US20240102267A1

US20240102267A1 - Excavating finger and associated excavating bucket

Info

Publication number: US20240102267A1
Application number: US17/754,804
Authority: US
Inventors: Vladimir Svitok; Franck MARTINET
Original assignee: Matisa Materiel Industriel SA
Current assignee: Matisa Materiel Industriel SA
Priority date: 2019-10-14
Filing date: 2020-10-14
Publication date: 2024-03-28
Also published as: WO2021074250A1; FR3101893B1; CA3153798A1; EP3850162B1; FR3101893A1; CN114585785A; BR112022006950A2; AU2020365389A1; EP3850162A1

Abstract

The invention relates to an excavating finger of a bucket that is designed to be fitted to an excavating chain for a device for excavating ballast beneath a railroad track, the finger being in one piece and comprising: a retention portion that is rotationally symmetric about a reference axis of the finger, the retention portion being designed to be accommodated in a cylindrical cavity of the bucket; and a tip designed to project out of the cylindrical cavity of the bucket, the excavating finger (132) wherein the retention portion comprises at least one annular channel that is configured to receive at least part of an immobilizing rod, designed to provide axial retention of the retention portion in the cylindrical cavity in such a way that the finger is free to rotate about its reference axis.

Description

TECHNICAL FIELD OF THE INVENTION

The invention relates, in a general manner, to the technical field of shovels which are intended to equip in particular clearing or excavation chains.
The invention relates more specifically to an excavating finger, or claw, of a shovel intended for equipping an excavation chain for a device for excavating ballast under a railroad.

PRIOR ART

In the prior art, work trains are known which are equipped with machines intended for removing the ballast located under the sleepers of a railroad, and for sorting it for possible re-use by tipping into onto the track. These machines are commonly referred to as “ballast clearing machines”. In a known manner, work trains of this kind more generally comprise a machine intended for screening the ballast in order on the one hand to keep the sound part of the ballast for re-use, and on the other hand to remove the spent part of the ballast, in trucks provided for this purpose. In this way, the ballast clearing machine/cleaner attachment makes it possible to remove and sort the spent ballast, and replace the entire ballast layer with the sorted sound ballast, as well as optional additional supply of new ballast.
Work trains of this kind are equipped with excavation chains made up of a succession of links which are articulated to one another, at least some of which are equipped with shovels intended for excavating the ballast. Said chain is arranged on the chassis of the rail vehicle, so as to be movable or height-adjustable. The chain is driven in an endless manner by a drive mechanism. The path of the chain is configured such that it comprises a straight excavation portion located under the sleepers of the railroad, the chain working on this excavation portion transversely with respect to the orientation of the rails of the railroad, carrying along and transporting the ballast with them. On either side of said straight excavation portion, brackets are arranged, which form return members for the excavation chain. Said brackets are located at the ends of the straight excavation portion, along which portion the ballast is removed, and are generally formed by a bent fixed wall on which the links of the chain slide successively. The chain moves along a longitudinal feed path and then moves over the straight excavation portion after having passed through a first bent portion formed by one of the brackets. The chain which follows its path then emerges from said straight excavation in order to move over the longitudinal outlet portion after having passed through a second bent portion formed by the other of the brackets. The shovels arrive on said straight excavation portion having been unloaded, and re-emerge therefrom loaded with ballast, towards the longitudinal outlet portion. The longitudinal feed and outlet portions are connected, in a region located at a height with respect to the rail vehicle, by a transverse discharge portion where the ballast is discharged onto conveyor belts. The shovels, offloaded of ballast, then continue their path towards the longitudinal feed portion, then repeating these operations.
Said shovels are designed to overcome a number of problems. In particular, they must be sufficiently resistant to ensure a certain number of predetermined cycles, in order to ensure the excavation and transport of ballast, requiring minimum maintenance. Said shovels must furthermore allow for effective transport of the ballast towards the discharge thereof, with a view to the screening operation, in order to improve the output of the ballast clearing machine by the excavation of the ballast, as well as that of the cleaner attachment, in order to make it possible to improve the reuse rate of the sound ballast.
Despite these objectives, and given the considerable stresses to which the shovel excavators are subjected, the improvement of their resistance with the aim of minimizing their maintenance is a constant problem for which an improvement is continually being sought.
In order to further improve their service life, it is also known to provide said shovels with reinforced fingers which form claws and are positioned in the extension of the shovel. Fingers of this kind are designed so as to be very resistant, and are easier to maintain than the link of the chain itself, and make it possible to more accurately adapt to localized wear, depending on the stresses experienced. This thus makes it possible to reduce the maintenance cost and the maintenance time, i.e. stoppage time of the machine, which accordingly limits the costs.
However, the problem of reducing the wear of the reinforcing fingers always prevails, all the more so because these fingers have a dual function of protecting against and limiting the wear of the shovel on the one hand, and of participating with the shovel in the excavation of the ballast on the other hand.

DISCLOSURE OF THE INVENTION

The invention aims to overcome all or some of the disadvantages of the prior art, by proposing in particular a reinforcing finger and an associated excavation shovel, which makes it possible to reduce the wear of the reinforcing fingers, so as to be able to reduce the maintenance operations aiming to replace these consumable parts.
In order to achieve this, according to a first aspect of the invention, an excavating finger of a shovel that is intended to be fitted to an excavating chain for a device for excavating ballast beneath a railroad track is proposed, the finger being in one piece and comprising:

- a retention portion that is rotationally symmetrical about a reference axis of the finger, the retention portion being intended to be accommodated in a cylindrical recess of the shovel, and
- a tip intended to project out of the cylindrical recess of the shovel,
  the excavating finger being notable in that the retention portion comprises at least one annular groove that is designed to receive at least part of a locking pin which is intended to provide axial retention of the retention portion in the cylindrical recess in such a way that the finger is free to rotate about the reference axis thereof.

By virtue of a combination of features of this kind, the finger is designed so as not to be prevented from rotating, which allows for even wear thereof. In this way, maintenance for replacing the fingers is less frequent, on account of reduced wear.
According to an embodiment, the retention portion comprises a plurality of annular grooves, the annular grooves being mutually parallel and spaced apart from one another. In this way, the excavating finger can receive a locking pin in one or other of its annular grooves, corresponding to different axial positions of the locking pin. Once the wear of the finger is noted by an operator, it is then possible to move the excavating finger into its cylindrical recess by moving it in translation towards the outside, i.e. in the direction of a increase in projection of a tip out of the cylindrical recess of the shovel. The annular grooves thus make it possible to index the finger according to a corresponding position, depending on the wear of said excavating finger. A feature of this kind allows for an extended use of the finger, and thus a reduction in maintenance consisting in replacing a finger, and limiting the associated costs.
According to an embodiment, the finger is rotationally symmetrical about the reference axis.
According to an embodiment, the excavating finger is preferably made of steel. The finger preferably comprises, at least in the region of the tip, a reinforcement made of a cutting material, in particular carbon steel, tungsten steel or carbide. In this case, the finger may be formed entirely of this reinforced material. In another embodiment, a part of the finger comprising the tip is formed of said reinforcing material forming the reinforcement, such as of carbide, and then assembled together with a second part formed for example of steel, said assembly preferably being performed by sintering and/or brazing. In this way, the structure of the excavating finger obtained is entirely resistant.
According to an embodiment, in cross section, the annular groove has a circular arc-shaped profile, in a plane containing the reference axis. In a general manner, the annular groove is designed to match, at least locally, the shape of a region of the locking pin which it receives.
The invention also relates to a shovel intended for equipping an excavation chain for a device for excavating ballast beneath a railroad track, the shovel comprising:

- a body comprising at least one cylindrical recess defining an insertion axis, and a fixing hole having an axis extending in a plane perpendicular to the insertion axis, at a distance from the insertion axis, the fixing hole leading into the cylindrical recess;
- at least one excavating finger as described above, the retention portion of which is accommodated in the cylindrical recess, and the tip projects with respect to the body of the shovel,
- a locking pin which penetrates into the fixing hole and into the groove of the finger in order to axially retain the finger on the shovel, the excavating finger being free to rotate about the reference axis thereof.

According to an embodiment, it comprises a plurality of cylindrical recesses which are intended to each receive one excavating finger. In this way, the shovel is better protected by the excavating fingers. The shovel preferably comprises at least three excavating fingers.
According to an embodiment, each recess is positioned on a rear part of the shovel, such that the associated excavating finger extends in an extension of the shovel. In particular, the excavating fingers are preferably positioned so as to project with respect to an outer edge of the shovel.
According to an embodiment, the locking pins comprise a screw, the fixing hole or a separate member having a tapped portion so as to receive the screw.

BRIEF DESCRIPTION OF THE FIGURES

Other features and advantages of the invention will become clear from the following description, given with reference to the accompanying drawings, in which:

FIG. 1 is a simplified side view of a work train equipped with a ballast clearing machine/cleaner attachment according to an embodiment;

FIG. 2 is a partial view of an excavation or clearing device according to this embodiment, viewed from the front, without an excavation chain;

FIG. 3 is a view of a link of an excavation chain bearing a shovel provided with excavating fingers, according to an embodiment;

FIG. 4A is a view of an excavating finger according to the embodiment of FIG. 3 ;

FIG. 4B is a view of an excavating finger according to another embodiment;

FIG. 5 is a plan view of a succession of links intended for equipping an excavation chain, including a link bearing a shovel provided with excavating fingers, according to the same embodiment as those shown in FIGS. 3 and 4 :

FIG. 6 is a front view of FIG. 5 ;

FIG. 7 is a rear view of a link of an excavation chain bearing a shovel equipped with excavating fingers according to an embodiment;

FIG. 8 is a cross section according to A-A in FIG. 7 ;

FIG. 9 is a cross section according to B-B in FIG. 8 .

For reasons of improved clarity, the identical or similar elements are indicated by identical reference signs in all the figures.

DETAILED DESCRIPTION OF AN EMBODIMENT

With reference to FIG. 1 , a rail vehicle 1 such as a ballast clearing machine/cleaner attachment equipped with a device for clearing or excavation 4 for cleaning the ballast of a railroad track 2 is shown. Said clearing or excavation device 4 is arranged between two bogies 3 of the train 1.
The ballast clearing device 4 comprises an excavation chain 8 that is driven in an endless manner by means of a drive mechanism 9, and guided by pipes, including a transverse pipe 5 located under the track 2 in the work position, along which the chain circulates over a substantially straight excavation portion 8A. The clearing device 4 also comprises riser pipes and downpipes 6, 7 which are connected on either side of the transverse pipe 5 to which they are connected by bent portions forming angle returns 40, also referred to as “brackets” (see FIG. 2 ). It is understood that the excavation portion is generally straight, although the excavation is ensured in a part of the curve of each of the angle returns.
The drive device 9 is arranged at a height with respect to the rail vehicle 1, above the railroad 2, on a side longitudinally opposite the transverse pipe 5, and between the riser pipe 6 and the downpipe 7. The drive device 9 is positioned on the path of the excavation chain 8 and comprises a drive wheel 9′ which engrains locally with the links 100 of the excavation chain 8 so as to move it. An endless path is thus formed, for guiding the excavation chain 8. Arrows shown in FIG. 2 indicate the direction of movement of the chain 8. At the top ends of the riser pipe 6 and downpipe 7, on the side of the drive device, idler wheels forming return members 40 are provided for ensuring expedient movement of the chain 8 in the region of these bent zones.
Once the ballast has been transported upwards in the riser pipe 6, it is discharged onto a conveyor belt 10 and then transported to a screening unit 11 with the aim of sorting the sound ballast from the spent ballast.
The vehicle 1 further comprises a unit for lifting 13 the railroad 2, which is connected to a chassis 14 of the vehicle 1 and which is located upstream of the clearing or excavation device 4, with respect to a work direction 12 of the vehicle 1. A height regulation device 16 is also provided, and connected to the frame 14 of the vehicle 1, which is designed to move the clearing device 4, using drive means 15, from a lifted position to a position lowered under the railroad 2, and which can be for example detachably connected to the transverse pipe 5 by a connection (not shown in the drawings).
FIG. 3 is a rear perspective view of an embodiment of a link 100 that is intended to from the excavation chain 8. The excavation chain 8 is formed of a succession of links 100 which are articulated in pairs, until the two ends of the chain 8 are connected end-to-end to form a closed chain 8, of the endless chain type. Some of the links 100 of the chain 8, like that shown in FIG. 3 , comprise a shovel 130 which allows for removal of ballast on the path over which it travels.
Each of the links 100 comprises a body 101 which extends longitudinally between a front end 110 and a rear end 120 provided, respectively, with at least one front hole 111 and a rear hole 121 which pass right through the link 100 and are designed to receive articulation means 160 with an adjacent link of the chain 8. In this case, the longitudinal direction extends as the direction of movement of the link 100. The front 111 and rear 121 through-holes extend in accordance with mutually parallel axes contained in a reference plane P of the body 101.
The link 100 shown in FIG. 3 comprises a projecting part formed by a shovel 130 extending from an outer side 100A of the body 101 of the link 100, with respect to the reference plane P, opposite to the inner side 100B of the body 8 of the link 100, the inner side comprising a surface that is intended to come into contact with return members 40 of the clearing device 4 during the movement of the chain 8.
The shovel 130 is in the shape of a plate, having a work face oriented to the front, i.e. it is oriented in the direction of advancement of the chain 8, and a back oriented to the rear. The shovel 130 extends from the body 101 of the link 100 as far as an outer end 130 a which extends generally in accordance with an axis in parallel with the reference plane and in parallel with the axes of the front 111 and rear 121 through-holes, and has two lateral edges, lower 130 b and upper 130 c.
The shovel 130 further comprises excavating fingers 132 which project towards the outside of the outer side 100A with respect to a reference plane P, in the extension of the shovel 130. In this embodiment, there are three of these fingers 132—a central finger, a lower finger, and an upper finger projecting with respect to the outer side 130 a of the shovel 130.
As is shown in detail in FIGS. 4A and 4B, each finger 132 comprises a cylindrical body equipped with at least one retention portion 132 b designed to come to rest in a corresponding cylindrical recess 134 provided for this purpose. Each finger 132 further comprises a tip 132 a which is intended to project outside of the cylindrical recess 134 of the shovel 130. In particular, in the position fixed to the shovel 130, the tips 132 a of each finger 132 are arranged so as to project from the outer edge 130 a of the shovel 130, in the extension of the shovel 130. Such projection allows each excavating finger 132 to be subjected to the majority of the frictional stresses, in place of the edge 130 a of the shovel 130 from which said excavating finger 132 projects. In this way, the wear on the corresponding edge 130 a of the shovel 130 is significantly reduced.
The retention portion 132 b is rotationally symmetrical about a reference axis X of the finger 132 and comprises a body which extends according to a cylindrical casing. In this embodiment, the finger 132 as a whole is rotationally symmetrical about the reference axis X. A cylindrical casing of this kind allows the finger 132 to move in translation in the associated cylindrical recess 134. Said cylindrical casing of the body of the finger 132 is dimensioned so as to be substantially complementary to the cylindrical recess 134, such that the body of the finger 132 may be guided, in its translational movement, by the cylindrical recess 134 itself. In order to achieve this, an outside diameter of the body of the finger 132 is slightly less than an inside diameter of the cylindrical recess 134 of the shovel 130. The tips 132 a of each finger 132 are located in the axial extension of the body of the associated finger. Furthermore, in this case the tips 132 a of each finger 132 are contained radially inside the cylindrical casing of the associated finger 132, i.e. the tips 132 a of a finger to not project radially with respect to the body thereof. In other words, at any point of the tip 132 a of one of the fingers, a diameter measured in the region of said tip is smaller, preferably strictly smaller, than the outside diameter of the body of the associated finger 132.
The retention portion 132 b further comprises at least one annular groove 132 c which is designed to receive at least a portion of a locking pin 135 intended for ensuring axial retention of the retention portion 132 b in the cylindrical recess 134 such that the finger 132 can rotate freely about the reference axis X thereof. In this way, the prevention of translation of the finger 132 is ensured, and the finger 132 is allowed to rotate freely when it is fixed to the shovel 130. The locking pin 135 is fixed in a detachable manner with respect to the shovel 130, such that it is possible to change the finger 132 in the event of wear that is too great.
Fingers 132 of this kind are designed so as to be very resistant, for example made of high-resistance steel, and are easier to maintain than the link 100 of the chain 8 itself, and this makes it possible to more precisely adapt to localized wear, depending on the stresses experienced. This thus makes it possible to reduce the maintenance cost and a maintenance time, i.e. stoppage time of the machine.
More precisely, the shovel 130 comprises a body 131 comprising a plurality of cylindrical recesses 134, three in this case, each defining an insertion axis W. In order to ensure the fixing of the finger 132, the shovel 130 is provided in the region of each cylindrical recess 134 of a fixing hole 136 having an axis W′ which extends in a plane that is perpendicular to the corresponding insertion axis W and is at a distance from the corresponding insertion axis W, the fixing hole 136 leading into the cylindrical recess 134 such that the locking pin 135 which penetrates into the fixing hole 136 also penetrates, in part, into the groove 132 c of the finger 132 in order to axially hold the finger 132 on the shovel 130 while leaving the excavating finger 132 free to rotate about the reference axis X thereof.
In such a locking position of the finger 132, the locking pin 135 comes into the vicinity of a base of the associated annular groove 132 c, in a manner tangential to said annular surface. In this way, the locking pin 135 is not an obstacle for the rotation of the finger 132 about itself, i.e. about the reference axis X thereof, which coincides with the insertion axis W. The locking pin 135 is preferably not in contact with the base of the annular groove 132 c. It may be in contact, however, but the bearing of the locking pin against the annular groove 132 c must be relatively light in order to limit the friction between the locking pin 135 and the annular groove 132 c, so as not to create difficulties for the free rotation of the finger 132. In FIG. 9 , the locking pin 135 has been shown centered on the axis W of the fixing hole 136, such that interference occurs between the locking pin 135 and the base of the groove 132 c, which interference does not exist in reality, on account of the functional clearances. In this case it is ensured, taking into account manufacturing tolerances, that a functional clearance always remains between the locking pin 135 and the base of the groove 132 c, which provides the excavating finger 132 with its freedom of rotation about the reference axis X thereof.
In this case, each finger 132 is retained in a manner fixed in translation, in the associated cylindrical recess 134, by one single locking pin 135.
In this embodiment, the locking pins 135 comprise, for each finger 132, a screw provided with a head 135 b at a first end, and a distal end 135 a, opposite the head 135 b thereof and comprising a threaded portion 135 c. In the fixed position, the had 135 b comes into contact with and bears against a periphery of an inlet of the fixing hole 136, the threaded portion 135 c being anchored by a nut 135′ provided with a tapped opening that cooperates with the thread of the threaded portion 135 c of the locking pin 135. A washer 135″ is interposed between a periphery of an outlet of the fixing hole 136 against which it is in contact and against which it bears, and the nut 135′. In this case, the nut 135′ bearing the tapped hole is an attachment part, but it is understood that other fixing means may be used. The fixing hole 136 may for example comprise a cylindrical insert provided with an inner tapped aperture. The fixing hole 136 may also be machined so as to bear a thread. Of course, the locking pin 135 may also be of a different type. and may comprise any suitable locking means, such as a pin locked by a nose. However, a screw is easier to change. Furthermore, the use of a screw as a fixing pin makes it possible to ensure tight and clearance-free retention, considerably reducing the noise during use of the shovel 130.
The excavating fingers 132 are fixed in a detachable manner with respect to the shovel 130, the withdrawal of the locking pin 135, for example by unscrewing it, makes it possible to unlock the finger 132 in question and to remove it from its cylindrical recess 134 by moving it in translation, or indeed by simply moving it axially in order to index it in the region of another annular groove 132 c.
In a general manner, the locking pin 135 preferably comprises a cylindrical or annular body, and, in cross section, the groove 132 c has a circular arc-shaped profile, in a plane containing the reference axis X. This shape is designed to locally match the shape of the fixing pin 135 so as to minimize the clearance between said fixing pin 135 and the associated excavating finger 132. The depth of the groove 132 c in a retention portion 132 b is preferably more than 10%, preferably more than 40%, and less than 60%, preferably less than 50%, of a radius of the associated excavating finger 132. Indeed, the annular groove 132 c must be sufficiently deep to ensure its axial locking, and sufficiently shallow in order not to fragilize the structural integrity of the excavating finger 132. In this embodiment, the depth of the groove 132 c in a retention portion 132 b is dimensioned so as to correspond to 50% of a radius of the associated excavating finger 132. Furthermore, the axis W of the fixing hole 136 extends in a plane perpendicular to the insertion axis W corresponding to a distance d from the insertion axis W that is approximately equal to the radius of the fixing hole 136. This corresponds to a favorable ratio between the effectiveness of retention of the finger 132 and limiting the fragility of said finger 132 on account of the presence of the annular groove.
Furthermore, the recesses 134 are positioned on a rear part of the shovel 130, such that the associated excavating finger 132 extends towards the outside of the shovel 130, in an extension of said shovel 130. The front part, or front workface, opposite the rear part of the shovel 130, is designed so as to have an effective area for the excavation of the ballast. In this embodiment, the locking pin 135 is oriented such that its head is in contact with or bears against a part of the front part of the shovel 130, while the nut 135′ bears, indirectly, due to the washer 135″, against a rear face of said shovel 130. The front part of the shovel 130 comprises a reinforcement 137, inside which the head 135 b of the locking pin 135 can be received entirely or in part, so as to limit the wear thereof (see for example FIG. 8 ).
As shown in FIG. 4B, it is particularly advantageous to provide the retention portion 132 b of a finger 132 with a plurality of annular grooves 132 c, the annular grooves 132 c being mutually parallel and spaced apart from one another so as not to overlap. An overlap would have the effect of reducing the effectiveness of the axial locking of the finger 132. A plurality of annular grooves 132 c of this kind allows for adjustment of the finger 132 in translation, and thus to cause it to move in translation in its cylindrical recess 134, in order to place one of the following annular grooves 132 c in engagement with the locking pin 135, and thus assume predetermined positions, depending on its wear. The distance between two annular grooves 132 c may vary depending on the material of the finger 132 and the speed of wear with respect to the ballast transported. For example, the annular grooves 132 c are spaced apart from one another by a distance corresponding at least to the axial width of the annular grooves 132 c, preferably between one and two times the axial width of the annular grooves 132 c. All or some of the annular grooves 132 c, preferably all the annular grooves, have an identical diameter around the cylindrical body of the associated finger 132.
The fingers 132 are each oriented in accordance with an axis that is inclined relative to the reference plane P, having an inclination a of between 65 and 80°, preferably between 70 and 75°.
The fingers 132 are also oriented in a plane P132 that is inclined relative to a mid-plane P130 of the shovel 130 that extends substantially vertically (see FIG. 8 ), the inclination a preferably being between 20 and 35°, and in this case equal to 30° in this embodiment. A feature of this kind makes it possible, compared with an equivalent effective work area of a shovel 130 having a greater inclination, to make the shovel 130 lighter, without loosing output or rigidity. In this case, the effective work area of the shovel 130 is understood to be the surface swept by the shovel 130 during its movement.
The fingers 132 are all located above a plane Pinf perpendicular to the parallel axes of the front 111 and rear 121 through-holes, and tangential to a lower end of said shovel 130, in particular in this embodiment, also below a plane Psup that is tangent to a top end of the shovel 130 (see FIG. 7 ). Given the orientation of the chain 8 and thus of the shovel 130 on the straight excavation portion 8A, the planes Pinf and Psup are generally horizontal. Said lower end is sensitive in that it is greatly subjected to wear by abrasion against the ballast, such that, if the wear becomes too great, this may adversely affect the favorable fixing of the fingers 132 on the back of the shovel 130. The use of a lower finger 132 located entirely above the plane Pinf ensures a longer service life of the link 100. Preferably, the hardness of the bottom surface of the shovel 130 is increased, for example by supplying chromium/manganese and vanadium, by welding, or by adding slices of tungsten carbide.
The shovel 130 further comprises an abutment surface 138 located on the back of the shovel 130, between the body 101 of the link and the cylindrical recesses 134, the abutment surface 138 being designed to receive a counter stop 140 of an adjacent rear link of the chain 8, so as to limit a relative rotation between the link 100 of the chain 8 and the adjacent rear link, about the axis of the rear through-hole 121. Such an abutment position of the shovel 130 against the counter stop 140 of the associated rear link 100 is shown in FIG. 5 . Indeed, along the straight excavation portion 8, the shovels 130 are subjected to a force when dragging the ballast, which causes a torque on the shovel 130 which tends to cause the rear link 100 to tilt, said tilting being a pivot motion of the shovel 130 about the axis of the rear through-hole 121 designed to receive articulation means 160.
Of course, the invention is described above by way of example. It will be understood that a person skilled in the art is able to implement different variants of the invention, without in any way departing from the scope of the invention.

Claims

1. An excavating finger of a shovel to be fitted to an excavating chain for a device for excavating ballast beneath a railroad track, the finger being in one piece and comprising:

a retention portion that is rotationally symmetrical about a reference axis of the finger, the retention portion being intended to be accommodated in a cylindrical recess of the shovel, and

a tip intended to project out of the cylindrical recess of the shovel,

wherein the excavating finger comprises at least one annular groove designed to receive at least part of a locking pin to ensure axial retention of the retention portion in the cylindrical recess to allow the finger to rotate about the reference axis thereof.

2. The excavating finger of claim 1, further comprising a body with at least one retention portion, the body of the finger extending in accordance with a cylindrical casing.

3. The excavating finger of claim 2, wherein the retention portion further comprises a plurality of annular grooves mutually parallel and spaced apart from one another.

4. The excavating finger of claim 1, wherein the finger is rotationally symmetrical about the reference axis.

5. The excavating finger of claim 1, wherein it is made of steel.

6. The excavating finger of claim 1, wherein it comprises, in the region of the tip, a reinforcement made of a cutting material, said cutting material chosen from either carbon steel, tungsten steel or carbide steel.

7. The excavating finger of claim 1, wherein the annular groove has a circular arc-shaped profile, in a plane containing the reference axis.

8. A shovel for equipping an excavation chain for a device for excavating ballast beneath a railroad track, the shovel comprising:

a body comprising at least one cylindrical recess defining an insertion axis, and a fixing hole having an axis extending in a plane perpendicular to the insertion axis, the fixing hole leading into the cylindrical recess;

at least one excavating finger comprising a retention portion of which is accommodated in the cylindrical recess, and a tip projecting from the body of the shovel,

a locking pin which penetrates into the fixing hole and into the groove of the finger to axially retain the finger on the shovel, the excavating finger being free to rotate about the reference axis thereof.

9. The shovel of claim 8, wherein it comprises a plurality of cylindrical recesses which receive one excavating finger.

10. The shovel of claim 8, wherein each recess is positioned on a rear part of the shovel, such that the associated excavating finger extends in an extension of the shovel.

11. The shovel off claim 8, wherein the locking pins comprise a screw, the fixing hole or a separate member having a tapped portion so as to receive the screw.