US3400576A - Stretch-testing machine for elastic fabric - Google Patents

Description

Sept. 10, 1968 S. F. SICILIANO STRETCH-TESTING MACHINE FOR ELASTIC FABRIC Filed July 15, 1965 2 Sheets-Sheet l STRETCH lbs. TENSION FIG. 4

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' P 1968 s. F. SICILIANO STRETCH-TESTING MACHINE FOR ELASTIC FABRIC Filed July 15, 1965 2 Sheets-Sheet 2 FIG?) Sfvf FIG. 5

United States Patent 3,400,576 STRETCH-TESTING MACHINE FOR ELASTIC FABRIC Samuel F. Siciliano, Westerly, R.I., assignor to George C.

Moore Company, Westerly, R.I., a corporation of Rhode Island Filed July 15, 1965, Ser. No. 472,141 4 Claims. (Cl. 73-95) ABSTRACT OF THE DISCLOSURE Means for simultaneously stretching two unequal lengths of identical elastic fabric for equal distances until the shorter one of them reaches the useful limit of its stretch, the resultant greater tension in this one enabling it to stop the machine, overpowering the longer piece, which strives to resist such stopping; indicates the extension and contractive effort of the shorter piece in inches and pounds on a graph.

This invention has as its aim the provision of mechanical means for determining accurately the maximum extension or stretch, and preferably also the contractive effort, of which an elastic fabric or other elastic material of narrow or medium width is capable in practical use. Lack of commonly available devices for this purpose in the industry has made it the conventional practice to stretch a sample of elastic fabric of measured length by hand over a table or fiat surface, marking the end-locations of the measured length, first with the fabric in relaxed condition, and then when it is stretched to what the person testing it thinks is the limit of its stretch, noting the increased total length in proportion to its unstressed length. Variations in the strength of hand and arm possessed or used by different persons testing the same sample have naturally led to different conclusions as to stretch. This method of course offers no basis for rating the strength of the contractive force in terms of pounds or other units helpful in determining its utility for various purposes.

The prior devices proposed and used for testing the stretch of elastic fabrics have so far as I am aware determined either the force in pounds required to extend the fabric to the limit of its stretch, or the length of such stretch when attained by applying a force in excess of that needed for this purpose, but in neither case have given both the length of extension and the force required to attain it. They have operated by applying a weight exerting increasing force through changing leverage in the first instance, as in the familiar Scott tester, or by choosing a weight expected to apply more force than needed and arranged to descend along an inclined plane of fixed grade, in the second instance. A drawback inherent in both modes is that many times the fabric is overloaded and strained beyond its natural elastic limit, the elastic elements are fatigued, the stretch-limiting non-elastic elements where present are strained and elongated somewhat, and false, variable, or unreliable results are recorded.

The present invention operates on the novel principle of using the fabric itself to limit the mechanically applied stretching force to substantially the precise amount needed to bring the fabric to the limit of its intended stretch. This principle is utilized by giving the test sample of the fabric control of the stop means of the stretch-applying mechanism, and limiting the exertion of this power of control to the stage when the desired degree of stretch has been reached, preferably at maximum useful extension.

In the present illustrative examples of mechanical testing devices, to determine this stopping-point without need for experiment, calculation, or prior knowledge, a piece 3,400,576 Patented Sept. 10, 1968 of the identical fabric being tested is used as a counterpoise to resist and restrain the test samples operation of the stop means provided in these devices. Thus, by attaching this control piece to the stop means in a way to oppose the latters operation by the test sample, for instance by making it slightly longer than such sample, and subjecting both simultaneously to substantially the same length of pull, the control piece will inhibit the test sample from actuating the stop motion until the sharp increase in tension in the test sample as it approaches the limit of its stretch overpowers the resistance of the control piece, and stops the stretching. In this manner the test sample is brought to full extension, but guarded from overstrain by the slight differential in length and resultant lesser tension of the control piece of identical fabric.

A very slight difference in the length of the test sample and the control piece is adequate; the latter will normally be merely about inch longer than the conventional 5 inch length of the tested portion of the sample, as a very small superiority of force is needd to overbalance the pull of the control piece and apply the stop motion.

Other objects of the invention and the manner of their attainment will be made plain hereinafter.

Illustrative embodiments of the invention are shown in the accompanying drawings, in which:

FIG. 1 is a front elevation of a device which uses a continuous strip of the elastic fabric to serve as both the test sample and the control piece.

FIG. 2 is a side elevation of the same.

FIG. 3 is a detail view in front elevation showing how two separate pieces of identical fabric of unequal length are used as the test sample and the control piece respectively.

FIG. 4 is a detail view in front elevation showing how two identical pieces of equal length are used to attain maximum useful extension of the test sample and stoppage of the stretching when such condition is reached.

FIG. 5 is an alternative arrangement of the rocker.

Having reference to FIGS. 1 and 2 of the drawings, a strip 1 of the narrow fabric to be tested is placed over a bar or roll 3 mounted by its ends non-rotatably in a yoke 5 forming a downward extension of a plunger 7 of a form of spring-balance type of scale, the plunger bearing an index finger 9 cooperating with graduations 11 on a body 13 in which the plunger is mounted for slidable vertical movement against the resistance of a coil-spring 15. The body 13 is mounted for vertical movement by vertical guides 17 and rollers 19, and is raised and lowered by struts 21 fixed to a header 23 aifixed to a rack shaft 25 slidable in a guide 27 mounted fixedly in the machine frame 29 and actuated both up and down by a pinion 31 rotated by drive train 33, 35, 37, 39, 41, 43, 45 from reversible electric motor 47.

The two ends of the fabric 1 are respectively gripped and held by separate clamps 51, 52, each comprising a fluted or knurled roll 49, of about the same length as roll 3, eccentrically pivoted in a rectangular box-like housing. These rolls are manually turned by radial handles 53 to jam the fabrics ends against the inside of the adjacent wall of each box 51, 52, and thus hold them while the fabric is being stretched.

These clamps are each mounted rigidly on the top ends of rods 55 freely slidable in bearings 57 in the frame member 29 and pivoted at 59 to a rocker 61 pivoted at 63 midway between pivots 59 to an L-shaped stand 65 bolted to the frame member 67. Thus arranged, the two clamps have capacity for equal but opposite vertical movement.

To apportion the continuous strip of fabric 1 into a test strip and a control strip so as to apply the invention principle, the roll 3 is equipped with a longitudinal row of short, sharp-pointed pins 69 about A inch to the right of its highest point which pierce and thus hold the fabric along a transverse line of the latter and so subdivide it (without parting it, of course) into a test sample and a control piece. These are thus made to have a slight difference in length corresponding to the degree of offset of the row of pins 69 from the high point of the roll 3, simply by the act of inserting the fabric over the roll 3, and clamping its end-portions in the clamps 51, 52, in taut but unstretched condition. The fabric is then in readiness for testing.

Thereupon, the motor 47 is started by closing switch 71 to raise the scale body 13 and through spring 15 and plunger 7 to raise the roll 3 and stretch both portions of the fabric simultaneously.

Because the test sample, held by clamp 51, is a bit shorter than the other length, the control piece, held by clamp 52, the tension therein builds up faster than in the control piece, and hence clamp 51 is pulled upward harder than clamp 52, thus rocking the rocker 61 and thereby causing it to open a micro-switch 73 in the motor-driving circuit and stop the motor. In other words, when the shorter leg reaches the limit of its stretch, the longer leg is still stretching longer. So the clamp 51 holding the shorter leg, the test sample, is pulled upwardly, rocking the rocker 61 and opening switch 73 to stop the drive of motor 47.

The length of stretch of the test sample when thus tested is the distance from the clamping point of roll 49 in clamp 51 to the pins 69. So with a known initial relaxed length, say, the conventional 5 inches, the maximum useful stretched length is the vertical displacement of roll 3 in inches with respect to roll 49 of clamp 51, plus the initial S-inch length of the sample.

Scale 11 can be calibrated both in inches of extension and in pounds of force applied by plunger 7 to create such extension. But preferably means is provided to record the results of the test graphically, in the form of a curve with the stretch indicated in inches as the ordinate and the applied tension shown in pounds as the abscissa. To this end, a guide 81 in fixed right-angle relation on the bottom end of plunger 7 carries a rack 83 to be displaced horizontally by a compound gear 85 pivoted in an extension on the plunger 7 and meshing with a rack 87 mounted in vertical relation on the scale body 13. A stylus 89 on the end of rack 83 traces on a sheet of paper or tablet mounted on a panel 91 fixed on the machine frame the curve whose coordinates give the stress in pounds and the corresponding resultant stretch in inches, from Zero to maximum extension, and a picture of the characteristic build-up of the contractive effort.

As is obvious, the limit of the stretching force applied by this form of device is set by the difference in length between the test sample and the control piece, and is inversely proportional to this differential, and very sensitive to such difference. It can be easily changed and adjusted by merely varying the angular relation of the row of pins 69 to the vertical axial plane of roll 3.

Other ways of establishing this difference in length of the two legs of the same piece of fabric are also contemplated without offsetting the pins 69, as by making one of the rods 55 longer than the other; or locating the bite of one clamp 51 higher than that of the other clamp 52. Or if separate pieces are used for the test sample and the control piece, a pair of clamps 51', 52', equivalent to 51, 52, will be fixedly mounted on the plunger 7 as shown in FIG. 3, and one of the rods 55 will be silghtly longer than the other rod 55. The testing may be effected with the two pieces end to end just as well as side by side. Or with the test sample and the control. piece of equal length, and the upper clamps 51, 52 on the plunger 7 as shown in FIG. 4, and rods 55 of equal length, the pivot 63 may be at unequal distances from the two pivots 59 as shown in FIG. 5.

Switch means (not shown) of usual sort is provided for reversing the motor 47 to lower the rack shaft 25 and scale body 13 after each test, a micro-switch engaged by the end of the rack shaft interrupting the current through the reversing switch.

If merely the length of stretch of the fabric is wanted, the roll 3 is mounted directly on the top end of rack shaft 25, and an index is mounted to move therewith over a scale graduated in inches alongside the path of the roll or rack shaft, no spring balance or weights being used.

In brief, the invention provides for each different kind, size, strength, or construction of fabric or other elastic material, a standard of comparison in the form of the control piece, whose values do not need to be determined quantitatively at any stage; no pre-setting of weights or springs for different fabrics is needed. All that is required is to establish a slight preponderance of tension in the test sample, by a difference in length or leverage with respect to the control piece.

While I have illustrated and described certain forms in which the invention may be embodied, I am aware that many modifications may be made therein by any person skilled in the art, without departing from the scope of the invention as expressed in the claims. Therefore, I do not wish to be limited to the particular forms shown, or to the details of construction thereof.

What I claim as my invention is:

1. A machine for determining the maximum useful extension of elastic material in sheet form having in combination a frame, a body mounted for relative movement on such frame, a plunger slidable in such body, spring means on the body resisting movement of the plunger in such body, means for holding the ends of at least one piece of the elastic material, means on the plunger for tensioning different portions of the material unequally, power means for moving the body relative to the frame, stop means for the power means responsive to the differential elongation between the said different portions, and means for indicating the relative movement of the plunger with respect to the body and the end-holding means.

2. A method of determining the maximum useful extension of elastic material in sheet form which includes providing a stretching force of unlimited power, forming a test specimen into two portions of predetermined and unequal length, gripping the two portions at each of their ends, providing the shorter portion with stopping control of such force, stretching the two portions at substantially equal rates by such force, stopping the stretching automatically when the initially shorter one thereof reaches its inherent practical limit of stretch and thereby exerts its control of the stretching force, and measuring the extension of the shorter portion when the stretching is stopped.

3. A machine for determining the maximum useful extension of elastic material in sheet form having in combination a frame, a.- body mounted for relative movement on such frame, a plunger slidable in such body, spring means on the body resisting movement of the plunger in such body, means on the frame for holding the ends of two sections of the elastic material, means on the plunger for holding the other ends of such sections, power means for moving the body relative to the frame and away from the first-named end-holding means to stretch the held material, power stop means, means to indicate differential extension of the two sections, means to actuate the power stop means in response to a change in differential elongation, and means recording graphically the tension and extension of one of the sections.

4. A machine for determining the maximum useful extension of elastic material in sheet form having in combination a frame, a body mounted for relative movement on such frame, means on the frame for holding the ends of two portions of the elastic material, a plunger slidable in the body, spring means on the body resisting movement of the plunger in such body, means on the plunger for holding the other ends of the two portions, power means for moving the body relative to the frame and away from the end-holding means on the frame to stretch the held 5 material, stylus means carried by the plunger, means in connection With the body for causing movement of the stylus means transversely of the plunger proportionately to the movement of the plunger in the body, a tablet inscribed by the stylus means, power stop means, and means 5 to actuate the power stop means in response to unequal stretch due to tension created in the two portions.

2,356,763 8/1944 Keinath 7389 2,949,188 8/1960 Hooker 73161 3,002,391 10/1961 Holmes 73517 FOREIGN PATENTS 206,243 11/ 1923 Great Britain.

342,382 2/ 1931 Great Britain.

836,581 6/ 1960 Great Britain.

10 RICHARD C. QUEISSER, Primary Examiner.

J. H. WILLIAMSON, Assistant Examiner.

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