected to fittings 39. A vacuum ranging between about 1 to 10 inches of mercury is desired.

As shown in FIG. 3, facial channels 35 are parallel, upwardly directed, and located in alignment with the 50 streams of droplets 24. Preferably the upper portion of the catching face 31 is smooth to promote uniformity of the drop deflecting field, and to minimize splattering of droplets 24 upon impact thereagainst. Channels 35 extend upwardly to a point just below the droplet im- 55 pact line so as to collect the impacting droplets and carry them away as discrete liquid rivulets. The rivulets of collected liquid flow down the face of the catcher, above bottom plate 36 and into cavity 34. It has been found that for a properly selected surface smoothness, 60 the collected droplets will flow downwardly in fairly straight rivulets for a fairly good distance, even without the help of facial channels 35. However, it is important that channels 35 be provided at least in the region of the curved transition area 40 so as to guide the col- 65 lected liquid onto the top of bottom plate 36. It will be ,675 appreciated that bottom plate 36 may be spaced apart from the surface area 37 (FIG. 4) or may be grooved, so that channels 35 need not necessarily extend the full distance across area 37. The spacing between adjacent channels 35 is the same as the spacing between adjacent orifices 22.

An alternative embodiment of the invention is illustrated in FIGS. 6 through 11 as comprising a supporting member 41, a rear wall member 42, a bottom plate 43 and a wire winding 44. Wire 44 is wound in tight parallel turns around main body portion 41 so as to produce a series of facial channels in the spaces between the turns thereof. The catcher is aligned with respect to the streams of droplets 24 such that the droplets strike these channels and flow down the catcher face as at 45 for injestion over the top of bottom plate 43 and into cavity 46. A passage 47 is provided for evacuating the collected fluid from the catcher.

This catcher has an advantage over the catcher embodiment described above in that costly channel machining operations are avoided. This embodiment is assembled by merely winding wire 44 around the supporting member 41 as shown in FIG. 11, and thereafter welding or soldering rear wall member 42 and bottom plate 43 in place. For accuracy of wire winding a series of wire receiving notches (not shown) may be milled into the nose area 48 of supporting member 41.

It will be seen that this invention provides an improved catcher which is easily fabricated, operative over a wide range of recording fluid flow rates and self cleaning in its action.

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.