The object of the present invention is a manhole cover, i.e. a device configured to close manholes that are located on the road pavement, such as manholes for sewers, water mains or intended for electricity and/or telephone line service and at fuel sales points.

Due to their location within the road pavement, manhole covers (which usually consist of a perimeter frame defining the cavity through which an operator may pass or which may otherwise serve various other purposes, and a lid connected and jointed to the perimeter frame determining the selective access to the cavity defined by the perimeter frame) are subject to stresses of various extents, and are therefore generally made of tough and strong materials such as steel and cast iron: such materials imply high weights, masses and moments of inertia, making it difficult for operators to move the lids.

Nevertheless, the Applicant has already developed a manhole cover wherein the lid is hinged to the perimeter frame and wherein a containment seat for the hinge, interposed between the lid and the perimeter frame, is present: such containment seat in turn has a walkable protection element that is an integral part of the frame within which a rotation shaft is at least partially housed, which determines the kinematic constraint between the lid and the perimeter frame, and on which at least one suitably sized torsion spring acts, which, as it is protected within the frame by such walkable area, is not subject to sand or debris which might jeopardise the proper functioning of the spring, thus avoiding the maintenance required and which is frequent in all the manhole covers provided with springs positioned outside the frame.

The Prior Art devices, including the above-shown manhole cover of the Applicant, are however subject to a drawback that is afflicted by dimension problems: in particular, there are problems related to the fact that the arms of the hidden hinges have, due to their geometry, such dimensions that the frame height (which due to technical constraints related to the Prior Art structural geometry is at least 150 mm) exceeds the normal height (generally set at 100 mm) of the frames of the manhole covers normally installed.

Since manhole covers are normally installed on thick reinforced concrete slabs to withstand the heavy loads of the vehicles passing over them, it follows that a normal-height manhole cover cannot be easily replaced by one having an increased height frame (as it would protrude from the so- called “zero height” of the road) unless the slab is replaced or modified, with a significant increase in installation costs.

The object of the present invention is thus to make available a manhole cover that overcomes the drawbacks of the Prior Art mentioned above, ensuring a normal-height frame, still having the hinges arranged within the frame and concealed and the springs protected by the same frame, but with a new kinematic mechanism by which the opening rotation of the lid will be divided into two rotation steps on different axes.

The specified technical task and the specified object are substantially achieved by a manhole cover comprising the features set forth in one or more of the claims hereinafter reported, as well as comprising the features subsequently shown in the description of the present invention, and further features and advantages of the present invention will thus become clearer from the indicative, and therefore non-limiting, description of a manhole cover.

Such description will be set forth hereinafter with reference to the accompanying drawings, provided for merely indicative and therefore nonlimiting purposes, wherein:

- Figure 1 is a perspective view of a first possible embodiment of the manhole cover according to the invention in a partially opened condition;

- Figure 2 is a perspective view of the first possible embodiment of the manhole cover according to the invention in a subsequent and additional partially open condition; - Figure 3 is a perspective view of the first possible embodiment of the manhole cover according to the invention from an angle different from that of Figures 1 and 2;

- Figure 4 is an enlarged view of a structural detail of the first embodiment of the manhole cover according to the invention shown in Figures 1 , 2 and 3;

- Figure 5 is a perspective view of a second possible embodiment of the manhole cover according to the invention in a partially open condition;

- Figure 6 is a perspective view of the second possible embodiment of the manhole cover according to the invention in a subsequent and further partially open condition;

- Figure 7 is a perspective view of the second possible embodiment of the manhole cover according to the invention from an angle different from that of Figures 4 and 5;

- Figure 8 is an enlarged view of a structural detail of the second embodiment of the manhole cover according to the invention shown in Figures 5, 6 and 7; and

- Figures 9 and 10 are, respectively, two enlarged views of the two possible embodiments of the manhole cover according to the invention already shown in the previous Figures 4 and 8, but removing - for graphic representation purposes - some structural components.

With reference to the enclosed Figures, reference number 1 globally denotes a manhole cover according to the present invention, which essentially comprises a frame, adapted to delimit an access opening 2a (which may be of any shape in terms of perimeter development and which may be typically used by an operator) and which defines a seat 3 perimetrally distributed on the frame 2 itself, as well as a lid 4 which may be housed in the seat 3; the manhole cover 1 further comprises rotatable coupling means, which are conveniently adapted to couple the lid 4 to the frame 2 and are simultaneously adapted to define a plurality of operating conditions between a closed condition, wherein the lid 4 is housed in the seat 3, and at least one open condition, wherein the lid 4 is instead at least partially arranged outside the seat 3.

Advantageously, the above-mentioned rotatable coupling means comprise a main rotation body 5 interposed between the lid (note that such main rotation body 5 is functionally adapted to determine a first rotation about a first axis 6 of the lid 4) and an additional rotation support 7 mounted on the main rotation body 5 (such additional support 7 is functionally adapted to determine a second rotation about a second axis 8).

It should now be noted that due to the presence and to the structural relationship between the axes 6 and 8, which is implemented by the main rotation body 5, the present invention achieves a breakdown of the overall movement of the lid 4 such that the heaviest movement (typically, the one that occurs in the first moments of the opening movement or in the last moments of the closing movement, when the weight of the lid generates considerable forces and/or torques due to its mass and angle) is performed with greater ease and control, by the operator who has to operate in a relatively small opening and/or closing angular range (i.e. the opening and/or closing angular range imposed by the rotation about the first axis 6), while the remaining rotation, which is relatively less demanding in terms of forces and/or torques to be exerted on the lid, is performed using the second axis 8.

The above mentioned facilitating effect is further amplified and enhanced, for the purposes of the invention, by appropriate structural components, which will be further detailed hereinafter.

Going into detail, it can be observed that the main rotation body 5 comprises a first hinging portion 5a which interfaces with the first axis 6 (for example, and as visible in the figures, by means of an appropriate housing intended to receive the first axis 6 itself), an intermediate expansion 5b extending from the first hinging portion 5a (and thus defining a predetermined “lever arm” relative to the first axis 6) which is housed inside the access opening 2a at least in the lid 4 closed condition and, finally, a second hinging portion 5c which is obtained from the intermediate expansion 5b and which, comprising the aforementioned additional rotation support 7, determines as such a spatial offset (in terms of relative distancing and/or possible diversity of orientation) of the second axis 8 relative to the first axis 6 (from a structural perspective, the above mentioned second hinging portion 5c comprises suitable engagement means for housing or receiving the second axis 8).

As it may be seen in the accompanying figures, the first hinging portion 5a, the intermediate expansion 5b and the second hinging portion 5c are mutually interconnected without interruption in the main rotation body 5 (which is therefore made in a single piece), but depending on the contingent requirements, it may be possible to form the main rotation body 5 in several interconnected and possibly separable/removable components (e.g. for applications where a quick separation of the lid 4 from the frame 2 is required).

In the embodiment shown in Figures 1 , 2 and 3, the first axis 6 and the second axis 8 are substantially parallel to each other (and thus their offset in space is such that their directrices are kept mutually parallel), so that the lid 4 is reversibly movable at least between the following conditions or configurations:

- the closed condition already mentioned several times;

- a “first” partially open condition corresponding to a first threshold value of a rotation angle of the main rotation body 5 relative to the frame 2 about the first axis 6 (and simultaneously corresponding to a zero value of a rotation angle of the lid 4 relative to main rotation body 5 about the second axis 8); and

- a totally open condition corresponding to the already mentioned first threshold value of rotation angle of the main rotation body 5 relative to the frame 2 (about the first axis 6) and a second threshold value of rotation angle of the lid 4, which is instead measured/detected relative to the main rotation body 5. In other words, the sequence of possible conditions/configurations introduced hereinabove may be considered as a “composite” stroke in opening or closing the lid 4, which first rotates about the first axis 6 along a (first) rotation arc with a relatively limited extent, and then, when the rotation of the lid 4 and the main rotation body 5 has reached the first threshold angle, the main rotation body 5 remains substantially stationary (relative to the frame 2) and it is only the lid 4 that rotates further, pivoting on the second axis 8, being able to reach the condition/configuration of maximum or total opening that is made possible by the geometry of interconnection and support insisting between the main rotation body 5 and the second axis 8.

In the embodiment shown hereinabove, the subsequent rotations of the lid about the axes 6 and 8 may be considered, from a specifically geometric perspective, as “fixed-axis rotations”: nevertheless, during the “first” rotation of the lid (the one about the axis 6), the second axis 8 also rotates integrally with the main rotation body, and only after stopping in space - at the first threshold angle - does the lid begin to rotate again, still maintaining its fixed axis of rotation but now rotating about the axis 8.

Still regarding structural details, it may now be observed how the main rotation body 5 can conveniently also comprise means for selectively adjusting an angular offset 9, which are operative on the lid 4 and are adapted to determine (e.g. by means of a screw spacer element as visible in the attached figures), a lying angle of the lid 4 relative to the main rotation body 5.

The main rotation body 5 in fact opposes, as long as the lid 4 reaches the first partially open condition mentioned several times, the so-called “overturning moment” of the lid 4 which is hinged on the second axis 8 and is held in a “static” position by the selective adjustment means 9.

On the other hand, the function of the selective adjustment means 9 is in practice to find an optimal adjustment/calibration point (or also “trimming”, in the technical jargon) of the lid 4 when it is in the closed condition in the frame 2: this balancing is in turn conveniently determined to compensate for possible misalignment to the frame 2 itself.

In the context of the present invention, the lying angle may be interpreted as basically corresponding to the rotation angle of the lid 4 when it takes on a zero value relative to the main rotation body 5 (or in other words, when the lid 4 is at the first partially open condition).

In the embodiment shown in Figures 4, 5 and 6, it may now be observed that the first axis 6 and the second axis 8 are substantially transverse (i.e. perpendicular to each other): in such a case, the offset introduced by the main rotation body 5 between the two axes is such that the axes themselves are not only spaced apart from each other, but are at a relative angle other than zero (thus causing a composite rotation of the lid 4 firstly about an axis and then about an axis which is not parallel to the first one).

Even in this second embodiment, the lid 4 is therefore reversibly movable at least between:

- the closed condition;

- a first partially open condition (corresponding to a first threshold value of a rotation angle of the main rotation body 5 relative to the frame 2 about the first axis 6 and a zero value of a rotation angle of the lid 4 relative to the main rotation body 5 about the second axis 8); and

- a totally open condition (corresponding to a first threshold value of the rotation angle of the main rotation body 5 relative to the frame 2 about the first axis 6 and a second threshold value of the rotation angle of the lid 4 relative to the main rotation body 5 about the second axis 8).

Similarly to what has already been said about the first embodiment, in this second embodiment as well, the two subsequent rotations of the lid 4 may be considered as “fixed-axis” rotations: in fact, in this case also the main rotation body 5 carries and causes a spatial displacement of the second axis 8, which is actually used for rotating the lid only when the first partially open condition/configuration has been reached.

Unlike what happens in the first embodiment of the invention shown hereinabove, in this second embodiment the rotation of the lid 4 about the second axis 8 can take place when the axis 8 itself has been brought to a quasi-vertical (or vertical) condition relative to the frame 2 or to the manhole cover installation plane 1 : the effects of the weight of the lid 4 are thereby significantly reduced, the lid 4 itself having to rotate about an axis that is already vertical - or almost vertical - and it is, once again, the operator of the manhole cover who benefits in terms of little muscular effort and greater ability to control/manipulate the lid 4.

As mentioned earlier in this description, the manhole cover 1 may advantageously comprise active servo-assistance means between the lid 4 and the frame 2: such servo-assistance means may be operatively interposed between the frame 2 and the main rotation body 5 (e.g., being active on the first axis 6) and/or between the main rotation body 5 and the lid 4 (being in this case active on the second axis 8).

In the enclosed figures, it may be seen that the servo-assistance means can comprise:

- at least one main torsion spring 10 (or if the contingent requirements so require, two or more torsion springs) keyed to the first axis 6, arranged in such a way as to have a first end connected to the frame 2 (according to structural arrangements more fully detailed hereinafter) and a second end, opposite the first end and connected to the main rotation body 5; and/or

- an additional torsion spring (not shown in the attached figures) keyed to the second axis 8 and having a first end connected to the main rotation body 5 and a second end opposite the first end and connected to the cover 4.

The calibration and/or dimensioning of the torsion springs shown above must be such that the invention as a whole obtains a significant effect of aiding operators who have to open or close the manhole cover 1 : for this purpose, it should be noted in particular that the torsion spring 10 is dimensioned in such a way as to exert an action that is expressed in these three effects: - helping lifting the lid 4 during rotation thereof (while being opened) about the first axis 6;

- maintaining a proper static balance condition during the so-called “first partially open condition/configuration” previously mentioned several times; and

- providing a proper amount of resisting force/torque during the strokes of closing the lid 4 (thus preventing the lid from slipping out of the operator's control and closing too violently).

In order to further enhance the effects of the servo-assistance means listed above, suitable means for adjusting a preload may also be present: these preload adjustment means are functionally slaved to at least the main torsion spring 10 and are active between the frame 2 and at least one of the first and second ends of the main torsion spring 10.

Should it also be necessary to provide the additional torsion spring (not shown) with such preload adjustment means, the latter may then be coupled to the additional torsion spring itself and will typically be active between the main rotation body 5 and at least one of the first and second end of the additional torsion spring itself.

In even greater detail, and referring to the attached figures, it may be seen how the preload adjustment means may comprise, in one possible (but by no means limiting) embodiment thereof:

- an adjustment kinematic mechanism 11 which is connected to the frame 2 (or, if necessary, connected to the main body 5 in case they are to be actuated on the additional torsion spring) and which defines a stroke along an operating axis selectively adjustable by an operator; and

- a prismatic block 12 movably engaged to the adjustment kinematic mechanism 11 and adapted to interface with the first and/or second end of the main torsion spring 10 (or, where necessary, to one or both ends of the additional torsion spring) and which also allows the first axis 6 to be fixed “on axis” and with the most suitable precision on the housing supports 13 (which will be discussed in greater detail later in this description) placed under the walkable protection element of the frame 2.

The aforementioned interfacing between the torsion spring(s) and the preload adjustment means may conveniently take place at an inclined face of the prismatic block 12, thereby achieving a sufficiently precise constraint such to exert a locking action on the end(s) of the torsion spring, while having a mechanical contact relationship which is sufficiently smooth and at the same time simple and cheap: conveniently, due to the functional synergy between the kinematic mechanism 11 , the prismatic block 12 and the end of the torsion spring, the preload of the main torsion spring 10 and/or the additional torsion spring will be proportional to a position of the prismatic block 12 along the aforementioned stroke.

It should be noted, with regard to the embodiment of the preload adjustment means just introduced, that due to this structural composition, it is possible to implement a manhole cover that is very effective in terms of adjustment and cheap to manufacture, especially if the housing spaces for these adjustment means are to be made by casting or with “foundry work”: in fact, due to the structural components just listed, it is advantageously possible to create cavities in the casting moulds with very simple geometries, into which the preload adjustment means can then be mounted with equal processing ease and cost-effectively.

In order to allow for a proper functioning of the entire invention, and to provide the necessary structural and kinematic abutment to the previously mentioned preload adjustment means, the manhole cover 1 may conveniently also comprise at least one, and preferably two, support housings 13 adapted to receive and engage with the first axis 6: said support housings 13 are obtained in the frame 2, and more precisely under the walkable element of the frame 2, and are configured to allow substantial “on-axis centring” of the main rotation body 5 through the prismatic blocks 12 (in other words, the support housings 13 are obtained in the frame 2 and are cooperatively operating with at least one prismatic block 12 to allow on-axis centring the main rotation body 5). The manhole cover disclosed hereinabove, in its various embodiments, achieves interesting functional advantages compared to the Prior Art.

Firstly, the peculiar “dual-axis rotation” kinematic mechanism insisting between the support frame and the lid allows to determine lid movement trajectories with an easy control and low muscular effort by the operators, while ensuring the necessary structural resistance to the entire device and, where environmental conditions are particularly aggressive or invasive, ensuring substantial protection of the manhole cover structural elements which might be damaged or wear excessively after being exposed to such environmental conditions.

Advantageously, the ability to determine different relative orientations between the two rotation axes can also result in particularly efficient lid movement trajectories in terms of space/operating volume savings, further facilitating operators and making it possible to install the manhole cover even where space is extremely limited.