The present invention relates to a pump for a hydromill.

Known to the art is digging equipment for constructing diaphragms, commonly referred to as hydromills, which is mainly constituted by a frame suspended from ropes, and milling drums with parallel horizontal axes set underneath the frame.

The drums turn, removing the soil and producing an excavation having a rectangular section in which the frame is let down vertically by means of ropes.

The walls of the excavation are withheld by the hydrostatic pressure of an appropriate drilling mud.

The debris is sucked in together with said mud by a pump, which is usually of a centrifugal type, and conveyed out of the excavation by a flexible pipe.

The dimensions of the frame are limited by the dimensions of the excavation and condition the possibilities of installation of the pump.

The pump basically has the shape of a disk with a diameter greater than the thickness of the frame and a more modest height.

Set on one of the faces of the disk is the motor for turning the impeller. Usually, the motor is of the hydraulic type with â€œinclined bodyâ€ .

A possibility of placing is described in the patent No. EP-0 249 555. In this solution, however, the projection in plan view of the overall encumbrance of the pump constitutes a non-negligible obstacle to the flow of the mud into the excavation and to the passage of the hydraulic pipes for supply of the motors of the drums, of control members, and of other mechanical items.

Another problem linked to the position of the pump is the abrasive effect that the debris has on the bends of the delivery pipe. If said vertical pipe has a rectilinear development, its service life increases.

Another problem consists in the poor accessibility of the pump for maintenance purposes or for complete replacement.

The present invention aims at providing an improved solution to the above problems by proposing a pump for digging equipment for the construction of diaphragms, in which the equipment envisages, in its end part, drums provided with bits, mounted so that they rotate on their own axes. The drums are carried by a top frame, inside which, in the proximity of the drums, a centrifugal pump is mounted, said pump being characterized in that it is positioned in such a way that its axis comes to lie in a substantially horizontal plane, parallel to the plane passing through the axes of the bits and is oriented with an angle of between 30Â° and 60Â° with respect to the sides of the rectangular section of the excavation, whilst the maximum diameter of the pump and its motor fall within the thickness of the frame.

The pump according to the invention will now be described with reference to the annexed plates of drawings, in which:

FIG. 1 is a front view of the bottom part of digging equipment for the construction of diaphragms provided with the pump according to the present invention;

FIG. 2 is an enlarged view of the equipment of FIG. 1 in an area corresponding to the pump; and

FIG. 3 is the view according to the section A-A of FIG. 2 of the pump.

As may be noted in FIG. 1, the end part of the equipment envisages two drums 10 and 11 provided with bits 12, mounted so that they rotate on their own axes A to perform the steps of excavation in the earth that are well known to a person skilled in the branch.

The drums 10 and 11 are carried by a top frame 13, which is also of a known type.

Mounted within the frame, in the proximity of the drum, is a centrifugal pump 14, once again of a known type, which, according to the invention, is positioned in such a way that its axis 15 comes to lie in a horizontal plane, parallel to the plane passing through the axes A of the bits 12. In this way, the projection in plan view is the absolutely minimum one and leaves the maximum section of surrounding passage free.

In addition, the axis of the pump 10 is oriented with a marked angle, of between 30Â° and 60Â° and, preferably, about 45Â°, with respect to the sides of the rectangular section of excavation, whereas the maximum diameter of the pump and the corresponding motor drive fall within the thickness of the frame 13.

Normally, the motor of the pump is aligned with the impeller of the pump, whilst, in the embodiment represented in FIGS. 2 and 3, the motor 21 of the pump is set out of line with respect to the impeller by means, by way of non-limiting example, of some gears with parallel axes contained in a purposely provided casing 22.

In a further variant, the axis of the pump lies in a plane slightly inclined with respect to the horizontal, preferably by 10Â°. In this way, the suction pipe can present a more rectilinear development within the allowed encumbrance.

The delivery pipe 16 of the pump is directed upwards, whilst the suction pipe 17 can have a section larger than that of the delivery pipe 16. In addition, the suction pipe is made up of various pipe elements 18, 19, 20, possibly with a non-circular cross section, to enable ease of maintenance.

Since the delivery mouth of the pump faces upwards and since the delivery pipe 16 rises in a substantially vertical way, as may be noted in the figures, the first significant curve falls outside of the excavation, and a possible perforation due to wear is immediately visible. In other solutions, the perforation occurs in the submerged equipment so that it is difficult to identify it immediately.

With the solution proposed by the present invention, the bends in the suction stretch, which present a larger number as compared to known solutions, are less critical because said stretch is short and can hence be conveniently made with a larger cross section, consequently reducing the rate of the fluid and debris contained therein.

The vertical pipe, instead, may be even some hundred metres long and is made of rubber reinforced with wire cloth, hence very sturdy and costly; in fact, an increase in diameter would entail considerable increase in cost.

Finally, with a placement of the pump of the type described above, accessibility for carrying out maintenance operations is very good, both as regards the pump itself and as regards the suction pipe, which can be made up of various flanged elements.