EP0700479B1 - 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 driving the movable members of a lock. The invention also relates to the key corresponding to this barrel and the assembly consisting of the barrel and the key associated therewith.

We know that we are constantly seeking to improve the security of safety barrels, that is to say to make it more difficult to break into them. Conventionally, a safety barrel is made up of a stator, inside which can rotate a rotor operated by a key; the key is engaged in a key housing made longitudinally in the rotor; to block the rotation of the rotor relative to the stator in the absence of the correct key, a plurality of keying members is used. According to a common embodiment, a locking member consists of a rotor pin and a stator pin placed inside 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 active edge of the key, which has teeth, positions each rotor pin so that the interface (rotor pin / stator pin) is exactly at the level of the interface (rotor / stator) and, under these conditions, the rotor can rotate relative to the stator. It can be seen that, in such a device, it is necessary for the rotor pins to protrude from the key housing in order to cooperate with the active edge of the key.

However, this arrangement allows break-in specialists to rotate the rotor by means of a simple tool, generally called a "hook". By means of this tool, a torque is exerted on the rotor which causes the rotor to be locked by that of the pins which has the least play in its housing; at this time, by pulling the hook over the entire length of the rotor, one successively pushes all the pins and, in particular, the one which ensured the blocking (rotor / stator): at this moment, the rotor turns at a slight angle which causes it to be locked by another pin, as long as the torque is maintained using the hook. It can therefore be seen that, by this technique, a specialist can, after n longitudinal displacements of the hook, rotate the rotor of a barrel comprising n locking members.

It has already been proposed to reinforce the security of this type of barrel by adding to the conventional pin device, which has just been described, additional devices such as, for example, lateral pins coming to bear on the lateral sides of the key body. in footprints provided for this purpose. It has also been proposed to place in the key a movable body capable of coming to push a rotor pin at the moment when the key is in the appropriate position in its housing. These devices certainly make burglary more difficult, but they are relatively expensive given the complexity of the corresponding barrel and the keys relating thereto.

The object of the present invention is to describe a security barrel and the corresponding key capable, despite its simplicity of construction, of making any break-in by means of a hook very difficult, if not impossible. According to the invention, a safety barrel is proposed in which the elastically pushed keying member passes through the entire key housing until it is in abutment against a longitudinal rib provided in said housing; the keying member penetrates, through a relief, in the rib, and a residual space is formed between said rib and the wall of the key housing which faces it. The key comprises, at the rib of the barrel, a groove of corresponding profile 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, presses on the keying member to obtain the relief of the relief outside the rib during the insertion of the key; when this clearance is achieved, the toothing of the active edge of the key cooperates, by a second ramp, with the relief of the keying member, which allows the subsequent insertion of the key to the member of following keying, with which the same operating mode is achieved. The presence of this double ramp at the end of the key therefore allows the maneuvering of the keying member while the relief carried by it is not directly accessible by the action of a hook. If the key had only one end ramp on its active edge, it would not be possible to insert the key since this ramp would abut against the rib, without being able to act on the relief of the keying member . Operation is only possible thanks to the presence of two ramps: the first, located in the residual space, comes to attack the locking member itself, to ensure the relief of the relief, after which the second comes to act on the relief.

The production of such a device does not present any particular complexity, which makes it possible to obtain a safety barrel of limited cost price. However, the breaking of such a barrel is extremely difficult because the hook cannot act on the relief of the locking member, which is concealed. It would therefore be necessary to act with a hook directly on the keying member, in the residual space, but, in this case, the hook abuts on another rib of the rotor, which comes below the lower wall of the groove of key; the action of this hook therefore only allows the relief to be released from the rib where it was concealed and, in this case, it would be necessary to act with a second hook to push the relief, as the active border of the key. The manipulation of two hooks inside a space as small as the key housing is practically impossible and, moreover, the key may comprise, between the aforementioned groove and the active edge, other grooves and ribs, of so that the second hook could very well not even be capable of pushing the relief of the keying member to the position, which ensures the release of the rotor relative to the stator. We therefore see that this device, despite its simplicity, gives the barrel a high degree of security.

FR-A-2 565 281 has already proposed a key for a safety barrel comprising an operating element linked to an elongated key body having a rectilinear longitudinal axis, through which the median longitudinal plane P1 of said body passes. key, said key body being intended to be inserted into a key housing of said barrel and being entirely comprised between, on the one hand, two lateral planes P3, P4, parallel to the longitudinal plane P1, and, on the other hand, two longitudinal edges disposed between the two aforementioned lateral planes, one of these edges constituting the back of the key body and the other constituting an active edge intended to cooperate with means for keying said safety barrel, the back and the active edge being interconnected by a profile comprising, in the vicinity of the back, a longitudinal groove, the bottom of which is a wall zone having, parallel to the longitudinal axis of the key body, a mean longitudinal plane P2, the line of the active border, which is equidistant from the two edges laterally delimiting said active border, being in a plane P3 offset transversely relative to the mean longitudinal plane P2, the free end region of the key body, which is opposite to the operating element, being, at least partially, oblique with respect to the longitudinal axis of the key body. This arrangement alone does not reduce the risk of burglary because the keying members are directly accessible at the end ramp of the active edge of the key and therefore directly accessible by the action of a hook put in place in the key housing. Compared to the prior art, the key according to the invention is characterized in that the free end zone of the key body comprises a first ramp, defined at the end of the wall zone of the profile which delimits the groove, and a second ramp, defined at the end of the active edge, the second ramp being set back relative to the first ramp, in the direction of driving the key into the key housing of the barrel, the two ramps forming acute angles with the longitudinal axis of the key body.

In a preferred embodiment of the key according to the invention, the free end zone of the key body is shaped as a point, a vertex thus being defined at one end of the first ramp; provision may be made for the top forming the end of the key body to be arranged at the middle part of the bottom of the groove. Advantageously, the median longitudinal plane P1 of the key body and the mean longitudinal plane P5 of the active edge are substantially combined. It is preferred that the free end of the active border intersects the first ramp along an edge, the midpoint of which is at a distance from the longitudinal center line of the back of the key less than that existing between said line and the face of the so-called wall. "lower" of the groove, which is furthest from the back of the key, said wall called "lower" being that which is connected to the active edge 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, which makes it possible to ensure the relief of the relief of the keying member by a shorter stroke of the key in its housing and, therefore, to shorten the total length of the key.

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

In a preferred embodiment, the keying member consists of a rotor pin and a stator pin, arranged in the same bore, the stator pin being pushed by a spring, the rotor pin s' pressing, by one of its bases, on the stator pin and carrying, on its other base, the relief which is intended to engage in the rib; it can be provided that the relief is a hemispherical stud 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 median longitudinal plane, which passes through the axis of the rotor, the face of the rib on which a rotor pin can bear, being perpendicular to said longitudinal median plane of the key housing.

The present invention finally relates to an assembly consisting of a barrel as defined above and a key as defined above, characterized in 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 keying member is released from its recess when the second ramp comes into contact with said relief.

In a preferred embodiment relating to an assembly comprising a barrel, each locking member of which consists of a rotor pin and a stator pin, it is provided that during the insertion of the key into its housing , the relief is supported on the active edge of the key, the design of said active edge being such that, in the position of maximum insertion of the key into its housing, the interface (rotor pin / stator pin) is brought to the interface (rotor / stator) level.

To better understand the object of the invention, we will now describe, by way of purely illustrative and non-limiting example, 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 represents, diagrammatically, the relative position of the key and of the rotor pin for FIG. 6A, the key being represented in section along the plane VIB of FIG. 6A and being seen according to arrow F;
• FIG. 6C represents a view along 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 shows a view similar to that of FIG. 6B for the key entry position corresponding to FIG. 7A;
• FIG. 7C shows a view similar to that of FIG. 6C in the position of the elements corresponding to FIG. 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 represents, 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 has the keyway, which makes it vis-à-vis.

When the appropriate key is inserted into the key housing 7 and fully pressed into said housing, the interface (pin 6 / pin 4) is located at the interface (rotor 1 / stator 2), for each locking members of the barrel according to the invention. This barrel comprises a plurality of parallel keying members, the axes of which 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 preceding 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 comprises 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 border lower 11 c , which extends transversely to join the sinuous profile of the key, which, downwards, 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 bears on the rib 7 b , which therefore limits the residual space 9 downwards.

The pins 4 and 6 move in cylindrical bores 16, which open at right angles to the rib 8. According to the axis of the bores 16, a drilling 17 has been made, with a smaller diameter than that of the bores, this drilling passing through right through the rib 8. The spring 5 pushes the pin 6 against the opposite face of the rib 8, said face being perpendicular to the median longitudinal plane of the key housing. On the face of the rotor pin 6, which comes to bear against the rib 8, a hemispherical stud 18, of the same diameter as the hole 17, has been arranged. The hemispherical stud 18 has the same axis as the rotor pin 6 and therefore constitutes a relief, which can penetrate into the recess formed by the hole 17.

The free end of the key body is shaped like a point. The top 19 of the key is located at the central area of the bottom 11a of the groove 11. The tip end is delimited, towards the back of the key, by a bevel 20 and in the opposite direction, 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 border 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 the key 10 is presented at the entrance to the key housing, the rotor is in the position shown in FIG. 2, that is to say that all of the rotor pins 6 are in abutment against the face lower of the rib 8. At the beginning of the introduction of the key, the ramp 21, in the residual space 9, bears against the edge of the upper base of the first rotor pin 6; under this support, the rotor pin 6 descends into its bore by compressing the spring 5. The start of this phase is shown in FIGS. 6A, 6B, 6C. When the key is continued to be pressed, the stud 18 which was pressed into the bore 17 comes to be released from the bore and the edge 23 then comes just above the top of the stud 18. The stud 18 then comes in contact with the ramp 22 and a subsequent depression of the key causes the rotor pin 6 to descend due to the support of the stud 18 on the inclined ramp 22 then on the active edge 15 of the key, which follows the ramp 22. It can therefore be seen that, in this way, although, in the rest position, the stud 18 is in the thickness of the rib 8, it is possible, with this key, to attack the stud 18 by the edge active of the key due to a prior action of the ramp 21 in the residual space 9. The descent of the rotor pin under the action of the ramp 21 must be sufficient to ensure the escape of the stud 18 from the drilling 17. When the rotor pin 6 of the first keying member reached by the key has been, by its pin 18, brought into contact with the active edge 15, the key can be pushed in until the ramp 21 comes into contact with the upper base of the rotor pin of the second locking member and, in this way , the stud 18 of this second keying member in turn comes to bear against the active edge 15. The progressive depression of the key thus puts all the studs 18 in abutment on the active edge of the key and, when the key is fully inserted into its key housing, all the pins 18 are located in the notches of the active border which are intended for them, 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 the stator;

As previously indicated, breaking in with a hook is practically impossible; one can put in place a first hook 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 nipple 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.
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 rib (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, characterised 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 of 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 of 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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