US 2834204 A
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FILAMENT CLAMP AND TENSILE TESTER May 13, 1958 United States Patent 2,834,204 FILAMENT CLAMP AND TENSILE TESTER Richard H. Braunlich, West Chester, Pa., assignor to American Viscose Corporation, Philadelphia, Pa., a corporation of Delaware Application March 30, 1955, Serial No. 497,899
4 Claims. (CI. 73-95) This invention relates to tensile testing apparatus, and more particularly to a device for obtaining elongation and tensile strength measurements on filamentary material such as thread and yarn.
In using conventional apparatus for obtaining readings of elongation and tensile strength of textile filaments, difficulty has been encountered in providing adequate means for securing the filament or tow in such a way that rupture does not occur at the point of attachment due to the sharp radii inherent in tying a knot. When a pressure type clamp is used, it is almost impossible to obtain equal clamping pressure on all the individual fibers or filaments and to avoid damaging or crushing the filaments in contact with the clamp. These disadvantages have introduced both large and small errors in the measurement of elongation and in stress-strain data.
The present invention avoids these disadvantages by securely anchoring the ends of the test sample in a medium comprising magnetizable metallic particles suspended in a fluid such as oil. These magnetic oil-metal mixtures are well known and form no part of the present invention. A typical mixture is described in Lucas Patent No. 2,148,782 but the mercury specified therein is not essential to the mixture for use with textile strands and filaments. When the tow or yarn is immersed in the magnetizable mixture, it is securely frozen or clamped so that there is no possibility of rupture due to knotting. With the use of a surface-active agent, the magnetizable fluid Will penetrate the tow so that each filament will be securely held in place without relative movement of the filaments occurring within the bundle. The surface-active agent should be chosen to provide satisfactory wetting of the particular filaments with the type of fluid being used.
A primary object therefore of the present invention is to provide a novel and improved clamp for yarn and tow bundles.
A further object of the invention is to provide a novel and improved clamp for yarn and tow bundles comprising a receptacle having a magnetizable fluid therein, and a magnetic field surrounding the receptacle which can be selectively energized to freeze the yarn sample in the receptacle.
A further object of the invention is to provide a novel and improved stress-strain testing apparatus in which highly accurate results can be obtained.
Further objects will be apparent from the specification and drawings in which:
Figure 1 is a side view showing a yarn tow stress-strain test apparatus embodying the present invention; and
Figure 2 is a vertical sectional view on an enlarged scale of one of the yarn clamps of the present invention.
The invention comprises essentially the provision of a pair of receptacles containing a magnetizable oil-metal mixture with each receptacle being surrounded by a coil which freezes the mixture when the coils are electrically energized. Each receptacle is mounted on supporting 2,834,204 Patented May 13, 19 58 trunnions in a saddle on a tensile testing machine so that both of the receptacles are horizontally positioned during the test. Under these conditions, the fluid is always frozen so that it will not run out of the receptacle; but when the coil for each receptacle is deenergized, the receptacles are always in a Vertical position with the fluid contained therein in a fluid state.
Referring now more particularly to the drawings, a stress-strain testing apparatus embodying the present invention comprises a central standard 5 to which a horizontal beam 6 is pivoted at 7. A suitable counterbalance 8 for the beam is adjustable on a rod 9 to balance the weight of the beam. The beam may be pivoted on standard 5 by means of a threaded shaft 10 pivoted to the outer end of the'beam at 11 and extending downwardly through a nut 12 which is turned by means of a reversible motor 13 and gear reduction unit 14. The beam 6 carries a track 15 on which a carriage 16 is movable by means of rollers 17, 17. The track 15 extends beyond the beam to the opposite side of pivot 7 and is graduated at .18 to enable clamped to the track at a desired predetermined position. Bracket 19 has a saddle 20 in which the yarn clamp as sembly 21 is pivoted. A bracket 22 is connected to carriage 16 and likewise carries a yarn clamp assembly 23 pivoted thereto.
Each of the clamp assemblies 21 and 23 is identical and is shown in greater detail in Figure 2; therefore, only one will be described. A receptacle or cup 24 is enclosed in a nonconductive housing 25 in which there is embedded a coil 26 which can be electrically energized when a circuit is closed through leads 27 and 28. The housing 25 and the receptacle are supported on trunnions 29, 29 as described above.
The yarn or tow sample 8 to be tested is submerged in A the magnetizable fluid F by means of a weight W tied to one end of the sample or it may be pushed into the fluid by means of a separate instrument. When the proper length of sample has been submerged, the fluid is solidified or frozen by energizing the coil 26. The same procedure is followed for attaching the other end of the test sample S to the clamp 23. With both ends of the sample securely clamped, the carriage 16 and the clamp 19 are secured at the proper zero positions on track 15 so that the clamps 21 and 23 are pivoted through arcs of with the sample stretched therebetween. The motor 13 is then started to pull shaft 10 downwardly in accordance with conventional test procedure. The weight of carriage 16 is therefore gradually applied to the test sample and the downward travel of the carriage on track 15 can be indicated or recorded by means of a suitable marker or stylus 30.
Suitable calibration between the angle through which beam 6 is pivoted or the time that motor 13 runs permits calculation of the stress applied to the sample and thus a stress-strain diagram can be plotted. If the ultimate strength is desired, motor 13 continues to run until the sample ruptures. The motor is reversed to return the beam to its initial zero position whereupon the clamps 21 and 23 will pivot to their vertical positions as shown in Figure 1, and the fluid is desolidified by breaking the circuit tothe coils so that the tested sample or broken ends thereof are readily removed.
The present invention provides an improved apparatus for clamping textile yarn test samples and other objects in which the ultimate strength of the sample or the stress applied is less than the force required 'to pull the sample out of the clamp.
Having thus described my invention, I claim:
1. A stress-strain testing apparatus for filamentary material and the like comprising a bracket, a receptacle pivotally mounted in said bracket, a magnetizable fluid the slidable bracket 19 to be t 3 miXturein said receptacle, a second receptacle, a bracket in which said second receptacle is pivotally mounted, a magnetizable fluid mixture in said second receptacle, means for magnetizing the fluid mixture in each of said receptacles to solidify the fluid mixture, and means for moving said receptacles away from each other when the fluids are solidified.
2. In stress-strain testing apparatus having a pivoting beam, means for controllably pivoting said beam, a carriage movable on said beam, and means for indicating the relative movements of the beam and the carriage, the improvement which comprises a pivotally mounted receptacle. on the beam, a pivotally mounted receptacle on the carriage, 'a magnetizable fluid mixture in said receptacles, a coil surrounding each receptacle, and an electrical circuit connected with each coil, said coil and circuit serving to magnetize the fluid mixture to solidify the fluid mixture.
3. Apparatus in accordance with claim 2 in which the receptacles "are mounted in trunnions.
4. A stress-strain testing apparatus for filamentary material and the like comprising a first pivotally mounted receptacle, a magnetizable fluid mixture in said receptacle, a second pivotally mounted receptacle, a magnetizable fluid mixture in said second receptacle, a coil surrounding each receptacle, an electrical circuit connected with each coil, said coil and circuit serving to magnetize the fluid mixture to solidify the fluid mixture, and means for moving said receptacles away from each other when the fluids are solidified.
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