ISO 7174-1 pdf download – Furniture一Chairs 一Determination of stability Part 1: Upright chairs and stools.
7 Test procedures
7.1 Experirnetital method — Chairs
7.1.1 Forwards overbalancing and sideways overbalancing for chairs without arms
Position the chair with stops against the front legs and against the legs on one side (as appropriate). Apply a force of 600 N vertically by means of the loading pad so as to act at a point 50 mm from the edge of the seat at those poSitions along its exposed periphery most likely to result iii imistdbility (usually tests on thc ccntrclinc arc ufficicnt). Apply a force, F, as spdfid in the annex or in requirement dnejments horizontally along a horizontal line extended forward from the point where the base of the loading pad meets the upper surface of the seat (see figure 1). Record whether the chair overturns and the force used.
Chairs with adjustable backrests, and reclining and tilting chairs shall be tested with their back assemblies locked or set so as to be imidimied redrwdrds fruiri the vertical by 15 ± 50 Free swivelling backrests shall be loaded on their axis of rotation even when this axis is no? adjLiceahle to the ahove requirement
7.1.2 Rearwards overbalancing
Position the chair with the stops against the rear legs. Apply a vertical force of 600 N to the seat by means of the loading pail at a point 175 mm forward of the centre of the line of intersection of the soot and back surfaccs. Dotcrmiric the distance, h, hetween the loaded seat height and the floor by measuring the distance between the horizontal bar and the base of the pad, and subtracting it from the distance between the horizontal bar and the floor.
Apply a force, F, as specified in the annex or in requirement documents horizontally to the back of the chair at a height of 300 rum above the unloaded seat or at the top edge of the backrest, whichever is the lower (see figure 2). Record whether the chair overturns and the force used.
Adjustable angle backrests shall be set at the rearmost point of the working adjustment range. Free swivelling backrests shall be loaded on their axis of rotation.
7.1.3 Sideways overbalancIng for chaIrs wIth arms
PositIon the chair with stops against the legs at one side. Apply a vertical Voice of 250 N dt a point 100 mm to one side of the fore and aft centreline of the seat and between 175 mm and 250 mm forward of the rear edge of the seat. Apply a vertical fue of 350 N by means of the loading pad at a point 37.5 mm inside the outer odge of the arm at the most adverse position along its length Apply a horizontal force as specified in the annex or in requirement documents outward at the upper surface of the arm rest end in line with the vertical arm force on the side with restrained feet (see figure 3). Record whether the chair overturns and the force used.
7.2 ExperImental method — Stools: all directions
Position the stool so that two feet are resting against the stops.
7.3 Calculative method — Chairs
7.3.1 General
In the calculative method, the seat loading pad is not used. Instead, the resistance to overturning (hut wuuld have been causod by such loading is takon into consideration in the calculation, which is based on the moments about the restrained feel. For this calculation distances a, b and h are
measured:
— distance a is the minimum horizontal distance from the line of the stopped feet to the vertical pcoection of the point of application of the seat load, W, had such been applied;
– distance b is the horizontal distance from the stopped feet to the arm load point;
— distance h is the vertical heiylit uF the point of application of the horizontal overturning force above the honyontal surface
This method is not suitable for chairs with spring suspension seats.
7.3.2 Forwards overbalancing and sid.ways overbalancing for chairs without arms
Position the chair firstly with the stops against the front legs and then with the stops against the legs on one side. Apply a gradually increasing force, F acting to tilt the chui uver the rostroinod legs horizontally at the intersection of the scat and hack surfaces, Recnd the value of F0 when the unrestrained legs lift off the floor. Measure distances h and a.
Calculate the farce F required to overturn the chair had it been loaded with a scat load. l4, of 6W N from the followlnq formula.
ISO 7174-1 pdf download – Furniture一Chairs 一Determination of stability Part 1: Upright chairs and stools
