EP0700479B2 - Key with double extremity ramp for security cylinder, corresponding cylinder and assembly comprised of such key and cylinder - Google Patents

Abstract

Key (10) for a security cylinder comprising a handling element linked to an elongate key body having a rectilinear longitudinal axis, said key body being intended to be inserted into a key housing of said cylinder and being entirely comprised between, on the one hand, two parallel lateral planes and, on the other hand, two longitudinal edges situated between the two lateral planes, one of said edges forming the back (14) of the key body and the other edge being an active edge (15) intended to cooperate with the keying members of the securing cylinder, the back (14) and the active edge (15) being interconnected by a profile section comprising at the vicinity of the back (14) a longitudinal groove (11), with the free extremity area of the key body which is opposite to the handling element being at least partially oblique with respect to the longitudinal axis of the key body, the free extremity region of the key body comprising a first ramp (21) and a second ramp (22) which is offset with respect to the first ramp (21) in the insertion direction of the key (10) in the key housing of the cylinder, both ramps (21, 22) forming acute angles with the longitudinal axis of the key body.

Description

The present invention relates to a safety barrel intended to be operated by a key, for example for the drive of the moving parts of a lock. The invention also concerns the key corresponding to this barrel and the assembly constituted by the barrel and the key which associated with it.

We know that we are looking for, permanently, to improve the security of the safety barrels, that is to say to make it more difficult to break and enter. Conventionally, a safety barrel is made up a stator, inside which can rotate a rotor operated by a key; the key is engaged in a housing wrench made longitudinally in the rotor; to block the rotation of the rotor relative to the stator in the absence of the right key, we use a plurality of organs keying. According to a common embodiment, a locking member consists of a pin rotor and stator pin placed inside of the same bore, the stator pin being pushed by a spring in the direction of the rotor axis; when the key is in position in its housing, the border active key, which has teeth, positions each rotor pin so that the interface (rotor pin / stator pin) is exactly at the interface (rotor / stator) and, in these conditions, the rotor can rotate relative to the stator. We see that, in such a device, it is necessary the rotor pins protrude into the housing key to cooperate with the active border of the key.

However, this provision allows break-in specialists, rotate the rotor with a simple tool, usually called "hook". By means of this tool, a torque is exerted on the rotor which causes the rotor to be blocked by that of the pins which has the least play in his home; at this time in pulling the hook over the entire length of the rotor, we just successively push in all the pins and, in particular, that which ensured the blocking (rotor / stator): at this moment the rotor turns a slight angle which brings it to be blocked by another pin, as soon as the couple rotation is maintained by means of the hook. We see so that, by this technique, a specialist can, after n longitudinal displacements of the hook, make turn the rotor of a barrel with n keying.

We have already proposed to strengthen the security of this type of barrel by adding to the classic device of pins, which has just been described, of the auxiliary devices like, for example, side pins coming lean on the lateral flanks of the key body in footprints provided for this purpose. We also offered to put in the body a body mobile likely to push a rotor pin when the key is in the correct position in his home. These devices certainly make the more difficult housebreaking but they are relatively expensive considering the complexity of the barrel correspondent and related keys.

The object of the present invention is to describe a barrel and the corresponding key likely, despite its simplicity of construction, to make it very difficult, if not impossible, any break-in by means of a hook. According to the invention, a safety barrel is proposed. in which the elastically pushed locking member crosses the entire key housing until it is in support against a longitudinal rib provided in said housing; the keying member penetrates, by a relief, in the rib, and a residual space is provided between said rib and the wall of the key housing which makes it vis-a-vis. The key includes, at the rib of the barrel, a corresponding profile groove and can therefore be engaged in the key housing. The end of the key is cut at a bevel, so that the bottom of the groove forms, at the end of the key, a first ramp which, in the residual space, comes to press on the organ of keying to obtain the relief of the relief out of the rib during the insertion of the key; when this clearance is achieved, the toothing of the border active key comes to cooperate, by a second ramp, with the relief of the keying member, which allows the subsequent insertion of the key to the locking member next, with which the same operating mode is realised. The presence of this double ramp at the end of the key therefore allows the operation of the organ of keying while the relief carried by it is not directly accessible by the action of a hook. If the key had only one end ramp practiced on its active border, pressing the key would not be possible since this ramp would come up against against the rib, without being able to act on the relief of the locking member. Operation is not possible that thanks to the presence of two ramps: the first, located in the residual space, comes to attack the organ of keying itself, to ensure the relief of the relief, after which the second acts on the clear relief.

The realization of such a device does not present any particular complexity, which makes it possible to obtain a barrel limited cost security. However, the break-in such a barrel is extremely difficult because the hook cannot act on the relief of the locking member, which is concealed. We should therefore act with a hook directly on the locking member, in residual space, but, in this case, the hook abuts on another rotor rib, which comes below the bottom wall of the key groove; the action of this hook therefore only allows the relief to be cleared of the rib where it was concealed and, in this case, you would have to act with a second hook to push the relief, as the active border of the key would have done. Manipulating two hooks inside a space as small as the key slot is practically impossible and, in addition, the key may include, between the aforementioned groove and the active border, other grooves and ribs, so the second hook might very well not even be likely push the relief of the locking member up to the position, which ensures the release of the rotor relative to the stator. So we see that this device, despite its simplicity, gives the barrel a high degree of security.

We have already proposed, in FR-A-2 565 281, a key for safety barrel with an operating element linked to an elongated key body having a straight longitudinal axis through which the plane passes median longitudinal P1 of said key body, said body of key being intended to be inserted in a housing of key of said barrel and being entirely between, on the one hand, two lateral planes P3, P4, parallel to the longitudinal plane P1, and, on the other hand, two longitudinal edges arranged between the two aforementioned lateral planes, one of these borders constituting the back of the body of key and the other constituting an active border intended to cooperate with means for locking said barrel safety, the back and the active border being connected between them by a profile comprising, in the vicinity of the back, a longitudinal groove, the bottom of which is a wall area having, parallel to the longitudinal axis of the key body, a mean longitudinal plane P2, the border line active, which is equidistant from the two edges delimiting laterally said active border, being in a plane P3 offset transversely to the longitudinal plane medium P2, the free end area of the body of key, which is opposite to the operating element, being, at least partially oblique to the longitudinal axis of the key body. This arrangement does not allow not alone to reduce the risk of break-ins because locking devices are directly accessible to the end ramp of the active border of the key and therefore directly accessible by the action of a hook place in the key housing. In relation to the state of the technique, the key according to the invention is characterized by the fact that the free end area of the key body has a first ramp, defined at the end of the zone of the wall of the profile which delimits the groove, and a second ramp, defined at the end of the active border, the second ramp being set back from the first ramp, in the direction in which the key is pushed into the key housing of the barrel, the two ramps forming acute angles with the longitudinal axis of the key body, the second ramp cutting in its thickness the lower wall of the groove, the so-called lower wall being that which is connected to the active border of the key body.

In a preferred embodiment of the key according to the invention, the free end area of the key body is shaped like a point, a vertex being thus defined at a end of the first ramp; we can predict that the top forming the end of the key body is disposed at the middle part of the bottom of the groove. Advantageously, the median longitudinal plane P1 of the key body and the P5 average longitudinal plane of the border active are significantly confused. We prefer that the free end of the active border cuts the first ramps along an edge, the midpoint of which is a distance from the longitudinal center line of the back of key lower than that existing between said line and the face of the so-called "lower" wall of the groove, which is the further away from the back of the key, said so-called "lower" wall being that which is connected to the active border of the body of key. It is also preferred that the angle formed with the axis of the key body by the first ramp is greater than that formed with said axis by the second ramp, this which ensures the relief of the relief of the organ keying through a shorter key stroke in its housing and, therefore, shorten the total length of the key.

The present invention also relates to a safety barrel intended to cooperate with a key such as defined above, said barrel comprising a rotor cylindrical capable of rotating in a stator, a housing of key being practiced longitudinally in the rotor, keying members being arranged in the assembly (rotor / stator) and being elastically pushed in key position in the absence of a key in the housing key, unclogging only occurs if the key appropriate is placed in said key housing, each locking member being able to move in translation along a rectilinear axis, a longitudinal rib projecting laterally into the housing of key, a residual space being provided between said rib and the opposite face of said key housing, characterized by the fact that in the absence of a key, each organ elastically pushed keying through the housing key until it comes into abutment against said rib, the keying member comprising a relief which, during the abutment of the keying member against the rib, enters a recess provided for this purpose in said rib, the residual space allowing to act on the keying member to release the relief from its recess.

In a preferred embodiment, the keying consists of a rotor pin and a stator pin, arranged in the same bore, the stator pin being pushed by a spring, the pin rotor supported by one of its bases on the stator pin and bearing, on its other base, the relief which is intended to engage in the rib; we can provide that the relief is a hemispherical nipple arranged along the axis of the rotor pin which carries it and that the rotor and stator pins are cylindrical, the axis of the bore being perpendicular to the axis of the rotor. advantageously, the key housing has a longitudinal plane median, which passes through the axis of the rotor, the face of the rib on which a pin can come to bear rotor being perpendicular to said median longitudinal plane key slot.

The present invention a. finally, for object a set constituted by a barrel as defined above and a key as defined above, characterized by the fact that the first ramp of the key acts on the locking member, in the residual space provided for this purpose, the obliquity of said ramp being such that the relief of the member is released from its recess when the second ramp comes into contact with said relief.

In a preferred embodiment relating to a set comprising a barrel each of which keying consists of a rotor pin and a stator pin, it is expected that during insertion of the key in its housing, the relief rests on the active border of the key, the drawing of said border active being such that, in the driving-in position maximum of the key in its housing, the interface (pin rotor / stator pin) is brought to the level of interface (rotor / stator).

To better understand the object of the invention, we will describe it now, as an example purely illustrative and not limiting, an embodiment shown in the accompanying drawing.

• la figure 1 représente, en élévation, et partiellement avec des pointillés représentant certaines parties cachées, un barillet selon l'invention ;
• la figure 2 représente une coupe selon II-II de la figure 1 ;
• la figure 3 représente, en perspective, l'extrémité du corps de clé de la clé associée au barillet de la figure 1 ;
• la figure 4 représente une coupe selon IV-IV de la figure 3 ;
• la figure 5 représente une coupe selon V-V de la figure 1 ;
• la figure 6A représente, dans le même plan de coupe que la figure 5, la position des divers éléments au début de l'introduction de la clé, lorsque la première rampe de la clé vient au contact de la première goupille de rotor, ce plan de coupe étant repéré par la ligne VIA-VIA de la figure 6B ;
• la figure 6B représente, schématiquement, la position relative de la clé et de la goupille de rotor pour la figure 6A, la clé étant représentée en coupe selon le plan VIB de la figure 6A et étant vue selon la flèche F ;
• la figure 6C représente une vue selon la flèche F1 de la figure 6B ;
• la figure 7A représente une vue analogue à celle de la figure 6A, lorsque la clé a été légèrement enfoncée dans son logement de façon que la deuxième rampe vienne en contact avec le téton hémisphérique de la goupille de rotor ;
• la figure 7B représente une vue analogue à celle de la figure 6B pour la position d'entrée de clé correspondant à la figure 7A ;
• la figure 7C représente une vue analogue à celle de la figure 6C dans la position des éléments correspondant à la figure 7B ;
• la figure 8A représente une coupe transversale du barillet de la figure 1 dans le plan V-V pour une position d'enfoncement de la clé qui a amené l'interface (goupille de rotor/goupille de stator) au niveau de l'interface (rotor/stator) ;
• la figure 8B représente, schématiquement, la position relative de la clé et de la goupille de rotor pour la représentation de la figure 8A, le plan de coupe de la figure 8A étant désigné par VIIIA-VIIIA sur la figure 8B ;
• la figure 9 représente, en perspective, une vue partielle du rotor coupé selon un plan parallèle au plan longitudinal médian du logement de clé, les goupilles de rotor et de stator étant représentées au droit de leur logement.

On this drawing :

• Figure 1 shows, in elevation, and partially with dotted lines representing certain hidden parts, a barrel according to the invention;
• Figure 2 shows a section on II-II of Figure 1;
• Figure 3 shows, in perspective, the end of the key body of the key associated with the barrel of Figure 1;
• Figure 4 shows a section on IV-IV of Figure 3;
• 5 shows a section along VV of Figure 1;
• FIG. 6A represents, in the same section plane as FIG. 5, the position of the various elements at the start of the introduction of the key, when the first ramp of the key comes into contact with the first rotor pin, this plane of section being marked by the line VIA-VIA of FIG. 6B;
• FIG. 6B schematically represents the relative position of the key and of the rotor pin for FIG. 6A, the key being shown in section along the plane VIB of FIG. 6A and being seen according to arrow F;
• FIG. 6C represents a view according to the arrow F1 of FIG. 6B;
• FIG. 7A represents a view similar to that of FIG. 6A, when the key has been slightly inserted in its housing so that the second ramp comes into contact with the hemispherical stud of the rotor pin;
• FIG. 7B represents a view similar to that of FIG. 6B for the key entry position corresponding to FIG. 7A;
• Figure 7C shows a view similar to that of Figure 6C in the position of the elements corresponding to Figure 7B;
• FIG. 8A represents a transverse section of the barrel of FIG. 1 in the plane VV for a position of insertion of the key which brought the interface (rotor pin / stator pin) to the level of the interface (rotor / stator);
• FIG. 8B schematically represents the relative position of the key and the rotor pin for the representation of FIG. 8A, the section plane of FIG. 8A being designated by VIIIA-VIIIA in FIG. 8B;
• FIG. 9 shows, in perspective, a partial view of the rotor cut along a plane parallel to the median longitudinal plane of the key housing, the rotor and stator pins being shown in line with their housing.

Referring to the drawing, it can be seen that the barrel rotor according to the invention has been designated by 1 and by 2 the stator in which said rotor pivots. The stator 2 has, in its lower part, an extension 3, where the stator pins 4 and their associated springs are partially housed 5. For the remainder of the description, it will be assumed that the extension 3 constitutes the lower part of the barrel. Each locking member of the barrel according to the invention consists of the assembly of a rotor pin 6 and a stator pin 4, arranged inside the same cylindrical bore 16. The rotor comprises a housing key 7, arranged longitudinally in an axial plane of the rotor. Inside this key housing protrudes a longitudinal rib 8; a residual space 9 is provided between the rib 8 and the flat face 7 a of the key housing, which makes it opposite.

When the appropriate key is inserted into the housing key 7 and fully inserted into said housing, the interface (pin 6 / pin 4) is located at the interface (rotor 1 / stator 2) for each of the components for locking the barrel according to the invention. This barrel comprises a plurality of parallel keying members, whose axes are arranged along the axial plane of symmetry Q of the barrel.

Below the rib 8, in the direction of the extension 3, the key housing 7 has a profile which corresponds to that of the associated key designated by 10 as a whole; this profile comprises, on the face of the key housing which extends the flat part 7 a , two ribs 7 b , 7 c and, on the opposite face, two ribs 8 b , 8 c , offset in height with respect to the previous ones, by so that the cross section of the key housing has, below the rib 8, a sinuous shape.

The key 10 has, of course, a general profile complementary to that of the key housing 7. In return for the rib 8, the key 10 has a groove with a complementary profile 11; in return for the ribs 7 b and 7 c , there are grooves 12 b and 12 c ; in return for the ribs 8 b and 8 c , there are grooves 13 b and 13 c . The key 10 is between two lateral planes P3 and P4 and it is delimited by two transverse edges: the upper edge 14 constitutes the back of the key and is slightly rounded to adapt to the shape of the interface (rotor / stator ), the back of the key coming from said interface when the key is placed in its housing; the border opposite the back of the key has been designated by 15 and constitutes the active border of the key, that is to say that which carries the teeth intended to cooperate with the keying members to ensure their proper positioning in order to release the rotor relative to the stator. The bottom of the groove 11 is constituted by a flat wall, the mean longitudinal plane of which has been designated by P2. The active border 15 of the key is delimited laterally between two edges and the average line equidistant from these two edges is in a plane P5. The plane P5 is offset transversely with respect to the plane P2. The entire key body has a median longitudinal plane P1, which is substantially coincident with P5. The groove 11 is therefore delimited by a bottom 11 a , having the median longitudinal plane the plane P2, by an upper border 11 b , which defines the key back 14, and by a lower border 11 c , which extends transversely to join the winding profile of the key, which, down, leads to the active border 15.

When the key is fully inserted into its key housing 7, the lower wall 11 c of the groove 11 comes to bear on the rib 7 b , which therefore limits the residual space 9 downwards.

Pins 4 and 6 move in bores cylindrical 16, which open to the right of the rib 8. According to the axis of the bores 16, drilling was carried out 17, of smaller diameter than that of the bores, this drilling going right through the rib 8. The spring 5 pushes the pin 6 against the face opposite the rib 8, said face being perpendicular to the plane longitudinal center of the key housing. On the face of the rotor pin 6, which bears against the rib 8, a hemispherical nipple 18 has been placed, likewise diameter than the hole 17. The hemispherical nipple 18 has the same axis as the rotor pin 6 and constitutes therefore a relief, which can penetrate into the recess formed by drilling 17.

The free end of the key body is shaped like a point. The top 19 of the key is located at the central zone of the bottom 11 a of the groove 11. This pointed end is delimited, in the direction of the back of the key, by a bevel 20 and, in the opposite direction, by two ramps: one, arranged in line with the bottom 11 a of the groove 11, has been designated by 21; the other, constituting the end of the active edge 15 of the key, has been designated by 22. The first ramp 21 has the same inclination as the bevel 20, relative to the longitudinal axis of the key 10, and the second ramp 22 has a lower inclination. The ramp 22 intersects the plane of the ramp 21 in an area located in the thickness of the wall 11 c , along an edge 23.

The operation of the device which has just been described will now be explained.

When you present the key 10 at the entrance of the accommodation key, the rotor is in the position shown in Figure 2, that is, all the pins rotor 6 are pressed against the underside of the rib 8. At the beginning of the introduction of the key, the ramp 21 comes, in the residual space 9, to bear against the border of the upper base of the first pin rotor 6; under this support, the rotor pin 6 descends into its bore by compressing the spring 5. The beginning of this phase is shown in the figures 6A, 6B, 6C. When we continue to push the key, the nipple 18 which was pressed into the hole 17 comes to be released from the bore and the edge 23 then just comes above the top of the nipple 18. The nipple 18 comes then in contact with the ramp 22 and a depression the key causes the pin to descend rotor 6 due to the support of the stud 18 on the ramp inclined 22 then on the active border 15 of the key, which follows ramp 22. So we see that, in this way, although, in the rest position, the nipple 18 is in the thickness of the rib 8, it is possible, with this key, attack the nipple 18 by the active edge of the key due to a prior action of the ramp 21 in residual space 9. Lowering the rotor pin under the action of ramp 21 must be sufficient to ensure the escape of the stud 18 from the bore 17. When the rotor pin 6 of the first locking member reached by the key was, by its nipple 18, put in contact with the active border 15, the key can sink until the ramp 21 comes into contact with the upper base of the rotor pin of the second member and thus the nipple 18 of this second locking member in turn comes to bear against the active border 15. Progressive penetration of the key thus places all of the nipples 18 on the active border of the key and, when the key is pressed fully in its key housing, all nipples 18 are find in the notches of the active border which their are intended, so that the interfaces (pin 6 / pin 4) are all at the interface (rotor 1 / stator 2): the rotor is free to rotate relative to stator;

As previously indicated, breaking in with a hook is practically impossible; a first hook can be put in place in the residual space 9 and press the rotor pin 6 to the upper level of the rib 7 b ; after which it is necessary to set up another hook to come to press on the stud 18 but, in any case, this other hook cannot descend lower than the rib 7 c ; and, of course, this operation should be repeated for all the other keying members. We see that the break-in is thus made practically impossible.

Claims (12)

1. Key (10) for safety cylinder comprising an operating element connected to a key body of elongate shape having a rectilinear longitudinal axis, through which passes the longitudinal centre plane P1 of said key body, said key body being designed to be inserted in a key receptacle (7) of said cylinder and being fully contained between on the one hand two lateral planes P3, P4 parallel to the longitudinal central plane P1 and on the other hand two longitudinal edges arranged between the above-mentioned two lateral planes, one of these edges constituting the back (14) of the key body and the other constituting an active edge (15) designed to cooperate with keying members (4, 6) of said safety cylinder, the back (14) and the active edge (15) being connected to each other by a profile comprising, in the vicinity of the back (14), a longitudinal groove (11) of which the bottom (11a) is a wall zone having, parallel to the longitudinal axis of the key body, a longitudinal mid-plane P2, the line of the active edge (15), which is equidistant from the two ridges laterally delimiting said active edge, being in a plane P5 offset transversely from the longitudinal mid-plane P2, the free end zone of the key body which is opposite the operating element being at least partially oblique relative to the longitudinal axis of the key body, characterised in that the free end zone of the key body comprises a first ramp (21) defined at the end of the wall zone of the profile, which delimits said groove (11), and a second ramp (22) defined at the end of the active edge (15), the second ramp (22) being set back from the first ramp (21) in the direction of insertion of the key (10) in the key receptacle (7) of the cylinder, the two ramps (21, 22) forming acute angles with the longitudinal axis of the key body, wherein the second ramp (22) cuts through the lower wall (11c) of the groove (11) in the thickness thereof, the said lower wall (11c) being that which is connected to the active edge (15) of the key body.
2. Key according to claim 1, characterised in that the free end zone of the key body is shaped to a point, an apex (19) thus being defined at one end of the first ramp (21).
3. Key according to claim 2, characterised in that the apex (19) forming the end of the key body is arranged at the level of the central portion of the bottom (11a) of the groove (11).
4. Key according to any of claims 1 to 3, characterised in that the longitudinal centre plane P1 of the key body and the longitudinal plane P5 of the active edge (15) substantially coincide.
5. Key according to any of claims 1 to 4, characterised in that the free end of the active edge (15) intersects with the first ramp (21) along a ridge (23) of which the midpoint is at a distance from the longitudinal centre line of the back (14) of the key shorter than the one existing between said line and the face of the lower wall (11c) of the groove (11) which is furthest from the back (14) of the key, said so-called "lower" wall being the one which is connected to the active edge (15) of the key body.
6. Key according to any of claims 1 to 5, characterised in that the angle formed with the axis of the key body by the first ramp (21) is greater than the one formed with said axis by the second ramp (22).
7. Safety cylinder designed to cooperate with a key (10) according to any of claims 1 to 6, said cylinder comprising a cylindrical rotor (1) capable of turning in a stator (2), a key receptacle (7) being formed longitudinally in the rotor (1), keying members (4, 6) being arranged in the assembly (rotor 1/stator 2) and being biased elastically into the keying position in the absence of a key in the key receptacle (7), release taking place only if the appropriate key (10) is placed in said key receptacle (7), each keying member (4, 6) being displaceable in translation along a rectilinear axis, a longitudinal rib (8) projecting laterally in the key receptacle (7), a residual space (9) being formed between said rib (8) and the opposite face (7a) of said key receptacle (7), characterised in that, in the absence of a key, each elastically biased keying member (4, 6) traverses the key receptacle (7) until it abuts against said ri (8), the keying member (4, 6) comprising a relief (18) which, on abutment of the keying member against the rib (8), enters a recess (17) provided for this purpose in said rib (8), the residual space (9) making it possible to act on the keying member to disengage the relief (18) from its recess (17).
8. Cylinder according to claim 7, charactised in that the keying member consists of a rotor pin (6) and a stator pin (4) arranged in the same bore (16), the stator pin (4) being biased by a spring (5), the rotor pin (6) being supported by one of its bases on the stator pin (4) and carrying on its other base the relief (18), which is designed to engage in the rib (8).
9. Cylinder according to claim 8, characterised in that the relief is a hemispherical projection (18) arranged along the axis of the rotor pin (6), which carries it, and in that the rotor (6) and stator (4) pins are cylindrical, the axis of the bore (16) being perpendicular to the axis of the rotor (1).
10. Cylinder according to any claims 7 to 9, characterised in that the key receptacle has a longitudinal centre plane which passes through the axis of the rotor (1), the face of the rib (8) against which a rotor pin (6) may abut being perpendicular to said longitudinal centre plane of the key receptacle (7).
11. Assembly consisting of a cylinder according to any of claims 7 to 10 and a key according to any of claims 1 to 6, characterised in that the first ramp (21) of the key (10) acts on the keying member in the residual space (9) formed for this purpose, the inclination of said ramp (21) being such that the relief (18) of the keying member is disengaged from its recess (17) when the second ramp (22) comes into contact with said relief (18).
12. Assembly according to claim 11, including a cylinder according to claim 8, characterised in that in the course of insertion to the key (10) in its receptacle (7), the relief (18) is supported on the active edge (15) of the key (10), the design of said active edge (15) being such that, in the position of maximum insertion of the key (10) in its receptacle (7), the interface (rotor pin 6/stator pin 4) is brought to the level of the interface (rotor 1/stator 2).

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