Abstract:
End-of-travel device ( 10 ) for roller blind actuating systems, comprising a member ( 22 ) displaceable as far as an end-of-travel position ( 26 ), coupling means ( 20 ) in engagement with the displaceable member ( 22 ) and rotationally actuated by a motor, and lever means ( 40 ) for converting the displacement of the displaceable member ( 22 ) into activation of an end-of-travel switch ( 60 ). The lever means ( 40 ) comprise a movable member ( 50 ) pivotably hinged on a frame and engageable with pressure by the displaceable member ( 22 ) when its reaches the end-of-travel position ( 26 ). The member ( 50 ) can be engaged with an actuating member ( 58 ) of the switch ( 60 ) where an actuating member of the switch ( 60 ) is positioned radially with respect to the axis of displacement of the member ( 22 ).

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an end-of-travel device for actuating systems of roller blinds or sun shades, such as shutters, sun awnings, etc. 
     It is known that in actuating systems for roller blinds (to which reference will be made henceforth for the sake of simplicity, but it being understood that the invention is not limited to this application) for some time automatic end-of-travel devices have been used, namely mechanical or electromechanical devices which cause stoppage of the roller blind when it reaches a predetermined final position. 
     Many examples of these devices exist in the state of the art. In the patent FR 2,076,529 two gear wheels which advance on associated female screws act on end-of-travel switches (microswitches) displacing flanges which slide coaxially on a smooth portion of the female screws. 
     In a very similar manner the patent EP 0,371,170 describes actuation of end-of-travel switches by means of gear wheels which advance on associated female screws, where, however, it is the gear wheel itself which acts by means of direct contact on the switch (for this purpose it is chamfered on the contact edge). 
     These systems, although managing to limit the longitudinal dimensions, do not allow precise adjustment of the end-of-travel stops, resulting in positioning errors of the roller blind. A first cause of error is the sensitivity of the microswitch which is actuated. The commercially available microswitches do not ensure constant operation as regards either the position or the moment of activation, namely they are not always activated at the same moment or in the same position (activation may occur after travelling a third or a half of their total travel path). Moreover, with time their characteristics change. Since the manufacturers of actuating systems use commercially available microswitches, this error cannot be eliminated. On the other hand it is likewise not economically advantageous to produce specific microswitches for this type of application. A second cause of error is the speed with which the microswitch is actuated. This parameter in fact influences the position and the moment of activation. The activation position may be rendered more constant by increasing the speed of actuation of the microswitch. 
     A commercially known solution is one where end-of-travel microswitches are actuated by gear wheels which advance on associated female screws. In this case, however, the movement of the gear wheels is transferred to the movable part of the microswitch by means of a lever able to multiply the operating speed owing to the different length of its arms. It can be easily understood that the dimensions of the arms of the lever determine directly the performance of the system, but at the same time they are also decisive for the space occupied by the system. However, the dimensions of the actuating system are dependent upon the end-of-travel system, which prevent any shortening thereof. Since the dimensions of the actuating system heavily influence both the practicality of assembly and its cost (production, packaging and storage), it is obvious that this system is not of an optimal nature. 
     BRIEF SUMMARY OF THE INVENTION 
     The main object of the present invention is to provide an improved end-of-travel device by means of which the problems and drawbacks briefly mentioned above are substantially solved. 
     This object is achieved with an end-of-travel device for rotational actuating systems of roller blinds or sun shades, which is mounted on a frame of the roller blind and coupled to a motor for actuating the roller blind, comprising a member displaceable as far as a desired adjustable end-of-travel position, coupling means in engagement with said displaceable member and rotationally actuated by said motor, so that the rotation of said motor and said coupling means causes said displacement of said member, lever means for converting the displacement of said displaceable member into activation of an end-of-travel switch for operating said motor, said lever means comprising a movable member pivotably mounted on the fixed frame and able to be engaged with pressure/thrust by said displaceable member when it reaches said end-of-travel position, the other end of said movable member being engageable with a member for actuating said end-of-travel switch, characterized in that said member for actuating said switch is positioned radially with respect to the axis of displacement of said member, so that when said rotating member reaches said end-of-travel position and engages by means of pressure/thrust with said movable member, said movable member is made to rotate about the pivoting point on the frame, consequently actuating said end-of-travel switch. 
     In the particular embodiment of the present invention, said arm of the lever means is L-shaped and has a first branch which has an end pivotably mounted on said frame and is engaged with pressure/thrust by said rotating member during its displacement when it reaches the end-of-travel position. The second branch of said arm engages by means of pressure/thrust with the member for actuating said end-of-travel switch. 
     This innovative idea allows the longitudinal dimensions of the actuating system to be reduced substantially, with all the advantages arising therefrom. 
    
    
     
       BRIEF DESCRIPTION OF THE INVENTION 
       These and further advantages will emerge more clearly from the following description of the device according to the invention, with reference to the accompanying drawings in which: 
         FIG. 1  shows a side view of the device according to the invention; 
         FIG. 2  shows an axonometric view of the device according to  FIG. 1  from above; 
         FIG. 3  shows an axonometric view of the device according to  FIG. 1  from below; 
         FIG. 4  shows schematically another side view of the device; 
         FIG. 5  shows schematically another side view of the device. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the figures of the entire structure of the roller blind only the portion of interest in the region of the end-of-travel system is shown. With reference to the accompanying figures, a device according to the invention is denoted by  10 . It normally and preferably consists of two identical end-of-travel devices which are arranged laterally alongside each other and only one of which for the sake of simplicity and brevity will now be described. 
     The device  10  comprises a rotating splined cylinder  20  mating with a gear wheel  22  which in turn engages, by means of its threaded central hole  23 , with the thread of a fixed female screw  24  arranged parallel to the cylinder  20 . Both the female screw  24  and the cylinder  20  are supported by a bracket  32  mounted on the frame of the roller blind (the other ends of the female screw  24  and the cylinder  20  are likewise supported by a similar bracket). 
     By means of a known mechanism, not shown, the motor for rotation of the roller blind (not shown) causes the rotation of said cylinder  20  about its longitudinal axis and consequently the gear wheel  22  advances on the female screw  24  in relation to the rotational movement of the roller blind (direction F in the figures). The advancing movement of the gear wheel  22  along the female screw  24  continues until it reaches an end-of-travel position where it encounters lever means  40  at a pressure/thrust point  26 . 
     The lever means  40  comprise a movable L-shaped arm  50  having the free end of a first branch  51  hinged about a pivot pin  70  on the aforementioned frame. From the figures it can be readily seen that the branch  51  of the lever means  40  has in its thickness a hole  52  inside which a smooth cylindrical portion  25 , i.e. without threading, of the female screw  24  passes in a freely slidable manner. In particular the diameter of the hole  52  has dimensions such that between the outer surface of the female screw  24  and the inner wall of the hole  52  there is sufficient play to allow pivoting of the lever means  40  about the fulcrum  70  in a plane passing through the axis of the female screw  24 . It is evident that this result may also be achieved by providing the smooth portion  25  with a diameter smaller than that of the main body of the female screw  24 . 
     The second branch  53  of the arm  50 , which in the embodiment shown is situated at an angle preferably of ninety degrees with respect to the branch  51 , engages, in the position indicated by the reference number  28 , with the actuating member or pushbutton  58  of an end-of-travel switch  60 , which is advantageously a microswitch. With this configuration it is possible to position the end-of-travel switch and in particular its actuating pushbutton  58  in a position radially spaced from the axis of the female screw  24 , but within the limits of the longitudinal dimensions of the said female screw, therefore allowing shortening of the longitudinal length of the roller blind to the length of the female screw without any further extension. As can be seen from the Figures, the operating principle of the invention is as follows: when the gear wheel  22  reaches the end-of-travel position at the pressure/thrust point, it exerts at this point  26  a force on the first branch  51 , so that the branch  50  rotates about the fulcrum  70 . Owing to this rotation, the second branch  53  of the arm  50  in turn exerts on the contact point  28  an activating force on the pushbutton  58  of the end-of-travel switch  60 . When the switch  60  is activated, actuating means (not shown) causes stoppage or reversal (and/or another function) of the roller blind. Then the roller blind may move only in the reverse direction, causing reverse rotation of the cylinder  20  and forward movement of the wheel  22  in a direction opposite to the previous direction F. 
     In order to provide two end-of-travel positions it is possible to use two separate devices (one per position), as shown in the figures, or arrange a second movable pivoting member on the other end of the female screw  24  so as to activate a second end-of-travel switch. 
     With reference to  FIGS. 4 and 5 , a schematic description is now given of two mechanical equivalents of the invention and which are third order levers, the parts of which constructionally identical to the already described parts will be distinguished by the suffixes “a” and “b”, respectively, parts not named remaining the same even if not shown. 
     In  FIG. 4  a gear wheel  22   a  advances rotating on the thread of a female screw  24   a  in relation to the movement of the roller blind (direction F in the figure). As it advances, the gear wheel  22   a  reaches an end-of-travel position at a pressure/thrust point  26   a  where it encounters lever means  40   a  comprising a straight movable arm  50   a  with its fulcrum on the pivot pin  7   a . The movable arm  50   a , when it is engaged by the gear wheel  22   a , rotates about its fulcrum  70   a  and exerts, at a point  28   a , an activating force on a pushbutton  58   a  of an end-of-travel switch  60   a . Here the movable member  50   a  is pivotably hinged in a position adjacent to the pressure point  26   a . With respect to the female screw  24 , the pin  70   a  and the pressure point  26   a  are radially on the same side. 
     In  FIG. 5  a gear wheel  22   b  advances rotating on the thread of a female screw  24   b  in relation to the movement of the roller blind (direction F in the figure). As it advances, the gear wheel  22   b  reaches an end-of-travel position at a pressure/thrust point  26   b  where it encounters lever means  40   b  comprising a movable V-shaped member  50   b  with its fulcrum on a pivot pin  70   b . The movable member  50   b  exerts, at a point  28   b , an activating force on a pushbutton  58   b  of an end-of-travel switch  60   b . In this case the movable member  50   b  is pivotably hinged in a position less than about halfway between the pressure/thrust point  26   b  and the point  28   b  of application of the activating force. The switch  60   b , unlike the previous examples, does not have its pushbutton  58   a  directed towards the female screw  24   b  (i.e. is directed radially away from the female screw  24   b ). 
     When the gear wheel  22   b  reaches the end-of-travel position at the pressure/thrust point  26   b , it exerts a force on the movable member  50   b  which, rotating about the fulcrum  70   b , exerts at the point  28   b  an activating force on the pushbutton  58   b  of the end-of-travel switch  60   b.    
     For the invention, as lever means it is possible to use any type of passive kinematic mechanism, for example hinged transmission or gear systems particular types of levers). Moreover, for the lever means, it is possible to make use of the activating bar already present in some commercially available microswitches. 
     It is mentioned that, instead of the female screw and the thread type system for coupling with the rotating member, it is possible to use equivalent mechanisms provided that they allow displacement of a movable member, controlled by rotation of the roller blind motor.