Recently, Goorej a well-known
lock company in China produced
a function changing padlock,
figure 11.
This is actually a very good
lock using the Kaba dimpled-key
principle. The master will lock
and unlock both sides. Both sides
must be unlocked for the lock to
open (figure 12). The change key
will only operate the left cylinder.
The right cylinder can lock-out
the left one at any time. The
lock goes from normal operation
to one where the change key’s
operation can be change with the
master.
Create a “Tour Key” System
Another use of a two key
locking system is the creation of
a Guard Tour Key route. Night
watchmen are required to walk
a certain route; checking doors
and locks. To ensure all locks are
checked and the correct route is
followed a system was developed
that required the guard to use
one key to open a lock which
would trap the current key and
give him the next one when the
lock was secured. At no time
could both keys be removed.
Once again, the Yale Bicentric
padlock is an excellent example
of a tour key system lock to use.
Figures 13 shows two Large
Yale Bicentric padlocks which
are a part of a tour key system.
To be sure a watchman walks
the same route and doesn’t take
any shot-cuts he must start at
the first lock which has one key
already in it. The key can open
the lock on a gate but can’t be
removed. This key is needed to
open the next gate. To release
the key the guard must take his
first key and also insert it in the
lock. The watchman’s key will
be trapped when the next key is
removed. The watchman takes
the released key and walks to the
next gate. The released key from
the first gate will open the second
gate, but will become trapped
releasing the key for the third
gate. This process goes on until
the last gate is opened. Today,
electronics have taken the place
of this type of system.
Note that one key always
remains trapped in the lock and
both keys are required to open
the lock. (figure 14)
Safety Interlock
Safety Interlocks are usually found in utilities and large
factories. One example of a safety
interlock is found in high voltage
switching equipment. To enter a
locked electrical enclosure a series of switches must be shut off
before a worker can safely enter
the enclosure and not get electrocuted. The worker starts with his
own key which must be inserted
in a box containing another key.
When both keys are present the
switch can be turned off. This
also releases the trapped key.
This key is necessary to open
the door of the locked electrical enclosure. This is just one
of many different combinations
that interlock keys can be used.
The idea is to have one event
occur before another one can. It
protects a worker from himself
basically. This concept is used
in industry to shut off large fans
or pumps in a certain sequence.
One of the largest manufacturers
of this system is “KIRK”. They
tend to use Yale products.
Figure 15 shows a typical
interlock. Both keys must be
turned in this configuration. The
cylinders are Schlage, but they
can be from any lock company.
Note the strike on the left.
Best also makes a universal
interlocking door lock. Figure 16
is one such lock. Both keys must
be present for the lock to open.
Best’s interlocking system can
be designed for most any con-
figuration. This particular con-
figuration requires two people
to be present when the door is
opened or the switch is thrown.
11. A Modern Function Changing
Padlock.
12. Bottom View.
13. Yale Tour Key System.
14. Bottom View.
15. Typical Interlock
Configuration.
