Abstract:
3An accident-prevention device for buildings, particularly for assembling prefabricated components made of concrete, which comprises at least one pole and elements for detachably connecting the base of the pole to the surface of a building. The pole has, proximate to its tip, guiding pulleys for a cable element which forms a safety parapet. The guiding means are adapted to divert, in a direction which is substantially parallel to the axis of the pole, at least part of the stresses transmitted from the cable element to the pole, and the pole is provided with shock-absorbing elements for cushioning the stresses transmitted from the cable element to the pole in a direction which is substantially parallel to the axis of the pole.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an accident-prevention device for buildings, particularly for assembling prefabricated components made of concrete or the like, which are designed to provide individual protection against falls of workers assigned to walking high above ground level on buildings being erected. 
     Such devices generally comprise a plurality of spaced metal poles which are connected, at their base, to a horizontal surface of the building, formed for example by a beam, and have, at their tip or in an intermediate region of their vertical extension, a passage for a cable which is fixed to the building at its ends and is tensioned by means of appropriate cable tensioning elements so as to form a safety parapet. 
     In these devices, the poles are designed only to keep the cable at a preset height so that it can be easily engaged by the spring-catches with which the safety belts or harnesses worn by workers are equipped. 
     In some accident-prevention devices, the poles are inserted in a cavity which is formed inside a concrete component of the building. 
     In other devices, the poles are provided with a threaded base which can be engaged in a female thread formed inside a bushing which is embedded beforehand into the concrete component. 
     In other devices, the poles are rigidly coupled to the concrete component by a bayonet coupling, such as for example the device disclosed in U.S. Pat. No. 4,045,003. 
     In these devices, the load-bearing function is mainly performed by the cable, which discharges the stresses produced by a fall of the worker mainly onto the building to which it is coupled at its ends. 
     The need to couple the ends of the cable to the building entails the problem of having, on the building, regions that cannot be protected, i.e., the regions that lie between the end poles of the row of poles and the region where the cable is anchored to the building, which is usually located on the same surface that supports the poles. In these regions the cable, by following an inclined path from the tip of the end pole to the surface that supports the poles, cannot be used as a fastening for safety harnesses or belts. 
     In some devices, the ends of the cable, instead of being anchored directly to the building, are anchored to the end poles. In this case, since they must withstand higher stresses, the end poles are provided with lateral supports or have a structure which is considerably bulkier than the other poles and in practice prevent access to the region of the building located in the immediate vicinity, in any case reducing the length of the cable that can actually be used as a fastening for safety belts or harnesses. 
     Many conventional safety devices have shock absorbers designed to reduce the peaks of the stresses discharged onto the cable and, by reaction, onto the worker when he falls. 
     The shock absorbers are usually constituted by springs arranged along the cable or between the cable and a pole or between the cable and the element for anchoring one end of the cable to the building. 
     Although these shock absorbers reduce the peaks of the stresses discharged onto the worker and onto the cable, they have a limited effect in reducing the peaks of the stresses discharged onto the end poles in a direction which is substantially transverse to the axis of the poles, if the cable is connected to said end poles with its ends. 
     Because of this, despite the presence of the shock absorbers, the end poles must be either provided with lateral supports, generating the above described problems, or oversized, with consequent cost increases. 
     SUMMARY OF THE INVENTION 
     The aim of the present invention is to solve the above problems, by providing an accident-prevention device for buildings, particularly for assembling prefabricated components made of concrete or the like, which allows to significantly reduce the stresses transmitted from the cable to the pole transversely to the axis of the pole, thereby avoiding or at least limiting the need to oversize the poles. 
     Within the scope of this aim, an object of the invention is to provide a device which allows to distribute over a plurality of poles the stresses that are transmitted along the cable, thus reducing the stresses discharged onto each pole. 
     Another object of the invention is to provide a device which also significantly reduces the peaks of the stresses which, by reaction, are transmitted to the user in case of a fall. 
     Another object of the invention is to provide a device which allows to protect substantially all the area of a building to which it is applied. 
     Another object of the invention is to provide a device which allows to arrange the cable even along a path having one or more lateral changes of direction. 
     Another object of the present invention is to provide a device which is highly reliable and can be manufactured at competitive costs. 
     These and other objects which will become better apparent hereinafter are achieved by an accident-prevention device for buildings, particularly for assembling prefabricated components made of concrete, which comprises at least one pole and means for detachably connecting a base of said pole to a surface of a building; said pole having, proximate to a tip thereof, guiding means for a cable element which forms a safety parapet, characterized in that said guiding means are adapted to divert, in a direction substantially parallel to the axis of said pole, at least part of the stresses transmitted from said cable element to said pole, and in that said pole is provided with means for cushioning the stresses transmitted from said cable element to said pole in a direction which is substantially parallel to the axis of the pole. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further characteristics and advantages of the invention will become better apparent from the following detailed description of some preferred but not exclusive embodiments of the device according to the invention, illustrated only by way of non-limitative example in the accompanying drawings, wherein: 
     FIGS. 1 to  11  are views of the device according to the invention in a first embodiment, and more particularly: 
     FIG. 1 is a lateral elevation view of the device according to the present invention; 
     FIG. 2 is a partially sectional lateral elevation view of a pole of the device according to the invention; 
     FIG. 3 is an enlarged-scale view of the pole of FIG. 2; 
     FIGS. 4 to  9  are views of the sequence for anchoring a pole of the device according to the invention to the surface of a building; 
     FIG. 10 is an enlarged-scale top plan view of a pole of the device according to the invention; 
     FIG. 11 is an enlarged-scale view of the pole, taken along the line XI—XI of FIG. 2; 
     FIG. 12 is a view of a different embodiment of the device according to the invention, in which the end poles are inclined with respect to the vertical; 
     FIGS. 13 to  18  are views of a second embodiment of the device according to the invention, and more particularly: 
     FIG. 13 is a partially sectional lateral elevation view of a pole of the device according to the invention; 
     FIG. 14 is a perspective view of the pole of FIG. 13, illustrating the possibility to secure one end of the cable element on the pole; 
     FIG. 15 is a sectional view of FIG. 13, taken along the line XV—XV; 
     FIG. 16 an enlarged-scale sectional view of the pole of FIG. 13, in one of its operating conditions; 
     FIG. 17 is a view of the same detail of FIG. 16, in another operating condition; 
     FIG. 18 is an enlarged-scale sectional view of FIG. 16, taken along the line XVIIII-XVIII. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to FIGS. 1 to  12 , the device according to the invention comprises at least one pole, generally designated by the reference numeral  1 , which has a main structure  2  which can be detachably fixed with its base, by virtue of connection means  3 , to a surface of a building  4  which is formed for example by a beam  5 . The pole  1  has, proximate to its tip, guiding means for a cable element  7  which forms a safety parapet. 
     According to the invention, the guiding means are adapted to redirect, in a direction which is substantially parallel to the axis  1   a  of the pole  1 , at least part of the stresses that are transmitted from the cable element  7  to said pole, and the pole  1  has shock-absorbing means. 8 -for damping the stresses transmitted by the cable element  7  to the pole  1  in a direction which is substantially parallel to the axis  1   a  of the pole. 
     More particularly, the base of the pole  1  is constituted by a base plate  9  resting with its lower face on the surface  4 , and the main structure  2  of the pole is preferably constituted by sections  10 , for example having a T-shaped or H-shaped cross-section, which are spaced around the axis  1   a  of the pole and rigidly connect the base plate  9  to a tip element  11  which constitutes the tip of the pole  1 . 
     In order to strengthen the main structure  2 , it is possible to provide, along the vertical extension of the pole  1 , a series of horizontal stiffening plates  42  which are spaced in a vertical direction and are rigidly connected, for example by welding, to the sections  10 . 
     The guiding means comprise guides for the cable element  7  which form, proximate to the tip of the pole, a portion of path of said cable element  7  which has a component which is parallel to the axis  1   a  of the pole. 
     At least one of the guides is mounted on a supporting element  12 , which can move with respect to the main structure  2  in a direction which is substantially parallel to the axis  1   a . The shock-absorbing means  8  are interposed between the main structure  2  and the supporting element  12 . 
     Conveniently, the guides comprise a pair of lateral pulleys  13   a  and  13   b  which are associated with the main structure  2  and are arranged so that their axes  14   a  and  14   b  are parallel, substantially at right angles to the axis  1   a , and are laterally spaced on opposite sides with respect to the axis  1   a.    
     Preferably, the pulleys  13   a  and  13   b  are supported, so that they can rotate about their respective axes  14   a  and  14   b , by two pairs of wings  15   a  and  15   b  which are associated with the tip element  11 . More particularly, two wings  15   a  are provided, which are arranged side by side and support the pulley  13   a , and two wings  15   b , also arranged side by side, which support the pulley  15   b.    
     Preferably, the wings  15   a  and  15   b  are rigidly fixed to the lateral surface of a sleeve  16  which is supported by the tip element  11  so that said sleeve can rotate-about its own axis, which coincides with the axis  1   a.    
     As shown, the sleeve  16  can be interposed between an axial shoulder, provided on the outer surface of the tip element  11 , and a washer  17  which is locked by means of a screw  18  at the upper end of the tip element  11 . 
     In this manner, the sleeve  16 , and therefore the pairs of wings  15   a  and  15   b , can rotate with respect to the tip element  11  about the axis  1   a  so as to allow lateral changes of direction of the path for the cable element  7 . 
     The above cited guides comprise, in addition to the pulleys  13   a  and  13   b , an intermediate pulley  19  which is arranged so that its axis  19   a  lies parallel to the axes  14   a  and  14   b  of the pair of pulleys  13   a  and  13   b  and is arranged between the pulleys  13   a  and  13   b  . Moreover, the intermediate pulley  19  is spaced from the pair of pulleys  13   a  and  13   b  in a direction substantially parallel to the axis  1   a  in order to guide the cable element  7  from the pair of pulleys  13   a  and  13   b  to the intermediate pulley  19  along two path portions, indicated by the arrows  20  and  21 , which have a component which is parallel to the axis  1   a  of the pole. 
     The supporting element  12 , on which the intermediate pulley  19  is fitted, is supported by the main structure  2  so that it is movable along the axis  1   a  of the pole, and the shock-absorbing means  8  are interposed between the main structure  2  and the supporting element  12 . 
     The shock-absorbing means  8  can be constituted, as shown, by a spring  22 , for example a helical spring orientated so that its axis is parallel to the axis  1   a , or can also be constituted by a hydraulic or pneumatic shock absorber which is interposed between the main structure  2  and the supporting element  12 . 
     Preferably, the pole  1  is arranged so that its axis  1   a  lies substantially vertically or is inclined with respect to the vertical, particularly if it is designed to be an end pole of a row of poles, as shown in FIG. 12, and the pulleys  13   a  and  13   b  are arranged at a same elevation which is higher than the elevation of the intermediate pulley  19 . 
     The supporting element  12  is provided with a sleeve  23  whose axis preferably coincides with the axis  1   a  of the pole and is coupled, so that it is slideable along its own axis, to a coaxial sliding seat  24  which is formed in the tip element  11 . 
     The spring  22  is fitted around the sleeve  23  and engages, with one of its ends, against a shoulder  25   a  formed by the supporting element  12  and, with its other end, against a shoulder  25   b  which is formed by the tip element  11  around the inlet of the sliding seat  24 . 
     Conveniently, means are provided for delimiting the sliding of the sleeve  23  along the sliding seat  24 . Said means for delimiting the sliding of the sleeve  23  along the sliding seat  24  comprise a traction element  26  which is accommodated within said sleeve  23  and engages, for example by means of a threaded coupling, the tip element  11 . The traction element  26  connects the supporting element  12  and the tip element  11  and delimits the sliding of the sleeve  23  away from the tip element  11  produced by the action of the spring  22 . 
     It should be noted that the sleeve  23  is coupled, in the sliding seat  24 , so that it can rotate about its own axis so as to allow the intermediate pulley  19  to rotate, together with the pair of pulleys  13   a  and  13   b , about the axis  1   a  of the pole in order to allow the cable element  7  to perform any lateral changes in direction. 
     Conveniently, means are provided for securing the cable element  7  to the supporting element  12 . Said securing means are preferably constituted by a screw-type clamping element  27  which couples to a threaded hole  28  formed in the supporting element  12  and can be operated so as to clamp the cable element  7  between the pulley  19  and said clamping element  27 . The clamping element  27  can be actuated or deactivated according to the requirements, as will become apparent hereinafter. 
     Preferably, the main structure  2  of the pole  1  has a shape which tapers from its base toward its tip. 
     The connection means  3  comprise an anchoring element  30  which can be fixed to the surface  4  of the building and forms a female seat  31  which lies along an axis which is substantially perpendicular to the surface  4  and has an access opening  32  formed in said surface  4  of the building. Said female seat  31  can be detachably coupled to a male-shaped end  33  of a securing element  34  which protrudes from the base of the main structure  2  of the pole  1 . 
     The female seat  31  has, starting from the access opening  32 , a first portion  35 , which can be crossed by the male-shaped end  33  which moves axially with respect to the female seat  31 , and a second portion  36  which forms, at its end directed toward the first portion  35 , at least one axial shoulder  37  which can be engaged by the male-shaped end  33  by a partial rotation of the securing element  34  about the axis of the female seat  31  and by means of an axial translatory motion of the securing element  34  in the opposite direction with respect to the insertion direction relative to the female seat  31 . 
     Substantially, the securing element  34  can turn about the axis of the female seat  31  with respect to said female seat  31  through a preset angle, preferably 90°, in order to transfer its male-shaped element  33  from an insertion position, in which it can pass through the first portion  35  and move laterally beyond the axial shoulder  37 , to an engagement position, in which it faces, with the male-shaped end  33 , the axial shoulder  37 . 
     Conveniently, the anchoring element  30  is constituted by a tubular body, preferably made of steel, which internally forms the female seat  31 . Said tubular body has an axial end which is open so as to form the access opening  32  and, in an intermediate region of its extension, at least one raised portion which protrudes from its internal surface and covers a limited arc around the axis of the female seat  31 , so as to form said axial shoulder  37 . 
     Preferably, the first portion  35  is obtained by means of a compression of the end with the access opening  32  of the tubular body  30  which gives the first portion  35  a non-circular shape. The transverse cross-section of the non-circular shape can be, according to the requirements, a rectangular, elliptical, rhomboidal one or another adapted one. 
     The compression that forms the first portion  35  at the same time forms the shoulder  37 . In the illustrated case, compression is applied to two diametrically opposite regions of the tubular body  30  and forms two axial shoulders  37 . 
     The second portion  36  of the tubular body  30  preferably has a cylindrical shape. 
     It should be noted that the second portion  36  of the tubular body  30  may also be shaped like a cylindrical sector or sectors, so as to allow the male-shaped element  33  to turn in any case about the axis of the tubular body  30  after passing from the first portion  35  to the second portion  36 . 
     The male-shaped end  33  is shaped complementarily to the first portion  35  of the female seat  31 . 
     The male-shaped end  33  is constituted by the lower end of a shaft  40  whose axis lies at right angles to the face of the base plate  9  that rests on the surface  4  and has a diameter which is smaller than the minimum transverse dimension of the first portion  35  of the female seat  31 . 
     The lower end of the shaft  40 , which constitutes the male-shaped end  33 , has two lateral protrusions, in two diametrically opposite regions, which form two axial shoulders  41  which can engage the axial shoulders  37  of the female seat  31 . 
     The locking element  34  is rigidly coupled to the main structure  2  of the pole  1  in rotating about the axis of the female seat  31 , and is movable with respect to the main structure  2  along the female seat  31  so as to engage, by means of the axial shoulders  41 , against the axial shoulders  37  of the female seat  31  after its male-shaped end  33  has been inserted in the female seat  31  until it lies below the axial shoulders  37  and has been turned through 90° about the axis of said female seat  31 . 
     The shaft  40  passes, so that it is slideable along its own axis, through a passage  60  which crosses the base plate  9 , and the translatory motion of the shaft  40  along the axis of the female seat  31  in order to achieve the engagement of the axial shoulders  41  against the axial shoulders  37  of the female seat  31  can be achieved by providing the upper end of the shaft  40 , i.e., its end that lies opposite the male-shaped end  33 , so that it is threaded and coupled to an adjustment nut  61  which rests on the upper face of the base plate  9  or in any case against a shoulder formed on the upper face of the base plate  9 . 
     Conveniently, the main structure  2  of the pole  1  has, on its base, a protrusion  50  which can engage a seat formed in the surface  4  of the building only as a consequence of the insertion of the male-shaped end  33  of the securing element  34  in the female seat  31  and as a consequence of the transfer of the securing element  34  from the insertion position to the engagement position cited above. 
     Preferably, the protrusion  50  lies around the male-shaped end  33  of the securing element  34  and is shaped complementarily to the first portion  35  of the female seat  31 . 
     Substantially, the configuration of the protrusion  50  is very similar to the configuration of the male-shaped end  33 , but is rotated with respect to it through 90°. 
     The protrusion  50  can be formed monolithically or otherwise rigidly coupled to the base plate  9 , protruding from the lower face thereof. The passage  60  passes through the protrusion  50  and the shaft  40  and is rigidly coupled, in rotation about its own axis, to the protrusion  50  and to the base plate  9 . The shaft  40  in fact has an axial portion which couples to the passage  60  and has a non-circular transverse cross-section complementary to the transverse shape of the passage  60 . The portion of the shaft  40  that engages the passage  60  can be, according to the requirements, rectangular, square, splined, star-shaped, or otherwise suitably shaped. 
     In the embodiment shown in FIGS. 13 to  18 , the device according to the invention comprises at least one pole  101  which is similar to the pole  1  already described with reference to the embodiment shown in the preceding figures. 
     The elements of the pole  101  that correspond to the elements of the pole  1  that have already been described have been designated by reference numerals incremented by  100  with respect to the reference numerals of the corresponding elements of pole  1 , and for the sake of simplicity only the differences of the pole  101  with respect to the pole  1  are indicated hereinafter. The anchoring of the pole  101  to the surface  4  of the building can again be performed by means of an already described anchoring element  30 . 
     Conveniently, the main structure  102  of the pole  101  is constituted by a lattice-like box-shaped structure which again tapers upwards. By virtue of this fact, the internal part of the pole  101  is freer and a membrane-like behavior of the pole  101  in withstanding the stresses applied to it by the cable element  7  is achieved. 
     The base of the main structure  102  of the pole  101 , constituted by a plate  109 , has a rectangular plan shape in order to better utilize the inertia of the pole in the direction in which the cable element  7  pulls, furthermore reducing the space occupation of the base of the pole  101  transversely with respect to the beam  5 . 
     Advantageously, the pole  101  is provided with means for preventing the accidental disengagement of the cable element  7  with respect to the lateral pulleys  113   a and  113   b . Such means comprise an extension of the pairs of wings  115   a and  115   b above the pulleys  113   a and  113   b so as to form two opposite lateral shoulders for the cable element  7 . The pairs of wings  115   a and  115   b are also joined, above the pulleys  113   a and  113   b , by pivots  170  whose axes are parallel to the axes of the pulleys  113   a and  113   b ; said pivots prevent the cable element  7  from climbing over the wings  115   a and  115   b.    
     The means for preventing the disengagement of the cable element  7  with respect to the lateral pulleys  113   a and  113   b also comprise a central groove  171 , in addition to conical flared portions of the cylindrical sides of the pulleys  113   a and  113   b , adapted to partially accommodate the cable element  7 . 
     Conveniently, as an alternative to the means for securing the cable element  7  on the intermediate pulley  19  of the embodiment shown in FIGS. 1 to  12 , there are means for securing the cable element  7  on the main structure  102  of the pole  101 . The securing means comprise a clamp  172  which is associated, for example by means of two screws  173 , with the main structure  102  of the pole  101  and can be actuated in order to clamp one end of the cable element  7  to the main structure  102  of the pole  101 , thus leaving the intermediate pulley  119  free to rotate. In this manner, even on the pole  101  on which one end of the cable element  7  is secured, both pulleys  113   a and  113   b can rotate and the shock-absorbing means  108  act symmetrically, centering on the axis of the pole  101  the stresses transmitted to said pole  101  by the cable element  7 . 
     Advantageously, the pole  101  has means for pre-loading the shock-absorbing means  108 . The pre-loading means comprise an adjustment screw  174  which is arranged so that its axis is parallel to, or coincides with, the axis  101   a of the pole  101  and is supported, so that it is rotatable about its own axis, by the tip element  111  of the pole  101 . The screw  174  engages a threaded seat formed in the supporting element  112 . By turning the adjustment screw  174  in one direction it is possible to move the supporting element  112  upward, i.e., closer to the tip element  111  of the pole  101 , reducing the distance of the pulley  119  from the pulleys  113   a  and  113   b  and compressing the spring  122 . By turning the adjustment screw  174  in the opposite direction, the supporting element  112  is lowered and therefore the pulley  119  is moved away from the pulleys  113   a  and  113   b , extending the spring  122 . The means for pre-loading the spring  122  can be used to tension the cable element  7  during the assembly of the device, as will become apparent hereinafter. 
     Conveniently, furthermore, the portion of the shaft  140  that engages the passage  160  and the passage  160  have a rectangular or elliptical transverse cross-section, so as to ensure correct orientation of the shaft  140  about its own axis with respect to the protrusion  150  and therefore to the main structure  102  of the pole  101  during the insertion of the pole  140  in the passage  160 . 
     Installation of the device according to the invention is as follows. 
     First of all, the poles  1  are installed by using the female seats  31  formed beforehand in the surface  4  during the provision of surface  4  by embedding the tubular body that constitutes the anchoring element  30  in the concrete casting that forms the surface  4 . 
     As shown in FIGS. 4 and 5, the pole  1  is arranged vertically so that the male-shaped end  33  is orientated so that it corresponds to the access opening  32  and can enter the female seat  31  by passing through the first portion  35  and reach the second portion  36 , passing beyond the axial shoulders  37 . 
     As shown in FIGS. 4 and 5, in this position the protrusion  50 , by being rotated with respect to the male-shaped end  33  through an angle of substantially 90°, rests on the edges of the access opening  32  and cannot enter the female seat  31 . 
     The pole  1  is then turned about the axis of the female seat  31  through an angle of 90° (FIG.  6 ), so that the male-shaped end  33  faces, with its axial shoulders  41 , the axial shoulders  37 . This rotation also causes the insertion of the protrusion  50  in the first portion  35  of the female seat  31 , as shown in FIG.  7 . 
     It should be noted that the correct rotation of the pole  1  about the axis of the female seat  31 , which brings the male-shaped end  33  into the correct position for locking with respect to the axial shoulders  37 , is indicated unequivocally to the worker by the descent of the pole  1 , with the protrusion  50 , into the first portion  35  of the female seat  31 , which also achieves the complete resting of the base of the pole  1  on the surface  4 . 
     At this point the worker, by acting on the adjustment nut  61 , causes the upward movement of the male-shaped end  33 , which engages against the axial shoulders  37 , firmly locking the pole  1  against the surface  4 , as shown in FIG.  8 . 
     The poles  101  of the type shown in FIGS. 13 to  18  are installed in a manner similar to the one described with reference to the poles  1 . 
     Once the installation of the poles  1 ,  101  as described has been completed, a cable element  7  is passed over the pairs of pulleys  13   a ,  113   a and  13   b ,  113   b and under the intermediate pulleys  19 ,  119  of the various poles  1 ,  101 . The cable element  7  is then rigidly coupled to the end poles and tensioned either manually or with the aid of conventional winches. One end of the cable element can be coupled to the main structure  2  of an end pole by means of a loop or by means of the clamp  172 , while the other end can be anchored to a winch located on the other end pole or secured by means of the clamping element  27 , as shown in FIGS. 1,  12  and  14 . 
     It should be noted that the cable element  7 , with the poles  101 , can also be tensioned by pre-loading the springs  122  of the various poles  101  by means of the adjustment screws  174  before securing the ends of the cable element  7  to the end poles  101  or, better still, before passing the cable element  7  over the pulleys  113   a ,  113   b  and  119 , as shown in FIG.  16 . After securing the ends of the cable element  7  on the end poles  101  by means of the clamps  172 , the springs  122 , by virtue of the adjustment screw  174 , are partially or fully released, thus tensioning by the required extent the cable element  7  as shown in FIG.  17 . 
     The workers can thus engage their safety harnesses or belts to the portions of the cable element  7  that lie between two contiguous poles. 
     Should a worker fall, the stress produced by the fall is transmitted from the cable element  7  to the various poles and its direction is changed, as a consequence of the particular arrangement of the pulleys  13   a ,  113   a ,  13   b ,  113   b  and  19 ,  119 , into a direction which has a component which is parallel to the axis of the corresponding pole. The change of direction places the shock-absorbing means  8 ,  108  in their ideal operating conditions. The stress transmitted from the cable element  7  to the various poles  1 ,  101  is adequately damped by the springs  22 ,  122 . The compression of the springs  22 ,  122  also causes an elongation of the portion of the cable element  7  that is affected by the fall, further reducing the jerk transmitted to the worker. 
     It should be noted that the stress transmitted by the cable element  7  to the various poles  1 ,  101  during a fall is distributed among the various poles  1 ,  101  and therefore a reduced stress peak affects each pole. 
     As a consequence of the shock-absorbing effect provided by the shock-absorbing asorbing means  8 ,  108 , the peaks of the stresses discharged by the cable element  7  onto the poles  1 ,  101  are reduced, and therefore the poles  1 ,  101  can effectively support the cable element  7  without requiring an excessive oversizing of the end poles. 
     Optionally, the end poles, as shown in particular in FIG. 12, can be inclined outwards so as to offer greater resistance to these stresses. In this case, the pole  1 , instead of being arranged with its axis  1   a at right angles to the plane of arrangement of the lower face of the plate  9 ,  109 , lies along an axis which is inclined with respect to the vertical plane that is perpendicular to the lower face of the plate  9 ,  109 . 
     It should be noted that the poles  1 ,  101  can be disassembled by fully disengaging the nut  61 ,  161  from the shaft  40 ,  140  and then manually extracting the shaft  40 ,  140  from the female seat  31 . The shaft  40 ,  140  is then assembled manually to the base of the pole  1 ,  101  before subsequent  15  use of the pole. 
     If a lateral change of direction of the path followed by the cable element  7  is required, the clamping element  27  arranged on the pole at which the lateral change of direction must occur can be moved to engage the cable element  7  so as to lock it on the intermediate pulley  19 . 
     The clamping element  27  can also be actuated so as to lock the cable element  7  if one intends to isolate, for example during the disassembly of the safety device, a portion of the cable element  7  from the remaining part of the cable element  7 . 
     In practice it has been observed that the device according to the invention fully achieves the intended aim, since by virtue of the change in the direction of the cable element along path portions which have a component parallel to the axis of the poles, and by virtue of the use of the shock-absorbing means, it significantly reduces the peaks of the stresses discharged by the cable element onto the poles, eliminating or in any case reducing the need to oversize the poles. 
     By virtue of this fact and of the fact that the stresses produced by a fall of a worker are distributed over a plurality of poles, it is possible to produce poles with a structure which can be manufactured at competitive costs yet offers the best assurances in terms of safety. 
     Another advantage of the device according to the invention is that it allows substantially complete protection of the region to which the device is applied, by virtue of the fact that a direct connection of the cable element to the building is not strictly necessary. 
     The device thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims; all the details may furthermore be replaced with other technically equivalent elements. 
     In practice, the materials used, as well as the dimensions, may be any according to requirements and to the state of the art. 
     The disclosures in Italian Patent Application No. MI99A001900 from which this application claims priority are incorporated herein by reference.