Liquid Ejection Nozzle Structure

Abstract

To provide for laminar flow of liquid ejected through a nozzle structure, the surface in the region of the edge zone of the ejection duct of the nozzle is covered with a layer of crystal columns of at least 2 .mu.m such that the axes of the crystal columns are essentially parallel to the axis of the ejection duct of the nozzle in the terminal region of the nozzle, the crystal columns, in a plane transverse to the axis of the nozzle, exhibiting a fine crystalline structure; the crystals are preferably made with at least one of the metals of titanium, vanadium, niobium, tantalum, chromium, molybenum, tungsten, iron, cobalt, nickle, gold, silver, copper, aluminum and platinum-type metals.

Description

The present invention relates to a liquid ejector, or nozzle structure for liquid under pressure.

Liquid ejectors or nozzles in which liquid is ejected under pressure from a duct, or nozzle structure is used in many technological fields. It is frequently desired that the liquid is ejected from the nozzle in laminar flow. Such ejection thus, however, in many instances lead to difficulties if the liquid wets the exit zone or surface of the nozzle structure or ejector, which tends to deviate the liquid from the predetermined direction of the nozzle axis. Such a case arises particularly if the exit edge of the exit duct or nozzle structure is not perfectly symmetrical, or geometrically exactly as designed, resulting in interference with the flow of the liquid through the nozzle. It is particularly important to maintain the accuracy and stability of the geometrical shape of the exit edge of the nozzle duct, and to prevent wetting of the edge zone of the exit surface of the ejector or nozzle by the liquid being ejected.

It has previously been proposed to decrease the tendency to wet the exit surface of nozzles by coating at least the edge zone of the exit surface of the nozzle with polytetrafluorethylene. Polytetrafluorethylene has, however, low resistance against creep and the stability of the geometric shape of the exit edge of the nozzle duct is insured only for a relatively short period of time.

It is an object of the present invention to provide a liquid ejector in which the exit zone of the nozzle or injector structure is so constructed that unstable conditions of the geometry or shape of the exit edge of the nozzle duct are avoided.

SUBJECT MATTER OF THE PRESENT INVENTION

It has been found, surprisingly, that by coating the exit surface of the nozzle structure in the region of the exit zone of the nozzle with crystalline columns of at least 2 .mu.m thickness, so that the axes of the crystalline columns extend in general parallel to the axis of the exit duct, such instabilities and deviation from design of the nozzle structure, are avoided. The crystal column structure, in a plane transverse to the axis of the nozzle duct, at the exit edge, has a fine crystalline structure. It is particularly desirable that the crystalline columnar layer is made of a metal, and metals which are particularly suitable for the columnar layer are titanium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, iron, cobalt, nickel, gold, silver, copper, aluminum and platinum-type metals; under platinum metals, the following are to be understood: platinum, palladium, rhodium, iridium, ruthenium, osmium. The results are particularly good when the crystalline columns are made of titanium, vanadium, niobium or chromium.

It is believed that the effect of the crystalline columnar layer, in accordance with the present invention, and the stability of the geometry of this layer is derived from the crystalline structure of the columnar layer itself. In the flow direction, which is essentially laminar, a coarsely crystalline, ideally single crystal structure is present, extending parallel to the laminar flow of the liquid, that is, to the axis of the nozzle. In a plane perpendicular to the flow direction, the crystalline columnar layer has a fine crystalline structure. Thus, on the one hand, interference of laminar flow in the flow direction by change of grain boundaries are avoided; on the other hand, the liquid cannot spread in the edge zone of the plane exit surface of the ejector, that is, perpendicular to the flow direction, and thus wetting of the edge zone by accumulation of changes in grain limits are avoided due to the fine crystalline structure.

In accordance with the feature of the invention, the crystalline columns are applied to a base, through which the ejector nozzle is formed, which is preferably a metal such as steel, in a vacuum of at least 10.sup..sup.-1 mm Hg, preferably less than 10.sup..sup.-4 mm Hg, by precipitation, preferably evaporation on the surface. In a preferred form of the process, the liquid ejector structure is maintained at an elevated temperature, for example in the order of 150.degree. C, depending on the metal which is being evaporated on the nozzle surface.

The invention will be described by way of example with reference to the accompanying drawing, wherein the single FIGURE illustrates a schematic cross sectional view of a liquid ejector made in accordance with the present invention.

The liquid ejector 1 is made of a base metal plate, for example steel, and is formed with an extrusion or ejection duct 2. The terminal zone of duct 2 extends along an axis 3, transverse to the exit surface 4. Duct 2 has a liquid applied therethrough, under pressure, to provide for essentially laminar flow of the liquid from the duct 2. The exit surface 5 of the nozzle structure 1 is coated, at least in the region of the terminal zone surrounding the exit plane 4 by means of a crystalline columnar layer 6. The axes of the crystalline columns extend in general parallel to axis 3 of the exit duct, at least in the region of the terminal zone. The crystalline columnar layer 6 exhibit a fine crystalline structure in a plane parallel to the exit plane 5.

The length of the crystal columns, that is, the thickness of the crystalline layer 6 is in excess of 2 .mu.m, preferably in excess of 6 .mu.m; the thickness is determined by designed considerations and by the process of application and may extend to 20 .mu.m or more, but may be less for various applications, for example may be between 6-12 .mu.m.

The base plate may be of metal other than steel, such as bronze, brass, hard metal, titanium, titanium alloy, zirconium, zirconium alloy, tantalum, tantalum alloy, molybdenum, molybdenum alloy, tungsten and tungsten alloy.

Claims

I claim:

1. Liquid ejector, or nozzle structure comprising

a base structural unit (1) having an exit plane (5), and a duct (2) formed therethrough extending through the exit plane to provide for ejection of liquid through the structure from the exit plane, the axis of the duct being perpendicular to the exit plane in the region of the terminal zone of the duct,

and a layer (6) applied to the exit plane (4) of the structural unit (1) of the ejector and applied at least in the region of the edge zone of the duct (2), said layer having a thickness of at least 2 .mu.m and comprising a crystalline columnar structure in which the axes of the crystal columns are essentially parallel to the axis (3) of the duct (2) in the exit zone of the duct, the crystal columns of the crystalline layer (6) exhibiting a fine crystalline structure transverse to the exit surface (5).

2. Ejector, or nozzle according to claim 1 wherein the crystal columns are of metal.

3. Ejector, or nozzle according to claim 1 wherein the crystal columns comprise at least one of the metals comprising the group of titanium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, iron, cobalt, nickel, gold, silver, copper, aluminum and platinum-type metals.

4. Ejector, or nozzle according to claim 3 wherein platinum metals comprise platinum, palladium, rhodium, iridium, ruthenium, osmium.

5. Ejector, or nozzle according to claim 1 wherein the crystal columns comprise at least one metal selected from the group of titanium, vanadium, niobium and chromium.

6. Ejector, or nozzle according to claim 1 wherein the thickness of the crystalline columnar layer is between 2 to 20 .mu.m.

7. Ejector, or nozzle according to claim 1 wherein the structure (1) through which the duct is formed and on which the crystal columnar layer (6) is applied comprises a metal including at least one of the metals of steel, beonze, brass, hard metal, titanium, titanium alloy, zirconium, zirconium alloy, tantalum, tantalum alloy, molybdenum, molybdenum alloy, tungsten and tungsten alloy.

8. Method of making a liquid ejector, or nozzle structure comprising

forming a duct (2) transverse to the thickness of a base material (1), the terminal end of the duct extending along an axis (3) transverse to the surface (5) of the structure to form an exit plane (4);

and coating said exit surface (5) with a crystalline structure of a metal comprising at least one of the metals of the group of titanium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, iron, cobalt, nickel, gold, silver, copper, aluminum and platinum-type metals, by precipitating at least one of said metals on said exit surface (5) under a pressure of less than 10.sup..sup.-1 mm Hg.

9. Method according to claim 8 including the step of maintaining the base structure (1) through which the duct (2) is formed, at least in the region of the exit plane (5) at an elevated temperature in the order of about 150.degree. C, or higher.

10. Method according to claim 8 wherein the metal is evaporated on the base structure at a pressure of less than 10.sup..sup.-4 mm Hg.