METHOD FOR PROTECTING A LIFTING DEVICE AGAINST OVERLOAD AND DEVICE IMPLEMENTING THIS METHOD

Abstract

This method for protecting a lifting device against overloading, the lifting device comprising a lifting drum (3) around which a cable (4) is wound, to the end of which a load (5) is attached, said lifting drum (3) being mechanically linked to an electric motor (6) capable of ensuring its rotation, the mechanical link comprising a clutch or equivalent device, includes at least two distinct operating thresholds: – a first threshold, exceeding which causes the lifting drum (3) to freewheel relative to the kinematic chain emanating from the electric motor (6); – a second threshold, with a value higher than that corresponding to the nominal load of the lifting device, but lower than that of the first threshold, causing the rotation of the lifting drum (3) to brake and an attempt to gradually stop said rotation of the drum. Figure for the abbreviation: Fig 1

Description

Title of the invention: METHOD FOR PROTECTING A LIFTING DEVICE AGAINST OVERLOAD AND DEVICE IMPLEMENTING THIS METHOD Scope of the invention

[0001] The present invention relates to the technical field of lifting devices, and more particularly of winches, and even more specifically of winches mounted on aircraft and in particular helicopters. Prior art of technique

[0002] A winch is traditionally made up of at least one drum, also called a lifting drum, associated with a kinematic system ensuring the rotation of the drum on itself, in order to allow the winding and unwinding of a lifting cable, at the end of which a load is attached.

[0003] One of the problems encountered when using such a winch lies in ensuring the safety of the winch and its associated kinematics in the event of an overload. Such an overload can result, particularly when the winch is mounted on a helicopter, from an operator falling while attached to the winch by the cable, or from the free end of the lifting cable becoming entangled in any fixed point such as a tree, pylon, etc.

[0004] In the absence of an appropriate safety device, this occurrence is likely to directly affect the integrity of said operator, and / or the integrity of the helicopter and in particular to cause its fall with the associated dramatic consequences.

[0005] Such safety devices are known which, in the event of detection of an exceeding of a limit load, induce the unwinding of the cable. These devices traditionally employ a friction clutch system, consisting of one or more friction discs and a spring, said spring being calibrated to a value corresponding to the limit mass or limit load beyond which the unwinding of the cable is to be triggered.

[0006] In this way, when the load limit is reached, the friction disc(s) no longer adhere, for example to the drum, freeing the drum's rotation and consequently the cable's unwinding, with, as a first approximation, the absence of frictional forces other than the simple frictional forces of the drum's axis on the bearings that support it. Thus, as long as the load exceeds the spring's setting value, the kinematic chain is free. Conversely, when the torque exerted on the drum decreases, particularly below the threshold defined by the spring setting(s), the friction disc(s), which still exists, regains its grip and allows the load to be dampened, or even stopped, from falling.

[0007] While such a system can provide some protection in case of overload, the implementation of a friction clutch is relatively sensitive and complex, and requires periodic checks to ensure its proper functioning according to the limit load that one wishes to impose on the system.

[0008] Thus, in addition to the fact that such a system lacks precision in terms of its triggering threshold due to the use of seals, the environment, and the operating principle, a faulty calibration of the spring(s) can lead to the risk of the load dropping freely, or even of failing to trigger in the event of an overload. Therefore, the control of such springs is crucial for optimizing safety.

[0009] Furthermore, due to the operating mode of such a system, in the event of an overload, the breakage of the drive chain can cause the cable to unwind completely without any way to prevent it. Consequently, such a system proves ineffective in preserving the integrity of an operator attached to the winch in the event of a fall, as the operator could be severely injured at the end of the cable's unwinding travel due to the sudden deceleration of said fall, or even in the event of the operator hitting the ground.

[0010] One of the objectives of the present invention is to propose a more reliable system in terms of safety, in terms of adjusting the triggering threshold in case of overload and also in terms of modularity of said triggering threshold of the system according to the operating conditions of the winch and corollarily of the helicopter in which said winch is mounted. Description of the invention

[0011] To this end, the invention relates first of all to a method of protecting a lifting device against an overload, the lifting device comprising a lifting drum around which a cable is wound, at the end of which a load is fixed, said drum being mechanically linked to an electric motor, in particular by a clutch or equivalent device.

[0012] This method includes at least two distinct operating thresholds: - a first threshold, the exceeding of which causes the lifting drum to operate in freewheel mode relative to the kinematic chain emanating from the motor; - a second threshold, with a value greater than that corresponding to the nominal load of the lifting device, but with a value less than that of the first threshold, causing the braking of the rotation of the lifting drum and an attempt to progressively stop said rotation of the drum.

[0013] In other words, and according to a first aspect of the invention, the method consists first of all in allowing free rotation of the drum according to the freewheel principle after the first threshold is triggered, that is to say, when a torque greater than a predetermined value is exerted on the drum by the cable, and then, after unwinding in a wheel-like fashion free of part of the cable due to the overload thus exerted, to attempt a slowing down or even the stopping of this free rotation of the drum by the effect of the second threshold, in order to oppose the complete unwinding of the cable in the event of the occurrence of an overload.

[0014] According to an advantageous feature of the invention, the method consists corollarily in attempting to re-couple the lifting drum onto the kinematic chain, and alternatively, when attempting to stop this free rotation is not possible due to, for example, the cable end being caught in a fixed point, in granting the operator of the lifting device sufficient time to possibly make the decision to cause the cutting of said cable.

[0015] Thus, according to the invention, the method consists, after applying a torque to the lifting drum greater than or equal to said first threshold, and when slowing down or stopping the drum's rotation is not possible, particularly due to the persistence of said torque applied to the drum beyond said first threshold, of automatically re-engaging the clutch or equivalent device at a predetermined interval, in this case less than or equal to 5 seconds, to mechanically re-couple the lifting drum and the electric motor. Typically, if, notwithstanding this re-engaging attempt, the torque remains greater than said first threshold, the free rotation of the drum relative to the drive train is again activated.

[0016] The invention also relates to a method for protecting a lifting device against overload, in which the lifting device consists of a capstan drum associated with a cable storage drum. The method of the invention, in such a configuration, is identical to that described above, the storage drum then being equipped with brakes capable of ensuring the minimum residual tension between the storage drum and the capstan in order to allow the lifting device to function correctly.

[0017] The invention finally relates to a device for protecting the lifting member against overload in order to allow the operation of said lifting member according to the method described above.

[0018] The lifting device comprises: - a lifting drum around which a lifting cable is wound, to the end of which a load is attached; - a motor equipped with a rotating shaft, capable of rotating the lifting drum; - a clutch or equivalent device mounted on the mechanical link connecting the motor to the lifting drum and capable of decoupling the rotating shaft of the motor and the drum.

[0019] According to the invention, the clutch or equivalent device is provided with elements capable of ensuring the free rotation of the drum relative to the motor shaft when the torque exerted by the lifting cable on the drum is greater than a predetermined threshold value - corresponding to the first threshold; the lifting member is further equipped with means capable of causing the slowing down, or even stopping, of the rotation of the lifting drum after the latter has been put into free rotation, so as to allow the recoupling of the rotating shaft of the motor onto the lifting drum.

[0020] Typically, these means consist of brakes, acting on the lifting drum, and whose maximum braking capacities correspond to said second threshold.

[0021] According to the invention, the clutch or equivalent device consists of a removable cartridge, referred to as an overload cartridge, which can be coupled respectively to the drive shaft and the lifting drum. This cartridge consists of a housing receiving two independent rings. These rings cooperate with each other via a plurality of balls received in specially shaped recesses in one of the rings and protruding from these recesses to also be received in through-holes formed within the other ring. Springs, advantageously housed within a cage, exert pressure on these balls, the assembly thus defining the first threshold. One of the rings is integral with the housing, which is itself mechanically connected to the drive shaft, and the other ring is integral with a means for rotating the lifting drum.

[0022] According to an advantageous feature of the invention, the housings provided within one of the rings and intended to receive the balls communicate with an internal annular groove provided within said ring, of a depth less than said housings, this communication being achieved by means of non-radial ramps.

[0023] Furthermore, according to the invention, the device of the invention also includes additional braking means, in this case consisting of friction discs, capable of cooperating with a component integral with said crown mechanically linked with the lifting drum, the upper limit of action of said brakes constituting said second threshold. Brief description of the figures

[0024] The manner in which the invention can be implemented, and the advantages arising therefrom, will be more apparent from the following example of implementation, given by way of illustration and not limitation in support of the attached figures.

[0025] Fig. 1 is a schematic representation illustrating the operating principle of the method and device according to the invention, in normal operational position within the framework of a lifting element consisting of a capstan.

[0026] Figure 2 is a view analogous to Figure 1, illustrating the operation of the process and of the device of the invention in overload mode below said first threshold.

[0027] Figure 3 is a view analogous to Figure 1, illustrating the operation of the process and of the device of the invention in overload mode exceeding said first threshold.

[0028] Figure 4 is a graph illustrating the function of time (abscissa) and load (in kg) (on the ordinate) applied to the lifting element incorporating the device of the invention the different modes of operation of said device.

[0029] Figure 5 is a schematic perspective representation of one of the elements of the overload prevention device according to the invention.

[0030] Figure 6 is a schematic perspective representation of the bell placed in work in the element of [Fig.5].

[0031] Fig. 7 is a view analogous to Fig. 6 from another angle.

[0032] Figure 8 is a schematic perspective representation of one of the crowns forming part of the element in [Fig.5], intended to be positioned at the bottom of the bell shown in figures 6 and 7.

[0033] Fig. 9 is a schematic perspective representation of the crown. tagoniste intended to cooperate with the crown of the [Fig.8], further associated with the removable connection means on the drive shaft.

[0034] Fig. 10 is a schematic representation illustrating the element of Fig. 5 in normal operation, that is to say in the absence of overload.

[0035] Figure 11 is a view analogous to Figure 10, illustrating the device of the invention in overload mode exceeding the first threshold.

[0036] Fig. 12 is a schematic exploded perspective representation of the assembly of the device of the invention.

[0037] Fig. 13 is a sectional view of the cooperation between the two anterior crowns. gonists of figures 8 and 9, in normal operating mode of the device of the invention.

[0038] Fig. 14 is a view analogous to Fig. 13 in upper overload mode first threshold.

[0039] Figure 15 is a partially exploded schematic representation of the device braking associated with the lifting drum of the lifting device of the invention. Detailed description of the invention

[0040] Figures 1 to 3 illustrate the general operating principle of the overload detection method according to the invention.

[0041] Within these, the device of the invention is integrated into a winch, and in this case, a capstan winch. It should be understood, however, that in the spirit of the invention, the device is capable of operating with a conventional winch, that is to say, whose lifting drum also ensures storage.

[0042] Thus, within these figures, we schematically distinguish the lifting assembly (1) and the storage assembly (2).

[0043] The lifting assembly (1) consists of a drum (3), known as a capstan drum, which winds and unwinds a cable (4), to the end of which a load (5) is attached. The drum (3) is rotated by an electric motor (6). While the example described illustrates only one capstan drum, the invention also relates to the implementation of a capstan comprising two drums mounted parallel to each other, each of said drums receiving only a single layer of cable turns around its periphery.

[0044] As a corollary, a storage drum (7) appears at the level of the storage assembly (2), on which several thicknesses of turns of the cable coming from the capstan drum(s) (3) are stored, said storage drum (7) being driven in rotation by an electric motor (8).

[0045] Figures 1 to 3 show schematically two coupling elements (9, 10) of the mechanical link between the electric motor (6) and the capstan (3), respectively in effective coupling position within Figures 1 and 2, i.e. in normal operation of the device and in case of overload below a first threshold, and in decoupled position within [Fig.3], i.e. in case of detection of overload above said first threshold.

[0046] These coupling elements will be described in detail later. However, they are designed so that, when an overload is detected, that is, when a torque exceeding a threshold value (the first threshold) is exerted on the capstan (3) by the cable (4), said elements (9, 10) disengage in a manner similar to a clutch, following an axial displacement of one of said elements relative to the other. In this case, the coupling element (9) attached to the capstan (3) automatically activates a switch (11) (schematically illustrated in contact with said coupling element (9) in [Fig. 3]).

[0047] Figure 1 illustrates, as already indicated, the normal operation of the lifting device, that is, in the absence of any overload. In this configuration, it can be observed that the two coupling elements (9) and (10) are schematically in contact with each other; in other words, there is coupling between the drive chain and the capstan drum (3). Consequently, the service brake (not shown) associated with the electric motor (6) allows the lifting device to be subjected to a payload exceeding the nominal load determined by the manufacturer, but obviously below said first threshold.

[0048] Figure 2 illustrates an intermediate operating mode, according to which an overload is detected, always below the first threshold, but nevertheless... greater than the payload mentioned previously. This operating mode is deemed to occur after the detection of an overload exceeding said first threshold, with the aim of allowing, as will be described later, the resetting or recoupling of the kinematic chain on the capstan drum (3).

[0049] Finally, [Fig. 3] illustrates the operating mode according to which an overload exceeding said first threshold is detected. Such an overload may, for example, result from the fall of an operator connected to the cable (4), or from the connection of the end of said cable, whether or not it is carrying a load, to a fixed point, such as a pylon, tree, etc.

[0050] In such a configuration, it is desired that the capstan drum (3) be able to rotate freely, and for this purpose, the kinematic chain linking the motor (6) to the capstan (3) is disengaged. This disengagement results in an axial displacement of one of the coupling members (9, 10), and in this case of member (9), which, due to this displacement, activates the switch (11).

[0051] This activation of the switch (11) causes the rotation of the electric motor (6) to stop by means of a ratchet wheel (13) (better known by the Anglo-Saxon expression "ratchet"), and more specifically the rotation inherent in inertia, since in fact, the activation of said switch causes the electrical supply of said motor (6) to stop first.

[0052] In addition, the activation of the switch (11) also causes the electric motor (8) to stop being powered, in addition to the ratchet wheel (14) closing.

[0053] Consequently, due to the nature of the winch described, in this case a capstan winch, it is necessary to maintain residual tension on the cable strand (16) extending between the capstan (3) and the storage drum (7). To this end, braking elements (15), typically consisting of friction discs, cooperate with the storage drum (7) to limit its free unwinding.

[0054] If an overload is detected on the capstan (3) exceeding the first threshold ([Fig. 3]), the capstan (3) is not only decoupled from the drive motor (6), but also operates relative to it like a freewheel, allowing the cable to unwind freely as needed. The brakes (15) acting on the storage drum (7) exert a braking force far less than the overload in question and therefore do not affect the free rotation of the storage drum, and consequently, the free unwinding of the cable.

[0055] The lifting device of the invention is thus designed so that the free rotation of the capstan (3) following the detection of an overload exceeding said first threshold is limited in time. This free rotation effectively results in the absence or near absence of torque exerted on the lifting drum or the capstan (3). As mentioned As a preliminary step, after this drastic reduction of the torque, an attempt is made to slow down, or even stop, this free rotation of the drum, in order to oppose the complete unwinding of the cable, and alternatively, when the attempt to stop this free rotation is not possible due, for example, to the gripping of the end of the cable in a fixed point, to allow the operator to cut the cable.

[0056] To this end, the brakes (12) associated with the lifting drum or capstan define a second threshold and attempt to slow down or stop the lifting drum as desired. Consequently, the device of the invention re-engages the components (9, 10) to engage the lifting drum with the motor (6), thus restoring normal operation of the lifting mechanism. If, however, the event causing the overload persists, the components (9, 10) are again disengaged, again allowing the lifting drum or capstan to rotate freely.

[0057] Typically, if the motor's rotational speed becomes greater than or equal to the cable unwinding speed, following a successful attempt to recouple the two coupling elements (9, 10), the lifting element returns to its normal operation.

[0058] If, on the other hand, this attempt at recoupling fails, due to the maintenance of the torque exerted on the capstan (3) exceeding the first threshold, for example due to the end of the cable being caught in a fixed point such as a pylon or tree, the free-wheeling continues, and after a further unsuccessful attempt at recoupling, the operator may then decide to cut the cable, in particular so as not to impact the integrity of the helicopter in which the lifting device is mounted.

[0059] In the described embodiment, these attempts to recouple the two coupling elements (9) and (10) occur every 4 or 5 seconds.

[0060] A graph illustrating, as a function of time (abscissa) and load (in kg) (ordinate), the different operating modes of the lifting device according to the invention, in this case, for a nominal load of 240 kg for example, has been represented in relation to [Fig.4].

[0061] The following are represented within this graph: - said first threshold, in this case set at 3.5 times the nominal load, i.e. 840 kg; - said second threshold, in this case set at 2.6 times the nominal load, i.e. approximately 624 kg-

[0062] Within this graph, the dashed curve (the leftmost one in the figure) illustrates the application of a sudden or abrupt overload, typically resulting from the fall of an operator attached to the free end of the cable, or following a slack in the cable which is followed by a sudden tension on said cable, and in any case exceeding said first threshold. In doing so, the device of the invention induces almost immediately the operation of the capstan (3) in freewheel mode, resulting on said curve in an inflection and a lowering of the value of the detected load until reaching the level of said second threshold, corresponding to the activation of the brakes (12) on the capstan.

[0063] At this point: - either the action of the brakes is sufficient to generate the effective slowing of the rotation of the lifting drum or capstan, and consequently the lasting recoupling of the coupling elements (9, 10), and therefore of the kinematic chain on said capstan, and we then return to the normal operating mode of the lifting element, resulting in a new inflection of the curve in the direction of the bottom, - If the overload persists, the aforementioned components (9, 10) are once again disengaged, resulting in a further upward movement followed by a downward inflection on the curve (solid line in the figure), due to the new freewheeling mode of operation of the lifting drum or capstan. Once again, the brakes (15) will attempt to slow the rotation of the lifting drum or capstan, and consequently re-engage components (9, 10). If this new attempt fails for the reasons mentioned previously, the operator, having had sufficient time, typically 10 seconds, to make a decision, may decide to cut the cable.

[0064] The dashed and irregular curve illustrates a progressive overload, which may result from the end of the cable becoming entangled in a pylon, tree, etc. If this occurs, when the load reaches the second threshold, the braking system (15) attempts to brake and reduce the load then applied to the lifting drum or capstan. If this braking is sufficient, the curve returns to normal operating mode. However, if this braking is insufficient, and the load increases further and exceeds the first threshold, the configuration described in the preceding paragraph is encountered.

[0065] The device of the invention is described in more detail below. Figure 5 shows a schematic overall view of the overload cartridge (20), which is one of the key elements of the device of the invention, and within which the coupling members (9, 10) operate. This overload cartridge (20) is removable, in that it can be interchanged with another cartridge having different characteristics, particularly in terms of overload detection thresholds. It is, in fact, provided with coupling means, in this case (22) on the capstan (3) and on the drive shaft from the motor (6) (not shown). Also shown in this figure is a toothed pinion (23), intended to cooperate with the braking device (12) of the lifting drum or capstan (3), and the teeth (45) of the ratchet (13), whose function will be described later.

[0066] Typically, the toothed pinion (23) is suitable for engaging in a toothed ring (51) of appropriate shape and size, provided inside the braking device (50), described in more detail in [Fig. 15].

[0067] This cartridge (20) is in fact made up of a bell (21), typically metallic, with a circular cross-section and rotational symmetry, as can be seen in Figures 6 and 7. The bell (21) has a bottom (24), in this case perforated, from which a central cylindrical projection (25) extends. Within this projection is housed the end of the shaft from the electric motor (6) that ensures the rotation of the lifting drum or capstan (3). The bell has, opposite the bottom (24), an opening (26) for inserting the various components of the device of the invention into the bell (21).

[0068] The base (24) of the bell (21) is intended to receive a first annular ring (27), illustrated in detail in [Fig.8]. This ring (27) is reversibly attached to the base of the bell by means of radial projections (28) capable of being received within through openings (29) provided within the base (24) in a corresponding manner, both in positioning and in dimensions.

[0069] The other face of the first ring (27) is provided with generally frustoconical housings (30) arranged periodically near the periphery of said ring. Each of these housings (30) communicates by means of an inclined ramp (31) with an annular groove or track (32), positioned near the internal diameter of said ring, and less deep than the housings (30). The function of these various elements will be described later. Each housing (30) is intended to receive a ball (33) made of a high-hardness material, typically steel.

[0070] Said first ring (27) is intended to cooperate with a second ring (35), illustrated for example on the [Fig.9], integral with a member (37) adapted to come onto an element of corresponding shape, to ensure the rotation of the lifting drum or capstan (3).

[0071] This cooperation results from the presence within said second ring (35) of racetrack-shaped through-holes (36), oriented obliquely with respect to the radial direction, located directly above the active area of ​​the first ring, i.e., the area comprising the housings (30) and the annular groove (32). The width of these through-holes (36) is slightly greater than the diameter of the balls (33), so that the balls can be received in these holes.

[0072] Figure 12 illustrates in exploded view the various constituent elements of this surcharge cartouche. The two following appear in this figure: respective crowns (27, 35) designed to cooperate with each other, and whose operating principle will be described in detail later.

[0073] In parallel, the organ (37) to which the second ring (35) is attached can rotate freely, subject to external constraints, around the projecting area (25) of the bell (21), a needle bearing (38) being interposed between the two.

[0074] Furthermore, the first overload triggering threshold mentioned above is ensured mechanically by means of a plurality of springs (40), enclosed in a cage defined by two opposing plates (41) and (42), coaxial with the bell (21) and the rings (27, 35). One (41) of said cage plates bears against the balls (33) (see Figures 10 and 11), and the other plate (42) is secured to the free upper rim of said bell by means of an annular flange (46), thereby constituting the fixed point of application of the springs (40).

[0075] Figures 10 and 11 illustrate the overload cartridge, respectively in the normal operating position, i.e. in which the rotation of the motor shaft causes the capstan to rotate, and in the uncoupling position, causing the capstan to rotate freely relative to the motor (3).

[0076] Figures 13 and 14 illustrate this operation. In [Fig. 13], corresponding to the normal operating mode, i.e., in which there is effective coupling between the drive shaft and the capstan, the balls (33) are present in the housings (30) of the first ring (27), and consequently cooperate with the latter via the through-holes (36) provided within the second ring (35). Three arrows A, B, and C illustrate the respective components of the action of the springs (40) acting on the balls (33), and of the cooperation between the balls (33) and the second ring (35), decomposed into a tangential component and a radial component. The torque exerted on the capstan due to the load (5) results in a lower force in the radial direction than that exerted by the springs (40), so that the two rings are coupled.

[0077] When the torque in question increases, particularly due to an overload, and more specifically when it exceeds a threshold value determined (the first threshold) by the stiffness constant resulting from the action of the springs (40) ([Fig. 14]), the radial component resulting from said torque becomes greater in value than the action exerted by the springs (40), inducing the balls (33) to exit their respective frustoconical housings (30) and move towards the internal annular groove (32). Because of the shallower depth of said groove (32) compared to the diameter of the balls, the latter cause axial displacement of the plate (41) and consequently of the plate (47). The balls (33), then present within the internal annular groove (32), thus forming a ball bearing, allow the two rings (27, 35) to rotate freely relative to the assembly (40 - 42), and in fact, the operation of the capstan (3) in freewheel mode relative to the motor shaft, and therefore the free unwinding of the cable (4).

[0078] This relative axial displacement of the plate (41) combined with the compression of the springs (40) also causes the displacement in the same direction of a plate (47), and consequently of a clutch system (48), thus mechanically linking the toothed pinion (23) and the coupling member (37).

[0079] Thus, by virtue of the cooperation of the pinion (23) with the braking device (50), which is fixed to the frame of the lifting member and consists of friction discs (52) interposed between counter-discs (53), the rotation of the lifting drum or capstan (3) is braked. Its action is determined by the clamping of said discs, typically achieved by a Belleville-type system (54) or even a spring system promoting redundancy, well known for this application. The maximum braking force constitutes said second threshold of the invention.

[0080] After the action of this braking device, which, it should be noted, intervenes after the detection of an overload, and therefore after the lifting drum or capstan has been set to free rotation, the rotational speed of said capstan is slowed down, and consequently, as the torque exerted on said capstan is drastically reduced precisely because of the free rotation, the re-engagement of the rings (27) and (35) is attempted. This attempt succeeds if the rotational speed of the drive shaft is greater than that of the lifting drum or capstan, causing, due to the shape and inclination of the through slots (36) of the second ring (35), the return of the balls (33) to their respective housing (30).

[0081] If, on the other hand, the rotational speed of the motor shaft remains lower than that of the lifting drum or capstan (3), due to the persistence of the overload, we find ourselves in the situation described above, and again, the platform (47) triggers the action of the braking device (12), to attempt once again to slow down or even stop the rotation of the capstan (3).

[0082] According to the invention, a ratchet wheel, illustrated by reference numeral (45) in Figures 5 and 10-12, is activated when the switch (11) is itself activated, that is, in the case of the detection of an overload greater than or equal to said first threshold. This ratchet is intended to stop the motor (6).

[0083] Consequently, a ratchet-type device (14) is also activated after overload detection by the switch (11). This ratchet (14) acts on the brakes (15) of the storage drum (7), in the case of a capstan winch, so that said drum can continue its rotation, in order to maintain sufficient tension on the cable strand (16) separating the capstan (3) from the storage drum (7), even when the capstan (3) is operating in freewheel mode.

[0084] According to a feature of the invention, the braking device (50) is also likely to be presented in the form of a removable element. By doing so, by modifying the characteristics of the components that make it up, it is possible to modify its braking characteristics, and therefore, consequently, the said second threshold.

[0085] It is therefore understood, on the one hand, that the two characteristic thresholds of the invention are completely independent of each other, and that it is possible, due to the removable nature of the cartridge (20) and the removable element (50) respectively, to adjust the general operation of the winch independently of each other.

Claims

Demands

1. A method for protecting a lifting device against overload, the lifting device comprising a lifting drum (3) around which a cable (4) is wound, to the end of which a load (5) is attached, said lifting drum (3) being mechanically linked to an electric motor (6) capable of ensuring its rotation, the mechanical link comprising a clutch or equivalent device, characterized in that said method comprises at least two distinct operating thresholds: - a first threshold, the exceeding of which causes the lifting drum (3) to operate in freewheel mode relative to the kinematic chain emanating from the electric motor (6); - a second threshold, of a value greater than that corresponding to the nominal load of the lifting device, but of a value less than that of the first threshold, causing the rotation of the lifting drum (3) to be braked and an attempt to progressively stop said rotation of the drum.

2. A method for protecting a lifting device against overload according to claim 1, further comprising, in the event of exceeding said first threshold, a step consisting of attempting to re-couple the lifting drum onto the kinematic chain occurring at a determined periodicity.

3. A method for protecting a lifting device against overload according to claim 2, wherein the determined periodicity is less than 5 seconds.

4. Method of protecting a lifting device against overload in which the lifting drum belongs to a capstan system (3) associated with a storage drum (7), according to any one of claims 1 to 3, method in which exceeding said first threshold causes the rotation of the storage drum to be braked, in order to maintain a minimum tension of the cable extending between the capstan (3) and the storage drum (7).

5. A device for protecting a lifting member against overload, said lifting member comprising: - a lifting drum (3) around which a lifting cable (4) is wound, at the end of which a load (5) is fixed; - an electric motor (6) equipped with a rotating shaft capable of ensuring the rotation of the lifting drum (3);

6.

7. - a clutch or equivalent device (20) mounted on the mechanical link connecting the electric motor (6) to the lifting drum (3) and capable of decoupling the motor from the drum; characterized: - in that the clutch or equivalent device is provided with elements capable of ensuring the free rotation of the lifting drum (3) relative to the drive shaft when the torque exerted by the cable (4) on said lifting drum (3) is greater than a predetermined threshold value, called the first threshold; - and in that the protection device also includes means of braking (23, 50) the rotation of the lifting drum, the maximum braking capacities of which constitute a second threshold, of a value greater than that corresponding to the nominal load of the lifting element, but of a value less than that of the first threshold. Overload protection device for a lifting member according to claim 5, characterized in that the clutch or equivalent device consists of an overload cartridge (20), which can be coupled respectively to the drive shaft of the electric motor (6) and to the lifting drum (3), said cartridge consisting of a bell (21) receiving two independent rings (27, 35) cooperating with each other by means of a plurality of balls (33) received in adaptedly shaped housings (30) formed within one (27) of said rings, and projecting out of said housings (30) in order to also be received in through slots (36) formed within the other ring (35), one (27) of said rings being fixed to the bell (21), itself mechanically connected to the drive shaft of the motor (6),and the other ring (35) being attached to a means (37) capable of rotating the lifting drum (3), springs (40) associated with a cooperating element with the braking means (50), exerting pressure on the balls (33). Overload protection device for a lifting member according to claim 6, characterized in that the housings (30) provided within one (27) of the rings and intended to receive the balls (33), communicate with an internal annular groove (32) provided within said ring (27), of a depth less than said housings, this communication being achieved by means of non-radial ramps (31).

8. A device for protecting a lifting member against overload according to one of claims 6 and 7, characterized in that the cartridge (20) is removable.

9. A device for protecting a lifting member against overload according to any one of claims 5 to 8, characterized in that the braking means (23, 50) of the rotation of the lifting drum (3) are made up of friction discs (52) attached to the lifting member, and cooperating with a toothed pinion (23) engaged on the axis of rotation of said lifting drum (3) in the event of exceeding said first threshold.

10. A device for protecting a lifting member against overload according to claim 9, characterized in that the braking means (50) are removable.

11. A device for protecting a lifting member against overload according to any one of claims 5 to 10, wherein the lifting drum (3) is a capstan, associated with a storage drum (7) driven in rotation by an electric motor (8), characterized in that the device further comprises a ratchet wheel (14), activated after exceeding said first threshold, and intended to act on the brakes (15) associated with said storage drum (7), so that said drum continues its rotation, in order to maintain sufficient tension in the strand of cable (16) separating the capstan (3) from the storage drum (7), even in the event of operation of the capstan (3) in freewheel mode.

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