ISO 7173:1989 pdf download – Furniture – Chairs and stools – Determination of strength and durability.
7.5 Seat fatigue test
Apply the force of 9O N by means of the seat loading pad (6.3) with the centre of the loading pad positioned at the seat loading po&tion determined as in the annex. Apply the force for the appropriate number of times specified in the table at a rate not exceeding 40 cycles ocr minute.
Measure the lowest position of the pad during the first and the last cycle of the test. Record the difference of the two values obtained as the deflection of the seat during the test.
If required, repeat the test on footrails or footrosts at the appropriate test level.
7.6 Back fatigue test
Position the centre of the back loading pad (6.5) either at the back loading position determined as in the annex, or at lOU mm below the top of the back, whichever is the lower. Prevent the chair from moving rearwards by placing stops behind the roar teet or castors. Conduct the test by the repeated application of a force of 330 N, or if the chair overbalances, of such lesser force as to prevent rearwards overbalancing. Carry out the test at a rate not ewreeeling 4fl cycles per minute for the appropriate number of applications specified In the table. During each cycle apply a force of 950 N to the seat (see figure 6).
When this test is applied to a chair fitted with a spring rocking action base that has a tension adjustment, adjust the tension to the middle of its range of adjustment.
When this test is applied to a stool without a backrest, or with a very low back, apply the backward force honiiuntally to the front edge of the seat. Test stools with four legs on which the seat surface is not symmetrical both with the seat major dimensions sideways, and with the major dimensions fore and aft for half the number of applications of the force in each of the two directions. Test stools with three legs along two of the principle axes of the three feet.
NOTE — Because the number of cycles and the seat load are common to both the seat and hack fatigue tests it is normally convenient in perform these two esis toqeihe’ as a combined seat and back fatigue
test In this ease, the coat load should he applied first and then maintuined while the back load is applied.
7.7 Leg forward static load test
Restrain the front feet of the chair or stool from movement whilst applying a horizontal force centrally to the roar of the chair at seat level in a forward direction, by means of the local loading pad (6.6). For stools with only three leqs, one foot on the fore and aft centre line and one other foot should be restrained. The maximum force shall be the appropriate force specified in the table.
Apply the appropriate seat load specified in the table at the seat loading position specified by the chair loading position template (see figure 20). If the chair or stool tends to overbalance. reduce the load to a magnitude that just prevents forward overbalancing, and record the actual force used. See figure 7 a).
7.8 Leg sideways static load test
Carry out this test in the same manner as the leg forward static loading test except restrain a pair of front and rear feet from movement whilst applying a horizontal force centrally to the side of the diticle dt sedt level, in d sidewdys direction towaids the rostraining foot. Apply the appropriato vertical &oat load specified in th tahl at a stiitahlp position across th seat hut not more than 150 mm from the unloaded edge of the seat. Apply the horizontal force 10 times, and during each application maintain the load for at least 10 s. The maximum force shall be that specified in the table. [See figure 7 b).]
If the article tends to overbalance with the vertical seat load in its furthermost position from the unloaded edge, reduce the horizontal seat loading force to a niagnitude that just prevents sideways overbalancing, and record the actual force used.