Year: 1886

page_text: I, CHRISTIAN JOHN LETZING of Boston in the County of Suffolk and State of
Massachusetts, one of the United States of America, Machinist, 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 object of the invention is to provide means whereby a door upon being unlocked
may be opened but a limited distance, and also in various details of construction, all of
which will be hereinafter fully described.
Referring to the drawings,
Figure 1 is a perspective view representing the application of a lock containing the
features of my invention to a door. Fig. 2 is a view in horizontal section, representing
the door closed in dotted lines and open in full outline.
Fig. 3 is an enlarged view in elevation of the lock, looking from behind, to show its
interior construction, and also to represent the parts when the latch bolt is in its
protracted position.
Fig. 4 is a view in elevation of the same parts when the latch bolt is in its normal
position. Fig. 5 is a detail view, and Fig. 6 is a modification hereinafter referred to.
A represents a 'door provided with a lock having the features of my invention.
B represents the frame work about the door.
C is the lock. It has a latch bolt, c, which is provided with the inclined edge or
face c', the long slot c², and the passage or entrance c³ to the slot, which extends from
the end of the slot.
This latch bolt is movable in relation to the casing of the lock, as hereinafter
specified, and it is adapted to engage with the catch D, which projects outwardly from
the inner surface of the frame of the door. This catch consists of the part d, having
screw holes d', by which the catch is fastened in place, and the comparatively thin
outward extending plate d², having the shoulders d³, Fig. 5. This plate d² is
somewhat less in thickness than the width of the passage or entrance c³ to the slot
of the latch bolt, and when the door is closed said latch bolt is adapted to project upon
this plate, the portions c¹ bearing against the shoulders d³, as represented in Fig. 5.
Date 07

page_text: These shoulders are formed by the ear d and the end d³ of the swinging bar E, which
is fastened to the said ear.
There is arranged at the end of this swinging bar a cross block, e, which acts as a
stop for the latch bolt and door, as hereinafter described.
For ordinary use the latch bolt c is moved inward into the lock casing to disengage
it from the catch. If, however, it is desired to limit the movement of the door so that
it may be opened a limited extent, and then locked, I move the latch bolt outward
beyond the plate d², so that the slot c³ comes beneath the shoulders d³ of the latch,
and, the slot being wider than the shoulders, I am then enabled to open the door, the
latch bolt passing by the shoulders on to the bar E, which is of a greater width than
the width of the entrance or passage to the slot, so that the latch as the door is
moved outward, rides on the swinging bar until it comes in contact with the stop e.
This construction effectually prevents the door from being opened a greater distance
than is desired, the distance being regulated by the length of the swinging bar.
In closing the door it may be shut in the ordinary manner, or the bar E may be
used as a lever in returning the latch bolt to a position within the line of the
shoulders d³, and it will automatically return to its normal position.
There are many ways, of course, by which this latch bolt may be provided with the
necessary movements, and in the drawings I have illustrated one of these ways only. The
latch bolt c has a shank, e, extending backward, and provided with a slot, c, which
receives the guides or blocks c', projecting outward from the casing of the lock, to act
as guides in connection with the slot. Projecting from the face of the shank, are two
pins c. When the handle is turned either to right or left, the barrel f' (which is
formed with the arm f.) is caused to rotate simultaneously with the handle, and the
said arm f, is brought to bear against either one or the other of the aforesaid pin (8,
and a further movement of the handle causes the bolt to slide upon the guides c' as
shown in Fig. 4. A spring f³ may be adapted to bear upon the barrel and serve to
return it to its normal position (Fig. 3) and a spring bears against the shoulder f
upon the latch bolt and tends to hold it outwards. The latch bolt may however be
manipulated by a key inserted into the key-hole and the recess H¹ formed in the pivot
stud H2 so that the lock may be opened from the opposite side to that upon which the
handle projects. When the aforesaid key is inserted into the key-hole and the
recess H the wards of said key engage with the tumblers f, which when kept in
their normal position by the springs h do not lie evenly upon each other as shown in
Fig. 3.
When the key is turned in the lock, and the tumblers f, the said tumblers
are brought all evenly together by reason of the different lengths of the wards of the
key and the notches h are brought to coincide one with another. By giving the key
a further turn, it is brought to bear upon the projecting catch formed upon the
arm f which is pivoted on the stud H2 and formed at its other end with the tongue fr
which is carried into the notches h¹ of the tumblers, (which are now even) and pressed
at the same time against the projecting piece H³ of the latch bolt which is forced back
in the same manner as when operated by the handle f2 Fig. 1. The spring f4 will
serve to return the bolt outwards. It will be observed that should any key other than
the one intended for the lock be inserted into the keyhole and the recess Hand
turned in the tumblers, the said tumblers will not be brought evenly together and the
notches h¹ remain unopened for the entry of the tongue as hereinbefore described.
The latch bolt also has a notch, g, in its shank, for the reception of the push block
whereby the latch may be held locked, (Fig. 4) and which block also acts to lock the
latch when it is pushed forward (Fig. 3) so that it cannot be unlocked by the key.
This block is adapted to be moved upward by the lever g² and push block g³, pivoted
thereto, the lever being pivoted at g².
A spring surrounds the pivot post and bears against the lever, to exert sufficient
friction thereon to maintain the block in any position in which it may be moved.
In Fig. 6 represent the latch bolt with a closed slot, instead of an open one, and
use in connection therewith a modified form of locking bar.
The locking bar in this case being in the form of a hook, the end is adapted to act
as an abutinent, against which the latch bolt shall come in contact when it is used in

page_text: the ordinary way; but when said latch bolt is moved outward sufficiently to bring
the slot in line with this portion of the hook it may then ride outward thereon, as
upon the portion shown in Fig. 1.
Of course this hook is pivoted to swing laterally.
The advantages of the invention arise from the simplicity of the construction, and
from the fact that the movement of the latch bolt only is required to bring the
controlling bar into effect.
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 :-
:-
1st. In a lock, the combination of a bolt or latch shaped as described, and adapted
to be moved by a spring to engage with a catch, and to be moved by the knob or
handle outwardly, to be disengaged from the catch, and to engage with the locking
bar, with the locking bar E, and the plate d, having the shoulders d³, all substantially
as described.
2nd. The combination, in a lock of the bolt or latch shaped substantially as described,
and adapted to be moved by a spring to engage with a catch, and to be moved by the
knob or handle outward, to be disengaged from the catch to engage with the locking
bar, the plate d having the shoulders d³, forming the catch, the swinging locking
bar E, secured to said plate, and the cross piece, block, or stop e, for limiting the
extent of movement of the bolt or catch, all substantially as and for the purposes
described.
3rd. The combination of the latch bolt c, shaped substantially as specified, to act as
a latch and as a locking device, the operating arm f, spring, and the guides c³, and the
latch knob or handle; whereby the latch bolt is adapted to automatically engage the
catch, and to be moved by hand both outward and inward from the position to which it
is automatically moved, all substantially as and for the purposes described.
Dated this 26th day of October 1886.