US2139527A - Impact testing machine - Google Patents

Description

Dec. 6, 1938. A. SONNTAG 2,139,527

IMPACT TESTING MACHINE Filed Dec. 9, 1935 3 Sheets-Sheet l INVENTOR.

Dec. 6, 1938. A. SONNTAG 7 IMPACT TESTING MACHINE Filed Dec. 9, 1935 5 Sheets-Sheet 2 i f j 3o. LEI-.133 & 5.

A 5' INVENTOR. E .2. IN 5 a 4 Dec. 6, 1938. A. SONNTAG 2,139,527

IMPACT TESTING MACHINE Fi 80- 1935 I5 Sheets-Sheet 5 INVENTO 8 wfiw w Patented Dec. 6, 1938 UNITED STATES PATENT OFFICE IMPACT TESTING mcnmn ware Application December 9. 1935, Serial No. 53,451

4Claims.

The invention relates to impact-testing mechanism and more especially to a. novel and useful mechanism for performing both Izod and Charpy impact tests.

Objects and advantages of the invention will be set forth in part hereinafter and in part will be obvious herefrom, or may be learned by practice with the invention, the same being realized and attained by means of the instrumentalities and combinations pointed out in the appended claims.

The invention consists in the novel parts, constructions, arrangements, combinations and improvements herein shown and described.

The accompanying drawingareferred to herein.

l5 and constituting a part hereof, illustrate one embodiment of the invention, and together with the description, serve to explain the principles of the invention.

Of the drawings:

Fig. 1 is a side elevation of a mechanism embodying the invention;

Fig. 2 is a front elevation of the mechanism shown in Fig. 1, certain parts being shown in section;

Fig. 3 is a fragmentary sectioned detail of the pendulum bob and specimen support arranged for making the Izod test;

Fig. 4 is a view similar to Fig. 3 with the mechanism arranged for making a Charpy test;

Fig. 5 is a central horizontal section of the mechanism shown in Fig. 4 on an enlarged scale;

Fig. 6 is an enlarged fragmentary view of the sectioned portion of Fig. 2, showing the pendulum support and braking mechanism in detail;

Fig. '7 is a fragmentary side elevation of the pendulum mechanism in position for making/ a tension test; and

Fig. 8 is a plan view of the mechanism shown in Fig. '7.

The invention is directed to providing a mechanism for performing several types of impact tests wherein the resistance of a specimen to breaking under sudden impact is measured by the terminal travel of a pendulum hammer after the breakage of the specimen. Several types of such tests are known, involving somewhat different technique and using arbitrarily chosen standards and specimens. The principal known impact-testing systems and machines are used in making the socalled Izod tests and the Charpy tests, both of which utilize a pendulum impacting device such as described above. A similar device is also used for ascertaining the strength in tension of speci mens under impact.

66 The present invention provides a new and useful testing mechanism which is adapted to perform Izod, Charpy and tension tests, all with great accuracy and efficiency and with a minimum of changing and. re-setting of parts of the machine, avoiding loss of time and sacrifices in the acg curacy of any of the tests. One object of the invention is to provide a single pendulum of simple mechanical construction which is adapted to make all three types of tests without change of the pendulum or even of the pendulum bob. 10 Furthermore the mechanism is adapted to remain in condition at all times to perform at least two of the tests and the pendulum bob is designed to avoid interfering with or being obstructed by any of the devices used in making any of the 15 tests. 'lhe invention provides a single unitary pendulum and bob for making all of said tests and requires only the interchange of the particular knife or specimen fracturing edge which is to be used with the specimen peculiar to the particular 20 test.

Another object of the invention is to provide a pendulum so constructed that it will always strike the specimen at the true center of gravity of the pendulum, thus avoiding any tendency to vibrate 25 or cause impact to occur at an incorrect point in the swing. For this purpose the pendulum bob is especially designed to compensate for the various clearances and shapings provided to impart its universal applicability to the several tests. 3

The invention further provides an improved braking mechanism for selectively controlling the damping or slowing down and stopping of the pendulum after completion of the test. The invention provides a very simple, efllcient and 35 strong braking device which forms an integral part of the pendulum frame and acts directly on the pendulum axis, thereby avoiding external application of braking friction and making for simplicity and strength of design. Thus unde- 40 sired wear on the pendulum bob is avoided and the brake-operating means are in a readily available location.

Broadly described, the mechanism of the invention comprises a strong and compact frame for 45 rotatably supporting the pendulum and having means for supporting the Izod and Charpy specimens at the bottom of the pendulum swing. The pendulum bob is bifurcated to clear the centrally disposed Izod-specimen anvil and support and is 50 narrowed and cut away on its lateral faces to clear the inwardly projecting ends of the Charpyspecimen anvils and supports. The bob is provided with a suitable knife-supporting seat which is adapted to hold interchangeably either the N Charpy knife or the Izod knife and said bob is provided with a knife clamping member which cooperates with either form of knife. Thus the only change required for making either test is simple replacement of the knife in the bob, which change requires less than one minute. The bob is also bored to receive suitable tension specimens and same can be applied to thbobwith no greater changes or delays than required for the other types of tests.

It will be understood that the foregoing general description and the following detailed description as well are exemplary and explanatory of the invention but are not restrictive thereof.

Referring now in detail to the present preferred embodiment of the invention illustrated by way of example in the accompanying drawings, the mechanism comprises a main frame of cast metal having a relatively heavy and large rectangular base I and two spaced-apart legs or standards 2 and 3. The lower parts of the legs are sloped downwardly and outwardly to join the base, thereby giving additional rigidity and stability to the frame, while the upper ends of the two legs are suitably curved and enlarged to provide for indicating mechanism and to rotatably support the pendulum as will be hereinafter described.

The invention provides a specimen-breaking hammer in the form of a pendulum comprising the relatively long, hollow rod 5 with the bob 8 rigidly attached to the lower end of the rod. The pendulum is mounted near the upper end of the rod to swing freely between the spaced apart legs 2 and I of the frame, the upper portion of the rod being fixed to rotate with horizontally disposed shaft or axle 'l by means of a casting 8 which is bored to receive and hold the rod and is also transversely bored and rigidly fixed to the shaft 1. The horizontal shaft 1 is iournalled to rotate freely in the legs 2 and 3, being supported in the leg 2 by the ball bearing 9 and'inleglbytheball bearing II. Aswillbe' clear from Figure 1 the axis of rotation of the pendulum is such that the center of the bob 0 normally hes adjacent the flat vertical faces of the legs 2 and 3 when the pendulum hangs freely stationary.

Referring now to the embodied means for enabling the mechanism to function as both an Izod and a Charpy tester, the base I of the machine is provided with a suitable T-shaped block for positioning and holding the Izod specimen anvil.

The base I! of the block is suitably bolted to the upper face of the machine base I so that the relatively long and narrow, upstanding rib ll of the block is centrally disposed with respect to the space between the legs 2 and I and thus is bisected by the plane of rotation of the pendulum.

'A suitable recess I4 is provided in the upper face of the rib l3 to receive the Izod anvil l5, which is seated and held in position by a grip screw Ii which is suitably threaded into the rib I2 (Fig. 3) and can be operated from the front of the machine. An Izod specimen I is shown in testing position in Fig. 3.

The pendulum bob 6 is provided with means for supporting an Izod knife or striking edge in proper position with respect to'the pendulum and the specimen. As shown (Fig. 3) the knife 20, of hardened tool steel is removably seated at the interior of the bob so that the forward or striking edge of the knife lies exactly in the plane of the axis of the pendulum and contacts the face of the specimen I in the vertical plane, so that the impact is made just as the pendulum is crossing through the nadir of its swing. It will be noted that the bob 6 is cutaway to form a substantial slot or window 2| extending horizontally from the leading edge of the bob to beyond the center thereof whereby the bob clears the specimen I until contact is made by the knife. The knife is removably seated against the top and rear edges of the slot 2| and is held in position by the screw bolt 22 which enters through the radial bore in the trailing face of the bob.

The bob is shaped so that it will clear the anvil block I3 during its entire swing and accordingly the lower portion of the bob is bifurcated at 26 to straddle the block I3, the upper portion of the slot 25 being narrowed and extended at 26 to provide clearance for the specimen.

Referring now to the embodied means for utilizing the mechanism for Charpy tests, Charpy anvil blocks 30 and 3| are seated in suitable horizontal recesses in the vertical front faces of the legs 2 and 3 and held in position as by bolts 82 and overlapping end blocks 23. The blocks 3| and 3| are provided with suitable horizontal grooves 34 in which the transversely disposed Charpy specimen C may be supported. Suitable anvils 35 are seated within the slots 34 against the rear faces thereof, while bridging plates or guards 36 are provided as shown.

The knife or striking edge for the Charpy tests comprises a wedge shaped member ll of hardened tool steel having its leading edge in the vertical plane (Figs. 4 and 5) at the moment of impact. The knife 4|! is removably seated in the bob in substantially the same manner as the Izod knife 20, being held in the upper rear corner of the slot 2| by the bolt 22 as hereinbefore described. The leading edge of the knife 40 also lies in the axis of the pendulum so that impact occurs at the nadir of the swing.

The disc-shaped bob 0 is likewise constructed so that it will clear the ends of the inwardly projecting Charpy anvil blocks II and II in its swing. For this purpose the upper portion of the bob 8 is of narrowed cross section, that is above the bottom of the horizontal slot 2|. In addition the lateral faces of the bob disc are recessed at ll to provide clearance for the inner ends of the Charpy blocks II and 2| and anvils II.

From the foregoing description it will be clear that to adapt the device for functioning either asanIzodoraCharpytesting mechanism,itis merelynecessarytounscrewthe bolt 22 and release the Izod knife, for example, and replace it with the Charpy knife or vice versa. No other change in the is necessary and the machine is ready for the test simply by seating the appropriate specimen in its anvil.

The bob is suitably constructed to give proper weight distribution and assure that the center of percussion or oscillation conforms exactly with the center of the striking edge of the knife. To assure this proper distribution of weight and location of center of gravity of the pendulum, the bob disc is suitably cut away at 5. in the upper, right hand quadrant so as to compensate for the weight-distribution distortion caused by the various other slots and irregularities in the disc. The bob construction and the shape and arrangement of the knives are so designed that the weight of the striking edges as well as their center of gravities in three directions are brought to coincide with each other very accurately and also there is no change in the weight, balance and center of percussion of the pendulum hammer as a whole when working with either the Izod or Charpy striking edge. I

The invention provides suitable means .for indicating the maximum height of swing of the pendulum after break of the specimen, said in-' dicating means beinglsuitably graduated to show the amount of energy consumed by the breaking of the specimen. As is usual in impact testing devices of the Izod and/or Charpy type, the pendulum is released from a predetermined starting position, fractures the specimen at the nadir of its arc and then swings up on the reverse side until the unconsumed energy is expended. The difference in height between the initial and reverse side positions of the bob is the measure of the energy consumed and means are provided for indicating said difference. As embodied, a pointer 55 is provided to rotate about the axis of the pendulum shaft, the pointer being pushed ahead during the reverse swing of the pendulum and is adapted to remain in the maximum reverse position as the bob falls. A suitable arcuate scale 55 is provided beneath the pointer on the curved upper end of the leg 2. The embodied means for moving the pointer on the reverse swing of the pendulum comprises an arm 51 fixed to and extending radially from the projecting end of shaft I and having an inwardly projecting pin 58 which lies in the path of movement of the pointer 55. The pointer itself is mounted to turn independently about the shaft 1 with a slight friction so 'that it will be advanced by the arm 51 on reverse swinging movement of the pendulum, but will remain in position to indicate the point of maximum reverse swing as the pendulum returns.

. Means are provided for holding the pendulum in its initial raised position and for releasing it to fall therefrom, said means comprising, a bifurcated catch or claw 50 at the top of the frame which is adapted to engage with a suitably shaped collar 5| on the pendulum rod 5. The catch arms 60 are mounted on a horizontal shaft 52 journaled in the top of the frame and a lever 53 is attached to the shaft for manually tripping the catch.

The invention further embodies novel means for braking or damping the fall of the pendulum after reaching its maximum height on its reverse swing after breaking the specimen. Said means comprises a friction disc I0 concentric with the pendulum shaft 1 and having rotary frictional contact with the inner surface of the leg 3 of the frame. The disc III is preferably made of bronze and is provided with a raised annular machined surface II on its inner face near its periphery.-

Said surface 'II is adapted to engage a correspondingly machined surface I2 on the inner face of the leg 3, the leg being formed with a circular boss 59 concentric with and slightly larger than the disc Ill. The disc I0 is mounted to rotate horizontally about the axis of the shaft I in the leg 3 and is provided with a horizontally extending hub or journal 13 which projects through a suitable bore in the leg 3. The hub I3 is hollow to accommodate the right hand end of shaft 1 and contains the race for the. ball bearing Ill on its inner surface as shown.

Except during the braking operation on the return fall of the pendulum, the disc I0 and its attached parts are adapted to remain stationary and permit free rotation of the shaft 1 within the hub I3. For this purpose the frictional surfaces II and 12 are tightly engaged, the disc I0 being forced toward the leg 3 by spring pressure. As embodied, the outer porton I5 of thehub 13 projects from the=leg 3 and has mounted about it a helical spring I5, the inner end of which is attached to a collar I'I which-lies against the le I while the outer end of the spring is connected to a collar I8 which has screw-threaded attach-- ment to the hub 15. The compression of the spring can be varied by turning the threadedccllar I8 on the hub. For convenience of assembly the hub member I5 may be a separate piece from the member I! and the two are preferably joined by screw-threaded attachment I9 as shown in Fig. 6.

For performing the braking operation, means are provided to temporarily connect the shaft I to the disc I0 and thereby cause the frictional engagement between the surfaces II and I2 to be exerted to retard the motion of the shaft. As embodied, a rod is pierced by the shaft I, said rod being mounted within the hollow pendulum rod 5 and having cross-wise pins 8| projecting horizontally at its either end. Said pins are adapted to lie in suitable channels 82 in either side of the casting 8. An annular series of spaced-apart holes 85 are formedin the brake disc 10 opposite the ends of the pins BI and in normal operation the rod 50 and pins 8| are so positioned that the ends of the pins clear the holes 85 in the disc I0 and thus permit free rotation of the shaft 1.

Means are provided for shifting the rod 80 and the pins 8| along the shaft 1 and thereby causing the pins 8| to enter the holes 85 in disc III at the will of the operator. As embodied, the rod 80 is loosely mounted on the shaft I but is caused to rotate therewith by a pin 85 which projects through the rod 80 and into the interior of shaft I by means of a horizontal slot 81 (Fig. 2) formed in the shaft. As shown in Fig.- 6 the shaft I is hollowed out from its left hand end to beyond the mounting of rod 85 and a push rod is slidably mounted therewithin. The inner portion of the pin 85 is fixed to the rod 90 and the slot'8I in the shaft I serves to limit the axial movement of the push rod 90 and the rod 80 which is carried therewith. The push rod 90 extends beyond the left hand end of shaft I and is fitted with a suitable push and pull hande or knob 9| at its protruding end.

The operation of the hereinbefore described braking mechanism is as follows:

During the normal operation of the testing mechanism, the pendulum is released by the catch 50 and falls freely to the nadir of its swing, there contacting and breaking the specimen. The pendulum then swings upwardly on its reverse arc until it reaches its upper limit, the pointer 55 being stationed to indicate that limit as hereinbefore described. Immediately thereafter the operator may push in the knob 9| and the pins 8| will find two of the holes 85 in the disc I0, thereby linking the pendulum shaft 1 to the frictionally retarded disc 10. This operation will effectively brake the falling of the pendulum, the deceleration thereof being adjustable by varying the compression of the spring I6 as previously described. The brake may be released by pulling out the knob when the pendulum has stopped.

The invention further comprises means for making tension impact tests on appropriate specimens therefor and such mechanism is illustrated in Figs. 7 and 8. As shown, suitable spacedapart anvils and 95 may be mounted on the faces of the legs 2 and 3 in place of the blocks 30 and 3| used for the Charpy tests. These anvils form a yoke-like projection from the machine and extend horizontally at the level of the center of the anvil hammer or bob 8 when same is at the nadir of its arc. The tension specimen T'is seated in the bob preferably by means of a screwthreaded plug '1 for which the bob is suitably recessed at 8!. The opposite end of the tension specimen T may be fixed to a cross bar III which is adapted to bridge and strike the ends of theanvils in a known manner. It will be clear that the impact on the tension specimen occurs just as the pendulum reaches its nadir and is thus in a horizontal plane.

The, invention inits broader aspects is not limited to the specific mechanisms shown and described but departures may be ma e therefrom means also in the path of swing of the pendulum for supporting a Charpy specimen anvil, the bob of said pendulum having passageways'for clearing both said supports and anvils, whereby either type of test may be performed without interference from the other support and anvil and said bob having means for removably and interchangeably supporting a centrally disposed knife with a horizontal edge for impacting the vertically disposed Izod specimen and having a centrally disposed knife with a vertical edge for impacting the horizontally disposed Charpy specimen.

2. An impact-testing machine including in combination a frame, a specimen-breaking hammer comprising a pendulum rotatably mounted pendulum for supporting an Izod specimen anvil, other means also in the path of swing of the pendulum for supporting a Charpy specimen anvil, the bob of said pendulum having means for removably and interchangeably supporting knives for impacting Izod specimens and for impacting Charpy specimens, said bob having passageways for clearing both said supports and anvils, whereby either type of test may be performed without interference from the other support and anvil.

3. An impact-testing machine including in combination a frame, a specimen-breaking hammer comprising a pendulum rotatably mounted on the frame, means in the path oi swing of the pendulum'for supporting an Izod specimen anvil, spaced apart supports for Charpy specimen anvils for holding a Charpy specimen across the path of the pendulum, said bob being bifurcated to straddle the Izod support and anvil and being of reduced width and thickness for clearing the Charpy supports and anvils and means for removably attaching a selected knife to said bob.

4. An impact-testing machine including in combination a frame, a pendulum rotatably mounted in said frame, means for supporting impact specimens in the path of swing of the pendulum, and a brake for damping the travel of the pendulum comprising friction means having wear surfaces independent of and acting at the axis of the pendulum and normally disengaged from the pendulum and manually operable means for selectively engaging the brake and the pendulum, whereby wear on the brake does not alter the momentum of the pendulum.

AIJ'RED SONNTAG on the frame, means in the path of swing of the

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