FR2743279A1 - SPRING ARMATURE FOR MATTRESSES AND BEDS, AND MANUFACTURING METHOD - Google Patents

Abstract

This is a frame (10) with springs for mattresses and box springs comprising compression springs (13) made of metal wire, the two ends of which form supporting structures (14) arranged in a matrix in the two main faces of the frame. , the supporting structures which belong to two neighboring transverse lines in the same main face of the frame, being connected together by a helical connecting spring (17). To strengthen certain parts of the reinforcement, some of the supporting structures are deformed, so as to at least partially take up the longitudinal play initially existing between these supporting structures and the connecting springs.

Description

Spring frame for mattresses and box springs, and manufacturing process.

  The present invention relates to spring frames for mattresses and box springs, and methods of

manufacture of such frames.

  The spring frames in question here

  are those which have two main sensitive faces-

  flat planes which are separated by a certain thickness and which are delimited by two longitudinal edges and two transverse edges, these reinforcements each comprising a plurality of compression springs which are made of metal wire wound in turns and which extend in thickness of said frame between two ends each forming a bearing structure, the bearing structures of

  different compression springs forming the main faces

  blades of the frame and being arranged in a row in rows parallel to the longitudinal edges and in lines parallel to the transverse edges, the supporting structures which belong to two adjacent transverse lines, in the same main face of the frame, being connected together by a spring of connection constituted by a helical metallic wire which passes around the metallic wires

  adjacent respectively belonging to the supporting structures

  of these two transverse lines.

  A general problem which arises in all reinforcement with springs of the kind in question, is to adapt their firmness according to the needs, on all or part of their surface, and this without having to entirely modify their

design.

  Of course, we already know how to adapt the overall firmness of a spring reinforcement, using a more or less large wire to constitute all

  compression springs of this frame.

  But this requires to multiply the types of spring metal wires used within each unit of

  manufacturing, which is never desirable.

  There are also methods for locally adapting the firmness of a spring reinforcement so that this reinforcement has firmer zones and less firm zones: - for reinforcements made of compression springs independent of each other, GB documents -A-0 760 958, US-A-4 052 760 and US-A-4 161 046 teach to realize some of the compression springs with a metallic wire of larger diameter in the places where it is desired that the armature springs be firmer; but here again, this makes it necessary to multiply the diameters of spring metal wires used within each manufacturing unit, which makes the manufacturing process more complex and obliges to increase the stocks of metal wires;

  - for reinforcements with compression springs -

  Zion form continuous longitudinal bands of metal son, WO-A-92/00693 teaches to use longitudinal bands made of a metallic wire of larger diameter for the longitudinal edges of the frame; but this process requires multiplying the diameters of spring metal wires used in each manufacturing unit; - And for a particular type of reinforcement whose compression springs form continuous longitudinal strips of metal wires, document US-A-4 705 079 teaches to cut in places the metal wire which

  constitutes each of these longitudinal strips for weakening

  locally blinding said longitudinal strips, thereby creating less firm zones in the spring reinforcement; but on the one hand, this process risks making the spring reinforcement less durable due to the local weakening which it undergoes, and on the other hand, the metallic wires which have been cut to locally weaken the spring reinforcement risk possibly puncture or damage the layers

  padding the mattress or box spring.

  The object of the present invention is in particular to overcome the aforementioned drawbacks, by proposing a method which makes it possible to locally or globally adapt the firmness of a spring frame, without substantially increasing the cost or the complexity of the manufacture of this frame, and which allows if necessary to produce transverse bands of different firmness extending over the entire

width of the spring frame.

  To this end, the invention provides a method of manufacturing a spring frame for mattresses and box springs comprising the following preliminary step: a) making a spring frame of the kind in question, all the load-bearing structures of which are engaged in the springs connecting with a certain play in the longitudinal direction, this method being characterized in that it further comprises the following subsequent step: b) deforming at least some of the bearing structures belonging to at least one main face of the frame, to at least partially make up for the above-mentioned clearance in the longitudinal direction, at least some of the deformed bearing structures not being

  adjacent to the transverse edges of the frame.

  It should be noted that this process does not normally induce

  dimensional variation of the spring frame.

  In preferred embodiments of the method according to the invention, recourse is also had to one and / or the other of the following arrangements: - the supporting structures are sufficiently deformed so that they are engaged in the springs of connection without play in the longitudinal direction, the deformed bearing structures then pressing against the interior of the two adjacent connection springs; - at least one main face of the frame has a firmed central zone which separates two non-firmed end zones adjacent to the transverse edges

  of the reinforcement, and the supporting structures which are deformed

  més within said main surface, during step b) above, are located in the central area strengthened by this main face;

  - at least all the load-bearing structures are deformed

  which are not adjacent to the longitudinal edges of

  the armature and which belong to several transverse lines

  dirty neighbors of each other; - The load-bearing structures adjacent to the edges of the frame are not deformed, the method further comprising a step consisting in fixing said bearing structures adjacent to the edges of the frame to at least one rigid frame; - the compression springs and the load-bearing structures form continuous longitudinal strips of metal wire, each load-bearing structure not adjacent to a transverse edge of the frame being common to two springs of

  adjacent compression belonging to the same longitu-

  dinale, this supporting structure with two branches

  lateral substantially parallel to the transverse direction

  dirty and interconnected by a base, these two lateral branches extending in the same direction from the base, to ends extended by the two adjacent compression springs, each connecting spring passing around two lateral branches adjacent respectively belonging to two neighboring supporting structures, and the aforementioned step b) consisting in deforming the base of at least some of the supporting structures to reduce the clearance between the lateral branches of these supporting structures

  and the connecting springs, in the longitudinal direction.

  the above-mentioned step b) consists in folding the base of at least certain load-bearing structures, in a V towards the inside of the two branches of said load-bearing structures, these two branches then extending slightly diagonally outwards from the base; the various compression springs are formed by as many independent metal wires, each of these metal wires having ends rigidly fixed at an intermediate point of said metal wire to form two closed terminal turns which constitute the load-bearing structures of the compression spring and who enter

  inside the connecting springs, step b) above-

  born consisting of deforming in the transverse direction at

  minus an intermediate portion of some turns

  the intermediate portion which is located between two adjacent connecting springs for the terminal turns not adjacent to the transverse edges of the frame; the aforementioned step b) consists in folding said intermediate portion of the terminal turns concerned,

  radially inward of these turns.

  Furthermore, the invention also relates to a spring frame of the kind in question, characterized in that in at least one of the main faces of the frame, at least some of the supporting structures not adjacent to the transverse edges of the frame , hereinafter said firmed bearing structures, bear parallel to the longitudinal direction against the inside of the two connecting springs which are fixed to said bearing structures, thereby eliminating any play between the structures

  firmer bearing beams and adjacent connecting springs.

  In preferred embodiments of the frame according to the invention, recourse is also had to one and / or the other of the following arrangements: at least one of the main faces has a firm central zone which separates two zones end

  not firm adjacent to the transverse edges of the arma-

  structure, and all the load-bearing structures strengthened on this main face belong to said central area, - the reinforcement comprises several adjacent transverse lines of load-bearing structures in which at least

  the load-bearing structures not adjacent to the longitudi-

  nals of the reinforcement are reinforced load-bearing structures, - the compression springs and the support structures form continuous longitudinal strips of metal wire, each load-bearing structure not adjacent to a transverse edge of the reinforcement being common to two springs of

  adjacent compression belonging to the same longitu-

  dinale, this supporting structure with two branches

  lateral substantially parallel to the transverse direction

  dirty and interconnected by a base, these two lateral branches extending in the same direction from the base, to ends extended by the two adjacent compression springs, each connecting spring passing around two lateral branches adjacent respectively belonging to two neighboring supporting structures, and each lateral branch of the reinforced supporting structures pressing parallel to the longitudinal direction, against at least two points of the interior of the corresponding connecting spring, - the base of each reinforced supporting structure s 'extends substantially V-shaped inwardly of the two lateral branches of this supporting structure, while said lateral branches extend slightly diagonally outward from the base, these two lateral branches pressing against the inside of the corresponding connecting springs, towards each other in the vicinity of the base, and towards the outside their ends remote from the base, - the different compression springs are formed by as many separate metal son, each of these metal son having ends rigidly secured to an intermediate point of said wire to form

  two closed terminal turns which constitute the structures

  load bearing of the compression spring and which penetrate

  inside the connecting springs, and each turn ends

  which constitutes a firming supporting structure presented

  both an intermediate portion which is located between two neighboring connecting springs and which is radially folded

towards the inside.

  Other characteristics and advantages of the invention

  tion will appear during the following description of

  two of its embodiments, given by way of example

  ples nonlimiting, with reference to the accompanying drawings.

In the drawings,

  - Figure 1 is a block diagram in perspective

  tive illustrating a mattress capable of comprising a spring frame according to the invention, - Figure 2 is a partial perspective view of a first spring frame usable in the mattress of Figure 1, - Figure 3 is a view of partial top of the spring frame of Figure 2, - Figure 4 is a partial top view of the frame of Figure 2, illustrating a phase of the manufacturing process of this frame, - Figure 5 is a view schematic in perspective of a compression spring which is part of a second frame capable of being used in the mattress of Figure 1, - Figure 6 is a partial top view of the frame of which the spring Figure 5, - and Figure 7 is a partial top view of the frame of Figure 6, illustrating a phase of the process

manufacturing this frame.

  In the different figures, the same references

  denote identical or similar elements.

  Figure 1 shows a mattress 1, or if necessary a box spring, which is constituted by a frame

  interior with springs covered by a filling.

  The mattress 1, like the spring reinforcement it contains, has a parallelepiped shape with two main faces 2, 3 which, in use, are horizontal and which extend along a longitudinal axis X (corresponding to the length of the mattress) and along an axis

  transverse Y (corresponding to the width of the mattress).

  These two main faces 2, 3 are delimited laterally by two longitudinal edges 4 and by two transverse edges 5, these edges 4, 5 extending over the thickness of the mattress along an axis Z perpendicular to the axes X,

Above mentioned.

  Figures 2 to 5 show a first frame

  with springs 10 usable in the mattress of FIG. 1.

  It is a spring frame consisting of a plurality of longitudinal strips 11 continuous in wire

  metallic, which are juxtaposed in the transverse direction

dirty.

  As we can see in particular on the fig-

  re 2, each longitudinal strip 11 can be produced as taught in particular in document DE-1 155 218 from

a single metal wire 12.

  The metal wire 12 is wound in turns to form compression springs 13, the turns of the

  different compression springs being wound alternately

  tively in one direction and in the other from one spring 13 to the other. These compression springs 13 are connected to each other in pairs, by crossing some of their

intermediate turns.

  In addition, the compression springs 13 are also interconnected by connecting sections 14 which are formed in the same metal wire 12 as said

compression springs.

  These connecting sections 14 initially initially all have a U-shaped plan comprising on the one hand a base 15 which extends in the longitudinal direction X, and on the other hand two lateral branches 16 which extend in the transverse direction Y. These two lateral branches 16 both extend in the same direction from the base 15, to ends which extend towards the inside of the frame to constitute the springs of

compression 13.

  The connecting sections 14 are arranged alternately

  in the main faces 2 and 3 of the frame.

  The different connecting sections 14 are matrically juxtaposed in longitudinal rows and in transverse lines in the two main faces of the frame, so that these connecting sections constitute bearing structures which effectively support the

filling the mattress 1.

  Furthermore, the different longitudinal strips 11 are connected to each other by connecting springs 17, which extend in the transverse direction

  Y in the two main faces 2, 3 of the frame.

  These connecting springs 17 are wound around the lateral branches 16 adjacent to the connecting sections 14

  successive, initially with a certain play in the direction

  longitudinal, at least as long as the main faces

  of the frame are not subject to any load.

  Finally, each of the main faces 2, 3 of the frame can, if necessary, be bordered by a rigid frame 18 which follows the longitudinal 4 and transverse edges of the frame and which is fixed to the connecting sections 14

adjacent by fasteners 19.

  Optionally, the frame 18 can be provided only-

  ment on one of the two main faces of the frame, in particular when the mattress 1 contains two superimposed frames 10, separated by a flexible layer, in which case the frame 18 can be provided only on the face of each

  frame which is arranged towards the inside of the mattress.

  According to the invention, in order to make certain areas of at least one of the main faces 2, 3 of the reinforcement 10 firmer, the bases 15 of the connecting sections 14 located in these areas are deformed (before or after installation rigid frames 18), so as to reduce the clearances which exist initially in the longitudinal direction between the lateral branches 16 of these connecting sections

and the connecting springs 17.

  Preferably, the bases 15 concerned are sufficiently deformed to eliminate any play between the corresponding lateral branches 16 and the connecting springs 17, the lateral branches 16 in question then being in elastic abutment against the interior of the two adjacent connecting springs 17, even when the main faces 2, 3 of

  the frame 10 is not subjected to any load.

  Thanks to these provisions, when a user of the mattress 1 leans on one of the zones o the sections of

  link 14 were deformed, the support force of the user

  tor is taken up not only by the compression springs

  sion located immediately under the fulcrum, but also by the neighboring portions of the frame, and this from the start of the support, since the deformed connecting sections 14 are connected without longitudinal play to the sections of

link 14 neighbors.

  On the other hand, in the areas where the connecting sections 14 have not been deformed, support from the user results first of all in a vertical displacement of the sections

  link 14 not deformed, to compensate for the longitu-

  which exists with the adjacent connecting springs 17.

  Consequently, the zones where the connecting sections 14 have been deformed are firmer than the zones where the

  connecting sections 14 have not been deformed.

  Advantageously, as shown in FIG. 1, each of the firmed areas of the reinforcement may consist of a central transverse area 6 of a main face, which separates two end areas 7, 8 which are not firmed at

  vicinity of the transverse edges 5 of the frame.

  The firmed central zone can for example represent substantially the central third of the main firmed face. Advantageously, in the firmed zone 6, all the connecting sections 14 are deformed, with the exception of the ll

  sections 14 adjacent to the longitudinal edges 4 of the arma-

  ture, which are advantageously left undeformed so as not to interfere with the proper fixing of these sections of

connection to the rigid frame 18.

  Optionally, an entire main face of the frame could be strengthened by deformation of all the connecting sections 14 of this main face, preferably with the exception of the connecting sections 14 which are

  adjacent to the longitudinal edges 4 or to the transverse edges

  saux 5 of the frame, so as not to interfere with the fixing of said connecting sections on the corresponding frame 18. Preferably, as shown in FIG. 3, the deformation which is imposed on the connecting sections 14 in order to strengthen the reinforcement, consists in bending the base 15 of the

  connecting sections 14 concerned in the form of a V towards the interior

  of the two corresponding side branches 16.

  These lateral branches 16 then extend slightly.

  obliquely outwards from the base 15, and these lateral branches bear elastically against the inside of the connecting springs 17 inwards in the vicinity of the base 15 and outwards in the vicinity of

  their ends far from the base.

  These deformations of connecting sections 14 can be obtained for example by successively arranging each

  face of the frame 10 which must have refined areas

  mies on a machine tool having a plurality of dies 20 and folding fingers 21. These dies and these folding fingers respectively engage on either side of the different deformed bases, each die 20 having a notch 22 in shape of V next to the

corresponding folding finger 21.

  The folding fingers 21 are then moved simultaneously

  nement towards the notches 22 in the direction of the arrows 23, which produces the desired deformations of sections

link 14 concerned.

  Preferably, the two main faces of the frame 10 have firmed areas, but of course, the frame 10 may also have a single main face firmed, in particular when it is a box spring frame or when the inside the mattress 1 is constituted by two superimposed reinforcements 10 separated by a flexible layer, in which case only the main faces of the reinforcements 10 which are oriented towards the outside of the mattress

have firmer areas.

  In the embodiment shown in the

  Figures 5 to 7, the spring frame 30 which forms the interior

  Laughing mattress 1 of Figure 1 is constituted by the

  juxtaposition of independent compression springs 31.

  As shown in Figure 5, each of these springs 31 is constituted by a metallic wire 32 wound

  in turns, for example in a biconical form.

  Each spring 31 has two end turns which are closed on themselves by a knot 34 or another fixing of the ends of the metal wire 32 in one

point of this thread 32.

  The terminal turns 33 are substantially flat and included in the main faces 2, 3 of the frame, and

  they constitute load-bearing structures for the lining

mattress wise 1.

  Within each main face of the frame, the terminal turns 34 are distributed in a matrix, in rows along the longitudinal direction X of the frame, and in lines along the transverse direction Y of said frame. In addition, in each main face of the frame, the end turns 33 are connected to each other from one transverse line to the other by helical connecting springs 35 which extend transversely and which are each wound around the adjacent portions of the metal wires 32 constituting two terminal turns 33

  neighbors in the longitudinal direction.

  Finally, the frame may also include frames

  similar to the frames 18 already described for the frame 10.

  The terminal turns 33 are initially all engaged with play in the connection springs 35, then at least some of these end turns are deformed, so as to limit this play and preferably to eliminate it, each deformed end turn 33 then pressing against the inside the connecting springs 35 in which it

is engaged.

  These deformations make it possible to firm up at least certain zones of at least one of the main faces of the frame 30, as already explained above for

the frame 10.

  The distribution of the terminal turns 33 deformed within the frame 30 may be similar to the distribution of the connecting sections 14 deformed within the frame 10

previously described.

  As shown in FIG. 6, the deformations imposed on at least some of the end turns 33 may in particular consist of a curvature, directed radially inwards in the transverse direction Y, this curvature being formed in at least one intermediate portion 36 located between two neighboring connecting springs 35, which causes a certain ovalization of the turns

33 corresponding terminals.

  As shown in Figure 7, this bending can be achieved for example by placing the face (s)

  main concerns of the frame 30 on a machine

  tool having groups of three folding fingers 37, 38, 39, which engage respectively on the turns

terminals 33 to be deformed.

  Each of these groups of folding fingers comprises two folding fingers 37, 38 which engage inside the corresponding end turn 33, and a folding finger 39 which is located outside the corresponding end turn 33 and which is movable in the direction of the arrow 40 towards the two fixed fingers 37, 38 to fold the

  terminal turn 33 forming the curve 36.

Claims (15)

  1. Method for manufacturing a spring frame for mattresses and box springs, comprising the following preliminary step:   a) make a spring frame (10, 30) present   both two main faces (2, 3) substantially planar which are separated by a certain thickness and which are delimited by two longitudinal edges (4) and two transverse edges (5), this frame comprising a plurality of compression springs (13, 31 ) which are made of wire   metallic wound in turns and which extend in the thick-   of said frame between two ends, each forming a bearing structure (14, 33), the bearing structures of the various compression springs forming the main faces (2, 3) of the frame and being arranged in rows parallel to the longitudinal edges   and in lines parallel to the transverse edges, the structures   load-bearing resins which belong to two adjacent transverse lines, in the same main face of the reinforcement, being   connected together by a connecting spring (17, 35) made up   killed by a helical metallic wire which passes around the adjacent metallic wires belonging respectively to   load-bearing structures (14, 33) of these two transverse lines   the neighbors, all the supporting structures of this frame being engaged in the connecting springs with a certain play in the longitudinal direction, this method being characterized in that it also comprises the following subsequent step: b) deforming at least some structures   load-bearing (14, 33) belonging to at least one main face   blade of the frame, to at least partially make up for the above-mentioned clearance in the longitudinal direction, at least some of the deformed bearing structures not being   adjacent to the transverse edges (5) of the frame.   2. Method according to claim 1, wherein, during the aforementioned step b), the supporting structures (14, 33) are sufficiently deformed so that they are engaged in the connecting springs (17, 35), without play in the longitudinal direction, the deformed supporting structures (14, 33) then pressing against the inside of the   two adjacent connecting springs (17, 35).   3. Method according to any one of the claims   above, in which at least one main face of the reinforcement has a central central area (6) which   separates two adjacent end zones (7, 8) which are not firmed up   tes at the transverse edges of the frame, and in which all the supporting structures (14, 33) which are deformed within said main face during the aforementioned step b), are located in the central zone (6) firming of this main face.   4. Method according to any one of the claims   previous, in which, during step b) above-   born, at least all the supporting structures (14, 33) which are not adjacent to the longitudinal edges (4) of the frame and which belong to several lines are deformed   transverse neighbors of each other.   5. Method according to any one of the claims   previous ones, in which the structures are not deformed   load-bearing (14, 33) adjacent to the edges (4, 5) of the frame   re, the method further comprising a step consisting in fixing said bearing structures close to the edges of   the frame has at least one rigid frame.   6. Method according to any one of the claims   previous, in which the compression springs (13) and   the supporting structures (14) form longitudinal strips   nales continuous (11) in metal wire, each supporting structure not adjacent to a transverse edge (5) of the frame being common to two adjacent compression springs (13) belonging to the same longitudinal strip, this structure   bearing having two lateral branches (16) sensitive-   parallel to the transverse direction (Y) and interconnected by a base (15), these two lateral branches extending in the same direction from the base, up to   ends extended by the two compression springs   adjacent sion (13), each connecting spring passing around two adjacent lateral branches (16) belonging respectively to two adjacent supporting structures (14), and the aforementioned step b) consisting in deforming the base (15) of at least some of the supporting structures to reduce the clearance between the lateral branches (16) of these supporting structures and the connecting springs (17), in the longitudinal direction.   7. Method according to claim 6, in which the aforementioned step b) consists in folding the base of at least certain load-bearing structures, in a V towards the inside of the two branches of said load-bearing structures, these two   branches then extending slightly diagonally outwards laughing from the bottom up.   8. Method according to any one of claims   1 to 5, in which the various compression springs (31) are formed by as many independent metal wires   (32), each of these metallic wires having extremi   tees rigidly fixed at an intermediate point (34) of said metal wire to form two closed end turns (33) which constitute the load-bearing structures of the compression spring and which penetrate inside the connection springs (35), step b ) mentioned above consisting of deforming   in the transverse direction at least one intermediate portion   diary (36) of certain terminal turns, intermediate portion   diary which is located between two adjacent connecting springs (35) for the terminal turns not near the edges transverse (5) of the frame.   9. The method as claimed in claim 8, in which the abovementioned step b) consists in folding said intermediate portion (36) of the terminal turns (33) concerned,   radially inward of these turns.   10. Spring frame (10, 30) for mattresses and box springs capable of being manufactured by a method according to claim 2, this frame having two main faces (2, 3) substantially planar which are separated by a certain thickness and which are delimited by two longitudinal edges (4) and two transverse edges (5), this frame comprising a plurality of compression springs (13, 31) which are made of metal wire wound in turns and which extend in the thickness of said reinforcement between two ends each forming a supporting structure (14, 33), the supporting structures of the various compression springs forming the main faces (2, 3) of the reinforcement and being arranged in rows in parallel rows to the longitudinal edges and in parallel lines at the transverse edges, the supporting structures which belong to two neighboring transverse lines, in the same main face of the reinforcement, being connected ées together by a connecting spring (17, 35) consisting of a helical metal wire which passes around the metal son   adjacent respectively belonging to the supporting structures   tes of these two adjacent transverse lines, characterized in that, in at least one of the main faces of the frame, at least some of the bearing structures (14, 33) not adjacent to the transverse edges (5) of the frame, called hereinafter firmer bearing structures, are based   parallel to the longitudinal direction against the interior   of the two connecting springs (17, 35) which are fixed to said load-bearing structures, thus eliminating any play between the firmed load-bearing structures and the springs of adjacent links.   11. Reinforcement according to claim 10, in which at least one of the main faces (2, 3) has a firmed central zone (6) which separates two unarmed end zones (7, 8) adjacent to the transverse edges (5) of the reinforcement, and in which all the firming supporting structures (14, 33) of this face   main belong to said central area (6).   12. Reinforcement according to any one of the claims.   tions 10 and 11, comprising several adjacent transverse lines of bearing structures (14, 33) in which at least the bearing structures not adjacent to the longitudinal edges (4) of the frame are bearing structures your firmings.   13. Reinforcement according to any one of the claims.   tions 10 to 12, in which the compression springs (13) and the supporting structures (14) form continuous longitudinal strips (11) of metal wire, each supporting structure (14) not adjacent to a transverse edge   (5) of the armature being common to two compression springs   adjacent zion (17) belonging to the same longitudi-   nale, this supporting structure having two lateral branches (16) substantially parallel to the transverse direction (Y) and connected together by a base (15), these two lateral branches extending in the same direction from the base, up to '' at ends extended by the two adjacent compression springs (13), each connecting spring (17) passing around two adjacent lateral branches (16) belonging respectively to two adjacent supporting structures (14), and each lateral branch of the structures load-bearing firmers leaning parallel to the longitudinal direction, against at least two points of   inside the corresponding connecting spring.   14. Reinforcement according to claim 13, in which the base (15) of each firm supporting structure (14) extends substantially in a V shape towards the inside of the two lateral branches of this supporting structure, while said lateral branches are 'extend slightly diagonally outward from the base, these two lateral branches pressing against the interior of the corresponding connecting springs (17), towards each other in the vicinity of the base, and towards outside to their   ends far from the base.   15. Reinforcement according to any one of the claims.   tions 10 to 12, in which the various compression springs (31) are formed by as many independent metal wires (32), each of these metal wires having   ends rigidly fixed each at an intermediate point   diary (34) of said metal wire to form two closed end turns (33) which constitute the supporting structures of the compression spring and which penetrate inside the connection springs (35), each turn   terminal (33) which constitutes a refined bearing structure   crank having an intermediate portion (36) which is located between two neighboring connecting springs (35) and which is folded radially inward.