Improvements in Locks for Fire-proof Safes, Safe Deposits, and the like.
Year: 1899

page_text: PROVISIONAL SPECIFICATION.
Improvements in Locks for Fire-proof Safes, Safe Deposits, and the
like.
I, JACOBUS LIPS (Bernarduszoon), of Dordrecht, in the Kingdom of Holland,
Manufacturer, do hereby declare the nature of this invention to be as follows:-
:-
The present invention relates to a double safety lock for fire-proof safes, safe
deposits and the like. The new lock is of that class of locks known as com-
bination locks, but offers however a greater security against theft than the usual
form of combination locks.
The new lock is also constructed as a double lock i.e. one in which two keys
are necessary to open it.
These double locks are particularly designed for employment in banks or safe
deposits, or under similar circumstances.
One of the keys remains in the possession of the banker the other key being
delivered to the tenant or owner of the deposit safe. The arrangement and
working of this kind of lock is as follows:
The banker locks the safe and withdraws his key; then the tenant turns his
key, thereby moving a second bolt so as to press against or come into the path
of the first, which is the locking holt proper, moving at the same time a cover
plate, in such a manner that the key-hole intended for the banker's key becomes
covered in such a manner that the lock is for the time being rendered absolutely
inaccessible to the key of the banker. The banker cannot therefore again unlock
his lock until the tenant by his key has replaced the cover plate in its original
position and removed the second bolt. The great disadvantage of this kind of
lock is that the lock of the tenant is always locked and unlocked by one and the
same key.
The public cannot therefore have an absolute confidence in these locks. For
if a tenant succeeds in having a duplicate of his key made for his use, the safe
remains accessible to him even after he has relinquished the tenancy of the same,
and the safe is let to another person.
Then again the attendants have the opportunity of having a duplicate key
made. In short the security against theft is not absolute.
The object of the present invention is to construct an adjustable double safety
lock for safes and the like, in which this drawback is remedied, and which there-
fore offers an absolute security against theft.
This result is obtained by so arranging the lock of the tenant that it is
capable of being locked by a number of keys, but unlocked only with the key
with which it had been locked last. The tenant chooses one of a number of
keys, all of which belong to the lock in question, and with this key he locks his
part of the lock. The bank officials do not know the key which he has chosen
.e. they do not know its shape, and he is therefore protected against any dis-
honest intentions on the part of the officials or of the previous tenant. A lock
according to the present invention will now be described the bolt being supposed
to operate from right to left for locking.

page_text: Both the bolts, that of the banker's lock and that of the tenant's lock can only
be moved longitudinally or horizontally and not vertically.
The banker's or front or left bolt is guided in the left side of the lock case,
and also by a pin projecting from the back of the lock case; the other or rear
bolt slides, by means of longitudinal slots, over pins and on projections or guides,
all secured to and projecting from the back of the lock case. The left hand
part of the lock i.e. the side which is accessible to the banker's key, is preferably
a so-called tumbler lock. The tumblers, of which there are, say, five in this
case, all turn round a fixed pivot and are placed in position in such a manner
that a pin projecting from the main bolt can pass through differently placed slots
in the several tumblers.
This tumbler principle is also employed in the right side of the lock, but
here it is employed in a peculiar manner. Here two kinds of tumblers are
used, each set consisting of a number, in this case five, of plates which are
exactly similar to each other.
One set of tumblers are, say, square and can only be moved in a vertical direc-
tion, when operated by means of a key, being guided by pins engaging in' slots,
and being also guided by the projection secured to the back of the lock.
The square tumblers are embraced on the upper and bottom edges by inter-
mediate angular tumblers, the upper arms of which are longer than the lower
arms.
The square tumblers can be moved vertically by reason of their slots, on pins
secured to the tenant's or rear bolt in such a manner that the intermediate
tumblers are forced to participate in the reciprocating movement of the bolt,
while they will participate with the movement of the square tumblers only, when
the latter are raised to a certain height by means of the key.
The intermediate tumblers are provided on the front side or edge with a set
of teeth fitting a corresponding set of teeth on a fixed projection or plate secured
to the lock or casing.
When the rear bolt and tumblers are moved forward the teeth interlock,
whereby the intermediate tumblers are held in the position into which they have
been brought by means of the key and of the square tumblers.
The latter tumblers at the same time become free of the short lower arms or
projections of the intermediate tumblers and drop down.
The guide pin at the right of the lock is formed to serve as a centre of rota-
tion for a cover plate for the banker's key hole. This cover plate is provided
with an oblique slot sliding over the upper più of the rear bolt for this purpose
the pin has obliquely shaped sides.
When the rear bolt is moved towards the left, i.e., when the tenant locks his
lock, this cover plate is turned around its pivot by the movement of the pin
engaging its oblique slot.
In this position the key-hole is obstructed by the cover thus rendering it inac-
cessible to the key of the banker.
The slot is so shaped that the pin is held when the lock is unlocked, owing to
this arrangement a displacement of the bolt cannot be produced during removal
of the safe or in consequence of careless handling.
The lock case is closed by a front plate which is somewhat sunk into the case
and secured to it by means of the screws, the plate being also provided with
the key-holes.
The lock is screwed against the door from the inner side. the door also being
provided with openings for the keys. From the above it will be clear that the
tumblers are not actuated by means of springs as in ordinary locks. Their
movements are regulated and effected by a key with double bits the two bits
being so cut that the recesses of the one correspond to the projections of the other.
This arrangement offers a great advantage that the several tumblers cannot
he raised too high when the key is carelessly handled, thereby being placed in a
wrong position.

page_text: The absence of springs ensures a greater durability and reliability than is the
case when springs are used, since springs are liable to fracture and breaking.
The key of the banker adapted for the arrangement of lock described has a
bit with seven cuts, the five central or lower ones of which are intended to raise
the tumblers. The two bits pass freely through a corresponding opening in the
cover plate and have no effect on the movement of this plate. A projection at
the outer end of the key, i.e., the projection which when in use is farthest from
the key opening extends only on one side and is the one by means of which the
bolt is operated or moved.
With the tenant's lock a key is employed by which each of the tumblers may
be raised to a certain height depending on the several cuts or wards of the key
bit, but always to such a height that when the intermediate tumblers are moved
forward their teeth properly interlock with those of the fixed projections.
The various heights at which the five tumblers can be set represent a great
number of possible combinations for five tumblers, and there may be as many
keys to the tenant's lock as the number of possible combinations. From this
set of keys the tenant may choose one, while the others are reserved.
In the key the five central or lower projections are intended for raising the
Tumblers.
Both bits of the key pass freely through an opening provided for that purpose
in the cover plate; while the outer projection, i.c., the one which, when the key
is in position, is farthest from the key-hole operates the bolt.
This projection is present in all the keys of the set, but only on one side of
the key. The operation when using the lock is as follows:-
Assume that the lock is open, the square and intermediate tumblers are sus-
pended on the pins and on the projection while the covering plate occupies the
position permitting the banker's key to be placed in the key-hole.
The banker employs his key and after having turned it round withdraws it,
thereby locking the safe.
The tenant having chosen his key out of the set inserts it with its top projec-
tion towards the right, in its key-hole.
On turning the key round the following takes place:-
-
The square tumblers and hence also the other tumblers are raised, each tumbler
to a heiglit corresponding with one of the recesses of the key bit.
By turning the key further in the same direction, the bolt is moved towards
the left by the top projection of the key until it presses against the main bolt.
Owing to the pins being fixed to the rear bolt the intermediate tumblers partici-
pate in the movement of the bolt.
These tumblers slide along the tumblers always keeping at the same height
as the corresponding square tumblers. On fully turning the key the teeth of
the intermediate tumblers interlock with the teeth of the fixed projection.
The teeth of the projection hold the several intermediate tumblers in posi-
tion, and the length of the lower arms of these tumblers supporting the square
tumblers being so calculated that in this position the square tumblers are no
longer supported by the corresponding shorter arms of the intermediate
tumblers the square tumblers fall and occupy their original position.
In this position the intermediate tumblers are locked between the fixed pro-
jection and the square tumblers the latter not being movable in a lateral direc-
tion. The rear bolt which is connected by means of the pins with the inter-
mediate tumblers thereby also becomes locked, owing to which the main bolt
cannot be moved backwards. The cover plate, has, during this time, been placed
owing to the movement of its operating pin, moving with the rear bolt so as to
obstruct the key-hole in such a manner as to render it inaccessible to the key
of the banker.
But even if the latter were able to remove the cover plate lie still would be
unable to open the lock, since the main bolt is held in fixed position by the rear
bolt. In order to be able to unlock the lock it is absolutely necessary that the

page_text: square tumblers should be raised so that each of these tumblers should corre-
spond as regards height, with the adjoining intermediate tumblers. Only when
this is the case, can the rear bolt be withdrawn, for these tumblers move with
this bolt and to do this the upper and lower arms of these tumblers must slide
over the square tumblers, which is possible only when the heights of each two
adjoining sets of tumblers absolutely correspond.
This condition, however, can only be secured by means of the key with which
the rear lock has been last locked for the several varying heights of the inter-
mediate tumblers had been obtained by means of this key and fixed in that posi-
tion by the interlocking teeth.
Any attempt to open the lock with another key must fail for there will always
be one or other of the tumblers the height of which does not correspond to that
of the corresponding intermediate tumbler which renders a displacement of the
tumblers and hence of the rear bolt connected with them, impossible.
The lock is also preferably provided with another device which renders it
impossible to withdraw the key as long as the lock is unlocked. The tenant is
therefore obliged to lock his lock before he can withdraw his key. This device
consists of a small screw pin at the right side of the key pin.
The pin is provided with an enlargement in the interior of the lock which
prevents it being turned out of its place. When the screw is unscrewed this
enlargement is withdrawn into a corresponding recess in the back of the casing,
in which position no obstruction is offered to the bit of the tenant's key. When
the key is inserted it is turned round while the safe is open.
The projection of the key bit is then on the left side. The screw is then
screwed inwardly so that the end of the screw is in the plane of the projection
of the key bit. Owing to this the key can now be turned so as to occupy a
horizontal position and withdrawn, while the projection and hence the rear bolt
is on the left side and this can only be the case when the lock is locked.
When the lock is unlocked, the further turning of the key so as to turn the
-bit into the horizontal position. necessary to be able to withdraw it, is rendered
impossible, owing to the presence of the pin. In order to be able to set the
lock for another key, all that is required is to withdraw the pin, then, with
the old key, to move the bolt wholly to the right, to withdraw the key, to insert
the new key and by turning the new key to place the bolt into the locked posi-
tion after which the pin is screwed forward:
The advantages of the new locks as compared with the locks of other known
constructions, may be enumerated as follows:-
First The lock offers security not only against the attempts of house-
breakers but also against any dishonesty on the part of the officials or others who
may have access to the safe or room to which the lock is applied.
Second-There are no springs employed in the locks. The tumblers fall
owing to their own weight and a failure in the working of the lock, a spring
breaking or losing its elastic force is absolutely prevented.
Third: The double bit of the key secures correct raising of the tumblers:
the throwing out of position of any of the tumblers owing to a careless and pre-
cipitate handling of the key is thereby obviated while each separate tumbler
can only be actuated by the ward of the key bit corresponding to it.
Fourth In order to force the lock with a false key it would be necessary to
bend or break the teeth of the fixed projection to meet which danger the said.
projection is made of steel and in suitable strength rendering an attempt at
forcing it almost impossible.
Fifth The re-setting of the lock for the use of another key is effected in
the simplest possible manner.
Dated this 11th of t
1.
1000
BOULT, WADE & KILBURN,
Agents for the Applicant.

page_text: COMPLETE SPECIFICATION.
Improvements in Locks for Fire-proof Safes, Safe Deposits, and the
like.
I, JACOBUS LIPS (Bernarduszoon), of Dordrecht, in the Kingdom of Holland,
Manufacturer, do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement;
The present invention relates to a double safety lock for fire-proof safes, safe
deposits and the like. The new lock is of that class of locks known as com-
bination locks, but offers however a greater security against theft than the usual
form of combination lock.
The new lock is also constructed as a double lock .c. one in which two keys
are necessary to open it.
These double locks are particularly designed for employment in banks or safe
deposits or under similar circumstances.
One of the keys remains in the possession of the banker the other key being
delivered to the tenant or owner of the deposit safe. The arrangement and
working of this kind of lock is as follows:
The banker locks the safe and withdraws his key; then the tenant turns his
key, thereby moving a second bolt so as to press against or come into the path
of the first, which is the locking bolt proper moving at the same time a cover
plate, in such a manner that the key hole intended for the banker's key becomes
covered in such a manner that the lock is for the time being rendered absolutely
inaccessible to the key of the banker. The banker cannot therefore again unlock
his lock until the tenant by his key has replaced the cover plate in its original
position and removed the second bolt. The great disadvantage of this kind of
lock is that the lock of the tenant must always be locked and unlocked by one
and the same key.
The public cannot therefore have an absolute confidence in these locks. For
if a tenant succeeds in having a duplicate of his key made for his use, the safe
remains accessible to him even after he has relinquished the tenancy of the same,
and the safe is let to another person.
Then again the attendants have the opportunity of having a duplicate key
made. In short the security against theft is not absolute.
The object of the present invention is to construct an adjustable double safety
lock for safes and the like, in which this drawback is remedied and which there-
fore offers an absolute security against theft.
This result is obtained by so arranging the lock of the tenant that it is
capable of being locked by a number of keys, but unlocked only with the key
with which it had been locked last. The tenant chooses one of a number of
keys, all of which belong to the lock in question, and with this key he locks his
part of the lock. The bank officials do not know the key which he has chosen
i.e. they do not know its shape, and he is therefore protected against any dis-
honest intentions on the part of the officials or of the previous tenant. A lock
according to the present invention is represented in the accompanying drawings.
Figures 1 to 8 show the interior of the lock and the various positions of the
several parts,
Figure 9 is a front view,
Figure 10 a section on line Y. V of hours 2

page_text: Figure 13 a view of the key with which the banker can close his part of the
lock.
Figures 6 and 7 represent the interior of the lock casing a after the loose
parts have been removed with the exception of the two bolts 6 and 6.
In Figure 6 the lock is represented as locked and in Figure 7 as unlocked,
the latter figure representing the key d of the banker and the key e of the
tenant as being in operation.
Both the boits that of the banker's lock and c that of the tenant's lock can
only be moved longitudinally or horizontally and not vertically.
The left bolt is guided in the left side of the lock casing a and also by a
pin f projecting from the back of the lock casing; the other bolt is guided
by means of longitudinal slots therein by pins g h and on projections or guides o
and all secured to and projecting from the back of the lock casing. The left
hand part of the lock i.e. the side which is accessible to the banker's key is pre-
ferably of the kind known as a tumbler lock. The tumblers of which there
are five in the case illustrated, all turn on a fixed pivot f (Figure 5) and are
formed and placed in position in such a manner that a pin projecting from
the main bolt can pass through differently arranged slots in the several
tumblers (Figure 5).
This principle is also employed in the right side of the lock, but here it is
employed in a peculiar manner. Here two kinds of tumblers or slides are used,
each consisting of a number, in. this case 5, of plates which are exactly similar
to each other.
The slides m (Figures 3, and 5) are, say, square and can only be moved in
a vertical direction when operated by a key such as e being guided by pins g
and h engaging in slots in said tumblers and being also guided by the projec-
tion o secured to the back of the lock casing.
The slides m are embraced on the upper and bottom edges by intermediate
- angular slides of which the upper arms are longer than the lower arms...
The slides m can be moved vertically and guided by slots therein, on pins p
and p secured to the bolt the slides being thus forced to participate in the
reciprocating movement of the bolt c, while they will participate in the move-
ment of the slides m only when the latter are raised to a certain height by
means of the tenant's key.
The slides n are provided on the left with a set of teeth adapted to engage a
corresponding set of teeth on a fixed projection or plate secured to the lock
and casing.
When after the tenant has locked the safe and the bolt and slides are moved
forward (Figure 3) the slide teeth interlock with the fixed teeth whereby the
slides are held in the position into which they had been brought by means of
the tenant's key and of the slides m.
The latter slides m at the same time owing to the moving forward of the
bolt and angular slides become free of the short lower arms or projections of
the slides and drop down behind them occupying the position represented in
Figure 3.
The guide pin at the right of the lock is formed to serve as a centre of rota-
tion for a cover plate 9 (Figures 1 and 2) for the banker's key hole. This cover
plate is provided with an oblique slot which is placed over the upper pin p
of the rear bolt e and for this purpose the pin has obliquely shaped sides.
When the rear bolt c is moved towards the left, i.e. when the tenant locks his
lock, the free end of this cover plate is moved downwards and turned into the
position as represented in Figure 1, the plate turning around its pivot h owing
to the movement of the pin p engaging its oblique slot r.
In this position the key holes (Figure 9) is obstructed by the cover 9 thus
rendering it inaccessible to the key of the banker.
The slot is so shaped that the pin p is held when the lock is unlocked, as
represented in Figure 2. Owing to this arrangement a displacement of the

page_text: bolt cannot be produced during removal of the safe or in consequence of care-
less handling.
The lock casing a is closed by a front plate u (Figures 9, 10 and 11) which
is somewhat sunk into the casing and secured to it by screws Fig. 9 the plate
being also provided with the key-holes s and t.
The lock is screwed against the door from the inner side, the door also being
provided with openings for the keys.
From the above description it will be clear that the tumblers or slides are not
actuated by springs, as in ordinary locks. Their movements are regulated and
effected by a key with double bits the two bits being so cut that the recesses of
the one correspond to the projections of the other.
This arrangement offers a great advantage that the several slides cannot be
raised too high when the key is carelessly handled, thereby being placed in a
wrong position.
The absence of springs ensures a greater durability and reliability than is the
case when springs are used, since springs are liable to fracture or break.
Figure 13 represents the key of the banker adapted for the arrangement of
lock described.
The bit is made with seven cuts, the five central ones of which are intended
to raise the tumblers j. The two bits pass freely through a corresponding open-
ing in the cover plate and have no effect on the movement of this plate. A
projection at the outer end of the key i.e. the projection, which, when in use
is farthest from the key opening, extends only on one side and is one by means
of which the bolt is operated and moved.
Figure 12 represents one of the many keys made for use in connection with
the tenant's lock. In the latter also five slides are provided.
Figure 10 shows clearly how each of the slides may be raised to a certain height
depending on the several cuts or wards of the key bit, but always to such a
height that when the slides occupy the position represented in Figure 3 their
teeth properly interlock with those of the fixed projections i.
The various heights at which the five slides can be set represent a great
number of possible combinations for five slides, and there may be as many keys
to the tenant's lock as the number of possible combinations. From this set of
keys the tenant may choose one, while the others are reserved.
In the key represented in Figure 12 the five central projections are intended
for raising the slides m and n.
Both bits of the key pass freely through an opening provided for that purpose
in the cover plate ; while the outer projection y e. the one which when the
key is in position is farthest from the key hole operates the bolte (Fig. 7).
This projection y is present in all the keys of the set, but only on one side of
the key. The operation when using the lock is as follows:
Assume that the position of the lock is such as represented in Figure 8. in
which the cover plate is not shown, and also as represented in Figure 7, in
which the slides m and are absent.
The lock is open, the square slides m and the intermediate slides embracing
the latter, are suspended on the pins ghp and on the projection o, while the
covering plate occupies the position represented in Figure 2, thus permitting
the banker's key to be placed in the key-hole Figure 9.
The banker employs his key d and after having turned it round withdraws it,
thereby locking the safe.
The tenant having chosen his key e out of the set inserts it with its top pro-
jection y towards the right, in its key-hole t.
On turning the key e round the following takes place:-
The square slides m and hence also the slides n are raiseil, each slide to a
height corresponding with one of the recesses of the key bit.
By turning the key further in the same direction. the bolt c is moved towards
the left by the top projection y of the key until it presses against the main

page_text: bolt b. Owing to the pins 2 being fixed to the rear bolt the slides n partici-
pate in the movement of the bolt.
These slides n slide along the slides m each one keeping at the same height
as its corresponding slide m. In Figure 4 is represented the position of the
slides when the key comes into a perpendicular position. On fully turning the
key still further, the teeth of the slides n interlock with the teeth of the pro-
jection i.
When the key is turned fully round the position is as represented in Figure 3.
The teeth of the projections hold the several slides in position, and the length
of the lower arms of these slides n which normally lie upon and support the
slides m being so calculated that in this position the slides m are no longer
supported by the corresponding lower arms of the slides n the slides m there-
fore fall and occupy their original position as represented in Figure 3.
In this position the slides n are locked between the fixed projection and the
slides m, the latter not being movable in a lateral direction. The rear bolt c
which is connected by means of the pins with the slides thereby also
becomes locked, owing to which the main bolt b cannot be moved backwards.
The cover plate has, during this time been placed as represented in Figure 1,
owing to the movement of its operating pin p, moving with the rear bolt e so
as to obstruct the key-holes in such a manner as to render it inaccessible to
the key of the banker.
But even if the latter were able to remove the cover plate 7 he still would be
unable to open the lock since the bolt is held in fixed position by the bolt c.
In order to be able to unlock the lock it is absolutely necessary that the slides m
should be raised so that each of these slides m should correspond, as regards
height, with the adjoining slides n. Only when this is done can the belt e be
withdrawn for these slides n move with this bolte and to do this the upper and
lower arms of these slides must slide over the slides m which is possible only
when the heights of each two adjoining sets of slides m and absolutely
correspond.
This condition, however, can only be secured by means of the key with which
the lock had been last locked, for the several varying heights of the slides n had
been obtained by means of this key and fixed in that position by the interlock-
ing teeth.
Any attempt to open the lock with another key must fail for there will always
be one or other of the slides m of a height which does not correspond to that
of the corresponding slides, thereby rendering a displacement of the slides n,
and hence of the rear bolt e connected with them impossible.
The lock is also preferably provided with another device which renders it
impossible to withdraw the key e as long as the lock is unlocked. The tenant
is therefore obliged to lock his lock before he can withdraw his key. This
device consists of a small screw pine at the right side of the key pin (Figures 6
and 10).
The pin is provided with an enlargement in the interior of the lock which
prevents it being turned out of its place. When the screw is unscrewed this
enlargement is withdrawn into a corresponding recess in the back of the casing
in which position no obstruction is offered to the bit y of the tenant's key.
When the key is inserted it is turned round while the safe is open.
The projection y of the key bit is then on the left side. The screw is then
screwed so as to occupy the position represented in Figure 10 so that the end
of the screw is in the plane of the projection y of the key bit.
Owing to this the key can now be turned so as to occupy a horizontal position
and withdrawn, while the projection y and hence the bolt is on the left side
as represented in Figure 6, and this can only be the case when the lock is locked.
In Figure 7 the position of the key is indicated when the lock is unlocked
from which it is clear that the further turning of the key so as to turn the bit
into the horizontal position, necessary to be able to withdraw it is rendered

page_text: impossible, owing to the presence of the pin it. In order to be able to set the
lock for another key, all that is required is to withdraw the pin, then with the
old key to move the bolt c wholly to the right, to withdraw the key, to insert
the new key and by turning the new key place the bolt into the locked position
after which the pin is screwed forward.
Some of the advantages of these locks, as compared with the locks of other
known constructions, may be stated as follows:-
First The lock offers security not only against the attempts of house-
breakers but also against any dishonesty on the part of officials or others who
may have access to the safe or room to which the lock is applied.
Second-There are no springs employed in the locks. The slides fall owing
to their own weight and a failure in the working of the lock, owing to a spring
breaking or losing its clastic force, is absolutely prevented.
Third: The double bit of the key secures correct raising of the slides the
throwing out of position of any of the slides owing to a careless and precipitate
handling of the key is thereby obviated, while each separate slide can only be
actuated by the ward of the key bit corresponding to it.
Fourth In order to force the lock with a false key it would be necessary
to bend or break the teeth of the fixed projection to meet which danger the
said projection is made of steel and of suitable strength, rendering a successful
attempt at forcing it almost impossible.
Fifth The re-setting of the lock for the use of another key is effected in
the simplest possible manner.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is:
1. A variable double safety lock provided with a main locking device adapted
to be operated by one key and a secondary locking device adapted to be operated
by a second key, the secondary locking device comprising a series of primary
slide plates adapted to be moved only in say a vertical direction by one of the
keys and openings in the body of the primary slide plates to receive a double
bitted key and to prevent undue movement of said slide plates, a corresponding
series of slide plates intermediate the primary slide plates and the main locking
device, said intermediate slide plates being carried on pins projecting from the
bolt plate, and having top and bottom extensions engaging the top and bottom
edges of the primary slide plates, and having teeth or recesses adapted to engage
with fixed teeth on the lock casing, and pins on the casing and bolt plate
engaging in slots in the slides to guide them in their movements, substantially
as described.
2. In a double safety lock of the kind described a stop pin as adjustable
from the back of the lock in such a manner that when screwed forwards,. it
stands in the path of that part of the key-bit which operates the locking bolt.
thereby preventing the key from being turned through a complete turn, and of
being withdrawn from the key-hole after unlocking the lock, while the key can
freely pass over the stop pin when the latter is screwed back, substantially as
and for the purpose described.
3. In a double safety lock of the kind described a key-hole obturating plate
as q pivotted on the casing and provided with an oblique slot in which a stud
fixed on the bolt plate engages, the obturating plate swinging about its pivot
when the secondary lock is locked thereby obturating the key-hole of the main
lock substantially as described.
4. In a double safety lock of the kind described movable slide plates such as m
provided with apertures for the receipt of a double bitted key substantially as
and for the purpose described.
5. In combination with a double safety locking device of the kind described
a double bitted key such as d or e substantially as and for the purpose described.

page_text: 6. A variable double safety locking device comprising a bolt plate such as
carrying a series of tumblers such as j, a series of slides such as m, a correspond-
ing series of slides, such as n, having teeth or recesses on their edges to engage
fixed teeth such as and a pivotted key-hole cover plate such as 7 adapted to
be raised and lowered by the operation of the key of the secondary locking
device.
7. The complete variable double safety locking device substantially as described
or illustrated in Figures 1 to 11 of the accompanying drawings.
Dated this 14th day of June 1900.
BOULT, WADE & KILBURN,
Agents for the Applicant.