BACKGROUND OF THE INVENTION
[0001] The present invention relates to an explosion mitigating manhole cover, and more
particularly to a manhole cover configured to release pressure in a directional manner
and limit movement during an explosion event.
[0002] Manhole covers are well known from e.g. document
US 6 161 984 A. Generally, a manhole cover is a removable plate forming the lid over an opening
providing access to an underground area also known as a manhole that may include utilities,
pipes, cables and passages. The lid may, among other things, prevent someone from
falling in and keep unauthorized persons out. Conventional manhole covers seat on
a frame installed over the manhole, sometimes flush with the surface of a road. The
frame may provide an interface for the manhole cover to seat over the manhole opening,
and often times, is secured to the manhole or surrounding structure so that the manhole
cover may be removed for access while the frame remains fixed in place.
[0003] Manhole covers often weigh more than 100 pounds, partly because the weight keeps
them in place when traffic passes over them, and partly because they are often made
out of cast iron, sometimes with infills of concrete. This makes them inexpensive
and strong, but heavy.
[0004] Despite this weight, electrical or gas explosions in the area underneath the cover
may unseat the manhole cover due to the sudden pressure build up from the explosion.
In many cases, the explosion event moves the manhole cover so that the manhole is
left fully or partially uncovered. And, in some explosion events, the manhole cover
may become a projectile, flying up to 20 feet or more in the air. To address these
potentially undesirable effects, manhole covers are sometimes bolted or fastened to
the frame. This configuration, however, may not relieve the pressure from an explosion
event, thereby potentially causing structural damage to the underground area or to
surrounding surface structure, such as the road.
[0005] More recently, manhole cover and frame assemblies have been developed to release
explosive pressure in a controlled fashion. These assemblies behave similar to a relief
valve by allowing the manhole cover to rise in response to explosive pressure and
to then reseat once the pressure has subsided. This way, the manhole cover may not
become a projectile, or leave the manhole uncovered, in response to an explosive event.
One type of manhole cover restraint configured to release explosive pressure in a
controlled fashion is available on the market under the brand name Swiveloc. This
manhole cover includes a locking lug and an extendable latch construction that interface
with a manhole frame to restrain the manhole cover during an explosive event. However,
this cover assembly is not without drawbacks. Although the locking lug appears to
be a simple component, the extendable latch includes multiple interfitting components,
which add expense to the overall product and may become susceptible to failure over
time.
SUMMARY OF THE INVENTION
[0006] The present invention provides a manhole cover assembly configured to behave as a
relief valve in an explosion event, enabling opening of the cover in response to such
an event so that fluid, such as air or explosive gas, may vent from the area underneath
the cover. The manhole cover assembly may include a manhole cover and a frame, and
may be configured to limit movement of the manhole cover with respect to the frame
in response to increased pressure on the manhole cover. For example, the manhole cover
assembly may be configured to allow limited vertical displacement of
all or a portion of the manhole cover with respect to the frame, thereby allowing pressure to release
from the underground area through the access opening.
[0007] In one embodiment, for example, the manhole cover may include legs having angled
surfaces adapted to guide or substantially center the manhole cover in the frame as
the manhole cover displaces to release pressure. In another embodiment, one or more
legs may be at least one of (a) pivotable with respect to the manhole cover and (b)
slidable within the manhole cover. This may enable configuring the manhole cover between
a restraint mode and a removal mode, where the restraint mode may prevent complete
removal of the manhole cover from the frame and the removal mode may allow complete
removal.
[0008] In one embodiment, the legs may extend away from an underside of the manhole cover
and toward an access opening of the underground area. Each of the legs may include
a foot at a first end thereof and that extends toward a peripheral wall of the frame.
The feet may contact the frame, limiting displacement of the manhole cover with respect
to the frame in response to pressure on the underside of the frame. For example, the
feet may contact a flange or ridge on the peripheral wall of the frame preventing
the manhole cover from further vertical displacement with respect to the frame.
[0009] In one embodiment, the manhole cover may include an opening through which a leg may
slide in a removal mode, and within which the leg may be anchored to the manhole cover
in a restraint mode. For example, in the restraint mode, a lug end of the leg may
be anchored to the manhole cover preventing the cover from being removed from the
frame. In the removal mode, the leg may slide freely within the opening to enable
removal of the cover. A projection at the lug end of the leg and a pin disposed at
an opposite end of the leg may prevent the leg from being decoupled from the manhole
cover.
[0010] In another embodiment, pivotable legs coupled to the manhole cover may be configurable
between the removal mode and the restraint mode. The legs may pivot freely toward
the peripheral wall of the frame but not in the opposite direction beyond a pivot
stop. In this way, the legs may interface with the peripheral wall in the restraint
mode to limit movement of the manhole cover with respect to the frame, and may enable
the manhole cover to be removed from the frame when configured in the removal mode.
[0011] For example, the pivotable legs may rotate up to 90 degrees between the pivot stop
and the underside adjacent a peripheral edge of the manhole cover. Two legs disposed
near each other and configured to pivot in this manner may enable horizontal displacement
of the manhole cover in one direction (e.g. a removal direction) while preventing
such displacement in the other direction. A third leg being configurable to prevent
horizontal displacement in the removal direction may therefore maintain the manhole
cover in the restraint mode. This third leg may also be configurable in the removal
mode to allow movement in the removal direction, thereby enabling the two legs to
pivot and complete removal of the manhole cover from the frame.
[0012] In another embodiment, the manhole cover adapted for angular movement when acting
as a relief valve. Such an assembly includes a cover having an upper surface, an outer
peripheral edge, and first and second legs extending from the cover. The legs including
radially outwardly extending feet aligned underneath the frame. One of the legs is
shorter than the other legs to provide the cover with a range of angular movement.
[0013] In a more particular version of this embodiment, the cover defines an opening extending
through the cover and one of the legs extends through the opening in the cover, wherein
the upper end includes a lug and the lower end includes a foot extending outwardly
from the leg and underneath a portion of the frame, wherein the first leg is slidably
movable within the cover opening to a closed position wherein the lug engages the
cover and the foot is spaced at a vertical distance below the underside of said cover
with the foot extending radially outwardly underneath the frame such that in response
to increased pressure a first portion of the cover has a range of movement with respect
to the cover receiving flange that is capable of providing a vertical clearance between
the first portion of the cover and the frame to enable the escape of fluids through
the access opening, wherein the foot contacts the frame at a limit of the range to
prevent the first portion of the cover from moving beyond the limit of the range.
As noted below, this embodiment may provide advantages in that it can enable the ability
to limit the direction of flow of any gases, flames or fluids will escape the manhole
during an explosion or other high pressure event.
[0014] These and other objects, advantages, and features of the invention will be more fully
understood and appreciated by reference to the description of the current embodiment
and the drawings.
[0015] Before the embodiments of the invention are explained in detail, it is to be understood
that the invention is not limited to the details of operation or to the details of
construction and the arrangement of the components set forth in the following description
or illustrated in the drawings. The invention may be implemented in various other
embodiments and of being practiced or being carried out in alternative ways not expressly
disclosed herein. Also, it is to be understood that the phraseology and terminology
used herein are for the purpose of description and should not be regarded as limiting.
The use of "including" and "comprising" and variations thereof is meant to encompass
the items listed thereafter and equivalents thereof as well as additional items and
equivalents thereof. Further, enumeration may be used in the description of various
embodiments. Unless otherwise expressly stated, the use of enumeration should not
be construed as limiting the invention to any specific order or number of components.
Nor should the use of enumeration be construed as excluding from the scope of the
invention any additional steps or components that might be combined with or into the
enumerated steps or components.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016]
Fig. 1 is a perspective view of a manhole cover assembly according to a current embodiment;
Fig. 2 is a bottom perspective view of the manhole cover assembly in a seated position
according to the current embodiment;
Fig. 3 is a sectional view of the manhole cover assembly according to the current
embodiment;
Fig. 4 is a top perspective view of a manhole cover according to the current embodiment;
Fig. 5 is a bottom perspective view of the manhole cover according to the current
embodiment;
Fig. 6 is a perspective view of the manhole cover being removed from a frame according
to the current embodiment.
Fig. 7 is a side view of a manhole cover and frame according to a second embodiment
of the present invention with the cover in a partially open position.
Fig. 8 is a side view of a manhole cover and frame according to a second embodiment
of the present invention with the cover in an open position.
Fig. 9 is a perspective view of a manhole cover and frame according to a second embodiment
of the present invention with the cover in an open position.
Fig. 10 is a side cross sectional view of a manhole cover and frame according to a
second embodiment of the present invention with the cover in an open position.
Fig. 11 is a side cross sectional view of a manhole cover and frame according to a
second embodiment of the present invention with the cover in a partially open position.
Fig. 12 is a side cross sectional view of a manhole cover and frame according to a
second embodiment of the present invention with the cover in a closed position.
Fig. 13 is a side cross sectional view of a manhole cover and frame according to a
second embodiment of the present invention with the cover in a closed position and
a control leg in a removal mode.
Fig. 14 is a perspective view of a manhole cover according to a second embodiment
of the present invention with the control leg in a restraint mode.
Fig. 15 is a perspective view of a manhole cover according to a second embodiment
of the present invention with the control leg in a restraint mode.
DESCRIPTION OF THE CURRENT EMBODIMENT
I. Overview
[0017] A manhole cover assembly according to one embodiment of the present invention is
shown in Figs. 1-3 and 6 and generally designated 10. The manhole cover assembly 10
generally includes a manhole cover 12 and frame 14 adapted to support the manhole
cover 12. The manhole cover 12 is configured to behave as a relief valve in an explosion
event, opening so that fluid, such as air, explosive gas, or another gas, may vent
through the manhole cover assembly 10. The manhole cover 12 is configured to limit
its movement with respect to the frame 14 in response to increased pressure on the
manhole cover 12 and to then return to a seated position once the pressure has subsided.
In the illustrated embodiment, the manhole cover 12 includes legs 22, 24, 26 that,
when in a locked position (e.g., a restraint mode), may engage the frame 14 to limit
displacement of the manhole cover 12 with respect to the frame 14. For example, as
shown in the illustrated embodiment of Fig. 1, the manhole cover 12 is fully open
with the legs 22, 24, 26 engaged with the frame 14, preventing further vertical displacement
of the manhole cover 12 along a central axis 18 of the frame 14 and allowing fluid
to flow through the access opening 15. And, in the illustrated embodiment of Fig.
2, the manhole cover 12 is fully closed or seated with the legs 22, 24, 26 disengaged
from the frame 14, enabling vertical movement of the manhole cover 12 along the central
axis 18 of the frame 14.
[0018] The legs 22, 24, 26 may be configurable from the restraint mode to a removal mode,
in which one or more of the legs 22, 24, 26 are adapted to pivot, release, or a combination
thereof, in order to clear the frame 14 and enable removal of the manhole cover 12
from the frame 14. Further, in the removal mode, one or more legs 22, 24, 26 may also
slide partially through an opening 58 in the manhole cover 12, allowing the one or
more legs to be used as a handle for removing the manhole cover 12 from the frame
14. Although described in connection with a manhole cover 12 having two legs 24, 26
capable of pivoting to clear the frame 14, and one leg 22 adapted to slide partially
through the opening 58 to clear the frame 14 and to be used as a handle, it should
be understood that the present invention is not limited to this configuration. The
manhole cover 12 may have any number of legs that slide partially and any number of
legs adapted to pivot. In another alternative embodiment, the manhole cover 12 may
have one or more legs that slide partially through a frame opening to clear the frame
14 without legs capable of pivoting. And in other alternative embodiments, the manhole
cover 12 may have one or more legs adapted to pivot to enable removal without legs
that partially slide through a frame opening.
II. Structure
[0019] The described embodiment may be used as a manhole cover assembly 10 to cover an access
opening 15 and to provide access to an infrastructure, such as a drainage or sewer
infrastructure system, underneath the opening 15. Although the manhole cover assembly
10 may be installed over any suitable hole, it will often be installed over a manhole
in a street or sidewalk. As noted above, the manhole cover assembly generally includes
a frame 14 and a cover 12, each of which is described in more detail below.
[0020] In the illustrated embodiments of Figs. 1 and 2, the frame 14 is a generally peripheral
structure including a base 34, and a peripheral wall 16 extending upwardly from the
base 34 including an inner surface 38 and an outer surface 40. The inner surface 38
of the illustrated embodiment may include a cover receiving support 42 configured
as a flange to support the manhole cover 12 in a seated position. The described frame
14 is annular and may be installed over a manhole (not shown), but it should be appreciated
that the frame 14 may be any shape, including rectangular or square. The configuration
of the top edge 44, inner surface 38, and cover receiving support 42 may be selected
to interface with the cover 12 to cover the manhole opening. Alternatively, a supporting
surface other than the cover receiving support 42, such as the top edge 44 of the
frame 14, may support the manhole cover 12 in a seated position to cover the manhole
opening 15. In one embodiment, the frame 14 is installed flush with the surface of
a road 8 and fastened to the manhole opening 15 using anchor bolts or angled anchor
rods fastened to either the underground area or surrounding road 8. The frame 14 may
also include cast-in bolts for securing the frame 14 to the manhole opening 15. The
frame 14 may be a pre-existing frame already installed to cover the manhole opening
15.
[0021] Turning to the cover 12 of the illustrated embodiments shown in Figs. 1-6, the cover
12 is depicted having a round shape to match the generally annular shape of the frame
14 and peripheral wall 16. Alternatively, the cover 12 may have a different shape
to cover a variety of differently sized access openings and to interfit with a variety
of differently sized frames 14. The cover 12 includes a peripheral edge 52, an upper
surface 54 and an underside 56. The underside 56 may include a seating surface 53
adjacent to the peripheral edge 52 and that interfaces with a supporting surface of
the frame 14, such as the cover receiving support 42, in a seated position. The cover
12 may include control legs 22, 24, 26 configurable between two modes: a removal mode
and a restraint mode. The illustrated embodiment includes three control legs 22, 24,
26, but there may be more or fewer legs in alternative embodiments. As shown in the
illustrated embodiments of Fig. 1-5, the legs 22, 24, 26 are configured in the restraint
mode such that movement of the cover 12 with respect to the frame 14 may be limited.
For example, the manhole cover 12 may move from a seated position as shown in Fig.
2 to an unseated position as shown in Fig. 1. The illustrated embodiment of Fig. 6
shows the cover 12 configured in a removal mode, enabling the cover 12 to be removed
from the frame 14.
[0022] In the illustrated embodiments of Figs. 1-5, each of the legs 22, 24, 26 includes
respectively an angled-guide surface 71, 72, 73 and a foot 74, 75, 76. The angled-guide
surface and feet may be integrally cast as part of each leg during manufacture. The
feet 74, 75, 76 extend outwardly toward the peripheral edge 52 of the cover 12, and
each may include a frame-stop surface 77, 78, 79 that may be configured to contact
the frame 14 in order to limit vertical displacement of the cover 12 with respect
to the frame 14 along the central axis 18. For example, the feet 74, 75, 76 may contact
the underside of the frame supporting surface 47 limiting movement of the cover 12
in an explosion event. It should be understood that the legs 22, 24, 26 may not include
angled-guide surfaces 71, 72, 73 in an alternative embodiment. For example, the angled-guide
surfaces 71, 72, 73 may not be angled.
[0023] As described herein, in the restraint mode and with the cover 12 seated on the frame
14, the cover 12 may displace vertically with respect to the central axis 18 as pressure
rises on the underside 56 of the cover 12, thereby behaving as a relief valve to allow
fluid through the access opening 15. As the cover 12 displaces vertically, the angled
guide surfaces 71, 72, 73 may interface with the inner surface 38 of the frame 14
to guide the cover 12 toward the center of the frame 12. In the illustrated embodiment,
the cover 12 is capable of displacing up to 8 inches vertically along the central
axis 18 from a seated position on the frame 14. The range over which the cover 12
is capable of moving may vary from application to application depending on the desired
pressure release capability of the manhole cover assembly 10. For example, if a lower
maximum pressure release is anticipated, then the distance between the seating surface
53 and the frame-stop surfaces 77, 78, 79 may be decreased so that the cover 12 is
capable of displacing up to 4 inches instead of 8 inches, decreasing the maximum allowable
fluid flow. Alternatively, if higher maximum pressure release is anticipated, then
the vertical displacement capability of the cover 12 may be increased in order to
allow greater fluid flow. The range may also vary depending on other constraints,
such a displacement height limitation.
[0024] Detailed views of the manhole cover 12 configurable between a removal mode and a
restraint mode are shown in the illustrated embodiments of Figs. 4-6. In particular,
the control legs 22, 24, 26 may be configurable between a removal mode and a restraint
mode. In either mode, two of the control legs 24, 26 may be pivotally mounted to the
underside 56 of the cover 12, though a greater or fewer number of control legs may
be pivotally mounted in alternative embodiments. The underside 56 of the cover 12
may include mounting flanges 61, 63 and pins 62, 64 capable of pivotally receiving
the legs 24, 26. The mounting flanges 61, 63 respectively include a pivot stop 65,
66 and may be configured to allow the control legs 24, 26 to rotate approximately
90 degrees between the seating surface 53 and the pivot stops 65, 66. Alternatively,
the manhole cover assembly 10 may be configured to enable more or less than 90 degree
rotation of the control legs 24, 26 depending on the desired configuration. As illustrated,
the pivot stops 65, 66 may prevent further rotation of the control legs 24, 26 beyond
90 degrees so that, in the restraint mode, the feet 75, 76 and angled-guide surfaces
71, 72 of the control legs 24, 26 interface with the frame 14 to limit movement of
the cover 12.
[0025] One or more of the control legs, leg 22 in the illustrated embodiment, may be fixedly
anchored to the cover 12 in the restraint mode while being slidably coupled to the
cover 12 in the removal mode. The control leg 22 may include a projection 23, or lug,
having a hole 25 capable of being fastened with an anchor bolt 27 to the cover 12
so that the control leg 22 is fixedly anchored to the cover 12. However, it should
be understood that, in the current embodiment, the control leg 22 need not be fixedly
anchored to the cover 12 in order to limit movement of the cover 12 with respect to
the frame 14 in response to increased pressure. If the anchor bolt 27 or a fastener
for the control leg 22 is misplaced, damaged or defective, the cover 12 and the control
leg 22 may remain inherently capable of limiting movement of the cover 12. In other
words, without the control leg 22 fixedly anchored to the cover 12, the cover 12 may
be in the removal mode but still configured for limited movement during an explosion
event. For instance, if the anchor bolt 27 is not present, the projection 23 may interface
with the cover 12 to enable the cover 12 to behave as a relief valve.
[0026] As illustrated, the cover 12 may include a control leg anchor opening 58 defining
an opening through the cover 12 from the upper surface 54 to the underside 56. The
control leg 22 may slide within this opening 58 in the removal mode so that the control
leg 56 can be slid up and away from the frame 14, thereby enabling removal of the
cover 12 from the frame 14. For example, by using the projection 23 as a handle to
pull the cover 12 from the frame 14, the control legs 24, 26 may rotate toward the
seating surface 53, thereby freeing the cover 12 from the frame 14 so that it can
be removed. The control leg 22 may include a pin 21 that prevents the control leg
22 from sliding completely through the opening 58 in the removal mode. This pin 21
may be installed during manufacture after the control leg 22 is inserted through the
opening 58.
II. Operation
[0027] In operation, the cover 12 of the illustrated embodiment may be configured between
two modes: a restraint mode and a removal mode. In the restraint mode, the cover 12
may behave as a relief valve, displacing vertically in response to a pressure on the
underside 56 exceeding a threshold and enabling fluid to vent through the access opening
15. The cover 12 may return to a seated position on the frame 14 after the pressure
has subsided. In this way, if an explosion event occurs, damage to the manhole cover
assembly 10 and surrounding structure, such as the road 8 or the underground area,
may be prevented or mitigated. The pressure threshold resulting in displacement of
the cover 12 may vary from application to application, generally depending on the
weight of the cover 12, and to the extent there are other fluid paths from the underground
area.
[0028] To place the cover 12 in the restraint mode, the pivotable control legs 24, 26 may
be placed within the access opening 15 such that they hang, possibly resting against
the pivot stops 65, 66. The seating surface 53 of the underside 56 may be positioned
to rest on the cover receiving support 42 of the frame 14. Next, the control leg 22
may slide within the control leg anchor opening 58 until the projection 23 of the
control leg 22 contacts the upper surface 54 of the cover 12. An anchor bolt 27 may
fasten the control leg 22 to the cover 12 so that the control leg 22 is stationary.
It should be appreciated that fastening systems other than an anchor bolt 27 may be
used to anchor the control leg 22 to the cover 12, and that the present invention
is not limited to using an anchor bolt 27. Further, in one embodiment, the anchor
bolt 27 or other fastener may be configured to be tamper resistant so that the cover
12 may be considered an unauthorized access deterrent. As an example, in embodiments
in which the anchor bolt 27 is a bolt, the bolt may be a penta-head bolt or another
bolt type capable of deterring unauthorized access.
[0029] With the cover in the restraint mode, the cover 12 may have a limited range of movement
with respect to the frame 14 such that it may behave as a relief valve. The cover
12, however, may not be removed completely from the frame 14 without being reconfigured
into the removal mode. For example, the feet 74, 75, 76 may interfere with a portion
of the frame 14 preventing vertical movement of the cover 12 beyond a certain point
with respect to the frame 14. A portion of the peripheral wall 16 of frame 14, such
as a flange, may be circular, and the feet 74, 75, 76 may be arranged such that a
circle circumscribed about the feet 74, 75, 76 has a diameter larger than an inner
diameter of the peripheral wall 16. A circle circumscribed about the angled-guide
surfaces 71, 72, 73, however, may have a diameter less than that of the peripheral
wall 16. In this way, the angled-guide surfaces 71, 72, 73 may enable the manhole
to move vertically with respect to the frame, while the feet 74, 75, 76 limit this
vertical movement by contacting the peripheral wall.
[0030] Removal of the cover 12 may be enabled by configuring the cover into the removal
mode. In this mode, any fastener holding the control leg 22 in place may be loosened
or removed so that the control leg 22 may clear the frame 14. The pivotable control
legs 24, 26 may pivot toward the seating surface, shown for example in Fig. 6, in
order to clear the frame as well. With the legs 22, 24, 26 in this configuration,
the cover 12 may be removed from the frame 14 in order to access the manhole or underground
area.
III. Second Embodiment
[0031] A second embodiment of the explosion mitigating manhole cover is shown in Figs. 7-15
and generally designated 100. In this second embodiment, the manhole cover assembly
100 generally includes a manhole cover 112 and frame 114 adapted to support the manhole
cover 112. As in the first embodiment, the manhole cover 112 is configured to behave
as a relief valve in an explosion event, opening so that fluid, such as air, explosive
gas, or another gas, may vent through the manhole cover assembly 100. The manhole
cover assembly 100 varies from the first embodiment in that upon the pressure under
the manhole cover 112 reaching a threshold, the manhole cover 112 lifts angularly
- rather than strictly vertically - with respect to the frame 114. As in the first
embodiment, the manhole cover 112 is configured to limit the movement of the cover
112 with respect to the frame 114 in response to increased pressure on the manhole
cover 112 and to then return the opened portion of the cover 112 to a seated position
once the pressure has subsided. In the illustrated embodiment of Figs. 7-15, the manhole
cover 112 includes legs 122 and 124 that, when in a locked position (e.g., a restraint
mode), may engage the frame 114 to limit displacement of the manhole cover 112 with
respect to the frame 114. The leg 122 may be longer than the leg 124, causing the
cover 112 to displace angularly. For example, as shown in the illustrated embodiment
of Fig. 10, the manhole cover 112 is fully open with the legs 122 and 124 engaged
with the frame 114, preventing further angular displacement of the manhole cover 112
about an axis that generally extends through the support flange of the frame 114,
about which the leg 124 rotates. This position allows fluid to flow through the access
opening 115 and directs such flow in a particular direction defined by the positioning
of the leg 122. And, in the illustrated embodiment of Fig. 12, the manhole cover 112
is fully closed or seated with the leg 122 disengaged from the frame 114, enabling
angular movement of the manhole cover 112.
[0032] The legs 122 and 124 may be configurable from the restraint mode to a removal mode,
in which one or more of the legs 122, 124 are adapted to pivot, release, or a combination
thereof, in order to clear the frame 114 and enable removal of the manhole cover 112
from the frame 114. Further, in the removal mode, one or more legs 122, 124 may also
slide partially through an opening 158 in the manhole cover 112, allowing the one
or more legs to be used as a handle for removing the manhole cover 112 from the frame
114.
[0033] The frame 114 of the second embodiment is substantially similar to the frame 14 of
the first embodiment and thus will not be described again in detail. In short, with
reference to Fig. 9, the frame 114 includes a base 134, and a peripheral wall 116
extending upwardly from the base 134 including an inner surface 138 and an outer surface
140. The inner surface 138 of the illustrated embodiment may include a cover receiving
support 142 configured as an inwardly extending flange to support the manhole cover
112 in a seated position with the underside of the cover 112 resting on the support
flange 142. As noted in the first described embodiment, although the described frame
114 is annular and may be installed over a manhole (not shown), it should be appreciated
that the frame 114 may be any shape, including rectangular or square. The configuration
may be selected to interface with the cover 112 to cover the manhole opening. Alternatively,
a supporting surface other than the cover receiving support 142, such as the top edge
144 of the frame 114, may support the manhole cover 112 in a seated position to cover
the manhole opening 115. The frame 114 as described is for illustrative purposes only,
as the cover 112 may be designed to retrofit onto many different types of frames 114
to convert those manhole cover assemblies into explosion mitigation assemblies.
[0034] The cover 112 is generally similar to that depicted in the first embodiment, having
a round shape to match the generally annular shape of the frame 114 and peripheral
wall 116. Alternatively, the cover 112 may have a different shape to cover a variety
of differently sized access openings and to interfit with a variety of differently
sized frames 114. The cover 112 includes a peripheral edge 152, an upper surface 154
and an underside 156. The underside 156 may include a seating surface 153 adjacent
to the peripheral edge 152 that interfaces with a supporting surface of the frame
114, such as the cover receiving support 142, in a seated position.
[0035] In the embodiment illustrated in Figs. 7-15, the cover 112 includes a pair of legs
122, 124. As in the first embodiment, the legs 122, 124 may be configurable between
two modes: a removal mode and a restraint mode. As shown in the illustrated embodiments
of Fig. 7-12, the legs 122, 124 are configured in the restraint mode such that movement
of the cover 112 with respect to the frame 114 may be limited. For example, the manhole
cover 112 may move from a seated position as shown in Fig. 12 to an unseated position
as shown in Fig. 10. The illustrated embodiment of Fig. 13 shows the cover 112 configured
in a removal mode, enabling the cover 112 to be removed from the frame 114.
[0036] As illustrated, each of the legs 122, 124 includes a foot 174, 175 respectively.
The feet may be integrally cast as part of each leg during manufacture. The feet 174,
175 may extend radially outwardly toward the peripheral edge 152 of the cover 112,
and each may include a frame-stop surface 177, 178 that may be configured to contact
the frame 114 in order to limit displacement of the cover 112 with respect to the
frame 114. The feet 174, 175 may project radially outwardly beyond the peripheral
edge 152 of the cover 112 in order to be aligned underneath the frame 114. The feet
174, 175 are thus aligned vertically underneath the frame 114, at least when the cover
112 is in the restraint mode. For example, the feet 174, 175 may contact the underside
of the frame supporting surface 142 limiting movement of the cover 112 in an explosion
event. In one embodiment at least one of the legs 122 may include an angled guide
surface 172; however, the angled guide surface of the leg 122 may be provided with
a generally curved, convex shape. This shape may aid in holding the cover 112 tightly
against the frame 114, particularly in the area of the second leg 124, as the cover
112 moves through an angular range of motion.
[0037] As illustrated, leg 122 may be the same as or similar to the leg 22 of the first
embodiment, wherein it can be fixedly anchored to the cover 112 in the restraint mode
while being slidably coupled to the cover 112 in the removal mode. This leg thus determines
whether or not the cover 112 is in the restraint mode or the removal mode. The control
leg 122 may include a projection 123, or lug, having a hole 125 capable of being fastened
with an anchor bolt 127 to the cover 112 so that the control leg 122 is fixedly anchored
to the cover 112. This fastens the leg 122 to the cover 112 and prevents the unwanted
movement of the leg 122. However, it should be understood that the control leg 122
need not be fixedly anchored to the cover 112 in order to limit movement of the cover
112 with respect to the frame 114 in response to increased pressure. If the anchor
bolt 127 or a fastener for the control leg 122 is misplaced, damaged or defective,
the cover 112 and the control leg 122 may remain inherently capable of limiting movement
of the cover 112. In other words, without the control leg 122 fixedly anchored to
the cover 12, the cover 112 may be in the removal mode but still configured for limited
movement during an explosion event. For instance, if the anchor bolt 127 is not present,
the projection 123 may interface with the cover 112 to enable the cover 112 to behave
as a relief valve.
[0038] The leg 122 may be inserted through a control leg anchor opening 158 defined in the
cover 112 from the upper surface 154 to the underside 156. When the control leg is
not secured to the cover 112 (i.e., in the removal mode) the control leg 122 may slide
within this opening 158 so that the control leg 122 can be slid up and away from the
frame 114, thereby enabling removal of the cover 112 from the frame 114. The movement
of the leg 122 is similar to that of the first embodiment, wherein the leg 122 can
move vertically, such that the upper end of the leg including the lug 123 extends
out of the upper surface 154 of the cover 112, as well as pivotally, wherein the foot
174 moves radially inwardly so that it is no longer aligned vertically underneath
the frame 114. For example, by using the projection 123 as a handle to pull the cover
112 from the frame 114, the second leg 124 may rotate about the frame 114 to a position
where the cover 112 is freed from the frame 114 so that it can be removed. The control
leg 122 may include a pin 121 that prevents the control leg 122 from sliding completely
through the opening 158 in the removal mode. This pin 121 may be installed during
manufacture after the control leg 122 is inserted through the opening 158.
[0039] As shown in Figs. 10-13 and 15, in this second embodiment, the second leg 124 is
spaced from the control leg 122 and also shorter in length than the control leg 122.
In the illustrated embodiment, the second leg is positioned diametrically opposite
the control leg 122. Alternatively, the second leg 124 may be spaced in a different
location, and the cover 112 may include multiple second legs 124 to aid retaining
the cover 112. One result of this variation is that the cover 112 - upon experiencing
a threshold level of pressure on the underside - will be displaced to open in an angular
fashion with respect to the frame 114. The portion 200 of the cover 112 proximate
the longer control leg 122 is capable of a range of movement determined by the length
of the control leg 122, which in the illustrated embodiment may be 8". This portion
200 of the cover thus is capable of clearing the frame 114 - with the underside 156
of the cover 112 above the upper edge 140 of the frame 114. The portion 202 of the
cover 112 proximate the shorter second leg 124 has a smaller range of movement than
the portion 200. In the illustrated embodiment, the length of the second leg 124 is
controlled such that the foot 175 of the second leg 124 contacts the frame 114 when
the cover 112 is closed. More particularly, as shown in Fig. 12, the foot 175 may
include a curved contact surface 178, such that a distal portion 179 contacts the
frame 114 when the cover is closed. This configuration enables the portion 202 of
the cover 112 to rotate about the frame mount flange 142, which extends between the
foot 175 and the underside 156 of the cover 112. The curved surface 178 may provide
clearance that enables such rotation. In this configuration, the portion 202 of the
cover 112 proximate the second leg 124 undergoes essentially no vertical movement
when the portion 200 is displaced, and the portion 202 of the cover 112 proximate
the second leg 124 does not clear the frame 114. In an alternative embodiment, the
second leg 124 may be longer than that shown in the illustrated embodiment, for example,
to interfit with a different frame 114 that may have a wider support flange 142, or
to provide some degree of vertical displacement for the second leg 124 and the portion
202 of the cover 112 proximate thereto.
[0040] The angular displacement of the cover 112 can be advantageous in that it limits the
direction in which exiting fluids can flow. Instead of allowing fluids to escape through
a 360 degree range, the angular displacement of the cover reduces the circumferential
range that exiting fluids can flow. In addition, it is possible to orient the cover
112 during installation to direct any gases or flames that may exit the cover assembly
100 during an explosion event. For example, in an arrangement wherein a cover assembly
100 is installed on a sidewalk near a building, the cover 112 may be keyed, for example,
by cooperating structure on the frame and cover, such that the longer leg 122 must
face the building, such that when the cover 112 is displaced angularly upon the pressure
under the cover reaching a threshold, escaping gases, fluids and flames will be directed
toward the building rather than toward the open sidewalk which may be likely to contain
people.
[0041] In operation, the cover 112 of the second embodiment may be configured between two
modes: a restraint mode and a removal mode. In the restraint mode, the cover 112 may
behave as a relief valve, displacing angularly in response to a pressure on the underside
156 exceeding a threshold and enabling fluid to vent through the access opening 115.
The cover 112 may return to a seated position on the frame 114 after the pressure
has subsided. In this way, if an explosion event occurs, damage to the manhole cover
assembly 100 and surrounding structure, such as the road or the underground area,
may be prevented or mitigated. The pressure threshold resulting in displacement of
the cover 112 may vary from application to application, generally depending on the
weight of the cover 112, and to the extent there are other fluid paths from the underground
area.
[0042] To place the cover 112 in the restraint mode, the second leg 124 may be placed within
the access opening 115 and interfitted with the frame 114 such that the foot 175 extends
underneath a portion of the frame 114. Next, the control leg 122 may slide within
the control leg anchor opening 158 until the projection 123 of the control leg 122
contacts the upper surface 154 of the cover 112. An anchor bolt 127 may fasten the
control leg 122 to the cover 112 so that the control leg 122 is stationary. It should
be appreciated that fastening systems other than an anchor bolt 127 may be used to
anchor the control leg 122 to the cover 112, and that the present invention is not
limited to using an anchor bolt 127. Further, in one embodiment, the anchor bolt 127
or other fastener may be configured to be tamper resistant so that the cover 112 may
be considered an unauthorized access deterrent. As an example, in embodiments in which
the anchor bolt 127 is a bolt, the bolt may be a penta-head bolt or another bolt type
capable of deterring unauthorized access.
[0043] With the cover in the restraint mode, the cover 112 may have a limited range of movement
with respect to the frame 114 such that it may behave as a relief valve. The cover
112, however, may not be removed completely from the frame 114 without being reconfigured
into the removal mode. For example, the feet 174, 175 may be aligned underneath the
frame 114 and thus interfere with a portion of the frame 114 preventing vertical movement
of the cover 112 beyond a certain point with respect to the frame 114. A portion of
the peripheral wall 116 of frame 114, such as a flange, may be circular, and the feet
174, 175 may be arranged such that a circle circumscribed about the feet 174, 175
has a diameter larger than an inner diameter of the peripheral wall 116. A circle
circumscribed about the angled-guide surfaces 171, 172, however, may have a diameter
less than that of the peripheral wall 116.
[0044] Removal of the cover 112 may be enabled by configuring the cover into the removal
mode. In this mode, any fastener holding the control leg 122 in place may be loosened
or removed so that the control leg 122 may clear the frame 114. The cover may be pivoted
open until the second leg 124 is capable of clearing the frame 114. With the legs
122, 124 in this configuration, the cover 112 may be removed from the frame 114 in
order to access the manhole or underground area.
[0045] Directional terms, such as "vertical," "horizontal," "top," "bottom," "upper," "lower,"
"inner," "inwardly," "outer" and "outwardly," are used to assist in describing the
invention based on the orientation of the embodiments shown in the illustrations.
The use of directional terms should not be interpreted to limit the invention to any
specific orientation(s).
[0046] Further, the disclosed embodiments include a plurality of features that are described
in concert and that might cooperatively provide a collection of benefits. The present
invention is not limited to only those embodiments that include all of these features
or that provide all of the stated benefits, except to the extent otherwise expressly
set forth in the issued claims. Any reference to claim elements in the
1. Schachtabdeckung, die dazu ausgebildet ist, als ein Entlastungsventil zu funktionieren,
um Druck abzubauen, wobei die Schachtabdeckung, in Bezug auf einen Rahmen, von einer
eingesetzten Position in eine nicht eingesetzte Position bewegbar ist, wobei der Rahmen
eine Umfangswand hat, die eine Zugangsöffnung definiert, wobei die Schachtabdeckung
aufweist:
ein Deckelteil (112) mit einer Oberseite, einer Außenumfangskante, und einer der Oberseite
entgegengesetzten Unterseite, gekennzeichnet durch
ein Steuerbein (122), das sich von der Unterseite des Deckelteils erstreckt und das
einen Fuß (174) aufweist, der sich von dem Steuerbein (122) radial nach außen zu einer
Position unterhalb des Rahmens erstreckt, wobei der Fuß (174) vertikal unter dem Rahmen
angeordnet ist, um zu erlauben, dass mindestens ein dem Steuerbein nahe gelegener
Teil des Deckels einen Bewegungsbereich aufweist, so dass der Teil des Deckel sich
innerhalb des Bewegungsbereichs bewegen kann, wenn ein Druckniveau auf der Unterseite
einen Schwellenwert erreicht, wobei an einer Grenze des Bewegungsbereichs der Fuß
(174) den Rahmen kontaktiert, wobei der Teil des Deckels den Rahmen freigibt, um einem
Fluidstrom zu erlauben, aus der Zugangsöffnung zu fließen; und
ein erstes Bein (124), das sich von der Unterseite des Deckelteils (112) erstreckt,
wobei das erste Bein (124) von dem Steuerbein (122) beabstandet ist, wobei das erste
Bein (124) einen Fuß (175) aufweist, der sich von dem ersten Bein (124) radial nach
außen zu einer Position unterhalb des Rahmens erstreckt, wobei der Fuß (175) an dem
ersten Bein (124) den Rahmen berührt, um zu verhindern, dass ein dem ersten Bein nahe
gelegener Teil des Deckels den Rahmen freigibt.
2. Schachtabdeckung nach Anspruch 1, ferner aufweisend:
eine Öffnung (158) durch das Deckelteil von der Oberseite zu der Unterseite;
wobei das Steuerbein (122) mit dem Deckelteil (112) gekoppelt ist und zwischen einem
Rückhaltemodus und einem Entfernungsmodus konfigurierbar ist, wobei das Steuerbein
(122) dazu ausgebildet ist, sich in dem Entfernungsmodus innerhalb der Öffnung (158)
zu verschieben, und dazu ausgebildet ist, in dem Rückhaltemodus an dem Deckelteil
(112) fixiert zu sein, so dass das Steuerbein (122) in dem Rückhaltemodus an seinem
Platz verriegelt ist.
3. Schachtabdeckung nach Anspruch 1, wobei das Steuerbein (122) eine konvexe gewinkelte
Fläche aufweist, die so konfiguriert ist, dass sie an die Umfangswand des Rahmens
anschließt, um eine Trennung zwischen dem ersten Bein (124) und dem Rahmen zu verhindern,
wenn sich der Deckel in der nicht eingesetzten Position innerhalb des Bewegungsbereichs
bewegt, wenn Fluid aus der Zugangsöffnung entlüftet wird.
4. Schachtabdeckung nach Anspruch 1, wobei die Schachtabdeckung dazu ausgebildet ist,
Fluid zu entlüften, indem der nahe dem Steuerbein (122) gelegene Teil des Deckels
in Bezug auf den Rahmen zwischen 2 und 8 Zoll vertikal verschoben wird.
5. Schachtabdeckung nach Anspruch 1, wobei der Fuß (175) an dem ersten Bein (124) den
Rahmen über den gesamten Bewegungsbereich des nahe dem Steuerbein (122) gelegenen
Teils des Deckels berührt.
6. Schachtabdeckung nach Anspruch 1, wobei das erste Bein (124) und das Steuerbein (122)
sich an dem Deckel diametral gegenüberliegen.
7. Schachtabdeckung nach Anspruch 6, wobei ein Teil des Fußes (175) an dem ersten Bein
(124) in den Rahmen eingreift, wenn sich der Deckel in der eingesetzten Position befindet.
8. Schachtabdeckung nach Anspruch 7, wobei sich der Fuß (175) an dem ersten Bein (124)
um einen Teil des Rahmens dreht, wenn sich der nahe dem Steuerbein (122) gelegene
Teil des Deckels innerhalb des Bewegungsbereichs bewegt.
9. Schachtabdeckung nach Anspruch 8, wobei der Deckel eine Öffnung (158) definiert und
das Steuerbein (122) verschiebbar von dem Deckel entfernt werden kann, indem ein Vorsprung
(123) an dem Steuerbein (122) angehoben wird, um das Steuerbein in der Öffnung (158)
zu schwenken (122) und das Steuerbein (122) durch die Öffnung (158) zu ziehen.
10. Schachtabdeckung nach Anspruch 9, wobei eine Länge des Steuerbeins (122) mindestens
viermal größer als eine Länge des ersten Beins (124) ist.