BECKHOFF BK4000 - Manual (Page 10)

Basic information
10 BK4000
Mechanical construction
The Beckhoff bus terminal system is distinguished by its small volume and
its high modularity. For project planning, one bus coupler and a number of
bus terminals must be planned. The bus coupler’s installation dimensions
are independent of the field bus system. The total height of the housings
may be exceeded if larger connectors are used, for example in the case of
some high bus connectors for the InterBus.
Dimensions of a bus
coupler
The overall width of the construction is the width of the bus coupler, inclu-
ding the bus end terminal, plus the width of the installed bus terminals. The
bus terminals are 12 mm or 24 mm wide, depending on their function. De-
pending on the gauge of cables used the overall height of 68 mm may be
overstepped by about 5 mm to 10 mm by the cables at the front.
Assembly and connections
It takes only a slight pressure to latch the bus coupler and the various bus
terminals onto a supporting 35 mm C rail and a locking mechanism then
prevents the individual housings from being removed. You can remove
them without effort if you first release the latching mechanism by pulling the
orange tab. You should carry out work on the bus terminals and the bus
coupler only while they are switched off: if you plug or unplug components
while the power is on you may briefly provoke some undefined state (and,
for instance, reset the bus coupler).
You can attach up to 64 bus terminals in series on the right-hand side of
the bus coupler. When you assemble the components, make sure that you
mount the housings so that each slot comes together with the correspon-
ding key. You cannot make any functional connections merely by pushing
the housings together along the supporting track. When they are correctly
mounted there should be no appreciable gap between the adjacent hou-
sings.
The right-hand side of a bus coupler is mechanically similar to a bus termi-
nal. There are eight connections on the top which can be used to connect
to thick-wire or thin-wire lines. The connection terminals are spring loaded.
You open a spring terminal by applying a slight pressure with a screwdriver
or other pointed tool in the opening above the terminal and you can then
insert the wire into the terminal without any obstruction. When you release
the pressure the terminal will automatically close and hold the wire secure-