US2436435A - Hardness penetrator - Google Patents

Description

' c. KENT 2,436,435

HARDNESS PENETRATOR Feb. 24, 1948.

Filed Feb. 26, 1945- IN V EN TOR. CARLETON V. KENT v ATTORNEY Patented Feb. 24, 1948 Carleton V. Kent, :East Moline;, :Ill.,,:3ssignog l. America-n- Machinis -and Metalsh-InenhlozmYorlt v 'N. Y., a corporation of'llelaware: Application February 26, I945, Serial-Wu; f5l9'g-85-T (CL. Z3e-85);

Jl-Glaim.

This invention relates tothe testing: of'tlre hardness of materials and more particularlwto penetrators or indenters used in zthez machines 'by which the hardness-of a specimen is testech. Gemerally' a test loadi-ot 'a given: magnitude i's:.used':iiio' forcesuch azpenetrator or indenter' against surface of the specimen whose hardness is tobe determined; A dimensiom of the resulting inrpression is: utilized" as an indication. of. theharctness of thespecimem Sometimes the depth of the: impression made by the penetrator" is measured, but more; commonly .arsurface dimension of the. impression-is used as the-'basisfor the computati'on of the hardiness indexof" the specimens. known systems fortesting hardness are those; us ing a hardened steel ball referred to asa Brinell ball; a e sided diamontrpyramid'whose Sidesare symmetrical with-each: other and intersecti'rr four cutting" edges having the same angle called 'the Vickers"" pyramid and 'ai-sided pyramid in which two: opposite cutting: diagonal edges make a large angle with: each other While two: other cutting edges i n a plane perpendicular to that of the first-two make asomewhatsmaller angle-with each other, known-as the Knoop pyramid.

Both types of" pyrami'ct =penetratorspermit greater accuracy in reading the size ofthe: irn pression than :therBr'inell' ball. The Knoop pyramid particularly has certainadvantages overthe;

other types of impression; specifically:

1. For the same area-ofimpression the length of thelonger diagonal of the impression created by-the Knoop: pyramid is greater than the length of the diagonalfin thevickers impression; There-- fore there will be a relatively smaller observational error in reading the Knoop-impression=..

2'; Withsome materials the 'material'displaced by-the indent'er causes a rounded-ridge-around-the impression: which makes: it reot treading. No such ridge is, formed' adjacent to the apexes of'the angles'forming the end's of the longer diagonal of impression;

3. In materials where the impression contracts after "the removal of the penetr tor, no: tion takes place on the long" diagonal of the line pressionofia Knoop indent'eri;

It'isw-aniobject of the present invention to provide a penetrator "for testing machine which retains the v aforementioned advantages the Knoop pyramid but is easier and Cheaper-to produce than -the:pyramidal. penetrator; To make the-readihgs-oi: pyramidal. penetrators: conform: to anexistin'g; standarwitris:necessary that thefour Among the. best hard 'to secure a-con the-penetrate: "which 'inventionwilllanpeareasmhe :hetWeer-r mush- .-.rpaiiar-cdfxpl'anes and all the planes :must: pass through: assume-point". By contrast there is only a single curved- 'outti'ng'edge, easily generated hy-existinagtmechanfcal equipment; in Forms thesubject of this :the: line =oI-aqoplioatibn of the test load; In.one?torm ofitheinventiorr theindentin'g surxfiace or the-:penetralior comprises portions of'two 'slmfaces fiarming parts of two Scrmicali similar :coamial: cones;- the common axis of the -men to:be-testedt Such coaxial conical surfaces readily-- homeroom-d ny conventional methods on a tool grinder.

Itdsanother'dlfiect ofthe invention to provide ts applied-tosaitrspecimeni further object ofthe invention "is to provide A- still further-object" of; the invention is to provideapenetrator havirig .a. single curved cutting edge whicn isremov'a-bly, and preferably *t'urnably'; mounted-leer on a; holder;

Another 'ohject'oflth'e' invention is. tov provide a penetrator of harden'edimaterial which ismagneti cally'supported'ln'.aholderof'adifi'erentcomposition.

Still: another. obiiect .of the. invention. is. to pror vrcle a penetrator:whichislpanticularly well-suit.- .edf.fornerforminghardness testsl on plastics.

Qthei: obiects features andladvantages oi the qescriptiomproceed's, reference being had to the accompanying; draw ings-imwlnch:

Fig h I fshowsa as front 'vievwof theinventiona.

Eighth lfiraz'siiierliiewdfi the penetratorshown-in ili igih sen-pram newton-the impression "leftin the specimen by the penetrator shown in- Figs. 1 and 2 Thar-modified" fOr-In-ofpenetrat'or shown Figsz antl -leaves'the' same impression;

Fig:- l 'i's a front vi'ewaxinartly in section, ofaa modified' renetratoirzsmall portions of the conical surfaces "that permits the comparison of readings Fig. is a side view of the modified form of the penetrator shown in Fig. 4.

In Figs. 1 to 3 the numeral I denotes a speciimen whose hardness is to be determined. 2 is a bar having its lower end ground so as to form two conical surfaces 3 and I3, each of these conical surfaces being part of a cone whose axis 4-5 extends perpendicularly'to th'axis "(i- 1 of the penetrator. Since hardness impressions are normally made with the penetrator at right angles to the surface of the specimen, ordinarily be parallel to men I. The two conical surfaces 3, l3 meet in an an: IB which forms the'singlecutting edge of the penetrator. any one of several angles 9, depending upon the angle most suitable for indenting the particular type of material. In Figure 1 this angle 9 is the surface of Cones 3, 13 may be formed with I the axis 4-5 will thespeci-.--

- projects.

shown as approximately 45 but it maybe se- I lected to suit the hardness and characteristics of particular types of specimens tov be tested. In general, the softer the specimena'the larger will ,be the angle chosen.

As will be seen from the:drawing, the trator has two planes of symmetry, one being defined by the axes 45 and B---'! and. the other being perpendicular thereto and containing axis 6-1. There is no cutting edge in the first-named .planeoi symmetry, the only cutting edge l5 being situated in said second plane perpendicular to the axis 4-5. The shape-of the cutting edge i5 is that of an arc of a circle. Any section taken through the active (conically ground) portion of the penetrator parallel to said last-named plane of symmetry is delimited by a circular curve having its center on the axis 4-5.

The section taken through the other plane of symmetry, that ;.is, the plane containing axis 4-5 as well as axis I6-l is of V-shape with the sides of the V straight lines.

. If the penetrator shown inrFigs. land 2 is forced against the specimen I so that the cutting edge 15 penetrates the specimen as shown at 8, the

impression made will be of lenticular shape. The lenticular figure l2 shownin Fig. 3, is bisected by the longitudinal line l9 created by' the cut- .ting edge (5 and the side walls I? and i8 of this impression are curved surfaces corresponding to 3 and i3 of the penetrator. At each-of the two ends and [5 of the lenticular figure l2 the sides of "the latter and theline i!) join in, a single point which can be readily observed, such; as by amicroscope. The distance between the points M and it will be used as index of the hardness of the particular specimen tested.

It has been found that thehardness readings obtained by the use of the double-cone penetratordescribed bear in .fixed relation to the readings secured by other penetratorsystems. in par ticular .by. the systems using pyramidal penetrators; This permits the'use of a'conversion factor o i ed under this system with "those "obtained under other systems. Q l

The body on which the conical surfaces 3, l3 are formed may "consist of hardened steel. In some cases it maybe advisable to tip the steel bar 2 with a particularly hard material, such as -Carboloy, and to grind" the conical surfaces 3, {-3 thereon. i

In the modification shown in Figs. 4 and 5 the penetrator proper, generally indicated at 2! is again of double conicalshape. but instead of being formed in one piece with the shaft has in -ous manners different from the -ed. In particular iprising, in combination.

' on both sides of the roller coaxially with the common axis of the two cones 3, l3. The holder 26 is fork-shaped having two downwardly extending prongs 30, 32 in which the studs 22, 24 find their bearings and which leave between themselves an opening 28, into which the roller 29 With this arrangement the roller 20 may be rotated from time to time to bring into play new indenting surfaces corresponding to a new section of the cutting edge l5, whereby the useful life of the penetrator may be greatly pr0 longed. 'T

It will be obvious that, if only a rotatable mounting of the {roller 20 relative to the holder 26 is desired, this may be achieved also in varione shown in Figs. 4 and 5, such as by proviidng the roller 20 with one or more axial bores and have this roller supported by two studs or by a shaft formed integral with, or secured to, the holder 26 so that the wheel may turn on said studs or on said shaft.

The arrangement shown in Figs. 4 and 5, however, wherein the studs 22, 24 form part of the roller 20 and the'holder 26 has two slots 34 which are open at their lower end so that the studs may be slippedinto these slots from below, is

very convenient'for the reason that it lends itself readily to holding the penetrator in place solely by magnetic means without the necessity of any mechanical retaining members. If the holder 26 34 and retained therein as soon as the studs 22, .24 of the roller-:20 are brought reasonably close to and below the slots 34 in the holder 25; A further advantage of this arrangement is that one penetrator can readily be exchanged for another having a different angle and the substitution of the one'penetrator for the other in the holder is only a matte'r of seconds.

Roller 20 may be of hardened steel, its symmetrical form lending itself readily to hardening.

One of the advantages of this system is that it permits the selection of the proper size of roller and the proper cone angle that is best adapted to the general-type of specimen that is to be testit has been found that a double-cone penetrjator of the proper size and angle gives better results in the testing of plastics than those systems of hardness testing that were primarily developed for use on metals.

, thefmaterial is distorted by the flat sides and numerous angles of the other indenters.

What I claim. is: A penetrator for adapted to make a hardness testing machines lenticular impression, coma hardened piece whose cutting edge is formed bythe intersection of two conical surfaces, means for loading any part of said circular cutting edge, said means including hearings on the axis of said cones and a shank Number having bearing surfaces so spaced as to transmit 1, 5

an axial load from the shaft axis to the speci- 5 2,254,162

men along a diameter of the circular cutting edge 2,335,235 which is normal to the specimen.

CARLETON V. KENT. Number REFERENCES CITED 1 10 358,509

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

6 UNITED STATES PATENTS Name Date Ames Apr. 1, 1919 Wyman Aug. 26, 1941 Clifton i. Nov. 30 1943 FOREIGN PATENTS Country Date Germany Sept. 11, 1922

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