U.S. patent number 3,783,658 [Application Number 05/228,713] was granted by the patent office on 1974-01-08 for door lock.
Invention is credited to Waichi Wada.
United States Patent |
3,783,658 |
Wada |
January 8, 1974 |
DOOR LOCK
Abstract
A door lock in which there is provided a latch bolt, a dead
bolt, a first lever secured to the dead bolt and having an abutting
portion being capable of abutting against the rear portion of the
latch bolt, a second lever pivotably connected at one end to the
first lever, abutting means on the second lever and being capable
of abutting against the rear portion of the dead bolt, and a third
lever pivotally connected at one end to the other end of said
second lever and rockable about its axis. The second lever and the
third levers move in a manner of toggle levers when the third lever
is rocked about its axis and, when the dead bolt is in its
projected position, the first, second and third levers are disposed
in such a manner that the first lever abuts against the rear
surface of the latch bolt and an external force acting directly on
the dead bolt to retract the same will tend to prevent rotation of
the second lever and the third lever by abutting engagement of the
abutting means with the rear portion of the dead bolt whereby both
the latch bolt and the dead bolt are restrained against
retraction.
Inventors: |
Wada; Waichi (Ohta-ku, Tokyo,
JA) |
Family
ID: |
22858298 |
Appl.
No.: |
05/228,713 |
Filed: |
February 23, 1972 |
Current U.S.
Class: |
70/110; 70/129;
292/139 |
Current CPC
Class: |
E05B
63/0021 (20130101); E05B 59/00 (20130101); Y10T
70/5319 (20150401); Y10T 70/5239 (20150401); Y10T
292/1015 (20150401) |
Current International
Class: |
E05B
59/00 (20060101); E05B 63/00 (20060101); E05b
059/02 () |
Field of
Search: |
;70/107,110,111,129,134
;74/520,521 ;292/139,158,167,DIG.49 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Champion; Marvin A.
Assistant Examiner: Tremblay; Richard P.
Attorney, Agent or Firm: John C. Holman et al.
Claims
What I claim is:
1. A door lock comprising a latch bolt, a dead bolt, a first lever
secured to said dead bolt and having an abutting portion capable of
abutting against the rear portion of said latch bolt, a second
lever pivotably connected at one end to said first lever, abutting
means provided on said second lever and capable of abutting against
the lower surface of the rear portion of said dead bolt, a third
lever pivotably connected at one end nearer to said dead bolt to
the other end of said second lever and rockable about its axis
between a first extreme position and a second extreme position,
said first extreme position corresponding to a retracted position
of said dead bolt in which the connecting point where said second
lever and said third lever are pivotably connected to each other is
substantially deviated on one side of a line connecting the point
at which said second lever is pivotably connected to said first
lever and said axis of said third lever and said second extreme
position corresponding to a projected position of said dead bolt in
which said connecting point is slightly deviated on the other side
of said line, and actuating means for rocking said third lever,
each of said first, second and third levers being disposed, when
said third lever is in said second extreme position, in such a
manner that said first lever abuts in said abutting portion against
the rear surface of said latch bolt, said abutting means abuts
against the lower surface of the rear portion of said dead bolt so
that an external force acting directly on said dead bolt to retract
the same will tend to prevent rotation of said second lever and
said third lever by abutting engagement of said abutting means with
the rear portion of said dead bolt whereby both said latch bolt and
said dead bolt are restrained against retraction.
2. The door lock as defined in claim 1 in which said abutting means
is a pawl portion formed at the end of said second lever nearer to
said dead bolt, a horizontal surface of said pawl portion being
engageable with the opposing lower horizontal surface of the rear
portion of said dead bolt.
3. The door lock as defined in claim 1 in which said dead bolt is
formed with a recess at a rear corner thereof and said abutting
means is the end portion of said second lever nearer to said dead
bolt which is engageable with said recess formed in said dead
bolt.
4. The door lock as defined in claim 1 in which said actuating
means are a key-actuated tang of a cylinder lock assembly
accessible from outside the door and a thumb-turn accessible from
inside the door.
Description
BACKGROUND OF THE INVENTION
This invention relates to a door lock and, more particularly, to a
locking mechanism for a door lock comprising a latch bolt and a
dead bolt.
There is a certain standard in what persons skilled in the art
calls throw which is the length of the portion of a dead bolt
projecting from the outer surface of a front plate of the door
lock. Currently, the standard throw is 3/4 inch. There has been a
recent tendency, however, for the throw to become longer and the
standard of three-fourths inch throw is gradually being replaced by
1 inch throw. Such lengthening of the throw is certainly desirable
from the standpoint of security but it poses a problem in the
design of a deadbolting mechanism in a door lock. Inasmuch as a
present standard of distance between the outer surface of the front
plate and the axis of a knob is 21/2 inches, it is rather difficult
according to constructions of prior art door locks to accommodate
the dead bolt having a prolonged throw of 1 inch together with a
mechanism comprising levers and other elements required for
reciprocating the dead bolt within the inside space of the door
lock.
PRIOR ART
For instance, a mechanism for moving the dead bolt between its
projected and retracted positions in a prior art door lock
comprises, as shown in FIG. 1, a dead bolt 3 having a three-fourths
inch throw, a lever 4 secured to the dead bolt 3 and formed with an
oblique slot 5 and an actuating lever 6 which engages the oblique
slot 5. FIG. 1 is an elevational view of the prior art door lock 1
with its upper plate 2 partly cut away. According to this prior art
mechanism, the foremost end portion 6a of the actuating lever 6 has
a projection which engages the oblique slot 5 of the lever 4
secured to the dead bolt 3. The actuating lever 6 is rotated by
known means such as a key-actuated tang 7. When the end portion 6a
is at the upper end of the oblique slot 5, the dead bolt 3 is in
the retracted position. As the actuating lever 6 is rotated
counterclockwise, the end portion 6a slides along the slot 5
thereby causing the dead bolt 3 to move forward to its projected
position. When the end portion 6a reaches the lower end of the slot
5 as shown in FIG. 1, the dead bolt 3 reaches its foremost
projected position. As will be apparent from the figure, the throw
of the dead bolt 3 is determined by the distance of the travel of
the end portion 6a of the actuating lever 6 in the oblique slot 5
and proper angle of which relative to a horizontal line is about 45
degrees. It will be understood that the upper end of the slot 5 is
nearly adjacent to the inner surface of the front plate 8 when the
dead bolt 3 is in the projected position and further obliquely
upward extension of the slot 5 is practically impossible. Likewise,
the lower end of the slot 5 is nearly adjacent to the hub portion
of the actuating lever 6 when the dead bolt 3 is in the retracted
position so that further obliquely downward extension of the slot 5
is also impossible. In other words, the conventional three-fourths
inch throw is the maximum throw which can be obtained by this
particular construction. Accordingly, this type of deadbolting
mechanism encounters difficulty in meeting the current requirement
for extending the throw to 1 inch.
Further, it has been a common practice in the art to provide some
stop means for restraining a dead bolt against retraction to
prevent unlocking of the door lock for unlawful purposes by
applying an external force directly to the dead bolt to forcibly
retract the same. It is, however, not sufficient from the
standpoint of security to provide such stop means only for the dead
bolt because in this case the latch bolt can be easily moved, for
retracted by applying an external force thereto by means, for
example, of a screw driver. It is, accordingly, desirable from the
standpoint of security not only to extend the throw but also to
provide means for simultaneously restraining retraction of both the
dead bolt and the latch bolt. There are some prior art door locks
in which such simultaneous locking means for the dead bolt and the
latch bolt are provided. However, such prior art locking means are
not appropriate or advantageous when used in combination with the
mechanism for lengthening the throw according to the invention
which will be described hereinbelow.
OBJECTS AND SUMMARY OF THE INVENTION
It is, therefore, a general object of the invention to provide a
novel and useful door lock which eliminates the above described
disadvantages of the prior art door locks.
It is another object of the invention to provide a door lock in
which a dead bolt of a longer throw is obtainable without enlarging
the casing or extending the standard distance between the front
plate and the axis of a knob. According to the present invention,
the dead bolt of a longer throw can be obtained by employing a pair
of levers which are pivotably connected to each other and cooperate
with each other in the manner of toggle levers to move the dead
bolt between its two extreme positions.
It is another object of the invention to provide a door lock in
which both a dead bolt and a latch bolt are simultaneously
restrained against retraction by a very simple mechanism when they
are in their projected positions. The dead bolt is restrained
against retraction by abutting means which are provided on one of
said pair of levers arranged nearer to the dead bolt and are
brought into a direct abutting engagement with the rear portion of
the dead bolt when an external force applied to the dead bolt tends
to rotate the pair of levers. The abutting means are advantageous
in that they do not require a plurality of parts which cooperate
with each other in a complicated manner to restrain the dead bolt
against retraction. Such mechanism comprising a plurality of parts
cooperating with each other would naturally be more expensive and
moreover would fail to prevent the retraction of the dead bolt if
only one of the parts becomes defective, whereas the abutting means
according to the invention is cheap and less likely to cause
failure because of its simple construction and a direct engagement
with the rear portion of the dead bolt. In the meanwhile, the latch
bolt is restrained against retraction by abutting engagement of a
portion of another lever secured to the dead bolt with the latch
bolt when the dead bolt is in its projected position.
It is another object of the invention to provide a door lock in
which said abutting means is a pawl portion formed at the end of
said one of the levers.
It is another object of the invention to provide a door lock in
which the dead bolt is formed with a recess at a rear corner
thereof and said abutting means is the end portion of said one of
the levers which is engageable with the recess formed in the dead
bolt.
Additional objects and features of the invention will become
apparent from the description set forth hereafter when considered
in conjunction with the accompanying drawings, in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an elevational view of a prior art door lock with its
upper plate partly cut away;
FIG. 2 is an elevational view of a door lock, with its upper plate
removed, which embodies the present invention, shown in a state in
which the dead bolt is in a retracted position;
FIG. 3 is a perspective of retractor hubs used for retracting the
latch bolt;
FIG. 4 is a view similar to FIG. 2 but shown in a state in which
the dead bolt is in a projected position; and
FIG. 5 is an elevational view of one modification of abutting means
employed for preventing retraction of the dead bolt.
DETAILED DESCRIPTION OF THE INVENTION
Referring now more particularly to the drawings, a door lock to
which the present invention is applicable is designated generally
by reference character L. This lock is of standard size as will be
well understood by those skilled in the art. In FIG. 2, a case
designated generally by reference numeral 10 comprises a box-like
element 11 with which is associated a cover plate, which is not
shown in the figure for clarity of illustration, to define a
chamber having an open edge 12. A front plate 13 carries lugs 14,
adapted to be received in the chamber through the open edge 12 for
engagement by screws 15, which retain the front plate 13 in closing
relationship to the open edge 12. The front plate 13 is formed with
an opening 16. A head 17a of a latch bolt 17 is guidingly received
in the opening 16. A stem 18 of the latch bolt 17 has a stop 19
rigidly secured to the proximal end thereof. The stop 19 has a
forked end 19a which straddles over the horizontal portion of a
lever 20 which will be described more in detail later. There are
also provided guide bosses 21 and 22 on floor 11a of the box-like
element 11 for guiding the stem 18. Thus, the stem 18 is guided in
the opening 16, the guide bosses 21 and 22 and along the horizontal
portion of the lever 20 for reciprocation on its own axis whereby
the head 17a may be projected or retracted through the opening 16.
An annular spring bearing 23 is loosely fitted on the stem 18. A
compression spring 24 is provided for the stem 18 between the
spring bearing 23 and the rear surface of the latch bolt head 17a.
The compression spring 24 urges, on one hand, the spring bearing 23
against the guide bosses 21 and 22 and, on the other hand, the head
17a to project from the front plate 13. The latch bolt 17 is
restrained against its forward movement by engagement of the stop
19 fixed thereto with the rear edge of a lever 25 to be described
later.
Nextly, a mechanism for actuating the latch bolt 17 will be
described. The actuator mechanism comprises a first actuator 26, a
second actuator 27, a first retractor hub 28, a second retractor
hub 29, and a leaf spring 30. The first actuator 26 is pivotally
mounted on pivot 31 which is disposed at the right bottom corner of
the case 10. The first actuator 26 has an extended arm portion 26a
which is in abutting engagement with the stop 19, when the latch
bolt 17 is in its projected position and thereby is cooperable with
the stop 19 to retract the latch bolt 17. The first actuator 26 is
formed with a slot 32 for engagement with a pin 27a of the second
actuator 27 as will be described later.
The actuator 26 is also provided with an uplift 26b in the middle
portion of one edge thereof, the function of which will be
described later. The second actuator 27, pivotally mounted on a
pivot 33 provided at a position above the pivot 31 in the case 10,
is disposed under the first actuator 26. The second actuator 27 has
the pin 27a which is rigidly secured thereto in the middle portion
thereof and slidably engages in the slot 32 formed in the first
actuator 26. The second actuator 27 is provided with an uplift 27b
at the foremost end thereof. The first retractor hub 28 is mounted
in the case 11 for oscillation about an axis 34. The first
retractor hub 28 is formed with a square opening 28a for receiving
the spindle of an inside knob (not shown). The first retractor hub
28 has two winged portions 28b and 28c. The second retractor hub 29
is also mounted in the case 10 for oscillation about the axis 34.
The second retractor hub 29 is formed with the square opening 29a
as shown in FIG. 3 for receiving the spindle of an outside knob
(not shown). The second retractor hub 29 has two winged portions
29b and 29c. These two hubs are conventional and are adapted to lie
one against the other. The leaf spring 30 which is substantially of
a U-shape is supported at one end thereof on a projection 35 formed
integrally with the box-like element 11 and is wound around the
pivot 31 at its curved portion. The other end of the leaf spring 30
constantly bears against the pin 27a of the second actuator 27 and
urges both the first and second actuators 26 and 27 against the
first and second retractor hubs 28 and 29 through the pin 27a. When
the first retractor hub 28 is rotated about the axis 34 in a
clockwise direction, the vertical end surface of the winged portion
28c pushes the uplift 26b of the first actuator 26 thereby rotating
the first actuator 26 about the pivot 31 in a clockwise direction
against the force of the leaf spring 30 to retract the latch bolt
17. When the first retractor hub 28 is rotated about the axis 34 in
a counterclockwise direction, the vertical end surface of the
winged portion 28b pushes the uplift 27b of the second actuator 27
thereby rotating the second actuator 27 about the pivot 33 in a
counterclockwise direction against the force of the leaf spring 30.
As the second actuator 27 rotates in a counterclockwise rotation,
the pin 27a of second actuator 27 which is engaged in the slot 32
in the first actuator 26 pushes the first actuator 26, while
sliding in the slot 32 from one extreme position to another thereby
rotating the actuator 26 about the pivot 31 in a clockwise
direction to retract the latch bolt 17. Thus, the first retractor
hub 28 is effective, upon rotary movement in either direction about
the axis 34, to move the first actuator 26b for retracting the
latch bolt 17. The second retractor hub 29 is likewise so
constructed and arranged that, upon rotary movement in either
direction about the axis 34, it will cause clockwise movement of
the first actuator 26 for retracting the latch bolt 17.
It will be apparent from FIG. 3 that the second retractor hub 29
extends in a lateral direction beyond the first retractor hub 29 so
as to allow for the forming of a locking slot 36. This locking slot
cooperates with a stop unit designated generally by reference
numeral 37. The stop unit 37 comprises a pair of buttons 38,39,
levers 40, 41 respectively connected to the buttons 38,39 and a
lever 42 interconnecting the levers 40 and 41. The buttons 38, 39
are operable through openings 38a, 39a formed in the front plate
13. The levers 40 and 41 are formd with notches 40a and 41a on one
side thereof in which ends 42a and 42b of the lever 42 are engaged.
The lever 42 is rockable about a pin 43. Guide bosses 44, 45 and 46
are formed integrally with the box-like element 11 for guiding the
levers 40 and 41 in their reciprocating sliding movement. A spring
47 is supported at one end thereof between the guide boss 22 and a
guide boss 48 and, at the other end, bears against the end 42a of
the lever 42 so as to hold the lever 42 against rotation and
thereby prevent an unintended sliding movement of the levers 40 and
41. Operation of the buttons 38, 39 brings the lever 41 into or out
of the locking slot 36 thereby locking or releasing the second
retractor hub 29. When the second retractor hub 29 is locked, it
cannot rotate to retract the latch bolt 17. Accordingly, the
outside knob which is connected to the second retractor hub 29
through its spindle is locked or released by the operation of the
buttons 38 and 39. Even when the second retractor hub 29 is locked,
the first retractor hub 28 is free to rotate so that the inside
knob connected to the first retractor hub 28 through its spindle is
operable to retract the latch bolt 17.
The locking mechanism embodying the invention comprises a dead bolt
49, the first lever 20, a second lever 50, a third lever 51,
abutting means for preventing retraction of the dead bolt 49 which
consist of a pawl portion 50b of the second lever 50 and rocking
means for rocking the third lever about its fixed axis both from
outside and inside the door including a cylinder lock assembly
53.
The front plate 13 is formed with another opening 54. The dead bolt
49 is guidingly received in the opening 54 for reciprocation. The
first lever 20 is substantially of an L-shape and consists of a
vertical portion 20a and a horizontal portion 20b. The vertical
portion 20a of the first lever 20 is rigidly secured to the rear
end portion of the dead bolt 49 by means of rivets 55. The
horizontal portion 20b is slidably received in a space between the
guide boss 21 and a boss 56 which is formed integrally with the
box-like element 11 for receiving the sleeve portion of the third
lever 51. Thus the first lever 20 is guided by the guide boss 21
and the boss 56 for reciprocation in a horizontal direction whereby
the dead bolt 49 may be projected or retracted through the opening
54. The first lever 20 is also provided with a lug 20c in the
horizontal portion 20b. The lug 20c is bent toward the floor of the
box-like element 11 for abutting engagement with a lever 57 to be
described later. The lower front end portion of the first lever 20
extends downwardly below the lower edge of the dead bolt 49 so as
to abut against the rear end surface of the latch bolt 17 when the
dead bolt 49 is in its projected position.
The second lever 50 is pivotally connected in one end portion
thereof to the lower portion of the vertical portion 20a of the
lever 20 by means of a pin 66. The second lever 50 is formed in the
other end portion thereof with a hole 50a. The second lever 50 has
a pawl portion 50b at the foremost end thereof. The lever 50 is so
disposed that the upper surface 50c of the pawl portion 50b abuts
against the rear portion of the lower surface of the dead bolt 49
when the dead bolt 49 is in its projected position.
The third lever 51 has a sleeve portion 51a which is rotatably
fitted in the opening of the boss 56. The third lever 51 is formed
in the middle portion thereof with a square opening 51b through
which the spindle of a thumb turn (not shown) provided inside the
door is inserted. Therefore, the axis of rotation of the third
lever 51 extends through the opening 51b. The third lever 51
carries at one end thereof nearer to the dead bolt 49 a pin 51c
which engages in the opening 50a of the lever 50 for pivotal
connection therewith. The third lever 51 further has two
projections 51d and 51e. The box-like element 11 is formed in its
floor portion with a threaded opening 58 with which the cylinder
lock assembly 53 is in threaded engagement. The cylinder lock
assembly 53 which is of a conventional type has a key-actuated tang
59. In the stage shown in FIG. 2 in which the dead bolt 49 is in
the retracted position, the tang 59 is disposed in the space
between the two projections 51d and 51e, being ready for pushing
the projection 51d and thereby rotating the third lever 51 in a
counterclockwise direction. The cylinder lock assembly 53 is held
against rotation in the threaded opening 58 by a screw 60 which
extends through the front plate 13 and engages in an axial slot 61
formed in the cylinder lock assembly 53.
A leaf spring 52 which is substantially of a U-shape is supported
at one end thereof on a projection 62 which is integrally formed
with the box-like element 11 and is wound around a pin 63 formed
integrally with the box-like element 11. In the state shown in FIG.
2, the other end of the leaf spring 52 bears against the upper edge
portion of said end of the third lever 51 remote from the dead bolt
49.
The lever 57 which is of a shoe-like configuration is pivotally
mounted on the floor of the box-like element 11 about a pin 64. The
lever 57 has two lugs 57a and 57b. The lug 57a is engageable with
the tang 59, whereas the lug 57b is engageable with a pin 25a
provided on the lever 25. The lever 25 has an opening in which the
sleeve portion of the third lever 51 loosely fits and therefore is
rotatable about the sleeve portion of the third lever 51. When the
key-actuated tang 59 is turned in a counterclockwise direction from
the position shown by a dotted line in FIG. 2, the tang 59 pushes
the lug 57a and thereby causes the lever 57 to rotate in a
clockwise direction. The clockwise rotation of the lever 57 causes
its lug 57b to push the pin 25a of the lever 25 downwardly. As the
pin 25a is pushed downwardly, the lever 25 rotates in a
counterclockwise direction thereby retracting the latch bolt 17.
Thus, these levers 57 and 25 cooperate with each other to retract
the latch bolt 17. It will be noted that this mechanism is
effective for opening the door from outside when the second
retractor hub 29 is locked by the stop 37 and therefore the outside
knob is not available for retracting the latch bolt 17.
Nextly, the operation of the locking mechanism according to the
invention will be described.
In the state shown in FIG. 2, the dead bolt 49 is in its retracted
position. The first lever 20 is in its innermost position with its
rear end abutting against a lug 65 of the box-like element 11. The
second lever 50 is nearly in an uplifted position with its end
connecting to the third lever 51 raised and its pawl portion 50b
disengaged from the lower rear corner of the dead bolt 49. The
third lever 51 is in its one extreme position with its end nearer
to the dead bolt 49 raised and the end remote from the dead bolt 49
lowered. It will be noted that in this position the connecting
point at which the second lever 50 and the third lever 51 are
pivotably connected to each other is substantially deviated on one
side of the line connecting the center of the pin 66 and the axis
of the third lever 51. The leaf spring 52 which bears against the
upper edge portion of said end of the third lever 51 remote from
the dead bolt 49 tends to rotate the third lever 51 in a clockwise
direction thereby transmitting a force to the dead bolt 49 through
the second lever 50 and the first lever 20 in a direction to
retract the dead bolt 49. When the tang 59 is turned by means of
the key in a clockwise direction, i.e., in the direction of arrow A
from the position shown in full lines in FIG. 2, the tang 59
engages the projection 51d and causes the third lever 51 to rock in
a counterclockwise direction against the force of the leaf spring
52. As the third lever 51 is rocked in the counterclockwise
direction, the second lever 50 which is operatively connected to
the third lever 51 pivots about the pin 66 in a clockwise
direction, causing the first lever 20 and the dead bolt 49 secured
thereto to slide to the left as viewed in the drawing, whereby the
dead bolt 49 is brought to its projected position as shown in FIG.
4. As the third lever 51 is rocked from its one extreme position
shown in FIG. 2 to the other extreme position shown in FIG. 4, its
end remote from the dead bolt 49 is raised and the leaf spring 52
which bore against the upper edge portion of said end in the first
extreme position now bears against the lower edge of said end.
Accordingly, the leaf spring 52 now tends to rotate the third lever
51 in a counterclockwise direction. It will be observed in FIG. 4
that the second lever 50 and the third lever 51 are disposed nearly
in a straight alignment. It will be understood that a relatively
long throw of the dead bolt 49 is obtainable by the locking
mechanism according to the invention in which the throw is the
difference between the maximum distance between the pivot 66 and
the axis of the third lever 51 which is obtained when the levers 50
and 51 are nearly in a straight alignment and the minimum distance
between said pivot and said axis which is obtained when the two
levers are rotated upwardly to the point at which the rear end of
the lever 20 abuts against the lug 65 and further retraction of the
dead bolt 49 is impossible. Since the distance between said pivot
and said axis can be minimized, if so designed, to a point at which
the second lever 50 is in close proximity to the sleeve portion of
the third lever 51, a maximum available throw of the dead bolt 49
is only slightly shorter than the distance between the front plate
13 and the axis of the third lever 51 and obviously larger than the
maximum throw of the previously described mechanism of the prior
art which is determined by the travel of the end of the actuating
lever in the oblique slot.
When the dead bolt 49 is in its projected position, the upper
surface 50c of the pawl portion 50b of the second lever 50 is in
abutting engagement with the lower surface of the rear portion of
the dead bolt 49. It is to be noted that when the dead bolt 49 is
in its projected position, the second lever 50 and the third lever
51 are disposed in a position slightly beyond the dead center
position relative to these levers 50 and 51 in a direction in which
an external force applied directly to the dead bolt 49 to retract
the same will tend to rotate the lever 50 in a clockwise direction
and the third lever 51 in a counterclockwise direction so that the
rotation of these levers 50 and 51 will be prevented by engagement
of the pawl portion 50b of the lever 50 with the dead bolt 49. It
will be understood from the foregoing description that retraction
of the dead bolt 49 by an external force can be prevented by the
hinge connection of the second and the third levers 50 and 51 and
the cooperation between the pawl portion 50b of the second lever 50
and the dead bolt 49 inasmuch as the second lever 50 and the third
lever 51 are disposed substantially in a position slightly beyond
the dead center position relative to these levers 50 and 51 in a
direction in which an external force applied to the dead bolt 49
will tend to prevent the rotation of these levers 50 and 51 by
engagement of the pawl portion 50b of the lever 50 with the dead
bolt 49. In the present embodiment, the leaf spring 52 serves to
apply a force to the second and third levers 50 and 51 which force
tends to rotate these levers beyond the dead center position
relative thereto and urge the upper surface 50c of the pawl
rotation 50b against the lower surface of the dead bolt 49. Thus,
the leaf spring 52 is effective to prevent retraction of the dead
bolt 49 due to the external force applied directly to the same.
When the dead bolt 49 is brought to its projected position, the
lower front surface of the lever 20 abuts against the upper rear
surface of the latch bolt 17 and holds the same against
retraction.
The foregoing is the operation of the locking mechanism when the
third lever 51 is actuated by the tang 59 by means of a key
inserted in the cylinder lock assembly 53 from outside the door. It
will be apparent, however, that the third lever 51 can also be
rocked by the thumb turn provided inside the door. Accordingly, the
third lever 51 is rockable by the rocking means which are
accessible both from outside and inside the door.
For retracting the dead bolt 49, the tang 59 is turned in a
counterclockwise direction. The third lever 51 is rocked from the
extreme position shown in FIG. 4 to the extreme position shown in
FIG. 2. The second lever 50 is pivoted in a counterclockwise
direction causing the first lever 20 and the dead bolt 49 to move
to the right. The leaf spring 52 now bears against the upper edge
of the end portion of the third lever 51 thereby applying force to
rotate it in a clockwise direction. Accordingly, the leaf spring 52
serves to retract the dead bolt 49 quickly to the position shown in
FIG. 2. After the dead bolt 49 is retracted, the leaf spring 52
acts on the third lever 51 to hold it in position. Accordingly,
unintended projection of the dead bolt 49 due to a shock given to
the door or other causes is prevented.
In FIG. 5, an alternative form of the means for engaging with the
rear portion of the dead bolt 49 is shown. The dead bolt 49 is
formed with a recess 49a in the lower rear portion thereof and the
foremost end 50b of the second lever 50 engages in the recess 49a
when the dead bolt 49 is in its projected position. It will be
readily understood that a force applied to the dead bolt 49 to
retract the same tends to rotate the second lever 50 in a clockwise
direction thereby causing the upper surface of the end portion 50b
to bear against the lower surface 49b of the rear portion of the
dead bolt 49.
* * * * *