Disengageable transmission device and agricultural machine comprising such a device

Abstract

Disengageable transmission device and agricultural machine comprising such a device The present invention relates to a device (1) for transmitting rotational movement with primary (2) and secondary (3) shafts, a first transmission element (4) mounted on the first shaft (2), a second transmission element (5) mounted on the second shaft (3) and kinematically connected to the first transmission element (4), and a coupling part (6) which makes it possible to kinematically connect the first transmission element (4) to the first shaft (2), as well as a sliding gear (7) mounted axially movable on the first shaft (2) so as to be able to occupy two positions in which the first shaft (2) transmits or does not transmit its rotational movement to the first transmission element (4), by means of the part (6).Transmission device (1) characterized in that, in the first position of the sliding gear (7), the or each coupling part (6) is subjected to a force directed substantially towards the axis (2') of the first shaft (2) so that the or each coupling part (6) cannot transmit rotational movement between the first shaft (2) and the first transmission element (4). Figure to be published with the abstract: Fig. 1.

Description

Title of the invention: Disengageable transmission device and agricultural machine comprising such a device

[0001] The present invention relates to the field of equipment for transmitting rotary movement or torque between an input and one or more outputs, in particular in relation to applications in agricultural machinery, and has as its objects a disengageable transmission device, advantageously with at least two speeds, and an agricultural machine comprising such a device.

[0002] Many constructions of devices for transmitting rotational movement or torque are already known.

[0003] In particular, a device for transmitting rotational movement is known, which comprises a first shaft capable of being driven in rotation about a first axis and a second shaft, a first wheel mounted on the first shaft, a second wheel integral in rotation with the second shaft at least in one direction of rotation and kinematically linked with the first wheel, and at least one primary coupling part mounted in a primary housing of the first shaft so as to be able to transmit rotation between the first shaft and the first wheel about the first axis at least in one direction of rotation.This device also comprises a sliding gear mounted axially movable on the first shaft so as to be able to occupy a first position in which the primary coupling part cannot transmit its rotation to the first wheel, and a second position in which the primary coupling part is engaged in an interior site of the first wheel so that the primary coupling part can transmit the rotation between the first shaft and the first wheel at least in one direction of rotation.

[0004] However, a first type of known devices of this kind has the disadvantage of requiring alignment of the primary coupling part with the internal site of the first wheel in order to be able to change the position of the sliding gear. In addition, it is risky to change the position of the sliding gear when the first shaft is rotated.

[0005] In a second type of known devices of this kind, the transmission of the rotational movement between the first shaft and the first wheel is carried out by means of friction discs, the production of which is expensive and complex and which has the additional disadvantage of being subject to slipping or skating, which leads to a limitation of the maximum transmissible torque, regular maintenance, significant wear and / or a limited service life.

[0006] The main aim of the present invention is to overcome the drawbacks of the aforementioned existing solutions.

[0007] To this end, the invention relates to a device for transmitting rotational movement of the type mentioned above and which is characterized in that, in its first position, the sliding gear induces a force on the primary coupling part directed substantially towards the first axis so that the primary coupling part cannot be engaged in a primary internal site nor transmit rotation between the first shaft and the first wheel.

[0008] The invention will be better understood from the following description, which relates to preferred embodiments, given as non-limiting examples, and explained with reference to the appended schematic drawings, in which:

[0009] [Fig.l] schematically represents a transmission device according to a first embodiment of the invention, in section along a plane passing through the first and second axes, with first and second shafts parallel to each other and a single possible path of transmission of movement, the device being illustrated in the second position of the sliding gear (coupling of the first shaft with the first wheel);

[0010] [Fig.2] schematically represents a transmission device according to a second preferred embodiment of the invention, in section along a plane passing through the first and second axes, with first and second shafts parallel to each other and two possible movement transmission paths, illustrated in the first position of the sliding gear (absence of coupling between first shaft and first wheel and coupling between first shaft and third wheel);

[0011] [Fig.3] schematically represents a transmission device according to a third embodiment of the invention, with first and second shafts perpendicular to each other and two possible movement transmission paths, illustrated in the second position of the sliding gear (absence of coupling between first shaft and third wheel and coupling between first shaft and first wheel);

[0012] [Fig.4] is a perspective view of a possible practical embodiment of the device of [Fig.2];

[0013] [Fig.5] is a sectional view, along a plane containing the first axis, of a part of the device of [Fig.4] comprising the first shaft and the elements mounted on the latter;

[0014] [Fig.ôA] and [Fig.ôB] are sectional views respectively along XX and along YY of the part of the device illustrated in [Fig.5].

[0015] The attached figures illustrate different embodiments of a device (1) for transmitting rotational movement. This device (1) comprises a first shaft (2) which can be driven in rotation about a first axis (2') and a second shaft (3). The device (1) also comprises a first wheel (4) mounted on the first shaft (2) and a second wheel (5) integral in rotation with the second shaft (3) at least in one direction of rotation and kinematically linked with the first wheel (4). The device (1) also comprises at least one primary coupling part (6) mounted in a primary housing (8) of the first shaft (2) so as to be able to transmit rotation between the first shaft (2) and the first wheel (4) around the first axis (2') at least in one direction of rotation. This device (1) further comprises a sliding gear (7) mounted axially movable on the first shaft (2) so as to be able to occupy a first position in which the primary coupling part (6) cannot transmit its rotation to the first wheel (4). Said sliding gear (7) can occupy a second position in which the primary coupling part (6) is engaged in a primary internal site (10) of the first wheel (4) so that the primary coupling part (6) can transmit rotation between the first shaft (2) and the first wheel (4) at least in one direction of rotation.

[0016] According to the invention, in its first position, the sliding gear (7) induces a force on the primary coupling part (6) directed substantially towards the first axis (2') so that the primary coupling part (6) cannot be engaged in a primary internal site (10), nor transmit rotation between the first shaft (2) and the first wheel (4). Thus, it can be indicated that the first shaft (2) and the first wheel (4) are rotationally uncoupled or free in this first position of the sliding gear (7).

[0017] Thanks to the provisions of the invention above, it is possible to axially move the sliding gear (7) even if the primary coupling part (6) is not aligned with a primary internal site (10). Indeed, after the movement of the sliding gear (7) from its first position to its second position, the (substantially radial) movement of the primary coupling part (6) is only possible at the moment when its radial position corresponds to the radial placement of a primary internal site (10), that is to say only when said part and said site are radially aligned, as illustrated for example in [Fig.6A]. Furthermore, whatever the radial or angular location of the primary coupling part (6) relative to that of the or each primary internal site (10), the movement of the sliding gear (7) between its second position and its first position is achievable.It is thus possible to move the sliding gear (7) axially when the primary (2) and secondary (3) shafts are stationary, regardless of their position.

[0018] The first axis (2') is the axis of rotation of the first shaft (2). In other words, the first axis (2') is the axis around which the first shaft (2) is guided in rotation. As illustrated for example in [Fig.5], the first shaft (2) is guided in rotation around the first axis (2') by roller bearings. It could, however, alternatively, be guided in rotation by plain bearings and / or ball bearings. The second axis (3') is the axis of rotation of the second shaft (3). The second axis (3') is the axis around which the second shaft (3) can be rotated.

[0019] In a simple and economical manner, the second wheel (5) is fixed relative to the second shaft (3). The second wheel (5) can for example be fixed to the second shaft (3) by a radial through pin. Alternatively, at least one additional coupling part makes it possible to kinematically connect the second wheel (5) with the second shaft (3) in a single direction of rotation.

[0020] As is apparent from [Fig. 2] in particular, in the first position of the sliding gear (7), the primary coupling part (6) is located at least partially between the first shaft (2) and the sliding gear (7). In the embodiments of the figures, when the primary coupling part (6) is located, even partially, between the first shaft (2) and the sliding gear (7), the force applied to the primary coupling part (6) directed substantially towards the first axis (2') is directly applied by the sliding gear (7). This force applied by the sliding gear (7) to the primary coupling part (6) maintains the primary coupling part (6) in a retracted or retracted position in the primary shaft (2). In this retracted position, the primary coupling part (6) is entirely located in the primary housing (8).In its retracted position, the primary coupling part (6) is included in a circle of diameter smaller than the inner diameter of the first wheel (4), so that the primary coupling part (6) cannot be engaged in a primary inner site (10). The inner diameter of the first wheel (4) is its minimum diameter.

[0021] As can be seen from Figures 1, 3, 5 and 6A, when the sliding gear (7) is in its second position, the primary coupling part (6) is in the extended or projecting position relative to the primary shaft (2). In this extended position, the primary coupling part (6) is engaged in a primary internal site (10) of the first wheel (4) and also partially in the respective primary housing (8), as shown in the aforementioned figures. In its extended position, the primary coupling part (6) bears on a surface of the first wheel (4), namely a wall of the site (10) receiving it, allowing rotation to be transmitted between the primary shaft (2) and the first wheel (4). In its extended position, the primary coupling part (6) can therefore transmit rotation between the first shaft (2) and the first wheel (4) in a single direction of rotation ([Fig. ôA]) or possibly in both (figures 1 to 3 depending on the case).In the second position of the sliding gear (7), the primary coupling part (6) is not located between the sliding gear (7) and the primary shaft (2), the sliding gear (7) being axially offset relative to the primary coupling part (6) and not inducing any force on the latter.

[0022] In accordance with a second and a third embodiment (illustrated in Figures 2 to 6), the device (1) also comprises a third wheel (4') mounted on the first shaft (2). In accordance with the second preferred embodiment in the [Fig.2], the device (1) further comprises a fourth wheel (5') integral in rotation with the second shaft (3) at least in one direction of rotation and kinematically connected to the third wheel (4'). In a simple and economical manner, the fourth wheel (5') is fixed relative to the second shaft (3), for example by means of a half-moon key. Alternatively, at least one additional coupling part makes it possible to kinematically connect the fourth wheel (5') with the second shaft (3) in a single direction of rotation.

[0023] In the second and third embodiments, the device (1) also comprises at least one secondary coupling part (6') mounted in a secondary housing (8') of the first shaft (2). In the first position of the sliding gear (7), the secondary coupling part (6') is engaged in a secondary interior location (10') of the third wheel (4') so that the secondary coupling part (6') can transmit rotation between the first shaft (2) and the third wheel (4') at least in one direction of rotation. In the second position of the sliding gear (7), the sliding gear (7) induces a force on the secondary coupling part (6') so that the secondary coupling part (6') cannot be engaged in a secondary interior location (10') of the third wheel (4'), nor transmit rotation between the first shaft (2) and the third wheel (4').Thanks to these arrangements, it is possible to axially move the sliding gear (7) into its first and second positions at any time, that is to say whatever the position of each coupling part (6, 6') relative to the internal sites (10, 10'), and whether the shafts (2, 3) are rotating or stationary.

[0024] Thus, this device (1) of simple construction and easy to control makes it possible to kinematically connect two shafts (2 and 3) together by at least two movement transmission paths. In the preferred embodiment, the transmission ratio between the first wheel (4) and the second wheel (5) is different from the transmission ratio between the third wheel (4') and the fourth wheel (5'), the device (1) thus making it possible to adapt the transmission according to the situation and / or the need. In the preferred embodiment, the device (1) is thus a two-speed transmission box. The speed change is controlled at the first shaft (2) by simple axial movement of the sliding gear (7).

[0025] As is apparent from [Fig. 5] in particular, in the preferred embodiment and in the second position of the sliding gear (7), the secondary coupling part (6') is located at least partially between the first shaft (2) and the sliding gear (7). In this embodiment, when the secondary coupling part (6') is located, even partially, between the first shaft (2) and the sliding gear (7), the force applied to the secondary coupling part (6') directed substantially towards the first axis (2') is directly applied by the sliding gear (7). This force applied by the sliding gear (7) to the secondary coupling part (6') holds the secondary coupling part (6') in a retracted or retracted position in the primary shaft (2) ([Fig.6B]). In the retracted position, the secondary coupling part (6') is entirely in the secondary housing (8'). In its retracted position, the secondary coupling part (6') is included in a circle of diameter smaller than the internal diameter of the third wheel (4'), so that the secondary coupling part (6') is not engaged in a secondary internal site (10'). The internal diameter of the third wheel (4') is its minimum diameter.

[0026] As can be seen from [Fig. 2], in the preferred embodiment, when the sliding gear (7) is in its first position, the secondary coupling part (6') is in the extended or projecting position relative to the primary shaft (2). In this extended position, the secondary coupling part (6') is engaged in a secondary internal site (10') of the third wheel (4') and partially in the respective secondary housing (8'). In its extended position, the secondary coupling part (6') bears on a surface of the third wheel (4'), allowing rotation to be transmitted between the primary shaft (2) and the third wheel (4'). In its first position, the secondary coupling part (6') is not located between the sliding gear (7) and the primary shaft (2), the sliding gear (7) being axially offset relative to the secondary coupling part (6') and not inducing any force on the latter.

[0027] In an embodiment not shown, the primary coupling part (6) may differ from the secondary coupling part (6'). In the same way, the primary (8) and secondary (8') housing(s) and / or the primary (10) and secondary (10') interior sites could be different. In order to harmonize the parts of the device (1) and / or their manufacture, reducing the production and maintenance costs, and simplifying the device (1), the primary (6) and secondary (6') coupling parts are preferably identical. Preferably, the primary (8) and secondary (8') housing(s) are also identical. And likewise, the primary (10) and secondary (10') interior site(s) are ideally identical. Furthermore, all of the provisions and characteristics relating to the first and second wheels (4, 5) apply preferentially, by transposition, respectively to the third and fourth wheels (4', 5').The same applies to the coupling parts (6, 6'), the housings (8, 8') and the internal sites (10, 10') which are respectively associated with them. It will be noted, however, that the first and second positions of the sliding gear (7) are reversed for the first and third wheels (4, 4').

[0028] According to a characteristic of the invention, an elastic means (16) is associated with each coupling part (6, 6') and generates a force tending to move away from the first axis (2') at least a part of the coupling part (6, 6') in question. This elastic means (16) guarantees a permanent centrifugal stress on the part coupling part (6, 6') considered, ensuring that it engages in an internal site (10, 10') when the sliding gear (7) does not induce any force on the coupling part (6, 6') considered and that the latter is aligned with an internal site (10, 10'). Preferably, the or each elastic means (16) is produced by at least one compression spring mounted between the first shaft (2) and the first wheel (4) or between the first shaft (2) and the third wheel (4'). The or each elastic means (16) is advantageously mounted in a respective housing (8, 8') of the primary shaft (2), capable of also receiving a respective coupling part (6, 6').

[0029] Alternatively or even additionally, during rotation of the primary shaft (2), at least a part of each coupling part (6, 6') could be moved away from the first axis (2') by centrifugal and / or magnetic force when the sliding gear (7) does not induce any force on the coupling part (6, 6') in question and the latter is aligned with an internal site (10, 10').

[0030] The primary shaft (2) comprises at least one primary housing (8) in which the primary coupling part (6) is movably mounted. The primary shaft (2) also comprises at least one secondary housing (8') in which the secondary coupling part (6') is movably mounted. Each primary housing (8) is adapted to the shape of the respective coupling part (6, 6'). Preferably, all the housings (8, 8') are identical. Each housing (8, 8') is slightly larger than the corresponding coupling part (6, 6'), allowing the latter to move in the respective housing (8, 8'), preferably with guidance by the walls of the housing concerned and in accordance with the permitted movement. In a simple manner, the first shaft (2) comprises as many housings (8) as there are coupling parts (6, 6'), avoiding weakening the mechanical strength of the first shaft (2).Each coupling part (6, 6') is preferably a key, preferably a parallel key extending parallel to the first axis (2'). Each housing (8, 8') is thus a keyway formed in the primary shaft (2) and parallel to the first axis (2'). The primary coupling parts (6) and the secondary coupling parts (6') could have different shapes. For the sake of standardization, all the coupling parts (6, 6') are identical.

[0031] The first wheel (4) comprises at least one primary inner site (10). Similarly, the third wheel (4') comprises at least one secondary inner site (10'). Each inner site (10, 10') allows the transmission of movement between the coupling part (6, 6') and the wheel (4, 4') concerned, respectively between the first shaft (2) and the wheel (4, 4') concerned. In a simple manner, to allow a transmission of movement in both directions of rotation of the first shaft (2), each coupling part (6, 6') could be slidably mounted in a direction substantially perpendicular to the first axis (2') in the housing (8, 8') respective. In this case, each internal site (10, 10') may be a straight internal groove.

[0032] In order to allow each coupling part (6, 6') to transmit rotation between the first shaft (2) and the respective wheel (4, 5) in a single direction of rotation, each coupling part (6, 6') is preferably pivotally mounted in a respective housing (8, 8') of the first shaft (2) around a respective offset axis (11) substantially parallel to the first axis (2'). Each offset axis (11) is located, seen along a section perpendicular to the first axis (2'), close to a lateral end of the respective housing (8, 8') and preferably to the bottom of said housing (8, 8').In order to reduce the force required to pivot each coupling part (6, 6'), the or each compression spring of the elastic means (16) is located, seen along a section perpendicular to the first axis (2'), at the lateral end of the housing (8, 8') opposite that of the respective offset axis (11).

[0033] As shown in [Fig.6A], in order to maintain each coupling part (6, 6'), in its extended position, partially in the respective housing (8, 8'), each internal site (10, 10') is preferably a rounded internal groove, seen along the first axis (2'). Preferably, the bottom of each internal site (10, 10'), seen along the first axis (2'), located, when aligned with a housing (8, 8') (see [Fig.6A]), on the side of an offset axis (11) is closer to the first axis (2') than the bottom of the groove at the other end of the internal site (10, 10') considered.

[0034] More specifically, each inner site (10, 10') may have, seen along the first axis (2'), the shape of a tooth of a ratchet wheel. Thus, when the first shaft (2) rotates in one direction of rotation (clockwise in [Fig.6A]), the coupling parts (6, 6') may engage with the inner sites (10, 10'), thereby transmitting the rotational drive between the first shaft (2) and the wheel (4, 4') concerned. When the first shaft (2) rotates in the other direction of rotation (counterclockwise in [Fig.6A]), the wheel (4, 4') concerned is freewheeling relative to the first shaft (2), involving no transmission of rotation between the first shaft (2) and the wheel (4, 4') concerned (in this other direction of rotation). Alternatively, each coupling part (6, 6') could be slidably and pivotably mounted in the respective housing (8, 8').

[0035] In order to increase the maximum torque transmissible by the device (1) between the first shaft (2) and the first and third wheels (4, 4'), the first wheel (4) and the third wheel (4') each have several internal sites (10, 10'). In addition, several coupling parts (6, 6') are also associated with each of the first and third wheels (4, 4'). As can be seen from Figures 6, the first wheel (4) and the third wheel (4') each have preferably more internal sites (10, 10') than coupling parts (6, 6') are associated with it, making it possible to reduce the angle of rotation of the first shaft (2) around its first axis (2') before that the or each coupling part (6, 6') engages in an internal site (10, 10') and transmits the rotational movement between the first shaft (2) and the first and third wheels (4, 4').

[0036] Preferably, each coupling part (6, 6') is pivotally mounted relative to the first shaft (2) around the respective offset axis (11) in the same direction of rotation. More precisely, the or each primary coupling part (6) and the or each secondary coupling part (6') are pivotally mounted relative to the first shaft (2) around the respective offset axis (11) in the same direction of rotation. Also, the freewheel operation of the first wheel (4) and third wheel (4') allows the second shaft (3) to be driven by the first shaft (2) in a single direction of rotation, and the free rotation of the second shaft (3) relative to the first shaft (2) in the other direction of rotation. Thus, the rotational inertia of the second shaft (3) does not influence the rotational speed of the first shaft (2), thus constituting a safety means capable of preventing damage to the device (1).

[0037] Preferably, the sliding gear (7) has a ring shape encircling the first shaft (2), making it possible to simply guide its axial movement along the first axis (2'). The sliding gear (7) is mounted between the first wheel (4) and the third wheel (4'). As is apparent from the above, an overlap, even partial, of the sliding gear (7) and a coupling part (6, 6') makes it possible to release this coupling part (6, 6') from the internal site (10, 10') concerned. In the preferred embodiment, in the first position of the slider (7), the primary coupling part (6) is located partially between the first shaft (2) and the slider (7), and, in the second position of the slider (7), the secondary coupling part (6') is located partially between the first shaft (2) and the slider (7), making it possible to limit or reduce the amplitude of axial movement of the slider (7) between its first and second positions.Therefore, the dimension of the device (1) along the direction of the first axis (2') can be reduced.

[0038] In order to reduce the size of the device (1) in the direction of the first axis (2'), the axial displacement of the sliding gear (7) between its first and second position is less than the axial dimension of the first wheel (4) at its inner diameter. Even more preferably, the axial displacement of the sliding gear (7) between its first and second position is less than the axial dimension of each of the first wheel (4) and third wheel (4') at their inner diameter. It is noted that the greater the axial dimension of a wheel (4, 4') at its inner diameter, the greater the maximum transmissible torque, the device (1) thus making it possible to transmit a significant torque with reduced dimensions.

[0039] The device may comprise at least one axial stop making it possible to stop the axial movement of the slider (7) in one direction. In order to limit the number of components of the device (1), an axial stop is provided by the first wheel (4). For the same reason, another axial stop is provided by the third wheel (4').

[0040] In order to increase the respective maximum transmissible torque with the first shaft (2), at least two coupling parts (6, 6') are associated with each of the first and third wheels (4, 4'). As shown in Figures 6, in the preferred embodiment, each of the first and third wheels (4, 4') is associated with three respective coupling parts (6, 6'). Preferably, the primary coupling parts (6) are distributed regularly around the first axis (2'). Similarly, the secondary coupling parts (6') are distributed regularly around the first axis (2').In order to allow correspondence with coupling parts (6, 6') equally distributed around the first axis (2'), the interior sites (10, 10') are also regularly distributed around the first axis (2'), as shown in [Fig. 6A].

[0041] Obviously, in its first position, the sliding gear (7) induces a force on each primary coupling part (6) directed substantially towards the first axis (2') so that each primary coupling part (6) cannot be engaged in a primary internal site (10), nor transmit rotation between the first shaft (2) and the first wheel (4). In the preferred embodiment, in its second position, the sliding gear (7) induces a force on each secondary coupling part (6') so that each secondary coupling part (6') cannot be engaged in a secondary internal site (10') of the third wheel (4'), nor transmit rotation between the first shaft (2) and the third wheel (4').

[0042] As is apparent from [Fig. 2] in particular, the device comprises a casing (17). The casing (17) can contain the wheels (4, 4', 5, 5'). It also contains the coupling parts (6, 6') and the sliding gear (7). Finally, the casing (17) at least partially contains the primary (2) and secondary (3) shafts. Preferably, the primary (2) and secondary (3) shafts are guided in rotation with the casing (17).

[0043] It can be noted that the kinematic connection between the first wheel (4) and the second wheel (5) is not affected or dependent on the position of the sliding gear (7). This kinematic connection can be for example a toothed gear (as shown in the figures), a belt, a toothed belt, a chain or a similar means of transmitting movement between two shafts. Similarly, the kinematic connection between the third wheel (4') and the fourth wheel (5') is not affected or dependent on the position of the sliding gear (7).

[0044] It is clear from the above that the coupling parts (6, 6') are integral in rotation with the first shaft (2). In order to avoid a large friction surface, the sliding gear (7) is also integral in rotation with the first shaft (2). Preferably, a radial pin (13) makes it possible to transmit the rotational movement between the first shaft (2) and the sliding gear (7). In order to allow the axial movement of the sliding gear (7), the latter may have at least one groove (14) oriented parallel to the first axis (2') and in which the radial pin (13) is slidably mounted.

[0045] When a coupling part (6, 6') is located, even partially, between the sliding gear (7) and the first shaft (2), the coupling part (6, 6') concerned is in contact with the sliding gear (7) at a bearing surface (9). The bearing surface (9) could be the cylindrical inner surface of the sliding gear (7). In order to reduce friction during axial movement of the sliding gear (7), in the preferred embodiment, the sliding gear (7) has a respective bearing surface (9) for each coupling part (6, 6'). As can be seen from [Fig.6B], each bearing surface (9) of the sliding gear (7) is slightly protruding inwards or towards the first axis (2'). Thus, each coupling part (6, 6') can enter entirely into the respective primary housing (8) and be completely released from the internal site (10) concerned while avoiding friction during the axial movement of the sliding gear (7).This excess thickness of each bearing surface (9) is internal and extends in the direction of the first axis (2'). Each excess thickness makes it possible to exert on each coupling part (6, 6') a force directed substantially towards the first axis (2').

[0046] In order to facilitate the axial movement of the slider (7), the or each inner end edge of the slider (7) and / or the outer end edge of the or each coupling part (6, 6') may have a bevel. Indeed, these edges constitute the areas coming into contact first when the slider (7) moves between its second position and its first position.

[0047] Alternatively, another (second) slider could allow the or each secondary coupling part (6') to be released from the secondary internal site (10') concerned. In order to reduce the number of components of the device (1) and to simplify the change of transmission path, the same slider (7) allows the or each primary coupling part (6) and the or each secondary coupling part (6') to be released from the internal site (10, 10') concerned.

[0048] According to the first and second embodiments, the first wheel (4) and the second wheel (5) are meshing pinions, preferably straight. In these embodiments, the third wheel (4') and the fourth wheel (5') are also meshing pinions, and preferably straight. Furthermore, the sliding gear (7) is arranged on the first shaft (2) between the first wheel (4) and the third wheel (4'). Thus, the device (1) forms a two-speed transmission box. Advantageously, the primary (2) and secondary (3) shafts are parallel to each other.

[0049] According to a third embodiment illustrated in [Fig. 3], the first axis (2') intersects with a second axis (3') around which the second shaft (3) can be rotated. In this third embodiment, the first, second and third wheels (4, 5, 4') are bevel gears. In addition, in this third mode, the second wheel (5) meshes with the first wheel (4) and with the third wheel (4'). The device (1) thus forms an inverter. On this inverter, the direction of rotation of the second shaft (3) depends on the position of the sliding gear (7).

[0050] When the first axis (2') is perpendicular to the second axis (3') (in addition to being intersecting), the first wheel (4) and the third wheel (4') have identical pitch diameters. However, in order to provide different transmission ratios depending on the position of the sliding gear (7), the first and third wheels (4, 4') may have different pitch diameters. In this case, the first axis (2') is not perpendicular to the second axis (3').

[0051] The dimension of the sliding gear (7) along the first axis (2'), on the one hand, and the distance along the first axis (2') between the or each primary coupling part (6) and the or each secondary coupling part (6'), on the other hand, are such that a third position of the sliding gear (7) is possible. The third position of the sliding gear (7) is intermediate between its first position and its second position. In this third position of the sliding gear (7), the coupling parts (6, 6') are all disengaged from the respective inner sites (10, 10'), so that the first wheel (4) and the third wheel (4') are both uncoupled from the first shaft (2). In the preferred embodiment, thanks to this third position of the slider (7), it is impossible for the first wheel (4) and the second wheel (5) to mesh at the same time as the third wheel (4') and the fourth wheel (5') mesh, avoiding damage to the device (1).

[0052] Even without the third position of the sliding gear (7) mentioned above, these two freewheel drive systems make it possible to avoid damage to the device (1) in the case where the position of the sliding gear would involve the engagement of all the coupling parts (6, 6') with the first and second transmission elements (4, 4').

[0053] It may also be noted that the axial displacement of the sliding gear (7) along the first axis (2') does not imply axial displacement (along the first axis (2')) of the coupling parts (6, 6'), thus advantageously making it possible to reduce the size of the device (1) along the first axis (2').

[0054] The invention also relates to an agricultural machine, in particular a disc mower, characterized in that it comprises a device (1) as described above, the sliding gear (7) being integral in translation, along the first axis (2'), with an operating member (12) or subjected to the action of an electric, hydraulic or pneumatic actuator, which determines the axial position of the sliding gear (7) on the first shaft (2). As shown in [Fig.4], the operating member (12) is actuated manually. Preferably, the first shaft (2) is the input shaft, connected to a motor element, and the second shaft (3) is the output shaft, connected to the mowing discs.

[0055] Of course, the invention is not limited to the embodiments described and shown in the attached drawings. Modifications remain possible, in particular from the point of view of the constitution of the various elements or by substitution of technical equivalents, without departing from the scope of protection of the invention.

Claims

Claims

1. Device (1) for transmitting rotational movement, which comprises a first shaft (2) rotatable about a first axis (2') and a second shaft (3), a first wheel (4) mounted on the first shaft (2), a second wheel (5) integral in rotation with the second shaft (3) at least in one direction of rotation and kinematically linked to the first wheel (4), and at least one primary coupling part (6) mounted in a primary housing (8) of the first shaft (2) so as to be able to transmit rotation between the first shaft (2) and the first wheel (4) about the first axis (2') at least in one direction of rotation, the device (1) also comprising a sliding gear (7) mounted axially movable on the first shaft (2) so as to be able to occupy a first position in which the primary coupling part (6) cannot transmit its rotation to the first wheel (4),and a second position in which the primary coupling part (6) is engaged in an internal site (10) of the first wheel (4) so that the primary coupling part (6) can transmit rotation between the first shaft (2) and the first wheel (4) at least in one direction of rotation, device (1) characterized in that, in its first position, the sliding gear (7) induces a force on the primary coupling part (6) directed substantially towards the first axis (2') so that the primary coupling part (6) cannot be engaged in a primary internal site (10), nor transmit rotation between the first shaft (2) and the first wheel (4).,

2. Device (1) according to claim 1, characterized in that it also comprises a third wheel (4') mounted on the first shaft (2), a fourth wheel (5') integral in rotation with the second shaft (3) at least in one direction of rotation and kinematically linked to the third wheel (4') and at least one secondary coupling part (6') mounted in a secondary housing (8') of the first shaft (2), and in that, in the first position of the sliding gear (7), the secondary coupling part (6') is engaged in a secondary interior site (10') of the third wheel (4') so that the secondary coupling part (6') can transmit rotation between the first shaft (2) and the third wheel (4') at least in one direction of rotation, and in that, in its second position, the sliding gear (7) induces a force on the secondary coupling part- secondary (6') such that the secondary coupling part (6') cannot be engaged in a secondary inner site (10') of the third wheel (4') nor transmit rotation between the first shaft (2) and the third wheel (4').

3. Device (1) according to any one of claims 1 or 2, characterized in that an elastic means (16) is associated with each coupling part (6, 6') and generates a force tending to move away from the first axis (2') at least a part of the coupling part (6, 6') in question.

4. Device (1) according to any one of claims 1 to 3, characterized in that each coupling part (6, 6') is pivotally mounted in a respective housing (8, 8') of the first shaft (2) around a respective offset axis (11) substantially parallel to the first axis (2').

5. Device (1) according to any one of claims 2 to 4, characterized in that each coupling part (6, 6') is pivotally mounted relative to the first shaft (2) around the respective offset axis (11) in the same direction of rotation.

6. Device (1) according to any one of claims 2 or 3 to 5, as long as they depend on claim 2, characterized in that, in the first position of the sliding gear (7), the primary coupling part (6) is located partially between the first shaft (2) and the sliding gear (7), and in that, in the second position of the sliding gear (7), the secondary coupling part (6') is located partially between the first shaft (2) and the sliding gear (7).

7. Device (1) according to any one of claims 2, 6 or 3 to 5, insofar as the latter depend on claim 2, characterized in that the sliding member (7) comprises, for each coupling part (6, 6'), a respective bearing surface (9) slightly protruding inwards or in the direction of the first axis (2').

8. Device (1) according to any one of claims 2, 6, 7 or 3 to 5, as far as they depend on claim 2, characterized in that the first axis (2') intersects with a second axis (3') around which the second shaft (3) can be rotated, in that the first, second and third wheels (4, 5, 4') are bevel gears, and in that the second wheel (5) meshes with the first wheel (4) and with the third wheel (4'), the device (1) forming an inverter.

9. Device (1) according to any one of claims 1 to 8, characterized in that the dimension of the sliding gear (7) along the first axis (2'), on the one hand, and the distance along the first axis (2') between the or each primary coupling part (6) and the or each secondary coupling part (6'), on the other hand, are such that a third position of the sliding gear (7) is possible, in which the coupling parts (6, 6') are all disengaged from the respective inner sites (10, 10'), so that the first wheel (4) and the third wheel (4') are both uncoupled from the first shaft (2).

10. Agricultural machine, in particular a disc mower, characterized in that it comprises a device (1) according to any one of claims 1 to 9, the sliding gear (7) being integral in translation, along the first axis (2'), with an operating member (12) or subjected to the action of an electric, hydraulic or pneumatic actuator, which determines its axial position on the first shaft (2).

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