ISO 16840-3:2006

INTERNATIONAL ISO
STANDARD 16840-3
First edition
2006-07-01
Wheelchair seating —
Part 3:
Determination of static, impact and
repetitive load strengths for postural
support devices
Sièges de fauteuils roulants —
Partie 3: Détermination des efforts statiques, d'impact et cycliques pour
les dispositifs de maintien de la posture

Reference number
©
ISO 2006
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ii © ISO 2006 – All rights reserved

Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 1
4 Test apparatus . 3
5 Failure modes. 9
6 Preparation of PSD for testing . 10
7 Test methods for static strength of PSDs.10
7.1 Preparation . 10
7.2 Test procedure . 11
7.3 Load application . 11
7.4 Lateral and medial support surface test methods . 11
7.4.1 Lateral supports: outward lateral forces. 12
7.4.2 Lateral supports: inward lateral forces . 12
7.4.3 Medial knee supports: inward forces . 13
7.5 Anterior pelvic support and anterior trunk support: anterior forces . 13
7.6 Head support: posterior forces . 15
7.7 Back support: posterior force . 15
7.8 Back support: anterior forces . 16
7.9 Arm supports, integral: downward forces . 17
7.10 Foot supports, integral: downward forces. 17
8 Test methods for impact strength. 17
8.1 Preparation . 17
8.2 Test procedure . 17
8.3 Back support resistance: posterior impact . 17
8.4 Head support resistance: posterior impact . 18
8.5 Foot supports: impact for PSDs with integral foot supports. 19
8.6 Seat surface: impact. 19
9 Test methods for repetitive load . 20
9.1 Preparation . 20
9.2 Test procedure . 20
9.3 Seat surface: repetitive load testing. 20
9.4 Back support: repetitive load . 21
9.5 Anterior pelvic support and anterior trunk support: repetitive load . 21
10 Test report . 22
11 Disclosure requirement. 23

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee has
been established has the right to be represented on that committee. International organizations, governmental
and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 16840-3 was prepared by Technical Committee ISO/TC 173, Assistive products for persons with disability,
Subcommittee SC 1, Wheelchairs.
ISO 16840 consists of the following parts, under the general title Wheelchair seating:
⎯ Part 1: Vocabulary, reference axis convention and measures for body segments, posture and postural
support surfaces
⎯ Part 2: Determination of physical and mechanical characteristics of devices intended to manage tissue
integrity — Seat cushions
⎯ Part 3: Determination of static, impact and repetitive load strengths for postural support devices
The following parts are under preparation:
⎯ Part 4: Seating systems for use in motor vehicles
⎯ Part 5: Determination of pressure relief characteristics of seat cushions intended to manage tissue
integrity
iv © ISO 2006 – All rights reserved

Introduction
Postural support devices (PSD), constructed as additional components to wheelchair seating or as wheelchair
seating in its own right, are widely available and used extensively by people with disabilities. The selection or
prescription of the most appropriate PSD should be, where appropriate, partially dependent on knowledge of
its ability to withstand static, impact and repeated loads. This part of ISO 16840 is intended to specify test
methods to provide this information.
The tests involve mounting the PSD on rigid test fixtures to simulate mounting on a wheelchair. Forces are
then applied to simulate static loads encountered during normal use. Impact and repeated loads are also
applied to simulate normal usage. The rigid test fixture is utilized to provide a worst-case situation, which is
repeatable and avoids destroying multiple wheelchairs during testing. There is no minimum performance
requirement currently specified in this part of ISO 16840. Usually tests are performed at increasing force until
one or more failures occur. Repeated load tests are performed at a specific force until one or more failures
occur. It is not required to test beyond a noted number of cycles.

INTERNATIONAL STANDARD ISO 16840-3:2006(E)

Wheelchair seating —
Part 3:
Determination of static, impact and repetitive load strengths for
postural support devices
1 Scope
This part of ISO 16840 specifies test methods for the determination of static, impact and repetitive load
strengths as well as disclosure requirements for postural support devices (PSD) with associated attachment
hardware intended for use with wheelchairs.
This part of ISO 16840 does not test the transportability or the use of the PSD in a motor vehicle.
NOTE At the present time there are no minimum or maximum strength requirements specified in the test procedures
for testing for PSDs. In the future, minimum or maximum loads for testing might be specified for testing on a pass/fail basis.
The maximum displacement, the maximum force achieved before failure and the type of failure that occurs is disclosed for
comparison purposes.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 554:1976, Standard atmospheres for conditioning and/or testing — Specifications
ISO 898-7, Mechanical properties of fasteners — Part 7: Torsional test and minimum torques for bolts and
screws with nominal diameters 1 mm to 10 mm
ISO 7176-8:1998, Wheelchairs — Part 8: Requirements and test methods for static, impact and fatigue
strengths
ISO 7176-15, Wheelchairs — Part 15: Requirements for information disclosure, documentation and labelling
ISO 7176-26, Wheelchairs — Part 26: Vocabulary
ISO 16840-2, Wheelchair seating — Part 2: Determination of physical and mechanical characteristics of
devices intended to manage tissue integrity — Seat cushions
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 7176-26 and the following apply.
3.1
elastic attachment hardware
hardware that allows a PSD to move when a force is applied and returns to its original position when the force
is removed
EXAMPLE A PSD designed with a spring that allows movement.
3.2
deformable support surface
support surface which conforms to the shape of the body part being supported
NOTE The surface might or might not return to its original shape but remains conformable over time.
EXAMPLE Foam or fluid seat supports are examples of deformable support surfaces.
3.3
passive support surface
PSD that moves with minimal resistance to follow the body part being supported
NOTE Passive support surfaces do not necessarily move back to a specific position.
EXAMPLE A mobile arm support is a passive support surface that allows movement with minimal resistance.
3.4
active support surface
PSD that is powered to change its position or support surface shape
EXAMPLE An alternating pressure seat support or an electronically operated back support surface that reclines.
3.5
continuous lateral support
support surface which has a depth that extends a minimum of 75 mm forward/upward of its uncompressed
adjacent support surface and has an angle between the adjacent support surface and the lateral support
which is less than or equal to 120°
See Figure 1.
NOTE 1 Figure 2 shows a support with a contoured surface that is not considered to be a lateral support.
NOTE 2 If there are difficulties in establishing the location of the adjacent support surface, use the reference planes as
specified in ISO 7176-26.
Dimensions in millimetres
Figure 1 — Cross-section of a support surface with continuous lateral support
2 © ISO 2006 – All rights reserved

Dimensions in millimetres
Figure 2 — Cross-section of a support surface with a contour not considered a lateral support
3.6
discontinuous lateral support
lateral support which is separate from the adjacent support surface
See Figure 3.
Figure 3 — Example of a lateral support discontinuous with the adjacent support surface
3.7
anchor point
intended attachment point or points of any PSD
4 Test apparatus
4.1 Rigid test fixtures, for securing or positioning PSDs during testing as specified below.
4.1.1 Adjustable rigid test frame, for simulating the tubes of a wheelchair frame, typically used to attach
the sling seat or sling back, which allows the full range of angle adjustment of PSD attachment hardware.
The outside dimensions between the adjustable rigid components of the test frame should be adjustable from
280 mm ± 30 mm to 580 mm ± 30 mm. An informative example of an adjustable rigid test frame is shown in
Figure 4.
Figure 4 — Example of an adjustable rigid test frame
4.1.2 Rigid surrogate support surface, of securing attachment hardware for PSDs intended to be used
with rigid flat support surfaces but which are provided without rigid flat support surfaces.
An example of a rigid surrogate support surface is shown in Figure 5. Holes may be drilled or other
modifications made to accommodate the mounting of a variety of attachment hardware.

Key
1 plywood
2 steel
Figure 5 — Example of rigid surrogate support surface for testing attachment hardware
4.2 Surrogate attachment hardware, to secure PSDs, intended for use with attachment hardware, but
provided without attachment hardware. Surrogate attachment hardware allows the attachment of PSDs to a
rigid test fixture.
An informative example of surrogate attachment hardware is shown in Figure 6.
4 © ISO 2006 – All rights reserved

a)  Set-up of surrogate attachment hardware

b)  Detail of surrogate attachment hardware
Key
1 rigid surrogate support surface
2 member of PSD
3 surrogate attachment hardware
Figure 6 — Example set-up of surrogate attachment hardware to secure PSD
4.3 Loading pads, as specified below, for the application of loads to PSDs.
4.3.1 Seat loading pad, comprising a rigid contoured loading indenter (RCLI) as specified in ISO 16840-2.
4.3.2 Variable convex loading pad, made of a rigid material, with convex surface elements and variable
width.
Based on anthropometric data for different body sizes, the following convex loading pads are specified:
⎯ 25 kg;
⎯ 50 kg;
⎯ 75 kg;
⎯ 100 kg.
Add a maximum of 10 mm foam padding to the outer surface of the loading pad with a vinyl or fabric cover to
reduce the friction between the loading pad and the PSD being tested. Select the smallest loading pad to
match the range application for the PSD. For example, if the PSD is designed for a user with a mass in the
range 25 kg to 49 kg, use the 25 kg loading pad for testing. The smaller radius and width of the pad will more
properly test for slippage.
Figure 7 illustrates the features of the variable convex loading pad when used with the specifications
contained in Table 1.
Figure 7 — Variable convex loading pad
Table 1 — Variable convex loading pad dimensions
User mass
Dimensions
25 kg 50 kg 75 kg W 100 kg Tolerance
Width (mm), w 210 270 323 360 ± 10
Height (mm), h 62 79 95 106 ± 5
a a a a
Length, l Variable Variable Variable Variable
Convex radius (mm), R 210 270 323 360 ± 10
Radius of side edge (mm), r 21 27 32 36 ± 3
a
To fit PSD being tested.
6 © ISO 2006 – All rights reserved

4.3.3 Variable torso convex loading pad, made of a rigid material, of variable size to simulate the upper
torso. Based on anthropometric data for different body sizes, the following torso convex loading pads are
specified:
⎯ 25 kg;
⎯ 50 kg;
⎯ 75 kg;
⎯ 100 kg.
Add a maximum of 10 mm foam padding to the outer surface of the loading pad with a vinyl or fabric cover to
reduce the friction between the loading pad and the PSD being tested. Select the smallest loading pad to
match the range application for the PSD. For example, if the PSD is designed for a user with a mass in the
range 25 kg to 49 kg, use the 25 kg loading pad for testing. The smaller radius and width of the pad will more
properly test for slippage.
Figure 8 illustrates the features of the variable torso convex loading pad when used with the specifications
contained in Table 1.
NOTE The top end of the loading pad in Figure 8 is curved to avoid cutting “over the shoulder” devices.
Figure 8 — Variable torso convex loading pad
4.3.4 Convex loading pad, made of a rigid material, as shown in Figure 9. Dimensions are illustrative only.
Dimensions in millimetres
Figure 9 — Example of a convex loading pad
4.3.5 Concave loading pad, made of a rigid material, as shown in Figure 10. Dimensions are illustrative
only.
Dimensions in millimetres
Figure 10 — Example of concave loading pad
4.3.6 Convex hemispherical loading pad, made of a rigid material such as metal or hardwood as shown
in Figure 11. Dimensions are illustrative only.
Dimensions in millimetres
Figure 11 — Example of convex hemispherical loading pad
8 © ISO 2006 – All rights reserved

4.4 Static loading device, for applying forces to a PSD, which
a) measures the applied force to an accuracy of ± 3 %,
b) applies the force at a rate no greater than 100 N/s,
c) maintains the applied force for a duration no less than 5 s, and
d) measures the movement of the loading pad during force application.
NOTE Pre-loading up to 5 N may assist with the set up and accuracy of measuring force application angles.
4.5 Impact loading device, for applying an impact load to the PSD as specified below.
4.5.1 Seat surface, back support and head support impact loading device, for applying an impact load
to the PSD, consisting of
a) an impact pendulum as specified in 5.5 of ISO 7176-8:1998, and
b) a means to measure the angle of the longitudinal axis of the pendulum prior to being dropped to an
accuracy of ± 1°.
4.5.2 Foot support impact loading device, consisting of
a) an impact pendulum as specified in 5.7 of ISO 7176-8:1998, and
b) a means to measure the angle of the longitudinal axis of the pendulum prior to being dropped to an
accuracy of ± 1°.
4.6 Repetitive loading device for repeatedly applying a load to the PSD, which
a) applies the applied force to an accuracy of ± 3 %,
b) applies the force at a rate not greater than 100 N/s,
c) releases the force,
d) reapplies the force until the specified number of cycles is achieved, and
e) avoids a frequency of loading that is the resonant frequency of any active support surface.
NOTE Pre-loading to 5 N can assist with the set up and accuracy of measuring load angles.
4.7 Test environment within which to conduct the tests and which can be maintained at 23 °C ± 10 °C,
with relative humidity of 50 % ± 35 % as defined in ISO 554.
5 Failure modes
Testing is conducted either until a device is considered to have failed or until completion of a test after which
the device is inspected for failure. The following are specifications indicating failure of a device:
a) fractures or visible cracks, tears or broken stitches (but cracks in surface finishes, such as paint, that do
not extend into the structure of the material do not constitute a failure);
b) any detached nut, bolt, screw, locking pin, component or similar item;
c) slippage in the position or adjustment of a PSD of more than 10 mm at the point of loading compared to
its original set-up;
d) in the case of any webbing-like material used in a support, either
⎯ an increase (elasticity), during any test condition, greater than 10 % of the length of the support, or
⎯ an increase, as a result of testing, in the pre-tensioned length greater than 5 % of the length of the
support;
e) displacement or disconnection of any electrical connector;
f) any parts intended to be removable, foldable or adjustable ceasing to operate as described by the
manufacturer;
g) any power operated PSDs ceasing to operate as described by the manufacturer;
h) any multi-position or adjustable PSD becoming permanently displaced more than 10 mm at the point of
loading from the preset position;
i) any component or assembly of parts exhibiting permanent deformation or maladjustment (in addition to
slippage);
j) the applied load starting to decrease as a result of the PSD beginning to yield or deform.
6 Preparation of PSD for testing
6.1 Secure the PSD to the rigid test fixture specified in 4.1, according to the PSD manufacturer’s
instructions for attachment to a wheelchair.
6.2 If a PSD is provided with its attachment hardware as a system from a manufacturer, s
...