US2746704A

US2746704A - Mount for metallographic specimens

Info

Publication number: US2746704A
Application number: US185702A
Authority: US
Inventors: Puglielli Alphonse; Rostislaw S Komarnitsky
Original assignee: Rockwell Spring and Axle Co
Current assignee: Rockwell Spring and Axle Co
Priority date: 1950-09-20
Filing date: 1950-09-20
Publication date: 1956-05-22
Anticipated expiration: 1973-05-22

Description

May 22, 1956 A. PUGLIELLI ET AL 2,745,704

MOUNT FOR METALLOGRAPHIC SPECIMENS Filed Sept. 20, 1950 Fig. 7

Fig. 5

Fig. 4

IN VEN TORS Alphonse Pug/ie/li BY Rasris/aw .S. Komarnitsky THE/R ATTORNEYS 2,746,704 Patented May 22, 1:

MOUNT FOR METALLOGRAPHIC SPECIMENS Alphonse Puglielli and Rostislaw S. Komarnitsky,.Coraopolis, Pa., assignors, by mesne: assignments, to Rockwell Spring and Axle Company, Coraopolis, Pin, a corporation of Pennsylvania Application September 20, 1950, Serial No. 185,702

1 Claim. (CL248-175) This invention is directed to improvements in'meansfor mounting a thin fiat metallographic specimen for examination under a microscope.

As explained in U. S. Patent No. 2,494,834, dated January 17, 1950, and issued to Richard S. Ringheim, in mounting a narrow transverse section of a metallographic test specimen for examination under a microscope, it is desirable to expose the transverse section in the base of a cylindrical plastic block in which the test specimen is encased or embedded by a molding process. It is also desirable to have the broad expansive faces of the test specimen perpendicular to the base of the cylindrical plastic block. However, in conventional molding methods difliculty is usually encountered in keeping this relationship during the molding operation when the plastic powder: having the test specimen therein issubjected to heat and pressure in a suitable molding press for obtaining the desired plastic block. The aforesaid Ringheim patent seeks to overcome this difficulty by the use of a pair of blanks which are relatively heavy and large in comparison with the specimen to be examined, and requires that the blanks be carefully bonded to the specimen.

An object of our invention is to provide an improved means that holds a test specimen edgewise on the platen of a molding press without being bonded, cemented or similarly positively attached to the test specimen.

A further object of our invention is to provide a mounting means for holding a test specimen edgewise on a flat platen of a molding press in such a manner that the specimen can be adjusted while in the press, preparatory to being molded in the plastic.

Another object of our invention is to provide an improved means of the type described that allows the test specimen to be solidly and properly encased in plastic.

Still another object of our invention is to provide an improved mounting means that properly exposes atransverse section or edge of a thin metallographic test speci men in the base of a plastic block so that characteristics of the specimen can be accurately ascertained.

A further object of our invention is to provide an exceedingly simple means for holding a thin metallographic test specimen edgewise on a platen of a molding press, with the edge of the specimen to be explored resting on the platen and the specimen extending vertically perpendicular to the platen; the means being of extremely low cost.

In accordance with our invention, we provide a clip of spring-wire which is shaped so that it will frictionally hold the specimen to be examined properly on the platen of a molding press. In the presently preferred embodiment, the spring-wire clip comprises a loop-portion having a narrow bottom and a wiened upper part. The loop-portion has side portions which frictionally hold or clamp the specimen therebetween; and legs extend from the lower ends of the side portions for positioning the clip and specimen perpendicularly on the platen.

Objects, features, and innovations of our invention, in addition to the foregoing, will be discernible from the 2 following description. The description is to be taken in conjunction with the. accompanying drawing in which:

Figure 1v is a diagrammatic vertical cross-sectional view of a loaded molding press for forminga plastic block having a metallographic test specimen properly encased therein;

Figure 2 is a side view of a completed plastic block having. the test specimen encased therein;

Figure 3 is a front view of the test block;

Figure 4 is an. enlarged front view, to scale, of a clip used to position the test specimen on the platen of the molding press;

Figures 5 and 6 are, respectively, to scale, a side view and a bottom plan view of the clip shown in Figure 4; and

Figure 7 is a side view of a modified clip in accordance with our invention.

Figure 1 diagrammatically shows. a molding press used in the process of encasing a thin metallographic test specimen in a cylindrical plastic block in a manner which will provide a transverse section or edge of the specimen at a base of the plastic block so that the transverse section or edge can be easily microscopically examined. The molding press is indicated in its entirety by the reference numeral 2 and comprises a cylinder 4, a stationary platen 6 having a flat horizontal face or surface 8, and a plunger 10 movable with respect to the platen to provide a workspace 12.

For forming the completed plastic block with a test specimen therein, a test specimen 14' is placed edgewise on the face 8 of the platen 6. The test specimen 14 is generally rectangular and has a narrow edge that rests on the platen, the edge being perpendicular to the larger rectangular expansive faces of the specimen so that the specimen rests edgewise on the platen. Molding powder 16, or the equivalent, is placed in the work-space 12. The quantity of molding powder can be measured in accordance with the desired size of the completed plastic block. In order tokeep the test specimen 14 perpendicularly on the face 8 of the platen 6' while the powder is placed in the work-space 12 and during the molding operations in which the powder is: converted into a solid. transparent plastic, a clip 18 is provided. During the molding operations' theplunger 10' is. forcibly lowered, and heat is applied to the powder so that the compressed powder cures and. setsinto a solid clear block of the type shown in Figs. 2 and3.

A finished plastic block is indicated in Figs. 2 and 3 by the reference numeral 20, and comprises a planar bottom surface or base 22 along which the edge of the test specimen 14 lies, this specimen-edge corresponding to the transverse section of the specimen that is to be microscopically examined. Accordingly, the plastic block 20 has embedded therein the test specimen 14 and the clip 18.

The clip 18 is a single piece of spring-wire shaped to have an upstanding open-bottomed loop-portion 28 and a pairof legs 3'9 and 32 extending from the open bottom of the loop-portion 28. The loop-portion 28 comprises a pair of lower straight parallel side-portions. 34 and 36; a relatively straight portion 40, the leg 30 extending away from the side-portion 34, and the leg 32 extending away from the side-portion 36. The side-

portions

34 and 36 are connected by a loop-part 38 of the loop-portion 28. In the preferred embodiment, the side-portion 34 is longer than the side-portion 36 so that the loop-part 38 can be conveniently made with an enlarged semi-circular section at the top of the loop-portion and a slanting straight section that extends from the end of the semi-circular section to the top of the side-portion 36.

The loop-portion 28 of the clip 18 is generally planar, and the leg 30 lies in this plane, extending outwardly generally perpendicular to the straight side-portion 34 of which it can be said to be a continuation. However, the leg 32 associated with the side-portion 36 of the loopportion 28 extends in a plane which is approximately perpendicular to the plane of the loop-portion. In the preferred embodiment, the two

legs

30 and 32 lie generally in a horizontal plane parallel to the face 8 of the platen 6, but extend in different angularly-related directions with respect to the loop-portion. In the preferred embodiment these directions make an angle which can be said to flare from the open bottom of the loop-portion, as shown in Figure 6. In this embodiment, the leg 30 extends perpendicularly from a broad face of the specimen held in the clip 18, and the leg 32 extends along the opposite face of the specimen held in the clip 18, substantially parallel thereto. Preferably, the legs are bent from the side portions with as small a radius as possible. We prefer to make the longer side-portion 34 of the clip 18 of a length that will embrace the maximum associated dimension of the test specimen to be held by the clip.

The manner of assembling the test specimen and clip in the molding press is believed to be fairly evident. A clip is chosen having a loop-portion whose height is greater than that of the test specimen, whose side portions 34- and 36 are spaced a distance which is less than the thickness of the specimen, and whose upper curved part has a width which is more than the thickness of the test specimen. Accordingly, when the test specimen is slipped between the two side-

portions

34 and 36, they contact and press against the broad faces of the test specimen at points above the lower edge of the specimen. terial is necessary to hold the test specimen in place when the clip and the specimen are pressed downwardly against the flat face 8 of the platen 6, and the specimen can be easily adjusted while on the platen. The angular spread of the

legs

30 and 32 maintains the test specimen firmly i on the platen, with the loop-portion 28 of the clip 18 and the specimen perpendicular to the face of the platen.

The clip is made from comparatively thin spring wire which allows its side portions to be spread apart beyond their normal spacing. Hence, the resiliency of the loopportion of the clip tends to restore the side portions to normal, so that they exert a pressure on a specimen therebetween. This pressure is, however, very slight for the displacements involved, and is easily manually counteracted.

An indication of the size of a clip in accordance with our invention can be gathered from the following characteristics of a clip found to be satisfactory for holding a test specimen which was /8 wide, 1 long and .125" thick. The clip was made from spring wire .040 in diameter. The upper semi-circular curved part of the loop had an internal radius of .120". The minimum space between the straight parallel side portions of the clip was .070". Each

leg

30 and 32 had an overall length of A" from its free edge to the extension of the far side of the associated side-portion of the clip. The legs were in a plane, with the leg corresponding to the leg 30 forming a right angle with the associated side portion 34. The axes of the legs formed an angle of 105 degrees. The overall width of the clip, corresponding to the maximum dimension in Fig. 6, was .520. The overall length or height of the clip was 5 In the finished product, the specimen was firmly and No bonding masolidly embedded in the cured plastic block, without crevices or holes therein. The thinness of the wire and its curved surface permit the plastic material to flow into contact with substantially the full area of the embedded surface of the test specimen.

While it is preferable to have the legs of the clip in a plane substantially parallel to that of the face of the platen on which they rest, it is obvious that these exact details need not be followed; and Fig. 7 discloses a modified form of clip which corresponds to the first-described clip, except for a leg 32 bent at an angle somewhat less than 90 with respect to the shorter side-portion 36 of the loop-portion of the clip; the other leg being in a plane perpendicular to the associated side-portion.

While we have described certain present preferred embodiments of our invention, it is to be understood that it may be otherwise embodied within the scope of the following claim.

We claim:

A spring wire clip adapted to hold a thin flat metallographic specimen of a desired thickness on edge on a flat support surface while embedding the specimen and clip in a molding composition, said clip comprising a loop, two straight side portions integral with the loop, extending to the bottom of said clip and lying in the plane of the loop, said straight side portions being of a height sufiicient and positioned such that a specimen is received and rigidly held against tipping therebetween, that part of each of said straight side portions adjacent the bottom of said clip being positioned relative to the other a distance less than the thickness of said specimen and forming a gap for yieldingly clamping said specimen perpendicular to the support surface, whereby a specimen inserted between said side portions is gripped thereby, said side portions and said loop being arranged to hold a specimen in a plane disposed at substantially right angles to the plane of said loop, and a relatively short straight leg integral with each of said straight side portions at the ends of said straight side portions opposite said loop, each of said legs extending outwardly from the gap between said straight side portions, one of said legs extending transversely to the plane of the loop, the junction of said legs with said straight side portions being in the same plane, the angle between said legs being an obtuse angle.

References Cited in the file of this patent UNITED STATES PATENTS 257,987 Strong May 16, 1882 535,596 Minto Mar. 13, 1895 710,477 Littell Oct. 7, 1902 867,379 Kaufmann Oct. 1, 1907 1,064,952 Allen June 17, 1913 1,337,816 Blackwell et al. Apr. 20, 1920 1,621,465 Hamrnes Mar. 15, 1927 1,734,626 Hulme Nov. 5, 1929 1,750,894 Kramer Mar. 18, 1930 1,933,474 Ekedahl et al. Oct. 31, 1933 2,494,834 Rinsheirn Jan. 17, 1951 FOREIGN PATENTS 445,379 France Sept. 2, 1912