IS: 5416 ( Part 2 ) - 1888 Indian Standard ( Reaffirmed 2002 ) METHODSOFTESTFOR STRENGTHANDSTABILITY OFCHAIRS ANDSTOOLS PART 2 DETERMINATION ( OF STABILITY OF CHAIRS AND STOOLS First Revision) UDC 684,435 : 620.17 @ Copylight 1989 BUREAU MANAK OF BHAVAN, INDIAN STANDARDS ZAFAR MARG 9 BAHADUR SHAH NEW DELHI 110002 Gr 4 July 1989 IS : 5416 ( Part 2 ) - 1988 Indian Standard METHODSOFTESTFOR STRENGTH AND STABILITYOFCHAIRS ANDSTOOLS PART 2 DETERMINATION ( OF STABILITY OF CHAIRS AND STOOLS First Revision ) 0. FOREWORD 0.4 In the formulation of this standard, considerable assistance has been derived from BS 4875 : Part 2 `Strength and stability of furniture Part 2 Methods for determination of stability of chairs and stools; issued by the British Standards Institution. 0.5 For the purpose of deciding whether a particular requirement of this standard is complied with, the final value, observed or calculated, expressing the result of a test, shall be roimded off in accordance with IS : 2- 1960*. The number of significant places retained in the rounded off value should be the same as that of the specified value in this standard. *Rules for rounding off numerical values (revised ). 0.1 This Indian Standard ( Part 2 ) ( First Revision ) was adopted by the Bureau of lndian Standards on 21 November 1988, after the draft finalized by the Furniture Sectional Committee had been approved by the Civil Engineering Division Council. 0.2 This standard was first published in 1969 covering the methods of test for general purposes of erect, wooden chairs. Now this standard is being issued in two parts. Part 1 covers methods of test for determination of strength of chairs and stools of all types. 0.3 This part ( Part 2 ) of the standard covers methods of test for determination of stability of chairs and stools. 1. SCOPE 1.1 This standard ( Part 2 ) prescribes the methods for determination of stability of all types of upright chairs and stools, easy chairs and tilting and reclining chairs. 2. TERMINOLOGY 2.0 For the purpose of this standard, the following definitions shall apply. 2.1 Stability turning. 3. PRINCIPLE 3.1 The principle is to determine the stability of an article by simulating the overturning forces that occur in use and determining whether the article overturns. 4. GENERAL REQUIREMENTS FOR TESTS The ability to withstand over- 4.1.1 The apparatus used to apply seat loading shall not restrain the article from overturning nor hinder horizontal movement of the article when the back force is applied. 4.2 Setting-Up of Furniture - The articles shall be tested as delivered. Self-assembly furniture shall be assembled according to instructions supplied with the articles. If the article can be combined in different ways, the most adverse combination shall be used for each test. 5. APPARATUS 5.1 Means Forces of Applying Required Loads or Dimensions to an 5.2 Means of Measuring Accuracy of f 0.2 mm 4.1 Test Loading - All loads and forces shall be measured to an accuracy of *5 percent. NOTE- The tests may in out by means of loads or forces. certain cases be carried l- 5.3 Loading Point Template ( see Fig. 1, 2 and3) - It shall consist of two shaped members fastened together by a pivot at one end. The contours of the shaped surfaces are so devised as to sink into the upholstery for a representative distance under moderate loads. For this purpose, the seat loading arm shall have a total mass of IS : 5416 ( Part 2 ) u 1988 20 kg, applied through the seat loading point. The apparatus is marked as shown in Fig. 1 so that the template is positioned easily with the two members at an angle of 90" to each other. 5.4 Floor surface. It shall comprise a level horizontal 5.8 Support Apparatus - It shall be used for carrying out the tests in 7.6.2 to 7.6.4, having a mass of not more than 2.5 kg. 6. DETERMINATION OF SEAT AND BACK LOADING POINTS 6.1 Chairs - Position the template ( 5.3 ) with its load applied at the seat loading point on the centre line of the chair as far towards the rear as possible. Adjust its position by pushing the back loading portion into the back, so levering the seat portion forward until the shape of the template correlates with that of the chair ( see Fig. 3 ). Mark the required loading points from the template. 6.2 Stools - Set up the template ( 5.3 ) at an angle of 90' with the aid of the mark as shown in Fig. 3. Place the template on the steel as shown in Fig. 2. Mark the required loading point from the template. 7. PROCEDURE 7.1 General - Position the chair or stool on the floor ( 5.4 ) with the legs restrained by stops ( 5.5 ). 7.1.1 For tests on articles with swivelling bases, rotate the base to the position relative to the seat that is most likely to cause overturning and tighten 5.5 stops - These shall prevent the article from sliding but not from overturning. Stops shall be not higher than 12 mm except in cases where the design of the article necessitates the use of higher stops, where the lowest stop that will prevent the article from moving shall be used. 5.6 Loading Pad - A rigid circular object 200 mm in diameter having a face with a convex spherical curvature of 300 mm radius and a 12 mm front edge radius. It shall be constrained to remain in position without restricting the freedom of the article to overturn ( see Fig. 4 ). The loading pad shall be attached to a force application 3 device capable of applying forces with an accuracy of&l N. NOTE - A recommended shown in Fig. 5. linkage arrangement is 5.7 Qiscs - There shall be a total of 14 discs each having a radius of 175 mm, thickness of 40 mm and mass of 10 kg. TYPICAL SECTION ii A = seat load ( chairs ) B = back load ( chairs ) C seat load ( stools ) All dimensions in millimetres. FIG. 1 LOADING POINT TEMPLATE 2 IS : 5416 ( Part 2 ) - 1988 SCALE:1 SQUARE=20x2dmn I FIG 2 POSITIONOF LOADINGPOINT TEMPLATE FIG. 3 LOADINGSURFACECURVES FOR CHAIR SEAT AND BACK LOADING TEMPLATE angle of 15 f 5'. Load free swivelling backrests on the axis of rotation even when this axis cannot be adjusted by an angle of 15 + 5". I any assembly fittings. Set adjustable height chairs at the height that is most likely to cause overturning. Place a chair or stool with a circular base with its edge against a stop in a position commensurate with that specified for four-legged chairs. Position three or five-star bases so that the two feet are against the stops ( 5.5 ). Record whether the article tends to overturn during each of the tests described in 7.2 to 7.6. 7.2 Forward Overturning Overturning for Chairs and Without Sideways Arms - I R12 / Position the chair with the stops against the front legs on one side ( as appropriate ). Apply a force of 600 N vertically by means of the loading pad ( 5.6 ) 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 in instability ( usually tests on the centre line are sufficient ). Apply a force, F, of 20 N horizontally along a horizontal line extended forwards from the point where the base of the loading pad meets the upper surface of the seat ( see Fig. 6 ). Test chairs with adjustable backrests and reclining and tilting chairs, with their back assemblies locked or set so as to be inclined rearwards from the vertical by an 3 I All dimensions in millimetres. FIG. 4 BACK LOADING PAD IS : 5416 ( Part 2 ) - 1988 min. 250 l---l7 0 LOW FRICTION BEARINGS HORIZONTAL BAR 100 min. V I I F- I ------- _ ---- -----750 min. ----cl h I I h = loaded seat height V = vertical load F = horizontal force All dimensions in millimetres. FIG. 5 SUGGESTED LINKAGE ARRANGEMENT CONSTRAINING LOADINGPAD h --MFIG. 6 7.3 Rearward Overturning 4+-- in millimetres. All dimensions FORWARDS OVERTURNING AND SIDEWAYSOVERTURNING FOR CHAIRSWITHOUT ARMS NOTE - The test applies only to chairs with backs extending 50 mm or more above the unloaded seat. This does not apply to tilting chairs or to chairs where the back reclines beyond those limits-jtated in 7.6.1. the seat by means of the loading pad ( 5.6 ) at the seat loading point ( see 6 and Fig. 7 ). Determine the distance, h (in mm), between the loaded seat height and the floor by measuring the distance between the horizontal bar ( see Fig. 5 ) 4 7.3.1 Position the chair with the stops against the rear legs. Apply a vertical force of 600 N to and the base of the pad, and subtracting it from the distance between the horizontal bar and the floor. For chairs having a value of h greater than 720 mm, use an overturning force, F, of 80 N. For chairs having a value of h less than 720 mm, calculate the overturning force, F (in N), required from the following formula: F 285.7 ( 1 h/l 000 ) Apply force F horizontally to the back of the chair at a height of 300 mm above the unloaded seat, or at the top edge of the backrest, whichever is the lower. IS : 5416 ( Part 2 ) - 1988 Set adjustable angle backrests ( unless they adjust to such a degree that they are covered by 7.6.2 or 7.6.3 ) at the rearmost point of their working range of adjustment. Load articles with free swivelling backrests on their axis of rotation even when this axis cannot be set at the rearmost point of their working range of adjustment. n F\\ 300 I h 3 6OOFJ the feet of the stool so that 7.5 Stools -Position the two feet are resting against the stops ( 5.5 ). Apply a vertical force of 600 N by means of the loading pad ( 5.6 ) at a point 50 mm from the 250N 350N , All dimensions in millimetres. All dimensions in millimetree. FIG: 7 REARWARDS OVERTURNING UNDE; LOADED CONDITION rearwards about its rear edge of the seat moves 100 mm duistanc:e of FIG. 9 SIDEWAYS OVERTURNING FOR CHAIRS WITH ARMS 7.3.2 Tilt the chair feet so that the front through a horizontal ( see Fig. 8 ). edge of the seat nearest the stopped feet ( see Fig. 10 ). Apply a horizontal force, F, of 20 N through the centre of the seat in a direction Tilt the stool rearwards towards the stopped feet. about two of its feet so that the front edge of the seat moves through a horizontal distance of 100 mm. c, t I 600N 2 50 _, *F b All dimensions in millimetres. FIQ. 8 REARWARDS OVERTURNINQ UNDER SELF WEIGHT 7.4 Sideways Overturning for Chairs with Arms - Position the chair with the stops ( 5.5 ) against the legs of one side. Apply a vertical force of 250 N at a point 100 mm to one side of the fore and aft centre line of the seat and between 175 and 250 mm forward of the rear edge of the seat ( see Fig. 9 ), Apply a vertical force of 350 N by means of the loading pad ( 5.6 ) at a position 37.5 mm inside the outer edge of the arm at the most adverse position along its length. Apply a horizontal force, F, of 20 N outwards at the upper surface of the armrest and in line with the vertical arm force on the side with stopped feet ( see 4 ). 5 All dimensions FIJ. 10 u 0 in millimetres. OVERTURNING FOR STOOLS with 7.6 Rearwards Overturning of Chairs Tilting or Reclining Mechanisms 7.6.1 General The tests in 7.6.2, 7.6.3 and 7.6.4 are applicable to chairs that are fully reclined or tilted; they are not alternative methods to those for upright chairs. The test for tilting chairs is valid for all values of 6 ( see Fig. 11 ) and values of y between y = 90 and 120". The test is not required when the minimum value of 0 is greater than 55". IS : 5416 ( Part 2 ) - 1988 The test for reclining chairs without footrests ( 7.6.3 ) is valid for values of 0 ( see Fig. 12 ) less than or equal to 55' and the test for reclining chairs with footrests ( 7.6.4 ) is valid for values of 19 ( see Fig. 13 ) less than or equal to 45". FIG. 11 TEST FOR TILTING CHAIRS 7.6.2 Tilting Chairs - Place 11 discs ( 5.7 ) on the chair seat firmly settled against the contours of the back of the chair. If the discs, stacked on top of each other, exceed the height of the chair back, it is necessary to use a light stick, or other means of support, to stop the upper discs ti-om sliding off. The apparatus of support is shown in Fig. 14. All dimensions in millimetres. FIG. 12 TEST FOR RECLINING CHAIRS WITHOUT FOOTRESTS All dimensions in millimetres. FIG. 13 TEST FOR RECLINING CHAIRS WITH FOOTRESTS 6 IS : 5416 ( Part 2 ) - 1988 ------l T .`,) r*IAk~MUM MASS 2.5kg All dimensions in millimetres. Fro. 14 SUPPORT APPARATUS point of the seat and back surfaces ( see Fig. 13 and Table 1 ). 8. INTERPRETATION OF RESULTS 7.6.3 Reclining Chairs Without FootrestsSet the chair in its fully reclined position. Determine the value of 0, the angle between the backrest and the floor, as illustrated in Fig. 12. Determine the value of X required 1 by interpolation of the values in Table 1. Place eight discs ( 5.7 ) firmly settled against the contours of the back of the chair at a point 168 mm above the intersection point of the seat and back surfaces. Place a further three discs with their centre at a distance X mm from the intersection point of the seat and back surfaces as illustrated in Fig. 12. 7.6.4 Reclining Chairs with Footrests - Carry out the test described in 7.6.3 except that three discs shall be position 5 mm from the intersection 8.1 Each article shall be considered to have passed the tests if the article did not overturn during the tests and if the requirements of the appropriate product specification are met. 9. TEST REPORT 9.1 The test report shall particulars: b) Whether testing. the contain the following a) Details of the article tested, and article overturns during TABLE 1 VALUES OF X AND 2 ( Clauses 7.6.3 and 7.6.4 ) B degrees 0 10 20 30 45 60 NOTE Intermediate values can be obtained X mm 474 424 375 325 252 194 by plotting graph from the,vahes given z mm 614 564 515 464 392 above. 7 BUREAU OF INDIAN Headquarters: Manak Bhavan, 9 Bahadur Shah Zafar Marg, NEW DELHI Telephones I 3310131, 3311375 STANDARDS 110002 Telegrams I Manaksanstha ( Common to all offices ) Telephone 3310131, 3311375 362499 Regional Offkes: Central: Manak Bhavan, 9 Bahadur Shah Zafar Marg, NEW DELHI 10002 l Eastern Northern I l/14 C. I. T. Scheme CALCUTTA 700054 VII M, V. I. P. Road, Manlktola, 160036 I SC0 445-446, Sector 35-CCHANDIGARH I C. I. T. 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