FR2918287A1 - ANTI-FALL DEVICE AND SECURITY INSTALLATION INCORPORATING SUCH A DEVICE - Google Patents

Abstract

This anti-fall device (20) comprises a braked pulley (32) and two rollers (33, 34) rotatably mounted relative to a body and each provided with a peripheral groove for receiving a belay cable (5). ). The braked pulley (32) is equipped with at least one pawl (321, 322) adapted to come, under the effect of the centrifugal force, bearing against a stop (21e) integral with the body. The rollers (33, 34) are mounted idle relative to the body (21) which defines a zone (21f) for attaching a safety member (10) linked to a user. The respective diameters (D32, D33, D34) of the pulley (32) and the rollers (33, 34) and the positions of their respective axes of rotation (X22, X23, X24) with respect to the body (21) are such that a cable (5) stretched and engaged in the grooves (328, 338, 348) of the pulley (32) and rollers (33, 34) is received in the groove (328) of the pulley (32), in support on the sides or the bottom of this groove, on a sector (S) whose angle at the apex (alpha) is less than or equal to 135 degrees.

Description

ANTI-FALL DEVICE AND SECURITY INSTALLATION INCORPORATING SUCH

DEVICE

  The invention relates to an anti-fall device and to an installation comprising, among others, at least one such device. It is known to ensure the safety of people working on generally vertical structures such as towers or poles by connecting them to a vertical cable, sometimes referred to as a slide, stretched between the top and the bottom of the structure, the user being equipped a harness connected by a strap to a device as known from FR-A-2 149 047 which moves along the cable following the normal movements of the operator uphill or downhill. Such a device defines, by means of a braked pulley and two rollers mounted crazy, a tortuous path that follows the cable being engaged in peripheral grooves of the pulley and rollers. In the event of a fall of the user, the rapid movement of this device along the cable induces rapid rotation of the pulley which is provided with two pawls which come to lock in corresponding notches, under the effect of the force centrifugal. The user is thus prevented from falling. This type of device gives overall satisfaction in terms of security but the locking effect obtained is violent, which does not always meet the requirements of the standard EN-353-2 which imposes a progressive blockage in case of a fall. It is these drawbacks that the invention intends to remedy more particularly by proposing a new fall arrest device whose efficiency is comparable to that of known equipment but which allows a progressive blocking of a user in case of a fall. In this spirit, the invention relates to an anti-fall device which comprises a braked pulley and two rollers, this pulley and these rollers being rotatably mounted relative to a body of the device and each provided with a peripheral receiving groove of a belay cable, the braked pulley being equipped with at least one ratchet adapted to come, under the effect of the centrifugal force bearing against an abutment integral with the body, while the rollers are mounted idle relative to the body which defines an attachment zone of a security organ linked to a user. This device is characterized in that the respective diameters of the pulley and rollers and the positions of their respective axes of rotation relative to the aforementioned body are such that a tensioned cable engaged in the grooves of the pulley and rollers is received in the groove of the pulley, resting on the sides or the bottom of the groove, on a sector whose angle at the summit is less than or equal to 135. Thanks to the invention, in the case of rapid movement of the device along a cable, the braked pulley is blocked when its pawl or pawls abut against the corresponding part of the body and, to the extent that the cable is received in the groove of this braked pulley on a relatively small corner angle at the relatively small vertex, this cable can slide slightly in the groove of this pulley, which allows a corresponding absorption of the impact energy and reduces the risk of injury to the patient. 'user. According to other advantageous aspects of the invention, which are not mandatory, such a device may incorporate one or more of the following characteristics: the angle at the apex of the receiving sector of the cable is less than or equal to 100, preferably of the order of 90. Such values have given quite satisfactory results in tests. In particular, they make it possible to comply with the CE-353-2 standard. - The axes of rotation of the rollers are arranged relative to the axis of articulation of the braked pulley, on the same side as the aforementioned angular sector. This arrangement facilitates the movement of the cable in the device. In this case, the body of the device advantageously comprises two flanges articulated with respect to each other about an axis, while the axes of rotation of the rollers are closer to the axis of articulation than the axis. rotation of the braked pulley. - The groove of the braked pulley has, in radial section, generally a V shape with a rounded bottom, the sides of this groove being more divergent from each other in a first zone, relatively close to the bottom of this groove, only in a second zone, relatively more distant from this bottom and extending to the outer radial edge of this pulley. With this aspect of the invention, the cable engaged in the groove and which tends to move towards the bottom thereof in the event of locking of the braked wheel, is then received in a portion of this relatively open groove, that is to say in which the sides of the groove diverge relatively quickly relative to each other, which allows a support of the cable at the bottom of the groove without deformation thereof. The half angle of divergence of the sides of the groove in the first zone is advantageously between 10 and 15, preferably between 12 and 13, while the half-angle of divergence of these sides in the second zone is between 5 and 10, preferably between 6 and 7. - The groove of each of the idle rollers has, in radial section, a V-shaped rounded bottom. Such a shape makes it possible, depending on the diameter of the cable, to obtain a support of the cable at the bottom of the groove on about 2/3 of its diameter, which avoids the crushing of the cable and its weakening to the extent that all strands and all the son constituting it work in substantially the same way. - The braked pulley and idlers are made of aluminum, aluminum-based alloy or composite material. The use of these materials avoids the risk of seizure between, on the one hand, the pulley and the rollers and, on the other hand, the cable which is made of stainless steel. This limits the risk of cable breakage, whereas, in particular, an aluminum-based material used for pulleys and rollers has good flowability and satisfactory resistance after annealing. The invention also relates to a safety installation, which can be reported on a vertical structure such as a pylon or a pole and which comprises at least one stretched belay cable and at least one device as previously described.

  Such an installation makes it possible to effectively ensure the safety of one or more users, whereas, in the event of a fall, the shock due to blockage of the braked wheel is partly absorbed. The security is improved, while the life of the components of the installation is increased. When the groove of the braked pulley or idler rollers has a geometry as mentioned above, its rounded bottom may be in an arc, with a radius of 50% and 70% of the nominal radius of the cable, preferably between 60 and 65% of this radius. 4

  The invention will be better understood and other advantages thereof will appear more clearly in the light of the following description of an embodiment of an installation according to its principle, comprising an anti-fall device according to its principle, given purely by way of example and with reference to the accompanying drawings in which: - Figure 1 is a schematic representation of a principle of an installation according to the invention mounted on a pylon and in use; - Figure 2 is an enlarged view of the detail II in Figure 1, one of the flanges of the device being omitted for the sake of clarity; - Figure 3 is a section along the line III-III in Figure 2, the two flanges of the device being shown; FIG. 4 is an enlarged view of detail IV in FIG. 3, the cable being shown, in phantom, in a position corresponding to the normal sliding of the device, and FIG. 5 is a view on a larger scale of FIG. detail V in Figure 3, the cable being shown in phantom, in the locking position of the device. The tower 1 shown in FIG. 1 is provided with a ladder 2 enabling a user 3 to climb up to the vicinity of its top 4 in order to carry out installation or maintenance operations, then to descend. A cable 5 is hooked by a loop 5a to a lug 6 provided in the vicinity of the top 4. The cable 5 is stretched under the effect of the weight of a ballast 7 fixed to the lower end of the cable 5. The user 3 is equipped with a harness 8 connected by a strap 9 to a carabiner 10 hooked on an anti-fall device 20 intended to circulate along the cable 5 by accompanying the user in his normal movement up and down the ladder 2. The device 20 comprises a body 21 formed of two flanges 21a and 21b, the flange 21b is not shown in Figure 2 for clarity of the drawing. The flanges 21a and 21b are articulated relative to each other about an axis X21 materialized by two hinges 21c and 21d. Alternatively, the flanges 21a and 21b are hinged relative to each other by means of a single hinge.

  The body 21 is equipped with three shafts 22, 23 and 24 respectively defining articulation axes X22, X23 and X24 for a braked pulley 32 and for two identical rollers 33 and 34 and mounted idle about the axes X23 and X24. Bearings 22a, 23a and 24a are arranged between the shafts 22 to 24 and the pulleys or rollers 32 to 34. The pulley 32 is equipped with two pawls 321 and 322 each articulated around a pin 323, respectively 324, extending parallel to the shaft 22. A coil spring 325 connects the pawls 321 and 322 and opposes a force centrifugal exerted on the pawls 321 and 322 in case of rotation of the pulley 32, under the effect of the inertia of these pawls. Two stops 326 limit the approaching action exerted by the spring 325 in the vicinity of the ends 321a and 322a pawls 321 opposite the pins 324 and 325. The pawls 321 and 322 are mounted on the side 327 of the pulley 32 turned towards the flange 21a which is equipped with four stops 21e intended to receive bearing one or the other of the ends 321a and 322a when the centrifugal force resulting from the rotation of the pulley 32 is sufficient to move the ends 321 and 322a of the stops 326 to the point that their trajectory meets one of the stops 21e. The pulley 32 is provided with a peripheral groove 328 in which a portion of the cable 5 is received when the device 20 is mounted on this cable.

  The rollers 33 and 34 are also each provided with a peripheral groove 338, respectively 348, in which is also received a portion of the cable 5 in the mounted configuration of the device. The flange 21b can pivot relative to the flange 21a, about the axis X21, to allow access to the elements 32 to 34 to install the cable 5 in the grooves 328, 338 and 348. When this operation is performed the flange 21a is folded over the elements 32, 33 and 34, which makes it possible to align two orifices, only one of which is visible in FIG. 2 with the reference 21f, into which the carabiner 10 can be inserted to connect the device The orifices 21f and the like therefore constitute a hooking zone of the safety snap hook 10 which is shown in section in FIG. 2. A not shown lock makes it possible to hold the flanges 21a and 21b in parallel configuration around elements 32 to 34. 6

  When the cable 5 has to be taken out of the device 20, the carabiner 10 is removed and the flanges 21a and 21b are opened to release the cable 5 from the grooves 328, 338 and 348. D32, D33 and D34 are respectively denoted by the diameters elements 32 to 34. The routing of the cable 5 in the device 20 is imposed by the positioning of the axes X22, X23 and X24 relative to the body 21, the value of the diameters D32, D33 and D34 and, to a lesser extent, the geometry grooves 328, 338 and 348. This positioning and this diameter are chosen such that the angular sector S on which the cable 5 is received in the groove 328, bearing on the sides or the bottom of this groove, an apex angle of about 90. This sector S is shown in gray in Figure 2 In practice, satisfactory operation is obtained for a device wherein the aforementioned apex angle is less than 135, preferably less than 100. Given the relatively low value of this angle at the top, in the event of a jamming of one of the pawls 321 and 322 on one of the stops 21e, a slight slipping of the cable 5 can take place in the groove 328 at the level of sector S, which absorbs some of the energy of the shock and avoids transmitting all this energy to the user. During such a sliding, the rollers 33 and 34, which are mounted idle, do not rotate about their respective axes X23 and X24 because of the penetration of the cable 5 into their respective grooves 338 and 348. The diameters D33 and D34 are smaller than the diameter D32. For example, the diameter D32 may be of the order of 70 mm, while the diameters D33 and D34 are of the order of 40 mm. Of course, other values can be selected according to design choices within the scope of the art. In practice, the diameter of the idle rollers is between 60 and 70% of the diameter of the braked pulley, preferably of the order of 2/3 of this diameter. The pulley 32 and the rollers 33 and 34 are made of aluminum type AU-7G, while the cable 5 is made of stainless steel. This avoids the risk of seizure between, on the one hand, the pulley and the rollers and, on the other hand, the cable, such a risk may occur if all these elements are made of stainless steel. It is important to avoid, as far as possible, the seizure of the cable in the grooves of the rotating parts. AU-7G aluminum can be easily cast for the production of parts 32 to 34 and has good mechanical stability, which allows it to effectively withstand the forces to which these parts are subjected. Alternatively, an aluminum alloy may be used for the manufacture of parts 32 to 34. Similarly, the use of a synthetic resin-based composite material filled with reinforcing fibers may be envisaged, for example polyamide heavily loaded with glass fibers or aramid fibers. Note that the X23 and X24 axes are offset in the direction of the X21 axis, which they are perpendicular, a distance d relative to the axis X22, which they are parallel. In other words, the axes X23 and X24 are located, with respect to the axis X23, on the same side as the angular sector S. This makes it possible to reduce the value of the angle a. The value of the angle α is greater than 60 to ensure that the cable 5 is resting on the sides or the bottom of the groove 328 over a length at least equal to the pitch of the strands constituting the cable 5, which allows to distribute the force exerted on this cable, especially in the event of a fall. The geometry of the groove 328 emerges more particularly from FIG. 4 where it is noted that it can be decomposed into three zones Z1, Z2 and Z3, the zone Z1 constituting the bottom of the groove 328, while the zone Z2 constitutes a transition zone between the zone Z1 and the zone Z3 extending to the outer radial surface 329 of the wheel 32. In an inner radial section of the pulley 32, the zone Z1 is defined by an arc of a circle of radius R1 equal to about 1.5 mm when the cable 5 has a diameter of 4.8 mm. In FIG. 4, the cable 5 is represented in its normal configuration during the displacement of the device 20 along the cable 5, at the level of the arrow IV-IV in FIG. 2. From the zone Z1, the groove 328 has generally an open V-shape towards the surface 329. In the zones Z2 and Z3, the sides 328a and 328b of the groove 328 move away from each other, approaching the surface 329. The half -angle at the top (3 opening of the groove 328 has a value between 10 and 15 at the zone Z2, while the opening half-angle y of the sides 328a and 328b of the groove 328 at Z3 zone level has a value between 5 and 10. In practice, the angle F3 advantageously has a value between 12 and 13, while the angle y has a value between 6 and 7.

  Thus, in the event of a fall and jamming of the pulley 32, the cable 5, which tends to slide towards the zone Z1 in which it does not fully enter, is partially engaged in the zone Z2 which is more open than the zone Z3, such that the cable 5 is received without being crushed or pinched near the bottom of the groove 328. In practice, the zones Z1 and Z2 have radial dimensions, equal to their heights in FIG. 4, which are substantially equal, of the order of 1 to 1.2 mm, while the zone Z3 has a substantially greater radial dimension, of the order of 5 to 6 mm. The zone Z3 plays a role of convergent entry of the cable 5 towards the zones Z1 and Z2 in the event of locking of the pulley 32. The geometry of the groove 338 is more particularly apparent from FIG. 5, it being understood that the groove 348 is identical. This groove is generally open V-shaped with a rounded bottom. It can be decomposed into two zones, namely a bottom zone Z'1 of geometry substantially identical to that of the zone Z1 of the groove 328 and a zone Z'2 diverging in the direction of the outer peripheral surface 339 of the roller 33. On the zone Z'2, the sides 338a and 338b of the groove 338 move away from each other from the zone Z'l towards the surface 339, with a half-angle at the peak including between 6 and 8, preferably of the order of 7. The cable 5 shown only in phantom in FIG. 5 can thus bear against the vicinity of the bottom of the groove 338 while being in contact with the bottom and the sides of this groove for about 2/3 of its diameter, which avoids a crushing of this cable as it could occur if the groove 338 was in the form of a circular arc to the level of the surface 339. The cable does not tend to deform and all the strands and the son constituting it work in substantially the same way, which is advantageous.

  Each axis materializing the hinges 21c and 21d and mounted with clearance in the corresponding hinge. Thus, even in the event of strong stress on the axis 22 of the pulley 32, the clearance in the hinges allows the opening of the body 21.

Claims (10)

  1. An anti-fall device (20) comprising a braked pulley (32) and two rollers (33, 34), said pulley and said rollers being rotatably mounted relative to a body (21) of said device and each provided with a groove device (328, 338, 348) for receiving a belay cable (5), said braked pulley being equipped with at least one pawl (321, 322) capable of coming, under the effect of the centrifugal force, in abutment against an abutment (21f) integral with said body, said rollers being mounted idly relative to said body which defines an attachment zone (21e) of a safety member (10) linked to a user, characterized in that the respective diameters (D32, D33, D34) of said pulley (32) and said rollers (33, 34) and the positions of their respective axes of rotation (X22, X23, X24) with respect to said body (21) are such that a cable (5) stretched and engaged in the grooves (328, 338, 348) of said pulley and said rollers is received in the groove (328) of said lie, resting on the sides (328a, 338a) or on the bottom (Z1) of said groove, on a sector (S) whose apex angle (a) is less than or equal to 135.   2. Device according to claim 1, characterized in that said apex angle (a) is less than or equal to 100, preferably of the order of 90.   3. Device according to one of the preceding claims, characterized in that the axes of rotation (X23, X24) of said rollers (33, 34) are arranged relative to the axis of rotation (X22) of said braked pulley (32). ), on the same side as said angular sector (S).   4. Device according to claim 3, characterized in that said body (21) comprises two flanges (21a, 21b) articulated with respect to each other about an axis (X21) and in that said axes of rotation (X23, X24) of said rollers (33, 34) are closer to said hinge axis (X21) than said axis of rotation (X22) of said braked pulley (32).   5. Device according to one of the preceding claims, characterized in that the groove (328) of said braked pulley (32) has, in radial section, generally a V shape with a rounded bottom, the sides (328a, 328b) of said groove being more divergent ([3> y) from each other in a first zone (Z2), relatively close to the bottom (Z1) of said groove, than in a second zone 10 (Z3), relatively more distant said bottom and extending to the outer radial edge (339) of said pulley.   6. Device according to claim 5, characterized in that the divergence half angle (F3) of said sides (328a, 328b) in said first zone (Z2) is between 10 and 15, preferably between 12 and 13, then that the diverging half-angle (8) of said sides in said second zone (Z3) is between 5 and 10, preferably between 6 and 7.   7. Device according to one of the preceding claims, characterized in that the groove (338, 348) of each of said rollers (33, 34) has, in radial section, generally a form of V rounded bottom.   8. Device according to one of the preceding claims, characterized in that said braked pulley (32) and said idler rollers (33, 34) are made of aluminum, aluminum-based alloy or a composite material.   9. Safety installation comprising at least one stretched belay cable (5) and at least one device (20) according to one of the preceding claims.   10. Installation according to claim 9, characterized in that said device (20) is according to one of claims 5 to 7 and in that the rounded bottom (Zl, Z'1) of said groove (328, 338, 348 ) is in an arc, with a radius (RI) between 50% and 70% of the nominal radius of said cable (5), preferably between 60 and 65% of said nominal radius.