MANHOLE COVER

Technical Field

The technical field of the invention is manhole covers for use to cover entrances to spaces such as tunnels, ducts for telecommunication cables, sewers, underground maintenance tunnels or the like. An application for embodiments of the present invention is to cover an entrance to an underground tunnel formed in a footpath or road.

Background of Invention

It is common in cities to have an underground tunnel network for routing various utilities such as power and telecommunication cables. Access to these tunnel networks is generally provided by manholes which extend downwardly from an upper surface such as a paved or unpaved surface into the tunnel. Manholes can also be provided for access into ducts, such as used for air conditioning or ventilation, or into other enclosed spaces. Manhole covers are provided to close the entrance of the manhole. Typically, manhole covers are formed of heavy metal or concrete and rest on a mounting within the entrance of the manhole so that the top of the cover sits flush with the upper surface, such as the pavement, in which the manhole is formed. When a worker requires access to the tunnel, the manhole is opened by lifting the heavy cover off the entrance to the manhole and leaving the cover to one side so that the manhole is open while workers are in the tunnel .

To limit unauthorised opening of manhole covers, they are made very heavy and awkward to remove without special tools or considerable effort. This requires a degree of

trust that people will not bother to expend the effort to open the manhole cover unnecessarily unless it is for an official reason.

There have been instances where tunnels have been used for vandalism, illicit or terrorist activities, or other unintended purposes. Thus, it is desirable to have a cover which can be secured closed to prevent unauthorised access to the tunnels or tampering of the cover.

Summary of the Invention

According to one aspect of the present invention there is provided a manhole cover for an entrance, the manhole cover comprising: a cover member moveable between an open position and a closed position; a securing means for, in use, engaging with the entrance to secure the cover in the closed position; a lock adapted to, when locked, inhibit a person from disengaging the securing means from the entrance to open the cover from above; and a lock bypass means adapted to, when locked, enable the securing means to be disengaged from the entrance by a person below to open the cover.

Preferably the securing means comprises one or more arms moveable between a secured position and an unsecured position, where, when the cover is closed, one end of each arm is engaged with or disengaged from the entrance respectively, and an actuator adapted to move the arms between the secured and unsecured positions. Locking the lock inhibits operation of the actuator to move the arms from the secured position to the unsecured position. The bypass means enable the actuator to be operated from below to move the arms from the secured to the unsecured

position .

A manhole cover as described above can further include one or more optional features . Examples of optional features include: a biasing means to bias the cover toward the open position to reduce any manual force required to open the cover; a crack-the-seal means accessible from below the cover to assist in overcoming sticking of the cover in a closed position; a prop means to prop the cover open; and an alarm adapted to be triggered by opening the cover. These and other optional features can be included singly or various combinations in a manhole cover according to an embodiment of the present invention.

Brief Description of the Drawings

Figure 1 illustrates an example of an embodiment of a manhole cover of the present invention.

Figure 2 illustrates an embodiment of a lock and lock bypass mechanism of an example of an embodiment of the present invention in a locked condition.

Figure 3 illustrates a side view of the lock and bypass mechanism of figure 2.

Figure 4 illustrates an example of a manhole cover according to an embodiment of the present invention with bias assisted opening.

Figure 5 illustrates a mechanism for bias assisted opening of figure 4.

Figure 6 illustrates an example of a crack-the-seal mechanism applied in a manhole cover according to an embodiment of the present invention.

Figure 7 illustrates an example of a closed manhole cover according to an embodiment of the present invention, viewed from the outside.

Description

According to a preferred embodiment of the present invention as shown in figure 1, a manhole cover assembly 100 comprises a manhole cover member 110 which is moveable between an open position and a closed position, and a securing means engageable with the manhole entrance to secure the cover in the closed position. The securing means can be locked when the cover is closed to prevent a person from outside the tunnel disengaging the securing means to open the cover.

A lock bypass means is also provided to enable a person inside the tunnel to disengage the securing means from the entrance to open the cover even when the locking mechanism is locked. This has the advantage of enabling a cover to be locked to prevent unauthorised access from outside while also being available for use for emergency opening, if necessary, by a person inside the tunnel. Thus a person can escape the tunnel, even if the cover is locked closed.

In figure 1, the manhole cover assembly 100 is set into a pavement 10 to provide access to a tunnel 120. The cover 110 is hingely mounted to a cover frame 150 which is set into the pavement 10. The securing means is provided by locking arms 140a and 140b. The arms 140a and 140b are each attached at one end to a turn-table 190 and extend

outwardly in opposite directions across the cover 110 with the other end of each of the arms 140a and 140b resting in guiding brackets 145a and 145b respectively. The turntable 190 is pivotally mounted to the cover 110 such that rotation of the turn-table 190 in one direction causes the arms 140a and 140b to extend outwardly beyond the edge of the cover 110 to engage with the cover frame 150 when the cover is closed. Rotation of the turn-table 190 in the opposite direction causes the arms 140a and 140b to retract such that they will disengage from the cover frame 150 when closed to enable the cover to be opened. For example, in the embodiment shown in figure 1 securing arm 140b has one end attached to turn-table 190 and the opposite end slidably retained in bracket 145b. When the cover 110 is closed _/ anticlockwise rotation of the turntable 190 will cause the arm 140b to extend outwardly to be received in aperture 160 in the cover frame 150 which is set in the entrance of the tunnel 120.

The manhole cover 100 assembly is provided with a locking mechanism which prevents opening the cover from above, outside the tunnel. However, the locking mechanism may be bypassed to open the cover from within the tunnel, such as in an emergency.

The turn-table 190, as shown in figure 2, is pivotally mounted to cover 110 by pivot mount 192. The first securing arm 140a is pivotally mounted to the turn-table 190 by pivot mount 142 and the second securing arm 140b is pivotally mounted to the turn-table 190 by pivot mount

143. A handle 180 is accessible from below the cover, inside the tunnel, when the cover is closed. A locking pin 170 extends downwardly from the cover 110 to be received between a shoulder 194 of the turn-table 190 and the handle 180 to inhibit rotation of the turn-table 190 when in the locked position as shown in figure 2. When the lock is unlocked the locking pin 170 is retracted to

disengage from the handle 180 and enable the turn-table 190 to be rotated.

In the embodiment shown in figure 3 the pivot mount 192 has a first portion 312 which is fixed to the turn-table 190 and a second portion 310 which is rotatable relative to the cover 110. This second portion 310 extends through the cover 110 into cavity 320 and is able to be rotated to move the turn-table 190, from above the cover, to extend and retract the securing arms 140a 140b, when the cover is unlocked. The second portion 310 can be provided with an end portion 315 shaped to be gripped by hand or a tool to make it easier to rotate the second portion 310 and the turn-table 190.

From below the cover 110 the turn-table 190 is accessible and, when unlocked, can be moved either by turning the turn-table 190 itself or with assistance of the handle 180.

To enable the cover to be opened for an emergency exit, without unlocking the lock to retract the locking pin 170, the handle 180 is able to be swung downwardly, using manual force, away from the cover 110 to disengage from the locking pin 170, thus enabling the turn-table 190 to be rotated. In the preferred embodiment the handle 180 is pivotally mounted by pivot pin 183 to mount 182 which, in turn, is attached to turn table 190. Guides 184, mounted to the turn-table 190, assist in holding the handle 180 in position. The handle is biased so that it will normally remain parallel to the turn-table 190 such that it will engage with the locking pin 170. The locking pin 170 and the handle 180 therefore provide the lock bypass means.

When a person inside the tunnel wishes to exit the tunnel, the person pulls downwardly on the handle 180, against the direction of the handle bias, so the free end of the

handle will be moved away from the plane of the turn-table 190 so that the handle can pass over the bottom or free end of the locking pin 170 and permit the turn-table 190 to be rotated. The handle 180 also provides leverage to assist the person rotate the turn-table 190. Thus, the cover 110 can be opened from within without needing to unlock the cover 110 to retract the locking pin 170. For example, as can be seen in figure 3, when the end of the handle 180 is pulled downwardly the handle moves so there will then be a clearance between the shoulder of the handle 185 and the locking pin 170 which permits the handle 180 to rotate past the locking pin 170. Thus the handle 180 also provides mechanical assistance for rotating the turn-table 190 to disengage the securing arms, enabling the cover to be opened.

When the manhole is to be opened from above, for example, during normal maintenance activities, the lock will be unlocked to retract the locking pin 170 into the locking pin barrel 172. As can be seen from figure 3, when the locking pin 170 is retracted into the locking pin barrel 172 there will be no obstruction engagement between the locking pin and the handle 180 enabling the turn-table 190 to be freely rotated.

A fixed stopper 197 (shown on figure 2) may also be provided to limit the range of rotational movement of the turn-table 190. In the secured position a shoulder 198 of the turn-table 190 rests against the stopper 197 and in the unsecured position shoulder 199 rests against the stopper 197. The stopper inhibits rotational movement of the turn-table 190 which in turn distributes any force which may be applied against the locking pin 170 if an attempt is made to open the cover when locked, for example by attempting to break the locking pin.

In the preferred embodiment, the lock is mounted in the

cover 110 and is accessible via lock cavity 330. In the preferred embodiment the lock is key operated and the locking pin 170 is spring loaded to automatically retract into the barrel 172 when unlocked using the key. However, other mechanisms such as a manually retractable locking pin or alternative biasing the locking pin have also been envisaged. Further, electronic or combination style locks may also be used as an alternative to keys. The keys, passwords or combinations can be held by a central authority and assigned out to individuals, such as construction and maintenance workers, using a manual or automated authorisation process which tracks information such as which manholes will be opened, at what times, for what purpose and by whom. Where electronic locks are used these may be linked to a central control system. In this embodiment the lock may be unlocked or lock enabled remotely by the central control system rather than by the maintenance worker. Further, the password or unlocking code may be changed after each opening to prevent an unauthorised later opening if the password is disclosed. It should be understood by a person skilled in the art that many alternative types of locks would be applicable to different embodiments of the invention.

Although the preferred embodiment of the invention uses a handle which is movable to disengage from the locking pin 170 any mechanism which enables manual disengagement from the locking pin to enable movement of the securing means from within the tunnel is envisaged and is within the scope of the present invention. For example, the securing means may comprise one arm only which is slideable to engage or disengage with the entrance of the tunnel to secure the cover closed. In this embodiment, a locking pin 170 may be received, in the locking position aperture in the securing arm, and a removable plug may be provided in the aperture to engage with the locking pin to prevent movement of the securing arm. The plug may be removable

from below the cover to enable the locking pin to slide within the aperture so that the cover may be opened from below without unlocking so the securing arm can be disengaged from the tunnel entrance and the manhole used in an emergency for exit.

One problem with using manhole covers as exits in an emergency is that typically manhole covers are made from heavy materials such as concrete or cast steel or iron and can be difficult to open from below simply due to the weight of the cover. Further, accumulation of grime or simply friction between the edges of the cover and the cover frame or mouth of the tunnel in which the cover is resting can act to seal the cover thus requiring additional force to be applied to crack-the-seal to enable the cover to be pushed open. For example, force exertions of 35kgs to 40kgs are required to push open large manhole covers measuring 670mm x 1000mm, and forces of 20kgs to 25kgs are required to push open smaller manhole covers measuring around 600mm x 900mm, with additional force also being required to crack-the-seal . Table 1 shows an analysis of human lifting strength capability for exertion of overhead force which predicts the percentage of the population that may be capable of opening a manhole cover from below, depending on the weight of the cover.

Table 1: Maximal strength capability (overhead push force)

This analysis indicates that only about 50% of the male population would be capable of exerting a two handed 43kg overhead push force to open a manhole cover. To avoid the problem of the weight of the cover preventing a person

opening the cover from below, some embodiments of the present invention provide a spring mechanism to assist with opening the cover by reducing the apparent weight of the cover to a person attempting to open it from below. An example of a preferred embodiment of the spring mechanism for the cover 410 is shown in figures 4 and 5. In figure 4 the cover is shown in the closed position, position A and in the opened position, position B. The spring loading mechanism comprises a spring 510 mounted below the cover frame 450 in a protective housing 520. A levering arm 411 has a circular mounting plate with a hub 412 axially aligned with the spring 510. One tail end 512 of the spring 510 engages with the cover frame 450 and the other tail end 515 of the spring 510 is engaged under tension with the levering arm 411 via bolt 530 inserted through one of the holes 413 in the levering arm 411. The tension of the spring 510 and hence the force exerted on the loading arm by the spring 510 can be adjusted by changing the position of hole 413 in which the bolt 530 is inserted in engagement with the tail end 515 of the spring. The bolt 530 can be inserted into the hole 413 to engage with the tail end 515 of the spring 510 when the cover 410 is in the open position such that as the cover 410 is closed, rotation of the end of the levering arm 411 about the hub 412 exerts force against the tail end 515 of the spring 510, via bolt 530, causing the spring to be wound more tightly so that the tension in the spring 510 biases the cover 410 towards the opened position. Thus, to a person attempting to open the cover 410 from below the perceived weight of the cover 410 is reduced due to the bias loading provided by the spring.

In the preferred embodiment, the levering arm is articulated and comprises a spring mounting portion 411, in engagement with the spring 510 as described above, pivotally jointed to a second portion of the arm 416 which, in turn, is pivotally mounted to the cover 410

using bracket 409. Optionally, a handle 418 may also be provided to assist in operation of the levering arm. To open the cover 410 from below, a person disengages the securing means and then pushes on the handle 418 and the spring mechanism assists in the lifting of the cover 410. When the cover is open, in position B, the two portions of the levering arm 411 and 416 form a reflex angle to prevent the cover being accidentally closed, for example via wind or an accidental bump. However other means for propping the cover open may be provided and are considered within the scope of the invention.

Although the biasing means of the preferred embodiment uses a single spring and articulated levering arm, alternative means for biasing open the cover are envisaged and are considered within the scope of the invention.

Accumulation of dirt or grime can cause an increase in friction between the cover and the surrounding frame causing the cover to stick or seem to be sealed which can require additional force to "crack the seal" and enable the cover to be opened from below. Sticking of the cover can also occur due to changes in ambient temperature and thermal expansion, for example expansion of a metal cover member in a concrete cover frame. This sticking can be a significant problem in covers which are tight fitting or air-tight to prevent ingress of dust, water or pollutants into the tunnel . In an embodiment of the present invention, a crack-the-seal mechanism 600 is provided to assist a person exert the additional force to start to open the cover and crack-the-seal .

An example of a crack-the-seal device is shown in figure 6. The crack-the-seal device 600 comprises a shaft 610 having a handle 620 at one end and an outwardly projecting levering portion 630 toward the other end of the shaft 610. The end of the shaft 610 is rotatably mounted within

an edge of the cover such that the levering portion 630 will be adjacent a portion of the cover frame 650 when the cover is closed. Applying pressure to the handle 620 to rotate the shaft about its longitudinal axis causes the levering portion 630 to apply pressure against the cover frame 650 such that the portion of the cover 640 in which the shaft is engaged will be pushed away from the cover frame 650 by the levering portion 630 to partially open the cover. The handle 620 provides a mechanical advantage enabling enough pressure to be applied by levering portion to cause the cover to move. A small amount of movement of the cover is sufficient to crack-the-seal to enable the cover to then be opened.

One or more crack-the-seal devices may be provided on the cover. Alternative embodiments of the crack-the-seal device may use a levering rather than rotating action to bring a levering portion into engagement with the cover frame to provide initial force to lever the cover open. The most desirable position for the crack-the-seal devices on the cover is on the opposite edge of the cover from the hinges •

An alarm may be provided on the cover to alert the user or others in the vicinity of opening by sounding an alarm. Alternatively the alarm may be linked to a network, for example a LAN or telecommunication network, such that when an alarm is triggered by opening the cover, a signal is sent from the alarm to a control centre to alert a controller for the tunnel network that a manhole cover has been opened. Each manhole cover may be identified by a unique identifier or a location which will enable a tunnel network controller to identify which cover and where the cover was opened, and identify whether this is an authorised or unauthorised opening of the cover. For example, the location of the cover where the alarm has been triggered may be displayed on a map or grid. The

alarm location can be compared with the locations of covers opened for construction or maintenance purposes and the appropriate action taken, such as inspection or contacting maintenance or security personnel. The alarm for a cover may also be remotely disable by a disabling action, for example the alarm may be disabled on command from a the control centre during a time when authorised maintenance activities are to occur .

The alarm may also have additional features of being connected to the lock so it can be determined whether the manhole cover was opened via the emergency exit route, from below, or whether the cover was unlocked before opening. For example, unlocking a cover may change the nature of an alarm to a "notification of authorised opening" for monitoring purposes rather than to illicit an emergency response.

Manhole covers according to embodiments of the present invention may be made of any suitable material. Because manhole covers are often used in public places and generally in pavements or roads where people or vehicles are travelling over them, strong durable materials such as metals, for example Aluminium or Steel or cast iron, are used in preferred embodiments. However, any material suitable for the purpose may be used for example plastics materials having high strength and rigidity may be suitable for some applications, composite materials may also be used. For a security manhole cover designed as a deterrent for terrorism or vandalism, it is desirable to have no apertures through the cover. For example holes that extend through the cover may allow dangerous material ingress into the tunnel through the cover without opening it. The cover of a preferred embodiment is designed to seal the tunnel entrance with no accessible holes extending through the cover and the means for opening the cover from above is made as difficult to use without the

appropriate tools .

In the preferred embodiment of the present invention, the cover is made from aluminium with the only holes through the cover being those for the fittings for the lock and securing means . These may then be covered by plugs or covers to both hide these mechanisms and also prevent ingress of grime or water. For example as shown in figure 7, the cover 700 has three plugs 710, 720, 730 for covering respectively a lock, a member for operating the securing means, and optionally for coving a cavity for an opening tool attachment. These plugs can be designed to require a special tool for opening to further inhibit unauthorised or accidental removal and access to the locking mechanism. A person authorised to open the manhole cover 700 will be provided with the required tools for removing the plugs 710, 720, 730 and a key to unlock the cover from above. A tool for engaging with the cover to assist in pulling the cover up and open can also be provided. For example, if the plugs that cover the lock and the opening mechanism have screw threads, a tool such as a handle may also be provided with screw threads to screwthreadingly engage where the plugs screwthreadingly engage, and then be used to assist the opening of the cover. Alternatively, an additional tool attachment may be provided. However, to minimise the possibilities of vandalism, it is desirable that such a tool attachment be either difficult to access or difficult to use unless it is the correct tool .

It will be appreciated that the embodiments of the present invention provide a manhole cover which is difficult to be opened or vandalised from outside. Such a manhole cover is easily opened from inside the tunnel enabling use in an emergency without compromising security of the tunnel system.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.