Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
SJ-8240A - 1 - 4482B/01018
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FIELD OF THE INVENTION
The present invention relates to a vented lockable
manhole cover where the lock on the cover does not affect
the vent through the cover.
aACKGROUND OF THE_INVENTION
It is important that manhole covers be l~cked in
position for a number of different reasons. For example,
without being locked in position manhole covers can become
dislodged simply by vibrations in the road surface to which
they are fitted. Also, they are subject to vandalism and
theft.
Conventional manhole covers include vent holes
which allow unauthorized prying of the covers from the
manhole frame. In some instances, young children after
removing a manhole cover have climbed down into the sewer
system below where they have been caught up in fast fiowing
20water and drowned. Also, the opening of the manhole covers
allow unauthorized persons to have undesirable access to the
sewer system.
There are presently in use several different
25manhole locking devices. One design is a J-bolt which goes
through the existing manhole hole and bolts the frame to the
cover. Another design is in the form of a water tight cover
which again bolts the manhole to the frame.
In both of the arrangements described immediately
above, the manhole cover is sealed and therefore does not
allow the upward escape of gases past the manhole cover.
This can and has resulted in explosions within the sewer
system beneath the manhole cover.
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In addition to being unsafe, the presently used
techniques for locking a manhole cover in position are very
labour intensive with respect to removing the covers for
maintenance and/or inspections.
Other locking systems for manhole covers have been
proposed in prior art patents. Such proposals are shown for
example in United States Patents 3,921,494, 3,772.828,
4,577,478, 4,964,755, 4,9û2,165, and 2,363,567.
The problem with the structures described in the
patents noted immediately above, is that they are not seif
locking and therefore are subject to human error, i.e. even
an authorized person opening the cover could well
15 inadvertently forget to lock the cover.
The cover plate in United States Patent 2,363,567
does show gravity operation of a lock bar on a manhole cover
for moving the lock bar to a locking position. However
20 admitted in the patent, gravity is not sufficient to ensure
proper locking of the bars and therefore a iocking key is
additionally provided to move the bars to a locking
position. The gravity operation of the bars requires that
they not only move in and out but also up and down making
25 them relatively loose fitting and complicated in their
operation.
SUMMARY OF THE PRESENT INVENTION
The present invention provides a very simple yet
efficient locking manhole cover and key combination. The
manhole cover includes a lock on its undersurface and a vent
hole through the manhole cover which is not blocked by the
lock. The lock itself comprises a plurality of locking bars
35 which are spring biased to a locking posltion, a rotatable
.
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actuator accessible through the vent hole for moving the
locking bars to an unlocking position with the key being
fittable through the vent hole to operate the actuator.
''.
The key includes a first shaft portion which is
turnable in the vent hole for rotating the actuator and
pulling ~he locking bars to the unlocking position and a
second shaft portion which when located in the vent hole,
prevents rotation of the actuator and holds the spring
10 bias~ed locking bars away from the locking position.
In order to remove the key from the vent hoie, it
must be released from the actuator with the locking bars
then automatically springing back to their locking position.
BRIEF DESCRIPTION OF THE DRAWINGS
The above as well as other advantages and features
of the present invention will be described in the detaiied
~description according to the preferred embodiments of the
present invention in which;
Figure 1 is a top view of a manhole cover in
accordance with the present invention;
Figure 2 is a sectiona~ view along the lines 2-~ of
.
Figure 1;
Figure 3 is a plan view of the lock secured to the
25 underside of the manhole cover in Figure l;
Figure 4 is a side view of the lock of Figure 3;
Figure 4A is a side view of a somewhat modified
lock according to a further preferred embodiment of the
present invention;
30 Figure 5 is a side view of the operating key used for
unlocking the lock of Figures 3 and 4;
Figure 6 is a'bottom plan view of the key shown in
Figure 5.
DETAILED DESCRIPTION ACCORDING TO THE PREFERRED
EM80DIMENTS OF THE PRESENT INVENTION:
Figure 1 shows a manhole cover 1. This manhole
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cover when seen from above appears to have a standard
construction including a combination vent and lift hoïe 3.
Figure 2 shows a sectionai view through the manhole
5 cover 1 as fitted to a manhoie support 5. This manhole
support includes an inwardly extending lip or ledge 7jon
which the manhole cover rests. iF 7 is additionaily useb
to lock the manhole cover in position by a lock general'y
indicated at 9 on the undersurface of the manhole cover.
Lock 9 which is better shown in Figures 3 and 4 of
the drawings includes a mounting frame 19 having a plurality
of attachment legs 21 which bolt directly to the cover.
Supported by the frame are a pair of movable locking bars
15 15, the movement of which is guided by frame 19.
The locking bars are pivotally secured to a
rotatable disk actuator or control member 11. Actuator 11
is provided with a centrally located key opening i~.
20 Typically key opening 13 has a square shape which matches
the shape of the lift or vent hole.
When the lock is mounted to the undersurface of the
manhole cover key opening 13 is aligned directly beneath the
25 vent hole through the cover. This allows a key, generally
indicated at 2g to be fitted down through the vent hole to
operate actuator 11.
Also proviaed in the lock is a spring 2~ securea at
30 25 to one of the locking arms 15 and at 27 to the frame 19.
This spring normally biases both of the locking bars to a
locking position as shown in Figure ~ of the drawings where
the locking bars project outwardly of the frame beneath lip
7 in the manhole frame. The pulling of the spring on one of
35 the locking bars is translatea through the freely rotatable
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actuator 11 to the other of the locking bars so that both
locking bars normally assume the locking position as noteo
above. With the locking bars in the Figure 2 position, the
manhole cover cannot be lifted out of position from the
manhole frame.
.
Figure 4A shows a lock slightly modified from the
lock described above with respect tc Figures 3 and 4.
Consistent with the earlier embodiment, the lock shown in
10 Figure 4A includes an actuator plate lla which controls a
pair of movable locking arms 15a. These arms are guided by
frame l9a of the lock which additionally includes mounting
legs 21a to mount the lock to the bottom side of the manhoie
cover.
The lock shown in Figure 4A includes a coil spring
24 mounted to the frame and also secured to actuator plate
lla to hold the actuator plate and the iocking arms in a
locked position as earlier described. The actuator plate,
20 although not seen from above, has the identicai
configuration and connections to the movable locking arms as
that shown in figure 3. The ~method of rotating actuator
plate lla is also the same as the method of rotating
actuator plate 11 to be described later in detail.
Key 29 is used to rotate actuator 11 and move bars
15 to an unlocking position against the bias of spring 23.
This key has an elongated shaft comprising different shaft
portions 31, 33, and 35. A rounded stop 37 is provided
30 above shaft portion 35 and an upper handle ~9 is used to
rotate the key.
- As best seen in Figure 6 of the drawings the bottom
shaft portion is of the key has a square configuration
35 matching that of key opening 13 in actuator 1l. Shaft
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portion 31 also matches the shape of the lift hole allowing
it to pass through the manhole cover to gain access to the
actuator. The key is pushed sufficiently far down through
the manhole cover so that the smaller diameter rounded
5 portion 33 of the key is located at the vent hole with shaft
portion 31 in the key opening 13 of actuator 11. In this
position the key can be rotated within the cover lift hole.
This in turn rot~tes the actuator to pull arms 15 to the
unlocking position.
As a result of the spring bias on the arms, if the
key was released in this position, the arms would simply
spring back to their locking position. This would then
necessitate holding the key in the unlocked position ~hiie
15 at the same time lifting on the manhole cover. Hawever,
this problem is avoided by the provision of shaft portion 35
above shaft portion 33 on the key. As will be seen in
Figure 6 of the drawings, shaft portion 35 again has a
square configuration matching that of the vent hole. Shaft
20 portion 35 is located at about 90 relative to shaft
portion 31. Therefore, after the key has been turned to
rotate actuator 11 to the unlocking position, the key is
pushed farther down to lock shaft portion 35 in the lift
hole. This prevents rotation of both the key and the
25 actuator and holds arms 15 away from their normally assumed
locking position.
Stop 37 prevents the key from being pushed down
overly far into the manhole cover so that shaft portion 35
30 remains nested within the cover hole. Handle 39 is then
used to pry the cover off of the manhole frame. Note that
the cover does not have to be pulled directly upwardly but
rather can be pried out of its position at an angle using
the handle 39 on the key. Here it is to be noted that the
35 positioning of the vent hole to one side rather than in the
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middle of the cover, provides assistance in prying the cover
from the frame. After the lock has been released one simply
pushes downwardly on the key which, as noted above, will not
go farther into the hole because of stop 37. This causes
the one side of the cover to effectively fulcrum downwardly
so that the other side of the cover pivots upwardly. One
can now grip the up side of the cover to pull it from the
frame.
In order to get the key back out of the manhoie
cover~ it must be lifted to release shaft portion 35 from
the left hole and then returned to a position in which lower
shaft portion 31 aligns with the lift hole. In this same
position, the actuator 11 is allowed to return to its
15 starting position where the lock bars 15 have once again
resumed their locking positions. Therefore, in order to get
the key out of the manhole cover, the lock bars must be in
the locked position. They wili continue to hold this locked
position because of the spring bias and can only be pulled
20 away from the locked position by the use of the operating
key.
In the Figures 3 and 4 embodiment lock, there is,
aQ noted above, a connection of the spring 23 between point
25 25 on arm 15 and point 27 on the frame of the lock. In the
embodiment shown in Figure 4A, the lower end of spring 24 is
connected to frame l9a while the upper end of the spring is
connected to the actuator plate. In a normal or relaxed
condition, spring 24 holas actuator plate lla in the locking
30 position. As the actuator plate is rotated to the unlocking
position, the spring is coiled because the one end of the
spring is free to rotate with the actuator plate while the
other end of the spring is secured to the frame. Tne spring
therefore wants to return the actuator plate to the locking
35 position but is prevented from doing so when shaft portion
35 of key 29 is locked ln the vent hole as described above.
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The coil spring arrangement shown in Figure 4A
provides a very strong bias on the actuator plate without
requiring an overly large spring. Furthermore, the
connection of the coil spring is achieved in a very simple
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yet efficient manner. The tight windings on coil spring 24
are such that it provides a very substantial resistance to
even a sl,ight unwinding of the spring and therefore the
spring has an essentialiy ùnlimited lifespan.
A further feature to be noted through the use of
coil spring 24 is that even though it is located directly in
line beneath key opening 13a in actuator plate lla, the
spring has a hollow core and therefore does not block
insertion of the key down ,through the key opening.
Although various preferred embodiments of the
invention have been described in detail, it will be
appreciated that variations can be made without departing
from the spirit of the invention or the scope of the
20 appended claims.
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