Note: Descriptions are shown in the official language in which they were submitted.
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ELECTROMECHANICAL LOCK
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to locks and, more particularly,
pertains to locks suited for use with safes and vaults.
2. Description of the Prior Art
It is well known to securely store valuable items in high security
enclosures, such as safes and vaults. It is essential to ensure against
unauthorized
unlocking of such security enclosures which can be subject to various attacks
from
persons employing conventional safe-cracking techniques or sophisticated
equipment for applying electrical or magnetic fields to manipulate elements of
the
locking mechanism to thereby open it.
Over the years numerous locking mechanisms and access control
1 S systems have been developed with various anti-tampering devices employing
mechanical and/or electrical elements to ensure against unauthorized operation
and
to effect cooperative movement among the elements for authorized locking and
unlocking operations.
For instance, United States Patent No. 5,592,838 issued on January
14, 1997 to Clark et al. discloses a safe lock having an interposer which is
adapted
to block the mechanism used for retracting a bolt when the back plate of the
lock
housing is removed from the housing.
Although the locking mechanism described in the above patent is
effective to prevent opening of a locked enclosure, it has been found that
there is a
need for a new electromechanical lock having high security features.
SUMMARY OF THE INVENTION
It is therefore an aim of the present invention to provide a new lock
that increases security.
It is also an aim of the present invention to provide a compact and
reliable lock.
It is also an aim of the present invention to provide a versatile lock
suited for used in a number of applications.
It is also an aim of the present invention to provide a lock having a
bolt which could be configured as a deadbolt or a spring-loaded bolt.
It is also an aim of the present invention to provide a lock having an
electronic access control system with a simple and efficient anti-tampering
system.
Therefore, in accordance with the present invention, there is
provided a lock comprising driver means adapted to be connected to a source of
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mechanical energy for opening the lock, latch lever means engageable by said
driver means for moving bolt means to open the lock, said latch lever means
having
a hook member adapted to be engaged in a catch defined in said driver means,
interfering means defining a recess, and state selection means for either
causing
said interfering means and said driver means to move jointly or not, said hook
member being biased against said driver means and said interfering means
without
engagement and operationally engaging said catch when said hook member moves
into said recess.
In accordance with a further general aspect of the present invention,
there is provided an anti-tampering device for an electronic access control
system
of the type used for allowing a lock to be unlocked when a valid access code
has
been entered. The device comprises at least two housing components adapted to
be
assembled together for housing a control circuit, a pair of conductive
components
adapted to assume a first relative position to maintain the control circuit in
a normal
operational mode when said housing components are assembled together and a
second relative position to cause said control circuit to fall in a tamper
mode when
said housing components are disassembled.
In accordance with a further general aspect of the present invention,
there is provided a lock comprising a casing, cover means for closing said
casing, a
bolt slidably disposed within said casing for movement between extended and
retracted positions, latch lever means adapted to be connected to a source of
mechanical energy for displacing said bolt between said extended and retracted
positions thereof, and a re-locking mechanism comprising an interfering member
normally maintained in an idle position and which upon alteration of the
relative
disposition of said cover means and said casing is automatically displaced to
a
functional position thereof in which said interfering member is engaged with
said
bolt so as to prevent said bolt from being displaced to said retracted
position
thereof.
In accordance with a further general aspect of the present invention,
there is provided a convertible bolt assembly for a lock, comprising a bolt
head
displaceable between extended and retracted positions, a bolt tail adapted to
be
connected to a source of mechanical energy for displacing said bolt head
between
said extended and retracted positions thereof, and interchangeable connection
means for one of spring-loading and fixedly securing said bolt tail relative
to said
bolt head for selectively configuring said convertible bolt assembly as a
spring-
loaded bolt and a deadbolt.
In accordance with a further general aspect of the present invention
there is provided an electromechanical lock comprising an access control
system
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adapted to be mounted on a first side of a door, a bolt retraction mechanism
mounted on a second side of the door for moving a bolt between extended and
retracted positions when a valid entry has been validated by said access
control
system, and a drive shaft extending through the door between said access
control
system and said bolt retraction mechanism for operatively coupling said lock
mechanism to a source of mechanical energy, said drive shaft defining a
passage
for allowing at least one elongated flexible conductor to extend between said
access
control system and said bolt retraction mechanism.
BRIEF DESCRIPTION OF THE DRAWINGS
Having thus generally described the nature of the invention,
reference will now be made to the accompanying drawings, showing by way of
illustration a preferred embodiment thereof, and in which:
Fig. 1 is an exploded perspective view of an access control system
of a lock in accordance with a first embodiment of the present invention;
1 S Fig. 2 is a cross-sectional view of a front enclosure of the access
control system of Fig. 1;
Fig. 3 is a cross-sectional view of a back enclosure of the access
control system of Fig. 1;
Fig. 4 is an elevational view of a locking device used in combination
with the access control system of Fig. 1 and shown in a locked position
thereof;
Fig. 5 is an elevational view of the locking device of Fig. 4 shown in
an unlocked position thereof.
Fig. 6 is an exploded perspective view of an actuator sub-assembly
of the locking device;
Fig. 7 is an exploded perspective view of a bolt sub-assembly of the
locking device;
Fig. 8 is an exploded perspective view of a cover adapted to be
mounted to the casing of the locking device illustrated in Figs. 4 and 5;
Fig. 9 is a perspective view of an interfering member of a re-locking
mechanism of the locking device;
Fig. 10 is an exploded perspective view of a re-locking mechanism
adapted to be installed in the casing of the locking device to prevent the
bolt from
being retracted if the cover is withdrawn from the casing in accordance with a
second embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Now referring to the drawings, an electromechanical lock 10
particularly suited for selectively preventing and enabling opening of safes
and
vaults will be described.
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According to a first embodiment of the present invention, the
electromechanical lock 10 generally comprises an access control system 12 and
a
locking device 14 (Figs. 4 to 9) respectively mounted to outer and inner
surfaces of
a door (not shown).
As seen in Fig. 1, the access control system 12 is housed in a
housing 16 in which an electronic system 18 is disposed for allowing or
preventing
a bolt 20 (see Figs. 4, 5 and 7) to be retracted by manual operation of a turn
wheel
22 rotatably mounted about the housing 16.
More specifically, the electronic system 18 includes an electronic
circuit board 24 and a keypad 26 provided in the form of a silicon membrane.
The
keypad 26 includes a number of data entry key buttons 28 for activation to
enter
combination and initialization data, as is well known in the art. The data
entry key
buttons 28 are provided with respective carbon contact points (not shown) to
activate contacts in the electronic board 24 in response of pressure exerted
on the
entry key buttons 28. A source of power (not shown), such as batteries, may be
disposed within the housing 16 for powering the electronic circuit board 24.
The housing 16 includes a front enclosure 30 having a circular front
wall 32 defining an array of openings 34 configured and disposed to receive
corresponding data entry key buttons 28 of the keypad 26. The circular front
wall
32 further defines two circular openings 36 for receiving corresponding visual
indicators 38 and a recess 39 adapted to accommodate a conductive contact 41
integrated in the keypad 26 for purposes to be described hereinafter. A
cylindrical
wall 40 extends rearwardly from the periphery of the circular front wall 32 so
as to
define therewith an internal space sized and configured to receive the keypad
26
and the electronic circuit board 24. As seen in Fig. 2, four circumferentially
distributed shoulders 42 extend integrally from the inner surface of the
circular
front wall 32 to receive the electronic circuit board 24. Three pegs 44 also
extend at
right angles from the inner surface of the circular front wall 32 for
engagement
within corresponding holes 46 defined in the electronic circuit board 24. The
shoulders 42 and the pegs 44 ensure proper positioning of the electronic
circuit
board 24 within the housing 16.
Once the keypad 26 and the electronic circuit board 24 have been
successively installed within the front enclosure 30 as described
hereinbefore, an
intermediate tamper cover 48 (see Fig. 1) is snapped in interlocking
engagement
within the top enclosure 30. The intermediate cover 48 comprises a circular
wall 50
and a cylindrical wall 52 extending on both sides of the circular wall 50. The
cylindrical wall 52 is provided at a front end thereof with four integral
circumferentially distributed flexible hooks 54 adapted to be pushed into
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engagement within corresponding grooves 56 (Fig. 2) defined in the inner
surface
of the cylindrical wall 40 of the front enclosure 30. A rectangular cavity 58
is
defined in the circular wall 50 for receiving a pair of AAA batteries for
powering
the electronic circuit board 24, as mentioned hereinbefore.
S As seen in Fig. 1, the housing 16 further comprises a rear enclosure
60 having a circular bottom wall 62 from the periphery of which a cylindrical
side
wall 64 extends. A pair of diametrically opposed internal grooves 66 are
defined at
the front end of the cylindrical side wall 64 for interlocking engagement with
corresponding flexible hooks 68 integrally formed at the rear end of the
cylindrical
wall 40 of the front enclosure 30. This arrangement advantageously allows the
batteries (not shown) to be readily replaced, when required, by simply urging
the
flexible hooks 68 of the front enclosure 30 out of the grooves 66 of the rear
enclosure 60.
Thereafter, the front and rear enclosures 30 and 60 can be readily
reassembled together by manually pushing the flexible hooks 68 back into the
grooves 66.
As seen in Fig. 1, a spacer or protrusion 70 extends frontwardly
from the circular bottom wall 62 of the rear enclosure 60 through a hole 72
defined
in the intermediate cover 48 and a hole (not shown) defined in the electronic
circuit
board 24 in order to push the conductive contact 41 away from the electronic
circuit
board 24 into the recess 39 so that there is no electrical continuity between
the
conductive contact 41 and the electronic circuit board 24 when the rear
closure 60
is assembled to the front closure 30. However, in the event that the front
closure 30
is removed from the rear closure 60, the protrusion 70 will no longer push on
the
conductive contact 41 to maintain the same away from the electronic circuit
board
24 and ,thus, the conductive contact 41 will engage the electronic circuit
board 24
at a point of contact thereof, thereby resulting in an electrical short across
circuit
traces on the circuit board 24. This will cause the electronic system 18 to
fall into a
tamper mode which allows the retraction of the bolt 20 when a valid entry is
detected but which provides a visual signal via one of the visual indicators
38 that
an illegal manipulation has been performed. It is understood, that the circuit
of the
electronic circuit board 24 can be configured to enable authorized person to
enter a
code which allows them to disassemble the housing 18 without causing the
electronic system 18 to fall into the tamper mode. The above described
arrangement constitutes an efficient and simple anti-tampering system which
could
be used in a variety of applications where it is desired to indicates
unauthorized
separation of parts of an enclosure housing a given electronic access control
system.
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As seen in Fig. 3, four circumferentially distributed hollow
projections 74 extend rearwardly from the bottom wall 62 of the rear closure
60 for
engagement with corresponding circumferentially spaced-apart curved slots 76
defined in the bottom wall 78 of the turn wheel 22. As seen in Fig. 1, an
externally
corrugated cylindrical side wall 80 extends from the periphery of the bottom
wall
78 and defines therewith a recess having a diameter slightly greater than the
external diameter of the front and rear enclosures 30 and 60, thereby enabling
the
turn wheel 22 to be fitted thereon for rotational movement with respect
thereto.
According to one embodiment of the present invention, the engagement of the
hollow projection 74 within the slots 76 limits the rotational movement of the
turn
wheel 22 relative to the housing 16 to 68 degrees.
The hollow projections 74 also allow fasteners (not shown) to
extend through the rear closure 60 in order to secure the same to the outer
surface
of a door (not shown) without interfering with the rotational movement of the
turn
1 S wheel 22 disposed therebetween. Accordingly, the housing 16 will remain in
a
fixed position relative to the door (not shown), while the turn wheel 22 will
be
allowed to rotate with respect thereto in order to displace the bolt 20, as
will be
explained hereinafter.
A central hollow projection 82 extends frontwardly from the bottom
wall 78 of the turn wheel 22 for receiving a portion of an hexagonal hollow
drive
shaft 84 (see Fig. 1 ), which extends through the door (not shown) and into
the
locking device 14 for enabling the retraction of the bolt 20 after a valid
entry has
been detected by the electronic circuit board 24. The hollow projection 82
defines
an internal shoulder 86 against which the leading end of the hollow drive
shaft 84
may abut to limit axial movement thereof.
As seen in Fig. 1, a central hole 88 is defined in the bottom wall 62
of the rear closure 60 for receiving the central hollow projection 82, thereby
allowing wires (not shown) to pass from the electronic circuit board 24 and
the
source of power (not shown) through the intermediate cover 48 via holes 88
defined therein, through the hollow drive shaft 84 and to the locking device
14. As
seen in Fig. 1, the hollow drive shaft 84 is open along one longitudinal side
thereof
to allow wires to pass from the drive shaft 84 to the locking device 14. A
square
base 89 having rounded corners is provided at the bottom of the central hollow
projection 82 for engagement within the central hole 88. This contributes to
ensure
proper positioning of the rear enclosure 60 in the turn wheel 22.
A back plate 90 defining four holes 92 adapted to be placed in
register with the hollow projections 74 of the rear closure 60 may be disposed
between the outer surface of the door (not shown) and the turn wheel 22. The
back
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plate 90 further defines a central hole 94 for allowing the hollow drive shaft
84 to
extend therethrough.
A recess 96 may be defined in the front enclosure 30 to
accommodate a face plate 98 defining an array of openings 100 corresponding to
the array of openings 34 defined in the front wall 32 of the front enclosure
30. The
face plate 98 further defines a pair of holes 102 configured and sized to be
disposed
about the openings 36 defined in the front wall 32 of the front enclosure 30.
The
face plate 98 may be fixed to the front wall 32 by means of an adhesive or by
any
other suitable means, such as snapped fasteners.
According to a preferred embodiment of the present invention, the
front enclosure 30, the intermediate cover 48, the rear enclosure 60 and the
turn
wheel 22 are all molded from a plastic material. In this case, a metal insert
104 may
be installed within the central hollow projection 82 to prevent premature wear
of
the turn wheel 22 due to the friction between the hollow drive shaft 84 and
the
internal surface of the central hollow projection 82.
The locking device 14 includes an electro-mechanical assembly
(Figs. 4 to 7) housed within a zinc alloy casing 106 with a zinc alloy cover
108
(Fig. 8).
As seen in Figs. 4 and 5, the casing 106 comprises a base plate 110
having an outer surface adapted to be mounted to the inner side of the door to
which the access control system 12 is mounted. A recess 109 (see Fig. 10) is
defined in the outer surface of the base plate 110 for defining a passage with
the
inner side of the door (not shown) for flexible conductors, such as wires, to
pass
from the open longitudinal side of the drive shaft 84 to a connector 113
attached to
the cover 108 (Fig. 8). The inner surface of the base plate 110 provides a
mounting
surface 111 for the various components of the electro-mechanical assembly
illustrated in Figs. 4 to 7.
Fig. 6 illustrates an actuator or driver sub-assembly 112 which is
adapted to displace the bolt 20 from an extended position to a retracted
position
when a valid entry has been registered by the electronic system 18. The
actuator
sub-assembly 112 comprises a driver hub 114 provided with a thick circular
disc
116 having an undersurface 118 from which a cylindrical projection 120
protrudes
at right angles. The driver hub 114 is installed in the casing 106 with the
cylindrical
projection 120 thereof extending through passage 122 (see Fig. 10) defined in
a
raised cylindrical structure extending from the mounting surface 111 of the
casing
106. An axially extending hexagonal hole 124 is defined through the
cylindrical
projection 120 for receiving one end portion of the drive shaft 84 (Fig. 4) so
as to
operatively connect the turn wheel 22 (Fig. 1) to the driver hub 114.
Accordingly,
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the driver hub 114 is driven by the turn wheel 22 via the drive shaft 84 which
extends through the door (not shown) to which the housing 16 and the casing
106
are mounted.
As seen in Figs. 4 to 6, a disc 126 is spring biased against a stop pin
128 (Figs. 4, 5 and 6) extending from the undersurface 118 of the driver hub
114 by
means of a torsion spring 130 in order to normally prevent access to a catch
provided in the form of a cutout portion 132 defined in the circumference of
the
circular disc 116. The torsion spring 130 is installed about the cylindrical
projection
120 in a groove 134 defined in the undersurface 118 of the circular disc 116
of the
driver hub 114.
A retaining member 136 provided in the form of a hook defines a
hole 138 configured to be fitted on a pivot pin 140 extending at right angles
from
the mounting surface 111 of the casing 106. A retaining ring (not shown) is
installed at the free end of the pivot pin 140 after the retaining member 136
has
been installed thereon to prevent dislodgment thereof, while at the same time
allowing the retaining member 136 to pivot about the pivot pin 140. As seen in
Figs. 4 and 5, an abutment pin 142 is pressure fitted in a hole 144 defined in
the
retaining member 136. A spring (not shown) installed on the pivot pin 140 is
engaged at one end thereof in a groove 146 defined in the retaining member 136
to
normally urge the same in an idle position, wherein the portion of the
abutment pin
142 extending below the retaining member 136 is biased against a spring blade
148
having a first connecting end 150 fitted over a pin 152 extending at right
angles
from the mounting surface 111 of the casing 106 and a second connecting end
154
engaged with a worm gear 156 pressure fitted on an output shaft 158 of a DC
motor
160 positioned on the mounting surface 111 of the casing 106. The spring blade
148 advantageously acts as a device to cumulate mechanical energy from the
motor
160 when the retaining member 136 cannot move due to rotation of the turn
wheel
22.
When a valid entry is registered by the electronic system 18, the
motor 160 is powered so as to rotate the worn gear 156 in a direction causing
the
second connecting end 154 of the spring blade 148 to be displaced towards the
motor 160. During this displacement, the spring blade 148 pushes on the
abutment
pin 142 so as to pivot the retaining member 136 to a functional position
thereof,
wherein a distal end portion 164 thereof is disposed to engage a pin 166 (Fig.
6)
depending downwardly from the disc 126. Accordingly, when the turn wheel 22
will be operated with a view to open the lock 10, the driver hub 114 and the
disc
126 will rotate conjointly from a rest position up to a point where the distal
end
portion 164 of the retaining member 136 will engage the pin 166 depending from
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the disc 126, thereby preventing the disc 126 from further rotating with the
driver
hub 114. Continuous rotation of the turn wheel 22 will cause the driver hub
114 to
rotate, thereby clearing the cutout portion 132 thereof by positioning the
same in a
recess 133 defined in the disc 126. A latch lever or spring-loaded arm 168
pivotally
connected to the bolt 20 slidably mounted in the casing at 170 will then fall
into the
cutout portion 132 so that further rotation of the turn wheel 22 will cause
the
retraction of the bolt 20. Then, the door (not shown) can be opened.
In the event that an invalid entry is registered, the motor 160 will not
be powered and, thus, the retaining member 136 will remain biased in its idle
position and will consequently not engage the pin 166 during the rotational
movement of the disc 126 with the driver hub 114. Therefore, rotation of the
turn
wheel 22 will cause the driver hub 114 and the disc 126 to rotate conjointly
with
the disc 126 blocking access to the cutout portion 132. Accordingly, the
spring-
loaded arm 168 will not be allowed to move into the cutout portion 132 and,
thus,
the bolt 20 will remain in its extended position.
A switch 172 is installed in the casing 106 for detecting the
displacement of the bolt 20. The switch 172 is connected to an electronic PCB
174
(Fig. 8) mounted on an undersurface of the cover 108 for controlling the lock
functions. The switch 172 will detect the retraction of the bolt 20 and send a
signal
to the electronic PCB 174 which will in turn control the operation of the
motor 160
in order to displace the second connecting end 154 of the spring blade 148
away
from the motor 160 so as to allow the retaining member 136 to return to its
idle
position. A second switch (not shown) may be mounted on the electronic PCB 174
to provide a signal that the driver hub 114 and thus the turn wheel 22 are
back to
the rest position after re-locking. The second switch (not shown) ensures that
the
lock 10 is locked and that the retaining member 136 and the actuator sub-
assembly
112 have been fully reset mechanically. A protrusion 176 (Figs. 4 and 5)
extends
from the top surface of the circular disc 116 of the driver hub 114 to trigger
the
second switch (not shown). The collected data are also used to provide visual
and
audible feedback to the user.
It is understood that the above described locking device 14 could be
used as a door mortise lock and is thus not limited to the above described
application.
According to a preferred embodiment of the present invention, the
bolt 20 can advantageously be spring loaded or, alternatively dead bolted
according
to the intended application. As seen in Fig. 7, the bolt 20 has a bolt head
provided
in the form of a generally rectangular body 178 defining a rectangular opening
180
in which a support member or core 182 is disposed. The spring-loaded arm 168,
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which acts as a bolt tail, is pivotally attached to the core 182 via a
shoulder screw
184 engaged in a vertical hole 186 defined in the core 182. A torsion spring
188 is
disposed about the vertical hole 186 and has a first end engaged with the core
182
and a second end engaged with the arm 168 to normally urge the same inwardly
towards the driver hub 114.
For spring loaded applications, a compression spring 190 having
leading and trailing ends 192 and 194 is inserted in an axially extending
threaded
bore 196 defined in the front end portion of the body 178. The leading end 192
is
received in a circular recess 198 defined in the core 182 and a dowel fastener
200 is
threadably engaged in the threaded bore 196 against the trailing end 194 of
the
compression spring 190 in order to maintain the same in compression between
the
core 182 and the body 178 of the bolt 20.
The above described spring-loaded bolt can be readily converted to a
dead bolt by driving the dowel fastener 200 out of the threaded bore 196 to
permit
the insertion of a solid pin 197 within the threaded bore 196. The solid pin
is sized
so as to extend through the cavity defined by the compression spring 190 and
into
the recess 198. The dowel fastener 200 is then screwed back into the threaded
bore
196 to retain the compression spring 190 and the solid pin (not shown) in
position.
In this case, the core 182 is rigidly connected to the body 178 of the bolt
20, since
the solid pin extends between the core 182 and the dowel fastener 200 which is
fixed relative to the body 178.
Referring now to Figs. 4 and 5, a re-locking mechanism 202 adapted
to prevent the lock 10 from opening under various types of attack, such as
impacts
on the lock itself or on the structure to which the lock 10 is mounted, will
be
described. More particularly, the re-locking mechanism 202 is adapted to
prevent
retraction of the bolt 20 in the event that the position of the cover 108 is
altered
relative to the casing 106.
The re-locking mechanism 202 comprises an interfering member
204 (see Fig. 9) in which a transversal bore 206 is defined for receiving a
pivot pin
in order to pivotally mount the interfering member 204 in a L-shaped recess
208
defined in the outer surface of the base plate 110 of the casing 106. The
interfering
member 204 includes a L-shaped portion 210 from which depends a curved end
portion 212. The curved end portion 212 is configured, once the interfering
member
204 has been installed in the L-shaped recess 208, to extend through a bore
214
defined in the bottom surface of the L-shaped recess 208.
In order to maintain the interfering member 204 in an ineffective
position, where the tip of the curved end portion 212 thereof is located in a
recess
215 (see Fig. 7) defined in the body 178 of the bolt 20 with surfaces 216 and
218 in
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sliding contact, a pin 220 extending through a bore 222 defined in the base
plate
110 is pushed against the free end of the L-shaped portion 210 of the
interfering
member 204 by a raised structure 224 (Fig. 8) extending from the inner surface
of
the cover 108. The length of the pin 220 is greater than that of the bore 222
in order
to allow the raised structure 224 to push the pin 220 partially outwardly of
the
casing 106 when the cover 108 is assembled to the casing 106. Under normal
lock
operations, the interfering member 204 is pushed by the pin 220 against a
compression spring 226 disposed in a small recess 227 defined in the bottom
wall
of the L-shaped recess 208. In this position, the interfering member 204 does
not
block the sliding movement of the bolt 20 and the same may thus be displaced
as
per the way described hereinbefore.
However, in the event that the cover 108 is removed from the casing
106, the raised structure 224 will no longer be in contact with the pin 220
and
consequently the same will no longer exert a force on the interfering member
204
and, thus, the compression spring 226 will cause the interfering member 204 to
pivot against a pin or a screw 300 retaining the interfering member 204 to the
casing 106, thereby retracting the curved end portion 212 of the interfering
member
204 in an indentation 228 defined in the recess 215 of the body 178 of the
bolt 20
so as to interfere with the retraction thereof. This thus prevents the opening
of the
lock 10.
It is noted that the cover 108 is attached to the casing 106 to be
readily disassembled therefrom due to impacts on the casing 106 or the
structure in
which the lock 10 is used.
Fig. 10 illustrates a re-locking mechanism 202' used in combination
with the casing 106 and the cover 108 in accordance with a second embodiment
of
the present invention. The re-locking mechanism 202' comprises an interfering
member 204' which is urged towards the bolt 20 by a spring 226'. The
interfering
member 204' and the spring 226' are received in a transversal bore 214'
defined in
the casing 106 in a direction perpendicular to the movement of the bolt 20'. A
threaded fastener 227' is threadably engaged in the bore 214 for preventing
withdrawal of the spring 226' and the interfering member 204' from the bore
214'.
A second bore 222' is defined in the casing 106 so as to intersect the bore
214 for
allowing a lock pin 220' to engage a catch 221' formed on the interfering
member
204'. The lock pin 220' is freely mounted in the second bore 222' and pushed
therein by the under surface of the cover 108. When the cover 108 is assembled
to
the casing 106, the lock pin 220' is pushed in interlocking engagement in the
catch
221' of the interfering member 204' so as to maintain the spring 226' in a
compressed state and prevent the bolt 20' from being engaged by the
interfering
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member 204'. However, in the event that the cover 108 is removed from the
casing
106, the lock pin 220' will no longer be pushed into the second bore 222',
thereby
allowing the spring-loaded interfering member 204' to become interlockingly
engaged in a recess 228 (see Fig. 7) defined in a side of the bolt 20 so as to
prevent
retraction thereof.
