US2514403A - Process for producing a replica of a surface - Google Patents

Description

y 1950 E. s. MACHLIN ETAL 2,514,403

PROCESS FOR PRODUCING A REPLICA OF A SURFACE Filed May 15, 1945 2 Shee'ts-Sheet 1 y 1950 E. s; MACHLIN ETAL 2,514,403

PROCESS FOR PRODUCING A REPLICA OF A SURFACE Filed May 15, 1945 2 Sheets-Sheet 2 its backings.

Patented July 11, 1950 PATENT OFFICE I OF A SURFACE PRocEss FOR PRODUCING A REPLICA.

Eugene S. Machlin, Cleveland Heights, and Louis L. Ornstein, East Cleveland, Ohio Application May 15, 1945, SerialNo. 593,897

2 Claims. (CI. 3550) (Granted under the act of March 3, 1883, as 1 amended April 30, 1928; 370 0. G. 757) The invention pertains to the replica r reproduction of the characteristics of a surface on a non-metallic film, said non-metallic replica film being preserved for examination, and to the process of producing and using the replica film.

Many items have been made in the past to obtain a measure of the surface finish of machine finished surfaces. Such methods have made use of expensive instruments which are not available for wide distribution because of their high cost. Other less expensive methods have been used to reproduce surfaces of specimens in the field. of scientific research. These latter methods make-use of replicas of the surfaces which are to be reproduced.

It is an object of this invention to make use of the replica type of reproduction process in a unique fashion which enables very quick determinations of the character or surface finish of a surface to be obtained.

A further object of this invention is to provide a method for obtaining the surface finish or measure of surface character of internal surfaces. For example, where a measure of the area of indentation of a surface i desired, ordinary tracer-type surface finish measuring instruments will not measure this area. However, the use of the replica reproduction process in conjunction with a standard comparison according to the present invention will enable these areas of indentation to be measured. Machines now available for measuring internal indentation areasare very costly and hence limited in use. The replica reproduction process according to the present invention offers an inexpensive, easy method of obtaining internal indentation area measurements.

A further object is to provide an inspection surface finish control by means of, for example, replica reproduction comparison measurements or other measurements.

Other objects and features of the invention will be apparent from the following description taken in conjunction with the accompanying drawings which are exemplary and in which:

. Fig. 1 is an exploded view of the elements of the article and showing the elements employed in the process of producing the replica.

Fig. 1a is a view of the prepared replica blank and its backing,

Fig. 2 is a View showing the parts in place after the solvent has been applied and ready for the application of pressure.

Fig. 3 is a view of the completed replica with Fig. 4 is a plan view of the same.

Fig. 5 is a view of a comparison apparatus.

The surface replica and process of the present invention has been found particularly advantageous for measuring the porosity of chromium plated surfaces, while not being limited thereto.

One of the mostpromising cylinder-bearing surfaces for piston rings operating in an aircraft engine at high power outputs is porous chromium plate. The chief difficulty in the use of chromium plating has been that some porous chromium-plated cylinders wore exceptionally well whereas others wore exceptionally poorly. Because of the uncertainty of the results chromium plating has not been generally adopted for cylinders of high-power engines. The reason for the difference in operation between two cylinders that are chromium plated by the same method may lie in the-type anddegree of porosity.

The lack of adequate methods of inspecting and specifying the optimum porosity of chromium-plated surfaces has greatly retarded progress in the used porous chromium plate. For

this reason a satisfactory method of measuring the'porosity of porous chromium-plated surfaces has been sought. Such instruments as the Brush surface analyzer, the Profilometer, and a lightreflection meter have been used with little success,

The process of the present invention-is simple, fast and sufficiently accurate to specify porosity of chromium-plated cylinders for aircraft engine tests. It is particularly suited for shop use as a means of inspection prior to engine operation.

The blank I' for the replica may desirably be prepared by brushing, spraying, dipping, pouririg or otherwise applying a liquid non-metallic substance such as stripping lacquer or plastic material in a thin film on a smooth, preferably very highly polished surface, the roughness of which is less than 3 microinches, R. M. S. After the film has dried on the smooth surface, it is stripped or peeled therefrom, and may be cut into strips or pieces of the desired size. Other methods may be used to prepare the blank film i, such as rolling a plastic or lacquer film or pressing said film, so long as the surfaces of the film are not marred by the surfaces of the rolls or press.

In the embodiment shown in the drawing, I represents the nonmetallic prepared film; 2 is the surface which is being reproduced; 3 is the solvent applied in any suitable way which is either placed on 2 or on the under side 4 of I; 5 is a backing for I having an adhesive layer on its under side '6. There is an opening I in the backing 5 through which pressure is applied by means of pad 8 which preferably is not soluble in solvent 3.

The film I may desirably be provided with the backing 5 of suitable material, such as paper or cardboard or other flexible material, having an opening therein, desirably such as indicated at I. The backing 5 is preferably provided on its side 6 with adhesive by means of which the side 6 of backing 5 is secured to the blank film I, as indicated in Fig. 1a. A supply of blanks for replicas may be prepared and stored for future use, if desired.

In obtaining a replica reproduction of the surface 2, solvent 3 for the film I is applied by spraying or otherwise, either on the surface 2 or on the side 4 of film I. A thin film of solvent is desirable. Immediately, or a few seconds after the solvent has been applied, the side 4 of the film I is pressed into intimate contact with the surface 2 desirably by hand pressure applied against the protecting pad 8, and through the opening I in backing 5. Fig. 2 shows the parts in place after the solvent has been applied, ready for pressure to be applied to the pad 8. Pressure is maintained for a short time, preferably not less than 15 seconds and not more than 1 minute. During the maintenance of pressure the film becomes dried in contact with the surface to be repro duced.

After the pressure and drying interval has been completed, the replica film I is gently peeled or stripped from the surface 2. It is then provided with a suitable mounting or backing means which may desirably comprise a backing such as indicated at It! having an adhesive side 9 to be attached to the replica film with the opening II in the backing I matching or registering with the opening I of the backing 5. This is shown in Figs. 3 and 4, in which I is the non-metallic replica film; 5 and I8 are the preferably fiexible backings for the film I; B and 9 are the adhesive sides of the backings 5 and ID; and I and !I represent the openings in the backings 5 and Ill.

The replica, as seen in Figs. 3 and 4, is then ready for viewing and examination, for example, by a standard comparison method or other surface finish measurements.

In order to measure porosity or examine the replica film; a magnified image of the replica may desirably be projected onto the screen of a film viewer, such as a 35 millimeter film viewer, as indicated in Fig. 5.

In Fig. 5, the film viewer or projection apparatus is indicated at I2. 1 A strip, desirably consisting of a number of standard replicas of known porosities or surface configuration, sandwiched between two strips of celluloid is mounted in place in the film viewer or projection apparatus l2, as indicated at I3. The standard or known replicas preferably have been accurately calibrated for percentage porosity by measuring the area of the pores. A strip in which is placed the sample replica whose surface finish or surface character is being compared to standard replica strip I3, is indicated at I4.

The projections of the standard and unknown porosity surface replicas are indicated at I5 and I6, respectively. To obtain a comparison, the sample unknown replica I4 is placed in the projection or viewing apparatus l2, so that its projection appears at l6 next to the projection of the standard replica l3 which appears at l5. Any known replica image can be quickly obtained by shifting the standard replica strip. The unknown porosity is obtained by matching the sample replica image to one of the known replica images.

The comparison method enables an untrained operator, to choose or bracket the limits of the unknown porosity or the percentage area of surface identation to nominal surface area, to within approximately 5 percent of the area of surface indentation of the sample replica.

An important feature of the method of the present invention is the action of the solvent 3 to soften the side 4 of film I so that the film I being placed in intimate contact with surface 2, the softened side 4 will conform to the asperities and hollows existing in the surface 2. Such conformity will become permanent as the softened side 4 of film I hardens and sets. Such an action and method provides for a very quick measurement of surface finish or surface indentation area to be obtained.

The surface porosity of a chromium-plated cylinder can be identified by the process of the present invention as to type and measured as to value in approximately one minute.

The replica method is suitable for use in machine shops and plating plants where a quick check of the type or the quality of the porosity of chromium-plating or other surfaces is required. The apparatus is simple and inexpensive. Inexperienced personnel can be trained to measure porosity in a relatively short time. Approximately two minutes are required for a complete measurement, the first minute being required to make the replica and the second minute to match the unknown porosity.

As a film material, it has been found that Ault and Wiborg Protektol No. 28 is particularly suitable. This material is easily stripped from the highly polished surface in forming the replica 'blank without marring the surfaces of the film in any way.

Materials other than the stripping lacquer or liquid plastic may be used in this method, with suitable solvents therefor.

A suitable solvent for the Protektol N0. 28 is Ault and Wibor No. 2069, Protektol Reducer.

If this method were used in a honing shop, removal of the cylinder from the honing machine would be unnecessary. The surface to be checked, may be cleaned, the replica taken, the porosity measured, and honing continued or stopped, depending upon what results showed.

Any standard film viewer that is inexpensive or readily portable may be used in the process, and

-' should preferably be installed in a darkened room.

It may be desirable to have the film of known replicas wound on a spool so that the known samples can be moved across the field of view with a minimum of difiiculty. The viewer may preferably be provided with reversible motor driven shafts. Both samples are subjected in the viewer to the same lighting conditions and are shown side by side to facilitate comparison. A magnification of 16 may desirably be employed. Magnifications as high as 50, however, are available with stock equipment. Lower magnification has the advantage that a larger area can be examined and a more representative sample of porosity can thus be obtained. Samples of both channeled and normal types of porosity have been examined and are readily distinguishable. Thus, type of porosity as well as percentage porosity can be obtained by this method.

It will be understood that various changes in the construction and arrangement of parts and in the process may be made without departing from the spirit of the invention and it is not intended to limit the invention other than by the terms of the appended claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. Steps in a method of obtaining a replica or reproduction of a surface comprising applying a backing having an opening therein to a strip of non-metallic film by means of adhesive to act as a protection against damage and for ease in handling, applying the unbacked side of said film to a surface, the features of which it is desired to reproduce, with the application of liquid solvent for said film, applying pressure to a localized portion of said film through said opening in the backing, allowing the film to dry in pressure contact with said surface, removing the film from said surface, adhesively applying a protecting backing having an opening therein to the unbacked side of said film with the opening substantially registering with the opening in the backing first mentioned, and exposing the replica on the said localized portion of the film which is formed in that part of the film bounded by the edges of the openings in the backings.

2. Steps in a method of obtaining a replica or reproduction of a surface comprising applying a backing having an opening therein to a strip of non-metallic film by means of adhesive to act as a protection against damage and for ease in handling, applying the unbacked side of said film to a surface, the features of which it is desired to reproduce, with the application of liquid solvent for said film, applying a protecting pad to said backing overlying the opening therein, applying pressure to a localized portion of said film through said opening in the backing by pressing on said protecting pad, allowing the film to dry in pressure contact with said surface, removing the film from said surf-ace, adhesively applying a protecting backing having an opening therein to the unbacked side of said film with the opening substantially registering with the opening in the backing first mentioned and thereby exposing the replica on the said localized portion of the film which is formed inthat part of the film bounded by the edges of the openings in the backings.

EUGENE S. MACI-ILIN.

LOUIS L. ORNSTEIN.

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

UNITED STATES PATENTS Number Name Date 241,005 Hart May 3, 1881 573,928 Stevens Dec. 28, 1896 934,214 Ratignier Sept. 14, 1909 1,028,296 Sohier June 14, 1912 1,146,855 Emerson July 20, 1915 1,387,488 Holmer Aug. 16, 1921 1,467,108 Hodgson Sept. 4, 1927 1,811,971 Sauer June 30, 1931 2,046,566 Lucas July 7, 1936 2,070,023 Olsen Feb. 9, 1937 2,074,704 Osborn Mar. 23, 1937 2,090,914 Porter Aug. 24, 1937 2,113,166 Zinser Apr. 5, 1938 2,116,536 McKee May 10, 1938 2,119,577 Gray June 7, 1938 2,184,672 Jackman Dec. 26, 1939 2,202,683 Baesgen May 28, 1940 2,243,674 Koch May 27, 1941 2,291,173 Simpson July 28, 1942 2,296,804 Winnek Sept. 22, 1942 FOREIGN PATENTS Number Country Date 4,874 GreatBritain 1880 54, by J. A. Broadston, Surface Checking Gage 00., Hollywood, California.

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