Abstract:
The actuator comprises: an actuator member which is moveable relative to the structure and can perform an actuation movement in one direction and a return movement in the opposite direction, an electric motor including a rotor portion which can translate from a first, rest axial position to a second, working axial position as a result of an energization of the stator and against the action of a spring, a gear transmission which is coupled to the actuator member and can be coupled for rotation with the rotor portion when the latter is in the working axial position in order to bring about an actuator movement of the actuator member, and a stop device with a retaining member which can adopt an inactive condition and an active condition and an active condition in which it permits and prevent a return movement of the actuator member, respectively. The retaining member is operatively coupled to the rotor portion of the motor in a manner such that it can adopt the inactive condition and the active condition when the rotor portion adopts the rest position and when it adopts the working position, respectively.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an electromechanical actuator usable, in particular but not exclusively, for operating a coupling and transmission device for the laundry drum of a washing and/or drying machine. 
     SUMMARY OF THE INVENTION 
     The aim of the present invention is to provide an improved electromechanical actuator which can be produced easily and economically and, in particular, with the use of a single electrically-operated device. 
     This and other aims are achieved, according to the invention, by an electromechanical actuator comprising: 
     a stationary support structure, 
     an actuator member which is movable relative to the structure and can perform an actuation movement in one direction and a return or release movement in the opposite direction, 
     an electric motor connected to the structure and including a rotor portion which can translate from a first, rest axial position to a second, working axial position as a result of an energization of the stator and against the action of resilient means, 
     a gear transmission which is coupled to the actuator member and can be coupled for rotation with the rotor portion of the motor when the rotor portion is in the working axial position, in order to bring about an actuation movement of the actuator member, and 
     a stop device comprising a movable retaining member which can adopt an inactive condition and an active condition in which it permits and prevents a return movement of the actuator member, respectively, 
     the retaining member being operatively coupled to the rotor portion of the motor in a manner such that it can adopt the inactive condition and the active condition when the rotor portion adopts the rest position and when the rotor portion adopts the working position, respectively. 
     In the electromechanical actuator according to the invention, the rotor portion of the electric motor, which is so advantageously a synchronous electric motor, also acts as a linear actuator for controlling the stop device without requiring a special electrically-operated actuator, for example, such as a solenoid, for this purpose. 
    
    
     BRIEF DESCRIPTION OF THE PREFERRED 
     Further characteristics and advantages of the invention will become clear from the following detailed description, given purely by way of non-limiting example, with reference to the appended drawings, in which: 
     FIG. 1 is a partial plan view of an electromechanical actuator according to the invention, 
     FIG. 2 is a partial section taken on the line II—II of FIG. 1, 
     FIG. 3 is a view similar to that of FIG.  2  and shows the actuator in a different operative condition, 
     FIG. 4 is a view similar to that of FIG.  1  and shows the actuator in another operative condition, and 
     FIG. 5 is a partial section taken on the line V—V of FIG.  4 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In FIG. 1, an electromechanical actuator according to the invention is generally indicated  1 . 
     The actuator comprises a support structure  2  which, in the embodiment shown by way of example, comprises a plate  3  from which a substantially annular lower skirt  4  extends (FIGS.  2  and  3 ). 
     The portion of the plate  3  around which the skirt  4  extends has an opening, indicated  5 . 
     An electric motor, generally indicated  6 , is fixed to the plate  3 , inside the skirt  4 . The motor is, for example, a synchronous, alternating-current motor and comprises a stator  7  which surrounds a rotor having permanent magnets and generally indicated  8 . In the specific embodiment illustrated, the rotor  8  is hollow axially and is mounted so as to be rotatable and axially slidable relative to a fixed shaft  9  secured to a casing  10  of the motor. The rotor  8  comprises, in particular, a tubular end appendage  11  provided externally with a pinion  12  in its intermediate region. 
     At its end remote from the tubular appendage  11 , the rotor  8  has an axial cavity  13  in which a helical spring  14  is arranged around the fixed shaft  9  and tends to urge the entire rotor  8  axially towards the plate  3 , that is, upwards as seen in FIGS. 2 and 3. 
     At the base of the tubular end portion  11 , the rotor  8  has a portion  15  which extends partially in the opening  5  of the plate  3 . 
     The free end of the tubular portion  11  of the rotor  8  carries a push rod  16  the functions of which will be described below. 
     In known manner, the electric motor  6  is formed in a manner such that its rotor portion  8  can translate axially from a first, rest position shown in FIG. 2 to a second, working axial position, shown, for example, in FIGS. 3 and 5, as a result of the energization of the stator  7  and against the action of the spring  14 . When the stator  7  is de-energized, the spring  14  arranges the rotor  8  in the rest position and then keeps it there (FIG.  2 ). 
     A plurality of substantially parallel support elements, indicated  17  to  21  in FIGS. 2,  3  and  5 , extend from the opposite face of the support plate  3  to the skirt  4 . 
     The support element  17  is substantially a pin around which a gear  31  is mounted so as to be rotatable and axially translatable. 
     The support elements  18 ,  19 ,  20  and  21  have respective prismatic base portions and respective cylindrical end portions acting as pins for respective gears  32 ,  33 ,  34  and  35 . 
     The gear  31  has a lower ring of teeth  31   a  which can mesh with the pinion  12  of the rotor of the electric motor  6  in operation, as will be described further below. The gear  31  also has a second ring of teeth  31   b  of smaller diameter, which can mesh with a lower ring of teeth  32   a  of the gear  32 , as will be described further below. The latter also has a second ring of teeth  32   b  of smaller diameter which meshes permanently with a lower ring of teeth  33   a  of the gear  33 . 
     The gear  33  in turn has an upper ring of teeth  33   b  of smaller diameter which meshes permanently with the upper ring of teeth  34   a  of the gear  34 . The latter also has a lower ring of teeth  34   b  of smaller diameter which meshes with the rack  40  (FIGS. 1 and 4) of an actuator member, generally indicated  50 . 
     The actuator member  50  is mounted so as to be translatable relative to the support structure  2  and, in particular, can perform an actuation movement in the direction of the arrow A of FIG. 1 and a return or release movement in the opposite direction, that is, in the direction of the arrow B of FIG.  4 . 
     In particular, the actuator member  50  may be connected by means of a transmission element such as, for example, a metal cable, to a coupling and transmission device associated with the laundry drum of a washing machine. 
     The gear  31  bears on a portion or arm of a lever  36  mounted for rotating in a plane parallel to the plate  3  about a pin  37  fixed to the plate (FIG.  1 ). 
     In the embodiment shown, the pin  37  extends through a slot  38  formed in an intermediate portion of the actuator member  50 . The actuator member has a further slot  39  through which a further pin  41  extends, the pin  41  being in alignment with the pin  37  along the axis of translation of the actuator member  50 . 
     With further reference to the lever  36 , this lever has a portion or arm  36 a which extends between two pins  51  and  52  that extend from the lower side of an intermediate portion of the actuator member  50 . The lever  36  has a further arm  36   b  which is remote from the arm  36   a  and extends partially beneath the gear  31 . The portion of the arm  36   b  of the lever  36  which extends beneath the gear  31  has a thickness which is differentiated peripherally in the manner of a cam profile. 
     In FIG. 1, the actuation member  50  is shown in the travel-limit position which is reached upon completion of a return or release movement. Starting from this position, the actuator member  50  can be moved (as will be described below) in the direction of the arrow A to reach the travel-limit position shown in FIG. 4, which corresponds to the final position of an actuation movement or the starting position for a subsequent return or release movement. 
     When the actuator member  50  approaches the position shown in FIG. 4, its pin  51  encounters and then acts on the portion or arm  36   a  of the lever  36 , causing the lever to pivot and arranging it in the position shown in FIG.  4 . Similarly, during the movement from the position shown in FIG. 4 to that shown in FIG. 1, as the actuator member  50  approaches the return travel limit, its pin  52  encounters the portion or arm  36   a  of the lever  36  and then urges it to the operative position shown in FIG.  1 . 
     One end of a spring  43  is connected to the end of the arm  36   b  of the lever  36  and the other end of the spring is restrained on the support structure  2 . The spring enables the lever  36  to be stabilized in either of the operative positions shown in FIGS. 1 and 4. 
     As pointed out above, the arm  36   b  of the lever  36  has a profile of variable thickness on which the gear  31  bears. This profile is formed in a manner such that, when the lever  36  is in the position shown in FIG. 1, the gear  31  is kept axially raised, in a position in which its ring of teeth  31   b  is coupled or meshes with the ring of teeth  32   a  of the adjacent gear  32 , as shown in FIGS. 2 and 3. 
     When the lever  36  is in the operative position of FIG. 4, however, the cam profile of its arm  36   b  allows the gear  31  to move downwards towards an axially lowered position in which its ring of teeth  31   a  is disengaged from the pinion  12  of the rotor of the electric motor  6  (FIG.  5 ). 
     Advantageously, but not necessarily, a spring  60  is arranged around the pin  17 , between the gear  31  and a cover  61  (shown partially in FIGS. 2,  3  and  5  and fixed to the support structure  2  in known manner), the spring  60  tending to urge the gear  31  towards the plate  3  and to stabilize its position in the uncoupling condition shown in FIG.  5 . 
     The gear  35  is a gear which has an upper ring of saw-tooth-shaped triangular teeth  35   a,  and a lower ring of radial teeth  35   b  which meshes with an intermediate ring of teeth  31   c  of the gear  31 . 
     A resiliently flexible plate is indicated  70  in the drawings. In the embodiment shown by way of example, the plate  70  is generally substantially V-shaped (FIGS.  1  and  4 ). The plate  70  has a portion  70   a  the two ends of which are fixed to two supports  71  and  72  which extend from the plate  3  of the support structure  2 . The plate  70  has a second portion  70   b  which projects from the support  72  in the manner of a cantilever, over the gear  35 . The free end of the portion  70   b  of the plate  70  carries beneath it a triangular tooth  73  which can be wedged in the space defined between two adjacent teeth of the ring of face teeth of the gear  35 . 
     As can best be seen in FIGS. 2 and 3, when the motor is in the deactivated condition and the rotor  8  is thus in the raised position, the end push rod  16  associated with the rotor  8  of the electric motor  6  can keep the portion  70   b  of the plate  70  in a raised position in which the tooth or pawl  73  is disengaged from the ring of face teeth of the gear  35 . When, as a result of the energization of the motor  6 , the rotor  8  is attracted magnetically downwards against the action of the spring  14 , the portion  70   b  of the plate  70  is lowered, owing to its own resilience, and the tooth or pawl  73  is engaged between two adjacent teeth of the gear  35 , as shown in FIGS. 3 and 5. In this condition, the pawl  73  allows the gear  75  to rotate in one direction (anticlockwise as seen in FIGS.  1  and  4 ), but prevents that gear from rotating in the opposite direction. 
     The device described above operates in the following manner. 
     At rest, that is, in the deactivated condition, the actuator  1  adopts the configuration shown in FIGS. 1 and 2. In this condition, the electric motor  6  is not energized and its rotor  8  is in the raised, rest axial position in which its pinion  12  is disengaged from the teeth  31   a  of the gear  31  and its end push rod  16  keeps the pawl  73  carried by the plate  70  in the raised position and disengaged from the face teeth of the gear  35 . Moreover, in this condition, the arm or portion  36   b  of the lever  36  keeps the gear  31  in the raised, coupling position. 
     When the electric motor  6  is energized, its rotor  8  is attracted axially towards the base of the casing  10  against the action of the spring  14 . The rotor is thus brought to the position shown in FIG. 3, in which its pinion  12  meshes with the ring of teeth  31   a  of the gear  31  and its end push rod  16  allows the pawl  73  to engage between two adjacent face teeth of the gear  35 . The rotation of the rotor  8  thus brings about rotation of the gear  31  which represents the input gear of the transmission (comprising the gears  32 ,  33  and  34 ) which, when coupled with the rack  40 , enables the actuator member  50  to be translated in the direction indicated by the arrow A in FIG.  1 . The rotation of the gear  31  also brings about rotation of the gear  35  with face teeth, in the direction permitted by the pawl  73 . 
     The actuation movement of the member  50  continues until the travel-limit shown in FIG. 4 is reached. As already described above, shortly before the travel-limit position is reached, the pin  51  of the actuator member  50  engages and pivots the lever  36  which is thus arranged in the position shown in FIGS. 4 and 5. The gear  31  is consequently lowered along the pin  17  under the effects of its own weight and of the spring  60  and adopts the position shown in FIG.  5 . In this condition, the gear  31  is disengaged from the pinion  12  of the rotor of the electric motor  6 . 
     In the condition shown in FIG. 5, however, the gear  31  is still in engagement with the lower radial teeth of the gear  35 . The electric motor  6  thus continues to rotate, but freely, that is, it is released from the gear transmission. The actuator  50  is kept in the position shown in FIG.  4  and is thus prevented from returning as a result of the locking performed by the pawl  73  on the gear  35  which prevents reverse rotation of the entire transmission. 
     The actuator is deactivated at the moment at which the electric motor  6  is de-energized; the rotor  8  of the motor is then returned to the raised, rest position shown in FIG. 2, by the action of the spring  14 , releasing the pawl  73  from the gear  35 . The actuator member  50 , which is subjected to tensile stress in the direction of the arrow B of FIG. 4 by the device with which it is associated, for example, a coupling and transmission device, thus brings about reverse rotation of the entire gear transmission and is returned to the travel-limit position shown in FIG.  1 . As it approaches this travel-limit position, the pin  52  of the actuator member  50  engages the lever  36  and causes its position to change to the position of FIG. 1 so that the gear  31  is returned to the raised starting position shown in FIG.  2 . 
     The actuator described above enables all of the functions (the actuation movement of the member  50 , stopping of the is return movement of the transmission  31 - 34 , release of the transmission  31 - 34  to return to the starting conditions) to be performed with the use of a single electrically-operated device constituted by the electric motor  6 . In particular, the control of the ratchet stopping mechanism comprising the gear  35  and the plate  70  with the associated pawl  73  does not require the use of a further electrically-operated device such as a solenoid actuator or the like. 
     The actuator according to the invention may also be used, for example, for controlling a gate valve. 
     Moreover, the electric motor included therein may be of the type in which at least a portion of the rotor can adopt two different axial positions according to whether a voltage having a first value or a second value is applied to the stator.