ERGONOMICS OF MANUAL MATERIALS HANDLING - Environmentally Conscious Materials Handling - page 46

Ta b l e 2 . 6 Classification of Couplings

Good Fair Poor

1. For containers of optimal
design, such as boxes,
crates, and so on, a “good”
hand-to-object coupling
would be defined as
handles, or hand-hold
cut-outs of optimal design
(see notes 1 to 3).
2. For loose parts or irregular
objects, which are not
usually containerized, such
as castings, stock, and
supply materials, a “good”
hand-to-object coupling
would be defined as a
comfortable grip in which
the hand can be easily
wrapped around the object
(see note 6).

1. For containers of
optimal design, a “fair”
hand-to-object coupling
would be defined as
handles or handhold
cutouts of less than
optimal design (see
notes 1 to 4).
2. For containers of
optimal design with no
handles or handhold
cutouts or for loose parts
or irregular objects, a
“fair” hand-to-object
coupling is defined as a
grip in which the hand
can be flexed about 90
degrees (see note 4).

1. Containers have less
than optimal design, or
loose parts or irregular
objects that are bulky,
hard to handle, or have
sharp edges (see note 5).
2. Nonrigid bags (i.e., bags
that sag in the middle)
would be considered
poor containers.

Notes:
1 . An optimal handle design has 0.75

− − ≥

4.5 inches (11.5 cm) length,
2 inches (5 cm) clearance, cylindrical shape, and a smooth, nonslip surface.
2 . An optimal hand-hold cut-out has the following approximate characteristics:

1.5 inches (1.9 3.8 cm) diameter,

≥ 1.5 inch (3.8 cm)

height, 4.5 inch (11.5 cm) length, semi-oval shape ≥ 2 inches (5 cm) clearance, smooth nonslip surface,

0.25 inches (0.60 cm) container thickness (e.g., double thickness cardboard).
3 . An optimal container design has

and ≥

≤ 16 inches (40 cm) frontal length, ≤ 12 inches (30 cm) height, and

a smooth nonslip surface.
4 . A worker should be capable of clamping fingers at nearly 90 degrees under the container, such as
required when lifting a cardboard box.
5 . A container is considered less than optimal if it has a frontal length > 16 inches (40 cm), height > 12
inches (30 cm), rough or slippery surfaces, sharp edges, asymmetric center of mass, unstable contents,
or requires the use of gloves. A loose object is considered bulky if the load cannot easily be balanced
between the hand-grasps.
6 . A worker should be able to comfortably wrap the hand around an object without causing excessive
wrist deviations or awkward postures, and the grip should not require excessive force.

2.4.5 Example Using the Revised Guide
Use the same example as was used previously for the 1981 guide:
For two hours per day, an employee lifts objects off a feed conveyor and
places them in a packing carton after a visual inspection. The objects are 25 cm
cubes and arrive at a rate of 4 per minute. The conveyor is 70 cm high and the
bottom of the packing station is 80 cm from the floor. Assume that the objects
on the conveyor are very close to the person lifting them (assume that H is