US2978900A - Materials testing machine - Google Patents

Description

D. E. LEE

MATERIALS TESTING MACHINE April 11, 1961 Filed April 16. 1956 VII/d All-Ill" 4 a rllllffdlir INVENTOR.

DONALD E. LEE

ATTORNEY United States Patent MATERIALS TESTING MACHINE Donald E. Lee, Springfield, Pa., assignor to Baldwin- Lirna-Hamilton' Corporation, a corporation of Pennsylvania Filed Apr. 16, 1956, Ser. No. 578,324

Claims. (Cl. 73-93 This invention relates generally to materials testing machines for tension and compression tests and more particularly to a machine of the type having a single loading screw and an electrical strain sensitive load measuring system.

Such single loading screw type machines have hereto fore been proposed and used but the same have been either costly or not sufliciently compact, or they had other deficiencies either structurally or functionally.

It is an object of my invention to provide an improved materials testing machine of the single loading screw type in which the various component elements are so cooperatively arranged as to insure not only a high degree of compactness and rigidity for operational purposes but also simplicity of construction and operation so as to insure minimum manufacturing and maintenance costs without in any Way reducing the flexibility of operation of the machine or its accuracy and sensitivity.

Other objects and advantages will be more apparent to those skilled in the art from the following description of the accompanying drawings in which:

Fig. l is a perspective of my improved machine with parts broken away to show details of construction;

Fig. 2 is a fragmentary plan view showing means for resisting any tendency of the loading platen to rotate upon rotation of the loading screw;

Fig. 3 is an enlarged plan view of one corner of the upper end of one of the load sensitive columns and the flexure plate therefor; and

Fig. 4 is a vertical sectional view of Fig. 3 taken on line'4-4, Fig. 3.

In the particular embodiment of the invention disclosed herein I have shown my improved machine as comprising a base 1, preferably rectangular in plan view, having a horizontal base member or plate 2 and side walls 3 formed preferably as an integral L-shaped structure upon which a horizontal top plate or member 4 is secured by suitable bolts 5. Mounted upon thetop plate 4 is a guide housing structure 5 preferably rectangular in plan view and having vertical walls 6 and a top plate 7 formed preferably as an integral unit bolted to the plate 4. This structure serves multiple guiding purposes one of which is to form a central guiding means 8 preferably in the form of a cylinder whose diameter is such that it preferably merges with the side walls 6 at the front and back as indicated at 9 thereby insuring a rugged interrelated tie between the guide cylinder 8 and the box-like structure 5. It will be understood that housing structure 5 may be either cast as a single unit or fabricated and welded together. Vertically slidably mounted within the guide cylinder 8 is a hollow member or ram 10 whose upper end carries a specimen loading platen 11 provided with a usual specimen grip opening 12. The platen is suitably secured symmetrically to the ram by bolts 13 and the guide cylinder is thus located centrally of the platen and also of the base 1 and housing 5. An elongated nut 15 is operatively connected to the ram as by being a fixed part thereof. To this end the nut, preferably 2,978,900 Patented Apr. 11, 1961 formed separately from the ram, is telescoped within the ram and is provided with a flange at its lower end which is suitably rigidly secured to the lower end of the ram by bolts or other means. This nut and a screw 16 are preferably of the ball bearing type, the screw being preferably substantially equal to the length of the ram 10 to insure a maximum stroke of loading platen 11. The lower end of the screw is secured in a bull gear 17 provided with upper and lower thrust bearings 18 and 19 preferably of the roller bearing type. The lower bearing is seated upon the base plate 2 and the upper bearing 18 bears against a plate 20 connecting the lower end of the cylinder 8 with the front and back portions of the side walls 6. The hull gear is suitably rotated by a driving motor and connecting gears, not shown as they do not form part of my present invention. By rotation of the gear 17 the screw 16 will drive the nut 15 and its attached ram 10 up and down to impart a loading force to the platen in either direction of movement for performing either tension or compression tests.

An upper crosshead 23 is mounted upon notched loadsensitive columns 24 in any desired vertical position thereon in accordance with the position of the notches 25 in a manner well known in the art. The lower ends of the sensitive columns 24 are connected to the upper ends of load cells 26 (one for each column) which extend freely through openings in the top plate 7. These load cells are preferably of the electrical impedance type having a column which is strain sensitive to the applied load force. These cells can be of the type generally disclosed in Ruge Patents 2,561,318 or 2,576,417 with any suitable variation of the cross-sectional area of the strain sensitive column therein depending upon the ca- .pacity of the machine. The strain sensing means arepreferably bonded wire strain gages connected intoany usual and well known measuring bridge circuit.

As disclosed in said Ruge patents, each cell includes an outer casing such as 26 which, in my present invention, is securely mounted on a heavy base block 27 bolted as at 28 to the base plate 4 which is connected to the bottom plate 2 by an insert block 27'. As also shown in said Ruge patents, the strain sensitive column within each cell is laterally guided by flexible stay plates which additionally guide the lower ends of the notched load sensitive columns 24. The upper ends of these notched columns are in turn laterally guided by a pair of flexible stay plates 29 one end of which is secured to the notched columns and the other end to a top stationary plate 30 by bolts 31. This plate is secured to four rigid supporting columns 32 which pass throughsuitahle ears 34 projecting from the top plate 7 of the cylinder housing 5. These rigid rods are securely held in ears 34 by nuts 35 and the lower ends of the rods extend through and are rigidly connected to base plate 4 by suitable shoulders and nuts on the rods. The notched rods 24 pass freely through enlarged openings in top stationary plate 30 so that the load sensitive frame consisting of notched rods the load sensitive frame in the event of off-center or eccentric loading of a specimen. This minimizes bending effects in the notched columns and eliminates excessive strains on the load cell flex plates:

To prevent the loading platen 11 from tending to ro tate during rotation of the screw, the back side of platen 11 is provided with a roller strap 38 secured to the rear side of the platen and having at its ends a pair of rollers 39 which engage the inner sides of the rear fixed columns 32 throughout vertical movement of platen 11.

From the foregoing disclosure it is seen that I have provided a single loading screw type materials testing machine that has a high degree of compactness and ruggedness by reason. of having the single screw telescopically disposed within the hollow ram 10 which in turn is laterally supported in a rugged manner by the guide cylinder 8 which is connected through the superstructure to the base 1. Thus the loading platen 11 has a high degree of stability against eccentric loads and can be moved through a Very long loading distance while still maintaining all the operating mechanism within a minimum vertical distance.

In testing specimens in tension the platen 11 would be initially raised a sufficient distance to suitably hold a specimen in a usual manner by grips in the upper crosshead 23 and in the platen 11 whereupon platen 11 is moved downwardly by relative rotation between the nut and screw elements, one of which, in the broad aspect of the invention, is operatively connected to the ram to move therewith and the other is in a fixed axial position. Specifically, the screw is shown as being the axially fixed member. Conversely, upon compression tests, a specimen is positioned between platen 11 and crosshead 23 and the loading platen moved upwardly upon rotation of the screw in the opposite direction. In either direction of loading the upper crosshead 23 floats freely but is rigidly supported in all lateral directions by the stay plates 29 thereby transmitting true specimen loads to the load cells 26 whose load responsive strain sensitive columns and strain responsive means will then measure the applied load. The screw, elongated loading nut, the ram and gear 17 are additionally completely enclosed which allows these parts to be lubricated completely free of foreign matter.

It will, of course, be-understood that various changes in details of construction and arrangement of parts may be made by those skilled in the art without departing from the spirit of the invention as set forth in the appended claims.

I claim:

l. A materials testing machine comprising, in combination, a base, a vertical guide cylinder supported thereby, a hollow ram disposed within and slidably guided by said cylinder for vertical movement therein, a specimen loading platen mounted on the upper end of the ram, screw and nut elements, said screw extending within the hollow ram in telescopic relation thereto, one of said elements being operatively connected to the ram to move axially therewith during loading of a specimen, means for supporting the other of said elements against axial movement, means for effecting relative rotation between said nut and screw elements thereby to raise and lower said ram and the loading platen thereon, a load sensitive frame having a specimen engaging crosshead disposed in opposed relation to the loading platen and means including columns rigidly supported by said base and extending upwardly therefrom to support said crosshead, the platen and crosshead having provision for loading a specimen in either tension or compression, and meansresponsive to either tension or compression specimen load transmitted through said columns and constituting a rigid portion thereof.

2. The combination set forth in claim 1 further characterized by the provision of means for connecting the nut in rigid relation to the ram to move non-rotatively but axially therewith, means for supporting the screw against axial movement, and the means for effecting relative rotation between said nut and screw elements comprising means for rotating the screw.

3. The combination set forth in claim 1 further characterized in that the means for rigidly securing the crosshead to the base includes load cells connected to said columns near their lower ends to laterally support the same, stationary means disposed near the upper end of said load columns, and flexure means connected to said stationary means and to said load columns to laterally support the upper ends thereof while allowing their free vertical movement, whereby a moment arm for resisting bending of the load columns, in the event of off-center loading of a specimen is equal to substantially the entire ber, nut and screw elementsone'of which is operatively connected to said vertically movable member to move therewith, a bull gear connected to the other of said elements for effecting said relative rotation between the screw and nut during loading movement of the platen, said bull gear being rotatable about a vertical axis coaxially of its connected element and extending into the space between the lower and upper horizontal members of said base, thrust bearings disposed between said horizontal base members andv each side of the bull gear, a load sensitive frame having a specimen engaging crosshead disposed in opposed relation to the platen and means including columns extending upwardly from and rigidly secured to said base for supporting said crosshead, and means responsive to either tension or compression specimen load transmitted through said columns and forming a rigid portion thereof.

5. A materials testing machine comprising, in combination, a base having guiding means extending vertically from said base from substantially a central point thereof, a vertically movable hollow member disposed within and guided by said central guiding means, a specimen loading platen mounted on the upper end of said vertically movable hollow member so that the latter is also substantially centrally disposed with respect to the loading platen,'nut and screw elements one of which extends axially and in an upward direction into the hollow portion of said vertically movable member, one of said elements being operatively connected to said hollow member for movement therewith during loading of a specimen and the other element being held against axial movement, means for eifecting relative rotation between said screw and nut elements to effect the loading move-' and means responsive to either tension or compression specimen load transmitted through said columns and forming a rigid portion thereof.

References Cited in the file of this patent UNITED STATES PATENTS 28,020 Taft Apr. 24, 1860 875,730 Olsen Jan. 7, 1908 2,291,106 Ruch July 28, 1942 2,356,763 Keinath Aug. 29, 1944 2,616,683 Le Feure Nov. 4, 1952 2,645,120 Scott July 14, 1953 2,756,589 Zeitlin et al July 31, 1956

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