TECHNICAL FIELD

The invention relates to a manhole arrangement for fluid tanks, for example, drinking water tanks or oil tanks. The manhole arrangement comprises a fixed part and lid that is pivotally attached to the fixed part by means of hinges, wherein the fixed part includes or is connected to an inner rim presenting an opening, which inner rim is arranged to sealingly interact with the lid and a lock arranged to enable locking of the lid in sealing contact with the inner rim. In a preferred embodiment the manhole arrangement includes an alarm device that emits an alarm signal when forcing or opening of the lid. Further the invention relates to methods for providing of an alarm and mounting a manhole arrangement respectively. PRIOR ART

Many types of liquid storage tanks, such as drinking water cisterns are, except in urban areas, often located in more remote locations without continuous surveillance. The tanks must be fitted with a manhole which allow maintenance such as inspection and cleaning of the tank which generally from a safety view is the weakest point in the cistern. A forcing or opening of the manhole provides access to the tank content, which then can be contaminated with foreign substances, such as poisons of various kinds, which can lead to catastrophic consequences for users, for example if drinking water. If the cistern contains dangerous and theft-prone liquids, such as crude oil, an unauthorized intrusion is of both safety and economic concern. Many tanks equipped with known types of locked manhole covers may be forced relatively fast, to thereby get access to the tank's contents. To increase safety it is known to apply safety measures, e.g. some kind of alarm device that may transmit a signal triggered by unauthorized activities in conjunction with manipulation of a manhole cover. A manhole shall preferably also fit tightly against the manhole rim to prevent air flow when pressure changes inside the tank, not to cause pollution to reach the interior of the tank. There are a number of embodiments of manhole covers with more or less easily accessible and forcible covers and/or locking devices, with and without signal sensors that are activated when the cover is manipulated. However, known systems either provide insufficient safety and/or are too complex and/or too expensive. From AT 349 340 there is known a safety manhole closure that comprises a frame and of a lockable lid which is pivotally connected to the frame via a hinge designed like a four-bar mechanism. The manhole closure can be locked by means of a lock on the side opposite the hinge. In order to prevent unauthorized forcing of the lid or to indicate such forcing an alarm device, in the form of a plate is suspended underneath the outer lid cover, and an alarm device responding to the displacement of this plate relative to the outer lid cover is arranged. This alarm device has a permanent magnet fastened to the plate and a reed contact fastened to the top wall. Accordingly it presents a relatively complex and therefore costly solution.

Other safety manhole solutions are known, e.g. US 20090303043, KR 101045024 and GB 2163467, none of which that in an optimal manner can solve the above problem.

SUMMARY OF THE INVENTION

It is an object of the present invention to solve or at least minimize at least one of the problems of the prior art, which is achieved by means of a manhole arrangement according to the in the appended dependent claims.

Thanks to the invention there is provided a manhole arrangement that in a cost efficient manner may provide a reliably sealed manhole for maintenance that is especially suitable for tanks including liquid or material that should not be contaminated, since the solution according to the invention may provide safe and reliable sealing of the opening of the manhole arrangement.

Moreover the manhole arrangement according to the invention in a flexible manner may facilitate application of an alarm system, either preinstalled or after installed that efficiently may prevent intruders from forcing a manhole arrangement according to the invention.

Further the preferred embodiment according to the invention provides a manhole arrangement that is difficult to force thanks to a design where critical parts may be covered and/or protected to make intrusions more difficult. Further a design according to a preferred embodiment of the invention may be combined with the use of various locking devices in a flexible manner, i.e. enabling a user to choose freely from a variety of existing locking devices.

Furthermore the invention may provide a beneficial method of mounting a manhole arrangement in situ around an existing manhole arrangement in a flexible and cost sufficient manner.

BRIEF DESCRIPTION OF FIGURES

In the following the invention will be described in more detail with reference to the appended figures, wherein:

Figure 1 shows a perspective view of an embodiment of a manhole according to the invention in unlocked and raised position,

Figure 2 shows a cross section of a closed manhole according to the invention and also disclosing a contact arrangement for achieving alarm signal, Figure 3 shows a perspective view of one side of a first part of a preferred

locking mechanism according to a further aspect of the invention, in the locked position, and

Figure 4 shows a perspective view of the second side of the first part of the locking mechanism.

DETAILED DESCRIPTION OF THE INVENTION

As shown in Fig. 1 the manhole arrangement 1 of the invention comprises a fixed part 4 and pivotal lid 2, which is pivotally arranged by means of hinges 5. The manhole arrangement 1 is intended for mounting on to the upper structure on the upper side of a large liquid container, such as a drinking water tank. It may either be applied directly to a tank or applied around an existing manhole, by removing the existing lid and providing the manhole arrangement 1 with a dimension enabling it to be fitted around the existing structure.

The lid 2 is made of metal (preferably stainless steel) and comprises an outer cover plate 20 with downward (preferably folded) cover sides 21. The fixed part 4 comprises a flat attachment part 40, which at its inner edge is arranged with an inner, upward rim 41. As shown in Fig. 1 the fixed part may be arranged with an outer rim 42, which when the lid 2 is closed, may enclose the cover sides 21 of the lid 2. As shown in Fig. 2, in the closed state, the cover sides 21 of the lid 2 will enclose the inner rim 41 of the fixed part 4. On the inside of the lid 2 there is movably arranged an inner plate 7 that is smaller than the outer cover plate 20 but larger than size of the opening 6 presented by the inner rim 41. Accordingly the plate 7 is dimensioned to cover the opening 6 and protrude past the periphery of the inner rim 41, but leave a gap G between its edges 70 and the inner sides of the cover sides 21. The plate 7 is movably mounted to the outer cover plate 20 by means of a plurality of brackets 9 (e.g. U-shaped) presenting a mid-portion 90 and lower leg portion 91, whereby the plate 7 is movable in the direction of its normal N along the mid-portion 90 within a zone Z defined by the end stop obtained by the leg portions 91 at one end. Further, in each of the four corners of the plate 7 insulators 8 are attached, comprising an insulator body 80 attached to the plate 7 by attachment devices 81, e.g. by screws. The height H of the body 80 is less then width W of the mid-portion 90 to obtain the zone Z of movement. As shown in Fig. 2 the insulator body 80 together with the springs 10 hold the inner plate at a distance from the inner sides of the mid portions 90, to avoid conductive contact between the edges of the inner plate 7 and the mid portions 90. Alternatively the inner surfaces of the mid portions 90 may either be produced in a non-conductive material or may be applied with a non-conductive surface layer to conductively isolate between the edges of the inner plate 7 and the mid portions 90.

Accordingly the second end of the zone Z is defined by the upper end 82 of the body 80. The upper end of the body 80, of the insulators 8, is inserted into a helical spring 10, which is in contact with the inner side of the outer cover plate 20 to thereby urge the plate 7 in a direction against the leg portions 91. At least one of the brackets 9 is of a conducting material (preferably metal brackets) or include conducting material or has conducting material applied thereto to enable a conducting bridge between the plate 7 and the outer cover 2 when the plate 7 is in contact with a leg portion 91. Thereby conducting contact may be achieved when the lid 2 is opened. A conducting circuit is achieved also when the lid 2 is closed if the outer cover plate 20 is forced with a conducting tool (e.g. drill). An in situ part 3 of an alarm arrangement (e.g. battery powered) may be arranged at an appropriate protected position that may sense when the circuit is closed (open lid 2 and/or forced lid 2) and also emit an alarm signal (as is known per se), preferably transmit a signal to a remote, manned monitoring center. When the lid 2 is closed, the circuit is open by means of having the plate 7 pushed away from contact with the leg portions 91 by the inner rim 41, thereby compressing the springs 10. Thanks to the invention an intruder may not get direct access the interior of the tank if the outer cover plate 20 is forced, but will thereafter also need to force the inner plate 7, providing extra time to hinder an attempt of intrusion, thanks to having the alarm signal triggered already when forcing the outer cover.

Thanks to the use of resilient devices 10 to urge the plate 7 there will be achieved a circumferentially evenly distributed pressure against the inner rim 41, which in cooperation with an appropriate sealing 12 safeguards a desired sealed opening 6 when the lid 2 is closed. Further this sealing 12 may provide an electrically insulating part sealing strip 12, eliminating any risk that a false alarm signal is given due to contact between the plate 7 and the rim 41.

In Fig. 1 it is shown that the sealing strip 12 may be applied directly on the plate 7.

In Fig. 2 it is shown that the sealing strip 12 may be applied onto the upper edge of the inner rim 41. Further Fig. 2 shows an embodiment without an outer rim, but merely a flat attachment part 40. Further Fig. 2 indicates that the novel lid arrangement 1 has been applied around an existing rim 60 of a tank T, wherein the old lid has been removed. Preferably the novel lid arrangement 1 is provided with an inner rim 41 having a substantially larger cross sectional with than the existing rim 60 to form a channel C them between that may be filled with a reinforcing and/or sealing material, e.g. concrete, which also provides the advantage of eliminating open spaces around the opening that otherwise can collect undesired matter.

Inside the lid 2, as shown in Figs 3 and 4, at a side opposite in relation to the hinges 5 there is arranged a locking device 11 according to a further aspect of the invention. The locking device 11 comprises a lock 13, preferably in the form of a pad lock, having a lock body 131 and a shackle 130, which are movable in relation to each other (as is well known per se). The lock body 131 is movably arranged within an opening 27 in one of the cover sides 21 and connected to sliding bolts 17, 18 by means of an attachment member 28. Further the locking device 11 comprises a support bracket 16 attached to the outer cover plate 20. The movable shackle 130 is fitted through a hole 160 in the fixed support bracket 16, and thereby fixed in relation to the bracket 16. The two sliding bolts 17, 18 interact with each one of locking eye lets 25, 26 attached to outer side of the inner rim 41, a first one 25 positioned further away from the lock body 131 at a higher level and the second one 26 positioned closer to the lock body 131 at a lower level. The first sliding bolt 17 interacts with the fist eye let 25 and is therefore longer than the second sliding bolt 18. The second sliding bolt 18 interacts with the second eye let 26 and may therefore be relatively short. Preferably merely one of the sliding bolts 17, 18, here 17, is fixed to the lock body 131, e.g. by means of the attachment member 28, to follow the movement of the lock body 131. The two sliding bolts 17, 18, are parallel fixed to each other by means of fixation bodies 23, 24, to enable synchronized movement in parallel.

Further two pairs of sliding members, 161; 162, 163, 164 are fixedly arranged onto the support bracket 16, to safely hold and control the movement of the ends of the sliding bolts 17, 18, for safe fit into the holes of the locking eye lets 25, 26.

When the lid 2 is open the lock body 131 will be in a protruding position B (see Fig 4) and the sliding bolts 17, 18 pulled out outside of the each pair of sliding members, 161; 162, 163, 164. When closing the lid the sliding members 164, 161; 162, 163 will enclose one each of the locking eye lets 25, 26, Then the lock body 131 may be pushed in (position A in Fig. 3) to force the locking bolts 17, 18 to pass through the locking eye lets 25, 26. The lock body 131 will then be fully inserted in the opening 27 and the locking mechanism is activated. In the embodiment shown in Fig. 1 the lower edge of the cover sides 21 of the outer cover 2 will then be positioned inside and the below the outer rim 6 and therefore make it more or less inaccessible for picking attempt. When unlocking the lock 13 the lock body 131 is pulled outward (to the dotted position B in Fig. 3) with the lock key, whereby the sliding bolts 17, 18 are pulled out from the locking eye lets 25, 26, whereby the lid 2 is released and can be swung up.

The invention is not limited by the examples described above but may be varied within the scope of the appended claims. For instance it is evident for the skilled person that a manhole arrangement according to the invention must not be fitted with an alarm system, because its design provides better safety than most traditional manhole arrangements also without an alarm, due to the fact that the arrangement according to the invention may drastically prolong the time that is required for an intruder to force the manhole arrangement. Hence, an arrangement according to the invention drastically improves the chances of detecting any attempt of intrusion visually and/or audibly than traditional manhole arrangements. Further it is evident that in the preferred embodiment, when using a resilient device between the outer cover 20 and the inner plate 7, many varieties of the resilient devices may be used, e.g. rubber members, etc., and also that in principle it may sufficient to merely use one resilient member, preferably centrally positioned to achieve the desired function. Furthermore it is evident for the skilled person that the brackets that arranged with the outer stop members 91 may be designed in various manners, e.g. as Z-shaped brackets, U-shaped brackets, L-shaped brackets, etc. and may be attached to outer cover 20 in various ways, e.g. welding, riveting, gluing, etc. Moreover it is evident that the functionality of the brackets may be achieved by the use of a variety of materials and especially that the desired feature of having a conducting material at the outer stop member 912 may be achieved by applying a separate conductive member or by having it integral in a metal body bracket or composite bracket member. Further it is evident for the skilled person that the alarm device may be applied in different forms and including different features. Moreover, it is evident that a big variety of locking devices may be used in connection with the invention and also that other locking means and sliding bolts may be used to achieve a locking function.