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2. TECHNICAL DESCRIPTION
2.1 SYSTEM OVERVIEW
A Tapeswitch safety mat system consists
of two elements: a sensor and a control
unit. The sensor may consist of a single
mat sensor or a combination of mat
sensors. When a person stands on the
sensor a stop signal is transmitted to the
control unit. On receiving a stop signal
from the sensor the control unit switches
off its output relays causing dangerous
motion to cease or be prevented.
The control unit contains the system
power supply, the sensor monitoring
circuit and the safety output relays. The
safety output relay contacts must be
connected into the machine control
circuit such that when the output relays
are switched off, power to the machine
primary control element(s) is removed.
A machine primary control element or
MPCE is defined as ‘an electrically
controlled
element
which
directly
controls the normal operating motion of a
machine such that it is the last (in time)
to operate when motion is initiated or
arrested’.
NOTE: On low to medium risk machines
a single MPCE is normally used. If two
MPCE’s are provided their function
should be such that each of them is
capable of stopping the machine,
regardless of the state of the other.
2.2 SENSORS
2.2.1 MAT SENSORS
The construction of the CKP/S1 sensor is
shown in figure 8. A network of
Tapeswitch ribbon switching elements is
sandwiched between two thick sheets of
PVC material. The switching elements
are connected in series. The switch
elements are glued to the bottom layer.
The top and bottom layers are sheets of
ribbed, heavy duty matting material. This
material is of laminated construction and
is PVC based with special additives and
fillers to increase its abrasion and
chemical resistance. This material can
withstand years of pedestrian traffic and
is resistant to most chemicals commonly
found in an industrial environment
including
water,
coolant,
oil
and
hydraulic fluid. The top sheet is 6.5
millimetres thick and the bottom sheet is
5 millimetres thick.
TOP LAYER
SWITCH LAYER
BOTTOM LAYER
Figure 8
-
Construction of CKP/S1 sensor
