US3323349A - Method and apparatus for testing floor coverings - Google Patents

Description

June 6, 1967 Y 3,323,349

METHOD AND APPARATUS FOR TESTING moon COVERINGS P. R. SAVAGE ETAL Filed Sept. 21, 1964 INVENTORS PRESTON R. SAVAGE GENE A. BROOKS ATTORNEZ Ml M &

W Pew United States Patent 3,323,349 METHOD AND APPARATUS FOR TESTING FLOOR COVERINGS Preston R. Savage and Gene A. Brooks, Decatur, Ala.,

assignors to Monsanto Company, St. Louis, Mo., a corporation of Delaware Filed Sept. 21, 1964, Ser. No. 397,790 8 Claims. (Cl. 73-7) This invention relates to a method and apparatus for testing wear resistance of floor coverings and the like. More specifically this invention relates to a method which simulates actual stair tread wear on carpet samples to produce data for predicting later stair tread wear of the carpet when placed into use and apparatus for performing the method.

An analysis of carpet wear which occur on a stair tread reveals that the section of carpet covering the front edge or nose of the stair tread receives the heaviest wear. It has been demonstrated that this accelerated wear is primarily produced when the foot rolls over the front edge of the carpeted stair step by persons ascending and descending the stairs. The impact and abrasive forces imparted to the tufts at the tread nose by footwear crushes and flexes the tufts. Continued wear on the carpet causes an initial flattening of the tufts followed by breaking and finally the actual attrition of fibers. Thus, the performance of a carpet is determined by the volume of traffic it can withstand before the tufts are no longer distinguishable as such. In order that a more exact definition may be employed, this indistinguishable condition will be referred to hereafter as the end point. By end point i meant the point during the test that one-half of the tufts along the line of heaviest wear are worn down to one-sixteenth of an inch.

Various attempts have been made to develop a laboratory test to simulate the wear received by a carpet laid on stairs before an end point occurs. None of the known aparatus is considered to be satisfactory, however, since the test data cannot be correlated with actual stair tread wear data. The performance of the known apparatus is limited for the reason that data is affected adversely by the type finish on the carpet fibers, and the data does not represent signficant differences between different types of carpet samples. Therefore, the end point cannot be predicted with an acceptable degree of accuracy from test data compiled using conventional carpet testing apparatus.

The currently accepted test for determining the wear resistance of carpets is by placing carpets on stairs which have a high volume of traffic such as in a plant where most of the employees pass over the carpet several times each day with each employee being counted and recorded by a suitable counter. There are several apparent disadvantages inherent in this method of testing carpets, the most objectionable being the time required for obtaining data, the number of samples which can be tested is limited to the number of Stairways available, lack of control over environmental conditions such as humidity and temperature, and variability of carpet wear from the different steps. In view of the foregoing discussion, it would be highly desirable to have apparatus capable of performing a simulated wear test on several carpet samples which can be correlated with stair tread wear in the shortest time period possible and yet predict wearability of carpets.

It is therefore an object of the present invention to provide a method and apparatus for simulating actual stair tread wear on several carpet samples simultaneously and ice in a uniform manner under controlled environmental conditions.

Another object of the present invention is to provide apparatus capable of imparting a simulated stair tread wear to several specimens of a carpet sample uniformly with respect to specimen positions.

Another object of the present invention is to provide apparatus capable of simulating the impact and sliding action which occurs between a persons shoe and carpet covering the front edge of stair steps.

Still another object of the present invention is to provide a method and apparatus to give carpets accelerated wear which represents significant differences between different types of carpet samples for obtaining test data in a minimum time period.

A still further object of the present invention is to provide a method and apparatus for obtaining from carpet samples simulated stair tread Wear data which can be repeated on like samples.

Yet another object of the present invention is to provide a simulated stair-wear test for carpets which reduces the specimen-to-specimen wear variation of a given carpet sample.

A preferred embodiment for accomplishing the objects of the present invention contemplates a frame having a plurality of weighted arms pivotally mounted to the frame with a shoe sole attached to one end of each arm and cam means for raising and lowering them in a manner which causes each shoe sole to strike a carpet sample fixed on a block. The block is mounted on a shorter pivotal radius than the shoe sole so that the carpet sample slips a short distance under the falling shoe sole as both members rotate together in contact with each other thereby simulating the action of footwear rolling and slipping over the edge of a stair step.

In accordance with the present invention, the discovery has been made that the performance of carpets laid on stairs can be accurately predictd from test data recorded in a matter of hours rather than the two or more weeks normally required by the best known method considered to be suitable for testing carpets fabricated from the natural and synthetic fibers, and more particularly, the Acrilan and nylon fibers.

Other objects and advantages of the present invention will become apparent when the following detailed specification is read in conjunction with drawings in which:

FIGURE 1 is a perspective view of the invention illustrating apparatus having six units;

FIGURE 2 is a side view of a single unit as seen from the cross-section 2-2 of FIGURE 1; and

FIGURE 3 is a perspective view of a carpet sample removed from the apparatus shown in FIGURE 1 at the end of a test and illustrates the end point.

Referring now in detail to the drawing, there is shown in FIGURE 1 a group of six units 10 mounted on a table-like frame 12 and connected to a power source 14 which operates all six units. As shown in FIGURE 2, a unit 10 is composed of a weighted member 16 and a block 18 positioned underneath member 16 to cooperate with each other as will be described hereafter. Member 16 is pivotally mounted to frame 12 by a pair of legs 20 rotatably mounted on an axle 22 which is supported by a pair of upright members 24 mounted on frame 12. A selected weight 17 which must be made to meet specific requirement is secured to member 16. On the bottom side of member 16, there is secured at the end opposite the pivotal connection a shoe sole 26 of the commercial type and intermediate the pivotal connection and the shoe sole a cam follower 28 is positioned for cooperation with a cam to agitate movement of member 16 as will be explained later.

The block 18 is pivotally mounted on frame 12 by a hinge 30 and is suspended at an angle elevated with respect to the frame by a tension spring 32 connected between the block and a support arm 34 mounted on frame 12. The spring is held in a slightly elongated condition by a stop means 36 which limits the upward movement of block 18, but leaving the block free to travel away from stop 36 when the tension of spring 32 is overcome. A sample specimen 40 of carpet is placed on the top side of elevated block 18 facing toward member 16 and is held securely by a clamp 42. The carpeted block 13 is elevated so that an edge thereof similar to a stair tread nose is exposed to the striking force of member 16. For better performance the sample specimen 40 is drawn tightly across the block and held in place to insure that wear is confined to the tread nose area.

A rotatable shaft 44 is journaled in a plurality of bearing housing mounts 46 spaced longitudinally along frame 12 for supporting the shaft. The shaft is connected to power source 14 through a coupling 48 and drive gear box 50. Positioned underneath each weighted member 16 is a cam 52 secured to a shaft 44 for cooperation with cam follower 28 to operate member 16 back and forth along an arcuate path upon rotation of the shaft. A variable speed changer 54 is associated with power source 14 and gear box 50 for selecting a preferred r.p.m. rate for the shaft and a conventional counter 56 is mounted on the end of shaft 44 for recording the total revolutions made by the shaft during a test period. A single counter has been found to be undesirable however when test specimens from different types of carpet are being tested simultaneously because of the delays caused by the different wear properties of the various samples. For these conditions, it is preferable to use an individual counter for each unit 10.

In operation of the invention described above, a test specimen of carpet 40 is clamped onto block 18 and the weighted member 16 is lowered toward the test specimen until the cam follower 28 engages the cam 52. The counter 56 is set to Zero and the shaft 44 is driven by power source 14 to raise and lower member 16. Rotation of the shaft 44 revolves the discontinuous peripheral edge of cam 52 causing the shoe sole 26 to strike the test specimen each time the cam moves through the position shown in FIGURE 2. Further rotation of the cam in the direction denoted by the arrow cams the shoe sole out of contact with the test specimen and spring 32 retracts block 18 to its normal position against stop 36. The number of strikes per minute can be varied by adjusting speed changer 54 to a preferred rate which is about 78 strikes per minute. This rate can be increased to approximately 100 however, before exceeding the recovery time of the carpet tufts between strikes.

The block on which the test sample is fixed moves downwardly under the weight imposed against the tension spring to produce a simulated action of footwear rolling and slipping over the edge of a stair tread. Since one edge of the block is elevated toward the weighted member, the shoe sole initially contacts the front edge of the covered block in a manner similar to a persons shoe on the edge of a carpeted stairstep. As the weight of member 16 elongates tension spring 32, the test specimen rolls downwardly on a lesser radius than member 16 causing a scrubbing action to occur between the test specimen and the shoe sole. In FIGURE 3 there is shown a test specimen 70 which has been subjected to the simulated traflic. The worn area '72 illustrates the end point condition referred to earlier herein.

The following table represents data recorded from a carpet sample tested for stair tread wear on a stairway having eighteen steps compared with data recorded from .a simulated test in accordance with the invention on eighteen test specimens selected from the same carpet sample.

TABLE L-SPECLVIEN VARIATION (ACTUAL vs. SIMULATED) Step and/or Traffic at End Point Tratfic at End Point Specimen Number (Steps) (thousands) (Simulated) (thousands) 22. 2 5. 6 .1 18. 8 5. 6 31 18. 8 5. 6 4. l8. 8 o. 1 5 28. 0 4. 4 6. 18.8 6 8 7 20. 8 5. 5 8 27. 2 5. 8 9 21. 8 5. 9 10" 21. 8 5. 4 11.. 28. 8 5. 5 12.. 28. 8 5. 8 131. 28. 5 6. 6 14.. 36. 5 6. 6 l5 .i 45.0 7.0 l6 o, 45.0 7. l 17 42. 8 6. 4 18 c. 45. O 6. 6

Average 28. 7 6.0 Range 26.2 2. 7

The data shown in Table I illustrates clearly that significant differences in wear occurs between different steps on the stairway. Some of the variance can be attributed to such conditions as the amount and type of abrasive particles tracked onto the carpet, the weight of the person using the stairway, the type shoe soles worn, and the weight of the persons. All of these factors tend to lower the confidence rate at which carpet performance can be predicted. It will be noted from the data above however, that a comparative test conducted in accordance with the invention reduces the amount of variation from specimento-specimen. Thus, the data compiled with the apparatus shown in FIGURE 1 provides a reliable basis for making an accurate prediction on carpet performance.

Carpet samples from eight carpets of a different type were subjected to simulated traffic and stair traffic until the wear reached end point. The results appear in Table II.

TABLE II Simulated Traflic Stair Traffic Sample No. at End Point End Point (thousands) (thousands) The data illustrates the correlation of the wear charac teristics of different samples of carpet when tested by the two methods shown. Although the simulated wear reaches the end point with substantially less traffic, the difference between the different samples may be correlated with the corresponding stairway data.

From the foregoing description and data it will be apparent that wearability produced by the apparatus in accordance with the procedures disclosed herein is uniform and reliable for accurately predicting future performance of carpets and other floor coverings. Moreover, the invention provides vmeans for testing several samples under controlled environmental conditions in a minimum time period.

Although the invention has been described as apparatus for testing wear resistance properties of carpets, it is to be understood that the invention is applicable to all types of floor coverings and may be adapted for testing the physical properties of other materials without departing from the inventive concept disclosed herein.

We claim:

1. Apparatus for testing wear resistance properties of a test specimen comprising, in combination, a table-like frame, a member having an abrasive surface at one end portion, said member being mounted to the frame and pivoted at the opposite end for movement of said abrasive surface along an arcuate path, a block covered with a test specimen and pivotally mounted to the frame, stop means associated with said block for limiting upward movement of said block away from said frame, a tension spring connected to the block for maintaining the block against said stop means to elevate the test specimen with respect to said frame, and means for agitating said abrasive surface along said arcuate path into contact with said test specimen and extending the tension spring whereby the test specimen is pivoted on a lesser radius than the abrasive surface to produce a sliding action between the abrasive surface and test specimen.

2. Apparatus for testing wear resistance properties of a carpet sample comprising, in combination, a table-like frame, a rectangular member pivotally mounted to the frame, said rectangular member having a shoe sole and cam follower mounted to the bottom side thereof with respect to the frame, a carpet covered block pivotally mounted to the frame, a support arm extending from the frame, a tension spring connected to said block and said arm, stop means for maintaining said block in an elevated position, a shaft mounted for rotation on the frame, a cam fixed to the shaft for rotation therewith, said cam being positioned to cooperate with the cam follower to agitate the shoe sole along an arcuate path wherein contact occurs intermittently between the shoe sole and the carpet covered block, and means for driving the shaft at variable speeds.

3. The apparatus of claim 2 further characterized by a plurality of positions for simultaneously testing a plurality of carpet samples independent of each other.

4. Apparatus for testing wear resistance properties of a test specimen comprising, in combination, a frame, a load member having an abrasive surface pivotally mounted on said frame for travel along a first arcuate path, a test specimen pivotally mounted or travel along a second arcuate path of substantially lesser radius than said first arcuate path, means for restraining said test specimen in an elevate-d position with respect to the frame against a stop limiting means, means for oscillating the load member back and forth along the first arcuate path to contact a portion of the test specimen causing the test specimen to travel along the second arcuate path in contact with the abrasive surface whereby a sliding and rolling action occurs between said specimen and said abrasive surface.

5. The apparatus of claim 4 wherein the abrasive surface is a conventional shoe sole.

6. The apparatus of claim 4 wherein means are provided for testing simultaneously a plurality of samples independently of each other.

7. A method for testing the wear resistance properties of a test sample comprising directing a pivoted member having an abrasive surface spaced from the pivotal point along a first arcuate path, positioning a test sample suspended on a pivot in the arcuate path of the abrasive surface, agitating the abrasive surface in a clockwise direction about its pivotal point into contact with the test sample causing said sample to rotate counter clockwise about its pivotal point along an arcuate path having a substantially smaller radius than said first arcuate path thereby producing a lateral sliding action between the abrasive surface and test sample, and returning the abrasive surface and test specimen to their normal position.

8. The method of claim 7 wherein a plurality of carpet samples are tested simultaneously and independent of each other.

References Cited UNITED STATES PATENTS 974,450 11/1910 Tully 73-7 X 2,942,463 6/1960 Mann et al 737 X 3,121,320 2/1964 Bauer 73-7 3,134,255 5/1964 Oliver et al 737 DAVID SCHONBERG, Primary Examiner.

Claims (1)

1. APPARATUS FOR TESTING WEAR RESISTANCE PROPERTIES OF A TEST SPECIMEN COMPRISING, IN COMBINATION, A TABLE-LIKE FRAME, A MEMBER HAVING AN ABRASIVE SURFACE AT ONE END PORTION, SAID MEMBER BEING MOUNTED TO THE FRAME AND PIVOTED AT THE OPPOSITE END FOR MOVEMENT OF SAID ABRASIVE SURFACE ALONG AN ARCUATE PATH, A BLOCK COVERED WITH A TEST SPECIMEN AND PIVOTALLY MOUNTED TO THE FRAME, STOP MEANS ASSOCIATED WITH SAID BLOCK FOR LIMITING UPWARD MOVEMENT OF SAID BLOCK AWAY FROM SAID FRAME, A TENSION SPRING CONNECTED TO THE BLOCK FOR MAINTAINING THE BLOCK AGAINST SAID STOP MEANS TO ELEVATE THE TEST SPECIMEN WITH RESPECT TO SAID FRAME, AND MEANS FOR AGITATING SAID ABRASIVE SURFACE ALONG SAID ARCUATE PATH INTO CONTACT WITH SAID TEST SPECIMEN AND EXTENDING THE TENSION SPRING WHEREBY THE TEST SPECIMEN IS PIVOTED ON A LESSER RADIUS THAN THE ABRASIVE SURFACE TO PRODUCE A SLIDING ACTION BETWEEN THE ABRASIVE SURFACE AND TEST SPECIMEN.

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