Ar IMPROVED METHOD OF AND APPARATUS FOR APPLYING ELECTRICITY TO LOCKS FOR OPERATING AND SECURING THE SAME
Year: 1873

page_text: PROVISIONAL SPECIFICATION left by Henry Brown Greenwood at the
Office of the Commissioners of Patents, with his Petition, on the
25th July 1878.
I, HENRY BROWN GREENWOOD, of Minson Road, in the County of
Middlesex, do hereby declare the nature of the said Invention for "Ar
IMPROVED METHOD OF AND APPARATUS FOR APPLYING ELECTRICITY TO LOCKS FOR
OPERATING AND SECURING THE SAME," to be as follows:-
My said Invention relates to the application of electricity to locks in
such a manner that the look when properly secured can only be opened
by a special key, and moreover any attempt to manipulate the lock-by
means of another key or any other instrument will be indicated by the
condition in which the lock is left by such attempt.
The said Invention may be applied to the locks of iron safes and other
strong receptacles, to locks on the doors of dwelling houses and other
buildings, and in all cases where it is desirable or necessary to obtain
greater security than can be obtained by ordinary looks, and moreover,
the said Invention is not attended with any great expense or incon-
venience in it's application or use.
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page_text: First. To the peculiar arrangement of two magnets and circuits, in
combination with the lock, and with a voltaic battery.
Secondly. To a contrivance for insulating the pin or other part of the
lock, with which the key is in contact when inserted into the same from
the other parts of the lock.
And, Thirdly. To the peculiar construction of the keys for operating
the said locks.
I arrange the battery in any convenient position with regard to the
lock, and from the positive and negative poles thereof I extend
suitable wires to make the circuit through the lock. One of these wires
extends to the back and is connected to the pin or other part of the lock
with which the key comes in contact and which is insulated, as herein-
after described. The other wire is connected to an ordinary electro-
magnet and also to the front plate of the lock. In combination with 1
this magnet I arrange an armature which occupies such a position that
when attracted to the magnet it will not permit the lock bolt to slide
back, but when released from the magnet it will not obstruct the
movement of the said lock bolt. With the wires arranged and con-
nected in this manner it is obvious there will be no current through 2
them as the circuit is not complete through the lock and the magnet
will remain inoperative. But if a key or pick or other instrument
should be inserted the circuit will be completed; then the armature is
attracted to the magnet and the lock will be immovable. It will be
kept in this condition by a stop lever, which when the said armature is
raised drops under a shoulder thereon. The said stop lever is attached
to the armature of the second magnet and can only be withdrawn to
release the first armature by completing the circuit through the second
magnet.
For making the circuit through the aforesaid second magnet branch a
wires are extended from the wires above described. One of these branch
wires is taken directly to the said magnet, but the other is divided into
two parts connected to terminals which project inward from a metal
plate placed outside the door. This metal plate is divided into two
parts which are separated or insulated from each other so that the
circuit is incomplete, except when a conductor is interposed between the

page_text: two parts of the said plate. For this purpose I prefer to use the key of
the lock. By placing this key for an instant between the two parts of
the said plate the current is caused to pass through the second magnet
which then attracts its armature, thereby moving the aforesaid stop
lever to release the armature of the first magnet and leave the lock bolt
free.
To facilitate the action of this armature I place. below it a small spring
which counteracts the weight of the said armature and assists the
magnet in raising the same.
In locks which have hollow keys a pin or stud is provided to receive
the key when the same is in the lock. I insulate this pin from the
other parts of the look by attaching it to a piece of ivory, ebonite, or
other suitable insulating material, which I secure at the back of the
lock, and I extend the said pin through this insulating piece or fix in the
same a small stud or terminal, which is in contact with the said pin. I
bore the lock plate slightly larger than the pin so that there will be no
contact between the said pin and plate. But when, as above described,
a key is inserted in the lock it is obvious that through the said key a
metallic connection between the pin and the other parts of the lock will
be established. Instead of having the circuit interrupted and completed
in the particular manner above described I may adopt any other con-
venient construction of the lock which will effect the same result.
Inside this
I adapt ordinary keys for the aforesaid locks in the following manner :—
I enlarge the hole in the key barrel and insert therein a thin tube of
paper or other insulating or non-conducting material.
insulating tube I fit a thin tube of iron, brass, or other suitable metal of
the proper size to fit the lock pin, and I cover the end of the key with a
thin piece of metal. By this contrivance it will be seen that the inside
and outside of the key barrel are insulated from each other, and there-
fore when this key is used the circuit through the lock remains
incomplete and the look works freely.