US2463239A - Apparatus for producing minute orifices - Google Patents

Description

March 1, 1949. J. R. BOWMAN EIAL 2,453,239

APPARATUS FOR PRODUCING MINUTE ORIFICES Filed Feb. 19, 1945 JOHN R. BOWMHN roman" 2r VLRSAW Fatented Mar. 1, 1949 APPARATUS FOR raonucmc MINUTE cannons I John R. Bowman, Pittsburgh, and Forest F. Versaw, Penn Township, Allegheny County, Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware Application February 19, 1945. Serial No. 578,786

3 Claims. i

This invention relates to an apparatus for reducing orifices to minute size and, more specificaliv, for producing minute orifices of a submicroscopic diameter for use in mass spectrometers.

Flow restricting devices have been used in mass spectrometers and similar equipment wherein a gas sample is admitted to an ionization chamber and is subjected to a stream of accelerated electrons. These devices should strongly impede the flow and for this purpose capillary tubes have been used. It is desirable that the gas be admitted through a plate or disc, but it has not been previously possible to provide a plate or disc with a hole of such extremely small diameter. The molecules of entering as should radiate symmetrically from the introduction point and consequently the orifice should be round.

It is accordingly a primary object of this invention to provide apparatus for producing a round minute orifice in a perforated plate or disc.

Other and further objects of the invention will be apparent from the following description of the invention whereby it will be seen that the objects are attained.

In general, the invention relates to an apparatus for producing a minute orifice in a plate. More specifically, the apparatus comprises an anvil having a fiat polished surface of at least as great a diameter as that of the plate which is to be provided with a minute orifice. A collar surrounding the anvil and extending beyond the facethereof retains and locates the plate. There is also provided a die which is received within and guided by the collar and'which has a surface accurately flat and polished. The die is so shaped that it transmits impact forces to the plate with radial symmetry.

In the accompanying drawing:

Fig. 1 is a side view of an apparatus for making impacts on a disc positioned thereon;

Fig. 2 is a plan view of the apparatus;

Fig. 3 is a sectional view along line 33 of Fig. 1;

Fig. 4 is a sectional view along line 4-4 of Fig. 1;

Fig. 5 is a magnified view taken through the center of a drilled blank; and

Fig. 6 is a similarly magnified view of the completed orifice.

Parallel guide rods 10 and II extend vertically from a base Bend are secured at their upper. threaded ends by a cross member l3 which is retained and secured by nuts l4 and IS. A weight I6 is mounted on the rods which guide it in vertical movement, and the weight carries a projectface such as a plane piece of quartz. It is sub-' jected to annealing by heating to a dull red heat I 2 ing hammer element H for delivering blows to an underlying anvil and die assembly. The anvil 18 comprises a flanged base l9 with a central 1 upstanding portion 20 which hasa flat and polished upper surface. Bolts or fillister screws 2! extend into arcuate cutout portions 22 of the flange l9 and. secure the anvil to the case n through the medium of a collar 23 which is count-ersunk to receive the heads of the bolts or screws. In this manner the anvil is anchored and is prevented elther from rotation or tilting.

A retaining ring 24 is adapted to slip-overthe end of the upright portion 20, to-retain and align a disc blank 25 and a superimposed die 28 for receiving impacts from the hammer member l1.

The top surface of the die 26 is rounded so that blows which are delivered to it will be transmitted symmetrically to the disc blank. It will be understood, however, that the die may have a conical upper surface, or may be of any other geometrical shape which willcause the forces of impact to be distributed uniformly over the area of the underlying disc. The lower surface of the die in contact with the disc is accurately fiat and polished.

In Figs. 5 and 6 are shown magnified views of the disc 25 wherein it is shown how the orifice 28 changes under the repeated impacts from the drilled hole shown in Fig. 5 to the Orifice of Fig. 6 upon successive impacts.

The invention depends upon the principle of isotropic flow of the material under impact and the capability of the material to set after each impact. Annealed fine gold has such an isotropic fiow and a gold plate or disc in the center of which a hole has been made as by drilling may be subjected to successive impacts such that the hole will be made smaller without distorting its initial round shape.

In one embodiment of the invention, therefore. a fine gold disc is first rolled to a thickness of 0.010 inch and a diameter of 1.0 cm. The disc is made very smooth and fiat and a hole is drilled through its center. The hole initially should be as small as practicable, for-which purpose an 0.0135 .inch drill may be used, although it is preferable to use an even finer drill, such as an 0.00185. inch drill of the kind employed in making injection nozzles for Diesel engines. The disc is carefully cleaned and placed on a flat surin a. muiile furnace and then allowed to cool slowly with the furnace. Desirable results may The annealed disc blank is then transferred to the accurately fiat surface of the supporting portion 20 of the anvil and the annular collar 24 is slipped into position to surround it and retain the die 28. The plane surfaces of the anvil and die between which the disc is received are highly polished and great care must be observed in keeping them clean throughout the operation of reducing the disc, for as the hole approaches submicroscopic size even oil is difiicult or impossible to remove from it.

The reduction in size of the orifice can be followed by microscopic examination for the first few blows that are delivered by the falling weight l6, but as the hole becomes progressively smaller its size can no longer be determined by visual in= spection, and therefore must be ascertained by test. In accordance with our invention the flow of air or gas at-a determined rate through the orifice is taken as a measure of its useful size. Our invention accomplishes this by subjecting one side of the orifice to reduced pressure of about 0.5 mm. of mercury, while its other side is exposed to atmosphere (760 mm. of mercury) at about 70 F. Under such standardized conditions the orifice will be found of proper size for use in mass spectrometers and other apparatus providing gaseous ion sources when air or gas will pass through it at the rate of 0.1 to 0.01 ml. per minute measured at atmospheric pressure.

The exact cross-sectional shape of the completed orifice is unknown, but it probably approxe imates that of a singie-sheeted hyperboloid of revolution, as shown in Fig. 6.

, The flow of material of the blank takes place outwardly as well as inwardly, but is so exceedingly slight that it is not affected by the retaining ring 24. The fiow is inward in the neigh borhood of the central hole, and decreasingly so out to about half the radius of the disc. Outside of this region the flow is outward, causing the edge surface to become slightly toroidal rather than cylindrical as it was originally. In practice the increase in diameter of the disc is not measurable.

While the above description of the invention has emphasized the preparation of a minute orifice for a mass spectrometer, the minute orifices of our invention have other uses in some of which the orifice need not be so small nor so perfectly round. For other purposes, other materials than gold which are capable of substantially isotropic fiow may be used, such as, for example, alloys of gold such as goldplatinum, tin. aluminum, silver, copper, and plastics. For purposes of obtamin a somewhat symmetrical orifice, the metals mentioned should be annealed.

a erable that the original hole be drilled in the exact center of a circular disc. If a plate other than a disc is used, impact should be upon a surface centered about the hole. Further, if the impact is not upon the whole area of the plate, it should at least be on an area covering the hole and many times greater than the crosssectional area of the hole to distinguish clearly from the method of making larger holes smaller, used by jewelers, in which the side walls of a hole are simply broken down by the impact of a die on the side walls of a hole, or from peening operations in general.

While the invention is preferably directed to the making of a minute orifice in a plate or prefr ly a disc, the making of minute orifices in blanks of other shapes is contemplated, such as the making of small orifices for use as spinnerets in the manufacture of artificial fibers. The spinneret may be a disc ora thimble. case of a thimble or other similar shape, the impact should take place against a surface conforming in shape. 'Thus, the term "plate" as used in the claims is intended to include a fiat piece of material including discs, as well as various shapes which may be formed from a plate.

From the foregoing it will be understood that our invention provides an apparatus for producing minute orifices, of a size smaller than can be drilled, by the application of impact applied to the surface of a pierced plate having suitable fiow characteristics.

What we claim is:

1. Apparatus for producing a minute orifice in a plate which is preliminarily formed with a small opening, comprising an anvil having an enlarged base and a central upstanding portion the upper face of which is flat and polished, a collar mounted on the central upstanding portion, fastening means extending through the collar and through cutout portions of the base to anchor the anvil and prevent it from either rotating or tilting, a ring closely fitting the upstanding portion and slidable thereon to rest on said collar and to project above the upper face of said upstanding portion, a die retained within said ring for delivering impacts to a perforated plate positioned on the polished face of the anvil, said die havinga fiat polished under surfaceand' a protuberant upper surface of geometrically symmetrical shape whereby impact forces are transmitted to the plate with radial symmetry in the area surrounding the perforation therein. I

2. Apparatus for reducing an orifice in a plate to minute size, comprising an anvil having an enlarged base and a central upstanding portion the upper face of which is fiat and polished, a

collar mounted on the central upstanding por-' tion, fastening means extending through the collar and through cutout portions of the base While the preferable operation of the appa -fratus of our invention has been described as sue:

cessive impacts, substantial reduction in the size, of an orifice may take place with a single impact.

However, it is preferable that the impacts be repeated and that they be made with a comparato anchor'the anvil and prevent it from either rotating or tilting, a ring closely fitting the upstanding portion and slidable thereon to rest on said collar and to project above the upper face of said upstanding portion, a die retained within said ring for delivering impacts to a perfo-a rated plate positioned on the polished face of the anvil, said die having a fiat polished under surface and a protuberant upper surface of conl-' cal shape whereby impact forces are transmitted to the plate with radial symmetry as the perforation therein is reduced to minute size.

3. Apparatusfor producing a minute orifice in In the a perforated plate, comprising an anvil having an enlarged base and a central upstanding portion the upper face of which is hat and polished, a collar mounted on the central upstanding portion, fastening means extending through the collar and through cutout portions of the base to anchor the anvil and prevent it from either rotating or tilting, a ring closely fitting the upstanding portion and siidable thereon to rest on said collar and to project above the upper face of said upstanding portion, a die retained within said ring for delivering impacts to a perforated plate positioned on the polished face of the anvil, said die having a flat polished under surface and a protuberant upper surface of a spherical shape whereby impact forces are transmitted to the plate with radial symmetry in the area surrounding the perforation therein.

JOHN R. BOWMAN.

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' REFERENCES CITED The following references are of record in the file of this patent:

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