Device for adjusting the extension of the seat cushion of a seat

Abstract

The invention relates to a device (1) for adjusting the extension of the seat cushion. The device includes a first plate (3), a second plate (5) slidably mounted to the first plate, and a locking arrangement (10) for selectively allowing or preventing sliding of the second plate relative to the first plate. The first plate includes a pair of longitudinal racks (7a, 7b) and the locking arrangement (10) is connected to the second plate and includes a driving element (17), a connecting element (19) and a pair of locking blocks (11a, 11b), provided with locking teeth for selectively engaging with / disengaging from the racks (7a, 7b); elastic means (15) urge the locking blocks away from each other, thus pushing the locking teeth of the locking blocks into the seats of the racks. Thanks to such construction of the locking arrangement, the device according to the invention is highly reliable.

Description

Device for adjusting the extension of the seat cushion of a seat

[0001] The present invention relates to a device for adjusting the extension of the seat cushion of a seat, namely by adjusting the longitudinal position of a front portion of the seat cushion.

[0002] More particularly, the present invention relates to a device that can be manually actuated for adjusting the extension of the seat cushion of a seat, namely by allowing the front portion of the seat cushion to be held in a plurality of different discrete longitudinal positions.

[0003] The invention can be preferably, yet not exclusively, applied to vehicle seats.

[0004] Vehicle seats provided with a seat cushion having an adjustable extension in the longitudinal direction (i.e. a direction parallel to the travelling direction of the vehicle) are known from the art.

[0005] More particularly, vehicle seats are known which include a seat cushion comprising a seat cushion body and a seat cushion front portion, the seat cushion body and the seat cushion front portion being separate components and the seat cushion front portion being movable in the longitudinal direction relative to the seat cushion body.

[0006] Thanks to this arrangement, the seat cushion front portion can be moved from a rearmost position, in which it abuts against the seat cushion body and the overall longitudinal extension of the seat cushion is at its minimum, to an advanced position, in which it has been moved away from the seat cushion body and the overall longitudinal extension of the seat cushion is correspondingly increased.

[0007] In some known arrangements, the seat cushion front portion can be continuously moved away from the seat cushion body.

[0008] Conversely, in some other known arrangements the seat cushion front portion can be locked relative to the seat cushion body in a plurality of different discrete positions arranged along the longitudinal direction, going from a rearmost position, in which the seat cushion front portion abuts against the seat cushion body, to a foremost position, in which the distance between the seat cushion front portion and the seat cushion body (and, consequently, the overall extension of the seat cushion in the longitudinal direction) is at its maximum.

[0009] In this latter kind of arrangements, a device for adjusting the longitudinal extension of the cushion of the vehicle seat is provided, which device comprises a first plate or base plate, intended to be fastened to a fixed structure of the vehicle seat, and a second plate or carrier plate, intended to be fastened to the movable front portion of the seat cushion.

[0010] The device further comprises a locking arrangement for selectively allowing the second plate to move relative to the first plate (more specifically, to slide in the longitudinal direction relative to the first plate) or preventing the second plate from moving relative to the first plate, thus blocking the second plate in a longitudinal position selected by the user relative to the first plate, and consequently blocking the seat cushion front portion in a longitudinal position selected by the user relative to the seat cushion body.

[0011] By way of example, the second plate may be provided with a longitudinal rack defining a plurality of seats arranged along the longitudinal direction and the locking arrangement may be mounted to the first plate and include a locking tooth and a driving mechanism for moving the locking tooth from a position in which it is retained in one of the seats of the rack of the second plate to a position in which it is disengaged from said rack, and vice versa. By inserting the locking tooth in a selected seat of the rack, a different position of the seat cushion front portion relative to the seat cushion body can be selected each time.

[0012] EP 3 254 890 discloses a device for adjusting the extension of the seat cushion of a vehicle seat which includes a first plate or base plate and a second plate or carrier plate, movable relative to the first plate. The base plate is provided with a pair of parallel racks arranged along the longitudinal direction. A locking arrangement is mounted to the carrier plate, which arrangement includes a driving handle pivotally connected to the carrier plate, a connecting rod and a pair of locking blocks, wherein each locking block is provided with a plurality of teeth suitable for engaging with the seats of a respective rack of the base plate. When the driving handle is at rest, the teeth of the locking blocks are engaged with the racks of the base plate, the carrier plate is locked relative to the base plate and the seat cushion front portion is consequently locked relative to the seat cushion body; when the user rotates the driving handle, the teeth of the locking blocks are disengaged from the racks of the base plate, the carrier plate is free to slide backwards / frontwards in the longitudinal direction relative to the base plate and the seat cushion front portion can be slid backwards / frontwards in the longitudinal direction relative to the seat cushion body; when the seat cushion front portion has been moved to the desired position relative to the seat cushion body, the user releases the driving handle and the teeth of the locking blocks are bought back to engagement with the racks of the base plate in anew, different position.

[0013] Further examples of devices for adjusting the longitudinal extension of the cushion of a vehicle seat of the kind above described can be found, for instance, in documents CN 111605446, CN 106864321, CN 108407687 and DE 102006018353.

[0014] These known devices, while allowing to manually adjust in an easy way the longitudinal extension of the seat cushion of a vehicle seat, are not free from drawbacks.

[0015] More particularly, the construction of these known devices is not suitable for preventing accidental switching of the locking arrangement to the unlocking configuration, in which the carrier plate is free to slide relative to the base plate.

[0016] As a consequence, accidental and undesired movements of the seat cushion front portion relative to the seat cushion body may occur.

[0017] Said accidental movements are annoying and they may also be dangerous in case the driver’s seat is concerned, as they represent a distraction for the driver while driving.

[0018] DE102015201232 discloses a device for adjusting the extension of a vehicle seat cushion comprising a locking arrangement, which locking arrangement comprises a pair of longitudinally arranged parallel racks, spaced from each other and facing each other, and a pair of locking blocks, arranged between said racks and provided with locking teeth facing a respective rack; the locking blocks are movable between a locking position, in which the locking teeth of each locking block are inserted and firmly retained in corresponding seats of the respective rack, and an unlocking position, in which they are closer to each other and the locking teeth of each locking block are disengaged from said seats of the respective rack.

[0019] The main object of the present invention is to overcome the limitations set forth above by providing a device for adjusting the extension of the cushion of a vehicle seat which is highly reliable in preventing accidental and undesired movements of the seat cushion front portion relative to the seat cushion body.

[0020] More in detail, the main object of the present invention is to overcome the limitations set forth above by providing a device for adjusting the extension of the cushion of a vehicle seat provided with a locking arrangement having a construction that reliably guarantees that accidental and undesired switching to an unlocking configuration is prevented.

[0021] This and other objects are achieved by the device as claimed in the appended claims.

[0022] The present invention relates to a device for adjusting the extension of the seat cushion of a seat, such as a vehicle seat, including a seat cushion body and a separate seat cushion front portion, which device includes a first plate or base plate, intended to be fastened to a fixed component of the vehicle seat, and a second plate or carrier plate, intended to be fastened to the seat cushion front portion.

[0023] The carrier plate is mounted to the base plate so as to be slidable in the longitudinal direction (i.e. a direction parallel to the traveling direction of the vehicle) and the device further includes a locking arrangement for selectively allowing or preventing sliding of the carrier plate relative to the base plate.

[0024] To this aim, the base plate includes a pair of longitudinally arranged parallel racks, correspondingly defining a pair of sets of longitudinally distributed seats, and the locking arrangement is connected to the carrier plate and includes a driving element, a connecting element and a pair of locking blocks, each locking block being provided with one or more locking teeth suitable for engaging the seats of a respective rack.

[0025] According to the invention, the racks of the base plate are spaced apart from each other and face each other, the locking blocks of the locking arrangement are received in the longitudinal gap between said racks, with the locking teeth of each locking block facing a respective rack, the locking blocks are constrained to the carrier plate in the longitudinal direction but they are movable relative to each other and to the carrier plate in a transverse direction (i.e. a direction lying in the same plane as the plane defined by the racks and perpendicular to the longitudinal direction), and elastic means are provided for urging the locking blocks away from each other in the transverse direction, thus pushing the locking teeth of the locking blocks into the seats of the racks of the base plate.

[0026] Thanks to such construction of the locking arrangement, the device according to the invention is highly reliable.

[0027] In detail, since the elastic means urge the locking blocks in the transverse direction, the locking teeth of the locking blocks are pushed against the bottom of the seats of the rack of the base plate, so that the engagement of the locking blocks with the racks is extremely firm and accidental disengagement of the locking blocks from the seats of the racks is effectively prevented.

[0028] The connecting element is made as a connecting rod that has a proximal end connected to the driving element and a distal end intended to cooperate with the locking blocks for moving said locking blocks from a locking position, in which the locking teeth are firmly engaged in the seats of the racks of the base plate, to an unlocking position, in which the locking teeth are disengaged from the seats of the racks of the base plate, and vice versa.

[0029] The distal end of the connecting rod is made as a fork-shaped element and the facing surfaces of the prongs of the fork are inclined. Correspondingly, each locking block is provided with a mating inclined surface co-operating with the inclined surface of the respective prong of the fork.

[0030] Thanks to the co-operation of the inclined surfaces of the prongs of the fork-shaped distal end of the connecting rod with the mating inclined surfaces of the locking blocks, a progressively increasing force is needed for moving the locking blocks closer to each other, thus causing the locking teeth of the locking blocks to disengage form the seats of the racks of the base plate.

[0031] According to a preferred embodiment of the invention, the driving element is made as a driving handle pivotally connected to the carrier plate.

[0032] When the driving handle is at rest, the distal end of the connecting rod does not exert any force on the locking blocks, which are reliably maintained in their locking position by the transverse elastic means.

[0033] When the user rotates the driving handle, the connecting rod moves backwards in the longitudinal direction, while the locking blocks are constrained to the carrier plate in the longitudinal direction; as a result, the inclined surfaces of the prongs of the fork-shaped distal end of the connecting rod slide along the mating inclined surfaces of the locking blocks, thus causing said locking blocks to move closer to each other; if a sufficient force is applied to the driving handle, the locking blocks are brought to the unlocking position and the carrier plate is free to slide relative to the base plate.

[0034] As long as the user applies said sufficient force to the driving handle, the carrier plate can slide relative to the base plate and, consequently, the position of the seat cushion front portion relative to the seat cushion body can be adjusted.

[0035] When the user releases the driving handle, the connecting rod moves forwards in the longitudinal direction; as a result, the distal end of the connecting rod does no longer apply a force onto the locking blocks, which are brought back to the locking position by the transverse elastic means, so that their locking teeth are pushed into the seats of the racks (in a new, different position along the longitudinal direction) and firmly retained therein.

[0036] According to a preferred embodiment of the invention, the device includes means for pushing the carrier plate forwards as soon as the locking blocks of the locking arrangement have been brought to the unlocking position.

[0037] According to a preferred embodiment of the invention, the device further comprises one or more free-play recovery elements arranged between the base plate and the carrier plate. Their role is to constantly apply horizontal and vertical forces that keep the carrier plate and base plate aligned to each other, while also avoiding collisions therebetween and noise.

[0038] Preferably, a plurality of free-play recovery elements is provided, and the free-play recovery elements are symmetrically arranged with respect to the longitudinal middle line and / or transverse middle line of the base plate and the carrier plate.

[0039] Further features and advantages of the present invention will become evident from the following detailed description of a preferred embodiment given by way of non-limiting example with reference to the annexed drawings, in which:Fig.1a

[0040] is a perspective view of a vehicle seat cushion including the device according to the invention, shown in a first configuration.Fig.1b

[0041] is a perspective view of the vehicle seat cushion of, shown in a second configuration.Fig.2

[0042] is an exploded view of the device according to the invention.Fig.3

[0043] is a perspective view of the locking arrangement of the device of.Fig.4

[0044] is a top perspective view of the device of, shown in a first configuration.Fig.5

[0045] is a bottom perspective view of the device of, shown in said first configuration.Fig.6

[0046] is a top perspective view of the device of, shown in a second configuration.Fig.7

[0047] is a bottom perspective view of the device of, shown in said second configuration.Fig.8

[0048] is a top perspective view of the device of, shown in a third configuration.

[0049] In the following detailed description of a preferred embodiment of the invention reference will be made to a vehicle seat.

[0050] However, this application is not to be understood as limiting the scope of application of the present invention, and the device according to the invention can also be applied to other kind of seats, whenever the possibility of adjusting the longitudinal extension of the seat cushion in desirable.

[0051] Figures 1a and 1b show a seat cushion 100 of a vehicle seat including the device according to the present invention.

[0052] The seat cushion 100 includes a seat cushion body 102 and a separate seat cushion front portion 104.

[0053] The seat cushion body 102 generally is fixed relative to the seat frame. The seat cushion front portion 104 is movable relative to the seat cushion body 102, and more specifically it can slide relative to the seat cushion body 102 in the longitudinal direction (i.e. a direction parallel to the traveling direction of the vehicle).

[0054] As a result, the seat cushion front portion 104 can be moved from a rearmost position (see), in which it abuts against the seat cushion body 102 and the overall longitudinal extension of the seat cushion is at its minimum, to an advanced position (see), in which it has been moved away from the seat cushion body 102 and the overall longitudinal extension of the seat cushion is correspondingly increased.

[0055] The device 1 for adjusting the extension of the seat cushion 100 according to the invention is shown in Figures 2.

[0056] The device 1 includes a first plate or base plate 3, intended to be fastened to a fixed component of the vehicle seat (such as the seat cushion body, the seat frame and the like), and a second plate or carrier plate 5, intended to be fastened to the seat cushion front portion.

[0057] The carrier plate 5 is mounted to the base plate 3 so as to be slidable in the longitudinal direction, so that sliding of the seat cushion front portion 104 relative to seat cushion body 102 can be correspondingly obtained.

[0058] The device 1 further includes a locking arrangement 10 (also shown in greater detail in) for selectively allowing or preventing sliding of the carrier plate 5 relative to the base plate 3.

[0059] The base plate 3 includes a pair of longitudinally arranged parallel racks 7a, 7b, spaced from each other and facing each other. Correspondingly, a set of longitudinally distributed seats 9a, 9b is defined in each rack 7a, 7b.

[0060] The locking arrangement 10 correspondingly comprises a pair of locking blocks 11a, 11b, arranged in the longitudinal gap defined between the racks 7a, 7b. Each locking block 11a, 11b is provided with locking teeth 13a, 13b facing a respective rack 7a, 7b.

[0061] The locking blocks 11a, 11b are constrained to the carrier plate 5 in the longitudinal direction by means of a pair of protruding transverse wall (non visible in the Figures), so that they move in the longitudinal direction together with the carrier plate 5.

[0062] On the other hand, the locking blocks 11a, 11b can move in a transverse direction (i.e. a direction lying in the plane defined by the racks 7a, 7b and perpendicular to the longitudinal direction), so that they can move between a locking position, in which they are far from each other and the locking teeth 13a,13b of each locking block are inserted and firmly retained in corresponding seats 9a, 9b of the respective rack 7a, 7b, and an unlocking position, in which they are moved closer to each other until the locking teeth 13a,13b of each locking block are disengaged from the seats 9a, 9b of the respective rack 7a, 7b.

[0063] Since the locking blocks are constrained to the carrier plate 5 in the longitudinal direction, when they are in their locking position sliding of the carrier plate 5 relative to the base plate 3 is prevented, while sliding of the carrier plate 5 relative to the base plate 3 is allowed when they are in their unlocking position.

[0064] According to the invention, the locking arrangement comprises transverse elastic means 15, such as a coil spring arranged in the transverse direction, for urging the locking blocks 11a, 11b away from each other in the transverse direction, thus pushing the locking teeth 13a, 13b of the locking blocks 11a, 11b into the seats 9a, 9b of the racks 7a, 7b and against the bottom of said seats 9a, 9b.

[0065] Thanks to the provision of the transverse elastic means 15 the engagement of the locking blocks 11a, 11b with the racks 7a, 7b is extremely firm, and accidental disengagement of the locking blocks from the racks is effectively prevented. As a consequence, accidental and undesired movements of the seat cushion front portion 104 relative to the seat cushion body 102 are also effectively prevented.

[0066] The locking arrangement 10 further includes a driving element, such as a driving handle 17, that can be operated by the user for switching the locking blocks from their locking position to their unlocking position by applying a force sufficient for overcoming the resistance of the transverse elastic means 15, and a connecting element, such as a connecting rod 19, for transferring the force applied to the driving handle by the user to the locking blocks 11a, 11b.

[0067] The connecting rod 19 has a proximal end 19a connected to the driving handle 17 and a distal end 19b acting on the locking blocks 11a, 11b for transferring thereto the force applied by the user to said driving handle 17.

[0068] As shown in Figures 2 and 3, the distal end 19b of the connecting rod 19 is shaped as a fork having a pair of parallel prongs 21a, 21b.

[0069] The facing surfaces 23a, 23b of said prongs 21a, 21b are inclined, so that the distance between the prongs 21a, 21b is maximum at their ends and then progressively decreases.

[0070] Correspondingly, each locking block 11a, 11b has a raised portion provided with a mating inclined surface 25a, 25b co-operating with the inclined surface 23a, 23b of a respective prong 21a, 21b of the distal end 19a of the connecting rod 19.

[0071] A spring 27 is provided for guaranteeing the contact between the inclined surfaces 23a, 23b of the prongs 21a, 21b of the connecting rod and the mating inclined surfaces 25a, 25b of the locking blocks 11a, 11b.

[0072] When a force is applied by the user to the driving handle 17, the connecting rod 19 is moved backwards in the longitudinal direction, while the locking blocks 11a, 11b are constrained to the carrier plate 5 in the longitudinal direction.

[0073] As a result, the inclined surfaces 23, 23b of the prongs 21a,21b of the connecting rod 19 slide along the mating inclined surfaces 25a, 25b of the locking blocks 11a, 11b, thus causing said locking blocks 11a, 11b to move closer to each other: if a sufficient force is applied to the driving handle 17, the locking blocks 11a, 11b are brought to the unlocking position and the carrier plate 5 is free to slide relative to the base plate 3.

[0074] Thanks to the co-operation between the inclined surfaces 23a, 23b and the mating inclined surfaces 25a, 25b, a progressively increasing force is needed for moving the locking blocks 11a, 11b closer to each other, and the operation of the locking arrangement 10 is smooth.

[0075] As shown in, the device 1 may be provided with longitudinal elastic means, such as longitudinally arranged coils springs 29, urging the carrier plate 5 forwards.

[0076] Thanks to the longitudinal coils springs 29, the carrier plate is pushed towards its foremost position as soon as the locking blocks 11a, 11b has been moved to their unlocking position.

[0077] It will be evident to the skilled person that this makes the adjustment of the longitudinal position of the seat cushion front portion easier and more comfortable for the user.

[0078] In the shown example, two longitudinal coils springs 29, symmetrically arranged with respect to the longitudinal middle line of the carrier plate 5, are provided.

[0079] According to the preferred embodiment disclosed herein, the device 1 further comprises a plurality of free-play recovery elements 31arranged between the base plate 3 and the carrier plate 5.

[0080] The free-play recovery elements 31 constantly apply horizontal and vertical forces that keep the carrier plate 5 and base plate 3 aligned to each other. In addition, they avoid collisions (and resulting noise) between said carrier plate 5 and said base plate 3.

[0081] In the shown example, four free-play recovery elements 31 are provided, symmetrically arranged with respect to the longitudinal middle line and to the transverse middle line of the base plate and the carrier plate.

[0082] The operation of the device 1 according to the invention will be briefly explained with reference to Figures 4 – 8.

[0083] In an initial configuration, shown in figures 4 and 5, the seat cushion front portion is at its rearmost position, abutting against the seat cushion body.

[0084] In this initial configuration, the driving handle 17 is at rest and the distal end of the connecting rod 19 does not exert any force on the locking blocks 11a, 11b.

[0085] As a result, the transverse elastic means 15 urge each locking block 11a, 11b towards the respective rack 7a, 7b, pushing their locking teeth towards the bottom of the seats of said racks and reliably maintaining the locking arrangement in the locking position.

[0086] In this configuration, the locking teeth of the locking blocks 11a, 11b engage the seats of the racks 7a, 7b at a rearmost section thereof.

[0087] When the user rotates the driving handle 17 (see Figures 6 and 7), the connecting rod 19 moves backwards in the longitudinal direction, while the locking blocks 11a, 11b are constrained to the carrier plate 5 in the longitudinal direction.

[0088] Therefore, the inclined surfaces of the prongs of the fork-shaped distal end of the connecting rod 19 slide along the mating inclined surfaces of the locking blocks 11a, 11b, overcoming the resistance of the transverse elastic means 15 and making said locking blocks 11a, 11b move closer to each other.

[0089] If a sufficient force is applied to the driving handle 17 by the user, the locking blocks 11a, 11b are brought to the unlocking position, in which the locking teeth are completely disengaged from the seats of the racks 7a, 7b of the base plate 3.

[0090] At this stage, the carrier plate 5 is free to slide relative to the base plate 3.

[0091] In the shown embodiment, the longitudinal springs 29 (see) urge the carrier plate forwards.

[0092] As long as the user maintains said sufficient force applied to the driving handle 17, the carrier plate 5 can slide relative to the base plate 3 and, consequently, the position of the seat cushion front portion relative to the seat cushion body can be adjusted.

[0093] As soon as the user releases the driving handle 17, the connecting rod 19 moves forwards in the longitudinal direction, so that the distal end of said connecting rod does no longer apply a force onto the locking blocks 11a, 11b.

[0094] As a result, said locking blocks 11a, 11b are brought back to the locking position by the transverse elastic means 15, so that their locking teeth are pushed again into the seats of the racks 7a, 7b and firmly retained therein.

[0095] For instance, the user can let the carrier plate 5 move forwards under the action of the longitudinal springs and then release the driving handle when the locking blocks 11a, 11b are close to the foremost section of the racks 7a, 7b, so that the locking teeth of said locking blocks 11a, 11b will engage the seats of said racks 7a, 7b at a foremost section thereof, as shown in.

[0096] In this final configuration, the seat cushion front portion will be close to its foremost position, moved away from the seat cushion body, so that the overall extension of the seat cushion will be increased with respect to the initial configuration.

[0097] It will be evident to the person skilled in the art that the embodiment described above is in no way to be understood in a limiting sense, and that several variations and modifications are possible without, however, departing from the scope of protection of the invention as defined by the appended claims.

[0098] In addition, although reference to a vehicle seat has been made when disclosing the preferred embodiment of the invention, this application is in no way to be understood in a limiting sense, and the claimed device could also be applied to other kind of seats.

Claims

Device (1) for adjusting the extension of a seat cushion (100) of a seat, said device (1) including a first plate (3), a second plate (5), mounted to said first plate so as to be slidable in the longitudinal direction relative to said first plate, and a locking arrangement (10) for selectively allowing or preventing sliding of said second plate relative to said plate, wherein said first plate (3) is provided with a pair of longitudinally arranged parallel racks (7a, 7b), spaced from each other and facing each other, wherein said locking arrangement (10) correspondingly comprises a pair of locking blocks (11a, 11b), arranged between said racks (7a, 7b) and provided with locking teeth (13a, 13b) facing a respective rack (7a, 7b), wherein said locking blocks (11a, 11b) are constrained to said second plate (5) in the longitudinal direction and are movable in the transverse direction, so that they can move between a locking position, in which they are far from each other and the locking teeth (13a,13b) of each locking block are inserted and firmly retained in corresponding seats (9a, 9b) of the respective rack (7a, 7b), and an unlocking position, in which they are closer to each other and the locking teeth (13a,13b) of each locking block are disengaged from said seats (9a, 9b) of the respective rack (7a, 7b), wherein said locking arrangement (10) comprises transverse elastic means (15) urging said locking blocks (11a, 11b) away from each other in the transverse direction and pushing said locking teeth (13a, 13b) of said locking blocks (11a, 11b) into said seats (9a, 9b) of the racks (7a, 7b), wherein the locking arrangement (10) further includes a driving element (17), on which a force can applied by a user for overcoming the resistance of said transverse elastic means (15) and switching said locking blocks (11a, 11b) from said locking position to said unlocking position, and a connecting element (19) for transferring the force applied to said driving element (17) to said locking blocks (11a, 11b), said connecting element being made as a connecting rod (19) connected at a proximal end (19a) thereof to said driving element (17), characterized in that the distal end (19b) of said connecting rod (19) is shaped as a fork having a pair of parallel prongs (21a, 21b) and the facing surfaces (23a, 23b) of said prongs (21a, 21b) are inclined, so that the distance between the said prongs is maximum at their ends and then progressively decreases, and wherein each locking block (11a, 11b) is provided with a mating inclined surface (25a, 25b) co-operating with the inclined surface (23a, 23b) of a respective prong (21a, 21b).Device (1) according to claim 1, wherein said driving element is made as a driving handle (17) pivotally connected to said second plate (5).Device (1) according to claim 1 or 2, wherein said connecting rod (19) is movable backwards and forwards in the longitudinal direction, and wherein said inclined surfaces (23a, 23b) of said prongs (21a, 21b) of the distal end of said connecting rod are slidable along said mating inclined surfaces (25a, 25b) of said locking blocks (11a, 11b) as said connecting rod (19) moves backwards and forwards in the longitudinal direction.Device (1) according to claim 1 or 2 or 3, wherein a spring (27) is provided for guaranteeing the contact between said inclined surfaces (23a, 23b) of said prongs (21a, 21b) and said mating inclined surfaces (25a, 25b) of said locking blocks (11a, 11b).Device (1) according to any of the preceding claims, further comprising longitudinal elastic means (29) which urge said second plate (5) forwards in the longitudinal direction.Device (1) according to any of the preceding claims, further comprising one or more free-play recovery elements (31) which are arranged between said first and second plates (3, 5) and apply horizontal and vertical forces for keeping said first and second plates (3, 5) aligned to each other.Device (1) according to claim 6, wherein a plurality of said free-play recovery elements (31) is provided, said free-play recovery elements (31) being symmetrically arranged with respect to the longitudinal middle line of said first and second plates (3, 5) and / or with respect to the transverse middle line of said first and second plates (3, 5).Seat cushion (100) comprising a seat cushion body (102) and a seat cushion front portion (104), which is separate from said seat cushion body and movable relative thereto, wherein said seat cushion (100) is provided with a device (1) according to any of the claims 1 – 7 and wherein said second plate (5) is fastened to said seat cushion front portion (104).

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