US2179116A - Method and apparatus for testing the folding endurance of paper and like materials - Google Patents

Description

NOV. 7, 1939. J CLARK v 2.179.116

METHOD AND APPARATUS FOR TESTING ,THE FOLDING ENDURANCE OF PAPER AND LIKE MATERIALS Filed March 13, 19:57

2 F76, 8. #769. 06/0. F/a/fi H612.

E1] in g 3 um INVENTOR Patented Nov. 7, 1939 LIKE MATERIALS James dA. Clark, Rose Valley, Pa.

Application March 13,

6 Claims.

This invention relates to a method and apparatus for determining the folding quality of paper, textiles and like materials.

l'n the principal form of apparatus hitherto employed for this purpose the test strip of material is. clamped between a pair of jawswhich can slide towards each other against the tension of two springs. The centre of this strip passes through a thin slotted member which is ar- 1c ranged to oscillate back and forth on a plane at right angles to that of the strip. As the slotted member moves from its centre position it pulls the test strip between and round a pair of guide rollers, bending or folding the strip round Li a small radius at one edge of slot. Meanwhile the clamping jaws move toward each other maintaining and increasing the tension on the strip.

The slotted member then returns to its central position and moves beyond it between a second of guide rollers, folding the strip in reverse across the opposite edge of the slotted member.

This cycle continues until the strip breaks and the number of cycles or double folds thus com 'pleted before fracture is counted.

While the above mechanism has been in use for many years it has not been entirely satisfactory as the results vary unpredictably, particu- 'larly because of uncertainty as to the tension. of the springs and also the friction of theguide 34) rollers. To overcome the disadvantages of the guide rollers another form of test instrument was later devised embodying several simplifications. 'In this second apparatus the test strip is clamped vertically between two jaws, the upper one of 1,; which, by means of a spring, is arranged to apply any desired tension to the strip while the lower jaw is wedge shaped and oscillates through 270 about its apex in which the strip is inserted. The outer wedge shaped edges of the lower jaw clamps are radiused and the strip is bent under tension round each radiused edge of the jaw as it oscillates, until the strip breaks. It has been found almost impossible in practice to construct and maintain the radiused edges and the axis of rotation to a preselected standard, so that test strips are equally affected in different instruments or in the same instrument after some wear has occurred; which prevents the rigid stand ardization of test results, especially when carried 50 out with different instruments.

The principal object of the present invention is to provide an improved method for testing the folding quality of paper, and like materials, which more nearly simulates the forces imposed 55 on the material during common usage and to 1937, Serial No. 130,669

provide a simple apparatus which may be readily and exactly calibrated so as toensure constancy in the test results among different instruments.

Another object is to provide a simply construted and compact apparatus to test a number -15 of specimen strips simultaneously, thus enabling an average test result to be quickly ascertained.

Other objects and advantages of the invention will be apparent from the drawing, from the description thereof and from the claims.

In the drawing:

Fig. 1 illustrates a diagrammatic front View of one form of the apparatus.

Fig. 2 shows an enlarged view of the catch I2 shown on Fig. l for releasing the arm of the counter as soon as the strip breaks.

Figs. 3 to 12 show ten successive steps in the position of the jaws and oscillating pins and the folding of the paper sample.

In this invention, the strip of material to be tested is folded over itself along a line, preferably at right angles, to the length of the strip. The fold. so made is subjected to a predetermined pressure; the strip is then unfolded and subjected to a predetermined tension, which is less than that required to break an uncreased strip, then the strip is folded again about the same line, either in the samemanner as before or else folded in the reverse way about the same line, the fold again subjected to the same pressure, the strip unfolded, subjected to the same tension and this cycle of operations repeated until the strip breaks at the fold. The number of folds so made before the strip breaks is recorded as the folding test of the material. I

In its simplest form, the apparatus required to carry the invention into effect comprises any suitable clamp having a weight less than the tensile breaking load of the strip and which may be attached to one end of the test strip, another weight of any convenient shape having as its base, a plane surface wider than that of the fold to be made in the test strip and another plane surface on which to rest the folded sample and the weight. The weighted clamp is fixed to one end of the test strip and with the fingers, the strip is doubled about itself to form a fold, which is laidon the plane surface and the weight is gently placed upon the fold so as to apply pressure to it. The weight is then removed and the free end of the strip is raised vertically with the fingers until the creased strip bears the weighted clamp in tension. The tension is released and the strip is refolded about the crease in the same or in the reverse direction, pressed between the plane surface and the weight, and

the free end of the strip raised till it is again in tension and this cycle repeated till the strip breaks at the crease, the number of folds so made before fracture, being counted.

A form of apparatus to carry out this procedure automatically, is shown in Fig. 1 where the strip of material to be tested, I, is clamped between a lower jaw 2 and upper jaw 3. The upper jaw assembly 3 is constrained to move vertically in guide 4 and at its tip is fixed a weight 5 so dimensioned that its weight and that of the moving parts of the jaw assembly is a fixed amount, for example, 1 kilogram. The weight of this assembly is normally supported on the adjustable screw 6.

The lower jaw assembly 2 is constrained to move vertically between flanged or grooved guide rollers 'I. The lower end of the assembly, in the absence of the test strip rests continually on an eccentric, almost circular shaped, cam 8, which is rotated at a suitable speed, for example '75 revolutions per minute, by a motor 9.

On the jaw assembly 2 is provision for holding 5 one or more slotted weights 13 so that the weight of the lower jaw assembly which, for example without added weights is adjusted to be exactly kilogram, may be increased in successive steps by added weights to become 4 kilograms. The centre of gravity of the weights l3 and also the entire lower jaw assembly are each arranged to be vertically beneath and in the centre of the test strip I, so that the guide rollers 1 are not subjected to any lateral pressure, so that by providing a very small clearance between the jaw assembly and each pair of rollers, any friction they might have, does not affect the tension in the test strip as produced by the weight of the lower jaw assembly.

The test strip l, is of such a length that when clamped between the jaws it supports the lower jaw assembly in such a position that when the top of cam 8 is in its lowest position, as illustrated in Fig. 1, there is a small distance between the bottom of the lower jaw assembly and the face of the cam 8. As the cam rotates it touches the assembly and then raises it until the faces or anvils of the two jaws meet and the upper jaw just raised off the stop 6. The horizontal faces or anvils of the jaws are accurately ground and lapped so as to be exactly parallel as they come together.

To the lower jaw assembly 2, is also affixed a recording counter 10 of any suitable well known type such as is actuated by the up and down movement of a lever arm ll. When set to count the folds this lever arm is held by a catch IQ of which a preferred form is shown in Fig. 2 as an enlarged view. As long as the strip is intact, the assembly 2 is suspended by the strip and the arm H remains in the hook I5, of the catch, so that each time the assembly 2 is pushed up by the cam 8, the lever ll being held up in the hook of the catch l2, actuates the counter 10. When the strip breaks, the assembly 2 being no longer supported, drops so as to bear continually upon the cam 8 so that in the lowest position of the cam 8, the lever H drops sufiiciently to rest upon the bottom of the slot [5 in the catch and opposite the entrance IA. The catch being shaped substantially as shown, then falls over to the right about its hinge It thus releasing the lever arm II so that the counter is actuated no longer and so the number of revolutions of the cam and thus the number of folds from the time when the catch is set till the strip breaks is recorded. The apparatus so far described will test the number of single folds which a specimen will withstand before breaking as, once a single fold has been made in a selected direction, the natural resiliency of the specimen will ensure that the fold is repeated in the same direction as the jaws move together in each cycle. If it is desired to test the number of double folds which the strip will withstand before breaking, then it becomes necessary to attach to the apparatus, some type of shuttle mechanism, a preferred form of which is also illustrated in Fig. 1. To the shaft holding cam 8 is attached gearing l1 driving cam l8 which rotates at a speed twice that of cam 8. Against the outer surface of cam I8 is pressed by means of spring 22 the lower end of a lever 20 which is pivoted at 2|. The upper end of the lever is forked and holds a pin IS in a strap 23 which slides in bearings 26. In the strap are two pins 24 and 25 which project beyond the width of the test strip l, and these are caused by the mechanism described to oscillate to and fro in a controlled manner according to the surface contour of the cam l8, completing their cycle in a half revolution of cam 8.

In order to more clearly explain the action of the shuttle mechanism and the working of the apparatus, Fig. 3, is a diagram of the relative 1 position of the jaws 2 and 3 and the two pins 24 and 25 when cam 8 in Fig. 1 is furthest from the bottom of the lower jaw assembly 2. As the cam 8 turns and commences to lift the lower jaw, as shown in Fig. 4, the left hand pin pushes the test strip to the right and as described, by suitably shaping the surface of the cam I8 the pin is made to move just fast enough but no faster than required to take up the slack in the test strip caused by the approach of the jaws to each other, so as not to put any substantial stress upon the test strip and yet prevent it from commencing to bend in a direction opposite to that which the pin is moving. As soon as the test strip is sufiiciently bent to ensure its continued bending in the required direction, the pin is withdrawn rapidly as is indicated in Fig. 5, so as to be clear of the lower jaw as it moves past it and meets the upper jaws as shown in Fig. 6. In Fig. 6 the weight of the upper jaw has been taken by the lower and the predetermined pressure is being applied to the crease. Ignmediately prior to contact by suitably shaping the contour of cam B the travel of the lower jaw preferably has been reduced to a very-small predetermined speed, for example, 3.2 mm. per second. The lower jaw assembly 3 is then rapidly lowered and the right hand pin now approaches the strip as indicated in Fig. '7. In the position indicated by Fig. 8, the downward speed of lower jaw preferably is reduced to a very small predetermined speed, for example 3.2 mm. per second, until the strip is put under a tension not appreciably greater than that corresponding to the weight of the lower jaw assembly. On the return of the lower jaw the right hand pin now pushes the strip to the left as indicated in Fig. 9 and the pin is rapidly withdrawn to the right as shown in Fig. 10 while the lower jaw rapidly moves upwards to reach the contact position indicated in Fig. 11, and as the lower jaw moves downwards again the left hand pin approaches the strip as shown in Fig. 12 and the cycle illustrated by Figs. 3 to 12 is repeated until the strip breaks.

So as to provide for cases where the initial fold on the test strip does not occur exactly in the middle, the anvils of one of or preferably both the jaws 2 and 3 are recessed or slotted as shown at 21 Fig. 3 and the excess slack in one side or other of the strip in the position shown by Fig. 6 or Fig. 11 is accommodated in the rectangular slot without tending to disturb the location of the initial folded crease.

It is obvious that any convenient number of test jaws may be mounted side by side operated by a single driving motor and all the associated shuttle pins contained in an extension of the strap 23.

The apparatus described may be simply and easily standardized by checking the weight of the jaw assemblies and the speeds of the lower jaw when subjecting the crease in the strip to both tension and compression, thus ensuring that every specimen tested in jaws of the same or different pieces of apparatus are folded and treated in a positive and unvarying manner.

It will be noted that in the described method of carrying out the test, the action of the repeated folding together of a piece of paper, for example, a currency note, applying pressure to the crease and then subjecting the note to repeated tension upon unfolding it, is simulated, but under controlled conditions. In this respect also, it is superior to testing methods and apparatus hitherto used for this purpose.

Having thus described the nature of the invention I declare that what I claim is as follows:

1. The method of testing the folding endurance of a strip of material which consists in folding it double about a line across its width; squeezing the strip together at the folded edge; unfolding the strip and subjecting its ends to a predetermined tension, then folding the strip double in the reverse way to the previous fold about the same line, reapplying the squeezing pressure; unfolding the strip, reapplying the tension and continuing these steps successively until the strip breaks and recording the number of double folds so made before fracture.

2. An apparatus for testing the folding endurance of a strip of material comprising sets of jaws adapted to grip the ends of a strip of the material to be tested, means for continuously and successively bringing the sets of jaws together, such movement causing the strip to be folded across its width; means for squeezing the end faces of the jaws together upon the fold; means for separating the jaws and applying an unvarying preselected tension to the unfolded strip by means of a freely hanging load, together with means for recording the number of cycles thus completed before the strip breaks.

3. In an apparatus for testing the folding endurance of a strip of material comprising, jaws adapted to grip the ends of a strip of the material to be tested, means for bringing the jaws together, such movement causing the strip to be folded across its width; means for squeezing the ends of the jaws together upon the fold; means for separating the jaws and applying a predetermined tension to the creased strip; means for successively reversing the direction of the fold about the crease each time the jaws come together, together with means for recording the number of cycles thus completed before the strip breaks.

4. In an apparatus for testing the folding en-- durance of a strip of material, two sets of jaws for gripping and holding the ends of the strip to be tested in one plane, said jaws having on both sides of the strip, pressure faces adapted for uniformly squeezing the resulting fold in the strip when they come together and the pressure faces in at least one of the jaws recessed along the line where the strip is gripped so as to accommodate any slack in the test strip caused by unsymmetry as the strip is folded and squeezed.

5. In an apparatus for testing the folding endurance of a strip of material a member having jaws for gripping one end of the strip, said jaws having, on both sides of the. strip, surfaces for squeezing a fold formed in the strip against another member, said surfaces being separated by a gap.

6. In an apparatus for testing the folding endurance of a strip of material two sets of jaws adapted to grip the ends of a test strip, means for folding the strip about itself while in the jaws to form a crease, a load for applying through one set of jaws an unvarying tension to the strip when unfolded, the sets of jaws being so mounted that the distance between them is determined only by the length of the unfolded strip between the gripped edges while being subjected to'the said tension.

\ JAMES DA. CLARK.

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