Abstract:
Method—and device for the implementation thereof intended to provide a protection system for barriers which are movable along an operating path and actuated by a motor, such as roller blinds, gates or the like, comprising the steps of connecting the barrier, with play, to a fixed part ( 30 ) so that the barrier is able to move independently of the action of the motor over a travel section ( 98 ); defining within the section ( 98 ) a set of safety positions corresponding to a safety position for the barrier; detecting along the travel section ( 98 ) the actual position of the barrier with respect to the fixed part ( 30 ); preventing or reversing the action of the motor and/or the movement of the barrier when the barrier, inside the travel section ( 98 ), does not have a position included within the set of safety positions.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to International Application PCT/EP/2006/068183, which was filed Nov. 7, 2006. This application claims priority to Italian Application TV2005A000169 filed Nov. 7, 2005. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a method and a device providing a safety system for roller blinds, sun awnings, gates and the like. 
     2. Description of the Related Art 
     It is known that the actuating systems for roller blinds, to which reference will be made by way of example although the invention is also applicable to other movable barriers, are provided with safety devices for detecting when the roller blind, during its movement—especially its downwards movement—strikes an obstacle. After making impact, normally the roller blind is driven so as to reverse its direction of travel. 
     Many solutions of this type are known. In particular, a subassembly of such solutions makes use of a mechanical play existing between the drive shaft of the actuating system and the roller onto which the roller blind is wound. EP 0,552,459 describes an actuating system in which play is provided between two teeth projecting from the casing of the motor (of the actuating system) and a bar perpendicular to a rod fixed to the wall, which rod supports the entire actuating system. The bar is provided with deformation sensors for detecting the deformation thereof and therefore, indirectly, the load acting on the motor, from which data for controlling it is obtained. 
     EP 0,497,711 describes an actuating system in which a free wheel is arranged between the shaft and the roller. Two concentric members in the free wheel have, associated with them, means which act so that the relative movement of these two members when the free wheel starts to function after the roller blind strikes an obstacle causes, by means of a switch arranged in the electric power supply circuit of the motor, the automatic reversal of the direction of rotation of the roller and the immediate upward movement again of the roller blind. 
     FR 2,721,62 describes an actuating system where the roller is connected to a sensor, the signal of which representing the angular speed of the roller—here as below relative to the stationary part of the actuating system which is fixed to the wall—is processed by a logic unit in order to produce a stopped condition for the motor of the roller blind. A free wheel is provided, arranged between the motor and the roller, and zeroes the speed of the roller when it strikes an obstacle. 
     DE 196 10 877 describes a control system for an actuating system of roller blinds, comprising a pressure bar (Druckbalken). This bar is activated upon rotation of the motor which actuates the roller blind and, by means of the pressure sensors in contact with the bar, a signal is obtained and used to control the actuating system. In particular, this signal is used to detect an obstacle encountered by the roller blind. 
     DE 197 06 209 describes a system for measuring variations in weight acting on a roller which carries a roller blind, depending on which a motor-driven actuating system (of the roller blind) is controlled and in particular is stopped. In order to achieve this result a sensor in the form of a mechanical switching component is used, said component comprising two parts which co-operate and the relative angular position of which (along a same axis) is variable. When the roller blind reaches the end-of-travel stop or an obstacle, the relative rotation of the two parts changes and may be detected by mechanical switches so as to perform control of the actuating system. 
     U.S. Pat. No. 6,215,265 describes a system for controlling a motor-driven actuating system for a roller blind which measures the torque of the motor and stops it when it exceeds a fixed maximum torque value or following a maximum variation in the torque per unit of time. In addition, the speed of the roller is measured and the motor is stopped below a predefined speed value (which can be obtained from a stored profile). A further characteristic feature is to leave rotational play between the roller and the shaft of the motor, so as to make use of it as a further way of deactivating the motor. No further information is provided in this connection. 
     DE 44 45 978 relates to a safety device for roller blinds in which the stationary part of the actuating system is fixed with a certain degree of play, allowing a limited angular movement about the axis of the shaft (onto which the roller blind is wound) and in which at least one pivoting interrupt lever with an associated spring is provided. During a dangerous event the spring pulls the lever against a switch so as to produce a malfunction signal. 
     All these solutions have drawbacks. 
     The solutions which, in order to detect the presence of an obstacle, control the consumption or the load of the motor must necessarily rely upon a variation in the consumption or load produced by the obstacle. This variation, in order to activate a protection system, must exceed a minimum activation threshold below which it is still possible for dangerous impact situations to occur. Moreover, since the controlled (or monitored) component is the motor of the actuating system, the component which actually causes the impact, namely the roller blind, which sometimes has considerable dimensions, is not monitored. It is particularly difficult to control the motors which are fitted to roller blinds such as shutters, Venetian blinds or external roller shutters which have a “bellows” structure where the variation in load following an impact with an obstacle is difficult to predict because it depends on the obstacle itself and the impact conditions. In fact, it is the deformation of the roller blind during impact which produces the variation in the load on the motor. Moreover, since it is dependent upon the characteristics of the motor, each system must be set for the specific application, which varies greatly depending on whether it is required to operate shutters, awnings, blinds, doors or entranceways which have a varying size, weight and characteristics. 
     With the solutions which instead make use of mechanical play between the roller and motor, a degree of uncertainty may arise during their operation. When the play is used to obtain protection by means of a slider travelling along the entire length thereof in order to activate a switch or similar solutions, necessarily the play must be gauged in relation to the particular application. Too small a play may trigger protection without an obstacle actually being present, since the roller blind may encounter along its path not an insignificant amount of resistance, such as that produced by dust which has accumulated (especially with time) or ice formations, or may simply encounter more friction than predicted, usually as a result of an increase in dimensions due to variations in temperature which may even occur on a daily basis. 
     Too great a play may trigger the protection when the entire weight of the roller blind is already acting on the obstacle, which is very dangerous if, for example, the obstacle is a person. 
     It is therefore easy to appreciate the difficulty of designing a reliable system which has acceptable operating margins and at the same time can be used in more than one application, in order to reduce the re-designing and adaptation costs. 
     If the mechanical play is associated with control of the roller speed, here too the already mentioned problems exist of having to choose the degree of play with a compromise between efficiency and the possibility of standardisation. Where, however, there is only control of the angular speed of the roller, whether or not a free wheel is used on the roller, the risks exists that this speed may fall and trigger activation only when the roller blind is already bearing dangerously on the obstacle, something which is all the more likely where the roller blind has a fold-up structure (for example a blind with several horizontal slats) since the edge of the roller blind subject to impact disengages from the roller. 
     Where, instead, mechanical play is used to monitor indirectly the parameters of the motor, the general performance of the actuating system suffers from the drawbacks of the systems where only the parameters of the motor itself are monitored. In this case the mechanical play is nothing other than an alternative sensor for an electrical or physical characteristic of the motor. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a protection device which is devoid of the drawbacks of the prior art. 
     This object is achieved with a method for providing a protection system for barriers which are movable along an operating path and actuated by a motor, such as roller blinds, gates or the like, comprising the steps of:
         connecting the barrier, with play, to a fixed part so that the barrier is able to move independently of the action of the motor over a travel section;   defining within the section a set of safety positions corresponding to a safety position for the barrier;   detecting along the travel section the actual position of the barrier with respect to the fixed part;   preventing or reversing the action of the motor and/or the movement of the barrier when the barrier, inside the travel section, does not have a position included within the set of safety positions.       

     In order to implement this method, the invention envisages a protection device for movable barriers which can be actuated by a motor, such as roller blinds, gates or the like, for implementing the method, comprising:
         a part fixed with respect to the movement of the barrier;   a kinematic chain by means of which the fixed part can be connected to the barrier with play, the barrier being able to move independently of the action of the motor over a travel section;   detection means for detecting, along the travel section, the relative position of the fixed part and the barrier;   a processing unit which acquires position data from the detection means and prevents or reverses the action of the motor and/or the movement of the barrier when the barrier, along the travel section, does not have a position included within a set of safety positions.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The advantages of a method and a device according to the invention will emerge more clearly from the following description, which refers mainly, by way of example, to an actuating system for a roller blind, but the comments of which are applicable to any variant of the invention, and which refers to the accompanying drawings, where: 
         FIG. 1  is an exploded view of an actuating system for roller blinds; 
         FIG. 2  is an exploded view of a device according to the invention; 
         FIG. 3  is a side view of one end of the actuating system according to  FIG. 1 ; 
         FIG. 4  is a top plan view of the end according to  FIG. 3 ; 
         FIG. 5  is a cross-sectional view along the plane B-B indicated in  FIG. 4-4 ; 
         FIG. 6  is a cross-sectional view along the plane C-C indicated in  FIG. 3 ; 
         FIG. 7  is a cross-sectional view along the plane A-A of  FIG. 3  in a first operating condition; 
         FIG. 8  is a cross-sectional view along the plane A-A of  FIG. 3  in a second operating condition; 
         FIG. 9  is a vertically and longitudinally cross-sectioned view of the actuating system according to  FIG. 1 ; 
         FIG. 10  is an exploded view of a second actuating system for roller blinds; 
         FIG. 11  is an exploded view of a second device according to the invention; 
         FIG. 12  is a side view of one end of the actuating system according to  FIG. 10 ; 
         FIG. 13  is a cross-sectional view along the plane F-F of  FIG. 12  in a first operating condition; 
         FIG. 14  is a cross-sectional view along the plane F-F of  FIG. 12  in a second operating condition; 
         FIG. 15  is a vertically and longitudinally cross-sectioned view of the actuating system according to  FIG. 10 ; 
         FIG. 16  is a view of a detail according to  FIG. 15 ; 
         FIG. 17  is a cross-sectional view of an accessory according to the invention. 
         FIG. 18  is an exploded view of a third device according to the invention for an actuating system for roller blinds; 
         FIG. 19  is another exploded view of the device in  FIG. 18 ; 
         FIG. 20  is a side view of the device in  FIG. 18  when assembled; 
         FIG. 21  is a front view of the device in  FIG. 18  when assembled; 
         FIG. 22  is a cross-sectional view along the plane H-H indicated in  FIG. 20 ; 
         FIG. 23  is a cross-sectional view along the plane J-J indicated in  FIG. 21 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In  FIG. 1 ,  18  denotes an actuating system for roller blinds, composed of:
         a device  50  for implementing the method according to the invention, associated with an end group  20 ;   a tubular body  22  which:   at one end contains a motor and all the devices for operation thereof (not shown), the output shaft of which is connected to a pinion  23  inserted inside a toothed adaptor  24  for a roller  25  (on which the roller blind—not shown—is wound). The roller  25  is arranged over the tubular body  22  in a coaxial position;   at the other end it is joined to a rotating part  70  by means of forced engagement between reliefs  28  on the rotating part  70  and corresponding recesses  29  of the tubular body  22 ;   a prism-shaped support body  26  which is fixed rotatably to a wall and in which one end of the roller  25  is engaged, a metal ring  27  being inserted inside the other end of the roller  25 .       

     The device according to the invention has been shown separately and in greater detail in  FIG. 2 . It comprises a base piece  30  and a rotating part  70  substantially with a circular cross-section, an electronic circuit board  99  and a wall bracket  90 . The latter is fixed to a wall and the base piece  30  is housed inside it. The tubular body  22  is inserted inside the roller  25  of the roller blind. 
     The base piece  30  acts as a fixed base on which the rotating part  70  is able to rotate over a limited section of angular travel, the amplitude of which is defined by mutual mechanical play. For this purpose, the base piece  30  comprises a cylindrical base  32  from which there projects a circular lip  34  which has, on the inside, in a cavity  33 , three identical teeth  36  which are situated in a relative 120° radial arrangement, with respect to the centre of the lip  34  where there is a hollow cylindrical relief  38  which is as high as the lip  32 . Two identical circular seats  40  are situated at the bottom of the relief  38  and contain two identical magnets  42  with corresponding dimensions. 
     With a screw  94 , tightened by a nut  96  which passes inside the relief  38 , the base piece  30  is rotatably connected to the rotating part  70  which also has a circular lip  72 , but with a diameter smaller than the lip  34  so as to be able to fit perfectly inside it and rotate with frictionless contact. The lip  72 , opposite the teeth  36 , is inset towards the centre, forming three identical concavities  74  with an arched bottom and width greater than that of the teeth  36  such that, when the rotating part  70  rotates relative to the base piece  30 , the teeth  36  move inside the concavities  74 . 
     The lip  72 , in the region of a concavity  74 , terminates in a shoulder  76  or continues directly with a circular edge  78  from the bottom surface  79  of which (see  FIGS. 5 and 6 ) a hollow cylindrical spacer  80  projects centrally, inside which spacer the nut  96  and part of the body of the screw  94  are contained. By tightening the screw  94  not too tightly using the nut  96 , the rotating part  70  rests against the relief  38  and is able to rotate inside the base piece  30  without becoming detached. The difference in width between the teeth  36  and the concavities  74  defines a limited angular section of travel (play)—denoted by  98 —along which the rotating part  70  is able to travel inside the base piece  30 . 
     The bottom surface  79  has a diametral slit (not shown) inside which the circuit board  99  (shown in schematic form) is inserted and retained by means of its fork-shaped end  82  with two sides  81   a ,  81   b ; therefore, the two sides  81   a,b  surround snugly the spacer  80  and extend beyond the bottom surface  79  into the space surrounded by the lip  34  (see  FIGS. 5 and 6 , where, in order to facilitate understanding thereof, the tubular body  22  not shown in  FIGS. 3 and 4  is also cross-sectioned). The ends of the sides  81   a,b  each support a Hall sensor  95  which is positioned, once the board is inserted, opposite a magnet  42 . It should be noted that the board  99  is shown in very schematic form, but contains all the logic components, the signal processing components and the connections necessary for the functions which will be described. Moreover, in order to increase the sensitivity of the system, the magnets  42  are directed so that a pole of their magnetic field is directed towards the sensors  95 . 
     Advantageously, resilient means  97 , for example a spring or rubber piece, may be inserted inside the section  98  so as to push resiliently the rotating part  70  into a zero reference angular position where each tooth  36  is situated approximately in a central position with respect to the width of the corresponding concavity  74  (see  FIG. 7 ), which condition is achieved only when the actuating system for roller blinds  18  is not installed. After installation of the actuating system  18  and the roller blind, the position of the teeth  36  with respect to the corresponding concavity  74  is mainly the result of the simultaneous action of the weight force of the roller blind and the opposing force provided by the resilient means  97 . Moreover, also present is the action of any friction or resistance which the roller blind encounters during its travel and which may in fact vary during the life of the roller blind and must be alternately added to or subtracted from the action of the weight force of the roller blind. By varying the resilience factor of the means  97  (or their size) it is possible to optimise the sensitivity of the system, preventing also false alarms or stray signals being emitted by the sensors  95 . 
     Operation of the device  50  is now described, with reference to  FIGS. 7 ,  8  and  9 . 
     The actuating system  18  comprises a kinematic chain consisting of the following components:
         the roller  25  is joined to the motor of the actuating system via the adaptor  24  and the pinion  23 ;   the motor is joined to the tubular body  22  (being rigidly contained inside it) and the latter is joined to the rotating part  70 .       

     During rotation of the roller  25 , the roller blind is wound onto or unwound from the roller  25 . The moment exerted by the weight of the roller blind on the roller  25  therefore varies and is transmitted via the kinematic chain to the rotating part  70 , which assumes a certain angular reference position within the section of play  98 . This position is the result of the action of the moment generated by the weight of the roller blind on the roller  25  and the opposing force of the resilient means  97  to which the moment of the motor is indirectly applied (the motor is controlled so as to rotate at a practically constant angular speed so as to move the roller blind at a constant speed). 
     If the roller blind encounters an obstacle and is stopped or in any case slowed down by it, the relative angular position of the rotating part  70  and base piece  30  varies and the sensors  95  detect instantaneously this variation. This is explained with reference to  FIGS. 7 and 8  where two different angular positions of the rotating part  70  with respect to the base piece  30  are shown. 
     In the angular position of the rotating part  70  shown in  FIG. 7 , the two sensors  95  detect a strong magnetic field (resulting from the proximity to the magnets  42 ). When the rotating part  70  is rotated as shown in  FIG. 8 , the magnetic field in the space occupied by the sensors  95  is smaller, as is the signal output by the latter and analysed by the board  99 . It is easy to understand that, in general, for each angle covered by the rotating part  70  within the section of play  98 , the magnetic field detected by the sensors  95 , and therefore their output signal, will be different and uniquely linked to the angular position of the rotating part  70  (suitable screening systems—not shown—prevent any interference from outside the system). 
     The board  99  processes the signal of the sensors  95  so as to extract the information relating to the angular position of the rotating part within the section  98 . At the same time, the board  99  may also acquire the current position of the roller blind (detected, calculated or estimated by means of devices of the known type, usually encoders, associated directly with the motor, inside the tubular body  22 , or with the roller  25 ). 
     During operation of the actuating system  18 , when the roller blind is moving, it is possible to detect a signal which corresponds to the actual angular position of the rotating part  70  within the section  98 . This signal may be sampled and stored so as to obtain a response curve (RC), namely a very compact sequence of data which correspond to the different positions occupied by the rotating part  70  within the play section  98 . Each sample may be associated with a precise instant or with the actual position of the roller blind, during the movement of the latter along the operating path. 
     All this allows at least two advantageous operating modes to be obtained: 
     i) it is possible to define a set of safety positions consisting simply of a range of positions of the rotating part  70  within the play section  98 . Each position outside this range is regarded as a danger signal and the actuating system is correspondingly controlled. Therefore the protection consists of operation which is of a “stepped” nature, but able to be adjusted with a programmable margin of freedom so as to take account of the tolerances during operation. 
     ii) at the time of installation, in order to adapt the actuating system  18  to the specific operating situation, or also afterwards, if it is considered that some operating conditions have varied considerably and it is necessary to re-configure the system, an actuating system which is fitted with the device  50  may perform an adaptation step during which:
         the roller blind completes one or more opening/closing cycles along the operating path;   at the same time the relative angular deviation of the base piece  30  and the rotating part  70  is sampled, if necessary averaged and/or filtered and stored in a memory of the board  99 . This thus produces a response curve (RC) for the angular deviation corresponding to the specific operating condition, in which the sampled data are associated with the position of the roller blind;   a tolerance value T to be added to the RC is defined, in order to take account of small variations—which are not significant for safety purposes—associated in a variable and unpredictable manner with the path of the roller blind;   subsequently the RC and the tolerance T are stored in a suitable non-volatile memory (not shown).       

     During subsequent operation of the actuating system  18 , the current position of the roller blind along the operating path and the corresponding current relative angular deviation of rotating part  70  and base piece  30  are detected, the latter is compared with the point of RC+T (which corresponds to a set of safety positions) relating to the current position and, if the limits values for the tolerance T are exceeded, the board  99  activates protection, for example reversing the direction of rotation of the motor or causing stoppage thereof and activating a danger signal. 
     Advantageously it is possible to store a set of positions of the barrier along the operating path. In this way it is possible to associate, biunivocally, a set of safety positions with a set of positions of the barrier along the operating path, namely a plurality of points is considered along the operating path and a value of the angular deviation is associated with each of them in a set of safety positions. When the barrier reaches a point belonging to the predetermined set of positions along the operating path, the current angular deviation is compared with the corresponding value present in the set of safety positions, and action is taken consequently. 
     This self-learning procedure may be activated by the user or performed by the actuating system automatically at periodic intervals. 
     Another advantage of the invention is that by detecting continuously and point-by-point the relative angular deviation of base piece  30  and rotating part  70 —this parameter indicating the resistance encountered by the roller blind along its travel path—it is possible to associate with different angular positions of the rotating part  70  within the section  98  one or more activation thresholds or different RC+T values within the memory, corresponding to different danger situations. These threshold values are not fixed, but may be established very easily in each case (configuring the electronic board  99 , advantageously via software), depending on the application and the operating environment of the said application. 
     On the basis of different threshold or tolerance levels, which are programmed and stored in the electronic board, it is possible to determine, during installation, the behaviour mode of the system depending on the environment. For example, it is possible to establish a “level 1” (low sensitivity), where the tolerance T will be 20% since the roller blind is used in industrial applications, “level 2” where the tolerance T will be 15% since the roller blind is used on a window of a dwelling, “level 3” where the tolerance T will be 10% since the roller blind is used on French windows which are frequently used in a home, “level 4” (high sensitivity), where the tolerance T will be 5% since the roller blind is used in special environments such as nurseries or shops. Obviously, said levels may also be used for applications in particular climatic conditions, where ice is present or large variations in temperature frequently occur. 
     Therefore the mechanical characteristics of the device  50  do not change, even though its functional capabilities change, allowing it to be easily mass-produced. The capacity for adaptation of the device  50  to each operating situation of a roller blind, or even to changes—as a result of ageing or environmental variations—encountered during its movement, are effectively compensated for in real time. This may be performed either by the user, who may re-program the activation thresholds as desired, or automatically, using the self-learning procedure described. 
     The safety device  50  may also be battery-powered and/or provided with a wireless transmission system (for example of the radiofrequency, infrared or Bluetooth type) for signalling, advantageously to a remote receiver component, the danger condition or transmitting the angular deviation. Alternatively it is possible to envisage integrated network and/or fast connection means. 
     Obviously, in order to measure the relative angular displacement of the base piece  30  and rotating part  70 , it is possible to use other transducers, such as a potentiometer, an optical system, an additional encoder, etc. 
     An actuating system, which comprises a second device according to the invention, is shown in  FIG. 10  and is denoted by the number  118 . It is composed of:
         a device for implementing the method according to the invention, associated with an end group  120 ;   a tubular body  122  which:   at one end contains a motor and all the devices for operation thereof (not shown), the output shaft of which is connected to a pinion  123  inserted inside a toothed adaptor  124  for a roller  125  (on which the roller blind—not shown—is wound), said roller being arranged over the tubular body  22  in a coaxial position;   at the other end is joined to connector  170  by means of forced engagement between reliefs  128  on the connector  170  and corresponding recesses  129  of the tubular body  122 ;   a prism-shaped support body  126  which is fixed rotatably to a wall and in which one end of the roller  125  is engaged, a metal ring  127  being inserted inside the other end of the roller  125 .       

     The end group  120  has been shown separately and in greater detail in  FIGS. 11 and 12 . It comprises a base piece  130 , the connector  170  and a wall bracket  190 . The latter is fixed to a wall and the base piece  130  is housed inside it. The tubular body  122  is inserted inside the roller  125  of the roller blind. 
     The base piece  130 —see FIGS.  15  and  16 —is joined to the connector  170  by means of a through-screw  194  which is tightened by a nut  196  and passes through these two parts. 
     The base piece  130 —see  FIGS. 13 and 14 , which for the sake of simplicity shows only some reference numbers—has a cross-section in the form of a cross with four equal rounded sides  134  which each have, between them, a zone  126  inset towards the centre and house a corresponding cavity  132  of the bracket  190  which follows the profile thereof. The cavity  132  also has a cross-section in the form of a cross with four equal rounded sides  194 , between each of which there is a zone  196  inset towards the centre. The extension of the inset zones  196  extends along an arc which is smaller than that of the inset zones  126  and therefore a mutual rotational mechanical play  198  is obtained between the bracket  190  and the base piece  130  (which has the function of a rotating part). This rotational play  198  has an angular amplitude which is equal to the difference between the widths of the inset zones  126  and  196 . 
     The base piece  130 , when it enters into the bracket  190 , touches the bottom of the cavity  132 , which is denoted by  138 . The bottom  138  is provided with a rectangular groove  140  inside which the electronic board  199  is housed; when the base piece  130  is inserted inside the cavity  132 , two circular seats  144  in the base piece  130  containing two magnets  142  are arranged opposite the said board. The board  199  comprises a Hall sensor  195  which is situated opposite each magnet  142 . It should be noted that the board is shown in very schematic form, but may contain all the logic components, the signal processing components and the connections necessary for the functions which will be described. Moreover, in order to increase the sensitivity of the system, the magnets  142  are directed so that a pole of their magnetic field is directed towards the sensors  195 . 
     Advantageously—as in the device already described—it is possible to insert within the angular play  198  resilient means  197  so as to push resiliently the base piece  130  and therefore the connector  170  into a zero reference angular position. The comments made in this connection for the first device are also applicable in this case and will not be repeated. 
     Operation of the second device is now described with reference to  FIGS. 10-16 . The actuating system  118  comprises a kinematic chain consisting of the following components:
         the roller  125  is integral to the motor of the actuating system via the adaptor  124  and the pinion  123 ;   the motor is integral to the tubular body  122  (being rigidly contained inside it) and the latter is integral to the connector  170  which is in turn integral to the base piece  130 .       

     During rotation of the roller  125 , the roller blind is wound onto or unwound from the roller  125 . The moment exerted by the weight of the roller blind on the roller  125  therefore varies and is transmitted via the kinematic chain to the base piece  130 , which assumes a certain angular position within the section of play  198 . This position is the result of the action of the moment generated by the weight of the roller blind on the roller  125  and the opposing force of the resilient means  197  to which the moment of the motor is indirectly applied (the motor is controlled so as to rotate at a practically constant angular speed so as to move the roller blind at a constant speed). 
     If the roller blind encounters an obstacle and is stopped or in any case slowed down by it, the relative angular position deviation of the base piece  130  and the bracket  190  varies and the sensors  195  detect instantaneously this variation. This is explained with reference to  FIGS. 13 and 14  where two different angular positions of the base piece  130  with respect to the bracket  190  are shown as an example. In the angular position of the connector  170  shown in  FIG. 14 , the two sensors  195  detect a strong magnetic field resulting from the proximity to the magnets  142 . Two axes X 1  and X 2  which respectively pass through the two sensors  195  and the two magnets  142  are arranged on top of each other. When the rotating part (connector)  170  is rotated as shown in  FIG. 13 , where the axes X 1  and X 2  are inclined with respect to each other at a certain angle, the magnetic field in the space occupied by the sensors  195  is smaller, as is the signal output by the latter and analysed by the board  199 . It is easy to understand that, in general, for each angle covered by the base piece  130  within the section  198 , the magnetic field detected by the sensors  195 , and therefore their output signal, will be different and uniquely linked to the angular position of the base piece  130  with respect to the bracket  190  (suitable screening systems—not shown—prevent any interference from outside the system). 
     The board  199  processes the signal of the sensors  195  so as to extract the information relating to the angular position of the base piece  130  within the section  198 . At the same time, the board  199  may also acquire the current position of the roller blind (detected by means of devices of the known type, usually encoders, associated directly with the motor, inside the tubular body  122 , or with the roller  125 ). 
     With the actuating system  118  it is possible to implement the same two control procedures indicated by i) and ii) (adjustable stepwise operation or acquisition of an RC for the angular position of the base piece  130 , definition of a tolerance T, etc.) which were described for the actuating system  18 , with the same advantages, and which will not be repeated here. In the same way it is possible to use for the actuating system  118  the constructional options already described for the actuating system  18 . 
     Advantageously the safety device according to the invention may also be constructed separately from the actuating system, and therefore also as an external accessory, able to be added, if necessary, to an actuating system which is without one, with a considerable cost saving as regards both production and warehouse management. 
     An accessory of this type can be seen in  FIG. 17  where it is shown in cross-section and denoted by  218 . An electronic board  299  and sensors  295 , which are fixed thereon, are inserted in a suitable seat formed in a fixed outer disk  290 , to which an inner disk  230  is coaxially connected in a rotatable manner with a holed rivet  220 . As can be seen, the cross-sections of the two disks  290 ,  230  have the same form as the bracket  190  and the base piece  130 , respectively, and provide an identical degree of rotational mechanical play  298  with an angular amplitude equal to the difference between the widths of the perimetral inset zones on the two disks—as in the case of the actuating systems  18  and  118 . The relative operation of the two disks  290 ,  230  is identical to that of the bracket  190  and the base piece  130  in the actuating system  118  and the base piece  30  and the rotating part  70  in the actuating system  18 : the angular position of the inner disk  230  with respect to the outer disk is detected by means of the two sensors  295  which are situated on the outer disk and which detect the magnetic field of two magnets  242  situated on the inner disk opposite the sensors  295 . Between the two disks  290 ,  230  it is possible to arrange resilient means  297 , with the same aims described above for the means  97  and  197 . 
     The functional properties, the advantages and the constructional possibilities for the accessory  218  are the same as for the two actuating systems  18  and  118  already described, and for the sake of brevity are not repeated. It is obvious that, in order to achieve anti-obstacle control of the roller blind in an actuating system which is without the safety device according to the invention, it is sufficient to install the accessory  218 , using it in place of the wall bracket of the actuating system. The actuating system must be fixed to the inner disk  230 , while the outer disk  290  is fixed to the wall. The accessory may comprise only the outer disk  290  with the board  299  integrated, without inner disk  230 , in place of which the end group of the actuating system to be controlled is inserted in the disk  290 . Magnets are mounted on the end group of the actuating system so that they are able to interact with the sensors of the board present in the outer disk. 
     Moreover, the board  299  may also be absent, being arranged either in a remote position or already equipping the actuating system, which may be enabled and/or re-programmed to manage the signal supplied by the accessory. 
     For the devices already described another applicational possibility is that of installing them with a pre-set RC and T, for example in the case of very standardized applications. As an unrestrained connection, in addition to the play as described, it is possible to employ other connection systems, for example the play between one gear and another or a rack, or linear play and not angular play as in the embodiments described, or a combination of the two. Moreover, the barrier may be directly connected to the rotating part, without the intermediate arrangement of a kinematic chain as described; a possible example would be a driving crown wheel which meshes with play in a rack arranged longitudinally and joined to a gate so as to move it backwards and forwards. 
     Even the play resulting from the assembly or manufacturing tolerances may be exploited with the invention. In precision applications or when desirable, it is also possible to consider a zero tolerance, i.e. T=0. Another variant relates to the form of the parts which define the angular play, from their shape to the number of projections/inset zones for defining the angular play, or the arrangement of the latter (on the fixed part or the rotating part). Another variant relates to the number of magnets and magnetic field sensors, or their arrangement. Another variant relates to the design of the control system for the actuating system: here a digital control system has been described, but it is also possible to use any similar signal processing and storage technology. 
     A third device according to the invention is shown in  FIG. 18  and the following. It comprises a head (or end group)  520 , while the other components of the actuating device which are not shown are similar to those previously described for the systems  18  and  118 , thus for sake of conciseness they are omitted. 
     The head  520  comprises, as before, a base piece  530  and a rotating part  570  substantially with a circular cross-section, an electronic circuit board  599  with sensors  595  (both functionally identical to those previously described) and a wall bracket  590 . The latter is fixed to a wall and the base piece  530  is joined to it. As before, the base piece  530  acts as a fixed base on which the rotating part  570  is able to rotate over a limited section of angular travel. The head  520 , for which all the technical considerations and ways of working described for the systems  18  and  118  still apply, differs from the preceding systems for the embodiment of the resilient means between the rotating part  570  and the base piece  530 . 
     Only these resilient means and related elements will be now described, for brevity. The rest of the system is similar to that of the other variants. 
     The base piece  530  comprises a cylindrical base  532  from which there projects a circular lip  534  which has, on the inside, in a cavity  533 , a set of identical flexible fins  536  (only some numerated), of rectangular section, which are situated in a radial arrangement, with respect to the centre of the lip  534  where there is a hollow cylindrical relief  538  which is as high as the lip  532 . 
     With a screw  591  tightened by a nut (not shown) which passes inside the relief  538 , the base piece  530  is rotatably connected to the rotating part  570  which also has a circular lip  572 , but with a diameter smaller than the lip  534  so as to be able to fit perfectly inside it and rotate with frictionless contact. 
     The lip  572  is provided with a set of identical slits  586  (only some numerated), of rectangular shape, which are situated in a radial arrangement, with respect to the centre of the lip  534  where there is a cylindrical cavity  573 . The radial arrangement and dimensions of the slits  586  corresponds to that of the fins  536 , such that each of the fins  536  can be inserted in a corresponding slit  586 , optionally with a little play, when the rotating part  570  is inserted in the base piece  530  (the relief  538  is mounted inside the cavity  573 ). 
     The play of the relative rotation of the part  570  in respect of the base piece  530  can be determined by two factors. First, an optional mutual mechanical play between the fins  536  and the slits  586  (the former being smaller than the latter and moving therein) and, second, the flexibility of the fins  536 . With or without play, when the part  570 , subject to torsion, rotates enough in respect of the base piece  530  the fins  536  begin to flex. This flexion has two effects: (i) it defines a mechanical play between the part  570  and the base piece  530 , and (ii) it provides a counter-force, able to withstand an excessive torsion of the part  570  and able to resiliently move the part  570  back in its original angular position when the torsion thereon zeroes. 
     Clearly, the shape and the material of the fins  536  are reliably chosen to over-resist the maximum expected torsion while providing at the same time the desired elastic response. The number of the fins  536  and the slits  586  can be variable, from one to a multiplicity. Another variant is possible, wherein the fins  536  are not flexible and/or resilient means, such as those previously described, are provided in the slits  586  to exert a force on the fins  536  against the torsion thereof. 
     It is understood that minor deviations from the inventive idea expressed by the above description and accompanying drawings are nevertheless included within the scope of protection of the following claims.