IMPROVEMENTS IN THE CONSTRUCTION OF LOCKS AND KEYS
Year: 1854

page_text: LETTERS PATENT to Richard Larkin, Lock Maker, of 2, St. John's Villas,
Highbury, in the County of Middlesex, for the Invention of "IMPROVE-
T
"
PROVISIONAL SPECIFICATION left by the said Richard Larkin at the
Office of the Commissioners of Patents, with his Petition, on the
12th December 1854.
I, RICHARD LARKIN, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN THE CONSTRUCTION OF LOCKS AND KEYS" to be as follows,
namely:
Various methods of constructing locks and keys, for the purpose of rendering
such locks secure against the possibility of picking, or of otherwise unlocking
the same without previously obtaining possession of the true key, and also
certain methods of constructing some kinds of the said locks and keys so
that the possessor of any such key may be enabled to vary its form at his
own pleasure, and by the act of locking so arrange and temporarily fix the
interior of the lock to which it belongs, as that no other form or arrangement
of key will unlock it but that by which it was thus for the time being locked.
I propose to make the ordinary tumbler lock secure by the use of a ward
attached to the case of the lock, and extending downwards to a level with the
bottom of the tumblers, so as to screen them from the action of any pick

page_text: working round the key pin; also, by the use of a revolving barrel and curtain,
fitted to and working round the said ward, and closing the key-hole as the
key turns. I also propose to fix a small stud on the outer surface of the
tumbler nearest the key-hole, for the purpose of catching against a cam pro-
jecting from the under side of the revolving curtain aforesaid. The position of
the said cam is so arranged, that whenever the revolving curtain is brought round,
so as to leave the key-hole open, the said cam shall catch against the stud affixed
to the tumbler aforesaid, and thus hold, it firmly down. By this arrangement,
whenever the interior of the lock is so exposed that the positions of the gatings
in the several tumblers might otherwise be ascertained by putting a pressure
on the bolt, and thus causing them to bind against the bolt stump, the entire
force of such pressure is received by the tumbler thus held fast by the cam
on the revolving curtain, as aforesaid, the walls of such tumbler being carried
out beyond all the others, and thus preserving them perfectly free. But I
only claim as new that portion of such arrangement of, the tumbler lock by
which one or more of the tumblers is held fast and made to receive the
force of any pressure given to the stump while the key-hole of such lock
remains open.
I propose to render certain modifications of the barrel lock secure by the
use of a catch movement, to receive or otherwise change the bearing of any
pressure given to the slides of any such lock, for-the purpose of causing them
to bind; and to accomplish this, I propose to construct and arrange the
circular catch plate (within or above, which the barrel turns, and which con-
tains the notches through which the slides work), so that instead of resisting
any pressure that might be given to the slides, for the purpose of causing them
to bind against it, it (the circular catch plate aforesaid) may yield freely to
any such pressure, and by such movement so act upon one end of a small
lever as to force the other end of the said lever into a notch cut in the barrel
itself, thereby fixing the said barrel, and thus effectually preventing any
further pressure being applied to the slides against the said circular catch
plate. I also propose, in some instances, to introduce wards or walls, passing
through or across the upper portion of the aforesaid slides, for the purpose of
preventing access to the interior of the lock.
And I propose to construct the revolving barrel in such a manner as that
the end of it which throws the bolt, shall consist of a separate piece, attached
to the barrel itself by small screws, of strength sufficient for throwing the bolt,
but not sufficient to resist any violent pressure, by which means any application
of violence to force round the barrel would detach it from such piece, and so
prevent the possibility of the bolt being thrown.

page_text: I propose to render certain arrangements of the barrel lock changeable, by
constructing each of the slides before mentioned, upon which the key acts, of
two separate pieces, the one to overlap, and be capable of moving freely on the
other; the purpose of the one piece being to contain the notch, which allows it
to pass round within the circular catch plate, (and the position of which notch
determines the form or special arrangement of the lock); that of the other
piece to be operated on by the key in the act of locking or of unlocking. These
two separate portions of the slides are also so arranged that they may be pressed
and firmly bound together by the action of a small excentric cam connected
with each of them, and working by means of a lever, which is so adjusted as
to turn the cam, and thus bind the two portions of the slides firmly together,
as aforesaid, while the key and barrel are in the act of turning in the lock
for the purpose of locking it; the reverse action taking place, and the two
portions of the slides being again detached from each other, during the act
of unlocking. By this arrangement, the possessor of the key, which is itself
changeable, is enabled to vary at pleasure, by a previous adjustment of the
key, the distances of the notches (by which the slides are able to pass round
within the circular catch plate) from the tops of the said slides, upon which
the key presses, and thus the interior of the lock may be arranged and varied
indefinitely, the various distances of the said notches from the tops of their
respective slides being accurately adjusted and secured, in exact correspond-
ence with the form or arrangement of the key by the act of locking. I
also propose to construct keys for such or similar locks having a hole through
the entire length of each of their shafts, the steps of which keys are formed
by the ends of moveable pieces, which slide freely in corresponding grooves
cut in the shaft of any such key parallel to its axis, the said moveable pieces
being fixed firmly in any given positions by the action of a screw nut which
encircles them.
I propose to construct certain changeable tumbler locks by means of a
similar arrangement of primary and complementary tumblers to that already
in use, the contiguous ends or portions of which tumblers are made to fit the
one into the other, so that each pair of such tumblers may be combined and
adjusted according to the form of the key, as if they were one tumbler. But
I propose to apply, instead of a clamp plate, or an arrangement of teeth and
notches as has been heretofore used or proposed, an excentric roller, which
by the movement of the bolt, in the act of its being thrown, is made to press
upon the complementary slides, and thus bind them firmly together in the
positions imparted to them by any given arrangement of the key, the action of
throwing the bolt also carrying away the primary slides, upon which the key

page_text: directly acts, and thus detaching them from their complementary slides, which
are meanwhile retained firmly in their positions by the excentric roller, as
aforesaid. When the key is then withdrawn from the lock, the primary slides
immediately resume, as in other changeable locks, one uniform level, and the
bolt can then only be withdrawn, or the lock unlocked, by again restoring
the said primary slides to the positions which had been imparted to them
by the arrangement of the key, as aforesaid, so that they may again fit in and
unite themselves with their complementary slides, the said complementary
slides in this my improved arrangement being, by the act of unlocking, again
liberated from the pressure of the excentric roller already described. I also
propose to convey the key (which consists of an arrangement of steps lides,
held in a small rectangular frame, and having an adjusting action in the same
plane, and parallel to each other,) into the lock by means of a carriage which
moves in a rectangular passage through which the key passes, and which
carriage so fits into the said rectangular passage as never to leave an open
thoroughfare into the interior of the lock. The key being thus conveyed to
its place by means of the said carriage, the bolt is then either thrown or with-
drawn, and the tumblers moved towards and against the steps of the key by
means of a handle, which turns a shaft, passing through the lock and acting
upon the said bolt and tumblers.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Richard Larkin in the Great Seal Patent Office on the
11th June 1855.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, RICHARD
LARKIN, Lock Maker, of 2, St. John's Villas, Highbury, in the County of
Middlesex, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twelfth day of December, in the year of our
Lord One thousand eight hundred and fifty-four, in the eighteenth year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said Richard Larkin, Her special licence that I, the said Richard
Larkin, my executors, administrators, and assigns, or such others as I, the
said Richard Larkin, my executors, administrators, and assigns, should at any
time agree with, and no others, from time to time and at all times thereafter
during the term therein expressed, should and lawfully might make, use,

page_text: exercise, and vend, within the United Kingdom of Great Britain and Ireland,
the Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
THE CONSTRUCTION OF LOCKS AND KEYS," upon the condition (amongst others) that
I, the said Richard Larkin, by an instrument in writing under my hand and
seal, should particularly describe and ascertain the nature of the said Inven-
tion, and in what manner the same was to be performed, and cause the same
to be filed in the Great Seal Patent Office within six calendar months next
and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Richard Larkin, do hereby declare the
nature of my said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement:-
My improvements in the construction of locks and keys consist in various
methods of constructing them, the said locks and keys, for the purpose of
rendering such locks secure against the possibility of picking or of otherwise
unlocking the same without previously obtaining possession of the true key;
and also certain methods of constructing some kinds of the said locks and
keys, so that the possessor of any such key may be enabled to vary its form
at his own pleasure, and by the act of locking so arrange and temporarily fix
the interior of the lock to which it belongs, as that no other form or arrange-
ment of key will unlock it but that by which it was thus for the time being
locked.
Figure 1, Sheet 1, of the Drawings accompanying this Specification, is a
plan of a lock indefinitely changeable, with a part of the circular case A cut
off, for the purpose of showing the contained works. Figure 2 is an elevation
of the same, with the outer case of the lock, the circular case A, and the bolt
B, in section. A, Figures 1 and 2, is the circular case aforesaid; B, the
bolt; C, a pin, working in an excentric slot cut in the bolt, for the purpose of
throwing the same; d, a circular plate, to which the pin C is fixed, and
which is attached to the barrel e by small screws; f, the drill pin on which the
key turns; g, a ring, to receive the pressure of the main spring h, shown in
dotted lines; i, i, i, i, i, i, six steel slides, to be pressed down by the key any given
distances in the act of locking; detached views of which slides are given,
Figures 3, 4, and 5. k, k, k, k, k, k, pieces of brass, against which the steel
slides move freely, and are held by the pins 7, passing through the slots m;
n, n, n, n, m, n, stiff springs of hammered brass, one end of each resting on
one of the pieces k, the middle bearing against its pin l, and the other end
resting on a small excentric cam o, which is so adjusted that a partial revo-
lution of the same produces a pressure on the spring n, causing it to bind

page_text: strongly at the three points aforesaid, namely, at the middle and at each end,
by which means each steel slide i is firmly held and bound to its adjoining
piece ; p, a circular plate or ring, containing notches through which the
pieces k, accompanied by the steel slides i, may pass freely after the bolt of
the lock is thrown; the pieces i and k, however, being conjointly pressed
upwards towards the key-hole by the action of the main spring h and of the
secondary springs 7, 9, 9, 7, 7, 9. In each of the pieces k also a similar notch
is cut, through which the circular catch plate p passes freely during the action
of throwing the bolt. In order that the bolt may be withdrawn, it will be
necessary, by the pressure of the key upon the ends of the slides i, to bring
all the notches in the pieces k into a line with the circular catch plate p, so
that the barrel e, to which is connected the pin c, may be able to revolve round
its axis. It may now be seen that the distance of the notch in each piece k,
from the top of its adjoining slide i, upon which the key presses, may be varied
at pleasure by loosening them and again binding them firmly together by the
action of the cams o, as above described. It is by virtue of this action that
the lock is indefinitely changeable. Supposing the lock to be unlocked, each
of the pieces will in that case be held by its notch on to the circular catch
plate p, so that it cannot be moved either up or down, as shown in the
Drawing; at the same time its adjoining slide i being loosened from it, is
forced up towards the key-hole by the action of the main spring h, and of its
secondary spring q. In this condition the lock may be said to be a blank,
ready to take the form of any arrangement of the key that may be determined
on. The key then being pressed on the ends of the slides i till it reaches its
bearing, will propel each of them down a certain distance, according to the
arrangement chosen, the pieces being meanwhile held stationary by the
circular catch plate p, as aforesaid. The barrel e is then caused to revolve,
carrying with it the six slides i, with their accompanying pieces k, the latter
holding on to and passing round by means of their notches the circular catch
plate p, until the revolution is completed and the bolt thrown. In the mean-
time the levers r, r, r, r, r, r, affixed to the cams 0, 0, 0, 0, 0, 0, are, at the com-
mencement of the revolution of the barrel e, moved by being pressed against the
small rods s, 5, 5, 8, 8, 5, by which action the cams o are firmly tightened against
the springs n, as above described. It will now be evident, that when the
pieces are carried round until they exactly correspond with the notches of
the catch plate p, being thus firmly bound to the slides i, they will, upon the
withdrawal of the key, be forced up conjointly with them towards the key-hole
by the action of the springs h and 9, 7, 9, 1, 2, 9. The action of this portion of
the lock will then, while the slides i and the pieces k are thus bound together,

page_text: be precisely similar to that of the regular Bramah lock. t is a rim, to which
the rods s are affixed; u, a catch, acted upon by a spring, and holding the
rim & stationary, while the rods s, which are affixed to it, are being pressed
against by the levers r, as described; v, a steel arm, attached to and re-
volving with the barrel e, for the purpose of pushing the nib of the catch u
out of the notch in the rim t, and thus allowing the rim t with its rods s
to revolve freely with the barrel. In order that the notches of the circular
catch plate p may correspond exactly with the pieces k when the bolt is
thrown, as before described, there is a small arm w attached to and revolving
with the barrel e, which catches against a stud a on the said catch plate p,
and moves it to the position required. y is a lever working on the fulcrum z,
for the purpose of changing the bearing of any pressure given to the pieces k
against the circular catch plate p, for the sake of causing them to bind. When
the pieces are thus pressed against the sides of the notches in the catch
plate p, the said catch plate, instead of causing the pieces to bind, is itself
forced round, until the upper end of the lever y is pushed out towards its
circumference by the action of the beveled notch a, and conversely, the lower
end of the said lever y is pushed into a similar beveled notch b, cut in the
circular plate d, which circular plate is attached to the barrel e, as before
described. By this movement it will be evident that instead of the pieces k
binding, by the force of the said pressure, against the circular catch plate p,
and thus affording an indication by which the lock might be picked, the
bearing of the pressure is taken up by the notch b in the plate d against
the lower end of the lever y, and thus any pressure so applied would simply
bring the barrel e to a dead stop, and totally prevent any clue to the interior
arrangement of the lock being obtained. In order afterwards to release the
barrel and thus re-adjust the lock, the motion of the barrel has simply to be
reversed, by which movement the beveled side of the notch b, acting against
the lower end of the lever y, forces it back to its original position; at the
same time, the pieces k being in the notches of the catch plate p, carry it also
back to its place. Should, however, a still greater pressure be applied for the
purpose of wrenching the barrel violently round, and so forcing the lock by
breaking through its points of resistance, any such attempt would be com-
pletely defeated by the circular plate d, to which is fixed the pin C which acts
upon the bolt, being attached to the barrel e by screws of strength sufficient
for throwing the bolt, but not sufficient to resist any such violent pressure;
consequently, as the circular plate & would in any such case be firmly held, by
its notch pressing against the lower end of the lever y, the effect of any such

page_text: violent attempt would be to wrench the barrel e away from the said plate d,
and so effectually preclude the possibility of obtaining access to the bolt. As
a further security, small steel walls c, c, c, c, c, are inserted in the barrel e,
the upper ends of which may be seen in Figure 1; which said walls pass
through a slot in the slides i, shown in Figure 5, and completely close the aper-
tures, which would otherwise be left in the barrel by the slides i, upon their
being pressed down.
Figure 6, Sheet 1, is a side view of an indefinitely changeable key, belong-
ing to the lock herein-before described, bored through the entire length of its
axis; the said key being represented as fixed, ready for use. Figure 7, the
case, for fitting on to the key. Figure 8, a sectional view of the key with
the case fitted on. a, a, a, are slides, the ends of which form the steps of the
key; b, b, b, small springs, pressing firmly against the slides a, and the lower
ends of which fit under the ring c; d, a ring or nut, working on the screw e,
the thread of which is cut upon the walls of the shaft of the key. When
the nut d is traversed down to the ring c, the upper ends of the springs bare
released, and their pressure being thus removed from the slides a, the said
slides may be shifted indefinitely at pleasure the entire length of the groove in
which they lie. In order again to fasten the said slides, the nut d is simply
re-traversed as far as the stop ring e. f, Figures 7 and 8, is a pin, fixed to the
bottom of the case, and terminating in a spring catch g. When the case is
fitted on to the key, the pin f passes through the bore of the said key, and
becomes fastened by the action of the spring catch g.
Figure 9 shows the application of the receding catch plate, for changing the
bearing of any pressure given to the slides, in order to cause them to bind
to the ordinary Bramah or barrel lock. a, Figure 9, is the lower end of the
barrel, showing the pin which works in the slot of the bolt for the purpose of
throwing it; b, the receding catch plate, containing the notches through which
the slides work; c, Figure 10, a secondary rim, placed above the said catch
plate, fastened to the case of the lock, and upon which the barrel works, thus
leaving the catch plate free; d, a lever, working freely on the fulcrum e, at
the end of which is an angular slot f, and a tooth, which catches in the notch
g, cut in the barrel a.
When the slides contained in the barrel a are pressed
in either direction against the sides of the notches in the catch plate b, the said
catch plate, instead of causing them to bind, recedes, until the stud working in
the slot f, which is attached to it, traverses towards one end of the said slot,
and so presses the tooth of the lever d into the notch g, thus fixing the barrel,
and preventing the possibility of the slides being made to bind against the

page_text: sides of the notches in the said catch plate. In order again to release the
barrel, its motion has simply to be reversed, by which means one of the inclined
planes at the bottom of the notch 7, acting against the tooth at the end of the
lever d, pushes it out of the said notches into its original position.
Figure 11 is an application of the same principle to any modification of the
barrel lock, in which the action of the slides, instead of being parallel to the
axis of the barrel, radiates from it at a given angle. The movement in this
case is precisely similar to that above described, with the exception that no
secondary rim is required.
Figure 1, Sheet II., is a plan of another arrangement of a lock indefinitely
changeable, having one side of the case removed to show the contained works.
Figures 2 and 3 are sections of the same; Figure 4 is an indefinitely change-
able key belonging to the said lock; Figure 5, a side view of the same.
a, a, a, a, a, a, a series of slides, having a slot in each, shown in dotted lines,
Figure 5, the ends of which slides form the steps of the key, which are thus
variable at pleasure; b, a case in which the slides a work; c, a pin, passing
through the slots in the slides a, one end of which pin is fastened firmly into
one side of the case b, the other end having a cam d, working against a
corresponding cam in the opposite side e of the case b; the said opposite
side e being made so as to turn upon the pin c, for the purpose of binding
together or loosening the slides a, by the action of the aforesaid cams against
each other.
Figures 6, another arrangement for binding together or loosening the slides
a. f is a movable side or lever attached to the case b, working on a fulcrum g,
for the purpose of pressing against and thus binding together the slides a;
h is an additional lever, working on the fulcrum i, and affording an increased
pressure by bearing against the upper end of the aforesaid lever f. Figure 7,
an outer case or sheath for protecting the key while not in use.
a, Figures 1, 2, and 3, is the outer case of the lock; b, the bolt; c, a shaft,
for the purpose of throwing the bolt, passing through to the exterior of the
lock, and to which a handle may be affixed; d, a tongue piece, shown in dotted
lines, Figure 1, projecting from the said shaft and acting against the sides of
the notch e cut in the bolt, as also shewn in dotted lines; ff.ff.f,f, a series
of slides, for the purpose of preventing the bolt being thrown until the proper
key is inserted; 9, 9, 9, 9, 9, 9, a series of corresponding and complementary
slides, against which the slides f would abut should any attempt be made to
throw the bolt before arranging the said slides f, so that the open slots h cut
in them may exactly correspond with the complementary tail pieces i projecting

page_text: from the slides g; k, k, two studs, fixed to the bolt and holding the slides f to
their places, but allowing them to be moved at right angles to the motion of
the bolt; 1, 1, 1, two similar studs and a wall, fixed to the case a, and holding in
like manner the slides g; m, an excentric roller, for the purpose of binding the
complementary slides g firmly together while the bolt is thrown; n, an arm,
projecting from the end of the bolt and moving with it, acting upon the lever
o, shown in dotted lines, Figure 2, fixed to one end of the said roller m, and
thus causing it alternately to bind and to liberate the complementary slides g,
according as the bolt is either thrown or withdrawn; p, a carriage, for the
purpose of conveying the key through the rectangular passage 9 to its place in
the interior of the lock, and having a stud working in a groove, against the end
of which it abuts, to prevent its being entirely withdrawn. In order to insert
the key, the said carriage must first be sufficiently withdrawn from its rect-
angular passage, as shown in Figure 8; the key is then placed in its chamber
r, when the carriage is again pushed home, until the slides or steps of the key
are brought directly over the slides f of the lock, as shown, Figure 3; s, a
lever, one arm of which is divided into a series of springs, shown in Figure 3;
t, a cam, projecting from the handle shaft c, and acting on the other arm of
the lever s, and so causing the said springs to press the slides f upwards
against the steps of the key; the said cam t being brought to bear upon the
lever s before the tongue piece d, above described, reaches the side of the notch
e, and thus before the bolt can be moved. u, a lever, one arm of which catches
into the bolt b, the other working in a slot which is cut in the extended
portion of an extra slide v placed below the slides f, already described. The
purpose of this lever is to prevent any collision between the slides f and the
complementary slides g, should the handle shaft c be turned while the key is
out of the lock. When the shaft c is thus turned, causing the spring lever s
to press the slides f upwards, the extra slide v, being in like manner carried
with them, traverses the arm of the lever u working in its slot, and so causes
the other arm of the said lever to catch firmly into the bolt, thereby pre-
venting the possibility of moving it, and thus also of forcing the two said sets
of slides into collision. Should the key, however, be in its place when the
handle shaft c is thus turned, the side of the case b, Figure 4, shown also in
Figure 3, will form a stop, against which the extra slide v will impinge; in
which case the lever u will remain in its position, as shown in Figure 1, leaving
the bolt with its accompanying slides f free. In order to prevent access to the
interior of the lock, the carriage p with its rectangular passage q, above par-
tially described, are so constructed, that before the key chamber of the said

page_text: carriage is brought to the interior aperture of the said rectangular passage, its
exterior aperture is completely closed by the solid portion of the said carriage,
as shown in dotted lines, Figure 8, by which arrangement it will be evident
that the key-hole of the lock is kept constantly and completely closed, even
while the key itself is being inserted. a is a steel plate, moving on the studs y,
for the purpose of holding the carriage p firmly and accurately in its place
during the acts of locking and unlocking; which said plate, passing completely
across the chamber of the said carriage, forms an effectual security against any
application of violence; is a second tongue piece, projecting from the handle
shaft c, working in an internal cam cut in the plate x, which is so formed
that the said plate x shall be moved into the position above described, as
shown in Figure 1, before the bolt can begin to be acted upon by the tongue
piece d.
Figure 9 is a front view of an unchangeable tumbler block; Figure 10, a
section of the same. a is the case of the lock; b, the bolt; c, c, c, c, the
tumblers; d, the drill pin; e, a ward attached to the case of the lock, and
extending downwards to a level with the bottom of the tumblers, so as to
screen them from the action of a pick working round the drill pin; f, a
revolving curtain and barrel, fitted to and working round the said ward e,
and closing the key-hole as the key turns; g, a stump, immovably fixed to
the bolt, to prevent its being thrown or withdrawn until the gatings h of the
tumblers are all raised to its level; i, a stud, attached to the upper tumbler c,
and catching against the cam k on the under side of the revolving curtain f.
It will be seen, by a reference to Figure 9, that whenever the key-hole is open,
the upper tumbler c is held firmly down by the action of the stud i and cam k
aforesaid. In order to prevent the possibility of the positions of the gatings
h, h, h, h, of the tumblers c being ascertained, by causing the stump g to bind
against the intermediate walls, by which the said gatings are formed, the sides
of the intermediate wall of the upper tumbler are extended beyond those of
the lower tumblers, as shown in Figure 11; by which arrangement, the entire
pressure of the stump g is received by the intermediate wall of the upper
tumbler c, preserving all the under tumblers perfectly free. The same object
may effected by extending a portion of the sides of the stump g, so as to
cause it to bind similarly against the upper tumbler c, as shown in Figure 12.
It will now be evident, that so long as the key-hole is open, it will be impos-
sible to cause the stump g to bind against the under tumblers c, and thus to
reveal the positions of their several gatings. It is only when the key-hole is
closed, by the revolution of the curtain f, which thus releases the stud i from

page_text: the hold of the cam k, that the upper tumbler c can be raised, or the bolt
thrown. Figure 13 is the key, in which is a notch cut close to the barrel, so
that it may pass the ward e, already described.
Having now described the nature and object of my improvements in the con-
struction of locks and keys, and in what manner the said improvements are to
be and may be carried into effect, I claim, in conclusion, as my Invention,-
1st, the combination in any suitable arrangement of the barrel lock of
secondary or complementary slides or stop pieces with the slides upon which
the key acts, for the purpose of making such lock changeable.
2nd, the application to any suitable arrangement of the barrel lock of a
catch movement, to receive or otherwise change the bearing of any pressure
given through the key-hole to the movable stop pieces or slides of any such
lock, for the purpose of causing them to bind.
3rd, the application to any such lock of a separate piece for moving the bolt,
so connected with the revolving barrel that any application of undue pressure
to force round the barrel would detach it from such piece, and preclude the
possibility of the said barrel acting on the bolt.
4th, the introduction to any such lock of walls, such as described in this
Specification, passing through the slides upon which the key acts, to prevent
access to the interior of the lock.
5th, the construction of a changeable key for any suitable arrangement of
the barrel lock with step slides, which are either loosened or secured in their
places by the action of a screw nut which encircles them.
6th, the construction of a key having a hole through the entire length of
its shaft or axis.
7th, the construction of a changeable lock, in which the secondary or com-
plementary slides are fixed in the places given to them by the form of the key,
by a binding pressure imparted by the act of locking.
8th, the construction of a changeable lock, in which the key remains
stationary during the acts of locking and unlocking.
9th, the construction of a changeable lock, the slides or tumblers of which,
in their arrangement for the purpose of locking or unlocking, are moved.
towards the steps of the key.
10th, the construction and application of a carriage for conveying the
key through the key-hole into the lock.
11th, the construction of an indefinitely changeable key, the step slides
of which are moved and fixed in one and the same plane and parallel to
each other.

page_text: And, 12th, the construction of a tumbler lock in which the upper tumbler
nearest the key-hole is made to receive the force of any pressure given by the
action of the bolt to the stump while the key-hole remains open, leaving the
rest of the tumblers free.
In witness whereof, I, the said Richard Larkin, have hereunto set my
hand and seal, the Eleventh day of June, in the year of our Lord
One thousand eight hundred and fifty-five.
Witnessed by me,
HENRY LARKIN.
RICHARD LARKIN. (L.S.)