WO2018225004A1

WO2018225004A1 - Disk cutter bar

Info

Publication number: WO2018225004A1
Application number: PCT/IB2018/054111
Authority: WO
Inventors: Gabriele Gualdi; Achille Brunazzi; Gianni Tenca
Original assignee: Comer Industries S.P.A.
Priority date: 2017-06-09
Filing date: 2018-06-07
Publication date: 2018-12-13
Also published as: IT201700063327A1

Abstract

A disk cutter bar (1), comprising a supporting frame (2), a plurality of knife supporting disks (3) which are associated with the frame (2) so that they can rotate about respective substantially parallel rotation axes (A), a gear transmission assembly (4) for the rotational actuation of the knife supporting disks (3), which comprises a series of idle gears (7) which move a plurality of pinions (8) for the rotational actuation each of a respective knife supporting disk (3), a pivot (9) for coupling to the corresponding knife supporting disk (3) that is associated with each one of the pinions (8), which is associated with the frame (2) by means of the interposition of rotational support means (10), has a first end (11) which is associated integrally with the corresponding pinion (8) and a second end (12) which is associated integrally with the disk and is provided with at least one shearing region (13) in an intermediate position between the ends, the pivot (9) being adapted to shear at the shearing region (13) following an overload of torque which acts thereon, forming a first portion (14) which comprises the first end (11) and a second portion (15) which comprises the second end (12), and retention means (16) associated with each one of the pivots (9) for the retention of the second portion (15) following the shearing of the pivot. The particularity of the invention resides in that the retention means (16) are associated with each one of the pivots (9) with axial play so as to allow the spacing in an axial direction of the second portion (15) with respect to the first portion (14) as a consequence of the shearing of the pivot, passing from an active configuration to a safety configuration of the corresponding knife supporting disk (3), and in that it comprises means (17) for the release of potential energy which are associated with each one of the pivots (9) and are adapted to activate as a consequence of the shearing of the pivot to space the second portion (15) from the first portion (14) and to keep the second portion in the safety configuration.

Description

DISK CUTTER BAR

The present invention relates to a disk cutter bar.

In the field of agricultural machines, apparatuses for cutting forage plants, so-called cutting bars, are known which are to be applied to the power takeoff of a self-propelled work machine and consist essentially of a supporting frame which is extended in a linear manner, is arranged transversely to the advancement direction of the machine itself and supports a plurality of knife supporting disks so that they rotate about respective substantially vertical axes. These apparatuses are provided with a gear transmission assembly for the rotary actuation of the knife supporting disks, which comprises a motion input device which can be associated with the power takeoff of the tractor, which is coupled to a series of idle gears which are interleaved by a plurality of pinions for the rotary actuation of respective knife supporting disks. Each pinion is provided with a pivot which is connected to the corresponding knife supporting disk and is supported rotationally by a flange associated with the supporting frame by means of the interposition of bearings.

If, during use, these apparatuses are used in the presence of rocks, obstacles of another kind or uneven ground, the knife supporting disks may be subject to impacts or instantaneous stops, which are capable of blocking their rotation and risk causing overloads in the kinematic motion transmission chain, such as to cause the failure of mechanical parts that are difficult to replace, such as in particular the gears involved.

In order to avoid this drawback, various solutions have been developed which incorporate a system for limiting the transmitted torque, which is capable of interrupting motion transmission between the driving pinion and the knife supporting disk if a predefined value of torque acting on said pinion is exceeded, preserving the integrity of the latter and of the elements connected thereto. These systems allow to shift the failure point to a predefined region of the mechanism, utilizing the yielding of elements which are sized appropriately to shear in case of excessive stresses.

In particular, a solution is known, from Italian patent no. 1,309,599 in the name of this same Applicant, which provides for the use of a driving pinion which has an annular groove cut into the corresponding pivot at the axial position for coupling to the rotational support bearings. In case of overload, the pivot of the pinion shears at said groove, generating two portions, of which one continues to rotate integrally with the pinion coupled to the adjacent idle gears and continues to be supported by the bearings and the other one remains connected to the knife supporting disk and is rendered free in rotation. Furthermore, this system provides for a retention screw which is inserted axially through the pivot and which, in case of failure, axially retains the free portion and the components connected thereto, avoiding their accidental expulsion.

These systems of the known type, however, are not free from drawbacks, which include the fact that despite allowing to protect the elements of the kinematic motion transmission chain from damage caused by accidental excesses of torque, they do not allow to avoid impacts between the knife supporting disk rendered free as a consequence of the shearing of the corresponding pivot and the ones adjacent thereto.

In fact, in these apparatuses the various knife supporting disks are angularly phased to rotate without interfering with each other in conditions of normal operation. When, as a consequence of an overload, one or more disks are no longer connected to the transmission system, they lose phasing with the adjacent ones, with the risk that collisions between them may occur such as to cause in any case the failure of mechanical parts of the transmission system.

In this regard, it should also be considered that the operator who drives the work machine that moves the apparatus may not realize immediately the occurrence of these overload episodes, and therefore might not stop the power takeoff in a timely manner, with an increase of the risk that damage may occur to the motion transmission system for the reasons described above.

In order to overcome these drawbacks, solutions have been developed which provide for safety systems which, in case of overload, in addition to providing a rotational uncoupling of the knife supporting disk from the corresponding driving pinion, cause an axial movement of the disk rendered free, so as to avoid collisions with the adjacent disks.

For example, US 6,675,563 Bl and EP 1,958,493 Bl relate to safety systems of this type, in which there is a threaded coupling between a female thread associated with the knife supporting disk and a threaded element which remains integral in rotation with the driving pinion even after the uncoupling from said disk caused by overloading. In this manner, as a consequence of the rotational uncoupling of the disk from the pinion, the rotation of the threaded element engaged in the female thread causes an axial displacement of the knife supporting disk, which arranges itself so that it is axially spaced from the adjacent disks, preventing the occurrence of impacts and allowing to continue to use the apparatus without compromising the integrity of the transmission assembly.

These solutions, despite being effective from the point of view of safety, entail the need to provide two versions of the safety system with oppositely oriented threads in the coupling between the female thread and the threaded element, to be mounted alternately as a function of the direction of rotation of the corresponding driving pinion. This fact complicates the management of the components both during the construction of the apparatuses and in the execution of replacement interventions following the occurrence of overloads.

Furthermore, the axial displacement of the knife supporting disk affected by the overload is not instantaneous, and therefore a residual risk remains that collisions might occur with the adjacent disks before the axial displacement of the freely rotating disk has been completed. The aim of the present invention is to eliminate the drawbacks described above of the prior art, by providing a cutter bar with a safety device that is universal in use, regardless of the direction of rotation of the knife supporting disk to which it is applied.

Within this aim, an object of the present invention is to provide a cutter bar that allows to simplify the management of the components both during the construction of the apparatus and if it is necessary to perform interventions for maintenance and component replacement following accidental overloads on apparatuses already in use.

A further object of the present invention is to provide a cutter bar that is capable of allowing rapid axial movement of the disk rendered free as a consequence of an overload situation, minimizing the risk of collision with the adjacent disks and optimizing the level of safety and reliability of the apparatus.

A further object of the present invention is to provide a cutter bar that can render it easy to perform maintenance interventions for the replacement of components damaged as a consequence of overload episodes caused by collisions or momentary stops of the knife supporting disks during use.

A further object of the present invention is to provide a cutter bar that is simple, relatively easy to provide in practice, safe in use, effective in operation, and relatively modest in cost.

This aim, as well as these and other objects which will become better apparent hereinafter are all achieved by the present disk cutter bar according to claim 1, optionally provided with one or more of the characteristics recited in the dependent claims.

Further characteristics and advantages of the present invention will become better apparent from the detailed description of three preferred but not exclusive embodiments of a disk cutter bar, illustrated by way of non- limiting example in the accompanying drawings, wherein:

Figure 1 is a schematic top view of a disk cutter bar according to the invention;

Figure 2 is an enlarged- scale view of a portion of the cutter bar of Figure 1 , highlighting the corresponding gear transmission assembly;

Figure 3 is a plan view of the cutter bar according to the invention at a knife supporting disk;

Figures 4 and 5 are respective sectional views, taken along the line IV-IV of Figure 3, of a cutter bar according to the invention in a first embodiment, respectively in the active configuration and in the safety configuration;

Figures 6 and 7 are respective sectional views, taken along the line

IV-IV of Figure 3, of a cutter bar according to the invention in a second embodiment, respectively in the active configuration and in the safety configuration;

Figures 8 and 9 are respective sectional views, taken along the line IV-IV of Figure 3, of a cutter bar according to the invention in a third embodiment, respectively in the active configuration and in the safety configuration.

With particular reference to the figures, the reference numeral 1 generally designates a disk cutter bar according to the invention.

The cutter bar 1 comprises a supporting frame 2 which generally has a linear extension and a plurality of knife supporting disks 3 which are distributed along said frame and are associated therewith so that they can rotate about respective rotation axes A which are substantially parallel and preferably with a vertical arrangement in use.

The knife supporting disks 3 are generally substantially oval in shape, with the blades arranged at the longitudinal ends, and are mounted in pairs, angularly offset by 90° so as to not strike each other during rotation. However, it is not excluded that the cutter bar 1 might use knife supporting disks 3 which are shaped differently but in any case need to maintain a predefined angular phasing during rotation. The cutter bar 1 further comprises a gear transmission assembly 4, which comprises a motion input device 5 which is coupled to a series of idle gears 7 which are interleaved by a plurality of pinions 8 for the rotational actuation each of a respective knife supporting disk 3.

In use, the cutter bar 1 is applied to a conventional self-propelled work machine, with the input device 5 connected to the corresponding power takeoff according to methods known to the person skilled in the art, in order to actuate rotationally about the respective axes A the knife supporting disks 3, while the cutter bar 1 is moved by the machine itself.

Each pinion 8 is arranged coaxially to the rotation axis A of the corresponding knife supporting disk 3 and is connected thereto by means of a coupling pivot 9 which lies along said axis, which is associated with the frame 2 by interposition of rotational support means 10, for example of the type of a conventional double ball bearing. Furthermore, each pivot 9 has a first end 11 which is integrally associated with the pinion 8 and a second end 12, arranged opposite the first one, which is integrally associated with said disk and is provided with at least one shearing region 13 which has a reduced transverse cross-section in a position that is intermediate between said ends. If a torque that exceeds the one for which the shearing region 13 is sized acts on the pivot 9, for example as a consequence of the impact of the corresponding knife supporting disk 3 with a rock or with a protrusion of the ground, the pivot 9 shears at said shearing region, forming a first portion 14 which comprises the first end 11 and a second portion 15 which comprises the second end 12.

The shearing region 13 of the pivot 9 can have, for example, an annular groove 27 which is defined externally to said pivot.

Preferably, the shearing region 13 of each pivot 9 is defined axially at the rotational support means 10, so that as a consequence of the shearing of said pivot the first portion 14 continues to support rotationally the corresponding pinion 8 and the kinematic chain for transmission of rotation to the knife supporting disks 3 arranged upstream and downstream thereof is not interrupted.

At each pivot 9, the frame 2 is provided with a rotational support flange 6, which forms an accommodation seat of the corresponding bearing 10.

Each knife supporting disk 3 is constituted by a flanged ring 31 for supporting an annular plate 32 which supports the blades and is associated therewith by means of screws 33. The flanged ring 31 is keyed to the second end 12 of the corresponding pivot 9, for example by means of a slotted or cylindrical coupling with a tab.

Furthermore, each pivot 9, at the second end 12, is provided with an externally threaded shank 23, which is inserted so as to pass through a corresponding hole which is formed in the corresponding flanged ring 31 and is coupled to a locking element 39 which is adapted to give the correct rolling preloading to the bearing 10 by means of the flanged ring itself, which presses thereon by interposition of a spacer 34.

Preferably, each pivot 9 and the corresponding pinion 8 are formed integrally and monolithically. However, it is not excluded that the pivot 9 might be applied to the pinion 8 by means of a coupling system such as to render its first end 11 integral with said pinion.

Finally, the cutter bar 1 comprises retention means 16 which are associated with each pivot 9 for the retention of the second portion 15 as a consequence of the shearing of said pivot.

Said retention means 16 are associated with each pivot 9 with axial play, so as to allow the spacing in the direction that is parallel to the corresponding rotation axis A of the second portion 15 with respect to the first portion 14 as a consequence of the shearing of said pivot. In this manner, the second portion 15, together with the corresponding knife supporting disk 3, passes from an active configuration (Figures 4, 6 and 8) for use, in which the knife supporting disk 3 is coplanar to the adjacent ones and rotates in phase without interfering with them, to a safety configuration (Figures 5, 7 and 9) in which said disk, rendered free by the shearing of the pivot 9, as a consequence of the axial displacement of the second portion 15, arranges itself so that it is axially spaced from the adjacent ones so as to not collide with them.

Furthermore, for each pivot 9 there are potential energy release means 17, which are adapted to be activated as a consequence of the shearing of said pivot in order to move away the second portion 15 and keep it in the safety configuration.

In this manner, the combined action of the retention means 16 and of the release means 17 allows to achieve the axial displacement of the knife supporting disk 3 affected by the overload and rendered free as a consequence of the shearing of the corresponding pivot 9 regardless of the direction of rotation of said pivot, thus allowing to provide a single technical solution of universal use.

Besides, as a consequence of the shearing of one of the pivots 9, the corresponding release means 17 act substantially instantaneously, minimizing the risk that collisions might occur between the knife supporting disk 3 rendered free and the adjacent ones, thus preserving the integrity and functionality of the cutter bar 1, without the need to stop its use promptly.

In a first embodiment and in a second embodiment (Figures 4-5, 6-7), for each pivot 9, the retention means 16 comprise a threaded element 18 which is inserted in an axial hole 19 formed along said pivot and the corresponding pinion 8, which is provided with a threaded stem 20 coupled to a female thread formed along the hole 19 proximate to the second end 12 of the pivot 9 and head 21 which is inserted so that it can slide in an axial direction along the hole itself at the first end 11 of the pivot 9. The retention means 16 further comprise stroke limiting means 22 which protrude inside the hole 19 in a position that is intermediate between the ends of the pivot 9 for the abutment of the head 21 in the safety configuration. The hole 19 is dead at the second end 12 of the pivot 9 and the locking element 39 is constituted by a nut which is coupled to the shank 23.

Said stroke limiting means 22 comprise a seat for the abutment of the head 21 in the safety configuration defined along the hole 19.

Furthermore, for each pivot 9, the release means 17 comprise at least one compressive elastic element which is accommodated along the hole 19 between the second end 12 of said pivot and a pusher ring 25 which is accommodated along said hole and is retained axially by an elastic ring 40 which is accommodated in a corresponding annular slot.

Preferably, the release means 17 comprise a helical compressive elastic spring 24, which is arranged externally to the stem 20 along the hole 19, between the pusher ring 25 and an abutment shoulder 26 which is formed along said hole.

It is not excluded, however, that the release means 17 might have a different structure and might provide a series of compressive elastic elements, i.e., a chamber for the compression of a fluid medium which acts on the pivot 9 in order to obtain the spacing of the second portion 15 as a consequence of the shearing of said pivot.

Furthermore, in order to ensure the correct arrangement of the knife supporting disk 3 in the transition from the active configuration to the safety configuration and during retention in the safety configuration and avoid the oscillation thereof, the so-called "hunting effect", means 28 for slidingly guiding in an axial direction the second portion 15 as a consequence of the shearing of the pivot 9 are provided.

In the first embodiment (Figures 4 and 5), for each pivot 9, said guiding means 28 provide a bushing 29 which is integral with the head 21 of the corresponding threaded element 18 which is associated in axial sliding along a corresponding seat 38 formed along the hole 19 by means of a cylindrical coupling 30 with two degrees of freedom (in rotation about the axis A in order to allow to screw/unscrew the threaded element 18 and in sliding along said axis). Appropriate machining tolerances in the execution of the cylindrical coupling 30 ensure that the correct arrangement of the knife supporting disk 3 is maintained in the transition from the active configuration to the safety configuration and during retention in the safety configuration.

In the second embodiment (Figures 6 and 7), the guiding means 28, in addition to what has been described above, provide for each knife supporting disk 3 a pair of tubular bodies which are mutually associated by means of a cylindrical coupling 37, of which one is a fixed body 35 associated with the flange 6 and one is a movable body 36 associated with the knife supporting disk 3, which are extended along the corresponding rotation axis A, are free to slide with respect to each other in an axial direction and can rotate about the rotation axis A. The radial play between the tubular bodies 35 and 36 is sized accurately in order to allow sliding and mutual rotation, maintaining in any case also the axial reference action for the knife supporting disk 3 rendered free.

One of the tubular bodies 35 or 36 is partially inserted in the other body 36 or 35 for an axial covering portion which is greater than the stroke of the knife supporting disk 3 between the active configuration and the safety configuration.

In the embodiment shown, it is the movable tubular body 36 that is partially inserted within the fixed body 35, but the opposite is not excluded.

In this manner, the tubular bodies 35 and 36 also perform a protective function, preventing any fibrous bodies from penetrating between the flange 6 and the knife supporting disk 3, reaching the bearing 10 and reducing its reliability.

It is not excluded that the guiding means 28 might provide the tubular bodies 35 and 36 with the corresponding cylindrical coupling 37 as a replacement of the cylindrical coupling 30 of the bushing 29 along the seat 38. In a third embodiment (Figures 8 and 9), for each pivot 9, the retention means 16 comprise a threaded element 41 which is inserted in an axial hole 42, which passes through said pivot and the corresponding pinion 8, which has a stem 43 which has at least one end portion 43a which is threaded and coupled in an internally threaded hole 39a formed in the locking element 39, which has the shape of an inverted cup. The end 43b of the stem 43 protrudes outside the locking element 39 and is coupled to a locking nut 44.

The stem 43 is therefore associated with the second end 12 of the pivot 9 by means of the locking element 39, which is coupled to both.

The threaded element 41 further has a head 45 which is accommodated along the hole 42 and is inserted so that it can slide along it. The head 45 is in an intermediate longitudinal position of the hole 42.

The retention means 16 further comprise a cylindrical bush 46, which is arranged along the hole 42 and has a first end 46a, which is externally contoured and threaded and is coupled internally to the hole 42 at the pinion 8, and a second end 46b which protrudes from the hole 42 and is inserted within the locking element 39 and is provided with a hole 46c which is crossed by the stem 43.

The stroke limiting means 22 are constituted by a shoulder 47 which is formed at the second end 46b of the bush 46 by the bottom wall that forms the hole 46c. Said shoulder 47 forms a seat for the abutment of the head 45 in the safety configuration.

Furthermore, for each pivot 9, the release means 17 comprise at least one compressive elastic element which is accommodated along the hole 42 inside the bush 46, between the first end 46a thereof and the head 45.

Preferably, the release means 17 comprise a helical compressive elastic spring 48, but alternative embodiments are not excluded.

Advantageously, there is a ring 49 which is threaded externally and coupled to the first end 46a of the bush 46, on which the spring 24 abuts and which allows to adjust the preloading of said spring.

Furthermore, it is noted that a cylindrical coupling 50 is formed between the head 42 of the threaded element 41 and the internal wall of the bush 46 and provides the guiding means 28 described above in order to maintain the correct arrangement of the knife supporting disk 3 in the transition from the active configuration to the safety configuration and during retention in the safety configuration.

Operation of the present invention is as follows.

During the normal operation of the cutter bar 1 , the knife supporting disks 3 rotate in phase about the respective axes A, actuated by the transmission assembly 4.

If an overload of torque occurs at one or more knife supporting disks 3, for example due to an impact with an accidental obstacle, the corresponding pivot 9 shears as described above and the disk itself moves into a safety configuration, allowing to continue the intervention in progress without compromising the operation of the cutter bar 1.

As a consequence of the shearing of one or more pivots 9, the replacement of a preassembled subassembly or kit constituted by the pinion 8 with the corresponding pivot 9, the retention means 16 and the release means 17, the locking element 39 and the flanged ring 31, is provided. In this manner the execution of maintenance interventions following damage caused by overloads of the transmission assembly 4 is rendered quick and easy.

In practice it has been found that the described invention achieves the proposed aim and objects and in particular the fact is stressed that the disk cutter bar according to the invention incorporates a safety system with limitation of the transmitted torque and axial displacement of the disk affected by the overload which is universal in use, regardless of the direction of rotation of the disk itself.

The cutter bar according to the invention further allows to achieve the axial displacement of the disk affected by the overload in rapid times, minimizing the risk that impacts might occur between adjacent disks.

Moreover, the cutter bar according to the invention allows to perform easily and rapidly maintenance interventions to restore the functionality of the knife supporting disk affected by the overload.

Not least, the guiding means incorporated in the invention allows to maintain a correct arrangement of the knife supporting disk affected by the overload following the shearing of the corresponding pivot for coupling to the pinion.

The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims.

All the details may further be replaced with other technically equivalent elements.

In practice, the materials used, as well as the contingent shapes and dimensions, may be any according to requirements and to the state of the art without thereby abandoning the protective scope of the appended claims.

The disclosures in Italian Patent Application no. 102017000063327, from which this application claims priority, are incorporated herein by reference.

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

1. A disk cutter bar (1), comprising

- a supporting frame (2),

- a plurality of knife supporting disks (3) which are associated with said frame (2) so that they can rotate about respective substantially parallel rotation axes (A),

- a gear transmission assembly (4) for the rotational actuation of said knife supporting disks (3), which comprises a series of idle gears (7) which move a plurality of pinions (8) for the rotational actuation each of a respective knife supporting disk (3),

- a pivot (9) for coupling to the corresponding knife supporting disk (3) that is associated with each one of said pinions (8), which is associated with said frame (2) by means of the interposition of rotational support means (10), has a first end (11) which is associated integrally with the corresponding pinion (8) and a second end (12) which is associated integrally with said disk and is provided with at least one shearing region

(13) in an intermediate position between said ends, the pivot (9) being adapted to shear at the shearing region (13) following an overload of torque which acts thereon, forming a first portion (14) which comprises the first end (11) and a second portion (15) which comprises the second end (12), and

- retention means (16) associated with each one of said pivots (9) for the retention of the second portion (15) following the shearing of said pivot, characterized in that said retention means (16) are associated with each one of said pivots (9) with axial play so as to allow the spacing in an axial direction of the second portion (15) with respect to the first portion

(14) as a consequence of the shearing of said pivot, passing from an active configuration to a safety configuration of the corresponding knife supporting disk (3), and in that it comprises means (17) for the release of potential energy which are associated with each one of said pivots (9) and are adapted to activate as a consequence of the shearing of said pivot to space the second portion (15) from the first portion (14) and to keep said second portion in the safety configuration.

2. The cutter bar (1) according to claim 1, characterized in that said retention means (16) comprise a threaded element (18; 41) which is inserted in an axial hole (19; 42) that is formed along said pivot (9), which comprises an at least partially threaded stem (20; 43) associated with said pivot proximate to said second end (12) and a head (21 ; 45) which is inserted so that it can slide in an axial direction along said hole (19; 42), stroke limiting means (22) being provided for the abutment of said head (21 ; 45) in the safety configuration.

3. The cutter bar (1) according to claims 1 and 2, characterized in that said means (17) for the release of potential energy comprise at least one compressive elastic element which is accommodated within said hole (19), between said stroke limiting means (22) and said second end (12).

4. The cutter bar (1) according to claim 3, characterized in that said elastic element comprises a helical compressive elastic spring (24) which is arranged outside said stem (20) along said hole (19).

5. The cutter bar (1) according to claims 1 and 2, characterized in that said retention means (16) comprise a bush (46) which is associated internally with said hole (42) and protrudes from the second end (12) of said pivot (9), inside which said head (45) is accommodated so that it can slide axially, the stem (43) protruding outside the bush (46) and being associated with the second end (12) of the pivot (9) by interposition of a locking element (39).

6. The cutter bar (1) according to claim 5, characterized in that said potential energy release means (17) comprise at least one compressive elastic element (48) which is accommodated inside said bush (46), between said head (45) and one end (46a) of said bush proximate to said pinion (8).

7. The cutter bar (1) according to claim 6, characterized in that said release means (17) comprise a ring (49) which is associated with said end (46a) of the bush (46) for the adjustment of the preloading of said elastic element (48).

8. The cutter bar (1) according to claim 1, characterized in that said shearing region (13) comprises at least one annular groove (27) that is cut externally into said pivot.

9. The cutter bar (1) according to claim 1 or 8, characterized in that said shearing region (13) is arranged at said rotational support means (10).

10. The cutter bar (1) according to claim 1, characterized in that it comprises guiding means (28) associated with each one of said pivots (9) for the sliding in an axial direction of the corresponding second portion (15) following the shearing of said pivot.

11. The cutter bar (1) according to claim 10, characterized in that said guiding means (28) comprise a bushing (29) which is associated with the head (21) of said threaded element (18) and is associated so as to slide axially by means of a cylindrical coupling (30) along a corresponding seat (38) that is formed along said hole (19).

12. The cutter bar (1) according to claim 10 or 11, characterized in that said guiding means (28) comprise a pair of tubular bodies (35, 36) which are mutually associated by means of a cylindrical coupling (37), of which one is a fixed body (35) associated with said frame (2) and one is a movable body (36) associated with the corresponding knife supporting disk (3), said bodies being extended along the corresponding rotation axis (A) and being able to slide freely with respect to each other in an axial direction and to rotate about the rotation axis (A).

13. The cutter bar (1) according to claims 5 and 10, characterized in that said guiding means (28) comprise a cylindrical coupling (50) which is formed between said head (45) and the internal wall of said bush (46).