IMPROVEMENTS IN COMBINATION LOCKS
Year: 1868

page_text: LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane,
in the County of Middlesex, Patent Agent, for the Invention of
"IMPROVEMENTS IN COMBINATION LOCKS." -A communication from
abroad by Isaac Wixom Lamb, of Salem, in the County of Wash-
tenaw, and State of Michigan, United States of America.
Sealed the 27th November 1868, and dated the 5th June 1868.
PROVISIONAL SPECIFICATION left by the said Alexander Melville Clark
at the Office of the Commissioners of Patents, with his Petition, on
the 5th June 1868.
I, ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the
County of Middlesex, Patent Agent, do hereby declare the nature of the
said Invention for "IMPROVEMENTS IN COMBINATION LOCKS," to be as
follows:-
This Invention is illustrated in the accompanying Drawings, Figure 1
of which shows a plan of the lock from the back side with the back
of the case removed, the parts being in the position they severally
occupy when they are unlocked; Figure 2 shows the same locked;
Figure 3 is a cross section of the lock showing the manner of attaching
the same to a door; Figure 4 is a plan of the wheels showing by dotted

page_text: lines the relative position of the key slots in each when the notches c
are together; Figure 5 shows the relative position of the notches c
when the key slots are together; Figure 6 shows the method of
numbering the dial; Figure 7 shows a plan of the key ring. Similar
letters of reference indicate corresponding parts in the several Figures of
the Drawing, the improvements being illustrated partly by colored lines.
A, A, A, is the frame or case in which the working parts are con-
tained; B is a bolt having in this case its rear or inner end made
forked to pass on both sides of wheels C. The rear end of bolt B is
only half as thick as tho front end, there being a shoulder at t. B¹ is
-a dog pivoted at p to the main bolt and having a projection 6 on its
rear end. A spring a tends to keep the rear end of the dog B' in
against the wheels C. C represents a series of wheels, six in number
in the present-case. Each wheel C has a notch c on its outer edge,
also a hole m through its centre, a key slot c¹ on the side of the
hole m, and ten small holes o, o, o, through its face. The relative
position of the notch c and the key slot c' is different in every wheel
so that when the notches are together the key slots are not, and vice
versa. Figure 1 shows the notches c of all the wheels together and
the projection 6 of the dog B' in such notches. When the parts are in
the position shown in Figure 1 the bolt B can be thrown out or in
by turning the knob G, Figure 3. But if either of the wheels has its
'notch in a different position from the notches of the other wheels, then
the dog B will be thrown back, as shown in Figure 2, when the
shoulder A¹ on the lock case will keep the bolt forward or locked, as
seen in Figure 2. D is the spindle to one end of which, see Figure 3,
a knob or handle G is attached. A key ring n is held by a nut N
on the rear end of the spindle, such spindle being turned down smaller
to receive it. The key ring and spindle are of the same size or diameter,
both being designed to pass through the holes, m in the wheels C. The
spindle D also carries a pin wheel E, such pin wheel being designed
to slide upon the spindle if required. The slot d in the spindle and
the pin E limit the movement of the pin wheel on the spindle and
also cause such wheel to turn with the spindle. Two pins e, e, are
rivetted into the pin wheel E, the size of such pins being such that they
will pass easily through the holes o, o, of the wheels C. The position
of the key ring and the pin wheel E upon the spindle is shown in
Figure 3, they being such that the extremities of the pins e, e, are on

page_text: a line with the inner end of the key ring n. There is a slot in the
back H of the lock case in which the key n' fits and by which the key
ring is prevented from turning. As the key ring and pin wheel are
both attached to the spindle, it follows that both move out and in
together, and as the pins e, e, enter the holes o, o, of any wheel the
key ring is pushed back out of such wheel and it is free to turn with
the spindle and pin wheel. I design to make the wheels C of sheet
steel about one thirty-second part of an inch thick, and harden them; in
the better class of locks I design to have ten wheels to a lock, although
there are but six in the present case. Every additional wheel multiplies
the number of possible combinations by ten if used only one side out,
and ten wheels give ten thousand million combinations. Each of the
wheels is numbered according to the relative position of its key slot c¹
and notch c. The wheel that has its notch c and key slot c' on the same
side is numbered 1. The wheel whose key slot is three-twentieths of
a circle to the right of its notch c is numbered 2, and so on, the key
slot of each concentric number being three-twentieths of a circle to
the right. Each wheel may be numbered on both sides, as it can be
used either side. In such case I place on one side of each wheel
the simple figure that indicates its number, and on the other side I
place the same figure with a dot over it; it is only necessary however
to number the wheels on one side, and then have one set of numbers
on the dial with a dot over each figure to represent the wheels when
one side out, then have another set of plain figures on the dial to
represent the wheels when the other side out. The different changes
in the combination are made by placing the wheels in the lock in
different order, and as the wheels can be arranged in any order I can
set the wheels in as many different ways as there can be permutations
in six figures. Then as each wheel can go in either side out that
number of permutations must be multiplied by the sixth power of two
to indicate all the possible ways in which the wheels may be arranged.
The permutations on ten figures amount to over three millions, and the
tenth power of two is ten hundred and twenty-four, so that there
are over three thousand million ways in which ten wheels can be put
in the lock. The chance of guessing the number of one of these locks
with ten wheels (each wheel being used both sides out) is found by
raising twenty to the tenth power, which is ten trillions two hundred
and forty billions, and the chance of guessing would be as one to that

page_text: number. Now when the key ring is in all the wheels the notch c
of one wheel is three-twentieths of a circle from that in the wheel
bearing the next consecutive number. It follows therefore that I
must turn one wheel three-twentieths of a circle to bring its notch
even with the notch of the wheel bearing the next number. I therefore
divide the dial K into twenty spaces, and number it in the following
order, namely, beginning at the top with No. 1, I place No. 2 three
spaces from No. 1, and No. 3 I place three spaces from No 2, and No. 4
three spaces, from No. 3, and so on up to ten numbers. Then if the
wheels are turned over it is evident that the consecutive numbers will
be on the other side of figure 1, each number being three spaces from
the number preceding; I therefore number the dial in both directions,
beginning with No. 1, as shown in Figure 6. Now as there are ten
holes in each wheel and as the wheels differ from one another in the
position of the key slots three-twentieths of a circle, it follows that
when a wheel with an even number is placed next to a wheel of an
odd number, then the spaces between the holes o, o, o, of the one wheel
will cover the holes o, o, o, and so on of the other when the key ring
is in the wheels. The object of this arrangement is that when the
knob G is pushed in the pins e, e, can pass through but a single wheel
at a time; that saves care in unlocking, but is not necessary. The
knob G is fastened to the spindle by a light screw g, which is split
'at its screw end g¹ so that if broken off it can be readily removed from
the spindle. A spring F keeps the pin wheel E in the position shown
in Figure 3, yet permits such pin wheel to slide on the spindle when
any great pressure is brought upon the spindle at any time when the
the pins e, e, are out of the wheels C. M represents a part of a door
to which the lock is attached, as shown in Figure 3. The spindle has
a shoulder 'd formed on its outer end which fits in a recess bored in
the safe door, as shown in Figure 3. A collar d¹ is also screwed on
or otherwise securely fastened to the spindle within the door. The
shoulder d and collar d' prevent the spindle from being driven in or
drawn out by a person on the outside of the safe.
The manner of unlocking this lock is as follows:-First, the handle
or knob G is turned round and drawn out until it will not come
out diy further. As it is turned the key slots of the wheels one by
one come under the key n', and such key enters the slots, and the

page_text: Now
pins e, e, draw out of each wheel as the key ring enters the same.
suppose that the wheels are in the lock in the order 1, 2, 3, 4, 5, 6,
they being the side out that would correspond with the dotted numbers..
After the knob is drawn out as far as it can come the key ring will
be througli every wheel. You turn the knob until the index r is over
figure of the dial, then push in the knob, and the pins e, e, will
enter wheel No.. 1, turn on and the wheel No. 1 turns also. When
the index is over figure 2. the notches c of the first and second
wheels will be together;. push in again, and the pins e, e, enter the
wheel No. 2, and the key ring passes out of the same. Now turn to
figure 3. on the dial. and the two first wheels are with the third,
push in the knob and take hold of wheel No. 3;. turn to Figure 4 on
the dial and push in and take wheel No. 4;, turn to figure 5 and
tako wheel No.. 5; turn on to figure 6 and take wheel No. 6. If
you have followed the directions you. will, now have the notches c of
all the wheels together and the pins e, e,. will be in all the wheels.
Now turn. the knob around to the left until the projection 6 of the
bolt B' springs into the notches c of the wheels, when the door is un-
locked. To lock the same you turn the knob around to the right until
the bolt B is thrown forward, continue to turn and the dog B¹ is forced
out into the position shown in Figure 2, turn on and draw out the knob,
and the key ring will enter the wheels one by one and the combination
is secure.. When these locks are used in safes the bolt B may be used
only as a secondary bolt to slide out behind the main bolt or bolts of
the safe. The pin wheel E. on an ordinary door lock could be rigidly
secured to the spindle D, and then as it would be within the case of the
lock the shoulder d or the collar d₁ would not be needed, neither
would the spring F be of any use, because the lock would be stronger
than a wooden door and would not therefore need protection..

page_text: WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Fifth day of June, in the year of
our Lord One thousand eight hundred and sixty-eight, in the thirty-
first year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Alexander Melville Clark, Her special
licence that I, the said Alexander Melville Clark, my executors, adminis-
trators, and assigns, or such others as I, the said Alexander Melville
Clark, 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,
exercise, and vend, within the United Kingdom of Great Britain and
Ireland, the Channel Islands, and Isle of Man, an Invention for "Im-
PROVEMENTS IN COMBINATION LOCKS," a communication to me from abroad by
Isaac Wixom Lamb, of Salem, in the County of Washtenaw and State of
Michigan, United States of America, upon the condition (amongst others)
that I, the said Alexander Melville Clark, my executors or adminis-
trators, by an instrument in writing under my, or their, or one of
their hands and seals, should particularly describe and ascertain the
nature of the said Invention, 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 Alexander Melville Clark, do hereby
declare the nature of the said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement, reference being had to the Sheet of Drawings
hereunto annexed, and to the letters and figures marked thereon (that
is to say):
Figure 1 of the accompanying Drawing is a plan of a lock seen from
the back side with the back of the case removed, the parts being in
the position they severally occupy when they are unlocked; Figure 2
shows the same locked; Figure 3 is a cross section of the lock, showing
the manner of attaching the same to a door; Figure 4 is a plan of the
wheels, showing by dotted lines the relative positions of the key slots
in each when the notches c are together; Figure 5 shows the relative
positions of the outer notches c when the key slots are together;
Figure 6 shows the method of numbering the dial, while Figure 7

page_text: shows a plan of the key ring. Similar letters of reference indicate
corresponding parts in the several Figures of the Drawing. The lock,
spindle bolt, and appendages, as also the wheels or discs, are drawn in
red and blue colors.
A, A, A, is the frame or case in which the working parts are
contained; B is a bolt having in this case its rear or inner end made
forked to pass on both sides of wheels C. The rear end of bolt B is
made only half as thick as the front end, there being a shoulder at t. B¹
is a dog pivotted at p to the main bolt, and having a projection b on its
rear end. A spring a tends to keep the rear end of the dog B' in against
the wheels C. C represents a series of wheels or discs, six in number,
in the present case.
Each wheel C has a notch c on its outer edge, also a
hole m through its centre, a key slot c¹ on the side of the hole m, and ten
small holes o, o, o, through its face. The relative position of the
notch c and the key slot c¹ is different in every wheel, so that when the
notches are together the key slots are not, and vice versa. Figure 1
shows the notches c of all the wheels coinciding together, and the
projection of dog B' in such notches. When the parts are in the
position shown in Figure 1 the bolt B can be thrown out or in by
turning the knob G. But if either of the wheels has its notch in a
different position from the notches of the other wheels then the dog B¹
will be thrown back, as in Figure 2, when the shoulder A' on the
lock case will keep the bolt forward or "locked," as seen in Figure 2.
D is the spindle, to one end of which (see Figure 3) a knob or handle G
is attached. A key ring n is held by a nut N on the rear end of the
spindle, such spindle being turned down smaller to receive it. The key
ring and spindle are of the same size or diameter, both being designed
to pass through the holes m in the wheels C. The spindle D also carries
a pin wheel E, such pin wheel being designed to slide upon the spindle
if required. The slot d in the spindle, and the pin e¹ limit the move-
ment of the pin wheel on the spindle, and also cause such wheel to turn
with the spindle. Two pins e, e, are rivetted into the pin wheel E, the
size of such pins being such that they will pass easily through the
holes o, o, of the wheels C. The position of the key ring n and the
pin wheel E upon the spindle is shown in Figure 3, they being such that
the extremities of the pins e, e, are in a line with the inner end of the
key ring n. There is a slot in the back H of the lock case in which

page_text: the key fits, and by which the key ring is prevented from turning.
As the key ring and pin wheel are both attached to the spindle, it
follows that both move out and in together, and as the pins e, e,
enter the holes o, o, of any wheel the key ring is pushed back out of
such wheel, and it is free to turn with the spindle and pin wheel.
I design to make the wheels C of slicet steel about on thirty-
second part of an inch thick, and harden them, and in the better class
of locks I design to have ten wheels to a lock, although there are
but six in the present case. Every additional wheel multiplics the
number of possible combinations by ten if used only one side out, and
ten wheels give ten thousand million combinations. Each of the wheels
is numbered according to the relative position of its key slot c¹ and
notch c. The wheel that has its notch c and key slot c¹ on the same
side is numbered 1. The wheel whose key slot is three-twentieths of a
circle to the right of its notch c is numbered 2, and so on, the key slot
of each consecutive number being three-twentieths of a circle to the
right. Each wheel may be numbered on both sides, as it can be used
either side. In such case I place on one side of cach wheel the simple
figure that indicates its number, and on the other side I place the same
figure with a dot over it. It is only necessary however to number the
wheels on one side, and then have one set of numbers on the dial, with a
dot over each figure to represent the wheels when one side out; then have
another set of plain or simple figures on the dial to represent the wheels
when the other side out. The different changes in the combination are
made by placing the wheels in the lock in different order, and as the
wheels can be arranged in any order I can set the wheels in as many
different ways as there can be permutations in six figures. Then as cach
wheel can go in either side out, that number of permutations must be
multiplied by the sixth power of two to indicate all the possible ways in
which the wheels may be arranged. The permutations on ten figures
amount to over three millions, and the tenth power of two is ten
hundred and twenty-four, so that there are over three thousand million
ways in which ten wheels can be put in the lock. . The chance of
guessing the number of one of these locks with ten wheels (each wheel
being used both sides out) is found by raising twenty to the tenth power,
which is ten trillions two hundred and forty billions, and the chance
of guessing would be as one to that number.
Now when the key ring
is in all the wheels, the notch c of one whcel is three-twentieths of a

page_text: circle from that in the wheel bearing the next consecutive number.
It follows, therefore, that I must turn one wheel three-twentieths of a
circle to bring its notch even with the notch of the wheel bearing the
next number. I therefore divide the dial K into twenty spaces and
number it in the following order, namely, beginning at the top with
No. 1. I place No. 2 three spaces from No. 1, and No. 3 I place three
spaces from No. 2, and No. 4 three spaces from No. 3, and so on up
to ten numbers. Then if the wheels are turned over, it is evident that
the consecutive numbers will be on the other side of figure 1, cach
number being three spaces from the number preceding. I therefore
number the dial in both directions, beginning with No. 1, as shown in
Figure 6. Now as there are ten holes in each wheel, and as the wheels
differ from one another in the position of the key slots three-twentieths
of a circle, it follows that when a wheel with an even number is placed
next to a wheel of an odd number, then the spaces between the
holes o, o, o, of the one wheel will cover the holes o, o, o, and so on
of the other when the key ring is in the wheels. The object of this
arrangement is that when the knob G is pushed in the pins e, e, can
pass through but a single wheel at a time. That saves care in unlocking,
but is not necessary. The knob G is fastened to the spindle by a light
screw g, which is split at its screw end g¹, so that if broken off it can
be readily removed from the spindle. A spring F keeps the pin wheel E
in the position shown in Figure 3, yet permits such pin wheel to slide on
the spindle when any great pressure is brought upon the spindle at
any time when the pins e, e, are out of the wheels C. M represents a
part of a safe door to which the lock is attached, as shown in Figure 3.
The spindle D has a shoulder d formed on its outer end, which fits in
a recess bored in the safe door, as shown in Figure 3. A collar d' is
also screwed on or otherwise securely fastened to the spindle within
the door. The shoulder d and collar d' prevent the spindle from being
driven in or drawn out by a person on the outside of the safe.
The manner of unlocking this lock is as follows:-First, the handle
or knob G is turned round and drawn out until it will not come out
any further. As it is turned the key slots of the wheels one by one
come under the key n', and such key enters the slots, and the pins e, e,
draw out of each wheel as the key ring enters the same. Now suppose
that the wheels are in the lock in the order 1, 2, 3, 4, 5, 6, they being

page_text: the side out that would correspond with the dotted numbers; after
the knob is drawn out as far as it can come the key ring will be through
every wheel, you turn the knob until the index r is over figure 1 of
the dial, then push in the knob, and the pins e, e, will enter No. 1, turn
on and the wheel No. 1 turns also; when the index is over figure 2
the notches c of the first and second wheels will be together; push in
again and the pins e, e, enter the wheel No. 2, and the key ring passes
out of the same; now turn to figure 3 on the dial and the two first
wheels arc with the third; push in the knob and take hold of wheel
No. 3; turn to figure 4 on the dial and push in and take hold of wheel
No. 4; turn on to figure 5 and take wheel No. 5; turn on to figure 6
and take wheel No. 6. If you have followed the directions you will
now have the notches c of all the wheels together, and the pins e, e,
will be in all the wheels. Now turn the knob round to the left until
the projection b of the bolt B¹ springs into the notches c of the wheels,
when the door is unlocked. To lock the same you turn the knob round
to the right until the bolt B is thrown forward. Continue to turn and
the dog B¹ is forced out into the position shown in Figure 2; turn on
and draw out the knob and the key ring will enter the wheels one by
one, and the combination is secure. When these locks are used on safes
the bolt B may be used only as a secondary bolt to slide out behind the
main bolt or bolts of the safe. The pin wheel E on an ordinary door
lock could be rigidly secured to the spindle D, and then as it would
be within the case of the lock the shoulder d or the collar d¹ would
not be needed, neither would the spring F be of any use, because the
lock would be stronger than a wooden door, and would not therefore
need protection.

page_text: 3rdly. I claim the combination of the spring F with the pin wheel E,
as and for the purpose herein explained.
4thly. I claim splitting the screw g at g' for the purpose specified.
In witness whereof, I, the said Alexander Melville Clark, have
hereunto set my hand and seal, this Fourth day of December,
in the year of our Lord One thousand eight hundred and sixty-
eight.
Witness,
JAMES DAISH,
53, Chancery Lane,
London.
A. M. CLARK. (L.S.)