System for screening ballast with two screens

Abstract

A system (10) for sieving ballast comprises a first sieve (26) and a second sieve (28) which is located behind the first sieve (26) in a first direction (100). A discharge collection conveyor (32.1) is located directly under a first discarded ballast outlet (42) of the first sieve (26) in order to collect a flow of discarded ballast which comes from the first sieve (26) and to convey it in a second direction (200) counter to the first direction (100). A rerouting collection conveyor directly collects the flow being discharged from a clean ballast outlet of the second sieve in order to convey it in the first direction (100). The rerouting collection conveyor extends under the first sieve (26) at a lower height than the discharge collection conveyor.

Claims

1. A ballast sieving system capable of moving parallel to a working direction, comprising a sieving installation comprising at least a first sieve having a first soiled ballast inlet, a first clean ballast outlet which is located in front of the first soiled ballast inlet in a first direction parallel to a working direction and a first discarded ballast outlet, and at least one second sieve having a second soiled ballast inlet which is located behind the first soiled ballast inlet in the first direction, a second clean ballast outlet which is located behind the first clean ballast outlet and in front of the second soiled ballast inlet in the first direction and a second discarded ballast outlet, a set of one or more rerouting conveyors capable of collecting and conveying, in the first direction, a flow leaving the second clean ballast outlet and a flow leaving the first clean ballast outlet, the set of one or more rerouting conveyors comprising one or more rerouting collection conveyors for directly collecting the flow leaving the second clean ballast outlet and conveying it in the first direction, the one or more rerouting collection conveyors comprising at least one common rerouting conveyor capable of conveying both the flow of clean ballast from the second clean ballast outlet and the flow of clean ballast from the first clean ballast outlet, in the first direction, at least part of the common rerouting conveyor being positioned under the first sieve, a set of one or more discharge conveyors capable of collecting and conveying, in a second direction parallel to the working direction and opposite the first direction, a flow of discarded ballast from the first discarded ballast outlet and a flow of discarded ballast from the second discarded ballast outlet, the set of one or more discharge conveyors comprising one or more first discharge collection conveyors, located directly below the first discarded ballast outlet to collect a flow of discarded ballast from the first sieve and to convey it in the second direction, wherein the one or more rerouting collection conveyors extend under the first sieve at a lower height than the first discharge collection conveyor(s), and the second sieve comprises a discarded ballast inlet suitable for being supplied by the first discharge collection conveyor(s), and a spout for passing the flow of discarded ballast coming from the first sieve from the discarded ballast inlet to the second discarded ballast outlet.

2. The ballast sieving system of claim 1, wherein the discarded ballast inlet of the second sieve is positioned above the second clean ballast outlet.

3. The ballast sieving system of claim 1, wherein the second sieve and the first sieve overlap.

4. The ballast sieving system of claim 1, further comprising an assembly for relining or storing clean ballast, supplied by the set of one or more rerouting conveyors, the assembly for relining or storing clean ballast being positioned in front of the first soiled ballast inlet, and in front of the first sieve, in the first direction.

5. The ballast sieving system of claim 1, further comprising a discarded ballast storage assembly, the set of one or more discharge conveyors comprising at least one common discharge conveyor capable of conveying both the flow of discarded ballast from the first discarded ballast outlet and the flow of discarded ballast from the second discarded ballast outlet to the discarded ballast storage assembly, in the second direction, at least part of the common discharge conveyor being positioned under the second sieve.

6. The ballast sieving system of claim 5, wherein the assembly for relining or for storing clean ballast is positioned between an excavation assembly and the first soiled ballast inlet, and between the excavation assembly and the first sieve.

7. A ballast sieving system capable of moving parallel to a working direction, comprising: a sieving installation comprising at least a first sieve having a first soiled ballast inlet, a first clean ballast outlet which is located in front of the first soiled ballast inlet in a first direction parallel to the working direction and a first discarded ballast outlet, and at least one second sieve having a second soiled ballast inlet which is located behind the first soiled ballast inlet in the first direction, a second clean ballast outlet which is located behind the first clean ballast outlet and in front of the second soiled ballast inlet in the first direction and a second discarded ballast outlet, a set of one or more rerouting conveyors capable of collecting and conveying, in the first direction, a flow leaving the second clean ballast outlet and a flow leaving the first clean ballast outlet, the set of one or more rerouting conveyors comprising one or more rerouting collection conveyors for directly collecting the flow leaving the second clean ballast outlet and conveying it in the first direction, a set of one or more discharge conveyors capable of collecting and conveying, in a second direction parallel to the working direction and opposite the first direction, a flow of discarded ballast from the first discarded ballast outlet and a flow of discarded ballast from the second discarded ballast outlet, the set of one or more discharge conveyors comprising one or more first discharge collection conveyors, located directly below the first discarded ballast outlet to collect a flow of discarded ballast from the first sieve and to convey it in the second direction, an excavation assembly, and a set of one or more excavation conveyors, capable of transferring soiled ballast from the excavation assembly to a first distributor while constituting an incident soiled ballast flow, wherein the one or more rerouting collection conveyors extend under the first sieve at a lower height than the first discharge collection conveyor(s), and the second sieve comprises a discarded ballast inlet suitable for being supplied by the first discharge collection conveyor(s), and a spout for passing the flow of discarded ballast coming from the first sieve from the discarded ballast inlet to the second discarded ballast outlet, and the first soiled ballast inlet is positioned between the excavation assembly and the second soiled ballast inlet, and the first sieve is positioned between the excavation assembly and the second soiled ballast inlet.

8. The ballast sieving system of claim 7, wherein the discarded ballast inlet of the second sieve is positioned above the second clean ballast outlet.

9. The ballast sieving system of claim 7, wherein the second sieve and the first sieve overlap.

10. The ballast sieving system of claim 7, wherein the set of one or more rerouting conveyors comprises at least one common rerouting conveyor capable of conveying both the flow of clean ballast from the second clean ballast outlet and the flow of clean ballast from the first clean ballast outlet, in the first direction, at least part of the common rerouting conveyor preferably being positioned under the first sieve.

11. The ballast sieving system of claim 7, further comprising an assembly for relining or storing clean ballast, supplied by the set of one or more rerouting conveyors, the assembly for relining or storing clean ballast being positioned in front of the first soiled ballast inlet, and in front of the first sieve, in the first direction.

12. The ballast sieving system of claim 7, further comprising a discarded ballast storage assembly, the set of one or more discharge conveyors comprising at least one common discharge conveyor capable of conveying both the flow of discarded ballast from the first discarded ballast outlet and the flow of discarded ballast from the second discarded ballast outlet to the discarded ballast storage assembly, in the second direction, at least part of the common discharge conveyor being positioned under the second sieve.

13. The ballast sieving system of claim 7, further comprising at least one first distributor, able to distribute an incident soiled ballast flow between the first soiled ballast inlet and the second soiled ballast inlet, according to one, two or three of the following operating modes: a distribution operating mode, in which the first distributor is able to distribute the incident soiled ballast flow between the first soiled ballast inlet and the second soiled ballast inlet; a return operating mode to the second sieve, in which the first distributor is able to direct the incident soiled ballast flow entirely toward the second soiled ballast inlet; a return operating mode to the first sieve, in which the first distributor is able to direct the incident soiled ballast flow entirely toward the first soiled ballast inlet.

14. A ballast sieving system capable of moving parallel to a working direction, comprising a sieving installation comprising at least a first sieve having a first soiled ballast inlet, a first clean ballast outlet which is located in front of the first soiled ballast inlet in a first direction parallel to the working direction and a first discarded ballast outlet, and at least one second sieve having a second soiled ballast inlet which is located behind the first soiled ballast inlet in the first direction, a second clean ballast outlet which is located behind the first clean ballast outlet and in front of the second soiled ballast inlet in the first direction and a second discarded ballast outlet, a set of one or more rerouting conveyors capable of collecting and conveying, in the first direction, a flow leaving the second clean ballast outlet and a flow leaving the first clean ballast outlet, the set of one or more rerouting conveyors comprising one or more rerouting collection conveyors for directly collecting the flow leaving the second clean ballast outlet and conveying it in the first direction, a set of one or more discharge conveyors capable of collecting and conveying, in a second direction parallel to the working direction and opposite the first direction, a flow of discarded ballast from the first discarded ballast outlet and a flow of discarded ballast from the second discarded ballast outlet, the set of one or more discharge conveyors comprising one or more first discharge collection conveyors, located directly below the first discarded ballast outlet to collect a flow of discarded ballast from the first sieve and to convey it in the second direction, at least one first distributor, wherein the one or more rerouting collection conveyors extend under the first sieve at a lower height than the first discharge collection conveyor(s), and the second sieve comprises a discarded ballast inlet suitable for being supplied by the first discharge collection conveyor(s), and a spout for passing the flow of discarded ballast coming from the first sieve from the discarded ballast inlet to the second discarded ballast outlet, and the first distributor is able to distribute an incident soiled ballast flow between the first soiled ballast inlet and the second soiled ballast inlet, according to one, two or three of the following operating modes: a distribution operating mode, in which the first distributor is able to distribute the incident soiled ballast flow between the first soiled ballast inlet and the second soiled ballast inlet; a return operating mode to the second sieve, in which the first distributor is able to direct the incident soiled ballast flow entirely toward the second soiled ballast inlet; a return operating mode to the first sieve, in which the first distributor is able to direct the incident soiled ballast flow entirely toward the first soiled ballast inlet.

15. The ballast sieving system of claim 14, wherein the discarded ballast inlet of the second sieve is positioned above the second clean ballast outlet.

16. The ballast sieving system of claim 14, wherein the second sieve and the first sieve overlap.

17. The ballast sieving system of claim 14, wherein the set of one or more rerouting conveyors comprises at least one common rerouting conveyor capable of conveying both the flow of clean ballast from the second clean ballast outlet and the flow of clean ballast from the first clean ballast outlet, in the first direction, at least part of the common rerouting conveyor preferably being positioned under the first sieve.

18. The ballast sieving system of claim 14, further comprising an assembly for relining or storing clean ballast, supplied by the set of one or more rerouting conveyors, the assembly for relining or storing clean ballast being positioned in front of the first soiled ballast inlet, and in front of the first sieve, in the first direction.

19. The ballast sieving system of claim 14, further comprising a discarded ballast storage assembly, the set of one or more discharge conveyors comprising at least one common discharge conveyor capable of conveying both the flow of discarded ballast from the first discarded ballast outlet and the flow of discarded ballast from the second discarded ballast outlet to the discarded ballast storage assembly, in the second direction, at least part of the common discharge conveyor being positioned under the second sieve.

20. The ballast sieving system of claim 14, further comprising a second distributor interposed between the first distributor and the second soiled ballast inlet that is capable, in at least one operating mode of the second distributor, of directing a flow of soiled ballast coming from the first distributor toward the second soiled ballast inlet and, in a second operating mode of the second distributor, of directing the flow of soiled ballast from the first distributor toward a conveyor of the set of one or more discharge conveyors.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Other features and advantages of the invention will emerge on reading the following description, with reference to the appended figures, which illustrate:

(2) FIG. 1, a railway works vehicle comprising a ballast sieving installation according to one embodiment of the invention, in an operating mode with two sieves operating in parallel;

(3) FIG. 2, the railway works vehicle of FIG. 1, the sieving installation of which operates in a mode where only a first of the two sieves is in operation;

(4) FIG. 3, the railway works vehicle of FIG. 1, the sieving installation of which operates in a mode in which only a second of the two sieves is in operation;

(5) FIG. 4, the railway works vehicle of FIG. 1, the sieving installation of which operates in a mode where neither of the two sieves is in operation.

(6) For greater clarity, identical or similar elements are identified by identical reference signs in all of the figures.

DETAILED DESCRIPTION OF EMBODIMENTS

(7) FIG. 1 shows a mobile system 10 for repairing a ballast bed capable of moving on a railway track 12 being repaired, parallel to a working direction T. The mobile system 10 is composed of a wagon 22 bearing a sieving installation 14, located between, on the one hand, an excavation assembly 15 and a relining assembly 16 and, on the other hand, a discarded ballast storage assembly 18. For the remainder of the description and arbitrarily, the following will be defined: a first direction 100 parallel to the working direction T and going from the sieving installation to the relining assembly 16 and the excavation assembly 15, and a second direction 200 parallel to the working direction T and opposite the first direction. The relining assembly 16 is preferably located between the excavation assembly 15 and the sieving installation 14. The first direction 100 is therefore a privileged direction of movement of the mobile system 10, at least in the operating modes during which relining is envisaged, insofar as the relining operations carried out by the relining assembly 16 are intended to be carried out after the excavation operations carried out by the excavation assembly 15. The excavation assembly 15, the relining assembly 16 and the storage assembly 18 are shown here only schematically, and can be borne by the same wagon as the sieving installation or by vehicles coupled or not coupled to the wagon of the sieving installation.

(8) The wagon 22 bearing the sieving installation 14 here comprises two bogies 20 on which a frame rests that bears the various elements of the sieving installation 14.

(9) The sieving installation 14, which comprises two sieves 26 and 28, is supplied by a set of one or more excavation conveyors 30, here conveyor belts, conveying soiled ballast coming from the excavation assembly 15, in the second direction 200. A set of one or more discharge conveyors 32 conveys the flow of discarded ballast, after passing through the sieves, in the second direction 200, to the discarded ballast storage assembly 18. A set of one or more relining conveyors 34 collects the flows of clean ballast after passing through the sieves, and conveys them to the relining assembly 16, in the first direction 100. The assembly of one or more relining conveyors 34 is preferably arranged under the assembly of one or more excavation conveyors 30, without crossing in the vertical direction.

(10) The first sieve 26 has a first soiled ballast inlet 38 at a first end 36 and, at a second end 40, located below and in front of the first end 36 in the first direction 100, a first discarded ballast outlet 42 and a first clean ballast outlet 44.

(11) The second sieve has a second soiled ballast inlet 48 at a first end 46 and, at a second end 50, located below and in front of the first end 46 in the first direction 100, a second discarded ballast outlet 52, a second clean ballast outlet 54 and a secondary discarded ballast inlet 56. The secondary discarded ballast inlet 56 is located above the second discarded ballast outlet 52 of the second sieve.

(12) The internal workings of the sieves 26, 28, known per se, allows the finer components of the soiled ballast to pass through vibrating sieves and to be directed to the discarded ballast outlet 42, 52, while the components retained by the sieves are directed toward the clean ballast outlet 44, 54. The passage through the sieves involves gravity as well as a vibratory movement of the sieves. Where appropriate, the discarded ballast outlets 42, 52 may not be located, or may not be located only, at the lower end of the sieves 26, 28, but may instead extend over all or part of the length of the sieves 26, 28. In practice, the thinnest discarded elements are discarded along the entire length of the sieve, while the larger gauge discarded elements travel to the lower end of the sieve.

(13) The two sieves 26, 28 overlap, in the sense where part of the first sieve, in this case the part comprising the first end 36 and the first soiled ballast inlet, is arranged above a part of the second sieve 28, in this case the end part 50 comprising the second clean ballast outlet 54. This makes it possible to reduce the distance between the inlets of each of the sieves 26, 28 as well as the distance between the outlets of each of the sieves 26, 28.

(14) A first distributor 58, positioned between a conveyor 30.1 of the set of one or more soiled ballast conveyors 30 and the first soiled ballast inlet 38 of the first sieve, is able, in a so-called distribution operating mode, to divide a soiled ballast flow between the first sieve 26 and the second sieve 28, or in a first orientation operating mode, to direct the entire soiled ballast flow toward the first sieve 26 or in a second orientation operating mode, to direct the entire soiled ballast flow toward the second sieve 28. It preferably has more intermediate positions to modulate the division ratio of the flow of soiled ballast between the two sieves, discretely or continuously.

(15) The set of excavation conveyors 30 comprises an intermediate conveyor 30.2 positioned between the first distributor 58 and the second sieve 28 in order to convey the flow of soiled ballast directed toward the second sieve 28 at the outlet of the first distributor 58.

(16) A second distributor 62, positioned between the intermediate conveyor 30.2 and the second soiled ballast inlet 48 of the second sieve 28, is suitable, in a first operating mode, for guiding the flow of soiled ballast toward the second soiled ballast inlet 48 of the second sieve or, in another operating mode, for directing the flow of soiled ballast toward a conveyor 32.2 of the set of at least one discharge conveyor 32. This second distributor 62 can, if necessary, have only two positions, if it is not envisaged to divide the incoming flow of soiled ballast in two. Alternatively, and according to a preferred embodiment, the second distributor 62 allows a continuous adjustment to divide the flow of soiled ballast between the second sieve 28 and the set of discharge conveyors 32, which makes it possible, if necessary, to work the second sieve 28 while removing excess soiled ballast exceeding the sieving capacities or requirements.

(17) The discharge conveyor assembly 32 comprises a first discharge collection conveyor 32.1, positioned under the first discarded ballast outlet 42 of the first sieve and extending to the second secondary inlet 56 of the second sieve, in order to collect the flow of ballast from the first discarded ballast outlet 42 of the first sieve 26 and to convey it to the second sieve 28. The second sieve is equipped with a spout 57 that connects the second secondary inlet 56 to the second discarded ballast outlet 52 while allowing crossing with the second clean ballast outlet 54, inside the second sieve 28. The two discarded ballast flows coming from the first sieve 26 and from the second sieve 28 are thus collected at the second discarded ballast outlet 52 of the second sieve 28 by a second discharge collection conveyor 32.2 of the set of discharge conveyors 32. The set of discharge conveyors 32 further comprises a conveyor 32.3 into which the discarded ballast flow from the conveyor 32.2 is discharged, and which transfers the flow of discarded ballast to the discarded ballast storage assembly 18.

(18) As illustrated in the figures, the conveyors 30.1, 30.2 of the set of excavation conveyors are positioned above the sieves 26, 28, which in turn are positioned above the conveyor(s) of the set of rerouting conveyors 34. The intermediate discharge conveyor 32.1 is positioned, in terms of height, midway between the set of excavation conveyors 30 and the set of rerouting conveyors 34.

(19) FIGS. 1 to 4 illustrate a conveyor 30.1 that conveys a flow of soiled ballast from the excavation assembly 15 to the first distributor 58.

(20) In FIG. 1, the first distributor 58 is illustrated in a distribution operating mode and the flow of soiled ballast is distributed between the first sieve 26 and the intermediate conveyor 30.2, which conveys a partial flow of soiled ballast to the second distributor 62. The second distributor 62 is in a first orientation operating mode, and directs the flow of soiled ballast entirely toward the second sieve 28.

(21) The flows of soiled ballast pass through the sieves 26, 28 and the flows of clean ballast and discarded ballast are collected. The set of one or more rerouting conveyors 34, working in the first direction 100, collects the flow of clean ballast coming from the second clean ballast outlet 54 of the second sieve 28, then the flow of clean ballast coming from the first clean ballast outlet 44 of the first sieve 26, and thus conveys a single flow of clean ballast in the first direction to the relining assembly 16, which ensures relining of the track, that is to say, spreading of the clean ballast on a bare portion of the track.

(22) The flow of discarded ballast coming from the first discarded ballast outlet 42 of the first sieve 26 is collected by the intermediate conveyor 32.1 and discharged into the second sieve 28, at the second secondary discarded ballast inlet 56 of the second sieve so as not to put unnecessary strain on the sieves of the second sieve 28. The flow of discarded ballast from the second discarded ballast outlet 52, coming from the first and second sieves 26, 28, is collected by the set of one or more discharge conveyors 32, which works in the same direction as the excavation conveyor 30, that is to say, in the second direction 200, toward the discarded ballast storage assembly 18.

(23) In FIG. 2, the first distributor 58 is illustrated in a first orientation operating mode, and directs the flow of soiled ballast entirely toward the first soiled ballast inlet 38 first sieve 26. The intermediate conveyor 30.2, the second distributor 62 and the second sieve 28 are inoperative.

(24) The flow of soiled ballast passes through the first sieve 26 and the flows of clean ballast and discarded ballast are collected. The set of one or more rerouting conveyors 34 collects the flow of clean ballast from the first clean ballast outlet 44 of the first sieve, and thus conveys only the flow of clean ballast, in the first direction 100, to the relining assembly 16.

(25) The flow of discarded ballast coming from the first discarded ballast outlet 42 of the first sieve 26 and collected by the intermediate conveyor 32.1 is discharged into the second sieve 28, at the second secondary discarded ballast inlet 56 of the second sieve. The flow of discarded ballast from the second discarded ballast outlet 52, coming from the second sieve 28, is collected by a common conveyor 32.2 of the set of one or more discharge conveyors 32, which works in the same direction as the excavation conveyor 30, that is to say, in the second direction 200, toward the storage assembly 18.

(26) In FIG. 3, the first distributor 58 is illustrated in a second orientation operating mode and the flow of soiled ballast is oriented entirely toward the intermediate conveyor 30.2, which conveys the entire flow of soiled ballast toward the second distributor 62, while the first sieve 26 is inoperative.

(27) The second distributor 62 directs the flow of soiled ballast toward the second soiled ballast inlet of the second sieve 28. The flow of soiled ballast passes through the second sieve and the clean ballast and discarded ballast flows are collected. The set of one or more rerouting conveyors 34 working in the first direction 100 collects the flow of clean ballast from the second clean ballast outlet 54 of the second sieve, and thus conveys only the flow of clean ballast to the second relining assembly 16.

(28) The flow of discarded ballast from the second discarded ballast outlet 52 of the second sieve 28 is collected by the set of one or more discharge conveyors 32, which works in the same direction as the excavation conveyor 30, that is to say, in the second direction 200, and conveyed toward the storage assembly 18.

(29) The sieving installation according to the invention therefore allows various sieving modes in which one or the other of the two sieves 26, 28, or both, are used. The sieving throughput can therefore be doubled when necessary.

(30) In FIG. 4, the first distributor 58 is illustrated in another orientation operating mode and the flow of soiled ballast is directed entirely toward the intermediate conveyor 30.2, which conveys the entire flow of soiled ballast toward the second distributor 62, while the first sieve is inoperative. The second distributor 62 is in a second orientation operating mode and the flow of soiled ballast is entirely collected by the set of one or more discharge conveyors 32, which works in the same direction as the excavation conveyor 30, that is to say, in the second direction 200, and is conveyed toward the storage assembly 18. The second sieve 28 is inoperative.

(31) The sieving installation according to the invention therefore makes it possible to carry out total excavation operations without sieving, that is to say, without going through either of the two sieves 26, 28.

(32) Other operating modes are also possible. In particular, it is possible to operate the first distributor 58 in the distribution operating mode (as illustrated in FIG. 1), in order to distribute the flow of soiled ballast between the first sieve 26 and the intermediate conveyor 30.2, and to operate the second distributor 62 in the orientation operating mode of FIG. 4, in order to direct the flow of soiled ballast from the intermediate conveyor 30.2 toward the set of one or more discharge conveyors 32 and toward the storage assembly 18.

(33) Insofar as the distributors 58, 62 allow continuous adjustment, all variations around the operating modes described above are authorized.

(34) Naturally, the example shown in the figures and discussed above is given only by way of illustration. Various variants are possible.

(35) In the event that the second sieve does not have a discarded ballast inlet 56, the discarded ballast from the first sieve 26 can be discharged directly by the intermediate discharge conveyor 32.1 onto the common discharge conveyor 32.2.

(36) The second distributor 62 can be arranged to discharge the flow of ballast directly onto the conveyor 32.3 rather than onto the conveyor 32.2.

(37) Each of the conveyors 30.1, 30.2, 32.1, 32.2, 32.3, 34 may, where appropriate, consist of several independent sections or conveyors. Regarding the rerouting conveyor 34 in particular, it is possible to provide a relatively narrow section running from the second clean ballast outlet 54 to the first clean ballast outlet 54 under the first sieve 26, and discharging into a second, wider section, therefore of higher capacity, also collecting the flow of clean ballast flow from the first clean ballast outlet 44. This makes it possible, where appropriate, to facilitate the positioning of the conveyors in the limited space available under the first sieve 26.

(38) It is conceivable to reinforce the sieving capacity of the installation with at least one intermediate sieve, positioned between the first sieve and the second sieve. The intermediate sieve is associated with an intermediate distributor capable of distributing the incident flow of soiled ballast (coming from the first distributor) between the intermediate sieve and the second distributor. The flow of discarded ballast from the first sieve is collected by the intermediate conveyor and discharged into the intermediate sieve, at the outlet end and above the outlet of the discarded ballast flow from the intermediate sieve. The discarded ballast flows from the first sieve and the intermediate sieve are collected by a second intermediate conveyor and discharged into the second sieve, at the outlet end and above the outlet of the discarded ballast flow from the second sieve. The discarded ballast flows from the first sieve, the intermediate sieve and the second sieve are collected by the set of one or more discharge conveyors that work in the same direction as the excavation conveyor, that is to say, in the second direction, toward the storage assembly.

(39) The set of one or more rerouting conveyors works in the first direction, collects the clean ballast flow at the clean ballast outlet of the second sieve, then collects the clean ballast flow at the clean ballast outlet of the intermediate sieve, then collects the clean ballast flow at the clean ballast outlet of the first sieve, and thus conveys a single clean ballast flow to the relining assembly.

(40) The sieving installation according to this variant of the invention makes it possible to multiply the operating methods by using one, two or three sieves in parallel while keeping the possibility of carrying out total excavation operations, without sieving, that is to say, without going through any of the three sieves.

(41) Of course, other variants are possible. A mobile system borne by a single car has been described. This arrangement is not, however, limiting, and it is possible to envisage more generally that the mobile system is carried by one or more railway, motorized or towed vehicles.