Air distribution device with a shutter of the drum type, in particular for a motor vehicle

An air distribution device comprises a casing (10) provided with a cylindrical wall (12) having at least one air passage opening (14, 16), a shutter (20) mounted so as to pivot with respect to an axis of rotation (X--X) and having a generally cylindrical obturation wall, which is mounted so as to movable with respect to a body of the shutter, consisting of two plates, in a direction substantially radial with respect to the axis of rotation (X--X) of the shutter by virtue of movement means (46, 48) synchronised with the rotation of the shutter, which makes it possible to move the obturation wall (24) away from the wall (12) when the shutter is in an open position (P1, P2) and bring the obturation wall (24) closer to the wall (12) of the casing when the shutter is in a closed position.

FIELD OF THE INVENTION
 The invention related to an air distribution device having a shutter of the
 drum type suitable for use in a motor vehicle heating and/or air
 conditioning installation.
 The invention concerns more particularly a device comprising a casing
 provided with a generally cylindrical wall having at least one air passage
 opening, a shutter mounted so as to pivot with respect to an axis of
 rotation and having a generally cylindrical obturation wall and rotational
 control means for bringing the shutter into chosen positions in which the
 obturation wall selectively controls the air passage opening or openings
 of the casing.
 BACKGROUND OF THE INVENTION
 Shutters of this type are already known, which are also referred to as
 "drum shutters", in which the obturation wall of the shutter is normally a
 length of a cylindrical wall which pivots inside a length of a cylindrical
 wall forming part of a distribution casing, the two cylindrical walls
 being coaxial.
 Generally the cylindrical wall of the casing has several passage openings
 which are spaced apart angularly and which can be closed off or opened
 selectively by the obturation wall of the shutter according to the angular
 position taken by the latter. These devices have the advantage of enabling
 all the air distribution to be controlled with a single shutter placed in
 a single casing, which simplifies the design and also affords greater
 compactness.
 One of the problems posed by this type of shutter is that of airtightness.
 It is in fact necessary for the shutter to guarantee perfect airtightness
 of the different air passage openings, also referred to as "vents", when
 the shutter is in a closure position.
 In the past, this airtightness is provided by a joint, for example by a
 foam joint covered with a polyamide cloth, bonded externally to the
 periphery of the obturation wall of the shutter.
 Such a joint theoretically guarantees good airtightness, but at the cost of
 a high maneuvering force, because of the friction generated by the joint.
 In addition, this joint has a tendency to lose its sealing capability
 because of wear, and is sensitive to ambient humidity.
 It must also be stated that producing such a joint is tricky and that the
 resulting cost is relatively high.
 SUMMARY OF THE INVENTION
 An object of the invention is notably to overcome the aforementioned
 drawbacks.
 The present invention proposes an improved air distribution device, in
 which the obturation wall is mounted so as to be movable with respect to a
 body of the shutter, consisting of two plates, in a direction
 substantially radial with respect to the axis of rotation of the shutter
 body, and in which the device comprises movement control means,
 coordinated with the rotation control means in order to move the
 obturation wall of the shutter away from the wall of the casing when the
 shutter is in an open position and to bring the obturation wall of the
 shutter closer to the wall of the casing when the shutter is in a closed
 position.
 Thus, whereas in the past the obturation wall was always situated at a
 constant distance with respect to the axis of rotation of the shutter, the
 invention makes provision for varying this distance according to the
 angular position of the shutter. When the shutter is in an open position,
 the obturation wall is away from the wall of the casing, so that there is
 no friction between these two walls. When the shutter is thereafter moved
 in the direction of a closed position, the obturation wall of the shutter
 is moved away from the axis in order to move closer to the wall of the
 casing and come into contact with it, when the obturation wall is opposite
 a passage opening in the casing. The movement of the shutter body and the
 movement of the obturation wall of the shutter are coordinated and can be
 effected either simultaneously or in succession.
 It is thus no longer necessary to provide sealing joints operating on
 rotation like the ones used in the past.
 When the device comprises a sealing joint, this is compressed only in the
 radial direction and at the moment when the obturation wall of the shutter
 arrives in the closed position.
 Thus the rotational movement of the shutter takes place without friction
 and therefore without maneuvering force. In addition, wear on the joint is
 minimal since the latter undergoes only compression in a substantially
 radial direction, at the moment of closure.
 The movement of the obturation wall with respect to the body of the shutter
 in a substantially radial direction can take place in two ways.
 In a first embodiment, the obturation wall is movable in translation with
 respect to the body of the shutter and the movement control means comprise
 translation control means.
 In a second embodiment, the obturation wall is movable in rotation with
 respect to the body of the shutter and the movement control means comprise
 rotation control means.
 In a first general embodiment of the invention, the movement control means
 comprise a lever fixed to a drive spindle coaxial with the axis of
 rotation of the shutter body, this lever being articulated on the
 obturation wall of the shutter, either directly, or indirectly by means of
 at least one connecting rod, transmission means having a chosen
 transmission ratio being connected to the rotation control means and to
 the movement control means.
 Thus the movement of the shutter is effected in a particularly simple
 fashion by means of a lever, the rotation of which is coordinated with
 that of the shutter body, and if applicable at least one connecting rod.
 In one embodiment of the invention, the device comprises a drive shaft on
 which there is fixed a driving pinion driving a toothed sector fixed to
 the body of the shutter and driving a pinion fixed to the spindle of the
 lever with the interposition of an intermediate pinion.
 The device of the invention applies in particular to the case where the
 shutter can be moved between two closed positions with a given angular
 movement. In such a case, the transmission ratio is chosen so that the
 lever turns through an angle of 360.degree. minus the value of the angular
 movement, when the shutter pivots from one of its two positions to the
 other.
 Thus, in each of the closed positions, the obturation wall of the shutter
 is always at the same distance from the axis of rotation of the shutter.
 Advantageously, in each of the closed positions of the shutter, the
 connecting rod is situated in line with the lever so that the obturation
 surface of the shutter is always furthest away from the axis of rotation
 of the shutter body.
 In another embodiment, the device comprises a drive shaft on which there
 are fixed a drive pinion driving a toothed sector fixed to the body of the
 shutter and a toothed sector driving a pinion fixed onto the rotation
 spindle of the shutter.
 This solution is particularly suitable in cases where the shutter can be
 moved between at least three closure positions with a given angular
 movement between two successive closed positions, the transmission ratio
 being chosen so that the lever turns through an angle of 360.degree. plus
 the aforementioned angular movement, when the shutter passes from one of
 two consecutive closure positions to the other.
 In another embodiment of the invention, the device comprises a drive shaft
 coupled to the body of the shutter and also comprises a transmission
 pinion mounted loose around a spindle fixed to the body of the shutter and
 meshing on the one hand with a pinion fixed onto the lever spindle and on
 the other hand with teeth in the shape of an arc of a circle carried by
 the casing and centered on the axis of rotation of the shutter body and of
 the lever.
 In this embodiment, the transmission pinion, the pinion fixed onto the
 lever spindle and the teeth in the shape of an arc of a circle can all be
 situated outside the shutter, or else inside the shutter.
 As a variant, the transmission pinion is a pinion in the form of an annulus
 rotating about a hub fixed to the shutter body, the transmission pinion,
 the pinion fixed onto the lever spindle and the teeth in the shape of an
 arc of a circle being situated outside the shutter.
 In another embodiment of the invention, the movement control means comprise
 at least one connecting rod articulated on the obturation wall of the
 lever and on a transmission pinion mounted loose around a spindle fixed to
 the body of the shutter, the transmission pinion meshing with teeth in the
 shape of an arc of a circle fixed with respect to the casing and centered
 with respect to the axis of rotation of the body of the shutter.
 In a variant embodiment, the connecting rod is articulated directly on the
 transmission pinion, the transmission pinion being situated outside the
 shutter and the teeth in the shape of an arc of a circle being formed on
 the casing.
 In a variant, the connecting rod is articulated directly on the
 transmission pinion, the transmission pinion being situated inside the
 shutter, and the teeth in the shape of an arc of a circle being integral
 with a fixed shaft on which the body of the shutter turns.
 In another variant, the connecting rod is articulated on a lever situated
 inside the shutter body and coupled to the transmission pinion, which is
 situated outside the shutter.
 In another embodiment of the invention, the lever forms part of a toothed
 pinion mounted so as to rotate freely with respect to the axis of rotation
 of the shutter and driven in rotation by an intermediate pinion
 cooperating with the toothed pinion and with internal teeth in the shape
 of an arc of a circle carried by the casing and centered on the axis of
 rotation of the shutter.
 In another embodiment of the invention, the lever forms part of a toothed
 pinion mounted so as to rotate loosely about a spindle fixed to the body
 of the shutter and meshing on external teeth in the shape of an arc of a
 circle fixed to the casing and centered on the axis of rotation of the
 shutter.
 It is also possible to provide the movement control of the obturation wall
 of the shutter without having recourse to a means of the connecting
 rod/lever type.
 Thus, in another embodiment of the invention, the movement control means
 comprise an actuator, chosen from amongst an electropneumatic cylinder and
 a solenoid valve, interposed between the obturation wall of the shutter
 and the axis of rotation of the shutter.
 This actuator is advantageously integrated into the obturation wall of the
 shutter.
 In another embodiment of the invention, the movement control means comprise
 at least one cam track carried by the casing and able to serve as guidance
 for a bearing finger, fixed to the obturation wall of the shutter, the
 bearing finger being returned elastically in the direction of the cam.
 In another embodiment of the invention, the movement control means comprise
 a cam track of annular configuration fixed to the body of the shutter and
 able to cooperate with at least one cam follower fixed to the casing.
 Advantageously, the movement control means comprise four cam followers in
 the form of fingers, disposed at 90.degree. with respect to each other,
 and dependent on an annulus surrounding the axis of rotation of the
 shutter.
 According to another aspect of the invention, the obturation wall carries a
 sealing joint so as to provide a seal when the shutter is in the closed
 position.
 Preferably the sealing joint is provided with a deformable lip extending at
 the periphery of the obturation wall.
 Thus this deformable lip undergoes only a compression in a substantially
 radial direction, which minimizes wear on the joint.
 In one embodiment of the invention, the deformable lip of the joint extends
 over four sides of the obturation wall, namely two longitudinal sides
 parallel to the rotation spindle of the shutter and two transverse sides
 perpendicular to the axis of the said rotation spindle.
 In a variant, the sealing joint comprises a foam joint carried on the
 outside of the obturation wall of the shutter.
 Preferably the sealing joint has a bellows extending between an external
 peripheral rim able to be attached to an edge of the body of the shutter
 and an internal peripheral rim able to be attached to an edge of the
 obturation wall.
 Thus this bellows also provides a seal between the body and the obturation
 wall of the shutter.
 In one embodiment of the invention, the edge of the shutter body and the
 edge of the obturation wall are parallel to the axis of rotation of the
 shutter, the external peripheral rim and the internal peripheral rim are
 substantially in line with each other when the shutter is in the closed
 position and offset with respect to each other when the shutter is in the
 open position.
 In this embodiment, the internal peripheral rim and the external peripheral
 rim are advantageously produced in the form of grooves moulded
 respectively onto the edge of the shutter body and the edge of the
 obturation wall.
 In another embodiment, the edge of the shutter body extends perpendicularly
 to the axis of rotation of the shutter and the edge of the obturation wall
 extends parallel to the axis of rotation of the shutter, the external
 peripheral rim and the internal peripheral rim extending perpendicularly
 to each other both in the open position and in the closed position of the
 shutter.
 In this embodiment, the external peripheral rim is advantageously produced
 in the form of a groove moulded onto the edge of the shutter body, while
 the internal peripheral rim is advantageously produced in the form of two
 parallel strips moulded on each side of the edge of the obturation wall.
 According to another advantageous characteristic of the invention, the
 bellows is moulded in one piece so as to have a configuration at rest
 which corresponds substantially to the configuration in the open position
 of the shutter.
 Thus the bellows has a tendency to act on the obturation wall in order to
 bring it closer to the axis of rotation of the shutter.

DETAILED DESCRIPTION OF THE INVENTION
 Reference is made first of all to FIGS. 1 and 2, which depict a
 distribution casing 10 comprising a cylindrical wall 12 with axis X--X
 (FIG. 2), interrupted in order to define two openings 14 and 16 offset
 angularly with respect to each other. The wall 12 is connected to two
 plates 18, one of which is depicted in FIG. 1. The casing 10 houses
 internally a shutter 20, referred to as a drum shutter, comprising two
 plates 22 constituting the shutter body, one of which is visible in FIG.
 1, and an obturation wall 24 mounted so as to be movable with respect to
 the plates 22, in a radial direction R with respect to the axis X--X. The
 shutter 20 is able to be moved in rotation about the axis X--X between two
 positions P1, P2 (FIG. 2) in which the obturation wall 24 respectively
 closes off the openings 14 and 16, the movement from the position Pi to
 the position P2 or vice versa taking place with an angular movement
 .alpha..
 Each of the plates 22 of the shutter 20 is fixed to a hub 26 passing
 through a hub 28 of the casing and fixed to a toothed sector 30 (FIG. 1).
 The shutter is driven in rotation between its positions P1 and P2 by means
 of an electric motor 32 fixed to the outside of the casing 10 and having a
 drive shaft 34 on which there is fixed a toothed pinion 36 which on the
 one hand meshes with the toothed sector 30 and on the other hand meshes
 with a transmission pinion 38 mounted loose on a support 40 fixed to the
 outside of the casing 10. The transmission pinion 38 cooperates so as to
 mesh with a pinion 42 fixed at one end of a shaft 44, which extends in the
 direction of the axis X--X and which carries, at its other end, a radial
 lever 46. A connecting rod 48 is articulated at 50, on the one hand on a
 support 52 provided inside the obturation wall 24 and on the other hand on
 an articulation 54 fixed to the lever. The wall 24 is fixed with respect
 to rotation to the shutter body and can be moved in translation with
 respect to the latter in the radial direction R (FIG. 1) by means of the
 lever 46 and connecting rod 48.
 In fact, the device comprises two connecting rods 48 and two levers 46
 provided respectively at the two ends of the movable obturation wall 24.
 In each of the closed positions P1 and P2, the connecting rod 48 is
 situated in line with the lever 46 (FIG. 2) so that the obturation wall 24
 is as far away as possible from the axis X--X.
 The aforementioned pinions offer a transmission ratio chosen so that, in
 each of the positions P1 and P2, the connecting rod 48 is situated in line
 with the lever 46 (FIG. 2). Thus, when the shutter moves from the position
 P1 to the position P2, or vice versa, with a movement .alpha., the lever
 46 pivots through an angle equal to 360.degree.-.alpha..
 When the shutter is in an intermediate position PI between the positions P1
 and P2, the connecting rod 48 and the lever are aligned, but not in line
 with each other, so that the distance between the obturation wall 24 and
 the axis X--X is at a minimum.
 Thus, when the shutter passes from the position P1 to the position P2, or
 vice versa, its obturation surface 24 is first of all in internal contact
 with the wall 12 of the casing, and then this obturation wall 24 moves
 progressively away from the wall 12, moving closer to the axis X--X in
 order to arrive at a minimum value in the intermediate position PI. Next,
 when the shutter moves towards the other end position, the wall 24 moves
 radially in the opposite direction in order to move progressively towards
 its closed position, in which the movable wall 24 is in contact with the
 wall 12 of the casing (FIG. 2).
 Consequently, passage from the position P1 to the position P2, or vice
 versa, takes place without friction between the wall 24 of the shutter and
 the wall 12 of the casing. When the shutter arrives in one of the closed
 positions P1 or P2, its obturation wall 24 moves radially closer to the
 wall 12, so that the seal is produced at the end of radial travel. It is
 possible to provide a sealing joint, for example on the external periphery
 of the movable wall 24. The joint is then compressed in a radial
 direction, but only when the shutter arrives in the end of travel
 position.
 As a variant, the spindle 44 and lever 46 could be situated on the internal
 side of the shutter, as indicated respectively at 44' and 46' in FIG. 1.
 In a variant, not shown, the connecting rod 48 could be omitted and the
 lever 46 would then be articulated directly on the obturation wall 24 of
 the shutter.
 Reference is now made to FIGS. 3 and 4, which depict another embodiment of
 the invention, in which the casing 10 has three openings 56, 58 and 60
 each offset angularly by an angle .beta., the total movement of the
 shutter 20 being equal to 2.beta..
 On the drive shaft 34 of the motor 32 there are fixed on the one hand a
 toothed pinion 62 which meshes with the toothed sector 30 fixed to the
 shutter and on the other hand a toothed sector 64 which meshes with a
 toothed pinion 42 similar to the one described above (FIG. 1). The toothed
 sectors 30 and 64, and the pinions 62 and 42, define a transmission ratio
 such that, in each of the three positions P1, P2 and P3 of the shutter
 (FIG. 4), the connecting rod 48 is situated, on each occasion, in line
 with the lever 46, so that the distance between the obturation wall 24 of
 the shutter and the axis X--X is at a maximum.
 When the shutter passes from one closed position to an adjacent closed
 position, it undergoes an angular movement .beta., and the lever pivots
 through an angle corresponding to 360.degree.+.beta. in order to satisfy
 the aforementioned condition.
 In passing from one closed position to another, the shutter on each
 occasion passes through an intermediate position PI (one of which is
 depicted in FIG. 4), in which the distance between the obturation wall 24
 and the axis X--X is at a minimum. The path of the articulation spindle 50
 (between the connecting rod 80 and the support 52) is depicted
 schematically (reference T) in FIG. 4.
 In the embodiment in FIG. 5, to which reference is now made, the shaft 34
 of the motor 32 carries a radial lever 61 provided with a finger 63
 cooperating with a lever 66 fixed to the barrel 26 of the shutter 20. This
 lever 66 is situated outside the plate 18 of the casing. The shutter also
 comprises another lever 68 situated opposite the lever 66 and also
 situated outside the plate 18 of the casing. This lever 68 carries a shaft
 70 on which there is loosely mounted a transmission pinion 72 which meshes
 on the one hand with a toothed pinion 42 similar to the one in FIGS. 1 and
 3 and on the other hand with teeth 74 in the shape of an arc of a circle,
 integral with the plate 18 of the casing and formed outside it. These
 teeth 74 are centred on the axis of rotation X--X common to the shutter
 body and to the lever.
 In the embodiment in FIG. 5, the transmission pinion 72, the pinion 42
 fixed onto the lever spindle and the teeth in the shape of an arc of a
 circle 74 are situated outside the shutter and also outside the casing.
 In the embodiment in FIG. 6, to which reference is now made, the
 transmission pinion 72, the pinion 42 fixed onto the lever spindle and the
 teeth in the shape of an arc of a circle 74 are situated on the inside of
 the shutter, that is to say also on the inside of the plate 18 of the
 casing.
 In the embodiment in FIG. 7, to which reference is now made, the
 transmission pinion 42 is a pinion in the form of an annulus rotating
 about the hub 26 fixed to the shutter body. In addition, the transmission
 pinion 72, the pinion 42 fixed onto the shutter spindle and the teeth 74
 in the shape of an arc of a circle are situated outside the shutter, but
 inside the casing.
 In the embodiments in FIGS. 5 to 7, the transmission pinion 72 makes it
 possible, in cooperation with the pinion 42 and teeth 74, to communicate a
 chosen transmission ratio between the shutter body and the lever actuating
 the obturation wall 24 of the shutter. Otherwise the operation of the
 device is identical, the principle being able to be applied to a device
 having two or more air passage openings.
 In the embodiment in FIG. 8, to which reference is now made, the connecting
 rod 48 is articulated not on the lever but on a transmission pinion 76
 mounted loose about a spindle 78 fixed to the body of the shutter and
 extending parallel to and at a distance from the axis X--X. This pinion 76
 meshes with teeth in the shape of an arc of a circle 80 formed on the
 plate 18 of the casing. These teeth 80 are centered about the axis X--X
 and are situated on the internal side of the casing and externally to the
 shutter. The rotational movement of the shutter is effected directly by
 the drive shaft 38, which is coupled to the hub 26 by any suitable means.
 When the shutter moves angularly, the transmission pinion 76 is driven in
 rotation about its axis because of the cooperation with the teeth 80,
 which causes the movement of the connecting rod 48 and the translational
 movement of the movable wall 24 of the shutter. By suitably choosing the
 transmission ratio afforded by the transmission pinion 76 and the teeth
 80, it is arranged so that the distance between the obturation wall 24 of
 the shutter and the axis X--X is at a maximum, each time the shutter
 arrives in a position of closing an air passage opening.
 In the embodiment in FIG. 9, which constitutes a variant of the previous
 embodiment, the transmission pinion 76 is situated inside the casing and
 cooperates with teeth in the shape of an arc of a circle 82 integral with
 a fixed shaft 84 about which the shutter body turns.
 In the variant embodiment in FIG. 10, which is related to that of FIG. 8,
 the connecting rod 48 is articulated on a lever 46 situated inside the
 shutter body, this lever 46 being coupled with respect to rotation to the
 transmission pinion 76, which is situated outside the shutter body and
 cooperates with teeth 80 similar to those in FIG. 8.
 Reference is now made to FIG. 11, which depicts another embodiment of the
 invention.
 As in the previous embodiments, the movable wall 24 of the shutter 20 is
 articulated at one end of a connecting rod 48, the other end of which is
 articulated on a lever. However, this lever forms part of a toothed pinion
 86 mounted so as to rotate freely with respect to the rotation spindle 90
 of the shutter and is driven in rotation by an intermediate pinion 88
 mounted so as to rotate freely about an axis X--X with respect to a radial
 lever 92 forming part of the shutter. This intermediate pinion 88
 cooperates with the toothed pinion 86 and with internal teeth 94 in the
 shape of an arc of a circle carried by the casing and centered on the axis
 of rotation X--X of the shutter.
 Thus, by choosing the respective diameters of the toothed pinions 86 and 88
 and of the teeth 94, it is arranged so that, in each of the closed
 positions of the shutter, the distance between the movable wall 24 of the
 shutter and the axis X--X is at a maximum. In the example in FIG. 11, two
 closed positions P1 and P2 are depicted, the movement of the shutter
 between one and other of these two positions being equal to .beta..
 Reference is now made to FIG. 12, which constitutes a variant very similar
 to that of FIG. 11. In the example, the connecting rod 48 is articulated
 on a lever carried by another intermediate pinion 96 mounted so as to
 rotate freely about a spindle 98 carried by the shutter body. The pinion
 96 meshes directly on external teeth 100 in the shape of an arc of a
 circle, integral with the casing, and centered on the axis of rotation of
 the shutter. As in the previous embodiments, the distance between the
 obturation wall 24 of the shutter and the axis X--X is at a maximum each
 time the shutter is in an obturation position, that is to say in the
 position P1 or P2 in the example under consideration.
 In the embodiment in FIG. 11, as in that of FIG. 12, the pinion 86 or
 respectively 96 undergoes a rotation of 360.degree. between two successive
 positions of the shutter, for example when passing from the position P1 to
 the position P2 or vice versa.
 In the embodiment in FIG. 13, to which reference is now made, the
 translation control means of the movable wall 24 of the shutter comprise
 an actuator 102, such as for example a pneumatic cylinder or an
 electromagnet, comprising a body 104 provided with two extensions 106 and
 108. The extension 106 is articulated on a support 52 connected to the
 wall 24, while the extension 108 is connected to a sleeve 110 surrounding
 a shaft 112, extending in the direction of the axis X--X, and around which
 the shutter pivots.
 In the embodiment in FIG. 14, to which reference is now made, the body 104
 of the actuator 102 is integrated directly into the shutter, that is to
 say more particularly into the wall 24, which makes it possible to omit
 the extension 106.
 As shown in FIG. 15, the obturation wall 24 of the shutter terminates in a
 peripheral sealing joint 114 which comes to cooperate internally with the
 cylindrical wall 12 of the casing when the shutter arrives in a closed
 position. Sealing is then provided by a deformation of the joint in the
 radial direction. When the shutter is next moved from one closed position
 to another, the movable wall 24 (and therefore the joint 114) moves closer
 to the axis X--X, so that the joint 114 does not undergo any friction.
 In the embodiment in FIGS. 16 and 17, the translation control means
 comprise a cam track 116 carried by the plate 18 of the casing 10, on the
 internal side of the plate turned towards the shutter. The cam track 116
 has a star-shaped profile (FIG. 17) and serves as a guide for a bearing
 finger 118 fixed to the obturation wall 24 of the shutter. The finger 118
 is returned elastically in the direction of the axis X--X by a spring 120
 depicted schematically in FIG. 16.
 The cam track 116 has apexes 122 situated in correspondence with each of
 the closed positions (in the example, positions P1 and P2) and recessed
 zones 124. Thus, when the shutter is in one or the other of the closed
 positions, the distance between the obturation wall 24 and the axis X--X
 is at a maximum, while, when the shutter is in an intermediate position,
 this distance is at a minimum.
 In the embodiment in FIGS. 18 to 22, the translation movement of the wall
 24 is also effected by a cam device, but with a different structure.
 In the example, the translation control means comprise at least one cam
 track 126 with an annular configuration, fixed to the body of the shutter
 20. The cam track 126 surrounds four cam followers 128 disposed at
 90.degree. to each other and fixed to an annulus 130 which surrounds a
 square-shaped spindle 132 cooperating with an aperture 134. When the
 shutter is moved from one obturation position to another, the cam track
 126 cooperates with the fingers 128, which are fixed with respect to the
 casing. The result is a radial translation movement of the wall 24,
 similar to the movement described previously.
 In the position depicted in FIG. 18, the shutter 20 is in a closed position
 and its obturation wall 24 is situated close to the cylindrical wall of
 the casing. On the other hand, in the intermediate positions of FIGS. 19
 to 21, the wall 24 moves closer to the spindle 132. When the shutter
 arrives in the closed position in FIG. 22, the obturation wall 24 moves
 further away from the axis X--X and comes to provide a seal with the wall
 of the casing around the corresponding opening.
 In the embodiment in FIG. 23, to which reference is now made, the
 obturation wall 24 is mounted so as to be movable in rotation between the
 plates 22 of the shutter 20 by means of pivots 136 along an axis Y--Y
 parallel to the axis X--X.
 The obturation wall 24 can be moved with respect to the shutter body
 (plates 22) by suitable control means identical or similar to those
 described previously. When the shutter is in the open position, the
 obturation wall 24 is brought closer to the axis X--X whilst, when the
 shutter is in the closed position, the obturation wall 24 is away from the
 axis X--X.
 In the embodiment in FIG. 23, the rotation movement of the shutter body and
 that of the obturation wall are simultaneous. As a result the free end 138
 of the obturation wall 24 follows a path T1 as shown in FIG. 23.
 In the variant embodiment in FIG. 24, the two rotation movements are
 successive. While the shutter is moved from the open position to the
 closed position, the obturation wall 24 remains in a position close to the
 axis X--X. As soon as the shutter body reaches the open position, that is
 to say opposite the air passage opening in the casing, the obturation wall
 24 is moved away from the axis X--X, while the shutter body remains
 immobile. As a result the end 138 of the obturation wall 24 follows a path
 T2 as shown in FIG. 24.
 Reference is now made to FIGS. 25 and 26, which show a sealing joint 140
 interposed between the plates 22 making up the shutter body and the
 obturation wall 24. The sealing joint 140 has a bellows 142 between an
 external peripheral rim 144 able to be attached to an edge 146 of the
 shutter body and an internal peripheral rim 148 able to be attached to an
 edge 150 of the obturation wall 24. In the example, the rims 144 and 148
 are produced in the form of grooves moulded respectively onto the edges
 146 and 150. The edge 146 delimits a kind of frame and is situated
 parallel to the axis of rotation X--X. Likewise, the edge 150, which
 extends over the entire periphery of the obturation wall 24, extends
 parallel to the axis of rotation X--X of the shutter. The bellows 142
 makes it possible to provide a seal between the shutter body and the
 obturation wall 24, whatever their respective positions. In the closed
 position (FIGS. 25 and 26), the peripheral rims 144 and 148 are
 substantially in line with each other. On the other hand, in the open
 position, these two rims are offset with respect to each other.
 The sealing joint 140 also has a sealing lip 152, which is produced in a
 single piece with the joint and which is attached to the internal
 peripheral rim 148 in order to provide a seal against the internal face of
 the wall 12 of the casing when the shutter is in the closed position (FIG.
 26). The lip 152 is a flexible lip which extends over four sides and thus
 has two longitudinal sides 152L parallel to the axis of rotation X--X of
 the shutter (FIG. 26) and two transverse sides 152T (FIG. 25) both
 perpendicular to the axis of rotation X--X.
 As a variant, the sealing joint is produced in the form of a foam joint 154
 (FIG. 26) carried outside the obturation wall 24 of the shutter.
 The bellows 142 is molded so as to have a configuration at rest which
 corresponds substantially to the configuration in the open position of the
 shutter. In the example in FIGS. 25 and 26, this corresponds to a
 configuration (not shown in the drawing) in which the peripheral rims 144
 and 148 are offset. As a result the bellows has a tendency to return the
 obturation wall 24 into a position close to the axis of rotation X--X.
 Reference is now made to FIGS. 27 and 28, which show another sealing joint
 156 interposed between the plates 22 constituting the shutter body and the
 obturation wall 24. The sealing joint 156 comprises a bellows 158
 extending between an external peripheral rim 160 able to be attached to an
 edge 162 of the shutter body and an internal peripheral rim 164 able to be
 attached to an edge 166 of the obturation wall 24. In the example, the
 edge 162 of the shutter body extends perpendicularly to the axis of
 rotation X--X, whilst the edge 166 of the obturation wall 24 extends
 parallel to this axis of rotation.
 The external peripheral rim 160 is produced in the form of a groove molded
 onto the edge 162 of the shutter body, whilst the internal peripheral rim
 164 is produced in the form of a two parallel strips 164A and 164B moulded
 on each side of the edge of the obturation wall. The strips 164A and 164B
 are advantageously joined together by bridges of material 168 passing
 through suitable holes formed in the thickness of the wall at regular
 intervals (FIG. 27).
 The joint 156 has a lip 170 similar to the lip 152 in FIGS. 25 and 26. This
 lip 170 also comprises two longitudinal sides 170L parallel to the axis of
 rotation X--X (FIG. 28) and two transverse sides 170T (FIG. 27)
 perpendicular to the axis X--X. As a variant, the sealing joint is
 produced in the form of a foam joint 172 similar to the foam joint 154 in
 the previous embodiment.
 There again, the bellows 156 is molded so as to have a configuration at
 rest which corresponds substantially to the configuration in the open
 position of the shutter. This means that the bellows has a tendency to
 force the obturation wall 24 in the direction of the axis X--X.
 Naturally, the invention is not limited to the embodiments described above
 by way of example and extends to other variants. Thus the nature of the
 means for providing the movement control for the obturation wall of the
 shutter and the nature of the transmission means for coordinating the
 rotation control means and movement control means are not limited to the
 examples described above.
 The invention is particularly applicable to the distribution of a flow of
 cold, heated or conditioned air, in a motor vehicle heating and/or air
 conditioning installation.