Piece of furniture for dental clinics comprising an improved system for moving an instrument-holder tray

Abstract

The present invention relates to a piece of furniture, preferably for dental clinics, comprising an improved system for moving a concealable instrument-holder tray (4). In particular, the movement system is very practical given that it allows various adjustments and safe positionings to ergonomically adapt to the uttermost its position and height with respect to the operator and also against accidental impacts. The system comprises a movement for lifting in various positions for extracting the tray (4) from the piece of furniture.

Description

“PIECE OF FURNITURE FOR DENTAL CLINICS COMPRISING AN IMPROVED SYSTEM FOR MOVING AN INSTRUMENT-HOLDER TRAY”DESCRIPTIONTECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a piece of furniture, preferably for dental clinics, comprising an improved system for moving a concealable instrument-holder tray. In particular, the movement system is very practical given that it allows various adjustments and safe positionings of the tray to ergonomically adapt to the uttermost its position and heigh with respect to the operator and it also safe against accidental impacts.STATE OF THE PRIOR ART

[0002] In the furniture industry, especially for dental clinics, there are known systems in which a piece of furniture provided with an upper surface for working and placing various instruments, comprises a compartment beneath said work surface adapted to allow the housing for a mechanism for supporting and moving an extractable object holder tray. Beneath said compartment, the piece of furniture may be completed by further surfaces defined by brackets and walls, and closed by door leaves or drawers for containing objects or instruments required by the physician or personnel designated to support the physician. Alternatively, the aforementioned compartment may be closed at the lower part by a panel of a bottom for separating the mechanism for moving the tray with respect to an underlying open space which may serve to allow an operator to use the piece of furniture even as a desk and, therefore, be able to position the legs therein.

[0003] In particular, substantially there are two types of mechanisms for moving the tray. The first consists of an articulated arm fixed beneath the work surface on a joint or on a guide so as to always keep the tray at a higher level with respect to the work surface. Furthermore, the arm may slide parallel to the work surface and it may extend far from the surface or approaching until it is positioned over the surface. Generally, the arm therefore consists of a first segment with a first end fixed under the work surface on a joint or on a guide which slides along the work surface and a second end protruding from the work surface and provided with a flat articulation which allows the rotation of a first end of a second segment whose second end carries an object-holder tray fixed thereon through a further flat articulation which allows the rotation of the tray around itself.

[0004] This type of structure allows to move the tray along the work surface and allows to extend it at will far from the surface or be moved over the surface. Despite being a good solution, it still reveals some drawbacks. As a matter of fact, also in the superimposed position of the tray with respect to the work surface, the articulation between the first and the second segment of the arm protrudes from the work surface and it may represent a hindrance or in any case a protruding part of the piece of furniture against which the operator may impact inadvertently. Furthermore, the position of the tray cannot be adjusted height-wise and, therefore, it cannot meet the different ergonomic needs of the operators. On the other hand, if the arm also provides for the recession of the articulation which carries the tray, in any case the position of the tray is fixed and lower than the work surface.

[0005] The second type of mechanism is represented by an arm which extends orthogonally to the edge of the work surface so as to protrude from or be recessed into a housing arranged under the work surface, for example through a telescopic extension or a guide orthogonal to the work surface and fixed beneath the latter, on which an arm slides. Simultaneously, the arm is also slidable along the work surface on a special further longitudinal guide. At the distal end of the arm with respect to the work surface there is then rotatably fixed the object-holder tray.

[0006] This structure allows the tray to be totally retracted with respect to the work surface, without articulations or protruding arm portions. Therefore, this allows to solve the problem relating to hindrances. Otherwise, just like in the case of the previous structure, the position of the tray is fixed with respect to the surface, in particular it is lower than surface and it is not easy for tall operators. Furthermore, should the tray in extracted position be inadvertently be impacted with instruments or various objects thereon, it tends to recede under the work surface with the risk of knocking down sensitive instruments or containers that may contain liquids.

[0007] Basically, all of the solutions described above relating to a piece of furniture carrying an object-holder tray such as a peninsula which can be moved with respect to the work surface reveal drawbacks such to make the piece of furniture not practical and safe, just like it cannot adapt to different needs of the operators.SUMMARY OF THE INVENTION

[0008] Therefore, the technical problem underlying the present invention lies in designing a piece of furniture comprising an object-holder tray which can be moved with respect to the work surface in a position that is safe and variable to morphologically adapt to anyoperator.

[0009] Such problem is overcome by a piece of furniture comprising an object-holder tray which can be moved with respect to the work surface of the piece of furniture by means of a mechanism which allows a wide variety of safe positioning thereof.

[0010] Therefore, a first object of the present invention is to provide a piece of furniture provided with a mechanism for moving an object-holder tray at various levels with respect to the work surface of the piece of furniture.

[0011] A second object is to provide a piece of furniture in which the tray may be completely retracted under the work surface.

[0012] A third object is to provide a piece of furniture in which the tray may be locked in extended position.BRIEF DESCRIPTION OF THE FIGURES

[0013] Further characteristics and advantages of the piece of furniture comprising an object-holder tray which can be moved with respect to the work surface of the piece of furniture according to the present invention, are described below according to embodiments provided purely by way of non-limiting example and with reference to the figures below, wherein:- figure 1 shows an axonometric top schematic view of a portion of a piece of furniture with an object-holder tray extracted from the work surface and in a lifted position thanks to a lifting mechanism according to a first embodiment of the invention;- figure 2 shows an axonometric bottom schematic view of the portion of the piece of furniture of figure 1 ;- figure 3A shows a lateral schematic view of the portion of the piece of furniture of figure 1 with the object-holder tray totally lowered and partially extracted from under the work surface of the piece of furniture;- figure 3B shows a lateral schematic view of the portion of the piece of furniture 1 with the object-holder tray totally lowered, extracted and in partial cross-section;- figure 4 shows a lateral and cross-sectional view of the object-holder tray of figure 3 in a first lifting position;- figure 5 shows a lateral and cross-sectional view of the tray of figure 4 in a second lifting position;- figure 6A shows a lateral view of the piece of furniture of the invention with the object-holder tray extracted and in a third lifting position;- figure 6B shows a lateral view of the piece of furniture of figure 6A with the lifting mechanism of the tray in partial cross-section and a relevant enlargement;- figure 7A shows a lateral view of the piece of furniture of the invention with the object-holder tray extracted and in a fourth lifting position;- figure 7B shows a lateral view of the piece of furniture of figure 7A with the lifting mechanism of the tray in partial cross-section and a relevant enlargement;- figure 8A shows a lateral and partial cross-sectional view of the portion of the piece of furniture of the invention with the object-holder tray totally lowered and partially extracted from under the work surface of the piece of furniture, with an enlarged detail;- figure 8B shows a lateral and cross-sectional view of the portion of the piece of furniture of figure 8A with the object-holder tray totally lowered and almost totally extracted from under the work surface of the piece of furniture, with an enlarged detail;- figure 8C shows a lateral and cross-sectional view of the portion of the piece of furniture of figure 8A with the object-holder tray totally lowered and totally extracted from under the work surface of the piece of furniture, with an enlarged detail;- figure 9A shows a lateral view of a portion of the piece of furniture with an objectholder tray extracted, in lowered position and provided with a lifting mechanism according to a second embodiment of the invention;- figure 9B shows a lateral view of the portion of the piece of furniture of figure 9A with the lifting mechanism in partial view;- figure 10A shows a lateral view of the portion of the piece of furniture with the object-holder tray 9, in lifted position;- figure 10B shows a lateral view of the portion of the piece of furniture of figure 10A with the lifting mechanism in partial cross-section.DETAILED DESCRIPTION OF THE INVENTION

[0014] The idea underlying the present invention is to design a piece of furniture that is particularly practical and ergonomic especially for dental clinics where the work position of the operators often requires prolonged sitting periods. Then there arises the need to have required instruments within reach without one being forced to carry out cumbersome and distracting displacements or movements. Therefore, it is important to make the positioning of the object-holder tray very comfortable so as to facilitate the use thereof.

[0015] With this idea in mind, it was firstly considered to make the position of the tray adaptable, and therefore ergonomic, substantially for any operator. In other words, the tray may be adjusted height-wise depending on the morphology of an operator.

[0016] Therefore, with reference to figures 1 and 2, the reference numeral 1 generally indicates a portion of the piece of furniture comprising a work surface 2 and an underlying box-like housing 3. The housing 3, and also the work surface 2 as a result, generally extends in a longitudinal direction so as to have two first 30 and second 31 larger sides, which are parallel and opposite which connect with two first 32 and second 33 smaller sides, which are parallel and opposite. Therefore, the portion of the piece of furniture 1 is preferably rectangular parallelepiped-shaped.

[0017] Furthermore, the first larger side 30 of the housing 3 is open so as to allow the protrusion and longitudinal sliding of a an object holder tray 4. Even any other side of the housing could alternatively or in a combined fashion be open so as to allow the protrusion and sliding of the tray or of multiple trays. Furthermore, a longitudinal track 35 (figure 1 ) slides along and in proximity of the entire opening for example of the first larger side 30. Preferably, a bottom 34 of the housing 3 is internally provided with said track 35.

[0018] An arm 5 (better observable in figure 2) is then fitted on said track 35, in a position preferably orthogonal to the track. In particular, the arm 5 may be telescopic or it may be fitted on a carriage (not shown) fitted on said track and provided with a shaped face for sliding on the track and a shaped face for allowing the sliding of the arm orthogonally with respect to the track 35, so as to also move to totally enter into or exit from said housing 3. In any case, the arm 5 comprises a first end 50 constrained inside the housing 3 and a second end 51 (figure 2) which can be extended outside the housing 3.

[0019] Advantageously, according to the present invention, the second end 51 of the arm 5 is fixed to said object-holder tray 4 by means of a lifting mechanism. According to a first embodiment, the lifting mechanism is an articulated quadrilateral 6 (figure 2). The quadrilateral is preferably a rectangle with four levers rotatably pivoted with a first end thereof on said second end 51 of the arm which protrudes from the housing 3 under the work surface 2 of the piece of furniture, and with a second end thereof on said tray 4. In particular, the levers are pivoted two by two on two opposite sides of said arm 5 so as to achieve for each side of the arm a first lever 60 and a second lever 61 . The first lever 60 is rotatably constrained to the side of the arm 5 through a first end 60A, at the terminal edge of the second end of the arm 5, while a second end 60B is rotatably constrained to said tray 4. The second lever 61 is rotatably constrained to the side of the arm 5 througha first end 61 A, far from said edge of the end of the arm, while the second end 61 B is rotatably constrained to said tray. Each second end 60B and 61 B of the first 60 and second 61 levers has a rounded profile which is connected on one side with a straight profile 60C, 61 C and on the other side with an inclined plane profile 60D, 61 D.

[0020] Preferably, the first 60 and second 61 levers are fixed to the tray by interposing a plate 7 which comprises a generally flat bottom 72 (figure 4) and two side walls 70 (figure 2) which rise from said bottom substantially orthogonally and parallel to the arm 5. The bottom is fixed on the side of the tray opposite to the placing one and on each of the side walls there are pivoted the aforementioned first 60 and second 61 levers through the respective second ends 60B and 61 B. Preferably, the plate 7 also comprises a handle 71 for gripping and extracting the tray 4 from the housing 3 or for the insertion thereof thereinto. As better shown in figure 4, the bottom 72 of the plate may comprise grooves 73.

[0021] According to a first variant, the two first levers 60 and the two second levers 61 are connected by a bridge 8 facing towards the terminal edge of the arm (figure 2). Such bridge confers greater stability to the lifting mechanism. Furthermore, preferably, the surface of the bridge facing towards said terminal edge of the arm 5 is passed through by ribs 80 adapted to engage the aforementioned grooves 73 (figure 4) of the bottom of the plate 7. The advantage of said engagement is to make the coupling between the liftable part and the fixed part more stable during the translation of the tray when lowered. Preferably, the respective surfaces may alternatively be made of soft material so as to make the end-stroke more ergonomic, or combined with the engagement they also increase the stability between the two pieces.

[0022] As shown in figures 3-5, the use of the piece of furniture according to the present invention provides for the possibility of extracting the object-holder tray 4 from the housing 3 under the work surface 2 by gripping on the handle 71 of the plate 7. Thanks to the aforementioned telescopic or guide structure, the arm 5 may be extended outwards therefore also moving the tray outwards. It should be observed that in this configuration the tray 4 is in the most lowered position and that is in the position in which the tray is almost in contact with the arm 5 and the first 60 and second 61 levers are substantially extended horizontally to the sides of the arm 5, each with the respective first end 60A, 61 A farthest from the work surface 2 with respect to the corresponding second end 60B, 61 B. Furthermore, in this configuration, the side walls 70 and the handle 71 of the plate 7 cover the articulated quadrilateral mechanism (figure 3). In addition, the bottom 72 ofthe plate 7 rests against the aforementioned first straight profile 60C, 61 C of the levers (not shown in figures 3-5). If present, the grooves 73 of the bottom of the plate 7 and the ribs 80 of the bridges 8, are in mutual engagement in this position.

[0023] Once the tray has been totally extracted, it can be lifted with respect to the arm 5 so as to near the height of the work surface 2 and advantageously exceed its height so that it can freely rotate without colliding with the fixed surface of the piece of furniture, as shown in figure 4. Such movement is carried out by gripping the tray and lifting it with a roto-translation movement moving away from the work surface 2. By so doing, the first 60 and second 61 levers rotate, pivoted on the arm 5, moving their respective second ends 60B and 61 B farther from the work surface 2. At the same time, the tray 4 is brought to a position that is farther from the surface with respect to the end edge of the arm 5.

[0024] In particular, as shown in figure 4, when upon lifting the tray 4 exceeds the highest point, the first 60 and second 61 levers rotate bringing the inclined plane profile 60D, 61 D towards the bottom 72 up to obtaining an abutment against the bottom (figure 5) so as to lock the tray 4 in the operative lifted position.

[0025] In order to position the tray in the lowered position and allow the reinsertion thereof into the houses 3, it will be sufficient to carry out a reverse roto-translation with respect to the one just described above.

[0026] According to a second variant embodiment, as shown in figures 6 and 7, the articulated quadrilateral lifting mechanism 6 comprises an element 9 for adjusting the height of the object-holder tray 4. This element advantageously allows to position the tray 4 at at least one height of the arm 5 that is different with respect to the position that it can take from the aforementioned direct engagement with the levers. This allows to obtain maximum adaptability to the needs of the operators and, as a result, this increases the ergonomics of the work station.

[0027] In particular, as shown in figure 6A, one of the two side walls 70 of the plate 7 is provided with a selector 10 which controls the aforementioned adjustment device 9 to move it between the bottom 72 of the plate and at least one of the aforementioned first 60 or second 61 levers in at least one lifting operative position. The selector is advantageously fitted on the side wall 70 of the plate 7. Preferably, the adjustment element is a wedge having a first surface 90 for sliding and engaging on the surface of the tray 4 opposite to the one for placing the objects and a second surface 91 for engagement with one of the first 60 and second 61 levers, preferably with the first lever 60 as reported in figure 6B. More preferably, the first surface 90 slides on the bottom 72of the plate 7. In particular, the second surface 91 is inclined with respect to the first surface 90 forming a ramp with a downward development moving away from the arm 5.

[0028] Figures 6A and 6B show a first lifting condition is shown which exploits the locking of the tray 4 in a first position by engaging the above-mentioned inclined profiles 60D and 61 D, respectively of the first 60 and second 61 levers, and the bottom 72 of plate 7.

[0029] In order to obtain a second lifting condition, which is higher than the first, it will suffice to lift the tray by roto-translating it in the reverse direction, that is approaching the work surface 2, returning to a position substantially like the one shown in figure 4. At this point, the inclined profiles 60D and 61 D are freed from the bottom 72 and, as shown by the arrow in figure 7A, the selector can be moved towards the handle 71 so as to move the wedge 9 between said bottom and at least one of the inclined profiles, for example the second surface 60D of the first lever 60 (figure 7B). In this position, the ramp of the second surface 91 of the wedge abuts against the inclined profile 60D, while the first surface 90 remains abutting against the bottom 72 of the plate 7.

[0030] According to a further embodiment of the invention, as shown in figures 8A-8C, the system for moving the object-holder tray 4 also comprises a mechanism 11 for reversibly locking the extracted position of the arm 5. This mechanism advantageously allows to maintain the arm stationary not only when lowering the tray 4, but it also allows to prevent inadvertent impacts from pushing the tray towards the work surface 2 knocking down the objects placed thereon.

[0031] In particular, the locking mechanism 11 comprises a tooth 12 protruding from the lower surface 52 of the arm 5, that is the surface facing towards the track 35 sliding along the work surface 2, so as to abut against said sliding track when the arm is extracted from the housing 3 and the tray 4 is fully outside the housing. Advantageously, the tooth is automatically activated upon removing the arm and it remains in locking position until it is deactivated manually.

[0032] As a matter of fact, as explained above, the arm 5 is slidably mounted on a track 35 fixed on the bottom 34 of the housing 3 under the work surface 2 (figure 8A). The lower surface 52 of the arm 5 comprises a seat 53 in which the tooth 12 is housed. This tooth at least partly elastically protrudes from said seat and it can be retracted totally when the arm 5 transversely traverses the track 35 both towards the extraction and towards the retraction in the housing.

[0033] Preferably, the tooth 12 comprise a first end 13 that is pivoted and totally housed in said seat 53 towards the part closest to the second end 51 of the arm 5, and a secondend 14 free to protrude with respect to the seat 53. Between said first and second ends, there is fixed an elastic element 15 which maintains the second end 14 of the tooth 12 protruding from the lower surface 52 of the arm 5. This configuration allows to create an inclined plane of the tooth 12 having the inclination towards the second end 51 of the arm 5.

[0034] As shown in figure 8A, when the arm 5 is extracted from the housing 3, the locking tooth 12 protrudes from the lower surface 52 until it abuts against the longitudinal side 35A of the track 35, that is the side facing towards the internal of the housing 3. Given that the first end 13 is inside the seat 53 of the lower surface 52 of the arm 5 and the inclined plane progressively protrudes as it proceeds towards the second end 14, the aforementioned extraction is facilitated by the guide element created by the development of the inclined plane on the track 35. Sliding transversely to the track to extract the track 4, also the second end 14 of the tooth 12 is pushed into the seat 53 (figure 8B) overcoming the thrust force of the elastic element 15.

[0035] Once the track 35 has been overcome transversely (figure 8C), the second end 14 is once again free to protrude from the seat 53 under the thrust of the elastic element 15. At the same time, the tray 4 is totally outside the housing 3 of the piece of furniture and far from the perimeter edge of the work surface 2, so that it can be freely lifted and positioned at the desired height as explained above.

[0036] Advantageously, with the position taken in figure 8C, the tray 4 may be moved along the work surface or it may be lowered without the drawback of moving in an unwanted fashion toward the inside of the housing 3. As a matter of fact, now the second end 14 abuts against the outer longitudinal side 35B of the track 35. This condition blocks the aforementioned unwanted movement toward the inside of the housing.

[0037] It should be observed that once there no longer arises the need for the objectholder tray 4, the latter can once again be positioned in the housing 3 under the work surface 2 by simply pressing the tooth 12, preferably near its second end 14, so as to overcome the force of the elastic element and make it recede into the seat 53. Now, the object-holder tray 4 can be pushed into the housing.

[0038] According to a further embodiment of the invention, the lifting of the object-holder tray 4 may be obtained with a pantograph mechanism 16, as shown in figures 9-10. In this different solution, two articulated levers (not shown) for each side of the arm 5 are connected to each other in a cross-like fashion by a rotation pin (not shown) and the respective ends are connected on one side to the second end 51 of the arm and on theother side to said tray 4 (figure 1 OA). A cam system (not shown) also allows to reversibly lock the pantograph lifting levers.

[0039] In the light of the above, it is clear that the drawbacks of the prior art mentioned above have been overcome and significant advantages have been achieved.

[0040] Firstly, the versatility limits of the pieces of furniture of the prior art provided with an object-holder tray which can be extracted from a space arranged beneath the work surface have been overcome. As a matter of fact, now the tray may be lifted in the object holder position or lowered so as to be positioned under the work surface when not being used.

[0041] Secondly, the safety of the operators is increased by locking the extracted position of the tray which, therefore, allows the operator to always have objects and tools always within reach even in case of emergencies.

[0042] Furthermore, the lifted position may take various heights so as to meet various needs. As a matter of fact, not only can the tray be positioned above the work surface, but it can also be positioned at different heights so as to adapt to any operator. As a result, the ergonomics of the working position for an operator, such as for example a dentist, a dental technician or a dental hygienist, is optimised and, at the same time it allows for great practicability.

[0043] Numerous variants of the work furniture comprising a movement mechanism for an object-holder tray according to the present invention may be adopted by the person skilled in the art, without departing from the scope of protection as defined by the attached claims.

[0044] For example, the object-holder tray may be connected to the underlying plate through a rotary engagement which allows them to rotate for a fine positioning with respect to the operator. The shapes and sizes of the individual elements which form the piece of furniture may vary depending on the specific needs or preferences.

[0045] The reversible locking mechanism of the extracted position of the arm 5 described for articulated quadrilateral lifting of the tray may also apply to the pantograph variant.

Claims

CLAIMS1. Work furniture comprising a work surface (2), a housing (3) underneath said work surface and an object-holder tray (4) capable of being alternatively housed in said housing or extracted from it by means of an extendable arm (5), characterised in that said object-holder tray (4) can be lifted on said arm (5) by means of a lifting mechanism (6, 16) so that the tray can be positioned outside the housing at least one height with respect to said work surface (2) and reversibly locked there.

2. Work furniture according to claim 1 , wherein said lifting mechanism (6) is an articulated quadrilateral comprising four levers (60, 61 ) rotatably pivoted with a first end (60A, 61 A) thereof on one end (51 ) of said arm (5) adapted to protrude from said housing (3), and with their second end (60B, 61 B) thereof on said tray (4).

3. Furniture according to claim 2, wherein said four levers are a first lever (60) rotatably constrained on one side to the arm (5) by means of a first end (60A) at the terminal edge of the second end (51 ) of the arm, and on the other side rotatably constrained to said tray (4) by means of a second end (60B), and a second lever (61 ) rotatably constrained on one side to the arm (5) by means of a first end (61 A) away from said edge of the second end (51 ) of the arm, and on the other side rotatably constrained to said tray (4) by means of a second end (61 B).

4. Furniture according to claim 3, wherein said first (60) and second (61 ) levers are fixed to the tray (4) by means of the interposition of a plate (7) comprising a generally flat bottom (72) and two side walls (70) which rise from said bottom substantially orthogonally and parallel to the arm (5), the bottom being fixed on the side of the tray opposite to the support side and said first (60) and second (61 ) levers being pivoted on each of the side walls by means of their respective second ends (60B) and (61 B).

5. Furniture according to claim 4, wherein each second end (60B, 61 B) of said first (60) and second (61 ) levers has a rounded profile that connects on one side with a straight profile (60C, 61 C) and on the other side with an inclined plane profile (60D, 61 D), said inclined plane profiles being such as to abut against said bottom (72) of said plate (7) to lock the tray (4) in a lifted position with respect to the arm (5).

6. Furniture according to any of claims 2 to 5, wherein said levers (60, 61 ) are connected two by two transversely with respect to the arm (5) by means of bridges (8) for strengthening the quadrilateral (6).

7. Furniture according to any of claims 1 to 5, further comprising an element (9) for adjusting the height of the object-holder tray (4).

8. Furniture according to claim 6, wherein said regulating element (9) is a wedge having a first surface (90) for sliding and engaging with the surface of the tray (4) opposite to that supporting the objects, or on the bottom (72) of the plate (7), and a second surface (91 ) for engaging with one of the first (60) and second (61 ) levers, the second surface (91 ) being inclined with respect to the first surface (90) forming a ramp with a downward trend away from the arm (5) so as to rest on said inclined profile (60D, 61 D) of said first (60) and second (61 ) levers.

9. Furniture according to claim 6 or 7, further comprising a selector (10) which controls said regulating element (9) to move it between the bottom (72) of the plate (7) and at least one of said first (60) and second (61 ) levers.

10. Furniture according to any of claims 1 to 7, further comprising a mechanism (11 ) for reversibly locking the extracted position of the arm (5) comprising a tooth (12) elastically protruding from the lower surface (52) of the arm (5) so as to abut against a rail (35) for sliding the arm along the work surface (2), when the arm is extracted from the housing (3).

11. Furniture according to claim 8, wherein said tooth (12) comprises a first end (13) hinged and totally housed in a seat (53) obtained on the lower surface (52) of the arm (5), the first end being also closer to the second end (51 ) of the arm itself, the tooth also comprising a second end (14) free to alternatively protrude or retract into the seat (53), between said first and second ends being then fixed an elastic element (15) which keeps the second end (14) of the tooth (12) protruding from the lower surface (52) of the arm (5).

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