US2422317A - Means for impact testing - Google Patents

Description

Jfirie 17,1947; c; R. STOCK ET AL 2,422,317

' MEANS FOR IMPACT TESTING Filed Oct. 4, 1944 3 Sheets-Sheet 1 INVE -ITORS WWW ATTORNEY June 17, 1947 t c. R. STQCKETAL I 2,422,317

MEANS FOR IMPACT TESTING Filed Oct. 4, 1944' 5 Sheets-Shed ATTORNEY June 17, 1947. Q R, STOCK ETAL 7 2,422,317:

MEANS FOR IMPACT TESTING Filed Ogt. 4, 1944 s Sheets-Sheet 3 I I I INVEN,TOR s 0/4, [I ,2 5 7o CK, I W/m /W c. THXWOOD,

Patented June 17, 1947 llfiEAN S FOR IMPACT TESTING Charles R. Stock, Greenwich, and Vincent 0. Taxwood, Stamford, Conn., assignors to American Cyanamid Company, New York, N. Y., a corporation of Maine Application October 4, 1944, Serial No. 557,184

2 Claims.

The present invention relates to a method and means for determining the capacity or relative capacity of a test piece to absorb impact blows from a hammer without breaking.

The principal object of the present invention is to provide a device of the above character which may be operated for long periods of time without attention, which will have an automatic cutoif device for stopping the machine upon breaking of the test piece and which will record the number of impacts absorbed by the test piece without breakage during the test.

In a device of this character where a hammer arm is provided which may be raised a predetermined distance above the test piece and then released to strike the latter, the hammer will rebound due to the natural resiliency of the piece. Near the top of the upswing due to rebound, the hammer may again be caught by the lifting device and raised. At this point unless damping means are provided there is a tendency for undue vibration in the hammer arm which may interfere with the regularity of the impacts on the test piece.

One of the principal objects of the invention therefore, is to provide a mechanism which will prevent this vibration to not only avoid undue wear on the machine but also to render more accurate the test which the piece is undergoing.

To this end the invention contemplates a hammer arm pivoted intermediate its length so as to form long and short portions. The long portion carries a weighted hammer. Means are provided to depress the short end of the hammer arm to raise the hammer to the desired degree. This means may conveniently take the form of a 1'0- tatable cam actuated by an electric motor. The cam may be provided with a leading edge and a trailing edge with a cut-away portion therebetween so that upon rotation and when the hammer is at a predetermined elevation above the test piece the short end will leave the trailing edge of the cam and due to the cut-away portion of the latter, the hammer wil1 be permitted to fall against the test piece. Due to the natural resiliency of the test piece, the hammer will rebound and when near the top of its upswing, the cam having continued its rotation meanwhile, the leading edge will engage the short portion of the hammer arm to again raise the hammer to its desired elevation. At or about this point, a damping arm carried by the hammer arm will also engage the cam. As the damping device is spring pulled in a direction toward the cam, the hammer arm will be firmly held between the short end thereof and the spring pressed damping arm to prevent vibration.

The invention further includes the novel construction, combination and arrangement of parts more fully hereinafter described and shown in the accompanying drawings in which:

Fig. 1 is a plan view of a device embodying the present invention.

Fig. 2 is a side view showing the lower and shorter end of the hammer arm about to leave the trailing edge of the cam.

Fig. 3 is a side view showing the short end of the ham-mer arm in the cut-away portion of the cam, the hammer having made contact with the.

test piece and at the moment of rebound.

Fig. d is a side view along the line 4-4 of Fig. 1 showing the hammer arm substantially at the top of its upswing due to rebound with the short end of the hammer and the damping device making contact with the cam.

Fig. 5 is a side View showing the short end of the hammer arm depressed slightly over the showing of Fig. 4.

Fig. 6 is a fragmentary side view showing the hammer arm near the top of its uppermost position.

Fig. 7 is a'fragmentary side View showing the normal position of the hammer arm when making contact with the test piece in dotted lines and in full lines showing the position of the parts when the test piece breaks.

Fig. 8 is a top plan View of the device of Fig. 7.

Fig. 9 is a sectional view along the lines of 9-9 of Fig. 8.

Referring now with particularity to the eme bodiment illustrated, a base is shown at l upon which is mounted an electric motor 2 suitably mechanically connected to a cam shaft 3 suitably journaled and carrying a cam 4.

The cam is provided with a leading edge 5 and a trailing edge 6 named according to the direction of rotation of the cam, which from the viewpoint of the drawings is in a clockwise direction.

On base I supports l are provided on which a test piece 8 may rest. The latter may conveniently be held in position by the fixtures 9. On one of the fixtures 9 a switch it is mounted and connected to the circuit ll supplying current to the motor. When the switch It is depressed, the circuit to the motor is interrupted and the latter stopped.

Between'the test piece holder and the cam is a mount l2 carrying a stub shaft l3 which passes through a journal M in a hammer arm I5. The arm is divided into a long portion l6 carrying a removable weight H and a short portion i8 which terminates in a roller i9 suitably journaled in the bifurcated end 2&3.

The parts are so arranged that as the cam t rotates, the surface of the leading edge will engage the roller it and depress the shorter end of the hammer arm l5, raising the hammer as the cam rotates and the roller l9 approaches the trailing edge 6 a shown in Fig. 2, due to the fact that the edge surface of the cam has an increasing radii from the leading to the trailin edge thereof.

Suitably mounted on the hammer arm i5 is a carriage 26 having journals 2| in which is mounted a shaft 22 to which a damping arm 23 is pivoted. The upper end of the damping arm is bifurcated as at 24 and carries roller 25. The fixture 28 is provided with an extension '26 having a coil spring 2? secured in an eye 28 at one end thereof and at the other end in an eye 29 on the damping arm 23. The fixture is also provided with an abutment 38 which is engaged by a set screw 3! and lock nut 32 carried by the damping arm.

The cam shaft 3 which carries the cam l is provided with a rotatable arm 33 which engages through pin 3? a spring pressed lever 35 on a usual type of counter mechanism 36.

In operation the switch Hi (Fig. 3) normally being on and a test piece 8 being in place, the motor 2 rotates the cam 1 clockwise until the parts have passed through the positions of Figs. 4, 5 and 6 to the position in Fig. 2. At this point the hammer arm is substantially at its predetermined highest elevation and ready to be dropped onto the test piece. Further rotation of the cam causes the trailing edge 5 to clear the roller 19 on the depressed and short end of the hammer arm which permits the hammer to drop, the fixture 31 on the bottom of the hammer arm making contact with the test piece as shown in full lines in Fig. 3 and in dotted lines in Fig. 4. Obviously a Weight I? of any desired mass may be used depending upon the impact to be given to the test piece.

It is to be noted that as the cam rotates into theposition of Figs. 2 and 3 the short end of the hammer arm and the damping arm are out of contact with the cam by reason of the cut-away portion of the latter between its leading and trailing edges. There is, therefore, no interference with the free fall of the hammer. The relative minimum distance between the rollers I9 and 25 may be determined and set by suitable adjusting of setscrew 3| and lock nut 32.

Due to the fact that the test piece 8 is supported near its end portions, the resiliency of the piece will cause the hammer to rebound from the position of Fig. 3 to the full line position of Fig. 4. It is important, of course, that the hammer mechanism not be permitted to again strike the test piece until it has been raised to its predetermined height as otherwise no uniformity of test conditions would result.

When the hammer arm on rebound is at substantially the position of Fig. 4, the cam continuing its rotation meanwhile the leading edge 5 makes contact again with the roller on the depressed end of the hammer arm l5. t or about this time the roller on the end of the damping arm 23 also engages the cam against the tension of coil spring 2? to thus hold the hammer arm I 5 securely and against vibration. This vibration damping feature is, a necessary adjunct to the device as it has been found that without it not only does undue wear take place on the stub shaft l3 with even some distortion of the hammer arm itself, wear on cam surface with which roller l9 first makes contact, but there is danger that such vibration will cause the hammer arm to become out of phase with the cam and thus miss a regular impact with the test piece.

Continued rotation of the cam carries the parts through the positions of Figs. 5 and 6. In the latter the damping arm is about to roll off of the trailing edge 6. As by this time the vibration of the arm has been completely prevented, the damping arm serves no further useful purpose in the cycle. It therefore, rolls off of the trailing edge 6 due to the cut-away portion between it and the leading edge. Further rotation of the cam continues the elevation of the hammer until the roller ii! on the depressed end of the hammer arm has reached the position of Fig. 2, that is making contact with the cam edge at its greatest radius. The cycle is then repeated.

Each rotation of the cam is registered on counter 36 by reason of the arm 33 made fast to the cam shaft 3 and its operations of the counting device.

From an inspection of Fig. '7 it will be seen that when the fixture 37 normally makes, contact with the test piece 8 without breaking the latter, the hammer arm occupies the position shown in the dotted lines and the cut oif switch I0 is not disturbed. If, however, the test piece 8 breaks as shown in full lines in Fig. 7 the hammer arm is permitted a further slight downward movement to move the switch iii to the off position, the hammer arm at that point resting upon the righthand fixture 9. Moving of the switch to the off position cuts oi? the motor and the test has been finished. At this point the counter will register the number of impacts required to break the test piece.

While the invention has been described with particular reference to specific embodiments, yet it is to be understood that the invention is not to be limited thereto, but it is to be construed broadly and restricted solely by the scope of the appended claims.

What is claimed:

1. An impact testing device including a hammer arm pivoted intermediate its ends to form a long hammer portion and a short portion, means to depress the short portion of the arm and to release the arm when depressed to a predetermined degree, means to hold a test piece to receive the impact of the hammer when the hammer arm is released, and damping means to prevent vibration of the hammer arm after rebound in which the depressing means is a rotatable cam engageable with the short portion of the ham mer arm to depress the same, the cam having a cut-away portion to clear the same when the hammer portion falls and means to rotate the,

cam and the damping means includes a damping arm carried by the hammer arm and engageable with the cam when the hammer arm is engaged by the leading edge of the cam.

2. An impact testing device including a hammer arm pivoted intermediate itsends. to form a,

long hammer portion and a short portion, means to depress the short portion of the arm and to re-v lease the arm when depressed to a predetermined degree, means to hold a test piece to receive the impact of the hammer when the hammer arm is released, and damping means to prevent, vibration of the hammer arm after rebound in which the depressing means is a rotatable cam engageable with the short portion of the hammer arm to depress the same, the cam having a cut-away UNITED STATES PATENTS portion to clear the same when the hammer por- Number Name Date tion of the hammer arm falls and means to ro- 1,604,141 Amsler Oct-h 1926 tate the cam, the dampin means includes a 5 1,869,067 Malmquist July 26, 1932 damping arm carried by the hammer arm and 2,231,324 Preston u APR 28, 2 engageable with the cam when the hammer arm 902,497 Landgmf et a] Oct. 27, 1908 is engaged by the leading edge of the cam; and 1,693,494 Pembroke 27 1928 a spring for yieldingly pressing said damping arm against t can 10 FOREIGN PATENTS CHARLES STOCK Number Country Date VINCENT TAXWOOD- 638,127 Germany Nov. 10, 1936 REFERENCES CITED The following references are of record in the 15 file of this patent:

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