Figure 8. Vertical guarding with reference contour monitoring
Typical considerations for vertical guarding:
•
In the example shown, the objective is to prevent an individual from entering an area; detecting the body (torso) is
required.
•
In this example, physical damage is not expected because the SX is mounted above and away from the probable
path of the forklift. If impact is possible, a mechanical guard/shroud can be added to protect the SX without blocking
the Safety Zones.
•
The typical manufacturing setting is well within the SX's environmental ratings.
•
The size and coverage of the Safety Zone must ensure that unrestricted or accidental entry to the work cell is
prevented. Two SXs are used to create four Safety Zones to cover each end of the pallet load/unload station (e.g. left
side SZ, right side SZ, and both sides SZ). When no pallets are at the station, the front SX has a Safety Zone that
covers both sides; the rear SX can be muted to allow pallets to be fed into the station (such as pallets exiting the cell).
As pallets are loaded, sensors monitoring the pallet position switch the Zone Sets to "turn off" the front Scanner's
right side and "turn on" (and unmute) the rear SX's Safety Zone for that side (as shown). This allows the forklift to pick
up the pallet and remove it.
•
When the front Safety Zone is inactive, the pallet must completely block the opening to prevent access. When the
pallet is removed, that Safety Zone must immediately be re-activated.
•
The use of the Reference Points is required for vertical guarding applications (e.g. the blue points).
•
In this example, no factors would require an increase in the safety distance.
•
For this example, assume a machine stopping time of 200 ms, SX response time of 62 ms; safety interfacing device
(UM-FA-9A safety module) response time is 25 ms. The resolution can be either 40 or 70 mm, since only body
detection 70mm can be selected, the
Dpf
adder is equal to 900 mm (U.S. formula). This gives a safety distance of:
Ds = 1600 mm/s x (0.2s + 0.062s + 0.025s) + 900 mm = 1359 mm (53.5 in).
In other words, the plane of the rear
Protective Field must be no closer than 1359 mm (53.5 in) from the nearest hazard (assuming no hazard inside the
load station).
•
Configure the SX for start/restart interlock (manual reset) to ensure that if an individual interrupts an active Safety
Zone while attempting to enter the guarded area that the SX's OSSD safety outputs remain OFF until manually reset
after the individual exits the cell.
•
For the purpose of this example, the UM-FA-9A Universal Input Safety Module was used and interfaced in a control
reliable (category 3 or 4) method as described by Section 3 and Figure 3-19.
Mobile Area Guarding with Side Vertical Guarding
Vertically guarding the sides of transfer carts, material-handling trolleys, and Automated Guided Vehicles (AGVs) prevents
contact with objects that may have overrun the stop position of a conveyor, which could result in damage to the mobile
vehicle and the conveyor. This type of guarding can also be used for situations that with a crushing/trapping hazard, for
example, a distance less than 500 mm (20 in) between the sides of the SX and a physical structure.
Two SXs are positioned to create horizontal Safety Zones, to prevent running over objects or individuals in the path of the
vehicle. A second pair of vertically mounted SXs is positioned to detect objects at or above the horizontal plane of the SXs
that are looking ahead of, and behind the vehicle. In this configuration, the "leading edge" of the Safety Zone is now provided
by the vertical edges on the sides of the SX. These edges will detect the torso of an individual; 70 mm resolution is typically
selected.
SX Safety Laser Scanner
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