Lock plate cover

Abstract

A cover for a plate (1) of a lock, wherein the plate (1) is adapted to be inserted and secured in a cavity (101) of a movable structure (100) such as a leaf or door, it includes at least one substantially flat member (17; 27) adapted to overlap the cavity (101) so that, in use, the edge (170; 270) of the substantially flat member (17; 27) at least partially overlaps the portion of the movable structure (100) that surrounds the cavity (101), and attachment means (18; 28; 29, 292) associated with the substantially flat member (17; 27) and adapted to removably attach the cover to the movable structure (100).

Description

[0001] DESCRIPTION

[0002] LOCK PLATE COVER

[0003] Technical field

[0004] The present invention relates to a cover for a lock plate .

[0005] The present invention also relates to a lock plate and a lock .

[0006] Background art

[0007] Locks comprise a case or plate, which can be inserted into a recess made in the door leaf , and a countercase (or counterplate ) which can be inserted into a recess made in the door jamb or in an additional door leaf . A bolt , provided with a latch at one end, is movable between a retracted position in the case, in which the latch is inside the latter, and a partially extended position from the case, in which the latch extends from the case and, when the door leaf is closed on the jamb or on the corresponding second door leaf , is inserted into a corresponding seat made in the countercase ( or counterplate ) .

[0008] The locks can be used in both swing and sliding leaf doors or doors . Both recessed portions of the lock have a respective front face provided with a through-hole for the passage of the bolt and / or its latch . When the door is closed, the front faces of the two recessed portions of the lock face each other, with the corresponding through holes for the latch positioned opposite each other . The front faces of the two recessed portions of the lock usually include functional elements ( such as mounting screw holes , abutment and locking elements , etc . . . . ) that remain visible on the front face .

[0009] It is known to apply a cover to the front face so as to conceal the functional elements , improving the aesthetics of the lock . The cover also has a through- hole at the one drilled in the front face for the passage of the latch .

[0010] In known locks , a gap remains between the plate and the leaf or door after the cover is applied .

[0011] This gap, in addition to negatively affecting the aesthetics of the lock, can easily deteriorate with the use of the lock . In addition, dust , dirt , or residues of products for cleaning or lubricating the lock collect in the gap between the plate and the door leaf and are difficult to remove .

[0012] Aim of the invention The aim of the present invention is to overcome the mentioned drawbacks .

[0013] In particular, the aim of the invention is to prevent damage to the area of the leaf surrounding the plate inserted into the cavity .

[0014] According to the present invention, there is provided a cover for a lock plate, wherein the plate is adapted to be inserted into and secured in a cavity of a movable structure such as a leaf or a door, wherein the cover includes at least one substantially flat member adapted to overlap the cavity so that , in use, the edge of the substantially flat member overlaps at least partially with the portion of the movable structure surrounding the cavity, and attachment means associated with the substantially flat member and adapted to removably secure the cover to the movable structure .

[0015] The cover can thus be inserted into the cavity by overlapping the leaf or door area surrounding the cavity so as to provide protection for the gap formed between the plate and the leaf or door .

[0016] According to another aspect of the present invention, a lock plate having the features defined in claim 14 is provided . According to a further aspect of the present invention, a lock having the features defined in claim 20 is provided .

[0017] Brief description of the drawings

[0018] Further advantages and features of the present invention will be more apparent in the following detailed description, made with reference to the attached drawings , which represent a non-limiting example of its execution, wherein :

[0019] - Figure 1 illustrates a lock schematically;

[0020] - Figure 2 illustrates a lock plate of a known type in a perspective view;

[0021] - Figure 3 schematically illustrates a leaf provided with a plate with a cover in a first embodiment of the present invention in a first perspective view;

[0022] - Figure 4 illustrates the cover of Figure 3 in a second perspective view;

[0023] - Figure 5 illustrates a front view of the leaf in Figure 3 ;

[0024] - Figure 6 illustrates a detail of the leaf in Figure 5 according to section VI-VI ; - Figure 7 illustrates a longitudinal section of the leaf in Figure 3 ;

[0025] - Figure 8 illustrates a detail of the leaf in Figure 7 ;

[0026] - Figure 9 schematically illustrates a leaf provided with a plate with a cover in a second embodiment of the present invention in a first perspective view;

[0027] — Figure 10 illustrates the cover in Figure 9 in a second perspective view;

[0028] - Figure 11 illustrates a front view of the leaf in Figure 9 ;

[0029] - Figure 12 illustrates a detail of the leaf in Figure 11 according to section XII-XII ;

[0030] - Figure 13 illustrates a longitudinal section of the leaf in Figure 9 ;

[0031] - Figure 14 illustrates a detail of the leaf in Figure 13 .

[0032] Detailed description

[0033] Figure 1 schematically illustrates a lock .

[0034] The lock includes a plate 1 that is inserted into a respective reces s made on a movable structure 100 such as a leaf or door . The leaf or door can be of the swinging or sliding type .

[0035] The lock also includes a counterplate 2 that is inserted into a respective recess made in a door jamb 200 of a door or leaf or in an additional leaf 201 .

[0036] Figure 2 illustrates a plate of a known type . The plate 1 includes a body 15 in which a latch 3 having a latch bolt 30 is inserted at one end thereof and movable between a first retracted position, in which the latch bolt 30 is located within the body 15 , and a second partially extended position .

[0037] The plate 1 includes a front face 11 in which an opening 10 is cut for the passage of the latch 30 . The front face 11 has an elongated shape bounded by two substantially rectilinear and parallel side edges 110 and two connecting edges 111 . The front face 11 has one or more through holes for the insertion of attachment means of the plate to the leaf or door .

[0038] The plate is associated with a cover 12 . The cover includes a flat member 125 adapted to overlap the front face 11 . The flat member 125 has two rectilinear and parallel edges 121 and two connecting edges 1210 . The flat member 125 includes an opening 120 adapted to be arranged at the opening 10 of the front face 11 for the passage of the latch 30 .

[0039] According to one aspect of the present invention, a cover for a lock plate, wherein the plate is adapted to be inserted into and secured in a cavity of a movable structure such as a leaf or door, includes at least one substantially flat member adapted to overlap the cavity so that , in use, the edge of the substantially flat member overlaps at least partially with the portion of the movable structure surrounding the cavity, and attachment means associated with the substantially flat member and adapted to removably secure the cover to the movable structure .

[0040] Advantageously, the attachment means include at least one protruding portion that extends in a substantially perpendicular direction to the substantially flat member and is adapted to be inserted into the gap between the movable structure and the plate when the plate is inserted and secured in the cavity .

[0041] Preferably, the attachment means include at least one protruding portion extending in a direction substantially perpendicular to the substantially flat member and being adapted to engage a corresponding portion of the plate to secure the cover to the plate . In this way, the cover is secured to the movable structure .

[0042] The leaf or door can be of the swinging or sliding type .

[0043] The substantially flat member preferably has an opening for the passage of the latch .

[0044] Advantageously, the attachment means comprise at least one wing extending in a substantially perpendicular direction to the substantially flat member and adapted to be inserted into the gap between the movable structure and the plate when the plate is inserted into the cavity, or to engage a corresponding portion of the plate in particular to be inserted into a corresponding opening or recess of the plate . Preferably, the wing is substantially rectilinear .

[0045] In a preferred embodiment , the attachment means include at least one pin provided with a head and adapted to be inserted into a corresponding hole in the plate .

[0046] In a further embodiment , the attachment means comprise at least one profile extending in a direction substantially perpendicular to the substantially flat member and adapted to be inserted into the gap between the movable structure and the plate when the plate is inserted into the cavity or to engage a corresponding portion of the plate, in particular to be inserted into a corresponding opening or recess of the plate .

[0047] In an advantageous embodiment , the attachment means include magnetic interaction means between the cover and the lock plate, wherein the magnetic interaction means generate magnetic interaction forces that result in the removable attachment of the cover to the plate when the cover is positioned adjacent to the plate .

[0048] The magnetic interaction means between the cover and the lock plate may include at least a localized portion of the plate having magnetic characteristics generating a magnetic field acting on magnetic field-sensitive parts of the cover . The cover may have at least one localized portion made of a magnetic field-sensitive material and attracted to the latter and affected by said magnetic field generated by the localized portion of the lock plate .

[0049] The magnetic interaction means between the cover and the lock plate may include at least one localized portion of the cover having magnetic characteristics generating a magnetic field acting on magnetic fieldsensitive portions of the lock plate . At least one localized portion of the plate may be made of a magnetic field-sensitive material and attracted to the magnetic field and affected by the magnetic field generated by the localized portion of the substantially flat member of the cover .

[0050] The localized portion of the recessed plate can be realized by one or more permanent magnets or portions of a permanent magnet .

[0051] The localized portion of the plate or cover can be realized by one or more areas of ferromagnetic material previously subjected to the action of a strong magnetic field until a permanent magnetization with the desired characteristics is determined .

[0052] The localized portion of the plate or cover may also be formed by dispersing, in localized areas of a matrix lacking magnetic properties , a certain percentage of portions of a material having magnetic characteristics that generate a magnetic field acting on magnetic field-sensitive parts . Specifically, portions of permanent magnet or permanently magnetized material can be dispersed in the desired direction .

[0053] In a preferred embodiment , the cover includes at least one portion made of a magnetic field-sensitive material . For example, the protruding portion and / or substantially flat member of the cover may include at least one portion made of a magnetic field-sensitive material .

[0054] Advantageously, the cover is made of magnetic fieldsensitive material . Specifically, the cover is made of ferromagnetic metal material, preferably steel .

[0055] In another embodiment , the cover comprises at least one magnet .

[0056] According to another aspect of the present invention, a lock plate, wherein the plate is adapted to be inserted into a cavity of a movable structure such as a leaf or door, includes a body, a front face associated with the body and adapted to face the outside of the cavity, and a cover having at least one substantially flat member having an extension greater than the front face to overlap the cavity so that the edge of the flat member overlaps at least partially with the portion of the movable structure surrounding the cavity when the plate is inserted into the cavity, wherein the cover has attachment means associated with the substantially flat member and adapted to removably attach the cover to the movable structure . According to a further aspect of the present invention, a lock plate, wherein the plate is adapted to be inserted into a cavity of a movable structure such as a leaf or a door, comprises a body and a front face, associated with the body and adapted to face the outside of the cavity, wherein the front face of the plate has at least one recess or at least one opening adapted to receive a corresponding protruding portion of a cover .

[0057] The front face may be made in one piece with the body of the plate or may be associable with the body via attachment means .

[0058] The substantially flat member may have shapes other than the shape of the front face of the plate . The extension of the flat member is greater than the dimensions of the front face so that when the protruding portion fits into the cavity, the portion of the flat member between the protruding portion and the edge overlaps the portion of the leaf or door surrounding the cavity .

[0059] The substantially flat member may have the same shape as the front face, with an extension greater than the cavity itself . The extension of the substantially flat member is greater than the extension of the front face of the plate .

[0060] Figures 3-8 illustrate a first preferred embodiment of the present invention .

[0061] The cover 16 includes a substantially flat member 17 that has substantially the same shape as the front face 11 of the plate 1 . This shape corresponds to the shape of the cavity in which the front face 11 of the plate 1 is inserted .

[0062] The extension of the substantially flat member 17 of the cover 16 is greater than the extension of the cavity and the front face 11 .

[0063] The edge 170 of the substantially flat member has two rectilinear and parallel portions 171 . The edge 170 has two connecting portions 172 that are preferably curved . The cover 16 has a protruding portion in the direction perpendicular to the substantially flat member 17 .

[0064] The protruding portion includes two wings 18 . Each wing 18 is arranged in the proximity of each rectilinear portion 171 of the edge 170 , in the inner area of the substantially flat member 17 . Preferably, the wings 18 are rectilinear . Preferably, the flat member 17 has a thickness between about 0 . 3 mm and about 2 mm, preferably between about 0 . 4 mm and about 1 mm .

[0065] Advantageously, the edge 170 of the flat member 17 overlaps the movable portion of the structure 100 by a distance between about 0 . 5 mm and about 2 mm .

[0066] Preferably, the protruding portion extends in a direction substantially perpendicular to the flat member 17 for a length between about 0 . 5 mm and about 2 mm .

[0067] The length of the protruding portion in the direction perpendicular to the flat member may vary .

[0068] For example, as shown in Figure 4 , a wing 18 may have a longer length portion and a shorter length portion .

[0069] The cover 16 is advantageously made of metal material, such as steel .

[0070] The cover 16 can be obtained by cutting and bending a metal sheet .

[0071] Alternatively, the cover 16 can be obtained by stamping .

[0072] The cover 16 can be made as a single body or by attaching the protruding portion, particularly the wings 18 , to the substantially flat member 17 . Advantageously, the protruding portion is obtained by bending at least a portion of edge 170 of the substantially flat member 17 .

[0073] In particular, the two rectilinear portions 171 of edge 170 are bent .

[0074] In the embodiment illustrated particularly in Figure 6, the portion 171 of the edge 170 is first bent over the substantially flat member 17 so as to overlap with it , and then it is bent in a substantially perpendicular direction with respect to the substantially flat member 17 so as to create the protrusion that will be inserted into the gap between the cavity 101 and the front face 11 of the plate 1 .

[0075] The edge 170 can also be bent at the connecting portions 172 .

[0076] In the embodiment shown particularly in Figures 6 and 8 , the front face 11 of plate 1 has a substantially rectilinear recess 112 on each longitudinal side . The recess 112 allows insertion of the wings 18 in contact with the inner surface of the cavity .

[0077] In an alternative embodiment , the wings 18 are arranged in a more central area of the substantially flat member 17 and are adapted to be inserted into corresponding openings or recesses made in plate 1 , particularly in front face 11 . The wings 18 may be adapted to be inserted in contact with corresponding portions of the plate 1 ( in particular, with external surfaces of a front portion thereof ) .

[0078] In the embodiment illustrated, the area of the flat member 17 at the connecting portions 172 of the edge 170 has no protrusions .

[0079] In an alternative embodiment , not illustrated, the cover 16 may have a protrusion, such as a wing, associated with the substantially flat member 17 at the connecting portion 172 and adapted to be inserted into the gap between the cavity 101 and the front face 11 of the plate 1 or in a corresponding opening or recess made in the plate 1 , particularly in the front face 11 . In the embodiment of Figure 6, the edge 170 of the substantially flat member 17 of the cover 16 rests on the portion of the movable structure 100 surrounding the cavity after being folded . In this way, the outermost face of the substantially flat member 17 is at a distance d from the movable structure . The distance d is advantageously between about 0 . 3 mm and about 2 mm, preferably between about 0 . 4 mm and about 1 mm, so that the cover does not interfere with the closing of the door or leaf . In an alternative embodiment , the wings 18 are attached to the substantially flat member 17 and the edge 170 is not folded, so that the substantially flat member 17 rests on the movable structure 100 .

[0080] In the embodiment shown particularly in Figure 6, the front face 11 of the plate 1 has a seat in which a magnet 113 is inserted .

[0081] The cover can be made of a plastic material or a metal material that is not sensitive to magnetic fields , such as a zinc-aluminium alloy ( commonly called "zamak" ) . In this case, the portion of the cover that comes to rest on the front face 11 of the plate 1 at the magnet 113 may include a magnetic field-sensitive element . The cover may all be made of a magnetic field-sensitive material .

[0082] The substantially flat member 17 has an opening 120 for the passage of the latch 30 .

[0083] Advantageously, at least on two opposite sides of the perimeter of the opening the flat member has respective centering protrusions 122 .

[0084] Centering protrusions 122 are intended to engage at least partially the edges of the opening of the front face 11 of plate 1 . The centering protrusions 122 have a seat 123 for inserting a tool ( such as a screwdriver) for removing the cover 12 from the plate 1 .

[0085] Figures 9-14 show a second preferred embodiment of the present invention .

[0086] In the illustrated embodiment , the substantially flat member 27 of the cover 26 has substantially the same shape as the front face 11 of the plate 1 . This shape corresponds to the shape of the cavity in which the front face of the plate is inserted .

[0087] The extension of the substantially flat member 27 of the cover 26 is greater than the extension of the cavity and front face 11 .

[0088] The edge 270 of the substantially flat member 27 has two rectilinear and parallel portions 271 . The edge 270 has two connecting portions 272 that are preferably curved .

[0089] The protruding portion includes a profile 28 , particularly a substantially continuous profile . The profile 28 extends parallel to the development of the edge 270 of the flat member 27 . The profile 28 is arranged close to the edge 270 and at a predetermined distance from the edge . The profile 28 is inserted into the gap between the plate 1 and the leaf or door, and the portion of the flat member 27 of the cover 26 between the profile 28 and the edge 270 rests on the leaf or door . The gap is then closed, is not visible, and remains protected by the cover .

[0090] In an alternative embodiment , the profile is inserted into a corresponding seat , such as an opening or groove, made in the plate, particularly in the front face, so that the edge of the substantially flat member rests on the portion of the movable structure surrounding the cavity . In this way, the gap between the plate and the cavity is closed, is not visible, and remains protected by the cover .

[0091] Preferably, the flat member 27 has a thickness between about 0 . 3 mm and about 2 mm, preferably between about 0 . 4 mm and about 1 mm .

[0092] Advantageously, the edge 270 of the flat member 27 overlaps the portion of the movable structure 100 by between about 0 . 5 mm and about 2 mm .

[0093] Preferably, the profile 28 extends in the direction substantially perpendicular to the flat member 27 for a length between about 0 . 5 mm and about 2 mm . The profile 28 has the same extension in the direction perpendicular to the flat member 27 .

[0094] In an alternative embodiment , the profile may have different lengths in the direction perpendicular to the flat member .

[0095] The substantially flat member has an opening 120 for the passage of the latch .

[0096] Advantageously, at least on two opposite sides of the perimeter of the opening the flat member has respective centering protrusions 122 .

[0097] The centering protrusions are intended to engage at least partially the edges of the opening of the front face 11 of the plate 1 .

[0098] The centering protrusions 122 have a seat 123 for inserting a tool for removing the cover from the plate 1 .

[0099] In the embodiment illustrated particularly in Figures 12 and 14 , the front face 11 of the plate 1 has a recess 112 , particularly, advantageously, around the entire perimeter . The recess 112 allows the insertion of the profile 28 in contact with the inner surface of the cavity .

[0100] In the embodiment in Figure 12 , the edge 270 of the substantially flat member 27 of the cover 26 rests on the portion of the movable structure 100 surrounding the cavity .

[0101] The front face 11 of plate 1 has a seat in which a magnet 113 is inserted .

[0102] Advantageously, the cover 26 includes at least one ferromagnetic element 291 , 292 associated with the substantially flat member 27 .

[0103] Preferably, as illustrated particularly in Figure 12 , the substantially flat member 27 has a portion, facing the plate 11 , in which a seat 290 is formed . A ferromagnetic element 291 , 292 is arranged in the seat 290 .

[0104] In a further embodiment , the portion of the substantially flat member that comes to be arranged on the front face at the magnet is made of a ferromagnetic material .

[0105] The cover can be made as a single body or by associating the substantially flat member with the protrusions .

[0106] The cover can be made of plastic material or metal material that is not sensitive to magnetic fields , such as zamak .

[0107] The cover can also be made of metal material that is sensitive to magnetic fields , particularly steel . In the embodiment illustrated particularly in Figures 10 , 12 and 13 , the cover 26 has a first ferromagnetic

[0108] 291 element and a second ferromagnetic 292 element . For example, in Figure 10 , the ferromagnetic elements 291 ,

[0109] 292 are arranged symmetrically with respect to the opening 120 for the passage of the latch 30 .

[0110] Advantageously, each ferromagnetic element 291 , 292 is arranged at a connecting portion 272 of the edge 270 of the substantially flat member 27 , more centrally than the profile 28 .

[0111] The cover object of the present invention may be inserted into the cavity overlapping the leaf or door area surrounding the cavity so as to provide protection for the gap formed between the plate and the leaf or door .

Claims

CLAIMS1. A cover for a lock plate (1) , wherein the plate (1) is adapted to be inserted into and attached to a cavity (101) of a movable structure (100) such as a leaf or door, wherein the cover includes at least one substantially flat member (17; 27) adapted to overlap the cavity (101) so that, in use, the edge (170; 270) of the substantially flat member (17; 27) at least partially overlaps the portion of the movable structure (100) surrounding the cavity (101) , and attachment means (18; 28; 291, 292) associated with the substantially flat member (17; 27) and adapted to removably attach the cover to the movable structure (100) .

2. The cover according to claim 1, characterized in that the attachment means comprise at least one protruding portion (18; 28) associated with the substantially flat member (17; 27) , wherein the protruding portion (18; 28) extends in a direction substantially perpendicular to the substantially flat member (17; 27) and is arranged in the inner area of the substantially flat member (17; 27) at a predetermined distance from the edge (170; 270) so as to be inserted at the inner surface of the cavity (101)when the plate (1) is inserted and fixed in the cavity (101) of the movable structure.

3. The cover according to claim 1 or 2, characterized in that the attachment means comprise at least one protruding portion (18) associated with the substantially flat member (17; 27) , wherein the protruding portion (18; 28) extends in a direction substantially perpendicular to the substantially flat member (17; 27) and is arranged in the inner area of the flat member (17; 27) at a predetermined distance from the edge (170; 270) so as to engage a corresponding portion of the plate to secure the cover to the plate ( 1 ) .

4. The cover according to any one of the preceding claims, characterized in that the attachment means comprise at least one wing (18) associated with the substantially flat member (17) , the wing (18) being adapted to be inserted into the gap between the movable structure (100) and the plate when the plate (1) is inserted into the cavity (101) or to engage a corresponding portion of the plate (1) to secure the cover to the plate (1) .

5. The cover according to claim 4, characterized in that the wing (18) is substantially rectilinear.

6. The cover according to claim 4 or 5, characterized in that the edge (170) of the substantially flat member (17) has two rectilinear and parallel portions (171) and two wings (18) , each wing (18) being disposed near each rectilinear portion (171) of the edge (170) .

7. The cover according to any of the preceding claims, characterized in that the attachment means comprise a profile (28) associated with the substantially flat member (18) , wherein the profile (28) is adapted to be inserted into the gap between the movable structure (100) and the plate (1) when the plate is inserted into the cavity (101) or to engage a corresponding portion of the plate (1) to secure the cover to the plate (1) .

8. The cover according to any of the preceding claims 2-7, characterized in that the protruding portion (18) is obtained by bending at least a portion of the edge (170) of the substantially flat member first onto the substantially flat member (17) and thereafter perpendicularly relative to the substantially flat member (17) .

9. The cover according to any of the preceding claims, characterized in that the attachment means include magnetic interaction means between the cover and the plate (1) of the lock, wherein the magnetic interactionmeans generate magnetic interaction forces that result in the removable attachment of the cover to the plate (1) , when the cover is positioned adjacent to the plate (1) •10. The cover according to any of the preceding claims, characterized in that it comprises at least one portion made of a magnetic field-sensitive material.

11. The cover according to any of the preceding claims, characterized in that it is made of a magnetic fieldsensitive material, preferably steel.

12. The cover according to any one of the preceding claims, characterized in that it comprises a magnetic field-sensitive element (291, 292) associated with the substantially flat member (27) .

13. The cover according to any of the preceding claims, characterized in that the substantially flat member (17; 27) has an opening (120) for the passage of a latch (30) and is provided with at least one wing (122) extending in a direction substantially perpendicular to the substantially flat member (17; 27) and arranged at the opening (120) .

14. A lock plate comprising a body (15) adapted to be inserted into a cavity (101) of a movable structure (100) such as a leaf or a door; a front face (11)associated with the body (15) and adapted to face the outside of the cavity (101) ; and a cover according to any of the preceding claims, wherein the substantially flat member (17; 27) of the cover has an extension greater than the front face (11) .

15. The lock plate according to claim 14, characterized in that it comprises magnetic interaction means for removably securing the cover to the body (15) .

16. The lock plate according to the preceding claim, characterized in that the magnetic interaction means comprise at least a localized portion of the plate having magnetic characteristics generating a magnetic field acting on magnetic field-sensitive parts of the cover .

17. The lock plate according to any of claims 14-16, characterized in that it includes two permanently magnetized areas arranged on the face facing the cover and located on opposite sides from the opening (20) for the latch passage (30) .

18. The lock plate according to any of claims 16-17, characterized in that the localized portion having magnetic characteristics comprises at least one seat and at least one magnet (113) inserted into the seat.

19. The lock plate according to any of claims 14-18, characterized in that the front face (11) of the plate has at least one recess or at least one opening adapted to receive a corresponding protruding portion of the cover .

20. A lock comprising a plate (1) according to any of the preceding claims 14 to 19; a counterplate (2) adapted to be inserted into a second fixed structure (200) or movable structure (200') , such as a frame or leaf, such that, when the first movable structure (100) is in the closed position, the plate (1) and the counterplate (2) are placed opposite each other, the plate (1) comprising a latch (30) movable between a retracted position in which it is retracted within a first seat in the plate (1) , and an extended position, in which it is partially extended from the seat, the counterplate (2) being provided with a second hollow seat that receives the extended part of the latch (30) when the plate (1) and counterplate (2) are facing each other and the latch (30) is in the extended position.

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