Version 10.12.2019
page 20
WERAC Elektronik GmbH
8.2
Combination light grid with 14/30 mm or 14/40 mm resolution
In the case of the combination light grid, modules with a 30 mm or 40 mm resolution and
modules with a 14 mm resolution are fitted in an aluminium profile. The combination light grid
is especially suitable for machines in which several danger spots have to be safeguarded. For
the use of combination light grids all safety distances (including the vertical position) shall be
taken into account.
The different resolutions are marked on both sides of the section tube. The 14 mm resolution
can be identified by the optical system (interconnected lenses) and a red range marking with
yellow inscription “14 mm”.
When using combination light grids, the respective range must be checked with the two test
rods for 14 mm and 30 mm and/or 40 mm.
Application example:
There are two danger spots in a miniload
storage/retrieval machine: firstly the lift shaft at a
distance S1 with a shearing hazard and secondly the
unloading station (distance S2
14
and S2
30
) with a
crushing hazard. A light grid with a combined
resolution of 14 mm and 30 mm allows both danger
spots to be safeguarded in very effective manner.
Calculation of the minimum value for S2
14
and S2
30
:
If the machine has a braking time of 80 ms and the
combination light grid a response time t
R
= 24.1 ms,
a safety distance
S2
14
= 2 m/s · (80 + 24,1) ms = 208.2 mm
results at a 14 mm resolution (see Section 6.2)
and S2
30
= 336,2 mm
at a 30 mm resolution.
The dimension for the height of the section with a
14 mm resolution is calculated as follows:
mm
264
2
S
2
S
H
2
14
2
30
14
On account of the 50 mm module sections, the following is obtained: H
14
= 300 mm.
A more accurate determination of H
14
is possible. Because of a diagonal entry through the
30 mm light grid the resolution is increased. Thus H
14
can possibly be chosen smaller. For
more information please contact us.
Note: This calculation depends on the application which the safety light grid is used for and is
not a part of the EC-type-test.
Also a combination light grid with 14/40 mm is possible. Then the 14 mm resolution has just an
additional, not safety relevant use. In this case the height of the 14 mm part can be only 50 or
100 mm.
The type designation code for the combination light grids is the same except for the three
points marked with "Yyy". These three reference numbers change as follows:
W G x x x x x x Y y y Z z z z - 0
Fig. 12: Application example
Miniload storage/retrieval machine
600
mm
H
14
=
300
mm
S2
14
Unloader
Vertical
movement
(Lift)
S1
S2
30
1
= res. 14 mm at cable entry, remain 30 mm
2
= res. 14 mm at casc. output, remain 30 mm
3
= res. 14 mm at cable entry, remain 40 mm
4
= res. 14 mm at casc. output, remain 40 mm
5
= res. 30 mm at cable entry, remain 40 mm
6
= res. 30 mm at casc. output, remain 40 mm
Height of light grid component with bigger res.
e.g.
20
= 200 mm
35
= 350 mm
Length of the filler element
in mm
e.g.
105
= 105 mm
I
= filler element cable entry
O
= filler element at cascade
output
